JP2018159811A - Image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control an amount of loop formation to an appropriate amount according to an amount of sheet height displacement and effectively correct the attitude of a sheet while avoiding having the sheet rucked.SOLUTION: An image formation device includes sheet height displacement amount detection means (S3) for detecting an amount of sheet height displacement (H1) over a sheet width direction (X) perpendicular to a sheet conveyance direction (Y) in a direction (Z) perpendicular to the sheet conveyance direction and sheet width direction. A control unit (a1) calculates a target amount of loop formation Ra referring to a relational expression or relational table between the amount of sheet height displacement and the target amount of loop formation on the basis of the amount of sheet height displacement detected by the sheet height displacement amount detection means, and controls the amount of loop formation of a sheet by a resist roller (b8) and a loop roller (b7) to converge at the target amount of loop formation. The relational expression or relational table is provided by the thickness of the sheet, by the stiffness strength of the sheet, and by the basis weight of the sheet.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an image forming apparatus.

  Conventionally, an electrostatic latent image formed on a photoreceptor is developed with toner to form a toner image, the formed toner image is transferred to a sheet of paper, and the transferred toner image is heated and fixed on the sheet of paper. There is known an electrophotographic image forming apparatus for forming an image.

  In the above image forming apparatus, a registration roller is disposed immediately before a transfer roller that transfers a toner image onto a sheet. After abutting the leading edge of the paper against the nip line of the registration roller in the stopped state, the paper is fed for a predetermined time by a loop roller or the like disposed immediately before the registration roller, thereby forming a loop on the paper to adjust the paper posture. The conveyance timing is accurately controlled by starting the registration rollers.

Patent Document 1 describes a technique for changing the suction condition of a paper feeding belt.
Patent Document 2 describes a technique for changing the loop amount according to the basis weight of the paper.
Patent Document 3 describes a technique for changing the loop amount in accordance with the sheet thickness.
Patent Document 4 describes a technique for changing the loop amount according to temperature and humidity.
Patent Document 5 describes a technique for detecting the amount of curling of a paper using a spur.
Patent Document 6 describes a technique for detecting a loop shape of a sheet by imaging.
Patent Document 7 describes a technique for detecting the stiffness of paper and controlling the loop roller.

JP-A-6-144617 JP 2013-238766 A Japanese Patent Laid-Open No. 10-81434 JP 2004-51340 A JP 2007-320668 A JP, 2015-107874, A JP 2006-347703 A

When the paper enters the nip line of the registration roller, as shown in FIG. 5, the paper is not in a straight line parallel to the X-axis direction parallel to the nip line on the plane XZ perpendicular to the conveyance direction Y, but in the Z-axis direction (high Deformation with displacement in the vertical direction may occur. That is, a height displacement amount H1 is generated on the sheet.
For example, as shown in FIG. 5 (a), the end portion hangs down and the central portion is convex, or as shown in FIGS. 5 (b) and 5 (c).
For example, in the configuration in which the paper P is sucked and conveyed by the paper feeding belt b2 as shown in FIG. 1, the paper is formed in a corrugated shape as shown in FIG. The corrugation shape may occur without being corrected by the time when it abuts against the registration roller b8. This is particularly noticeable when the nip line of the registration roller b8 is almost a straight path.
If a loop is formed with this deformation, the deformation and the loop shape as shown in FIG. 7 compete with each other, and a paper wrinkle 101 may occur as shown in FIG.
Such a paper wrinkle is likely to occur even when the paper is inclined in the height direction as shown in FIG.

As a countermeasure against the above, it has been found that paper wrinkles can be suppressed by reducing the loop amount in the resist portion.
However, if the loop amount is reduced regardless of the conditions, particularly in the case of thick paper having high rigidity, the curving correction is not sufficiently performed in the resist portion, and the paper is conveyed to the image transfer portion in a bent posture, resulting in an image defect. This is because high-stiffness paper has a large amount of energy that enters the resist portion, so that it is difficult to stop at the target stop position (nip portion), and the bending correction cannot be sufficiently performed unless the loop amount is increased.
Also known is a technology that changes the loop amount according to the basis weight and thickness of the paper, but the waviness shape and paper inclination during paper feeding vary depending on the suction force of the paper feeding belt and the paper production lot, paper Therefore, it is difficult to determine an appropriate loop formation amount according to conditions only by information on the basis weight and thickness of the paper.

  The present invention has been made in view of the above-described problems in the prior art, and is effectively controlled while avoiding wrinkling of the paper by controlling the loop formation amount to an appropriate amount according to the paper height displacement amount. The task is to correct the posture.

An invention according to claim 1 for solving the above-described problems includes an image forming unit for forming a toner image,
A transfer unit that transfers the toner image formed by the image forming unit to a sheet;
A registration roller disposed upstream of the transfer section along the paper conveyance path;
A loop roller that is disposed upstream of the registration roller and that strikes a sheet against the nip portion of the registration roller to form a loop on the sheet;
A paper feeder disposed upstream of the loop roller;
A control unit for controlling the operation of the registration roller and the loop roller,
In the image forming apparatus having a paper feeding belt that sucks and feeds the paper to the paper feeding path in the paper feeding unit,
A sheet height displacement detecting means for detecting a sheet height displacement amount in a direction perpendicular to the sheet conveying direction and the sheet width direction across the sheet width direction perpendicular to the sheet conveying direction;
The control unit calculates a target loop formation amount based on a paper height displacement amount detected by the paper height displacement detection unit, and a paper loop formation amount by the registration roller and the loop roller is the target loop formation amount. The image forming apparatus is controlled to converge to a quantity.

  According to a second aspect of the present invention, the sheet height displacement amount detection means is provided so as to detect a sheet in a conveyance section from the sheet feeding unit to the nip portion of the registration roller. The image forming apparatus described in the above.

  According to a third aspect of the present invention, the sheet height displacement amount detecting means is provided so as to detect a sheet in a conveyance section from a nip portion of the loop roller to a nip portion of the registration roller. The image forming apparatus according to Item 1.

Invention of Claim 4 has a paper thickness detection means to detect the thickness of paper,
The control unit can refer to a relational expression or a relation table between the paper height displacement amount and the target loop formation amount for each paper thickness, and the relational expression corresponding to the thickness detected by the paper thickness detecting means. Alternatively, the image forming apparatus according to any one of claims 1 to 3, wherein the target loop formation amount is calculated with reference to a relation table.

The invention according to claim 5 has stiffness detecting means for detecting the stiffness of the paper,
The control unit can refer to a relational expression or relation table between the paper height displacement amount and the target loop formation amount for each stiffness of the paper, and corresponds to the stiffness detected by the stiffness detecting means. The image forming apparatus according to claim 1, wherein the target loop formation amount is calculated with reference to a relational expression or a relation table.

  In the invention according to claim 6, the control unit can refer to a relational expression or relation table between the paper height displacement amount and the target loop formation amount for each paper basis weight, and corresponds to the paper basis weight. 4. The image forming apparatus according to claim 1, wherein the target loop formation amount is calculated with reference to the relational expression or the relation table.

  In the invention according to claim 7, the control unit abuts the sheet on the nip portion of the registration roller to form a loop on the sheet so as to converge to the target loop formation amount, and then restarts the registration roller. The loop is re-formed on the paper so as to converge to the target loop formation amount by speed control of the loop roller or the registration roller after the restart until the rear end of the paper passes through the loop roller. 6. The image forming apparatus according to claim 1.

The invention according to claim 8 has a loop amount detection means for detecting a loop amount of the paper between the registration roller and the loop roller,
The image forming apparatus according to claim 1, wherein the control unit performs control so that a loop amount detected by the loop amount detection unit is maintained at the target loop formation amount.

  According to the present invention, it is possible to control the posture of the paper effectively while controlling the amount of loop formation according to the amount of displacement of the paper height and avoiding wrinkling of the paper.

1 is a schematic diagram illustrating a main part of an image forming apparatus according to an embodiment of the present invention. 1 is a block diagram of an image forming apparatus according to an embodiment of the present invention. 4 is a graph showing a relationship between “paper height displacement amount (horizontal axis)” and “loop formation amount (vertical axis) where paper wrinkles occur”. 6 is a flowchart illustrating a flow of control executed by the image forming apparatus according to the embodiment of the present invention. FIG. 6 is a sheet cross-sectional view illustrating an example in which a sheet is deformed on a surface orthogonal to a conveyance direction. FIG. 4 is a perspective view (a) of a sheet on which a corrugation shape that can be generated by suction of a sheet feeding belt is formed, and a cross-sectional view (b) perpendicular to the transport direction. FIG. 3 is a perspective view of a sheet on which a loop shape formed by the image forming apparatus is formed. It is a top view of paper.

  An embodiment of the present invention will be described below with reference to the drawings. The following is one embodiment of the present invention and does not limit the present invention.

  As shown in FIGS. 1 and 2, an image forming apparatus 1 according to this embodiment is an electrophotographic image forming apparatus, and an electrostatic latent image formed on a photoreceptor is developed with toner to form a toner image. An image forming part b11 to be formed, a transfer part b9 for transferring the toner image carried on the intermediate transfer body b10 formed by the image forming part b11 to the paper P, and a fixing for heating and fixing the toner image transferred to the paper P Part b13 (not shown in FIG. 1).

In addition, the image forming apparatus 1 includes a sheet feeding unit b1, a stiffness detecting unit b3, a conveying roller b4, a sheet thickness detecting unit b12, a conveying roller b6, a loop roller b7, and a registration roller b8 along the sheet conveying path b5. . The image forming apparatus 1 also includes a loop roller driving unit a2, a registration roller driving unit a3, paper detection sensors S1, S2, and S5, a paper height displacement amount detection unit S3, a loop amount detection unit S4, and the like.
Further, the image forming apparatus 1 includes a control unit a1 that controls the above-described units.
The registration roller b8 is disposed upstream of the transfer portion b9 along the paper conveyance path b5. The loop roller b7 is disposed upstream of the registration roller b8 along the paper conveyance path b5, and has a function of abutting the paper P on the nip portion of the registration roller b8 to form a loop on the paper P.
The paper feeding unit b1 is disposed upstream of the loop roller b7, and has a paper feeding belt b2 that accommodates a plurality of papers P, sucks the papers P, and feeds the papers P to the paper transport path b5. The size, basis weight, and other paper type information of the paper P stored in the paper supply unit b1 are previously input to the image forming apparatus 1 via the input unit a5, stored in the storage unit a4, and can be referred to by the control unit a1. To be.

The sheet height displacement detection means S3 detects the sheet height displacement amount in the sheet conveyance direction Y and the height direction Z perpendicular to the sheet width direction X over the sheet width direction X perpendicular to the sheet conveyance direction Y. The paper height displacement amount detection means S3 is configured with a configuration in which a laser distance measuring device is scanned in the paper width direction X.
The sheet height displacement amount detection means S3 can be implemented if it is provided so as to detect the sheet P in the conveyance section from the sheet feeding portion b1 to the nip portion of the registration roller b8. This is because a “relational expression or relationship table” to be described later may be created in advance in relation to the amount of paper height displacement at the detection target position. However, in the present embodiment, the sheet P in the conveyance section from the nip portion of the loop roller b7 to the nip portion of the registration roller b8 is provided for detection. This is because the detection at the downstream side of the loop roller b7 can more accurately detect the amount of paper height displacement that occurs when the leading edge of the paper P reaches the nip portion of the registration roller b8, and the stability is increased. .

The stiffness detecting means b3 is attached to the corner path on the downstream side of the paper feeding belt b2, and detects the stiffness of the conveyed paper.
The presence or absence of a sheet on the sheet detection sensors S1, S2, S5 and the sheet conveyance path b5 is detected. The sheet detection sensor S1 targets the position immediately after the nip portion of the loop roller b7. The sheet detection sensor S2 targets the position immediately before the nip portion of the registration roller b8. The sheet detection sensor S5 targets the position immediately after the nip portion of the registration roller b8.
The loop amount detection means S4 is provided for a position where the displacement is increased by the loop formation before the registration roller b8.

Next, the loop amount control of the paper P will be described.
(Creation of relational expression or relational table)
Prior to executing the loop amount control of the paper P, a relational expression or relation table between the paper height displacement amount and the target loop formation amount is created and stored in the recording unit a4 so that it can be referred to by the control unit a1.
In order to create the “relational expression or relation table”, first, as shown in the graph of FIG. 3, “paper height displacement amount (horizontal axis)” detected by the paper height displacement amount detection means S3, and “paper wrinkle” The relationship with the “loop formation amount (vertical axis) where” occurs is investigated. The graph of FIG. 3 shows the boundary value of whether or not paper wrinkles occur for each “paper height displacement amount (horizontal axis)”. If it is below the graph, paper wrinkles will not occur. As shown in FIG. 3, it can be seen that the larger the “sheet height displacement (horizontal axis)”, the lower the boundary value at which wrinkles occur. Since this relationship differs depending on the thickness, stiffness, and basis weight of the paper, a relational expression or a relation table based on the difference in these conditions is created in advance and stored in the storage unit a4. The control unit a1 calculates the target loop formation amount with reference to the “relational expression or relationship table” stored in the storage unit a4. It should be noted that the target loop formation amount is appropriately set below the above boundary value by providing an appropriate safety margin.
FIG. 3 shows, as a representative example, the amount of loop formation that causes paper wrinkles due to the difference in paper thickness. In the graph of FIG. 3, the relationship between the paper thickness is as follows: paper thickness condition (1)> paper thickness condition (2)> paper thickness condition (3). It's easy to do.

(Control flow)
The flow of controlling the loop amount of the paper P will be described with reference to FIG.
First, the control unit a1 starts the conveyance of the paper P by controlling the paper supply unit b1 and the like (E0).
Next, the control unit a1 detects the paper thickness T1 by the paper thickness detection means b12 (E1).
Next, the control unit a1 detects the leading edge of the paper P in the transport direction by the paper detection sensor S1 (E2).
Since the detection of the paper P by the paper detection sensor S1 reveals that the paper P has reached the detection position of the paper height displacement detection means S3, the controller a1 uses the paper height displacement detection means S3 to detect the paper height. The maximum value Hmax and the minimum value Hmin of the displacement are detected (E3), and the difference between these values is detected to detect the sheet height displacement amount H1 (see FIG. 6) (E4).
Next, the control unit a1 calculates the target loop formation amount Ra with reference to the above-described “relational expression or relation table” based on the paper thickness T1 and the paper height displacement amount H1 (E5).
Next, the front end of the paper P in the transport direction is detected by the paper detection sensor S2 (E6).
Since the detection of the sheet P by the sheet detection sensor S2 starts the bump of the sheet P against the nip portion of the registration roller b8, the control unit a1 executes a loop forming operation (E7-E11).
As the loop forming operation, the control unit a1 detects the loop amount Rb by the loop amount detecting means S4 while forming the loop on the paper P that is fed by the loop roller b7 and hits the nip portion of the registration roller b8. When (E8) and (loop amount Rb) <(target loop forming amount Ra), loop formation by feeding of the loop roller b7 is maintained (E9), and (loop amount Rb) = (target loop forming amount Ra). Then, the loop forming operation is completed (E11).

Next, the control unit a1 restarts the registration roller b8 and sends the sheet P toward the transfer unit b9 (E12).
Next, until the trailing edge of the sheet P passes through the loop roller b7 (until YES at E20), the controller a1 controls the sheet P so that it converges to the target loop formation amount by controlling the speed of the loop roller b7 or the registration roller b8. Reform the loop (E13-E19). That is, the control unit a1 detects the loop amount Rc after the registration roller b8 is restarted by the loop amount detecting means S4 (E14), and when (loop amount Rc)> (target loop forming amount Ra), the loop roller b7 is decelerated (or the registration roller b8 is accelerated) (E15), (loop amount Rc) = (target loop forming amount Ra) is set (E16), and (loop amount Rc) <(target loop forming amount Ra). At this time, the loop roller b7 is accelerated (or the registration roller b8 is decelerated) (E17), and (loop amount Rc) = (target loop formation amount Ra) is set (E18). When (loop amount Rc) = (target loop formation amount Ra), the registration roller b8 and the loop roller b7 are transported at a constant speed, and the trailing edge of the sheet has passed the loop roller b7 by the sheet detection sensor S1. Is detected (YES in E20), and the loop forming operation is terminated (E21). The sheet detection sensor S5 detects that the trailing edge of the sheet has passed through the registration roller b8, stops the registration roller b8, and waits for the next sheet to be abutted.

For the above control example, when the control unit can refer to “a relational expression or a relation table between the paper height displacement amount and the target loop formation amount” for each paper stiffness, the stiffness detection means The stiffness detected by b3 is applied in steps E1 and E5.
For the above control example, when the control unit can refer to “a relational expression or relation table between the paper height displacement amount and the target loop formation amount” for each paper basis weight, the basis weight information is displayed. , Applied in steps E1 and E5.

  Regardless of the above embodiment, when the loop amount detecting means S4 is not provided or not used, the loop amount to be formed is determined based on “the sheet feeding amount by which the sheet P is fed by the rotation of the loop roller b7 after stopping the registration”. Estimated and applied to step E8, based on the loop amount in step E11 (ie, Ra) and the “difference in the amount of paper fed in the paper P of the registration roller b8 and loop roller b7 after registration restart” It is also possible to estimate the amount of loop formed and apply it to step E14.

  According to the above-described embodiment, control is performed to a limit target loop formation amount that does not generate paper wrinkles according to the amount of paper height displacement, and the paper posture is effectively corrected while avoiding wrinkling of the paper. be able to.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 101 Paper wrinkle b1 Paper feeding part b2 Paper feeding belt b3 Strength detection means b4 Conveying roller b5 Paper conveying path b6 Conveying roller b7 Loop roller b8 Registration roller b9 Transfer part b10 Intermediate transfer body b11 Image forming part b12 Paper thickness Detection means H1 Paper height displacement P Paper S1, S2, S5 Paper detection sensor S3 Paper height displacement detection means S4 Loop amount detection means X Paper width direction Y Paper conveyance direction Z Height direction

Claims (8)

An image forming unit for forming a toner image;
A transfer unit that transfers the toner image formed by the image forming unit to a sheet;
A registration roller disposed upstream of the transfer section along the paper conveyance path;
A loop roller that is disposed upstream of the registration roller and that strikes a sheet against the nip portion of the registration roller to form a loop on the sheet;
A paper feeder disposed upstream of the loop roller;
A control unit for controlling the operation of the registration roller and the loop roller,
In the image forming apparatus having a paper feeding belt that sucks and feeds the paper to the paper feeding path in the paper feeding unit,
A sheet height displacement detecting means for detecting a sheet height displacement amount in a direction perpendicular to the sheet conveying direction and the sheet width direction across the sheet width direction perpendicular to the sheet conveying direction;
The control unit calculates a target loop formation amount based on a paper height displacement amount detected by the paper height displacement detection unit, and a paper loop formation amount by the registration roller and the loop roller is the target loop formation amount. An image forming apparatus that controls to converge to a quantity. The image forming apparatus according to claim 1, wherein the sheet height displacement amount detection unit is configured to detect a sheet in a conveyance section from the sheet feeding unit to a nip portion of the registration roller. 2. The image forming apparatus according to claim 1, wherein the sheet height displacement detection unit is configured to detect a sheet in a conveyance section from a nip portion of the loop roller to a nip portion of the registration roller. . Having paper thickness detection means for detecting the thickness of the paper;
The control unit can refer to a relational expression or a relation table between the paper height displacement amount and the target loop formation amount for each paper thickness, and the relational expression corresponding to the thickness detected by the paper thickness detecting means. Alternatively, the image forming apparatus according to claim 1, wherein the target loop formation amount is calculated with reference to a relation table. Having a stiffness detecting means for detecting the stiffness of the paper,
The control unit can refer to a relational expression or relation table between the paper height displacement amount and the target loop formation amount for each stiffness of the paper, and corresponds to the stiffness detected by the stiffness detecting means. The image forming apparatus according to claim 1, wherein the target loop formation amount is calculated with reference to a relational expression or a relation table. The control unit can refer to a relational expression or relation table between the paper height displacement amount and the target loop formation amount for each paper basis weight, and the relational expression or relation table corresponding to the paper basis weight can be referred to. The image forming apparatus according to claim 1, wherein the target loop formation amount is calculated with reference to the image forming apparatus. The control unit abuts the sheet on the nip portion of the registration roller, forms a loop on the sheet so as to converge to the target loop formation amount, restarts the registration roller, and the trailing end of the sheet is the loop roller. 7. The loop is re-formed on the sheet so as to converge to the target loop forming amount by speed control of the loop roller or the registration roller after the restart until exiting from. Image forming apparatus. Loop amount detection means for detecting a loop amount of the paper between the registration roller and the loop roller;
The image forming apparatus according to claim 1, wherein the control unit performs control so that a loop amount detected by the loop amount detection unit is maintained at the target loop formation amount.

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