JP2017030883A - Paper thickness detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect paper thickness regardless of a difference of paper type.SOLUTION: In a paper P conveyed between a light projecting part 3a and a light-receiving part 3b of a transmission sensor 3, even if a front end part A goes along a conveyance route R, a rear end part Z comes off from the conveyance route due to air resistance or the like. Deflection is different corresponding to paper thickness even if conveyance speed is constant, and a thin paper deflects the most. Even the same paper has different light-receiving voltages of the light-receiving part depending on a position between the light projecting part and the light-receiving part, and a variation rate of the light-receiving voltage corresponds to a paper thickness regardless of a paper type. Relationship between the variation rate of light-receiving voltages at two points of the front end part and the rear end part of a paper having passed through the transmission sensor 3 and the paper thickness is acquired by experiment, and stored in a memory as comparison data. When the paper is actually conveyed to obtain the variation rate in the same manner, and compared with the comparison data, a paper thickness can be detected regardless of a paper type without an error.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a sheet thickness detection apparatus that detects a sheet thickness using a transmission sensor, and more particularly to a sheet thickness detection apparatus that can accurately detect the sheet thickness regardless of the type of sheet. .

The following Patent Document 1 discloses an invention of a thickness measuring device using a contact type mechanism.
The thickness measuring device 400 includes a thickness detection sensor 1 having an operating unit 4, a thickness detection roller 2, a fixed roller 5, and a paper detection sensor 6. The thickness detection sensor 1 has a structure in which a lever-shaped operating portion 4 is connected to the shaft of the encoder sensor, and the sheet S is moved to the thickness detection roller 2 and the fixed roller when the operating portion 4 is in contact with the thickness detection roller 2. When the thickness detection roller 2 moves in the thickness direction of the sheet S, the operating unit 4 swings upward to rotate the encoder, and the displacement of the thickness detection roller 2 is measured. A paper detection sensor 6 is installed on the upstream side of the thickness detection roller 2.

  In this thickness measuring apparatus, an electromagnet is provided in either one of the thickness detection roller 2 or the operating unit 4, and the other is made of a magnetic material. The energization control unit energizes the electromagnet when measuring the thickness of the paper, and does not energize the electromagnet when not measuring the thickness. Since the operating unit 4 and the thickness detection roller 2 come into contact with each other when energized, the operating unit 4 is displaced following the displacement of the thickness detection roller 2 as the sheet S passes. Since 2 are separated from each other, even if the thickness detection roller 2 is displaced, the operating portion is not displaced. It is not necessary to provide a mechanism such as a solenoid for driving at least one of the thickness detection roller 2 and the thickness detection sensor 1, and space saving of the thickness measuring device can be achieved. In addition, since the operating unit 4 and the thickness detection roller 2 come into contact only at the time of thickness detection, deterioration of the sensor due to contact when thickness measurement is unnecessary is prevented.

  Patent Document 2 below discloses an invention of an image forming apparatus having a transmissive sheet thickness sensor. As the paper thickness sensor included in this image forming apparatus, a transmission sensor configured by a combination of a light emitting unit and a light receiving unit can be used, and a sheet thickness can be measured from a difference in the amount of transmitted light. It is said that.

JP 2014-101214 A JP 2003-95484 A

  According to the thickness measuring apparatus described in the above-mentioned Patent Document 1, a contact type constituted by a thickness detection roller 2 that comes into contact with the conveyed paper and an operation unit 4 that swings in contact with the thickness detection roller 2. Since the encoder is rotated using a mechanism and the thickness of the paper is detected by the amount of rotation, there is a problem of high cost due to the complicated configuration, and the thickness detection roller wears out due to contact with the paper and is stable. There is also a problem that it is difficult to detect the thickness of the used paper.

  According to the transmission type paper thickness sensor described in Patent Document 2, since it is a non-contact type, there is no problem as described above in the thickness measuring device of Patent Document 1. However, according to the transmissive paper thickness sensor of Patent Document 2, depending on the type of paper, the magnitude relationship between the values of the received light voltage output from the transmissive sensor may not correspond to the magnitude relationship between the paper thicknesses. There was a problem that there was.

  FIG. 1 shows the result of an experiment by the inventor of the present application that uses a transmission sensor for different types of paper and measures the received light voltage under the same conditions. The transmission sensor includes a light projecting unit that irradiates light and a light receiving unit that outputs a light reception voltage corresponding to the amount of light received. In the invention of Patent Document 2, a sheet is provided between the light projecting unit and the light receiving unit. It is considered that the thickness of the sheet can be detected from the voltage value output from the light receiving unit when the light projecting unit emits light.

  In FIG. 1, four types of paper, thick paper A, standard paper A, thin paper A, and thin paper B, are listed. These types of paper are mainly classified by the type and composition of the fibers that make up the paper, but the names of cardboard, standard paper, and thin paper are consistent with their thickness (dimensions). . That is, the thickness decreases in the order of thick paper, standard paper, and thin paper.

  As shown in FIG. 1, the received light voltage is 0.25V for the thick paper A, 0.80V for the standard paper A, and 1.28V for the thin paper A. The thicker the paper, the smaller the received light voltage. It is considered that the larger the value is, the more difficult it is to transmit light. However, with different types of compositions and the like, for example, even with thin paper of the same thickness, the light reception voltage is different between thin paper A and thin paper B. The light receiving voltage of the thin paper B is 0.63 V, which is an intermediate value between the thick paper A and the standard paper A. As described above, depending on the type of paper, the magnitude relationship between the values of the received light voltage may not correspond to the magnitude relationship between the paper thicknesses. Therefore, the transmission sensor is used as in the invention of Patent Document 2 described above, There are cases where the thickness of the sheet cannot be detected accurately only by looking at the value of the received light voltage.

  The present invention has been made on the basis of the above-described conventional technique and problems that the present inventor has experimentally learned from the examination of the prior art, and detects the thickness of the paper using a transmission sensor. An object of the present invention is to make it possible to accurately detect the thickness of a sheet regardless of the type of sheet.

The sheet thickness detecting device according to claim 1 is provided.
Conveying means for conveying paper;
A transmission sensor that is disposed at a position sandwiching the paper conveyed by the conveying means, and includes a light projecting unit that irradiates light and a light receiving unit that outputs a light reception voltage corresponding to the amount of light received;
A control unit that determines the thickness of the sheet based on a variation rate of the first voltage value and the last voltage value of the two or more received light voltages output by the light receiving unit of the transmission sensor at different positions for one sheet; ,
It is characterized by comprising.

The paper thickness detection device according to claim 2 is the paper thickness detection device according to claim 1,
The control unit includes data indicating the relationship between the sheet thickness and the variation rate, and compares the acquired variation rate with the data to determine the sheet thickness.

  According to the sheet thickness detection apparatus of the first aspect, the sheet conveyed by the conveying unit passes between the light projecting unit and the light receiving unit of the transmission sensor, and is output 2 at different positions for one sheet. Of the above received light voltages, the control unit determines the thickness of the sheet based on the voltage value output first and the variation rate of the voltage value output last.

  The paper transported along the transport path set between the light projecting section and the light receiving section is separated from the transport path by the air resistance received by the paper, even if the leading edge is along the transport path. It deforms in a form that soars in the direction (this is called “deflection”). When the conveyance speed is constant, the deflection differs depending on the thickness of the paper, and the thin paper is most likely to bend. Hereinafter, the deflection becomes smaller in the order of the standard paper and the thick paper. This tendency is constant depending on the thickness regardless of the type of paper.

  In addition, even for the same paper, the value of the light reception voltage output by the light receiving unit varies depending on the position between the light projecting unit and the light receiving unit, and the mode of the change is independent of the type of the paper. Corresponds to the thickness of the paper.

  Therefore, in the paper transported between the light projecting unit and the light receiving unit, the transmission sensor detects the paper at two points: the leading end passing through a position close to the transport path and the trailing end where the position is displaced due to deflection. If the light receiving unit detects the light reception voltage at each position on the paper, the two light reception voltages should be different, and the degree of difference (variation rate) depends on the thickness of the paper that affects the deflection of the paper. Should correspond.

  The relationship between the thickness of the paper and the value of the light-receiving voltage of the light-receiving unit at two specific points of the paper that passes between the light projecting unit and the light-receiving unit is obtained in advance by experiment and compared with the memory of the device. If the paper is actually stored between the light projecting unit and the light receiving unit and the received light voltage is obtained as an actual measured value at the two specific points, the actual measured value is compared with the comparison data. The thickness of the paper can be detected without error regardless of the type of paper.

  According to the sheet thickness detection apparatus of the second aspect, the control unit includes data indicating the relationship between the sheet thickness and the two voltage value fluctuation rates acquired at different positions of the sheet. The sheet thickness can be determined by comparing the actually obtained variation rate with the data.

It is a table | surface figure which shows the result of having measured the light reception voltage on the same conditions, when different types of paper passes between the light projection part and the light-receiving part of the transmission sensor. It is a perspective view which shows schematic structure of the experimental apparatus which this inventor used. 3 is a graph showing the results of an experiment conducted by the inventor of the present application using the experimental apparatus shown in FIG. 2, wherein the thickness of the relationship between the position of the transmission sensor from the light receiving unit and the light receiving voltage of the light receiving unit is different. Plotted for each type of paper. 1 is an overall configuration diagram of an image forming apparatus according to an embodiment of the present invention. It is a schematic diagram for demonstrating the behavior of the rear-end part of the paper which passes a permeation | transmission sensor in embodiment. It is the graph which plotted the fluctuation | variation of the value of the light reception voltage which the light-receiving part of a permeation | transmission sensor outputs in embodiment for every three types of paper from which thickness differs. From the graph of FIG. 6, for each of the three types of paper having different thicknesses, the light reception voltage values at the leading edge (no sagging) and the trailing edge (with sagging) are read and displayed, and the fluctuation rate is calculated. FIG.

1. About experiment of this inventor (FIGS. 2 and 3)
The inventor of the present application has studied a method for detecting the thickness of a sheet with a transmission sensor, but as described in the section “Problems to be solved by the invention”, depending on the type of sheet, A problem has been discovered in which the magnitude relationship between the values of the received light voltage may not correspond to the magnitude relationship between the sheet thicknesses. Therefore, we have experimentally studied whether there is a method that can detect the thickness of the paper using the light reception voltage of the transmission sensor regardless of the type of paper.

  FIG. 2 is a perspective view showing a schematic configuration of an experimental apparatus used by the present inventors. The transmission sensor 3 is configured such that the light projecting unit 3a and the light receiving unit 3b are opposed to each other with a predetermined distance L (for example, 40 mm in this example). In the experiment, the paper P is placed between the light projecting unit 3a and the light receiving unit 3b, light is emitted from the light projecting unit 3a, and the light receiving unit 3b that has received the light through the paper P generates light reception voltage.

  Here, the inventor of the present application uses the position (mm) of the sheet P increasing toward the light projecting unit 3a with the position of the light receiving unit 3b as a reference (0 mm), and the received light voltage output from the light receiving unit 3b as the vertical axis A graph with axes is assumed. With respect to the paper P having three types of thickness, thin paper, standard paper, and thick paper, the position of the paper P was changed from 5 mm to 35 mm, and the value of the received light voltage was plotted in the graph. This is the graph shown in FIG.

  As shown in FIG. 3, originally, the value of the received light voltage is the largest for thin paper (broken line), next is standard paper (thin line), and the minimum is thick paper (thick line). When P is set to a position at a minute distance (around 10 mm) from the light receiving side, the light receiving voltage of each of the thin paper, the standard paper, and the thick paper is slightly increased, and the degree is smaller as the thickness of the paper is smaller (thinner is thinner). ) Turned out to be bigger. That is, the thinner the paper P, the more the light reception voltage changes when measured at a position away from the light receiving unit 3b and closer to the light projecting unit 3a. .

2. Image Forming Apparatus of Embodiment (FIGS. 4 to 7)
The inventor of the present application considered that the thickness of the paper P can be detected by using the received light voltage of the transmission sensor 3 regardless of the type of the paper P by using such a tendency. That is, when transporting the paper P, even if the leading end is transported along a predetermined path, the rear end is deflected due to air resistance or the like, and the amount of deflection is determined by the thickness of the paper P. It corresponds to the rigidity of. Since the deflection amount appears as a change in the positions of the light projecting unit 3a and the light receiving unit 3b of the transmission sensor 3, the thickness of the paper P can be determined by looking at the changes in the received light voltage at the leading edge and the trailing edge of the paper P. Should be understood.

Hereinafter, an image forming apparatus having the sheet P thickness detection apparatus of the embodiment will be described with reference to FIGS.
FIG. 4 is a schematic configuration diagram of the image forming apparatus 1 according to the embodiment. In the following description, the paper surface direction in FIG. Also, as shown in FIG. 4, when viewed from the user, the vertical and horizontal directions are the vertical and horizontal directions. Further, a path indicated by a broken line in FIG. 4 is a transport path R along which the paper P that is a print medium is transported, and a direction from left to right is a transport direction. In the following description, upstream and downstream mean upstream and downstream in the transport path R of the paper P.

  As shown in FIG. 4, the image forming apparatus 1 includes a paper feeding unit 2, a transmission sensor 3 as a paper sensor, a belt conveyance unit 4 as a conveyance unit, an inkjet head unit 5 as an image formation unit, and a control. Part 6 is provided. Note that a sheet thickness detection device that is a part of the image forming apparatus 1 includes a transmission sensor 3 and a control unit 6.

  The paper feeding unit 2 feeds the paper P. The sheet feeding unit 2 includes a sheet feeding table 11, a sheet feeding roller 12, a sheet feeding motor 13, a registration roller 14, a registration motor 15, and an encoder sensor 16. A sheet P used for printing is stacked on the sheet feeding table 11.

  The transmission sensor 3 detects the paper P to be conveyed at a predetermined position between the registration roller 14 and the belt conveyance unit 4. The transmission sensor 3 includes a light projecting unit 3a and a light receiving unit 3b, detects the paper P at a plurality of locations of the conveyed paper P, and the light receiving unit 3b outputs a light reception voltage corresponding to the plurality of locations of the paper P. Output. Further, the transmission sensor 3 may be used to detect double feeding of the conveyed paper P.

  The light projecting unit 3 a is disposed above the transport path R at a predetermined position between the registration roller 14 and the belt transport unit 4. The light projecting unit 3a emits light downward toward the transport path R. The light projecting unit 3a is composed of a light emitting diode, a laser diode, or the like.

  The light receiving unit 3b receives light from the light projecting unit 3a and outputs a light reception voltage corresponding to the amount of light received. The light receiving unit 3b is disposed to face the light projecting unit 3a with the conveyance path R interposed therebetween. The light receiving unit 3b is made of, for example, a photodiode.

  The belt conveyance unit 4 conveys the paper P that has been conveyed from the registration rollers 14. The belt conveyance unit 4 is disposed on the downstream side of the registration roller 14. The belt conveyance unit 4 includes a conveyance belt 21, a driving roller 22, driven rollers 23, 24, and 25, and a belt motor 26.

  The conveyor belt 21 is an annular belt that is stretched around the driving roller 22 and the driven rollers 23 to 25. A number of belt holes, which are through holes for sucking and holding the paper P, are formed in the transport belt 21. The conveyance belt 21 sucks and holds the paper P by the suction force generated in the belt hole by driving a fan (not shown). The conveyor belt 21 rotates in the clockwise direction in FIG. 4 by driving the driving roller 22 to convey the sheet P held by suction to the right.

  The inkjet head unit 5 includes a line-type inkjet head in which a plurality of nozzles are arranged in a direction (front-rear direction) substantially orthogonal to the conveyance direction of the paper P. The inkjet head unit 5 is disposed above the belt conveyance unit 4. The inkjet head unit 5 prints an image by ejecting ink from the inkjet head onto the paper P conveyed by the belt conveyance unit 4.

  The control unit 6 controls the operation of each unit of the image forming apparatus 1. The control unit 6 includes a controller board on which a CPU, a memory, and the like are arranged.

FIG. 5 is a schematic diagram for explaining the behavior of the trailing end Z of the paper P passing through the transmission sensor 3 in the image forming apparatus 1 of the embodiment.
When the paper P is transported in the image forming apparatus 1, paper P having various thicknesses such as thin paper, standard paper, and thick paper is used as a print target. However, the paper P is transported due to a difference in thickness. The paper P is deformed. Even if the transport speed in the transport direction F of the paper P is constant, if the thickness of the paper P is different, even if the leading edge A is along the transport path R, the trailing edge Z is affected by the air resistance received by the paper P. Bends in a direction away from the transport path R. When the conveyance speed is constant, the deflection differs depending on the thickness of the paper P, and the thin paper is most likely to bend. Hereinafter, the deflection becomes smaller in the order of the standard paper and the thick paper. This tendency is constant depending on the thickness regardless of the type of paper P. Note that FIG. 5 shows the double feed state for convenience in order to show the behavior of the leading edge and the trailing edge of the paper at the same time, but it is a matter of course that the leading edge and the trailing edge usually do not overlap.

  FIG. 6 illustrates a situation where the thickness of the light receiving voltage output from the light receiving unit 3b of the transmission sensor 3 varies with time when the paper P passes through the transmission sensor 3 in the embodiment. 6 is a graph plotted for each of three types of paper P. The conveyance speed is constant. In the case where the received light voltage data as shown in this graph is obtained, a case will be described in which the second measurement timing and the second measurement timing from the last are taken as a reference after the measurement is started. These two measurement timings are indicated by two hollow bars parallel to the vertical axis in FIG. The second measurement timing after the start of measurement is considered to be the timing at which the leading end A of the paper P passes through the transmission sensor 3 along the specified transport path R (see FIG. 1) with no deflection. The second measurement timing from the last is the moment when the trailing edge Z of the paper P passes, and the trailing edge Z bends according to the thickness (or rigidity) of the paper P, as shown in FIG. It is thought that it is in a state of soaring upward and close to the light projecting portion 3a.

  First, in the graph of FIG. 6, the thin paper (Δ mark) has the highest light reception voltage, and the light reception voltage at the leading end A of the paper P is 1.265 V (no sagging (A)). The light reception voltage at the end Z is 1.481 V (with sagging (B)). FIG. 7 is a table showing these values and the fluctuation rates calculated from these values. Here, the fluctuation rate is a value defined by 1- (A / B). In the case of thin paper, the fluctuation rate is 14.6%.

  In the graph of FIG. 6, the standard paper (x mark) has an intermediate light reception voltage, and the light reception voltage at the leading end A of the paper P is 0.797 V (no sagging (A)). The received light voltage at the rear end Z is 0.900 V (with slack (B)). FIG. 7 is a table showing these values and the fluctuation rates calculated from these values. In the case of standard paper, the rate of change (1- (A / B)) is 11.5%.

  In the graph of FIG. 6, the thick paper (♦ mark) has the smallest light reception voltage, and the light reception voltage at the leading end A of the paper P is 0.258 V (no sagging (A)). The light reception voltage at Z is 0.261 V (with sagging (B)). FIG. 7 is a table showing these values and the fluctuation rates calculated from these values. In the case of cardboard, the rate of change (1- (A / B)) is 1.2%.

As described above, in the image forming apparatus 1 according to the embodiment, with respect to the thin paper, the standard paper, and the thick paper using the transmission sensor 3 (the light projecting unit 3a and the light receiving unit 3b), the rear end Z of the paper P is from the front end A of the paper P. FIG. 6 shows the result of actually measuring the change in the received light voltage until it passes. 6 is a table in which values at the leading edge A of the paper P and the trailing edge Z of the paper P are cut out and shown together with the variation rate. As described above, the fluctuation rates of the thin paper, the standard paper, and the thick paper are 14.6%, 11.5%, and 1.2%, respectively. Even if the thickness of the paper P is determined based on these values, it is erroneous. The paper thickness criteria are met. In other words, using the above numerical example, an example of a specific criterion for determining the paper thickness can be determined as follows.
Thick paper is 7% or less, standard paper is over 7% and less than 13%, and thin paper is 13% or more.

  After such a reference value is obtained, when the paper P passes through the transmission sensor 3, it is 2 at the same measurement timing (that is, at the front end portion A and the rear end portion Z of the paper P at the same measurement position). If the light reception voltage values at the places are obtained, the fluctuation rate is calculated from these, and the fluctuation rate is compared with the reference value, whereby the paper P is a thin paper, a standard paper, or a thick paper. It can be reliably determined. Then, according to the determined type of the paper P, the control unit 6 controls the belt conveyance unit 4, the inkjet head unit 5 and the like, and executes a series of image forming operations suitable for the thickness of the paper P. The control unit 6 performs creation and storage of the reference value, calculation of the variation rate from the measurement value, and determination of the thickness of the paper P by comparing the reference value and the variation rate.

  If the type of the paper P is a specific paper P that is always used, the thickness of the paper P can be detected almost accurately only by measuring the normal light reception voltage of the transmission sensor 3. Therefore, the function of measuring the thickness of the paper P described above may be a function that is exhibited in a special mode in the present apparatus. For example, in the case of using a special type of paper P that is not normally used in the image forming apparatus 1 of the present embodiment, if the paper thickness measurement mode is selected as the special mode, the thickness of the paper P to be conveyed is set. Accordingly, it is possible to automatically perform control such as conveyance and image formation.

  In the example described above, the received light voltage is measured at a plurality of points for each sheet P having different thicknesses, and the variation rate is calculated by adopting the second value from the beginning and the second value from the last. However, the order of the two points to be adopted is not limited as long as the difference between the front end portion A and the rear end portion Z is likely to occur, and may be appropriately changed according to the actual situation. For example, the variation rate may be calculated by adopting the first value and the last value at which the measurement is started. Further, the variation rate may be calculated from the maximum voltage value and the minimum voltage value of the two or more received light voltages output by the light receiving unit 3b of the transmission sensor 3 for one sheet P.

  As described above, according to the sheet thickness detection device included in the image forming apparatus 1 of the present embodiment, the variation rate of the value of the received light voltage measured at the leading end A of the sheet P and the trailing end Z of the sheet P is as follows. Regardless of the type of paper P, it is almost constant for thin paper, standard paper, and thick paper. Therefore, when the paper P other than the specific paper P is used, the thickness of the paper P can be determined by applying the actually measured fluctuation rate of the paper P to the paper thickness judgment range divided by the fluctuation rate. Regardless of the paper type, the thickness of the paper P can be accurately detected.

  In the embodiment, the paper thickness detection device is provided in the image forming apparatus, and the paper thickness detected by the paper thickness detection device is applied to the control for image formation. However, this is merely an example, and the paper thickness of the present invention is used. There is no particular limitation on the purpose of detecting the sheet thickness by the detection device.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 3 ... Transmission sensor 3a ... Light projection part 3b ... Light-receiving part 4 ... Belt conveyance part 6 as a conveyance means 6 ... Control part P ... Paper R ... Conveyance path A ... Paper front end Z ... Paper rear end Part

Claims (2)

Conveying means for conveying paper;
A transmission sensor that is disposed at a position sandwiching the paper conveyed by the conveying means, and includes a light projecting unit that irradiates light and a light receiving unit that outputs a light reception voltage corresponding to the amount of light received;
A control unit that determines the thickness of the sheet based on a variation rate of the first voltage value and the last voltage value of the two or more received light voltages output by the light receiving unit of the transmission sensor at different positions for one sheet; ,
A sheet thickness detecting device comprising:   The control unit includes data indicating a relationship between a sheet thickness and the variation rate, and compares the acquired variation rate with the data to determine the sheet thickness. The paper thickness detection apparatus as described.

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