JP5927767B2 - Wrinkle occurrence determination method, program, wrinkle occurrence determination apparatus, and image forming apparatus - Google Patents

Description

  The present invention relates to a method for determining wrinkle occurrence of a sheet material sandwiched and conveyed at a nip portion of a pair of opposing rollers provided in an image forming apparatus such as a copying machine, a facsimile machine, a printer, or a complex machine thereof.

A sheet material such as a transfer sheet on which an image is transferred by the image forming apparatus or a document on which an image is read is conveyed in the image forming apparatus while being sandwiched by a nip portion of a roller pair including a roller and a counter roller. . When the sheet material is conveyed, its shape changes due to curling, wrinkling, floating, etc., which may cause clogging or jamming. To prevent clogging and jamming, it is necessary to investigate the cause and take appropriate measures.
Patent Document 1 describes an invention for measuring a three-dimensional shape of a sheet material from a pattern of the sheet material made of fibers or the like. When it is determined that there is an abnormality such as a float or wrinkle on the sheet material, the image forming process is stopped and the abnormality is notified to the user, so that the jam processing time can be shortened. Furthermore, by feeding back the measurement result to the simulation, it is possible to improve the accuracy of predicting an abnormality occurring in the sheet material and contribute to improving the reliability of the product.

However, in the above prior art, in order to prevent the occurrence of jam or shorten the jam processing time, the state of the sheet material after the fixing roller (whether wrinkles are present) is measured based on the pattern on the sheet. It is difficult to evaluate the margin of wrinkle generation based on the prior art. Therefore, further techniques are required to improve the prediction accuracy of wrinkle generation.
The present invention has been made in view of the above problems, and its purpose is to provide a technique for evaluating the margin of wrinkle generation of a sheet material for a wide range of sheet material types and preventing the generation of wrinkles. is there.

In order to solve the above problem, the invention according to claim 1 determines whether or not wrinkles are generated in the sheet material when the sheet material is nipped and conveyed at the nip portion of the opposed roller pair. In the wrinkle generation determining method, the corrugated shape calculating means reads a conveyance speed distribution in a direction orthogonal to the conveyance direction of the sheet material in the nip portion from the storage means, and corrugates the sheet material from the conveyance speed distribution. A wrinkle generation determining step for determining whether or not wrinkles are generated in the sheet material on the basis of the wavy shape calculated by the wavy shape calculating means. It features an occurrence determination method.
According to the first aspect of the present invention, it can be determined whether or not the sheet material is wrinkled from the corrugated shape of the sheet material obtained from the conveyance speed distribution. That is, it is possible to predict whether or not wrinkles will occur without actually passing the sheet material through the nip portion.

According to a second aspect of the present invention, the corrugated shape calculating means calculates a corrugated angle of the sheet material immediately before the nip portion is bitten, and the wrinkle occurrence determining means uses the corrugated inclination angle as a representative characteristic value. The wrinkle occurrence determining method according to claim 1, wherein it is determined whether or not the sheet material is wrinkled.
The invention according to claim 3 is characterized in that the wrinkle occurrence determining means determines that wrinkles occur when the wavy angle is equal to or greater than a buckling limit.
In the inventions of claims 2 and 3, it is determined whether or not wrinkles are generated in the sheet material using the waving angle obtained from the waving shape. Since the presence or absence of wrinkle generation can be determined using a quantified value such as the waving angle, the margin of wrinkle generation can be evaluated.
A fourth aspect of the present invention is characterized in that the wrinkle occurrence determining method according to any one of the first to third aspects, wherein the roller pair is a fixing roller pair.
According to the fourth aspect of the present invention, it is possible to prevent the sheet material of the paper passing through the fixing roller pair.

According to a fifth aspect of the present invention, there is provided a program for causing a computer to execute the wrinkle occurrence determining method according to any one of the first to fourth aspects.
The invention of claim 5 has the same effect as that of claim 1.
The invention according to claim 6 is a wrinkle generation determination device for determining whether or not wrinkles are generated in the sheet material when the sheet material is nipped and conveyed at the nip portion of the opposed roller pair, Based on the corrugated shape calculation means for calculating the corrugated shape of the sheet material from the conveyance speed distribution in the direction perpendicular to the conveyance direction of the sheet material in the nip portion, based on the corrugated shape calculated by the corrugated shape calculation means Wrinkle occurrence determining means for determining whether or not wrinkles occur in the sheet material.
The invention of claim 6 has the same effect as that of claim 1 .

The invention according to claim 7 is a wrinkle generation determination device for determining whether or not wrinkles are generated in the sheet material when the sheet material is nipped and conveyed at the nip portion of the opposed roller pair, Storage means for storing a conveyance speed distribution in a direction orthogonal to the conveyance direction of the sheet material at the nip portion, and reading the conveyance speed distribution from the storage means, and calculating a corrugated shape of the sheet material from the conveyance speed distribution And a wrinkle generation determination device that determines whether or not wrinkles are generated in the sheet material based on the wavy shape calculated by the wavy shape calculation unit. And

According to an eighth aspect of the present invention, there is provided an image forming apparatus including the wrinkle occurrence determining apparatus according to the sixth or seventh aspect.
The inventions of claims 7 and 8 have the same operation as that of claim 1.

According to the wrinkle generation determination method of the present invention, it is possible to provide a technique for evaluating the margin of wrinkle generation of recording paper for a wide range of paper types and preventing wrinkle generation.
According to the speed measuring device of the present invention, it is possible to measure the speed distribution in the width direction of the recording paper when the recording paper is conveyed in the fixing device.
According to the shape measuring apparatus of the present invention, it is possible to measure the shape of a wide range of paper types without depending on the state of the surface of the recording paper and for deformation of the recording paper from less than several millimeters to tens of millimeters or more. It becomes possible.

1 is a schematic configuration diagram of a digital copying machine according to an embodiment of the present invention. (A) and (b) are diagrams showing a velocity distribution in a direction perpendicular to the sheet conveyance direction in the nip portion. FIG. 10 is a cross-sectional view showing a conventional fixing roller pair. It is a schematic diagram when wrinkles occur in the nip part, (a) shows the initial state of nip biting when there is a convex conveyance speed deviation in the nip part, and (b) conveys from the state of (a). It is the schematic diagram which showed the time of wrinkle generation | occurrence | production when progressed. FIG. 6 is a model diagram illustrating a deformation state of a sheet when a convex velocity distribution is exhibited in a sheet conveyance direction at a nip portion. It is the perspective view which showed the state by which a wave was bitten by the nip part. It is the model which showed the state of the paper at the time of a waving passing a nip part, (a) shows a slipping state, (b) shows a buckling state, (c) is a figure which shows a slipping state. . It is a functional block diagram of a wrinkle occurrence determination device. 3 is a flowchart for determining wrinkle occurrence according to the present invention. It is a schematic block diagram which shows a fixing device and the control block diagram of a speed measuring device. FIG. 3 is a schematic configuration diagram of the fixing device observed from the line sensor side. (A) (b) is a figure which shows the example of a time change of the pattern on a paper. (A) (b) is a figure which shows the conveyance speed distribution obtained by the speed measurement apparatus. It is a schematic block diagram which shows a fixing device and the control block diagram of a shape measuring device. (A) and (b) are figures which show the example of an area sensor picked-up image. (A) (b) is a figure which shows the example of a deformation | transformation shape detection result. It is a figure which shows the relationship between roller shape and paper conveyance speed distribution. FIG. 6 is a diagram illustrating a relationship between a speed deviation that is a difference between a maximum value and a minimum value of a paper conveyance speed deviation distribution and a roller shape. It is a figure which shows the deformation | transformation shape of the paper at the time of using a crown roller. It is a figure which shows the deformation | transformation shape of the paper at the time of using a reverse crown roller. It is a figure which shows the change of the corrugation angle at the time of using a crown roller. It is a figure which shows the change of the corrugation angle at the time of using a reverse crown roller. It is a figure which shows the relationship between the maximum corrugation angle at the time of using a crown roller, and the paper height at that time. It is a figure which shows the relationship between the maximum corrugation angle at the time of using a reverse crown roller, and the paper height at that time.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The wrinkle occurrence determining method according to the present invention is characterized in that it is determined from wavy shapes at the nip portion of the sheet material whether or not wrinkles are generated in the sheet material nipped and conveyed by the roller pair of the image forming apparatus. In the present specification, “sheet material” includes sheet-like materials such as paper, film, and steel plate.

[Image forming apparatus]
The present invention is applied to an image forming apparatus such as a copying machine, a facsimile, a printer, or a complex machine of these. FIG. 1 is a schematic configuration diagram of a digital copying machine according to an embodiment of the present invention. An automatic document feeder (hereinafter simply referred to as “ADF”) 110, an image reading unit 120 that photoelectrically converts a document image conveyed by the ADF 110, and an image processing of the document image are performed on the photoconductor. An image information writing unit 130 that exposes image information with a laser beam to form an electrostatic latent image, a developing unit 140 that forms a toner image by attaching toner to an electrostatic latent image on a photoreceptor, and a toner image is recorded The transfer unit 150 for transferring to the paper, the fixing unit 160 for fixing the toner image transferred to the recording paper, the paper feeding unit 170 for feeding the recording paper, and the recording paper fed from the paper feeding unit 170 are developed. A vertical conveyance unit 180 that conveys toward the section 140. Note that the operation of the digital copying machine of this embodiment is well known, and thus the description thereof is omitted.
The paper feeding unit 170, the vertical conveyance unit 180, the transfer unit 150, the fixing unit 160, and the like of the copying machine 100 are provided with roller pairs that sandwich and convey the sheet material. The present invention is applied to all of these roller pairs. Is possible. In particular, the present invention is suitable for a pair of rollers that convey while sandwiching the entire area of the sheet material in the roller axial direction, more specifically, a pair of fixing rollers of the fixing unit 160.

Hereinafter, the principle of the present invention will be described.
[Paper transport speed distribution]
The conveyance speed distribution in the nip portion of the paper will be described. 2A and 2B are diagrams illustrating velocity distributions in a direction perpendicular to the sheet conveyance direction in the nip portion.
As shown in FIG. 2A, when the nip portion Pa of the opposing roller pair has a convex velocity distribution Va with respect to the conveyance direction B of the paper P, the conveyance direction of the paper P is in the nip portion Pa. On the other hand, an inward velocity vector Ca from the end in the width direction of the paper P toward the center in the width direction is generated. For this reason, as the paper P is transported through the nip portion Pa, both ends in the width direction of the paper P are gradually transported inward, and there is a high possibility that the paper P will eventually be wrinkled.

On the other hand, as shown in FIG. 2B, when the nip portion Pb exhibits a concave velocity distribution Vb with respect to the conveyance direction B of the paper P, the nip portion Pb has the conveyance direction of the paper P with respect to the conveyance direction B. Then, an outward velocity vector Cb from the central portion in the width direction of the paper P toward the end portion in the width direction is generated. For this reason, since both ends in the width direction of the paper P are pulled outward in the nip portion Pb, the paper P is less likely to be wrinkled.
In view of the above circumstances, in the prior art, an inverted crown roller is used as one of the driving roller or the opposing roller constituting the roller pair so that a velocity distribution as shown in FIG. It is customary. FIG. 3 is a schematic diagram showing a conventional fixing roller pair using reverse crown rollers. The illustrated fixing roller pair 40 includes a pressure roller 42 and a pressed roller 44, and the roller diameters of both ends in the axial direction of the pressure roller 42 are formed larger than the roller diameter of the central portion in the axial direction. Has an inverted crown shape. When a reverse crown roller is used as the pressure roller 42, the applied pressure at the central portion of the roller shaft in the axial direction with respect to the pressed roller 44 is lower than the applied pressure at both axial ends. Thereby, the peripheral speed near the both ends of the pressure roller 42 in the nip portion N becomes faster than the vicinity of the center. As a result, the paper velocity distribution in the nip portion is as shown in FIG. 2B, and the paper wrinkles are suppressed. However, since the roller diameter changes in the axial direction, the pressure distribution in the axial direction becomes non-uniform, and there is a problem that it is difficult to keep the fixing property uniform in the axial direction.

[Prediction of paper conveyance speed distribution and wavy shape]
FIG. 4 is a schematic diagram when wrinkles are generated in the nip portion. FIG. 4A shows an initial state of nip biting when there is a convex conveyance speed deviation in the nip portion, and FIG. It is the schematic diagram which showed the time of wrinkle generation | occurrence | production when conveyance progresses from the state.
FIG. 4B shows an out-of-plane deformed shape (waving W1) in the sheet width direction at the nip portion. Here, “out-of-plane deformation” refers to deformation of a sheet so that a z-axis component perpendicular to the sheet plane appears when the horizontal sheet plane before deformation is the xy plane. In the figure, Nc is a center line of the nip portion N and is a line parallel to the roller shaft.

As described above, as shown in FIG. 4A, when the nip portion N exhibits a convex velocity distribution Va with respect to the conveyance direction B of the paper P, the conveyance direction of the paper P is in the nip portion N. An inward velocity vector Ca from B in the width direction toward the center in the width direction is generated with respect to B. For this reason, as the paper P is transported through the nip portion N, both end portions in the width direction of the paper P are gradually transported inward, and a undulation W1 is generated in which the paper P is deformed out of plane.
At the initial stage of paper conveyance with a small wavy W1, the wavy W1 is absorbed by elastic deformation of a roller or the like and the paper is flattened, so that wrinkles do not occur. However, as shown in (b), as the conveyance of the sheet P proceeds, the amount of conveyance of the sheet P to the inside of both ends in the width direction increases, so that the undulation W1 grows and the nip N absorbs the undulation W1. A limit occurs, and the paper P is finally buckled, resulting in the generation of paper wrinkles W2.

The relationship between the corrugated shape of the paper and the presence or absence of wrinkles due to the non-uniformity of the paper conveyance speed distribution will be described with reference to FIG. FIG. 5 is a model diagram illustrating the deformation state of the sheet when the nip portion exhibits a convex velocity distribution with respect to the sheet conveyance direction. In the figure, the lines at times T = 0, t1, and t1 + Δt correspond to observation reference lines parallel to the roller shafts set at appropriate positions in the nip portion N, respectively. In the following description, for the sake of convenience, it is assumed that the observation reference line is placed at the nip center Nc (Nc0, Nc1, Nc1Δ). Further, the description will be made assuming that the sheet width direction end portion separated from the point O by X1 or more maintains the rigidity of the sheet, that is, the sheet does not cause out-of-plane deformation.
Consider points O, B1, and B2 arranged on a sheet P in a straight line parallel to the roller axis at time T = t1. Assume that the sheet conveyance speed exhibits a linear distribution as illustrated by V0, V1, and V1 corresponding to each point, and is constant during sheet conveyance.
If the conveyance speed distribution is constant in the roller axis direction, the points O, B1, and B2 should be aligned on a straight line even at time T = t1 + Δt when time has elapsed by Δt. However, due to the nonuniformity of the conveyance speed, the conveyance amounts at points B1 and B2 are smaller than point O, and the positions of the points are shifted by δ to B1 ′ and B2 ′, respectively. In other words, since the conveyance of the points B1 and B2 is delayed with respect to the point O, a conveyance delay amount δ is generated. With the conveyance delay, the sheet P is deformed out of plane and generates a wave W1 having a height hy, a width L, and a wave angle α at a point y away from the nip center Nc1Δ. Here, the undulation angle α is the maximum of the inclination angles formed between the tangent line of the undulation W1 surface in the roller axis direction and the horizontal sheet plane before deformation.

Here, if it is assumed that no slip occurs between the paper P and the roller and that the paper P on the side in the width direction from the points B1 and B2 maintains a flat surface, the amount of delay is not generated. δ can be expressed as a distance between points B1-B1 ′ and B2-B2 ′,
δ = (v0−vt) Δt (1)
It can be expressed. Further, the waving angle α can be obtained from the delay amount δ. For example, the deformation shape of the paper P in the portion where the waviness W1 is generated is obtained from the delay amount δ by simulation or the like, and the wavy angle α can be calculated from this shape. In this manner, the wavy shape can be predicted from the paper conveyance speed distribution.
Here, even if the delay amount δ is large and the undulation W1 is generated, if the rigidity of the sheet P is high, slippage occurs between the sheet P and the roller pair 50 at the entrance of the nip portion N, and the growth of the undulation W1 stops. To do. In this case, a slip state occurs at the nip entrance, and no wrinkle is generated. Hereinafter, the threshold value indicating whether or not the wavy W1 grows at the nip entrance is referred to as a delay limit δ0. When “delay amount δ ≦ delay limit δ0”, the growth of undulation W1 proceeds, and when “delay amount δ> delay limit δ0”, the growth of undulation W1 stops.

[Occurrence of wrinkles and paper condition at the nip]
It is considered that the wavy whose shape is predicted as described above is caught in the nip portion.
FIG. 6 is a perspective view showing a state in which waviness is caught in the nip portion. In the case where the undulation W1 occurs in the paper P and the undulation W1 is not absorbed at the entrance of the nip portion N composed of the roller 52 and the opposing roller 54, the undulation W1 in the nip portion N as shown in the figure. Will be bitten. In FIG. 6, a part of the roller 52 is shown in cross section.
FIGS. 7A and 7B are schematic views showing the state of the paper when the undulation passes through the nip portion, where FIG. 7A shows a slipping state, FIG. 7B shows a buckling state, and FIG. 7C shows a slipping state. FIG.
Even when the undulation W1 is caught in the nip portion N, when the undulation angle α is small and the paper P has a high rigidity, the paper P that has caused the undulation W1 slides in the nip portion N in the roller axis direction. Waves are eased. In this case, wrinkles do not occur ((a) slip state).
Hereinafter, a threshold value indicating whether or not the sheet P slides in the nip portion N is referred to as a nip slip limit α0. When “the undulation angle α <the slip limit α0 in the nip”, the paper slides in the nip portion N, and the undulation W1 is relaxed. Further, when “waving angle α ≧ slip limit in nip α0”, the wave is further bitten into the nip portion N without being relaxed.

When the paper P is caught in the nip portion without the undulation W1 being relaxed, if the undulation angle α is large and the rigidity of the paper P is small, the paper P in which the undulation W1 is generated buckles in the nip portion N. Self-generated ((b) buckling state). If the threshold value indicating whether or not the paper is buckled in the buckling state is the buckling limit α1, the wrinkling condition can be written as “waving angle α ≧ buckling limit α1”.
When the wavy angle α and the rigidity of the paper P are between the buckled state of (a) and the slipped state of (b), the wavy W1 passes through the nip portion N without being relaxed ((c) slipping state) ). The slip-through condition can be written using the buckling limit α1 as “waving angle α <buckling limit α1”.
As described above, the wavy shape of the paper is calculated from the paper conveyance speed distribution at the nip portion of the roller pair and the characteristics (rigidity, etc.) of the paper, so whether or not wrinkles occur in the system before passing the paper. It becomes possible to predict. Further, it is possible to determine whether or not wrinkles are generated by classifying and determining the state of the paper P passing through the nip portion into the above three states using the wave angle α as a representative characteristic value. Further, whether or not wrinkles are generated can be expressed using the delay amount δ and the wavy angle α, so that the margin of wrinkle generation can be quantitatively evaluated. The undulation angle α used for the above determination is obtained from the undulation shape immediately before the nip portion N is bitten.

[Wrinkle occurrence determination device]
A wrinkle occurrence discriminating apparatus for realizing the wrinkle occurrence discriminating method will be described with reference to FIG. FIG. 8 is a functional block diagram of the wrinkle occurrence determining apparatus.
The wrinkle occurrence determination device 60 is configured by a computer including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The wrinkle occurrence determining device 60 stores data necessary for determining whether or not wrinkles are generated, a storage unit 62 that stores data, a calculation formula, and the like, and reads necessary data from the storage unit 62 to calculate a corrugated shape of the sheet. The wavy shape calculating means 64, the wavy shape calculated by the wavy shape calculating means 64, the calculation formula stored in the storage means 62, and the like. And. The corrugated shape calculating means 64 and the wrinkle occurrence determining means 66 are realized by a CPU (Central Processing Unit).

The storage means 62 is a non-volatile memory, and information relating to paper types input by the user in advance, a table relating to paper characteristic values such as Young's modulus E and secondary moment I of each paper type, and a paper conveyance speed distribution ( V0, V1) is stored. Further, a calculation formula for calculating the conveyance delay amount δ and the undulation angle α, a calculation formula for calculating the delay limit δ0, the slip limit α0 in the nip, and the buckling limit α1 from the sheet characteristic value are stored. .
The corrugated shape calculating means 64 calculates a transport delay amount δ and a corrugated angle α as the corrugated shape of the paper from the paper transport speed distribution (V0, V1).
The wrinkle occurrence determining unit 66 obtains the rigidity of the sheet from the sheet characteristic values (E, I) and the like stored in the storage unit 62, and the conveyance delay amount δ calculated by the undulating shape calculating unit 64 and the undulation angle α. Then, the shape of the sheet when passing through the nip portion is classified into three states to determine whether or not wrinkles occur.

〔flowchart〕
A wrinkle occurrence determination method will be described with reference to a flowchart. FIG. 9 is a flowchart for determining wrinkle occurrence according to the present invention.
First, in determining whether or not wrinkles occur, it is necessary to specify the paper type that passes through the nip portion and read the paper conveyance speed distribution (step S1). For specifying the paper type, for example, when the paper P is set in the paper feed tray, the user inputs information such as the paper type of the paper P set in the paper feed tray, and the input information is stored in the storage unit 62. Remember. The corrugated shape calculation means 64 reads out paper characteristic values such as the Young's modulus E and the cross-sectional secondary moment I of the paper from the information on the paper type set in the paper feed tray and the table stored in the storage means 62. . The paper characteristic value is acquired by referring to information of another server via the network when the user inputs information such as the paper type of the paper P set in the paper feed tray, and is stored in the storage unit 62 in advance. You may keep it.
Since the sheet conveyance speed distribution can be uniquely determined by the roller shape, it is possible to use a roller-specific value stored in advance in the storage means 62. However, since there are environmental fluctuations and changes with time, an appropriate time It is desirable to measure at intervals and store the data in the storage means 62.

Next, based on the paper conveyance speed distribution, the corrugated shape calculating means 64 calculates the delay amount δ and the corrugated angle α as the corrugated shape of the paper (step S2).
When the calculated delay amount δ exceeds the delay limit δ0, that is, when the delay amount δ is large or the rigidity of the sheet is high (N in step S3), slip occurs between the sheet and the roller at the entrance of the nip portion. It is determined that the vehicle is slipping (step S4). At this time, since the conveyance delay amount δ is small with respect to the rigidity of the sheet, the growth of undulation stops. In this case, it is determined that no wrinkle is generated (step S5).
If the calculated delay amount δ is equal to or less than the delay limit δ0 (Y in step S3), the paper conveyance delay due to the paper conveyance speed distribution advances, and the undulation angle α is then compared with the slip limit α0 in the nip. (Step S6). If the wavy angle α is smaller than the slip limit α0 in the nip (N in step S4), that is, if the wavy angle is small with respect to the rigidity of the paper, Slips in the nip portion in the roller axis direction, and the undulation is alleviated. Also in this case, it is determined that it is in a slip state (step S4), and it is determined that no wrinkle is generated (step S5).
When the calculated undulation angle α is greater than or equal to the slip limit α0 in the nip (Y in step S6)
) Since the undulation passes through the nip portion while being held, the undulation angle α is then compared with the buckling limit α1 (step S7). If the calculated undulation angle α is smaller than the buckling limit α1 (N in step S5), it is determined that the undulation is not relaxed and the slipping state passes through the nip portion (step S8), and wrinkles do not occur. Determine (step S5). If the calculated undulation angle α is greater than or equal to the buckling limit α1 (Y in step S7), that is, if the undulation angle α is larger than the rigidity of the paper, the paper is in a buckled state where it buckles in the nip portion. Judgment is made (step S9), and it is determined that wrinkles occur (step S10).

As described above, knowing the paper conveyance speed distribution at the nip portion of the roller pair and the paper characteristics (rigidity, etc.) makes it possible to predict whether wrinkles will occur in the system. Furthermore, the state of the sheet passing through the nip portion is classified into the above three states using the wavy angle α as a representative characteristic value, and can be quantitatively evaluated.
In addition, since the rigidity of the paper greatly varies depending on the environment (for example, temperature, humidity, etc.), the above-described various characteristic values vary depending on the environment as well as the paper type. Therefore, it is desirable that the above-described various limit value and threshold value tables are stored in the storage means for each paper type and environment.

  The wrinkle occurrence determination method described in the present embodiment can be realized by a personal computer, a workstation, or the like by a program executed by a computer including a CPU, a ROM, a RAM, and the like. In this case, a program capable of causing the computer to execute the method is stored in a recording medium such as a magnetic disk (floppy (registered trademark) disk, hard disk, etc.), an optical disk (CD-ROM, DVD, etc.), or a semiconductor memory. Can be distributed.

[Speed measuring device]
A speed measurement device that measures a conveyance speed distribution generated in a sheet material conveyed through the roller nip will be described. The paper conveyance speed distribution obtained by the speed measuring device can be used in the above-described wrinkle occurrence determination method. In the present embodiment, the speed measuring device will be described with reference to an example of a fixing device, but it can also be applied to a roller pair other than the fixing device.
FIG. 10 is a schematic configuration diagram showing the fixing device and a control block diagram of the speed measuring device.
The fixing device 200 includes a fixing roller pair 201 including a heating roller 202 as a heating unit and a pressure roller 203. The fixing roller 200 is provided so that the pressure roller 203 is in pressure contact with the heating roller 202, and a fixing nip (nip portion N) is formed. Forming. The sheet P is conveyed and fixed in the direction of arrow B by the fixing device 200 to form an image.
The speed measurement device 210 includes a line illumination light source 211 that illuminates the paper P, a line sensor 212 (imaging means) that images the surface of the paper P illuminated by the line illumination light source 211, and the paper P imaged by the line sensor 212. A screen for displaying a control unit 213 that calculates the conveyance speed distribution of the paper P from the front image, a non-volatile memory 214 that stores programs and various data necessary for calculating the conveyance speed distribution, settings and measurement results of the speed measurement device 210, and the like. A display unit 215 for displaying.

A line illumination light source 211 is provided above the paper P, and is irradiated onto the paper P in a straight line perpendicular to the transport direction B. Further, a line sensor 212 is provided above the paper P, and the paper P irradiated by the line illumination light source 211 is photographed. A pattern (not shown) is printed on the paper P, and the line sensor 212 captures the time change of the pattern while the paper P is being conveyed.
The control unit 213, which is a control unit, includes a CPU, a ROM, a RAM, and the like, and realizes the functions of each unit by executing a predetermined program. The control unit 213 receives an image including a pattern on the paper P photographed by the line sensor 212, calculates a time change in the conveyance direction of the pattern on the paper P by image processing, and digitizes the image. That is, in the present embodiment, the line illumination light source 211, the line sensor 212, and the control unit 213 constitute a recording paper speed measuring unit. The control unit 213 is connected to a non-volatile memory 214 (storage unit) serving as a storage unit. The non-volatile memory 214 includes a quantity of features extracted from the pattern in the captured image and the conveyance speed of the paper P. Reference information for which the relationship has been obtained in advance through experiments is stored. Further, the non-volatile memory 214 stores information on the conveyance speed that has been imaged and calculated for each sheet passing. The display unit 215 is a known display device or the like, and displays the setting of the measurement device, the measurement result, and the like on the screen.

  FIG. 11 is a schematic configuration diagram of the fixing device observed from the line sensor side. The paper Pt passed through the fixing device for speed measurement is composed of a plurality of strips 221 arranged in parallel in a direction (paper width direction) orthogonal to the transport direction B. Each of the strips 221 is connected and integrated with each other at the front end portion with respect to the transport direction B, while the rear end portion is independent. And since there is a cut 221a having a sufficient width between the strips 221, they do not receive mutual interference. Therefore, each strip 221 can take a free behavior independently. Further, on each strip 221, a linear pattern 222 perpendicular to the paper transport direction B is printed at equal intervals in the paper transport direction B. While the sheet Pt is conveyed in the conveyance direction B, the line pattern 212 on the sheet Pt passing through the imaging line D is imaged for a certain time using the line sensor 212.

FIGS. 12A and 12B are diagrams illustrating an example of a temporal change in the pattern on the paper. FIGS. 12A and 12B show examples of changes over time in an image photographed by the line sensor 212 when the paper Pt in FIG. 11 is passed, that is, a pattern passing through the photographing line D. FIG. Since the one-dimensional images acquired by the line sensor 212 are arranged in chronological order to form a two-dimensional image, in this figure, the horizontal direction of the image represents the position in the paper width direction, the time downward in the vertical direction of the image, and the lighter the color Indicates that the luminance value is large. From this luminance distribution, the sheet conveyance speed distribution and its time change can be calculated.
In FIG. 12A, the pattern 222 on the paper Pt passes through the photographing line D in a straight line in the paper width direction, and keeps the straight line even if time passes. On the other hand, in FIG. 12B, the pattern 222 on the paper Pt passes through the photographing line D in a straight line in the paper width direction at the beginning of conveyance. However, it is shown that a delay occurs when the pattern 222 on the strip 221 near the center of the paper Pt passes through the photographing line D as the transport amount of the paper Pt increases with time. That is, in this case, in FIG. 12A, the sheet Pt is conveyed with a uniform speed distribution in the width direction, whereas in FIG. 12B, the speed of the strip passing through the center portion of the fixing roller pair 201 is The paper Pt is transported with a non-uniform speed distribution, which is slower than the speed of the strip passing through the end portion.

FIGS. 13A and 13B are diagrams illustrating the conveyance speed distribution obtained by the speed measuring device. FIGS. 13A and 13B are conveyance speed distributions obtained by the calculation in the control unit 213 (speed distribution calculating means) from FIGS. 12A and 12B, respectively. Assuming that the interval in the conveyance direction B of the pattern 222 of each strip 221 in FIG. 11 is known and that the imaging time interval of the line sensor 212 is also known, the time interval during which the pattern 222 passes the imaging line D during conveyance. Can be calculated from the pattern interval on the image of FIG. That is, based on the image photographed by the line sensor 212, the control unit 213 can calculate the transport speed distribution of the paper Pt and the temporal change of the transport speed distribution.
FIG. 13A shows that the sheet Pt is conveyed with a uniform velocity distribution because the pattern interval on the image of FIG. 12A is the same in any strip 221. On the other hand, in FIG. 13B, since the pattern interval on the image of FIG. 12B is as wide as the strip 221 in the central portion, the strip 221 passing through the vicinity of the central portion in the width direction of the fixing device 200 is shown. It is shown that the paper Pt is transported with a low speed distribution, that is, a downward convex speed distribution. These results are displayed on the display unit 215.

Further, the conveyance speed distribution measurement result for the sheet Pt is stored for each sheet in the nonvolatile memory 214, and further, the conveyance speed distribution when the sheet is fed after changing the setting of the fixing device and the surrounding environment. Can also be memorized. It is possible to evaluate by a quantitative speed distribution comparison, such as under what conditions the conveyance speed distribution different from the ideal distribution occurs.
In addition, by transferring the conveyance speed distribution measured by the speed measurement device 210 to the wrinkle generation determination device 60, the actually measured data of the conveyance speed distribution can be used for the above-described wrinkle generation determination. The speed measuring device 210 may be incorporated in the wrinkle occurrence determining device 60. Further, the storage unit 62 and the nonvolatile memory 214 may be combined. Further, the image forming apparatus such as the copying machine 100 may include the speed measuring unit.

According to the speed measuring device, since the pattern is printed on the recording paper to be conveyed to the fixing device, the pattern is read during conveyance of the recording paper, and the time variation of the read pattern is analyzed to thereby determine the conveyance speed of the recording paper. Can be calculated.
Further, since the recording paper is composed of a plurality of strips, the conveyance speed in each strip can be calculated, and the speed distribution in the recording paper width direction can be measured. Each strip that passes through the nip portion of the fixing device can be transported at an independent speed.For example, when a recording paper composed of a plurality of strips is transported to a fixing device that uses an inverted crown roller, The strips passing near the center of the roller are passed at a slower speed than the strips passing near the end of the roller. If exactly the same pattern is printed on each strip, the temporal change of the pattern in the photographed image differs depending on the speed. Therefore, the velocity distribution in the recording paper width direction can be acquired by performing the same analysis on the area corresponding to each strip in the image.

[Shape measuring device]
A shape measuring apparatus for measuring the deformed shape of the paper P will be described. In this shape measuring apparatus, the out-of-plane deformation shape of the paper P before and after the nip portion can be measured. On the entrance side of the nip portion, the waviness W1 as a predictive phenomenon before the occurrence of wrinkles can be captured. Can be used for degree evaluation. Furthermore, useful data can be obtained in clarifying the correlation between the paper property and the wrinkle on the inlet side of the nip, such as the posture of the paper entering the nip. In addition, on the outlet side of the nip portion, it is possible to capture the wrinkle occurrence state under each set condition.

FIG. 14 is a schematic configuration diagram illustrating a fixing device and a control block diagram of the shape measuring device, and FIG. 15 is a schematic diagram of a photographed illumination pattern.
The fixing device 200 includes a fixing roller pair 201 including a heating roller 202 as a heating unit and a pressure roller 203. The fixing roller 200 is provided so that the pressure roller 203 is in pressure contact with the heating roller 202, and a fixing nip (nip portion N) is formed. Forming. The sheet P is conveyed and fixed in the direction of arrow B by the fixing device 200 to form an image.
The shape measuring apparatus 230 includes an illumination pattern projector 231 (illuminating unit) that irradiates a predetermined pattern on the surface of the paper P, an area sensor 232 (imaging unit) that captures the pattern irradiated by the illumination pattern projector 231, and Settings of the control unit 233 that calculates the deformation amount of the sheet P from the surface image of the sheet P captured by the area sensor 232, the nonvolatile memory 234 that stores programs and various data necessary for calculating the shape, and the setting of the shape measuring device 230 And a display unit 235 for displaying measurement results on the screen.

An illumination pattern projector 231 is provided above the paper P, and the laser pattern LP spread in a straight line perpendicular to the transport direction B is irradiated onto the paper P. The laser pattern LP shown in FIG. 14 is a single straight line, but a laser pattern composed of a plurality of laser beams spread linearly in a direction orthogonal to the transport direction may be used.
Further, an area sensor 232 is provided above the paper P at an arbitrary distance from the illumination pattern projector 231 to photograph the laser pattern LP.
The control unit 233, which is a control unit, includes a CPU, a ROM, a RAM, and the like, and realizes functions of each unit by executing a predetermined program. The control unit 233 receives an image including the laser pattern LP on the paper P photographed by the area sensor 232, and calculates the deformation amount in the width direction of the paper P by image processing. That is, in this embodiment, the illumination pattern projector 231, the area sensor 232, and the control unit 233 constitute a recording paper deformation shape measuring unit. The control unit 233 is connected to a non-volatile memory 234 serving as a storage unit. The non-volatile memory 234 is previously tested for a quantitative relationship between the distortion of the laser pattern in the captured image and the deformation amount of the paper P. The obtained reference information is stored. In addition, the non-volatile memory 234 stores information on the deformed shape that has been photographed / calculated in time series for each sheet.

Hereinafter, a specific operation of the apparatus will be described.
The sheet P is conveyed in the direction of arrow B through the nip formed by the fixing device 200. The illumination pattern projector 231 is installed on the nip entrance side with a predetermined angle with respect to the recording surface of the paper P, and irradiates the pattern LP over the entire width of the paper P near the nip entrance. The area sensor 232 is arranged at a predetermined angle different from that of the illumination pattern projector 231 with respect to the recording surface of the paper P, and images the pattern LP formed on the paper P at predetermined time intervals. FIGS. 15A and 15B are diagrams illustrating examples of area sensor captured images. When the sheet P is not bent, the pattern LPn at a certain time tn is captured by the area sensor 232 as a straight line as shown in FIG. However, if the sheet P is bent at a certain time tn, the height of the sheet is locally changed by the bending, so the pattern LPn is obtained from the area sensor 232 as shown in FIG. It will be perceived as a distorted curve.
By examining the positional relationship between the height of the paper and the pattern LP in advance, the deformation amount ε can be obtained for each position in the width direction of the paper P from the output of the area sensor 232. Further, since it is known that when the deformation amount ε of the paper P increases and exceeds a predetermined value, wrinkles are generated in the vicinity thereof. Whether the wrinkles are generated by measuring the deformation amount ε of the paper P. I can predict.

  FIG. 16 is a diagram illustrating an example of a deformed shape detection result. FIG. 16A shows a sheet deformation shape detection result when wrinkles occur. In this figure, the out-of-plane deformation amount of the sheet obtained from the shape of the pattern LP photographed by the area sensor 232 in the process of conveying one sheet is described in time series from time t0 to time tn. A change in the amount of distortion of the laser pattern LP is shown in which the position of the sheet bend and the amount of deformation change as the time passes and the sheet is bent during the conveyance of the sheet. FIG. 16B shows an out-of-plane deformed shape detection result in a state where wrinkles are not generated. Since the sheet P is not bent and is transported in a flat state, the sheet shape change is shown as an array of undistorted laser patterns. These results are displayed on the display unit 235 in FIG.

The deformation shape measurement result for the paper P is stored in the nonvolatile memory 234 for each paper passing, and the deformation shape measurement when the paper is passed by changing the paper type, the surrounding environment, and other fixing device condition settings. Results can also be stored. The wrinkle of the fixing device is determined by quantitative comparison of the shape and deformation amount, such as when the deformation amount ε is maximized or minimized when the paper is passed, that is, the wrinkle is most likely or hardly generated. It is possible to evaluate the margin of occurrence.
Further, by passing the paper shape measured by the shape measuring device 230 to the wrinkle generation determining device 60, the above-described wrinkle generation determination can be performed using the wavy angle α obtained from the actually measured paper shape. it can. Of course, the shape measuring device 230 (or the shape measuring device) may be incorporated in the wrinkle occurrence discriminating device 60 instead of the corrugated shape calculating device 64. The image forming apparatus such as the copying machine 100 may be provided with the shape measuring unit.

According to the present shape measuring apparatus, the recording paper to be conveyed to the fixing device is irradiated with the illumination pattern, and the illumination pattern shape and the mechanism for reading the time change of the shape are provided. It is possible to quantify the deformation shape generated in the paper and the temporal change of the deformation shape.
In addition, by using a laser beam spread in a direction perpendicular to the recording paper conveyance direction as a form of the illumination pattern irradiated to the recording paper, the time change of the shape when the recording paper passes a certain position is measured. be able to.
In addition, according to this shape measuring device, it does not depend on the state of the recording paper surface for a wide range of paper types, and measures the shape of recording paper deformation from less than a few millimeters to several tens of millimeters or more. Can do.

[Measurement results of paper behavior]
Generally, a fixing device of a printer uses a roller whose diameter changes in the longitudinal direction to prevent wrinkles. Therefore, several types of rollers having different shapes were prepared, and the relationship between the roller shape, the paper conveyance speed distribution, and the paper deformation shape was evaluated using the speed measuring device and the shape measuring device.
In addition, the thing with a small diameter of a center part with respect to both ends is called "reverse crown shape", and the thing with a large diameter of a center part with respect to both ends is called "crown shape."

(1) Measurement of paper conveyance speed distribution The test paper Pt on which the pattern 222 was printed and the speed measuring device 210 were used, and the paper conveyance speed distribution was measured under cold conditions. The results are shown in FIG. FIG. 17 is a diagram illustrating a relationship between the roller shape and the sheet conveyance speed distribution. Here, a speed deviation distribution based on the speed in the central portion in the roller axial direction is shown. The roller shape is indicated by the difference in diameter at the center when the end diameter is used as a reference.
When a straight roller (0.0 mm) having no diameter difference between both ends and the center is used, the speed distribution is almost flat. When the crown shape is noticeably (plus direction), the speed near the roller center increases, and when the inverse crown shape is noticeably (minus direction) in the convex speed distribution, It can be seen that the velocity decreases and has a concave velocity distribution.

FIG. 18 is a diagram illustrating the relationship between the speed deviation, which is the difference between the maximum value and the minimum value of the paper conveyance speed deviation distribution, and the roller shape. Here, the speed deviation in the case of the concave speed deviation distribution in FIG. 17 is expressed as a negative value. From this figure, it can be confirmed that the speed deviation under each condition changes almost linearly with respect to the reverse crown amount of the roller. In addition, in this measurement, the influence of pressing force is not recognized so much.
From the above results, the relationship between the roller shape and the paper conveyance speed distribution (speed deviation) can be quantified.

(2) Measurement of deformation shape outside sheet surface The deformation shape when the sheet was conveyed using the same roller as that used for measurement of the conveyance speed distribution was measured using the shape measuring device 230. As a typical result, the results in a crown shape (+0.3 mm) and an inverted crown shape (−0.2 mm) are shown in FIGS. 19 and 20, respectively. 19 and 20 are diagrams showing a deformed shape of the paper. In this figure, the deformed shape of the paper at the observation position at a certain time is shown by one line, and the measurement results at predetermined time intervals (0.03 s) are displayed while being shifted upward in the figure.
When a crown-shaped roller is used (FIG. 19), it can be observed that the initially flat sheet has undulations as the conveyance proceeds and further increases as the conveyance proceeds. In the above-described paper corrugation model (see FIG. 5 and the like), one mountain is considered in the paper width direction, but a plurality of waves are actually observed. In addition, when the reverse crown-shaped roller is used (FIG. 20), no undulation is observed in the conveyance process, and it can be confirmed that the sheet is conveyed while maintaining a flat shape. The large change in the shape of the paper at the rear edge of the paper (the uppermost line in the figure) captures the phenomenon that the paper rebounds when it leaves the nip.

  As described above, since the generation of wrinkles can be evaluated based on the corrugated shape of the paper, the corrugated angle at each position at each time is calculated from the deformed shape data of the paper of FIGS. The results are shown in FIGS. 21 and 22, respectively. 21 and 22 are diagrams showing changes in the waving angle. In this figure, each area of the paper is plotted with different colors according to the waving angle. When a crown-shaped roller is used (FIG. 21), it can be observed that the corrugation angle increases as the conveyance of the paper proceeds, as in the change in the deformed shape. When paper is passed by the roller used in this experiment, wrinkles are generated on the rear end side of the paper, but it has been confirmed that the wrinkle generation position after paper passes and the area of 8 deg or more in FIG. On the other hand, when a reverse crown-shaped roller is used (FIG. 22), the waviness angle is 2 deg or less in most regions. When this roller is used, the paper does not wrinkle.

23 and 24 are diagrams showing the relationship between the maximum waving angle and the paper height at that time. Here, the maximum waving angle is the maximum waving angle that is the maximum value of the waving angle in a single sheet. FIG. 23 shows a case where a crown-shaped roller is used, and FIG. 24 shows a case where an inverted crown-shaped roller is used. This figure shows the difference in the wavy shape. The closer the graph is to the lower left of the graph, the more the paper is transported while keeping the flatness. means.
In FIG. 23, the data transitions to the upper right of the graph as the crown amount of the roller increases. In the experiment shown in FIG. 23, wrinkles are generated when the crown amount is 0.3 mm, and extremely slight wrinkles are generated in a part when the crown amount is 0.15 mm. In FIG. 23, these wrinkle generation regions are also shown, and it can be confirmed that the presence or absence of wrinkle generation can be evaluated by the wavy angle.
On the other hand, in FIG. 24, there is no increase in the maximum waving angle corresponding to the increase in the reverse crown amount of the roller. In the experiment shown in FIG. 24, no wrinkle is generated, and it can be understood that wrinkles do not occur because the wavy angle does not reach the wrinkle generation threshold. Note that some of the data shown in FIG. 24 have a slightly larger waving angle. This is due to the phenomenon that the trailing edge of the paper is lifted due to the inverted crown shape, and the waving evaluated in FIG. It is different from the phenomenon.

The process of wrinkles is considered from the above results. When a crown-shaped roller is used, the paper conveyance speed distribution tends to be faster at the center (FIG. 17), and therefore, an inward force with respect to the roller axis direction (speed vector Ca: see FIG. 2A). Acts on the paper to cause undulations in the paper and grows as the conveyance proceeds (FIG. 19). When the undulation (angle) is small, the paper does not buckle in the nip, so wrinkles do not occur. However, when the undulation (angle) exceeds the allowable value as the paper is conveyed, buckling occurs and wrinkles occur. (See FIGS. 21 and 23).
On the other hand, when the reverse crown-shaped roller is used, the conveyance speed distribution of the paper tends to be fast at both ends (FIG. 17), and the outward force with respect to the roller axial direction (speed vector Cb: see FIG. 2B). ) Acts on the paper, so that the undulation of the paper is suppressed and stable conveyance can be realized (see FIGS. 20, 22, and 24). However, if the outward force is too large, the paper will be bounced away from the nip, resulting in unstable paper transport behavior.

  The above trends are consistent with the experience that has been known empirically, using the speed measuring device and shape measuring device, the roller shape (diameter difference between the center of the roller and the end), the paper conveyance speed distribution, and the paper It was confirmed that the relationship between the undulation shapes (the undulation angle and height) generated in the graph can be quantified. Furthermore, the prospect that the wrinkle generation limit can be evaluated by the corrugation angle derived based on the corrugation model of paper was obtained. Since the wrinkling angle at the wrinkle generation limit can be defined by the conveyance speed distribution in addition to the basic physical properties based on the corrugated paper biting model, it is possible to evaluate the margin for the wrinkle of the paper conveyance unit in advance.

  DESCRIPTION OF SYMBOLS 40 ... Fixing roller pair, 42 ... Pressure roller, 44 ... Pressurized roller, 50 ... Roller pair, 52 ... Roller, 54 ... Opposite roller, 60 ... Wrinkle generation discriminating device, 62 ... Storage means, 64 ... Shape calculation means , 66 ... wrinkle occurrence determining means, Nc ... nip center, 100 ... copying machine, 110 ... ADF, 120 ... image reading part, 130 ... image information writing part, 140 ... developing part, 150 ... transfer part, 160 ... fixing part, DESCRIPTION OF SYMBOLS 170 ... Paper feed part, 180 ... Vertical conveyance unit, 200 ... Fixing device, 201 ... Fixing roller pair, 202 ... Heating roller, 203 ... Pressure roller, 210 ... Speed measuring device, 211 ... Line illumination light source, 212 ... Line sensor 213: Control unit, 214: Non-volatile memory, 215: Display unit, 221 ... Strip, 221a ... Cut, 222 ... Pattern, 230 ... Shape measuring device, 231 ... Illumination Turn projector, 232 ... area sensor 233 ... controller, 234 ... non-volatile memory, 235 ... display unit, P, Pt ... paper, LP ... laser pattern

JP 2008-224227 A

Claims (8)

A wrinkle generation determination method for determining whether or not wrinkles occur in a sheet material when the sheet material is nipped and conveyed at a nip portion of an opposing roller pair,
A corrugated shape calculating means reads out a conveying speed distribution in a direction perpendicular to the conveying direction of the sheet material in the nip portion from the storage means, and calculates the corrugated shape of the sheet material from the conveying speed distribution;
A wrinkle occurrence determining unit that determines whether or not wrinkles occur in the sheet material based on the wavy shape calculated by the wavy shape calculating unit;
A wrinkle occurrence determination method characterized by comprising: The corrugated shape calculating means calculates the corrugated angle of the sheet material immediately before the nip portion bites,
2. The wrinkle occurrence determining method according to claim 1, wherein the wrinkle occurrence determining means determines whether or not wrinkles are generated in the sheet material using the waving angle as a representative characteristic value.   3. The wrinkle occurrence determining method according to claim 2, wherein the wrinkle occurrence determining means determines that wrinkles occur when the waving angle is equal to or greater than a buckling limit.   4. The wrinkle occurrence determining method according to claim 1, wherein the roller pair is a fixing roller pair.   The program for making a computer perform the wrinkle generation | occurrence | production determination method as described in any one of Claims 1 thru | or 4. A wrinkle occurrence determination device for determining whether or not wrinkles are generated in a sheet material when the sheet material is nipped and conveyed at a nip portion of an opposing roller pair,
Corrugated shape calculating means for calculating a corrugated shape of the sheet material from a conveyance speed distribution in a direction perpendicular to the conveyance direction of the sheet material in the nip portion;
Wrinkle occurrence determining means for determining whether or not wrinkles occur in the sheet material based on the wavy shape calculated by the wavy shape calculating means;
A wrinkle occurrence discriminating apparatus characterized by comprising: A wrinkle occurrence determination device for determining whether or not wrinkles are generated in a sheet material when the sheet material is nipped and conveyed at a nip portion of an opposing roller pair,
Storage means for storing a conveyance speed distribution in a direction orthogonal to the conveyance direction of the sheet material in the nip portion;
A corrugated shape calculating means for reading the conveying speed distribution from the storage means and calculating the corrugated shape of the sheet material from the conveying speed distribution;
A wrinkle occurrence determining device comprising: wrinkle occurrence determining means for determining whether or not wrinkles are generated in the sheet material based on the wavy shape calculated by the wavy shape calculating means. An image forming apparatus comprising the wrinkling discriminating apparatus according to claim 6 or 7, wherein.

Images