JP2001232876A - Printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of color misregistration caused by the difference between the feed-out quantity and return quantity of recording paper. SOLUTION: A feed roller 21 for feeding recording paper 14 in a feed direction and a return direction is provided to a printer 11. A spike is provided on the outer peripheral surface of a capstan roller 41 and, since the biting-in quantity of the spike is changed at the position of an auxiliary roller 43 corresponding to the rigidity of the recording paper 14, the feed quantity of the recording paper 14 changes. The quantity of rotation of a drive motor 18 during a period when the recording paper 14 is fed first by a distance LO is counted and the rigidity value of the recording paper 14 is determined from this quantity of rotation. A pressure force regulator 44 regulates the pressure force of the auxiliary roller 43 corresponding to the rigidity of the recording paper 14. By this constitution, the slaking or flotation of the recording paper 14 at the position of the auxiliary roller 43 is removed and the feed quantity of the recording paper 14 is corrected to become same as the return quantity thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printer for recording an image while reciprocating a recording sheet, and more particularly, to a printer for preventing a difference between a feeding amount and a retraction amount of the recording sheet. Things.

[0002]

2. Description of the Related Art On a support, at least three types of thermosensitive coloring layers, for example, a cyan thermosensitive coloring layer, a magenta thermosensitive coloring layer,
2. Description of the Related Art A color thermal printer (hereinafter, referred to as a printer) that prints a full-color image by using a color thermal recording paper (hereinafter, referred to as a recording paper) in which yellow thermosensitive coloring layers are sequentially formed is known. In this printer, a thermal head is pressed against a recording sheet during printing, and a yellow image, a magenta image, and a cyan image are sequentially recorded in three color planes. Thereby, a full-color image is obtained.

In a one-head type printer, as shown in FIG. 11, a transport roller unit 102 alternately performs feeding of the recording paper 101 from a paper feeding unit and pulling back of the recording paper 101 to the paper feeding unit. The transport roller unit 102 includes the drive motor 10
6, a pinch roller 104 disposed at a position facing the capstan roller 103 and nipping the recording paper 101 together with the capstan roller 103, and a capping roller 103 for moving the recording paper 101 to the capstan roller 103. It comprises an auxiliary roller 107 for increasing the winding angle.

[0004] The auxiliary roller 107 increases the winding angle of the recording paper 101 around the capstan roller 103 and improves the conveyance force of the recording paper 101. Auxiliary roller 1
Reference numeral 07 is pressed by the capstan roller 103 and is driven to rotate when the recording paper 101 is conveyed.

[0005] When the auxiliary roller 107 is provided, the recording paper 10 is interposed between the pinch roller 104 and the auxiliary roller 107.
1 slack occurs. This slack is likely to occur at the time of feeding, and hardly occurs at the time of pulling back. This is because at the time of feeding, the recording paper 101 fed by the pinch roller 104 and the capstan roller 103 is
This is because, while being extruded toward 7, it is pulled out from the auxiliary roller 107 at the time of retraction.

When the recording paper 101 is slackened at the time of feeding, when the recording paper 101 is reciprocated and conveyed, the recording paper 1 when the drive motor 106 is rotated forward by a predetermined amount (at the time of feeding).
A difference occurs between the transport amount of No. 01 and the transport amount of the recording paper 101 when the drive motor 106 is rotated in the reverse direction by a predetermined amount (at the time of retraction).

When this difference occurs, the positions at which the recording of each image is started do not match, and a so-called misregistration occurs in the printed image. To solve this problem, conventionally, by increasing the wrap angle of the recording paper around the capstan roller, the conveying force of the capstan roller has been enhanced,
By predicting and correcting the difference between the transport amount at the time of sending out and at the time of pulling back from empirical values, and by improving the transport mechanism,
By suppressing the difference in the amount of conveyance, the occurrence of misregistration is suppressed to a practically allowable range.

[0008]

However, the lower the stiffness of the recording paper, the more easily it bends. Therefore, as shown in FIG. 12, the slack amount of the recording paper increases as the stiffness of the recording paper decreases. The rigidity of the recording paper differs depending on the type of the recording paper. Further, even the same type of recording paper differs depending on environmental conditions such as temperature. For this reason, even if the stiffness of the recording paper is assumed in advance, the stiffness of the actually fed recording paper may deviate from the assumed value, and the occurrence of the misregistration cannot be suppressed to a practically allowable range. was there.

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an object of the present invention is to provide a printer which eliminates the occurrence of registration error based on the rigidity of a recording sheet.

[0010]

According to a first aspect of the present invention, there is provided a printer according to the first aspect, wherein a color image is recorded on a recording sheet in a frame-sequential manner while feeding and pulling back the recording sheet alternately by a conveying means. A printer for recording, wherein the transporting means includes a capstan roller driven by a motor, a pinch roller for nipping recording paper together with the capstan roller, and a recording paper wrapping angle around the capstan roller. Means for measuring the stiffness of the recording paper, and a capstan according to the measured stiffness at the time of sending out the recording paper by a predetermined amount in a direction from the pinch roller to the auxiliary roller. It is characterized in that the pressing force of the auxiliary roller against the roller is adjusted.

According to a second aspect of the present invention, there is provided a printer for recording a color image on a recording sheet in a sequential manner while alternately sending and pulling back the recording sheet by a transporting means, wherein the transporting means is driven by a motor. A capstan roller, a pinch roller for nipping the recording paper together with the capstan roller, and an auxiliary roller for increasing the winding angle of the recording paper around the capstan roller. The stiffness is measured by adjusting the rotation amount of the motor according to the measured stiffness when the recording paper is fed by a predetermined amount in the direction from the pinch roller to the auxiliary roller.

A printer according to a third aspect is characterized in that a plurality of fine projections are formed on the outer peripheral surface of the capstan roller so as to bite into the recording paper.

According to a fourth aspect of the present invention, in the printer, the stiffness measuring means includes means for measuring a rotation amount of the motor while the leading end of the recording paper moves from the first position to the second position, and the measured rotation. A memory storing a relationship between the amount and the stiffness, and reading the stiffness from the memory based on the measured rotation amount of the motor.

According to a fifth aspect of the present invention, in the printer, the recording paper is a color thermosensitive recording paper in which a plurality of thermosensitive coloring layers for developing different colors are formed on a support. It is characterized in that a plurality of color images are heat-recorded in a frame-sequential manner by heating.

According to a sixth aspect of the present invention, in the printer, the motor is a pulse motor, and the means for measuring the rotation amount of the motor is a pulse counter for counting a driving pulse given to the pulse motor. Things.

According to a seventh aspect of the present invention, the number of drive pulses is changed in accordance with the stiffness so that the amount of recording paper transported during feeding and retraction is kept constant.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A printer 11 shown in FIG. 1 comprises a printing unit 12 and a paper feeding unit 13. In the paper feed unit 13,
A recording paper roll 16 in which a long recording paper 14 is wound in a roll shape
Is set. The recording paper roll 16 is driven by a drive motor 18 via a paper feed roller 17 that comes into contact with the outer peripheral surface thereof. When the drive motor 18 rotates forward, the recording paper roll 16 rotates counterclockwise, and the recording paper 14 is sent to the printing unit 12. When the drive motor 18 rotates reversely,
The recording paper roll 16 rotates clockwise, and the recording paper 14 is rewound on the recording paper roll 16.

As the drive motor 18, a pulse motor that rotates by a predetermined angle when one drive pulse is given is used. The amount of rotation of the drive motor 18 is measured by counting the number of drive pulses.

The recording paper 14 is provided with a cyan thermosensitive coloring layer, a magenta thermosensitive coloring layer, and a yellow thermosensitive coloring layer in this order on a support. The yellow thermosensitive coloring layer, which is the uppermost layer, has the highest thermal sensitivity and develops yellow with small heat energy. The cyan thermosensitive coloring layer, which is the lowermost layer, has the lowest thermal sensitivity and develops cyan with large thermal energy. Further, the yellow thermosensitive coloring layer loses its coloring ability when irradiated with near-ultraviolet rays of 420 nm. The magenta thermosensitive coloring layer develops magenta color with a thermal energy approximately between the yellow thermosensitive coloring layer and the cyan thermosensitive coloring layer, and loses its coloring ability when irradiated with 365 nm ultraviolet rays.

In the printing section 12, a transport roller section 21, a thermal head 22, an optical fixing device 23, a cutter 24, and a paper discharge roller pair 26 are arranged on a transport path. A first detection sensor 27 and a second detection sensor 28 are provided near the transport roller pair 21 and the optical fixing device 23, respectively. The first detection sensor 27 detects the fed recording paper 1
This is for detecting the leading end of No. 4 and obtaining the timing to start counting the driving pulses. The second detection sensor 28 is used to obtain the timing for reading the count value of the drive pulse when measuring the stiffness, and is disposed at a position separated from the first detection sensor 27 by a distance L0.

As the first and second detection sensors 27 and 28, for example, a photo interrupter including a light source and a light receiving unit for receiving light from the light source is used. When the first and second detection sensors 27 and 28 detect the leading end of the recording paper 14, they send a detection signal to the controller. Note that a reflection type photo sensor or the like may be used instead of the photo interrupter.

The thermal head 22 is provided with a heating element array 22a in which a large number of heating elements are arranged in a line along the width direction of the recording paper 14. Each heating element generates heat in accordance with image data, and presses and heats the recording paper 14 to record dots in color. The thermal head 22 is provided movably between a position where the heating element array 22 a is pressed against the recording paper 14 and a position where the heating element array 22 a is retracted from the recording paper 14. A platen roller 31 is arranged to face the thermal head 22. The platen roller 31 supports the recording paper 14 pressed against the thermal head 22 from the back. Thermal recording is performed while transporting the recording paper 14 in the pullback direction.

The optical fixing device 23 is provided with a fixing lamp 3 for yellow.
2, a magenta fixing lamp 33 and a reflector 34. The yellow fixing lamp 32 has a light emission peak of 420.
The magenta fixing lamp 33 emits an ultraviolet ray having an emission peak of 365 nm. And
Each of the fixing lamps 32 and 33 performs fixing so that the recorded yellow thermosensitive coloring layer and the magenta thermosensitive coloring layer are not further colored.

When the thermal recording and the optical fixing are completed, the recording paper 1
4 is sent to the cutter 24 position. The printed recording paper 14 is cut by the cutter 24 and cut into sheets.
The recording paper 14 cut into sheets is discharged by a discharge roller pair 26. The discharge roller pair 26 is connected to the discharge motor 3.
7 is driven.

Although not shown, a guide member for guiding the recording paper 14 is appropriately provided in the printer. Recording paper 1 sent out from recording paper roll 16
4 is conveyed along these guide members.

The transport roller section 21 includes a capstan roller 41 driven by the drive motor 18, a pinch roller 42 and an auxiliary roller 43 disposed at positions facing the capstan roller 41. The auxiliary roller 43 increases the winding angle of the recording paper 14 around the capstan roller 41 to improve the conveyance force of the recording paper 14. The transport roller unit 21 nips the recording paper 14 by pressing the pinch roller 42, and the capstan roller 41
The recording paper 14 is reciprocated in the feeding direction and the retraction direction by the rotation of. The pinch roller 42 and the auxiliary roller 43 rotate following the rotation of the capstan roller 41.

Since thermal recording is performed when the recording paper 14 is pulled back, the thermal head 22 is pressed against the recording paper 14. Therefore, when the recording paper 14 is pulled back, the pinch roller 42
2, the recording paper 14 is stretched between the auxiliary roller 43 and the thermal head 22.

However, when the recording paper 14 is fed out, if the rigidity of the recording paper 14 is low, the recording paper 14 is loosened between the auxiliary roller 43 and the pinch roller 42. On the other hand, if the stiffness of the recording paper 14 is high, the auxiliary roller 43 floats up, and a sufficient conveying force cannot be obtained. Due to the slack or floating, the amount of the recording paper 14 fed out when the drive motor 18 is rotated by a predetermined amount is different from the design value, and a difference is generated between the amount of the recording paper 14 and the amount of retraction.

In order to correct this difference, the pressing force adjusting device 4
4 are provided. At the time of feeding, the pressing force adjusting device 44 adjusts the pressure at which the auxiliary roller 43 and the capstan roller 41 nip the recording paper 14 in accordance with the rigidity of the recording paper 14 to prevent loosening and lifting. Keep feed rate constant.

As shown in FIG. 2, the auxiliary roller 43 is attached to the shaft support 46 at both ends 43a. The pressing force adjusting device 44 is incorporated in the main body 47 of the shaft support 46. The pressing force adjusting device 44 adjusts the pressing force of the auxiliary roller 43 on the capstan roller 41.
It comprises a piezoelectric element 48, a pressing spring 49, a bearing 50, and a return spring 51. The bearing part 50 is provided with a bearing hole 50a. The both ends 43a of the auxiliary roller 43 are inserted into the bearing holes 50a, and the auxiliary roller 43 is rotatably supported.

The bearing portion 50 is provided so as to be movable in the vertical direction. A pressing spring 49 is disposed above the bearing portion 50, and a return spring 51 is disposed below the bearing portion.
Is biased from above and below.

The piezoelectric element 48 is an element that generates a slight distortion in accordance with the applied voltage value. Due to this distortion, the bearing portion 50 is pressed downward via the pressing spring 49. The auxiliary roller 43 moves downward, and the pressing force of the auxiliary roller 43 on the capstan roller 41 is changed. When the urging force of the pressing spring 49 is weakened, the bearing 50 is pushed upward by the urging of the return spring 51 and returns to the initial position. As the piezoelectric element 48, a ceramic, a polymer, a composite thereof, or the like is used.

As shown in FIG. 3, the capstan roller 4
Spike portions 52 are provided at both ends of 1 to increase the conveying force. Many spikes 52a, which are fine projections, are provided on the surface of the spike portion 52. The height t of the spike 52a is formed to be about 60 μm.

The recording paper 14 is pressed by the pinch roller 42 and the auxiliary roller 43, and
4 wrapped around. By this winding, the recording paper 14
Is pressed against the outer peripheral surface of the capstan roller 41, and the spike 52 a cuts into the surface of the recording paper 14.

When the recording paper 14 is fed, no tension is applied to the recording paper 14 by the pinch roller 42. Therefore, when the auxiliary roller 43 presses the recording paper 14 against the capstan roller 41 with the pressing force P0, the amount D of the spikes 52a biting into the surface of the recording paper 14 varies depending on the rigidity of the recording paper 14. That is, as shown in FIG. 4, when the stiffness of the recording paper 14 is high, the digging amount D is shallow, and when the stiffness is low, the digging amount D becomes deep. When the bite amount D changes, the winding diameter R of the recording paper 14 changes, so that the transport amount L of the recording paper 14 also changes. The transport amount L is a value per one step of the drive motor 18.

FIG. 5 shows the transport amount when the capstan roller 41 is rotated by a predetermined amount (α). Biting amount D is D
In the case of 1, since the biting amount is shallow, the winding diameter R is R1, and the carrying amount is L1. Conversely, when the biting amount D is D2, the winding diameter R is R2, so the transport amount is L2 (L2 <L1).

Therefore, the recording paper 14 is pressed against the capstan roller 41 with the pressing force P0.
The stiffness of the recording paper 14 can be determined by checking the amount of rotation of the drive motor 18 necessary to transport the recording paper 14 by the distance L0.

The pressing force Pf of the auxiliary roller 43 when the recording paper 14 is sent out is represented by a solid line 53 in FIG.
The recording paper 14 is adjusted so as to increase as the rigidity of the recording paper 14 increases. When the stiffness is low, the amount of slack in the recording paper 14 increases. For this reason, the pressing force of the auxiliary roller 43 is reduced in order to loosen the recording paper 14. On the other hand, when the stiffness is high, loosening is less likely to occur, but since the recording paper 14 is less likely to wind around the capstan roller 41, the recording paper 14 tends to float from the outer peripheral surface of the capstan roller 41. Therefore, the recording paper 14 is moved to the capstan roller 4.
In order to hold down to 1, the pressing force of the auxiliary roller 43 is increased.

When the recording paper 14 is pulled back, the thermal head 22 is pulled by the pinch roller 42 in a pressed state, so that the pinch roller 42, the auxiliary roller 43,
A predetermined tension is applied to the recording paper 14 between the thermal heads 22. Therefore, at the position of the auxiliary roller 43, the bite amount of the spike 52a is not affected by the rigidity.
Therefore, as shown by the solid line 54 in FIG. 6, at the time of retraction, the pressing force of the auxiliary roller 43 is kept constant (Pr).

When the recording paper 14 is sent out, a predetermined tension is applied to the recording paper 14 between the pinch roller 42 and the paper feed roller 17, and when the recording paper 14 is pulled back, as described above, A predetermined tension is applied between the thermal head 22 and the thermal head 22. Therefore, at the position of the pinch roller 42, the spikes 52a
Is substantially constant without being affected by the rigidity of the recording paper 14. Therefore, the transport amount at the time of sending out and pulling back is kept substantially constant. Therefore, the pinch roller 4
2 is maintained at a constant pressing force during the reciprocation of the recording paper 14. Of course, when the tension changes depending on the structure of the transport system, the pressing force of the pinch roller 42 is changed according to the rigidity.

FIG. 7 shows the electrical configuration of the printer. The controller 61 includes a CPU 62, a memory 63, an LUT 64,
A pulse counter 66 is provided, and controls each unit of the printer 11 according to the input signal. The print instruction is
This is performed by the operation panel 67. The drive motor 18 and the paper discharge motor 37 are driven by drive pulses from motor drivers 68 and 69, respectively.

The pulse counter 66 counts the number of drive pulses applied to the drive motor 18. The conveyance amount of the recording paper 14 is controlled by counting the driving pulses. The pulse counter 66 starts counting when the first detection sensor 27 detects the leading end of the recording paper 14. The CPU 62 counts up the pulse counter 66 when the recording paper 14 is conveyed in the feed-out direction, that is, when the drive motor 18 rotates forward with the leading end detection position as a reference position, and the recording paper 14 is pulled back. Count down when transported in the direction.

When the recording paper 14 is conveyed by a predetermined distance L0 in a state where the recording paper 14 is pressed against the capstan roller 41 with the pressing force P0, and the second detection sensor 28 detects the leading end of the recording paper 14, , Pulse counter 66
Read the count value of This count value is set as the number N0 of drive pulses. The LUT 64 has a driving pulse number N0,
The relationship with the rigidity of the recording paper 14 is set as a table. The CPU 62 determines L based on the driving pulse number N0.
The stiffness value of the recording paper 14 is read from the UT 64.

The CPU 62 calculates the pressing force Pf of the auxiliary roller 43 at the time of feeding the recording paper 14 based on the measured stiffness value. This calculation formula is set in the memory 63 in advance. The pressing force adjusting device driving section 71 drives the pressing force adjusting device 44 based on the calculated pressing force Pf.

The image data processing section 72 converts the image data into an image signal. The controller 61 sends the converted image signal to the head driving unit 73. The head driving unit 73
Each heating element array 22a generates heat according to the image signal. The lamp driving unit 74 drives the optical fixing device 23,
The fixing lamps 32 and 33 emit light. Cutter driver 7
6 drives the cutter 24.

The operation of the above configuration will now be described with reference to FIG.
This will be described based on the flowchart shown in FIG. When a print instruction is issued, the drive motor 18 starts rotating forward to start feeding. When the leading edge of the recording paper 14 is detected by the first detection sensor 27 through the transport roller pair 21, the drive motor 18 is stopped once. When the drive motor 18 is stopped, the pressing force adjusting device 44 operates to adjust the pressing force of the auxiliary roller 43 to P0, and the stiffness measurement is started.

Next, in this state, the normal rotation of the drive motor 18 is restarted, and the pulse counter 66 starts counting the drive pulses. When the recording paper 14 is conveyed in the feeding direction and the leading end of the recording paper 14 is detected by the second detection sensor 28, the count value of the pulse counter 66 is extracted as the driving pulse number N0. Based on the number N0 of drive pulses, the stiffness value of the recording paper 14 is read from the LUT 64, and the stiffness measurement of the recording paper 14 ends.

When the drive motor 18 rotates forward by a predetermined number of drive pulses, the feeding of the recording paper 14 ends. The pressing force of the auxiliary roller 42 is adjusted to the pressing force Pr at the time of retraction. In this state, the drive motor 18 is rotated in the reverse direction, and the recording paper 14
Is started. During this pullback, the thermal head 22 records a yellow image line by line. When the drive motor 18 rotates in the reverse direction by a predetermined number of drive pulses, the drive motor 18 is stopped once, and the pressing force of the auxiliary roller 43 is adjusted to the pressing force Pf at the time of feeding based on the measured rigidity. In this state, the drive motor 18
Starts normal rotation, and the recording paper 14 is conveyed in the feeding direction. During this conveyance, the yellow fixing lamp 32 is turned on, and the yellow thermosensitive coloring layer is optically fixed.

When the recording paper 14 is conveyed in the feeding direction, the auxiliary roller 43 is set in accordance with the rigidity of the recording paper 14.
Therefore, the recording paper 14 is not loosened between the pinch roller 42 and the auxiliary roller 43, and the auxiliary roller 43 is not pushed up by the floating of the recording paper 14. Therefore, there is no difference between the feed amount of the recording paper 14 and the retraction amount when the drive motor 18 is rotated by a predetermined amount.

When the drive motor 18 rotates by a predetermined amount,
The second feeding of the recording paper 14 is completed. As described above, after adjusting the pressing force of the auxiliary roller 43 to Pr,
The drive motor 18 rotates reversely, and recording of a magenta image is started. When the retraction of the recording paper 14 is completed, the pressing force of the auxiliary roller 43 is adjusted to the pressing force Pf at the time of feeding, and the third feeding is performed. During this conveyance, the magenta fixing lamp 33 is turned on, and the magenta thermosensitive coloring layer is optically fixed. At the time of the third pullback, recording of a cyan image is performed.

As described above, by adjusting the nip pressure according to the rigidity of the recording paper 14 at the time of feeding, the feeding amount of the recording paper 14 matches the pullback amount. As a result, the recording start positions of the three color images do not shift, and a high quality color image can be obtained. Also, the adjustment of the nip pressure
Since the adjustment is performed in accordance with the rigidity of the recording paper 14, the recording paper 14 having various rigidities can be handled.

When the recording of the cyan image is completed, the pressing force of the auxiliary roller 43 is adjusted to Pf, and the cut position of the recording paper 14 is conveyed to the cutter 24. When the recording paper 14 reaches the cutter position, the cutter 24 operates, whereby the printed recording paper 14 is cut into sheets and discharged. The unrecorded recording paper 14 is rewound on the recording paper roll 16.

In the above example, by adjusting the pressing force of the auxiliary roller based on the measured stiffness of the recording paper, the occurrence of looseness of the recording paper and the lifting of the recording paper are eliminated, and the amount of recording paper sent out is reduced. Although the example in which the difference from the pullback amount is corrected has been described, the number of drive pulses to be applied to the drive motor is changed between the time of feeding and the time of pullback based on the measured stiffness of the recording paper in consideration of the looseness and lifting that occur. By doing
The recording paper feed amount and the pullback amount may be the same.

FIG. 9 is a block diagram showing the electrical configuration of the printer of this example. The same members as those in the first example are denoted by the same reference numerals. The CPU 62 controls the measured recording paper 14
Is calculated based on the stiffness. The number Nf of drive pulses is determined in consideration of the difference between the amount of feeding of the recording paper 14 and the amount of pullback caused by the slack or lifting of the recording paper 14 when the number of driving pulses at the time of pullback is Nr. This calculation formula is set in the memory 63 in advance. The motor driver 68 is
Based on the calculated number Nf of drive pulses, the drive motor 1
8 is driven.

As shown in the flowchart of FIG. 10, the number Nf of drive pulses is calculated based on the measured stiffness. The drive motor 18 rotates forward and backward upon receiving the drive pulse numbers Nf and Nr. A yellow image, a magenta image, and a cyan image are printed while the recording paper 14 is reciprocated by the rotation of the drive motor 18.

In the above example, the auxiliary roller is pressed against the capstan roller. However, the auxiliary roller may be slightly separated from the capstan roller.

In each of the above examples, there is no deviation between the amount of recording paper sent out and the amount of retraction, but depending on the rigidity of the recording paper,
The transport amount itself is slight but changes. Therefore, it is preferable to increase or decrease the number of pulses at the time of feeding and pulling back according to the rigidity of the recording paper.

A plurality of first and second detection sensors are provided in the width direction of the recording paper, and the count value of the pulse counter when a detection signal is received from each sensor is read out. May be used to measure the stiffness of the recording paper. According to this, even when the recording paper is skewed due to looseness of the recording paper or the like, the timing of detecting the leading edge is averaged, so that the accuracy of the stiffness measurement of the recording paper can be improved.

Although a pulse motor has been described, for example, a DC motor may be used. Furthermore, although a color thermal printer has been described as an example, the present invention may be applied to a monochrome thermal printer. Further, the present invention is not limited to a thermal printer, and may be applied to a thermal transfer printer or the like using an ink film.

[0060]

As described above in detail, the printer according to the present invention has a pinch roller and an auxiliary roller arranged on the outer periphery of the capstan roller so that the recording paper can be reciprocated, and the recording paper can be sent out. Since the pressing force of the auxiliary roller against the capstan roller is adjusted according to the stiffness of the recording paper, or the rotation amount of the motor driving the capstan roller is adjusted according to the stiffness of the recording paper, the recording paper is fed. The amount matches the withdrawal amount. Therefore,
It is possible to prevent the occurrence of color misregistration due to the difference between the feeding amount and the retraction amount.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of a printer.

FIG. 2 is a schematic diagram illustrating a configuration of a pressing force adjusting device that adjusts a pressing force of an auxiliary roller.

FIG. 3 is a schematic view showing a capstan roller.

FIG. 4 is a graph showing a relationship between the rigidity of the recording paper, the amount of bite of the spike, and the conveyance amount of the recording paper.

FIG. 5 is a schematic diagram illustrating a relationship between a rotation amount of a capstan roller and a conveyance amount of a recording sheet.

FIG. 6 is a graph showing the relationship between the stiffness of recording paper and the pressing force of an auxiliary roller.

FIG. 7 is a block diagram illustrating an electrical configuration of the printer.

FIG. 8 is a flowchart illustrating a printing procedure.

FIG. 9 is a block diagram illustrating an electrical configuration of a printer that adjusts the number of driving pulses of a motor and corrects a variation in a feeding amount of a recording sheet.

FIG. 10 is a flowchart showing a printing procedure by the printer of FIG. 9;

FIG. 11 is an explanatory diagram illustrating a state of occurrence of looseness of a recording sheet.

FIG. 12 is a graph showing the relationship between the stiffness of recording paper and the amount of slack.

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 printer 14 recording paper 18 drive motor 21 transport roller unit 27, 28 detection sensor 41 capstan roller 42 pinch roller 43 auxiliary roller 44 pressing force adjusting device 52 spike unit 52a spike 64 LUT 66 pulse counter

Claims (7)

[Claims] 1. A printer for recording a color image on a recording sheet in a sequential manner while alternately sending and pulling back a recording sheet by a transporting means, wherein the transporting means includes a capstan roller driven by a motor and a capstan roller. A means for measuring the stiffness of the recording paper, wherein the printer comprises a pinch roller for nipping the recording paper together with the capstan roller, and an auxiliary roller for increasing a winding angle of the recording paper around the capstan roller. According to the measured stiffness, at the time of feeding in which the recording paper is conveyed by a predetermined amount in a direction from the pinch roller to the auxiliary roller,
A printer for adjusting the pressing force of an auxiliary roller against a capstan roller. 2. A printer for recording a color image on a recording sheet in a face-sequential manner while alternately sending and pulling back the recording sheet by a transport unit, wherein the transport unit includes a capstan roller driven by a motor and a capstan roller. A means for measuring the stiffness of the recording paper, wherein the printer comprises a pinch roller for nipping the recording paper together with the capstan roller, and an auxiliary roller for increasing a winding angle of the recording paper around the capstan roller. According to the measured stiffness, at the time of feeding in which the recording paper is conveyed by a predetermined amount in a direction from the pinch roller to the auxiliary roller,
A printer characterized by adjusting a rotation amount of a motor. 3. An outer peripheral surface of the capstan roller,
3. The printer according to claim 1, wherein a plurality of fine projections are formed so as to bite into the recording paper. 4. The stiffness measuring means includes means for measuring a rotation amount of a motor during a movement of a leading end of a recording sheet from a first position to a second position, and a relation between the measured rotation amount and the stiffness. 4. The printer according to claim 3, further comprising a memory storing the stiffness, and reading the stiffness from the memory based on the measured rotation amount of the motor. 5. The recording paper is a color thermosensitive recording paper in which a plurality of thermosensitive coloring layers which develop different colors on a support are provided. The color thermosensitive recording paper is heated by a thermal head to form a plurality of colors. 5. The printer according to claim 3, wherein the image is thermally recorded in a frame-sequential manner. 6. The pulse motor according to claim 3, wherein said motor is a pulse motor, and said means for measuring a rotation amount of said motor is a pulse counter for counting a driving pulse given to said pulse motor. Or described printer. 7. The printer according to claim 3, wherein the number of drive pulses is changed in accordance with the stiffness so as to keep the recording paper transport amount constant during feeding and retraction.