JP7106985B2 - Measuring device, conveying device and image forming device - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to measurement technology, and more particularly to a measuring device, a transporting device, and an image forming device for measuring the size of a medium to be transported.

Copiers, printers, facsimiles, and multi-function machines that combine these using the electrophotographic process are configured to print on standard size paper as well as on non-standard size paper. Are known. A sensor that detects the presence or absence of paper in the main scanning direction of the paper within the paper transport area as a method of detecting the width of the paper in the main scanning direction (perpendicular to the paper transport direction) when printing on non-standard paper. is known. In this method, the main scanning width is detected by the number of sensors detecting the presence of paper.

However, in the conventional method of installing a plurality of sensors for detecting the presence or absence of paper in the main scanning direction of the paper in the paper transport area, a larger number of sensors are required to accurately detect the main scanning width of the paper. .

Japanese Patent Application Laid-Open No. 08-073073 (Patent Document 1) is known as a technique for measuring the size of paper. The prior art disclosed in Japanese Patent Application Laid-Open No. 2002-200001 is composed of an electrode pair of a certain length which is arranged obliquely to the paper conveying direction in the paper intake section and whose state changes depending on whether the paper is present or not. A paper width detection device is disclosed that includes means for measuring capacitance and means for detecting passage of the top edge of the paper at a specific position in the paper transport path. Measure the relative time between multiple measurement points and the point at which the upper edge of the paper passes through a specific point, and set the capacitance at each measurement point and the measured time. The paper width is calculated and obtained according to the conversion formula.

However, in the prior art disclosed in Patent Document 1, in order to measure the relative time, a means that is arranged at a specific position in the paper transport path and detects the passage of the upper edge of the paper is required. Therefore, it is not sufficient in that it is necessary to use a plurality of sensors when determining the size of a medium to be transported such as paper.

The present disclosure has been made in view of the above points, and an object of the present disclosure is to provide a measuring device capable of determining the size of a medium to be transported with a smaller number of sensors.

In order to solve the above problems, the present disclosure provides a measuring device for measuring the size of a medium to be transported, which has the following characteristics. The measuring device forms a passage through which the medium to be conveyed passes within the conveying path, and both ends of the medium to be conveyed in a direction perpendicular to the conveying direction of the medium to be conveyed enter and leave the passage with a time lag. At least one electrode is provided at an angle to the transport direction. The measuring device also includes measuring means for measuring the capacitance associated with the at least one electrode during transport of the transported medium. The measuring device further determines a first time from when the medium to be transported starts entering or exiting the path to when it is completed at both ends based on the predetermined angle and the change in capacitance over time. and a first calculating means for calculating a first size of the transported medium by evaluating.

According to the above configuration, the size of the transported medium can be determined simply by measuring the capacitance associated with at least one electrode, so fewer sensors are required.

1 is a diagram showing a configuration example of an image forming apparatus according to an embodiment; FIG. FIG. 2 is a diagram showing a configuration example of a capacitive sensor according to the embodiment; FIG. 7 is a diagram for explaining the positional relationship between the sheet and the electrode pair at each time point during transport; 4 is a graph schematically showing changes over time in capacitance output values when the positional relationship between a sheet of paper and an electrode pair during conveyance changes as shown in FIG. 3 ; 4 is a flowchart showing a process of calculating a main scanning width of a sheet, which is executed by the capacitance sensor according to the embodiment; FIG. 5 is a diagram explaining how to calculate a main scanning width of a sheet in one or more embodiments; 10 is a flowchart showing a process of calculating a main scanning width of a sheet, which is executed by a capacitance sensor according to another embodiment; 5 is a flow chart showing processing for calculating a sub-scanning width of a sheet, which is executed by the capacitance sensor according to the embodiment; FIG. 5 is a diagram explaining how to calculate a sub-scanning width of a sheet in one or more embodiments; FIG. 10 is a diagram for explaining another procedure for calculating the slope S of the change over time of the capacitance value;

The present embodiment will be described below, but the embodiment is not limited to the embodiment described below.

FIG. 1 is a diagram showing a configuration example of an image forming apparatus. The image forming apparatus shown in FIG. 1 is a multifunction machine having the functions of a copier, printer, facsimile, and scanner, but the image forming apparatus may be a copier, printer, facsimile, scanner, or the like.

An image forming apparatus is composed of a plurality of devices and units. The image forming apparatus includes an automatic document feeder (ADF) 10, an image reader 11, a printer unit 12 as image forming means, a paper feed unit 13, a manual feed unit 14, a paper discharge unit 15, an operation panel 16, and a measuring device. A capacitive sensor 17 is included. Since this is an example, a configuration without the ADF 10 and the manual feed unit 14 may be employed, or a configuration including other devices and units may be employed.

The ADF 10 includes a platen on which a document is placed, a transport mechanism for transporting the document on the platen, and a discharge tray for discharging the transported document, and moves the document onto the contact glass of the image reading device 11 . The image reading device 11 includes a light source, a plurality of mirrors, an imaging lens, and an imaging device. The light is made incident on the image pickup device via the image lens. A CCD (Charged Coupled Device) image sensor, a CMOS (Complementary metal oxide semiconductor) image sensor, or the like can be used as the imaging element, which converts incident light into an electrical signal and outputs it as image data.

The printer unit 12 includes a writing unit 20 , a photoreceptor drum 21 , a developing device 22 , a conveying belt 23 and a fixing device 24 . The writing unit 20 receives an instruction from a controller that controls the image forming apparatus, irradiates the photoreceptor drum 21 with light, and forms a latent image on the surface of the photoreceptor drum 21 . The developing device 22 is filled with toner and ejects the toner onto the photoreceptor drum 21 to visualize the latent image formed on the surface of the photoreceptor drum 21 . The transport belt 23 transports the paper and transfers the developed image to the paper. The fixing device 24 applies heat and pressure to the sheet on which the image has been transferred and is conveyed by the conveying belt 23 to fix the image on the sheet.

The paper feed unit 13 includes a paper feed tray 25 that stores paper, and a paper feed roller 26 that feeds the paper stored in the paper feed tray 25 one by one. supply. The manual feed unit 14 includes a manual feed tray on which paper is placed and a paper feed roller that feeds the paper on the manual feed tray one by one, and supplies paper in response to instructions from the controller. The paper discharge unit 15 includes a paper discharge tray for discharging the paper on which the image is fixed by the fixing device 24 .

The operation panel 16 accepts a user's operation and instructs the controller to read a document, print, and the like. The operation panel 16 also displays buttons for selecting functions for accepting user operations, buttons for starting execution of printing and the like, and displays the execution status, errors, and the like.

The capacitance sensor 17 as a measuring device is provided in a transportation path that transports paper fed from the paper feed unit 13 or the manual feed unit 14, and the transported paper constitutes the capacitance sensor 17. It is configured to pass between the electrode pairs 18 . Each of the electrode pairs 18 has conductivity, has surfaces facing each other, and includes two electrode plates provided in parallel, and the two electrode plates are not limited. , typically of the same shape, size and thickness. A metal plate can be used for each electrode plate, and as the metal plate, for example, a stainless steel plate, a copper plate, an aluminum plate, or the like can be used.

The electrode pair 18 can be attached at any location within the paper feed unit 13, the manual feed unit 14, or the transport mechanism 27 between the paper feed unit 13, the manual feed unit 14, and the photosensitive drum 21 as a transport device. may be located, or may be elsewhere. An image forming apparatus generally has a plurality of housing sheet metals arranged for grounding, and one electrode plate of the electrode pair 18 may be the ground GND. Therefore, one housing sheet metal 19 included in the image forming apparatus can be used as one of the electrode plates, as shown as the capacitance sensor 17' in FIG.

FIG. 2 is a diagram showing a configuration example of the capacitance sensor 17. As shown in FIG. The capacitance sensor 17 includes an electrode pair 18 , a current generator 31 , a capacitance measurement device 32 and a controller 33 . The electrode pair 18 is composed of two electrode plates spaced apart in parallel. Between the two electrode plates, there is a space (hereinafter referred to as a passage) through which the paper 34 as a medium to be transported enters and passes. ) 35 is formed.

A current generator 31 generates a current between the electrode plates of the electrode pair 18 . Electrode pair 18 functions as a capacitor, and when a voltage is applied, charge is stored between the plates. The amount of charge stored per unit voltage is called electrostatic capacity, and electrostatic capacity C [F] is the area s [m ² ] of the electrode plate and the distance d between the two electrode plates that make up the electrode pair 18. [m] and the dielectric constant ε [Fm ⁻¹ ], it can be calculated by the following formula (1).

The dielectric constant ε varies with the insulator present between the electrode plates. Therefore, the dielectric constant ε varies depending on whether the insulator between the electrode plates is air alone or includes paper when the paper passes. In addition, since water conducts electricity, the dielectric constant ε varies depending on the moisture content of the paper, unlike dry paper and paper containing moisture (moisture). Since the water content is not uniform even in one sheet of paper, the dielectric constant ε may change depending on the position on the paper when the water content is distributed.

The capacitance measuring device 32 measures the capacitance of the electrode pair 18 while the paper 34 as the medium to be transported is being transported. The capacitance measuring device 32 detects the amplitude ratio and phase difference of the voltage and current when, for example, an alternating current is passed through the electrode pair 18 to be measured, and calculates the impedance R from the detected amplitude ratio and phase difference. Then, an LCR meter that calculates the inductance L and the capacitance C from the impedance R and the frequency of the alternating current can be used. Although an LCR meter is used as an example of the capacitance measuring device 32 here, the present invention is not limited to this, and any device capable of measuring the capacitance C may be used.

The controller 33 controls the current generating device 31 and the capacitance measuring device 32 and performs processing for calculating the size of the paper 34 based on the capacitance C measured by the capacitance measuring device 32 . The controller 33 may also be configured to calculate a characteristic value such as the moisture content of the paper 34 .

The controller 33 stores control programs, conversion programs, and the like in order to control the current generator 31 and the capacitance measuring device 32, calculate the size of the paper 34, and calculate characteristic values such as moisture content. A ROM (Read Only Memory) or a flash memory can be provided as a storage device. The controller 33 can also include a CPU (Central Processing Unit) that reads and executes a program from its storage device, a RAM (Random Access Memory) that provides a work area for the CPU, and the like. Alternatively, the controller 33 may be configured as an application-specific integrated circuit (ASIC) that includes circuitry for executing the processes described above, or may store configuration data for executing the processes described above. It may be configured as a programmable device such as an FPGA (Field-Programmable Gate Array) comprising a plurality of circuit elements that operate based on storage and configuration data.

Note that the controller 33 may be dedicated to the capacitance sensor 17 as a component of the image forming apparatus, or may be a conveying device as a component of the image forming apparatus (e.g., the paper feed unit 13, manual feed unit 14, The controller for the sheet feeding unit 13, the manual feed unit 14, and the transport mechanism 27) may also be used, or the controller for controlling the entire image forming apparatus may be used.

In the capacitance sensor 17 according to this embodiment, the electrode pair 18 is provided at a predetermined angle with respect to the sub-scanning direction (conveyance direction) of the paper 34 as the medium to be conveyed. More specifically, the electrode pair 18 is provided so that the direction in which it extends forms an angle θ with the main scanning direction of the paper 34 (perpendicular to the conveying direction). As a result, when the paper 34 is conveyed along the conveying path, both ends 34L and 34R of the paper 34 in the main scanning direction enter the passage 35 between the electrodes of the electrode pair 18 with a time difference, and the passage 35 configured to exit from

Although FIG. 2 exemplifies the electrode pair 18 having an elongated rectangular shape extending at an angle θ with respect to the main scanning direction, the shape of the electrode pair 18 is limited to this. not to be From the viewpoint of accurately detecting the timing at which both ends 34L and 34R of the paper 34 enter the passage 35 between the electrode pairs 18, it is preferable to adopt a long rectangular shape extending at an angle θ as shown in FIG. can be done. However, it is formed in a staircase shape having a predetermined angle θ on average, and a plurality of intermediate points between both ends 34L and 34R of the paper 34 in the main scanning direction enter and leave the passage 35 with time lags. It does not exclude being configured.

Note that FIG. 2 illustrates a configuration in which the capacitance sensor 17 includes a pair of electrode plates forming a passage 35 through which the paper 34 passes on surfaces facing each other. However, the configuration of the electrodes of the capacitance sensor 17 is not limited to this. The configuration of the electrodes is not limited to one pair, and plural pairs of electrode plates may be provided. Further, as described above, the housing sheet metal provided in the image forming apparatus can be used as one of the electrode plates of the electrode pair 18, so the capacitive sensor 17 is provided with at least one electrode. It means that it should be.

The function of measuring the size of the paper 34 using the capacitance sensor 17 will be described in more detail below with reference to FIGS. 3 to 10. FIG.

FIG. 3 is a diagram for explaining the positional relationship between the paper 34 and the electrode pair 18 at each time during transportation. 3 shows a state (state A) before the paper 34 enters the path 35 between the electrode pairs 18, the paper 34 enters the path 35 between the electrode pairs 18, and a part of the main scanning width of the paper 34 is The paper 34 enters the path 35 between the electrode pairs 18, and the entire main scanning width of the paper 34 overlaps the electrode plates (state C). A state in which a part of the main scanning width of the paper 34 overlaps the electrode plate again (state D), and the paper 34 has left the passage 35 between the electrode pairs 18, and the paper 34 and the electrodes A state (state E) is shown in which the plates no longer overlap.

FIG. 3 also shows the positional relationship between the paper 34 and the electrode pair 18 at the timing of the boundary between the two states among the plurality of states A, B, C, D, and E described above. . More specifically, when the paper 34 starts entering the passage 35 between the electrode pairs 18 (state A→state B), the paper 34 completes entering the passage 35 between the electrode pairs 18 at both ends, that is, A state in which the main scanning width is completed (state B→state C), a state in which the paper 34 starts to leave the passage 35 between the electrode pairs 18 (state C→state D), and a state in which the paper 34 passes between the electrode pairs 18 35 is completed at both ends, that is, the state (state D→state E) is shown.

FIG. 4 is a graph schematically showing the change over time of the output value of the capacitance when the positional relationship between the paper 34 and the electrode pair 18 during transportation changes as shown in FIG. As described above, the dielectric constant ε varies depending on whether or not the paper 34 exists between the electrode plates of the electrode pair 18. And it changes depending on the degree of overlap.

3 and 4 together, the capacitance C has a substantially constant value before the paper 34 enters the path 35 between the electrode pairs 18 (state A). , when it starts entering the passage 35, it begins to rise (state B), completes entry into the passage 35 at both ends, and saturates when the entire main scanning width of the paper 34 overlaps the electrode plate, and reaches a substantially constant value. becomes (state C). Capacitance C further begins to fall when paper 34 begins to exit path 35 between electrode pairs 18 (state D), and exits path 35 at both ends to complete main scanning of paper 34. When the width no longer overlaps the electrode plate, it returns to a substantially constant value similar to that before the approach (state E).

FIG. 4 shows time (timing) T ₁ when the paper 34 starts to enter the passage 35 between the electrode pairs 18 (state A→state B), and the paper 34 enters the passage 35 during main scanning. Time T 2 when the width is completed (state B→state C), time T ₃ when the paper 34 starts to leave the passage ₃₅ (state C→state D), and the paper 34 reaches the electrode Also shown is time _T4 when the exit from the path 35 between the pair 18 is completed over the main scanning width (state D→state E).

The controller 33 shown in FIG. 2 utilizes the overlapping state of the paper 34 and the electrode pair 18 at each time during transportation and the relationship of the capacitance C at that time, based on the change in the capacitance C over time. to detect each of the timings T ₁ , T ₂ , T ₃ and T ₄ described above. The controller 33 calculates the size of the paper 34 (the size in the main scanning direction and the sub-scanning direction) based on the calculated timings T ₁ , T ₂ , T ₃ and T ₄ . At this time, the angle θ formed by the extending direction of the electrode pair 18 and the main scanning direction and the conveying speed V of the paper 34 are appropriately referred to.

5 to 10, the process of measuring the paper size based on the change in capacitance over time, which is executed by the capacitance sensor 17, will be described in more detail.

FIG. 5 is a flow chart showing the calculation process of the main scanning width of the paper executed by the capacitance sensor 17 according to this embodiment. The processing shown in FIG. 5 is executed by the controller 33 of the capacitance sensor 17, for example.

The process shown in FIG. 5 starts from step 100 in response to a request for calculating the main scanning width of the paper. The paper main scanning width calculation request is issued from the image forming engine, for example, when starting printing output on paper in response to an instruction to start printing from the user.

_At step S101, the controller 33 controls the current generator 31 and the capacitance measuring device 32 to measure the capacitance value C1 of the electrode pair 18 before the paper is conveyed. In step S<b>102 , the controller 33 starts transporting the paper 34 at the transport speed V. FIG.

After starting the transport, in step S103, the controller 33 controls the current generator 31 and the capacitance measuring device 32 to measure the capacitance value _C2 of the electrode pair 18 again. In step S104, the controller 33 determines whether or not the capacitance value _C2 measured after the start of transportation is greater than the value obtained by adding _a predetermined value α to the capacitance value C1 before the paper transportation. _In step S104, the loop to step S103 is repeated until the capacitance value _C2 exceeds the value after addition (C1+α) (while NO), and the capacitance value _C2 is repeatedly acquired. Here, the predetermined value α is _a positive value for detecting significant changes in the capacitance value C1.

If it is determined in step S104 that the capacitance value _C2 after the start of transportation has become larger _than the comparison value (C1+α) (YES), control proceeds to step S105. In this case, it is considered that state A has changed to state B, so in step S105 the controller 33 records the time when C ₂ >C ₁ +α as T ₁ in the memory, for example. Here, the time _T1 corresponds to the time _T1 shown in FIGS. Since the capacitance of the electrode pair 18 increases as the paper 34 enters the passage 35 between the electrode pairs 18, the capacitance begins to increase from a substantially constant value before conveyance (C ₂ >C ₁ +α) is detected as the _timing when the sheet 34 starts entering the path 35 .

In step S106, the controller 33 controls the current generator 31 and the capacitance measuring device ₃₂ , and measures the capacitance value C3 of the electrode pair 18. The controller 33 waits for a predetermined time t in step S107, measures the capacitance value _C4 of the electrode pair 18 again in step S108, and measures the capacitance values before and after the predetermined time t in step S109. Based on C3 _{and C4, the} slope S of the change over time of the capacitance value is calculated. The slope S of the change over time of the capacitance value can be calculated by the following formula (2).

The slope S of the change over time of the capacitance value takes a positive value while the capacitance is increasing, and becomes substantially zero when the capacitance saturates and stops changing. In step S110, it is determined whether or not the slope S of the change over time of the capacitance value has become smaller than a predetermined threshold value _STH . While it is determined to be large in step S110 (while NO), the capacitance is increasing, so the process returns to step S106 to measure the capacitance values C ₃ and C ₄ and calculate the slope S. Repeat and continue monitoring. Note that the threshold S _TH is a small positive value for detecting that the capacitance has stopped changing. In addition, in FIG. 5, in the case of NO in step S110, it is shown to return to step S106, but it is also possible to return to step S107 with the current capacitance value _C4 as the _next capacitance value C3. can.

If it is determined in step S110 that the slope S of the change over time of the capacitance value has become smaller than the predetermined threshold value _STH (YES), control proceeds to step S111. In this case, it is considered that the state has changed from state B to state C. Therefore, in step S111, the controller 33 records the _time when S< _STH as T2 in the memory, for example. Here, _time T2 corresponds to _time T2 shown in FIGS. When the electrode pairs 18 are arranged at an angle to the conveying direction, the overlapping area of the paper 34 and the electrode pairs 18 when the entire width of the paper in the main scanning direction has completed entering the path 35 of the electrode pairs 18 becomes constant (maximum), the capacitance no longer increases. From this fact, the time T2 when it is detected that the slope S of the change over time of the capacitance value becomes smaller _than the predetermined threshold value S _TH (S<S _TH ) is when the sheet 34 enters the passage 35. Detected as timing completed at both ends.

_In step S112, the controller 33 uses the recorded _times T1 and T2 to calculate the paper main scanning width (the size in the main scanning direction), and in step S113, the paper main scanning width calculation process ends. do.

FIG. 6 is a diagram explaining how to calculate the main scanning width of a sheet in one or more embodiments. FIG. 6A shows an example. As shown in FIG. 6A, the main scanning width X of the paper 34 is determined based on the angle θ formed by the extending direction of the electrode pair 18 and the main scanning direction, the transport speed V, and the change over time of the capacitance C. , can be calculated by the following formula (3).

In equation (3) above, ΔT ₁ is the first time from when paper 34 begins entering passage 35 to when it completes entering at both ends, evaluated based on the change in capacitance C over time. and is calculated by ΔT ₁ [sec]=T ₂ [sec]−[sec]T ₁ .

FIG. 7 is a flow chart showing a process of calculating the main scanning width of a sheet, which is executed by the capacitance sensor according to another embodiment. The processing shown in FIG. 7 is started from step 200 in response to a request for calculating the main scanning width of the paper.

In step S<b>201 , the controller 33 starts conveying the paper at the conveying speed V. FIG. After the sheet is started to be conveyed, the controller 33 controls the current generator 31 and the capacitance measuring device 32 to measure the capacitance value _C1 of the electrode pair 18 in step S202. The controller 33 waits for a predetermined time t in step S203, measures the capacitance value _C2 of the electrode pair 18 again in step S204, and determines the capacitance value C measured before and after the predetermined time t in step S205. ₁ and _C2 , the slope S1 of the change _over time of the capacitance value is calculated. _The slope S1 of the change over time of the capacitance value can be calculated by the following formula (4).

The slope S1 is _{approximately} zero while the capacitance is approximately constant, and becomes positive when it starts to rise. In step S206, it is determined whether or not the slope S1 of the change over time of the capacitance value has become larger than _a predetermined threshold value _STH1 . While it is determined to be small in step S206 (while NO), the capacitance remains at a substantially constant value, so the process returns to step S202 to measure the capacitance values C ₁ and C ₂ and _The calculation of the slope S1 is repeated to continue monitoring. Note that the threshold S _TH1 is a small positive value for detecting that the capacitance has started to rise significantly. If NO in step S206, the current capacitance value _C2 can be used as the _next capacitance value C1, and the process can be returned to step S203.

If it is determined in step S206 that the slope S1 of the change over time of the capacitance value has become larger _than the predetermined threshold value S _TH1 (YES), control proceeds to step S207. In this case, it is considered that state A has changed to state B, so in step S207, the controller 33 records the time when S>S _TH1 as T1 in, for example, _a memory.

Steps _S208 to _{S215 are} the same as the processing of steps S106 to S113 shown in FIG. Therefore, detailed description is omitted. In the process shown in FIG. ₅ , the time T1 is detected based on whether or not the capacitance value after transfer exceeds the value obtained by adding a predetermined value α to the value before transfer. detects the _time T1 based _on the slope S1 of the change _over time of the capacitance value in the same manner as the detection of the time T2.

FIG. 8 is a flowchart showing processing for calculating the sub-scanning width of the sheet, which is executed by the capacitance sensor 17 according to this embodiment. The processing shown in FIG. 5 is executed by the controller 33 of the capacitance sensor 17 .

The processing shown in FIG. 8 is started from step 300 in response to a request for calculating the paper sub-scanning width. In step S301, the paper main scanning width calculation process shown in FIG. 5 or 7 is executed, and _times T1 and T2 _are measured. At step S102 shown in FIG. 5 or step S201 shown in FIG. 7, the transport of the paper 34 at the transport speed V is started.

_In step S302, the controller 33 controls the current generator 31 and the capacitance measurement device 32 to measure the capacitance value C5 of the electrode pair 18. FIG. The controller 33 waits for a predetermined time t in step S303, measures the capacitance value C6 of the electrode pair ₁₈ again in step S304, and determines the capacitance value C measured before and after the predetermined time t in step S305. _{5 and C6 ,} the slope S3 of the change over time of the capacitance value is similarly calculated. The slope S3 of the change over time of the capacitance value can be calculated by the following formula ( ₅ ).

After the times T ₁ and T ₂ are measured by the processing shown in FIG. 5 or 7, the capacitance value is a large, substantially constant value as shown by state C in FIG. The slope S3 of change over time is _{approximately} zero while the capacitance is approximately constant, and becomes a negative value when it starts to fall. In step S306, it is determined whether or not the slope _{S3 of the change over time of the capacitance value has become smaller than a predetermined threshold value STH3 .} While it is determined to be large in step _{S306 (} while NO), it means that the capacitance remains at a substantially constant value. Repeat the calculation of _S3 and continue monitoring. The threshold value S _TH3 is a negative value with a small absolute value for detecting that the capacitance has started to decrease significantly. If NO in step S306, the current capacitance value _C6 can be used as the _next capacitance value C5, and the process can be returned to step S303.

If it is determined in step S306 that the slope _{S3 of the change over time of the capacitance value has become smaller (more negative) than the predetermined threshold value STH3 (} YES), control proceeds to step S307. In this case, it is considered that state C has shifted to state D, so in step S307 the controller 33 records the time when S ₃ <S _TH3 as T ₃ in the memory, for example. Here _, time _T3 corresponds to time T3 shown in FIGS. When the paper 34 begins to leave the path 35 between the electrode pairs 18, the capacitance of the electrode pairs 18 begins to decrease, and the slope _{S3 of the capacitance value change over time becomes more negative than the predetermined threshold value STH3 .} The time T3 at which it is detected ₍ S3<S _TH3 ) is detected as the timing at which the sheet 34 starts to leave the passage ₃₅ .

_In step S308, the controller 33 controls the current generator 31 and the capacitance measurement device 32 to measure the capacitance value C7 of the electrode pair 18. The controller 33 waits for a predetermined time t in step S309, measures the capacitance value C8 of the electrode pair ₁₈ again in step S310, and determines the capacitance value C measured before and after the predetermined time t in step S311. _{7 and C8} , the slope _S4 of the change over time of the capacitance value is similarly calculated. The slope S4 of the change over time of the capacitance value can be calculated by the following formula ( ₆ ).

The slope _S4 of change over time takes a negative value while the capacitance is decreasing, and becomes substantially zero when the capacitance stops changing. In step S312, it is determined whether or not the slope _{S4 of the change over time of the capacitance value has become larger than a predetermined threshold value STH4 .} While it is determined to be smaller (more negative) in step S312 (while NO), the process returns to step S308, repeats the measurement of the capacitance values C7 _{and C8} and the calculation of the slope _S4 , and monitors continue. It should be noted that the threshold value S _TH4 is a negative value with a small absolute value for detecting that the capacitance has returned to the state before transportation and that the capacitance has not changed significantly. If NO in step S312, the current capacitance value _C8 can be used as the _next capacitance value C7, and the process can be returned to step S309.

If it is determined in step S312 that the slope S4 of the change over time of the capacitance value has become larger than the predetermined threshold value S _{TH4 (} YES), control proceeds to step S313. In this case, it is considered that state D has shifted to state E, so in step S313 the controller 33 records the time when S ₄ >S _TH4 as T ₄ in the memory, for example. Here, time _T4 corresponds to time _T4 shown in FIGS. If the electrode pairs 18 are arranged at an angle to the conveying direction, the electrode pairs 18 will no longer overlap the paper 34 when the paper 34 completes withdrawal from the path 35 at both ends, and the electrode pairs 18 will no longer overlap the paper 34 . capacitance will no longer drop. Therefore, the time _{T4 when it is detected that the slope S4 of the change in the capacitance value over time becomes larger than the predetermined threshold value STH4 ( S4} > _STH4 ) is when the paper ₃₄ is removed from the path 35. It is detected as the timing when exit is completed at both ends.

_In step S314, the controller 33 calculates the paper sub _- scanning width using the saved times T2 and T4, and in step S315, the controller 33 ends the paper sub-scanning width calculation process.

FIG. 9 is a diagram explaining how to calculate the sub-scanning width of a sheet in one or more embodiments. FIG. 9A shows an example. As shown in FIG. 9A, the sub-scanning width Y of the paper 34 is determined based on the angle θ formed between the extending direction of the electrode pair 18 and the main scanning direction, the transport speed V, and the change over time of the capacitance C. , can be calculated by the following formula (7).

In equation (7) above, ΔT ₂ is evaluated based on the change in capacitance C over time, allowing paper 34 to complete entry into path 35 at both ends before completing exit from path 35 at both ends. is the second time to ΔT ₂ [sec]=T ₄ [sec]−T ₂ [sec].

In the processing shown in FIG. 8, it has been described that T3 is recorded in step S307 _, but in the embodiment described _, time T3 is not used and may be omitted. Time _T3 may be used in other embodiments described below.

Another example of the processing for calculating the paper main scanning width and the paper sub-scanning width will be described below with reference to FIGS. 6B and 9B.

FIG. 6B shows another example of the method of calculating the main scanning width of the paper. In the embodiment described with reference to FIG. 6A, the timing T1 at which it is detected that the capacitance starts to rise from _a substantially constant value is the timing at which the paper 34 starts entering the path 35, _The timing T2 at which it is detected that the capacitance has finished increasing and has reached a substantially constant value is the timing at which the paper 34 has completed entering the path 35 at both ends, and these _times T1 and T2 _are was used to calculate the main scanning paper width. On the other hand, as a method for calculating the width of the main scanning paper, the method shown in FIG. 6B is also conceivable in addition to the method shown in FIG. 6A.

In the method shown in FIG. 6(B), the slope on the falling side of the capacitance is obtained instead of the slope on the rising side of the capacitance shown in FIG. In the case of the method shown in FIG. 6(B), the timing T3 at which it is detected that the capacitance has started to decrease from a substantially constant value is taken as the timing at which the paper 34 starts to leave the path ₃₅ , and the capacitance Timing T4 at which it is detected that the paper ₃₄ has finished descending and has reached a substantially constant value is taken as timing at which both ends of the paper 34 have left the path ₃₅ , and the main scanning paper width is calculated using times T3 and _T4 . do. In this case, it can be calculated by ΔT ₁ ′=T ₄ −T ₃ .

FIG. 9B shows another example of the method of calculating the sub-scanning width of the paper. In the embodiment described with reference to FIG. 9A, the sheet 34 reaches the path 35 between the electrode _pairs 18 at the timing T2 when it is detected that the capacitance has finished increasing and reached a substantially constant value. The timing T4 is defined as the timing at which the advance is completed, and the timing _T4 at which it is detected that the capacitance has started to decrease from the steady value and has reached a substantially constant value after the , and the paper width in the sub-scanning direction is calculated using the times T ₂ and T ₄ . On the other hand, as a method for calculating the paper sub-scanning width, in addition to the method shown in FIG. 9A, the method shown in FIG. 9B is also assumed.

In the method shown in FIG. 9B, the timing T1 at which it is detected that the capacitance starts to rise from _a substantially constant value is the timing at which the paper 34 starts entering the path 35 between the electrode pairs 18, Timing T3 at which it is detected that the capacitance starts to fall after finishing the rise and reaching a substantially constant value is defined as the timing at which the paper 34 starts to leave the path ₃₅ between the electrode _pairs 18, and time T1. _, T3 to calculate the paper width in the sub-scanning direction. In this case, it can be calculated by ΔT ₂ ′=T ₃ −T ₁ .

5, steps S202 to S205 in FIG. 7, steps S208 to S211 in FIG. 7, steps S302 to S305 in FIG. 8, and step S308 in FIG. Another procedure for calculating the slopes S (S ₂ , ), S ₁ , S ₃ , S ₄ of the capacitance value change with time in step S311 will be described. In the above-described embodiment, the slopes S(S ₂ , ), S ₁ , S ₃ and S ₄ were calculated.

On the other hand, in the embodiment shown in FIG. 10, the capacitance Cn is acquired n times each time t elapses, and according to the method of calculating the regression coefficient of the regression line by the least squares method shown in the following equation (8), the By obtaining the slope S of the approximate curve shown in ₁₀ , the slope S ₍ S _, S1, S2, S3, _S4 ) of the change over time of the capacitance value can be obtained.

A method of using the size information (main scanning width and sub-scanning width) of the paper 34 obtained by the above-described processing will be described below. In the electrophotographic process, the moisture content of the paper on which the toner is adhered affects the image quality, so it is preferable to detect the moisture content of the paper using a capacitance sensor and reflect it in image formation control. Here, since there is a correlation between the size of the paper and the output value of the capacitance sensor, it is preferable to measure the size of the paper in advance when calculating the moisture content of the paper using the capacitance sensor. Therefore, in a specific embodiment, the size of the paper 34 (main scanning width and sub-scanning width) obtained above can be used when calculating the moisture content as a characteristic value of the paper.

The controller 33 can use the capacitance measured by the capacitance measuring device 32 and the detected size of the paper 34 to calculate the moisture content as a characteristic value representing the characteristics of the paper 34 . The moisture content can generally be calculated from the measured capacitance using a table, conversion formula, or the like. The moisture content can be calculated by measuring the capacitance of the paper 34 as it passes between the electrodes of the electrode pair 18 and based on the measured capacitance. Then, the water content distribution of the paper 34 can be obtained from the calculated water content of the paper 34 and the water content of each region of the paper 34 . In a specific embodiment, the calculated moisture content (the value or distribution of the entire paper) is corrected based on the calculated size of the paper 34, and the corrected paper moisture content is calculated as the characteristic value. This makes it possible to calculate the moisture content of the paper more accurately.

According to the embodiments described above, it is possible to provide a measuring device, a transporting device, and an image forming device that can determine the size of a medium to be transported with a smaller number of sensors.

In the above-described embodiment, the positional relationship between the electrode pairs 18 arranged obliquely with respect to the transport direction and the paper 34 can be obtained from the time-dependent change characteristics of the capacitance value when the paper 34, which is the medium to be transported, is transported. Then, the size of the transported medium can be measured based on the obtained positional relationship.

Conventional paper moisture content detection technology using a capacitance sensor requires a sensor/mechanism for detecting the paper size in addition to the capacitance sensor. In the above-described embodiment, the electrostatic capacitance sensor 17 used to determine the moisture content is used to measure the size of the paper 34, which is the medium to be transported. This eliminates the need for additional sensors/mechanisms, simplifies the structure, and reduces instrumentation costs. A sensor for detecting that the upper edge of the sheet passes through a specific point on the sheet conveying path, which is required in the prior art of Patent Document 1, is also not required.

In the above-described embodiments, paper is used as an example of a medium to be transported. It can be applied to media of various materials that have a significant difference in dielectric constant from air. Moreover, it is not limited to the configuration provided on the paper conveying path of the image forming apparatus, and a measuring device for any application that measures the size of a medium to be conveyed such as a fabric, a resin plate, a metal plate, etc. It can be used as part of the device.

Although the embodiments of the present invention have been described so far, the embodiments of the present invention are not limited to the above-described embodiments, and other embodiments, additions, modifications, deletions, etc. may occur to those skilled in the art. It is included in the scope of the present invention as long as it can be changed within the possible range and the action and effect of the present invention can be obtained in any aspect.

DESCRIPTION OF SYMBOLS 10...ADF, 11...Image reader, 12...Printer unit, 13...Paper feed unit, 14...Bypass unit, 15...Paper discharge unit, 16...Operation panel, 17...Capacitance sensor, 18...Electrode pair, 19 Housing sheet metal 20 Writing unit 21 Photoreceptor drum 22 Developing device 23 Conveying belt 24 Fixing device 25 Paper feed tray 26 Paper feed roller 27 Conveying mechanism 31 Current generator 32 Capacitance measuring device 33 Controller 34 Paper 34L, 34R End 35 Passage

JP-A-08-073073

Claims (10)

A measuring device for measuring the size of a medium to be transported,
A path through which the medium to be transported passes is formed in the transporting path, and both ends of the medium to be transported in a direction perpendicular to the transporting direction enter the path with a time lag and exit from the path. at least one electrode positioned at an angle to a direction;
measuring means for measuring the capacitance associated with the at least one electrode during transport of the transported medium;
a first time period from when the medium to be conveyed starts entering or exiting the path to when it is completed at both ends based on the predetermined angle and the change in the capacitance over time; and a first calculating means for calculating a first size of the transported medium by evaluating. The timing at which the medium to be transported starts entering or exiting the path is the timing at which it is detected that the capacitance has started to rise or fall from a substantially constant value, and the medium to be transported is 2. The method according to claim 1, wherein the timing for completing entry into or exit from said passage at said both ends is timing when it is detected that said capacitance has finished rising or falling and has reached a substantially constant value. measuring device. The first size is the size in the direction perpendicular to the conveying direction of the medium to be conveyed, and the size X in the perpendicular direction is defined by the perpendicular direction and the direction in which the at least one electrode extends. a predetermined angle θ, a first time ΔT ₁ from when the medium to be conveyed starts entering or exiting the path until it is completed at both ends, and a conveying speed V of the medium to be conveyed The measuring device according to claim 1 or 2, which is calculated by the following formula (3) using

The measuring device evaluates a second time from when the medium to be conveyed starts entering or completes entry into the path to when it starts exiting the path or completes exit from the path. 4. The apparatus according to any one of claims 1 to 3, further comprising second calculating means for calculating a second size of said medium to be transported, wherein said second size is a size of said medium to be transported in said transport direction. The measuring device according to the item. The size Y of the medium to be transported in the transport direction is calculated by the following formula (7) using the _second time ΔT2 to be evaluated and the transport speed V of the medium to be transported. 5. The measuring device according to 4.

The measuring apparatus according to any one of claims 1 to 5, further comprising third calculating means for calculating a characteristic value representing characteristics of the medium to be conveyed based on the calculated size of the medium to be conveyed. The third calculation means calculates a moisture content of the medium to be transported based on the capacitance measured by the measuring means, and calculates the calculated moisture content based on the size of the medium to be transported. 7. The measuring device according to claim 6, wherein the corrected moisture content of the transported medium is calculated as the characteristic value. The at least one electrode includes a pair of electrodes forming the passage through which the medium to be conveyed passes on surfaces facing each other, or provided by the measuring device or provided by a device including the measuring device. The measuring device according to any one of claims 1 to 7, further comprising one electrode facing the housing sheet metal and forming the passage through which the transported medium passes together with the housing sheet metal. A transport device for transporting a medium to be transported,
a transport mechanism that transports a medium to be transported along a transport path;
In the conveying path, a passage is formed through which the medium to be conveyed passes, and both ends of the medium to be conveyed in a direction perpendicular to the conveying direction enter the passage with a time lag and exit from the passage. at least one electrode provided at a predetermined angle with respect to the transport direction;
measuring means for measuring the capacitance associated with the at least one electrode during transport of the transported medium;
a first time period from when the medium to be conveyed starts entering or exiting the path to when it is completed at both ends based on the predetermined angle and the change in the capacitance over time; and a first calculating means for calculating a first size of the transported medium by evaluating. A passage is formed in the conveying path through which the medium to be conveyed passes, and both ends of the medium to be conveyed in the direction perpendicular to the conveying direction enter the passage with a time lag and exit the passage in the conveying direction. at least one electrode disposed at an angle with respect to
measuring means for measuring the capacitance associated with the at least one electrode during transport of the transported medium;
a first time period from when the medium to be conveyed starts entering or exiting the path to when it is completed at both ends based on the predetermined angle and the change in the capacitance over time; a first calculation means for calculating a first size of the transported medium by evaluating;
and image forming means for forming an image on the medium to be transported based on the first size of the medium to be transported calculated by the first calculating means.

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