JPH0890883A - Thermal transfer printer - Google Patents

Abstract

PURPOSE: To make it possible to wind stably an ink sheet in a perfectly smooth state at all times and thereby to improve the quality of a print by providing a power transmission system switching means which switches the winding torque of the ink sheet over to a strong one when the diameter of the winding of a winding roll becomes larger than a prescribed value. CONSTITUTION: When an ink sheet supply roll 5 rotates, the force of rotation thereof is transmitted to a gear 22 through a supply bobbin 20 and thereby the gear 22 is made to rotate, sliding on a frictional material 24, and gives a back tension to an ink sheet 1. At this time, besides, the diameter of the winding of a winding roll 6 is detected, and when the diameter is larger than a prescribed value, a motor 13 is rotated in the direction CW. Thereby a one- way clutch 41 is made to operate, a gear 42 rotates, sliding on a frictional material 43, and a gear 34 rotates jointly and thus gives a fore tension to the ink sheet l. When the diameter of the winding is smaller than the prescribed value, on the other hand, the motor 13 is rotated in the direction CCW and thereby another fore tension is given to the ink sheet 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer printer for transferring and recording ink on an ink sheet onto paper by using a printing head such as a thermal head.

[0002]

2. Description of the Related Art FIGS. 8 and 9 show, for example, Japanese Patent Publication No. 4-10.
FIG. 8 is a schematic mechanical view showing a conventional thermal transfer printer described in Japanese Patent Publication No. 869, wherein FIG. 8 shows a printing state and FIG. 9 shows an ink sheet idle feeding state. In the figure, 1 is an ink sheet formed by applying or printing a heat-melting or heat-subliming ink in the order of yellow, magenta, and cyan on a thin base material, 2 is a recording paper, 3 is a thermal head, and 4 is a platen. is there. The recording paper 2 is wound around the outer periphery of the platen 4 and conveyed by the rotation of the platen 4. The thermal head 3 is supported by a head drive device (not shown) in a pressed state and a separated state with respect to the platen 4, that is, movably in the vertical direction in the drawing. 5 is an unused ink sheet 1
Is an ink sheet supply roll, and 6 is an ink sheet take-up roll for taking up the ink sheet 1 after transfer printing. A torque limiter 8 is provided coaxially with the take-up roll 6, and the torque capacity TW of the torque limiter 8 causes the ink sheet 1
Give the forertion FW to. Reference numeral 9 denotes a torque limiter provided coaxially with the supply roll 5, and its torque capacity TB is TBL by the switching circuits CL and CH in the control circuit 11.
And TBH, the back tension of the ink sheet 1 is also changed in two stages (FBL <FBH) corresponding to FBL and FBH. Reference numeral 10 is a sensor including, for example, an optical sensor, and the sensor 10 includes a thermal head 3 and a platen 4
Detects whether it is in the pressed state or the separated state,
The detection signal is input to the control circuit 11, and the torque capacity of the torque limiter 9 is switched between TBL and TBH according to the detection signal.

The operation of the conventional thermal transfer printer will be described. First, the recording paper 2 is wound around and fixed to the outer periphery of the platen 4. Then, the platen 4 is rotated until the printing start position of the recording paper 2 reaches the position of the thermal head 3. Here, the thermal head 3 is moved in the direction of the platen 4 by the head drive device, the recording paper 2 is superposed on the ink sheet 1, and the thermal head 3 presses and holds it on the platen 4. Therefore, as shown in FIG. 8, the platen 4 is rotated in the direction of arrow A while sending a print signal to the thermal head 3, and at the same time, the ink sheet 1 sent out by the rotation of the platen 4 is taken up by the take-up roll 6. Print the first color (yellow). At this time, in order to prevent the occurrence of wrinkles in the ink sheet 1, the winding tension (foreground tension) and the back tension are set to strong forces FW and FBH (acting by TBH) to some extent. Even if FW <FBH, the ink sheet 1 is sent out by the rotation of the platen 4, so the ink sheet 1 is sent out stably.

After the printing of the first color is completed, as shown in FIG. 9, the head driving device moves the thermal head 3 in a direction away from the platen 4. Then, the sensor 10 detects that the thermal head 3 is separated from the platen 4, and the back tension of the ink sheet 1 is switched from FBH to FBL (acting by TBL) by the detection signal. Back tension FBL at this time
Is set to a very small force that can sufficiently feed the ink sheet 1 by the fore tension FW of the ink sheet 1. That is, FBL <FW is always set in the separated state of the thermal head 3.
In this state, the ink sheet 1 is idly fed to the cue position of the second color (magenta). During this time, the recording paper 2 is also conveyed to the printing start position. Then, when the cueing operation of each of the recording paper 2 and the ink sheet 1 is completed, the thermal head 3 is again driven by the head driving device to press the printing paper 2 and the ink sheet 1 against the platen 4. At this time, the sensor 10 detects that the thermal head 3 is pressing the platen 4, and the ink sheet 1
The back tension of FBL is switched from FBL to FBH again. From this state, the print signal of the second color is sent to the thermal head 3
In addition to the above, the second color is printed by the same operation as the first color. Hereinafter, a color print can be obtained by performing the same operation for the third color print.

[0005]

Since the conventional thermal transfer printer is configured as described above, the winding diameter of the take-up roll becomes larger at the end of winding the ink sheet than at the start of winding.
As shown in FIG. 10, the ink sheet tension F
W will be a very small value. For this reason, the tension for expanding the heated and partially stretched ink sheet during thermal transfer cannot be obtained, and printing under low fore tension leads to wrinkling of the ink sheet, and at the end of the ink sheet winding, There is a problem that the print quality is significantly deteriorated due to the wrinkles of the sheet.

The present invention has been made in order to solve the above problems, and by constantly giving a fore tension of a certain strong value enough to spread a heated and partially stretched ink sheet, the ink sheet is The purpose of the present invention is to obtain a thermal transfer printer which is capable of stably winding a sheet with no wrinkles and which has a good print quality.

[0007]

In a thermal transfer printer according to the present invention, a motor for driving a take-up roll of an ink sheet via a power transmission system, and a means for recognizing a take-up roll diameter around which the ink sheet is taken up. And a power transmission system switching means for switching the winding torque of the ink sheet to a strong torque when the diameter of the winding roll becomes larger than a predetermined value.

A thermal transfer printer according to a second aspect of the present invention is configured such that the motor is reversible in the first aspect of the present invention, and the power transmission system switching means operates on the output shaft of the motor in opposite directions. It is composed of two one-way clutches.

A thermal transfer printer according to a third aspect of the present invention is the thermal transfer printer according to the second aspect of the present invention, wherein the reduction ratio between the motor and the torque limiter of the first power transmission system is:
The reduction gear ratio between the motor of the second power transmission system and the torque limiter is made large.

The thermal transfer printer according to a fourth aspect of the present invention is the thermal transfer printer according to the second aspect, wherein the motor is configured so that the motor rotation speed is variable, and the motor is driven through the second power transmission system during printing. The number of rotations of the motor is switched so that the number of rotations of the motor when transmitting the torque is slower than the number of rotations of the motor when transmitting the torque of the motor through the first power transmission system.

Further, in the thermal transfer printer according to the fifth aspect of the present invention, in the second aspect of the invention, the motor is configured so that the motor rotation speed is variable, and either the first or the second power transmission during printing. Even when a system is used, the rotation speed of the motor is changed according to the printing speed.

A thermal transfer printer according to a sixth aspect of the present invention is the thermal transfer printer according to any one of the first to fifth aspects, wherein a length corresponding to a detection mark provided on the ink sheet when the ink sheet is idly fed before printing is started. The time required for transport is counted to recognize the winding roll diameter.

Further, in the thermal transfer printer according to the seventh invention of the present invention, in the first to fifth inventions, a step motor is used as a motor for driving the take-up roll, and the thermal transfer printer is provided on the ink sheet before starting printing. The number of input pulses to the motor necessary for idling the length of the cue detection mark and the color recognition detection mark is counted, and the winding roll diameter is recognized.

[0014]

In the first aspect of the present invention, the brake device connected to the ink sheet supply roll is actuated to apply a predetermined back tension to the ink sheet regardless of the time of printing or the idle feeding. At the time of printing, when the winding roll diameter is smaller than the predetermined value, a weak winding torque is transmitted to the winding roll through the first power transmission system, but within the predetermined width because the winding roll diameter is small. Take up the ink sheet with the fore tension. Further, when the winding roll diameter becomes larger than the predetermined value, a strong winding torque is transmitted to the winding roll via the second power transmission system. The ink sheet can be wound by increasing the tension and fore tension within a predetermined width.

According to the second aspect of the present invention, since the output shaft of the motor is composed of two one-way clutches operating in opposite directions, the two one-way clutches are rotated by rotating the motor in the forward or reverse direction. One of the clutches operates to switch between the first power transmission system and the second power transmission system.

In the third invention of the present invention,
Since the reduction ratio between the motor of the second power transmission system and the torque limiter is set larger than the reduction ratio between the motor of the first power transmission system and the torque limiter, The input shaft speed of the torque limiter used in the second power transmission system becomes slower than that in the transmission system. Also, since the first power transmission system is used when the winding roll diameter is small,
The output shaft speed of the torque limiter is faster than that of the second power transmission system. Therefore, it is possible to minimize the relative sliding speed caused by the difference between the output shaft rotation speed and the input shaft rotation speed of the first and second power transmission system torque limiters.

In the fourth aspect of the present invention,
The motor has a variable rotational speed, and the motor rotational speed at the time of transmitting the torque of the motor through the second power transmission system is
Since the number of rotations of the motor is switched so as to be slower than the number of rotations of the motor when transmitting torque through the first power transmission system, the number of rotations of the motor is changed from that of the first power transmission system to that of the second power transmission system. The input shaft speed of the used torque limiter becomes slow. Further, since the first power transmission system is used when the winding roll diameter is small, the output shaft speed of the torque limiter is faster than that of the second power transmission system. Therefore, it is possible to minimize the relative sliding speed caused by the difference between the output shaft rotation speed and the input shaft rotation speed of the first and second power transmission system torque limiters.

In the fifth aspect of the present invention,
The motor has a variable rotational speed, and both the first and second power transmission systems switch the motor rotational speed according to the printing speed during printing, thereby increasing the motor rotational speed when the printing speed is high. However, when the printing speed is slow, the motor speed is slowed down.When the printing speed is fast, the take-up roll speed is fast, so the torque limiter output shaft speed is fast and the motor speed is high. Since the number becomes faster, the rotational speed of the input shaft of the torque limiter also becomes faster. Further, when the printing speed is slow, the rotation speed of the take-up roll becomes slow, so that the rotation speed of the output shaft of the torque limiter becomes slow, and the rotation speed of the motor becomes slow, so that the rotation speed of the input shaft of the torque limiter also becomes slow. Therefore, the relative sliding speed caused by the difference between the output shaft speed and the input shaft speed of the first and second power transmission system torque limiters can be minimized.

In the sixth aspect of the present invention,
When the ink sheet is idly fed, the sensor detects the start-side edge and end-side edge of the cue detection mark or color identification mark before printing, and counts the time required to convey the length between them. The diameter of the winding roll immediately before the start of printing is calculated and recognized based on the time.

According to the seventh aspect of the present invention,
A step motor is used as the motor that drives the take-up roll, and the cue detection mark provided on the ink sheet before the start of printing or the start-side edge and end-side edge of the color identification mark is detected and the length between them is determined. The number of input pulses to the motor required for conveyance is counted, and the winding-side ink sheet roll diameter immediately before the start of printing is calculated from the number of pulses.

[0021]

【Example】

Example 1. FIG. 1 is a schematic configuration diagram of a thermal transfer printer according to the present invention. In the figure, the same or corresponding parts as those of the conventional thermal transfer printer shown in FIGS. 8 and 9 are designated by the same reference numerals, and the description thereof will be omitted. Reference numeral 12 denotes a pair of pinch rollers arranged with the platen 4 interposed therebetween. The recording paper 2 is inserted between one of the pinch rollers 12 and the platen 4, and the outer periphery of the platen 4 on the side facing the thermal head 3 is fixed. It is mounted so as to be discharged from between the other pinch roller 12 and the platen 4. Reference numeral 13 is a motor that is configured to be capable of rotating in the forward and reverse directions and that drives the winding roll 6. Reference numeral 14 is a brake device that is connected to the ink sheet supply roll 5 and applies back tension to the ink sheet.
Is a power transmission system for transmitting the torque of the motor 13 to the winding roll 6. Reference numeral 44 is a sensor for detecting the cue position of each color of the ink sheet, 44a is a light emitting side sensor, and 44b is a light receiving side sensor.

Reference numeral 51 is a microswitch, the actuator 52 of which is in contact with the outer circumference of the winding roll 6,
When the ink sheet 1 is wound up and the outer diameter of the take-up roll 6 exceeds a predetermined value, a switch signal is output to the control circuit 11 to recognize the diameter of the take-up roll 6.

The construction of the ink sheet drive system of this thermal transfer printer will be described with reference to FIG. The ink sheet supply roll 5 is rotatably supported by the bearing 21. The supply roll 5 is integrated with a supply bobbin 20 having teeth formed on the outer periphery of its shaft. A gear 22 is meshed with the supply bobbin 20. The side surface of the gear 22 is pressed against the friction material 24 fixed to the case by the urging force of the spring 23. Then, when the supply roll 5 rotates, the rotational force of the supply roll 5 is transmitted to the gear 22 via the supply bobbin 20, and the gear 22 rotates while sliding on the friction material 24 to generate a friction torque, and the ink sheet Back tension is given to 1.

The take-up roll 6 is rotatably supported by the bearing 31. A winding bobbin 30 having teeth formed on the outer periphery of the winding roll 6 is fitted into and integrated with the winding roll 6. Also, the shaft of the motor 13
The one-way clutch 41 is installed in the direction in which the torque is transmitted only when the shaft rotates in the CW direction, and the one-way clutch 40 is installed in the direction in which the torque is transmitted only when the shaft rotates in the CCW direction to configure the output shaft of the motor 13. ing. Further, the winding bobbin 30 is provided with gears 32 to 34 so as to mesh with each other. Further, gears 35 and 36 are meshed with the one-way clutch 40. A gear 42 is meshed with the one-way clutch 41. And between the gears 34 and 42 and the gear 3
Friction materials 43, 38 between 6 and 42 are gears 34, 4 respectively.
It is clamped in the state of being fixed to 2. Also, the gear 36
The side surface of the friction material 38 by the urging force of the spring 37.
Has been pressed. At the same time, the gear 42 is pressed by the friction material 43.

The outer diameter of the friction material 43 is set larger than that of the friction material 38. That is, the friction torque generated by the urging force of the spring 37 is the same as that of the gear 42 and the friction material 43.
The friction torque generated between the gear 36 and the friction material 3
It is set so as to be larger than the friction torque generated during 8 times.

Therefore, when the shaft of the motor 13 rotates in the CW direction, only the one-way clutch 41 rotates in the CW direction, the rotational force of the motor 13 is transmitted to the gear 42, and the gear 4
The reference numeral 2 rotates while sliding on the friction material 43 to generate friction torque. The gear 34 is rotated by this frictional force, the winding bobbin 30 is rotated via the gears 33 and 32, and the winding roll 6 is rotated in the CW direction. At this time, the motor 1
The torque of 3 is gear 42, spring 37 and friction material 4
It is reduced to a constant torque by 3 and transmitted to the winding roll 6.

On the other hand, when the shaft of the motor 13 rotates in the CCW direction, only the one-way clutch 40 rotates in the CCW direction, the rotational force of the motor 13 is transmitted to the gears 35, 36, and the gear 36 moves on the friction material 38. It rotates while sliding to generate a friction torque, and the friction force causes the gear 42 to rotate. Here, since the friction torque generated between the gear 36 and the friction material 38 is smaller than the friction torque generated between the gear 42 and the friction material 43, the gear 42 and the gear 34 are integrally rotated, The winding bobbin 30 is rotated via 33 and 32, and the winding roll 6 is rotated in the CW direction. At this time, the torque of the motor 13 is controlled by the gear 36, the spring 37 and the friction material 38 so that the motor shaft C
It is transmitted to the winding roll 6 after being reduced to a constant torque smaller than the friction torque obtained when rotating in the W direction.

Next, the operation of the thermal transfer printer according to the first embodiment will be described. First, when the ink sheet supply roll 5 rotates, the rotational force of the supply roll 5 causes the supply bobbin 2 to rotate.
Is transmitted to the gear 22 via the friction material 24
The ink sheet 1 is rotated while sliding on top to generate friction torque, and back tension is applied to the ink sheet 1. At this time, the urging force of the spring 23 and the friction material 24 are selected so that the back tension has a strength to prevent wrinkles of the ink sheet 1, for example, FBH. Therefore, the back tension FBH is applied to the ink sheet 1 regardless of the time of printing or the idle feeding.

FIG. 3 shows the relationship between the fore tension and back tension of the ink sheet in the ink sheet winding mechanism constructed as described above. First, when the winding roll diameter is recognized by the micro switch 51 and is larger than the boundary value, that is, a predetermined value, the shaft of the motor 13 is rotated in the CW direction during printing. Then, the one-way clutch 41 operates, the gear 42 rotates while sliding on the friction material 43, and friction torque is generated. This friction torque causes the gear 34 to rotate together, and the rotational force of the gear 34 is transmitted to the take-up bobbin 30 via the gears 33 and 32 to generate the fore tension FWB on the ink sheet 1.

Further, when the winding roll diameter is recognized by the micro switch 51 and is smaller than the boundary value, that is, a predetermined value, the shaft of the motor 13 is rotated in the CCW direction during printing. Then, the one-way clutch 40 operates and the gears 35 and 36 are rotated. And the gear 36
Rotates while sliding on the friction material 38, and friction torque is generated. This friction torque causes the gear 42 to rotate together. As described above, the friction torque generated here is set to be smaller than the friction torque generated between the gear 42 and the friction material 43 when the motor rotates in the CW direction. 43 and the gear 34 rotate integrally, and the friction torque generated between the gear 36 and the friction material 38 is transmitted to the take-up side bobbin 30 via the gears 33 and 32, and the fore tension FWF is generated in the ink sheet 1. . Therefore, the biasing force of the spring 37 and the friction materials 38 and 43 are selected so that the fore tensions FWF and FWB have appropriate tensions that do not adversely affect the printing.
Thus, during printing, when the recognized winding roll diameter is smaller than the boundary value in FIG. 3, the shaft of the motor 13 is rotated in the CCW direction, and when it is larger, it is rotated in the CW direction to switch the winding torque. As a result, it is possible to suppress a decrease in fore tension due to an increase in the diameter of the take-up roll due to the execution of printing, and it is possible to prevent wrinkles of the ink sheet caused by insufficient fore tension.

On the other hand, when the ink sheet 1 is idly fed, the shaft of the motor 13 is rotated in the CW direction. Then, the fore tension FWB is generated on the ink sheet 1.
As shown in (3), FWB> FBH is always established, and the ink sheet 1 is stably conveyed. Then, after the ink sheet 1 is conveyed to a predetermined position, the winding is stopped.

It goes without saying that the thermal transfer printer according to the first embodiment can be applied to both color printing and monochrome printing.

Example 2. In the second embodiment, the one-way clutch 4 is used in the thermal transfer printer of the first embodiment.
The number of teeth of gears 0 and 41 is Z40, Z41, and gear 36, respectively.
When the number of teeth of Z is 36 and the number of teeth of gear 42 is Z42,
The gear ratio is set so that (Z36 / Z40) <(Z42 / Z41).

As shown in FIG. 7, the rotation speed of the gear 34 decreases as the outer diameter of the take-up roll 6 increases during printing.
Gear 36 when it is rotated in the CCW direction, that is, when the winding operation of the ink sheet 1 is performed by the first power transmission system.
The rotation speed of the gear 42 and the rotation speed of the gear 42 when the motor 13 is rotated in the CW direction, that is, when the ink sheet 1 is wound by the second power transmission system are set to be always slightly higher. I am doing it. Therefore, the relative sliding speed of the gear 36 and the friction material 38 or the gear 42 and the friction material 43 when generating the friction torque can be minimized, so that the torque limiter can generate a stable friction torque. , The life can be extended.

Example 3. In the second embodiment, the gear ratio is changed and the reduction ratio between the motor 13 and the gear 42 of the second power transmission system is reduced with respect to the reduction ratio between the motor 13 and the gear 36 of the first power transmission system. Although the ratio is set to be large, in the third embodiment, the rotation speed of the motor 13 is variable,
The rotation speed when rotating the motor 13 in the CCW direction is C
It is supposed to be faster than the rotation speed when rotating in the W direction. Therefore, the rotational speed of the motor 13 is set so that the rotational speed of the gear 36 or the gear 42 is slightly faster than the rotational speed of the gear 34 that decreases as the outer diameter of the winding roll 6 increases during printing. By setting
Gear 36 and friction material 38, or gear 42 and friction material 43
Since the relative sliding speed of (1) can be minimized, the same effect as that of the above-described second embodiment is obtained.

Example 4. In the fourth embodiment, in the thermal transfer printer of the first embodiment, the number of rotations of the motor 13 corresponds to the printing speed at the time of printing in both cases of the first power transmission system and the second power transmission system. Is made variable. That is, if the printing speed is high, the rotation speed of the motor 13 is increased, and if the printing speed is low, the motor 13 is rotated.
Slow down the rotation speed of.

Therefore, when the motor 13 is rotated in the CCW direction with respect to the rotation speed of the gear 34 which changes according to the printing speed at the time of printing, the gear 36 causes the motor 13 to CW.
The rotation speed of the motor 13 is controlled so that the gear 42 rotates slightly faster when the gear 42 and the friction member 38 are rotated in the same direction. Since it can be minimized, the same effect as that of the second embodiment can be obtained. In each of the above-described embodiments, the gear train wheel mechanism is used in the power transmission system, but the present invention is not limited to this, and a V-belt or the like may be used, for example.

Example 5. Next, FIG. 4 shows an ink application pattern of an ink sheet used in the thermal transfer printer of the present invention. The ink sheet 1 shown in FIG. 4 is a three-color ink sheet of yellow, magenta, and cyan. The portion 1a is the cue detection mark, and the portion 1b is the color identification mark.

The axis of the motor 13 is moved to C before printing is started.
The ink sheet 1 is fed by rotating in the W direction. At this time, the diameter of the winding roll is recognized by the means described below. First, the sensor 44 is used to detect the cue detection mark 1a.
Edge portion 1a 'of the rear end portion is detected, and further, the ink sheet is idly fed to detect the edge portion 1a''at the rear end portion. Edge part 1
The time required to convey the ink sheets 1 of a ′ to 1a ″ is counted. FIG. 6 shows the relationship between the time and the diameter of the ink sheet take-up roll. Since the number of rotations of the motor 13 at the time of idling of the ink sheet 1 is always set to a constant value, the time required for the conveyance between the edge portions 1a ′ to 1a ″ of the cue detection mark 1a and the winding roll diameter The relationship is as shown in FIG. As a result, the winding roll diameter can be recognized before printing starts. At the time of printing, when the recognized winding roll diameter is smaller than the boundary value in FIG. 6, the motor 13
The shaft is rotated in the CCW direction, and when it is large, it is rotated in the CW direction to switch the winding torque.

Further, as shown in FIG. 5, even if the color identification mark 1c provided separately from the cue detecting mark 1a is used on the ink sheet 1, the winding roll diameter can be recognized from the transport time in the same manner. is there. After the completion of the yellow print of the ink sheet 1 and before the start of printing, the shaft of the motor 13 is rotated in the CW direction to idle feed the ink sheet 1. Sensor 4
4, the edge portion 1c 'of the color identification mark 1c is detected, and further, the ink sheet 1 is idly fed and the edge portion 1c''at the rear end portion is detected. Then, the edge portions 1c 'to 1
The time required to convey the c ″ ink sheet 1 is counted. After that, the winding roll diameter can be recognized in the same manner as above.

Example 6. In the sixth embodiment, in the thermal transfer printer of the first embodiment, a step motor is used as the motor 13 for winding and driving the ink sheet 1. Thereby, the number of input pulses to the step motor is counted for the time required to convey the ink sheet 1 from the front end to the rear end of the cue detection mark 1a or the color identification mark 1c shown in FIG. 4 or FIG. Substituting by
The winding roll diameter can be recognized in the same manner as above.

[0042]

Since the present invention is constituted as described above, it has the following effects.

According to the present invention, it is possible to suppress the decrease in the fore tension due to the increase in the diameter of the take-up roll by executing the printing by switching the take-up torque. Therefore, the ink generated due to the insufficient fore-tension at the time of printing. Wrinkles on the sheet can be prevented and the printing quality can be maintained.

According to the second aspect of the present invention, it is possible to switch between the first power transmission system and the second power transmission system by changing the rotation direction of the motor. This can be achieved with a simple structure.

Further, according to the third, fourth and fifth aspects of the present invention, the torque limiter, that is, the relative sliding speed of the gear and the friction material is minimized to prevent the sliding surface from excessively moving. It is possible to prevent heat generation and obtain stable friction torque for a long time.

Further, according to the sixth aspect of the present invention, the diameter of the winding roll can be recognized by counting the time required to convey the length of the mark previously provided on the ink sheet. As a means for recognizing the diameter of the winding roll, it is possible to achieve a simple structure by sharing the sensor.

Further, according to the seventh aspect of the present invention, since the step motor is used as the drive source for winding and driving the ink sheet, the rotational speed of the motor can be accurately controlled, and the motor can be controlled accurately. Since the rotation angle of the motor with respect to the number of pulses input to is also accurate, the number of pulses required to convey the length of the cue detection mark or color identification mark is counted to accurately measure the winding roll diameter. Can be recognized.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a thermal transfer printer according to the present invention.

FIG. 2 is a development view showing an ink sheet drive system of the thermal transfer printer according to the present invention.

FIG. 3 is a diagram illustrating tension acting on an ink sheet in the thermal transfer printer according to the present invention.

FIG. 4 is a diagram showing a pattern of an ink sheet in the thermal transfer printer according to the present invention.

FIG. 5 is a diagram showing another ink sheet pattern in the thermal transfer printer according to the present invention.

FIG. 6 is a diagram showing the relationship between the mark transport time or the number of pulses and the winding roll diameter in the thermal transfer printer according to the present invention.

FIG. 7 is a diagram showing the relationship between the winding roll diameter and the input or output gear rotation speed of the torque limiter in the thermal transfer printer according to the present invention.

FIG. 8 is a schematic configuration diagram showing a printing state of a conventional thermal transfer printer.

FIG. 9 is a schematic configuration diagram showing an idle feeding state of a conventional thermal transfer printer.

FIG. 10 is a diagram illustrating tension acting on an ink sheet in a conventional thermal transfer printer.

[Explanation of symbols]

1 ink sheet, 2 recording paper, 3 thermal head,
4 Platen 5 Ink Sheet Supply Roll, 6 Ink Sheet Winding Roll, 11 Control Circuit, 12 Pinch Roller, 13 Motor, 14 Brake Device 15 Power Transmission System, 44 Sensor, 51 Micro Switch, 2
0 supply bobbin, 21 bearing, 22 gear, 23 spring, 24 friction material, 30 winding bobbin, 31 bearing, 40 one-way clutch, 41 one-way clutch, 32-36 gear, 37 spring, 42 gear, 38, 43 friction material

Claims (7)

[Claims] 1. A thermal head that selectively heats a heating element, a platen that opposes the thermal head and presses and holds a recording paper and an ink sheet coated with thermal transfer ink, and the platen and the thermal head. A head drive device for contacting and separating the ink sheet, a brake device that is connected to the ink sheet supply roll and applies a predetermined back tension to the ink sheet, a motor that drives the ink sheet take-up roll through a power transmission system, and an ink sheet A means for recognizing the diameter of the winding roll to be wound, and a power transmission system switching means for switching the winding torque of the ink sheet to a strong torque when the diameter of the winding roll becomes larger than a predetermined value. Thermal transfer printer. 2. A motor capable of rotating in the forward and reverse directions, two one-way clutches operating in opposite directions on an output shaft of the motor, and a winding roll from one of the one-way clutches to a predetermined torque via a first torque limiter. A first power transmission system for transmitting a torque to be rotated by a second torque limiter having a transmission torque stronger than the first torque limiter from the other one-way clutch to rotate the winding roll at a predetermined torque. 2. A thermal transfer according to claim 1, further comprising a second power transmission system for transmitting torque, wherein the first power transmission system and the second power transmission system are switched by changing the rotation direction of the motor. Printer. 3. A reduction ratio between the motor and the second torque limiter in the second power transmission system with respect to a reduction ratio between the motor and the first torque limiter in the first power transmission system. In the second power transmission system which is large in construction and has a small output rotation speed of the torque limiter during printing when the winding roll diameter is larger than a predetermined value, the second rotation speed is reduced by decreasing the input rotation speed to the torque limiter. The thermal transfer printer according to claim 2, wherein the difference between the input rotation speed and the output rotation speed of the torque limiter of the power transmission system is reduced. 4. A motor having different rotation speeds for forward rotation and reverse rotation,
When the motor reverse rotation speed of the second power transmission system during printing is made smaller than the motor normal rotation speed of the first power transmission system during printing, and when the winding roll diameter is larger than the specified value, The output speed of the torque limiter is small.The input speed to the torque limiter of the second power transmission system is made small, and the difference between the input speed and the output speed of the torque limiter is reduced in both the first and second power transmission systems. The thermal transfer printer according to claim 2, wherein the thermal transfer printer is reduced in size. 5. The motors of both the first and second power transmission systems are configured so that the motor rotation speed is variable, and the rotation speed of the take-up ink sheet roll during printing changes due to a change in printing speed during printing. Correspondingly, when the number of revolutions of the take-up ink sheet roll is large, the number of revolutions of the motor is large, and when the number of revolutions of the take-up ink sheet roll is small, the number of revolutions of the motor is small. 3. The thermal transfer printer according to claim 2, further comprising a motor rotation speed control means capable of reducing a difference between an input rotation speed and an output rotation speed of the torque limiter caused by a change in co-printing speed of the system. 6. An ink sheet provided with a cue detection mark or a color recognition mark, and means for measuring the time for carrying the length of any one of the marks when the ink sheet is empty before the start of printing. 6. The diameter of the winding roll at the start of printing is recognized based on the transport time.
The thermal transfer printer according to any one of 1. 7. A stepping motor is used as a motor to count the number of input pulses required to convey a length corresponding to a cue detection mark or a color recognition mark, and the winding roll diameter at the start of printing from the number of pulses. The thermal transfer printer according to claim 1, wherein the thermal transfer printer recognizes the following.