JP2012086417A - Thermal printer, control method and electronic appliance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal printer which reduces printing stain while being prevented from becoming large to avoid a large burden on a user of a conventional thermal printer loaded in a portable information terminal or the like or in a conventional thermal printer designed to be carried because the conventional thermal printer cannot help being large for the installation of a retracting mechanism of a head to prevent printing stain, and to provide a control method of a thermal printer and an electronic appliance equipped with a thermal printer.SOLUTION: A temperature near the thermal head is detected. When the temperature is not lower than a coloring temperature of a stored thermal recording medium, a conveyance speed control means performs control for changing a relative position between the thermal head and the thermal recording medium so that the conveyance of the thermal recording medium may suppress the coloring of the thermal recording medium.

Description

The present invention relates to a thermal printer, a method for controlling a thermal printer, and an electronic apparatus including the thermal printer.

A thermal printer such as a thermal line printer is provided with a large number of heating elements that are independently driven and heated in a row, and selectively drives and heats the corresponding portions of the opposed thermal paper to generate color. Thus, printing is realized. The thermal paper used in this type of printer varies in color depending on the amount of thermal energy (applied energy) applied to the heating element. That is, by changing the application time of the current flowing through the heating element, the amount of applied energy is changed and the color development state of the thermal paper is changed. The dynamic color development characteristic diagram of the thermal paper D and the thermal paper E shown in FIG. 8 is shown. In the thermal paper, the color density with respect to the applied energy applied to the thermal head is individually determined. The relationship between the color density of the thermal paper and the applied energy is a dynamic color characteristic chart. For example, with thermal paper D, it can be seen that color development starts when the applied energy is about 0.2 mj / dot and color development is almost completed at 0.4 mj / dot. The thermal paper D shown in FIG. 8 is a highly sensitive thermal paper that develops color with less applied energy than the thermal paper E.

FIG. 9 shows the static color development characteristics of thermal paper D and thermal paper E. Further, when the thermal paper is in a state of being in contact with the thermal head for a long time of 3 seconds to 5 seconds or more, the temperature at which the coloring state changes due to the thermal storage of the thermal head is individually determined. The relationship between the color density of the thermal paper and the temperature is a static color characteristic chart. For example, it is understood that the thermal paper D has a characteristic that the thermal head starts color development from about 70 ° C. and color development is almost completed at 85 ° C. The thermal paper D shown in FIG. 9 has a characteristic of coloring at a lower temperature than the thermal paper E. There is a correlation between the dynamic coloring characteristics shown in FIG. 8 and the static coloring characteristics shown in FIG. 9, and the static coloring temperature of the thermal paper having the characteristic of developing colors with little applied energy is generally low. Although this characteristic value is almost the temperature of the thermal paper, a similar color characteristic chart depending on the temperature can be obtained by measuring the temperature in the vicinity of the thermal head. In that case, it is expected that the coloring temperature transitions to the high temperature side according to the distance from the thermal head.

Conventionally, an example of a handy terminal as an electronic device equipped with a thermal line printer has been used for meter reading operations such as electricity, gas, and water. In these meter reading operations, the usage amount read from the usage meter at the company or private home is input to the handy terminal. Then, the result of meter reading is output to a notification slip made of thermal paper from a thermal line printer mounted on the handy terminal or a thermal line printer connected to the handy terminal by wire or wirelessly. The output notification slip is directly delivered to the user of electricity, gas, and water, or when the user is absent, it is dropped to a post box or the like and indirectly passed to the user.

In this way, the handy terminal is used for meter reading work indoors and outdoors, in cold areas in winter, it is used in a sub-zero environment, and in hot weather in the summer and in warehouses, it is used in a high temperature environment near 40 ° C. On the other hand, in order to increase the printing speed, high-sensitivity thermal paper having a characteristic of developing color with a small applied energy has been developed and used. As a method for preventing the thermal paper from being soiled due to thermal storage of a thermal head using a thermal printer, a method of providing a head retracting mechanism has been devised, as shown in Patent Document 1.

Japanese Patent Registration No. 0356611

In Patent Document 1 described above, since the head retracting mechanism is provided, there is a problem that the apparatus becomes large. For this reason, a thermal printer mounted on a portable information terminal or a thermal printer that is carried is a heavy burden on the user. Therefore, an object of the present invention is to provide a thermal printer, a control method for the thermal printer, and an electronic device including the thermal printer that can reduce printing stains without increasing the size of the apparatus.

In order to solve the above-described problems, a recording means for energizing a thermal head to record on a thermal recording medium, a conveying means for conveying the thermal recording medium, and a temperature detection means for detecting a temperature in the vicinity of the thermal head And information storage means for storing information including color temperature information of the thermal recording medium, a conveyance speed control means for controlling the conveyance speed of the thermal recording medium by the conveyance means,
And when the temperature detection means detects a temperature exceeding the temperature at which the thermal recording medium starts color development based on the color development temperature information, the transport speed control means moves the transport means to the thermal recording medium. This is solved by using a thermal printer that controls to change the relative position of the thermal recording medium and the thermal head so as to suppress the color development.

Further, as a control method of the thermal printer for solving the above-described problems, a recording unit for energizing the thermal head to perform recording on the thermal recording medium, a conveying unit for conveying the thermal recording medium, and the vicinity of the thermal head Temperature detection means for detecting the temperature of the recording medium, information storage means for storing information including color temperature information of the thermal recording medium, and a conveyance speed control means for controlling the conveyance speed of the thermal recording medium by the conveyance means, And when the temperature detection unit detects a temperature exceeding a temperature at which the thermal recording medium starts color development based on the color development temperature information, the transport speed control unit sets the transport unit to the thermal recording medium. A control method for a thermal printer, wherein control is performed to change the relative position of the thermal recording medium and the thermal head so as to suppress color development. It is solved by using.

In addition, as an electronic apparatus provided with a thermal printer for solving the above-described problems, a recording means for energizing a thermal head to record on a thermal recording medium, a conveying means for conveying the thermal recording medium, and the thermal head Temperature detecting means for detecting the temperature in the vicinity of the recording medium, information storage means for storing information including color development temperature information of the thermosensitive recording medium, and a conveying speed control means for controlling the conveying speed of the thermosensitive recording medium by the conveying means. When the temperature detection unit detects a temperature exceeding the temperature at which the thermal recording medium starts color development based on the color development temperature information, the transport speed control unit causes the transport unit to detect the thermal recording. A thermal printer is provided that performs control to change a relative position between the thermal recording medium and the thermal head so as to suppress color development of the medium. It is solved by the use of electronic equipment.

According to the present invention, information including the color development temperature information of the thermal recording medium is stored, and the relative position between the thermal recording medium and the thermal head is changed based on the color development temperature information, so that the possibility of printing smear can be reduced, It is possible to obtain a printing result with less risk of quality deterioration.

Print control flowchart of CPU 2 according to the embodiment of the present invention. 1 is a block diagram of a thermal printer 20 according to an embodiment of the present invention. A handy terminal 21 which is an example of an electronic device including a thermal printer 20 according to an embodiment of the present invention. Proper energization time table for thermal paper D Thermal paper D stop possible time table Printing control flowchart of the CPU 2 according to the first embodiment of the present invention. CPU 2 print control flowchart according to the second embodiment of the present invention. Dynamic coloring characteristics of thermal paper D and thermal paper E Static color characteristics of thermal paper D and thermal paper E

The configuration of the thermal printer 20 in this embodiment will be described. FIG. 2 shows a block diagram in the embodiment of the present invention. The thermal printer 20 according to the embodiment of the present invention includes an interface 1, a CPU 2, a ROM 3, a RAM 4, a shift register 5, a latch circuit 6, a drive circuit 7, a thermal head 8, a temperature detection circuit 9, a motor drive circuit 10, a stepping motor 11, A platen roller 12 and a voltage detection circuit 13 are provided. The print data is supplied from the host device to the interface 1. The interface 1 performs communication processing between the CPU 2 and a host device such as an electronic device provided with the thermal printer 20 or a communication-connected electronic device. The thermal head 8 functions as a recording means for recording on a thermal recording medium such as the thermal paper D by being energized and generating heat.

Print data fetched from the host device via the interface 1 is supplied to the CPU 2. The CPU 2 is an arithmetic device equipped with an arithmetic register, an input / output circuit, an A / D converter, an arithmetic unit, and a UART, and executes processing based on a program stored in the ROM 3. The ROM 3 also stores information corresponding to the type of thermal paper such as the type of thermal paper to be printed, an appropriate energization time table, and a stoppable time table described later. The print data fetched from the interface 1 is expanded in the RAM 4. It functions as information storage means for recording various information including the ROM 3 and RAM 4. Information about the color development temperature including the temperature at which color development is started and the concentration and time corresponding to the temperature are also stored in the ROM 3. It is also possible to compress the data and store it in the ROM 3, and expand it in the RAM 4 when used.

Further, the CPU 2 is supplied with temperature information from the temperature detection circuit 9 and voltage information from the voltage detection circuit 13. Based on the temperature information and the voltage information and the information on the recording medium stored in the ROM 3, the CPU 2 receives one dot line. The total energization time is calculated. Various alternative means can be considered for the temperature detection circuit 9 functioning as the temperature detection means, and a temperature sensor can be installed in the vicinity of the thermal head 8 to measure the ambient atmosphere temperature.

The print data developed in the RAM 4 by the CPU 2 is, for example, “1” for colored dots, that is, black dots, and “0” for non-colored dots, that is, white dots. The print data developed in the RAM 4 is sequentially supplied to the shift register 5 in units of one line. The shift register 5 holds “0” or “1” print data set according to the heating element line of the thermal head 8.

The latch circuit 6 latches the print data held in the shift register 5 for each line by a control signal from the CPU 2. The print data latched by the latch circuit 6 is supplied to the drive circuit 7. The drive circuit 7 supplies an energization current to the thermal head 8 according to the print data latched by the latch circuit 6. The thermal head 8 has a configuration in which a large number of heating elements are arranged on a line. A current is supplied from the drive circuit 7 to each heating element. Each heating element generates heat to a high temperature of 200 ° C. or higher according to the energization current from the drive circuit 7.

In the vicinity of the thermal head 8, a platen roller 12 is provided as a conveying means in the embodiment of the present invention. The platen roller 12 conveys the thermal head 8 and the thermal paper D in contact with each other. In the thermal paper D, heat is applied from the heating element in the portion of the thermal head 8 facing the heating element that generates heat, and the black color changes. Further, in the portion facing the heating element that does not generate heat, if the amount of heat applied is not the amount of heat that leads to coloring, it is maintained to be the white color that is the background color of the thermal paper D.

The temperature detection circuit 9 includes a thermistor disposed in close contact with the thermal head 8 and a voltage dividing resistor, and converts the temperature of the thermal head 8 as a voltage signal. The voltage signal converted by the temperature detection circuit 9 is supplied to the A / D converter of the CPU 2. The CPU 2 stores the level of the voltage signal supplied to the A / D converter in the RAM 4 as temperature information. The voltage detection circuit 13 detects an applied voltage signal to the thermal head 8. The temperature detection circuit 9 functions as temperature detection means for detecting the temperature of the thermal head 8. The applied voltage signal detected by the voltage detection circuit 13 is supplied to the A / D converter of the CPU 2. The CPU 2 stores the applied voltage signal level supplied to the A / D converter in the RAM 4 as voltage information.

Further, the motor drive circuit 10 supplies a current to a stepping motor 11 connected to the platen roller 12 by a gear gear (not shown) according to a control signal from the CPU 2. The stepping motor 11 performs forward rotation or reverse rotation by supplying current from the motor drive circuit 10. The platen roller 12 is rotated by being transmitted to a gear gear attached to the platen roller 12 by a gear gear to which power generated by the rotation of the stepping motor 11 is coupled. As the platen roller 12 rotates, the thermal paper D is conveyed along a conveyance path (not shown), and the platen roller 12 functions as a conveyance unit. The temperature of the heated thermal head 8 is lowered by heat radiation to the atmosphere lower than the temperature of the thermal head 8 and contact with the platen roller 12 or the like via the thermal paper D or the thermal paper D.

The thermal paper D on which printing is performed is a thermal recording medium in which dynamic color development characteristics and static color development characteristics are in a proportional relationship between color development density and applied energy or color development temperature. In the present invention, the thermal recording medium to be transported is not limited to thermal paper, but may be limited by the type of thermal recording medium, the gradient of color development characteristics, etc., as long as it is a thermal storage medium that performs color development at a predetermined temperature. Absent.

When the platen roller 12 rotates, the thermal paper D sandwiched between the thermal head 8 and the conveyance path and the platen roller 12 is conveyed. When the temperature information Ta detected by the temperature detection circuit 9 is equal to or higher than the temperature Tp at which the thermal paper D corresponding to the static color development characteristic diagram stored in the ROM 3 starts color development, the CPU 2 controls the conveyance speed. If Tp is a temperature at which static color development starts based on the background color and color density of thermal paper D, it is color temperature information that can be set as appropriate depending on how much the color of thermal paper is concerned by the user. Yes, stored in ROM3. The CPU 2 controls the conveyance speed so as to change the relative position of the thermal head 8 and the thermal paper D so that the thermal head 8 and the thermal paper D are stopped for a certain period of time at a temperature at which color development starts and do not continue to contact.

FIG. 3 shows a handy terminal 21 of an electronic device which is a portable information terminal suitable for mounting the thermal printer 20 according to the embodiment of the present invention. The display unit 14 displays a plurality of types of thermal paper that can be selected. The thermal paper selected in the selection button 15 and printed in the roll paper storage unit 17 is printed and discharged from a paper discharge port 16 provided with a cutter.

 FIG. 4 shows a data configuration diagram of the proper energization time table. The proper energization time table is one piece of information regarding the thermal paper D, and an appropriate energization time tc corresponding to the temperature information Ta and the voltage information Vb is set. In addition, a plurality of pieces of information relating to a thermal recording medium such as an appropriate energization time table and a stoppable time table described later are prepared for each type of thermal recording medium.

FIG. 5 shows a data structure of the stoppable time table. The stoppable time table is one piece of information about the thermal paper D, and a plurality of different stoppable times tg corresponding to the values of a plurality of different temperature information Ta detected by the temperature detection circuit 13 are set. The stoppable time is a time during which color development can be suppressed even when the thermal paper D is in contact with the thermal head 8 that has accumulated heat above the temperature at which static color development starts. By measuring the temperature of the thermal head 8, it can be obtained and set from the coloring state of various thermal papers. As shown in the static color development characteristic diagram of FIG. The stoptable time table is stored in the ROM 3. The control of the thermal printer 20 for the thermal paper D will be described.

When selecting the type of thermal paper, if the type used in the thermal printer 20 is specified, a preset data table of the thermal recording medium is used. The type of the thermal paper can be discriminated by various means such as a paper thickness sensor, a sensor for detecting the surface state, and selection in advance. In the case of a thermal printer mounted on an electronic device, a heat-sensitive paper stored in the ROM 3 is displayed by an operation means such as a selection button 15 before displaying the selectable thermal paper stored in the ROM 3 on the display unit 14 serving as a display means. It is convenient to select and determine the type of recording medium from a plurality of thermal recording media. The embodiment of the present invention when the thermal recording medium is thermal paper D will be described below.

FIG. 1 shows a control flowchart at the time of print control of the CPU 2 in the embodiment of the present invention. The conveyance speed control in the printing of FIG. 1 illustrates the operation between the lines of the print data, but can also be applied during the discharge conveyance operation at the end of the printing operation in S15 to S19. The thermal head 8 may print and convey one line at a time, but depending on the contact state between the thermal head 8 and the thermal paper D, a line is formed by a plurality of heating elements and a predetermined line is printed simultaneously. You can also. Preferably, stable printing results can be obtained by controlling each line.

Each process in the control flowchart is represented by S (step). In S <b> 11, when the CPU 2 receives the print data supplied from the host device and receives the print data from the interface 1, the CPU 2 develops the print data received from the interface 1 in the RAM 4. Thereafter, the platen roller 12 conveys the thermal paper D to the printing start position where printing is performed by the thermal head 8 so as to leave a predetermined margin.

In S12, the CPU 2 detects the temperature of the thermal head 8 by the temperature detection circuit 9, and acquires the voltage Vb and time Tc suitable for heating based on the temperature information Ta from the appropriate energization time table of FIG. In S13, the CPU 2 heats the thermal head 8 by supplying current to the drive circuit 7 through the voltage and time acquired in S12 through the heating element corresponding to the print data. The print data of a predetermined line in which the thermal paper D is in contact with the thermal head 8 heated in S14 is printed. Depending on the shape of the thermal head 8 and the feed amount of the stepping motor 11, the number of lines of predetermined print data to be printed, the width to be colored at a time, and combinations thereof can be changed as appropriate.

When recording by printing with the thermal head 8 is completed for a predetermined line, preparation for transporting the thermal paper D is performed for printing the next print data or print line or transporting the paper discharge. In S <b> 15, the CPU 2 acquires temperature information Ta from the temperature detection circuit 9 and compares it with the color development temperature Tp stored in the ROM 3. When the comparison result is Ta ≧ Tp, the CPU 2 changes the power supply of the motor driving circuit 10 and changes the driving of the stepping motor 11 in S16 so that the thermal paper D has a conveyance speed capable of suppressing color development as much as possible.

As a transport control method in S16, the relative positions of the thermal head 8 and the thermal paper D are continuously changed within the stoppable time determined from the stoppable time table of FIG. 5 corresponding to the temperature of the thermal head 8. If so, the color of the thermal paper D can be suppressed. If the conveyance for changing the relative position of the thermal paper D and the thermal head 8 is not stopped for the stoppable time or longer, the color development can be suppressed by speeding up the paper feed of the platen roller 12 that conveys the thermal paper D. In addition to this, it is possible to control the CPU 2 to send the color so slowly that it is inconspicuous, to stop intermittently within the stoppable time, and not to change the rotation speed of the stepping motor 11. Further, the paper may be returned by changing the sign of the conveyance speed. In that case, it stops temporarily just before becoming a negative speed. The stop time table obtained from FIG. 5 stored in the ROM 3 for this stop period is set to a negative transport speed after the transport of the thermal paper D is stopped within a time within which the color is not noticeable. .

Further, in the paper discharge conveyance operation, the thermal paper D can be sent at a constant speed until Ta <Tp so as not to cause color development. In these conveyance speed controls, the CPU 2 functions as a conveyance speed control means because the control signal from the CPU 2 instructs the platen roller 12 to drive via various circuits, motors, and gears. Information on how to control the conveyance of the thermal paper D in S16 is stored in the RAM 4 by the CPU 2.

In S17, the CPU 2 controls the motor drive circuit 10 with the information stored in the RAM 4, generates a pulse voltage determined by the storage, rotates the stepping motor 11, and rotates the thermal paper D by the platen roller 12. Transport. Next, the CPU 2 returns to S15 and acquires the temperature information Ta from the temperature detection circuit 9 again.

If the temperature information Ta acquired from the temperature detection circuit 9 in S15 is less than the temperature Tp at which the influence of color development is small even if the CPU 2 has stopped for a predetermined time, the process proceeds to S18. Since it is the thermal paper D, if the temperature information Tp of the thermal head 8 is set to 70 ° C. from FIG. 9, the dirt is hardly noticeable. The information stored in the RAM 4 in S18 confirms whether or not the thermal paper D has moved from the planned stop position. If the stop position has been changed, the platen roller is moved by the amount the thermal paper D has been moved in S17 in S19. 12 is rotated and returned. S17 may pass a plurality of times depending on the temperature condition. If the RAM 4 stores that the control has been performed a plurality of times, the CPU 2 adds the results of the plurality of controls stored in the RAM 4. Return only the difference.

If the print data has not been completely printed in S20, the CPU 2 proceeds to S21 and rotates the platen roller 12 to the position where printing of the next print data is started, and conveys the thermal paper D. When the printing of the print data has been completed for all lines in S20, the CPU 2 proceeds to S22, rotates the platen roller 12 to a discharge completion position where an appropriate margin is maintained and the cutter can be easily cut, and the thermal paper D is discharged and conveyed. To do. When the discharge conveyance is completed, the printing of the print data completes the print discharge operation.

The idea of the present invention can also be applied when the printing operation of the print data by the thermal head 8 on the thermal paper D is temporarily completed and when the printing operation is completed for all lines and the paper is being conveyed.
If the concept of the present invention is applied in the paper discharge conveyance, the platen roller 12 is rotated in the direction opposite to the printing direction or in the positive direction, and the cutting position that becomes the specified position where the thermal paper D can be cut by the cutter. Or after returning to a specified position where the next printing can be easily performed. If the control is between print lines, the process ends after returning the next print data to the printing position. If the temperature of the thermal head 8 becomes Tp or less simply by temporarily stopping, the next print data can be printed after one line drive.

In particular, when the thermal printer 20 having such a configuration is used in a portable electronic device such as the handy terminal 21 in which the thermal printer as shown in FIG. 3 is integrally mounted, it can be used by an operator without increasing the size of the apparatus. Can be maintained and printing stains can be prevented. If the conveyance control method of the thermal printer 20 according to the embodiment of the present invention is performed, the roll paper is in contact with the thermal head 8 inside the handy terminal 21 where the operator cannot see it, and the notice slip provided to the customer is soiled. The possibility of unpleasant feelings can be reduced. Further, when the thermal printer 20 and the host device are integrated, the thermal printer 20 can be operated under the control of the CPU of the host device. The thermal printer 20 performs printing on the roll-shaped thermal paper D stored in the roll paper storage unit 17 and sends out the printed thermal paper D from the paper discharge port 16.

A print control operation according to the first exemplary embodiment will be described. The hardware configuration of the thermal printer is the same as that shown in FIG. FIG. 6 shows a control flowchart when the CPU 2 performs print control.

When the CPU 2 receives the print data from the interface 1, the CPU 2 develops the print data received from the interface 1 in the RAM 4 in S101, and conveys the thermal paper D to the print start position.

In S <b> 102, the CPU 2 transfers the print data to the shift register 5. Next, in S <b> 103, the CPU 2 acquires temperature information from the temperature detection circuit 9 and voltage information from the voltage detection circuit 13, and acquires an appropriate energization time tc with reference to an appropriate energization time table stored in the ROM 3. .

The CPU 2 refers to the appropriate energization time table as shown in FIG. 4 based on the temperature information, the voltage information, and the recording medium type, and acquires the appropriate energization time tc used for printing the current line. For example, if the recording medium D, temperature information Ta = Ta2, and voltage information Vb = Vbn, the appropriate energization time tc is tcd2n.

Next, in S <b> 104, the CPU 2 latches the data held in the shift register 5 by the latch circuit 6. In step S <b> 105, the CPU 2 controls the drive circuit 7 to energize the heating element of the thermal head 8. At the same time, a timer built in the CPU 2 is activated to start counting the energization time tf.

In S106, the CPU 2 compares the count value tf of the timer with the value of the proper energization time tc, and if the timer count value tf is equal to or greater than the proper energization time tc, the energization from the drive circuit 7 is stopped. The heated thermal printer 8 contacts the thermal paper D and is printed.

In step S107, the CPU 2 determines whether printing of all lines has been completed. If the printing of all lines is not completed in S107, the CPU 2 controls the motor drive circuit 10 in S108, and rotates the stepping motor 11 by which the platen roller 12 feeds the thermal paper D by one line to rotate the thermal paper D. Send one line. The CPU 2 returns to S102 and transfers the print data of the next line to the shift register.

On the other hand, if the printing of all lines has been completed in S107, the CPU 2 controls the platen roller 12 so as to carry out the paper discharge to a specified position where the thermal paper D can be cut by the cutter in S109.

Next, in S110, the CPU 2 acquires the temperature information Ta from the temperature detection circuit 9 and compares it with the coloring temperature Tp stored in the ROM 3. When the comparison result is Ta ≧ Tp, the timer incorporated in the CPU 2 is started and counting of the stop time ts is started.

In S111, the CPU 2 refers to the stoppable time table of FIG. 5 stored in the ROM 3 and acquires the stoppable time tg.

The CPU 2 refers to the stoppage time table of the thermal paper D as shown in FIG. 5 based on the temperature information and the recording medium type, and acquires the set stoppage time tg in the predetermined temperature information. If the thermal paper D and temperature information Ta = Ta2, the stop possible time tg is tgd2.

In S111, the CPU 2 compares the count value ts of the timer with the value of the stoppable time tg. If the comparison result indicates that the count value ts of the timer is equal to or greater than the stoppable time tg, the process proceeds to S112, and the motor driving circuit 10 is controlled to rotate the stepping motor 11 by which the platen roller 12 feeds the thermal paper D by one line. Then, an additional conveyance is performed in which the thermal paper D is sent by one line. The CPU 2 returns to S110 and acquires the temperature information Ta of the thermal head 8 from the temperature detection circuit 9 again.

At this time, the temperature of the thermal head 8 is lowered by the amount of stopping and driving for one line. If the temperature information Ta = Ta1 and the color development temperature Tp is exceeded even after the operations of S111 and S112 are performed, the CPU 2 executes the steps of S111 and S112 again. The stoppable time tg is tgd1, and after stopping at a stoppable time different from tgd2, the platen roller 12 rotates the stepping motor 11 by which the thermal paper D is fed by one line, and additional transport is performed to send the thermal paper D by one line.

When the temperature information Ta acquired from the temperature detection circuit 9 in S110 becomes less than the color development temperature Tp, the CPU 2 confirms whether or not the additional conveyance in S112 has been performed in S113. When the additional conveyance has been performed, the motor driving circuit 10 is controlled by the same feed amount as the thermal paper D sent in S114, and the platen roller 12 is rotated in the direction opposite to the printing, so that the thermal paper D is cut. After returning to the prescribed position where cutting is possible, the print discharge operation is completed.

As described above, when the temperature of the thermal head 8 is detected and the heat-sensitive recording medium may develop color due to heat accumulation, the same place does not continue to contact until the temperature of the thermal head 8 becomes lower than the temperature at which color development starts. In this way, the relative position of the thermal paper D and the thermal head 8 is changed. Thereby, when the thermal head 8 is in a high temperature state equal to or higher than the static color development temperature, the thermal head 8 and the thermal paper D can be prevented from coming into contact with each other for a long time and the thermal paper is unintentionally colored. In this embodiment, the thermal paper D is suitably used when it is a roll-shaped thermal paper. When printing on roll paper, after cutting the printed portion with a cutter, the paper is stopped and held with the thermal paper D in contact with the thermal head 8 located downstream from the paper cutting position. For this reason, it is possible to prevent the portion used for the next printing from being stained. In addition, when the thermal paper D is in the form of a roll paper, the thermal paper D is transported back to the specified position after additional transport, so that the thermal paper D is not wasted and the margin in the next printing is minimized. Limit.

Next, a second embodiment of the present invention will be described. An example will be described in which the conveyance control is performed at the end of printing of one line during printing or in the discharge conveyance process to the cutting position of the thermal paper after the completion of printing of all lines. The hardware configuration of the thermal printer is the same as that shown in FIG. FIG. 7 shows a control flowchart for print control of the CPU 2 in this embodiment.

Since the printing control operation from S201 to S206 is the same as S101 to S106 in the first embodiment, the description thereof is omitted.

In step S207, the CPU 2 determines whether printing of all lines has been completed. If the printing of all lines is not completed in S207, the CPU 2 acquires the temperature information Ta from the temperature detection circuit 9 in S208 and compares it with the coloring temperature Tp stored in the ROM 3. If the comparison result is Ta ≧ Tp, the process proceeds to S209. When the comparison result is Ta <Tp, the process proceeds to S212, and the normal conveyance is performed without changing the conveyance speed, and the process proceeds to S213 as it is.

Next, in step S209, the CPU 2 controls the motor driving circuit 10 so that the platen roller 12 rotates the motor by which the thermal paper D is fed in the positive direction by a predetermined line to feed the thermal paper D by a predetermined line. The order of the predetermined line feeding here may be from the positive direction in which the conveyance is performed in the paper discharge direction first or from the negative direction in which the conveyance is reverse. From the standpoint of preventing printing stains, the positive direction is preferred because the printed portion is less likely to be stained. Further, the change of the transport direction in S210 is performed within the time of the stoptable table of FIG. The fact that there has been a stop in S210 is stored in the RAM 4 by the CPU 2. In step S211, the platen roller 12 controls the motor drive circuit 10 to rotate the amount motor that feeds the thermal paper D in the negative direction by a predetermined line to feed the thermal paper D by a predetermined line. If it is sent in the negative direction in S209, the thermal paper D is sent in a predetermined line in the positive direction.

In S212, when the CPU 2 stores that the temperature of the thermal head 8 may be high after passing through S211, the CPU 2 determines to proceed to S209. Whether the RAM 4 stores the control of the conveyance speed or whether there is a time when the conveyance is stopped is used as the determination reference. If the CPU 2 determines in step S209 that the temperature information Ta from the temperature detection circuit 9 is lower than the color development temperature Tp, the process proceeds to step S213, the motor is driven for one line, and the print data is sent to the specified position on the thermal paper D. .

If printing of all lines has been completed in step S207, the process proceeds to S214 and proceeds to the paper discharge conveyance operation. In S <b> 214, the CPU 2 acquires the temperature information Ta from the temperature detection circuit 9 and compares it with the color development temperature Tp stored in the ROM 3. When the comparison result is Ta ≧ Tp, the process proceeds to S215. When the comparison result is Ta <Tp, the process proceeds to S216, and the sheet is normally conveyed to the print completion position through a process described later.

In step S216, the CPU 2 controls the motor driving circuit 10 so that the platen roller 12 rotates the motor for feeding the thermal paper D in the positive direction by one line to feed the thermal paper D by one line. The one-line feed here may be from the negative direction in which the forward direction in which the conveyance is performed in the paper discharge direction is sent first or reversely. The first one-line feed is preferably in the positive direction that does not return to the printed portion from the viewpoint of preventing print stains. When the comparison result is Ta ≧ Tp, the process proceeds from S214 to S215, and the CPU 2 controls the current to the motor drive circuit 10 and adds wait to the normal operation timing. The waiting time is a value equal to or less than the stoppable time tg obtained from the stoppable time table of FIG. 5 of the thermal paper D in the temperature information Ta. When the wait is added, the conveyance is temporarily stopped within the stoppable time. In step S216, the motor drive circuit 10 is controlled to feed the thermal paper D by a predetermined line by rotating the stepping motor 11 to feed the thermal paper D in one of positive and negative directions by a predetermined line. Information on the number of lines sent including the time of stopping in S215 and the positive and negative directions is stored in the RAM 4. In the case of passing through S215, the CPU 2 records that the control of the conveyance speed has been performed due to the high temperature of the thermal head 8 through the RAM 4 in S215.

In S217, if the process passes through S215, the information that has passed through S215 stored in the RAM 4 is deleted, and the process returns to S214. When not passing through S215, the process proceeds to S218. In S218, the CPU 2 determines whether or not the thermal paper D is deviated from the specified position for recording the next line based on the information stored in the RAM 4. In S218, if the thermal paper D is deviated from a specified position such as a cutting position in the cutter by calculating the direction in which the CPU 2 sends the line and the number of rotations stored in the RAM 4, the process returns to S214, and at the specified position. If it is confirmed, the printing and discharging operation is completed.

At this time, when the comparison result becomes Ta <Tp, the CPU 2 may determine whether or not the discharge conveyance has been sent for a specified number of lines in S214 and end the discharge conveyance. Alternatively, the specified position may be set before the cutting position, and the paper may be further conveyed from the specified position.

In this way, when the temperature of the thermal head 8 is detected and it is determined that the thermal paper D can be colored by the thermal storage of the thermal head 8, the thermal paper D is transported within a time range in which the color development can be suppressed. Therefore, it is possible to suppress the thermal paper D from being colored and soiled. Further, by slowing the conveyance so that the temperature of the thermal head 8 is lowered in the process of discharging the thermal paper D to the cutting position, the thermal paper to be used for the next printing or the portion to be used of the thermal paper D becomes dirty. Can be prevented. Note that the conveyance speed control during printing or the conveyance speed control in the paper discharge conveyance process to the thermal paper cutting position in the above-described second embodiment is not directly related. You can go. Further, if the conveyance control for returning to the specified position is performed, the same control can be performed for both after printing without distinguishing between the control after printing and the control during printing.

As described above, according to the present invention, it is possible to prevent the thermal paper from being unintentionally colored and soiled without increasing the size of the apparatus by adding a retracting mechanism or the like. Further, since the thermal paper is controlled to be transported only when there is a possibility that the thermal paper may be colored due to the heat accumulation of the thermal head 8, it is possible to efficiently prevent the thermal paper from being stained without controlling the transport when unnecessary. it can.

1 Interface 2 CPU
3 ROM
4 RAM
5 Shift register
6 Latch circuit 7 Drive circuit 8 Thermal head 9 Temperature detection circuit 10 Motor drive circuit 11 Stepping motor 12 Platen roller 13 Voltage detection circuit 20 Thermal printer 21 Handy terminal

Claims (7)

Recording means for energizing the thermal head to record on a thermal recording medium;
Conveying means for conveying the thermal recording medium;
Temperature detecting means for detecting the temperature in the vicinity of the thermal head;
Information storage means for storing information including color temperature information of the thermal recording medium;
Transport speed control means for controlling the transport speed of the thermal recording medium by the transport means;
Have
When the temperature detection means detects a temperature exceeding the temperature at which the thermal recording medium starts color development based on the color development temperature information,
The transport speed control means controls the transport means to suppress color development of the thermal recording medium.
A thermal printer that performs control to change a relative position between the thermal recording medium and the thermal head. 2. The thermal printer according to claim 1, wherein the control for changing the relative position by the transport speed control means changes the transport speed of the thermal storage medium by the transport means. The information storage means stores a stoppable time during which the thermal recording medium can be inhibited from developing color at a predetermined temperature detected by the temperature detection means,
The control for changing the relative position by the transport speed control unit includes a temporary stop of the transport of the thermal storage medium by the transport unit, and the stop time of the thermal storage medium in the vicinity of the thermal head is the stop. 3. The thermal printer according to claim 2, wherein the thermal printer is performed so as not to exceed a possible time. 4. The thermal printer according to claim 3, wherein the control for changing the relative position by the transport speed control means makes the transport speed negative after stopping the transport of the thermal storage medium by the transport means. The information storage unit stores a plurality of stoppable times corresponding to the plurality of different temperatures at the plurality of different temperatures detected by the temperature detection unit for the thermal storage medium,
For each of the plurality of different temperatures detected by the temperature detection means, the conveyance speed control means controls the conveyance means so as not to exceed the stoppable time stored in the information storage means. The thermal printer according to claim 3 or 4, wherein the thermal printer is characterized. Recording means for energizing the thermal head to record on a thermal recording medium;
Conveying means for conveying the thermal recording medium;
Temperature detecting means for detecting the temperature in the vicinity of the thermal head;
Information storage means for storing information including color temperature information of the thermal recording medium;
Transport speed control means for controlling the transport speed of the thermal recording medium by the transport means;
Have
When the temperature detection means detects a temperature exceeding the temperature at which the thermal recording medium starts color development based on the color development temperature information,
The transport speed control means controls the transport means to suppress color development of the thermal recording medium.
A control method for a thermal printer, wherein control is performed to change a relative position between the thermal recording medium and the thermal head. Recording means for energizing the thermal head to record on a thermal recording medium;
Conveying means for conveying the thermal recording medium;
Temperature detecting means for detecting the temperature in the vicinity of the thermal head;
Information storage means for storing information including color temperature information of the thermal recording medium;
Transport speed control means for controlling the transport speed of the thermal recording medium by the transport means;
Have
When the temperature detection means detects a temperature exceeding the temperature at which the thermal recording medium starts color development based on the color development temperature information,
The transport speed control means controls the transport means to suppress color development of the thermal recording medium.
An electronic apparatus equipped with a thermal printer, wherein control is performed to change a relative position between the thermal recording medium and the thermal head.

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