JP2006027217A - Thermal printer apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal printer apparatus in which a surface temperature of an erasure roller is controlled to be a preliminarily set correct temperature. <P>SOLUTION: The thermal printer apparatus is equipped with a thermal head movable up and down, and the erasure roller with a heater built inside of an aluminum pipe at the upstream side of the thermal head. A control circuit carries out temperature control towards a set temperature lower than a target temperature and turns OFF the heater for only a compulsive OFF time when the temperature reaches the set temperature. Temperature control towards the set temperature is carried out again after the compulsive OFF time elapses. The set temperature and the compulsive OFF time are changed in accordance with a roller temperature when the heater is started to be turned ON. When the temperature reaches the target temperature by this temperature control, paper transfer is started. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thermal printer apparatus capable of recording an image with a thermal head using a coloring type reversible thermosensitive recording material using a leuco dye and a reversible developer, and other thermosensitive recording materials.

Many proposals have been made for thermal printers that record images by bringing a thermal head into contact with a thermal recording material, but some types of thermal printers, such as leuco dyes and reversible developers, are used. In a thermal printer that performs image recording using a color-developable reversible thermosensitive recording material (see, for example, Patent Document 1), an image is recorded by a thermal head and an image can be erased using an erasing roller. (For example, refer to Patent Document 2).
JP 2002-270931 A Japanese Patent Application No. 2002-331697

  However, in the thermal printer as described above, since the heat capacity of the erasing roller is large and the temperature sensor is arranged to detect the roller surface temperature, the energization is turned off when the target temperature is confirmed by the temperature sensor. Even so, the temperature rise continues for a while, and as a result, the temperature of the roller surface exceeds the target.

  An object of the present invention is to provide a thermal printer apparatus in which the surface temperature of the erasing roller is controlled to a preset correct temperature.

The present invention provides a paper transport path for transporting a reversible thermosensitive recording paper that enables printing and erasing by changing the cooling rate after heating,
A thermal head for recording an image on a sheet conveyed on the sheet conveyance path;
An erasing roller that is disposed in a conveyance path on the upstream side of the thermal head and that heats the paper to erase the image on the paper by gradual cooling after the heating;
A controller that controls the power applied to the erasing roller based on a detection value of a temperature sensor that detects the temperature of the erasing roller;
The control unit sets a control target temperature after power supply to the erasing roller is started to a temperature lower than a target target temperature by a predetermined temperature, and the detection value of the temperature sensor is When the control target temperature is reached, the power supply is turned off for a predetermined time, and then the temperature control for the control target temperature is performed again. In the present invention, the erasing roller is a pipe-shaped metal made of, for example, an aluminum pipe. A roller with a heater inside is used. In the temperature control of the roller, a temperature sensor is brought into contact with the roller surface, and electric power applied to the heater is turned on / off based on a detection value of the sensor. That is, the heater is turned on until the sensor detection value reaches the control target temperature, and turned off when the control target temperature is reached. Furthermore, after that, the temperature is controlled again after the predetermined time has elapsed after maintaining OFF for a predetermined time.

  By controlling in this way, when the roller temperature reaches the control target temperature, the temperature rises for a while even if the heater is turned off. Therefore, when the temperature control is performed next by appropriately setting a predetermined time for turning off the heater. The roller temperature is close to the final target temperature.

  In a preferred embodiment, the control target temperature is changed according to a detection value of a temperature sensor when power supply to the erasing roller is started. More preferably, in addition to this, the predetermined time is changed according to a detection value of the temperature sensor when power supply to the erasing roller is started. The rate of increase in the roller temperature changes depending on the roller temperature when power supply to the erasing roller is started due to the relationship between the heat capacities. Therefore, by controlling as described above, temperature control close to the target temperature can be performed.

  According to the present invention, the temperature of the roller can be brought closer to the desired target temperature more accurately, so that the image on the paper can be erased reliably.

  FIG. 1 shows an external view of a thermal printer apparatus according to an embodiment of the present invention.

  The thermal printer device 1 includes a thermal head that is a print head and an erasing roller. The thermal printer 1 prints an image received from a host computer (not shown) by the thermal head on a paper made of a color reversible heating recording material using a leuco dye and a reversible developer, and once by the erasing roller. By erasing the printed image on the heated recording paper, it can be reused. By using the above paper, when energy is applied to each pixel by the thermal head, the pixel is rapidly cooled after passing through the head, and when the entire paper is heated by the erasing roller having a large heat capacity, the entire paper is Since the heat is stored, each pixel is gradually cooled after passing through the roller. With such a behavior, recording for each pixel by the thermal head and erasing of the entire sheet by the erasing roller are performed.

  In FIG. 1, a thermal printer device 1 includes a paper tray 2 for setting paper (hereinafter referred to as “paper”) made of the color-type reversible heating recording material on the upper back surface (upper supply side). A paper discharge tray 5 is provided on the lower front surface (lower paper discharge side). Between the paper tray 2 and the paper discharge tray 5, a paper transport unit is disposed in the apparatus main body, and a thermal head and an erasing roller, which will be described later, are disposed along the paper transport unit. Further, a top cover 3 is provided at the top of the apparatus body so as to be openable and closable, and an operation unit 4 is provided on the right side of the top cover 3. The operation unit 4 can select one of three modes: (1) recording mode, (2) erasing / recording mode, and (3) erasing mode. The recording mode is a mode that only records images on paper, the erasing mode is the mode that only erases images recorded on paper, and the erasing / recording mode is after erasing images recorded on paper. This is a mode for recording images continuously. The sheet conveyance speed V in each mode is not the same but is different. That is, for the same speed V, the recording mode> erase / record mode (= erase mode).

  FIG. 2 is a configuration diagram when the paper transport unit is viewed from the side.

  The paper transport unit disposed between the paper tray 2 and the paper discharge tray 5 has a paper feed roller 20, a paper transport path 22, an erasing processing unit 28, a cooling fan 25, and a recording processing unit 29 in order from the upstream side to the downstream side. A thermal head lift position detection sensor 33 and a thermal head lift cam 32 are disposed.

  The erasing processing unit 28 includes a heater lamp inside, and includes an erasing roller 23 made of an aluminum pipe, and a platen roller 24 disposed to face the roller 23 with the paper conveyance path 22 interposed therebetween.

  In addition, the recording processing unit 29 includes a thermal head 27 and a platen roller 26 disposed to face the head 27 with the paper transport path 22 interposed therebetween.

  Among these members, the one located above the sheet conveyance path 22 is accommodated in the movable portion 21, and the movable portion 21 has the end on the paper feed side as the fulcrum and the end on the paper discharge side upward. It has a rotatable structure. By turning the movable portion 21 as the fulcrum, it is easy to remove jammed paper on the conveyance path.

  The top cover 3 is located above the paper conveyance path, and an elevation motor 30 for raising and lowering the thermal head 27 and an LF (line feed) motor 31 for conveying the paper are arranged below the paper conveyance path. Has been.

  The cooling fan 25 is for forcibly air-cooling the entire sheet that has passed through the erasing roller so that the density of the recorded image by the thermal head does not decrease in the erasing / recording mode.

  As sensors, a cover opening / closing sensor S4 that detects the opening / closing of the top cover 3 and a paper conveyance path 22 are arranged between the thermal head 27 and the erasing roller 23, and the paper is conveyed to a specific position. A paper detection sensor S1 for detecting the state is provided. Specifically, this sensor detects the leading edge of the conveyed paper. Further, as will be described later, the trailing edge of the sheet is also detected. Further, although not shown, an ambient temperature detection sensor for detecting the ambient temperature α of the apparatus is provided.

  The elevating motor 30 is connected to an elevating cam 32 and raises a thermal head holder (not shown) for storing the thermal head 27 in the erasing mode, and lowers the thermal head holder in the recording mode or erasing / recording mode. Let An elliptical elevating cam 32 is in contact with the thermal head holder, and the thermal head holder is pushed up and raised by rotating it so that its long diameter portion is at an upward angle, and the short diameter portion is upward. By rotating to an angle, the thermal head holder is lowered by the spring pressure and its own weight. The rotation angle of the lift cam is detected by lift position sensors 33 of two thermal heads arranged at right angles.

  The paper detection sensor S1 combines detection of the front end of the paper and detection of the rear end of the paper. When detecting the leading edge of the paper, the detection signal is sent to the control circuit, and the control circuit starts to lower the thermal head 27. When the trailing edge of the sheet is detected, the signal is sent to the control circuit. In the control circuit, the remaining number of print lines is the number of printable lines up to the trailing edge of the sheet (the distance between the sensor S1 and the recording position by the thermal head 27). The remaining number of print lines is set to be equal to or less than the number of printable lines.

  The thermal head 27 is provided with a temperature sensor (not shown) therein, and the sensor output is monitored by a control circuit. Further, a temperature sensor for the erasing roller 23 made of an aluminum pipe is also provided, and the sensor output is monitored by a control circuit.

FIG. 3 is a block diagram of the control unit. From the control circuit 50, print data for recording is output to the thermal head 27, and a drive signal is output to the lift motor 30 and the LF motor 31 via the drive units 51 and 52. To the drive unit 52 that outputs a drive signal to the LF motor 31, a motor drive pulse for the speed V1 in the recording mode and a motor drive pulse for the speed V2 in the erase / record mode or the erase mode are output. The In addition, a drive signal is output to the heater lamp 53 formed of a halogen lamp disposed in the erasing roller 23 via the drive unit 54.
The thermal head 27 has a head part 27a, a drive part 27b, a history control part 27c, and a temperature sensor S2 for monitoring the temperature of the head part 27a. The temperature detection signal of the temperature sensor S2 is input to the control circuit 50. Similarly, the erasing roller 23 is provided with a temperature sensor S <b> 3 for detecting the surface temperature, and this sensor output is input to the control circuit 50.

  The control circuit 50 is connected to an interface 55 for connecting to the operation unit 4, various sensors S, and a host computer. A printer driver is implemented in the host computer. When a print command for image data is generated in the host computer, the image data is input to the control circuit 50 via the interface 55.

  Further, the tables TB1 to TB3 are connected to the control circuit 50, respectively. The table TB1 is a table for setting a printing pulse pattern per dot (one pixel) based on the sheet conveyance speed. The conveyance speed is set faster in the recording mode than in the erasing / recording mode. When the conveyance speed is high, when printing a certain line, the influence of heat when printing the previous line is large, so the applied energy to that line must be smaller. When V is fast, the pulse width of the print pulse pattern is set short. FIG. 4 shows the print pulse pattern for one dot. The pulse width of the print pulse pattern shown in the figure is TE. The print pulse pattern is composed of 1 to 20 control sections. As will be described later, data (1 or 0) of each control section is transmitted from the control circuit to the thermal head history control section 27c by the DMA. The

  The table TB2 shows the control section T (timer value) based on the ambient temperature α. If the value of the control section T is increased, the pulse width TE is increased, so that the applied energy per dot is increased.

  Accordingly, the amount of energy applied per dot varies depending on the conveyance speed V and the ambient temperature α. In this example, the parameters for determining the amount of energy applied per dot are the conveyance speed V and the ambient temperature α. However, other parameters can be set.

  Another table TB3 connected to the control circuit 50 shows a temperature control table of the heater lamp 53, and sets a target set temperature and forced OFF time based on the ambient temperature α at the start of driving. Detailed control operations using these tables will be described later.

  The history control unit 27c provided in the thermal head 27 controls the print pulse pattern for the current dot in consideration of the ON / OFF history of each dot on the same line in the transport direction. FIG. 5 shows the operation of the history control unit 27c. In FIG. 5A, when attention is paid to the dots A to C on the print line to be printed this time, the previous dot A1 and the previous dot A2 are not printed for A. For B, the previous dot B1 and the previous dot B2 are both printed. For C, the previous dot C1 is printed, and the previous dot C2 is not printed. Therefore, this time, when the print pulse pattern selected in the table TB1 is input to the history control unit 27c, energy that maintains the pulse width TE of the input print pulse pattern as it is is applied to A. Since the influence of the thermal energy based on the energy applied to the previous dot B1 and the dot 1B2 last time remains for the B dot, 70% energy is applied to A, and for C, Since heat energy based on the energy applied to the dot C1 last time remains, 85% energy is applied.

  In this way, the history control unit 27c controls the amount of energy applied this time based on the previous energy ON / OFF history. This makes it possible to apply energy accurately to the current dot.

  Next, the detailed operation of the control circuit 50 will be described with reference to a flowchart.

  FIG. 6 is a flowchart showing the operation when the recording mode is selected. This recording mode is executed when the recording mode or the erasing / recording mode is selected.

When data of an image to be recorded is received from the host computer (ST1), “waiting for temperature drop” of the thermal head is executed in ST2. When the temperature of the thermal head decreases in ST2, the sheet is transported to the recording position in ST3, and “thermal head lowering” control is performed in ST4.
Subsequently, a print pulse pattern within one dot is selected (ST5). The selection of the print pulse pattern is performed with reference to the table TB1 based on the paper conveyance speed V at that time. That is, when the recording mode is selected, the speed is V1, and when the erasing / recording mode is selected, the speed is V2 (V2 <V1). Therefore, whether the set mode is the recording mode or the erasing / recording mode. Each print pulse pattern is selected by.

  Subsequently, the print data of the first line is transferred from the control circuit 50 to the head unit 27a (ST6).

  Subsequently, in step ST7, the timer value T is set with reference to the table TB2. This timer value T is set based on the ambient temperature α at that time. The timer value T is for determining the control section T of the print pulse pattern as described in FIG.

  Next, in ST8, the DMA (direct memory access) transfer of the print pulse pattern (including the timer value) determined in ST5 to ST7 is performed to the history control unit 27c. That is, since the control section is 1 to 20, data (0 or 1) corresponding to each control section T is DMA-transferred to the history control unit 27c 20 times. Since the control circuit 50 has a built-in DMA control unit, when performing the DMA transfer of ST8, the control circuit 50 only needs to set the DMA (actually the CPU), and the CPU is immediately released after the setting. Other processing can be performed. For this reason, it is very efficient and can contribute to speeding-up.

  In ST9, the print data of the next line is transferred to the head portion 27a of the thermal head 27 (preparation for processing of the next line). Subsequently, in ST10, the paper is fed by one step, and in ST11, “paper end processing” described later is performed. If printing of all lines has not been completed (ST12), the processing from ST7 onward is performed again. When printing of all lines is completed, the thermal head 27 is raised (ST13), the paper is ejected (ST14), and the process ends.

  FIG. 7 shows the control operation of “waiting for temperature decrease” in ST2.

  In ST20, the upper limit temperature flag is checked, and if it is in the reset state, nothing is done. This upper limit temperature flag is a flag set by “temperature detection” described later. If this flag is set, the temperature of the thermal head is read by the temperature sensor S2 (ST21) and waits until it becomes 65 ° C. or less (ST22). If the temperature is 65 ° C or lower, the upper limit temperature flag is cleared (ST23), and the process returns.

  FIG. 8 shows a control operation of “temperature detection” executed at regular intervals by a timer interrupt.

  First, the temperature of the thermal head is read by the temperature sensor S2 (ST30), and it is determined whether or not it is 68 ° C or higher (ST31). If it is lower than 68 ° C, the upper limit temperature flag is cleared (ST32) and the return. To do. If it is 68 ° C or higher, an upper limit temperature flag is set (ST33) and the process returns.

  Next, “thermal head lowering” in ST4 of FIG. 6 will be described.

  FIG. 9 is a diagram showing an outline of the operation of “thermal head lowering”.

  When the sheet detection sensor S1 detects the leading edge of the sheet 60 conveyed on the sheet conveyance path 22, the detection signal is output to the control circuit 50, and the control circuit 50 drives the lifting motor 30 based on the detection timing. The timing is determined and the descent of the thermal head 27 is started. FIG. 9A shows the time when the leading edge of the sheet 60 is detected by the sheet detection sensor S1. FIG. 9B shows a state in which the paper 60 is further conveyed and advanced by a distance L1. At this time, the thermal head 27 starts to descend. When the paper 60 reaches the recording position P, the head heating portion of the thermal head 27 comes into contact with the front end of the paper at the same time. Thereafter, the printing operation of the image by the thermal head 27 is performed as the paper 60 is conveyed. The distance L1 is changed according to the conveyance speed of the paper 60. If the conveyance speed is fast, L1 becomes short.

  FIG. 10 shows a control operation of “thermal head lowering”.

  When the leading edge of the paper 60 is detected by the paper detection sensor S1 in ST40, the number of pulses N (represented by the number of conveyance steps of the paper 60 and corresponding to the distance L1) N is set to the thermal head 27 start position. Note that the pulse number N varies depending on the recording mode and the erasing / recording mode because the conveyance speed of the paper 60 is different. The number of pulses N is set larger in the recording mode in which the conveyance speed is faster. Therefore, in ST41, the number of pulses N is set according to the set mode. In ST42 and ST43, it waits until the set pulse number N becomes 0, and when N = 0, the thermal head 27 starts to descend. The state where N = 0 is the state shown in FIG.

  With the above operation, the head heating portion of the thermal head 27 and the leading edge of the paper 60 can be exactly matched at the recording position P, and there is no need to stop the paper 60 at the recording position P. Further, since the control circuit 50 can know the timing at which the leading edge of the paper 60 reaches the recording position P and the head heating portion of the thermal head 27 is in contact with the leading edge of the paper at that time, the thermal head from this time. By applying printing energy based on image data to 27, it is possible to prevent energy from being applied to the thermal head 27 without any load, and the thermal head 27 contacts the rotating platen roller. Can also be prevented.

  Next, operations in ST5 to ST9 in FIG. 6 will be described with reference to FIG.

  In ST5, the print pulse pattern within one dot is selected based on the table TB1 (see FIG. 3), and the print data of the first line is transferred to the head portion 27a of the thermal head 27 in ST6. In FIG. 11, the print data of the first line corresponds to A of “print data transfer”. In this example, the sheet conveyance speed is set to 50 mm / s, whereby a timer interrupt is generated every 2.5 ms and the motor is fed.

  When the first print data indicated by A is transferred to the head portion 27a and latched, printing energization is started at the timing (A) in the figure. That is, the DMA transfer of the print pulse pattern is performed in ST8. At the same time, the next line print data (indicated by B) is transferred. The print pulse pattern DMA-transferred to the history control unit 27c of the thermal head 27 at the timing (A) is set by ST5 and ST7 with reference to the tables TB1 and TB2 as described above. In the example shown in the figure, the print energization section is divided into the right half and the left half of the thermal head. In this way, the print pulse pattern is DMA-transferred at the timing (A), so that the CPU of the control circuit 50 is released from the software burden related to the print pulse pattern transmission immediately after the timing (A). It becomes possible to perform an operation. For this reason, high-speed processing is possible.

  Next, the “paper end process” in ST11 of FIG. 6 will be described with reference to FIGS.

  FIG. 12A shows a state in which the paper detection sensor S1 has detected the trailing edge of the paper 60. FIG. The image data storage memory M included in the control circuit 50 stores image data to be printed by the thermal head 27 and is updated for each page. In addition, the remaining print line number R by the thermal head 27 is stored on the RAM. When the remaining print line number R becomes zero, printing of the thermal head 27 is completed.

  In FIG. 12, an interval Q between the sensor S1 and the recording position P indicates the number of printable lines up to the rear end of the sheet. In this state, as shown in FIG. 12, if R> Q, the remaining number of print lines on the RAM is rewritten as R ← Q so that R = Q. Thus, as will be described later, when the paper trailing edge 60 passes the recording position P, the thermal head 27 is raised even if image data to be printed remains in the image data storage memory M. Thereafter, the thermal head No energy is applied to the thermal head 27, and the thermal head 27 does not contact the rotating platen roller.

  FIG. 13 is a flowchart showing the control operation of “paper end processing”.

  In ST50, when the trailing edge of the sheet is detected by the sheet detection sensor S1, a determination of R> Q is made, and if R> Q, R is set to Q (ST52).

  When the printing operation is performed as described above and printing for all lines is completed (ST12 in FIG. 6), the control circuit drives the lifting motor 30 to raise the thermal head 27 (ST13 in FIG. 6).

  Next, the operation in the erase mode will be described. This erase mode is executed in the erase mode and the erase / record mode.

  FIG. 14 is a flowchart showing the control operation in the erase mode.

  In ST60, “erasing roller energization start” is executed. Subsequently, the surface temperature of the erasing roller 23 is measured by the temperature sensor S3, and in ST62, the table TB3 is referred to, and the set temperature and the forced OFF time as the control target corresponding to the temperature at that time (starting temperature) are obtained. Set. Referring to the table TB3, for example, if the starting temperature is 100 ° C. or higher, the set value is 147 ° C. and the forced OFF time is 100 ms. When the starting temperature is between 20 ° C. and 100 ° C., the set value is 145 ° C. and the forced OFF time is 50 ms.

  Next, the process proceeds to ST63 and "erase interrupt start" is executed by a timer interrupt. In ST64, it is determined whether or not the target temperature has been reached. If it has reached, the conveyance of the sheet is started in ST65. Although the thermal head 27 is raised at this time, in the erasing / recording mode, when the leading edge of the paper reaches the paper detection sensor S1, the thermal head 27 starts to descend.

  FIG. 15 shows a configuration diagram and a waveform diagram for executing “erasing roller energization start” in ST60. The commercial power supply 70 is supplied to a heater lamp 53 formed of a halogen lamp via a reactor 71 and a triac 72. The triac 72 is zero-cross controlled by a zero-cross control circuit 73, and a control pulse is input to the zero-cross control circuit 73 from the drive unit 54. The zero-cross control circuit 73 is a circuit that performs zero-cross control in which the ON / OFF timing of the triac 72 is the zero-cross timing of the power supply voltage. By performing this zero-cross control, an inrush current at the time of energization can be prevented. Further, as shown in FIG. 15C, a control pulse for gradually increasing the zero cross control period is input to the zero cross control circuit 73 as shown in FIG. As a result, as shown in FIG. 15B, the time for energizing the triac 72 can be gradually increased while performing the zero cross control. Therefore, no current flows through the heater lamp 53 at a stretch, and it is possible to prevent performance deterioration and damage of parts due to the inrush current flowing, and adverse effects on surrounding electronic devices.

  FIG. 16 is a diagram illustrating the set temperature and forced OFF time set in ST62. When the erasing roller temperature at the start of energizing the heater lamp is low and high, the behavior of the temperature rise associated with subsequent energization differs. That is, when the heat capacity of the erasing roller is large, the change in temperature rise due to heating becomes dull. Even when the energization is turned off when the target temperature is confirmed by the temperature sensor, the temperature rise continues for a while. The degree of temperature rise differs depending on whether the erasing roller temperature at the start of energizing the heater lamp is low or high. Therefore, when energization of the heater lamp is started, a certain set temperature is set before the target temperature, and the setting is made according to the starting temperature (erasing roller temperature) when energization of the heater lamp is started. Change the temperature (increase the set temperature when the starting temperature is high). Then, when the set temperature is reached, the power supply is turned off. In addition, a fixed forced OFF time is set from when the set temperature is reached, and temperature control is enabled after the OFF time has elapsed, and the forced OFF time is the start when the heater lamp is energized. The length is changed according to the temperature.

  The reason for controlling as described above is that when the temperature at the start of energization of the heater lamp is higher, the amount of heat stored in the erasing roller is larger, so that the set temperature is increased or the forced OFF time is longer. This is because it is preferable to set.

  Therefore, as shown in the table TB3 of FIG. 3, when the starting temperature is 20 ° C. to 100 ° C., the set temperature is set to 145 ° C., the forced OFF time is set to 50 ms, and the starting temperature is set to 100 ° C. In the case of C or higher, the set temperature is set to 147 ° C. and the forced OFF time is set to 100 ms.

  When the forced OFF time ends, the roller temperature becomes the final target temperature or a temperature very close to that temperature. Therefore, immediately after that, since it is highly possible that the roller temperature is equal to or higher than the set temperature, the heater energization is kept off. However, when the temperature is lower than the set temperature, the above temperature control is performed again.

  In the above embodiment, both the set temperature and the forced OFF time are changed according to the starting temperature, but either one is set to a constant value and the other is changed according to the starting temperature. good.

  FIG. 17 shows the timer interrupt operation of “erase interrupt start” in ST63 of FIG.

  In ST70, it is determined whether the forced OFF flag is set. In ST71, the temperature sensor 53 measures the temperature of the erasing roller. If the temperature is abnormal (ST72), an error flag is set (ST73), the heater lamp is turned off (ST74), and the process returns.

  In ST72, when the measured temperature is normal, it is determined in ST75 whether the measured temperature exceeds the set value. This set value is a value obtained by referring to the table TB3 in ST62 of FIG. If the set value is not exceeded, the heater lamp is turned on in ST76 and the process returns.

  If the set value is exceeded in ST75, a forced OFF flag is set in ST77, a forced OFF time M is set in ST78, and the heater is turned off (ST79).

  In ST70, if the forced OFF flag is set, in ST80, 1 unit time (25 ms in this case) is decremented from the forced OFF time M. In ST81, it is determined whether M = 0, and M = 0. At this time, the forced OFF flag is cleared (ST82). If not M = 0, the process proceeds to ST74 and the heater is turned off. Therefore, when the forced OFF flag is set, the power supply to the heater lamp is turned OFF for the forced OFF time M set in ST78.

  In this manner, during the erasing period in the erasing mode and the recording / erasing mode, the temperature control is performed on the heater lamp 53 of the erasing roller 23 with respect to the set temperature just before the target temperature, and in ST64 of FIG. Waiting for the temperature to be reached, the sheet is transported when the target temperature is reached. Therefore, according to this control, the target temperature is more accurately controlled in consideration of the heat capacity of the erasing roller 23.

  In the present embodiment, the following control is further performed.

  First, in order to protect the thermal head 27, the raising / lowering state of the thermal head 27 is constantly monitored by the raising / lowering position sensor 33 of the thermal head, and the thermal head is not in contact with the raised position (standby position) or the platen roller 26. Then, the drive signal is not output to the thermal head 27, and the drive voltage to the thermal head is cut off. As a result, when the thermal head is in the raised position, it is possible to prevent energy from being erroneously applied to the thermal head.

  Second, when a printing operation is performed by applying energy to the thermal head 27, whether or not a paper jam has occurred due to the paper detection sensor S1 and a sensor provided on another conveyance path (not shown). To monitor. When a paper jam occurs, the application of energy to the thermal head 27 is immediately stopped. This can prevent the temperature rise of the thermal head from becoming excessive.

  Thirdly, in ST72 of FIG. 17, it is determined whether or not the temperature measurement value of the erasing roller 23 is an abnormal value. This determination is performed when the measured temperature itself is abnormal. Even when an abnormal change is made from the measured temperature value (the differential value is large), it is detected as an abnormal value.

1 is an external view of a thermal printer apparatus according to an embodiment of the present invention. Configuration diagram around the paper transport path Configuration diagram of control unit Diagram explaining printing pulse pattern The figure explaining operation | movement of a log | history control part Flow chart showing control operation in recording mode Flow chart showing control operation of “Waiting for temperature drop” Flow chart showing control operation of “temperature detection” Diagram explaining control when the thermal head is lowered Flow chart showing control operation of “thermal head descent” Timing waveform diagram of print energization and print data transfer The figure explaining the operation contents of “paper end processing” Flow chart showing control operation of “paper end processing” Flow chart showing control operation in erase mode Configuration diagram and operation explanatory diagram for starting energization to the erasing roller Diagram explaining set temperature and forced OFF time Flow chart showing timer interrupt operation in erase mode

Claims (4)

A paper transport path for transporting reversible thermosensitive recording paper that enables printing and erasing by changing the cooling rate after heating;
A thermal head for recording an image on a sheet conveyed on the sheet conveyance path;
An erasing roller that is disposed in a conveyance path on the upstream side of the thermal head and that heats the paper to erase the image on the paper by gradual cooling after the heating;
A controller that controls the power applied to the erasing roller based on a detection value of a temperature sensor that detects the temperature of the erasing roller;
The control unit sets a control target temperature after starting power supply to the erasing roller to a temperature lower than a final target target temperature by a predetermined temperature, and a detection value of the temperature sensor is When the control target temperature is reached, the power supply is turned off for a predetermined time, and then the temperature control for the control target temperature is performed again.   The thermal printer apparatus according to claim 1, wherein the control unit changes the control target temperature according to a detection value of the temperature sensor when power supply to the erasing roller is started.   3. The thermal printer apparatus according to claim 2, wherein the control unit changes the predetermined time according to a detection value of the temperature sensor when power supply to the erasing roller is started.   The thermal printer apparatus according to claim 1, wherein the control unit starts conveying the paper when a detection value of the temperature sensor reaches the final target temperature.

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