JP2019034815A - Medium physical property detection device, image forming apparatus and medium physical property detection program - Google Patents

Abstract

To provide a medium physical property detection device, an image forming apparatus and a medium physical property detection program capable of detecting a parameter indicative of a water content of a medium by use of conveyance torque of the medium.SOLUTION: An image forming apparatus allows a positioning roller downstream in a conveyance direction of a sheet to convey a sheet by gripping it at two positions where conveyance speed is slower than the conveyance roller upstream in the conveyance direction, allows a load detection part 114 to detect a load of a motor M1 driving the positioning roller, and allows a CPU 100 to detect a value indicative of a stiffness of a medium by use of a detection result.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a medium property detection device, an image forming apparatus, and a medium property detection program.

  In Patent Document 1, it is proposed to form a loop by abutting a sheet against a sheet stopping unit, and to detect the thickness of the sheet by measuring a driving current flowing in a motor that is a sheet feeding drive source at the time of forming the loop. Has been.

  In Patent Document 2, a speed signal is output by detecting the speed of a DC motor that drives an entrance transport roller that transports a sheet, and the output speed signal is frequency-converted into a speed change amount. Only arbitrary high-frequency components are extracted. Then, it has been proposed to extract a non-periodic component of load fluctuation using an extracted arbitrary high-frequency component and discriminate the paper thickness of the paper based on the extracted non-periodic component.

JP 2004-018127 A JP 2013-189260 A

  As the physical properties of the medium, there are parameters other than the thickness. For example, when image formation is performed, the image formation conditions change depending on the moisture content of the medium. Therefore, it is necessary to detect the physical properties of the medium other than the thickness. is there. SUMMARY An advantage of some aspects of the invention is that it provides a medium property detection device, an image forming apparatus, and a medium property detection program capable of detecting a parameter representing the moisture content of a medium using the conveyance torque of the medium.

  The medium physical property detection apparatus according to claim 1 grips and conveys the medium at two positions where the conveyance speed at the first position downstream in the conveyance direction of the medium is slower than the second position at the upstream side in the conveyance direction. A detection unit that detects a load of a driving unit that drives conveyance of the first position in the conveyance unit, and a detection unit that detects a value representing the stiffness of the medium using a detection result of the detection unit.

  According to a second aspect of the present invention, in the first aspect of the present invention, the detection unit may be configured such that the leading edge of the medium enters the first position and the trailing edge of the medium is discharged from the second position. A value representing the stiffness is detected using a detection result of the detection unit in the period.

  According to a third aspect of the present invention, in the invention according to the second aspect, the detection unit causes the trailing end of the medium to be discharged from the first position after the trailing end of the medium is discharged from the second position. A value representing the stiffness is detected by integrating a difference between the reference and the load detected by the detection unit in the period with the average value of the detection results of the detection unit in the interval until.

  According to a fourth aspect of the present invention, in the second aspect of the present invention, the detection unit is configured based on the detection result of the detection unit when the rear end of the medium is ejected from the second position. And a value representing the stiffness is detected by integrating a difference between the load and the load detected by the detection unit in the period.

  The invention according to claim 5 is the invention according to claim 2, wherein the detection unit detects a value representing the stiffness from a slope of a detection result of the detection unit in the period.

  The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the medium is being transported by the transport unit and the detection period is different from the detection period of the detection unit. A sub-detecting unit that detects the thickness of the medium using the detection result of the detecting unit is further provided.

  According to a seventh aspect of the present invention, in the invention of the sixth aspect, the sub-detecting unit is configured such that the rear end of the medium is discharged from the second position and the rear end of the medium is discharged from the first position. The thickness of the medium is detected using the detection result of the detection unit in the interval up to.

  The invention according to claim 8 is the invention according to claim 7, wherein the sub detection unit detects the thickness of the medium by integrating or averaging the detection results of the detection unit in the section.

  An image forming apparatus according to a ninth aspect uses the medium property detection device according to any one of the first to eighth aspects, an image forming unit that forms an image on a medium, and a detection result of the detection unit. And a correction unit that corrects a variable related to image formation by the image forming unit.

  A medium physical property detection program according to a tenth aspect causes a computer to function as each unit of the medium physical property detection apparatus according to any one of the first to eighth aspects.

  According to the medium property detection device of the first aspect, it is possible to provide a medium property detection device capable of detecting a parameter representing the moisture content of the medium by using the conveyance torque of the medium.

  According to the second aspect of the present invention, it is possible to detect the value representing the stiffness of the medium in a period in which the stiffness of the medium appears more than in the case of detecting the value representing the stiffness of the medium in another period.

  According to the third aspect of the present invention, it is possible to detect a more accurate value representing the stiffness of the medium than when a value representing the stiffness of the medium is detected based on a single detection result.

  According to the fourth aspect of the present invention, it is possible to detect the value representing the stiffness of the medium more easily than the case of sensing the value representing the stiffness of the medium based on the average value of the detection results.

  According to the fifth aspect of the present invention, it is possible to detect a value representing the stiffness of the medium more easily than when measuring the stiffness of the medium.

  According to the sixth aspect of the present invention, it is possible to detect both the value representing the stiffness of the medium and the thickness during conveyance.

  According to the seventh aspect of the present invention, the thickness of the medium can be detected more accurately than when the thickness of the medium is detected in another period.

  According to the eighth aspect of the present invention, the thickness of the medium can be detected more accurately than when the thickness of the medium is detected using a single detection result.

  According to the image forming apparatus of the ninth aspect, it is possible to provide an image forming apparatus capable of detecting a parameter representing the moisture content of the medium using the conveyance torque of the medium.

  According to the medium property detection program of the tenth aspect, it is possible to provide a medium property detection program capable of detecting a parameter representing the moisture content of the medium by using the conveyance torque of the medium.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an exemplary embodiment. 1 is a block diagram illustrating a main configuration of an electrical system of an image forming apparatus according to an embodiment. It is a figure for demonstrating the case where the rotational speed of the motor M1 is faster than the motor M0, (B) is a figure for demonstrating the case where the rotational speed of the motor M1 and the motor M0 is equal, (C). It is a figure for demonstrating the case where the rotational speed of the motor M1 is slower than the motor M0. (A) is a figure which shows an example of the detection result of the load detection part for every thickness of the paper P when the rotational speed of the motor M1 is faster than the motor M0, and (B) is the motor M0 for the motor M1. It is a figure which shows an example of the detection result for every thickness of the paper P when rotation speed is slower. FIG. 5 is a diagram for explaining detection timings of a value representing the stiffness of a sheet and a thickness. It is a figure for demonstrating an example of the detection method of the thickness of a paper. It is a figure for demonstrating an example of the detection method of the value showing the stiffness of a paper. (A) is a figure which shows an example of the transfer voltage according to moisture content, (B) is a figure which shows an example of the fixing temperature according to moisture content, (C) is decurler pushing-in amount according to moisture content It is a figure which shows an example. 6 is a flowchart illustrating a part of processing relating to setting of image forming parameters performed by the image forming apparatus according to the present embodiment.

  Hereinafter, the present embodiment will be described with reference to the drawings. FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus according to the present embodiment.

  First, the configuration of the image forming apparatus 10 according to the present embodiment will be described with reference to FIG. In the following, yellow is indicated by Y, magenta color is indicated by M, cyan color is indicated by C, black is indicated by K, and each component and toner image (image) need to be distinguished for each color. The description will be made with the reference numerals (Y, M, C, K) corresponding to the colors at the end. Further, in the following, when the component parts and the toner image are collectively referred to without being distinguished for each color, the description of the color at the end of the code is omitted.

(overall structure)
As shown in FIG. 1, an image processing unit that performs image processing for converting input image data into four-color gradation data of Y, M, C, and K is provided inside the apparatus main body 10 </ b> A of the image forming apparatus 10. 12 is provided.

  Further, an image forming unit 16 as an example of an image forming unit that forms toner images of respective colors is disposed at a central side of the apparatus main body 10A with an interval in a direction inclined with respect to the horizontal direction. Further, a primary transfer unit 18 is provided above the image forming unit 16 for each color in the vertical direction. The toner image formed by the image forming unit 16 for each color is transferred in multiple layers.

  Further, on the side of the primary transfer unit 18 (on the left side in FIG. 1), a sheet P as an example of a medium transported along a transport path 60 by a supply transport unit 30 described later is multiplexed with the primary transfer unit 18. A secondary transfer roll 22 for transferring the transferred toner image is provided.

  A fixing device 24 is provided on the downstream side of the secondary transfer roll 22 in the conveyance direction of the paper P (hereinafter referred to as “paper conveyance direction”) and conveys the image formation surface of the paper P with the image forming surface interposed therebetween. The fixing device 24 fixes the toner image transferred onto the paper P onto the paper P by heat and pressure.

  The fixing device 24 according to the present embodiment includes a heating belt 24A and a pressure roll 24B as a pair of rotating bodies. The fixing device 24 is a so-called IH (Induction Heating) fixing device in which the heating belt 24A generates heat using electromagnetic induction. Further, the pressure roll 24B is driven (rotated) by a motor (not shown), and the heating belt 24A is driven to rotate as the pressure roll 24B rotates.

  Further, on the downstream side of the fixing device 24 in the paper conveyance direction, a discharge roll 28 that discharges the paper P on which the toner image is fixed to a discharge portion 26 provided on the upper portion of the apparatus main body 10A of the image forming apparatus 10 Is provided.

  On the other hand, a supply transport unit 30 that supplies and transports the paper P is provided below and to the side of the vertical direction of the image forming unit 16. Also, above the primary transfer unit 18 in the vertical direction, there are four toner cartridges 14 that can be attached to and detached from the apparatus main body 10A from the front of the apparatus main body 10A and are filled with toner to be supplied to the developing device 38 by color. (14K to 14Y) are arranged side by side in the apparatus width direction. Each color toner cartridge 14 has a cylindrical shape extending in the depth direction of the image forming apparatus 10 and is connected to each color developer 38 via a supply pipe (not shown).

(Image forming unit)
As shown in FIG. 1, the image forming units 16 for the respective colors are all configured similarly. The image forming unit 16 includes a rotating columnar image carrier 34 and a charger 36 that charges the surface of the image carrier 34.

  Further, the image forming unit 16 includes an LED (Light Emitting Diode) head 32 that irradiates the surface of the charged image carrier 34 with exposure light. Further, the image forming unit 16 develops the electrostatic latent image formed by the exposure light irradiation by the LED head 32 with a developer (in this embodiment, toner charged on the negative electrode) and visualizes it as a toner image. 38. Further, the image forming unit 16 includes a cleaning blade (not shown) that cleans the surface of the image carrier 34.

  A developing roll 39 is disposed in the developing unit 38 so as to face the image holding member 34. The developing unit 38 uses the developing roll 39 to convert the electrostatic latent image formed on the image holding member 34 with a developer. Develop and visualize as a toner image.

  The charger 36, the LED head 32, the developing roll 39, and the cleaning blade are arranged in this order from the upstream side to the downstream side in the rotation direction of the image carrier 34 so as to face the surface of the image carrier 34. Has been.

(Transfer section (primary transfer unit, secondary transfer roll))
The primary transfer unit 18 includes an endless intermediate transfer belt 42 and a drive roll 46 around which the intermediate transfer belt 42 is wound and driven to rotate by a motor (not shown) to rotate the intermediate transfer belt 42 in the direction of arrow A. ing. In addition, the primary transfer unit 18 is wound around the intermediate transfer belt 42, a tension applying roll 48 that applies tension to the intermediate transfer belt 42, and a position vertically above the tension applying roll 48 so as to be driven by the intermediate transfer belt 42. And an auxiliary roll 50 that rotates. Further, the primary transfer unit 18 includes primary transfer rolls 52 disposed on the opposite sides of the image holders 34 of the respective colors with the intermediate transfer belt 42 interposed therebetween.

  With the above configuration, the toner images of each color Y, M, C, and K, which are sequentially formed on the image carrier 34 of the image forming unit 16 for each color, are transferred onto the intermediate transfer belt 42 by the primary transfer roll 52 for each color. Multiple transcriptions are made.

  Further, a cleaning blade 56 that contacts the surface of the intermediate transfer belt 42 and cleans the surface of the intermediate transfer belt 42 is disposed on the opposite side of the drive roll 46 with the intermediate transfer belt 42 interposed therebetween.

  Further, on the opposite side of the auxiliary roll 50 with the intermediate transfer belt 42 interposed therebetween, a secondary transfer roll 22 for transferring the toner image transferred onto the intermediate transfer belt 42 onto the conveyed paper P is provided. The secondary transfer roll 22 is grounded, the auxiliary roll 50 forms a counter electrode of the secondary transfer roll 22, and the secondary transfer voltage is applied to the auxiliary roll 50, whereby the paper P The toner image is transferred to the toner image.

(Supply transport unit)
The supply / conveyance unit 30 includes a plurality of sheet storage portions 62 that are disposed below the image forming unit 16 in the vertical direction in the apparatus main body 10 </ b> A and that store a plurality of sheets P. Each paper storage unit 62 stores different types of paper (size, paper type, etc.).

  Further, the supply and transport unit 30 includes a paper feed roll 64 that feeds the paper P stored in the paper storage unit 62 to the transport path 60, and a separation roll 66 that separates the paper P sent out by the paper feed roll 64 one by one. A conveyance roll 67 that conveys the sheets separated one by one and a positioning roll 68 that matches the conveyance timing of the sheet P are provided. And each roll is arrange | positioned in this order toward the downstream from the upstream in the paper conveyance direction.

  Further, the alignment roll 68 is connected to a motor as a drive unit for rotating the alignment roll 68 via a clutch mechanism (not shown). The image forming apparatus 10 keeps the clutch mechanism in an unconnected state until the paper P reaches the installation position of the alignment roll 68 and abuts the front end of the paper P in the paper conveyance direction against the alignment roll 68. Accordingly, the image forming apparatus 10 performs alignment by correcting the inclination of the paper P with respect to the paper transport direction. Then, after the alignment, the alignment mechanism 68 is rotated by bringing the clutch mechanism into a connected state, and the paper P is conveyed.

  With the above configuration, the paper P supplied from the paper storage unit 62 is set at a timing determined by the rotating alignment roll 68 to the contact portion (secondary transfer position) between the intermediate transfer belt 42 and the secondary transfer roll 22. Sent out.

  The sheet P conveyed to the fixing device 24 is heated by the heating belt 24A and is pressed by the heating belt 24A and the pressure roll 24B, so that a toner image is formed on one surface (image forming surface) of the sheet P. It is fixed.

  Further, the supply conveyance unit 30 corrects and flattens the deformation (wrinkles, deflection, etc.) of the paper P fixed by the fixing device 24 on the downstream side of the fixing device 24 in the conveyance direction of the paper P. A decurler 25 is provided.

  Further, the supply / conveyance unit 30 forms the toner image on the other side without discharging the paper P, on which the toner image is fixed on one side by the fixing device 24, to the discharge unit 26 by the discharge roll 28 as it is. The double-sided conveyance device 70 used for the above is provided.

  The double-sided conveyance device 70 conveys the paper P along the double-sided conveyance path 72, and the double-sided conveyance path 72 where the paper P is conveyed by reversing the front and back of the paper P from the discharge roll 28 toward the alignment roll 68. A roll 74 and a transport roll 76 are provided.

  The image forming apparatus 10 may be provided with a sheet detection sensor on at least one of the upstream side and the downstream side of the fixing device 24 along the conveyance path 60. As the paper detection sensor, for example, a reflective sensor including a set of light emitting elements and light receiving elements may be used. In this case, the paper detection sensor irradiates the detection position on the transport path 60 corresponding to the installation position from the light emitting element. The paper detection sensor outputs a signal level signal (hereinafter referred to as “detection signal”) corresponding to the amount of light received by the light receiving element. During the period when the paper P is transported through the detection position, the light emitted from the light emitting element is reflected by the paper P. Accordingly, the paper detection sensor outputs detection signals having different signal levels depending on the period during which the paper P is transported through the detection position and the period during which the paper P is not transported. In addition to the reflective sensor, other sensors such as a transmissive sensor may be applied as the paper detection sensor.

(Image formation process)
First, gradation data of each color is sequentially output from the image processing unit 12 to the LED head 32 of each color. The exposure light emitted from the LED head 32 in accordance with the gradation data is applied to the surface of the image carrier 34 charged by the charger 36. Thereby, an electrostatic latent image is formed on the surface of the image carrier 34. The electrostatic latent image formed on the image carrier 34 is developed by each color developer 38 and visualized as a toner image of each color of Y, M, C, K.

  Further, the primary transfer rolls 52 of the primary transfer unit 18 transfer the toner images of the respective colors formed on the image carrier 34 onto the rotating intermediate transfer belt 42 in a multiple manner.

  The toner images of each color transferred in multiple on the intermediate transfer belt 42 are transferred to the sheet P conveyed along the conveyance path 60 by the sheet feeding roll 64, the separation roll 66, and the alignment roll 68 from the sheet storage unit 62. Secondary transfer is performed at the secondary transfer position by the secondary transfer roll 22.

  Further, the paper P on which the toner image is transferred is conveyed to the fixing device 24. Then, the toner image is fixed on the paper P by the fixing device 24. The sheet P on which the toner image is fixed is forced to be deformed by the decurler 25 and discharged to the discharge unit 26 by the discharge roll 28.

  On the other hand, when images are formed on both sides of the paper P, the paper P on which the toner image is fixed on one side (front surface) by the fixing device 24 is not directly discharged to the discharge unit 26 by the discharge roll 28. The transport direction of the paper P is switched by the reverse rotation of the discharge roll 28. The sheet P is transported along the duplex transport path 72 by transport rollers 74 and 76.

  The sheet P transported along the duplex transport path 72 is transported again to the alignment roll 68 with its front and back reversed. Then, after the toner image is transferred and fixed on the other side (back side) of the sheet P, the sheet P is discharged to the discharge unit 26 by the discharge roll 28.

  Next, with reference to FIG. 2, the main configuration of the electrical system of the image forming apparatus 10 according to the present embodiment will be described. FIG. 2 is a block diagram showing a main configuration of the electrical system of the image forming apparatus 10 according to the present embodiment.

  As illustrated in FIG. 2, the image forming apparatus 10 according to the present embodiment includes a CPU (Central Processing Unit) 100 that controls the overall operation of the image forming apparatus 10, and a ROM that stores various programs, various parameters, and the like in advance. (Read Only Memory) 102 is provided. The image forming apparatus 10 also includes a RAM (Random Access Memory) 104 that is used as a work area when the CPU 100 executes various programs, and a non-volatile storage unit 106 such as a flash memory.

  In addition, the image forming apparatus 10 includes a communication line I / F (Interface) unit 108 that transmits and receives communication data to and from an external device. In addition, the image forming apparatus 10 includes an operation display unit 110 that accepts an instruction from the user to the image forming apparatus 10 and displays various types of information regarding the operation status of the image forming apparatus 10 to the user. The operation display unit 110 includes, for example, a display button that realizes reception of an operation instruction by executing a program, a display provided with a touch panel on a display surface on which various information is displayed, and hardware keys such as a numeric keypad and a start button. including.

  Further, the image forming apparatus 10 is connected to a motor M1 that rotates the alignment roll 68, a motor M0 that rotates the transport roll 67, and the like, and the driving of the motors M1 and M0 is controlled.

  Further, the image forming apparatus 10 includes a load detection unit 114 as an example of a detection unit that detects the load of the motor M1. The load detection unit 114 according to the present embodiment is connected to the motor M1, and detects the load of the motor M1 as a current value flowing through the motor M1.

  The configuration of the load detection unit 114 according to the present embodiment is not particularly limited as long as the load of the motor M1 can be detected. For example, the load detection unit 114 may be configured to detect the load of the motor M1 as a current value flowing through the motor M1, convert the detected current value into a voltage value, and output the voltage value. Further, the load detection unit 114 may be configured to measure the voltage between the shunt resistors and detect the current. Further, for example, as the load detection unit 114, a configuration in which a resistor is provided on a path through which a current flows in the motor M1, and a voltage between the resistors is measured to detect the current may be applied. Further, for example, the load detection unit 114 may be configured to detect a current by providing a current sensor using a Hall element on a path through which a current flows in the motor M1. Furthermore, for example, a torque detector that detects the torque of the motor M1 may be applied as the load detector 114.

  The CPU 100, the ROM 102, the RAM 104, the storage unit 106, the communication line I / F unit 108, the operation display unit 110, the motor M1, and the load detection unit 114 are each a bus 116 such as an address bus, a data bus, and a control bus. Are connected to each other.

  With the above configuration, the image forming apparatus 10 according to the present embodiment allows the CPU 100 to access the ROM 102, the RAM 104, and the storage unit 106, and communication data with the external device via the communication line I / F unit 108. Are sent and received respectively. In the image forming apparatus 10, the CPU 100 acquires various instruction information via the operation display unit 110 and displays various information on the operation display unit 110. In addition, the image forming apparatus 10 performs control of the motors M1 and M0 and acquisition of the voltage value output from the load detection unit 114 by the CPU 100, respectively.

  Incidentally, the image forming apparatus 10 according to the present embodiment is equipped with a detection function for detecting physical properties of the paper P. Here, a detection function for detecting physical properties of the paper P will be described. In the present embodiment, as the physical properties of the paper P, values indicating the thickness of the paper P and the stiffness of the paper P are detected. Note that “stiffness” is also called stiffness or stiffness, and is an index representing resistance when paper is bent. The stiffness is greatly affected by the thickness, and is proportional to the second to the third power of the thickness. Also, the vertical and horizontal directions of the paper differ greatly, and the vertical direction is generally about twice the horizontal direction. Moisture also affects stiffness, and generally the more moisture, the less stiffness.

  In the present embodiment, the load detection unit 114 detects the load of the motor M1 that drives the alignment roll 68 as the first position, and the physical properties of the paper P based on the detection result by the CPU 100, the thickness of the paper P, And a value representing the stiffness of the paper P is detected. That is, the CPU 100 functions as a detection unit and a sub detection unit.

  In the present embodiment, it is assumed that the distance between the alignment roll 68 and the conveyance roll 67 as the second position on the upstream side in the conveyance direction of the alignment roll 68 is set shorter than the length of the paper P. Thereby, the load detection unit 114 detects the load of the motor M1 that drives the alignment roll 68, and the load of the motor M1 is that of the motor M0 that drives the conveyance roll 67 on the upstream side of the alignment roll 68 in the conveyance direction. Varies depending on the rotation speed.

  For example, when the rotational speed of the motor M1 is faster than that of the motor M0, the paper P is pulled when the leading edge of the paper P enters the alignment roll 68. As a result, as shown in FIG. 3A, the current value detected by the load detection unit 114 gradually decreases after the current rises. The current value is substantially constant from when the paper P is discharged from the transport roll 67 to when the alignment roll 68 is discharged.

  When the rotation speeds of the motor M1 and the motor M0 are equal, as shown in FIG. 3B, the current value detected by the load detection unit 114 is such that the leading edge of the paper P enters the alignment roll 68. Until the rear end is discharged from the alignment roll 68.

  On the other hand, when the rotational speed of the motor M1 is slower than that of the motor M0, when the leading edge of the paper P enters the alignment roll 68, the paper P starts to loosen. As a result, as shown in FIG. 3C, the current value detected by the load detection unit 114 gradually increases after the current value rises. Then, a substantially constant current value is obtained from when the trailing edge of the paper P is discharged from the transport roll 67 to when the alignment roll 68 is discharged.

  FIG. 4A shows an example of the detection result of the load detection unit 114 for each thickness of the paper P when the rotation speed of the motor M1 is faster than that of the motor M0. FIG. An example of a detection result for each thickness of the paper P when the rotational speed of M1 is slower than that of the motor M0 is shown.

  Here, when the paper P is slackened between the alignment roll 68 and the transport roll 67, the detection result of the load detection unit 114 is changed due to the change in the slackness depending on the stiffness of the paper. Therefore, in this embodiment, the motor M1 is set to a rotational speed that is slower than the motor M0.

  In the present embodiment, as shown in FIG. 5, detection by the load detection unit 114 in a period from when the leading edge of the paper P enters the alignment roll 68 until the trailing edge of the paper P is discharged from the transport roll 67. Based on the result, a value representing the stiffness of the paper P is detected. Then, based on the detection result of the load detection unit 114 during the period from when the trailing edge of the paper P is discharged from the transport roll 67 to when the trailing edge of the paper P is discharged from the alignment roll 68, the thickness of the paper P is determined. Detect. In addition, a sensor is provided at each position for the timing of entry of the paper P into the alignment roll 68, ejection from the conveyance roll 67 at the rear end of the paper P, and ejection from the alignment roll 68 at the rear end of the paper P. Alternatively, the sheet P provided in the transport path may be detected by counting time from the detection result.

  In the present embodiment, by integrating the detection results of the load detection unit 114 in a period from the time when the trailing edge of the paper P is discharged from the conveying roll 67 to the time when the trailing edge of the paper P is discharged from the alignment roll 68. The thickness of the paper P is detected. That is, the thickness of the paper P is detected by calculating the area indicated by the oblique lines shown in FIG. FIG. 6 shows the area corresponding to the thickness of the thin paper. Note that the thickness of the sheet P is a result of detection by the load detection unit 114 during a period from the time when the trailing edge of the sheet P is discharged from the conveying roll 67 to the time when the trailing edge of the sheet P is discharged from the alignment roll 68. The thickness of the paper P may be detected by calculating the average value.

  Then, with the value of the detection result of the load detection unit 114 during the period when the thickness of the paper P is detected as a reference, the rear end of the paper P is discharged from the transport roll 67 after the paper P has entered the alignment roll 68. The difference between the detection value of the load detection unit 114 and the reference in the period up to is integrated. For example, the average value of the detection results of the load detection unit 114 during the period when the thickness of the paper P is detected is calculated as a reference. Since the integration result changes according to the stiffness of the paper P, the integration result is a value indicating the stiffness. That is, a value representing the stiffness of the paper P is detected by calculating the area of the triangle indicated by the oblique lines shown in FIG. Note that the area of the triangle in FIG. 7 may be calculated using a method other than the product portion. The method for detecting the value representing the stiffness of the paper P is not limited to this. For example, when the rear end of the paper P is discharged from the transport roll 67 after the paper P enters the alignment roll 68. A value representing the stiffness may be detected by integrating the difference between the detection value of the load detection unit 114 and the reference with the value of the detection result of the load detection unit 114 as a reference. Alternatively, the inclination of the period from when the paper P enters the alignment roll 68 until the trailing edge of the paper P is discharged from the transport roll 67 may be calculated.

  In the present embodiment, parameters as variables when forming an image are corrected using values representing the thickness and stiffness of the paper P detected as described above. Since the value representing the stiffness of the paper P is related to the moisture content of the paper P, the moisture content of the paper P is obtained from the value representing the stiffness. For example, the moisture content of the paper P is obtained from the value representing the stiffness by obtaining the relationship between the stiffness of the paper P and the moisture content in advance through experiments or the like.

  Further, since the moisture content of the paper P is related to the transfer process, fixing process, and decurler process of image formation, the transfer voltage, the fixing temperature, and the decurler push-in amount are corrected according to the moisture content. For example, as shown in FIGS. 8A to 8C, the transfer voltage, the fixing temperature, and the decurler push-in amount are determined in advance according to the moisture content, so that each process is performed on the paper P. Correct according to the moisture content.

  Next, processing relating to image forming parameter correction performed by the image forming apparatus 10 according to the present embodiment configured as described above will be described. FIG. 9 is a flowchart showing a part of processing relating to setting of image forming parameters performed in the image forming apparatus 10 according to the present embodiment. Note that the processing in FIG. 9 is started when, for example, an instruction for image formation is given by the operation display unit 110 or the like.

  In step S100, the CPU 100 starts driving the motors M1, M0, etc., thereby starting the conveyance of the paper P, and proceeds to step S102. That is, the paper P stored in the paper storage unit 62 is sent out to the transport path 60 and transported to the alignment roll 68. In the present embodiment, the motor M1 is driven at a lower rotational speed than the motor M0, and the paper P is loosened between the transport roll 67 and the alignment roll 68.

  In step S102, the CPU 100 starts detecting the motor current by the load detection unit 114, and proceeds to step S104.

  In step S104, the CPU 100 detects a value indicating the stiffness of the sheet and the thickness based on the detection result of the load detection unit 114, and proceeds to step S106. For example, by integrating the detection results of the load detection unit 114 in a period from the time when the trailing edge of the paper P is discharged from the transport roll 67 to the time when the trailing edge of the paper P is discharged from the alignment roll 68, the paper P Detect the thickness. Further, based on the value of the detection result of the load detection unit 114 during the period when the thickness of the paper P is detected, the rear end of the paper P is discharged from the transport roll 67 after the paper P enters the alignment roll 68. A value representing the stiffness of the paper P is detected by integrating the difference between the detection value of the load detection unit 114 and the reference in the period up to.

  In step S106, the CPU 100 calculates correction values for various parameters relating to image formation, and proceeds to step S108. In the present embodiment, the moisture content of the paper P is calculated from a value representing stiffness, and the transfer voltage, the fixing temperature, and the decurler pressing amount corresponding to the calculated moisture content are calculated as examples of parameters.

  In step S108, the CPU 100 corrects the transfer voltage applied to the secondary transfer roll 22 so that the calculated transfer voltage is obtained, and the process proceeds to step S110.

  In step S110, the CPU 100 corrects the temperature of the heating belt 24A so that the calculated fixing temperature is reached, and the process proceeds to step S112.

  In step S <b> 112, the CPU 100 corrects the push amount of the decurler 25 so that the calculated decurler push amount is obtained, and ends the series of processes.

  In the present embodiment, various parameters (transfer voltage, fixing temperature, and decurler push-in amount) are corrected while the paper P is being transported, but the correction is not in time for the first paper P due to the process speed such as the transport speed. The correction is reflected on the next paper P.

  In the above embodiment, the load detection unit 114 detects the load of the motor M1 that drives the alignment roll 68 using the alignment roll 68 and the transport roll 67, and the sheet P is detected based on the detection result. Although values representing thickness and stiffness were calculated, the present invention is not limited to this. For example, the load detection unit 114 may detect the load of the motor that drives the fixing device 24 using the interval between transfer and fixing, and calculate values representing the thickness and stiffness of the paper P. The conveyance load of the paper P may be detected using the portion between the conveyance rolls, and values representing the thickness and stiffness of the paper P may be calculated.

  Further, in the above embodiment, based on the load of the motor M <b> 1 during the period from when the trailing edge of the sheet P is discharged from the transport roll 67 to when the trailing edge of the sheet P is discharged from the alignment roll 68, Although thickness was detected, it is not restricted to this. For example, the load detection unit 114 can detect the load of the motor M0, and after the end of the sheet P enters the transport roll 67 as a detection period different from the detection period for detecting the value indicating the stiffness of the sheet P. The thickness of the paper P may be detected based on the load of the motor M0 during the period until it enters the alignment roll 68.

  Further, the process (FIG. 9) performed in the image forming apparatus 10 according to the above-described embodiment may be a process performed by software, a process performed by hardware, or a process combining both. Also good. Further, the processing performed in the image forming apparatus 10 may be stored and distributed as a program in a storage medium.

  Further, the present invention is not limited to the above, and it is needless to say that various modifications can be made without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 67 Conveyance roll 68 Positioning roll 100 CPU
114 Load detector M1, M0 Motor

Claims (10)

Drives the transport of the first position in the transport unit that grips and transports the medium at two positions where the transport speed of the first position downstream of the transport direction of the medium is lower than the second transport speed upstream of the transport direction. A detecting unit for detecting a load of the driving unit,
A detection unit for detecting a value representing the stiffness of the medium using the detection result of the detection unit;
A device for detecting physical properties of media.   The detection unit detects a value representing the stiffness using a detection result of the detection unit during a period from when the leading edge of the medium enters the first position until the trailing edge of the medium is ejected from the second position. The medium property detecting device according to claim 1.   The detection unit is based on an average value of detection results of the detection unit in a section from when the rear end of the medium is ejected from the second position to when the rear end of the medium is ejected from the first position. The medium property detection device according to claim 2, wherein a value representing the stiffness is detected by integrating a difference between a reference and the load detected by the detection unit in the period.   The detection unit integrates a difference between the reference and the load detected by the detection unit during the period, based on a detection result of the detection unit when the rear end of the medium is ejected from the second position. The medium physical property detection apparatus according to claim 2, wherein a value representing the stiffness is detected.   The medium physical property detection apparatus according to claim 2, wherein the detection unit detects a value representing the stiffness from an inclination of a detection result of the detection unit in the period.   The sub detection part which detects the thickness of a medium further using the detection result of the said detection part in the detection period different from the detection period of the said detection part during the conveyance of the medium by the said conveyance part. The medium physical property detection apparatus according to any one of?   The sub-sensing unit uses the detection result of the detection unit in a section from when the rear end of the medium is ejected from the second position to when the rear end of the medium is ejected from the first position. The medium property detection device according to claim 6, wherein   The medium physical property detection device according to claim 7, wherein the sub detection unit detects the thickness of the medium by integrating or averaging the detection results of the detection unit in the section. The medium property detection device according to any one of claims 1 to 8,
An image forming unit for forming an image on a medium;
A correction unit that corrects a variable related to image formation by the image forming unit using the detection result of the detection unit;
An image forming apparatus.   The medium physical property detection program for functioning a computer as each part of the medium physical property detection apparatus of any one of Claims 1-8.