JPH0873073A - Detection of paper sheet width for printer and device therefor - Google Patents

Abstract

PURPOSE: To detect the paper sheet width by the simple mechanism with high precision by calculating the relative time between the time point detected by the first detecting means and the time point detected by the second detecting means and calculating the paper sheet width according to a certain conversion equation from the measured time. CONSTITUTION: Each horizontal distance between a suction detecting points 601 and the end points 605 and 606 of the paper sheet angle detection lines 602 and 603 is Lw , and the vertical distance is Lo . Further, each vertical distance between the suction detection point 601 and the crossing point 604 between the angle detection lines 602 and 603 is Lv , paper sheet speed is Vp , the time up to the reach of a paper sheet to the angle detection line 602 after passing through the suction detection point 601 is t1, and the time up to the reach to the angle detection line 603 is t2. The conversion equation for calculating the width of the paper sheet is represented by the following equation: 2×L2 -(Vp ×(t1+t2)-2×Lo )×(Lw /-(Lv -Lo )). Accordingly, the width of the sucked paper sheet can be calculated by measuring the time up to the reach of the left upper corner of the paper sheet to the left paper sheet angle detection line 602 after the sucked paper sheet passes through the suction detection point 601 and the time up to the reach of the right upper corner to the right paper sheet angle detection line 603.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet width detecting method and apparatus for detecting the width of a cut sheet set in an electrophotographic printer for printing on a single sheet.

[0002]

2. Description of the Related Art Generally, in this type of electrophotographic printer, printing paper is printed on a paper of a standard size. Therefore, normally, a cassette corresponding to each paper size is prepared, and the paper corresponding to each cassette is stored, and the paper is sucked from the inside of the paper cassette to the printer by the paper suction mechanism when used. The method of sequentially sucking into the printing mechanism is adopted. In this method, if a means for identifying the type of the paper cassette is provided, the type of the paper cassette is identified, so that the currently set paper can be known and the width of the paper can be detected at the same time.

Further, in this kind of electrophotographic printer, not only standard size paper but also non-standard size paper can be printed, so that a general-purpose cassette capable of storing any size paper can be stored. There are also printers that are provided with a manual feed tray or the like on which the operator sets sheets one by one. When printing on non-standard size paper, this printer uses a sensor that detects the presence or absence of paper in the paper width direction (direction perpendicular to the paper conveyance direction) as a method of detecting the width of the paper. A plurality of sheets are installed and the width of the sheet is detected by the position of the sensor that detects the presence of the sheet.

Further, the sensor is, for example, (1)
A part of the lever that is moved to different positions depending on the presence or absence of paper is used as a shield plate, and this shield plate is moved in and out of the sensor optical path that connects the light emitting element and the light receiving element to transmit the sensor light. And a non-transmissive state, and a technique for detecting the presence or absence of paper by using a transmission type optical sensor (hereinafter referred to as "photointerrupter") that obtains this state from the output of the light receiving element and identifies the presence or absence of paper. (2) A technique of irradiating the detection light from the light emitting element by utilizing the fact that the sensor light is reflected when the paper is present, and detecting the presence or absence of the paper depending on whether the detection light is incident on the light receiving element or the like. There is.

19 and 20 schematically show a detection structure using the former sheet detection method (1).
In FIGS. 19 and 20, a portion 208 encircled by a one-dot chain line is a transport area surface occupied by the paper when the paper of the maximum width size is used in this printer. A plurality of (seven in this example) sensors 201, 202, 203, 204, 205, 20 corresponding to the transport region surface 208.
6,207 are installed, and each sensor 201-2
Reference numeral 07 is composed of a photo interrupter 200a and a lever 200b.

Then, the sheet 301 is placed on the transport area surface 208.
(See FIG. 20) is not arranged, the lever 20 is provided in the photo interrupter 200a as shown in FIG.
0b is arranged so that the light from the light emitting element (not shown) is prevented from entering the light receiving element (not shown) by the lever 200b and is in a non-transmissive state. On the contrary,
When the sheet 301 is placed on the transport area surface 208, the sheet 301 is pushed by the sheet 301 and the sensor of the portion corresponding to the sheet 301 (in the example of FIG.
The lever 200b of the three (4, 205) is rotated to a position deviated from the photo interrupter 200a to release the interruption, and the transmission state is established. On the other hand, the sensor of the portion not corresponding to the sheet 301 (in the example of FIG. 20, the sensor 201,
Four of 202, 206, and 207) are in a non-transmissive state. Therefore, with this paper detection structure, the presence or absence and the width of the paper can be detected by monitoring the signals from the sensors 201 to 207.

[0007]

However, in the paper detection method using the above-described conventional structure, it is not possible to detect which sensor the sensor in the width direction of the paper is between. Therefore, in order to detect the position of the edge of the paper in the width direction with higher accuracy, the sensors may be arranged in high density.
There is a problem that the structure becomes complicated when the density is increased.

The present invention has been made in view of the above problems, and an object thereof is a paper width of a printer that can detect the position of the edge of the paper in the width direction with higher accuracy and with a simple mechanism. It is to provide a detection method and device.

[0009]

The object of the present invention is, in the apparatus of the present invention, a paper width detecting device for an electrophotographic printer capable of printing on a paper having an arbitrary width. A member having a constant length, which is arranged obliquely to the paper conveyance direction and whose state changes depending on whether or not there is no sheet, and means for detecting the time when the state of the member is changed. , Or a means for measuring the electrostatic capacity formed by the electrode pair, a means for detecting passage of the upper end of the sheet placed at a specific position in the sheet conveying path, and a state of the member is changed. Means for measuring the relative time between the time point when the upper edge of the paper passes a specific point, or a plurality of times of measurement and the time when the upper edge of the paper passes a specific point, The measured time or the measured time Is accomplished by a structure provided with means for determining by calculation the paper width in accordance with a predetermined conversion formula and the capacitance of the measurement fulcrum by said measured time.

Further, the object of the method of the present invention is to detect when there is no paper in the paper width detection method for an electrophotographic printer capable of printing on paper having an arbitrary width. A member or electrode pair of a certain length whose state is changed by is arranged obliquely to the sheet feeding section in the sheet conveying direction, and when the state of the member is changed is detected, or the electrode pair is configured. When the state of the member is changed and the upper edge of the sheet passes a specific point, a plurality of measurement points and the upper edge of the sheet are measured at a specific point. This can be achieved by measuring the relative time with respect to the time when the paper passes, and calculating the paper width according to a certain conversion formula based on the measured time or the time with the capacitance at each measurement time.

[0011]

According to this, the detection at the time when the state of the member having a constant length and arranged obliquely to the sheet conveying direction in the sheet suction section is changed, or the capacitance of the electrode pair is measured. , The width of the paper can be simplified by measuring the relative time between the time when the state of the member is changed and the time when the upper edge of the paper passes a specific point and calculating the measurement result according to a certain conversion formula. You can ask.

[0012]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 2 is a main part configuration diagram of the electrophotographic printer shown as the first embodiment of the present invention, and schematically shows a portion of a mechanism for sucking a sheet from a manual feed tray. In FIG. 2, reference numeral 401 is a manual feed tray on which an operator places paper (not shown), and 402 is a paper presence / absence detection sensor for detecting that the paper is placed on the manual feed tray 401, and the paper is arranged. It is provided in the paper transport area. This paper presence / absence detection sensor 402 is shown in FIG.
Similarly to the sensors 201 to 207 shown in FIG. 20, the photo interrupter 402a and the lever 402b are provided, and when the paper is not placed on the lever 402b, the lever 402b is used as the photo interrupter 402a.
The sensor light is blocked so as to be in a non-transmissive state, and when a sheet is placed, the lever 402b is disengaged from the photo interrupter 402a to be in a transmissive state.

Reference numeral 403 denotes a hopping roller for carrying the paper on the manual feed tray 401 into the printing mechanism section. This hopping roller 403 receives a command from a host device to print on the paper sucked from the manual feed tray 401 by a control circuit (not shown), and when the paper is detected by the signal from the paper presence detection sensor 402, It has a structure in which it is rotationally driven by a driving force transmission mechanism such as a motor and a gear (not shown).

Reference numeral 404 is a paper suction sensor, which is similar to the paper presence / absence detection sensor 402 in the photo interrupter 404.
a and lever-404b, lever 404
When there is a sheet on the sheet b, the lever 404b blocks the sensor light of the photo interrupter 404a to put it in a non-transmissive state, and when the sheet is placed, the lever 402b is disengaged from the photo interrupter 402a to be in a transmissive state. . In the figure, the dotted line 405 indicates the sheet suction /
The conveyance route is shown.

In the suction mechanism section, the sheet is conveyed by the hopping roller 403 and the sheet suction sensor 4
When the arrival at 04 is detected, this signal is used as the position reference for the subsequent paper. That is, the distance conveyed by the hopping roller 403 from the time when the paper reaches the paper suction sensor 404 is recognized as the distance between the leading end position of the paper and the position of the paper suction sensor 404.

FIG. 1 is a schematic diagram for explaining the principle of detecting the width of the sheet sucked by the sheet suction mechanism shown in FIG.
In the following description of the embodiments of the present invention, the direction in which a sheet is conveyed is referred to as the “vertical direction” and the direction orthogonal to the direction in which the sheet is conveyed is referred to as the “horizontal direction” unless otherwise specified. In FIG. 1, reference numeral 501 denotes a point at which the sheet suction sensor 404 of FIG.
"Paper suction detection point"), and when the leading edge of the paper reaches this point 501, the lever 404b of the paper suction sensor 404 is rotationally moved to the outside of the photo interrupter 404a, and the sensor light is in a transmissive state. .

Reference numerals 502 and 503 denote left and right sheet angle detection lines, which are used to detect when the upper corner of the sheet sucked by the sheet suction mechanism reaches any point on the sheet angle detection line. Is. That is, when the sheet of width L1 is sucked up to the position indicated by reference numeral 505, the upper left corner of the sheet is at the point 50.
When reaching 6, the left paper angle detection line 502 detects the upper left corner of the paper, and when the upper right corner of the paper reaches the point 508 at the time when the sheet is inhaled to the position indicated by reference numeral 507, the right paper angle detection line is reached. 503 detects the upper right corner of this sheet.
Further, when the upper left corner of the paper reaches the point 511 at the time when the paper of width L2 is sucked up to the position indicated by reference numeral 510, the left paper angle detection line 502 detects the upper left corner of this paper and is indicated by reference numeral 512. When the sheet is inhaled to the position, the upper right corner of the sheet reaches the point 513, and the right side sheet angle detection line 503 detects the upper right corner of the sheet. Therefore, if the leading edge position of the sheet at the time when the upper left and right corners of the sheet reach the left and right sheet angle detection lines 502 and 503, the horizontal distance between points 506 and 508 can be calculated, and the result is inhaled. It is the width L1 of the paper. Further, regarding the points 511 and 513, the value of the paper width L2 can be obtained in the same manner.

It should be noted that the means for detecting that the paper has reached the paper suction detection point 501 and the corner of the paper is the paper angle detection line 5.
The means for detecting the arrival at any point on 02 and 503, and the means for measuring the time between the respective detection time points will be sequentially described in detail in the following description.

First, the left and right upper corners of the sheet are the sheet angle detection lines 50.
A method of calculating the horizontal positions of the points that have reached 2 and 503 (points 506 and 508 or points 511 and 513 in FIG. 1) will be described with reference to FIG. FIG.
Shows an example of the relative positions of the sheet suction detection point 501 and the left and right sheet angle detection lines 502 and 503 in FIG.
Reference numeral 01 is a paper suction detection point, like the position 501 shown in FIG. The intersection 604 of the extension lines of the left and right paper angle detection lines 602 and 603 corresponding to the paper angle detection lines 502 and 503 of FIG. 1 is located at the same horizontal position as the paper suction detection point 601, and both the left and right paper angle detection lines are detected. End point 6 of 602 and 603
Reference numerals 05 and 606 are on the edge lines (607 and 608) of the paper transportable area.

Here, in the present embodiment, the sheet suction detection point 60
Since 1 is on the center line of the paper transportable area, the horizontal distance between the paper suction detection point 601 and the end points 605 and 606 of the left and right paper angle detection lines 602 and 603 is Lw, and the vertical distance is
Lo. Also, the vertical distance between the sheet suction detection point 601 and the intersection point 604 of the left and right sheet angle detection lines 602 and 603 is L
v, Vp is the speed of the sucked / conveyed paper, t1 is the time from when the sucked paper passes the paper suction detection point 601 until the upper left corner of the paper reaches the left paper angle detection line 602, and the upper right corner When the time required for the sheet to reach the right sheet angle detection line 603 is t2, the conveyance distance from the passage of this sheet through the sheet suction detection point 601 until the upper left corner reaches the left sheet angle detection line 602 is (Vp × t1). Therefore, the horizontal distance between the left edge of the sheet and the sheet suction detection point 601 is given by the following equation (1).
It is represented by.

[0021]

[Formula 1] Lw− (Vp × t1−Lo) × (Lw / (Lv−Lo)) (1)

Similarly, the horizontal distance between the right edge of the sheet and the sheet suction detection point 601 is expressed by the following equation (2).

[0023]

[Formula 2] Lw− (Vp × t2−Lo) × (Lw / (Lv−Lo)) (2)

Therefore, the width of the sheet is expressed by the following equation (3).

[0025]

[Equation 3] 2 × Lw− (Vp × (t1 + t2) −2 × Lo) × (Lw / (Lv−Lo)) (3)

As a result, the time t1 from when the sucked sheet passes through the sheet suction detection point 601 until the upper left corner of the sheet reaches the left sheet angle detection line 602 and the upper right corner detects the right sheet angle. If the time t2 until reaching the line 603 can be measured, the width of the inhaled sheet can be calculated.

4 to 11 show a first embodiment of the method for detecting the width of the paper by measuring the times t1 and t2. 4 to 6, the upper left corner or the upper right corner of the paper in FIG. 3 is the paper angle detection line 602 or 6
FIG. 4 is a diagram showing an example of a lever in a sensor that detects when the position reaches 03, FIG. 4 is its top view, FIG. 5 is its front view, and FIG. 6 is its side view. 4 to 6,
Reference numerals 103 and 108 are left and right levers, and the levers 103 and 108 have the same structure.
In both the levers 103 and 108, the shaft 701 serves as a fulcrum of the operation of the levers 103 and 108 as a whole, and the ridge 702 corresponds to the left paper angle detection line 602 or the right paper angle detection line 603. Reference bottom 70
3 is more prominent. Further, a shield plate 704 for detecting the movement of the levers 103 and 108 by the photo interrupter 105 (see FIGS. 7 and 8) is provided at the ends of the levers 103 and 108 opposite to the fulcrum. Also, the shaft 7 of the levers 103 and 108 here
The operation with 01 as the fulcrum is rotated in the vertical direction with the shaft 701 as the fulcrum, and the operation amplitude of the ridge 702 here results in the amplified operation amplitude of the shielding plate 704.
Further, in this motion, the motion of the same movement distance results in the motion of the same shield plate 704 regardless of which point of the edge 702 is the action point.

FIG. 7 is a schematic view showing a mounting example of the levers 103 and 108, and FIG. 8 is an enlarged perspective view of a portion A of FIG.
In this structure, when the lever 103 is indicated by a dotted line in FIGS. 7 and 8, the lever 103 is in a lowered position because there is no paper, and the shield plate 704 is used for the photo interrupter 1
05 is placed outside of 05 to shield the sensor light. When the paper is placed, the lever 103 is pushed up, and the shield plate 704 is placed inside the photo interrupter 105 to shield the sensor light. There is no state. In the figure, reference numeral 101 is a lever of the sheet suction sensor, and 10
2 indicates that when the lever 101 operates, the paper is
It is a photo interrupter for identifying whether or not it is at the position.

Therefore, the ridge 702 is arranged like the sheet angle detection line 602 or 603 in FIG. 3 and the lever is arranged so that the ridge 702 is pushed up by the passage of the sheet, and the position of the shielding plate 704 in the absence of the sheet is set. If the difference in the position of the shielding plate 704 when the ridge 702 is pushed up by the passage of the paper is identified, the upper left and right corners of the paper are the ridges 70 of the left and right levers.
It can be detected that 2 is reached.

FIG. 9 is an example of a circuit diagram showing an example of a sensor circuit for detecting the leading edge and the left and right upper corners of the sheet conveyed by the levers 103, 108 and the like. In FIG.
7 corresponds to the photo interrupter 101b for identifying whether or not the paper is at this sensor position according to the operation of the lever 101a of the paper suction sensor 101 shown in FIG. 7, and the sensor of this photo interrupter 801 It has a light emitting diode 802 for generating light. The light emitting diode 802 is connected to a power source 804 via a current limiting resistor 803, and emits sensor light when a light emitting current flows. Reference numeral 805 denotes a light receiving transistor which forms the photo interrupter 102 in pairs with the light emitting diode 802. When sensor light reaches the light receiving transistor 805, the impedance between the collector and the emitter is lowered, and the light receiving transistor 805 is installed between the collector of the light receiving transistor 805 and the power supply 804. A current flows through the load resistance 806 that is being operated, and a photo interrupter output (hereinafter, referred to as “PSIN-N signal”) 80
7 becomes a low potential and becomes the zero level of the theoretical circuit (hereinafter, this state is referred to as “ON state of the light receiving transistor 805”).
Say). Then, the sensor light is shielded by the shield plate so that the light from the light emitting diode 802 is received by the light receiving transistor 80.
If it does not reach 5, the impedance between the collector and the emitter becomes high, current does not flow through the load resistor 806, and P
The SIN-N signal 807 becomes the potential of the power supply 804 and becomes the "1" level of the theoretical circuit (hereinafter, this state is referred to as the OFF state of the light receiving transistor). Therefore, the PSIN-N signal 807 has a logic "1" level when the lever 101a blocks the sensor light when there is no paper, and has a logic "0" level when the lever 101a does not block the sensor light.

Similarly, reference numeral 808 corresponds to the photo interrupter 105 of FIGS. 7 and 8 for detecting the state of the left paper angle detection lever 103. The photo interrupter 105 has a light emitting diode 809 and a light receiving transistor 810, and is connected to the power supply 804 via a current limiting resistor 811 and a load resistor 812, respectively. Then, the output 813 of the photo interrupter 808 (hereinafter, referred to as "LEFTDGE-N signal")
Becomes a logical “0” level when the lever 103 is pushed up by the sheet, and a logical “1” level when the sheet is not in the area of the lever 103.

Similarly, reference numeral 814 corresponds to the photo interrupter 105 of FIGS. 7 and 8 for detecting the state of the right paper angle detection lever 108. The photo interrupter 814 has a light emitting diode 815 and a light receiving transistor 816, and is connected to the power supply 804 via a current limiting resistor 817 and a load resistor 818, respectively. The output 819 of the photo interrupter 814 (hereinafter, referred to as "RIGHTEDGE-N signal") is at a logical "0" level when the lever 108 is pushed up by the paper, and when the paper is not in the area of the lever 108, a logical "0" level. 1 ”level.

FIG. 10 is a block diagram showing an example of a circuit for controlling the sensor circuit shown in FIG. In FIG. 10, reference numeral 901 denotes a microprocessor (hereinafter referred to as “C
902 is a storage element (hereinafter, referred to as “RO”) in which a program that determines the operation of the CPU 901 is stored.
M ”), 903 is a storage element (hereinafter referred to as“ RAM ”) in which the CPU 901 temporarily stores information according to a program written in the ROM 902, and 904 is a timing circuit (hereinafter referred to as“ timer ”). Yes, the elapsed time after being reset by the timer reset signal 905 (hereinafter referred to as “TMRST signal”) is held as the number of cycles of the clock signal 906 (hereinafter referred to as “elapsed time value”).
Reference numeral 907 denotes an IO port (hereinafter referred to as “port”). This IO port 907 has a PSIN-N signal 80
7, LEFTEDGE-N signal 813, and RIGHT
The EDGE-N signal 819 is input, the printer drive circuit 908 is connected to the output side, and the timer reset signal 905 can be output. Then, the CPU 901 controls the input / output signals of the port 907 in accordance with the program written in the ROM 902, so that the drive circuit 908 performs the normal printing operation, and similarly, the PSIN-N signal 807 and the LEFTEDGE-N signal 813, Then, the state of the RIGHTEDGE-N signal 819 is read and the TMRST signal 905 is controlled. Also,
In the timer 904, the elapsed time value after the CPU 901 resets the timer 904 by the TMRST signal 905 according to the program written in the ROM 902 is stored in the bus 91.
Read through 2. The CPU 9 in this circuit
01, the ROM 902, the RAM 903, the timer 904, and the port 907 are connected to each other via a bus 912.

FIG. 11 is a flow chart showing an example of an algorithm for detecting the width of the paper in the first embodiment. FIG.
1, LEFT DTCT and RIGHT DT
CT is a flag to which a specific address of the RAM 903 is assigned, and “1” or “0” is written by the CPU 901 according to the program stored in the ROM 902, and the written content is read. Similarly, LEFT TIME and RIGHT TIME
Is a data register to which a specific address of the RAM 903 is assigned, and an arbitrary value can be written by the CPU 901 according to a program stored in the ROM 902, and the written content can be read. In addition,
In this flowchart, the flag LEFT DTCT is set to "0" until the upper left corner of the sheet reaches the left side sheet detection line 602 after the start of sheet suction, and is set to "1" after it reaches the flag RI.
The GHT DTCT is set to "0" until the upper right corner of the sheet reaches the right side sheet detection line 603 after the start of sheet suction, and is set to "1" after the sheet reaches the sheet width when both flags become "1". Calculate. In LEFT TIME, the elapsed time value from when the sucked sheet reaches the sheet suction detection point 601 to when the upper left corner of the sheet reaches the left sheet detection line 602 is stored as a value held by the timer 904. R
In the IGHT TIME, the upper right corner of the sucked sheet reaches the sheet suction detection point 601 and the upper right corner is the right sheet detection line 6
The value of the elapsed time until reaching 03 is stored as the numerical value of the held value of the timer 904.

Therefore, each process will be described in order with reference to the flowchart of FIG. 11, and the process here is performed under the control of the CPU 901 in accordance with a program stored in the ROM 902. First, in step 1001, the drive circuit 908 is controlled via the port 907 to rotate the hopping roller 403 and convey the paper to the printing mechanism unit.
The sheet here is conveyed at a constant speed throughout the process. In step 1002, the PSIN-N signal 807 is monitored via port 907. In the PSIN-N signal 807, when the conveyed sheet reaches the sheet suction point 601, the sheet is switched from "1" to "0". When the PSIN-N signal 807 becomes "0", step 1
Move to 003. In step 1003, PSIN-
When the N signal 807 indicates "0", it is recognized that the conveyed sheet reaches the sheet suction point 601, and the TMRST signal 905 is made effective via the port 907 in order to reset the timer 904. In step 1004,
LEFTTD to indicate that the upper corners of the left and right paper sheets have not been detected
Write "0" to TCT and RIGHT DTCT,
The process moves to step 1005. Step 1005 is a step 1013 if the flag LEFT DTCT is “0”.
If it is "1", the process proceeds to step 1006.

If the flag RIGHT DTCT is "0" in the case of shifting to step 1006, the routine proceeds to step 1009, and if it is "1", the step 1007.
Move to In step 1007, the flag LEFT is set.
If DTCT is “0”, the process proceeds to step 1013,
If "1", the process proceeds to step 1008. Step 10
08 reaches the data registers LEFT TIME and RIGHT TIME before reaching this step 1008.
The width of the sheet is calculated according to the above equation (3) based on the elapsed time value stored in.

On the other hand, in the case of shifting to step 1009, the RIGHTEDGE-N signal 819 is read through the port 907, and if the value is "1", step 100
If it is "0", the process proceeds to step 1010.
Here, the RIGHTEDGE-N signal 819 becomes “0” when the upper right corner of the sucked paper reaches the right paper detection line 603. When the process proceeds to step 1010, the flag LEFTDTCT is determined in step 1010.
"1" is written in and the process proceeds to step 1011. In step 1011, the value held by the timer 904, that is, the elapsed time value from when the suctioned sheet suction detection point 601 is reached to when the upper right corner thereof reaches the right side sheet detection line 603 is stored in the data register RIGHT TIME, The process moves to step 1012. In step 1012, if the flag LEFT DTCT is “0”, step 1005
If it is "1", the process proceeds to step 1008.

Next, steps 1005 to 10
Step 1
013, LEFTEDGE-N via port 907
Read the signal 813. If the value is "1", step 1
If it is "0", the process proceeds to step 1014. Here, as described above, the LEFTEDGE-N signal 813 indicates that the upper left corner of the sucked paper is the left paper detection line 60.
When it reaches 2, it becomes “0”. Step 101
In step 4, "1" is written in the flag LEFT DTCT, and the process proceeds to step 1015. In step 1015, the value held by the timer 904, that is, the elapsed time value from when the sucked paper reaches the paper suction detection point 601 to when the upper left corner thereof reaches the left paper detection line 602 is stored in the data register LEFT TIME. Step 101
Go to 6. In step 1016, the flag RIGH
If TDTCT is “0”, the process branches to step 1009,
If "1", the process proceeds to step 1008.

Next, the processing procedure at each relative position in the vertical direction with respect to the sheet suction detection point 601 of the sheet and the left and right sheet detection lines 602 and 603 will be described with reference to the same FIG. First, in step 1001, the hopping roller 403
Is rotated and the sheet is conveyed to the printing mechanism side. In step 1002, the PSIN-N signal 807 is monitored via port 907. In the PSIN-N signal 807, when the upper end of the conveyed sheet reaches the sheet suction point 601, the sheet is switched from "1" to "0". And this PSIN
When the -N signal 807 becomes "0", the process proceeds to step 1003.

In step 1003, when it is recognized that the conveyed sheet reaches the sheet suction detection point 601 because the PSIN-N signal 807 indicates 0, the TMRST signal 905 is output to reset the timer 904. It is validated via 907, and the process proceeds to step 1004. In step 1004, LEFTDTCT and RIGHT D are displayed to indicate that the upper corners of the left and right paper sheets have not been detected.
"0" is written in TCT, and the process proceeds to step 1005. Further, the step 1005 shifts to the following (1)-
It is processed for each of (9).

(1) In step 1005, the flag LE
If the FT DTCT is "0", the process proceeds to step 1013, and if it is "1", the process proceeds to step 1006.

(2) When the right and left upper corners of the sheet are not detected after the sheet passes the sheet suction detection point 601, the steps 1005 to 1013 to 1006 to step 1009 are performed again to step 1
The procedure is returned to 005.

(3) If the upper left and right paper upper corners of the paper have not been detected and the upper left corner is detected after the paper passes the paper suction detection point 601, steps 1005 to 1013 to 1014 to step 1015 −
Processing is performed in the procedure of returning from step 1016 to step 1009 to step 1005 again.

(4) If the upper right corner of the sheet has not been detected while the upper left corner of the sheet has been detected after the sheet has passed the sheet suction detection point 601, steps 1005 to 1006 to 1009 are executed. After that, processing is performed again in the procedure of returning to step 1005.

(5) If the upper right corner of the sheet is detected after the upper edge of the left sheet has been detected after the sheet has passed the sheet suction detection point 601, step 1005 to step 1006-step 1009-step 1010
-Step 1011-Step 1012-Step 10
It is processed in the procedure of passing through 08.

(6) If the upper right corner of the sheet is not detected yet and the upper right corner is detected after the sheet passes through the sheet suction detection point 601, step 1005 to step 1013 to step 1006 -step 1009
-Step 1010-Step 1011-Step 10
Processing is performed in the procedure of returning to step 1005 via step 12.

(7) If the upper corner of the right paper has been detected and the upper left corner has not been detected, steps 1013 to 1
006-Step 1007 and step 1013 again.
The procedure is returned to.

(8) When the upper left corner of the right paper has already been detected and the upper left corner is to be detected, step 1013 to step 1014 to step 1015 to step 1016 to step 1008.
It is processed in the procedure to shift to.

(9) Steps 1005-Step 1013-Step 1014-Step 1015-Step 1016-Steps 1009-Step 1010-
Step 1011-Step 1012-Step 100
It is processed in the procedure of shifting to 8.

Therefore, by performing the processing according to the flow chart of FIG. 11, even if the inhaled sheet reaches the left / right sheet angle detection line 602 or 603 in any order after passing through the sheet inhalation detection point 601, the sheet is detected. The width of can be calculated.

FIG. 12 is a schematic view of the essential parts of an electrophotographic printer according to the second embodiment of the present invention, showing the mechanism for sucking paper from the manual feed tray. In FIG. 12, reference numeral 1101 is a strip-shaped electrode, and the paper transport surface 11
It is installed in 03. Reference numeral 1102 denotes an electrode paired with the electrode 1101, which is placed apart from the electrode 1101 by the thickness of the paper. Both electrodes 1101, 1 here
102 have the same shape, and their surfaces are parallel to each other. Further, both electrodes 1101 and 1102 are installed in a state of being inclined with respect to the sheet conveying direction indicated by arrow 1104. A sheet 1105 is inserted between the electrodes 1101 and 1102. Although only the left electrode is shown in FIG. 12, the electrodes 1101 and 11
02 are installed respectively.

FIG. 13 shows electrodes 1101 and 11 shown in FIG.
2 is a schematic diagram for explaining a change in electrostatic capacity when a sheet 1105 is inserted between sheets 02. An electrode pair 1201 is installed at an angle θ with respect to a sheet conveyance direction 1202,
The long side length of the electrode pair is a1 and the short side length is a2. The capacitance Co formed by the electrode pair when there is no sheet 1105 between the electrodes 1101 and 1102 is
When the proportional multiplier including the distance between 101 and 1102 is α and the permittivity of air is ρa, it is expressed by the following equation (4).

[0053]

[Equation 4] Co = α · (a1 · a2) ρa (4)

Further, the electrostatic capacitance C1 when the sheet having the dielectric constant ρp is located between the electrodes at the position indicated by reference numeral 1206, that is, the position where the sheet edge 1207 has advanced the distance r1 after reaching the electrode pair.
Is the sum of the capacity of the dielectric constant ρp of the area where the paper is present and the capacity of the dielectric constant ρa of the area where the paper is absent. Here, considering the area of the portion where the paper and the electrode pair overlap, the following equation (5) is given because of the difference between the area of the triangle ABC and the area of the triangle DEC:

[0055]

[Equation 5] r1 · r1 · tan θ / 2− (r1−a2 / sin θ) ² · tan θ / 2 = r1 · a2 / cos θ−a2 ² / (2 · sin θ · cos θ) (5 )

Thus, the electrostatic capacitance C1p of the portion where the paper is present is given by the following equation (6).

[0057]

[Equation 6] C1p = α · (r1 · a2 / cos θ−a2 ² / (2 · sin θ · cos θ)) ρp (6)

On the other hand, in the area without the paper, the capacitance of the electrode having the area smaller than the area of the entire electrode by the area where the paper and the electrode pair are overlapped (first right side of the following equation (7))
Therefore, the total capacitance C1 is given by the following equation (7).

[0059]

[Equation 7] C1 = C0 '+ C1P = α ・ (a1 ・ a2-(r1 ・ a2 / cos θ-a2 ² / (2 ・ sin θ ・ cos θ))) ρa + α ・ (r1 ・ a2 / cos θ −a2 ² / (2 ・ sin θ ・ cos θ)) ρp (7)

Further, in FIG. 13, the width a2 of the electrode pair 1201 is
Considering the approximate values when the width a1 and the distance r1 are sufficiently small, the term of the square of a2 can be ignored, and therefore the above equation (7) becomes the following equation (8).

[0061]

[Equation 8] C1 = r1 · a2 · α / cos θ · (ρp −ρa) + a1 · a2 · α · ρa (8)

Therefore, the electrostatic capacitance C1 when there is a sheet having a dielectric constant ρp between the electrodes 1101 and 1102 is the distance r1 that the sheet edge 1207 travels after reaching the electrode pair 1201.
Increases in proportion to. Further, the distance r1 is proportional to the elapsed time when the paper conveyance speed is constant. That is, when the transport speed is constant, the electrostatic capacitance of the electrode pair 1201 changes in proportion to the elapsed time after the corner of the paper reaches the electrode pair 1201.

FIG. 14 is a graph showing the elapsed time before and after the corner of the sheet conveyed at a constant speed reaches the electrode pair 1201 on the X axis and the electrostatic capacity of the electrode pair 1201 on the Y axis. In FIG. 14, timing 0 is the time when the corner of the conveyed paper reaches the electrode pair 1201, and the electrostatic capacity formed by the electrode pair 1201 at this time is C0, which is expressed by the above equation (4). To be done. Also, the change in capacitance from timing 0 changes in proportion to the elapsed time as described in the above equation (8), and this change indicates that the permittivity ρp of paper is lower than the permittivity ρa of air. Since it is large, the change increases with time as shown in FIG. Timing 1 and timing 2 are examples of two time points at which the capacitance is measured.

Therefore, the elapsed time from timing 0 to timing 1 is t3, the elapsed time from timing 0 to timing 2 is t4, and the elapsed time from timing 1 to timing 2 is td. Let C1-1 be the electrostatic capacity at timing 2 and C1-2 be the electrostatic capacity at timing 2, and using this FIG. 14 and the above-mentioned formula, the electrostatic force at any two time points after the corner of the paper reaches the electrode pair 1201. By measuring the capacity, the corner of the paper is
It will be described that the time when 1 is reached can be calculated.

First, if the time when the corners of the left and right sheets reach the electrode pair can be detected, the width of the conveyed sheet can be calculated in the same manner as described in the first embodiment. That is, if the paper transport speed is Vp, the paper transport distance from timing 0 to timing 1 is (Vp.t3), and since this distance is the distance r1 in FIG. 13, the electrostatic capacitance C1-1 at timing 1 is higher. Equation (8) is given by the following equation (9).

[0066]

## EQU9 ## C1-1 = Vp.multidot.t3.a2.alpha. / Cos .theta..multidot. (. Rho.p-.rho.a) + a1.a2.alpha..rho.a (9)

The timing 2 is similarly given by the following equation (10).

[0068]

## EQU10 ## C1-2 = Vp.multidot.t4.a2 .alpha. / Cos .theta..multidot. (. Rho.p-.rho.a) + a1 .a2 .alpha..rho.a (10)

The measured time is not t3 and t4 (t
d = t4 -t3). Further, the dielectric constant ρp of the paper, which is different depending on the type of paper, is treated as an unknown number, and is substituted into the above formula (9) and (t4 = t3 + td).
When ρp is deleted from 0), the following equation (11) is obtained.

[0070]

T3 = td. (C1-1-a1.a2..alpha..rho.a) / (C1-2-C1-1) (11)

From the above equation (4), (a1 ・ a2 ・ α ・ ρa
= C0), the above equation (11) becomes the following equation (12).

[0072]

T3 = td. (C1-1-C0) / (C1-2-C1-1) (12)

Therefore, the electrostatic capacitance C0 when no paper is inserted
By measuring the electrostatic capacitances C1-1 and C1-2 at two time points that change depending on the inserted sheet and the time td between the time points, the first static state after the sheet reaches the electrode pair 1201. The time t3 until the time of measuring the capacitance is calculated. further,
Similar to the first embodiment, the relative position between the sheet suction detection point and the electrode is already known, and the time t5 from the sheet suction detection point to the measurement point of the first capacitance is measured for the left electrode pair. For example, (t5 -t3) is added to t1 in the above equation (3) and t2
The width of the sheet is calculated by substituting the difference in time from the measured and calculated sheet inhalation detection point until the upper corner of the sheet reaches the right electrode to t5.

Further, as an example of means for measuring the electrostatic capacitance of the electrode pair 1201, there is a method in which the electrode is C of the LC oscillation circuit and the oscillation frequency of this oscillation circuit is observed to calculate the electrostatic capacitance. FIG. 15 is a circuit diagram showing an example of the oscillation circuit. In FIG. 15, this oscillating circuit is a circuit known as a Hartley oscillator, and the symbol Cx is shown in FIG.
Of the electrode pair 1201, L1 and L2 are inductances that determine the oscillation frequency by the capacitance Cx, Vcc is the power supply of this circuit, Tr is a transistor, and Re
Is a load resistance, Rb is a bias resistance that determines the base bias of the transistor Tr, and Cb is a capacitor that determines the base bias of the transistor Tr. The oscillation waveform of the output of this circuit appears on OSCOUT, and the oscillation frequency f is expressed by the following equation (13).

[0075]

F = 1 / (2 · π · sqrt (Cx · (L1 + L2))) (13)

Sqrt () in the above equation (12) is
Represents the square root in parentheses. Therefore, if the oscillation frequency f of FIG. 15 is measured, the electrostatic capacitance Cx of the electrode pair 1201 is calculated by the following equation (14).

[0077]

[Expression 14] Cx = 1 / (4 · π ² · f ² · (L 1 + L ² )) (14)

FIG. 16 is an example of a block diagram of a circuit for detecting the width of the paper using the oscillation circuit of FIG. In FIG. 16, reference numeral 1501 denotes a microprocessor (hereinafter,
“CPU”), 1502 is a storage element (hereinafter, referred to as “ROM”) in which a program that determines the operation of the CPU 1501 is stored, and 1503 temporarily stores information according to the program written in the ROM 1502 by the CPU 1501. A storage element (hereinafter, referred to as "RAM") 1504, a timing circuit (hereinafter, referred to as "timer") 1504
That is, the elapsed time after being reset by the timer reset signal 1505 is held as the number of cycles of the clock signal 1506 (hereinafter, referred to as “elapsed time value”).

Reference numeral 1507 denotes an IO port (hereinafter, “port”).
The printer drive circuit 1508 is connected to the output side and the PSI of the detection circuit shown in FIG.
Paper suction sensor circuit output 1 corresponding to NN signal 807
509 is connected as an input to port 1507.
Further, the above-mentioned timer reset signal 1505 (hereinafter referred to as “TMRST signal”) is connected to the port 1507 as an output. The input / output signals of the port 1507 are controlled by the CPU 1501 according to the program written in the ROM 1502, so that the drive circuit 1508 normally performs the printing operation, and similarly, the PSIN
-N signal 1509 is read and TMRST signal 1505
Control. ROM 1502 for timer 1504
According to the program written in
The elapsed time value after resetting the timer 1504 by the MRST signal 1505 is read via the bus 1515.
Reference numeral 1510 denotes a frequency counter, which outputs the output (hereinafter, referred to as “left electrode pair oscillation circuit”) of the oscillation circuit 1511 for measuring capacitance of the left electrode pair described below with reference to FIG. 15.
The output from the right electrode pair oscillation circuit 1513 (hereinafter referred to as "OSCOUTL") having the same configuration as that of "OSCOUTL" (hereinafter referred to as "OSCOUTR") is used as an input, and the CPU 1501 performs a read operation to the frequency counter according to the program written in the ROM 1502. And input OSCOUTR or OS
The frequency of COUTR can be read via bus 1515. Note that in FIG. 16, the CPU 1501 and the ROM 1
502, RAM 1503, timer 1504, port 15
07 and the frequency counter 1510 are connected to each other via a bus 1515.

FIGS. 17 and 18 are flow charts showing an example of an algorithm for detecting the width of the sheet by using the respective means shown in FIGS. 12, 13, 15, and 16. In addition, LEFT DTCT and RIGHT DT appearing in this flowchart
CT is a flag to which a specific address of the RAM 1503 is assigned, and "0", "1" or "2" is written by the CPU 1501 according to the program stored in the ROM 1502, and the written content is read. Similarly, LEFT0, LEFT1, LEFT
2, and LEFT TIME1, LEFT TIME2
And RIGHT0, RIGHT1, RIGHT2 and R
IGHT TIME1 and RIGHT TIME2 are RA
This is a data register to which a specific address of M1503 is assigned, and an arbitrary value can be written by the CPU 1501 according to a program stored in the ROM 1502, and the written content can be read.

In this flow chart, the flag LEFT is also used.
In the DTCT, the electrode pair 120 is located at the upper left corner after starting the sheet suction.
After reaching 1, until the capacitance measurement time (timing 1) of the first left electrode pair is “0”, from the timing 1 to the capacitance measurement time (timing 2) of the second left electrode pair. "1", "2" after timing 2. The flag RIGHT DTCT is "0" until the electrostatic capacitance measurement time (timing 1) at the first right electrode pair after the upper right corner reaches the electrode pair 1201 after the start of sheet suction, and from the timing 1 to the second right electrode. It is "1" until the capacitance measurement time (timing 2) in the pair, and "2" after timing 2. LEFT0 to LEFT
2 stores the oscillation circuit frequencies at timing 1 and timing 2 regarding the time when the paper has not reached the left electrode pair and the left electrode pair, respectively, and RIGHT0 to RIGHT2.
Similarly, the right side oscillation circuit frequency is stored. LEFT
TIME1 and LEFT TIME2 store the reading values of the timer 1504 at timing 1 and timing 2 for the left electrode pair, respectively.

Next, a processing procedure according to the flowcharts of FIGS. 17 and 18 will be described. Note that all the processing here is performed by the CPU 1501 according to a program stored in the ROM 1502. First, in step 1601, the drive circuit 1508 is controlled via the port 1507 to rotate the hopping roller 403 and convey the paper to the printing mechanism unit. In this embodiment, the paper is conveyed at a constant speed during processing. In step 1602, the PSIN-N signal is monitored through the port 1507 and the PSIN-N signal is monitored.
Step 1 when the IN-N signal changes from "1" to "0"
Move to 603. At step 1603, PSIN-
The TMRST signal is validated via the port 1507 to reset the timer 1504 because it is recognized that the conveyed sheet reaches the sheet suction detection point 601 because the N signal indicates "0", and the process proceeds to step 1604. Transition. In step 1604, the flags LEFT DTCT and RI are set to indicate that the upper corners of the left and right paper sheets have not been detected.
Write "0" to GHT DTCT, and step 160
Go to 5. In step 1605, the frequency of the output OSCOUTL of the left electrode pair oscillation circuit 1511 is read from the frequency counter 1510 (hereinafter, this process is referred to as “left frequency reading”), and the read value is stored in the data register LEFT0 in step 1606. , And shifts to step 1607. In step 1607, the frequency of the output OSCOUTR of the right electrode pair oscillation circuit 1513 is read from the frequency counter 1510 (hereinafter, this processing is referred to as “right frequency reading”), step 1608.
The read value is stored in the data register RIGHT0.

At step 1609, the flag LEFT is set.
If DTCT is “0”, the process proceeds to step 1610,
If it is not "0", the process proceeds to step 1615.

In step 1610, the left frequency is read, and in step 1611 the read value is compared with the data register LEFT0. If they are the same, the process proceeds to step 1701 via a connector.
Move to 12. In Step 1612, Step 16
Read the left frequency at 10 in the data register LEF
Store in T1 and move to step 1613. In step 1613, the timer value at that time is read, the elapsed time value of the timer is stored in the data register LEFT TIME1, and the process proceeds to step 1614. Step 1614
Then, "1" is stored in the flag LEFT DTCT.
After the end of step 1614, the process proceeds to step 1701 via the connector.

On the other hand, steps 1609 to 16
If the flag LEFT DTCT is “1” in step 1615, the process proceeds to step 1616, and if the flag LEFT DTCT is not “1”, the process proceeds to step 17 via the connector.
Move to 01. Then, when the process proceeds to step 1616, the left frequency is read in step 1616,
In step 1617, the read value is stored in the data register LE.
Store in FT2 and move to step 1618.
In step 1618, the timer value at that time is read, the elapsed time value of the timer is stored in the data register LEFT TIME2, and the process proceeds to step 1619. In step 1619, “2” is stored in the flag LEFT DTCT, and then the process proceeds to step 1701 via the connector.

At step 1701, the flag RIGHT is set.
If DTCT is “0”, the process proceeds to step 1702,
If it is not "0", the process proceeds to step 1707.

When the step 1701 shifts to the step 1702, the right frequency is read in the step 1702, the read value is compared with the data register RIGHT0 in the step 1703, and if they are the same, the step 1
If not, the process proceeds to step 1704.

In step 1704, step 1702
Read the right frequency at the data register RIGHT
1 and the process proceeds to step 1705. Step 1
At 705, the timer value at that time is read and the overtime value of the timer is stored in the data register RIGHT TIME1, and the routine proceeds to step 1706. In step 1706, "1" is stored in the flag RIGHT DTCT, and then the process proceeds to step 1712. Step 1701
If the procedure proceeds from step 1707 to step 1707, step 170
In step 7, if the flag RIGHT DTCT is "1", the process proceeds to step 1708, and if it is not "1", the process proceeds to step 17
Move to 12.

In the case of shifting from step 1707 to step 1708, the right frequency is read in step 1708, the read value is stored in the data register RIGHT2 in step 1709, and the process shifts to step 1710. In step 1710, the timer value at that time is read and the overtime value of the timer is stored in the data register RIGHT TIME2, and the process proceeds to step 1711. In step 1711, 2 is stored in the flag RIGHT DTCT, and the process moves to step 1712.

At step 1712, the flag RIGHT is set.
If DTCT is “2”, the process proceeds to step 1713,
If it is not "2", step 1609 is executed via the connector.
Move to In step 1713, the flag LEFT is set.
If DTCT is “2”, the process proceeds to step 1714,
If it is not "2", step 1609 is executed via the connector.
Move to In step 1714, the time it takes for the upper end of the sheet to reach the left and right electrode pairs after passing through the sheet suction point is calculated based on the value stored in the data register.

Describing the calculation means here on the left side, the respective capacitances C0, C1-1, C1-2 in FIG. 14 are calculated using the above equation (14) from LEFT0, LEFT1 and LEFT2, LEFT TIME2
And LEFT TIME1 are calculated as td in equation (12), and t3 is calculated. The difference between LEFT TIME1 and t3 is the time required for the upper end of the sheet to reach the left electrode pair after passing through the sheet suction point. Similarly, for the right side, the time until the upper end of the sheet reaches the right electrode pair after the upper edge of the sheet has passed the sheet suction point can be calculated. Step 1
In 715, the time calculated in step 1714 is used in the above equation (3) to calculate the width of the paper.

Therefore, according to the processing according to this flow chart, the electrostatic capacity that changes as the paper reaches the electrode pair with respect to the electrostatic capacitance (LEFT0 and RIGHT0) of each electrode pair when the paper does not reach the left and right electrode pairs. The capacitance is measured twice for each electrode pair, and the timer value reset at the time when the upper end of the paper reaches the paper suction point at the time of the measurement to read the time when the paper suction point is reached and each measurement time. It can be seen that the relative time of is measured and the width of the sheet can be calculated from the measurement results.

[0093]

As described above, according to the present invention,
The state of a member of a certain length, which was placed diagonally to the sheet conveying direction in the sheet suction section, was detected or the capacitance of the electrode pair was measured, and the state of the member was changed. The width of the paper can be easily obtained by measuring the relative time between the time and the time when the upper edge of the paper passes a specific point and calculating the measurement result according to a certain conversion formula. In comparison, the structure is simple and highly accurate detection can be realized.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of sheet width detection according to the present invention.

FIG. 2 is an explanatory diagram of a mechanism of a sheet suction unit in the apparatus according to the embodiment of the present invention.

FIG. 3 is an explanatory view of a main part mechanism arrangement in the device of the embodiment of the present invention.

FIG. 4 is a top view of a lever alone in an apparatus according to an embodiment of the present invention.

FIG. 5 is a front view of a lever alone in an apparatus according to an embodiment of the present invention.

FIG. 6 is a side view of a lever alone in an apparatus according to an embodiment of the present invention.

FIG. 7 is a lever mounting state diagram in the device of the embodiment of the present invention.

FIG. 8 is an enlarged view of part A in FIG.

FIG. 9 is a diagram showing an example of a detection circuit in the device of the embodiment of the present invention.

FIG. 10 is a diagram showing an example of a CPU circuit in the device of the embodiment of the present invention.

FIG. 11 is a flow chart showing an example of a paper width detection procedure in the apparatus of the embodiment of the present invention.

FIG. 12 is an explanatory diagram of a main part configuration in an apparatus according to another embodiment of the present invention.

FIG. 13 is an explanatory diagram of a main part configuration in an apparatus according to another embodiment of the present invention.

FIG. 14 is a diagram illustrating a change in capacitance of an electrode pair in a device according to another embodiment of the present invention.

FIG. 15 is a diagram showing an example of an oscillator circuit in a device according to another embodiment of the present invention.

FIG. 16 is a diagram showing an example of a CPU circuit in a device according to another embodiment of the present invention.

FIG. 17 is a flow chart showing an example of a paper width detection procedure in the apparatus of another embodiment of the present invention.

FIG. 18 is a flow chart showing an example of a paper width detection procedure in the apparatus of another embodiment of the present invention.

FIG. 19 is an explanatory diagram of a main part configuration of a conventional device.

FIG. 20 is an explanatory diagram of a main part configuration of a conventional device.

[Explanation of symbols]

 105 Photointerrupter 108 Lever 402 Paper presence / absence detection sensor 404 Paper suction sensor 501 Paper suction detection point 502,602 Paper angle detection line 503,603 Paper angle detection line 704 Shield plate 901,1501 CPU 904,1504 Timer 1201 Electrode pair

Claims (8)

[Claims] 1. A sheet width detection device for an electrophotographic printer capable of printing on a sheet having an arbitrary width, wherein the sheet suction unit is arranged obliquely with respect to the sheet conveyance direction and there is no sheet. A member having a constant length whose state changes with time, a first detecting unit that detects a time when the state of the member changes, and a member arranged at a specific position in the paper conveyance path to Second detecting means for detecting passage of the upper end, and means for measuring a relative time between the time point detected by the first detecting means and the time point detected by the second detecting means A paper width detection device for a printer, comprising: and a means for calculating and obtaining the paper width according to a constant conversion formula based on the measured time. 2. The paper width detection device for a printer according to claim 1, wherein the members are provided on both left and right sides of a passage through which the paper is conveyed. 3. A sheet width detecting device for an electrophotographic printer capable of printing on a sheet having an arbitrary width, wherein the sheet suction unit is arranged obliquely to the sheet conveying direction and there is no sheet. An electrode pair of a certain length whose state changes depending on time, a means for measuring the electrostatic capacity formed by the electrode pair, and an upper end of the sheet which is arranged at a specific position in the sheet conveyance path. And a means for measuring a relative time between a plurality of measurement times measured by the measuring means and a time when the upper end of the paper passes a specific point, and A paper width detection device for a printer, comprising: a means for calculating and obtaining a paper width according to a constant conversion formula based on the capacitance at each measurement time point and the measured time. 4. The paper width detection device for a printer according to claim 3, wherein the electrode pairs are provided on both left and right sides of a passage through which the paper is conveyed. 5. A method for detecting a paper width of an electrophotographic printer capable of printing on a paper having an arbitrary width, wherein a member having a constant length whose state changes depending on whether there is no paper, It is arranged diagonally to the paper transporting direction in the paper suction unit to detect the time when the state of the member is changed, and the time when the state of the member is changed and the upper end of the paper passes a specific point. A paper width detection method for a printer, characterized in that the paper width is calculated by measuring a time relative to the point of time, and calculating the paper width according to a constant conversion formula based on the measured time. 6. The paper width detection method for a printer according to claim 5, wherein the member is provided on each of the left and right sides of a passage through which the paper is conveyed. 7. A method for detecting a paper width of an electrophotographic printer capable of printing on a paper having an arbitrary width, wherein an electrode pair of a certain length whose state is changed between when there is no paper and when there is paper is provided. , Is arranged obliquely with respect to the paper conveyance direction in the paper suction unit, and measures the capacitance formed by the electrode pair, and measures a plurality of times and a time when the upper end of the paper passes a specific point. The paper width of the printer is characterized in that the paper width is calculated according to a constant conversion formula from the measured electrostatic capacity at each measurement time point and the measured time. Detection method. 8. The paper width detection method for a printer according to claim 7, wherein the electrode pair is provided on each of the left and right sides of a passage through which the paper is conveyed.