Sheet resistance detection device, image forming system, and sheet resistance detection method

Abstract

To detect resistance information corresponding to sheet resistance including the amount of electric charges that move in association with conveyance of a sheet.SOLUTION: A sheet characteristic detection device 2 according to an aspect of the present invention comprises: an AC voltage application unit 212 that applies AC voltage to a sheet; an output value detection unit 213 that detects an output value of the AC voltage applied to the sheet; and a sheet resistance calculation unit 214 that detects resistance information corresponding to sheet resistance on the basis of the output value.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a paper resistance detection device, an image forming system, and a paper resistance detection method. [Background technology]

[0002] Conventionally, in an image forming apparatus, resistance information corresponding to the paper resistance, such as a volume resistance value, is detected, and image creation (image formation) parameters such as a transfer voltage and a fixing temperature are adjusted according to the magnitude of the detected resistance information. For example, Patent Document 1 discloses a method in which a voltage is applied from a high-voltage power supply to a paper held by a registration roller, and the resistance value of the transfer material is obtained based on an output voltage from a current detection resistor and known resistance values ​​of the registration roller and the current detection resistor.

[0003] In the technology described in Patent Document 1, it is assumed that the resistance value is calculated while the paper is being transported. In this case, the electric charge stored in the capacitor component of the paper flows in the paper transport direction, resulting in a resistance value that is lower than the resistance value calculated when the paper transport is stopped.

[0004] Meanwhile, as a technique for detecting resistance information of a sheet while the conveyance of the sheet is stopped, there is a technique described in Patent Document 2. Patent Document 2 discloses that a registration roller temporarily stops the conveyance of the sheet and a resistance measuring unit measures the resistance value of the sheet. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2006-215383 A [Patent Document 2] JP 2020-91420 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, when the transport of the paper is temporarily stopped in order to measure the resistance value of the paper, the throughput of the image forming apparatus decreases accordingly.

[0007] The present invention has been made to solve the above-mentioned problems, and its purpose is to make it possible to detect resistance information corresponding to paper resistance, including the amount of charge that moves as the paper is transported. [Means for solving the problem]

[0008] A paper resistance detection device according to one embodiment of the present invention includes an AC voltage application unit that applies an AC voltage to paper, an output value detection unit that detects an output value of the AC voltage applied to the paper, and a resistance information detection unit that detects resistance information corresponding to the paper resistance of the paper based on the output value. Effect of the Invention

[0009] According to the present invention, it is possible to detect resistance information corresponding to the paper resistance, including the amount of charge that moves as the paper is transported, based on the output value of the AC voltage, so that the resistance value of the paper can be detected without stopping the transport of the paper. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing an overview of the problem to be solved by the present invention. [Diagram 2] 1 is a diagram showing a schematic configuration of an image forming system according to a first embodiment of the present invention. [Diagram 3] 1 is a block diagram showing an example of the configuration of each control system of a paper characteristic detection device 2 and an image forming device 3 that constitute an image forming system according to a first embodiment of the present invention. [Figure 4] 5A to 5C are diagrams illustrating three types of currents that flow through a sheet when an AC voltage is applied by an AC voltage application unit according to the first embodiment of the present invention. [Diagram 5] 4 is a diagram showing the area of ​​a sheet in a nip portion formed by a resistance detection roller according to the first embodiment of the present invention; FIG. [Figure 6] 4 is a diagram showing a phase difference θ between an output AC current and an output AC voltage according to the first embodiment of the present invention. FIG. [Figure 7] 5 is a diagram showing the relationship between the phase difference, the output AC current, and the AC current flowing in the nip region according to the first embodiment of the present invention. FIG. [Figure 8] 5 is a diagram showing the area of ​​a sheet in a region downstream of a nip portion in the transport direction according to the first embodiment of the present invention. FIG. [Figure 9] 5 is a flowchart showing an example of a procedure of a paper resistance detection process performed by a paper resistance detection unit according to the first embodiment of the present invention. [Figure 10] FIG. 11 is a circuit diagram showing an example of the configuration of a pulse voltage application unit and an output value detection unit according to a second embodiment of the present invention. [Figure 11] 10 is a graph showing the relationship between the pulsed power supply voltage of the pulsed voltage application unit and the voltage at point A according to the second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In this specification and the drawings, elements having substantially the same functions or configurations are denoted by the same reference numerals, and duplicated explanations will be omitted.

[0012] Before describing the embodiments of the present invention, the problems to be solved by the present invention will be described. Fig. 1 is a diagram showing an overview of the problems to be solved by the present invention.

[0013] The upper part of Fig. 1 shows a state in which the resistance detection roller 211C is nipping the paper Sh transported in the transport direction Df. The resistance detection roller 211C is composed of a resistance detection roller 211a and a resistance detection roller 211b. A high-voltage power supply 212C is connected to the resistance detection roller 211a, and a high-voltage DC voltage is applied to the paper Sh from the high-voltage power supply 212C. More specifically, the high-voltage DC voltage is applied to the paper Sh by a voltage application unit formed in a nip portion 211n between the resistance detection roller 211a and the resistance detection roller 211b.

[0014] An output current detection unit (not shown) is connected to the resistance detection roller 211b, and detects the output current Iout relative to the input voltage. Then, a paper resistance calculation unit (not shown) calculates the volume resistance value (hereinafter also simply referred to as "resistance value") of the paper Sh by dividing the applied voltage Vout by the output DC current Iout.

[0015] However, if the transport of the paper Sh is not stopped, the resistance value of the current flowing into the surface of the paper Sh, i.e., the charge current Ip that forms the charge of the capacitor component of the paper Sh, is carried in the transport direction Df of the paper Sh, as shown in the lower part of Fig. 1. As a result, the current that the output current detection unit can detect is only the output DC current Iout excluding the charge current Ip, i.e., the output DC current Ir that conducts the resistance component of the paper Sh. Therefore, if the resistance value of the paper is calculated by regarding the output DC current Ir as the output DC current Iout, the calculated resistance value will be smaller than the resistance value calculated when the paper Sh was stopped.

[0016] The equivalent circuit of the paper Sh is represented by a parallel circuit of a capacitance component and a resistance component. A current flows through the capacitance component of the paper Sh until the charge is filled, but the current stops when the filling is complete. However, when the paper Sh is transported, a new portion of the paper Sh reaches the voltage application section (nip section 211n) after the capacitance component of the paper Sh is filled at the voltage application section until the filling is completed. In other words, the charge current Ip filled in the capacitance component of the paper Sh flows in the transport direction Df of the paper Sh.

[0017] In addition, the faster the transport speed of the paper Sh, the shorter the time from when the capacitor component of the paper Sh is filled at the voltage application section until other parts of the paper Sh reach the position of the voltage application section. This causes the value of the charge current Ip carried in the transport direction Df by the capacitor component of the paper Sh to increase. In other words, the faster the transport speed of the paper Sh, the lower the resistance value calculated by the paper resistance calculation section.

[0018] Therefore, in order to accurately detect the resistance value of the paper Sh, it is desirable to stop the transport of the paper Sh. However, stopping the transport of the paper Sh also reduces the throughput of the image forming apparatus accordingly. Therefore, there has been a demand for proposing and providing a technology that can accurately detect the resistance value of the paper Sh while the paper Sh is being transported.

[0019] <First embodiment> [Image formation system configuration] Next, a schematic configuration of an image forming system 100 according to a first embodiment of the present invention will be described with reference to Fig. 2. Fig. 2 is a diagram showing a schematic configuration of the image forming system 100 according to this embodiment. As shown in Fig. 2, the image forming system 100 includes a paper feeder 1, a paper characteristic detector 2, an image forming device 3, and a paper discharge unit 4.

[0020] The paper feed device 1 includes paper feed trays 11 to 13, which store paper of various paper types and sizes. Based on a print job transmitted from a terminal device (not shown), the paper feed device 1 feeds paper from paper feed trays 11 to 13 and conveys the paper to the paper characteristic detection device 2. Note that while FIG. 1 shows an example in which the paper feed device 1 includes three paper feed trays, the present invention is not limited to this. The number of paper feed trays may be two or less, or may be four or more.

[0021] The paper characteristic detection device 2 is a device that detects the characteristics of the paper Sh, and includes a paper resistance detection unit 21 that detects the volume resistance value of the paper Sh. The paper resistance detection unit 21 includes a resistance detection roller 211, which is composed of a resistance detection roller 211a and a resistance detection roller 211b.

[0022] In this embodiment, the paper resistance detection unit 21 applies a high AC (alternating current) voltage to the paper Sh in a conveyed state, and detects the resistance value of the paper Sh based on information on the phase difference between the output AC voltage and the output AC current of the AC voltage applied to the paper Sh. Then, the paper resistance detection unit 21 outputs the detected resistance value to the control unit 300 (see FIG. 4) of the image forming apparatus 3.

[0023] 2 shows an example in which the paper characteristic detection device 2 includes only the paper resistance detection unit 21, but the present invention is not limited to this. The paper characteristic detection device 2 may include various media sensors such as a paper size detection sensor, a paper thickness detection sensor, a moisture content detection sensor, a basis weight detection sensor, a stiffness detection sensor, and a surface property detection sensor. In addition, in the present embodiment, an example is shown in which the paper characteristic detection device 2 is provided separately from the image forming device 3, but the present invention is not limited to this. Media sensors such as the paper resistance detection unit 21 may be provided within the image forming device 3.

[0024] The image forming apparatus 3 includes a paper feed tray 30 , a transport path 311 , an operation display unit 32 , an image forming unit 33 , a fixing unit 34 , and a paper reversing unit 35 . The paper feed tray 30 stores paper sheets Sh. The paper sheets Sh stored in the paper feed tray 30 are fed and transported to the image forming unit 33 under the control of a paper feed control unit (not shown).

[0025] Based on the control of the transport control unit 31 (see FIG. 3), the transport path 311 transports the paper Sh fed from the paper feed device 1 or the paper feed tray 30 to the paper discharge unit 4 via the image forming unit 33. The transport path 311 is provided with a plurality of rollers (transport rollers: not shown) for transporting the paper Sh.

[0026] The operation display unit 32 is composed of a display unit such as an LCD (Liquid Crystal Display) or an organic EL (Electro Luminescence) display, and an operation input unit including keys, buttons, etc. The display unit and the operation input unit may be integrally formed as a touch panel.

[0027] The operation display unit 32 generates an operation signal representing the content of the operation input by the user to the operation unit, and supplies the operation signal to the control unit 300 (see FIG. 3). For example, when an operation instructing the start of image formation processing is input by the user, the operation display unit 32 generates a signal for starting the image formation processing, and supplies the signal to the control unit 300. Also, for example, the operation display unit 32 displays the content of the operation by the user, setting information, etc. on the display unit based on the display signal supplied from the control unit 300.

[0028] The image forming section 33 includes four image forming units 331Y, 331M, 331C, and 331K for forming toner images of the respective colors of Y (yellow), M (magenta), C (cyan), and K (black). The image forming units 331Y, 331M, 331C, and 331K include a charging section, an LED writing unit (laser light source) (all not shown), photoconductor drums 332Y, 332M, 332C, and 332K, and developing sections 333Y, 333M, 333C, and 333K, respectively.

[0029] The developing units 333Y, 333M, 333C, and 333K form latent images on the surfaces (outer peripheries) of the photoconductor drums 332Y, 332M, 332C, and 332K, and cause toner supplied from a developing device (not shown) to adhere to the latent images, thereby forming toner images on the photoconductor drums 332Y, 332M, 332C, and 332K.

[0030] In the following description, when it is not necessary to distinguish between the image forming units 331Y, 331M, 331C, and 331K, they will be collectively referred to as image forming units 331. When it is not necessary to distinguish between the photoconductor drums 332Y, 332M, 332C, and 332K, they will be collectively referred to as photoconductor drum 332. When it is not necessary to distinguish between the developing units 333Y, 333M, 333C, and 333K, they will be collectively referred to as developing unit 333.

[0031] The image forming unit 33 also includes an intermediate transfer belt 334 and a secondary transfer unit 335. The intermediate transfer belt 334 is a belt onto which the toner images formed on the photoconductor drums 332 of each color are primarily transferred, and rotates in a clockwise direction as indicated by a downward arrow in the figure. The secondary transfer unit 335 is a roller that secondarily transfers the toner images of each color primarily transferred onto the intermediate transfer belt 334 onto the paper Sh transported on the transport path 311.

[0032] The fixing unit 34 is provided downstream of the secondary transfer unit 335 on the conveying path 311, and performs a fixing process of fixing the toner image transferred to the paper Sh by the secondary transfer unit 335 onto the paper Sh. The fixing process of the toner image by the fixing unit 34 is performed by pressing and heating the paper Sh onto which the toner image has been transferred with a roller (not shown). The paper Sh onto which the toner image has been fixed by the fixing unit 34 is conveyed on the conveying path 311 and discharged to the paper discharge tray 41 or the purge tray 42 of the paper discharge unit 4.

[0033] When double-sided printing is specified in the print job, the paper reversing unit 35 reverses the paper Sh and conveys it to the image forming unit 33 .

[0034] In the present embodiment, the image forming method of the image forming apparatus 3 is an electrophotographic method, but the present invention is not limited to this. The image forming method of the image forming apparatus 3 may be another method such as an inkjet method.

[0035] [Configuration of the control system of the image forming system] Next, the configuration of a control system of the image forming system 100 according to one embodiment of the present invention will be described with reference to Fig. 3. Fig. 3 is a block diagram showing an example of the configuration of each control system of the paper characteristic detection device 2 and the image forming device 3 that constitute the image forming system 100.

[0036] (Paper characteristic detection device) As shown in FIG. 3, the paper characteristic detection device 2 includes a control unit 200, a storage unit 204, a paper resistance detection unit 21, and a communication unit 22.

[0037] The control unit 200 includes a central processing unit (CPU) 201, a random access memory (RAM) 202, and a read only memory (ROM) 203.

[0038] The CPU 201 reads out various control programs and setting data stored in the ROM 203, and loads the programs into the RAM 202 to execute the programs. The CPU 201 also controls the operations of the components constituting the paper characteristic detection device 2.

[0039] The RAM 202 provides a working memory space for the CPU 201 and stores temporary data. The RAM 202 may include a non-volatile memory.

[0040] The ROM 203 stores various control programs and setting data executed by the CPU 201. The programs are stored in the form of computer-readable program codes in the ROM 203. Note that a rewritable non-volatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash memory may be used instead of the ROM 203.

[0041] The storage unit 204 is configured, for example, with a hard disk drive (HDD) or a solid state drive (SSD). The programs stored in the ROM 203 may be stored in the storage unit 204. That is, the ROM 203 or the storage unit 204 is used as an example of a computer-readable non-transitory recording medium that stores a program executed by a computer.

[0042] The paper resistance detection unit 21 includes a resistance detection roller 211 , an AC voltage application unit 212 , an output value detection unit 213 , and a paper resistance calculation unit 214 . 2, the paper resistance detection unit 21 includes resistance detection rollers 211a and 211b. An AC voltage application unit 212 is connected to the resistance detection roller 211a, and an AC voltage application unit is formed at a nip portion 211n (see FIG. 2) between the resistance detection roller 211a and the resistance detection roller 211b.

[0043] The AC voltage application unit 212 (an example of an AC voltage application unit) applies a high AC voltage to the resistance detection roller 211a. The AC voltage applied by the AC voltage application unit 212 is, for example, 1 kHz and 100 V. However, this value is only an example, and AC voltages of other voltages and frequencies may be used. The AC voltage described in this specification includes not only AC voltages whose voltage changes like a sine wave, but also pulse voltages (described in the second embodiment) whose pulse waveforms are output at regular intervals.

[0044] The output value detection unit 213 is connected to the resistance detection roller 211b, and detects the output AC voltage value and the output AC current value (an example of an output value) of the AC voltage applied to the paper Sh. Then, the output value detection unit 213 outputs the detected output AC voltage value and output AC current value to the paper resistance calculation unit 214.

[0045] The paper resistance calculation unit 214 (an example of a resistance information detection unit) calculates the phase difference between the output AC voltage value and the output AC current value detected by the output value detection unit 213, and calculates the resistance value (volume resistance value) of the paper Sh based on the phase difference and the conveyance speed of the paper Sh. An overview of the calculation process of the resistance value of the paper Sh by the paper resistance calculation unit 214 will be described later with reference to Figs. 4 to 8, and the procedure of the calculation process of the resistance value of the paper Sh by the paper resistance calculation unit 214 will be described later with reference to Fig. 9.

[0046] The communication unit 22 controls the transmission and reception of various signals, image data, and the like between the image forming apparatus 3 connected via a communication cable or the like.

[0047] (Image forming device) As shown in FIG. 3, the image forming apparatus 3 includes a control unit 300, a storage unit 304, a transport control unit 31, an operation display unit 32, an image forming unit 33, a fixing unit , and a communication unit .

[0048] The control unit 300 includes a CPU 301 , a RAM 302 , and a ROM 303 . CPU 301 reads out various control programs and setting data stored in ROM 303 and loads the programs in RAM 302, thereby executing the programs. CPU 301 also controls the operation of each unit constituting image forming apparatus 3. For example, CPU 301 calculates image creation (image formation) parameters such as the transfer voltage by photoconductor drum 332 (see FIG. 2) and the fixing temperature in fixing unit 34 based on information on the resistance value of paper Sh transmitted from paper characteristic detection device 2. CPU 301 then controls the image creation (image formation) operation based on the image creation parameters.

[0049] The RAM 302 provides a working memory space for the CPU 301 and stores temporary data. The RAM 302 may include a non-volatile memory.

[0050] The ROM 303 stores various control programs and setting data executed by the CPU 301. The programs are stored in the form of computer-readable program codes in the ROM 303. Note that a rewritable non-volatile memory such as an EEPROM or a flash memory may be used instead of the ROM 303.

[0051] The storage unit 304 is configured with, for example, an HDD, an SSD, etc. The program stored in the ROM 303 may be stored in the storage unit 304. In other words, the ROM 303 or the storage unit 304 is used as an example of a computer-readable non-transitory recording medium that stores a program executed by a computer.

[0052] The transport control unit 31 controls the transport operation of the paper sheet Sh in a transport path 311 (see FIG. 2). The image forming unit 33 and the fixing unit 34 have already been described with reference to FIG. 2, and therefore will not be described here.

[0053] The communication unit 36 ​​controls the transmission and reception of various signals, image data, etc., between the paper characteristic detection device 2 connected via a communication cable, etc. The communication unit 36 ​​also controls the transmission and reception of various signals, image data, etc., between the communication unit 36 ​​and a terminal device (not shown) connected via a network (not shown).

[0054] [Overview of paper resistance detection process] Next, an overview of the paper resistance detection process performed by the paper resistance detection unit 21 will be described. FIG. 4 is a diagram for explaining three types of currents that flow through the sheet Sh when an AC voltage is applied by the AC voltage application unit 212 (see FIG. 3).

[0055] 4, when the AC voltage application unit 212 applies the AC voltage Vout, an AC current Ip_ac (an example of resistance information corresponding to paper resistance) that forms a charge on the capacitor component of the paper Sh, and an AC current Ir_ac (an example of a resistance conduction current value) that conducts the resistance component of the paper Sh flow through the paper Sh. Furthermore, when the AC voltage Vout is applied, an AC current Ic that conducts the capacitor component of the paper Sh flows through the paper Sh. In this embodiment, the paper resistance detection unit 21 detects these current values ​​to calculate the resistance value (volume resistance value: an example of resistance information corresponding to paper resistance) of the paper Sh in a state in which the paper Sh is being transported.

[0056] 5 is a diagram showing the area of ​​the sheet Sh at the nip portion 211n formed by the resistance detection roller 211. When the sheet Sh is considered as a parallel plate capacitor, the region of the nip portion 211n in the sheet Sh (hereinafter also referred to as the "nip portion region") can be considered as a capacitor having the following area charged with the electric charge of the AC current Ip_ac.

[0057] Nip area = nip width Lnip * axial length of resistance detection roller 211 Lroll * thickness of paper d

[0058] Then, an AC current Ic flowing in the nip region of the paper Sh due to application of an AC voltage Vout_ac of frequency f can be expressed by the following formula (1): In the above formula (1), "εp" represents the dielectric constant of the paper Sh.

[0059] Ic=2*π*f*εp*Lnip*Lroll*Vout_ac / d...Formula (1)

[0060] As described above, the equivalent circuit of the paper Sh is represented by a parallel circuit of a capacitance component and a resistance component. Therefore, as shown in Fig. 6 described later, when an AC voltage is applied to the paper Sh, a phase difference occurs between the waveform Wi of the output AC current Iout_ac and the waveform Wv of the output AC voltage Vout_ac. That is, a delay corresponding to the phase difference θ exists between when the output value detection unit 213 (see Fig. 3) detects the output AC voltage Vout_ac and when it detects the output AC current Iout_ac.

[0061] Fig. 6 is a diagram showing a phase difference θ between the output AC current Iout_ac and the output AC voltage Vout_ac. In Fig. 6, the waveform Wi (sine wave) of the output AC current Iout_ac is indicated by a dashed line, and the waveform Wv (sine wave) of the output AC voltage Vout_ac is indicated by a solid line.

[0062] Fig. 7 is a diagram showing the relationship between the phase difference θ, the output AC current Iout_ac, and the AC current Ic flowing in the nip region. The output AC current Iout_ac shown as a diagonal vector in Fig. 7 can be decomposed into the AC current Ic shown as a vertical vector and the sum of the AC currents Ip_ac and Ir_ac shown as horizontal vectors. As a result, the AC current Ic that conducts the capacitor component of the paper Sh can be expressed by the following equation (2).

[0063] Ic = Iout_ac * sinθ ... Equation (2)

[0064] Substituting equation (2) into equation (1) above gives equation (3) below.

[0065] Iout_ac*sinθ=2*π*f*εp*Lnip*Lroll*Vout_ac / d…Formula (3)

[0066] Further, based on the above formula (3), the dielectric constant εp of the paper Sh can be calculated by the following formula (4).

[0067] εp=Iout_ac*sinθ*d / (2*π*f*Lnip*Lroll*Vout_ac) …Equation (4)

[0068] When the dielectric constant εp of the paper Sh is known and there is a table (not shown) that associates the paper quality of the paper Sh with environmental information, the thickness d of the paper Sh can be calculated based on the dielectric constant εp and the temperature, humidity, etc., surrounding the image forming system 100. In other words, the paper resistance calculation unit 214 can calculate the resistance value of the paper Sh even when the thickness d of the paper is unknown.

[0069] Furthermore, when the dielectric constant εp of the paper Sh and the thickness d of the paper Sh are known, and there is a table (not shown) that associates the paper quality of the paper Sh with environmental information and moisture content, the moisture content of the paper Sh can be calculated based on the dielectric constant εp and the temperature, humidity, etc., surrounding the image forming system 100. In other words, the paper resistance calculation unit 214 can calculate the resistance value of the paper Sh even if the moisture content of the paper is unknown.

[0070] 8 is a diagram showing the area of ​​the sheet Sh in the region downstream of the nip portion 211n in the transport direction Df. When the sheet Sh is considered as a parallel plate capacitor, the region downstream of the nip portion 211n in the sheet Sh (hereinafter also referred to as the "nip downstream region") can be considered as a capacitor charged with the AC current Ip_ac and having the following area:

[0071] Downstream area of ​​the nip portion = length in the conveying direction of the paper Sh passed through in 1 second Lsys * axial length of the resistance detection roller 211 Lroll * thickness of the paper d

[0072] Therefore, the capacitance Cp of the capacitor in the downstream region of the nip can be expressed by the following formula (5).

[0073] Cp=εp*Lsys*Lroll / d...Equation (5)

[0074] The downstream region of the nip, which has the capacitance shown in the above formula (5), is charged by the voltage Vout_ac. The downstream region of the nip is also the region through which the charge current Ip of the capacitor component of the paper Sh flows. Therefore, the amount of charge Qp charged to the capacitor in one second is the charge current Ip (current value). The charge current Ip can be expressed by the following formula (6). Formula (5) is substituted for the capacitor capacitance Cp.

[0075] Ip=Cp*Vout_dc=εp*Lsys*Lroll*Vout_dc / d...Formula (6)

[0076] Then, substituting the above formula (5) into the above formula (6) gives the following formula (7).

[0077] Ip=Iout_ac*sinθ*Lsys*Vout_dc / (2*π*f*Lnip*Vout_ac) …Equation (7)

[0078] Since all the parameters constituting the right side of the above formula (7) are known values, the paper resistance calculation unit 214 (see FIG. 3) can calculate the charge current Ip of the charge of the capacitor component of the paper Sh that flows in the paper transport direction Df by using the above formula (7). Then, the paper resistance calculation unit 214 can accurately measure the output AC current Ir_ac that conducts the resistance component of the paper Sh by subtracting the calculated charge current Ip from the AC current Iout applied to the paper Sh. Furthermore, the paper resistance calculation unit 214 can calculate the volume resistance value of the paper Sh by dividing the output AC voltage Vout_ac by the output AC current Ir_ac. Therefore, according to this embodiment, the paper resistance calculation unit 214 can measure the accurate resistance value (volume resistance value) of the paper Sh even in a state where the paper Sh has been transported.

[0079] [Paper resistance detection process procedure] Next, a paper resistance detection process by the paper resistance detection unit 21 of the paper characteristic detection device 2 will be described with reference to Fig. 9. Fig. 9 is a flowchart showing an example of the procedure of the paper resistance detection process by the paper resistance detection unit 21.

[0080] First, the AC voltage application unit 212 (see FIG. 3) of the paper characteristic detection device 2 applies a high AC voltage to the paper Sh being conveyed (step S1). Next, the output value detection unit 213 of the paper resistance detection unit 21 detects the output AC voltage Vout_ac and the output AC current Iout_ac applied to the paper Sh (step S2).

[0081] Next, the paper resistance calculation unit 214 calculates the phase difference θ between the output AC voltage Vout_ac and the output AC current Iout_ac detected in step S2 (step S3). Next, the paper resistance calculation unit 214 calculates the resistance value (volume resistance value) of the paper Sh based on the output AC voltage Vout_ac, the output AC current Iout_ac, the phase difference θ, the dielectric constant εp of the paper Sh, and the length Lsys of the paper Sh in the transport direction that is passed in one second (see FIG. 8) (step S4). The length Lsys of the paper Sh in the transport direction that is passed in one second is calculated based on the transport speed of the paper Sh.

[0082] In the above-described embodiment, the paper resistance detection unit 21 can calculate the charge Ip of the charge of the capacitor component of the paper Sh that is transported in the transport direction Df of the paper Sh based on information on the phase difference θ between the output AC voltage Vout_ac and the output AC current Iout_ac when a high voltage AC voltage is applied to the paper Sh. Then, the paper resistance detection unit 21 can calculate the volume resistance value of the paper Sh based on the current value excluding the charge current Ip, that is, the output AC current Ir_ac that conducts the resistance component of the paper Sh. Therefore, according to this embodiment, the paper resistance detection unit 21 can accurately calculate the volume resistance value of the paper Sh even when the paper Sh is being transported.

[0083] <Second embodiment> Next, a paper resistance detection process according to a second embodiment of the present invention will be described. In the first embodiment, the paper resistance detection unit 21 includes the AC voltage application unit 212, but in the second embodiment, a pulse voltage application unit 212A is used as a power source, and an output value detection unit 213A detects a pulse voltage and a pulse current. The pulse voltage application unit 212A here repeatedly turns on and off a pulsed voltage waveform of, for example, 100V at a constant cycle.

[0084] Fig. 10 is a circuit diagram showing an example of the configuration of the pulse voltage application unit 212A and the output value detection unit 213A according to this embodiment. Fig. 10 shows a circuit in which the pulse voltage application unit 212A configured as a pulse power supply and the output value detection unit 213A configured as a current detection resistor are connected to a parallel circuit of a capacitor component Shc and a resistor component Shr, which is an equivalent circuit of the paper Sh.

[0085] Fig. 11 is a graph showing the correspondence between the pulsed power supply voltage Vout_ps of the pulsed voltage application unit 212A and the voltage at point A (hereinafter also referred to as "point A voltage") of the circuit shown in Fig. 10. Point A is a point between the capacitor component Shc of the paper Sh and the output value detection unit 213A.

[0086] 11 shows the fall time (time constant) τ from the peak voltage Va, which is the voltage when the capacitor component Shc is charged to an equilibrium state, to the discharge of the charge of the capacitor component Shc. The discharge of the charge of the capacitor component Shc starts when the pulse of the pulsed power supply voltage Vout is turned off, and ends when the voltage becomes the peak voltage Va*0.36. It can be said that the fall time τ indicates the amount of delay of the output voltage with respect to the applied (input) voltage by the pulsed voltage application unit 212A. Note that the amount of delay of the output voltage with respect to the applied (input) voltage by the pulsed voltage application unit 212A may be found based on the rise time of the output voltage.

[0087] In this embodiment, the output current Iout_ps can be expressed by the following formula (8): "Rsense" in the following formula (8) indicates the resistance value of the output value detection unit 213A (current detection resistor).

[0088] Iout_ps=(Vout_ps-Va) / Rsense...Equation (8)

[0089] Moreover, the resistance value Rmove of the resistance component Shr of the sheet Sh when the sheet Sh passes through the resistance detection roller 211 (see FIG. 2) can be calculated by the following formula (9).

[0090] Rmove=Va / Iout_ps …Equation (9)

[0091] Moreover, the capacitance C of the capacitor component Shc of the paper Sh can be calculated by the following formula (10).

[0092] C=τ(Rmove+Rsense) / (Rmove*Rsense) …Equation (10)

[0093] Based on the above formula (10) and the information on the nip region shown in FIG. 5, the dielectric constant εp of the paper Sh can be calculated by the following formula (11).

[0094] εp=τ(Rmove+Rsense) / (Rmove*Rsense)*d / (Lnip*Lroll) …Equation (11)

[0095] The nip area having the capacitance shown in the above formula (10) is charged by the voltage Va, so the amount of charge Qp charged to the capacitor in one second is determined by the charging current Ip. The charging current Ip can be expressed by the following formula (12).

[0096] Ip=Cp*Va=εp*Lsys*Lroll*Va / d=τ(Rmove+Rsense) / (Rmove*Rsense)*Lsys*Va / Lnip...Equation (12)

[0097] Since all of the parameters constituting the right side of the above formula (12) are known values, the paper resistance calculation unit 214 (see FIG. 3) can calculate the charge current Ip of the charge of the capacitor component of the paper Sh that flows in the paper transport direction Df using the above formula (12). The paper resistance calculation unit 214 can then accurately measure the output pulse current Ir_ac that conducts the resistance component of the paper Sh by subtracting the calculated charge current Ip from the pulse power supply current Iout_ps applied to the paper Sh. This allows the paper resistance calculation unit 214 to measure an accurate resistance value (volume resistance value) of the paper Sh even when the paper Sh has been transported.

[0098] The volume resistance value of the paper Sh can be calculated from the pulse current, and the basic principle is the same as in the first embodiment, in that the volume resistance value of the paper Sh is calculated from the AC current.

[0099] Furthermore, according to the second embodiment, the pulse voltage application unit 212A applies a pulse voltage to the paper Sh, and therefore the configuration of the voltage generation portion can be simplified compared to the AC voltage application unit 212 according to the first embodiment that generates a sine wave.

[0100] In addition, each of the above-mentioned embodiments provides a detailed and specific description of the configuration of the device and system in order to clearly explain the present invention, and is not necessarily limited to having all of the configurations described.

[0101] In addition, the control lines and information lines shown in solid lines in Figure 2 are those considered necessary for explanation, and do not necessarily show all control lines and information lines in the product. In reality, it can be considered that almost all components are connected to each other.

[0102] In addition, in this specification, the processing steps describing chronological processing include not only processing that is performed chronologically in the order described, but also processing that is not necessarily performed chronologically but is performed in parallel or individually (for example, parallel processing or processing by objects). [Explanation of symbols]

[0103] 2...paper characteristic detection device, 3...image forming apparatus, 21...paper resistance detection section, 33...image forming section, 100...image forming system, 200...control section, 211...resistance detection roller, 212...AC voltage application section, 212A...pulse voltage application section, 213...output value detection section, 213A...output value detection section, 214...paper resistance calculation section

Claims

1. an AC voltage application unit that applies an AC voltage to the paper; an output value detection unit that detects an output value of the AC voltage applied to the paper; a resistance information detection unit that detects resistance information corresponding to the paper resistance of the paper based on the output value. Paper resistance detection device.

2. The AC voltage application unit applies the AC voltage to the paper in a conveyed state.

2. The paper resistance sensing device of claim 1.

3. The resistance information detection unit detects resistance information corresponding to a paper resistance of the paper based on information on a delay of the AC voltage applied to the paper by the AC voltage application unit, the delay information being detected by the output value detection unit.

3. The paper resistance sensing device of claim 2.

4. The resistance information detection unit detects resistance information corresponding to a paper resistance of the paper based on information on the delay of the AC voltage and information on the paper conveying speed.

4. The paper resistance sensing device of claim 3.

5. The waveform of the AC voltage is a sine wave, and information on the delay of the AC voltage is represented by a phase difference between an output voltage value and an output current value of the AC voltage detected by the output value detection unit.

5. The paper resistance sensing device of claim 4.

6. the resistance information corresponding to the paper resistance is a volume resistance value of the paper, The resistance information detection unit calculates an amount of charge of a current flowing in a paper transport direction based on a phase difference between an output voltage value and an output current value of the AC voltage and information on a paper transport speed, calculates a resistance conduction current value that conducts the paper's capacitor component by subtracting the amount of charge from the output current value, and calculates a volume resistance value of the paper by subtracting the resistance conduction current value from the output current value.

6. The paper resistance sensing device of claim 5.

7. The AC voltage is a voltage in which on and off of a pulse-like voltage waveform are repeated at a constant cycle, The resistance information detection unit detects resistance information corresponding to a paper resistance of the paper based on information on a peak voltage of the AC voltage.

5. The paper resistance sensing device of claim 4.

8. The information on the delay of the AC voltage is information on a delay in an output voltage value of the AC voltage detected by the output value detection unit with respect to the AC voltage applied to the paper by the AC voltage application unit.

8. The paper resistance sensing device of claim 7.

9. The information on the delay of the AC voltage is indicated by a rise time or fall time of the AC voltage detected by the output value detection unit with respect to the AC voltage applied to the paper by the AC voltage application unit.

9. The paper resistance sensing device of claim 8.

10. an AC voltage application unit that applies an AC voltage to the paper; an output value detection unit that detects an output value of the AC voltage applied to the paper; a resistance information detection unit that detects resistance information corresponding to a paper resistance of the paper based on the output value; an image forming section for forming an image on the paper; a control unit that adjusts an image forming parameter in the image forming unit based on resistance information corresponding to the paper resistance detected by the resistance information detection unit. Image forming system.

11. applying an AC voltage to the paper; detecting an output value of the AC voltage applied to the paper; and detecting resistance information corresponding to the paper resistance of the paper based on the output value. Paper resistance detection method.

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