JP2007268918A - Open circuit checking apparatus and open circuit checking method of line thermal head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten the time for open circuit check and to improve throughput in choosing heating elements one by one for open circuit check. <P>SOLUTION: A CPU controls an open circuit checking section and a line thermal head through a head controller, and performs turning on electricity one by one for the open circuit check. In turning on the electricity control to each heating element, S18 detects the amount of voltage changes of a unit time in a transient state at the time of turning on an electricity start, and judges whether a difference of the last amount of voltage changes and this amount of voltage changes is below -aV or more than +bV. If it is not below aV nor more than +bV, either, then S19 judges whether the absolute value of this amount of voltage changes is more than x2 or less than y2. If it is not more than x2 or less than y2, either, the heating element judges that it does not disconnect and shifts to the open circuit check of the following dot. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a disconnection check device and a disconnection check method for a line thermal head in which a plurality of heating elements are provided in a line.

  In the line thermal head, a plurality of, for example, 2560 heating elements are arranged in a line in the printer, and the heads are arranged so that the heating elements are arranged in a direction perpendicular to the paper transport direction. The line thermal head always performs printing by melting the leuco dye of the thermal paper and the ink of the ink ribbon by heat generation while being in contact with the thermal paper and the ink ribbon.

In such a line thermal head, the heating element is damaged due to physical impact or thermal wear, resulting in disconnection. When the heating element is disconnected, the portion cannot be printed. Therefore, when a thin line such as a barcode is printed, the barcode is cut and the scanner cannot read correctly. In addition, the print quality is adversely affected by the occurrence of streaks in the vertical direction, which is the paper transport direction.
For this reason, in the line thermal head, it is necessary to frequently check the disconnection of the heating element to constantly check the state of the head.

As the line thermal head disconnection check, since it takes time to check the heating elements one by one, it is known to select a plurality of heating elements simultaneously and check the disconnection (see, for example, Patent Document 1). ).
JP 2002-67361 A

  However, in the case where the disconnection check is performed by selecting a plurality of heating elements at the same time, the resistance of the heating element can be reduced even though the time required for the disconnection check can be shortened compared to the case where the disconnection check is performed by selecting each heating element one by one. If the values vary, there is a possibility that the disconnection of each heating element cannot be reliably detected.

  The present invention provides a disconnection check device and disconnection check method for a line thermal head that can shorten the time required for the disconnection check and improve the throughput in selecting the heating element one by one and performing the disconnection check.

  The present invention relates to a line thermal head in which a plurality of heating elements are provided in a line, a control unit that sequentially controls energization of each heating element of the line thermal head to check disconnection, and energization control of each heating element. The difference between the voltage change amount detecting means for detecting the voltage change amount per unit time in the transient state at the start of energization and the previous voltage change amount detected by the voltage change amount detecting means and the current voltage change amount is set tolerance. A difference determination means for determining whether or not the difference is out of the range is provided. When the difference determination means determines that the difference is not out of the range of the tolerance, it is assumed that there is no disconnection and the next heating element The line thermal head disconnection check device shifts to the disconnection check.

  In addition, the present invention performs sequential energization control for line heating heads in a line thermal head in which a plurality of heating elements are provided in a line shape so as to check the amount of voltage change per unit time in a transient state at the start of energization. Detects whether the difference between the voltage change amount detected last time and the voltage change amount detected this time is outside the set tolerance range, and confirms that the difference is not outside the tolerance range. If it is determined, there is a disconnection check method for the line thermal head that shifts to a disconnection check for the next heating element because there is no disconnection.

  According to the present invention, it is possible to provide a disconnection check device and disconnection check method for a line thermal head that can shorten the time required for the disconnection check and improve the throughput in selecting the heating element one by one and performing the disconnection check.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this embodiment, the present invention is applied to a label printer.

  In FIG. 1, 1 is a CPU (central processing unit) constituting the control unit body, 2 is a ROM (read only memory) storing program data for the CPU 1 to control each unit, and 3 is processed by the CPU 1 Or a random access memory (RAM) in which various memories used for control are formed.

  In FIG. 1, 4 is a communication I / F (interface) for communicating with the host computer 5 via a line, 6 is various keys, 7 is an operation panel for controlling the key 6 and taking in key signals, 8 Is a stepping motor that transports the label paper, 9 is a stepping motor driver that drives and controls the stepping motor 7, 10 is a plurality of heating elements, for example, 2560 heating elements arranged in a line, A line thermal head that prints a bar code, characters, and the like, 11 is a head controller that drives and controls the line thermal head 10, and 12 is a disconnection check unit that checks disconnection of each heating element of the line thermal head 10.

The operation panel 7, stepping motor driver 9, and head controller 11 are electrically connected to a gate array (G / A) 13, respectively. The gate array 13 controls the operation panel 7, the stepping motor driver 9, and the head controller 11, respectively.
The CPU 1, ROM 2, RAM 3, communication I / F 4, and gate array 13 are electrically connected to each other via a bus line 14.

  The CPU 1 communicates with the host computer 5 via the communication I / F 4, and when receiving a command from the host computer 5, controls each unit according to the command. That is, as shown in FIG. 2, when a command is received from the host computer 5 in S1, it is determined whether the received command is a disconnection check command or another command in S2, and if it is a disconnection check command, In S3, disconnection check command processing is performed. If the command is other than the disconnection check command, other command processing corresponding to the command is performed in S4.

  As shown in FIG. 3, the disconnection check unit 12 includes a power source switching unit 22 that switches between a head power source used for original printing and a disconnection check power source 21 provided therein. The disconnection check power source 21 applies a voltage to the line thermal head 10 so that each heating element generates heat and does not perform a printing operation.

  The series circuit of the heating element HE and the NPN transistor Tr in the line thermal head 10 is connected in parallel to the number of heating elements through the voltage detection resistor 23 and the line 24 in series with the output terminal of the power supply switching unit 22. A parallel circuit connected to is connected. Each transistor Tr is turned on and off by a shift register and an on / off control unit 31.

  In the disconnection check unit 12, the line 24 is grounded through a resistor 25 and an NPN transistor 26 in series. That is, the series circuit of the resistor 25 and the transistor 26 is connected in parallel to a parallel circuit in which a plurality of series circuits of the heating element HE and the transistor Tr in the line thermal head 10 are connected in parallel.

  The disconnection check unit 12 detects a voltage generated in the voltage detection resistor 23 by the disconnection check power source 21 output from the power source switching unit 22 by a voltage detection unit 27 constituting a voltage detection unit, and detects the detected voltage. The value is amplified by the amplifier 28 and then supplied to the head controller 11. The transistor 26 is turned on and off by a signal from the head controller 11. The shift register and on / off control unit 31 is supplied with print data and disconnection check data from the CPU 1 constituting the control means via the head controller 11.

  The head controller 11 includes an analog / digital converter therein, and converts the voltage value taken from the disconnection check unit 12 into a digital value by the analog / digital converter and then supplies the converted value to the CPU 1.

  The disconnection check command process (S3) in FIG. 2 is configured to perform the process shown in FIG. That is, in S11, the CPU 1 controls the power supply switching unit 22 to switch the power supply to the disconnection check power supply 21 and perform a discharge process. In the discharge process, the transistor 26 is turned on for a certain period of time in order to discharge the charges accumulated in the line thermal head 10 and the line 24. As a result, the charges accumulated in the line 24 and the heating element HE of the line thermal head 10 are discharged through the resistor 25 and the transistor 26.

  Subsequently, in S 12, the count value n = 1 of the counter provided in the RAM 3 is set, and the n-th dot data is output to the shift register and the on / off control unit 31 of the line thermal head 10. That is, check data is output with the first dot set to “1” and all other dots set to “0”. At this time, the data output timing is long. This is because it takes time for the analog / digital converter and the disconnection check power supply 21 to rise and stabilize.

  Subsequently, a disconnection determination process for the first dot is performed in S13. That is, the transistor Tr connected to the heating element HE of the first dot is turned on to energize the heating element HE. At this time, the voltage detector 27 detects the voltage across the resistor 23. The detected voltage is amplified by an amplifier 28 and then input to the head controller 11 and converted into digital data by an analog / digital converter.

  The CPU 1 determines whether or not the absolute value of the detected voltage data when the energization to the heating element HE is stable is outside a predetermined range set in advance (disconnection determination unit). That is, it is determined whether or not the absolute value of the detected voltage data is not less than the upper limit value x1V or not more than the lower limit value y1V. The time until the energization of the heating element HE is stabilized is, for example, about 1.2 msec.

If the absolute value of the detected voltage data is equal to or higher than the upper limit value x1V or lower than the lower limit value y1V, it is determined that the circuit is disconnected. If it is not more than x1V and not more than y1V, it is determined that there is no disconnection.
In S14, the determination result is stored in the corresponding memory in the RAM 3.

  Subsequently, in S15, it is checked whether the count value n is the last dot. Since it is the first dot now, the counter is incremented in S16 to set the count value n to n + 1. In S 17, the second dot data is output to the shift register and on / off control unit 31 of the line thermal head 10. That is, check data is output with the second dot set to “1” and all other dots set to “0”. The data output timing at this time is shortened because the analog / digital converter and the power supply 21 for disconnection check have already been started.

  Subsequently, in S18, a voltage change amount (dV / dT) per unit time in a transient state is detected. That is, the voltage change amount (dV / dT) per unit time immediately after the transistor Tr is turned on and energization to the heating element HE is started is detected (voltage change amount detecting means). The amount of voltage change per unit time at this time is, for example, a short time after 300 μsec has elapsed since the transistor Tr was turned on. The detected voltage change amount (dV / dT) is stored in the memory.

  Then, it is determined whether or not the difference between the current voltage change amount and the previous voltage change amount is outside a preset tolerance range (difference determining means). That is, it is determined whether the difference is −aV or less or + bV or more. Since the current check is the second dot, the difference in voltage change from the first dot is determined.

  If the difference between the current voltage change amount and the previous voltage change amount is not −aV or less or + bV or more, then in S19, the absolute value of the current voltage change amount is set to a preset tolerance. It is determined whether or not the value is out of the range (absolute value determination means). That is, it is determined whether or not the absolute value is not less than x2V or not more than y2V.

  If the absolute value of the current voltage change amount is not x2 or more or y2V or less, it is determined in S20 that the second-dot heating element HE is not disconnected. Then, returning to S15, it is determined that it is not the last dot, and in S16, the counter is incremented to set the count value n to n + 1. In step S17, the third dot data is output to the shift register and on / off control unit 31 of the line thermal head 10. That is, check data is output in which the third dot is “1” and all other dots are “0”.

  In S18, if it is determined that the difference between the current voltage change amount and the previous voltage change amount is −aV or less or + bV or more, there is a possibility of disconnection, and S13 is performed. Disconnection determination processing is performed. Even if it is determined in S18 that the difference between the current voltage change amount and the previous voltage change amount is not less than -aV or + bV, the current voltage change amount is determined in S19. If it is determined that the absolute value is greater than or equal to x2V or less than or equal to y2V, there is a possibility of disconnection, and disconnection determination processing in S13 is performed.

  The disconnection determination process in S13 is as described above, and the absolute value of the detected voltage data detected by the voltage detector 27 is equal to or higher than the upper limit value x1V at the stable time after 1.2 msec from turning on the transistor Tr, or This is done by determining whether or not the lower limit value is y1V or less. If the absolute value of the detected voltage data is greater than or equal to x1V or less than or equal to y1V, it is determined that the circuit is disconnected, and the determination result is stored in the corresponding memory in the RAM 3 in S14.

  Thereafter, this process is repeated until the disconnection check of the heating element HE of the last dot. When it is determined in S15 that n is the last dot, that is, the 2560th dot, the corresponding memory in the RAM is found in S21. 2 is transmitted to the host computer 5 from the communication I / F 4 to complete the series of disconnection check processing.

  In such a configuration, when a disconnection check command for the heating element HE is received from the host computer 5, the CPU 1 of the label printer starts a disconnection check process. In the disconnection check process, first, the power source switching unit 22 is controlled to switch the power source from the head power source to the disconnection check power source 21.

  Then, check data for checking the first heating element HE of the first dot is created and output to the shift register and on / off control unit 31 of the line thermal head 10. At the first dot, it takes time for the operation of the disconnection check power supply 21 and the analog / digital converter to become stable, so the timing for outputting the check data is lengthened.

  The transistor Tr connected to the heating element HE of the first dot is turned on to energize the heating element HE, and the voltage detection unit 27 detects the voltage across the resistor 23. The detected voltage is amplified by an amplifier 28 and then input to the head controller 11 and converted into digital data by an analog / digital converter.

  Then, the absolute value of the voltage data detected at the timing when the energization to the heating element HE is stabilized, that is, the timing when 1.2 msec has elapsed from the start of the energization is x1V or more, or y1V or less. Judge whether it is.

  If the absolute value of the detected voltage data is not greater than x1V or less than y1V, it is determined that no disconnection has occurred. However, if the absolute value of the voltage data is greater than x1V or less than y1V, it is determined that the circuit is disconnected. The determination result is stored in the memory.

  When the first dot disconnection check is completed, the counter is incremented and the second dot disconnection check is started. From the second dot, the operation of the disconnection check power supply 21 and the analog / digital converter is already stable, so the output timing of the check data is shortened.

  The transistor Tr connected to the heating element HE of the second dot is turned on to energize the heating element HE, and the voltage across the resistor 23 is detected by the voltage detector 27. The detected voltage is amplified by an amplifier 28 and then input to the head controller 11 and converted into digital data by an analog / digital converter.

  The second dot captures the detected voltage data from the voltage detection unit 27 at the timing of the transient state before the energization to the heating element HE is stabilized, that is, the timing when 300 μsec has elapsed since the start of energization. The amount of voltage change (dV / dT) is detected. Then, the voltage change amount (dV / dT) per unit time of the previous detection voltage data is compared.

  If the difference between the previous voltage change amount and the current voltage change amount is not −aV or less or + bV or more, then whether or not the absolute value of the current voltage change amount is x2 V or more or y2 V or less is determined. judge. If the absolute value of the voltage change amount this time is neither x2 V nor more than y2 V, it is determined that the second-dot heating element HE is not disconnected, and the process proceeds to the next third-dot disconnection check.

  Similarly, in the disconnection check of the third dot, if the difference between the previous voltage change amount and the current voltage change amount is not −aV or less or + bV or more, then the absolute value of the current voltage change amount is It is determined whether or not x2V or more or y2V or less. If the absolute value of the voltage change amount at this time is neither x2 V nor more than y2 V, it is determined that the third-dot heating element HE is not disconnected, and the process proceeds to the next fourth-dot disconnection check.

  In this way, as long as it is determined that the heating element HE is not disconnected, the heating element HE for the disconnection check is switched at a transitional timing before the energization of the heating element HE is stabilized. That is, the disconnection check can be performed by switching the heating element HE at an early timing of 300 μsec.

  On the way, it is determined that the difference between the previous voltage change amount and the current voltage change amount is −aV or less, or + bV or more, or the current voltage change amount. If it is determined that the absolute value of the quantity is greater than or equal to x2V or less than or equal to y2V, then there is a possibility of disconnection, and the energization to the heating element HE is stabilized, 1.2 msec. After the elapse of time, disconnection determination processing is performed.

  When it is determined that the absolute value of the voltage data detected after the elapse of 1.2 msec is equal to or higher than the upper limit value x1V or lower than the lower limit value y1V, it is determined that the circuit is disconnected for the first time. Thus, when the heating element to be checked is disconnected, the disconnection can be reliably detected.

  For example, when checking the disconnection of the heating element of a line thermal head in which 2,560 heating elements are arranged in a line, most heating elements are not disconnected. In response to this, it is possible to determine that no disconnection has occurred at an extremely early timing and to proceed to the next disconnection check. Then, when a heating element with a possibility of disconnection is detected on the way, a disconnection check is performed using the absolute value of the voltage data detected at the timing after 1.2 msec when the energization to the heating element HE is stabilized. .

  Therefore, the time required for the disconnection check as a whole can be shortened and the throughput can be improved. In addition, select heating elements one by one and check for disconnection. For heating elements that may be disconnected, check the disconnection using the absolute value of the voltage data at the timing when power to the heating element HE is stable. As a result, a reliable disconnection check can be performed.

  The individual results of the heating element disconnection check are stored in the memory, and are transmitted to the host computer 5 when all the heating element disconnection checks are completed. Therefore, when the label printer is used, if the heating element is always checked for disconnection first, the host computer 5 can always grasp the state of each heating element HE of the line thermal head 10 before issuing the label. It is possible to determine whether or not the label issuance can be performed without any problem from the relationship between the label contents and the disconnected heating element.

  In this embodiment, in S18, the difference between the current voltage change amount and the previous voltage change amount is compared with -aV and + bV, and when it is not less than -aV or more than + bV, in S19, The absolute value of the voltage change this time is compared with x2V and y2V, and it is determined that there is no disconnection when it is not greater than x2V or less than y2V. However, the present invention is not necessarily limited to this. The steps may be interchanged. Moreover, the process which uses only one of the step of S18 and the step of S19 may be sufficient.

  Furthermore, in this embodiment, the processing of step S18 and step 19 is performed once for one dot, but these steps may be performed a plurality of times. In this case, the determination value for the second and subsequent times is set to a value different from the determination value for the first processing. It is also possible to take a plurality of voltage values and predict the final result by calculation.

1 is a block diagram showing a main configuration of a label printer according to an embodiment of the present invention. 6 is a flowchart showing command reception processing by the CPU of the label printer according to the embodiment. The figure which shows the circuit structure of the disconnection check part of the label printer which concerns on the embodiment, and a line thermal head. The flowchart which shows the disconnection check command process in FIG. 2 in detail.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... CPU (central processing unit), 10 ... Line thermal head, 11 ... Head controller, 12 ... Disconnection check part.

Claims (8)

A line thermal head provided with a plurality of heating elements in a line;
Control means for sequentially energizing the heating elements of the line thermal head to check disconnection,
In the energization control to each of the heating elements, voltage change amount detecting means for detecting a voltage change amount per unit time in a transient state at the start of energization;
A difference determination means for determining whether or not a difference between the previous voltage change amount detected by the voltage change amount detection means and the current voltage change amount is outside a set tolerance range;
If it is determined by the difference determination means that the difference is not outside the tolerance range, the disconnection check device for the line thermal head is shifted to the next heating element disconnection check because there is no disconnection. . In energization control to each heating element, voltage detection means for detecting the voltage when energization is stable,
When the difference determination means determines that the voltage is out of the tolerance range and the voltage value detected by the voltage detection means is outside the predetermined range set, the disconnection of the corresponding heating element is determined. A disconnection judging means for
2. The line thermal head disconnection check device according to claim 1, wherein when the disconnection determination means determines the presence or absence of disconnection, the process proceeds to a next disconnection check of the heating element.   3. The disconnection determining means determines the disconnection of the corresponding heating element based on the voltage value detected by the voltage detecting means at the time of the first disconnection check of the heating element, irrespective of the determination result by the difference determining means. Line thermal head disconnection check device as described. A line thermal head provided with a plurality of heating elements in a line;
Control means for sequentially energizing the heating elements of the line thermal head to check disconnection,
In the energization control to each of the heating elements, voltage change amount detecting means for detecting a voltage change amount per unit time in a transient state at the start of energization;
Absolute value determination means for determining whether or not the absolute value of the voltage change amount detected by the voltage change amount detection means is outside the set allowable value range;
If the absolute value determination means determines that the absolute value of the voltage change amount is not outside the range of the allowable value, the line shifts to the next heating element disconnection check on the assumption that there is no disconnection. Thermal head disconnection check device. In energization control to each heating element, voltage detection means for detecting the voltage when energization is stable,
If the voltage value detected by the voltage detection means is outside the predetermined range when the absolute value determination means has determined that it is outside the allowable value range, the corresponding heating element is disconnected. A disconnection judging means for judging,
5. The line thermal head disconnection check device according to claim 4, wherein when the disconnection determination means determines the presence or absence of disconnection, the process proceeds to the next disconnection check of the heating element.   The disconnection determination means, at the time of the first disconnection check of the heating element, determines the disconnection of the corresponding heating element based on the voltage value detected by the voltage detection means regardless of the determination result by the absolute value determination means. 5. Line thermal head disconnection check device according to 5. To each heating element of the line thermal head provided with a plurality of heating elements in a line, sequential energization control is performed for disconnection check to detect the voltage change amount per unit time in the transient state at the start of energization,
Determine whether the difference between the voltage change amount detected last time and the voltage change amount detected this time is outside the set tolerance range,
If it is determined that the difference is not outside the range of the tolerance, it is determined that there is no disconnection, and the process proceeds to the next heating element disconnection check. To each heating element of the line thermal head provided with a plurality of heating elements in a line, sequential energization control is performed for disconnection check to detect the voltage change amount per unit time in the transient state at the start of energization,
It is determined whether or not the absolute value of the detected voltage change amount is outside the set allowable value range,
If it is determined that the absolute value is not outside the range of the allowable value, the disconnection check method for the line thermal head is characterized in that the process proceeds to the next check for disconnection of the heating element because there is no disconnection.

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