JP2013220880A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a decrease in accuracy of resist oscillation correction when printing is performed on paper having different front/back surface properties.SOLUTION: A control unit 50 acquires paper-type information, which indicates whether paper for image formation is an envelope, one-sided coated paper or plain paper, from an operation display unit and the like (S100). When image forming processing is started (S102), it is determined whether the paper is an envelope or not, from the acquired paper-type information (S102). When the paper is the envelope, it is determined whether a printing surface is an address surface (S106). When it is determined that the printing surface is the address surface of the envelope, oscillation amount correction I in consideration of surface characteristics of the address surface (back side) is performed (S108). On the other hand, when it is determined that the printing surface is the backside of the envelope, oscillation amount correction II in consideration of surface characteristics of the back side (address surface) is performed (S112).

Description

  The present invention relates to an image forming apparatus that performs image misalignment correction by swinging in a state where a sheet is sandwiched in a sheet width direction that is perpendicular to the sheet conveyance direction before the sheet is conveyed to an image forming position. .

  In the image forming apparatus, for example, the direction in which the paper is orthogonal to the transport direction (hereinafter referred to as the paper width direction) due to factors such as side restrictions when the paper is placed in the paper feed tray and variations in the attachment position of the paper feed tray. There are times when it comes close to. When the image forming process is executed in such a state where the paper is shifted, there arises a problem that an image is formed at a position deviated from a preset image reference position.

  In general, resist swing correction is performed as a method for solving this problem, that is, as a method for accurately aligning an image and a paper in consideration of a deviation of the paper. In the registration swing correction, a registration roller is installed upstream of the secondary transfer unit in the paper transport direction, and the paper transported by this registration roller is clamped and moved in the paper width direction to offset the paper. Is corrected. The registration roller is composed of, for example, a driven roller made of metal, and a drive roller made of a resin such as rubber disposed opposite to the driven roller.

  For example, in Patent Document 1, a registration roller is arranged on the upstream side of the image forming position, and a line sensor is arranged on the downstream side of the registration roller, and the sheet is fed based on the deviation amount of the sheet detected by the line sensor. An image forming apparatus that corrects a deviation of a sheet by swinging in the sheet width direction is disclosed. According to this image forming apparatus, the sheet can be accurately aligned with the image forming position.

JP 2007-22680 A

  However, the conventional image forming apparatus has the following problems. In other words, in the conventional resist fluctuation correction, even when using paper with different surface characteristics on the front and back, such as envelopes and single-side coated paper, the same resist fluctuation correction is performed without considering the surface properties of each side of the paper. ing. In many cases, the front and back surfaces of the paper having different surface properties have different friction coefficients, nipping states by registration rollers, and the like. Therefore, when the same resist swing correction is performed on the front surface and the back surface, there is a problem that the response of the swing varies depending on the printing surface of the paper.

  FIG. 7 shows an example of the relationship between the command value and the actually measured value (swing amount) with respect to this command value when an envelope is used as the paper. The horizontal axis is the command value, and the vertical axis is the actual measurement value. Of the correction formulas, the solid line is a correction formula used when printing the address side of the envelope, and the broken line is a correction formula used when printing the back side of the envelope.

  When printing on the address side of the envelope and when printing on the back side of the envelope, due to the difference in the surface shape due to the crease or overlap on the back side of the envelope, the state of the envelope sandwiched by the registration rollers may also be It is different. As a result, the responsiveness to the command value also differs between when printing on the address side of the envelope and when printing on the back side of the envelope. For example, in the example of FIG. 7, the response to the command value is worse when printing the address side of the envelope than when printing the back side of the envelope.

  As described above, when using paper with different surface properties on the front and back sides, if the resist swing correction is performed without considering the surface property of the paper, the response to the command value to the swing drive unit on the front and back surfaces of the paper. Will be different. As a result, the amount of rocking movement differs between the front surface and the back surface of the paper, and there is a problem that the accuracy of resist rocking correction is reduced.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to prevent a decrease in accuracy of resist swing correction when printing on sheets having different surface properties on the front and back sides. An object is to provide an image forming apparatus.

  In order to solve the above-described problems, the present invention provides an image forming unit that forms an image on a sheet, and a sheet that is provided upstream of the image forming unit in the sheet conveying direction and that is relative to a reference position in a direction orthogonal to the sheet conveying direction. A detection unit for detecting the passage position of the paper, and provided upstream of the detection unit in the paper conveyance direction, and corrects the deviation of the paper calculated based on the paper passage position and the reference position detected by the detection unit. When a sheet having different surface properties on the front and back sides is used as the sheet, the amount of movement is adjusted in consideration of the surface property of the printing surface of the sheet. And a control unit for controlling the swinging unit.

  For paper with different surface properties on the front and back sides, for example, envelopes with different surface shapes on the address side and the back side with folds or overlapping parts, or one side that has been subjected to clear coating and the other side that has not been subjected to clear coating And single-side coated paper having different surface friction coefficients. The printing surface of the paper is a surface on which an image is transferred to the paper by the image forming unit.

  According to the present invention, since the swing amount is adjusted in accordance with the surface properties of the front and back surfaces of the paper, the swing accuracy can be improved even when printing is performed using paper having different front and back characteristics. Thus, the image and the paper can be accurately aligned on the front and back of the paper.

1 is a diagram illustrating a configuration example of an image forming apparatus according to an embodiment of the present invention. FIG. 5 is a diagram for explaining a configuration example of a registration roller and a paper detection unit and a deviation amount of the paper. 1 is a diagram illustrating a block configuration example of an image forming apparatus. It is a figure which shows the structural example of a rocking | fluctuating table. It is a figure for demonstrating a correction formula. 3 is a flowchart illustrating an operation example of the image forming apparatus. It is a figure which shows the example of a relationship between the command value and registration value of the registration rocking | fluctuation correction in the past.

  Hereinafter, the best mode for carrying out the invention (hereinafter referred to as an embodiment) will be described.

[Configuration example of image forming apparatus]
The image forming apparatus 100 according to the present invention, when using paper such as envelopes or single-side coated paper having different surface properties on the front and back sides as the paper P, takes into account the surface properties of the front and back surfaces of each paper. By adjusting, the swing accuracy on the front and back of the paper P is improved.

  FIG. 1 shows an example of the configuration of an image forming apparatus 100 according to the present invention. In addition, the dimension ratio of drawing is expanded on account of description and may differ from an actual ratio. As shown in FIG. 1, an image forming apparatus 100 is called a tandem type image forming apparatus, and includes an operation display unit 70, an automatic document feeder 80, an image reading unit 90, an image forming unit 10, and a resist. The rocking unit 30, the fixing unit 44, and the paper feeding unit 20 are provided.

  The operation display unit 70 is attached to the upper surface of the casing constituting the image forming apparatus 100. For example, a position input device such as a capacitance method or a resistance film method and a display device such as an LCD (Liquid Crystal Display) are combined. And a hard key including a numeric button and a print start button provided on the periphery of the touch panel. The operation display unit 70 accepts input of a document setting by a user operation, selection of whether the printing surface is the front surface or the back surface at the time of correcting the resist swing, a constant of a correction formula, and the like. The automatic document feeder 80, also called ADF (Auto Document Feeder), conveys the document set on the ADF sheet feed tray 82 to the document reading slit glass 84, and the document read by the image reading unit 90 described later. Are discharged to the ADF discharge tray 86.

  The image reading unit 90 irradiates light from a light source to a document conveyed one by one from the ADF sheet feed tray 82 of the automatic document feeder 80 or a document placed on the platen glass 92, and the reflected light is emitted from the CCD ( The image data of the document is acquired by receiving light with a charge coupled device (94). Image data acquired by the image reading unit 90 is subjected to analog processing, analog / digital (hereinafter referred to as A / D) conversion processing, image compression processing, and the like by an image processing unit (not shown), and then an HDD (Hard disk drive) or the like. Is stored in the memory unit 58 constituted by

  The image forming unit 10 forms an image by electrophotography, and includes an image forming unit 10Y that forms a yellow (Y) image, an image forming unit 10M that forms a magenta (M) image, The image forming unit 10C forms a cyan (C) color image, and the image forming unit 10K forms a black (K) color image. In this example, common function names, for example, Y, M, C, and K indicating colors to be formed are added to the back of the reference numeral 10. The image forming unit 10 also includes an intermediate transfer belt 8 that holds an image formed by the image forming units 10Y, 10M, 10C, and 10K, and a secondary for transferring an image on the intermediate transfer belt 8 to the paper P. And a nip forming roller 42 for forming the transfer portion N.

  The image forming unit 10Y includes a photosensitive drum 1Y, a charging unit 2Y, an exposure unit (optical writing unit) 3Y, a developing unit 4Y, and a cleaning unit 6Y disposed around the photosensitive drum 1Y. The image forming unit 10M includes a photosensitive drum 1M, and a charging unit 2M, an exposure unit 3M, a developing unit 4M, and a cleaning unit 6M disposed around the photosensitive drum 1M. The image forming unit 10C includes a photosensitive drum 1C, and a charging unit 2C, an exposure unit 3C, a developing unit 4C, and a cleaning unit 6C disposed around the photosensitive drum 1C. The image forming unit 10K includes a photosensitive drum 1K, and a charging unit 2K, an exposure unit 3K, a developing unit 4K, and a cleaning unit 6K disposed around the photosensitive drum 1K.

  Respective photosensitive drums (image carriers) 1Y, 1M, 1C, and 1K in the image forming units 10Y, 10M, 10C, and 10K, charging units 2Y, 2M, 2C, and 2K, exposure units 3Y, 3M, 3C, and 3K, development The parts 4Y, 4M, 4C, and 4K and the cleaning parts 6Y, 6M, 6C, and 6K have a common content configuration. In the following description, Y, M, C, and K are not used unless particularly distinguished.

  The charging unit 2 charges the surface of the photosensitive drum 1 almost uniformly. The exposure unit 3 includes, for example, an LPH (LED Print Head) having an LED array and an imaging lens, and a polygon mirror type laser exposure scanning device, and scans the photosensitive drum 1 with laser light based on image data. Thus, an electrostatic latent image is formed. The developing unit 4 develops the electrostatic latent image formed on the photosensitive drum 1 with toner. As a result, a toner image which is a visible image is formed on the photosensitive drum 1. The intermediate transfer belt 8 is stretched by a plurality of rollers and supported so as to be able to run. When the primary transfer roller operates, the intermediate transfer belt 8 travels, and the toner image formed on each photosensitive drum 1 is transferred to the image transfer position of the intermediate transfer belt 8 (primary transfer).

  The paper feed unit 20 includes a plurality of paper feed trays 20A and 20B that accommodate paper sizes such as A3 and A4, a pickup roller 22 that picks up the paper P from each paper feed tray, and a second paper P in each paper feed tray. It has the roller 24 which prevents heavy conveyance. Each paper feed unit 20 takes out the paper P from each paper feed tray selected by the operation display unit 70 and the like by the pickup roller 22 and the separating roller 24, and the taken paper P is transferred to the registration rollers via the transport rollers 26 and 28, etc. 32. Note that the number of paper feed trays is not limited to two. Further, a single or a plurality of large-capacity paper feeders that can accommodate a large-capacity paper P may be connected as necessary.

  The resist rocking unit 30 includes a resist roller 32 including a pair of driven rollers 32a and a drive roller 32b. The registration roller 32 is an example of a swinging unit, and forms a loop by abutting the leading edge of the paper P by the loop creation roller 36 to correct the skew of the paper P. The registration roller 32 nips the paper P and swings it in the paper width direction based on the detection results of the paper detection unit 40 and the printing surface detection unit 38 installed on the downstream side of the registration roller 32. The deviation of P is corrected (resist swing correction). At this time, in this example, the necessary swing amount ΔX is adjusted in consideration of the surface characteristics of the paper P. The resist swing correction will be described later. The registration roller 32 and the loop forming roller 36 include a press-contact separation mechanism for pressing the roller pair and releasing the press-contact. The pressure contact / separation mechanism includes, for example, a cam in contact with the roller shaft, a motor for rotating the cam, and the like. When the resist swing correction is performed, the loop forming roller 36 is brought into the nip release state by the press-separation mechanism. In addition, about a detailed description, since a well-known technique is employable, description is abbreviate | omitted.

  When the registration correction is completed, the paper P is conveyed to the secondary transfer portion N of the nip creation roller 42 at a predetermined timing. In the secondary transfer unit N, the color image transferred to the image forming position of the intermediate transfer belt 8 is collectively transferred onto the surface of the paper P conveyed from the paper supply unit 20 (secondary transfer). The second-transferred sheet P is conveyed to the fixing unit 44. The fixing unit 44 is provided downstream of the secondary transfer unit N in the sheet conveyance direction, and includes a pressure roller, a heating roller, and the like. The fixing unit 44 fixes the toner image on the surface of the paper P to the paper P by performing pressure and heat treatment on the paper P on which the image is transferred by the secondary transfer unit N.

  On the downstream side of the fixing unit 44 in the sheet conveyance direction, a conveyance path switching unit 48 for switching the conveyance path of the sheet P to the discharge path side or the reverse path side is provided. The conveyance path switching unit 48 includes, for example, a solenoid and a motor, and performs conveyance path switching control based on a selected printing mode (single-sided printing mode, double-sided printing mode). The paper P on which single-sided printing has been completed in the single-sided printing mode or the paper P on which double-sided printing has been completed in the double-sided printing mode is subjected to fixing processing by the fixing unit 44 and then is discharged by a paper discharge roller 46 to a paper discharge tray (not shown). Discharged to the top.

  On the other hand, when the paper P is turned upside down in the duplex printing mode, the paper P on which the image is formed on the front side is conveyed to the reversal path unit 60 via the conveyance path switching unit 48. The sheet P conveyed to the reversing path unit 60 is conveyed to the switchback path via the conveyance roller 62 and the like. In the switchback path, reverse rotation control of the ADU roller 64 causes switchback conveyance with the trailing edge of the paper P as the head, and the paper P is turned over to the registration roller 32 via the conveyance roller 66 and the like. Re-feed. As in the case of the image forming process on the front side of the paper P, the paper P that has been re-fed to the registration roller 32 is subjected to registration swing correction, and a predetermined transfer is applied to the back surface of the paper P by the secondary transfer unit N. An image is formed. The sheet P on which the image has been transferred to the back surface by the image forming unit 10 is subjected to a fixing process by the fixing unit 44, and is then discharged onto the paper discharge tray via the conveyance path switching unit 48 and the paper discharge roller 46.

[Configuration example of registration roller and paper detection unit and calculation example of required swing amount]
FIG. 2 is a diagram for explaining an example of the configuration of the registration roller 32 and the paper detection unit 40 and for explaining a calculation method of the required swing amount ΔX of the paper P by the paper detection unit 40. In the image forming apparatus 100, as shown in FIG. 2, an image center C is set as an image reference position. With reference to the image center C, the distance from the image center C eg to the left side edge Pa of the sheet P for forming an image it is previously set as the reference position X _0. The reference position X ₀ is set to a different value for each paper size of the paper P. The length in the width direction of the paper P is the size W.

The paper detection unit 40 includes a line sensor in which photoelectric exchange elements are arranged in a line shape, or an image sensor in which photoelectric exchange elements are arranged in a matrix, and the downstream side of the paper conveyance direction D1 of the registration roller 32. It is installed such that its longitudinal direction is parallel to the paper width direction D2. The paper detection unit 40 detects the passing position of, for example, the side edge Pa of the passing paper P, and in the paper width direction D2 between the detected passing position of the side edge Pa of the paper P and the image center C. obtaining the distance as a detection value X _1. The control unit 50 obtains a value obtained by subtracting the detection value X ₁ from a preset reference position X ₀ as a necessary swing amount ΔX for aligning the paper P with the image center C. In this example, when the swing direction of the required swing amount ΔX is the left direction (front side of the image forming apparatus 100) in FIG. 2, the sign of the swing direction is “+”, and the required swing amount ΔX. 2 is the right direction (the back side of the image forming apparatus 100) on the paper surface of FIG. Therefore, in this example, the required swing amount ΔX is “+”.

  The registration roller 32 is installed on the upstream side of the paper conveyance direction D1 of the paper detection unit 40 so that the rotation axis thereof is parallel to the paper width direction D2, and when the registration swing correction is not performed. Located in the home position. The registration roller 32 holds the paper P in a state where the paper P is held based on the swing command value Y output from the control unit 50 in accordance with the detection result of the side edge Pa at the image center C of the paper detection unit 40. The shift of the sheet P is corrected by moving in the direction D2. When the paper P is swung and conveyed to the secondary transfer unit, the nipping of the roller is released and the paper P is moved to the home position, and the roller is again nipped in order to hold the next paper P.

[Block Configuration Example of Image Forming Apparatus]
FIG. 3 shows an example of a block configuration of the image forming apparatus 100. As shown in FIG. 3, the image forming apparatus 100 includes a control unit 50 that controls the overall operation of the image forming apparatus 100. The control unit 50 includes, for example, a CPU (Central Processing Unit) 52, a ROM (Read Only Memory) 54, a RAM (Random Access Memory) 56, and the like. The CPU 52 reads out a program stored in the ROM 54, develops it in the RAM 56 and executes it, thereby executing an image forming process, a resist swing correcting operation, and the like. The control unit 50 includes an operation display unit 70, an image forming unit 10, a memory unit 58, a paper detection unit 40, a printing surface detection unit 38, a registration swing unit 30, a fixing unit 44, a paper supply unit 20, and a communication unit 72. Are connected to each other.

  The operation display unit 70 includes, for example, a touch panel type display panel and an input device. The display panel detects input information based on the touch operation on the operation screen of the user, and supplies an operation signal corresponding to the detection to the control unit 50. The input device supplies an operation signal based on a user's button pressing operation to the control unit 50. For example, the display panel and the input device accept information such as an inclination and an intercept for setting and correcting a correction formula in the resist swing correction operation, and print surface information of a print surface to be printed.

  The memory unit 58 includes, for example, a non-volatile semiconductor memory, HDD (Hard Disk Drive), and the like, and a program for executing “correction formulas I, II, III, IV” and the like used for resist swing correction In addition, a swing table TB in which the inclination a and the intercept b constituting each correction formula are associated with each paper type is stored. Such information may be stored in another memory such as the ROM 54.

  The registration rocking unit 30 has a resist driving unit 34 for rocking the registration roller 32 in the paper width direction D2. The registration drive unit 34 includes, for example, a stepping motor, a gear, and the like, and is driven to rotate based on a swing command value Y (drive signal) corresponding to a required swing amount ΔX supplied from the control unit 50 during a registration swing correction operation. As a result, the registration roller 32 is moved in the paper width direction D2. The swing command value Y is a pulse signal generated based on the required swing amount ΔX. As a result, the paper P swings in the paper width direction D2, and the deviation of the paper P is corrected.

  The paper detection unit 40 detects, for example, the side edge portion Pa of the paper P passing therethrough and supplies a detection signal obtained by the detection to the control unit 50. The printing surface detection unit 38 is configured by, for example, a reflective sensor having a light source and a light receiving element, and is installed in a conveyance path between the registration roller 32 and the loop creation roller 36. For example, when a single-side coated paper is selected as the paper P, the printing surface detection unit 38 irradiates light on the surface of the single-side coated paper being conveyed, detects the reflectance of the light irradiated on the surface, A detection signal based on the detection is supplied to the control unit 50. The installation position of the printing surface detection unit 38 is not limited between the registration roller 32 and the loop creation roller 36, and may be installed upstream of the loop creation roller 36.

  The image forming unit 10 controls the image forming units 10 </ b> Y, 10 </ b> M, 10 </ b> C, and 10 </ b> K based on the image data signal supplied from the control unit 50 to transfer a predetermined image onto the paper P. The fixing unit 44 fixes the toner image on the paper P by pressurizing and heating the paper P on which the image is fixed by the image forming unit 10 based on the control signal supplied from the control unit 50. The paper feed unit 20 feeds the paper from the corresponding paper feed tray based on the paper feed tray information selected by the operation display unit 70 and the like and feeds it to the image forming unit 10.

  The communication unit 72 includes various interfaces such as NIC (Network Interface Card), MODEM (Modulator-DEModulator), and USB (Universal Serial Bus), and communicates with an external device such as a personal computer connected via the interface. Do.

[Configuration example of swing table]
FIG. 4 shows an example of the configuration of the swing table TB stored in the memory unit 58. As shown in FIG. 4, the swing table TB includes paper types, correction formula numbers set corresponding to the front and back surfaces of each paper type, and inclinations a and intercepts b used for the respective correction formulas. They are stored in association with each other. In this example, “correction formula I” is used when an envelope is used as the paper P and the printing surface is the address side, and “correction formula II” is used as an envelope as the paper P and the printing surface is the back surface. Used when. “Correction Formula III” is used when single-side coated paper is used as the paper P and the printing surface is the coated surface, and “Correction Formula IV” is single-side coated paper as the paper P and the printing surface is the back surface. Used when.

For example, when the correction formula I is used as the correction formula at the time of resist swing correction, the inclination a ₁ and the intercept b ₁ are read from the swing table TB. The read inclination a ₁ and intercept b ₁ are substituted into a correction equation Y = aΔX + b for correcting the required swing amount ΔX according to the surface property of the paper P, whereby the swing command value Y is calculated. The Note that the inclination a and intercept b of each correction formula of the swing table TB can be arbitrarily changed by the user through an operation on the operation display unit 70.

[About correction formula]
FIG. 5 is a diagram for explaining a correction formula for correcting the required swing amount ΔX calculated from the detection value (deviation deviation amount) X ₁ according to the printing surface of the paper P. The horizontal axis is the required swing amount ΔX, and the vertical axis is the swing command value Y. In the first quadrant of the Cartesian coordinate system of FIG. 5, a correction formula used when the paper P is swung to the “+ side (front side)” is set, and in the third quadrant, the paper P is placed on the “− side”. The correction formula used when swinging to “(back side)” is set.

  The correction formula is set for each paper type such as an envelope or a single-side coated paper having different surface characteristics on the front and back sides, and is set for each front and back side of each paper type. The paper P is set independently for the case where the paper P is swung to the “+ side” and the case where the paper P is swung to the “− side”. Specifically, when an envelope is used as the paper P, as shown in FIG. 5, correction equations I and I ′ used when the printing surface is the front surface side, and when the printing surface is the back surface side are used. Correction formulas II and II ′ are set. When single-side coated paper is used as the paper P, as shown in FIG. 5, correction formulas III and III ′ used when the printing surface is the front side and correction formulas IV used when the printing surface is the back side. , IV 'are set. For example, in the manufacturing stage, these equations are obtained by actually obtaining the deviation amounts of a plurality of envelopes or the like by the paper detection unit 40 and correcting the resist swing based on the command value corresponding to the obtained deviation amounts. The actual measured value is acquired at, and is set based on the difference between the actually measured value obtained at this time and the command value.

Subsequently, “Correction Formula I” used when an envelope is used as the paper P and the address side of the envelope is a printing surface will be described. When the address side of the envelope is the printing surface, the back side of the envelope with the folds or overlaps is the drive roller 32b side of the registration roller 32. The state will also be different. Therefore, in this case, since the envelope is easily slipped with respect to the registration roller 32, the swing command value Y is set so that the swing amount of the “correction formula I” is larger than the required swing amount ΔX. In this example, among the registration rollers 32, the driving roller 32b has a larger friction coefficient μ than the driven roller 32a and has a larger influence on the paper P. Therefore, the paper between the driving roller 32b and the paper P is larger. Only the difference in the surface shape of P and the difference in the friction coefficient μ are considered. The “correction formula I” is described by the following formula (1).
Y ₁ = a ₁ ΔX + b ₁ (1)

Y ₁ is a swing command value obtained by correcting the required swing amount in accordance with the printing surface, and is a pulse signal supplied to the resist swing unit 30. a ₁ is an inclination (correction coefficient). This inclination a ₁ is a value determined by the printing surface of the envelope. b ₁ is an intercept. The intercept b ₁ is a value determined by, for example, rattling of the registration rocking unit 30 that drives the registration roller 32 and a driving load. ΔX is a necessary swing amount (mm) calculated based on the detection value X ₁ detected by the paper detection unit 40.

For example, when the detection value X ₁ for the image center C of the paper P is detected by the paper detection unit 40, the necessary swing amount ΔX is calculated by subtracting the detection value X ₁ from the preset reference position X _0. The When the required swing amount obtained by the calculation is ΔX ₁ , as shown in FIG. 5, by substituting the required swing amount ΔX ₁ into the above equation (1), the required swing amount ΔX _{1 is} converted into a pulse signal. The swing command value Y ₁ can be obtained.

Next, “Correction Formula II” used when an envelope is used as the paper P and the back side of the envelope is the printing surface will be described. Note that a description of points in common with the “correction formula I” will be omitted. When the back side of the envelope is the printing side, the address side of the envelope is the driving roller 32b side of the registration roller 32. It will be better than Therefore, in this case, since the envelope is less likely to slip with respect to the registration roller 32, in the “correction formula II”, the swing command value Y is set so that the swing amount is slightly larger than the required swing amount ΔX, and the inclination a ₂ is smaller than the inclination a ₁ of the “correction formula I”. The “correction formula II” is described by the following formula (2).
Y ₂ = a ₂ ΔX + b ₂ (2)

Next, “Correction Formula III” used when the single-side coated paper is used as the paper P and the coated surface of the single-side coated paper becomes the printing surface will be described. Note that a description of points in common with the “correction formula I” will be omitted. When the coated surface side of the single-sided coated paper is a printing surface, the back surface of the single-sided coated paper is on the drive roller 32b side of the registration roller 32, so the friction coefficient μ with the registration roller 32 is small. For this reason, the single-side coated paper is easy to slip with respect to the registration roller 32, and therefore the “correction formula III” sets the swing command value Y so that the swing amount is larger than the required swing amount ΔX. The “correction formula III” is described by the following formula (3).
Y ₃ = a ₃ ΔX + b ₃ (3)

Next, “correction formula IV” used when the single-side coated paper is used as the paper P and the back side of the single-side coated paper becomes the printing surface will be described. Note that a description of points in common with the “correction formula I” will be omitted. When the reverse side of the single-sided coated paper is the printing surface, the coated surface of the single-sided coated paper is on the drive roller 32b side of the registration roller 32, so the friction coefficient μ with the registration roller 32 increases, and the relationship with the registration roller 32. It is hard to slip. Therefore, the “correction formula IV” is set so that the correction amount is smaller than the “correction formula III” with respect to the required swing amount ΔX, and the inclination a ₄ is smaller than the inclination a ₃ of the “correction expression I”. ing. The “correction formula IV” is described by the following formula (4).
Y ₄ = a ₄ ΔX + b ₄ (4)

  The “−side” correction formulas I ′ to IV ′ are different from the correction formulas I to IV only in the swing direction, and thus detailed description thereof is omitted.

[Operation example of image forming apparatus]
FIG. 6 is a flowchart illustrating an operation example of the control unit 50 of the image forming apparatus 100 during image formation. In this example, a case where an envelope and a single-side coated paper are used as sheets having different surface properties on the front and back sides will be described. Further, it is assumed that the surface side of the single-sided coated paper is a coated surface that has been subjected to a clear coating treatment, and the coated surface generally has a higher friction coefficient μ than the back side of the single-sided coated paper due to the coating layer.

  As shown in FIG. 6, in step S <b> 100, the control unit 50 acquires the paper type information of the paper P. For example, the control unit 50 acquires paper type information based on the paper feed tray and paper type selected by the user operation on the operation screen of the operation display unit 70, or from a personal computer connected to the image forming apparatus 100. Paper type information is acquired from the transmitted PDL data. The paper type information includes information such as plain paper, envelopes, and single-side coated paper. The acquired paper type information is stored in the memory unit 58, for example.

  Also, when paper P having different surface properties is used on the front and back, whether the printing surface on which the current image is to be formed is “front” or “back” on the operation screen of the operation display unit 70 The selection is made by the user. For example, when an envelope is selected as the type of the paper P, the control unit 50 displays “address button” or “back button” for selecting a print surface on the operation screen. On this operation screen, the user selects whether the print side is “address side” or “back side”. The control unit 50 acquires the print surface information input on the operation screen, and stores the acquired print surface information in, for example, the memory unit 58. When the paper type information and the printing surface information are acquired, the process proceeds to step S102.

  In step S102, the control unit 50 determines whether or not the start of the printing process has been selected by the user. For example, the control unit 50 determines whether or not the start of the printing process is selected based on whether or not the start button is selected on the operation display unit 70. In the image forming operation, the control unit 50 takes out the paper P from the corresponding paper feed tray based on the image forming conditions such as the paper type selected by the user, and transports the paper P to the registration roller 32 via the transport roller or the like. To do.

  In step S104, the control unit 50 determines whether or not the paper P to be printed is an envelope. The control unit 50 reads the paper type information selected on the operation screen of the operation display unit 70 from the memory unit 58, and determines whether or not the paper P to be printed based on the read paper type information is an envelope. to decide. If the control unit 50 determines from the paper type information that the paper P is an envelope, the control unit 50 proceeds to step S106. If the control unit 50 determines that the paper P is not an envelope, the control unit 50 proceeds to step S114.

  If it is determined that the paper P to be printed is an envelope, in step S106, the control unit 50 determines whether the printing surface on which the envelope is printed is a destination surface. The control unit 50 reads the printing surface information selected by the user on the operation screen before the image forming operation (S100) from the memory unit 58, and uses the read printing surface information to determine whether the printing surface of the envelope is the address surface. Judge whether or not. When it is determined that the printing surface of the envelope is the address surface, the control unit 50 proceeds to step S108, and when it is determined that the printing surface of the envelope is not the address surface, that is, the back surface, the control unit 50 proceeds to step S112.

  If the printing surface is the address side of the envelope, in step S108, the control unit 50 uses the correction equation I for correcting the swing amount to be larger than the necessary swing amount ΔX obtained by actual deviation detection. Execute dynamic amount correction I.

In the swing amount correction I, for example, when the skew correction of the paper P by the registration roller 32 is completed, the control unit 50 uses the detection value X ₁ as the passing position of the side edge Pa of the paper P with respect to the image center C as the paper detection unit 40. Get from. Then, the control unit 50 subtracts the detection value X ₁ of the side edge portion Pa of the sheet P detected by the sheet detection unit 40 from the reference position X ₀ which is set in advance, the position of the sheet P to the image center C A necessary swing amount ΔX for matching is calculated (see FIG. 2).

Further, when the required swing amount ΔX is calculated, the control unit 50 reads the inclination a ₁ and the intercept b ₁ corresponding to the correction formula I from the swing table TB stored in the memory unit 58 (see FIG. 4). By inputting the inclination a ₁ , the intercept b ₁ and the calculated required swing amount ΔX into a preset correction formula I “Y ₁ = a ₁ Δx + b ₁ ”, the correction is made according to the surface property of the printing surface of the envelope. The swing command value Y is calculated. The control unit 50 supplies the calculated swing command value Y ₁ to the registration swing unit 30, so that the swing command value Y _{1 in} a state where the sheet P is held between the registration rollers 32 of the registration swing unit 30. It is swung in the paper width direction D2 by the amount. In this way, it is possible to execute a highly accurate swing correction in consideration of the printing surface of the envelope having different surface properties on the front and back sides. When the swing amount correction I is completed, the process proceeds to step S110.

  On the other hand, when the printing surface is the back side of the envelope, in step S112, the control unit 50 calculates a correction formula II for performing correction so that the swing amount is slightly larger than the required swing amount ΔX obtained by actual deviation detection. The used swing amount correction II is executed. In the swing amount correction II, the envelope is held between the registration rollers 32 as compared with the case where the printing surface for printing on the envelope is the address surface. Therefore, the swing correction amount is smaller than the swing amount correction I. Shall.

In the swing amount correction II, for example, when the skew correction of the paper P by the registration roller 32 is completed, the control unit 50 uses the detection value X ₂ as a passing position of the side edge Pa of the paper P with respect to the image center C as the paper detection unit 40. Get from. Then, the control unit 50 subtracts the detection value X ₂ of the side end Pa of the sheet P detected by the sheet detection unit 40 from the reference position X ₀ which is set in advance, the position of the sheet P to the image center C A necessary swing amount ΔX for matching is calculated (see FIG. 2).

When calculating the required swing amount ΔX, the control unit 50 reads the inclination a ₂ and the intercept b ₂ corresponding to the correction formula II from the swing table TB stored in the memory unit 58 (see FIG. 4). By inputting the inclination a ₂ , the intercept b ₂ and the calculated required swing amount ΔX into a preset correction formula II “Y ₂ = a ₂ ΔX + b ₂ ”, the correction is made according to the surface property of the printing surface of the envelope. The swing command value Y ₂ is calculated. The control unit 50 supplies the calculated swing command value Y ₂ to the registration swing unit 30, so that the swing command value Y _{2 is held in} a state where the sheet P is held between the registration rollers 32 of the registration swing unit 30. It is swung in the paper width direction D2 by the amount. In this way, it is possible to execute a highly accurate swing correction in consideration of the printing surface of the envelope having different surface properties on the front and back sides. When the swing amount correction II is completed, the process proceeds to step S110.

  If the paper P is not an envelope, in step S114, the control unit 50 determines whether or not the paper P to be printed is single-sided coated paper. Based on the paper type information selected on the operation screen of the operation display unit 70, the control unit 50 determines whether or not the paper P to be printed is single-sided coated paper. If the control unit 50 determines from the paper type information that the paper P is single-sided coated paper, the control unit 50 proceeds to step S116. On the other hand, if it is determined that the paper P is not single-sided coated paper, it is also known in step S104 that the paper P is not an envelope. Therefore, it is determined that the type of the paper P is plain paper with the same front and back surfaces. Proceed to step S122.

  When it is determined that the sheet P to be printed is single-sided coated paper, in step S116, the control unit 50 determines whether the printing surface on which single-sided coated paper is printed is a coated surface. When the paper P is single-side coated paper, the control unit 50 determines whether or not the printing surface of the single-side coated paper is a coated surface based on the response value (reflectance) of the single-side coated paper detected by the printing surface detection unit 38. Judging. Of course, it may be determined based on the printing surface information selected on the operation screen of the operation display unit 70 whether the printing surface of the single-sided coated paper is the addressed surface or the back surface. When the reflectance is high (exceeding the threshold value), the control unit 50 determines that the printing surface of the single-sided coated paper is the coated surface, and proceeds to step S118. When the reflectance is low, the printing surface of the single-sided coated paper Is not the coat surface, that is, the back surface, and the process proceeds to step S120.

  When the printing surface of the single-side coated paper is a coated surface, the back side of the single-side coated paper comes into contact with the driving roller 32b of the registration roller 32 having a high friction coefficient μ. The back side of the single-side coated paper has a lower coefficient of friction μ than that of the coated surface, so it is slightly slippery in relation to the drive roller 32b. Therefore, in step S118, the control unit 50 executes the swing amount correction III using the correction formula III that performs correction so that the swing amount is larger than the required swing amount ΔX obtained by actual deviation detection.

Control unit in the swing amount correction III 50 is necessary by subtracting the detection value X ₃ detected value X ₃ of the side edge portion Pa of the paper P taken from the paper detection unit 40, from the reference position X ₀ set in advance The swing amount ΔX is calculated (see FIG. 2). When the required swing amount ΔX is calculated, the control unit 50 reads the inclination a ₃ and the intercept b ₃ corresponding to the correction formula III from the swing table TB stored in the memory unit 58 (see FIG. 4), and this read inclination By inputting a ₃ , intercept b ₃ and the calculated required swing amount ΔX into the preset correction formula III “Y ₃ = a ₃ Δx + b ₃ ”, the correction was made according to the surface property of the printing surface of the envelope. A swing command value Y ₃ is calculated. The control unit 50 supplies the calculated swing command value Y ₃ to the registration swing unit 30, and keeps the paper P by the registration roller 32 of the registration swing unit 30 by the swing command value Y _3. The resist rocking unit 30 is controlled to rock in the width direction D2. In this way, it is possible to execute a highly accurate swing correction in consideration of the printing surface of the envelope having different surface properties on the front and back sides. When the swing amount correction III is completed, the process proceeds to step S110.

  When the printing surface of the single-side coated paper is the back surface, the coated surface side of the single-side coated paper comes into contact with the driving roller 32b of the registration roller 32 having a high friction coefficient μ. The coated surface side of the single-side coated paper has a high friction coefficient μ due to the coated layer, and therefore is less slippery in relation to the driving roller 32b. Therefore, in step S120, the control unit 50 executes the swing amount correction IV using the correction formula IV that slightly corrects the required swing amount Δx obtained by actual deviation detection.

In the swing amount correction IV, the control unit 50 acquires the detection value X ₄ of the side edge Pa of the paper P from the paper detection unit 40 and subtracts the detection value X ₄ from the preset reference position X _0. The swing amount ΔX is calculated (see FIG. 2). When the required swing amount ΔX is calculated, the control unit 50 reads the inclination a ₄ and the intercept b ₄ corresponding to the correction formula IV from the swing table TB stored in the memory unit 58 (see FIG. 4), and this read inclination By inputting a ₄ , intercept b ₄ and the calculated required swing amount ΔX into a preset correction formula IV “Y ₄ = a ₄ ΔX + b ₄ ”, the correction was made in accordance with the surface property of the printing surface of the envelope. The swing command value Y ₄ is calculated. The control unit 50 supplies the calculated swing command value Y ₄ to the registration swing unit 30, and the sheet is moved by the swing command value Y _{4 in} a state where the paper P is held between the registration rollers 32 of the registration swing unit 30. The resist rocking unit 30 is controlled to rock in the width direction D2. In this way, it is possible to execute a highly accurate swing correction in consideration of the printing surface of the envelope having different surface properties on the front and back sides. When the swing amount correction IV is completed, the process proceeds to step S110.

  On the other hand, if it is determined that the paper P on which the printing process is to be performed is plain paper, the control unit 50 executes the swing amount correction V in step S122. In the swing amount correction V, for example, since the surface property is the same on the front and back surfaces of the paper P, the required swing amount ΔX is not corrected on the front and back surfaces of the paper P as in the swing amount corrections I to IV described above. That is, normal resist swing correction is performed without using a correction formula. Of course, when a common deviation amount between the front and back sides of the paper P is known in advance, the resist swing correction can be performed using a correction formula based on this deviation amount. When the resist swing correction is completed, the process proceeds to step S110.

  When the registration swing correction is completed, in step S110, the control unit 50 determines whether all printing processes (print jobs) have been completed. When it is determined that all the printing processes have been completed, the control unit 50 ends the series of printing processes, and when it is determined that all the printing processes have not been completed, the control unit 50 returns to step S100 to perform the printing processes. The paper type information of the next paper P is acquired, and thereafter, the registration swing correction as described above is executed.

  As described above, according to the present embodiment, the necessary swing amount ΔX calculated in consideration of the surface properties of the front and back surfaces of the paper P is adjusted, so that the printing process is performed using paper having different front and back characteristics. Even when it is performed, the swing accuracy can be improved. That is, when paper P having different surface properties is used on the front surface and the back surface, even if the same paper type is set and the same transport path is transported, the responsiveness of swinging between the front surface and the back surface (swing amount) ) Can be prevented from being different. Thus, the image and the paper can be accurately aligned on the front and back of the paper. Further, by using the swing table TB, the correction formula can be configured easily and the correction formula can be easily updated.

  It should be noted that the technical scope of the present invention is not limited to the above-described embodiments, and includes those in which various modifications are made to the above-described embodiments without departing from the spirit of the present invention. In the above embodiment, envelopes and single-sided coated papers are mentioned as the paper P having different surface properties on the front and back sides. However, the present invention is not limited to this, and other papers having different surface properties on the front and back sides are appropriately adopted. can do. Moreover, the relationship between the friction coefficient between the front and back sheets having different surface properties and the registration roller 32 and the state of clamping by the registration roller 32 described in the above embodiment is merely an example. The form is not limited.

  In addition, when using sheets with different surface properties on the front and back sides, the required swing amount ΔX was corrected using correction formulas set in consideration of the surface properties on the front and back surfaces, but the swing response is When there is a good surface (front surface or back surface), the necessary swing amount ΔX can be corrected only by using a correction formula for a surface with poor swing response.

  Furthermore, in the above-described embodiment, the registration roller 32 is used as means for correcting the skew of the paper P, but the invention is not limited to this. For example, instead of the registration roller 32, a shutter member provided so as to be able to appear and retract in the transport path is used, and when the paper P is transported, the leading edge of the paper P is abutted against the shutter member to form a loop, thereby skewing the paper P. May be corrected.

30 Resist oscillating part (oscillating part)
32 Registration roller (swinging part)
38 Printing surface detection unit 40 Paper detection unit (detection unit)
50 control unit 58 memory unit 70 operation display unit (operation unit)
100 Image forming apparatus TB Swing table

Claims (7)

An image forming unit for forming an image on paper;
A detection unit that is provided upstream of the image forming unit in the sheet conveyance direction and detects a passage position of the sheet with respect to a reference position in a direction orthogonal to the sheet conveyance direction;
Provided upstream of the detection unit in the paper transport direction, and is used to correct the deviation of the paper calculated based on the passage position and the reference position of the paper detected by the detection unit. A swinging section that swings the sheet in the orthogonal direction by a moving amount;
A control unit that controls the swinging unit so as to adjust the swinging amount in consideration of the surface property of the printing surface of the sheet when using sheets having different surface properties on the front and back sides as the sheet. An image forming apparatus. The image forming apparatus according to claim 1, wherein the paper is an envelope or a single-side coated paper. 2. The control unit according to claim 1, wherein the control unit adjusts the swing amount using a correction formula set in consideration of the surface property for each of the front and back surfaces of the paper having different surface properties on the front and back sides. Item 3. The image forming apparatus according to Item 2. The image forming apparatus according to claim 3, further comprising a table that stores the constants of the correction formula in association with each front surface and back surface of the sheet. The operation part for inputting the printing surface information whether the printing surface of the said paper is a front side or a back side is provided further. The operation part as described in any one of Claims 1-4 characterized by the above-mentioned. Image forming apparatus. A printing surface detection unit provided on the upstream side in the sheet conveyance direction from the swinging unit and detecting whether the printing surface of the sheet is the front side or the back side; The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The said rocking | fluctuation part has a resist part comprised by the roller pair which forms a loop by abutting the front-end | tip of the said paper, and correct | amends the curvature of the said paper. The image forming apparatus according to claim 1.

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