Stiffness measuring device, image forming system, and stiffness measuring method

Abstract

To provide a stiffness measuring device capable of measuring stiffness of a recording material such as paper with high precision, and an image forming system including the stiffness measuring device.SOLUTION: The stiffness measuring device comprises a holding section that holds a recording material so that a recording surface of the recording material is substantially parallel to a vertical direction, a pressing section, and a stiffness acquisition section. The pressing section presses a measurement point located vertically below a portion in the recording material held by the holding section. The stiffness acquisition section acquires the stiffness of the recording material by measuring a reaction force obtained when the measurement point is pressed by the pressing section.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a stiffness measuring apparatus, an image forming system, and a stiffness measuring method.

Background Art

[0002] In an image forming apparatus that forms an image on a sheet serving as a recording medium, a technique of detecting the stiffness of the sheet and setting various control parameters based on the detection result is known. Patent Document 1 describes a technique for detecting the stiffness of a sheet. The image forming apparatus described in Patent Document 1 presses a conveyed sheet against a lever, and detects the displacement amount of the lever at this time as the stiffness of the sheet.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0004] However, the image forming apparatus described in Patent Document 1 holds a sheet conveyed in the horizontal direction at a predetermined position and measures the stiffness of the sheet. Therefore, the measurement result of stiffness includes the influence of gravity acting on the sheet. Accordingly, there has been a problem that the stiffness of the sheet cannot be accurately measured.

[0005] To cancel the influence of gravity, for example, it is conceivable to lift the sheet by an amount corresponding to the sag caused by gravity. However, it is difficult to lift only the portion sagged by the influence of gravity with high accuracy. Further, as the distance from the sheet holding portion to the lever increases, the influence of gravity becomes greater, so it is also difficult to accurately grasp the influence of gravity that needs to be canceled.

[0006] The object of the present invention is to provide a stiffness measuring device capable of measuring the stiffness of recording materials such as paper with high precision, an image forming system equipped with the stiffness measuring device, and a method for measuring stiffness. [Means for solving the problem]

[0007] To achieve this objective, the stiffness measuring device of the present invention comprises a holding unit that holds a recording material in a position where the recording surface is substantially parallel to the vertical direction, a pressing unit, and a stiffness acquisition unit. , pressing part moving mechanism and The device includes the following: The pressing section presses the measurement point located vertically below the portion of the recording material that is held by the holding section. The stiffness acquisition section measures the reaction force obtained when the measurement point is pressed by the pressing section and acquires the stiffness of the recording material. The pressing mechanism moves the pressing part. The vertical position of the pressing part is changed according to the vertical length of the recording material.

[0008] The image forming system of the present invention comprises an image forming unit for forming an image on a recording material, a recording material storage unit capable of accommodating the recording material, a recording material transport path provided between the recording material storage unit and the image forming unit, the stiffness measuring device described above installed on the recording material transport path for measuring the stiffness of the recording material, and a control unit for setting image forming parameters according to the measurement results of the stiffness measuring device.

[0009] The stiffness measurement method of the present invention involves a holding unit that holds the recording material so that the recording surface of the recording material is substantially parallel to the vertical direction. Next, the pressing mechanism changes the vertical position of the pressing part according to the vertical length of the recording material. Next, the pressing unit presses the measurement point located vertically below the portion of the recording material that is held by the holding unit. Then, the stiffness acquisition unit measures the reaction force obtained when the pressing unit presses the measurement point and acquires the stiffness of the recording material. [Effects of the Invention]

[0010] According to the present invention, the stiffness of a recording material can be measured with high precision. [Brief explanation of the drawing]

[0011] [Figure 1] This figure shows a schematic configuration of an image forming system according to one embodiment of the present invention. [Figure 2]This is a system block diagram of an image forming system according to the first embodiment of the present invention. [Figure 3] This is a functional block diagram of the control unit in the image forming system according to the first embodiment of the present invention. [Figure 4] This figure shows a schematic configuration of a stiffness measuring device according to the first embodiment of the present invention. [Figure 5] This is a block diagram showing an example of the configuration of the control system of a stiffness measuring device according to the first embodiment of the present invention. [Figure 6] This flowchart shows the procedure for parameter setting processing of an image forming system according to the first embodiment of the present invention. [Figure 7] This figure shows a schematic configuration of a stiffness measuring device according to a second embodiment of the present invention. [Modes for carrying out the invention]

[0012] Embodiments to which the present invention is applied will be described in detail below with reference to the drawings. In this specification and the drawings, elements having substantially the same function or configuration are denoted by the same reference numerals, and redundant descriptions are omitted.

[0013] 1. First Embodiment Hereinafter, an image forming system according to the first embodiment of the present invention will be described with reference to Figures 1 to 6.

[0014] <Configuration of the image forming system> First, the configuration of an image forming system according to one embodiment will be described with reference to Figure 1. Figure 1 is a diagram showing a schematic configuration of an image forming system according to one embodiment.

[0015] As shown in Figure 1, the image forming system 10 includes a recording material supply device 100, a recording material transport device 400, an image forming apparatus 200, and a post-processing device 300.

[0016] When forming an image on a recording material S in an image forming system 10, first, the recording material S is supplied from a recording material supplying apparatus 100 to a recording material conveying apparatus 400. Then, the recording material conveying apparatus 400 conveys the recording material S to an image forming apparatus 200. The recording material conveying apparatus 400 includes a stiffness measuring apparatus 410 that measures the stiffness of the recording material S.

[0017] Next, the image forming apparatus 200 forms an image on the supplied recording material S. Then, the image forming apparatus 200 sends the recording material S on which an image has been formed to a post-processing apparatus 300. The post-processing apparatus 300 performs predetermined post-processing on the recording material S on which an image has been formed. Thereafter, the post-processing apparatus 300 discharges the recording material S.

[0018] [Recording Material Supplying Apparatus] The recording material supplying apparatus 100 accommodates recording materials S for image formation. When the recording material supplying apparatus 100 receives an image forming job from a control unit 90 described later of the image forming system 10, it supplies the recording material S corresponding to the image forming job to the recording material conveying apparatus 400. The recording material supplying apparatus 100 includes a conveying unit 50 and a recording material supplying unit 70.

[0019] The recording material supplying unit 70 includes a plurality of recording material accommodating portions. Recording materials S of different types and sizes are individually accommodated in the plurality of recording material accommodating portions. In the present embodiment, the recording material S is a recording medium on which an image is formed, for example, a sheet of paper. The recording material S may be a material other than paper as long as stiffness measurement can be performed thereon.

[0020] The conveying unit 50 includes a plurality of pick-up rollers (not shown) that pick up the recording material S from the recording material supplying unit 70, and a plurality of conveying rollers 54. The plurality of conveying rollers 54 are provided along a predetermined recording material conveying path. The plurality of conveying rollers 54 convey the recording materials S picked up from the recording material supplying unit 70 one by one to the recording material conveying apparatus 400.

[0021] [Recording Material Conveying Apparatus] The recording material transport device 400 includes an inlet 55, a first transport section 51, a second transport section 52, a third transport section 53, a discharge section 56, an outlet 57, a stiffness measuring device 410, and a recording material detection section 420.

[0022] The loading entrance 55 receives the recording material S supplied from the recording material supply device 100. The first transport section 51, the second transport section 52, and the third transport section 53 transport the recording material S received from the loading entrance 55 to the discharge section 56 or the discharge exit section 57. The first transport section 51, the second transport section 52, and the third transport section 53 are equipped with a plurality of transport rollers 54 for transporting the recording material S.

[0023] The stiffness measuring device 410 is a device for acquiring the stiffness of the recording material S. The stiffness of the recording material S is an index that indicates the resistance when the recording material S is bent, and can be expressed in various physical quantities. The recording material detection unit 420 detects when the recording material S has been transported to the position where the stiffness is to be measured (hereinafter referred to as the "stiffness measurement position").

[0024] The recording material transport device 400 has a branching section 58 that branches the transport path of the recording material S. The recording material transport device 400 has a first transport path 41 located upstream of the branching section 58 in the direction of transporting the recording material, and a second transport path 42 and a third transport path 43 located downstream of the branching section 58 in the direction of transporting the recording material.

[0025] The first transport path 41 is the path from the entrance 55 to the branching section 58. The first transport section 51 is provided along the first transport path 41. The first transport section 51 transports the recording material S along the first transport path 41. The recording material S transported along the first transport path 41 is guided to the second transport path 42 or the third transport path 43 by the branching section 58.

[0026] The second transport path 42 is the path from the branching section 58 to the discharge section 56. The second transport section 52 is provided along the second transport path 42. The second transport section 52 transports the recording material S along the second transport path 42. The stiffness measuring device 410 measures the stiffness of the recording material S when its transport is stopped midway along the second transport path 42. The recording material S whose stiffness has been measured is transported again along the second transport path 42 and discharged from the discharge section 56.

[0027] The third transport path 43 is the path from the branching section 58 to the discharge port 57. The third transport unit 53 is provided along the third transport path 43. The third transport unit 53 transports the recording material S along the third transport path 43. The recording material S transported along the third transport path 43 is discharged from the discharge port 57. The recording material S discharged from the discharge port 57 is supplied to the image forming apparatus 200.

[0028] [Image forming apparatus] The image forming apparatus 200 includes an operation display unit 220, a scanner 230, an image forming unit 240, and a transport unit 250.

[0029] The operation display unit 220 comprises an operation unit and a display unit. The display unit is composed of a display device such as an LCD (Liquid Crystal Display). The display unit displays various screens according to the instructions of the display signals input from the control unit 90 (see Figure 2), which will be described later. The operation unit comprises a touch panel formed to cover the display screen of the display unit, as well as various operation buttons such as number buttons and a start button. The operation unit receives operation instructions from the user. The operation unit outputs operation signals based on the user's operation to the control unit 90, which will be described later.

[0030] Scanner 230 is equipped with an automatic document feeder (ADF) and a document image scanning device (scanner). The automatic document feeder transports documents placed on the document tray via a transport mechanism and sends them to the document image scanning device. The document image scanning device optically scans documents transported onto the contact glass by the automatic document feeder, or documents placed on the contact glass by the user, and reads the image of the document by forming an image of the reflected light from the document on a light-receiving surface such as a CCD (Charge Coupled Device) sensor. Scanner 230 generates image data based on the reading results from the document image scanning device.

[0031] The image forming unit 240 forms an image on the recording material S based on the image data. The image forming unit 240 includes photosensitive drums 241Y, 241M, 241C, and 241K corresponding to yellow (Y), magenta (M), cyan (C), and black (K), charging units 242Y, 242M, 242C, and 242K, exposure units 243Y, 243M, 243C, and 243K, developing units 244Y, 244M, 244C, and 244K, and primary transfer rollers 245Y, 245M, 245C, and 245K. The image forming unit 240 also includes an intermediate transfer belt 246, a secondary transfer roller 247, and a fixing unit 248.

[0032] Hereafter, the photoreceptor drums 241Y, 241M, 241C, and 241K will be collectively referred to as "photoreceptor drum 241". The charging sections 242Y, 242M, 242C, and 242K will be collectively referred to as "charging section 242", and the exposure sections 243Y, 243M, 243C, and 243K will be collectively referred to as "exposure section 243". Furthermore, the developing sections 244Y, 244M, 244C, and 244K will be collectively referred to as "developing section 244", and the primary transfer rollers 245Y, 245M, 245C, and 245K will be collectively referred to as "primary transfer roller 245".

[0033] The photoreceptor drum 241 is an image carrier that holds the toner image. The photoreceptor drum 241 rotates according to the drive of a photoreceptor drive motor (not shown). Around the photoreceptor drum 241, the charging unit 242, the exposure unit 243, and the developing unit 244 are arranged in order from the upstream side to the downstream side in the direction of rotation of the photoreceptor drum 241. The charging unit 242 uniformly charges the photoreceptor drum 241.

[0034] The exposure unit 243 consists of a laser light source, a polygon mirror, a lens, and the like. The exposure unit 243 scans and exposes the surface of the photoreceptor drum 241 with a laser beam to form an electrostatic latent image. Scanning exposure by the exposure unit 243 is performed based on image data read by the scanner 230 or image data received from an external device.

[0035] The developing unit 244 develops the image by attaching toners of each color to the electrostatic latent image formed on the photoreceptor drum 241. As a result, a toner image is formed on the image-bearing surface of the photoreceptor drum 241. Specifically, yellow, magenta, cyan, and black toner images are formed on the image-bearing surfaces of the photoreceptor drums 241Y, 241M, 241C, and 241K, respectively.

[0036] The intermediate transfer belt 246 is stretched across multiple belt support rollers and arranged in a loop. A primary transfer roller 245, a secondary transfer roller 247, an anti-static roller (not shown), and a cleaning unit 249 are arranged along the movement path of the intermediate transfer belt 246.

[0037] The outer surface of the intermediate transfer belt 246 serves as the image-bearing surface. The outer surface of the intermediate transfer belt 246 is positioned in contact with the outer surface of the photoreceptor drum 241. The intermediate transfer belt 246 rotates in the opposite direction to the rotation of the photoreceptor drum 241. Specifically, the photoreceptor drum 241 rotates counterclockwise in Figure 1, and the intermediate transfer belt 246 rotates clockwise in Figure 1.

[0038] The primary transfer roller 245 is positioned opposite the photoreceptor drum 241. The primary transfer roller 245 is positioned on the inner circumference side of the intermediate transfer belt 246 and sandwiches the intermediate transfer belt 246 between itself and the opposing photoreceptor drum 241.

[0039] The primary transfer roller 245 applies a charge of opposite polarity to the toner to the intermediate transfer belt 246, thereby transferring the toner adhering to the image-bearing surface of the photoreceptor drum 241 to the image-bearing surface of the intermediate transfer belt 246 (primary transfer). As a result, a color toner image is formed on the image-bearing surface of the intermediate transfer belt 246, in which the four toner images are superimposed.

[0040] The secondary transfer roller 247 transfers the color toner image from the image-bearing surface of the intermediate transfer belt 246 onto one of the recording surfaces of the recording material S in one go (secondary transfer). The secondary transfer roller 247 sandwiches the intermediate transfer belt 246 between itself and the belt support roller. The position where the secondary transfer roller 247 and the belt support roller face each other is the transfer position where the toner image transferred to the image-bearing surface of the intermediate transfer belt 246 is transferred to the recording material S.

[0041] The cleaning unit 249 is positioned upstream of the primary transfer roller 245 and downstream of the static elimination roller (not shown) in the rotational direction of the intermediate transfer belt 246. The cleaning unit 249 removes toner remaining on the image-bearing surface of the intermediate transfer belt 246.

[0042] The fixing unit 248 comprises a fixing roller 248a and a pressure roller 248b. The fixing roller 248a has a built-in heater. The pressure roller 248b is pressed against the fixing roller 248a. As a result, the fixing roller 248a and the pressure roller 248b are pressed against each other, and a fixing nip is formed at this pressed portion. The recording material S is heated and pressurized as it passes through the fixing nip. This fixes the toner image transferred to the recording material S.

[0043] The transport unit 250 is equipped with a plurality of transport rollers 54 for transporting the recording material S along a predetermined transport path. The transport unit 250 transports the recording material S supplied from the recording material transport device 400 to the transfer position. The transport unit 250 also transports the recording material S after image formation to the post-processing device 300.

[0044] [Post-processing equipment] The post-processing device 300 receives the recording material S that has been image-formed in the image forming apparatus 200. The post-processing device 300 comprises a plurality of post-processing units, a transport unit 350, an discharge unit 351, and a paper output tray 352.

[0045] When the post-processing device 300 receives a post-processing job from the control unit 90 (described later), it performs predetermined post-processing in the post-processing unit specified by the post-processing job. Examples of post-processing include perforation, folding, foil stamping, binding, cutting, stapling, gluing, and stitching.

[0046] The transport unit 350 is equipped with a plurality of transport rollers (not shown) for transporting the recording material S along a predetermined transport path. The transport unit 350 transports the recording material S supplied from the image forming apparatus 200 to a post-processing unit corresponding to the type of post-processing to be performed. The transport unit 350 also transports the recording material S after post-processing and discharges it from the discharge unit 351. The recording material S discharged from the discharge unit 351 is placed on the output tray 352.

[0047] <System Block Diagram> Next, an example of the configuration of the control system of the image forming system 10 will be explained with reference to Figure 2. Figure 2 is a system block diagram of the image forming system 10.

[0048] As shown in Figure 2, the image forming system 10 comprises a control unit 90, a storage unit 98, a communication unit 99, an operation display unit 220, a scanner 230, an image processing unit 80, a recording material supply unit 70, an image forming unit 240, a stiffness measuring device 410, a recording material detection unit 420, and transport units 51, 52, 53, 250, and 350. In the following description, components that overlap with the description of the image forming system 10 shown in Figure 1 above will be omitted.

[0049] The control unit 90 is composed of, for example, a CPU (Central Processing Unit) 91, a ROM (Read Only Memory) 92, a RAM (Random Access Memory) 93, etc. The CPU 91 reads various processing programs stored in the ROM 92 and loads them into the RAM 93, and centrally controls the operation of each part of the image forming system 10 according to the loaded programs.

[0050] ROM92 stores various processing programs for controlling each part of the image forming system 10, parameters and table data necessary for executing these programs, and various files.

[0051] RAM93 is composed of volatile semiconductor memory. RAM93 forms a work area that temporarily stores various processing programs, input or output data, and parameters read from ROM92 during various processes controlled by the CPU91.

[0052] The storage unit 98 stores, for example, image data received from an external device. The storage unit 98 also stores various processing programs executed by the CPU 91, information regarding the processing functions of the device necessary for executing the programs, image data read by the scanner 230, image data input from a client device (not shown), and the stiffness of the recording material S measured by the stiffness measuring device 410. The storage unit 98 may be composed of, for example, a non-volatile memory such as an HDD (Hard Disk Drive), an SSD (Solid State Drive), or flash memory.

[0053] The communication unit 99 consists of a NIC (Network Interface Card), a modem, and other components. The communication unit 99 connects the recording material supply device 100, the recording material transport device 400, the image forming apparatus 200, the post-processing device 300, and the stiffness measuring device 410 to a communication network such as a LAN (Local Area Network) or WAN (Wide Area Network). The communication unit 99 then transmits and receives various types of data between each device and external information devices (e.g., client devices).

[0054] As described above, the operation display unit 220 functions as both a display unit and an operation unit. The display unit displays various operation screens according to the display control signals input from the control unit 90. The operation unit receives various input operations from the user and outputs operation signals corresponding to those input operations to the control unit 90.

[0055] The scanner 230 outputs the scanned image (analog image signal) to the image processing unit 80.

[0056] The image processing unit 80 consists of circuits that perform analog-to-digital (A / D) conversion and circuits that perform digital image processing. The image processing unit 80 performs A / D conversion on the analog image signal supplied from the scanner 230 to generate digital image data. The image processing unit 80 also analyzes print jobs acquired from external information devices (e.g., client devices) and rasterizes each page of the original document to generate digital image data. Furthermore, the image processing unit 80 performs image processing on the image data as needed, such as color conversion, correction processing according to initial settings or user settings (e.g., shading correction), and compression processing. The image processing unit 80 outputs the processed image data to the image forming unit 240.

[0057] The stiffness measuring device 410 is installed in the recording material transport device 400 (see Figure 1). When the stiffness measuring device 410 receives a stiffness measurement signal output by the control unit 90, it measures the stiffness of the recording material S. The stiffness measuring device 410 also outputs the measurement result to the control unit 90.

[0058] The recording material detection unit 420 is provided in the recording material transport device 400 (see Figure 1). The recording material detection unit 420 detects when the recording material S is placed at the stiffness measurement position. The recording material detection unit 420 outputs the detection result to the control unit 90.

[0059] <Functional Configuration of the Control Unit> Next, the functional configuration of the control unit 90 will be explained with reference to Figure 3. Figure 3 is a functional block diagram of the control unit 90.

[0060] As shown in Figure 3, the control unit 90 includes a paper feeding control unit 94, a transport control unit 95, a stiffness acquisition control unit 96, and an image forming control unit 97.

[0061] The paper feed control unit 94 controls the supply of recording material S from the recording material supply unit 70 to the transport unit 50 in the recording material supply device 100. The paper feed control unit 94 supplies the recording material S to the transport unit 50 in accordance with the transport control of the recording material S by the transport control unit 95.

[0062] The transport control unit 95 controls the drive of the transport units 50, 51, 52, 53, 250, and 350 provided in the recording material supply device 100, recording material transport device 400, image forming apparatus 200, and post-processing device 300. As a result, the recording material S is transported to various locations in the image forming system 10. The transport control unit 95 also controls the transport mechanism, such as the branching section 58 of the recording material transport device 400, to change the transport path of the recording material S.

[0063] When transporting multiple recording materials S according to an image forming job, the transport control unit 95 guides at least one recording material S to the second transport path 42 (the path transported by the second transport unit 52) ​​of the recording material transport device 400. The transport control unit 95 then controls the second transport unit 52 to position the recording material S at the stiffness measurement position in the second transport path 42. The stiffness of the recording material S positioned at the stiffness measurement position is measured by the stiffness measuring device 410.

[0064] The transport control unit 95 corrects the control parameters related to the transport of the recording material S according to the rigidity of the recording material S. A specific example of the transport control parameters is the transport speed of the recording material S.

[0065] The stiffness acquisition control unit 96 controls the stiffness measuring device 410. Specifically, the stiffness acquisition control unit 96 controls the drive of the recording material pressing motor 451 (see Figure 5), which will be described later, of the stiffness measuring device 410. The stiffness acquisition control unit 96 also acquires the detection result of the pressing force detection unit 432, which will be described later, of the stiffness measuring device 410.

[0066] The image forming control unit 97 controls the image forming operation of the image forming unit 240. The image forming control unit 97 also determines control parameters related to image forming according to the stiffness of the recording material S measured by the stiffness measuring device 410. Specific examples of control parameters related to image forming include the charging potential by the charging unit 242, the transfer current supplied to the primary transfer roller 245 and the secondary transfer roller 247, and the fixing temperature and fixing pressure in the fixing unit 248.

[0067] <Configuration of the stiffness measuring device> Next, the configuration of the stiffness measuring device 410 will be explained with reference to Figures 4 and 5. Figure 4 shows a schematic configuration of the stiffness measuring device 410.

[0068] As shown in Figure 4, the stiffness measuring device 410 is installed in the second transport path 42 through which the second transport unit 52 transports the recording material S. In the second transport path 42, the transport direction of the recording material S is the vertical direction Z. Therefore, the stiffness measuring device 410 measures the stiffness of the recording material S while it is being transported in the vertical direction Z.

[0069] Hereinafter, the transport direction of the recording material S will be defined as the vertical direction Z. Furthermore, the direction perpendicular to the recording surface of the recording material S being transported in the second transport path 42 will be defined as the horizontal direction Y, and the direction perpendicular to the vertical direction Z and the horizontal direction Y will be defined as the width direction of the recording material X.

[0070] The stiffness measuring device 410 includes a recording material holding unit 411 that holds the recording material S, and a stiffness measuring unit 412 that measures the stiffness of the recording material S held by the recording material holding unit 411.

[0071] The recording material holding section 411 includes a pair of holding rollers 421a and 421b, a roller drive section 422, and a biasing spring 423.

[0072] The rotation axes of the pair of holding rollers 421a and 421b are parallel to the recording material width direction X. Preferably, the pair of holding rollers 421a and 421b also serve as conveying rollers. The roller drive unit 422 rotates the holding roller 421a. The roller drive unit 422 consists of a motor 424 for the holding roller and a gear train 425 that transmits the rotation of the motor 424 to the holding roller 421a.

[0073] The biasing spring 423 biases the retaining roller 421b toward the retaining roller 421a. The pair of retaining rollers 421a and 421b hold the recording material S by clamping it with a predetermined pressure. The pair of retaining rollers 421a and 421b hold the recording material S in a position where the recording surface is approximately parallel to the vertical direction Z.

[0074] The recording material detection unit 420 described above is located in the second transport path 42. The recording material detection unit 420 detects the lower end of the recording material S when it is placed at the stiffness measurement position. The recording material detection unit 420 outputs the detection result (detection result) that the lower end of the recording material S has been detected to the control unit 90 (see Figure 2). As a result, the control unit 90 detects that the recording material S has been placed at the stiffness measurement position.

[0075] The stiffness measuring unit 412 is located below the pair of holding rollers 421a and 421b in the recording material holding unit 411. The stiffness measuring unit 412 comprises a pressing unit 431, a pressing force detection unit 432, a support mechanism 433, a moving mechanism 434, a home position sensor 435, and a frame 436. The support mechanism 433, the moving mechanism 434, and the home position sensor 435 are provided within the frame 436.

[0076] The pressing section 431 presses the lower end of the recording material S. The pressing section 431 has a blade 431a and a base 431b that is continuous with one end of the blade 431a in the horizontal direction Y. The blade 431a is formed in a long, plate-like shape that is long in the recording material width direction X so that it can contact the entire width of the recording material S as it is conveyed in the vertical direction Z. The blade 431a contacts a position (measurement point) that is a specific distance above the lower end of the recording material S in the vertical direction Z. That is, the measurement point is located vertically below the portion of the recording material S that is held by the recording material holding section 411.

[0077] The pressing force detection unit 432 is connected to the surface of the base 431b of the pressing unit 431 that is opposite to the surface continuous with the blade 431a. The pressing force detection unit 432 detects the pressing force when the pressing unit 431 is pressed in the horizontal direction. That is, the pressing force detection unit 432 detects the pressing force when the pressing unit 431 presses and bends the recording material S. For example, a load cell (pressure sensor) can be used as the pressing force detection unit 432.

[0078] The support mechanism 433 supports the pressing section 431 and the pressing force detection section 432 so that they can move in the horizontal direction Y. The support mechanism 433 includes a detection section holding member 441, a stopper member 442, a worm gear 443, and a biasing spring 444. The detection section holding member 441 and the stopper member 442 are attached to the frame 436.

[0079] The detection unit holding member 441 is supported on the frame 436 so as to be movable in the horizontal direction Y. The frame 436 is also provided with a locking part (not shown) that locks the rotation of the detection unit holding member 441 around an axis extending in the horizontal direction Y. The detection unit holding member 441 holds the pressing force detection unit 432. The side of the pressing force detection unit 432 opposite to the side connected to the pressing part 431 is connected to the detection unit holding member 441.

[0080] The abutment member 442 faces the detection unit holding member 441 in the horizontal direction Y. The abutment member 442 is fixed to the frame 436. The abutment member 442 also rotatably supports one end of the worm gear 443.

[0081] The rotation axis of the worm gear 443 extends in the horizontal direction Y. The movement of the worm gear 443 in the horizontal direction Y is locked by the abutment member 442. The other end of the worm gear 443 is screwed into the detection unit holding member 441. As a result, when the worm gear 443 rotates, the detection unit holding member 441 moves horizontally.

[0082] The biasing spring 444 is connected to the detection unit holding member 441 and the abutment member 442. It biases the detection unit holding member 441 toward the abutment member 442. For example, a tension coil spring or a compression coil spring can be used as the biasing member 444.

[0083] Backlash occurs between the detection unit holding member 441 and the worm gear 443. Therefore, the detection unit holding member 441 can move slightly in the horizontal direction Y regardless of the rotation of the worm gear 443. In this embodiment, since a biasing spring 444 is provided, the detection unit holding member 441 does not move toward the abutment member 442 due to the effect of backlash. This prevents the detection unit holding member 441 (pressing part 431) from shifting toward the abutment member 442 when measuring the stiffness of the recording material S. As a result, the stiffness of the recording material S can be measured with high accuracy.

[0084] The moving mechanism 434 moves the pressing part 431 in the horizontal direction Y via the support mechanism 433. The moving mechanism 434 consists of a recording material pressing motor 451 and a gear train 452 that transmits the rotation of the recording material pressing motor 451 to a worm gear 443. The recording material pressing motor 451 can be, for example, a stepping motor.

[0085] The home position sensor 435 detects the home position of the detection unit holding member 441 (pressing unit 431). The home position of the pressing unit 431 is the position where the pressing unit 431 begins to contact the recording surface of the recording material S. The home position sensor 435 detects the home position of the pressing unit 431 from the position of the detection unit holding member 441.

[0086] The home position of the pressing unit 431 varies depending on the thickness of the recording material S. The correspondence between the thickness of the recording material S and the home position can be determined using table data stored in the storage unit 98 beforehand. The pressing force detection unit 432 detects the pressing force received from the recording material S when the pressing unit 431 moves a predetermined amount from the home position towards the recording material S in the horizontal direction Y.

[0087] The stiffness measuring device 410 has a measuring unit movement mechanism (not shown) that moves the stiffness measuring unit 412 in the vertical direction Z. The measuring unit movement mechanism corresponds to the pressing unit movement mechanism according to the present invention. The position of the pressing unit 431 in the vertical direction Z described above is changed according to the vertical length of the recording material S (length along the transport direction).

[0088] Specifically, the measuring unit movement mechanism moves the stiffness measuring unit 412 (pressing unit 431) in the vertical Z direction so that the blade 431a contacts a specific distance above the lower end of the recording material S in the vertical Z direction. This allows the blade 431a to press on the same measurement point at the same distance from the lower end of each recording material S when measuring the stiffness of multiple types of recording materials S with different lengths in the vertical Z direction. As a result, the stiffness of multiple types of recording materials S with different lengths in the vertical Z direction can be measured under the same conditions.

[0089] Furthermore, the pressing part movement mechanism according to the present invention may be a mechanism that moves the pressing part 431 and the pressing force detection part 432 on the detection part holding member 441. In addition, the stiffness measuring device according to the present invention may be configured such that the blade 431a contacts a position a specific distance above the lower end of the recording material S in the vertical direction Z by moving a pair of holding rollers 421a and 421b (holding parts) in the vertical direction.

[0090] <Functional Configuration of the Stiffness Measurement Device> Next, the functional configuration of the stiffness measuring device 410 will be explained with reference to Figure 5. Figure 5 is a block diagram showing an example of the configuration of the control system of the stiffness measuring device 410.

[0091] As shown in Figure 5, the stiffness measuring device 410 includes a holding roller motor 424, a pressing force detection unit 432, a home position sensor 435, and a recording material pressing motor 451. The holding roller motor 424, the pressing force detection unit 432, the home position sensor 435, and the recording material pressing motor 451 are connected to the control unit 90 by wire or wireless.

[0092] The motor 424 for the holding roller, the pressing force detection unit 432, the home position sensor 435, and the motor 451 for pressing the recording material are controlled by the stiffness acquisition control unit 96 of the control unit 90. If the pair of holding rollers 421a and 421b (see Figure 5) also serve as transport rollers, the motor 424 for the holding roller may be controlled by the transport control unit 95 (see Figure 3).

[0093] The stiffness measuring device 410 acquires the stiffness of the recording material S by operating as follows. First, the stiffness acquisition control unit 96 of the control unit 90 detects that the recording material S has been placed at the stiffness measurement position based on the detection result from the recording material detection unit 420 (see Figure 5). Then, the stiffness acquisition control unit 96 controls the drive of the holding roller motor 424 to hold the recording material S, which has been placed at the stiffness measurement position, with the pair of holding rollers 421a and 421b. At this time, the pair of holding rollers 421a and 421b hold the recording material S across its entire width in the recording material width direction X.

[0094] The recording material S, held by the pair of holding rollers 421a and 421b, is positioned so that its recording surface is approximately perpendicular to the horizontal direction Y. This ensures that the direction of pressure applied to the recording material S is the horizontal direction Y, minimizing the influence of gravity when applying pressure to the recording material S. As a result, the rigidity of the recording material S can be measured with high precision.

[0095] Next, the stiffness acquisition control unit 96 controls the drive of the recording material pressing motor 451 to move the pressing unit 431 and the pressing force detection unit 432 in the horizontal direction Y via the detection unit holding member 441. As a result, the pressing unit 431 begins to contact the recording surface of the recording material S. At this time, the home position sensor 435 detects the position of the detection unit holding member 441 and outputs the detection result to the control unit 90. As a result, the stiffness acquisition control unit 96 detects the home position of the pressing unit 431 (detection unit holding member 441).

[0096] Next, the stiffness acquisition control unit 96 controls the drive of the recording material pressing motor 451 to move the pressing unit 431 from the home position to a predetermined distance (for example, 3 mm). As a result, the pressing unit 431 presses and bends the recording material S. At this time, the pressing force detection unit 432 detects the pressing force received from the recording material S and outputs it to the control unit 90. As a result, the stiffness acquisition control unit 96 acquires the pressing force detected by the pressing force detection unit 432 as the stiffness of the recording material S.

[0097] After acquiring the stiffness of the recording material S, the stiffness acquisition control unit 96 releases the pressing state of the recording material S by the pressing unit 431. That is, the stiffness acquisition control unit 96 controls the drive of the recording material pressing motor 451 to move the pressing unit 431 from the home position toward the abutment member 442 (see Figure 5). This releases the pressing state of the recording material S by the pressing unit 431.

[0098] <Parameter setting process> Next, the parameter setting process of the image forming system 10 according to this embodiment will be described with reference to Figure 6. Figure 6 is a flowchart showing the procedure for setting the parameters of the image forming system 10.

[0099] First, when a print job is started, the transport control unit 95 controls the drive of the transport unit 50 to take out the recording material S specified in the print job from the recording material supply unit 70. Then, the transport control unit 95 controls the drive of the first transport unit 51 and the second transport unit 52 to transport the recording material S along the second transport path 42 of the recording material transport device 400 (S1).

[0100] Next, when the lower end of the recording material S is detected by the recording material detection unit 420 in the second transport path 42, the transport control unit 95 controls the drive of the second transport unit 52 to stop the transport of the recording material S (S2). As a result, the recording material S stops at the stiffness measurement position. Then, the stiffness acquisition control unit 96 stops the drive of the holding roller motor 424 and holds the recording material S positioned at the stiffness measurement position with the pair of holding rollers 421a and 421b.

[0101] Next, the stiffness acquisition control unit 96 operates the stiffness measuring unit 412 of the stiffness measuring device 410 to acquire the stiffness of the recording material S (S3). At this time, the stiffness acquisition control unit 96 controls the drive of the recording material pressing motor 451 so that the recording material S is pressed in the horizontal direction Y by the pressing unit 431. Then, the pressing force detection unit 432 detects (measures) the pressing force received from the recording material S which has been bent by the pressing unit 431, and the stiffness acquisition control unit 96 takes in the detection result. In this way, the stiffness of the recording material S is obtained.

[0102] Next, the transport control unit 95 controls the drive of the second transport unit 52 to discharge the recording material S whose stiffness has been measured from 56 (S4). At this time, the stiffness acquisition control unit 96 drives the holding roller motor 424 to release the holding of the recording material S by the pair of holding rollers 421a and 421b.

[0103] Next, the control unit 90 sets control parameters based on the stiffness of the recording material S (step S5). The correspondence between the stiffness of the recording material S and the control parameters can be determined using table data that has been previously stored in the storage unit 98. That is, the control unit 90 reads the control parameters corresponding to the measured stiffness of the recording material S from the storage unit 98.

[0104] The control parameters to be set include at least one of the following parameters: recording material transport parameters, recording material curl correction parameters, image formation parameters, and post-processing parameters.

[0105] Specific examples of recording material transport parameters include transport speed. Specific examples of recording material curl correction parameters include the pressure applied to the recording material by the curl correction roller and the contact time between the curl correction roller and the recording material. Specific examples of image formation parameters include the charging potential by the charging unit 242, the transfer current supplied to the primary transfer roller 245 and secondary transfer roller 247, and the fixing temperature and fixing pressure in the fixing unit 248. Specific examples of post-processing parameters include the stapling pressure for stapling and the drive torque for paper folding.

[0106] The transport parameters and curl correction parameters are set by the transport control unit 95. The image forming parameters are set by the image forming control unit 97. The post-processing parameters are set by the post-processing control unit (not shown) provided in the control unit 90. Note that the control parameters set in step S5 may be other control parameters than those listed here.

[0107] 2. Second Embodiment Hereinafter, a stiffness measuring device according to a second embodiment of the present invention will be described with reference to Figure 7. Figure 7 shows a schematic configuration of the stiffness measuring device according to the second embodiment.

[0108] As shown in Figure 7, the stiffness measuring device 470 according to the second embodiment is provided in the second transport path 42 through which the second transport unit 52 transports the recording material S. The stiffness measuring device 470 measures the stiffness of the recording material S while it is being transported in the vertical direction Z. The stiffness measuring device 470 includes a recording material holding unit 411 that holds the recording material S, and a pair of stiffness measuring units 412A and 412B that measure the stiffness of the recording material S held by the recording material holding unit 411.

[0109] The configuration of the recording material holding section 411 is the same as that of the recording material holding section 411 according to the first embodiment, so its description is omitted. The pair of stiffness measuring sections 412A and 412B face each other in the horizontal direction Y with the recording material S placed at the stiffness measuring position in between. The configuration of the pair of stiffness measuring sections 412A and 412B is the same as that of the stiffness measuring section 412 according to the first embodiment, so its description is omitted.

[0110] The recording material S has a first recording surface (e.g., the front surface) and a second recording surface (e.g., the back surface). The stiffness measuring unit 412A faces the second recording surface of the recording material S. The stiffness measuring unit 412A presses against the second recording surface of the recording material S to measure the stiffness of the first recording surface of the recording material S. The pressing unit 431 of the stiffness measuring unit 412A corresponds to the first pressing unit according to the present invention. The pressing force detection unit 432 of the stiffness measuring unit 412A corresponds to the first stiffness acquisition unit according to the present invention.

[0111] The stiffness measuring unit 412B faces the first recording surface of the recording material S. The stiffness measuring unit 412B presses against the first recording surface of the recording material S to measure the stiffness of the second recording surface of the recording material S. The pressing unit 431 of the stiffness measuring unit 412B corresponds to the second pressing unit according to the present invention. The pressing force detection unit 432 of the stiffness measuring unit 412B corresponds to the second stiffness acquisition unit according to the present invention.

[0112] The stiffness measuring device 470 according to the second embodiment can measure the stiffness of the first recording surface and the second recording surface of the recording material S placed at the stiffness measuring position. Therefore, it is effective, for example, when performing a print job that performs double-sided printing.

[0113] If it is desired to measure the stiffness of the first recording surface and the second recording surface of a recording material S using a single stiffness measuring unit, it is necessary to invert the recording material S and transport it back to the stiffness measuring position. In contrast, the stiffness measuring device 470 according to the second embodiment does not require inverting the recording material S, and the time required to measure the stiffness of the first recording surface and the second recording surface of the recording material S can be shortened.

[0114] 3. Variant In the stiffness measuring devices 410 and 470 of the first and second embodiments, the pressing unit 431 is configured to press the measurement location of the recording material S. However, the pressing unit according to the present invention may be connected to the measurement location of the recording material S and pull the recording material S. In this case, the stiffness acquisition unit detects the reaction force (tensile force) when the recording material S is pulled. In this case as well, the stiffness of the recording material S can be measured. Examples of pressing units that connect to the measurement location of the recording material include those formed in the shape of a frame with a through hole through which the lower end of the recording material passes, and those having a suction unit that sucks up the recording material.

[0115] Furthermore, the pressing unit according to the present invention may be configured to be able to press the measurement location on the recording material S and also be able to pull the measurement location on the recording material S. In this case, the stiffness acquisition unit detects the reaction force (pressing force) when the recording material S is pressed and the reaction force (tensile force) when the recording material S is pulled. As a result, the stiffness of the first recording surface and the second recording surface of the recording material S can be measured using a single pressing unit without having to invert the recording material S.

[0116] 4. Summary As described above, the stiffness measuring device 410 according to the first embodiment comprises a recording material holding unit 411 (holding unit), a pressing unit 431, and a pressing force detection unit 432 (stiffness acquisition unit). The recording material holding unit 411 holds the recording material S in a position where the recording surface is substantially parallel to the vertical direction Z. The pressing unit 431 presses the measurement point on the recording material S located below the portion held by the recording material holding unit 411 in the vertical direction Z. The pressing force detection unit 432 obtains the stiffness of the recording material S by measuring the reaction force obtained when the measurement point is pressed by the recording material holding unit 411. This allows the stiffness of the recording material S to be obtained while minimizing the effects of gravity. As a result, the stiffness of the recording material S can be measured with high accuracy.

[0117] Furthermore, the measurement location according to the first embodiment described above is the end of the recording material S. This minimizes the effects of gravity.

[0118] Furthermore, the pressing portion 431 according to the first embodiment described above presses the measurement location in the horizontal direction Z. This allows for reliable pressing of the recording material S with the recording surface positioned approximately parallel to the vertical direction Z. Furthermore, the relationship between the pressing distance and the reaction force of the recording material S can be accurately obtained. As a result, the reaction force of the recording material S can be accurately detected.

[0119] Furthermore, the recording material holding unit 411 according to the first embodiment described above keeps the recording material S in a stationary state. This allows for accurate detection of the reaction force of the recording material S.

[0120] Furthermore, the stiffness measuring device 410 according to the first embodiment described above includes a pressing part moving mechanism for moving the pressing part 431. The position of the pressing part 431 in the vertical direction Z is changed according to the length of the recording material S in the vertical direction Z. This allows the pressing unit 431 to press on the same measurement point at the same distance from the lower end of each recording material S when measuring the stiffness of multiple types of recording materials S with different lengths in the vertical Z direction. As a result, the stiffness of multiple types of recording materials S with different lengths in the vertical Z direction can be measured under the same conditions.

[0121] Furthermore, the pressing unit in the modified example described above may press the measurement point or connect to the measurement point and pull on the measurement point. The stiffness acquisition unit in the modified example measures the reaction force when the pressing unit presses and pulls on the measurement point, and acquires the stiffness of both recording surfaces of the recording material. This allows the rigidity of both recording surfaces of a recording material to be measured using a single pressing unit, without having to invert the recording material.

[0122] Furthermore, the stiffness measuring device 470 according to the second embodiment described above includes a pressing section 431 (first pressing section) of a stiffness measuring unit 412A that presses the first recording surface of the recording material S, and a pressing section 431 (second pressing section) of a stiffness measuring unit 412B that presses the second recording surface of the recording material S. The stiffness measuring device 470 also includes a pressing force detection section 432 (first stiffness acquisition section) of a stiffness measuring unit 412B that measures the reaction force via the pressing section 431 of the stiffness measuring unit 412A, and a pressing force detection section 432 (second stiffness acquisition section) of a stiffness measuring unit 412B that measures the reaction force via the pressing section 431 of the stiffness measuring unit 412B. The stiffness of the first recording surface and the stiffness of the second recording surface of the recording material S are then acquired. This makes it possible to obtain the stiffness of the first and second recording surfaces without inverting the recording material S. As a result, the time required to measure the stiffness of the first and second recording surfaces of the recording material S can be reduced.

[0123] Furthermore, the image forming system 10 according to the first embodiment described above includes an image forming unit 240 for forming an image on a recording material S, a recording material supply unit 70 (recording material storage unit) capable of accommodating the recording material, and a second transport path 42 (recording material transport path) provided between the recording material supply unit 70 and the image forming unit 240. In addition, the image forming system 10 includes a stiffness measuring device 410 installed in the second transport path 42 for measuring the stiffness of the recording material S, and a control unit 90 for setting image forming parameters according to the measurement results of the stiffness measuring device 410. The stiffness measuring device 410 includes a recording material holding unit 411 (holding unit), a pressing unit 431, and a pressing force detection unit 432 (stiffness acquisition unit). The recording material holding unit 411 holds the recording material S in a position where the recording surface is substantially parallel to the vertical direction Z. The pressing unit 431 presses a measurement point located vertically Z below the portion of the recording material S held by the recording material holding unit 411. The pressing force detection unit 432 measures the reaction force obtained when the recording material holding unit 411 presses the measurement point and obtains the stiffness of the recording material S. This allows the stiffness of the recording material S to be obtained while minimizing the effects of gravity. As a result, the stiffness of the recording material S can be measured with high accuracy.

[0124] Furthermore, in the stiffness measurement method according to the first embodiment described above, a recording material S is held by a recording material holding unit 411 (holding unit) in a position where the recording surface is approximately parallel to the vertical direction, and a pressing unit 431 presses a measurement point located below the portion of the recording material S held by the recording material holding unit 411 in the vertical direction Z. Then, a pressing force detection unit 432 (stiffness acquisition unit) measures the reaction force obtained when the measurement point is pressed by the pressing unit 431 and acquires the stiffness of the recording material S. This allows the stiffness of the recording material S to be obtained while minimizing the effects of gravity. As a result, the stiffness of the recording material S can be measured with high accuracy.

[0125] The embodiments of the stiffness measuring device and image forming system of the present invention, including their effects, have been described above. However, the stiffness measuring device and image forming system of the present invention are not limited to the embodiments described above, and various modifications can be made without departing from the gist of the invention as described in the claims.

[0126] Furthermore, the embodiments described above are explained in detail for the purpose of clearly illustrating the present invention, and are not necessarily limited to those comprising all the described configurations. It is also possible to replace parts of the configuration of one embodiment with those of another embodiment, and to add configurations from other embodiments to the configuration of one embodiment. Additionally, it is possible to add, delete, or replace parts of the configuration of each embodiment with those of other embodiments.

[0127] For example, the image forming system 10 of the above-described embodiment is configured to have a stiffness measuring device 410 installed on the recording material transport device 400. However, the location where the stiffness measuring device according to the present invention is installed can be appropriately set as long as it is upstream of the image forming unit in the direction of transport of the recording material. The stiffness measuring device according to the present invention may be installed, for example, on the image forming apparatus 200 or the recording material supply device 100. [Explanation of Symbols]

[0128] 10…Image forming system, 41…First transport path, 42…Second transport path, 43…Third transport path, 50…Transportation unit, 51…First transport unit, 52…Second transport unit, 53…Third transport unit, 54…Transport roller, 55…Inlet, 56…Outlet, 57…Outlet, 58…Branching unit, 70…Recording material supply unit, 80…Image processing unit, 90…Control unit, 91…CPU, 92…ROM, 93…RAM, 94…Paper feeding control unit, 95…Transportation control unit, 96…Stiffness acquisition control unit, 97…Image forming control unit, 98…Storage unit, 99…Communication unit, 100…Recording material supply device, 200…Image forming device, 220…Operation display unit, 230…Scanner, 240…Image forming unit, 300…Post-processing device, 400…Recording material transport device, 410, 470…Stiffness measuring device, 411…Recording material holding unit, 412, 412A, 412B…Stiffness measuring unit, 420…Recording material detection unit, 421a, 421b…Holding roller, 422…Roller drive unit, 424…Motor for holding roller, 425…Gear train, 431…Pressing unit, 431a…Blade, 431b…Base, 432…Pressing force detection unit, 433…Support mechanism, 434…Moving mechanism, 435…Home position sensor, 436…Frame, 441…Detection unit holding member, 442…Butt member, 443…Worm gear, 444…Biasing member, 451…Motor for pressing recording material, 452…Gear train

Claims

1. A holding part that holds the recording material so that the recording surface of the recording material is substantially parallel to the vertical direction, A pressing part that presses on a measurement point located vertically below the portion of the recording material that is held by the holding part, A stiffness acquisition unit that obtains the stiffness of the recording material by measuring the reaction force obtained when the measurement location is pressed by the pressing unit, The system includes a pressing mechanism for moving the pressing portion, The vertical position of the pressing portion is changed according to the vertical length of the recording material. Stiffness measuring device.

2. The measurement location is the end of the recording material. The stiffness measuring device according to claim 1.

3. The pressing part presses the measurement location in a horizontal direction. The stiffness measuring device according to claim 1.

4. The holding unit holds the recording material in a stationary state. The stiffness measuring device according to claim 1.

5. The pressing part may press the measurement point or connect to the measurement point and pull the measurement point. The stiffness acquisition unit measures the reaction force when the pressing unit presses and pulls on the measurement point, respectively, and acquires the stiffness of both recording surfaces of the recording material. The stiffness measuring device according to claim 1.

6. The pressing portion includes a first pressing portion that presses the first recording surface of the recording material and a second pressing portion that presses the second recording surface of the recording material. The stiffness acquisition unit includes a first stiffness acquisition unit that measures the reaction force via the first pressing unit, and a second stiffness acquisition unit that measures the reaction force via the second pressing unit, and acquires the stiffness of the first recording surface and the stiffness of the second recording surface. The stiffness measuring device according to claim 1.

7. An image forming unit that forms an image on the recording material, A recording material storage section capable of accommodating the aforementioned recording material, A recording material transport path is provided between the recording material storage section and the image forming section, A stiffness measuring device is installed on the recording material transport path and measures the stiffness of the recording material, The system includes a control unit that sets image forming parameters according to the measurement results of the stiffness measuring device, The stiffness measuring device is, A holding part that holds the recording material such that the recording surface of the recording material is substantially parallel to the vertical direction, A pressing part that presses on a measurement point located vertically below the portion of the recording material that is held by the holding part, A stiffness acquisition unit that obtains the stiffness of the recording material by measuring the reaction force obtained when the measurement location is pressed by the pressing unit, The system includes a pressing mechanism for moving the pressing portion, The vertical position of the pressing portion is changed according to the vertical length of the recording material. Image forming system.

8. The holding part holds the recording material so that the recording surface of the recording material is substantially parallel to the vertical direction. The pressing mechanism changes the vertical position of the pressing part according to the vertical length of the recording material. The pressing portion presses a measurement point located vertically below the portion of the recording material that is held by the holding portion. The stiffness acquisition unit obtains the stiffness of the recording material by measuring the reaction force obtained when the measurement point is pressed by the pressing unit. Stiffness measurement method.

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