JP2001002290A - Skewing detecting device for sheet material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a skewing detecting device for a sheet material, capable of preventing cost related to adjustment of a sensor from being increased and capable of detecting skewing without depending on the sheet width. SOLUTION: The type of a recording paper sheet 14 to be used for a printer 10 is detected by a paper type detecting sensor, and the paper width of the recording paper sheet 14 is discriminated. Photocouplers 56L, 56R having tapered (wedge-shaped) slits 54L, 54R are arranged on both right and left sides of a conveying passage of the recording paper sheet 14. The detecting output values of phototransistors 60L, 60R are continuously changed according to the skewing amount of the recording paper sheet 14. A reference value indicative of the skewing reference amount of the recording paper sheet 14 and a set value corresponding to a threshold value indicative of an allowable limit value of the skewing amount are stored in a reference value and set value recording memory 74. A mechanically controlled microcomputer 34 reads the reference value and the set value corresponding to the recording paper sheet 14 from the memory 74 and automatically sets the set value for judgment of skewing on the basis of the discriminated result of the paper width.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a skew detection apparatus for a sheet material, and more particularly to a skew detection apparatus suitable as a means for detecting skew when a sheet is conveyed in a printer.

[0002]

2. Description of the Related Art In a device such as a copying machine or a printer, as means for detecting skew during paper conveyance, for example, Japanese Patent Application Laid-Open Nos. Hei 5-33859 and Hei 10-139215
Japanese Patent Application Laid-Open Publication No. H11-157210 discloses a method of detecting the type and skew of a sheet based on a detection time difference using a plurality of sensors.
Japanese Utility Model Laid-Open No. 6-38370 discloses a method of detecting skew by using a CCD sensor and comparing data read by the CCD with a predetermined reference value.

In addition, in a conventional printer, a sensor (mechanical sensor) composed of mechanical means is fixedly installed at a position separated by a fixed distance from both edges of the paper on the left and right sides of a transport path where the continuous paper (roll paper) is transported. Some printers are configured to detect the presence or absence of skew of the paper by the sensor.

[0004]

However, the method disclosed in JP-A-5-338859 or the like requires a plurality of sensors (at least two sensors), and such a method requires a limited type of sensor. There is a drawback in that it can only detect skew of paper and cannot handle paper of various sizes.

On the other hand, Japanese Utility Model Laid-Open No. 6-38370 discloses that
Although it is described that data read by a CCD is compared with a reference value, there is no mention of adjustment of a set value in manufacturing (adjustment of a reference value).

[0006] The method using a mechanical sensor is as follows.
There is a disadvantage that the mechanical gap length needs to be adjusted for each device (for each device), and the manufacturing cost increases. In addition, the mechanical sensor determines whether there is skew or not.
There is a problem that only value control can be performed and detection becomes critical.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a skew detecting apparatus for a sheet material capable of preventing an increase in sensor adjustment cost and detecting skew of a sheet material having various widths. The purpose is to do.

[0008]

In order to achieve the above object, the present invention provides a skew detecting apparatus for detecting skew of a fed sheet material, the apparatus comprising: Identification means for detecting the skew amount of the sheet material, detection means for detecting a skew amount of the sheet material, and outputting a detection value which can be continuously changed according to the skew amount, and a width dimension of the sheet material identified by the identification means Threshold value automatic setting means for automatically setting a threshold value required for skew determination for the sheet material, and determination for determining whether a detection value obtained from the detection means exceeds the threshold value Means.

As used herein, the term "sheet material" refers to printed continuous paper, cut paper that has been cut in advance to a predetermined size, sticker paper having an adhesive layer covered with release paper, characters and images, and the like. A document, a transparent resin sheet for an overhead projector (OHP), and other similar sheet-like media are generally used. Further, “exceeding the threshold value” is an expression including both a case where the value exceeds the upper limit value and a case where the value exceeds the lower limit value.

According to the present invention, the width dimension of the sheet material to be used is identified by the identification means, and based on the sheet identification,
Automatic threshold setting means automatically changes the threshold for skew determination. The skew amount of the sheet material is detected as a continuous (analog) value by the detection means, and when the detected value exceeds the threshold value, the determination means determines that the skew amount has exceeded the allowable limit.

As described above, in the present invention, the threshold value suitable for the identified sheet material is automatically set.
Adjustment time for sensors and the like can be reduced as compared with the conventional apparatus, and an increase in manufacturing cost can be prevented.

Further, even when different types of sheet materials are used in the same device, mechanical readjustment of the detecting means is not required, and skew can be detected corresponding to sheet materials having various widths. .

According to another aspect of the present invention, in the skew detecting apparatus for a sheet material, the apparatus has a storage unit for storing the data indicating the threshold value, and the data should be stored in the storage unit. It is configured so that data can be received from external data providing means.

According to still another aspect of the present invention, in the above-described skew detecting apparatus for sheet material, the apparatus stores data of threshold values required for skew feeding determination for a plurality of types of sheet materials having different sheet widths. The threshold value is automatically set by reading data corresponding to the sheet material from the storage means according to the identification result by the identification means.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a skew detecting apparatus for a sheet material according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a diagram schematically showing a configuration of a printer to which the present invention is applied. This printer 10
A digital color printer adopting a printing method called a Thermo-Autochrome method (hereinafter referred to as a TA method). In the printer 10, the color is developed when heat is applied, and the color is fixed when irradiated with ultraviolet rays. Printing paper (TA paper) having the property of performing printing is used.

The TA roll paper 12 is stored in a paper storage unit (not shown). Paper (hereinafter, referred to as recording paper) 14 fed from this roll is used as a paper type detection sensor 1.
6, paper feed roller 18, skew sensor 20, nip roller 2
The print head 2 is sent to the position of the thermal head 24 via the printer 2, is printed by the thermal head 24, and is fixed by the fixing lamp 26.

A capstan roller 28 is disposed opposite to the nip roller 22. The capstan roller 28 is driven by transmitting the power of a step motor 30 via a transmission mechanism (not shown). You.

The width of the TA roll paper 12 can be of various sizes, and is 125 mm in the printer 10 of this embodiment.
Two types of roll paper, a roll paper having a width of 95 mm and a roll paper having a width of 95 mm, can be used.

On the back surface of the TA roll paper 12, an identification mark (not shown) for identifying a paper type (at least information including information capable of identifying the width of the paper) is attached in advance. The paper type detection sensor 16 is means for detecting the identification mark, and an appropriate means for detecting the identification mark is used according to the form of the identification mark. For example, when an identification mark having a form such as a bar code is attached, the paper type detection sensor 16 that detects the identification mark is formed of an optical reflection sensor. As a form of the identification mark, a hole or notch of a special shape may be used instead of the barcode. When the roll paper is stored in a predetermined cartridge, an identification mark may be formed on the cartridge.

The paper type detection sensor 16 is driven by a sensor drive / detection circuit 32, and the detection result of the paper type detection sensor 16 is transmitted via the sensor drive / detection circuit 32 to a mechanism part control microcomputer (hereinafter referred to as a mechanical control microcomputer). .) 34.

A mechanical control microcomputer 34 controls each block such as a step motor drive circuit 38, a print control circuit 40, and a lamp drive control circuit 42 in accordance with a command from a system control microcomputer (hereinafter, referred to as a system microcomputer) 36. This is a processing unit.

The system microcomputer 36 is connected to the printer 10
The system microcomputer 36 is a processing unit that controls the whole of the system. The system microcomputer 36 performs image data processing, read / write processing of the buffer memory 44, provision of image data to the print control circuit 40, and the like. Various instructions are given. In addition,
The image data to be printed is taken into the buffer memory 44 via the SCSI interface 46.

Instructions for various processes to the system controller 36 are given based on a user operation from an operation unit 48 provided on a front panel of the printer 10. The operation unit 48 includes a display lamp (LE) as well as an operation key, an operation dial, and other input means.
D) and display devices such as liquid crystal displays.

When the recording paper 14 sent from the paper supply storage unit is conveyed to a predetermined printing start position, the thermal head 2
4 is pressed against the recording paper 14 to start printing. The platen roller 5 is located at a position facing the thermal head 24.
0 is arranged.

The driving of the thermal head 24 is controlled by a print control circuit 40. The print control circuit 40 obtains the image data of the print target image recorded in the buffer memory 44 in response to the print execution instruction given from the mechanical control microcomputer 34, and based on the image data. Then, the gradation (print gradation value) of each color of Y, M, and C in each pixel of the print image is set in a range of 8-bit resolution (0 to 256), for example. Then, the data of the print gradation values of each of the colors Y, M, and C at each pixel of the print image is synchronized with the running of the recording paper 14 in the direction (main scanning direction) perpendicular to the running direction (sub-scanning direction). Each line is supplied to a thermal head drive circuit (not shown).

The thermal head drive circuit receives the print gradation value data of each of the Y, M and C colors, and the thermal heads 2 arranged in the main scanning direction based on the print gradation values.
The voltage applied to the heating element of each dot 4 and the energizing time (pulse width) are controlled in synchronization with the running of the recording paper 14. Accordingly, the amount of heat given to each point of the recording paper 14 from the heating element of each dot of the thermal head 24 is Y, M,
C is controlled in accordance with the print gradation value of each color, and a color having a density corresponding to the print gradation value specified by the print control circuit 40 is formed on each color forming layer of the recording paper 14.

When a print execution instruction is given from the system microcomputer 36, the mechanical control microcomputer 34 controls the step motor drive circuit 38 to feed the recording paper 14 from the paper feed storage unit to the print processing unit. When the recording paper 14 is fed to the printing processing unit, the mechanical control microcomputer 34 controls the rotation of the capstan roller 28 to cause the recording paper 14 to run in synchronization with the printing processing for color development and fixing.

The lamp drive control circuit 42 synchronizes with the Y print and M print processes of the recording paper 14 by the thermal head 24 in accordance with an instruction from the mechanical control microcomputer 34, and the Y fixing fluorescent lamp 26Y and the M fixing fluorescent lamp. Controls turning on / off of 26M. The Y fixing fluorescent lamp 26Y is
The Y-fixing fluorescent lamp 26Y is turned on to emit ultraviolet light having a wavelength of about 425 nm.
4 is fixed. On the other hand, the M fixing fluorescent lamp 26M is a lamp that emits ultraviolet light having a wavelength of about 365 nm. When the M fixing fluorescent lamp 26M is turned on and the recording paper 14 is irradiated with ultraviolet light from the lamp, recording is performed. The M coloring layer of the paper 14 is fixed.

After the printing is completed, the recording paper 14 is cut into a predetermined size by a cutter 52 and discharged by a discharge means (not shown).

In FIG. 1, the image data is input via the SCSI interface 46. However, other data communication means may be used, or a memory card interface or a medium for reading a medium such as a floppy disk drive in a printer. An interface may be provided so that image data can be directly input from a recording medium.

Next, the structure of the skew sensor 20 will be described.

As shown in FIGS. 2 and 3, a photocoupler 56L in which tapered (wedge-shaped) slits (hereinafter, referred to as oblique slits) 54L and 54R are formed on both left and right sides of the conveyance path of the recording paper 14. , 56R are arranged. The skew sensor 20L arranged on the left side from the upstream side of the paper transport path toward the downstream side of the paper feed is called an L skew sensor, and the skew sensor 20R installed on the right side is called an R skew sensor. I do.

The light emitting diode 58L and the phototransistor 60L of the photocoupler 56L constituting the L skew sensor 20L are called an L-LED and an L photo Tr, respectively.
The light emitting diode 58R and the phototransistor 60R of the photocoupler 56R constituting the R skew sensor 20R will be distinguished by expressing them as R-LED and R photo Tr, respectively.

L-LED that makes L-LED 58L emit light
R for driving the drive circuit 62 and the R-LED 58R
-The LED drive circuit 64 is controlled by the mechanical control microcomputer 34. L photo Tr60L, R photo Tr60R
Detects an analog amount corresponding to the amount of light incident through the oblique slits 54L and 54R in the form of a voltage signal. The detection signal from the L photo Tr 60L is guided to a detection amplifier (L) 66, and the detection signal from the R photo Tr 60R is guided to a detection amplifier (R) 68.

The output terminal of the detection amplifier (L) 66 is connected to one input terminal 70 A of the changeover switch 70.
The output terminal of the detection amplifier (R) 68 is connected to the other input terminal 70B of the changeover switch 70. The movable contact 70C of the changeover switch 70 is
Is connected to the input terminal 7 by the control signal from the
It is selectively switched to one of 0A and 70B.

The detection signals output from the detection amplifier (L) 66 and the detection amplifier (R) 68 are input to the A / D converter 72 via the changeover switch 70, where they are converted into digital signals. The detection value digitized by the A / D converter 72 is input to the mechanical control microcomputer 34.
The mechanical control microcomputer 34 distributes (time-shares) the connection time of the changeover switch 70, and performs the L photo Tr 60L on the left and right.
And a detection signal from the R photo Tr 60R.

When the recording paper 14 is fed, the L-LED 58
Since the irradiation light of the L and R-LEDs 58R is partially shielded by the recording paper 14, the detection values (values corresponding to the skew amount of the recording paper 14) detected by the L photo Tr 60L and the R photo Tr 60R change. . In particular, in the case of the present embodiment, when the recording paper 14 moves obliquely, the oblique slits 54L, 5L
Since the amount of light blocked by the 4R changes continuously,
The value (analog voltage value) of the detection signal indicating the detection value also changes continuously in accordance therewith.

The reference value / set value storage memory 74 stores a reference value indicating a skew reference amount of the recording paper 14 and a set value corresponding to a threshold indicating an allowable limit value of the skew amount. I have. The mechanical control microcomputer 34 reads a reference value and a set value corresponding to the recording paper 14 from the memory 74, and automatically sets a set value for skew determination.

FIG. 4 shows the skew state of the recording paper 14 and the L photo T
It is a figure showing the relationship of the detection output of r60L and R photo Tr60R. As shown in the column of FIG. 3A, when the recording paper 14 is fed along a normal conveyance path without skew, the outputs (analog values) of the left and right L-photo Trs 60L and 60R are These become the reference values VrL and VrR, respectively. When photocouplers having left and right equivalent specifications are symmetrically arranged, the reference values VrR and VrL are equal.

If the recording paper 14 is skewed leftward during paper feeding, as shown in the column of FIG.
The amount of light reaching r60L decreases rapidly, and the R photo Tr
The amount of light reaching 60R increases. As a result, the detection output of the L photo Tr 60L becomes smaller than the reference value VrL, and the detection output of the R photo Tr 60R becomes the reference value VrL.
This value is larger than rR.

On the other hand, as shown in FIG.
When 4 moves obliquely to the right, the amount of light reaching the L photo Tr 60L sharply increases, and the amount of light reaching the R photo Tr 60R decreases. As a result, the detection output of the L photo Tr 60L becomes a value larger than the reference value VrL, and the detection output of the R photo Tr 60R becomes a value smaller than the reference value VrR.

When the skew sensor 20 configured as described above is built in the printer 10, the following adjustment work is performed during manufacturing.

At the time of manufacture, the output reference values of the L photo Tr 60L and the R photo Tr 60R are obtained using reference paper. The reference paper refers to a sheet material (or a plate material) having a high rigidity and a light-shielding property, in which the right and left edges are parallelized with high accuracy. This reference paper is introduced into the paper traveling path as a substitute for the recording paper 14, and the detection output (reference paper detection value) of the L photo Tr 60L and the R photo Tr 60R at this time is used as a reference value for the memory (reference value) of the mechanical control microcomputer 34.・ Setting value storage memory) 7
4 is stored. Then, based on this reference value, the upper limit set value and the lower limit set value of each of the skew on the R side and the L side are determined as shown in FIG. 5, and the data indicating the upper limit set value and the lower limit set value are described above. Stored in the memory 74.

In FIG. 4A, the dotted line indicates the reference paper detection value, the one-dot chain line indicates the L upper limit set value, and the two-dot chain line indicates the L lower limit set value. In FIG. 7B, the dotted line indicates the reference paper detection value, the one-dot chain line indicates the R upper limit set value, and the two-dot chain line indicates the R lower limit set value (the same applies to FIGS. 6 and 7).

The skew reference value, upper limit value, and lower limit value are determined according to the width (paper type) of the recording paper 14 to be used. For example, if the paper width is 125 mm, the width 12
Adjustments are made using 5 mm reference paper. As shown in FIG. 6, the detected values of the reference paper having a width of 125 mm are set as reference values (W1rL, W1rR), and based on these reference values, the L upper limit value W1LU, the L lower limit value W1LL, the R upper limit value W1RU, and R A lower limit set value W1RL is determined.

When the paper width is 95 mm, the adjustment is performed using a 95 mm wide reference paper. As shown in FIG. 7, the detected value of the 95 mm wide reference paper is set to the reference value (W2rL, W2
rR), the reference value is set as the detected value of the reference paper as the reference value, and based on this reference value, the R upper limit value W2RU, the R lower limit value W2RL, the L upper limit value W2LU, L
A lower limit set value W2LL is determined.

The reference value and the set value of the upper limit / lower limit are stored in the reference value / set value storage memory 74. By storing reference values and upper / lower limit values corresponding to a plurality of types of recording paper (Wi: i = 1, 2, 3,...) Having different paper widths in the memory 74, the number of paper types can be increased. Can respond.

According to the printer 10 having the above configuration, the TA roll paper 12 attached to the printer 10
The paper type detection sensor 16 detects the paper type, and reads the reference value and the upper and lower limit values corresponding to the paper type from the memory 74 according to the detection, and sets them in the mechanical control microcomputer 34. Then, the detection value detected by the skew sensor 20 is compared with the upper limit set value or the lower limit set value, and when the detected value exceeds the upper limit set value, or when the detected value falls below the lower limit set value, the skew exceeds the allowable amount. Is determined to have occurred.

When the occurrence of the skew exceeding the allowable amount is detected, a warning is displayed on the display device provided on the operation unit 48 of the front panel through the system microcomputer 36, and the paper take-up reel is reset. Is performed. This makes it possible to prevent the occurrence of jams, dirt on paper, and the like. Examples of the warning display method include a mode in which a warning lamp (LED) is turned on and blinked, and a warning message is displayed on a screen of a liquid crystal display.

FIG. 8 is a flowchart showing the operation procedure of the printer according to the present embodiment. When the printing process starts (step S810), first, a sheet feeding motor (not shown) is driven to perform a sheet cueing process (step S812). Then, it is determined whether or not the leading edge of the TA roll paper 12 has been sent from the paper supply storage unit to a predetermined cueing position and cueing of the paper has been completed (step S814). if,
If the cueing is not completed, the process returns to step S812, and the driving of the sheet feeding motor is continued. When the cueing of the paper is completed, the paper feeding operation of the TA roll paper 12 is started (step S816). The recording paper 14 is conveyed by such a paper feeding operation, and when the identification mark reaches the position of the paper type detection sensor 16, the paper type is detected by the paper type detection sensor 16 (step S818).

Then, the paper type of the TA roll paper 12 is determined based on the information read via the paper type detection sensor 16 (step S820).

If it is determined that the recording paper is a recording paper having a paper width of 95 mm (step S822), the memory
The reference value, the upper limit value, and the lower limit value corresponding to mm are read, and these values (referred to as skew limit values) are set as skew determination data in the RAM of the mechanical control microcomputer 34 (step S824). .

In the paper type determination in step S820, when it is determined that the recording paper has a paper width of 125 mm (step S826), a reference value, an upper limit set value, and a lower limit set value corresponding to the paper width of 125 mm are read from the memory 74. The skew limit values are set in the RAM of the mechanical control microcomputer 34 as skew determination data (step S82).
8).

In step S824 or S828, the skew limit value suitable for the paper width is automatically set, and then the printing operation is started again (step S828).
832). Then, it is determined whether a skew exceeding the range of the skew limit value is detected (step S834). If skew is not detected in step S834, the print operation process is performed by controlling the step motor drive circuit 38, the print control circuit 40, and the lamp drive circuit 42 (step S836).

Next, it is determined whether the printing is completed (step S838). If the printing has not been completed, the process returns to step S834, and the determination of skew detection (step S834) and the subsequent print operation processing (step S836) are continued.

If it is determined in step S838 that printing has been completed, the process exits the above loop, executes print ending operation processing (step S840), and ends printing processing (step S842).

If a skew exceeding the skew limit value is detected in step S834, the flow branches to step S844 to stop the printing operation. Then, a paper feed operation stop process (step S846) is executed, and after the paper rewinding process (step S848), the motor drive is stopped (step S850). Then, the warning LED on the front panel blinks,
Alternatively, a message indicating that skew has occurred is displayed on the liquid crystal display. Note that the warning means can be in various modes such as lighting and blinking of a warning lamp, displaying a message on an LCD, outputting a buzzer sound, outputting a warning message by voice, or any combination thereof.

In the paper type determination in step S820, when a paper type other than the one to be used in the printer 10 is set, or when the identification mark cannot be read, the corresponding paper type is determined. If it is determined that there is no seed (step S830), the process proceeds to step S84.
Then, the process proceeds to step S6, where the paper feed stop processing and the paper rewinding processing (step S848) are performed, the motor drive is stopped (step S850), and a warning is displayed (step S8).
52).

According to the present embodiment, the threshold value for skew detection is automatically changed to a value suitable for the paper type even if roll paper having a different sheet width is fed. It is not necessary to reset the detection value for each paper type, or to mechanically adjust the skew sensor.

In the above description, the width of the paper is automatically detected by the paper type detection sensor 16. However, the user manually inputs the paper type (width information) by operating means such as a paper type setting switch. Alternatively, the input may be performed by using the following.

Next, another embodiment of the present invention will be described.

FIG. 9 is a main part configuration diagram showing another embodiment of the present invention. As shown in the figure, a skew detection lever 80 that slides in contact with the edge of the recording paper 14 instead of the skew slit 54 described with reference to FIG.
L and 80R may be used. Skew detection lever 80L, 8
0R is a light shielding plate 82L, 82 having a sector shape, respectively.
R, and each of the skew detection levers 80L, 80R
It is rotatably supported by 4R and 84L. Paper sliding portions 86L, 8 of skew detection levers 80L, 80R
6R has a curved shape to reduce sliding friction. A roller may be provided instead of this curved shape.

Also, springs 88L and 88R are connected to the skew detection levers 80L and 80R so that the paper sliding portions 86L and 86R can surely come into contact with the edge of the recording paper 14, and the springs 88L and 88R By the action, the paper sliding portions 86L and 86R are urged upward in FIG.

According to this configuration, the skew of the recording paper 14 causes the skew detection levers 80L and 80R to swing according to the "leverage principle", and the light shielding plates 82L and 82R are moved by the light passage openings (slits) of the photocoupler. Part) is partially shielded from light, and the amount of light shielding is continuously changed. This makes it possible to detect the skew amount of the paper as a continuous value in an analog manner.

In the event of failure due to paper curl, jam, tear, etc., the above-described skew sensor 20 may be installed on either R or L, unless detection by one sensor is impossible. Similarly, skew can be detected. Further, even if the paper width is changed to a roll paper having a different paper width, only the reference value and the upper and lower limit setting values need to be reset, and there is no need to mechanically adjust the gap.

In the above embodiment, the reference value and the upper and lower limit set values were input in advance at the time of manufacture, but the data is stored in the memory 74 by a wired or wireless communication function using a host device such as a personal computer (corresponding to data providing means). Is downloaded, the contents of the memory 74 can be rewritten at any time.

In the above description, an example in which the present invention is applied to a TA printer using roll paper has been described. However, the present invention is not limited to a printer, but may be a copying machine, a scanner, or the like.
The present invention can be widely applied to equipment provided with a means for conveying a sheet material.

[0069]

As described above, according to the skew detecting apparatus for a sheet material according to the present invention, means for detecting the skew amount of the sheet material as a continuous amount is provided, and the type of paper used is detected. Thus, the skew detection threshold value suitable for the paper type can be automatically set, so that the mechanical adjustment of the sensor, which is conventionally required every time the paper type is changed, becomes unnecessary.
As a result, the adjustment time can be shortened, and the manufacturing cost can be reduced.

Even when it is desired to use different types of paper in the same printer, it is not necessary to readjust the skew sensor mechanically, and skew of different types of paper can be detected by one type of detecting means. Can be detected.

[Brief description of the drawings]

FIG. 1 illustrates a configuration of a printer to which the present invention is applied.

FIG. 2 is a diagram showing a slit shape of a skew sensor used in the printer shown in FIG. 1;

FIG. 3 is a diagram illustrating a configuration of a skew sensor used in the printer illustrated in FIG. 1;

FIG. 4 is a diagram illustrating a relationship between a skew state of recording paper and a detection output of a phototransistor for skew detection.

FIG. 5 is a diagram used to explain a method of setting the output of a phototransistor for detecting skew;

FIG. 6 is a diagram used to explain a method of setting a reference value and a set value corresponding to a paper width of 125 mm;

FIG. 7 is a diagram used to explain a method of setting a reference value and a set value corresponding to a paper width of 95 mm;

FIG. 8 is a flowchart showing an operation procedure of the printer shown in FIG.

FIG. 9 is a main part configuration diagram showing another embodiment of the present invention.

[Explanation of symbols]

10 ... printer, 12 ... TA roll paper (sheet material),
14: recording paper (sheet material), 16: paper type detection sensor (identification means), 20: skew sensor (skew detection device), 54
L, 54R: diagonal slit, 56L, 56R: photo coupler (detection means), 34: mechanical control microcomputer (automatic threshold setting means, judgment means), 36: system microcomputer (automatic threshold setting means, judgment means) .. 74 memory (storage means)

Claims (3)

[Claims] 1. A skew detection device for detecting skew of a fed sheet material, the device comprising: identification means for identifying a width dimension of a used sheet material; and detecting a skew amount of the sheet material. Detecting means for outputting a detection value which can be continuously changed in accordance with the amount of skew; and a threshold necessary for skew determination of the sheet in accordance with the width of the sheet identified by the identifying means. A threshold value automatic setting unit for automatically setting a value; and a determination unit for determining whether a detection value obtained from the detection unit exceeds the threshold value. Skew detector. 2. The sheet skew detecting apparatus according to claim 1, further comprising a storage unit for storing the data indicating the threshold value, wherein the data to be stored in the storage unit is externally stored. A sheet material skew detecting device configured to be received from the data providing means. 3. The sheet skew detecting apparatus according to claim 1, wherein the apparatus stores threshold data necessary for skew determination of a plurality of types of sheet materials having different sheet widths. Means for automatically setting a threshold value by reading data corresponding to the sheet material from the storage means in accordance with the result of identification by the identification means. Material skew detector.