Paper feeder and image forming apparatus

Abstract

To provide a paper feeding device that can improve the accuracy of discriminating the type of a sheet.SOLUTION: When a sheet type used by a user is fixed from among a plurality of sheet types of different sheets that can be fed from a tray, input of the sheet type is received from the user and registered in a specific threshold table 182. The basis weights of sheets corresponding to two or more registered sheet types are measured and representative values of the basis weights are determined. A specific threshold Th for discriminating the sheet types is determined from the determined representative values in terms of the magnitude of the basis weight, and stored in the specific threshold table 182. The basis weight of a sheet fed in the subsequent image forming job is measured, and the sheet type of the fed sheet is discriminated from the comparison between the measured basis weight and the specific threshold Th stored in the specific threshold table 182.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a sheet feeding device that feeds sheets stored in a tray, and more particularly to an improvement in technology for determining the type of sheets. [Background technology]

[0002] Some electrophotographic image forming devices, which form images on sheets such as paper fed from a paper feeder, use sensors or the like to determine the type of sheet, such as plain paper, thick paper, thin paper, etc., and then change image forming conditions such as transfer current and fixing temperature depending on the determined paper type, thereby forming an image suitable for that sheet (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-93896 Summary of the Invention [Problem to be solved by the invention]

[0004] A common method for determining the type of paper is to predetermine a threshold value for distinguishing between, for example, plain paper and thick paper based on the basis weight, and then compare the basis weight of the paper detected by a sensor with the predetermine threshold value to determine the type of paper.

[0005] However, this method is prone to the following problems.

[0006] For example, if a threshold value α for distinguishing between thin paper and regular paper by basis weight and a threshold value β (>α) for distinguishing between regular paper and thick paper by basis weight are set, if the basis weight value of the paper detected by the sensor is less than α, the paper is determined to be thin paper, if it is within the range of α to β, the paper is determined to be regular paper, and if it exceeds β, the paper is determined to be thick paper.

[0007] However, on the market, there is plain paper with a basis weight in the middle of the range of α to β, as well as plain paper with a basis weight close to α and plain paper with a basis weight close to β. If a user uses plain paper with a basis weight close to β, depending on the degree of variation in the sensor's detection value, each time the paper type is identified, the detection value may fall within the range of α to β and be correctly identified as plain paper, or it may slightly exceed β and be erroneously identified as cardboard.

[0008] In reality, even if the same paper type, plain paper, is used, sometimes an image may be formed on the plain paper under image forming conditions for plain paper due to a correct discrimination result, and at other times an image may be formed on the plain paper under image forming conditions for cardboard due to a misdiscrimination result from cardboard, which may result in a deterioration in the quality of the formed image.

[0009] Although the above describes an example of plain paper, the same problem occurs with other types of paper, such as thick paper and thin paper. Also, the above describes an example of distinguishing sheet types by basis weight, but this is not limiting. For example, when determining sheet types from sheet characteristic values ​​such as sheet thickness, the same problem can occur due to detection variations.

[0010] Furthermore, although an example of an electrophotographic image forming apparatus has been described, the same problem as described above can occur in other cases, such as an inkjet image forming apparatus that controls image forming conditions such as the amount of ink ejected according to the identified sheet type.Furthermore, the same problem as described above can occur in other cases, such as an image forming apparatus that performs post-processing such as stapling on fed sheets, and a post-processing device that controls post-processing using the results of identifying the sheet type.

[0011] The present disclosure has been made in consideration of the above-mentioned problems, and has an object to provide a paper feeder and an image forming apparatus that can further improve the accuracy of determining the type of sheet. [Means for solving the problem]

[0012] In order to achieve the above object, a paper feeder according to the present disclosure is a paper feeder that feeds sheets on a tray, and includes a registration unit that receives and registers input of two or more different types of sheets used by a user, and a register that stores, for each registered type, characteristic values ​​of the sheets of the type. , by receiving an input from a user or from a storage unit in which the characteristic values ​​of the sheet are stored. a calculation unit that calculates a specific threshold value for determining the type of each sheet from the characteristic values ​​of the sheet obtained for each type; and a calculation unit that calculates the characteristic values ​​of the sheet fed from the tray after the calculation. With sensors and a discrimination unit that discriminates which type of sheet among the registered types the fed sheet is based on the detected characteristic value of the sheet and the calculated specific threshold value. The calculation unit calculates one specific threshold for each of two types of sheets whose characteristic values ​​are adjacent to each other among two or more different sheet types, and the discrimination unit sets a non-discrimination area, which is an area between a first characteristic value belonging to a first type and smaller than the one specific threshold, and a second characteristic value belonging to a second type and larger than the one specific threshold, on either side of the calculated one specific threshold, and when it determines that the characteristic value of the sheet detected by the detection unit is within the non-discrimination area, it notifies that a sheet of a type other than the registered type is being fed. It is characterized by:

[0013] The acquisition unit may be an operation unit into which information on characteristic values ​​of sheets of each type is input.

[0014] Also, A paper feeding device according to another aspect of the present disclosure is a paper feeding device that feeds sheets on a tray, and includes: a registration unit that receives input of two or more different types of sheets used by a user and registers them; an acquisition unit that acquires characteristic values ​​of sheets of that type for each registered type; a calculation unit that calculates a specific threshold value for discriminating the type of each sheet from the characteristic values ​​of sheets acquired for each type; a detection unit that detects the characteristic values ​​of sheets fed from the tray after the calculation; and a discrimination unit that discriminates which type of sheet from the registered types the fed sheet is from the detected characteristic values ​​of the sheets and the calculated specific threshold value; The acquisition unit instructs the user to store one or more sheets of the type in the tray for each type of sheet, and then, upon receiving a paper feed instruction from the user, performs registration paper feed by feeding the sheet from the tray and causing the detection unit to detect characteristic values ​​of the sheet, and acquires the characteristic values ​​of the sheet from the detection result of the detection unit. The calculation unit calculates one specific threshold for each of two types of sheets whose characteristic values ​​are adjacent to each other among two or more different sheet types, and the discrimination unit separately sets a non-discrimination area, which is an area between a first characteristic value belonging to a first type and smaller than the one specific threshold, and a second characteristic value belonging to a second type and larger than the one specific threshold, across the calculated one specific threshold, and when it determines that the characteristic value of the sheet detected by the detection unit is within the non-discrimination area, it notifies that a sheet of a type other than the registered type is being fed. .

[0015] Here, the registration unit may further accept input of the nominal characteristic values ​​of each registered type of sheet, and store the accepted nominal characteristic values ​​in correspondence with the characteristic values ​​of the sheet detected by the detection unit.

[0016] In addition, characteristic classification information is stored that associates each of a plurality of different types of sheets that can be fed one-to-one with a range of characteristic values ​​of the sheets corresponding to that type, and the plurality of different types of sheets that can be fed include two or more different types of sheets used by the user, and if the type of sheet is not registered by the registration unit, the discrimination unit may perform a standard discrimination mode in which the type of sheet is discriminated based on which of the ranges indicated in the characteristic classification information the characteristic value of the sheet detected by the detection unit belongs to, without using the specific threshold value.

[0017] Here, when the specific discrimination mode is set to discriminating the type of sheet using the specific threshold value, a selection input receiving unit is provided that receives a selection input from the user as to whether to execute the specific discrimination mode or the standard discrimination mode, and when the type of sheet is registered by the registration unit, the discrimination unit may switch the discrimination mode to be executed depending on whether the specific discrimination mode or the standard discrimination mode is selected.

[0018] Here, a tray separate from the tray may be provided, the selection input receiving unit may receive the selection input for each tray, and the discrimination unit may switch the discrimination mode for each tray.

[0019] Furthermore, paper may be fed from the tray for each job, the selection input receiving unit may receive the selection input for each job, and the discrimination unit may switch the discrimination mode for each job.

[0021] Also, A paper feeding device according to another aspect of the present disclosure is a paper feeding device that feeds sheets on a tray, and includes: a registration unit that receives input of two or more different types of sheets used by a user and registers them; an acquisition unit that acquires, for each registered type, characteristic values ​​of sheets of that type by receiving input from the user or from a memory unit in which the characteristic values ​​of the sheets are stored; a calculation unit that calculates a specific threshold value for discriminating the type of each sheet from the characteristic values ​​of the sheets acquired for each type; a detection unit that, after the calculation, detects the characteristic values ​​of sheets fed from the tray using a sensor; and a discrimination unit that discriminates which type of sheet from the registered types the fed sheet is from the detected characteristic values ​​of the sheet and the calculated specific threshold value, The acquisition unit further acquires, after calculating the specific threshold, a characteristic value of the sheet detected by the detection unit each time a sheet is fed from the tray, and stores the acquired characteristic value of the sheet in association with the type of the sheet identified by the identification unit, and the calculation unit, after calculating the specific threshold, calculates a new specific threshold for each type of sheet from one or more characteristic values ​​stored in association with the type, and updates the new specific threshold. and when a difference between the characteristic value of the sheet detected by the detection unit and the specific threshold is equal to or greater than a predetermined value, the acquisition unit does not store the detected characteristic value of the sheet in association with the determined type of sheet. .

[0022] Furthermore, a paper feeding device according to yet another aspect of the present disclosure is a paper feeding device that feeds sheets on a tray, and includes: a registration unit that receives and registers input of two or more different types of sheets to be used by a user; an acquisition unit that acquires, for each registered type, characteristic values ​​of sheets of that type; a calculation unit that calculates a specific threshold value for discriminating the type of each sheet from the characteristic values ​​of sheets acquired for each type; a detection unit that detects the characteristic values ​​of sheets fed from the tray after the calculation; and a discrimination unit that discriminates which of the registered types of sheets the fed sheet is from the detected characteristic values ​​of the sheets and the calculated specific threshold value. The acquisition unit instructs the user to store one or more sheets of that type in the tray for each sheet type, and then, upon receiving a paper feeding instruction from the user, (i) performs registration feeding to cause the detection unit to detect the characteristic values ​​of the sheet, and acquires the characteristic values ​​of the sheet from the detection result of the detection unit; further, after calculating the specific threshold, each time a sheet is fed from the tray, acquires the characteristic values ​​of the sheet detected by the detection unit, and stores the acquired characteristic values ​​of the sheet in correspondence with the type of sheet identified by the discrimination unit; after calculating the specific threshold, the calculation unit calculates and updates a new specific threshold for each type of sheet from one or more characteristic values ​​stored in correspondence with that type; further, if there is a difference of a predetermined value or more between the characteristic values ​​of the sheet detected by the detection unit and the specific threshold, the acquisition unit does not store the characteristic values ​​of the detected sheet in correspondence with the identified type of sheet. Here, an update permission / refusal input accepting unit may be provided that accepts a selection input as to whether or not to allow the update of the specific threshold, and the calculation unit may execute the update of the specific threshold on the condition that permission to update the specific threshold is selected.

[0023] In addition, the acquisition unit may acquire multiple characteristic values ​​of sheets of each registered type, and the calculation unit may calculate a representative value of the characteristic values ​​of sheets of that type from the multiple characteristic values ​​acquired for each type, and calculate the specific threshold value using the representative value of each type of sheet thus obtained.

[0024] Here, the calculation section may determine the average value, median value, or mode of the acquired plurality of characteristic values ​​as the representative value.

[0025] Furthermore, the characteristic value of the sheet may be the basis weight or thickness of the sheet.

[0026] The calculation unit may also correct the calculated specific threshold value in accordance with at least one of an environmental condition and a durability condition.

[0027] Furthermore, the printer may be provided with a conveying path that conveys the sheet fed from the tray to an image forming unit, and a branching path that branches off from a branching point midway along the conveying path and discharges the sheet fed from the tray without passing it through the image forming unit, the detection unit being located upstream of the branching point in the sheet conveying direction, and the acquisition unit discharging the sheet fed from the tray through the branching path when performing the registration time paper feeding.

[0028] The apparatus may also include a transport path for transporting the sheet fed from the tray to an image forming unit, the image forming unit having a transfer member for transferring an image on an image carrier to the transported sheet, and a fixing member for fixing the image to the sheet after the image has been transferred, and at least one of the transfer member and the fixing member is movable between a contact position where it contacts the transported sheet and a separation position where it is separated from the sheet, and when performing the registration time paper feeding, the acquisition unit may instruct the image forming unit to move the member of the transfer member and the fixing member that can be separated from the sheet to the separation position.

[0029] The tray used for the registration paper feed may be a manual feed tray.

[0030] Furthermore, if the registration unit receives input of another sheet type after the registration, it may also register the received type, and the acquisition unit may further acquire characteristic values ​​of the sheet of the additionally registered type, and the calculation unit may recalculate and update a specific threshold value for distinguishing all currently registered sheet types from both the characteristic values ​​of each sheet that were acquired before the additional registration and the characteristic values ​​of the sheets that were acquired in conjunction with the additional registration.

[0031] Further, the characteristic value of the sheet may be the basis weight or thickness of the sheet, and in the reference discrimination mode, if the characteristic value of the sheet, that is, the basis weight or thickness, detected by the detection unit coincides with the boundary between two adjacent ranges indicated in the characteristic classification information, or if the difference from the boundary is within a predetermined range, the discrimination unit may discriminate the type of sheet as corresponding to the range of the larger basis weight or thickness of the two ranges.

[0032] Furthermore, the calculation unit may calculate one specific threshold value for each two types of sheets whose characteristic values ​​are adjacent to each other among two or more different types of sheets.

[0033] In addition, the image forming apparatus according to the present disclosure is an image forming apparatus equipped with the above-described paper feeding device, and is characterized in that it forms an image on the sheet based on image forming conditions according to the type of sheet identified by a discrimination unit of the paper feeding device. [Effects of the Invention]

[0034] By doing as described above, a user can register two or more sheet types that they use from among multiple different sheet types, and a threshold value for distinguishing each registered sheet type will be automatically calculated, making it possible to distinguish the type of each sheet registered by the user with high accuracy. [Brief explanation of the drawings]

[0035] [Figure 1] 1 is a diagram showing an overall configuration of an image forming apparatus according to an embodiment; [Figure 2] FIG. 2 is a diagram showing the configuration of a transport path for paper fed from a tray. [Figure 3] FIG. 2 is a diagram showing the main configuration of a media detection sensor. [Figure 4] FIG. 2 is a block diagram showing the main configuration of a control unit. [Figure 5] FIG. 10 is a diagram illustrating an example of the contents of a reference threshold table. [Figure 6] FIG. 10 is a diagram illustrating an example of the contents of a specific threshold table. [Figure 7] FIG. 10 is a diagram illustrating an example of the contents of another specific threshold value table. [Figure 8] FIG. 10 is a graph showing an example of the frequency distribution of the basis weight of each sheet detected by a media detection sensor when five sheets are passed one by one. [Figure 9] FIG. 10 is a graph showing another example of the frequency distribution of the basis weight of each sheet detected by the media detection sensor when five sheets are passed one by one. [Figure 10] FIG. 10 is a diagram showing an example of the contents of an image forming condition table. [Figure 11] 10 is a flowchart showing the contents of a paper type registration process. [Figure 12] FIG. 10 is a diagram illustrating a display example of a paper type registration screen. [Figure 13] 10 is a flowchart showing the contents of a subroutine of a specific threshold calculation process. [Figure 14] 10 is a flowchart showing the contents of a paper type discrimination process and an image condition setting process when an image forming job is executed. [Figure 15] FIG. 10 is a graph showing a modified example of the frequency distribution of the basis weight of each sheet detected by the media detection sensor when five sheets are passed one by one. [Figure 16] 10 is a partial flowchart showing the contents of a changed part of the flowchart of paper type registration according to a modified example. [Figure 17] 10(a) and 10(b) are diagrams showing the contents of a specific threshold table according to a modified example. [Figure 18] 10 is a partial flowchart showing the contents of modified portions of the flowchart of the paper type discrimination process and the image condition setting process according to a modified example. [Figure 19] FIG. 10 is a diagram showing an example of the contents of a correction table according to a modified example. [Figure 20] 10 is a partial flowchart showing the contents of modified portions of the flowchart of the paper type discrimination process and the image condition setting process according to another modified example. [Figure 21] FIG. 10 is a diagram showing an example of the contents of a basis weight detection value table according to a modified example. [Figure 22] 10 is a flowchart showing the contents of a specific threshold value update process according to a modified example. [Figure 23] 10 is a flowchart showing the content of a specific threshold calculation process according to another modified example. DETAILED DESCRIPTION OF THE INVENTION

[0036] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a paper feeder according to the present disclosure and an image forming apparatus including the same will be described with reference to the accompanying drawings.

[0037] [1] Overall configuration of image forming device FIG. 1 is a diagram showing the overall configuration of an image forming apparatus 1. As shown in FIG.

[0038] As shown in the figure, the image forming device 1 is a so-called tandem color multifunction peripheral (MFP) that is capable of executing image reading jobs, print jobs, copy jobs, etc., and is equipped with an image reading unit 110, an image forming unit 120, a paper feed unit 130 that feeds paper (sheets) to the image forming unit 120, an operation panel 140, and a control unit 150.

[0039] The image reading unit 110 executes an image reading job and includes an automatic document feeder (ADF) and a scanner device, both not shown. The automatic document feeder feeds and conveys documents one by one from a stack of documents placed on a document tray, while causing the scanner device to read the documents and generate image data.

[0040] Image forming unit 120 is an electrophotographic type and executes a copy job in which an image is formed based on image data generated by image reading unit 110 and printed on paper, and a print job in which an image is formed based on image data received from an external device and printed on paper. When a print job and a copy job are collectively referred to, they are called an image forming job.

[0041] In this embodiment, image forming units 121Y, 121M, 121C, and 121K are provided, and toner images of the respective colors of yellow (Y), magenta (M), cyan (C), and black (K) are formed.

[0042] The toner images of the colors Y, M, C, and K formed by the image forming units 121Y, 121M, 121C, and 121K are electrostatically transferred (primary transfer) from the photosensitive drums of the image forming units 121Y to 121K onto the intermediate transfer belt 122 in succession so as to be superimposed on top of each other, thereby forming a color toner image. The intermediate transfer belt 122 is an endless belt that conveys the color toner image to the secondary transfer roller 123 (transfer unit) by rotating.

[0043] In parallel with this, paper S (sheets) are fed and transported from a tray designated by the user among paper feed trays 131a, 131b, and manual feed tray 131c provided in paper feed unit 130. The process of feeding and transporting paper S stored in a tray is called paper feeding.

[0044] For example, the sheets S stored in the first sheet feed tray 131a are picked up one by one from the sheet feed tray 131a by the pickup roller 132a, and are transported toward the timing roller pair 124 by the sheet feed roller 133a.

[0045] The sheets S stored in the second-stage paper feed tray 131b are picked up one by one from the paper feed tray 131b by a pickup roller 132b, and are transported toward the timing roller pair 124 by a paper feed roller 133b and a vertical transport roller 134b.

[0046] The sheets S placed on the manual feed tray 131c are picked up one by one from the manual feed tray 131c by a pickup roller 132c and transported by a paper feed roller 133c toward the timing roller pair 124. Hereinafter, when there is no need to particularly distinguish between the paper feed tray and the manual feed tray, they will be referred to as tray 131. Note that the paper types that can be fed from the tray 131 (nine types in the example described below) are predetermined according to the specifications of the image forming apparatus 1.

[0047] The sheet S thus fed from the tray 131 is conveyed along the conveying path 201 to the timing roller pair 124 by the media detection sensor 210, which detects the characteristic value of the sheet, such as the basis weight (g / m 2 The type of paper S (hereinafter referred to as "paper type") is determined from the detected basis weight, and image forming conditions such as transfer bias and fixing temperature are set according to the determination result.

[0048] Thereafter, the leading edge of the sheet S in the transport direction (sheet transport direction) comes into contact with the stopped timing roller pair 124, forming a loop on the leading edge side of the sheet S. The formation of this loop corrects the skew of the sheet S in the transport direction.

[0049] At the timing when the color toner image that has been primarily transferred onto the intermediate transfer belt 122 reaches the secondary transfer position 125, which is the contact position between the intermediate transfer belt 122 and the secondary transfer roller 123, as the intermediate transfer belt 122 rotates, the timing roller pair 124 begins to rotate and transport the paper S to the secondary transfer position 125.

[0050] When the paper S passes through the secondary transfer position 125, the color toner image on the intermediate transfer belt 122 is secondarily transferred onto the paper S by the secondary transfer bias supplied to the secondary transfer roller 123. The secondary transfer bias is set according to the detected paper type.

[0051] The paper S onto which the color toner image has been secondarily transferred is transported to a fixing unit 100. The fixing unit 100 includes a heating member 101, such as a heating belt, heated by a heater 104 to a temperature required for thermal fixing (fixing temperature), and a pressure member 102, such as a pressure roller, that is pressed against the heating member 101. When the transported paper S passes through a fixing nip 103 formed between the heating member 101 and the pressure member 102, the color toner image on the paper S is thermally fixed. The fixing temperature is set according to the detected paper type. The paper S onto which the image has been fixed in the fixing unit 100 is discharged onto a paper discharge tray 127 by a pair of paper discharge rollers 126.

[0052] An operation panel 140 (operation unit) is located on the front of the device in a position that is easy for the user to operate. The operation panel 140 is provided with a touch panel 141 that displays an input screen that accepts input of printing conditions such as the number of copies and density by the user, a paper type registration execution key 142, and the like. The touch panel 141 displays a paper type registration screen, which will be described later.

[0053] The control unit 150 monitors and controls the operation of each unit of the image forming apparatus 1.

[0054] [2] Media detection sensor configuration The media detection sensor 210 (detection means) is disposed along the conveyance path 201 formed by the conveyance guide 202 and the conveyance guide 203 opposite to the conveyance guide 202 shown in FIG.

[0055] The media detection sensor 210 is an optical sensor, and as shown in Fig. 3, it includes a reflective light source 211, transmissive light sources 212 and 213, and a light receiving sensor 214. Note that Fig. 3 is a diagram of the media detection sensor 210 as seen from the rear side of the device. Hereinafter, the reflective light source and transmissive light source will be abbreviated to light source. Each of the light sources 211 to 213 uses light sources that emit light with different wavelengths, for example, LEDs (Light Emitting Diodes).

[0056] Specifically, light source 211 is an LED that emits green (G) light (near 530 nm), light source 212 is an LED that emits blue (B) light (near 450 nm), and light source 213 is an LED that emits near-infrared (IR) light (near 850 nm). The reason for using multiple LEDs with different wavelengths is to more accurately detect different paper types, such as plain paper, thick paper, and thin paper. Note that each light source only needs to be able to detect the basis weight of the paper, and other types of light sources may be used, or the number of light sources may be varied. Light-receiving sensor 214 is, for example, a photodiode (PD), but other types of light-receiving elements may also be used.

[0057] Light source 211 irradiates light onto paper S being transported in the direction of arrow A via through-hole 301 provided in transport guide 203. Light sources 212 and 213 irradiate light onto paper S via through-hole 302 provided in transport guide 202. Light-receiving sensor 214 detects the amount of light reflected from and transmitted through paper S. Here, one light-receiving sensor 214 is shared by three light sources 211 to 213, so that only one of light sources 211, 212, and 213 emits light in sequence for a fixed period of time, and light-receiving sensor 214 receives the reflected light or transmitted light from the emitting light source, thereby detecting the amount of reflected or transmitted light received for each light source.

[0058] The basis weight of the paper S is detected based on the amount of reflected light and transmitted light received, and the detected basis weight is used as a characteristic value of the paper S to distinguish the paper type, such as plain paper or thick paper, by referring to the paper characteristic information described below. Hereinafter, the basis weight value of the paper S detected (actually measured) by the media detection sensor 210 will be referred to as the "detected basis weight value."

[0059] The media detection sensor 210 is not limited to an optical sensor as long as it can detect the basis weight of the paper S, but may also be one that uses other detection methods, such as an electrostatic sensor or a paper thickness sensor, or, if possible, an ultrasonic sensor.

[0060] [3] Configuration of the control unit FIG. 4 is a block diagram showing the main components of the control unit 150.

[0061] As shown in the figure, the control unit 150 is composed of a CPU (Central Processing Unit) 151, a ROM (Read Only Memory) 152, a RAM (Random Access Memory) 153, an image memory 154, an image processing circuit 155, a network communication circuit 156, a scanner control circuit 157, an input / output circuit 158, a printer control circuit 159, input / output circuits 160 and 161, a memory circuit 180, and a bus 166.

[0062] The CPU 151, ROM 152, RAM 153, image memory 154, image processing circuit 155, network communication circuit 156, scanner control circuit 157, input / output circuit 158, printer control circuit 159, and input / output circuits 160 and 161 are connected to one another via a bus 166. The memory circuit 180 is connected to the input / output circuit 161.

[0063] The CPU 151 , the ROM 152 and the RAM 153 constitute a main control unit 170 .

[0064] The RAM 153 temporarily stores various control variables and data such as the number of copies set on the operation panel 140, and also provides a work area when the CPU 151 executes a program.

[0065] The ROM 152 stores control programs for executing various jobs such as copying and printing. The control programs may also be stored in the storage circuitry 180.

[0066] The CPU 151 operates according to a control program stored in the ROM 152 .

[0067] The image memory 154 temporarily stores image data included in a print job or the like.

[0068] The image processing circuit 155 performs various data processing on the image data of the R, G, and B color components obtained by the image reading unit 110, converting them into image data of the Y, M, C, and K reproduction colors.

[0069] The network communication circuit 156 receives print jobs from external terminal devices via a network.

[0070] The scanner control circuit 157 controls the image reading unit 110 to execute the operation of reading the document.

[0071] Input / output circuit 158 ​​receives an input signal from operation panel 140 and outputs the received input signal to main control unit 170. It also receives message data from main control unit 170 and outputs the received data to operation panel 140 to display the message.

[0072] The printer control circuit 159 controls the image forming unit 120 and the paper feeding unit 130 to perform the image forming operation.

[0073] The input / output circuit 160 receives the detection result of the media detection sensor 210 and sends it to the main control unit 170. The input / output circuit 161 writes data to the memory circuit 180 or reads data from the memory circuit 180.

[0074] The storage circuit 180 will be described later.

[0075] [4] Main control unit The main control unit 170 functions as a general control unit 171, a paper type registration unit 172, a specific threshold calculation unit 173, a paper type discrimination unit 174, an image forming condition setting unit 175, and a display control unit 176 as a result of the CPU 151 operating in accordance with the control program.

[0076] The general control unit 171 controls the image memory 154, image processing circuit 155, network communication circuit 156, scanner control circuit 157, input / output circuits 158, 160, 161, printer control circuit 159, etc. in an integrated manner, thereby smoothly executing various jobs such as printing and copying.

[0077] The paper type registration unit 172 receives and registers input of two or more paper types and nominal basis weights specified by the user (including one or more users) using the image forming device 1 from among multiple different paper types that can be fed, and also performs a process of actually feeding multiple sheets of paper S of the received paper type one by one, detecting the basis weight using the media detection sensor 210, and calculating and registering a representative value of the basis weight of the paper S from the actual detection results.

[0078] The specific threshold calculation unit 173 calculates a specific threshold used to distinguish each of the two or more paper types registered by the paper type registration unit 172 based on the representative value of the basis weight of the paper S of each paper type.

[0079] The paper type discrimination unit 174 discriminates the paper type of the paper S by comparing the detection result of the media detection sensor 210 for the paper S fed during the execution of an image forming job, in this case the detected basis weight of the paper S, with a pre-stored threshold value.

[0080] The image forming condition setting unit 175 sets image forming conditions suitable for the paper type of the paper S identified by the paper type identification unit 174 when an image forming job is executed. Image formation on the paper S is executed based on the image forming conditions set here.

[0081] The display control unit 176 causes the display of the touch panel 141 of the operation panel 140 to display various screens, for example, a paper type registration screen (described later) used for setting the specific threshold value.

[0082] [5] Memory circuit The storage circuit 180 (storage means) is configured from a nonvolatile semiconductor memory. Note that the storage circuit 180 may also be configured from a hard disk.

[0083] The memory circuit 180 has areas for storing a reference threshold table 181, a specific threshold table 182, an image forming condition table 183, a discrimination mode flag 184, and the like.

[0084] Here, the discrimination mode flag 184 is a flag that indicates which of the two modes for discriminating the paper type of paper S the user has selected, the specific discrimination mode or the standard discrimination mode described below, and is configured to store 1 if the specific discrimination mode is selected, and 0 if the standard discrimination mode is selected.

[0085] [6] Reference threshold table The reference threshold table 181 is a table in which the names of paper types are associated with reference basis weight thresholds Tp (lower and upper limits) for identifying the paper types, as shown in FIG.

[0086] There are nine paper types available for use, specifically thin paper, ECO, plain paper, plain paper+, thick paper 1, thick paper 1+, thick paper 2, thick paper 3, and thick paper 4, and the names of the paper types in order of increasing basis weight are written in advance in the paper type column. Note that the number and types of paper that can be used may vary depending on the device configuration.

[0087] The reference basis weight threshold Tp is a threshold for distinguishing each paper type, and is expressed as basis weight (g / m 2 ) is shown as a value indicating the magnitude of the basis weight. Specifically, if the basis weight detected by the media detection sensor 210 is, for example, 80, this value 80 falls within the range between the lower limit value 71 and the upper limit value 90 of the reference basis weight threshold Tp, and so the paper is determined to be plain paper. Depending on which range the basis weight detected value falls within between the lower limit value and the upper limit value determined for each paper type, the type (paper type) of the paper S is determined, and image formation conditions (transfer bias, etc.) appropriate for the determined paper type are set.

[0088] It can be said that the reference threshold table 181 stores characteristic classification information in which the range of the reference basis weight threshold Tp (characteristic classification range) is associated one-to-one with each of the different paper types. Identifying the paper type of the paper S using the reference basis weight threshold Tp is referred to as executing the reference discrimination mode.

[0089] Among the paper types, ECO refers to so-called recycled paper, which has a basis weight greater than thin paper but less than plain paper. Plain paper+ refers to what is generally called plain paper, but with a basis weight close to that of thick paper. If plain paper and plain paper+ were combined to form plain paper, the basis weight range (71-105) would be too wide, so the paper types are divided into two so that image formation conditions suitable for each paper type can be set. The same applies to thick paper1+.

[0090] The basis weight threshold field on the right side of the paper type field shows the relationship between paper type and basis weight worldwide for Japan, the United States, and Europe, and these are summarized as the reference basis weight threshold Tp on the left side of the paper type field. Of course, the basis weight threshold ranges for each paper type are not limited to those described above, and each paper type may be identified using a threshold different from those described above.

[0091] [7] Specific threshold table As shown in Figure 6, the specific threshold table 182 is a table that has columns for the paper type name of the paper used by the user, the nominal basis weight, the representative value of the basis weight detected by the media detection sensor 210, and the specific threshold value Th, and each of these is associated with another.

[0092] The "paper type name of paper used by user" field indicates the type of paper S used in an image formation job by a user of the image forming apparatus 1, and is written into this field through the user's registration operation. This indicates that only paper S with the paper type name written in this field will be used by the user, that is, it will be set in one of the trays 131.

[0093] By referring to this column, the image forming device 1 can determine which two or more paper types (thin paper, regular paper, thick paper 1, etc.) the paper S set in its tray 131 is of among the multiple paper types shown in the standard threshold table 181.

[0094] If the paper type of paper S used by a user is limited to a certain extent, that is, if it is known in advance that only a specific type of paper S will be used, the user enters that paper type in the relevant field through a registration operation. This is the registration of the paper type. The registered paper type is the paper type specified by the user from among the nine paper types in the reference threshold table 181.

[0095] The figure shows an example in which two paper type names, "plain paper +" and "cardboard 2," are registered, but it is also possible that three names, "plain paper +," "cardboard 1+," and "cardboard 2," are registered, as in the specific threshold table 182a illustrated in Figure 7.

[0096] The type of paper S used by the user will vary depending on how the user uses the image forming device 1. For example, if the main task is to create a booklet with a body made up of a stack of multiple sheets of plain paper + and a cover made of cardboard 2, the user will almost always use only plain paper and cardboard 2. Also, if the user normally uses plain paper but uses cardboard 1 to create documents with a fixed format, such as invoices, the user will almost always use only plain paper and cardboard 1. This is because paper of unused paper types is not usually kept around the image forming device 1, and the type of paper used is often fixed depending on how the user uses the image forming device 1.

[0097] The reason why the user is required to register the paper type of the paper S that he or she uses in this way is to improve the accuracy of identifying the paper type of the paper S by using a specific threshold value Th other than the reference basis weight threshold value Tp for the registered paper type of the paper S. This will be explained below with reference to FIG. 8.

[0098] FIG. 8 is a graph showing an example of the frequency distribution of the basis weight of each sheet S detected by the media detection sensor 210 when sheets S of the same paper type (here, five sheets S) are fed one by one, with the horizontal axis representing the basis weight of the sheet S, and the vertical axis representing the frequency distribution of the basis weight detected by the media detection sensor 210. The figure also shows the reference basis weight threshold Tp and the specific threshold Th. In the example shown in the figure, the basis weight indicating the boundary of the range of the reference basis weight threshold Tp for each paper type is shown numerically; for example, the boundary between plain paper+ and thick paper 1 is 105.5. The paper types of plain paper and sheets S with a basis weight greater than that are also shown, with thin paper and ECO paper omitted from the illustration.

[0099] The frequency distribution indicated by the symbol 10 shows the frequency distribution (measured basis weight distribution) of the basis weight detection values ​​detected by the media detection sensor 210 when five sheets of "plain paper +" used by the user are actually passed through one by one, and the frequency distribution indicated by the symbol 20 shows the frequency distribution (measured basis weight distribution) of the basis weight detection values ​​detected by the media detection sensor 210 when five sheets of "cardboard 2" used by the user are actually passed through one by one.

[0100] First, looking at frequency distribution 10 for plain paper+, due to detection variation A of media detection sensor 210, three sheets of plain paper+ were detected as having a basis weight of 98, one sheet of plain paper+ was detected as having a basis weight of 103, and the remaining sheet of plain paper+ was detected as having a basis weight of 108. When the basis weights are detected as 98 and 103, they fall within the range (characteristic classification range) of the reference basis weight threshold Tp for identifying plain paper+, that is, the range from a minimum value of 90.5 to a maximum value of 105.5, and are therefore identified as plain paper+. On the other hand, when the basis weight is detected as 108, it exceeds the maximum value of 105.5 and does not fall within the above range, so it is not identified as plain paper+ and would be mistaken for thick paper 1 in the example shown in the figure.

[0101] This misclassification due to detection variation A for plain paper+ corresponds to a situation where misclassification can occur for paper having a basis weight close to the maximum value β, as explained in the above section [Problem to be solved by the invention].

[0102] Paper S sold on the market, known as plain paper, often has slightly different basis weights depending on the paper manufacturer, and if the plain paper+ used by the user happens to have a basis weight close to the maximum value of 105.5, the above-mentioned misidentification is likely to occur.

[0103] Similarly, looking at the frequency distribution 20 for cardboard 2, due to detection variation B of the media detection sensor 210, only one sheet of cardboard 2 has a detected basis weight value of 213, which is outside the range (characteristic classification range) of the reference basis weight threshold Tp for identifying cardboard 2, that is, the range from the minimum value of 157.5 to the maximum value of 209.5. As a result, that single sheet of cardboard 2 is not identified as cardboard 2, and in the example shown in the figure, is mistakenly identified as cardboard 3.

[0104] To prevent such misidentification of paper types, this embodiment accepts and registers only two or more paper types used by the user from among multiple different types of paper S (plain paper, thick paper, thin paper, etc.) as types specified by the user, calculates a specific threshold value Th for discriminating only the registered paper types, and thereafter uses the calculated specific threshold value Th to discriminate between paper S of the two or more registered paper types. The same figure shows an example where the calculated specific threshold value Th1 is 154.5. Discriminating the paper type of paper S using this specific threshold value Th is called executing the specific threshold value discrimination mode.

[0105] This specific threshold value Th1 is calculated as follows: That is, a representative value of the five detected basis weight values ​​of plain paper+, for example, the median (=103), is calculated based on the frequency distribution 10 for plain paper+. Similarly, a representative value of the five detected basis weight values ​​of thick paper 2, for example, the average (=206), is calculated based on the frequency distribution 20 for thick paper 2. Note that the representative value may be unified to either the average or the median.

[0106] Then, the intermediate value (=154.5) between the calculated representative value for plain paper+ (=103) and the representative value for thick paper 2 (=206) is calculated. The calculated intermediate value is set as the specific threshold value Th1 used to distinguish between only plain paper+ and thick paper 2 registered by the user.

[0107] In an image forming job after the specific threshold value Th1 is calculated, if plain paper+ is fed from paper feed tray 131a out of plain paper+ and thick paper2 registered as the paper type of paper S used by the user, even if the basis weight detected by media detection sensor 210 is 108, it can be correctly identified as plain paper+ because it is smaller than specific threshold value Th1 (=154.5).

[0108] In another image forming job, if cardboard 2 is fed from paper feed tray 131a, even if the basis weight detected by media detection sensor 210 is 213, it can be correctly identified as cardboard 2 because it is greater than specific threshold value Th1 (=154.5).

[0109] When the specific threshold value Th1 is stored in association with the user's paper type registration, the paper type is subsequently determined using the specific threshold value Th1, rather than the reference basis weight threshold value Tp. The specific threshold value Th1 is different from the reference basis weight threshold value Tp and falls within a range that is not affected by the detection variations A and B, making it possible to accurately determine between plain paper+ and thick paper 2.

[0110] The image forming conditions for an image forming job are predetermined for each paper type distinguished by a reference basis weight threshold Tp, as will be described later. Therefore, in order to obtain image forming conditions suitable for a paper type, it is important to accurately identify the paper type.

[0111] Even if the detection variation A becomes larger and the basis weight detection value for plain paper+ becomes approximately 125, which falls within the threshold range for thick paper 1+, since the paper type of paper S used by the user is originally registered as plain paper+ and thick paper 2, it is possible to set image formation conditions suitable for plain paper+ by determining that the plain paper+ is the one with a basis weight detection value smaller than the specific threshold value Th1, out of plain paper+ and thick paper 2.

[0112] 9 is a diagram showing examples of specific thresholds Th1 and Th2 when plain paper+, thick paper 2, and thick paper 1+ are registered as paper types for paper S used by a user, with the horizontal axis representing basis weight and the vertical axis representing frequency, as in FIG. 8. In this example, if the representative values ​​for plain paper+ and thick paper 2 are calculated as 103 and 206, respectively, as in the above, and the representative value for thick paper 1+ is calculated as 127 from the frequency distribution indicated by reference numeral 30, the intermediate value (=115) between the representative value for plain paper+ (=103) and the representative value for thick paper 1+ (=127) is set as the specific threshold Th1 for distinguishing between plain paper+ and thick paper 1+, and the intermediate value (=166.5) between the representative value for thick paper 1+ (=127) and the representative value for thick paper 2 (=206) is set as the specific threshold Th2 for distinguishing between thick paper 1+ and thick paper 2.

[0113] Looking at frequency distribution 30, the detected basis weight value for one sheet of cardboard 1+ is 117, which is within the range of the standard basis weight threshold Tp for cardboard 1, but is greater than the specific threshold Th1 (= 115) and smaller than the specific threshold Th2 (= 166.5), so it can be correctly identified as cardboard 1+.

[0114] Even if three paper types (plain paper+, thick paper 1+, thick paper 2) are registered in this way, the paper type can be accurately determined by calculating specific threshold values ​​Th1 and Th2 from the representative values ​​of the basis weight detection values ​​of each paper type.

[0115] In the above, a representative value is calculated from the basis weight detection value for each registered paper type, and the representative values ​​are arranged in order from smallest to largest (in the example of Figure 9, the representative value for plain paper+ is 103, the representative value for thick paper 1+ is 127, and the representative value for thick paper 2 is 206).Then, the median value of two adjacent representative values ​​among these is set as the specific threshold value Th1, 2... (115, 166.5 in the example of Figure 9), but the present invention is not limited to the median value.

[0116] For example, the intermediate value between 108, where the basis weight detection value is maximum in the frequency distribution 10 for plain paper+, and 117, where the basis weight detection value is minimum in the frequency distribution 30 for the adjacent thick paper 1+, such as 112, can be used as the specific threshold value Th1 for distinguishing between plain paper+ and thick paper 1+.

[0117] Returning to FIG. 6, the "nominal basis weight" column of the specific threshold table 182 contains the nominal basis weight of the registered paper type. Here, nominal basis weight refers to the basis weight published as the quality standard for paper S by the paper manufacturer or sales company that produces and sells the paper S. The nominal basis weight may also be printed on the packaging paper that seals the paper S in batches of, for example, 500 sheets. The user can register the nominal basis weight value for the paper for which the user is registering the paper type, and the registered value is written in the nominal basis weight column (registering nominal basis weight).

[0118] The type of paper used by the user and its nominal basis weight are registered by the user through the paper type registration screen (Fig. 12) described below.

[0119] 8 and 9, that is, the detected value of the basis weight of each sheet S detected by the media detection sensor 210 when multiple registered sheets S are actually passed through one by one, and a calculated value such as the average or median is written (registered) as the representative value. FIG. 6 shows an example in which 103 is registered as the representative value for plain paper+ and 206 is registered as the representative value for thick paper 2. The paper type registration unit 172 registers these representative values.

[0120] The "specific threshold value Th" field is written (stored) with specific threshold values ​​Th1 and Th2 (FIG. 7) used to distinguish between only two or more paper types registered by the user, as described with reference to FIGS. 8 and 9. FIG. 6 shows an example in which 154.5 is registered as the specific threshold value Th1 for distinguishing between plain paper+ and thick paper2. The specific threshold value Th is calculated by the specific threshold value calculation unit 173.

[0121] Figure 7 is an example of a specific threshold table 182a when the three paper type names shown in Figure 9 (plain paper+, thick paper 1+, thick paper 2) are registered, and the ``specific threshold Th'' column shows an example in which 115 is registered as the specific threshold Th1 for distinguishing between plain paper+ and thick paper 1+, and 166.5 is registered as the specific threshold Th2 for distinguishing between thick paper 1+ and thick paper 2.

[0122] [8] Image formation condition table FIG. 10 is a diagram showing an example of the contents of the image forming condition table 183. As shown in FIG.

[0123] As shown in the figure, the image forming condition table 183 is a table in which image forming conditions, in this case, transfer bias and fixing temperature, are associated with each paper type (thin paper, regular paper, etc.) distinguished by the reference basis weight threshold Tp.

[0124] The transfer bias is the transfer current or transfer voltage during secondary transfer. If plain paper is used as the reference value Tb, for thin paper with a smaller basis weight than plain paper, the transfer bias value Tb1 is smaller than the reference value Tb, and for thick paper 1+ and thick paper 2 with a larger basis weight than plain paper, the transfer bias values ​​Tb2 and Tb3 (>Tb2) are larger than the reference value Tb.

[0125] The fixing temperature is the target temperature of the fixing member such as the heating roller of the fixing unit 100. If plain paper is taken as the reference value Ft, for thin paper with a smaller basis weight than plain paper, the fixing temperature Ft1 is lower than the reference value Ft, and for thick paper 1+ and thick paper 2 with a larger basis weight than plain paper, the fixing temperatures Ft2 and Ft3 (>Ft2) are higher than the reference value Ft.

[0126] For each paper type, the transfer bias and fixing temperature necessary to maintain a certain level of image quality for the formed image are determined in advance through experiments, and the determined transfer bias and fixing temperature are written into the image forming condition table 183. Note that, although an example in which the image forming conditions are the transfer bias and fixing temperature has been described above, the present invention is not limited to this.

[0127] Any variable control parameter that affects the image quality of the image formed on paper S depending on the paper type may be used, and may include, for example, one or more of the charging bias, exposure amount, development bias, transfer bias, fixing temperature, paper transport speed, etc.

[0128] [9] Paper type registration process FIG. 11 is a flowchart showing the contents of the paper type registration process, which is executed by the paper type registration unit 172 when the user presses the paper type registration execution key 142 (FIG. 1), which is a hard key located on the operation panel 140.

[0129] As shown in FIG. 11, first, a paper type registration screen is displayed on the touch panel 141 of the operation panel 140 (step S1).

[0130] FIG. 12 is a diagram showing a display example of the paper type registration screen 145. As shown in FIG.

[0131] As shown in the figure, the paper type registration screen 145 is provided with a message display field 50, a paper type registration button field 51, a basis weight detection result display field 52, a nominal basis weight display field 53, and a nominal basis weight input key group 54. Below the paper type registration screen 145, there are arranged hard keys: a start key 55, an end key 56, and a registration continuation key 57.

[0132] In the message display field 50, an instruction message (described later) for the user is displayed.

[0133] The paper type registration button field 51 displays paper type registration buttons 51a, 51b, 51c, etc., which indicate the names of the paper types written in the reference threshold table 181. In the figure, thin paper and ECO, which are included in the paper types, are not displayed, but they can be displayed by operating a scroll button (not shown).

[0134] Here, when the specific discrimination mode button 51d included in the paper type registration button column 51 is touched and pressed (for example, highlighted) by the user, the specific discrimination mode is entered, which automatically discriminates the paper type of paper S in subsequent image formation jobs such as printing using a specific threshold value Th calculated according to the paper type registered by the user.

[0135] On the other hand, if the specific discrimination mode button 51d is not pressed (for example, not highlighted), the specific discrimination mode will not be used in subsequent image forming jobs, and the standard discrimination mode will be used, which does not use the specific threshold value Th, i.e., the standard basis weight threshold value Tp. Each time the specific discrimination mode button 51d is pressed, the display alternates between highlighted and non-highlighted.

[0136] The user can select and input either the specific discrimination mode or the reference discrimination mode using the specific discrimination mode button 51d. When the specific discrimination mode is selected, 1 is written to the discrimination mode flag 184 in the memory circuit 180, and when the reference discrimination mode is selected, 0 is also written to the discrimination mode flag 184. By referring to the value of the discrimination mode flag 184, it is possible to determine which mode has been selected by the user. The specific discrimination mode button 51d constitutes a selection input receiving unit that receives a selection input from the user as to whether to execute the specific discrimination mode or the reference discrimination mode.

[0137] Instead of the user having to select and input, the discrimination mode may be configured to automatically switch depending on whether or not a paper type has been registered, without user operation. For example, if no paper type registration has been performed, the discrimination mode flag 184 remains at 0, and if a paper type registration is performed, the discrimination mode flag 184 switches to 1. Also, a discrimination mode flag 184 may be individually provided for each tray 131, and a configuration may be adopted in which a selection input between the specific discrimination mode and the standard discrimination mode is accepted. Furthermore, a configuration may be adopted in which a selection input between the specific discrimination mode and the standard discrimination mode is accepted for each copy or print job.

[0138] The user can specify the paper type by touching the button that indicates the paper type name of the paper S that they wish to register from among the multiple paper type registration buttons 51a, 51b, 51c, etc., which indicate paper type names. For example, if the paper type they wish to register is plain paper+, they can simply touch the plain paper+ button 51b. The procedure after touch input will be described later.

[0139] The basis weight detection result display field 52 displays the representative value of the basis weight detection values ​​explained in Figures 8 and 9. This display is performed in step S8 shown in Figure 11, which will be described later.

[0140] The nominal basis weight entered by the user is displayed in the nominal basis weight display field 53. The user can enter the nominal basis weight of the paper sheet S that they wish to register using the numeric keys of the nominal basis weight input key group 54, and the entered nominal basis weight value is displayed in the nominal basis weight display field 53. These displays and input reception are performed by the display control unit 176.

[0141] 11, in step S2, the user inputs the paper type and the nominal basis weight of that paper type using one of the paper type registration buttons (51a, 51b, etc.) on the paper type registration screen 145. Below, an example will be described in which the user specifies the paper type "Plain Paper+" by pressing the paper type registration button 51b for "Plain Paper+."

[0142] A message is displayed in the message display field 50 requesting the user to load multiple sheets of paper S of the paper type to be registered, in this case five sheets of plain paper+, into the manual feed tray 131c (step S3). The user sees this message and simply loads the five sheets of plain paper+ they will use into the manual feed tray 131c in a bundled state.

[0143] Here, the reason why manual tray 131c is used is as follows.

[0144] 1, manual feed tray 131c is located outside the device body, and unlike paper feed trays 131a and 131b housed in slots (not shown) in the device body, there is no need for the user to perform an operation (tray opening / closing operation) of pulling it out of the device body, setting paper S, and then pushing it back into the device body, making it easier for the user to set several sheets of paper S. Note that instead of manual feed tray 131c, for example, five sheets of plain paper+ may be set in paper feed tray 131a.

[0145] When it is determined that paper S has been set on manual tray 131c, a message instructing the user to press start key 55 is displayed in message display field 50 (step S4). The determination that paper S has been set on manual tray 131c is made by receiving a signal indicating that paper S has been set from a paper detection sensor (not shown) provided on manual tray 131c.

[0146] When start key 55 is pressed, paper S set in manual feed tray 131c, here plain paper+, is fed one sheet at a time (step S5). This paper feeding is called paper feeding when paper type (sheet type) is registered.

[0147] As each sheet S fed one by one by this paper type registration paper feeding passes the detection position of the media detection sensor 210 while being transported in order on the transport path 201, the media detection sensor 210 detects the basis weight of each sheet S (step S6). This allows the basis weight detection value to be obtained for each of the five sheets S, in this case, plain paper+.

[0148] Next, a representative value is calculated from each detected basis weight value (step S7). As described above, this representative value is calculated by statistical processing in which the average or median of the five detected basis weight values ​​is taken. Note that the method is not limited to the average or median, and methods such as taking the mode (most frequent value) can also be used. Another possible method is to use the center or a value close to the center as the representative value based on the variation in frequency distribution. The method to be used can be determined in advance.

[0149] The number of sheets fed during registration feeding is not limited to five. If it is meaningful to actually measure the basis weight of the paper S used by the user, it is desirable to feed as many sheets as possible during registration feeding. However, since even one sheet is equivalent to an actual measurement, it is also possible to feed more than one sheet. In the case of one sheet of paper S, the detected basis weight value of that sheet S becomes the representative value.

[0150] The representative value calculated in step S7 becomes the characteristic value of the fed paper (sheet). In this sense, the paper type registration unit 172 can be said to constitute an acquisition unit that acquires the characteristic value of the sheet from the basis weight detection value of the paper S when feeding at the time of paper type registration.

[0151] The calculated representative value of the basis weight is displayed as the basis weight detection result in the basis weight detection result display field 52 on the paper type registration screen 145 (step S8). The user can visually check the actual measured value of the basis weight of the paper type to be registered.

[0152] Then, the paper type name of the sheet S for which the basis weight has been detected, here plain paper+, the calculated representative value of the basis weight, and the input nominal basis weight are stored in a one-to-one correspondence in the specific threshold table 182 (step S9). The specific threshold table 182 shown in FIG. 6 shows an example in which the paper type name "plain paper+", its nominal basis weight (=100), and its representative value (=103) are stored in correspondence with each other. Note that at this point, the specific threshold Th1 has not yet been written in the specific threshold Th column. The specific threshold Th1 is written into the specific threshold table 182 in the specific threshold calculation process (step S13) described below.

[0153] Next, the five fed sheets S are transported further downstream in order and discharged (step S10). This transport and discharge of the sheets S can be performed using the same route as that for an image forming job such as a normal print, that is, the sheet S fed from manual feed tray 131c travels along transport path 201 (FIG. 1) through timing roller pair 124, secondary transfer position 125, fixing unit 100, and sheet discharge roller pair 126 to sheet discharge tray 127.

[0154] 1, a branch path 139 (shown by a broken line) branching off from a branch point midway along the conveying path 201 can be provided between the timing roller pair 124 and the secondary transfer position 125, and the media can be discharged outside the machine via the branch path 139. The media detection sensor 210 is located upstream of this branch point in the conveying direction.

[0155] With this configuration, each of the five sheets of paper S fed in the paper type registration paper feed will not pass through the secondary transfer position 125 or the fixing unit 100. In other words, each of the five fed sheets of paper S can be discharged without passing through the image forming unit 120, and the transport distance until discharge can also be shortened.

[0156] This reduces the stress (such as bending force) that the paper S receives during transport due to the long and curved transport path, and the stress (such as pressure and heat) that the paper S receives when it passes between the intermediate transfer belt 122 and the secondary transfer roller 123, and when it passes through the fixing nip 103 between the heating member 101 and the pressure member 102, making it possible to reuse the five sheets of paper S after ejection as if they were new.

[0157] Furthermore, the above-mentioned stress can be reduced by making at least one of the intermediate transfer belt 122, secondary transfer roller 123 (transfer member), heating member 101, and pressure member 102 (fixing member) movable between a contact position where it contacts the paper S being transported on the transport path 201 and a separated position where it is separated from the paper S, and by moving the transfer member and fixing member that can be separated from the paper S to the separated position when performing paper feeding during registration.

[0158] For example, this can be achieved by making the secondary transfer roller 123 and the intermediate transfer belt 122 movable in a direction in which they move relatively closer to or farther from each other using the driving force of an actuator such as a linear motor or a solenoid, and by issuing an instruction to the image forming unit 120 to move the secondary transfer roller 123 and the intermediate transfer belt 122 to a spaced position where they do not come into contact with the paper S during registration paper feeding. The same applies to the contact and separation between the fixing member 101 and the pressure member 102.

[0159] In step S11, it is determined whether or not the registration continuation key 57 (FIG. 12) on the operation panel 140 has been pressed. In the above, an example has been described in which the user registers the paper type of plain paper+, but if the user also wants to continue registering the paper type of another paper type, paper S, the user can continue the registration operation by pressing the registration continuation key 57. Also, if the user wants to end the registration operation, the user can end the registration operation by pressing the end key 56.

[0160] When it is determined that the registration continuation key 57 has been pressed ("Yes" in step S11), the process returns to step S2 and executes the processes from steps S2 to S10 again. For example, if the user wants to register cardboard 2, he or she touches the cardboard 2 button out of the multiple paper type registration buttons 51a, 51b, 51c, etc. displayed on the paper type registration screen 145, and inputs the nominal basis weight of the cardboard 2 (step S2), and then sets five sheets of cardboard 2 that the user himself or herself wants to use in a bundle on the manual feed tray 131c, and then presses the start key 55 (step S5).

[0161] By pressing the start key 55, the thick sheets 2 set in the manual feed tray 131c are fed one by one in the same manner as above (step S5), the basis weight of each thick sheet 2 is detected by the media detection sensor 210 (step S6), the representative value of the basis weight is calculated and displayed (steps S7 and S8), and the paper type name and the like are stored in the specific threshold table (step S9) in sequence. The specific threshold table 182 shown in Figure 6 shows an example in which the paper type name "thick sheet 2" is stored in association with its nominal basis weight (= 200) and representative value (= 206).

[0162] Then, once each of the fed sheets S is conveyed and discharged in order (step S10), the process proceeds to step S11. In this way, the user can register each of the multiple paper types that he or she wishes to register by repeating the operations of pressing the paper type registration button, entering the nominal basis weight, placing the paper S in the manual feed tray 131c, and pressing the start key 55 one by one.

[0163] If it is determined that the registration continuation key 57 has been pressed again ("Yes" in step S11), the process returns to step S2 and registers the paper type of another sheet S (steps S2 to S11). On the other hand, if it is determined that the registration continuation key 57 has not been pressed ("No" in step S11) and the end key 56 has been pressed ("Yes" in step S12), the specific threshold calculation process is performed (step S13) and the paper type registration is terminated.

[0164] It is also possible for the user to select whether or not to register the paper type for each of the paper feed trays 131a, 132b and manual feed tray 131c via the operation panel 140, for example.

[0165] Specifically, when the paper types of the paper S used only in the paper feed tray 131a (for example, plain paper and thick paper 2) are different from the paper types of the paper S used only in the paper feed tray 131b (for example, plain paper + and thick paper 3), paper type registration is performed to create a specific threshold table 182 dedicated to the paper feed tray 131a (specific thresholds for distinguishing plain paper and thick paper 2). Separately from this, paper type registration is performed to create a specific threshold table 182 dedicated to the paper feed tray 131b (specific thresholds for distinguishing plain paper + and thick paper 3).

[0166] Then, in the image forming job for feeding the paper S from the paper feed tray 131a, paper type discrimination is performed in a specific discrimination mode using the specific thresholds stored in the specific threshold table 182 dedicated to the paper feed tray 131a. Also, in the image forming job for feeding the paper S from the paper feed tray 131b, paper type discrimination is performed in a specific discrimination mode using the specific thresholds stored in the specific threshold table 182 dedicated to the paper feed tray 131b.

[0167] For example, if paper type registration is not performed only for the manual feed tray 131c, then in the image forming job for feeding the paper S from the manual feed tray 131c, paper discrimination is performed in the reference discrimination mode. Since various paper types different from plain paper are likely to be set in the manual feed tray 131c, if it is difficult to register all of those paper types in advance, a choice can be made to deliberately not perform paper type registration for the manual feed tray 131c.

[0168]

[10] Specific Threshold Calculation Process [[ID=第十四条]]Figure 13 is a flowchart showing the content of the subroutine of the specific threshold calculation process. The specific threshold calculation process is executed by the specific threshold calculation unit 173.

[0169] As shown in the figure, first, the variable i is set to 1 (step S21). This variable i is an integer used to distinguish which paper type name is specified when the J registered paper type names (J is an integer of 2 or more) are arranged in ascending order of basis weight (representative value). It has the magnitude relationship of 1 ≤ i < J.

[0170] Of the plurality of paper type names registered in the specific threshold table 182, identify the paper types with the i-th and (i + 1)-th smallest basis weights, here, the paper types with the 1st and 2nd smallest basis weights (step S22). In the example shown in FIG. 6, plain paper + is identified as the paper type with the smallest basis weight, and cardboard 2 is identified as the paper type with the second smallest basis weight. Also, in the example shown in FIG. 7, plain paper + is identified as the paper type with the smallest basis weight, and cardboard 1+ is identified as the paper type with the second smallest basis weight.

[0171] Subsequently, calculate an intermediate value Z1 between the representative value of the basis weight corresponding to the identified first paper type and the representative value of the basis weight corresponding to the second paper type (step S23). In the example shown in FIG. 6, 154.5 is calculated as the intermediate value Z1 between the representative value of the basis weight corresponding to the first plain paper + (= 103) and the representative value of the basis weight corresponding to the second cardboard 2 (= 206).

[0172] Then, store the calculated intermediate value Z1 in the specific threshold column of the specific threshold table 182 as a specific threshold Th1 for discriminating the first and second paper types (step S24). In FIG. 6, an example where 154.5 is written as the specific threshold Th1 for discriminating the first plain paper + and the second cardboard 2 is shown.

[0173] When the number of registered paper type names is J, determine whether the relationship (i + 1) < J is satisfied (step S25). In the example shown in FIG. 6, J = 2, and this relationship is not satisfied (so "No" in step S26), and return to the main routine.

[0174] On the other hand, in the example shown in FIG. 7, J = 3, and this relationship is satisfied (so "Yes" in step S26). Set the value obtained by incrementing the current variable i by "1" to a new variable i (step S27), and return to step S22. In the above, since i = 1, the new variable i is set to 2.

[0175] [[ID=二十一]] In step S22, with i = 2, the i-th and (i + 1)-th, that is, the second and third smallest paper types are identified. In the example shown in FIG. 7, as the second smallest paper type, cardboard 1+ is identified, and as the third smallest paper type, cardboard 2 is identified.

[0176] Then, the median value Z2 of the representative basis weights corresponding to the identified second and third paper types is calculated (step S23), and the calculated median value Z2 is stored in the specific threshold value column of the specific threshold value table 182 as the specific threshold value Th2 for discriminating the second and third paper types (step S24). In the example shown in FIG. 7, an example where 166.5 is written as the specific threshold value Th2 for discriminating the second cardboard 1+ and the third cardboard 2 is shown.

[0177] When it is determined that the relationship (i + 1) < J is satisfied (\"Yes\" in step S26), the processes of steps S27 and S22 - S26 are repeatedly executed. When it is determined that the relationship (i + 1) < J is no longer satisfied (\"No\" in step S26), the routine returns to the main routine. [[ID=⑨]] [[ID=⑩]]

[0178] [[ID=⑪]] [[ID=⑫]]As a result, for each of the plurality of paper types registered in the specific threshold value table 182, specific threshold values Th1, 2,... for discriminating two paper types whose basis weights are adjacent in magnitude are calculated and stored in the specific threshold value table 182. [[ID=⑬]] [[ID=⑭]]

[0179] [[ID=⑮]] [[ID=⑯]]Each time an image forming job is executed hereafter, based on the comparison between the result of the basis weight detected by the media detection sensor 210 for the paper S fed in that job and the specific threshold values Th1, 2,... stored in the specific threshold value table 182, it is possible to discriminate which paper type the fed paper S is among the plurality of paper types pre-registered by the user. [[ID=⑰]] [[ID=⑱]]

[0180] [[ID=⑲]] This threshold calculation process currently calculates specific thresholds Th1, 2, etc. for multiple paper types registered in the specific threshold table 182. However, if the user registers a new paper type, for example, the specific thresholds Th1, 2, etc. corresponding to the paper type calculated before this registration will be updated by the registration of the new paper type.

[0181] Specifically, this is the case when plain paper+ and thick paper2 are registered as shown in Fig. 6, and then thick paper1+ is added and registered as shown in Fig. 7. With the additional registration of thick paper1+, three paper types, plain paper+, thick paper1+, and thick paper2, are currently registered in the specific threshold table 182a. In this case, "J" in step S26 shown in Fig. 13 becomes "3," and calculation of specific threshold Th1 for distinguishing between plain paper+ and thick paper1+ (steps S22 to S24) and calculation of specific threshold Th2 for distinguishing between thick paper1+ and thick paper2 (steps S22 to S24) are performed in order, and the specific thresholds are automatically updated.

[0182] In other words, a process is executed to re-determine and update specific threshold values ​​Th1 and Th2 for distinguishing all currently registered paper types (plain paper+, thick paper 1+, thick paper 2) from both the representative values ​​of grammage (characteristic values ​​of each sheet) of plain paper+ and thick paper 2 obtained before the additional registration of the paper type, and the representative value of grammage (characteristic value of the sheet) of thick paper 1+ obtained upon the additional registration.

[0183]

[11] Paper type discrimination processing and image condition setting processing FIG. 14 is a flowchart showing the contents of the paper type discrimination process and the image condition setting process when an image forming job is executed.

[0184] As shown in the figure, it is determined whether an image forming job has started (step S31). If it is determined that an image forming job has not started ("No" in step S31), the process returns to the main routine.

[0185] When it is determined that an image forming job has started ("Yes" in step S31), the basis weight of the sheet S fed from any of the trays 131 is detected by the media detection sensor 210 (step S32).

[0186] It is determined whether the specific discrimination mode is selected (step S33) by referring to the value of the discrimination mode flag 184 (FIG. 4).

[0187] When it is determined that the specific discrimination mode has been selected ("Yes" in step S33), the paper type of the fed paper S is discriminated by comparing the basis weight (detected basis weight value) of the paper S detected by the media detection sensor 210 with the specific threshold values ​​Th1, 2, ... stored in the specific threshold value table 182 (step S34). This paper type discrimination is performed by the paper type discrimination unit 174. Specifically, in the example shown in FIG. 8, the registered paper types are plain paper+ and thick paper2, and if the detected basis weight value is smaller than the specific threshold value Th1 (=154.5), the paper is discriminated as plain paper+, and if the detected basis weight value is larger than the specific threshold value Th1, the paper is discriminated as thick paper2.

[0188] Next, the image forming condition table 183 (FIG. 10) is referenced to set the image forming conditions corresponding to the determined paper type (step S35). The setting of the image forming conditions is performed by the image forming condition setting unit 175.

[0189] Specifically, if the identified paper type is plain paper, the transfer bias is set to a standard Tb, and the fixing temperature is set to a standard Ft. If the identified paper type is thick paper 2, the transfer bias is set to Tb3, which is larger than the standard, and the fixing temperature is set to Ft3, which is higher than the standard. Here, the setting of the transfer bias is performed, for example, by setting Tb or Tb3 as the output value of a high-voltage transformer that outputs the transfer bias. Furthermore, the setting of the fixing temperature is performed, for example, by setting Ft or Ft3 as the target temperature in a configuration that controls the amount of power supplied to heater 104 so that the temperature of fixing member 101 (FIG. 1) of fixing unit 100 is maintained at the target temperature.

[0190] Then, image formation on the fed paper S is performed based on the set image formation conditions (step S36), and the process returns to the main routine (not shown). Specifically, the set transfer bias is output from the high-voltage transformer, and the amount of power supplied to the heater 104 is controlled so that the temperature of the fixing member 101 is maintained at the set fixing temperature.

[0191] The above describes an example of determining the paper type and setting image forming conditions for the first sheet of paper S fed at the start of an image forming job, but for each sheet of paper S from the second sheet onwards, the same image forming conditions can be set, for example, by using the determination results for the first sheet as is.

[0192] This is because a stack of sheets S stored in the paper feed tray 131a (or 131b) is usually of the same paper type, and the productivity of image formation jobs such as printing and copying can be improved by omitting paper type determination for the second and subsequent sheets S. Of course, the paper type determination and image formation conditions may also be performed for each sheet S.

[0193] Furthermore, the paper type determination can be performed only in the image forming job immediately after the paper feed tray 131a (or 131b) to be used is opened or closed, the first image forming job of the day, the image forming job immediately after the device is turned on, or when feeding the first sheet of paper S in the first image forming job after a paper jam has occurred and been cleared.

[0194] Alternatively, the user may be able to switch through the operation panel 140 whether or not to perform the paper type discrimination.

[0195] On the other hand, if it is determined that the standard discrimination mode has been selected rather than the specific discrimination mode ("No" in step S33), the standard threshold table 181 is referenced, and the paper type of the fed paper S is determined by comparing the basis weight detection value detected by the media detection sensor 210 with the standard basis weight threshold Tp stored in the standard threshold table 181 (step S37), and the process proceeds to step S35.

[0196] The paper type determination in this reference determination mode is a conventional determination method that does not use a specific threshold value Th. If the detected basis weight value is, for example, 100, it is determined to be plain paper+ because it is within the range of the reference basis weight threshold value Tp for plain paper+ (lower limit 91 to upper limit 105) as shown in Figure 5. On the other hand, if the detected basis weight value becomes, for example, 106 due to the influence of the detection variation A described above, it may be erroneously determined to be thick paper 1.

[0197] The reason why the reference discrimination mode can be selected in this way is as follows: In the above, it is assumed that the user knows the paper type of the paper S that he or she will be using, and the user selects the paper type that he or she wants to register one by one from the plurality of paper type registration buttons 51 a, 51 b, 51 c, etc. displayed on the paper type registration screen 145.

[0198] However, if the user has no idea what type of paper S they want to register, they will not be able to select the paper type registration button in the first place. In such a case, selecting the standard discrimination mode makes it possible to discriminate the paper type equivalent to that of the conventional method.

[0199] In the reference discrimination mode, if the detected basis weight value for the paper S fed by the job matches the boundary between two ranges of the reference basis weight threshold Tp for paper types whose basis weights are adjacent to each other as shown in the reference threshold table 181 (Figure 5) (for example, the boundary between plain paper+ and thick paper 1: 105.5), or if the difference from the boundary is within a specified range (for example, about 5 in basis weight), the paper can be discriminated as being of the paper type corresponding to the larger basis weight range (for example, thick paper 1 of plain paper+ and thick paper 1).

[0200] In this way, the image forming conditions for the paper S are set to the transfer bias etc. for a paper with a large basis weight, so that the transferability and fixability can be improved compared to the image forming conditions for a paper with a small basis weight.

[0201] Furthermore, in the above-described paper type discrimination process and image condition setting process, if, for example, a discrimination mode flag 184 is provided for each tray 131, it is determined in step S3 which discrimination mode has been selected from the discrimination mode flag 184 corresponding to the tray 131 that contains the fed paper S. For example, if the discrimination mode flag 184 corresponding to the manual feed tray 131c is 0, it is determined that the reference discrimination mode has been selected ("No" in step S33), and the reference discrimination mode is executed (step S37).

[0202] In addition, if the user determines that paper type determination using the media detection sensor 210 is unnecessary, for example, if the user himself / herself registers the paper type from the operation panel 140, the configuration can be such that the detection of basis weight by the media detection sensor 210 is not performed, and instead the process can be switched to setting image formation conditions according to the paper type registered by the user.

[0203] As described above, in this embodiment, when the paper type of paper S to be used by the user is known in advance, and input of two or more paper types specified by the user from among multiple different paper types that can be fed is accepted, a specific threshold value Th is calculated for each paper type of the paper S from the paper type and basis weight to determine the paper type of the paper S by the basis weight.

[0204] Then, in an image forming job executed after calculation of this specific threshold value Th, the basis weight of the actually fed sheet S is measured by the media detection sensor 210, and the paper type of the sheet S is determined from the measured basis weight and the specific threshold value Th calculated in advance. This improves the accuracy of determination compared to a conventional configuration in which the sheet S is determined from a fixed threshold value and the detection result of the media detection sensor 210.

[0205] Here, the specific threshold value Th may be the median value (115 or 166.5 in the example of FIG. 7) of the representative values ​​of a first and second paper type (plain paper+ and thick paper 1+, or thick paper 1+ and thick paper 2 in the example of FIG. 7) that have adjacent basis weights among two or more paper types registered by the user, or may be, for example, the following cases: That is, the specific threshold value Th may be set to the lower and upper limit values ​​of the range for each paper type, or, as in the example of FIG. 8, the upper limit value Tα for plain paper+ may be set as the specific threshold value Th for distinguishing plain paper+, or the lower limit value Tβ for thick paper 2 may be set as the specific threshold value Th for distinguishing thick paper 2.

[0206] The present disclosure is not limited to paper feeders and image forming apparatuses, but may also be a method for determining the type of sheets being fed. Furthermore, the method may also be a program executed by a computer. The program according to the present disclosure can be recorded on various computer-readable recording media, such as magnetic disks (e.g., magnetic tape, flexible disks), optical recording media (e.g., DVD-ROMs, DVD-RAMs, CD-ROMs, CD-Rs, MOs, and PDs), and flash memory recording media. The program may be produced or transferred in the form of such a recording medium, or may be transmitted or supplied in the form of a program via various wired or wireless networks (e.g., the Internet), broadcasting, telecommunications lines, satellite communications, etc.

[0207] <Modification> The present disclosure has been described above based on the embodiments, but it goes without saying that the present disclosure is not limited to the above-described embodiments, and the following modified examples can be implemented.

[0208] (1) In the above embodiment, an example was described in which only one type of paper S used by a user belongs to one paper type, specifically, as shown in Figure 8, only plain paper +, whose representative basis weight is 103, belongs to the paper type ``plain paper +'', and only thick paper 2, whose representative basis weight is 206, belongs to the paper type ``cardboard 2'', and the specific threshold value Th1 for distinguishing between plain paper + and cardboard 2 is set to the midpoint (=154.5) between the representative basis weight values ​​of 103 and 206.

[0209] However, depending on the environment in which the user uses the image forming device 1, there may be a case where another thick paper, specifically a paper S having a representative basis weight value of 168, is classified as the paper type "thick paper 2" and has a frequency distribution of detected basis weight values ​​(measured basis weight distribution) 40, as shown in Figure 15, for example.

[0210] In such a case, it becomes necessary to distinguish between a thick sheet of paper with a representative basis weight of 168 and a thick sheet of paper with a representative basis weight of 206 as the same paper type, thick sheet 2. Therefore, when two or more sheets S with different representative basis weights belong to the same paper type, the paper type is distinguished in the following way.

[0211] That is, the average value (=187) of the representative values ​​(168, 206) of different basis weights is calculated, and a representative value change process is performed to regard the calculated average value as the representative value of two cardboards 2 with different basis weights. The intermediate value (=145) between the changed representative value of the basis weight of the cardboard 2 (=187) and the representative value of the basis weight of plain paper+ (=103) is rewritten as the new specific threshold value Th1. As a result, both cardboard with a representative value of basis weight of 168 and cardboard with a representative value of basis weight of 206 are determined to be cardboard 2 of the same paper type. This representative value change process will be explained using FIG. 16.

[0212] Fig. 16 is a partial flowchart showing the contents of the changed part of the flowchart for registering paper types shown in Fig. 11, which corresponds to the representative value change process. This partial flow is executed after the determination of "Yes" in step S12 and before proceeding to the specific threshold calculation process (step S13).

[0213] That is, when the user has completed all the registration operations for the paper type he or she wishes to register in steps S1 to S12 of the paper type registration shown in FIG. 11 ("Yes" in step S12), the specific threshold table 182 is referenced to determine whether or not two or more records with the same paper type name exist (step S51).

[0214] If it is determined that there are no records with the same paper type name, for example, if it is determined that only records with different paper types exist in the paper type name field as shown in the specific threshold table 182 in Fig. 6 ("No" in step S51), the process proceeds to step S13. In this case, the process is the same as in the above embodiment.

[0215] On the other hand, if it is determined that two or more records with the same paper type name exist, for example, if there are two records for the same paper type, cardboard 2, in the paper type name column in the specific threshold value table 182 shown in Fig. 17(a) ("Yes" in step S51), the process proceeds to step S52. Note that the specific threshold value Th column in Fig. 17(a) is blank because, at the time step S51 is being executed, the specific threshold value Th has not yet been calculated in step S13, as described above.

[0216] In step S52, the average value of the representative values ​​of each record is regarded as the representative value of the same paper type, in this case, cardboard 2, and the contents of the specific threshold value table 182 are rewritten. After this, the process proceeds to step S13.

[0217] 17(b) is a diagram showing an example of the contents of the specific threshold value table 182b after "Yes" is selected in step S51 and the table has been rewritten by the process of S52 (representative value change process). As shown in the figure, only one item, cardboard 2, is written in the paper type name column, and its representative value is 187, which is the average value mentioned above.

[0218] Even when two or more sheets S having different representative values ​​of basis weight belong to the same paper type, it is possible to calculate a specific threshold value Th suitable for distinguishing between each paper type registered by the user.

[0219] In the above example, the average value (=187) of the representative values ​​(168, 206) of different basis weights is taken, but the present invention is not limited to this.

[0220] For example, in the example shown in Figure 15, when distinguishing between plain paper+ and thick paper 2, which has a larger basis weight, the smallest representative value (=168) of the representative values ​​of the basis weight of thick paper 2 (168, 206) can be considered as the representative value of thick paper 2, and the median (=135.5) with the representative value of plain paper+ (=103) can be calculated as the specific threshold value Th.

[0221] (2) In the above embodiment, in the example shown in Fig. 8, the specific threshold value Th1 is calculated to be 154.5, which is the intermediate value between the representative value of the basis weight of plain paper+ (=103) and the representative value of the basis weight of thick paper 2 (=206). This method of taking the intermediate value is effective in eliminating detection variations A and B of the media detection sensor 210.

[0222] On the other hand, the difference (=51.5) between the representative value of the basis weight of plain paper+ (=103) and the specific threshold value Th1 (=154.5) becomes considerably large.

[0223] Assuming that the paper types of paper S used by the user are only two, plain paper+ and thick paper2, if the basis weight detection value by the media detection sensor 210 is smaller than the specific threshold value Th1, then highly accurate discrimination can be made by distinguishing between plain paper+ and thick paper2 and identifying it as plain paper+.

[0224] However, if the detected basis weight value is slightly lower than the specific threshold value Th1, for example, around 150, this is significantly different from the representative basis weight value of plain paper+ (=103), and it is not due to the influence of the detection variation A of the media detection sensor 210, but rather to the occurrence of an irregularity in which paper type other than the registered paper type, in the example of Figure 6, paper S of a paper type other than plain paper+ and thick paper 2, has been fed into tray 131.

[0225] Therefore, when such an irregularity occurs, the user can be warned by notifying the user from the operation panel 140 by displaying a message or by voice that paper S other than the registered paper type is being fed, or by controlling the prohibition of subsequent image formation jobs.

[0226] The determination of whether an irregularity has occurred can be made by setting an irregular range Eg (non-discrimination area) of threshold values ​​Tα (for example, 134.5) to Tβ (for example, 174.5) for determining whether an irregularity has occurred as shown in Fig. 8, and if the basis weight detection value of the paper S by the media detection sensor 210 during execution of an image forming job falls within the irregular range Eg, it can be determined that an irregularity has occurred, that is, paper S of a type other than the registered paper type has been fed. This process of determining whether an irregularity has occurred will be described with reference to Fig. 18.

[0227] Fig. 18 is a partial flowchart showing the contents of the modified portion of the flowchart of the paper type determination process and image condition setting process shown in Fig. 14, which corresponds to the irregularity occurrence determination process. This partial flow is executed after step S32 and before proceeding to step S33.

[0228] That is, it is determined whether or not the basis weight value of the sheet S detected by the media detection sensor 210 in the image forming job is within the irregular range Eg (step S61).

[0229] If it is determined that the detected basis weight value is not within the irregular range Eg ("No" in step S61), the process proceeds to step S33. In this case, the process is the same as in the above embodiment.

[0230] On the other hand, if it is determined that the detected basis weight value is within the irregular range Eg ("Yes" in step S61), it notifies that an irregularity has occurred (step S62), interrupts the current image formation job (step S63), and returns to the main routine. Note that instead of the partial flow in the same figure, for example, after notifying that an irregularity has occurred, it is also possible to proceed to step S33 without interrupting the image formation job, or to execute only the current image formation job and then prohibit execution of subsequent image formation jobs.

[0231] (3) In the above embodiment, the ambient environment of the image forming apparatus 1 is not particularly considered. However, it is also possible to adopt a configuration in which a correction process for the specific threshold value Th is performed in accordance with environmental conditions such as temperature and humidity.

[0232] 19 is a diagram showing an example of the contents of the correction table 70 used in the correction process of the specific threshold value. The correction table 70 is provided in the storage area of ​​the storage circuit 180, for example.

[0233] The correction table 70 shown in the figure divides environments into three: a normal temperature and normal humidity environment, a low temperature and low humidity environment, and a high temperature and high humidity environment. Here, a normal temperature and normal humidity environment refers to an environment of approximately 20°C and 55% RH, a low temperature and low humidity environment refers to an environment of approximately 10°C and 15% RH, and a high temperature and high humidity environment refers to an environment of approximately 30°C and 85% RH. Thresholds for distinguishing between the environments are stored, and a temperature and humidity sensor (not shown) detects the temperature and humidity in the space surrounding the image forming apparatus 1, and the detection results can be used to determine which of the three environments the image forming apparatus 1 currently belongs to.

[0234] In a normal temperature and normal humidity environment, the correction amount of the specific threshold Th is 0 (zero), in a low temperature and low humidity environment, the correction amount is -U1, and in a high temperature and high humidity environment, the correction amount is +U2. The reason for using such correction amounts is as follows.

[0235] That is, in a high-humidity, high-temperature environment, the amount of moisture absorbed by the sheet S is greater than in a normal-temperature, normal-humidity environment, and the basis weight detected by the media detection sensor 210 for the sheet S is likely to be higher. Therefore, to compensate for this increase, the specific threshold value Th is corrected to be larger than in a normal-temperature, normal-humidity environment. Here, the values ​​obtained by adding a correction amount (= +U2) to each of the specific threshold values ​​Th1, Th2, etc. stored in the specific threshold table 182 are used as the corrected specific threshold values ​​Th1, Th2, etc. This makes it possible to suppress the effects of a high-humidity, high-temperature environment.

[0236] On the other hand, in a low-temperature, low-humidity environment, unlike a high-humidity, high-temperature environment, the amount of moisture absorbed is less than in a normal-temperature, normal-humidity environment, and the detected basis weight value of the paper S is likely to be lower. Therefore, the specific threshold value Th is corrected accordingly to be smaller than in a normal-temperature, normal-humidity environment. Here, the values ​​obtained by adding a correction amount (=-U1) to each of the specific threshold values ​​Th1, Th2... are used as the corrected specific threshold values ​​Th1, Th2.... This makes it possible to suppress the effects of a low-temperature, low-humidity environment.

[0237] Fig. 20 is a partial flowchart showing the contents of modified portions of the flowcharts for the paper type discrimination process and image condition setting process shown in Fig. 14, and corresponds to the specific threshold correction process. This partial flow is executed by the paper type discrimination unit 174 in place of step S34, and is executed after "Yes" in step S33 and before proceeding to step S35.

[0238] That is, when it is determined that the specific determination mode is selected ("Yes" in step S33), all the specific thresholds Th1, Th2, etc. stored in the specific threshold table 182 are read (step S71), and it is determined which of the above three the current environment around the image forming apparatus 1 belongs to (step S72).

[0239] If it is determined that the environment is normal temperature and humidity, the correction table 70 is referenced, and the correction amount is set to "0" corresponding to the normal temperature and humidity environment (step S73), and the process proceeds to step S76. If it is determined that the environment is low temperature and low humidity, the correction table 70 is referenced, and the correction amount is set to "-U1" corresponding to the low temperature and low humidity environment (step S74), and the process proceeds to step S76. If it is determined that the environment is high temperature and high humidity, the correction table 70 is referenced, and the correction amount is set to "+U2" corresponding to the high temperature and high humidity environment (step S75), and the process proceeds to step S76.

[0240] In step S76, the correction amount set in one of steps S73 to S75 is added to each of the specific thresholds Th1, Th2, etc. read in step S71, and the result is rewritten as the corrected specific thresholds Th1, Th2, etc., and then the process proceeds to step S77.

[0241] In step S77, the paper type of the fed paper S is determined by comparing the basis weight detected by the media detection sensor 210 with the corrected specific threshold values ​​Th1, 2, etc. Then, the process proceeds to step S35.

[0242] By correcting the specific threshold value Th in this way according to the environmental conditions, even if there is a change in the surrounding environment of the image forming apparatus 1, it becomes possible to accurately determine the paper type of the paper S using the specific threshold value Th according to the change in the environment.

[0243] In the above, the environmental conditions are defined as changes in temperature and humidity, but they are not limited to this and, for example, only temperature changes or only humidity changes can be used as environmental conditions.Furthermore, instead of being limited to temperature and humidity, for example, if the atmospheric pressure differs depending on whether the image forming apparatus 1 is installed at a high altitude or not and this difference in atmospheric pressure affects paper type discrimination, atmospheric pressure changes can also be considered as environmental conditions.

[0244] In the above, the correction amount is set to "- (minus)" in a low-temperature, low-humidity environment and "+ (plus)" in a high-temperature, high-humidity environment, but this is not limiting. For example, the correction amount can be set to "0" for either the low-temperature, low-humidity environment or the high-temperature, high-humidity environment, or, depending on the device configuration, the correction amount can be set to "+" for a low-temperature, low-humidity environment and "-" for a high-temperature, high-humidity environment. Correction amounts appropriate for each environment can be determined in advance through experiments or the like and stored in the correction table 70. Furthermore, environmental conditions are not limited to the surrounding environment, and may also include, for example, the temperature or humidity inside the device itself.

[0245] In addition, it is not limited to environmental conditions, but for example, when a difference occurs in the basis weight detection value by the media detection sensor 210 for paper S of the same paper type as the cumulative number of images formed in the image forming device 1 increases due to durability conditions, specifically, when the difference occurs in the basis weight detection value by the media detection sensor 210 for paper S of the same paper type as the cumulative number of images formed in the image forming device 1 increases, it is also possible to adopt a configuration in which the specific threshold value Th is corrected according to the durability conditions.

[0246] This is effective in cases where the detection accuracy of the media detection sensor 210 gradually decreases over a long period of time as the cumulative number of images formed on the image forming apparatus 1 gradually increases from the time the image forming apparatus 1 is new. The durability conditions can include not only the cumulative number of images formed on, but also at least one of the cumulative usage time of the image forming apparatus 1 and the cumulative rotation time of the photosensitive drum or intermediate transfer belt 122. The appropriate amount of correction can be determined by experiment or the like depending on the cumulative number of images formed on, the cumulative usage time, and the cumulative rotation time.

[0247] Furthermore, the specific threshold value Th can be corrected based on either or both of environmental changes and durability conditions. In addition to or instead of correcting the specific threshold value Th, for example, a representative value of the paper basis weight calculated before calculating the specific threshold value Th can be corrected according to at least one of environmental conditions and durability conditions, and the corrected representative value can be used to calculate the specific threshold value Th. The amount of this correction can also be determined in advance through experiments or other means, depending on environmental changes.

[0248] (4) In the above embodiment, the five sheets of paper S that the user placed in the manual feed tray 131c when registering the paper type are actually fed one by one, a representative value is calculated from the basis weight detection values ​​of each of the five sheets of paper S by the media detection sensor 210, and the specific threshold value Th is calculated from the calculated representative value, but this is not limited to this.

[0249] For example, a specific threshold update process can be performed in which the representative value calculated when the paper type was registered is recalculated using the basis weight detection value of the paper S measured by the media detection sensor 210 when an image formation job is executed after the paper type is registered, and the specific threshold Th is updated from the recalculated representative value.

[0250] 21 is a diagram showing an example of the content of the basis weight detection value table 75 used in the specific threshold value update process. The basis weight detection value table 75 is provided in the storage area of ​​the storage circuit 180, for example.

[0251] As shown in the figure, the basis weight detection value table 75 corresponds to the paper type "plain paper +" and has columns 1 to 5 for the number of sheets of paper fed at the time of paper type registration, and columns 1, 2, 3, etc. for the number of sheets of paper S fed during the image formation job.

[0252] In each of the fields for the number of sheets 1 to 5 when registering the paper type, the detected basis weight values ​​actually measured for each of the five sheets S fed when registering the paper type when the user specifies the paper type "plain paper+" are written. This writing is performed by the paper type registration unit 172.

[0253] In addition, in each column of the number of sheets of paper 1, 2, 3, etc. during an image formation job, each time the paper S fed during the execution of an image formation job is determined to be "plain paper+" based on the basis weight detection value of the paper S, The number of sheets column increases by one, and the detected basis weight value is written into that column. This writing is performed by the paper type discrimination unit 174.

[0254] By referring to the detected basis weight table 75, it is possible to know the actual measured basis weight values ​​for all sheets S that have been determined to be "plain paper+" from the time the paper type was registered until the present time.

[0255] 22 is a flowchart showing the contents of the specific threshold update process. This specific threshold update process is executed separately from the above-mentioned specific threshold calculation process by the specific threshold calculation unit 173. Note that this specific threshold update process is shown as an example for the paper type "plain paper+".

[0256] As shown in the figure, it is determined whether paper type registration is being executed for the paper type "plain paper+" (step S91). If it is determined that paper type registration is being executed ("Yes" in step S91), the basis weight detection values ​​by the media detection sensor 210 for each of the five sheets of paper S (plain paper+) fed one by one from the manual feed tray 131c at the time of paper type registration are stored in paper number columns 1 to 5 at the time of paper type registration in the basis weight detection value table 75 (step S92), and the process proceeds to step S93. If it is determined that paper type registration is not being executed ("No" in step S91), the process proceeds to step S93.

[0257] In step S93, it is determined whether an image formation job is to be executed. If it is determined that an image formation job is to be executed ("Yes" in step S93), it is determined whether the sheet S fed from tray 131 has been identified as "plain paper+" (step S94). If it is determined that the sheet S has been identified as "plain paper+" ("Yes" in step S94), the basis weight detection value for that sheet S by media detection sensor 210 is stored in the sheet number column next to the largest sheet number column in which the basis weight detection value is stored in the basis weight detection value table 75, among the sheet number columns 1, 2, 3, etc., during image formation (step S95), and the process proceeds to step S96. If it is determined that an image formation job is not to be executed ("No" in step S93), the process proceeds to step S96. If it is determined that the sheet S has not been identified as "plain paper+" ("No" in step S94), the process proceeds to step S96.

[0258] In step S96, it is determined whether it is time to update the setting. The update timing can be, for example, every time image formation on a certain number of sheets of paper S is completed by an image formation job after the paper type is registered, or every time the device is turned on.

[0259] When it is determined that the update timing has arrived ("Yes" in step S96), all detected basis weight values ​​currently stored in the detected basis weight value table 75 are read out and a representative value thereof is calculated (step S97). This representative value (sheet characteristic value) is calculated by the above-mentioned statistical processing, for example, by finding an average value.

[0260] At this point, the total number of detected basis weight values ​​has increased from the five detected basis weight values ​​at the time of paper type detection due to the execution of image formation jobs after paper type registration, and the total number of detected basis weight values ​​increases significantly as the number of executed image formation jobs increases. The greater the total number of detected basis weight values, the more accurate the calculation of the representative value, so that it approaches the true value of the basis weight of plain paper+ used by the user, and the more accurately the specific threshold value Th1 for identifying plain paper+ can be calculated.

[0261] Then, in step S98, the representative value calculated in step S97 is used as the new representative value, and the representative value in the representative value column corresponding to "plain paper +" in the specific threshold table 82 is updated, overwritten and saved, and then the process proceeds to step S99.

[0262] In step S99, the specific threshold value is calculated, and then the process returns to the main routine. This specific threshold value calculation process is substantially the same as the specific threshold value calculation process shown in FIG.

[0263] In the specific threshold calculation process executed in step S99, the representative value of the basis weight of "plain paper+" updated in step S98 is used to newly calculate a specific threshold Th1 for distinguishing between "plain paper+" and another paper type, in the above example, cardboard 2 (FIG. 13: step S23). The calculated specific threshold Th1 is then stored in the specific threshold table 182 as the new specific threshold Th1 (FIG. 13: steps S23 and S24). This storage constitutes an update. By updating (recalculating) the specific threshold Th1, it is possible to further improve the accuracy of distinguishing between plain paper+ and paper before the update. Note that if it is determined that the time for updating has not yet arrived ("No" in step S96), the process returns to the main routine.

[0264] The above describes the paper type "plain paper+," but for other paper types (such as cardboard 2), the paper type is registered (steps S91 and S92), the basis weight detection value is stored when that paper type is determined during an image formation job (steps S93 to S95), and a representative value for that paper type is calculated and updated when the update timing arrives (steps S96 to S98).

[0265] It is also possible to adopt a configuration in which the user selects and inputs whether or not to execute the specific threshold update process from the operation panel 140. For example, when plain paper and thick paper 2 are registered, if a need arises to feed thin paper and the thin paper is fed and the paper is determined to be plain paper, the detected basis weight value of the thin paper will also be stored in the detected basis weight value table 75. If the specific threshold Th for plain paper is calculated subsequently including the detected basis weight value of this thin paper, this may affect the calculation result of the threshold for plain paper. Therefore, by making it possible to select whether or not to execute the specific threshold update process, if it becomes necessary to pass a paper S of a type other than the registered paper type, it is possible to avoid the risk of affecting the calculation result of the threshold by selecting not to execute the specific threshold update process (refusing to update) for only that paper S. When this configuration is adopted, the operation panel 140 constitutes an update permission / refusal input receiving unit that receives a selection input of whether or not to permit the update of the specific threshold, and the update of the specific threshold can be executed on the condition that permission of the update is selected.

[0266] Also, if the passed sheet S is thin paper and its detected basis weight value is smaller than the range of the registered reference basis weight threshold Tp for regular paper by a predetermined value, for example, 10 or more, it can be configured not to be stored (excluded) as an outlier. Similarly, if the passed sheet S is thick paper 4 and its detected basis weight value is larger than the range of the registered reference basis weight threshold Tp for thick paper 2 by a predetermined value, for example, 30 or more, it can be configured not to be stored as an outlier.

[0267] (5) In the above embodiment, one or more sheets of paper S used by the user are actually fed during registration paper feeding, the basis weight of the paper S is measured using the media detection sensor 210, a representative value is found from the actual measured value, and the specific threshold value Th is calculated using the found representative value, but the calculation of the specific threshold value Th is not limited to this.

[0268] For example, the specific threshold value Th can be calculated from the nominal basis weight of each paper type. The nominal basis weight should be, to a certain extent, at or near the median value of the distribution of basis weight variations. Therefore, even if the nominal basis weight is used instead of the actual measurement value to calculate the specific threshold value Th, it is unlikely that the result will deviate significantly from the specific threshold value Th obtained from the actual measurement value. In the example shown in FIG. 6 above, the nominal basis weight of plain paper+ is 100, and the representative value obtained from the actual measurement value is 103, which are fairly close values. This nominal basis weight is information entered from the operation panel 140 (operation unit) during paper type registration as information on the basis weight (characteristic value) of the paper (sheet). In this sense, the operation panel 140 functions as an acquisition unit that acquires information on the characteristic value of the paper.

[0269] Fig. 23 is a flowchart showing the specific threshold calculation process according to this modification. In the specific threshold calculation process shown in Fig. 23, steps S22 and S23 of the specific threshold calculation process shown in Fig. 13 are replaced with steps S221 and S231.

[0270] That is, in step S221, the paper types with the ith and (i+1)th smallest nominal basis weights, in this case the first and second smallest, are identified from among the multiple paper type names registered in the specific threshold table 182. If i=1, in the example shown in Fig. 6, plain paper+ is identified as the paper type with the smallest nominal basis weight, and cardboard 2 is identified as the paper type with the second smallest nominal basis weight.

[0271] Then, in step S231, the intermediate value Zi between the nominal basis weight corresponding to the identified ith paper type and the nominal basis weight corresponding to the (i+1)th paper type is calculated. If i=1, in the example shown in Fig. 6, 150 is calculated as the intermediate value Z1 between the nominal basis weight (=100) of the first plain paper + and the nominal basis weight (=200) of the second thick paper 2. In the next step S24, the value of this intermediate value Z1, 150, is stored in the specific threshold table 182 as the specific threshold value Th1.

[0272] If the specific threshold value Th is automatically calculated using this nominal basis weight, there is no need to perform registration time feeding, and the user can be spared the trouble of setting the paper S on the manual feed tray 131c for registration time feeding.

[0273] (6) In the above embodiment, the paper characteristic value is the basis weight of the paper, but this is not limited to this. Any sheet characteristic that can be used to determine the paper type (sheet type) can be used, and for example, the thickness, glossiness, or smoothness of the paper can also be used as the sheet characteristic value.

[0274] For example, if the thickness of paper differs, the amount of light transmitted through that paper will differ, so if the amount of transmitted light is associated with a threshold value for each paper type, it is possible to determine the paper type by detecting (actually measuring) the thickness of the paper. Also, if the glossiness or smoothness of paper differs, the amount of reflected light when light is irradiated onto the main surface of the paper will differ, so if the amount of reflected light is associated with a threshold value for each paper type, it is possible to determine the paper type by detecting (actually measuring) the glossiness or smoothness of the paper.

[0275] (7) In the above embodiment, the image forming apparatus 1 is described as a tandem type, but it goes without saying that the present disclosure is not limited to this, and the image forming apparatus 1 may be an image forming apparatus other than a tandem type, or may be a monochrome multifunction printer.

[0276] Furthermore, the image forming apparatus 1 is not limited to an electrophotographic type, and may be, for example, an inkjet type. In the inkjet type, if the sheet conveyance speed, the amount of ink droplets ejected from the inkjet nozzles, and the ejection speed are set according to the type of paper S being fed, the settings of the conveyance speed, the amount of droplets, etc. become the settings of the image forming conditions.

[0277] In addition, in a post-processing device (not shown) that stores paper sheets S fed one by one from the paper feed section 130 in a tray, staples a stack of paper sheets consisting of multiple paper sheets S stacked on the tray, or punches holes in one or more sheets of paper, the above control can be applied to a configuration that limits the number of sheets of paper that can be stapled or determines whether the paper can have holes punched in it, depending on the paper type of the identified paper sheet S.

[0278] Furthermore, the configurations of the above-described embodiment and the above-described modified examples may be combined as much as possible. [Industrial Applicability]

[0279] The present disclosure can be widely applied to a sheet feeding device that feeds sheets on a tray and an image forming apparatus that includes the same. [Explanation of symbols]

[0280] 1. Image forming device 51a, 51b, 51c Paper type registration button 100 Fixing unit 120 Image forming unit 130 Paper feed section 131a, 132a paper tray 131c Manual feed tray 150 control section 172 Paper Type Registration Department 173 Specific threshold calculation unit 174 Paper type discrimination section 175 Image formation condition setting unit 176 Display control unit 181 Standard Threshold Table 182, 182a Specific threshold table 183 Image formation condition table 184 Discrimination mode flag 210 Media detection sensor (detection means) 201 Transport path

Claims

1. A sheet feeding device that feeds sheets on a tray, a registration unit that receives input of two or more different types of sheets to be used by a user and registers them; an acquisition unit that acquires, for each registered type, characteristic values ​​of sheets of the corresponding type by accepting an input from a user or from a storage unit that stores the characteristic values ​​of the sheets; a calculation unit that calculates a specific threshold value for identifying the type of each sheet from the characteristic values ​​of the sheet acquired for each type; a detection unit that detects the characteristic value of the sheet fed from the tray using a sensor after the calculation; a discrimination unit that discriminates which type of sheet among the registered types the fed sheet is based on the detected sheet characteristic value and the calculated specific threshold value; Equipped with the calculation unit calculates one specific threshold value for each of two types of sheets whose characteristic values ​​are adjacent to each other among two or more different types of sheets; The discrimination unit separately sets a non-discrimination area, which is an area between a first characteristic value belonging to a first type of the two types and smaller than the one specific threshold value, and a second characteristic value belonging to a second type and larger than the one specific threshold value, across the calculated one specific threshold value, and when it determines that the characteristic value of the sheet detected by the detection unit is within the non-discrimination area, it notifies that a sheet of a type other than the registered type is being fed. A paper feeder characterized by:

2. 2. The sheet feeding device according to claim 1, wherein the acquisition unit is an operation unit into which information on characteristic values ​​of sheets of each type is input.

3. A sheet feeding device that feeds sheets on a tray, a registration unit that receives input of two or more different types of sheets to be used by a user and registers them; an acquisition unit that acquires characteristic values ​​of sheets of each registered type; a calculation unit that calculates a specific threshold value for identifying the type of each sheet from the characteristic values ​​of the sheet acquired for each type; a detection unit that detects the characteristic value of the sheet fed from the tray after the calculation; a discrimination unit that discriminates which type of sheet among the registered types the fed sheet is based on the detected sheet characteristic value and the calculated specific threshold value; Equipped with the acquisition unit instructs the user to store one or more sheets of each type of sheet in the tray, and then, upon receiving a sheet feeding instruction from the user, feeds the sheet from the tray, performs registration sheet feeding in which the detection unit detects characteristic values ​​of the sheet, and acquires the characteristic values ​​of the sheet from the detection result of the detection unit; the calculation unit calculates one specific threshold value for each of two types of sheets whose characteristic values ​​are adjacent to each other among two or more different types of sheets; The discrimination unit separately sets a non-discrimination area, which is an area between a first characteristic value belonging to a first type of the two types and smaller than the one specific threshold value, and a second characteristic value belonging to a second type and larger than the one specific threshold value, across the calculated one specific threshold value, and when it determines that the characteristic value of the sheet detected by the detection unit is within the non-discrimination area, it notifies that a sheet of a type other than the registered type is being fed. A paper feeder characterized by:

4. The registration unit The paper feeding device according to claim 3, further comprising: a means for receiving input of nominal characteristic values ​​for each registered type of sheet; and storing the received nominal characteristic values ​​in correspondence with the characteristic values ​​of the sheet detected by the detection unit.

5. characteristic classification information is stored, which is a one-to-one correspondence between each of a plurality of different types of sheets that can be fed and a range of characteristic values ​​of the sheets corresponding to that type; the plurality of different types of sheets that can be fed include two or more different types of sheets that the user uses; A paper feeding device described in any one of claims 1 to 4, characterized in that when the type of sheet is not registered by the registration unit, the discrimination unit performs a standard discrimination mode in which the type of sheet is determined based on which of the ranges indicated in the characteristic classification information the characteristic value of the sheet detected by the detection unit belongs to, without using the specific threshold value.

6. a selection input receiving unit that receives a selection input from a user as to whether to execute the specific discrimination mode or the reference discrimination mode when the specific discrimination mode is set to discriminating the type of sheet using the specific threshold value; The paper feeding device according to claim 5, characterized in that, when the type of sheet is registered by the registration unit, the discrimination unit switches the discrimination mode to be executed depending on whether the specific discrimination mode or the standard discrimination mode is selected.

7. a tray separate from the tray; the selection input receiving unit receives the selection input for each of the trays, 7. The paper feeder according to claim 6, wherein the discrimination unit switches the discrimination mode for each of the trays.

8. Paper is fed from the tray for each job, the selection input receiving unit receives the selection input for each job; 7. The paper feeder according to claim 6, wherein the discrimination unit switches the discrimination mode for each job.

9. A sheet feeding device that feeds sheets on a tray, a registration unit that receives input of two or more different types of sheets to be used by a user and registers them; an acquisition unit that acquires, for each registered type, characteristic values ​​of sheets of the corresponding type by accepting an input from a user or from a storage unit that stores the characteristic values ​​of the sheets; a calculation unit that calculates a specific threshold value for identifying the type of each sheet from the characteristic values ​​of the sheet acquired for each type; a detection unit that detects the characteristic value of the sheet fed from the tray using a sensor after the calculation; a discrimination unit that discriminates which type of sheet among the registered types the fed sheet is based on the detected sheet characteristic value and the calculated specific threshold value; Equipped with the acquisition unit further acquires, after calculating the specific threshold value, each time a sheet is fed from the tray, a characteristic value of the sheet detected by the detection unit, and stores the acquired characteristic value of the sheet in association with the type of the sheet identified by the identification unit; the calculation unit, after calculating the specific threshold value, calculates a new specific threshold value for each type of sheet from one or more characteristic values ​​stored corresponding to the type, and updates the specific threshold value; Furthermore, the paper feeding device is characterized in that when the difference between the characteristic value of the sheet detected by the detection unit and the specific threshold value is greater than a predetermined value, the acquisition unit does not perform the process of correlating and storing the detected characteristic value of the sheet with the determined type of sheet.

10. A sheet feeding device that feeds sheets on a tray, a registration unit that receives input of two or more different types of sheets to be used by a user and registers them; an acquisition unit that acquires characteristic values ​​of sheets of each registered type; a calculation unit that calculates a specific threshold value for identifying the type of each sheet from the characteristic values ​​of the sheet acquired for each type; a detection unit that detects the characteristic value of the sheet fed from the tray after the calculation; a discrimination unit that discriminates which type of sheet among the registered types the fed sheet is based on the detected sheet characteristic value and the calculated specific threshold value; Equipped with the acquisition unit instructs the user to store one or more sheets of each type of sheet in the tray, and then, upon receiving a sheet feeding instruction from the user, feeds the sheet from the tray, performs registration sheet feeding in which the detection unit detects characteristic values ​​of the sheet, and acquires the characteristic values ​​of the sheet from the detection result of the detection unit; Furthermore, after calculating the specific threshold value, each time a sheet is fed from the tray, the characteristic value of the sheet detected by the detection unit is acquired, and the acquired characteristic value of the sheet is stored in association with the type of the sheet identified by the identification unit. the calculation unit, after calculating the specific threshold value, calculates a new specific threshold value for each type of sheet from one or more characteristic values ​​stored corresponding to the type, and updates the specific threshold value; Furthermore, the paper feeding device is characterized in that when the difference between the characteristic value of the sheet detected by the detection unit and the specific threshold value is greater than a predetermined value, the acquisition unit does not perform the process of correlating and storing the detected characteristic value of the sheet with the determined type of sheet.

11. an update permission / prohibition input receiving unit that receives a selection input of whether or not to permit updating of the specific threshold value; 11. The paper feeding device according to claim 9, wherein the calculation unit executes updating of the specific threshold value on condition that permission to update the specific threshold value is selected.

12. The acquisition unit acquires a plurality of characteristic values ​​of the sheet of each registered type, A paper feeding device described in any one of claims 1 to 11, characterized in that the calculation unit calculates a representative value of the characteristic values ​​of each type of sheet from the multiple characteristic values ​​acquired for that type, and calculates the specific threshold value using the representative value of each type of sheet obtained.

13. 13. The paper feeding device according to claim 12, wherein the calculation unit sets the average value, median value, or mode value of the acquired plurality of characteristic values ​​as the representative value.

14. 14. The paper feeder according to claim 1, wherein the characteristic value of the sheet is a basis weight or a thickness of the sheet.

15. 15. The paper feeding device according to claim 1, wherein the calculation unit corrects the calculated specific threshold value in accordance with at least one of an environmental condition and a durability condition.

16. a conveying path that conveys the sheet fed from the tray to an image forming unit; and a branching path that branches off from a branching point on the conveying path and discharges the sheet fed from the tray without passing it through the image forming unit, the detection unit is disposed upstream of the branch point in a sheet conveyance direction, 11. The sheet feeding device according to claim 3, wherein the acquisition unit causes the sheet fed from the tray to be discharged through the branch path when the registration-time sheet feeding is performed.

17. a conveyance path for conveying the sheet fed from the tray to an image forming unit; the image forming unit includes a transfer member that transfers an image on an image carrier to a conveyed sheet, and a fixing member that fixes the image on the sheet after the image has been transferred; At least one of the transfer member and the fixing member is movable between a contact position where it contacts the conveyed sheet and a separation position where it is separated from the sheet, The paper feeding device according to claim 3 or 10, characterized in that when performing the registration paper feeding, the acquisition unit instructs the image forming unit to move the transfer member and fixing member that can be separated from the sheet to the separation position.

18. 11. The paper feeding device according to claim 3, wherein the tray used for the registration paper feeding is a manual feed tray.

19. When the registration unit receives input of another sheet type after the registration, the registration unit additionally registers the received type; The acquisition unit further acquires characteristic values ​​of the additionally registered type of sheet, A paper feeding device described in any one of claims 1 to 18, characterized in that the calculation unit recalculates and updates a specific threshold value for distinguishing the types of all currently registered sheets from both the characteristic values ​​of each sheet obtained before the additional registration and the characteristic values ​​of the sheets obtained in conjunction with the additional registration.

20. the characteristic value of the sheet is the basis weight or thickness of the sheet, The paper feeding device described in claim 5, characterized in that in the reference discrimination mode, the discrimination unit determines that the sheet type corresponds to the range of the larger sheet basis weight or thickness of the two ranges when the sheet characteristic value, which is the basis weight or thickness, detected by the detection unit coincides with the boundary between two adjacent ranges shown in the characteristic classification information or when the difference from the boundary is within a predetermined range.

21. 11. The sheet feeding device according to claim 9, wherein the calculation unit calculates one specific threshold value for each two types of sheets that have adjacent characteristic values ​​among two or more different sheet types.

22. An image forming apparatus comprising the paper feeder according to any one of claims 1 to 21, an image forming apparatus for forming an image on the sheet based on image forming conditions corresponding to the type of sheet identified by a discrimination unit of the sheet feeding device;

Images