JP2008183770A - Wire breaking checker of thermal head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wire breaking checker which can shorten the time required for checking a head to detect the wire breaking or degradation of a heating element included in a thermal head. <P>SOLUTION: The wire breaking checker includes: two or more head power circuits for applying a current to the 1st terminal of the heating element included in two or more blocks of the thermal head, respectively; two or more comparison circuits which forms two or more signals, respectively, showing whether the heating element chosen in each block is disconnected by comparing the voltage generated at the 1st terminal of the heating element included in two or more blocks with a predetermined value; and a logic circuit which generates the signal showing whether at least one of the heating elements chosen in two or more blocks is disconnected by performing a logic operation based on the output signals of two or more comparison circuits. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a disconnection check device for checking disconnection or deterioration of a heating element included in a thermal head used in a printer such as a label printer.

  The thermal head includes a set of a plurality of fine heating elements that generate heat when an electric current is applied. When these heating elements generate heat, the thermal paper is discolored or the ink applied to the ribbon is transferred to the paper for printing. FIG. 4 shows an example of an equivalent circuit of a thermal head used in a conventional label printer. In the thermal head 100, N heating elements R1 to RN, which are equivalently represented by resistors, are arranged in a line. A driving voltage is supplied to the first terminals of the heating elements R1 to RN from the head power supply circuit 200 connected to the power supply voltage, and the NAND terminals are connected to the second terminals of the heating elements R1 to RN. The output terminals of the gates G1 to GN are connected to each other.

  The strobe signal STROBE is supplied to one input terminal of the NAND gates G1 to GN, and the other input terminal is connected to the output terminal of the latch circuit 11. The latch circuit 11 temporarily stores print data DATA for one line that is serially input in synchronization with the clock signal CLK from the outside. Each NAND gate obtains the logical product of the corresponding print data and the strobe signal STROBE, and inverts the result for output. For example, when the J-th print data is at a high level and the strobe signal STROBE is also at a high level, the output terminal of the J-th NAND gate GJ is at a low level, and the output of the NAND gate GJ from the head power supply circuit 200 via the heating element RJ. A current flows through the terminal and the heating element RJ generates heat.

  On the other hand, in order to check the disconnection of the heating elements included in the thermal head, the heating elements R1 to RN to be checked are energized one by one so that a constant current is supplied from the head power supply circuit 200. To. Between the output terminal of the head power supply circuit 200 (first terminals of the heating elements R1 to RN) and the ground potential, resistors RA and RB having a resistance value sufficiently larger than the resistance value of the heating element are connected in series. A check terminal is provided at a connection point between the resistor RA and the resistor RB.

  When the heating element is not disconnected, most of the current supplied from the head power supply circuit 200 flows through the heating element, so that the voltage at the check terminal is lowered. On the other hand, when the heating element is disconnected, all of the current supplied from the head power supply circuit 200 flows through the resistors RA and RB, so that the voltage at the check terminal increases. Therefore, by measuring the voltage at the check terminal, it is possible to detect the presence or absence of disconnection of the heating element. In the present application, self-diagnosis of disconnection or deterioration of the heating element of the thermal head is referred to as head check.

  The time required for the head check by the conventional method is substantially proportional to the number of heating elements included in the thermal head. In recent years, the printing width and accuracy of label printers have been increasing, the number of heating elements is increasing, and the time required for head check tends to increase. However, for a user whose purpose is to obtain a print result by a printer, the time required for head check is wasted, and it is desired to check a large number of heating elements in a short time.

  Further, the print data for one line supplied to the thermal head is stored in a plurality of memory blocks as shown in FIG. In this example, 32-bit data for one line is divided into two 16-bit data (print data A and B) and stored in two memory blocks 61 and 62.

  In the print data shown in FIG. 5, “1” represents a dot that generates heat, and “0” represents a dot that does not generate heat. These print data are transferred to the memory bit by bit in synchronization with a print data transfer clock signal called a head clock. In the head check, first, as shown in FIG. 5A, check data in which only one bit corresponding to the dot to be checked is “1” is transferred in the memory blocks 61 and 62. Next, as shown in FIGS. 5B to 5D, the data “1” corresponding to the dot to be checked is shifted bit by bit by supplying a head clock for each dot check. .

  However, if the memory for storing print data is divided into a plurality of blocks, the data “1” corresponding to the dot to be checked cannot be shifted beyond the boundary of the divided memory. As shown in FIG. 5E, it is necessary to newly create check data and transfer it again. As described above, since the check data of the print data A portion is transferred and checked in the past, the check data of the print data B portion is transferred and checked. There was a problem that it was necessary and inefficient.

  As a related technique, the following Patent Document 1 discloses a head check device that quickly and accurately determines disconnection of a thermal head. The head check device includes a thermal head having a plurality of heating elements arranged in a line, first supply means for individually supplying a check signal to the heating elements from the head, and a check signal from the tail. The second supply means for supplying and the first and second supply means output from the output terminal of the thermal head in synchronism with the supply of the check signal to the input terminal of the thermal head. Both the counting means for counting the number of defective signals when it is determined that the check result signal is not normal and the count numbers of the first and second defective signals counted by the counting means both exceed a predetermined count number Control means for outputting an error signal at times.

According to this head check device, it is possible to quickly determine whether some of the heating elements are disconnected or whether the connector is not connected between the printer control board and the thermal head. It becomes. However, the time required for supplying the check signal to the heating element of the thermal head and taking out the check result signal has not been shortened.
Japanese Patent Laying-Open No. 2003-305878 (first page, FIG. 4)

  Therefore, in view of the above points, an object of the present invention is to provide a disconnection check device that can shorten the time required for head check for detecting disconnection or deterioration of a heating element included in a thermal head. And

  In order to solve the above problems, in the disconnection check device according to the first aspect of the present invention, a predetermined number of heating elements are divided into a plurality of blocks, and the first terminals of the heating elements included in each block are provided. A disconnection check device for checking disconnection of a heating element in a thermal head that is connected in common and the second terminal of the heating element included in each block is connected to each gate circuit. A plurality of head power supplies respectively supplying current to first terminals of the heating elements included in the plurality of blocks when one gate circuit is activated in each block in order to select a target heating element. By comparing the voltage generated at the first terminal of the heating element included in the circuit and the plurality of blocks with a predetermined value, the heating element selected in each block is disconnected. A plurality of comparison circuits for generating a plurality of signals each indicating whether or not, and by performing a logical operation based on the output signals of the plurality of comparison circuits, at least one of the heating elements selected in the plurality of blocks And a logic circuit that generates a signal indicating whether or not it is disconnected.

  Further, in the disconnection check device according to the second aspect of the present invention, the predetermined number of heating elements are divided into a plurality of blocks, and the first terminals of the heating elements included in each block are connected in common. A disconnection check device for checking disconnection of a heating element in a thermal head in which a second terminal of the heating element included in each block is connected to a respective gate circuit, wherein the heating element to be checked When one gate circuit is activated in each block for selection, a plurality of head power supply circuits that respectively supply current to the first terminals of the heating elements included in the plurality of blocks, and the plurality of blocks In a head check, a plurality of analog / digital conversion circuits that respectively convert voltages generated at the first terminals of the heating elements included in the circuit into a plurality of digital signals, Check data for sequentially selecting one of the plurality of heating elements included in the block is supplied to the thermal head together with the clock signal, and the plurality of digital signals respectively output from the plurality of analog / digital conversion circuits are supplied. And control means for determining disconnection and / or deterioration of the heating element based on the above.

  According to the present invention, the time required for the head check can be reduced by supplying currents to the plurality of heating elements from the plurality of head power supply circuits, and determining disconnection or deterioration of the heating elements based on the voltage generated in the heating elements. It can be shortened.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same component and description is abbreviate | omitted.
FIG. 1 is a diagram showing a configuration of a disconnection check device according to an embodiment of the present invention, together with an equivalent circuit of a thermal head. As shown in FIG. 1, in the thermal head 10, a plurality of heating elements equivalently represented by resistances are arranged in a line. In the present embodiment, these heating elements are divided into a plurality of blocks. In FIG. 1, three blocks 1 to 3 are shown as an example.

  The block 1 includes a plurality of heating elements R11, R12,. A drive voltage is supplied from the head power supply circuit 21 connected to the power supply voltage to the first terminals of the heating elements R11, R12,..., And NAND gates G11, G12,. Output terminals are connected to each other.

  The block 2 includes a plurality of heating elements R21, R22,. A driving voltage is supplied from the head power supply circuit 22 connected to the power supply voltage to the first terminals of the heating elements R21, R22,..., And NAND gates G21, G22,. Output terminals are connected to each other.

  The block 3 includes a plurality of heating elements R31, R32,. A driving voltage is supplied from the head power supply circuit 23 connected to the power supply voltage to the first terminals of the heating elements R31, R32,..., And NAND gates G31, G32,. Output terminals are connected to each other.

  .., G31,... Are supplied with a strobe signal STROBE, and the other input terminal is connected to a plurality of output terminals of the latch circuit 11. Has been. The latch circuit 11 temporarily stores print data DATA for one line that is serially input in synchronization with the clock signal CLK from the outside. Each NAND gate obtains the logical product of the corresponding print data and the strobe signal, and inverts the result for output. A current flows from the head power supply circuits 21 to 23 to the heating element connected to the gate circuit whose output terminal is activated at a low level, and the heating element generates heat to print on a printing medium such as thermal paper. Do.

  Next, the thermal head disconnection check device 20 will be described. The disconnection check device 20 includes head power supply circuits 21 to 23, switch circuits 24 and 25, resistors RA1 to RA3 and RB1 to RB3, comparison circuits 31 to 33, an OR circuit 40, an A / D (analog / digital). ) Converters 51 to 53, a control circuit 60, and a CPU (central processing unit) 71. One of the comparison circuits 31 to 33 and the OR circuit 40 and the A / D converters 51 to 53 may be omitted.

  The control circuit 60 supplies the strobe signal STROBE, the print data DATA, and the clock signal CLK to the thermal head 10. In the print mode for printing characters, barcodes, etc., the control circuit 60 reduces the output impedance of the head power supply circuits 21 to 23 so that the head power supply circuits 21 to 23 are energized. It operates as a voltage source that supplies a driving voltage to the heating element. Further, when the control circuit 60 turns on the switch circuits 24 and 25, a uniform drive voltage can be supplied to the heating elements of any block.

  In the head check mode for checking the disconnection of the heating element of the thermal head, the control circuit 60 supplies check data for simultaneously selecting the three heating elements included in the blocks 1 to 3 to the thermal head 10. To do. Thereby, in each block, only one heating element specified by the check data is energized. Further, the control circuit 60 increases the output impedance of the head power supply circuits 21 to 23 so that the head power supply circuits 21 to 23 supply a constant current to one heating element included in each group. Act as a source.

  Resistors RA1 to RA3 and RB1 to RB3 having resistance values sufficiently larger than the resistance values of the heating elements between the output terminals (first terminals of the heating elements) of the head power supply circuits 21 to 23 and the ground potential. Are connected in series. The voltages generated at the first terminals of the heating elements are respectively divided by the resistors RA1 to RA3 and RB1 to RB3, and the check voltages VC1 to VC3 divided at the check terminals are compared with the comparison circuits 31 to 33 and A / The signals are supplied to the D converters 51 to 53, respectively.

  When the heating elements are not disconnected, most of the current supplied from the head power supply circuits 21 to 23 flows through the respective heating elements, so that the check voltages VC1 to VC3 are lowered. On the other hand, when the heating element is disconnected, all of the current supplied from the head power supply circuits 21 to 23 flows through the resistors RA1 to RA3 and RB1 to RB3, respectively, so that the check voltages VC1 to VC3 are increased. Therefore, by measuring the check voltages VC1 to VC3, it is possible to detect the presence or absence of disconnection of the heating element.

  The comparison circuits 31 to 33 generate a plurality of signals indicating whether or not the heating element selected in each block is disconnected by comparing the check voltages VC1 to VC3 with the reference voltage VREF. Here, the reference voltage VREF is larger than the voltage at the check terminal when the output current of the head power supply circuit 21 flows in parallel connection of the resistors RA1 and RB1 and one heating element, for example, for the block 1, and the resistor It is set in advance to a value smaller than the voltage at the check terminal when current flows only through RA1 and RB1.

  The OR circuit 40 as a logic circuit generates a check result signal by obtaining a logical sum of the output signals of the comparison circuits 31 to 33 and outputs the check result signal to the control circuit 60. When the check result signal becomes high level, it can be seen that at least one of the three heating elements designated by the check data is disconnected.

  The control means constituted by the control circuit 60 and the CPU 71 supplies check data for sequentially selecting one of a plurality of heating elements included in each block to the thermal head 10 together with the clock signal CLK. Based on the output signal of the OR circuit 40, when at least one of the heating elements included in the thermal head 10 is disconnected, an error message indicating the disconnection of the heating element is displayed on the display unit. As described above, when at least one heating element is disconnected, the thermal head may be immediately replaced.

  However, for example, when printing on a label attached to a product, the barcode is misread if the heating element located in the barcode printing area is disconnected. Even if the heating element located in the printing area is disconnected, the problem is not so great.

  Therefore, the control means monitors the output signals of the comparison circuits 31 to 33 while counting the set number of check data, and when it is found that at least one heating element is disconnected, which heating element Find out if it is broken. Further, the control means recognizes the barcode printing area based on the print data, thereby determining whether or not the disconnected heating element is located in the barcode printing area, and disconnecting the heating element. Is positioned in the barcode printing area, an error message indicating that is displayed on the display unit.

  When the A / D converters 51 to 53 are provided, the A / D converters 51 to 53 convert the check voltages VC1 to VC3 into a plurality of digital signals (resistance value data), respectively, and the control circuit 60 Output to. The control means constituted by the control circuit 60 and the CPU 71 supplies check data for sequentially selecting one of a plurality of heating elements included in each block to the thermal head 10 together with a clock signal. Based on the plurality of resistance value data respectively output from the / D converters 51 to 53, disconnection and / or deterioration of the heating element is determined.

  For example, the control means can determine whether or not the heating element selected in each block is disconnected by comparing the value of the resistance value data with the value of the reference voltage VREF as described above. . Thereby, the control means displays an error message indicating the disconnection of the heating element on the display unit or is disconnected when at least one of the heating elements included in the thermal head 10 is disconnected. When the heating element is located in the barcode printing area, an error message indicating that fact is displayed on the display unit.

  Furthermore, the control means sets the appropriate range of the resistance value based on the variation range of the resistance value of the heating element or based on the previous measurement value, so that the value of the resistance value data is within the appropriate range. It can be determined whether it is within the range. If the value of the resistance value data exceeds the appropriate range, it is presumed that the heating element has deteriorated and is close to disconnection, so the control means displays an error message indicating that fact on the display unit.

  FIG. 2 is a block diagram illustrating a configuration example of a printer in which the disconnection check device according to the embodiment of the present invention is mounted. The printer includes a thermal head 10 that performs printing on a printing medium such as a label temporarily attached to a mount, a motor 12 that rotates a platen roller that conveys the printing medium, a sensor 13 that detects the position of the label, and the like. The display unit 15 includes an input unit 14 including a keyboard and the like, an LCD panel for displaying an error message, and the like, and a control unit 70.

  The control unit 70 includes a CPU 71, a ROM (read only memory) 72, a RAM (random access memory) 73, a motor control unit 74 that controls the motor 12, a thermal head control unit 75 that controls the thermal head 10, A sensor control unit 76, an internal interface 77, and an external interface 78 are included. Parts other than the CPU 71 of the disconnection check device shown in FIG. 1 are built in the thermal head control unit 75.

  The CPU 71 is connected to the input unit 14 and the display unit 15 through the internal interface 77 and is connected to the host computer 80 through the external interface 78. The ROM 72 stores a control program for controlling each part of the printer and check data for head check. On the other hand, the RAM 73 temporarily stores print data input from the input unit 14 or the host computer 80 and check data read from the ROM 72. The CPU 71 controls each unit in accordance with a control program stored in the ROM 72 and transmits print data or check data stored in the RAM 73 to the thermal head 10 via the thermal head control unit 75.

  Next, print data supplied to the thermal head will be described with reference to FIG. The print data for one line supplied to the thermal head is stored in RAM memory blocks 61 to 63 as shown in FIG. In this example, 48-bit data for one line is divided into three 16-bit data (print data A to C) and stored in three memory blocks 61 to 63. As described above, in a printer having a thermal head including a large number of heating elements, a memory area for storing print data for one line is divided into a plurality of memory blocks, and the print data is received simultaneously in the plurality of memory blocks. This is common.

  In the print data shown in FIG. 3, “1” represents a dot that generates heat, and “0” represents a dot that does not generate heat. These print data are transferred to the RAM bit by bit in synchronization with a print data transfer clock signal called a head clock. In the head check, first, as shown in FIG. 3A, check data in which the first print data is “1” (active) is transferred in each memory block. As shown in (b) to (d), by supplying a head clock for each check, data “1” is shifted bit by bit in each memory block. Thereby, all the heating elements included in each block of the thermal head are sequentially checked. In this way, by transferring check data using a plurality of memory blocks at the same time, it is possible to improve efficiency by eliminating the need to re-transfer check data.

  As described above, according to the present embodiment, even when a thermal head having a wide print width and a high accuracy is used, a plurality of heating elements can be checked in a short time by simultaneously checking a plurality of heating elements. You can check with

It is a figure which shows the structure of the disconnection check apparatus which concerns on one Embodiment of this invention with the equivalent circuit of a thermal head. 1 is a block diagram illustrating a configuration example of a printer in which a disconnection check device according to an embodiment of the present invention is mounted. It is a figure for demonstrating the check data stored in a memory block in one Embodiment of this invention. It is a figure which shows an example of the equivalent circuit of the thermal head used in the conventional label printer. It is a figure for demonstrating the check data stored in a memory block in the conventional label printer.

Explanation of symbols

1 to 3 Heating element block 10 Thermal head 11 Latch circuit 12 Motor 13 Sensor 14 Input unit 15 Display unit 20 Disconnection check device 21 to 23 Head power supply circuit 24 and 25 Switch circuit 31 to 33 Comparison circuit 40 OR circuit 51 to 53 A / D converter 60 Control circuit 61-63 Memory block 70 Control unit 71 CPU
72 ROM
73 RAM
74 Motor control unit 75 Thermal head control unit 76 Sensor control unit 77 Internal interface 78 External interface 80 Host computer G11, G12, ... NAND gate R11, R12, ... Heating elements RA1-RA3, RB1-RB3 Resistance

Claims (5)

A predetermined number of heating elements are divided into a plurality of blocks, the first terminals of the heating elements included in each block are connected in common, and the second terminals of the heating elements included in each block are respectively connected A disconnection check device for checking disconnection of a heating element in a thermal head connected to the gate circuit of
When one gate circuit is activated in each block to select a heating element to be checked, a plurality of currents are respectively supplied to the first terminals of the heating elements included in the plurality of blocks. A head power supply circuit;
By comparing the voltage generated at the first terminal of the heating element included in the plurality of blocks with a predetermined value, a plurality of elements indicating whether or not the heating element selected in each block is disconnected A plurality of comparison circuits each generating a signal;
A logic circuit that generates a signal indicating whether at least one of the heating elements selected in the plurality of blocks is disconnected by performing a logical operation based on the output signals of the plurality of comparison circuits;
A disconnection check device comprising:   In the head check mode, check data for sequentially selecting one of a plurality of heating elements included in each block is supplied to the thermal head together with a clock signal, and based on the output signal of the logic circuit, The disconnection check device according to claim 1, further comprising a control means for displaying an error message on the display unit when at least one of the predetermined number of heating elements is disconnected.   When at least one of the predetermined number of heating elements is disconnected, the control means determines that the disconnected heating element is a barcode based on output signals and print data of the plurality of comparison circuits. 3. The disconnection check device according to claim 2, wherein it is determined whether or not the heater is located in the print area, and a second error message is displayed on the display unit when the disconnected heating element is located in the barcode print area. A predetermined number of heating elements are divided into a plurality of blocks, the first terminals of the heating elements included in each block are connected in common, and the second terminals of the heating elements included in each block are respectively connected A disconnection check device for checking disconnection of a heating element in a thermal head connected to the gate circuit of
When one gate circuit is activated in each block to select a heating element to be checked, a plurality of currents are respectively supplied to the first terminals of the heating elements included in the plurality of blocks. A head power supply circuit;
A plurality of analog / digital conversion circuits that respectively convert voltages generated at first terminals of the heating elements included in the plurality of blocks into a plurality of digital signals;
In the head check mode, check data for sequentially selecting one of a plurality of heating elements included in each block is supplied to the thermal head together with a clock signal, and the plurality of analog / digital conversion circuits respectively supply the check data. Control means for determining disconnection and / or deterioration of the heating element based on a plurality of output digital signals;
A disconnection check device comprising:   5. The disconnection check device according to claim 1, further comprising a plurality of switch circuits that short-circuit output terminals of the plurality of head power supply circuits in a print mode.

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