Image formation device

Abstract

In the present invention, a conveyance means conveys a recording material in a conveyance path. A guide means guides the recording material conveyed by the conveyance means in the conveyance path. A control means stops the recording material in a state in which the recording material is held by the conveyance means. A detection means comes into contact with part of the recording material after the recording material stops, and detects the rigidity of the recording material by pushing into the recording material. In relation to the stopped recording material, the detection means is arranged on one side of the recording material, and part of the guide means is arranged on the other side of the recording material. The control means controls the stop position of the recording material so that the recording material and the guide means arranged on the other side do not come into contact with each other in a state in which the recording material is pushed in from the one side to the other side by the detection means.

Description

Image forming apparatus

[0001] The present disclosure relates to an image forming apparatus.

[0002] The image forming apparatus uses image forming conditions according to the stiffness of a sheet on which an image is to be formed. According to Patent Document 1, a sensor that detects stiffness by bending a sheet is described.

[0003] Japanese Patent Application Laid-Open No. 2022-092683

[0004] By the way, while the stiffness sensor is detecting the stiffness of the sheet, the sheet must not be moving or falling apart. For example, it is conceivable that the stiffness sensor sandwiches the stiffness of a stationary sheet sandwiched between the nip portions of a pair of conveyance rollers. Conventionally, it has not been clear about the arrangement of the stiffness sensor or the correction method of the measured value for accurately measuring the stiffness of the sheet.

[0005] The present disclosure provides, for example, conveyance means for conveying a recording material in a conveyance path, guiding means for guiding the recording material conveyed by the conveyance means to the conveyance path, control means for stopping the recording material in a state where the recording material is sandwiched by the conveyance means, and first detection means for detecting the stiffness of the recording material by contacting a part of the recording material after the recording material has stopped and pushing the recording material in. The first detection means is arranged on one side with respect to the stopped recording material, and a part of the guiding means is arranged on the other side. The control means controls the stop position of the recording material so that the recording material and the guiding means arranged on the other side do not contact each other in a state where the recording material is pushed from the one side toward the other side by the first detection means.

[0006] According to the present disclosure, it becomes possible to measure the stiffness more accurately.

[0007] Other features and advantages of the technical idea derived from the present disclosure will become clear from the following description with reference to the accompanying drawings. In the accompanying drawings, the same or similar configurations are given the same reference numerals.

[0008] The attached drawings are included in the specification and constitute a part thereof, illustrating embodiments in this disclosure and used to explain the technical ideas derived from this disclosure together with their descriptions. Figure 1 is a diagram illustrating an image forming system. Figure 2 is a diagram illustrating an image forming unit. Figure 3 is a diagram illustrating a fuser. Figure 4A is a diagram illustrating the detection process of the stiffness sensor. Figure 4B is a diagram illustrating the detection process of the stiffness sensor. Figure 5 is a diagram illustrating the detection process of the stiffness sensor. Figure 6A is a diagram illustrating a stiffness sensor. Figure 6B is a diagram illustrating a stiffness sensor. Figure 7 is a diagram illustrating a control system. Figure 8 is a diagram illustrating the function of the CPU. Figure 9 is a flowchart illustrating the control method. Figure 10 is a flowchart illustrating an image forming method. Figure 11 is a diagram illustrating the function of the CPU. Figure 12 is a diagram illustrating a correction table. Figure 13 is a flowchart illustrating the control method. Figure 14 is a diagram illustrating a controller. Figure 15 is a diagram illustrating the amount of deviation of the rear end stop position. Figure 16 is a diagram illustrating the function of the CPU. Figure 17 is a flowchart illustrating the control method. Figure 18 is a diagram illustrating an image forming system. Figure 19 is a diagram illustrating the smallest size sheet detectable by the stiffness sensor. Figure 20 illustrates the arrangement of the stiffness sensor. Figure 21 illustrates the surface quality sensor. Figure 22 illustrates the basis weight sensor. Figure 23 illustrates the resistance sensor.

[0009] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the scope of the claims. While the embodiments describe multiple features, not all of these features are necessary, and the features may be combined in any way. Furthermore, in the attached drawings, identical or similar configurations are given the same reference numerals, and redundant descriptions are omitted.

[0010] 1. Image Forming System According to Figure 1, the image forming system 100 includes an image forming apparatus 101, a sheet processing apparatus 102, and a feeding apparatus 103. The image forming apparatus 101 includes a main body 104 and a fixing apparatus 105. The main body 104 and the fixing apparatus 105 may be housed in a single housing.

[0011] 1-1. The image forming apparatus body 104 has feeding decks 9a and 9b for loading multiple recording materials (sheets). Sheets fed from the feeding decks 9a and 9b are carried along the transport path 14 while being held by a pair of transport rollers 8. In this way, the sheets are transported to the secondary transfer section 7.

[0012] Image forming units 10Y, 10M, 10C, and 10K form toner images using yellow toner, magenta toner, cyan toner, and black toner, respectively, and transfer them to the intermediate transfer belt 6. YMCK are abbreviations for the toner colors. The intermediate transfer belt 6 may also be called the intermediate transfer body. As the intermediate transfer belt 6 rotates, the toner image is transported to the secondary transfer unit 7. The secondary transfer unit 7 has an outer roller and an inner roller. The outer roller and inner roller rotate while gripping the intermediate transfer belt 6. Furthermore, the outer roller and the intermediate transfer belt 6 transport the sheet while gripping it. By applying a secondary transfer voltage between the outer roller and the inner roller, the toner image is transferred from the intermediate transfer belt 6 to the sheet. The sheet with the transferred toner image is transported from the main body 104 to the fixing device 105.

[0013] The fuser unit 105 includes a first fuser 21 and a second fuser 22. In normal fuser mode, the sheet is supplied with heat and pressure in the first fuser 21. This fixes the toner image onto the sheet. The sheet is then transported along the first fuser transport path 15 and discharged to the sheet processing device 102. In duplex printing mode, the sheet with the image formed on the first side is guided to the duplex transport path 17 and transported again to the secondary transfer unit 7. The secondary transfer unit 7 transfers the toner image to the second side of the sheet. The sheet passes through the first fuser 21 again, fixing the toner image to the second side.

[0014] The second fuser 22 receives a sheet when the sheet and toner image require more heat (gloss fuser mode). That is, the sheet discharged from the first fuser 21 is guided to the second fuser transport path 16 and transported to the second fuser 22. In the second fuser 22, the sheet and toner image are again supplied with heat and pressure. After that, the sheet is discharged to the sheet processing device 102. The gloss fuser mode increases the gloss (glossiness) of the sheet.

[0015] 1-2. Sheet Processing Device The sheet processing device 102 is a post-processing device that performs post-processing on sheets discharged from the image forming apparatus 101. For example, a sheet (e.g., interleaving paper) supplied from the sorter 35 is inserted between a preceding sheet and a succeeding sheet discharged from the image forming apparatus 101. The sheet processing devices 34a and 34b include a puncher for making holes in sheets, a binding device (e.g., a stapler) for binding multiple sheets together, and an alignment device for aligning multiple sheets. Sheets that are not subjected to post-processing are discharged to the discharge tray 31. Sheets that have been subjected to post-processing in the sheet processing device 34a are discharged to the discharge tray 32. Sheets that have been subjected to post-processing in the sheet processing device 34b are discharged to the discharge tray 33.

[0016] 1-3. Feeding device Feeding device 103 is an optional feeding device. Feeding device 103 has, for example, large capacity decks 40a, 40b, 40c that can accommodate more sheets compared to feeding decks 9a, 9b. Feeding device 103 may have a manual feed tray 48.

[0017] Sheets fed from the large capacity decks 40a, 40b, 40c and the manual feed tray 48 are transported along the first transport path 11 by a plurality of transport roller pairs 47 arranged along the transport path. The first transport path 11 is a transport path that extends from the large capacity decks 40a, 40b, 40c. The first transport path 11 branches into a second transport path 12 and a third transport path 13. The flapper 49 is a guide member that guides the sheets that have been transported along the first transport path 11 to the second transport path 12 or the third transport path 13. The second transport path 12 is a transport path that connects the first transport path 11 and the escape tray 46. The escape tray 46 is a tray from which sheets that should not be transported to the image forming apparatus 101 are discharged. Sheets that should not be transported to the image forming apparatus 101 include, for example, sheets whose type is not registered, multiple sheets that have been double-feeded, and sheets that are not recommended for use with the image forming apparatus 101. The third transport path 13 is a transport path connecting the first transport path 11 and the image forming apparatus 101. Registered sheets, single sheets, and sheets recommended by the image forming apparatus 101 are guided to the third transport path 13.

[0018] Several sensors for measuring or detecting the physical properties of the sheets may be placed in the first transport path 11 and the second transport path 12. The double-feed sensor 41 is a sensor that detects "double-feeding," which is the phenomenon in which multiple sheets are transported stacked on top of each other. The double-feed sensor 41 is composed of, for example, an ultrasonic oscillating element and an ultrasonic receiving element. The ultrasonic receiving element receives ultrasonic waves emitted from the ultrasonic oscillating element and that have passed through the sheets. The double-feed sensor 41 detects double-feeding based on the attenuation of the ultrasonic waves.

[0019] The basis weight sensor 42 detects the basis weight of the sheet. The basis weight sensor 42 is also composed of, for example, an ultrasonic emitting element and an ultrasonic receiving element. The ultrasonic receiving element receives ultrasonic waves emitted from the ultrasonic emitting element and that have passed through the sheet. The basis weight sensor 42 detects the basis weight or thickness of the sheet based on the attenuation of the ultrasonic waves received by the ultrasonic receiving element. The basis weight sensor 42 may include, for example, a light-emitting element that irradiates the sheet with light having a predetermined wavelength (for example, visible light or infrared light), a first light-receiving element that receives the transmitted light that has passed through the sheet on the opposite side of the transport path, and a second light-receiving element that receives the reflected light reflected by the sheet. The basis weight sensor 42 may also detect the basis weight of the sheet based on the ratio of the amount of transmitted light and reflected light to the amount of irradiated light (e.g., attenuation rate). The basis weight sensor 42 can also detect the thickness of the sheet using a similar mechanism.

[0020] The surface properties sensor 43 detects the surface properties of the sheet. Surface properties refer to, for example, the smoothness, glossiness, or both of these of the sheet's surface. The surface properties sensor 43 includes a light-emitting element that irradiates the sheet with light at a predetermined incident angle, a first light-receiving element that receives specularly reflected light, and a second light-receiving element that receives diffusely reflected light. The surface properties sensor 43 can detect the surface properties of the sheet based on the ratio of the amount of specularly reflected light and diffusely reflected light to the amount of irradiated light. The double-feed sensor 41, basis weight sensor 42, and surface properties sensor 43 can perform detection without stopping the sheet, that is, while the sheet is being transported.

[0021] The stiffness sensor 44 is a sensor that detects the stiffness of the sheet. The resistance sensor 45 is a sensor that detects the volumetric resistance of the sheet. The stiffness sensor 44 and the resistance sensor 45 detect physical properties by contacting the sheet. Therefore, the sheet transport is stopped at the detection positions of the stiffness sensor 44 and the resistance sensor 45. When a preceding sheet comes to a stop in the first transport path 11, subsequent sheets must also stop, reducing the throughput of the image forming system 100. Here, throughput is the number of sheets that the image forming system 100 can process per unit time. The stiffness sensor 44 and the resistance sensor 45 may perform detection during a single stop period. This may improve throughput.

[0022] 2. Image forming section Figure 2 shows the structure of image forming sections 10Y, 10M, 10C, and 10K. The structure of image forming sections 10Y, 10M, 10C, and 10K is the same except for the toner color.

[0023] The photoreceptor drum 1 is an image carrier that is rotated by a motor or the like. The charger 2 is a charging roller or charging wire that charges the surface of the photoreceptor drum 1. The charger 2 is subjected to a predetermined charging voltage, which is an example of the image formation conditions. The exposure device 3 irradiates the surface of the photoreceptor drum 1 with light corresponding to the image signal, forming an electrostatic latent image corresponding to the image signal. The amount of light from the light source of the exposure device 3 is an example of the image formation conditions. The toner container 50 is a container that holds toner T. The developing sleeve 4 is a rotating body that supplies toner supplied from the toner container 50 to the surface of the photoreceptor drum 1. The toner container 50 and the developing sleeve 4 may also be called a developer. The developing sleeve 4 is subjected to a developing voltage, which is an example of the image formation conditions. The electrostatic latent image on the surface of the photoreceptor drum 1 is developed into a toner image by the toner T. The developing voltage is a voltage that promotes the adhesion of toner T to the photoreceptor drum 1. As the photoreceptor drum 1 rotates further, the toner image is transported to the primary transfer unit. The primary transfer section is formed by a photoreceptor drum 1 and a primary transfer roller 5. A primary transfer voltage, which is an example of image formation conditions, is applied between the primary transfer roller 5 and the photoreceptor drum 1. The primary transfer roller 5 transfers the toner image from the photoreceptor drum 1 to the intermediate transfer belt 6. The primary transfer voltage promotes the primary transfer of the toner image. The drum cleaner 51 cleans the toner T remaining on the photoreceptor drum 1.

[0024] 3. Fuser Figure 3 shows the structure of the first fuser 21 and the second fuser 22. It is assumed that the structure of the first fuser 21 and the structure of the second fuser 22 are the same. In Figure 3, the sheet P is conveyed along the conveying direction X.

[0025] The heating belt 64 is a heating member or heating rotating body consisting of an endless belt. The heating belt 64 may also be called a heating film. The pressure roller 65 is a roller-shaped pressure member or heating rotating body. The heater 60 is a heating element positioned to slide against the inner circumferential surface of the heating belt 64. The pressure roller 65 has a core metal 66 and an elastic layer 67. The core metal 66 is made of, for example, iron or aluminum. The elastic layer 67 is a rubber layer made of, for example, silicone rubber. Thus, the pressure roller 65 has a rubber layer that forms a nip portion together with the heater 60 via the heating belt 64. The heater 60 is provided on the inner surface side of the heating belt 64 and is held by a holding member 61. The holding member 61 is held by a metallic stay member 63. The stay member 63 presses the heater 60 against the inner circumferential surface of the heating belt 64 via the holding member 61.

[0026] A pressure is applied between the stay member 63 and the pressure roller 65 by a pressure mechanism (e.g., a spring) not shown. The pressure roller 65 is pressed against the heater 60 via the heating belt 64, forming a fixing nip 130. As the pressure roller 65 rotates counterclockwise, the heating belt 64 also rotates clockwise in response to the pressure roller 65. The sheet P passes over the fixing nip 130, fixing the toner image onto the sheet P.

[0027] The heater 60 is, for example, a ceramic heater having a ceramic substrate and a heating element provided thereon. The thermistor 62 is a temperature sensing element positioned in contact with the heater 60. The power supplied to the heater 60 is controlled based on the detection result of the thermistor 62. This maintains the temperature of the heating belt 64 at a target temperature. Here, the target temperature is an example of an image formation condition.

[0028] 4. Method for Measuring Stiffness Figures 4A and 4B show a method for measuring the stiffness of the sheet P using a stiffness sensor 44. X is the direction parallel to the conveying direction of the sheet P (length direction). Z is the direction perpendicular to the conveying direction (height direction). The conveying guide 400 is formed by two parallel guide members (guide plates) and defines the conveying direction of the sheet P. The sheet P is conveyed along the conveying guide 400. In the conveying direction of the sheet P, a pair of conveying rollers 47a is arranged on the upstream side and a pair of conveying rollers 47b is arranged on the downstream side. The distance between the center of the nip portion of the conveying roller pair 47a and the center of the nip portion of the conveying roller pair 47b is Lz. The stiffness sensor 44 is provided on the upstream side of the conveying roller pair 47a. The stiffness sensor 44 may also be provided on the downstream side of the conveying roller pair 47b. In this case, the conveyor roller pair 47a in the following explanation should be read as the conveyor roller pair 47b, and the rear end of the sheet should be read as the front end of the sheet.

[0029] As shown in Figure 4A, when the rear end of the sheet P reaches a predetermined position, the transport roller pair 47a and 47b stop. As shown in Figure 4B, the stiffness sensor 44 extends its probe 404, and the probe 404 makes contact with the sheet P. Furthermore, the probe 404 pushes down on the sheet P. The stiffness sensor 44 detects the stiffness of the sheet P by determining the pressing force (reaction force) of the sheet P against the probe 404.

[0030] As shown in Figure 4A, the distance from the center of the nip portion of the transport roller pair 47a to the detection position of the stiffness sensor 44 is S. Distance S is a distance specified in advance by the specifications of the stiffness sensor 44. The distance from the detection position to the rear end of the sheet P is T. Incidentally, in order for the stiffness sensor 44 to detect the stiffness of the sheet P, the sheet P must be stationary. In particular, in order to accurately detect the stiffness, it is necessary to stop the sheet P at an accurate position. In this embodiment, the tolerance in the stopping control of the sheet P is assumed to be D. The tolerance D mainly originates from the manufacturing errors of the transport roller pair 47a and the drive mechanism that drives the transport roller pair 47a.

[0031] A sheet sensor 402 is placed in either the first transport path 11 or the second transport path 12. When the rear end of the sheet P has traveled a distance L after a predetermined time t seconds has passed the sheet sensor 402, the distance from the detection position of the stiffness sensor 44 to the rear end of the sheet P should be T.

[0032] Figure 5 shows how to determine the distance T. Note that, as shown in Figure 4A, the height of the transport guide 400 (the distance between the two guide members in a direction perpendicular to the transport direction of the sheet P) is assumed to be G. The sheet P is transported along the center line 501 at the center of the transport guide 400. The center line 501 is also a straight line that passes through the nip portion of the transport roller pair 47a and the nip portion of the transport roller pair 47b.

[0033] For the stiffness sensor 44 to accurately measure the stiffness of sheet P, the stiffness sensor 44 needs to press sheet P in the width direction by a distance of H. H is a value determined by the specifications of the stiffness sensor 44. At this time, if the rear end of sheet P touches the transport guide 400 and bends, the stiffness sensor 44 cannot accurately measure the stiffness. In other words, when the stiffness sensor 44 presses sheet P by a distance of H, the position of the rear end of sheet P in the height direction is at a maximum distance of about 0.5G from the center line 501. Considering the similarity condition of the triangles, the following equation holds.

[0034] S:H = (S + T + D): 0.5G ... Eq1 T = S(0.5G - H) / H - D ... Eq2 Here, the transport time t from the moment the sheet sensor 402 detects the rear end of sheet P to the moment the rear end of sheet P is stopped can be expressed by the following equation.

[0035] t = L / v = (L0 - T) / v ... Eq3 Here, v is the transport speed of the sheet P. L0 is the transport distance along the transport path to the sheet sensor 402 and the stiffness sensor 44. Therefore, by stopping the transport roller pair 47a and 47b t seconds after the sheet sensor 402 detects the rear end, the rear end of the sheet P stops at the ideal position. Note that if the tolerance D is sufficiently small, the tolerance D may be treated as zero in equations Eq1 and Eq2.

[0036] 5. Distance between the two transport roller pairs As shown in Figure 4A, the distance between the transport roller pairs 47a and 47b is Lz. Here, it is necessary for the sheet P to be nipped by the upstream transport roller pair 47a, but it is not necessary for it to be nipped by the downstream transport roller pair 47b. However, if the sheet P is nipped by both the upstream transport roller pair 47a and the downstream transport roller pair 47b, the measurement result by the stiffness sensor 44 may improve.

[0037] Furthermore, once the stiffness measurement is complete, the transport roller pair 47a and 47b resume transporting the sheet P. At this time, it is expected that the transport of the sheet P will be stabilized and jamming of the sheet P will be suppressed. In other words, when the stiffness sensor 44 measures the stiffness, it is important that the transport roller pair 47a and 47b keep the sheet P stationary while nipping it.

[0038] By the way, the size of the sheet P that can be transported by the image forming apparatus 101 is assumed in the design. That is, there is a minimum length of sheet P in the transport direction. Here, the distance from the nip portion of the upstream transport roller pair 47a to the rear end of sheet P is S + T + D. Therefore, the distance Lz between the upstream transport roller pair 47a and the downstream transport roller pair 47b can be expressed by the following equation.

[0039] Lz = Lmin - (S + T + D) ... Eq4 Here, Lmin is the minimum length of the sheet P in the transport direction that is permitted in the design of the image forming apparatus 101. For example, the length of a postcard in the transport direction is 148 mm. Assume that 148 mm is the minimum size permitted for the image forming apparatus 101 or the feeding device 103. Assume that S + T + D is 50 mm. In this case, the distance Lz should be 98 mm or less. Note that if the radius of the upstream transport roller pair 47a and the radius of the downstream transport roller pair 47b are R, the distance Lz must be greater than 2R and satisfy equation Eq4.

[0040] 6. Structure of the stiffness sensor Figures 6A and 6B show an example of a stiffness sensor 44. The probe 404 is a contact element that contacts the surface of the sheet P. The transport guide 400 has two guide plates 410 and 420 that form the second transport path 12. The two guide plates 410 and 420 are metal plates that are arranged to be roughly parallel. Guide plate 410 has a passage opening 411 through which the probe 404 for pressing the sheet P passes.

[0041] The pressure detection unit 601 is connected to the probe 404 and detects the pressure applied to the probe 404 by the sheet P. The holding member 602 is connected to the pressure detection unit 601 and is a holding member that holds the pressure detection unit 601. The lifting member 603 moves up and down in accordance with the rotation of the cam 604, and is a dependent link of the cam mechanism that raises and lowers the probe 404 via the holding member 602 and the pressure detection unit 601. The cam 604 is the driving link of the cam mechanism which is rotated by the motor M1. In other words, the rotation of the motor M1 is converted into the up and down movement of the probe 404 by the cam mechanism.

[0042] The cam mechanism is just one example; any mechanism that can raise and lower the probe 404 can be used. For example, the mechanism for raising and lowering the probe 404 could be a lifting mechanism consisting of a rack gear and a pinion gear, a crank mechanism including a crank arm and a crank pin, or a ball screw mechanism including a nut and a screw shaft.

[0043] The retaining member 602 may be connected to an elastic body 605 such as a spring or rubber. When the retaining member 602 rises, the elastic body 605 stretches, and elastic energy is stored. When the retaining member 602 descends, the elastic body 605 expands and contracts, and the elastic energy is released. In other words, the elastic body 605 assists the retaining member 602 in returning to its home position.

[0044] 7. Control System Figure 7 shows the control system of the image forming system 100. The controller 700 is a control device that controls the image forming apparatus 101, the sheet processing apparatus 102, and the feeding apparatus 103. The controller 700 may be built into any one of the image forming apparatus 101, the sheet processing apparatus 102, and the feeding apparatus 103, or may be installed outside these. Also, the control functions of the controller 700 may be distributed among the image forming apparatus 101, the sheet processing apparatus 102, and the feeding apparatus 103.

[0045] The CPU 701 controls the image forming system 100 according to the control program stored in the ROM area of the memory 702. ROM is an abbreviation for read only memory. The ROM area may include a hard disk drive in addition to the semiconductor memory device. The memory 702 further has a random access memory (RAM) area. The CPU 701 displays messages, images, user interfaces (UIs), etc. on the display device 703. The CPU 701 may receive information and instructions input by the user through an input device 704 such as a touch sensor.

[0046] Figure 7 further illustrates the loads of the feeding apparatus 103. The motor M2 rotationally drives a plurality of conveying roller pairs 47. The motor M3 rotationally drives a feeding roller that feeds the sheet P from the large capacity deck 40a. The motor M4 rotationally drives a feeding roller that feeds the sheet P from the large capacity deck 40b. The motor M5 rotationally drives a feeding roller that feeds the sheet P from the large capacity deck 40c. The motor M6 rotationally drives a feeding roller that feeds the sheet P from the manual feed tray 48. The solenoid SL1 drives the flapper 49. For example, when the solenoid SL1 is turned on, the flapper 49 guides the sheet P to the second conveyance path 12. When the solenoid SL1 is turned off, the flapper 49 guides the sheet P to the third conveyance path 13.

[0047] Figure 8 shows a plurality of functions realized by the CPU 701 executing the control program. One or more of these functions may be implemented by a hardware circuit such as a specific application integrated circuit (ASIC) or a field programmable gate array.

[0048] The measurement control unit 801 controls the basis weight sensor 42, the surface property sensor 43, the stiffness sensor 44, and the resistance value sensor 45 in order to measure the physical property values of the sheet P. For example, when the rear end of the sheet P is detected by the sheet sensor 402, the measurement control unit 801 sets a predetermined time t in the timer 802. When the timer 802 finishes counting the predetermined time t, the measurement control unit 801 stops the motor M2. As a result, the distance from the detection position of the stiffness sensor 44 to the rear end of the sheet P becomes T + D. Note that the sheet P is stationary for a predetermined stop period. The stop period is the period from the timing when the conveyance of the sheet P stops to the timing when the conveyance of the sheet P restarts. The length of the stop period may change dynamically. The measurement control unit 801 drives the motor M1 of the stiffness sensor 44, raises the probe 404, and detects the stiffness Sd of the sheet P. When the detection of the stiffness Sd of the sheet P is completed, the measurement control unit 801 drives the motor M1, lowers the probe 404, and returns the probe 404 to the home position. The home position of the probe 404 is, for example, a position where the tip of the probe 404 does not enter the inside of the conveyance guide 400. As long as the tip of the probe 404 does not obstruct the conveyance of the sheet P, the tip of the probe 404 may enter the inside of the conveyance guide 400.

[0049] When the registration process of the type of the sheet P is started, the flapper control unit 803 turns on the solenoid SL1. As a result, the sheet P is conveyed to the second conveyance path 12. Note that when the double feed sensor 41 detects double feeding of the sheet P, the flapper control unit 803 turns on the solenoid SL1. When the basis weight detected by the basis weight sensor 42 does not match the basis weight associated with the ID input from the input device 704, the flapper control unit 803 may turn on the solenoid SL1. When the surface property detected by the surface property sensor 43 does not match the surface property associated with the identification information (type information) input from the input device 704, the flapper control unit 803 may turn on the solenoid SL1. As a result, a failure in image formation may be prevented in advance.

[0050] The determination unit 804 determines the image formation conditions corresponding to the physical properties of the sheet P obtained through the measurement control unit 801. For example, these conditions include stiffness Sd, surface quality Sf, basis weight Gr (or thickness), volume resistivity Rv, presence or absence of coating, and material (e.g., paper, recycled paper, synthetic paper). Here, the image formation conditions may include, for example, the transport speed v of the sheet P, the target temperature Ttg of the heater 60, the charging voltage Vc, the developing voltage Vd, the primary transfer voltage Vt1, and the secondary transfer voltage Vt2. The method for determining the image formation conditions from physical properties such as stiffness Sd, surface quality Sf, basis weight Gr, and volume resistivity Rv is known in the industry and will not be described in detail here.

[0051] The registration unit 805 performs a process to register the type of sheet P to the image forming system 100. There are many types of sheet P. Therefore, the image forming conditions are switched according to the type of sheet P. The registration unit 805 associates the identification information (e.g., name, brand, identification number) entered by the user with the image forming conditions determined according to the combination of physical property values ​​and stores it in the ROM area of ​​memory 702. The identification information may be abbreviated as ID. The identification information can be assigned by the user so that the user can distinguish between different types.

[0052] The condition determination unit 811 determines the image formation conditions corresponding to the ID input from the input device 704. For example, the condition determination unit 811 may read the image formation conditions corresponding to the ID from the ROM area of ​​the memory 702. The motor control unit 812 rotates the motor M2 so that the transport speed of the transport roller pair 47 matches the transport speed v determined by the condition determination unit 811. The heater control unit 813 controls the power supplied to the heater 60 so that the fixing temperature detected by the thermistor 62 matches the target temperature Ttg determined by the condition determination unit 811. The voltage control unit 814 applies the charging voltage Vc determined by the condition determination unit 811 to the charging roller 2. The voltage control unit 814 applies the developing voltage Vd determined by the condition determination unit 811 to the developing sleeve 4. The voltage control unit 814 applies the primary transfer voltage Vt1 determined by the condition determination unit 811 to the primary transfer roller 5. The voltage control unit 814 applies the secondary transfer voltage Vt2, which has been identified by the condition identification unit 811, to the secondary transfer unit 7.

[0053] 8. Flowchart 9 is a flowchart showing the control method executed by the CPU 701 according to the control program. When registration processing is instructed via the input device 704, the CPU 701 turns on the solenoid SL1 and then executes the following processes. It is assumed that the sheet P is to be fed from the manual feed tray 48 as specified by the user via the input device 704.

[0054] At S901, the CPU 701 (measurement control unit 801, motor control unit 812) starts motors M2 and M6 and begins transporting the sheet P. Motor M6 for the manual feed tray 48 is stopped when the feeding of the sheet P is complete. When the sheet P passes through the basis weight sensor 42, the basis weight sensor 42 detects the basis weight Sd of the sheet P. When the sheet P passes through the surface quality sensor 43, the surface quality sensor 43 detects the surface quality Sf of the sheet P.

[0055] In S902, the CPU 701 (measurement control unit 801) monitors the detection result of the sheet sensor 402 and determines whether the rear end of the sheet P has been detected by the sheet sensor 402. If the rear end is detected, the CPU 701 proceeds from S902 to S903.

[0056] In step S903, the CPU 701 (measurement control unit 801) sets a predetermined time t in the timer 802 and starts the timer 802. The predetermined time t is the time calculated by equation Eq3.

[0057] In S904, the CPU 701 (measurement control unit 801) determines whether a predetermined time t has elapsed. If the predetermined time t has elapsed, the CPU 701 proceeds from S904 to S905.

[0058] At S905, the CPU 701 (measurement control unit 801, motor control unit 812) stops the motor M2 and stops the transport of sheet P. Since the transport time t is based on the distance T, sheet P is expected to stop at the desired position. However, the stopping position may vary within the tolerance D.

[0059] In S906, the CPU 701 (measurement control unit 801) starts the motor M1 of the stiffness sensor 44 and raises the probe 404. In S907, the CPU 701 detects the stiffness of the sheet P using the stiffness sensor 44.

[0060] In S908, the CPU 701 (measurement control unit 801, motor control unit 812) rotates the motor M1 and lowers the probe 404. In S909, the CPU 701 (determination unit 804) detects the volume resistivity Rv of the sheet P using the resistance sensor 45. Alternatively, the CPU 701 may calculate the volume resistivity by dividing the volume resistivity Rv by the basis weight (thickness) of the sheet P obtained by the basis weight sensor 42.

[0061] In S910, the CPU 701 (registration unit 805) registers the type of sheet P. For example, the CPU 701 determines the image formation conditions corresponding to the measurement results (e.g., basis weight Gr, surface properties Sf, stiffness Sd, volumetric low Rv) and registers the image formation conditions linked to the type (ID).

[0062] At S911, the CPU 701 (measurement control unit 801, motor control unit 812) restarts the motor M2 and resumes transporting the sheet P. As a result, the sheet P is discharged into the escape tray 46.

[0063] 9. Image formation diagram 10 shows the image formation operation performed by the CPU 701 according to the control program.

[0064] In S1001, the CPU 701 (condition identification unit 811) receives the type (ID) specification through the input device 704. In S1002, the CPU 701 (condition identification unit 811) identifies the image formation conditions corresponding to the type (ID) specified by the user. For example, the CPU 701 reads the image formation conditions associated with the type (ID) specified by the user from the memory 702. In S1003, the CPU 701 controls the image formation system 100 and performs image formation on sheet P using the identified image formation conditions.

[0065] 10. Correction of Detected Stiffness The tolerance D described above is a tolerance that originates from manufacturing variations in the conveying mechanism. The stopping position of sheet P further changes depending on the basis weight and surface properties of sheet P. For example, if the surface smoothness of sheet P increases, the coefficient of friction of sheet P decreases, and the variation in the stopping position of sheet P increases. Similarly, if the basis weight of sheet P increases, the variation in the stopping position of sheet P increases. As a result, if the stopping position of sheet P shifts upstream in the conveying direction of sheet P, the stiffness Sd becomes larger than the actual value. If the stopping position of sheet P shifts downstream in the conveying direction of sheet P, the stiffness Sd becomes smaller than the actual value. Therefore, if the stiffness Sd is corrected according to the physical properties of sheet P that affect the conveying of sheet P, a stiffness Sd can be obtained with higher accuracy.

[0066] Figure 11 is a block diagram illustrating the stiffness Sd correction function. In the following, parts that have already been described are given the same reference numerals, and their explanations are omitted. Compared to Figure 8, Figure 10 adds a correction value acquisition unit 1101 and a correction unit 1102. The correction value acquisition unit 1101 acquires a correction value Csd based on one or more physical properties obtained from the sheet P. The one or more physical properties can be any physical properties that cause an error in the stopping position of the sheet P. For example, the correction value acquisition unit 1101 acquires a correction value Csd based on the basis weight Gr obtained by the basis weight sensor 42 and the surface properties Sf obtained by the surface properties sensor 43. The correction unit 1102 corrects the stiffness Sd based on the correction value Csd and determines the corrected stiffness Sd'. The determination unit 804 determines the image formation conditions using the corrected stiffness Sd'.

[0067] Figure 12 shows an example of a correction table 1200. The correction value acquisition unit 1101 may refer to the correction table 1200 stored in the ROM area of ​​memory 702 and acquire a correction value Csd corresponding to the combination of basis weight Gr and surface quality Sf. In this example, surface quality Sf is assumed to be the glossiness (reflectance) of the sheet P. The correction value associated with the combination of a relatively small glossiness (first glossiness, e.g., glossiness of plain paper) and a basis weight Gr of 80 g / mm² is 0. This is because the combination of surface quality Sf and basis weight Gr corresponds to the most common combination of surface quality Sf and basis weight Gr for plain paper. mm² is an abbreviation for square millimeters. The correction value associated with the combination of a relatively large glossiness (second glossiness, e.g., coated paper) and a basis weight Gr of 120 g / mm² is -2. The correction value associated with the combination of primary gloss and a basis weight of 200 g / mm² is -3. Note that these values ​​are merely examples.

[0068] Figure 13 shows a control method that includes a correction process for stiffness Sd. Compared to Figure 9, in Figure 13, S1301 and S1302 are added between S901 and S902. S1310 is added between S907 and S908.

[0069] In S1301, the CPU 701 (measurement control unit 801) detects the basis weight Sd and surface quality Sf of the sheet P using the basis weight sensor 42 and the surface quality sensor 43. In S1302, the CPU 701 (correction value acquisition unit 1101) acquires a correction value Csd corresponding to the combination of the basis weight Sd and surface quality Sf of the sheet P. Note that S1302 may be executed at any time after S1301 and before S1310. The correction value Csd is temporarily stored in the RAM area of ​​memory 702.

[0070] In S1310, the CPU 701 (correction unit 1102) reads the correction value Csd from the memory 702 and corrects the stiffness Sd detected by the stiffness sensor 44 with the correction value Csd. For example, the following formula may be used.

[0071] Sd' = Sd + Csd ... Eq5 Note that S1310 may be executed at any time after S1302 and before S910. In S910, the CPU 701 determines the image formation conditions using the corrected stiffness Sd' instead of the stiffness Sd, and registers the type (ID) associated with the image formation conditions.

[0072] 11. Modifications 11-1. Method for Determining Correction Values ​​As described above, if the stopping position of sheet P deviates from the ideal position in the design, the detection accuracy of the stiffness Sd decreases. In other words, the CPU 701 may determine the amount of deviation E between the stopping position of the rear end of sheet P and the ideal position, and determine the correction value Csd based on the amount of deviation E.

[0073] Figure 14 shows that an image sensor 1401 for imaging the rear end of the sheet P is added to the feeding device 103. For example, the image sensor 1401 images the rear end of the sheet P through a slit provided in the transport guide 400. The image sensor 1401 can be positioned in any location as long as it can image near the ideal stopping position assumed in the design. For example, the image sensor 1401 may be positioned so that its surface is parallel to the transport guide 400. Alternatively, the image sensor 1401 may be positioned so that its surface is perpendicular to the transport guide 400. In the latter case, an optical system (e.g., a mirror) is required to bend the optical axis of the image sensor 1401 at a right angle.

[0074] Figure 15 shows an image 1500 of the area near the rear end of sheet P, acquired by the image sensor 1401. X indicates the transport direction (length direction) of sheet P. Y indicates the width direction of sheet P. The X and Y directions are perpendicular to the height direction (Z direction) of the transport guide 400. Ps0 is the ideal stopping position of the rear end of sheet P as assumed in the design. Ps1 is the actual position of the rear end of sheet P. In this example, the rear end of sheet P is shifted upstream in the transport direction of sheet P. The amount of shift E at this time is acquired as the distance between Ps1 and Ps0.

[0075] Figure 16 shows the CPU 701 with the displacement amount acquisition unit 1601 added. The displacement amount acquisition unit 1601 calculates the displacement amount E from the image 1500 acquired by the image sensor 1401. Here, the ideal stopping position Ps0 is known. Therefore, the displacement amount acquisition unit 1601 performs edge detection on the image 1500 to identify the actual stopping position Ps1 of the sheet P. Then, the displacement amount acquisition unit 1601 determines the difference between the ideal stopping position Ps0 and the actual stopping position Ps1 as the displacement amount E. The correction value acquisition unit 1101 acquires a correction value Csd corresponding to the displacement amount E. For example, a conversion formula, a conversion table, or a conversion program joule may be used to convert the displacement amount E to the correction value Csd.

[0076] Figure 17 shows the control method executed by the CPU 701 according to the control program. Compared to Figures 9 and 13, in Figure 17, S1701 and S1702 are added between S905 and S906. When the transport of sheet P stops at S905, the CPU 701 proceeds from S905 to S1701.

[0077] In step S1701, the CPU 701 (measurement control unit 801) controls the image sensor 1401 to capture an image of the rear end of the sheet P. As a result, image 1500 is acquired.

[0078] In S1702, the CPU 701 (shift amount acquisition unit 1601) analyzes the image 1500 including the rear end of the sheet P, determines the shift amount E, and acquires a correction value Csd based on the shift amount E. Note that S1701 and S1702 may be executed at any timing after S905 and before S1310. However, if the image sensor 1401 performs imaging when the sheet P is parallel to the transport guide 400, the measurement accuracy of the shift amount E will improve. For this reason, the image sensor 1401 may perform imaging when the sheet P is stationary and the probe 404 is stopped in the home position. The probe 404 being stopped in the home position means that the probe 404 is not pressing down on the sheet P. In S1310, the CPU 701 (correction unit 1102) corrects the stiffness Sd based on the correction value Csd obtained from the shift amount E.

[0079] 11-2. The arrangement diagram 18 of the stiffness sensor and resistance sensor shows another example of the arrangement of the stiffness sensor 44 and the resistance sensor 45. In this example, the stiffness sensor 44 and the resistance sensor 45 are arranged on the first transport path 11. In this case, the second transport path 12 and the escape tray 46 may be omitted, or they may still be provided. If the stiffness Sd detected by the stiffness sensor 44 exceeds a predetermined threshold Sth, the flapper 49 may guide the sheet P to the second transport path 12 and discharge the sheet P to the escape tray 46. This will prevent the image forming apparatus 101 and the sheet processing apparatus 102 from malfunctioning due to a sheet P with excessively high stiffness Sd.

[0080] 12. Other 12-1. Relationship between minimum size sheet and stiffness sensor Figure 19 shows the relationship between the stiffness sensor 44 and the minimum size sheet P assumed in the design. As an example, the minimum size sheet P is assumed to be a postcard measuring 100 mm x 139.7 mm. The minimum size may be other sizes. In this example, the leading edge of the sheet P is nipped by the transport roller pair 47b, and the rear edge of the sheet P is nipped by the transport roller pair 47a. The outer diameter of each transport roller constituting the transport roller pairs 47a and 47b is 24 mm. That is, the radius of each transport roller is 12 mm. In this example, the leading edge of the sheet P protrudes about 10 mm forward from the center of the nipped portion of the transport roller pair 47b. The rear edge of the sheet P protrudes about 10 mm backward from the center of the nipped portion of the transport roller pair 47a.

[0081] Here, the probe 404 of the stiffness sensor 44 needs to be able to contact the rear end of the sheet P. As is clear from Figure 19, the probe 404 of the stiffness sensor 44 should be positioned in a range that is more than 12 mm but less than or equal to 30 mm from the center of the nip portion of the transport roller pair 47a that nip the rear end of the sheet P.

[0082] The size of sheet P is input, for example, from input device 404. Information indicating the minimum size is stored in advance in the ROM area of ​​memory 402. The CPU 401 may output notification information from display device 403 if the size of sheet P specified by the user is less than the minimum size. The notification information may include a message or image indicating that the size of sheet P is less than the minimum size. The message may also include information indicating that the sheet P is unsuitable as an inspection target because its size is less than the minimum size.

[0083] The size of the sheet P from which the stiffness can be detected by the stiffness sensor 44 may differ from the size of the sheet P from which an image can be formed. For example, if a postcard can be used to form an image but cannot be detected, the CPU 401 may display notification information on the display device 403 when the user selects or specifies a postcard as the sheet P. The notification information may also be output as sound.

[0084] 12-2. Arrangement of Stiffness Sensors The arrangement of stiffness sensors 44 in the direction of conveying sheet P has already been described. Below, the arrangement of stiffness sensors 44 in the direction perpendicular to the conveying direction of sheet P will be described.

[0085] Figure 20 shows the arrangement of the stiffness sensor 44. The image forming system 100 is configured to transport the sheet P such that the center of the sheet P passes through the center of the transport guide 410. Here, it is assumed that the smallest size sheet P is a postcard measuring 100 mm × 139.7 mm. 139.7 mm is the length of the sheet P in the transport direction. 100 mm is the length of the sheet P in the direction perpendicular to the transport direction.

[0086] Figure 20 shows that the sheet P is transported with respect to its center. Therefore, in a direction perpendicular to the transport direction of the sheet P, the stiffness sensor 44 should be positioned within 50 mm of the center of the transport guide 410.

[0087] In this way, the position of the stiffness sensor 44 is designed based on the minimum size. Therefore, the stiffness sensor 44 can detect the stiffness of any sheet P, as long as it is larger than the minimum size and is the maximum size that can be transported by the transport guide 410.

[0088] 12-3. Structural diagram 21 of the surface sensor shows a surface sensor 43 in which a gloss sensor and a smoothness sensor are integrated. The surface sensor 43 includes a light-emitting element 2101, light-receiving elements 2102 and 2103, and apertures 2104, 2105, and 2106. The light-emitting element 2101 is, for example, a light-emitting diode. The light-emitting element 2101 emits light such that the incident angle is 75 degrees. The light emitted from the light-emitting element 2101 is focused by passing through the aperture 2104 and directed toward the surface of the sheet P. The light reflected from the surface of the sheet P (specular reflection) is focused by the aperture 2105 and incident toward the light-receiving element 2102.

[0089] The light-receiving element 2102 is configured to receive specularly reflected light, and the angle between the optical axis of the light-receiving element 2102 and the normal direction of the sheet P is 75 degrees. The light-receiving element 2102 is, for example, a photodiode (PD). The light-receiving element 2102 outputs a detection signal corresponding to the intensity of the specularly reflected light incident on the light-receiving element 2102. This detection signal indicates the glossiness of the sheet P.

[0090] The light-receiving element 2103 receives diffused light that diffuses according to the smoothness of the surface of the sheet P. The light-receiving element 2103 is, for example, a photodiode (PD). The angle between the optical axis of the light-receiving element 2103 and the normal direction of the sheet P is 30 degrees so that the light-receiving element 2103 can receive diffused light. The diffused light from the sheet P is focused by passing through the aperture 2106 and then incident on the light-receiving element 2103.

[0091] The higher the glossiness of sheet P, the greater the amount of light received by the light-receiving element 2102. Conversely, the lower the glossiness of sheet P, the greater the amount of light received by the light-receiving element 2102. Therefore, the amount of light received by the light-receiving element 2102 indicates the glossiness.

[0092] The higher the smoothness of sheet P, the greater the amount of light received by the photodetector 2102; and the lower the smoothness of sheet P, the greater the amount of light received by the photodetector 2102. The lower the smoothness of sheet P, the greater the amount of light received by the photodetector 2103; and the higher the smoothness of sheet P, the greater the amount of light received by the photodetector 2103. Therefore, the combination of the amount of light received by the photodetector 2102 and the amount of light received by the photodetector 2103 indicates the smoothness of sheet P.

[0093] Aperture 2104 may be replaced with a collimator lens.

[0094] 12-4. Structure of the basis weight sensor Diagram 22 shows the structure of the basis weight sensor 42. The basis weight sensor 42 is installed in the first transport path 11. The first transport path 11 is formed by two transport guides 2205. The light-emitting element 2201 is a light-emitting diode that emits blue light (wavelength: approximately 450 nm). The light-emitting element 2202 is a light-emitting diode that emits near-infrared light (wavelength: approximately 850-950 nm). The light-emitting element 2203 is a light-emitting diode that emits green light (wavelength: approximately 530 nm). The light-receiving element 2204 is positioned opposite the light-emitting elements 2201 and 2202. The light-emitting elements 2201 and 2202 are mounted on the first substrate 2211. The light-emitting element 2203 and the light-receiving element 2204 are mounted on the second substrate 2212. The first substrate 2211 and the second substrate 2212 are parallel to the transport direction of the sheet P. A reference plate 2206 for adjusting the light output from the light-emitting element 2203 may be placed on the first substrate 2211.

[0095] The basis weight sensor 42 measures the transmittance and reflectance of sheet P to detect the basis weight of sheet P. The transmittance of sheet P can be measured using blue light and near-infrared light, respectively. The reflectance can be measured using green light.

[0096] The light-receiving element 2204 receives green light reflected from the surface of sheet P, as well as transmitted blue and near-infrared light that has passed through sheet P, and outputs a detection signal indicating their intensity. If the surface of sheet P is smooth, the specular reflection component will be strong and the diffuse component will be weak. If the surface of sheet P is rough, the proportion of the diffuse component will increase. Note that the light-emitting elements 2201, 2202, and 2203 do not light up simultaneously, but light up selectively. This allows a single light-receiving element 2204 to selectively receive green, blue, and near-infrared light of different wavelengths.

[0097] The CPU 401 calculates the basis weight of sheet P based on the measurement results of green, blue, and near-infrared light. For example, the CPU 401 may select one conversion formula from several based on the measurement results and use the selected conversion formula to convert the amount of near-infrared light received into basis weight.

[0098] 12-5. Resistance Sensor Figure 23 shows the structure of the resistance sensor 45. When sheet P stops between electrode 2301 and electrode 2302, the CPU 401 rotates motor M7. The drive shaft of motor M7 is connected to the rotation axis 2304 of cam 2303. This connection may be made via multiple gears. The cam surface of cam 2303 presses against electrode 2301. Electrode 2302 is fixed. As cam 2303 rotates, electrode 2301 gradually approaches electrode 2302 and presses against sheet P. The pressing force increases as cam 2303 rotates. It is sufficient that the pressing force can be variably controlled by the relative movement of electrode 2301 to electrode 2302. Therefore, electrode 2302 may move. Motor M7 may be a stepping motor that can freely rotate in both forward and reverse directions. This makes it possible to control the rotation angle of cam 2303 one step at a time.

[0099] Meanwhile, a voltage is applied between electrode 2301 and electrode 2302 from the power supply 2311. The voltage detection circuit 515 detects the voltage applied to sheet P. The current detection circuit 2313 detects the current flowing through sheet P. When the resistance sensor 45 is in standby mode, electrode 2301 is in standby position. That is, electrode 2301 and electrode 2302 are separated. When electrode 2301 contacts the first surface of sheet P and electrode 2302 contacts the second surface of sheet P, a voltage is applied to sheet P and current begins to flow through sheet P. The CPU 401 acquires and monitors the value of the current detected by the current detection circuit 2313. As the pressing force applied by the cam 2303 to sheet P via electrode 2301 and electrode 2302 increases, the current flowing through sheet P also gradually stabilizes. Once the current flowing through sheet P stabilizes, the CPU 401 stops the motor M7 and measures the voltage applied to sheet P using the voltage detection circuit 2315. Furthermore, the CPU 401 measures the current flowing through sheet P using the current detection circuit 2313. The CPU 401 calculates the resistance value (volume resistance value) by applying Ohm's law to the measured current and voltage. Once the measurement of current and voltage is complete, the CPU 401 reverses the motor M7, thereby reversing the cam 2303 and releasing the pressing force acting between electrode 2301 and electrode 2302. The CPU 401 then resumes transporting sheet P.

[0100] 13. Summary The transport roller pair 47a is an example of a transport means for gripping and transporting recording material. The transport roller pair 47a is an example of a transport means for transporting recording material along a transport path. The transport guide 400 is an example of a guidance means for guiding the recording material being transported by the transport roller pair 47a. The transport guide 400 is an example of a guidance means for guiding the recording material being transported by the transport means along a transport path. The stiffness sensor 44 is an example of a first detection means that detects the stiffness of the recording material by contacting the recording material that is stopped and being gripped by the transport roller pair 47a and pushing the recording material. The stiffness sensor 44 is an example of a first detection means that detects the stiffness of the recording material by contacting a part of the recording material after the recording material has stopped and pushing the recording material. The controller 700 is an example of a control means that stops the transport of the recording material by the transport roller pair 47a before the stiffness sensor 44 starts detecting the stiffness of the recording material. The controller 700 is an example of a control means that stops the recording material while it is being held by the transport means. The controller 700 is an example of a control means that resumes transporting the recording material by the transport roller pair 47a after the stiffness sensor 44 has finished detecting the stiffness of the recording material. As shown in Figures 4A and 6A, the first detection means is located on one side of the stopped recording material, and part of the guiding means may be located on the other side. The controller 700 controls the stopping position of the recording material so that, when the recording material is pushed from one side to the other by the first detection means, the recording material and the guiding means located on the other side do not come into contact. The distance T from the stopping position of the rear end of the recording material to the detection position of the stiffness sensor 44 may be given, for example, by equation Eq2. This makes it possible to measure the stiffness with even greater accuracy.

[0101] The controller 700 and the determination unit 804 are examples of determination means that determine image formation conditions based on the stiffness detected by the stiffness sensor 44. The image formation units 10Y, 10M, 10C, and 10K are examples of image formation means that form an image on the recording material using the image formation conditions determined by the determination unit 804. Since image formation conditions based on accurately measured stiffness are used, a more reproducible image will be formed on the sheet P.

[0102] The controller 700 and registration unit 805 are examples of registration means that associate identification information for distinguishing the type of recording material with the image forming conditions determined by the determination unit 804 and register the identification information and image forming conditions. The input device 704 is an example of input means into which the specification of identification information is input. The image forming units 10Y, 10M, 10C, and 10K form an image on the recording material using the image forming conditions associated with the identification information specified through the input device 704. Since the transport of the sheet P is stopped during the registration process, the registration process is a time-consuming process. On the other hand, the quality of the sheet P produced in large quantities is stable. By acquiring physical property values ​​for any sheet P from among many sheets P of the same type, the image forming conditions suitable for that type can be determined with high accuracy. Furthermore, by inputting identification information indicating a specific type, the controller 700 can identify appropriate image forming conditions. Therefore, the efficiency of continuously forming images on sheets P of the same type is improved. In other words, appropriate image forming conditions can be determined without stopping the transport of the sheet P to measure the stiffness in the middle of image formation.

[0103] The large-capacity decks 40a to 40c and the manual feed tray 48 are examples of storage means for storing recording material. The first transport path 11 is an example of a first transport path extending from the storage means. The escape tray 46 is an example of a holding means for holding recording material discharged from the second transport path 12. The image forming unit 10Y and the like are arranged to form an image on the recording material transported along the third transport path 13. When the registration unit 805 performs registration processing, the recording material may be guided to the second transport path 12. This will make it possible to protect the image forming apparatus 101 from unregistered sheets P.

[0104] As shown in Figure 1 and other figures, a pair of transport rollers 47a and a stiffness sensor 44 may be arranged in the second transport path 12. The flapper 49 is an example of a guide member that guides the recording material that has been transported along the first transport path 11 to the second transport path 12 or the third transport path 13. The flapper 49 may also be called a switching means for switching the transport direction of the sheet P, a regulating means for restricting the transport direction of the sheet P, or a specifying means for specifying the transport direction of the sheet P.

[0105] The resistance sensor 45 is positioned on the second transport path 12 and is an example of a second detection means for detecting physical properties of the recording material that are different from stiffness (e.g., volume resistivity). The determination unit 804 may determine the image formation conditions by considering the physical properties detected by the resistance sensor 45. Since multiple physical properties are considered, the image formation conditions will be determined with greater accuracy. The resistance sensor 45 may also detect the physical properties of the recording material during a stop period when the transport of the recording material is stopped. The stiffness sensor 44 may also detect the stiffness during the same stop period. This makes it possible to detect multiple physical properties with only one stop of sheet P transport.

[0106] The basis weight sensor 42 and the surface quality sensor 43 are arranged on the first transport path 11 and are an example of a second detection means that detects physical properties of the recording material that are different from stiffness (e.g., basis weight, thickness, surface quality). The determination unit 804 may determine the image formation conditions by considering the physical properties detected by the second detection means. Since multiple physical properties are considered, the image formation conditions will be determined with greater accuracy. The physical properties may be at least one of the basis weight of the recording material, the thickness of the recording material, and the surface quality of the recording material.

[0107] The correction value acquisition unit 1101 and the correction unit 1102 are examples of correction means that correct stiffness according to physical property values ​​detected by a second detection means (e.g., basis weight sensor 42, surface property sensor 43). This will further improve the accuracy of stiffness measurement. The correction value acquisition unit 1101 and the correction unit 1102 may determine a correction value according to the physical property values ​​and correct the stiffness based on the correction value. The correction value acquisition unit 1101 may determine a correction value according to a combination of multiple physical property values ​​of different types.

[0108] The controller 700 is configured such that the transport roller pair 47a, 47b stops transporting the recording material while the stiffness sensor 44 detects the stiffness of the recording material. The correction unit 1102 may correct the stiffness based on the amount of deviation in the stopping position of the rear end of the recording material.

[0109] The image sensor 1401 is an example of an imaging means that captures an image of the rear end of the recording material when the transport roller pair 47a stops transporting the recording material. The displacement amount acquisition unit 1601 may determine the displacement amount of the stopping position based on the image 1500 of the rear end acquired by the image sensor 1401.

[0110] The height G of the transport guide 400 may be such that the rear end of the sheet P, which has been pushed in by the probe 404 by a distance H, does not come into contact with the transport guide 400. (Other embodiments) The present invention can also be realized by supplying a program that implements one or more of the functions of the above embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that implements one or more functions.

[0111] The technical ideas derived from this disclosure are not limited to the exemplary embodiments disclosed, but are intended to encompass various modifications of the exemplary embodiments, or substitutions with equivalent structures or functions. The scope of the following claims should be interpreted in the broadest way to encompass all such modifications and equivalent structures and functions.

[0112] This application claims priority based on Japanese Patent Application No. 2025-017909, filed on February 5, 2025, and all of its contents are incorporated herein by reference.

Claims

1. An image forming apparatus comprising: a transport means for transporting recording material onto a transport path; a guide means for guiding the recording material transported by the transport means onto the transport path; a control means for stopping the recording material while it is held by the transport means; and a first detection means for detecting the stiffness of the recording material by contacting a part of the recording material and pushing it after it has stopped, wherein the first detection means is positioned on one side of the stopped recording material, and a part of the guide means is positioned on the other side, and the control means controls the stopping position of the recording material such that, when the recording material is pushed from one side to the other side by the first detection means, the recording material and the guide means positioned on the other side do not come into contact.

2. The image forming apparatus according to claim 1, wherein the control means controls the transport means such that the distance T from the stopping position of the rear end of the recording material to the detection position of the first detection means satisfies T = S(0.5G - H) / H - D, where S is the distance between the transport means and the detection position of the first detection means, G is the height of the transport path formed by the guidance means, H is the distance the first detection means pushes the recording material to detect the stiffness, and D is the tolerance of the stopping position by the transport means.

3. The image forming apparatus according to claim 1 or 2, further comprising: a determination means for determining image forming conditions based on the stiffness detected by the first detection means; and an image forming means for forming an image on the recording material using the image forming conditions determined by the determination means.

4. The image forming apparatus according to claim 3, further comprising: a registration means for registering the identification information and the image forming conditions by associating the identification information for distinguishing the type of recording material with the image forming conditions determined by the determination means; and an input means for inputting the specification of the identification information, wherein the image forming means forms an image on the recording material using the image forming conditions associated with the identification information specified through the input means.

5. The image forming apparatus according to claim 4, further comprising: a storage means for storing recording material; a first transport path extending from the storage means; a second transport path and a third transport path branching from the first transport path; and a holding means for holding the recording material discharged from the second transport path, wherein the image forming means is arranged to form an image on the recording material transported along the third transport path, and when the registration means performs a registration process, the recording material is guided to the second transport path.

6. The image forming apparatus according to claim 5, wherein the transport means and the first detection means are arranged in the second transport path.

7. The image forming apparatus according to claim 5 or 6, further comprising a switching means for switching the transport path of the recording material from the first transport path to the second transport path or the third transport path.

8. An image forming apparatus according to any one of claims 5 to 7, further comprising a second detection means arranged on the second transport path for detecting a physical property value of the recording material that is different from the stiffness, wherein the determination means determines the image forming conditions taking into consideration the physical property value detected by the second detection means.

9. The image forming apparatus according to claim 8, wherein the second detection means detects the physical properties of the recording material during a stop period when the transport of the recording material is stopped, and the first detection means detects the stiffness during the stop period.

10. The image forming apparatus according to claim 8 or 9, wherein the physical property value is the volume resistivity of the recording material.

11. The image forming apparatus according to any one of claims 5 to 7, further comprising a second detection means arranged on the first transport path for detecting a physical property value of the recording material that is different from the stiffness, wherein the determination means determines the image forming conditions taking into consideration the physical property value detected by the second detection means.

12. The image forming apparatus according to claim 11, wherein the physical property value detected by the second detection means is at least one of the basis weight of the recording material, the thickness of the recording material, and the surface properties of the recording material.

13. An image forming apparatus according to any one of claims 1 to 6, further comprising: a second detection means for detecting a physical property value of the recording material that is different from the stiffness; and a correction means for correcting the stiffness according to the physical property value detected by the second detection means.

14. The image forming apparatus according to claim 13, wherein the correction means determines a correction value according to the physical property value and corrects the stiffness based on the correction value.

15. The image forming apparatus according to claim 14, wherein the correction means determines the correction value according to a combination of multiple physical property values ​​of different types detected by the second detection means.

16. The image forming apparatus according to claim 15, wherein the plurality of physical properties include the surface properties of the recording material and the basis weight of the recording material.

17. The image forming apparatus according to any one of claims 1 to 12, wherein the transport means is configured to stop transporting the recording material while the first detection means detects the stiffness of the recording material, and the image forming apparatus further has a correction means for correcting the stiffness based on the amount of displacement of the stopping position of the rear end of the recording material.

18. The image forming apparatus according to claim 17, further comprising an imaging means for imaging the rear end of the recording material when the transport means stops transporting the recording material, wherein the correction means determines the amount of displacement of the stopping position based on the image of the rear end obtained by the imaging means.

19. The image forming apparatus according to any one of claims 1 to 18, wherein the guiding means has a plate that forms the transport path, and the plate has a passage opening through which a contact of the first detection means for pressing the recording material passes.

20. The image forming apparatus according to any one of claims 1 to 19, wherein the height G of the transport path is such that the rear end of the recording material, which has been pushed in by a distance H by the contactor of the first detection means, does not come into contact with the guiding means.

Images