JP5311217B2 - Recording material length measuring apparatus, image forming apparatus, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the influence of measuring errors caused by the state of an image formed on recording material and/or the difference of the quality of the recording material, in a technology to measure length of the recording material from rotation of a rotating body that rotates in contact with the conveyed recording material. <P>SOLUTION: An image forming apparatus includes: a paper basis weight specifying device 411 which allows a user to input basis weight of paper in order to suppress an error of measured value caused by basis weight of the paper and a difference of image density of the already formed image when measuring the length of the paper based on a rotational amount of a length measuring roll; and an image detection device 321 which detects the image density of the image formed on the paper. In measurement of length of the paper based on output from a rotary encoder 119, a paper length arithmetic operation means 410 performs correction processing considering the influence of the image density of the already formed image and the basis weight of the paper. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a recording material length measuring apparatus, an image forming apparatus, and a program.

  Japanese Patent Application Laid-Open No. 2004-228561 describes a configuration for correcting the influence of sheet inclination in a configuration for detecting the length of a conveyed sheet. Japanese Patent Application Laid-Open No. H10-228561 describes a configuration for calculating a sheet conveyance speed based on a temperature detected by a temperature sensor.

JP 2005-112543 A

  The present invention relates to a technique for measuring the length of a recording material from the rotation of a rotating body that rotates in contact with the conveyed recording material, and relates to the state of an image formed on the recording material and / or the type of recording material. The purpose is to reduce the influence of the measurement error due to.

According to the first aspect of the present invention, there is provided a rotating body that rotates in contact with a recording material to be conveyed, a detecting unit that detects a rotation amount of the rotating body, and at least information on an image density formed on the recording material. And an information acquisition means for acquiring any one of the basis weight information of the recording material, an output from the detection means and a correction coefficient from the information acquired by the information acquisition means , and based on the correction coefficient A recording material length measuring apparatus comprising: a calculating unit that calculates a length of the recording material in the transport direction.

  According to a second aspect of the present invention, in the first aspect of the present invention, the rotating body contacts the recording material after the image formed on the recording material is fixed.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, detection means for detecting passage of an edge portion of the recording material is disposed on the upstream side and the downstream side in the conveyance direction of the rotating body. It is characterized by.

According to a fourth aspect of the invention, in the invention according to any one of the first to third aspects, the basis weight information of the recording material is stored in advance.

According to a fifth aspect of the present invention, there is provided a recording material length measuring apparatus according to any one of the first to fourth aspects of the present invention, and an image forming condition formed on the recording material based on an output of the measuring apparatus. An image forming apparatus comprising: an image forming unit that performs control.

The invention according to claim 6 is a program that is read and executed by a computer, wherein the computer detects a rotation amount of a rotating body that rotates in contact with a recording material conveyed, and at least the An information acquisition step for acquiring any one of information on the image density formed on the recording material and information on the basis weight of the recording material, the amount of rotation of the rotating body detected in the detection step, and the information acquisition A program for obtaining a correction coefficient from the information acquired in the step and calculating a length of the recording material in the transport direction based on the correction coefficient .

According to the first aspect of the present invention, the present invention relates to a technique for measuring the length of a recording material from the rotation of a rotating body that rotates in contact with the conveyed recording material, and the image density of an image formed on the recording material and The influence of measurement error due to the difference in at least one basis weight of the recording material is reduced.

  According to the second aspect of the present invention, measurement is performed without being affected by the dimensional change of the recording material before and after fixing.

  According to the third aspect of the present invention, the measurement error at the time when the recording material enters and leaves the rotating body is suppressed as compared with the case where no detection means for detecting the passage of the edge portion of the recording material is provided. It is done.

According to the fourth aspect of the present invention, the recording material information input operation is simplified.

According to the fifth aspect of the present invention, there is provided an image forming apparatus in which an adverse effect on image formation due to a difference in length in the recording material conveyance direction is suppressed.

According to the sixth aspect of the present invention, when the operation of measuring the length of the recording material from the rotation of the rotating body that rotates in contact with the conveyed recording material is performed, the image of the image formed on the recording material A program is provided that can reduce the influence of measurement errors due to differences in at least one of density and basis weight of recording material .

It is a conceptual diagram which shows an example of the length measuring apparatus of a recording material. 1 is a conceptual diagram illustrating an example of an image forming apparatus. FIG. 3 is a block diagram illustrating a configuration of a control system of the image forming apparatus in FIG. 2. It is a flowchart which shows an example of the length measurement procedure. It is a conceptual diagram which shows the principle of length measurement in embodiment. It is a conceptual diagram which shows the principle of length measurement in embodiment.

(Configuration of measuring device)
FIG. 1 is a conceptual diagram showing an example of a recording material length measuring apparatus. FIG. 1 shows a length measuring device 100 as an example of a recording material length measuring device. The length measuring device 100 includes a length measuring roll 101 that is an example of a rotating body for measurement. The length measuring roll 101 has a wide disk shape and includes a rotation shaft 102.

  A rotary encoder 119, which is an example of a means for detecting the amount of rotation, is connected to the rotating shaft 102, and information about the rotation of the rotating shaft 102 (information about the amount of rotation and its change) is obtained electrically. Yes. The output of the rotary encoder 119 is sent to the controller 120 described later. The rotating shaft 102 is attached to the swing arm 103 in a rotatable state. The swing arm 103 is attached to the swing arm support member 105 by a swing shaft 104 so as to be rotatable (swingable). The swing arm support member 105 is fixed to a housing (not shown) of the length measuring device 100.

  An extension arm 106 extends on the opposite side of the swing arm 103 where the length measuring roll 101 is attached, and one end of a coil spring 107 is attached thereto. The other end of the coil spring 107 is attached to an arm 108 extending from the support member. The coil spring 107 is in a tensioned state and is in a state of generating a force to rotate the swing arm 103 in the counterclockwise direction in the drawing.

  Conveying rolls 110 and 111 are disposed on the upstream side of the length measuring roll 101 (left side in FIG. 1). The transport rollers 110 and 111 sandwich the paper 112 and transport the paper 112 in the right direction in the figure. The transport roll 110 is driven by a motor, and the transport roll 111 rotates by receiving the driving force of the transport roll 110. Conveying rolls 123 and 124 are arranged on the downstream side of the length measuring roll 101. The transport rollers 123 and 124 sandwich the paper 112 and transport the paper 112 in the right direction in the figure. The transport roll 123 is driven by a motor, and the transport roll 124 rotates upon receiving the driving force of the transport roll 123. The side in the direction before the flow of the conveyed paper 112 (the side opposite to the flow) is referred to as the upstream side, and the direction in which the conveyed paper 112 flows (the conveyance direction) is referred to as the downstream side.

  The paper 112 is an example of a recording material (recording sheet) having a sheet shape, and is, for example, a paper material for forming an image. As a material constituting the recording material, in addition to the paper material, a resin material used for OHP paper or the like, or a material obtained by coating the surface of the paper material with a resin film can be used.

  Reference numeral 114 denotes a lower chute that constitutes a surface in contact with the sheet. The lower chute 114 is a member on the surface, and the paper 112 is conveyed in contact with the chute 114. Opposing to the lower chute 114, the upper chute 115 is arranged with a predetermined gap size. The upper chute 115 is a planar member that regulates the paper 112 from above so that the paper 112 is not displaced above the position.

  An edge sensor 116 is disposed on the upstream side of the length measuring roll 101, and an edge sensor 117 is disposed on the downstream side. The edge sensors 116 and 117 are photoelectric sensors composed of LEDs and photosensors, and optically detect the passage of the front and rear edges of the conveyed paper 112.

  The outputs of the edge sensors 116 and 117 are sent to the controller 120. The controller 120 has a function as a computer and includes a CPU, a memory, and an interface, and has a function of calculating the length of the paper 112 in the transport direction and a function of a control device of the image forming apparatus described later. ing. These functions will be described later.

(Image forming device)
An example of an image forming apparatus using the invention will be described. FIG. 2 is a conceptual diagram showing an example of an image forming apparatus using the invention. FIG. 2 shows the image forming apparatus 30. The image forming apparatus 30 includes a paper supply unit 20 that supplies paper, an image forming unit 300 that includes an image forming unit, and a fixing device 400.

(Paper supply unit)
The paper supply unit 20 includes a storage device 21 that stores a plurality of sheets, a delivery mechanism (not shown) that sends the paper from the storage device 21 in the right direction in the drawing, and a paper that is sent from the delivery mechanism to the right in the drawing. A transport roll 22 for transporting in the direction is provided.

(Image forming unit)
The image forming unit 300 includes a transport roll 301 that transports the paper fed from the paper supply unit 20 into the image forming unit 300. On the downstream side of the transport roll 301, a transport roll 302 that transports a sheet fed from the transport roll 301 or a sheet fed from a later-described transport roll 315 toward the secondary transfer unit 303 on the transport path 304 is disposed. Has been. The secondary transfer unit 303 includes a transfer roll 306 and a counter roll 307, and the transfer belt 305 and the paper are sandwiched therebetween to transfer the toner image on the transfer belt 305 onto the paper.

  On the downstream side of the secondary transfer unit 303, a fixing device 400 having a function of fixing a toner image on a sheet onto the sheet by heating and pressurization is disposed. A transport roll 311 is disposed on the downstream side of the fixing device 400. The transport roll 311 sends the paper sent from the fixing device 400 to the outside of the apparatus or to the transport roll 312.

  When forming an image on both sides of the paper, the transport roll 311 sends the paper to the transport roll 312 when the image formation on the first surface (first surface) is completed. This sheet is sent from the transport roll 311 to the reversing device 313. The reversing device 313 sends the fed paper back toward the transport roll 312, and the transport roll 312 sends the paper discharged from the reversing device 313 to the transport path 314.

  The length measuring device 100 illustrated in FIG. 1 is disposed on the transport path 314. The length of the sheet sent to the transport path 314 is measured by the length measuring device 100 in the transport direction, sent from the transport roll 315 to the transport roll 302, and further sent to the transport path 304. At this time, the front and back surfaces of the first transport route 304 are reversed. The sheet conveyed again along the conveyance path 304 is sent to the secondary transfer unit 303, and the image is transferred to the second surface (the back surface of the first surface).

  The control of the primary transfer process and the secondary transfer process of the image formed on the second surface is performed based on the length information in the sheet conveyance direction measured by the length measuring apparatus 100. This is to suppress a phenomenon in which the formation position of the image formed on the second surface is shifted due to a change in the size of the sheet caused by the influence of the image formed on the first surface.

  An image detection device 321 is arranged in the conveyance path 314 that reverses the sheet. The image detection device 321 optically detects the image after the fixing process formed on the first surface of the paper 112 and acquires the image density. The image density is acquired as an area coverage value by comparing the data of the reference image density with the detected data. The area coverage value is the density of each basic color image. If the image is a color image, the three YMC colors are to be detected, and the maximum value is 300% (each color 100% × 3). In the case of a monochrome image, the maximum area coverage value is 100%.

  The image forming unit 300 includes primary transfer units 317, 318, 319 and 320. Each of these primary transfer units includes a photosensitive drum, a cleaning device, a charging device, an exposure device, a developing device, and a transfer roll. The primary transfer units 317, 318, 319, and 320 transfer Y (yellow), M (magenta), C (cyan), and K (black) toner images while being superimposed on the rotating transfer belt 305. As a result, a color toner image on which the YMCK toner images are superimposed is formed on the transfer belt 305.

  The controller 120 controls the operation of each component described above. The controller 120 also performs processing related to the measurement of the paper length. The controller 120 controls the image forming process based on the measured sheet length in the image forming process on the second surface when the image is formed on both sides of the sheet. At this time, the paper length to be used is obtained by correcting the paper length data obtained from the output of the length measuring device 100 based on the information on the material of the paper and the information on the image density of the image formed on the first surface. Used. The contents of this correction process will be described later.

  In the configuration shown in FIG. 2, the installation position of the length measuring device 100 is the upstream side of the secondary transfer unit 303 in the transport path 304, and the length in the transport direction of the paper is set at the stage before image formation regardless of the front and back of the paper. It is good also as a structure which measures and uses the information for image formation.

(Control system configuration)
An example of the configuration of the control system of the image forming apparatus 30 illustrated in FIG. 2 will be described. FIG. 3 is a block diagram illustrating an example of the configuration of the control system of the image forming apparatus 30. FIG. 3 shows the controller 120 shown in FIGS. 1 and 2.

  The controller 120 is a unit that functions as a computer, and has functions described below in terms of software. Moreover, it has the function with which normal computers, such as a timer function, is provided. Note that a program for executing the following functions and operations described below is stored in a memory (not shown) provided in the controller 120.

  The controller 120 includes a paper length calculation unit 401. The paper length calculation unit 401 has a calculation function for calculating the paper length, and includes a length measurement roll rotation amount storage area 402 and an edge sensor output storage area 403 which are memory areas necessary for the calculation. The length measurement roll rotation amount storage area 402 stores data related to the rotation amount of the length measurement roll 101. The edge sensor output storage area 403 stores output information from the edge sensors 116 and 117.

  The controller 120 includes a parameter setting storage area 404. The parameter setting storage area 404 stores parameter setting values necessary for calculation in the paper length calculation unit 401. The parameter setting storage area 404 includes a length measurement roll size storage area 405, an edge sensor distance storage area 406, and a correction table 407. The length measuring roll size storage area 405 stores data related to the circumferential length of the length measuring roll. The edge sensor distance storage area 406 stores data on the distance between the edge sensors 116 and 117. The correction table 407 is provided with a data table that determines the relationship between parameters necessary for the calculation that has been examined in advance. The contents of the correction table 407 will be described in relation to the description of the operation described later.

  The controller 120 includes an image formation processing control unit 408. The image formation processing control unit 408 performs overall processing related to image formation. The apparatus that performs processing relating to image formation includes a main motor drive control circuit 431, a power supply circuit 432, a transport roll drive control circuit 437, and primary transfer units 317 to 320. An apparatus for performing processing related to image formation will be described later.

  A UI (user interface) 410 is connected to the controller 120. A UI (user interface) 410 is provided in the image forming apparatus 30 of FIG. 2 (not shown in FIG. 2). The UI (user interface) 410 includes a touch panel mechanism, and is configured to allow a user to input various information and various settings. In this example, the UI (user interface) 410 includes a paper type designation device 411 and a paper basis weight designation device 412 (other UI functions are also provided, but description thereof is omitted here).

  The paper type designation device 411 receives input of information regarding the type of paper designated by the user. Information on paper types includes paper basis weight, paper thickness dimensions (including not only specific thickness but also information such as “thick paper” and “thin paper”), and paper material (plain paper, coated paper) , Information for distinguishing materials such as OHP paper), and the name of the paper (model number when the type of paper to be used is specified).

The paper basis weight designation device 412 accepts input of the paper basis weight (g / m ² ) by the user. Input basis weight information may be of entering specific ^{_{values, m 1 g~m 2 g / m}} 2 to the segment _A, up to _{^{m 2 g / m 2 ~m 2}} g / m 2 It is also possible to determine the category B, category C from m ₃ g / m ^{2 to} m ₃ g / m ² ,... And input (or specify) this category information.

  The above-described data obtained from the UI (user interface) 410 is used when performing a paper length correction process described later. The UI (user interface) 410 may function on the terminal side that sends image data to the image forming apparatus 30.

  Image data from the image data receiving device 413 is input to the controller 120. The image data receiving device 413 functions as an input unit that receives image data of an image to be formed sent to the image forming device 30 via a communication line (not shown) (not shown). Further, the controller 120 receives data related to the image density from the image detection device 321 shown in FIG. The data relating to the image density is used when a paper length correction process described later is performed.

  Further, the controller 120 receives signals from the edge sensors 116 and 117 shown in FIG. This signal is used when a paper length correction process described later is performed. Further, the controller 120 receives a pulse count signal from the rotary encoder 110 shown in FIG. This pulse count signal is used when a paper length correction process described later is performed.

  An apparatus for performing processing related to image formation, the operation of which is controlled by the image forming processing control unit 408, will be described. The apparatus that performs processing relating to image formation includes a main motor drive control circuit 431, a power supply circuit 432, a transport roll drive control circuit 437, and primary transfer units 317 to 320.

  The main motor drive control circuit 431 is a drive circuit that drives a motor that generates a driving force for rotating the transfer belt 305 in FIG. The power supply circuit 432 includes a development bias power supply circuit 433, a charging device power supply circuit 434, a transfer bias power supply circuit 435, and a fixing heater power supply circuit 436. The developing bias power supply circuit 433 generates a bias voltage to be applied when toner is supplied from the developing device to the photoreceptor roll in the primary transfer units 317 to 320 in FIG. The charging device power supply circuit 434 is a power supply circuit for a charging device that charges the photosensitive rolls in the primary transfer units 317 to 320.

  The transfer bias power supply circuit 435 generates a bias voltage applied at the time of primary transfer to the transfer belt 305 in the primary transfer units 317 to 320 and a bias voltage applied at the secondary transfer unit 303. The fixing heater power supply circuit 436 is a power supply for the heat generating heater provided in the fixing device 400. The transport roll drive control circuit 437 is a drive circuit that drives a motor that moves a roll of a transport mechanism for transporting paper such as the transport roll 302.

(Operation example)
Hereinafter, an example of the operation of the control system shown in FIG. 3 will be described. FIG. 4 is a flowchart showing an example of the operation. Here, an example of processing performed when forming an image on the second surface in forming an image on both sides of a sheet will be described. Note that the operation program for determining the operation procedure shown in FIG. 4 is stored in a memory included in the controller 120, and is read and executed in an appropriate storage area (RAM area).

  In the case of forming an image on both sides of a sheet, after the image is formed on the first side, the sheet is switched back by the reversing device 313 in FIG. 2 and sent out to the conveyance path 314. At this timing, the process shown in FIG. 4 is started.

  When the process shown in FIG. 4 is started (step S501), it is determined whether or not the edge sensor 117 is ON (step S502). If the edge sensor 117 is ON, the process proceeds to step S503; The process of S502 is repeated. Here, when the edge sensor is ON, there is a sheet at the edge sensor, and the edge sensor detects the sheet.

  In step S503, the measurement of the timer t1 is started from t1 = 0. In synchronization with the start of the measurement of the timer t1, measurement of the encoder pulse p2 output from the rotary encoder 119 is started (step S504). Then, when the encoder pulse p2 that has started the measurement becomes a rising part or a falling part of the pulse, the determination in step S505 is YES, and the measurement of the timer t1 is ended (step S506). At this time, the count value of the timer t1 is acquired as the measurement parameter t1.

  Next, the measurement of the timer t3 is started from t = 0 (step S507), and it is determined whether or not the edge sensor 116 is OFF, that is, whether or not the sheet has passed the preceding edge sensor (step S508). If the edge sensor 116 is OFF, the measurement of the encoder pulse p2 is terminated (step S509), and the measurement of the timer t3 is terminated (step S510). At this time, the count value of the timer t3 is acquired as the measurement parameter t3.

  On the other hand, if the edge sensor 116 is not OFF in step S508, it is determined whether the encoder pulse p2 is a pulse rising part or a pulse falling part (S511). The timer t3 is reset (S512), and the process returns to step S507 to restart the measurement of the timer t3. If it is not the rising part of the pulse or the falling part of the pulse, step S508 is repeated again.

  According to this processing, after the measurement of the timer t3 is started, if the edge sensor 116 is turned off at the stage before the edge of the first pulse waveform is output, the processing from step S509 is performed. In addition, when the edge sensor 116 is not turned OFF before the edge of the first pulse waveform is output and the edge (rising or falling) of the first pulse waveform is output, the timer t3 is reset, and again. The processing in step S507 and subsequent steps is executed.

  Step S513 is performed after step S510. In step S513, first, L1 and L2 are calculated using the measured values t1 and t2 of the timer t1 and the timer t2. Such a calculation is performed for the following reason.

  FIG. 6 is a conceptual diagram showing changes in main force waveforms of the edge sensor and the rotary encoder 119. In FIG. 6, changes in the output waveform of the rotary encoder 119 are exaggerated. As shown in FIG. 6, the first pulse output from the rotary encoder 119 immediately after the length measuring roll 101 enters the paper 112 and the rotary encoder 119 immediately before the length measuring roll 101 leaves the paper 112. The last one pulse cannot be expected to have a measurement accuracy less than the pulse interval (in other words, the resolution of the rotary encoder). Further, since the length measuring roll 101 rotates by inertia even after the contact of the paper 112 is finished, the timing at which the paper is separated from the length measuring roll 101 cannot be specified only from the rotation information of the rotary encoder.

  Therefore, in this example, L1 and L2 using the above t1 and t2 are calculated. FIG. 5 is a conceptual diagram showing the positions of L1 and L2 in an easy-to-understand manner. FIG. 5 also shows L2 and L4 described later.

  After calculating L1 and L2, the correction coefficient β is retrieved from the correction table 407 (see FIG. 3) based on X1, X2, and X3. In this example, a case will be described in which the sheet basis weight designation device 410 is operated by the user and a sheet basis weight value is input. An example of the data table stored in the correction table 407 used in this case is shown in Tables 1 and 2 below. These data tables are created based on values experimentally acquired in advance.

Table 1 shows the relationship between the paper basis weight and the correction coefficient β with respect to a predetermined image density σ ₁ . Table 2 shows the relationship between the paper basis weight and the correction coefficient β for an image density σ ₂ different from σ ₁ . Here, as an example, a data table relating to σ ₁ and σ ₂ is shown, but similar data tables are prepared in a number that provides the required accuracy.

  In this example, the image density (σ value) of the image already formed on the first surface is detected by the image detection device 321 of FIG. 3, and the image density (σ value) is exemplified in Table 1 or Table 2. The data table to be searched is searched. On the other hand, since X1 is input by the user and the basis weight m of the used paper is known, the corresponding β value is retrieved from the retrieved data table. Then, the sheet correction function f (p2, α, β) is calculated using this β value.

  The paper correction function f (p2, α, β) corrects the influence of the measurement error caused by the output pulse (encoder pulse p2) of the rotary encoder 119 and the basis weight of the paper and the image density of the already formed image. This is a function for determining the length measured by the length measuring roll 101 based on the value of the coefficient β. By using this function, the paper length is calculated by correcting the influence of the measurement error caused by the basis weight of the paper and the image density of the already formed image. Here, the length measurement roll distance conversion coefficient α in step S513 is a coefficient related to the circumferential dimension of the length measurement roll 101 stored in the length measurement roll size storage area 405 of FIG. As the paper correction function f (p2, α, β), an experimentally obtained function is used.

  Thus, L2 = f (p2, α, β) is calculated to obtain L2. Then, using the distance L4 between the edge sensors 116 and 117, L = L1 + L2 + L3 + L4 is calculated, and the length L of the paper 112 is obtained. The above is the content of the process of step S513.

  Next, based on the paper length L obtained in step S513, image forming processing is controlled on the second surface of the paper (step S514). This control is performed in the image forming process control unit 408 in FIG. When the image forming process on the second surface of the sheet is completed, the process is terminated (step S515).

(Operation 1)
First, the operation of measuring the paper length when an image is formed on the second surface of the paper will be described. When images are formed on both sides of a sheet, the dimensional change of the sheet occurs due to the formation of the image on the first side. For this reason, in order to accurately match the image forming positions on the front and back surfaces, the size of the paper is measured after the image is formed on the first surface, and the measured value is used in the image forming process on the second surface. Reflecting is effective.

(Operation 2)
Next, an operation for correcting the measurement value based on the basis weight of the paper and the image density of the image formed on the first surface in the measurement of the paper length will be described. The difference in the basis weight of the paper mainly affects the difference in the thickness of the paper. It has been experimentally found that the difference in the length measurement value of the paper length varies with the thickness of the paper. This is due to the thickness of the paper, but the degree of the measurement roll being squeezed into the paper and the position of the rotation axis of the measurement roll change.This change affects the measured value based on the rotation of the measurement roll. It is thought to give. In order to correct the influence of this error, a correction coefficient corresponding to the basis weight as shown in Table 1 or Table 2 is obtained in advance, and the measurement value is corrected using this correction coefficient. As a result, the occurrence of an error in the measured value of the paper length due to the difference in basis weight is suppressed.

  It has also been experimentally determined that when an image is formed on the first surface, the error in the length measurement value of the paper length varies depending on the image density. This is presumably because the state of the surface of the paper changes due to the influence of the fixed toner material constituting the image, for example, the degree of sag at the time of contact with the length measuring roll or the friction state with the length measuring roll. This change is considered to cause an error in measurement using the length measuring roll. Accordingly, a correction coefficient as shown in Table 1 or Table 2 corresponding to the image density is obtained in advance, and the measurement value is corrected using this correction coefficient, whereby the measured value of the paper length caused by the difference in image density. The occurrence of errors is suppressed.

(Modification)
In the example described above, the image density is obtained by optically detecting an image formed on the paper. As another example, there is a method in which the electronic data of the image received by the image data receiving device 413 in FIG. 3 is subjected to image processing by software to acquire the image density of the image formed on the paper. . In this case, since the image density is not detected from the actually formed image, the image density information of the portion that cannot be detected by the image detection device 321 can be acquired. Also, it is easier to obtain information on the distribution of image density in the paper.

  In the above example, the example in which the correction considering the influence of both the basis weight of the paper and the image density of the image formed on the first surface is applied to the measurement value using the rotary encoder has been described. Only, or only the image density, can be used as a correction parameter. In this case, the other element adopts a fixed value.

  It is also possible to obtain the basis weight of the paper with a sensor. In this case, the thickness of the paper is detected by the thickness detection sensor, and the basis weight of the paper is acquired based on the detection result. As the thickness detection sensor, a configuration in which a movable member is brought into contact with a sheet and the thickness of the sheet is obtained from the displacement of the movable member can be employed.

  In the above example, the case where the basis weight is used as the parameter relating to the type of paper has been described. It can also be reflected.

  The program for executing the processing procedure shown in FIG. 4 may be stored in an appropriate recording medium and provided from there.

  The present invention is applicable to a technique for measuring the length of a recording material.

DESCRIPTION OF SYMBOLS 100 ... Measuring apparatus, 101 ... Measuring roll, 102 ... Rotating shaft, 103 ... Swing arm, 104 ... Swing axis, 105 ... Swing arm support member, 106 ... Extension arm, 107 ... Coil spring, 108 ... Arm, DESCRIPTION OF SYMBOLS 110 ... Conveyance roll, 111 ... Conveyance roll, 112 ... Paper, 114 ... Lower chute, 115 ... Upper chute, 116 ... Edge sensor, 117 ... Edge sensor, 119 ... Rotary encoder

Claims (6)

A rotating body that rotates in contact with the recording material to be conveyed;
Detecting means for detecting the amount of rotation of the rotating body;
At least the information obtaining means for obtaining either the basis weight of the information of the information and the recording medium of the image density formed on the recording material,
Calculating means for obtaining a correction coefficient from the output from the detection means and the information acquired by the information acquisition means, and calculating a length of the recording material in the transport direction based on the correction coefficient. Recording material length measuring device.   2. The recording material length measuring apparatus according to claim 1, wherein the rotating body contacts the recording material after fixing of an image formed on the recording material.   The length of the recording material according to claim 1, wherein detection means for detecting passage of an edge portion of the recording material is arranged on the upstream side and the downstream side in the conveyance direction of the rotating body. measuring device. The recording material having a basis weight information length measuring apparatus of a recording material according to any one of claims 1 to 3, characterized in that previously stored. A recording material length measuring device according to any one of claims 1 to 4 ,
An image forming apparatus comprising: an image forming unit that controls a forming condition of an image formed on the recording material based on an output of the measuring device. A program that is read and executed by a computer,
On the computer,
A detection step for detecting a rotation amount of a rotating body that rotates in contact with the recording material to be conveyed;
At least, an information acquisition step of acquiring either one of the basis weight of the information of the information and the recording medium of the image density formed on the recording material,
Calculation for obtaining a correction coefficient from the rotation amount of the rotating body detected in the detection step and the information acquired in the information acquisition step, and calculating the length of the recording material in the transport direction based on the correction coefficient A program characterized by causing steps to be executed.

Images