JP2001151377A - Sheet conveying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet conveying device capable of conveying a sheet-like material stably for a long time. SOLUTION: The sheet conveying device comprises a conveying roll pair for conveying the sheet-like material by nipping and rotating it with nip pressure, and has a control means for changing the nip pressure of the conveying roll pair based on a situation of the conveyed sheet-like material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying method and a sheet conveying apparatus for conveying a sheet such as paper or film.

[0002]

2. Description of the Related Art Conventionally, there has been widely known a sheet conveying apparatus for conveying a sheet-like material such as paper or film without displacement. For example, in an image forming apparatus such as a copying machine, a printer, a facsimile, etc., recording paper stored in a paper tray is sequentially conveyed, and an image is formed on the recording paper with toner or the like. In general, such a sheet is transported by providing a plurality of rotating roll pairs on a transport path, and transporting the sheet while being sandwiched between the roll pairs (for example, Japanese Patent Application Laid-Open No. 5-246584). Reference).

[0003]

Here, if the nip pressure at the time of pinching the sheet is too low, the roll pair slips with respect to the sheet, and the conveyance speed of the sheet tends to be delayed. In some cases, it may not be possible to carry the sheet. Generally, the size of the paper increases,
When the shape of the transport path is R-shaped, S-shaped, or the like, the transport resistance acting on the sheet-like material increases, and a higher nip pressure is required. Further, when conveying coated paper or the like having a low frictional resistance, a higher nip pressure is required. On the other hand, if the nip pressure is too high, an unnecessary load is applied to each roll constituting the roll pair, and the life thereof is shortened. In particular, in order to reduce the human and financial costs for replacing the roll pair, it is necessary to extend the life of the roll pair.

The present invention has been made in view of such problems, and an object of the present invention is to provide a sheet conveying apparatus which can stably convey a sheet material for a long period of time.

[0005]

In other words, the present invention relates to a sheet conveying apparatus provided with a pair of conveying rolls for conveying a sheet by sandwiching the sheet at a predetermined nip pressure and rotating the sheet. The sheet conveying device includes a control unit that changes the nip pressure of the conveying roll pair based on the control information.

FIG. 1 illustrates the concept of the present invention. As shown in the figure, the control means controls the nip pressure N of the transport roll pair based on the state of the transported sheet. Here, the state of the sheet-like material is roughly divided into a conveying force F acting on the sheet-like material (claim 2).
And the transport resistance λ acting on the sheet-like material (claim 6). Hereinafter, these will be described in detail.

First, the conveyance resistance λ acting on the sheet-like material
Varies depending on the weight (size, weighing), rigidity, transport path and the like of the sheet material to be transported (claim 7). That is, the transport resistance λ increases as the weight of the sheet increases, and the transport resistance λ decreases as the weight of the sheet decreases. In addition, as the rigidity of the sheet-like object increases, the transport resistance λ at the curved portion on the transport path increases, and as the rigidity of the sheet-like object decreases, the transport resistance λ decreases.

Further, when the number of curved portions on the transport path is large or the radius of curvature is small, the transport resistance λ at the curved section becomes large, and the number of curved sections on the transport path is small or When the radius of curvature is large, the transport resistance λ at the curved portion becomes small. Furthermore, even if the number of curved portions on the transport path is the same, if the length of the sheet-like material is short, the number of contacts with the curved portion is small, so that the transport resistance λ decreases, and conversely, the length of the sheet-like material decreases. If the length is long, the number of contacts with the curved portion is large, so that the transport resistance λ increases. In addition, as a type of sheet-like material, for example, a material having a smooth surface (mirror surface) such as coated paper tends to stick on the transport path due to ambient humidity,
The transport resistance λ increases.

[0009] The weight (size,
Weighing) and stiffness can be recognized by the control means by the user setting it to the control means each time the type of sheet is changed or by automatically transmitting the information to the control means. it can. On the other hand, since the transport path is generally determined at the stage of designing the sheet transport apparatus, it is set in the control unit in advance. However, when the sheet conveying apparatus has a plurality of conveying paths having different conveying resistance λ,
Which transport path a certain sheet-like material passes through, is set in the control means each time the user changes the transport path,
By automatically transmitting the information to the control unit, the control unit can be made to recognize the information.

Next, the conveying force F acting on the sheet-like material is
The equation “F = μ_PR× N ”. Where the symbol N
Indicates the nip pressure of the transport roll pair as described above,
This is the control target of this control system. On the other hand, the symbol μ_PRIs a sheet
It is a coefficient of frictional resistance between an object and a transport roll pair. In addition,
Friction coefficient μ_PRIs the coefficient of frictional resistance μ of the sheet _P
Friction coefficient μ of the roll of_RAffected by
(Claim 3). That is, μ_PR= Μ₀× μ_P× μ_RAs
Can be expressed. Where μ₀Is a constant
Friction coefficient μ_PChanges depending on the state of the sheet.
Variable (transmittance), and the frictional resistance coefficient μ_RIs the roll
It is a variable (transmittance) that changes depending on the state.

Here, the coefficient of frictional resistance μ of the sheet is
_P changes depending on the type of sheet-like material, the surrounding environment, whether or not a double-sided mode by an electrophotographic image forming apparatus is used, and the like. That is, as the type of sheet, OHP sheet, coated paper, the order in friction coefficient mu _P of plain paper is lower. The high moisture content of the sheet is in a high-temperature, high-humidity environment as the surrounding environment, generally the higher the frictional resistance coefficient mu _P. Conversely, the lower the water content of the sheet is a low-temperature and low-humidity environment, the lower the general its friction coefficient mu _P.
In particular, when the sheet-like object is made of coated paper decreases the friction coefficient mu _P is remarkable. In double-sided mode,
After one side of the image is fixed is lower water content of the sheet is by fixing, typically its friction coefficient mu _P (than that of the sheet which has not undergone fixing) becomes lower.

The type of the sheet, the surrounding environment, and whether or not the double-side mode is used by the electrophotographic image forming apparatus are determined by the user every time the type of the sheet is changed. Or the information can be automatically transmitted to the control means by various sensors.

Further, the frictional resistance coefficient μ _R of the transport roll is:
It varies depending on the number of sheets to be conveyed, the service period of the conveying rolls, (mainly) the type of sheet to be conveyed, and the like. That is, over time the friction resistance coefficient mu _R of the roll The more transport number of the sheet is low. Further, the friction resistance coefficient mu _R over time rolled longer the service life of the transfer roll is lowered. Furthermore, for example, when a coated paper is mainly conveyed as a type of sheet-like material, a coat layer is formed on the surface of the conveying roll, and a frictional resistance coefficient μ of the conveying roll (compared to when mainly conveying plain paper) _R decreases.

Here, the frictional resistance coefficient μ _R of the transport roll decreases significantly with the increase in the number of transported sheets from the initial state to about several thousand sheets, and the friction of the transport rolls is determined based on the number of transported sheets. to determine the resistance coefficient mu _R, it is particularly preferred to determine therefore conveying force F. Also, significantly reduced the friction coefficient mu _R of the conveyor rolls when the sheet-like material to be conveyed is coated paper, (mostly) the frictional resistance of the transfer sheet to be transported on the basis of whether or not coated paper roll to determine the coefficient mu _R, it is particularly preferred to determine therefore conveying force F.

The number of sheets to be conveyed, the period of use of the conveying rolls, the type of (mainly) the sheet to be conveyed, and the like are automatically transmitted to control means by various sensors and counters. Each time the type of sheet is changed, or the like, the user can set it in the control means.

Now, in the sheet conveying apparatus according to the present invention,
The condition of the sheet-like material to be conveyed from these conditions, that is, the conveyance force F and the conveyance resistance λ acting on the sheet-like material are determined, and an appropriate nip pressure N is applied to the conveyance roll pair based on the judgment. is there. Here, in order to be able to convey the sheet-like material, it is necessary to satisfy the conveying force F> the conveying resistance λ. Moreover, as mentioned earlier, the length of the sheet-like object,
The nip pressure is considerably increased in order to ensure the transport force depending on the type, the state of the roll, and the like. In other words,
Transport force F (= μ _PR × N) = Transfer resistance force λ + ΔF (> 0)
Needs to be satisfied. On the other hand, the nip pressure is preferably low in consideration of elongation of the transport roll. In other words, it is preferable that ΔF (> 0) is smaller. From these viewpoints, the control means determines that the transport force F (= μ
The nip pressure N of the transport roll pair is controlled so as to give ( _PR × N) to the sheet. Needless to say, it is necessary to secure a predetermined safety margin for the conveying force F in design.

The condition of the above-mentioned sheet-like material depends on the condition that the "conveying force F> conveyance resistance λ" is a condition for properly conveying the sheet-like material. The determination may be made based on the transport time of the object (claim 8). In other words, in the state of “conveyance force F ≦ conveyance resistance force λ”, the conveyance time tends to be delayed because the sheet-like material slips at the nip portion of the conveyance roll pair. By detecting the transport time, it is possible to determine the state of the sheet.

Incidentally, in the sheet conveying apparatus, the sheet-like material may be conveyed by a plurality of pairs of conveying rolls (1, 2,..., N). In such a case, the transport force F acting on the sheet-like material is equal to each transport roll pair (1, 2,.
,..., N) applied to the sheet-like material (F ₁ , F ₂ ,.
_FN ) (F ₁ + F ₂ +... + F _N ).

When the transport force F is obtained in this manner, the transport forces (F ₁ , F ₂ ,..., F _N ) applied to the sheet-like material by each transport roll pair (1, ₂ ,. It depends on the type and the number of the roll pairs (1, 2,..., N).
Therefore, according to the present invention, the total (F ₁ + F ₂ +... + F _N ) of the transporting force applied to the sheet-like material is determined by the number of transport roll pairs (1, 2,. It is also determined by the type of the transport roll pair (claim 5).

FIG. 2 illustrates the concept of the present invention. Here, a plurality (three) of transport roll pairs A,
The case where the sheet material is sequentially conveyed by B and C is shown. Each transport rolls A, B, C, respectively the conveying force F _A applied to the sheet, F _B, is F _C. Note that the respective conveying forces F _A , F _B , and F _C may be equal or different.

First, as shown in FIG. 2A, when a sheet is transported by the transport roll pairs A and B, F _A +
The control means controls the nip pressure of the transport roll pair so that F _B = F (= transport resistance λ + ΔF). Here, the control means controls the nip pressure (N
_A or N _B ) may be controlled, or the nip pressures (N _A and N _B ) of both transport roll pairs A and B may be controlled.

Next, as shown in FIG. 2B, when the sheet is transported by the transport roll pairs A, B, and C, F
_{A + F B + F C =} F control means such that (= conveying resistance lambda + [Delta] F) controls the nip pressure of the conveying roller pair. The control means may transport rolls A, B, to either one of the nip pressure or (in N _A or N _B N _C) of C may control only the transport roller pair A, B, either C Only two or more nip pressures (N _A and N _B , or N _B and N _C , N _C and N _A ) may be controlled, or all the nip pressures of the transport roll pairs A, B and C (N _A , N _B and N _C ).

Furthermore, as shown in FIG. 2 (c), the transport roller pair B, and when transporting the sheet by C, F _B
The control means controls the nip pressure of the transport roll pair so that + F _C = F (= transport resistance λ + ΔF). Here, the control unit the transport roller pair B or the nip pressure of the conveying rolls C (N _B or N _C) in which only may be controlled, both the transport roller pair B, C of the nip pressure (N _B and N _C) May be controlled.

By controlling the sheet conveying device in this way, the conveying force F acting on the sheet-like material can be more accurately controlled.

It is particularly preferable that the transport roll pair for controlling the nip pressure N is a skew roll pair in which the axial directions of the rolls are different from each other. This is because the skewed roll pair conveys the sheet while slipping the sheet, and it is generally difficult to stabilize the conveying force F applied to the sheet. According to the present invention, since the nip pressure N of the skew roll pair is controlled, it is not necessary to set the nip pressure high in advance in consideration of a safety margin, which contributes to extending the life of the roll and conveys the sheet-like material. Also, it is possible to prevent an excessive load from being applied.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 shows a tandem-type digital color printer as an image forming apparatus according to an embodiment of the present invention.

As shown in FIG. 3, the tandem-type digital color printer is disposed on the image forming apparatus main body 1 and on one side (the left side in the figure) of the image forming apparatus main body 1.
A paper feeder 2 for feeding recording paper (sheet-like material) as a recording material of a predetermined size to the image forming apparatus main body 1, and an image provided in a state mounted on the upper part of the paper feeder 2 Reader 3 (Image Input Termina)
l) and a user interface 4 (User I) which is disposed over the sheet feeding device 2 and the upper portion of the image forming apparatus main body 1 and has a display screen for setting conditions of an image forming operation and the like.
and the recording paper on which an image is formed in the image forming apparatus main body 1 is arranged on the other side (the right side in the drawing) of the image forming apparatus main body 1, where necessary, such as sorting and stapling. And a sheet discharging device 5 that discharges the sheet after the post-processing is performed.

FIG. 4 shows an image forming apparatus main body 1 of the tandem type digital color printer.

For example, image data of a document read by the above-described image reading device 3 is input to the image forming apparatus main body 1. Further, the image forming apparatus main body 1 is connected to a host computer such as a personal computer (not shown) via a network such as a LAN as necessary, so that image data is transmitted from the host computer or the like. Has become.

As shown in FIG. 3, the image reading device 3 illuminates a document (not shown) placed on the platen glass 6 with a light source, and reflects a reflected light image from the document on a plurality of mirrors and a plurality of mirrors. C via a reduction optical system 7 composed of a lens
A scanning exposure is performed on an image reading element 8 such as a CD, and the color reading light image of the original is read by the image reading element 8 at a predetermined dot density (for example, 16 dots / mm).

The color material reflected light image of the original read by the image reading device 3 is, for example, red (R), green (G),
Image processing device (Image Processes, not shown) as original reflectance data of three colors of blue (B) (8 bits each)
Sing System), the image processing apparatus performs predetermined processing such as shading correction, position shift correction, lightness / color space conversion, gamma correction, frame erasure, and color / movement editing on the reflectance data of the document. Image processing is performed.

Then, the image data subjected to the predetermined image processing by the image processing apparatus as described above is processed by the same image processing apparatus into yellow (Y), magenta (M), cyan (C), black (BK) ( The image output device 10 (I) is converted into original color material gradation data of four colors (each of 8 bits) and disposed inside the image forming apparatus main body 1 as described below.
image Output Terminal).

As shown in FIG. 4, the image output device 10 includes yellow (Y), magenta (M), cyan (C),
Four image forming units 1 corresponding to black (BK)
1Y, 11M, 11C, and 11K, and these four image forming units 11Y, 11M, 11C, and 11K.
K are arranged in parallel in the image forming apparatus main body 1 at a fixed distance in the horizontal direction.

The four image forming units 11Y, 11Y
11M, 11C, and 11K have the same configuration, and are roughly divided into a photosensitive drum 12 as an image carrier that rotates at a predetermined speed in the direction of the arrow, and a uniform surface of the photosensitive drum 12. And a ROS 14 (Raster Outp) as image exposing means for exposing an image corresponding to a predetermined color on the surface of the photosensitive drum 12 to form an electrostatic latent image.
out Scanner) and a developing device 1 for developing an electrostatic latent image formed on the photosensitive drum 12 with toner of a predetermined color
5 and a cleaning device 16 for removing untransferred toner remaining on the photosensitive drum 12.

In the image output device 10, FIG.
As shown in FIG. 5, yellow (Y), magenta (M), cyan (C), black (B
K) (8-bit each) original color material gradation data of the four colors is formed of image forming units 11Y, 11M, 11Y, 11M, of yellow (Y), magenta (M), cyan (C), and black (BK).
ROS 14Y, 14M, 14C, 14 of 11C, 11K
K, these ROS 14Y, 14M, 14C,
At 14K, image exposure with laser light LB is performed in accordance with original color material gradation data of a predetermined color.

The ROSs 14Y, 14M, 14C, 14
At K, as shown in FIG. 4, the semiconductor laser 17 is modulated according to the document color material gradation data, and the laser light LB is emitted from the semiconductor laser 17 according to the gradation data. The laser beam LB emitted from the semiconductor laser 17 is deflected and scanned by the rotating polygon mirror 20 via the reflection mirrors 18 and 19, and again via the reflection mirror 19 and the plurality of reflection mirrors 21 and 22.
The upper part is exposed by scanning.

From the image processing apparatus, as described above, yellow (Y), magenta (M), cyan (C),
Black (BK) image forming units 11Y and 11
ROS14Y, 14M, 14C of M, 11C, 11K,
14K, the image data of each color is sequentially output.
Laser light LB modulated according to image data from the OSs 14Y, 14M, 14C, and 14K is scanned and exposed on the surface of each of the photosensitive drums 12 to form an electrostatic latent image. The electrostatic latent images formed on the respective photosensitive drums 12 are respectively subjected to yellow (Y), magenta (M), cyan (C), and black (BK) by the respective developing units 15Y, 15M, 15C, and 15K. Are developed as toner images of the respective colors.

Each of the image forming units 11Y, 11M,
The toner images of yellow (Y), magenta (M), cyan (C), and black (BK) sequentially formed on the photoconductor drums 12 of 11C and 11K are image forming units 11Y, 11M, On an intermediate transfer belt 25 as an intermediate transfer member disposed below 11C and 11K,
Multiple transfer is performed by the primary transfer rollers 26Y, 26M, 26C, and 26K. The intermediate transfer belt 25 includes a driving roller 27, a driven roller 28, and a tension roller 2.
9, a backup roller 30 for secondary transfer, and an idle roller 31, which are stretched with a constant tension, and are driven to rotate by a dedicated drive motor (not shown) having excellent constant speed. Thus, the circulating drive is performed at a predetermined speed along the direction of the arrow.
As the intermediate transfer belt 25, for example, a synthetic resin film such as polyimide having flexibility is formed in a belt shape,
An endless belt-shaped synthetic resin film is used by connecting both ends of the synthetic resin film formed in a belt shape by means such as welding.

The yellow (Y), magenta (M), cyan (C),
The toner image of each color of black (BK) is secondarily transferred onto a recording paper 33 as a recording medium by pressure and electrostatic force by a secondary transfer roller 32 pressed against a backup roller 30 via an intermediate transfer belt 25. The recording paper 33 on which the toner images of these colors are transferred is conveyed to a fixing device 36 by two continuous paper suction conveyance belts 34 and 35. Then, the recording paper 33 onto which the toner images of the respective colors are transferred is subjected to fixing processing by heat and pressure by a fixing device 36, and in the case of single-sided printing, as shown in FIG. The paper is discharged onto a discharge tray 37 via a paper discharge device 5 provided outside.

At this time, as shown in FIG. 3, the recording paper 33 is supplied to a plurality of paper feed cassettes 38 of the paper feeder 2 disposed on one side (the left side in FIG. 1) of the image forming apparatus main body 1. 3
9 or 40, a sheet of a predetermined size is fed by a feed roller 41 and is fed into the image forming apparatus main body 1 via a feed path 43 including a pair of rollers 42 for feeding a sheet. Conveyed. The recording paper 33 conveyed to the inside of the image forming apparatus main body 1 is once conveyed to a registration roller 46 via a paper conveyance path 45 provided with a plurality of skew rollers 44 for conveying paper, and stopped there. You. And
The recording paper 33 is rotated by a registration roller 46 at a predetermined timing in synchronization with the toner image transferred onto the intermediate transfer belt 25, and the intermediate transfer belt 25
The sheet is sent to a secondary transfer position where the upper backup roller 30 and the secondary transfer roller 32 are pressed against each other.

In the image forming apparatus main body 1,
When recording a color image on both sides of the recording paper 33,
The recording paper 33 on which an image is recorded on one side is not directly discharged onto the discharge tray 37 via the paper discharge device 5, but is discharged by a paper reversing and conveying member 47 provided in a discharge portion of the image forming apparatus main body 1. Then, the transport direction of the recording paper 33 is changed downward. Then, the recording sheet 33 on which the image is recorded on one side is once conveyed by a sheet reversing conveying member 47 to a sheet reversing path 48 provided at a lower end portion in the sheet discharging device 5 and stopped there. The sheet is transported again into the image forming apparatus main body 1 in a state where the transport direction is reversed, and is provided with a plurality of sheet transporting roller pairs 49 provided at the bottom of the image forming apparatus main body 1. , And is conveyed to the inside of the paper feeding device 2.

Thereafter, the recording paper 33 on which the image is formed on one side is passed through a paper reversing conveyance path 51 provided inside the paper feeding device 2, this time with the normal recording paper with its back face up. Similarly to 33, the sheet is again conveyed to the secondary transfer position on the intermediate transfer belt 25 at a predetermined timing via a sheet conveyance path 45 having a plurality of skew roller pairs 44 for sheet conveyance and a registration roller 46. An image is recorded on the back surface of the recording paper 33. The recording paper 33 on which the color images are recorded on the front and back sides is discharged onto the discharge tray 37 via the paper discharge device 5, and the double-sided color image recording process is completed.

Embodiment FIG. 5 is a perspective view of a transfer device according to this embodiment. Here, the roller pairs 42a, b, y, and z are part of the transport path 43, the roller pairs 49a, b, 42y, and z are part of the transport path 51, and the skew roller pairs 44a to 44c are the transport path 45. Part of each. Then, each skew roller pair 44
A guide member (not shown) parallel to the transport direction is provided closer to the guide direction indicated by the arrow than a to c.

First, the recording paper 33 has a pair of rollers 42b,
The sheet is conveyed in a predetermined conveying direction by 42y, and is then once moved to the left side in the traveling direction by a roller pair (hereinafter referred to as a "swing roller pair") 42z. The recording paper 33 is conveyed by the skew rollers 44a to 44c while being moved toward the right side in the traveling direction, that is, toward the guide member, and the skew thereof is corrected. Further, the recording paper 33 is moved leftward in the traveling direction by the registration rollers 46.

The structure and operation of the pair of swinging rollers 42z and the pair of skew rollers 44a to 44c will be described below.

The swing roller pair 42z includes a drive roller 42z (D) that is rotationally driven through a drive system such as a motor and gears (not shown), and a driven roller 42z () that rotates following the drive roller 42z (D). I). FIG.
Describes the configuration of the drive roller 42z (D) in detail. The driving roller 42z (D) is a metal roller shaft 420z (D) provided substantially perpendicular to the transport direction.
And a cylindrical first roller 421z (D) attached to the roller shaft 420z (D) and formed of an elastic body, and a first roller 421z (D) of the roller shaft 420z (D).
And a cylindrical second roller 422z (D) that is attached to the guide member side and made of an elastic body. The first roller 421z (D) and the second roller 422z
The distance d from (D) is 66 [mm].

The relationship between the diameter D _{1 of} the first roller 421 z (D) and the diameter D ₂ of the _second roller 422 z (D) is D ₁ <D ₂ (D ₁ = 20 mm), ₂ = 22
[Mm]). The roller diameter of the driven roller 42z (I) does not have a diameter difference.

On the other hand, each skew roller 44 includes a driving roller 44 (D) that is driven to rotate via a driving system such as a motor and gears (not shown), and a driven roller that rotates following the driving roller 44 (D). 44 (I) and driven roller 44 (I)
And a motor for changing the nip pressure N between the motor and the drive roller 44 (D).

FIG. 7A shows the driven roller 44 (I).
This is for describing a configuration for changing the nip pressure N between the driving roller 44 and the driving roller 44 (D). As shown in the figure, the driven roller 44 (I) and the driving roller 44 (D) face each other. Here, one end of the first arm 444 urges the roll axis of the driven roller 44 (I), and the other end of the first arm 444 is swingably attached to one end of the second arm 443. . The second arm 443 is configured to be rotatable around its center, and one end of a compression spring 442 is fixed to the other end. The other end of the compression spring 442 is attached to one end of the third arm 441. The other end of the third arm 441 is fixed to the rotation shaft of the motor 440. The motor 440 is a stepping motor.

FIG. 7B shows the driven roller 44 (I).
The operation for changing the nip pressure N between the drive roller 44 and the drive roller 44 (D) will be described. When a predetermined control signal is transmitted to the motor 440, the motor 440 rotates by an amount corresponding to the control signal. With the rotation, first, the third arm 441 rotates in the direction of the arrow in the figure. Then, the compression spring 442 is pulled, and the elastic force of the compression spring 442 moves the roll axis of the driven roller 44 (I) through the second arm 443 and the first arm 444 to the driving roller 44 (D).
Acts in the direction of biasing to the side. Thus, the motor 44
If the rotation direction and the rotation angle of 0 are controlled, the driven roller 4
4 (I) and the nip pressure N between the drive roller 44 (D) can be controlled.

FIG. 8 is a block diagram for explaining a control system for controlling the nip pressure N of the skew roller pairs 44a to 44c. This control system is a main controller of the image forming apparatus,
A control unit (control means) 400 to which information indicating the status of the recording paper 33 from various user interfaces (UI) and various sensors is input, and a motor rotated at a predetermined angle at a predetermined timing by a control signal from the control unit 400 440a
To c.

FIGS. 9 and 10 to 12 all illustrate an example of the operation of the control system shown in FIG. 8. The driving roller 44 (D) and the driven roller The operation for controlling the nip pressure N with 44 (I) has been described.

FIG. 9 is a timing chart for explaining the presence or absence of the recording paper 33 in the nip portion between the swing roller pair 42z, the skew roller pairs 44a to 44c, and the registration roller pair 46. In the drawing, whether or not the recording paper 33 exists in the nip portion of the swing roller pair 42z, -a indicates whether or not the recording paper 33 exists in the nip portion of the skew roller pair 44a, -b is Whether or not the recording paper 33 exists at the nip portion of the skew roller pair 44b, -c indicates whether or not the recording paper 33 exists at the nip portion of the skew roller pair 44c, Recording paper 33
Indicates whether or not exists.

FIGS. 10 to 12 show the swing roller pair 42.
z, the state of the recording paper 33 passing through the skew roller pairs 44a to 44c, the registration roller pair 46, and the skew roller pair 44a.
1 to 3 show the transfer forces Fa to c (nip pressures Na to c) with time. Incidentally, the conveying force F (nip pressure) of the swing roller pair 42z, registration roller pair 46 are each a constant _{F 1, F 2 (N 1} , N 2).

Control Example 1 Hereinafter, the skew roller pair 4 will be described with reference to FIGS.
The control operations of the nip pressures Na to c (transport forces Fa to c) of 4a to 4c will be described in detail as control example 1.

First, the leading edge of the recording paper 33 is set at time t.
_{In 1} (S), the nip portion of the swing roller pair 42z is reached (see FIG. 10A). In this case, since none of the skew roller pairs 44a to 44c sandwich the recording paper 33, the control unit 440 controls each motor so that the conveying forces Fa to c are all relatively low “1”. A control signal is transmitted to 440a to 440c to control each nip pressure Na to c.

Next, the leading edge of the recording paper 33 is set at time t.
_{In 2A} (S), the nip portion of the skew roller pair 44a is reached (see FIG. 10B). In this case, of the skew roller pairs 44a to 44c, only the skew roller pair 44a pinches the recording sheet 33, and none of the other pairs pinch the recording sheet 33. Therefore, the control unit 440 sends a control signal to each motor 440a such that the conveying force Fa is relatively high “6” and the conveying forces Fb and c are (as it is) both relatively low “1”. Transmit and control each nip pressure Na-c.

Next, the leading end of the recording paper 33 is set at time t.
_{In 2B} (S), the nip portion of the skew roller pair 44b is reached (see FIG. 10C). In this case, of the skew roller pairs 44a to 44c, the skew roller pairs 44a and 44b pinch the recording paper 33, and the skew roller pair 44c does not pinch the recording paper 33. Therefore, the conveying force Fc is (as it is) so that the conveying forces Fa and Fb both become "3" in order to make the necessary conveying force "6" as the sum of the conveying forces Fa and Fb.
The control unit 440 transmits a control signal to each of the motors 440a and 440b so that the nip pressure is set to a relatively low “1”.
To c.

Next, the leading edge of the recording paper 33 is set at time t.
_{In 2C} (S), the nip portion of the skew roller pair 44c is reached (see FIG. 11A). In this case, all the skew roller pairs 44a to 44c pinch the recording paper 33. Therefore, the control unit 440 sets each of the motors 440 so that each of the transport forces Fa, Fb, and Fc becomes “2” so that the required transport force is “6”.
Control signals are transmitted to a to c to control the nip pressures Na to c.

Next, after the time t _2C (S), the time t
Prior to ₃ (S), the recording paper 33 is not pinched by the swing roller pair 42z nor the registration roller pair 46, but is pinched by only the skew roller pairs 44a to 44c (FIG. 11B).
reference). Therefore, it is necessary that the control unit 440 controls each motor 4 so that the transport force increases from “6” to “18” and all the transport forces Fa, Fb, and Fc become “6”.
A control signal is transmitted to 40a to 40c to control each nip pressure Na to c.

Next, the leading edge of the recording paper 33 is set at time t.
_{3 In} (S), the nip portion of the pair of registration rollers 46 is reached (see FIG. 11C). In this case, all the skew roller pairs 44a to 44c pinch the recording paper 33. Therefore, the control unit 440 sets each of the motors 440 so that each of the transport forces Fa, Fb, and Fc becomes “2” so that the required transport force is “6”.
Control signals are transmitted to a to c to control the nip pressures Na to c.

Next, the rear end of the recording paper 33 is set at time t.
_{In 2A} (E), the nip portion of the skew roller pair 44a is removed (see FIG. 12A). In this case, of the skew roller pairs 44a to 44c, the skew roller pairs 44b and 44c pinch the recording sheet 33, and the skew roller pair 44a does not pinch the recording sheet 33. Therefore, the conveying force Fa is set to a relatively low value of "1" so that the conveying forces Fb and Fc are both set to "3" in order to make the necessary conveying force "6" in total of the conveying forces Fb and Fc. , The control unit 440 controls each motor 440
Control signals are transmitted to a to c to control the nip pressures Na to c.

Next, the rear end of the recording paper 33 is set at time t.
_{In 2B} (E), the nip portion of the skew roller pair 44b is removed (see FIG. 12B). In this case, of the skew roller pairs 44a to 44c, only the skew roller pair 44c sandwiches the recording sheet 33, and the skew roller pairs 44a and 44b
3 is not sandwiched. Therefore, the control unit 440 sets the transport force Fc to be the required transport force “6” with only the transport force Fc, the transport force Fc to be “6”, and the transport forces Fa and Fb to be relatively low “1”. A control signal is transmitted to each of the motors 440b and 440c to control each of the nip pressures Na to c.

Next, the rear end of the recording paper 33 is set at time t.
_{In 2C} (E), the nip portion of the skew roller pair 44c is removed (see FIG. 12C). In this case, none of the skew roller pairs 44a to 44c sandwich the recording paper 33. Therefore, the control unit 440 controls the motor 440 so that the conveying forces Fa, Fb, and Fc become relatively low “1”.
A control signal is transmitted to the respective nip pressures Na to c.

The operation for controlling the nip pressures Na to c (conveying forces Fa to c) of the skew roller pairs 44a to 44c has been described above. In order to perform such nip pressure control, regardless of the number of transport roll pairs and the type of transport roll pair, the recording paper 33 is conveyed regardless of the number of transport roll pairs.
3, an appropriate conveying force can be applied. At the same time, when the magnitude of the conveying force to be applied by each of the skew roller pairs 44a to 44c is small, the nip pressures Na to c of each of the skew roller pairs 44a to 44c are set low. Life can be extended.

Control Example 2 The control example 2 is a control in the case where the recording paper 33 having a longer length in the conveyance direction than the control example 1 is conveyed. Hereinafter, the operation of the nip pressure control will be described focusing on the difference from the control example 1. The length of the recording paper 33 to be transported in the transport direction is determined by, for example, a size sensor (not shown) provided on a paper feed tray,
Information indicating the length of the recording paper 33 in the transport direction is transmitted to the control unit 400 by setting by the user via the user interface.

FIG. 13 is a timing chart for explaining the presence or absence of the recording paper 33 in the nip portion between the swing roller pair 42z, the skew roller pairs 44a to 44c, and the registration roller pair 46. In the drawing, whether or not the recording paper 33 exists in the nip portion of the swing roller pair 42z, -a indicates whether or not the recording paper 33 exists in the nip portion of the skew roller pair 44a, -b is Whether or not the recording paper 33 exists at the nip portion of the skew roller pair 44b, -c indicates whether or not the recording paper 33 exists at the nip portion of the skew roller pair 44c, Recording paper 33
Indicates whether or not exists.

In this control example, the length of the recording paper 33 to be transported in the transport direction is long. Therefore, compared to the timing chart according to the control example 1 shown in FIG. There is a long time that exists. As a result, over the time t ₃ (S) to the time t ₁ (E), swing rollers 42z, skew rollers 44A～c, all conveying rollers of the registration roller pair 46 by sandwiching the recording paper 33 I have.

FIG. 14 shows a state in which all the conveying roller pairs are nipping the recording paper 33 and conveying forces Fa to c (nip pressures Na to c) of the skew roller pairs 44a to 44c at that time. It is. Incidentally, the conveying force F (nip pressure) of the swing roller pair 42z, registration roller pair 46 are each a constant _{F 1, F 2 (N 1} , N 2).

In this case, since the recording paper 33 is sandwiched between both the swing roller pair 42z and the registration roller pair 46, the necessary conveying force is (for example, the registration roller pair 46
(3), which is smaller than the necessary conveying force “6” in the case of the control example 1 shown in FIG. Therefore, the control unit 440 controls each of the motors 440 so that the transport forces Fa, Fb, and Fc are all “1”.
Control signals are transmitted to a to c to control the nip pressures Na to c.

In order to perform such nip pressure control, regardless of the number of transport roll pairs and the type of transport roll pair, the recording paper 33 to be transported is held regardless of the number of transport roll pairs. , A more appropriate conveying force can be applied. At the same time, each skew roller pair 44a-
When the magnitude of the conveying force to be applied by c is small, the nip pressures Na to c of the skew roller pairs 44a to 44c are set lower, so that the life of these rollers can be further extended. .

Control Example 3 Control example 3 is a control for conveying a recording sheet 33 of a relatively large size, and controls the nip pressure in accordance with an increase in the conveyance resistance. Hereinafter, the operation of the nip pressure control will be described focusing on the differences from the control examples 1 and 2. The size of the recording paper 33 to be conveyed is set by a user through a size sensor (not shown) provided on a paper feed tray or a user interface, for example.
Information indicating the size is transmitted to control section 400.

In this control example, the required conveying force is appropriately changed according to the size of the recording paper 33 to be conveyed. For example, in the control example 1, when the leading end of the recording paper 33 reaches the nip portion of the skew roller pair 44c at the time t _2C (S) (see FIG. 11A), the conveying forces Fa and F
The necessary transfer force of the sum of b and Fc was “6”,
In the present control example, when the size of the recording paper 33 is large, for example, the total required conveying force of the conveying forces Fa, Fb, and Fc is “6 × 1.5”, which is “9”. Then, the conveying force Fa,
The control unit 44 sets Fb and Fc to “3”.
0 sends a control signal to each of the motors 440a to 440c to control each of the nip pressures Na to c. Other states (FIGS. 10 to 1)
2, see FIG. 14).

Since such nip pressure control is performed, an appropriate conveying force can be applied to the recording paper 33 regardless of whether the size of the recording paper 33 being conveyed is large or small. At the same time, when the size of the recording paper 33 is small and the magnitude of the conveying force to be applied by the skew roller pairs 44a to 44c is small, the nip pressures Na to c of the skew roller pairs 44a to 44c are set low. Therefore, the life of these rollers can be further extended.

In this control example, the operation of performing the nip pressure N control based on the size of the recording paper 33 has been described as an example of the conveyance resistance. However, the present invention is not limited to this. The nip pressure may be controlled based on a transport path along which the recording paper 33 is transported.

Control Example 4 The control example 4 is based on a skew roller pair 44a to 44c that is used over time.
The nip pressure is controlled in accordance with the decrease in the friction coefficient of the nip. Hereinafter, the operation of the nip pressure control will be described focusing on the difference from the control example 1. When the friction coefficient of the skew roller pair decreases, information indicating the print history is transmitted to the control unit 400 via the print number counter provided in the digital color printer according to the present embodiment.

In this control example, the required conveying force is appropriately changed in accordance with the decrease in the friction coefficient of the skew roller pairs 44a to 44c. For example, in the control example 1, the time t _2C (S)
In the case where the leading end of the recording paper 33 reaches the nip portion of the skew roller pair 44c (see FIG. 11A), the conveyance force F does not take into account the decrease in the friction coefficient of the skew roller pair 44a to 44c.
The necessary conveying force of the sum of a, Fb, and Fc was set to “6”.

In this control example, for example, after counting the number of prints of several thousand from the initial state, the skew roller pair 44 is used.
When the reduction of the friction coefficient of a to c is progressing, for example,
The required conveying force in total of the conveying forces Fa, Fb and Fc is “6 ×
"9" of "1.5". Then, the conveying forces Fa, Fb,
The control unit 440 sets the Fc to “3” so that
A control signal is transmitted to each of the motors 440a to 440c to control each of the nip pressures Na to c. Other states (FIGS. 10 to 12, FIG. 1)
4)).

In order to perform such nip pressure control, it is possible to apply an appropriate conveying force to the recording paper 33 regardless of whether the friction coefficient of the skew roller pair 44a to 44c is reduced. it can. At the same time, the skew roller pair 44a-
When the decrease in the coefficient of friction of c has not progressed, the nip pressures Na to c of the respective skew roller pairs 44a to 44c can be set low while securing the necessary conveying force. Can be further extended.

In this control example, the friction coefficient of the pair of skew rollers 44a to 44c is determined based on the number of prints of the printer, that is, the number of conveyed recording sheets 33, and the nip pressure N is controlled based on the friction coefficient. The operation has been described. However, the present invention is not limited to this. The friction coefficient of the skew roller pairs 44a to 44c is determined based on the usage period of the transport roll, the type (mainly) of the sheet material to be transported, and the like. Nip pressure N
Control may be performed. Further, the skew roller pair 44a-
The nip pressure N control may be performed based on not only the friction coefficient of c but also the friction resistance coefficient of the recording paper 33. The coefficient of frictional resistance of the recording paper 33 can be determined based on the type of the recording paper 33, the surrounding environment, and whether or not a double-sided mode is performed by an electrophotographic image forming apparatus.

Control Example 5 In Control Example 5, the nip pressure is controlled according to the transport time of the recording paper 33 being transported. Hereinafter, the operation of the nip pressure control will be described focusing on the difference from the control example 1.

First, a method for detecting the transport time of the recording paper 33 will be described. FIG. 15 illustrates an example of a method for detecting the transport time of the recording paper 33. As shown in the figure, _two recording sheet detection sensors 44S ₁ and 44S ₂ are provided at an interval ₁ on the transport path on the downstream side in the transport direction of a certain skew roller pair 44. Then, these detection sensors 44S ₁ , 4
Detection signal from 4S ₂ is transmitted to the control unit 400. When the recording paper 33 is conveyed along a conveyance path indicated by a dotted line in FIG.
There is a shift in the timing at which S ₁ and 44S ₂ detect the recording paper 33. In the present control example, the nip pressure N of the skew roller pair 44 is controlled based on the timing shift.

In this control example, the detection sensors 44S ₁ , 44S
When the timing of S ₂ detects the recording paper 33 is slower than the predetermined timing, they sensor 44S _1, 44S ₂
Is determined to be insufficient, and the nip pressure N is set to a higher value. For example, when the conveying force of the skew roller pair 44 is “2”, it is changed to “3”.
The control unit 440 sends a control signal to the motor 440 to control the nip pressure N so that Conversely, if the timing at which the detection sensors 44S ₁ and 44S ₂ detect the recording paper 33 is earlier than the predetermined timing, the detection sensors 44S ₁ and 44S ₂
It is determined that the conveying force of the skew roller pair 44 immediately before S ₁ , 44S ₂ is excessive, and the nip pressure N is set lower. For example, the control unit 440 controls the motor 44 so that the conveyance force of the skew roller pair 44 is changed from “3” to “2”.
The control signal is transmitted to 0 to control the nip pressure N.

Since such nip pressure control is performed, an appropriate conveying force can be applied to the recording paper 33 stably. At the same time, the nip pressures Na to c of each of the skew roller pairs 44a to 44c can be set low while securing the necessary conveying force, and the life of these rollers can be extended.

The control operation of the nip pressures Na to c (transport forces Fa to c) of the skew roller pairs 44a to 44c has been described in detail based on the control examples 1 to 5. It should be noted that the value of the conveying force F (“1”, “6”, etc.) shown in these control examples is one of the guidelines for the conveying force, and it is a matter of course that it can be set as appropriate.
In these control examples, the value of the conveying force (nip pressure) is changed discontinuously. However, it is needless to say that the value can be changed continuously. Further, the control unit 400 stores the necessary value of the conveying force (nip pressure) as a table in advance, and it is a matter of course that an appropriate value can be selected from these values based on the status of the recording paper 33. is there.

[0086]

As described above in detail, according to the present invention, it is possible to provide a sheet conveying apparatus which can stably convey a sheet material for a long period of time.

[Brief description of the drawings]

FIG. 1 illustrates the concept of the present invention.

FIG. 2 illustrates another concept of the present invention.

FIG. 3 shows the entire image forming apparatus to which the sheet conveying device according to the present invention is applied.

FIG. 4 illustrates a part of the image forming apparatus illustrated in FIG. 4 in more detail.

FIG. 5 is a perspective view illustrating a part of the sheet conveying apparatus according to the embodiment.

FIG. 6 schematically illustrates a configuration of a swing roll of the sheet conveying apparatus according to the embodiment.

FIG. 7 illustrates a configuration for changing a nip pressure of a skew roller pair of the sheet conveying apparatus according to the embodiment in detail.

FIG. 8 illustrates a nip pressure control system of a skew roller pair of the sheet conveying apparatus according to the embodiment with reference to a block diagram.

FIG. 9 is a timing chart illustrating control timings of the sheet conveying apparatus according to the embodiment (control example 1).

FIG. 10 is a diagram illustrating an operation of skew roller-nip pressure control of the sheet conveying apparatus according to the embodiment (control example 1).

FIG. 11 is a diagram for explaining the operation of skew roller-nip pressure control of the sheet conveying apparatus according to the embodiment (control example 1).

FIG. 12 is a diagram illustrating an operation of skew roller-nip pressure control of the sheet conveying apparatus according to the embodiment (control example 1).

FIG. 13 is a timing chart illustrating control timings of the sheet conveying apparatus according to the embodiment (control example 2).

FIG. 14 illustrates an operation of skew roller-nip pressure control of the sheet conveying apparatus according to the embodiment (control example 2).

FIG. 15 illustrates a configuration for measuring a transport time of a sheet transport apparatus according to an embodiment (control example 5).

[Explanation of symbols]

42z: swing roller pair, 44a-c: skew roller pair,
46: registration roller pair, 440: motor, 400: control unit (control means), 44S: recording paper detection sensor

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3F049 AA07 DA12 DA19 LA02 LA05 LA07 LB03 LB08 3F102 AA02 AA11 AB01 AB05 DA08 EA03 EC04 FA02

Claims (9)

[Claims] 1. A sheet conveying apparatus having a pair of conveying rolls for conveying a sheet by pinching and rotating the sheet at a predetermined nip pressure, wherein the nip of the conveying roll pair is determined based on a state of the sheet to be conveyed. A sheet conveying device having control means for changing a pressure. 2. The sheet conveying apparatus according to claim 1, wherein the state of the sheet includes a conveying force acting on the sheet. 3. The conveyance force acting on the sheet-like material is determined based on a frictional resistance coefficient of a conveyance roll.
3. The sheet conveying device according to 1. 4. When the sheet is transported by a plurality of transport roll pairs, the transport force acting on the sheet is the sum of the transport forces applied to the sheet by each transport roll pair. The sheet conveying device according to claim 2. 5. The total conveying force applied to the sheet-like material is determined by the number of conveying roll pairs conveying the sheet-like material and / or
The sheet conveyance device according to claim 4, wherein the determination is made based on a type of the conveyance roll pair. 6. The sheet conveying apparatus according to claim 1, wherein the state of the sheet includes a conveyance resistance acting on the sheet. 7. The sheet conveyance device according to claim 6, wherein the conveyance resistance is determined based on at least one of a size, a weighing, and a rigidity of the conveyed sheet. 8. The sheet conveying apparatus according to claim 1, wherein the status of the sheet is determined based on a conveyance time of the conveyed sheet. 9. The conveying roll pair is a skew roll pair in which the axial directions of the respective rolls are different from each other.
The sheet conveying device according to any one of the above.