JPH0812146A - Medium carrying device - Google Patents

Abstract

PURPOSE:To simply converge a skew of continuous paper such as roll paper by detecting a prescribed skew quantity of a medium, and controlling a back tension adjusting mechanism to respectively adjust left and right back tensions in the carrying direction of the medium according to the detecting result. CONSTITUTION:A medium skew quantity detecting part 2 is composed of a sensor 5 to detect an end surface position of a medium 1 and a skew quantity detecting part 6 to detect a difference between a present sensor output value and a sensor output value at the prescribed time point of the medium 1 as a skew quantity of the medium 1. A back tension adjusting mechanism 3 is composed of two sets of rollers to respectively press prescribed parts of left and right half surfaces of the medium 1 and two sets of power generating brakes to respectively control back tensions to the medium 1 by the respective rollers. The back tension adjusting mechanism 3 is controlled by a back tension control part 4 according to a detecting result of a skew quantity of the medium 1, and a skew is converged by making back tensions of a paper sheet different from each other on the left and the right.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a medium conveying device in a printer or the like which prevents the medium from skewing.

For example, in a printer using roll paper, once skew of the paper occurs, even if the printed portion is cut and issued, the skew tendency is maintained as it is, and a jam is finally generated.

For this reason, there is a demand for a medium conveying device that converges the skew of the medium with a simple mechanism.

[0004]

2. Description of the Related Art FIG. 12 is a diagram showing an example of a conventional receipt printer, which shows an example of a printer for issuing receipts provided in an automatic transaction device or the like.

In this printer, the roll paper 18 is normally used, and when the roll paper 18 is replenished, the roll paper 18 is first fixed at a predetermined position by the paper holder 19, and then two holder rollers 12 are used. The paper leading edge 18a
Is passed between the platen 15 and the print head 16 via the position fixing rollers 14a and 14b, and then the holder roller 12 is lowered.

The roll paper 18 is provided with perforations at predetermined intervals and a timing mark 17 immediately after that, and a timing mark sensor 13 provided on the paper bed 11 is provided.
(In the case of the reflection type, the timing mark 17 is used as the reference to detect the timing mark by the back side of the sheet shown in the drawing), and the printing of the transaction statement by the print head 16 is started, and the transaction is cut off at the next perforation and discharged as a receipt.

The paper is fed by the tension (tension) generated by the rotation of the platen 15. However, the constant back tension (the rearward tension) by the holder roller 12 which is rotated by the paper feeding causes the paper to be slackened. It can be sent.

[0008]

The roll paper 18 is usually
The paper is conveyed by the frictional force between it and the rotating platen 15, but if there is a certain amount of deviation between the set position of the roll paper 18 and the paper position on the platen 15, the paper is pulled by the platen 15 and skewed. Tends to do. Since the roll paper 18 is continuous paper, once the skew starts, the skew amount gradually increases as the sheet is conveyed, and finally, the printed portion protrudes from the sheet or a jam occurs.

Further, the tension of each roller with respect to the medium is not uniform on the left and right, which also causes skewing.
In order to solve such a problem, the side surface of the paper, A in FIG.
It is conceivable to provide a wall on the surface or the like to stop skewing, but when thin paper is used, jamming is particularly likely to occur.

In view of the above problems, it is an object of the present invention to provide a medium carrying device having a simple mechanism for converging the skew of the medium.

[0011]

In order to solve the above problems, the medium carrying device of the present invention is a diagram showing the principle (1) of the present invention in FIG. 1, and the principle (2) of the present invention in FIG. (1) The back tension applied to the medium 1 is controlled to show the medium 1
A medium conveying device for preventing the skew of the medium 1, a medium skew detecting unit 2 for detecting a predetermined skew of the medium 1, and a back tension adjustment for adjusting left and right back tensions of the medium 1 in the transport direction. A mechanism 3 and a back tension controller 4 that controls the back tension adjusting mechanism 3 according to the skew amount of the medium 1 to converge the skew of the medium 1 are provided. (2) The medium skew amount detection unit 2 of the above (1) is one sensor 5 that detects the position of one end face of the medium 1 with respect to the transport direction, the current sensor output value and the medium 1 at a predetermined time. A skew amount detection unit 6 that detects a difference from the sensor output value as the skew amount of the medium 1 is provided. (3) The other medium skew feeding amount detection unit 2 of the above (1) has two sets of sensors 8 for detecting the left and right end face positions with respect to the transport direction of the medium 1 and a difference between the two sets of current sensor output values. A skew amount detection unit 9 that detects the skew amount of the medium 1 based on the difference between the two sensor output values at a predetermined time of the medium 1. (4) In the above (2) or (3), the sensor output value at a predetermined time is configured to store the sensor output value at the time of initial setting of the medium. (5) In (2) or (3) above, the sensor output value at the time of initial setting of the medium 1 is measured, and an alarm is generated if the sensor output value or the difference between the two sensor output values is outside the specified range. To configure. (6) The back tension adjusting mechanism 3 of (1) above is the medium 1
Of the pair of rollers for pressing predetermined portions of the left half surface and the right half surface with respect to the conveying direction of the sheet, and two pairs of power-generating brakes respectively connected to the rollers and controlling back tension to the medium 1 by the rollers. To configure. (7) The other back tension adjusting mechanism 3 of (1) above is composed of a roller that presses the medium 1 in the left-right direction that is perpendicular to the transport direction, and an eccentric cam that changes the inclination of the roller in the pressing direction. (8) In the above (3), 2 provided in the medium skew amount detection unit 2
A medium width discriminating unit 10 for discriminating the medium width based on the output values of the pair of sensors 8 is provided. (9) In the above (2) or (3), the medium skew amount detection unit 2
A mark detection unit for detecting the mark attached to the medium 1 is provided by the output of the sensor included in.

[0012]

[Action]

(1) The medium skew amount detection unit 2 detects a predetermined skew amount of the medium 1 (including a deviation from a predetermined position of the medium 1 and a skew direction),
The back tension control unit 4 controls the back tension adjusting mechanism 3 based on the detected skew feeding amount, and the medium 1
The skew convergence control is performed. (FIG. 1) To explain by applying it to FIG. 10 of the conventional example, for example, the sensor detects the position of the sheet end face at the position after printing, and the skew amount (deviation from the initial set position, the symbol indicates the skew direction). ) Is detected,
A back tension adjusting mechanism 3 provided between the platen 15 and the roll paper holder 19, for example, at the position of the paper bed 11.
Control the paper back tension (backward tension)
The left and right sides are different depending on the skew direction.

As a result, the tension (difference between the tension of the platen 15 and the back tension by the back tension adjusting mechanism 3) applied in the sheet conveying direction differs depending on the skew amount and skew direction on the left and right of the sheet. , Converge the skew. It should be noted that the convergence of the skew feeding is realized by a slip or the like between the paper and the platen. (2) As the medium skew amount detecting section 2, as described above, one set of sensors 5 for detecting the end face position of the medium 1 is provided at a predetermined position after printing, and the skew amount detecting section 6 is The difference (corresponding to the skew amount of the medium 1) between the current sensor output value of the sensor 5 and the sensor output value when the medium 1 is initially set (at a predetermined time) is detected as the skew amount. (FIG. 1) Then, the back tension control unit 4 controls the back tension adjusting mechanism 3 so that the skew feeding amount (difference in sensor output value) becomes "0". (3) As another medium skew amount detection unit 2, two sets of sensors 8 for detecting the left and right end surface positions of the medium 1 are provided, and the skew amount detection unit 9 detects, for example, the difference between the output values of the two current sensors. (ΔXn)
And the difference (ΔX0) between the two sensor output values when the medium 1 is initially set (predetermined time point) are compared to determine the skew amount (ΔX0−ΔXn) of the medium 1 (in this case, the symbol also represents the skew direction). ) Is calculated. (FIG. 2) Then, the back tension adjusting mechanism 3 is controlled so that (ΔX0−ΔXn) becomes “0” or the difference between the outputs of one of the sensors becomes “0”. (4) As the predetermined time point, the sensor output value at the initial setting is used as described above. Therefore, the sensor output value at the time of initial setting or the difference between the two sets of sensor output values is stored in a memory or the like. (5) Further, when the sensor output value at the initial set position is out of the predetermined range, an alarm is generated. This can help the operator during initial set up. (6) The back tension adjusting mechanism 3 includes two sets of rollers that press the left and right surfaces of the medium 1, and two sets of power generation that are respectively connected to the rotating shafts of the rollers and that can adjust the load current. Composed of a brake. Then, the back tension control unit 4 controls one or both of the power-generating brakes according to the skew amount to change the left and right back tensions. (FIG. 1) (7) As another back tension adjusting mechanism 3, a roller that presses the medium 1 in a direction orthogonal to the transport direction and a lateral pressing force of the roller that is variable in the transport direction, that is, the roller is used. The eccentric cam has a variable inclination in the pressing direction, and the rotation angle of the eccentric cam is controlled according to the skew amount. (8) When two sets of sensors 8 are used as the medium skew amount detection unit 2, the medium width determination unit 10 determines the medium width based on the sensor output value. As will be described later, the media width can be identified by the average value of the two sensor outputs. This allows
The medium width detecting sensor and the skew amount detecting sensor can be shared. (9) When detecting the mark attached to the medium 1, the mark detection unit outputs to the end face detection sensor (the sensor may be one set or two sets, depending on the mark position). Detect the mark based on. As a result, the mark detecting sensor and the skew amount detecting sensor can be used in common.

As described above, the skew amount of the medium 1 is detected from the current sensor output value and the sensor output value at the predetermined time, and the back tension of the medium is controlled based on this skew amount. Particularly in a printer or the like that uses roll paper, the skew of the paper can be easily converged.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 is an explanatory view when one sensor is used, FIG. 4 is an explanatory view when two sensors are used, and FIG.
Is a perspective view of the first embodiment, FIG. 6 is a detailed view of the eccentric cam mechanism in the first embodiment, FIG. 7 is a configuration diagram of the first embodiment, FIG. 8 is a flowchart view of the first embodiment, and FIG. 9 is a perspective view of the second embodiment, FIG. 10 is a configuration diagram of the second embodiment, and FIG.
FIG. 7 is a flow chart of the second embodiment. Note that the same reference numeral represents the same object throughout the drawings.

In the present embodiment, a printer device will be described in which roll paper is used and the roll paper is conveyed by tension caused by rotation of a platen. The skew amount of the paper shall be detected by the paper end face position at a predetermined position after printing, and the paper end face position shall be measured for each predetermined paper transport distance to obtain the deviation from the paper end face position at the time of initial setting. Convergence control.

FIGS. 3 and 4 show a light receiving sensor (hereinafter referred to as a light amount detecting element) of the method for detecting the position of the end surface of the sheet.
For detecting the position of the end face by the change in the amount of light in the CCD
Each of the methods for detecting the position of the end face from the image data near the end face of the paper obtained by the (charge coupled device) is described.

A light transmission type or light reflection type sensor (light amount detecting element) as a sensor for detecting the end face position by a change in light amount.
There is. This is because the light receiving surface is a straight line, as shown in FIG.
And a wide-angle one, for example, one in which a plurality of light-receiving elements are arranged in a straight line and the sum of the outputs is obtained,
That is, an output corresponding to the light receiving area shielded by the paper is obtained, and the light receiving surface is arranged so as to be orthogonal to the paper transport direction.

FIG. 3 shows the case of detecting the amount of skew when one sensor is used, and shows the case of using a transmission type sensor as the sensor and skewing in the direction of the arrow shown in the figure. Is. Here, when using the light intensity detection element as described above, the standard media set position (sensor output value XS) is set when the paper edge is at the center of the light receiving sensor, and the initial paper set position (sensor output value X0) is set. The quality of the initial set position is determined from the difference with XS.

Further, the difference between the initial set position X0 and the current position (sensor output Xn) is taken as the skew amount at that time, and the skew amount becomes "0", that is, the sheet returns to the initial set position. Back tension control.

The same applies when a CCD is used.
From the image data (transmitted light in the figure) of one line read from the CCD, the number of pixels from the read start position to the end face position is counted, and the standard set position (the number of pixels of one line is 1
/ 2), the initial set position (the number of pixels at the time when the paper is set), and the current position are respectively discriminated, and the back tension control for discriminating the quality of the initial set position and correcting the deviation from the initial set position is performed.

FIG. 4 shows the case where two light transmission type sensors are used, and the case is slanted in the direction of the arrow shown in the figure. Normally, the difference between the outputs of the two sets of sensors S1 and S2 is "0".
At this time, the sensors S1 and S2 are arranged so as to be the standard set position.

When the light quantity detecting element is used, assuming that the sensor output values at the initial setting are S1 = X01 and S2 = X02, respectively, the difference between the sensor output values at the initial setting a0 = S1-S2 = X0
1 −X02 represents the deviation from the difference (here "0") in the sensor output value at the time of standard setting, so compare this value (absolute value) with the allowable value to judge the quality of the initial setting position. .

The difference between the sensor output values at the current position
The difference between an = S1−S2 = Xn1−Xn2 and a0 represents the amount of skew at that point (deviation from the initial set position, including the sign), so this (a0−an) becomes “0”. Back tension control.

The same applies to the case where two sets of CCDs are used. Similarly, the deviation is calculated from the number of pixels from the reading start position to determine whether the initial set position is good or bad, and the back tension control is performed.

When the above two sensors are used, the medium width can be discriminated. Hereinafter, it is assumed that the setting positions of sheets having different medium widths are sorted from the center. FIG.
When the light amount detection element is used in, the physical paper edge position PS1, P01, Pn1 is the output of the sensor S1, XS1,
Corresponds to X01, Xn1 and PS2, P02, Pn2 correspond to the output of sensor S2 and XS1, X01, Xn1.
It is possible to determine the medium width from the difference between and the output value itself.

For example, if the medium width is detected at the initial set position (P01, P02), the difference a0 between S1 and S2 is within a predetermined range (preferably "0"), and the difference between S1 and S2 is When the output value (X01 or X02) is within the predetermined value range, the medium width can be specified.

That is, even if a0 is "0" for other medium widths, the medium width can be specified because the output value of S1 or S2 is different. In FIG. 4, a small output value of the sensor S2 indicates that the medium width is large, and a large output value of S2 indicates that the medium width is small. Therefore, A4, B5
For example, when there is a difference in medium width, the medium width can be easily determined. In this case, the detection width of the sensor is expanded so that all the end face positions of the medium used can be detected.

The same applies when a CCD is used. Two sets of C
The medium width can be determined from the pixel position on the edge surface of the CD sheet. In particular, if the intersensor distance and interpixel distance are known, the approximate absolute value of the medium width can also be measured.

When detecting the timing mark 17, C
It is easy to use a CD. Since the image data of the timing mark 17 is obtained from the CCD on the side to which the timing mark 17 is attached, this is detected and a detection signal is output. This signal is used for timing such as printing start.

An example of a printer using the above sensor will be described below. [First Embodiment] In the first embodiment, the skew amount is detected by detecting the end face position with one sensor, and the inclination of the roller that presses the sheet by the eccentric cam is changed to change the left and right sides of the sheet. An example of controlling the back tension will be shown.

FIG. 5 shows an example applied to FIG. 10 of a conventional example, in which an eccentric cam mechanism 31 is provided instead of the holder roller 12 (roller 32 in FIG. 6). Figure 6
FIG. 3 is a detailed view of the eccentric cam mechanism 31. The roller 32 corresponding to the holder roller 12 includes a spring mechanism 52 and two right and left.
A predetermined gap is provided between the pair of eccentric cams 51 and the paper bed 11, and the inclination of the shaft 53 of the roller 32 is changed by the rotation of the two eccentric cams 51.

That is, the two sets of eccentric cams 51 are fixed to the rotation shaft of the stepping motor 29 (held on the paper bed 11) so that the eccentric positions are different from each other, and when the stepping motor 29 rotates, The eccentric cam 51 rotates and the inclination of the shaft 53 of the roller 32 changes. This allows
The back tension applied to the paper 18 passing through the gap between the paper bed 11 and the roller 31 changes between the left and right of the paper. Normally, the back tension is constant on the left and right,
The position of the eccentric cam 51, that is, the position of the stepping motor 29 is set, and the stepping motor 29 is rotated forward or backward by a predetermined number of steps according to the skew direction and the skew amount.

FIG. 7 is a block diagram of the first embodiment using the eccentric cam mechanism 31 described above. Where 21
Is a standard medium set position memory in which the sensor output value XS of the standard medium set position shown in FIG. 3 is stored. This value is output from the paper end surface detection sensor 25 by, for example, accurately setting the paper at the standard medium setting position (for example, the device has a mark) and pressing the set button when the device is installed. The value XS is stored.

Reference numeral 22 denotes a medium set position determination unit, which detects the sensor output value X0 at the time of initial medium setting and calculates the absolute value of (XS-X0) (if the left and right set position allowable values are different, by sign). If the value is larger than the allowable value, "abnormal" is notified to the main control unit (not shown) as a set status notification, and a message for resetting is displayed. If the value is "normal" within the allowable value, the medium setting status lamp 23 is turned on.

Reference numeral 24 is a medium skew amount detection unit. Where 25
Is a paper edge detection sensor (either a reflective type or a transmissive type, but a reflective type in the figure) as a light amount detection element, and is set at a predetermined position after printing, for example, as shown in FIG.

Reference numeral 26 is an A / D converter which converts the analog output of the sensor 25 into a digital signal. 27 is an initial medium set position memory, which is the output value X0 of the sensor 25 when the paper is normally set, that is, the roll paper 18 is set in the paper holder 19, and the leading edge of the paper is guided to the position after the sensor 25. The value of the A / D conversion unit 26 when set (for example, by detecting that the holder roller 12 is lowered) is set. It should be noted that this value is used for determining whether the initial set position is correct or not and for the skew convergence control.

Reference numeral 28 denotes a back tension control unit, which outputs a sensor output at each time when the paper 18 is conveyed by a predetermined distance.
Xn is acquired from the A / D conversion unit 26, and the eccentric cam is controlled by controlling the rotation of the stepping motor 29 so that X0−Xn → 0.
Rotate 51. The encoder 30 outputs the control result for the stepping motor 29 and is used for controlling the rotation of the stepping motor 29.

A stepping motor 34 rotates the platen 15 and rotates according to the number of pulses output from the print controller 35. As a result, the paper 18 is conveyed at a predetermined speed at the time of line feed, for example.

A step counter 33 counts the number of pulses to the stepping motor 34, and outputs a control command to the back tension control unit 28 every time a predetermined number is counted, and the back tension control unit 28 outputs each control command. Performs skew control.

A print control unit 35 develops the input print data into a pattern, and a stepping motor 34 is provided for each line feed.
The print head 16 is driven while controlling the rotation of the paper, and the roll paper 18 is printed.

The following operation is performed by the receipt issuing printer having the above configuration. See FIG. 8 (S1) The operator performs the initial setting for supplying the roll paper 18. (S2) At this time, the medium set position determination unit 22 reads the sensor output X0 at the initial setting from the A / D conversion unit 26, reads XS from the standard medium set position memory 21, and compares it with X0. (S3) If the initial set position is within the error (within the allowable value), an alarm is generated and the set is restarted. (S4) If normal, the medium setting status lamp 23 is turned on and the sensor output value X0 is set to the initial medium setting position memory.
Store in 27. (S5) When printing is started, the print control unit 35 develops print data into a dot pattern and drives the print head 16 to serially print on the roll paper 18. Then, each time one line is printed, a predetermined number of pulses are output to the stepping motor 34, and the platen 15 is rotated by the distance between lines. This causes a line break and the next line is printed.

The step counter 34 counts the number of pulses to the stepping motor 34, and outputs a control command to the back tension controller 28 each time a predetermined number is counted. (S6) By this control command, the back tension control unit 28
Retrieves the initial medium set position information X0 stored in the initial medium set position memory 27, reads the current output value Xn of the A / D converter 26, and calculates (X0−Xn),
The number of pulses for rotating the eccentric cam 51 (the rotation direction is determined according to the sign) to the angle corresponding to this value is output to the stepping motor 29. At this time, the rotation angle of the control result is confirmed by the output of the encoder 30.

The above-described skew convergence control shown by S5 and S6 is repeatedly performed every time the paper 18 is conveyed by a predetermined distance, for example, every several lines are printed. [Second Embodiment] In this embodiment, two sets of CCDs (reflective type) are used as the medium skew amount detection unit 2 in FIG. 1, and the back tension adjusting mechanism 3 is used in FIG. As shown in Fig. 1), two sets of rollers 49a, 49b are provided on the left and right sides of the paper conveyance direction, and the motors 48a, 48b (power generation brakes) connected to these rollers 49a, 49b respectively apply brakes to the left and right sides of the paper. Is an example of controlling the back tension of the.

Further, here, it is assumed that the medium width and the timing mark 17 are detected by the CCD output. In FIG. 9, the CCD 38 and the CCD 40 are arranged so as to detect the images on both side end surfaces of the paper leading end portion 18a as shown in FIG. 8, and by widening the detection width,
It allows the use of paper of different widths.

Reference numeral 39 denotes an image processing section, which is the CCD 38,
The accumulated charge amount is read from the CCD 40 in a predetermined cycle and converted into multi-valued image data. The timing mark 17 is discriminated by this multi-valued conversion.

Reference numeral 42 denotes a comparison unit, which detects the end face position at each time point from the image data read from the CCD 38 and CCD 40 by the method described with reference to FIG.
Is output.

Reference numeral 43 is an initial medium set position determination unit, which is a comparison unit.
End face position information ΔP0 at initial setting output from 42
The normality of the initial set position (normal when ΔP0 is less than or equal to the allowable value) is determined by [absolute value of (ΔP01-ΔP02)].

Reference numeral 37 denotes a medium width determination unit, which is obtained from one of the CCDs (here, CCD 40) output from the image processing unit 39 when the initial medium setting position determination unit 43 notifies that the medium is normal. The image data
The medium width is determined by comparing the edge position obtained from the number of pixels with the edge position corresponding to the medium width stored in advance in the medium information memory 36. The print start position in the row direction is set by this media width determination.

Reference numeral 41 denotes a mark detection unit, which verifies the image data (multi-valued) from the CCD 38, in either case,
When the timing mark 17 is detected (for example, when a region represented by a black signal exists at a predetermined position and has a predetermined size is determined as a timing mark), a mark detection notification is output. This mark detection notification determines the print start timing (print start line). Since the CCD is set to receive the reflected light here,
The timing mark 17 is attached to the back surface (print surface) of the paper in FIG.

Reference numeral 46 denotes a back tension control section, which is a platen.
Back tension control is performed every time 15 rotates by a predetermined angle (control command from the step counter 33). This back tension control is performed by the difference ΔPn between the end face positions obtained from the CCDs 38 and 40 at the present time and the difference ΔP0 between the end face positions at the time of initial setting.
And the motor 48a / so that ΔP0−ΔPn = 0.
The back tension of the rollers 49a / 49b is controlled by the braking force of either or both of the rollers 48b. Note that FIG. 10 shows only one of the left and right two sets.

As one of the methods of applying back tension to the roller 48a, the motor 48a (and the motor 48b
There is a method of changing the resistance between the winding terminals.
In this case, a plurality of resistors R1 and Rn having different resistance values are provided, and the corresponding driver 47a is turned on / off to connect one of these resistors between the winding terminals. At this time, as an initial value, the braking force of both the motors 48a and 48b is set to be the same, and one braking force is increased and the other is weakened according to the skew direction and the skew amount.

Another method is to apply a regenerative brake. When the regenerative brake is applied, for example, in the case of PWM (pulse width modulation) driving, the brake duty is increased when the back tension is increased, and the brake duty is decreased when the back tension is decreased.

With the above configuration, the control as shown in FIG. 11 is performed. (S1) First, the roll paper 18 is set. (S2) At this time, the comparison unit 42 obtains the difference ΔP0 between the sensor output values at the time of initial setting, and the initial medium set position determination unit 43 stores in the medium information memory 36 whether or not ΔP0 is within an error. Judge from the allowable value. (S3) If it is out of the error range, an alarm is issued to instruct to set again. (S4) If it is in the error range, the medium set status lamp 23 is turned on and its ΔP0 is set to the initial medium set position memory 27.
To be stored. (S5) When printing is started, the step counter 33 calculates the transport distance of the medium, and outputs a control command to the back tension controller 46 each time the medium is transported by a predetermined distance. (S6) As a result, the back tension control unit 46 reads ΔPn from the comparison unit 42, obtains the resistance value corresponding to ΔP0−ΔPn, and turns on the corresponding driver 47a (same for the other driver) to turn on the motor. Control the braking force.

This back tension control is repeated every time the paper 18 is conveyed by a predetermined amount, and the balance of the left and right back tension is changed so that the skew feeding is converged. As described above, since the skew amount is detected based on the initial setting position and the current position of the sheet and the left and right back tensions of the sheet are controlled based on this skew amount, the skew amount of the roll sheet or the like is controlled. Can be easily converged.

Needless to say, the combination of the sensor and the back tension adjusting mechanism is not limited to the above embodiment.

[0057]

As described above, according to the present invention, the skew amount is calculated based on the initial set position of the medium and the current position, and the left and right back tensions of the sheet are controlled based on the skew amount. The effect of easily converging the skew of the medium, especially continuous paper such as roll paper. In addition, since skew can be converged without providing a wall or the like to prevent skew in the vicinity of the end face of the paper, it is easy to use thin paper as a medium. There is an effect that it can be widely adopted in general printers, such as being able to notify the operator of whether the set position is good or bad, and can be realized at low cost because it can be shared with a sensor for detecting the medium width and a mark detecting sensor.

[Brief description of drawings]

FIG. 1 is a diagram showing the principle (1) of the present invention.

FIG. 2 is a diagram showing the principle (No. 2) of the present invention.

FIG. 3 is an explanatory diagram when one sensor is used.

FIG. 4 is an explanatory diagram when two sensors are used.

FIG. 5 is a perspective view of the first embodiment.

FIG. 6 is a detailed view of the eccentric cam mechanism in the first embodiment.

FIG. 7 is a configuration diagram of a first embodiment.

FIG. 8 is a flowchart of the first embodiment.

FIG. 9 is a perspective view of the second embodiment.

FIG. 10 is a configuration diagram of a second embodiment.

FIG. 11 is a flowchart of the second embodiment.

FIG. 12 is a diagram showing an example of a conventional receipt printer.

[Explanation of symbols]

1 medium 2 medium skew amount detecting unit 3 back tension adjusting mechanism 4 back tension control unit 5 sensor 6 skew amount detecting unit 8 sensor 9 skew amount detecting unit 10 medium width determining unit 11 paper bed 12 holder roller 13 timing mark sensor 14a, 14b Position fixing roller 15 Platen 16 Print head 17 Timing mark 18 Roll paper 18a Paper leading edge 19 Paper holder 21 Standard media set position memory 22 Media set position determination unit 23 Media set status lamp 24 Media skew amount detection unit 25 Paper End face detection sensor 26 A / D converter 27 Initial medium set position memory 28 Back tension control unit 29 Stepping motor 30 Encoder 31 Eccentric cam mechanism 32 Roller 33 Step counter 34 Stepping motor 35 Print control unit 36 Medium information memory 37 Medium width determination unit 38, 40 Paper edge detection sensor CCD 39 Image processing unit 41 Mark detection Part 42 comparison unit 43 the initial medium setting position determination unit 46 back tension controller 47a driver 48a, 48b motor 49a, 49b roller 51 eccentric cam 52 spring mechanism 53 rotation axis R1, Rn resistor

Claims (9)

[Claims] 1. A medium conveying device for controlling a back tension applied to a medium (1) to prevent the medium from skewing, and a medium skewing amount detecting unit (1) for detecting a predetermined skewing amount of the medium (1). 2)
A back tension adjusting mechanism (3) for adjusting the left and right back tensions of the medium with respect to the conveying direction, and controlling the back tension adjusting mechanism according to the skew amount of the medium to control the skew of the medium. A medium conveying device comprising a back tension control unit (4) for converging. 2. The medium skew amount detection unit (2) detects one of the end face positions in the transport direction of the medium.
A number of sensors (5), and a skew amount detection unit (6) for detecting a difference between the current sensor output value and the sensor output value at a predetermined time of the medium as a skew amount. The medium carrying device according to claim 1. 3. The medium skew amount detection unit (2) detects the positions of the left and right end surfaces with respect to the transport direction of the medium, respectively.
A pair of sensors (8) and a skew amount detection unit (9) for detecting the skew amount of the medium based on the difference between the output values of the two current sensors and the difference between the sensor output values of the two sets at a predetermined time of the medium. 3. The medium transport apparatus according to claim 1, further comprising: 4. The sensor output value at the predetermined time point is
4. The medium carrying device according to claim 2, wherein a sensor output value when the medium is initially set is stored. 5. A sensor output value at the initial setting of the medium is measured, and an alarm is generated when the sensor output value or the difference between the two sensor output values is outside a predetermined range. The medium carrying device according to claim 2 or 3. 6. The back tension adjusting mechanism (3) comprises:
Two sets of rollers that respectively press a predetermined portion of the left half surface and a predetermined portion of the right half surface with respect to the medium transport direction;
2. The medium conveying apparatus according to claim 1, wherein the medium conveying device is composed of two sets of power-generating brakes that are respectively connected to the rollers and control back tensions of the rollers to the medium. 7. The back tension adjusting mechanism (3) comprises:
2. The medium carrying device according to claim 1, comprising a roller that presses the medium in a left-right direction that is perpendicular to the carrying direction, and an eccentric cam that changes the inclination of the roller in the pressing direction. 8. A medium width discriminating unit (10) for discriminating the medium width based on the output values of two sets of sensors (8) provided in the medium skew amount detecting unit (2). 3. The medium transport device described in 3. 9. The mark detecting unit for detecting a mark attached to the medium by the output of a sensor provided in the medium skew amount detecting unit (2). 3. The medium transport device described in 3.