JP6772871B2 - Sheet discrimination device, sheet discrimination method, and image forming device - Google Patents

Description

The present invention relates to a sheet discrimination device, a sheet discrimination method, and an image forming device.

An image forming apparatus that forms an image on a sheet, such as a copier and a printer, has a function of setting operating conditions so that an appropriate image can be obtained according to the type of the sheet.

For example, in an electrophotographic image forming apparatus, sheets are classified according to the basis weight, and the transfer speed, transfer voltage, fixing temperature, and the like are set according to the basis weight. With this setting, it is possible to prevent jams, transfer defects, fixing defects, and the like.

As a method for the image forming apparatus to specify the basis weight of the sheet, there is a method in which the user selects and specifies the type of the sheet from several options (plain paper, thick paper 1, thick paper 2, etc.). The image forming apparatus specifies the basis weight associated with the type specified by the user in advance as the basis weight of the sheet, and sets the operation conditions according to the specified basis weight.

However, in recent years, since the types of sheets that can be used in the image forming apparatus have been diversified, it has become difficult to appropriately set the operating conditions by the method of specifying the basis weight according to the user's specification.

There is a technique described in Patent Document 1 as a prior art for the image forming apparatus to automatically discriminate a sheet.

Patent Document 1 discloses an image forming apparatus that measures both the thickness and rigidity of a sheet using one displacement sensor and sets image forming conditions such as transfer bias and fixing conditions based on these measurement results. Has been done. In addition, as a method of measuring rigidity, a sheet is abutted against a stopped transfer roller and bent, and the shaft of the transfer roller is displaced by the restoring force of the sheet generated when the bent portion abuts on the guide plate, and the displacement thereof. A method of quantifying the amount by a Hall element is disclosed.

JP-A-2010-202347

In order to measure the rigidity of the sheet during transportation, it is necessary to bend the sheet so that a curved portion (so-called loop) is formed. When the loop is formed, the sheet is pushed into the transport roller on the downstream side of the loop from the upstream side, so that a load larger than that during normal transport is applied to the transport roller and the transport mechanism including its drive source. Therefore, there is a problem that the life of the transport mechanism is shortened. The surface of the transport roller may be damaged by pushing the sheet, in which case the transport roller must be replaced.

In addition, the formation of the loop delays the transfer. Therefore, there is a problem that the printing productivity of the image forming apparatus is lowered.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a sheet discrimination device and an image forming device capable of discriminating the type of sheet while suppressing the burden on the transport mechanism.

The sheet discriminating device according to the embodiment of the present invention is a sheet discriminating device for discriminating the type of the sheet carried into the transport path for transporting the sheet, and is a thickness measuring unit for measuring the thickness of the sheet. When the first discriminating unit that discriminates the type of the sheet based on the measured thickness and the measured thickness is a value that cannot discriminate the type by itself, the said It has a rigidity measuring unit for measuring the rigidity of the sheet, and a second discriminating unit for discriminating the type based on the measured thickness and the rigidity.

The sheet discrimination method according to the embodiment of the present invention is a sheet discrimination method for discriminating the type of the sheet carried into the transport path for transporting the sheet, and the thickness of the sheet is measured and measured. When the thickness is a value at which the type cannot be discriminated by itself, the rigidity of the sheet is measured, and the type is discriminated based on the measured thickness and the rigidity.

According to the present invention, it is possible to determine the type of sheet while suppressing the burden on the transport mechanism.

It is a figure which shows the outline of the structure of the image forming apparatus provided with the sheet discrimination apparatus which concerns on one Embodiment of this invention. It is a figure which shows the example of the structure of the displacement detection mechanism. It is a figure which shows the structure of the displacement sensor. It is a figure which shows the structure of the displacement amount measuring part, and the example of the input / output. It is a figure which shows the functional structure of the sheet discriminating device. It is a figure which shows the displacement by a sheet schematically. It is a figure which shows the example of the transition of the displacement amount. It is a figure which shows the example of the relationship between the bending amount and the rigidity of a sheet. It is a figure which shows the example of the type information used for discriminating the type of a sheet. It is a figure which shows other example of the type information used for discriminating the type of a sheet. It is a figure which shows the flow of processing in a sheet discriminating apparatus. It is a figure which shows the flow of the process of rigidity measurement. It is a figure which shows the example of the processing flow in an image forming apparatus. It is a figure which shows another example of the process flow in an image forming apparatus. It is a figure which shows the structure of the automatic document feeder.

FIG. 1 shows an outline of the configuration of an image forming apparatus 1 provided with a sheet discriminating apparatus 7 according to an embodiment of the present invention.

The image forming apparatus 1 is an MFP (Multi-functional Peripheral) having functions such as a copying machine, a printer, and a facsimile machine. The image forming apparatus 1 includes an automatic document feeder (ADF: Auto Document Feeder) 21, a scanner 22, a printer unit 23, a paper feeding unit 24, and a main control unit 20.

The automatic document feeder 21 conveys the sheet 9 (original document) set in the document tray to the reading position of the scanner 22. The automatic document feeder 21 ejects the sheet 9 whose one side has been read by the scanner 22 to the paper output tray 16.

The scanner 22 is a flatbed type, and generates image data by reading images written on various documents set on a sheet 9 or a platen glass conveyed from an automatic document feeder 21.

The printer unit 23 forms an image on a sheet based on raster data generated by, for example, the main control unit 20 in printing jobs such as copying, network printing (PC printing), and facsimile reception. The configuration of the printer unit 23 will be described later.

The paper feed unit 24 is a sheet supply unit capable of storing a large number of sheets, and includes a plurality of paper feed cassettes. Sheets 8 (recording paper) having different sizes or basis weights can be stored in each paper cassette. In the print job, the paper feed unit 24 takes out the sheet 8 from the selected paper feed cassette and feeds it into the transport path 50 leading to the printer unit 23. That is, the sheet 8 is supplied to the printer unit 23.

The main control unit 20 is in charge of overall control of the image forming apparatus 1. That is, it controls the automatic document feeder 21, the scanner 22, the printer unit 23, and the paper feeding unit 24. The main control unit 20 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), an auxiliary storage device, an image processing unit, and the like.

In the main control unit 20, a computer program for controlling the operation of the image forming device 1 is stored in the ROM or the auxiliary storage device. Further, a sheet discriminating program for operating a part of the constituent elements of the image forming apparatus 1 as the sheet discriminating device 7 is stored. These programs are loaded into RAM as needed and executed by the CPU.

The printer unit 23 has a printer engine 30B that forms an image by an electrophotographic method. The printer engine 30B has four imaging stations 31, 32, 33, and 34, and parallelizes toner images of four colors of yellow (Y), magenta (M), cyan (C), and black (K). To form. Each of the imaging stations 31, 32, 33, 34 has a tubular photoconductor, a charged charger, a developing device, a cleaner, a print head for exposure, and the like.

The four-color toner image is primarily transferred to the intermediate transfer belt 35, and is secondarily transferred to the sheet 8 transported from the paper feed unit 23 through the transport path 50. After the secondary transfer, the sheet 9 is fed through the inside of the fuser 37 to the output tray or finisher. When passing through the fuser 37, the toner image is fixed to the sheet 8 by heating and pressurizing. The fuser 37 has a function of collecting ultra fine particles (UFP).

In the printer unit 23, the transport path 50 is provided with a first transport roller 61, a second transport roller 62, a third transport roller 63, a resist roller 64, and a paper ejection roller 65 in this order from the upstream side. The sheet 8 is conveyed by these rollers 61 to 65.

The transport path 50 includes a front-back reversal path 58 for double-sided printing. In the case of double-sided printing, the sheet 8 printed on the first side and passing through the fuser 37 is carried into the front-back reversing path 58, and the front and back are reversed by switchback transfer and returned to the first transfer roller 61. Then, it is discharged after printing on the second surface.

By the way, the image forming apparatus 1 is a sheet discriminating device that discriminates the type of the sheet 8 carried into the transport path 50 by the paper feeding unit 23 in order to set the image forming conditions according to the basis weight of the sheet 8 to be used. 7 is provided. The sheet discriminating device 7 includes a displacement detecting mechanism 40 for measuring the thickness and rigidity used for discriminating the type. The displacement detection mechanism 40 is arranged near the center of the transport path 50 between, for example, the second transport roller 62 and the third transport roller 63.

Hereinafter, the configuration and operation of the image forming apparatus 1 will be described with a focus on the function of determining the type of the sheet 8. The "type" of the sheet 8 is a name given for convenience to an index for distinguishing various contents set as a condition for image formation. The "type" can be replaced with any other suitable phrase (eg, "attribute").

FIG. 2 shows an example of the configuration of the displacement detection mechanism 40, FIG. 3 shows a configuration of the displacement sensor 45, and FIG. 4 shows an example of the configuration of the displacement amount measuring unit 700 and its counting operation.

As shown in FIG. 2A, the displacement detection mechanism 40 is mainly composed of a reference roller 41, a detection roller 42, and a displacement sensor 45. As shown in FIG. 2B, the reference roller 41 is composed of a pair of rollers 41a and 41b separated in the axial direction, and the detection roller 42 is a pair of rollers 42a facing the reference roller 41 (rollers 42a and 41b). , 42b.

The reference roller 41 and the detection roller 42 are arranged so as to sandwich the sheet 8 transported from the upstream side in the transport direction M1. The position of the rotation shaft 41S of the reference roller 41 is fixed, whereas the position of the rotation shaft 42S of the detection roller 42 is variable. That is, the rotating shaft 42S of the detection roller 42 is supported by the movable bearing 43.

The bearing 43 is composed of a pair of bearings 43a and 43b that support one end and the other end of the rotating shaft 42S, and is guided by a guide 44 fixed to the support frame 46 in the MA direction, which is the thickness direction of the seat 8. It is provided so that it can be moved in the MB direction. The guide 44 is composed of a pair of guides 44a and 44b.

The MA direction is the direction in which the detection roller 42 approaches the reference roller 41. The MB direction is the opposite direction to the MA direction, and is a direction in which the detection roller 42 moves away from the reference roller 41. The bearing 43 is always urged in the MA direction, so that the detection roller 42 comes into contact with the reference roller 41 (including a state close to it) in the absence of the sheet 8. The position of the rotating shaft 42S of the detection roller 42 in contact with the reference roller 41 is the reference position for displacement.

The rotating shaft 41S of the reference roller 41 is connected to the rotating shaft 62S of the second transport roller 62 via a pulley 47 and a belt 48, and the reference roller 41 rotates integrally with the second transport roller 62. The sheet 8 is conveyed downstream by the rotation of the reference roller 41.

When the sheet 8 is inserted between the reference roller 41 and the detection roller 42 in contact with each other, the detection roller 42 moves in the MB direction by the thickness of the sheet 8. After that, when the sheet 8 passes by, the detection roller 42 moves in the MA direction. Further, when the sheet 8 is bent as described later, the detection roller 42 moves in the MB direction more than the thickness of the sheet 8.

The displacement sensor 45 detects such movement of the detection roller 42, that is, displacement of the rotating shaft 42S. As shown in FIG. 2B, the displacement sensor 45 is arranged between the pair of rollers 42a and 42b.

As shown in FIG. 3A, the displacement sensor 45 includes an actuator 451 and an encoder 452.

The actuator 451 is a so-called cord wheel, and its end surface abuts on the peripheral surface of the rotating shaft 42S of the detection roller 42. The actuator 451 rotates according to the displacement of the rotation shaft 42S of the detection roller 42.

The encoder 452 is, for example, an optical 2-channel encoder, and outputs A-phase and B-phase square wave signals according to the rotation of the actuator 451 as shown in FIGS. 3 (B) and 3 (C). The details are as follows.

As shown in FIG. 3B, when the rotating shaft 42S is displaced in the MA direction, the A phase changes from the L level to the H level (rising) later than the B phase, and changes to the L level later than the B phase. Become (fall down). On the contrary, when the rotating shaft 42S is displaced in the MB direction, the B phase rises later than the A phase and falls later than the A phase. That is, the direction of displacement of the rotating shaft 42S can be known from the phase relationship between the A phase and the B phase.

The deviation (pulse edge interval) Δt between the pulse edge of the A phase and the pulse edge of the B phase corresponds to the unit displacement amount Dm of the rotating shaft 42S. That is, when the B phase rises or falls after the A phase rises or falls, the rotating shaft 42S is displaced by a unit displacement amount Dm during that time. Therefore, by counting the number of pulse edges, the displacement amount DM of the rotating shaft 42S can be measured.

As shown in FIG. 4A, the displacement amount measuring unit 700 for measuring the displacement amount DM includes a counter 701 and a displacement amount calculating unit 702.

The counter 701 updates the count value N according to the eight input patterns shown in FIG. 4B for each of the A-phase and B-phase pulse edges in the output signal S45 of the displacement sensor 45. As a result, as shown in FIG. 4C, the count value N changes according to the output signal S45.

Of the eight input patterns, for example, the input pattern (1) is a pattern in which the B phase rises when the A phase is at the H level. In this case, since the displacement in the MB direction in which the displacement amount DM increases occurs, the count value N is increased by one. Further, the input pattern (2) is a pattern in which the B phase rises when the A phase is at the L level. In this case, since the displacement in the MA direction in which the displacement amount DM decreases has occurred, the count value N is reduced by one.

A count value N is input from the counter 701 to the displacement amount calculation unit 702 each time the count value N is updated. The displacement amount calculation unit 702 calculates the product of the input count value N and the unit displacement amount Dm as the displacement amount DM.

For example, assuming that the displacement sensor 45 having a unit displacement Dm of 2 μm is used, the displacement DM when the count value N is “1” is 2 μm, and the displacement when the count value N is “49”. The amount DM is 98 μm.

FIG. 5 shows the functional configuration of the sheet discriminating device 7, and FIG. 6 schematically shows the displacement due to the sheet 8. Further, FIG. 7 shows an example of the transition of the displacement amount DM, FIG. 8 shows an example of the relationship between the bending amount ΔDM and the rigidity of the sheet 8, and FIG. 9 shows the discrimination table T1 used for discriminating the type Dk of the sheet 8. Examples of are shown respectively.

In FIG. 5, the sheet discriminating device 7 includes a thickness measuring unit 71, a first discriminating unit 72, a rigidity measuring unit 73, a second discriminating unit 74, and a storage unit 77.

The thickness measuring unit 71 measures the thickness Dt of the sheet 8. The thickness measuring unit 71 has the displacement sensor 45 and the displacement amount measuring unit 700 described above, and further includes a first roller 60A, a second roller 60B, a rotation driving unit 600, a normal transport unit 751, and a thickness. It has a calculation unit 710.

The first roller 60A is arranged in the transport path 50 to transport the sheet 8. As the first roller 60A, for example, a second transfer roller 62 can be used.

The second roller 60B is arranged on the downstream side of the first roller 60A in the transport path 50 to transport the sheet 8. As the second roller 60B, for example, a third transfer roller 63 can be used.

The rotation drive unit 600 rotationally drives the first roller 60A and the second roller 60B. The rotary drive unit 600 includes a motor, a clutch, and the like.

The normal transfer unit 751 is a part of the transfer control unit 75 that controls the transfer of the sheet 8 in the main control unit 20, and causes the first roller 60A and the second roller 60B to have the same speed (peripheral speed) V1. Performs normal transport control to rotate with.

In the normal transfer control, as shown in FIG. 6A, the sheet 8 passes through the displacement detection mechanism 40 in a stretched state between the first roller 60A and the second roller 60B. The displacement amount DM1 of the detection roller 42 at this time is measured as the thickness Dt of the sheet 8 by the displacement sensor 45, the displacement amount measuring unit 700, and the thickness calculating unit 710.

In the thickness calculation unit 710, the displacement amount DM obtained by the displacement amount measuring unit 700 before the sheet 8 being conveyed arrives at the nip portion between the reference roller 41 and the detection roller 42, that is, the nip portion does not have the sheet 8. The displacement amount DM0 at that time is stored. After that, as shown in FIG. 6A, the difference between the displacement amount DM1 when the sheet 8 is passing through the nip portion and the stored displacement amount DM0 is obtained, and the obtained difference is the thickness Dt of the sheet 8. Output as a measured value.

For example, if the count value N at a certain time point t1 is "1" and the count value N at a subsequent time point t2 is "50", the difference ΔN of the count value N is "49". Assuming that the displacement sensor 45 having a unit displacement amount Dm of, for example, 2 μm is used, in this case, the thickness of the sheet 8 from the time point t1 to the time point t2 is 2 μm × 49 = 98 μm.

The first discriminating unit 72 discriminates the type Dk of the sheet 8 based on the measured thickness Dt. At the time of discrimination, the first discrimination unit 72 refers to the discrimination table T1 stored in the storage unit 77.

The rigidity measuring unit 73 measures the rigidity Ds of the sheet 8 when the thickness Dt measured by the thickness measuring unit 71 is a value at which the type Dk cannot be determined by itself.

The rigidity measuring unit 73 includes a displacement sensor 45, a displacement amount measuring unit 700, a first roller 60A, a second roller 60B, a rotation driving unit 600, a loop forming unit 752, and a rigidity calculating unit 730. Among these components, except for the loop forming unit 752 and the rigidity calculation unit 730, they are the same components as the thickness measuring unit 71.

The loop forming unit 752 is a part of the transfer control unit 75, and is a transfer control in which the transfer speed V1 by the first roller 60A is made relatively larger than the transfer speed V2 by the second roller 60B. Perform formation control.

In the loop formation control, as shown in FIG. 6B, when the seat 8 has a certain degree of rigidity or more, the seat 8 bends between the first roller 60A and the second roller 60B. That is, a so-called loop (curved portion) 8L is formed. The displacement in the thickness direction due to bending is greatest near the center between the first roller 60A and the second roller 60B. The displacement detection mechanism 40 is arranged near such a center.

Since the position of the reference roller 41 is fixed, the detection roller 42 is displaced to the thickness Dt or more of the sheet 8 due to the bending of the sheet 8.

The rigidity calculation unit 730 obtains a deflection amount ΔDM (see FIG. 8), which is the difference between the displacement amount DM2 of the detection roller 42 when the loop formation control is being performed and the displacement amount DM1 before bending, and obtains the obtained deflection. Based on the quantity ΔDM, a measured value (rigidity) representing the rigidity Ds is calculated using a predetermined calculation formula. The predetermined calculation formula is a formula representing the relationship shown in FIG. Hereinafter, the measured value calculated by the rigidity calculation unit 730 may be referred to as rigidity Ds.

The second discriminating unit 74 discriminates the type Dk of the sheet 8 based on the thickness Dt measured by the thickness measuring unit 71 and the rigidity Ds measured by the rigidity measuring unit 73. At the time of discrimination, the second discriminant unit 74 refers to the discriminant table T1 stored by the storage unit 77. An example of the discrimination table T1 will be described later.

Of the sheet discriminating devices 7, the first discriminating unit 72, the second discriminating unit 74, the displacement amount measuring unit 700, the thickness calculating unit 710, and the rigidity calculating unit 730 are based on the hardware configuration of the main control unit 20. And it is realized by executing the program described above by the CPU.

The type Dk of the sheet 8 determined by the first determination unit 72 or the second determination unit 74 is notified to the print job control unit 201 of the main control unit 20.

Upon receiving the notification of the type Dk, the print job control unit 201 instructs the engine control unit 30A that controls the printer engine 30B to set the operation according to the notified type Dk. The engine control unit 30A sets, for example, the fixing temperature and transfer voltage of the fixing device 37 according to a command. Further, the print job control unit 201 commands the transfer control unit 75 to set the paper feed rate in the paper feed unit 24 according to the type Dk.

In FIG. 7A, normal transport control is performed at time point t1. However, before the sheet 8 arrives at the displacement detection mechanism 40, the displacement amount DM is almost zero.

When the sheet 8 arrives at the displacement detection mechanism 40, the displacement amount DM increases according to the thickness Dt of the sheet 8. The displacement amount DM at the time point t2 when the sheet 8 passes through the displacement detection mechanism 40 by the normal transfer control is set to the thickness Dt of the sheet 8.

As described above, when the thickness Dt is a value at which the type Dk cannot be determined by itself, the normal transfer control is switched to the loop formation control. In the example of FIG. 7A, at a time point between the time point t2 and the subsequent time point t3, for example, loop formation control for reducing the speed of transfer by the second roller 60B is started. In the loop formation control, the speed of transportation by the first roller 60A is maintained at the speed V1 at the time of normal transportation.

Since the transfer on the downstream side is slower than that on the upstream side due to the start of the loop formation control, the sheet 8 begins to bend. The displacement amount DM increases as the bending progresses.

At the time point t3, the speed of transportation by the second roller 60B is reduced to a speed V2 smaller than the speed V1 at the time of normal transportation, and the speed V2 is maintained until the subsequent time point t5. During the period TL from the time point t3 to the time point t5, the displacement amount DM becomes substantially constant.

The amount of deflection ΔDM (ΔDMa, ΔDMb), which is the difference between the amount of displacement DM at the time point t4 and the amount of displacement DM at the time point t2, which is the difference between the displacement amount DM at the time point t4 and the displacement amount DM at the time point t2, is a value representing the rigidity Ds of the sheet 8. As shown in FIG. 8, the larger the amount of deflection ΔDM, the larger the rigidity Ds (rigidity). The relationship between the amount of deflection ΔDM and the rigidity shown in FIG. 8 is an experiment in which, for example, the amount of deflection ΔDM when various sheets 8 having different rigidity (stiffness) are conveyed by the loop formation control described above is measured. Obtained by

At the time point t5, the loop formation control is switched to the normal transport control, and the speed of transport by the second roller 60B is returned to the speed V1 at the time of normal transport. At the time point t6, when the sheet 8 finishes passing through the displacement detection mechanism 40, the displacement amount DM returns to the value in the state without the sheet 8.

As shown in FIG. 7B, when the type Dk can be determined only based on the displacement amount DM at the time point t2 (that is, the thickness Dt of the sheet 8), the loop formation control is not performed and the sheet 8 is conveyed at a speed V1 from the beginning to the end and passes through the displacement detection mechanism 40. Since the transport time is shorter than when loop formation control is performed, printing productivity is improved. Further, since the number of times a larger load is applied to the second roller 60B than during normal transportation is reduced, deterioration of the second roller 60B can be reduced.

In FIG. 9, the discrimination table T1 indicates which of the seven types (thin paper, plain paper, thick paper 1, thick paper 2, thick paper 3, thick paper 4, thick paper 5) classified by the basis weight of the type Dk of the sheet 8 is used. It is created so that it can be identified. The discrimination table T1 is composed of a table T11 referred to by the first discrimination unit 72, a table T12 referred to by the second discrimination unit 74, and a table T10 added as reference information.

The image formation conditions are set as described above according to the type Dk discriminated using the discriminating table T1. Among the conditions for image formation, it is preferable to set a value of the fixing temperature according to the basis weight. However, it is difficult to equip the image forming apparatus 1 with a basis weight measuring device. Therefore, as an alternative to the basis weight, it is conceivable to discriminate the type Dk by the thickness Dt. Even if the thickness is the same, if the density is different, the basis weight is different. Therefore, the basis weight is not uniquely determined by the thickness Dt, but the thickness Dt can be a guideline for the basis weight.

In the table T10, a “basis weight (b)” and a “thickness range (c)”, which is a guideline for the thickness Dt, are associated with each of the seven types (a).

In the table T11, the measured value of the thickness Dt when it should be discriminated from each of the seven types is shown as the “thickness measured value (d)”, and the thickness measured value (d) and the discriminant result (e). ) Is associated with. The range of the thickness measurement value (d) is a part of the thickness range (c) of the table T10, and is a range in which the type Dk may be discriminated without measuring the rigidity Ds. ..

For example, for thin paper, the range of the measured thickness value (d) is 66 μm or less, which is equal to or less than the median value of 52 to 80 μm, which is the guideline thickness range (c) for thin paper. This is because if the measured thickness Dt is equal to or less than the median value in the thickness range (c), the density is slightly different from the general value, or the thickness of the same type of sheet 8 is uneven. Even so, it is based on the idea that the basis weight is a value (52 to 59 g / m2) corresponding to thin paper.

Based on the same idea, for plain paper, 98 to 99 μm near the median of 81 to 116 μm in the thickness range (c) is set as the thickness measurement value (d). The thickness measurement value (d) is determined for the thick papers 1 to 5 based on the same idea.

When the measured thickness Dt is a value of any of the seven ranges defined as the thickness measurement value (d) in the table T11, the first determination unit 72 is associated with the range. The determination result (e) is output as the type Dk of the sheet 8. The output of the discrimination result (e) corresponds to the discrimination of the type Dk. For example, when the measured thickness Dt is 134 to 138 μm, the type Dk of the sheet 8 is determined to be “thick paper 1”.

In the table T12, the measured value of the thickness Dt when it should be discriminated from each of the seven types is shown as the "thickness measured value (f)", and the "rigidity measured value" is shown in the thickness measured value (f). (G) and the discrimination result (h) are associated with each other. The range of the thickness measurement value (f) is the thickness measurement value (d) of the table T11 in the thickness range (c) of the table T10. That is, it is a range in which the rigidity Ds must be measured and the type Dk must be determined based on the measured value of the thickness Dt and the measured value of the rigidity Ds.

For example, for thin paper, the thickness measurement value (f) is in the range of more than 66 μm and 80 μm or less, and the rigidity measurement value (g) is in the range of 10 or less. For plain paper, the thickness measurement value (f) is in the range of 81 to 97 μm and 100 to 116 μm, and the rigidity measurement value (g) is in the range of 11 to 16.

FIG. 10 shows another example of the discrimination table T2 used for discriminating the type Dk of the sheet 8.

When the measured thickness Dt is a value at which the type Dk cannot be discriminated by itself, that is, when it is necessary to measure the rigidity Ds of the sheet 8, the discriminating table T2 has the loop forming unit 752 and the third. It is referred to by the discriminating unit 74 of 2.

The discrimination table T2 shows the corresponding loop feed amount (j) and the discrimination result (j) for each thickness range (i) in which the assumed thickness Dt of the sheet 8 that can be used in the image forming apparatus 1 is divided into, for example, four. k) and. The discrimination result (k) is determined according to the measurement of the rigidity Ds.

The loop feed amount (j) is the difference between the transfer amount by the first roller 60A and the transfer amount by the second roller 60B during the period TL in which the loop formation control is performed. The loop feed amount (j) is an example of processing parameters related to the measurement of the rigidity Ds.

Generally, the thicker the sheet 8, the greater the rigidity and the easier it is to bend. That is, even if the loop feed amount (j) is small, the difference in rigidity tends to appear as a difference in the amount of deflection ΔDM. In order to discriminate the type Dk, it is sufficient that the minimum deflection that can discriminate the rigidity Ds occurs. Therefore, in the discrimination table T2, when the sheet 8 is thick, the loop feed amount (j) is smaller than when it is thin. By reducing the loop feed amount (j), the time for controlling the loop formation is shortened, and the printing productivity is increased. Further, since the pressure contact force applied to the second roller 60B becomes smaller, the life of the second roller 60B is extended.

In the mode of switching the loop feed amount (j), the loop forming unit 752 reads the loop feed amount (j) corresponding to the measured thickness Dt from the determination table T2 so that the read loop feed amount (j) is generated. Loop formation control is performed.

The second discriminating unit 74 has rigidity based on the deflection amount ΔDM measured by the displacement amount measuring unit 700, using the equation expressing the relationship shown in FIG. 8, as in the case where the loop feed amount (j) is not switched. (Rigidity) Ds is calculated. Then, the determination result (k) associated with the calculated rigidity Ds is output.

FIG. 11 shows the flow of processing in the sheet discriminating device 7, and FIG. 12 shows the flow of processing for rigidity measurement.

In FIG. 11, the thickness Dt of the sheet 8 is measured (# 101), and it is determined whether or not the type Dk can be discriminated only from the measurement result (# 102).

If the discrimination is possible (YES in # 102), the type Dk is discriminated based on the measurement result of the thickness Dt without measuring the rigidity Ds (# 104).

On the other hand, if the discrimination is not possible (NO in # 102), the rigidity Ds is measured (# 103), and the type Dk is discriminated based on the measurement result of the thickness Dt and the measurement result of the rigidity Ds (# 104). ..

As shown in FIG. 12, in the rigidity measurement, the value of the loop feed amount (j) is determined according to the measured thickness Dt (# 201), and the loop formation control is performed to specify the rigidity Ds (# 202). , # 203).

FIG. 13 shows an example of the processing flow in the image forming apparatus 1, and FIG. 14 shows another example of the processing flow in the image forming apparatus 1.

In FIG. 13, when the print job is executed, it is checked whether or not the paper feed unit 24 has been in the open state (cassette open) in which the sheet 8 can be replenished after the previous print job is executed (# 301). ).

If the cassette has been opened (YES in # 301), only the thickness Dt or the thickness Dt and the rigidity Ds are measured to determine the type Dk (# 303). Then, the discriminated type Dk is stored in the storage unit 202 (# 304). At the same time, the image formation conditions are set so as to match the type Dk.

On the other hand, if the cassette has never been opened (NO in # 301), the type Dk stored in the storage unit 202 is read out (# 302). Then, the image formation conditions are set so as to match the read type Dk. That is, it is assumed that the sheet 8 used in this print job is of the same type as the previously used sheet, and the determination of the type Dk is omitted.

In FIG. 14, in a multi-printing job using a plurality of sheets 8, for the first sheet 8 (YES in # 401), only the thickness Dt or the thickness Dt and the rigidity Ds are measured and the type Dk. Is determined (# 402).

For the second and subsequent sheets 8 (NO in # 401), first, the thickness Dt is measured (# 403). Whether or not the measured thickness Dt corresponds to the type Dk of the first sheet 8 is checked with reference to the determination table T1 (# 404).

If it corresponds to the type Dk of the first sheet 8 (YES in # 404), the determination of the type Dk of the second and subsequent sheets is omitted, and the process proceeds to step # 407.

On the other hand, when it does not correspond to the type Dk of the first sheet 8 (NO in # 404), the rigidity Ds is measured (# 405), and the discrimination table T1 is measured based on the measurement results of the thickness Dt and the rigidity Ds. The type Dk is determined by referring to (# 406).

In step # 407, it is checked whether or not the second and subsequent sheets 8 are the final sheets 8. If it is not the final sheet 8 (NO at # 407), the process returns to step # 403.

By the way, the position where the displacement detection mechanism 40 is arranged is not limited to the upstream side of the secondary transfer position. The sheet 8 can be arranged at an arbitrary position on the route to be conveyed. For example, when the sheet 8 after fixing is conveyed to the finisher (post-processing device), the displacement detection mechanism 40 may be arranged on the finisher. When transporting from the image forming apparatus 1 to the finisher via the relay device, it may be arranged in the relay device.

Further, the sheet for measuring the thickness Dt or the thickness Dt and the rigidity Ds by using the displacement detection mechanism 40 is not limited to the sheet 8 used for printing, and may be a copy original. An example will be described below.

FIG. 15 shows the configuration of the automatic document feeder 21.

The automatic document feeding device 21 includes a document tray 11, a transport mechanism 12, a transport path 13, an image sensor 15, a paper output tray 16, a displacement detection mechanism 40b, and the like. As the displacement detection mechanism 40b, a mechanism having the same configuration as the displacement detection mechanism 40 described above can be used. However, different configurations may be used.

The transport mechanism 12 transports a plurality of sheets 9 (original documents) set on the document tray 11 one by one from the document tray 11 toward the reading position P1 of the scanner 22 and passes them through the reading position P1. After that, it is conveyed to the output tray 16. The transport mechanism 12 includes a pickup roller 12a, a paper feed roller pair 12b, a plurality of feed roller pairs 12c, 12d, 12e, 12f, 12g, a transport guide forming the transport path 13, and the like.

The pickup roller 12a takes out the top sheet 9 from the document tray 11. The paper feed roller pair 12b feeds the taken-out sheet 9 into the transport path 13. The feed roller pairs 12c to 12g are arranged at intervals along the transport path 13, transport the sheet 9 taken out from the document tray 11, pass through the reading position P1, and then eject the sheet 9 to the paper output tray 16. To do.

In the case of double-sided reading, the image of the second surface (back surface) of the sheet 9 that has passed the reading position P1 is read by the close contact type image sensor 15.

Since the paper output tray 16 is arranged below the document tray 11, the transport path 13 is curved in a substantially semicircular shape with a predetermined curvature. The sheet 9 is conveyed from top to bottom along the transfer path 13 and passes through the reading position P1 in a state in which the front and back sides are reversed from the state when the sheet 9 is set in the document tray 11. After that, the paper is discharged to the paper output tray 16 without being inverted.

The displacement detection mechanism 40b is provided near the center of a semicircularly curved portion extending from top to bottom in the transport path 13. The configuration of the displacement detection mechanism 40b is as shown in FIGS. 2 and 3.

The displacement detection mechanism 40b is arranged so that the reference roller 41 serves as a transport roller outside the curve of the transport path 13. As a result, the thickness Dt can be measured while the sheet 9 is conveyed in a stable posture.

When measuring the rigidity Ds, the closest feed roller pair 12c on the upstream side of the displacement detection mechanism 40b is set as the first roller 61A (see FIG. 6), and the closest feed roller pair 12d on the downstream side is the second roller. Loop formation control is performed as 61B.

According to the type Dk of the sheet 9 measured in this way, the image forming apparatus 1 sets the conveying speed of the sheet 9 in the automatic document feeder 21b to a preferable value.

According to the above embodiment, the measurement of the rigidity Ds that bends the sheets 8 and 9 during transportation is performed only when there is a risk of erroneous determination based only on the result of the measurement of the thickness Dt that does not need to be bent. The types of sheets 8 and 9 can be discriminated while suppressing the burden on the transport mechanism.

According to the embodiment described above, since the displacement detection mechanisms 40 and 40b are provided at the intermediate position between the second transfer roller 62 and the third transfer roller 63 for bending the sheet 8 where the amount of deflection ΔDM is large, the rigidity is increased. Ds can be measured efficiently and with high accuracy.

In the embodiment described above, the content of the discrimination table T1 is an example and can be changed as appropriate. For example, the thickness Dt of sheets 8 and 9 is affected by the increase or decrease of moisture in the atmosphere. According to the experiment, when the humidity (relative humidity RH) increases from 10% to 80%, the sheets 8 and 9 expand and the thickness Dt increases by about 2%. Therefore, the humidity may be measured and the measurement result of the humidity may be fed back when referring to the discrimination table T1. That is, the value of the discrimination table T1 can be read as a value that takes into account the change in the thickness Dt according to the humidity.

In addition, the temperature and humidity conditions specified by temperature and humidity are divided into a plurality of condition ranges, and a plurality of discrimination tables T1 whose contents are defined for each condition range are prepared, and these discriminations are made according to the temperature and humidity. The table T1 may be used properly.

In the embodiment described above, the thickness Dt and the rigidity Ds may be measured using separate displacement detection mechanisms 40 and 40b corresponding to each. The displacement detection mechanisms 40 and 40b can switch the pressure contact force of the detection roller 42, that is, the urging force that brings the detection roller 42 closer to the reference roller 41. For example, when the sheet 8 is thin, the pressure contact force is reduced as compared with when the sheet 8 is thick, and a degree of deflection required for specifying the rigidity Ds is generated. The pressure contact force is one of the examples of the processing parameters related to the measurement of the rigidity Ds.

In the embodiment described above, the sheet discriminating device 7 discriminates the sheet type Ds when the image forming apparatus 1 returns from the state in which it cannot detect whether or not it is in the open state to the state in which it can be detected. Then, the determination result stored in the storage unit 202 can be updated. The state in which it is not possible to detect whether or not it is in the open state is a state in which the power is off, a state in which the power saving mode is set, or the like. The state that can be detected is a state in which the power is turned off, a state in which the power saving mode is restored to the normal mode, and the like.

In the loop formation control, the second roller 60B (downstream side) may be stopped and conveyed by the first roller 60A (upstream side) to bend the sheets 8 and 9.

In addition, the configuration, processing content, order, timing, etc. of the entire image forming device 1 and the sheet discriminating device 7 can be appropriately changed according to the gist of the present invention.

1 Image forming device 7 Sheet discriminating device 8, 9 Sheet 13, 50 Transport path 20 Main control unit (control unit)
24 Paper feed section (sheet supply section)
30B Printer engine 45 Displacement sensor 60A First roller 60B Second roller 71 Thickness measuring unit 72 First discriminating unit 73 Rigidity measuring unit 74 Second discriminating unit 77 Storage unit 752 Loop forming unit (convey control unit)
DM Displacement amount Dk Type Ds Rigidity Dt Thickness M2 Thickness direction T1 Discrimination table

Claims (12)

It is a sheet discriminating device that discriminates the type of the sheet carried into the transport path for transporting the sheet.
A thickness measuring unit that measures the thickness of the sheet,
A first discriminating unit that discriminates the type of the sheet based on the measured thickness, and
When the measured thickness is a value at which the type cannot be discriminated by itself, a rigidity measuring unit for measuring the rigidity of the sheet and a rigidity measuring unit.
It has a second discriminating unit that discriminates the type based on the measured thickness and the rigidity.
A sheet discriminating device characterized by this. The rigidity measuring unit includes a first roller that conveys the sheet and
A second roller arranged on the downstream side of the first roller and conveying the sheet, and a second roller.
A displacement sensor provided between the first roller and the second roller to detect the amount of displacement of the surface of the sheet in the thickness direction, and
It has a transport control unit that controls loop formation, which is a transport control that increases the speed of transport by the first roller to be higher than the speed of transport by the second roller.
The rigidity is measured based on the displacement amount detected by the displacement sensor during the period when the loop formation control is performed.
The sheet discriminating device according to claim 1. The rigidity measuring unit measures the rigidity by switching the parameters of the process related to the measurement of the rigidity according to the measured thickness.
The sheet discriminating device according to claim 2. As the parameter, the loop feed amount, which is the difference between the transport amounts of the first roller and the second roller by the loop formation control, is switched.
The sheet discriminating device according to claim 3. The thickness measuring unit measures the displacement amount detected by the displacement sensor as the thickness before the loop formation control is performed in a state where the displacement sensor and the sheet are in contact with each other.
The sheet discriminating device according to any one of claims 2 to 4. It has a storage unit that stores a discrimination table indicating the type of the sheet corresponding to the combination of the thickness and the rigidity of the sheet.
The second determination unit extracts the type corresponding to the measured thickness and rigidity from the determination table and outputs the determination result.
The sheet discriminating device according to any one of claims 1 to 5. The discrimination table shows the type corresponding to the combination according to the environmental conditions including the temperature or humidity.
The second determination unit extracts the type corresponding to the measured thickness and rigidity from the determination table according to the environmental conditions.
The sheet discriminating device according to claim 6. An image forming device that forms an image on a sheet.
A sheet supply unit that can store multiple sheets,
A printer engine that forms an image on the sheet supplied from the sheet supply unit,
A sheet discriminating device that discriminates the type of the sheet carried into the transport path for transporting the sheet from the sheet supply unit to the printer engine, and
It has a control unit that controls the formation of the image according to the discriminated type.
The sheet discriminating device is
A thickness measuring unit that measures the thickness of the sheet,
A first discriminating unit that discriminates the type of the sheet based on the measured thickness, and
When the measured thickness is a value at which the type cannot be discriminated by itself, a rigidity measuring unit for measuring the rigidity of the sheet and a rigidity measuring unit.
It has a second discriminating unit that discriminates the type based on the measured thickness and the rigidity.
An image forming apparatus characterized in that. The sheet discriminating device discriminates the type of the sheet each time the sheet supply unit changes from an open state in which the sheet can be replenished to a loaded state in which the sheet can be supplied to the printer engine. Remember the result,
The control unit controls the formation of the image according to the type of the latest stored determination result.
The image forming apparatus according to claim 8. The sheet discriminating device discriminates and stores the type of the sheet when the image forming device returns from a state in which it cannot detect whether or not it is in the open state to a state in which it can be detected. Update the judgment result,
The image forming apparatus according to claim 9. In a printing job using a plurality of the sheets, the sheet discriminating device stores the measured thickness of the first sheet, and the measured thickness and the memorized thickness of the second and subsequent sheets. When the above is different, the rigidity is measured.
The image forming apparatus according to any one of claims 8 to 10. It is a sheet discrimination method for discriminating the type of the sheet carried into the transport path for transporting the sheet.
Measure the thickness of the sheet and
When the measured thickness is a value at which the type cannot be discriminated by itself, the rigidity of the sheet is measured.
The type is discriminated based on the measured thickness and rigidity.
A sheet discrimination method characterized by this.

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