JPH1199683A - Thermal printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a time for checking cutting of a heating element. SOLUTION: An output value of a heating element is fetched to be temporarily stored in a memory as a reference value (S5) immediately after an energizing signal is applied to each heating element on a thermal print head. An output value of a heating element to which an energizing signal is continuously applied to be left for a predetermined period of time is fetched as a comparing value (S7). The comparing value is compared with the reference value temporarily stored in the memory to obtain the compared result (S8). Cutting of the heating element is checked by judging whether or not the value of the compared result exceeds a predetermined tolerance value (S9). The variation of the actual output value of the heating element is monitored by comparing the comparing value with the reference value. As a result, it is possible to obtain the adequate judgment result even when an interval time between the fetching time of the reference value and the fetching time of the comparing value is short. Consequently, it is possible to markedly reduce the time for checking the cutting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer such as a label printer which prints characters, bar codes, etc. on a label using a line thermal printer head in which a large number of heating elements are arranged in the width direction of the label.

[0002]

2. Description of the Related Art Heretofore, there has been known a label printer in which a label paper having a label attached to a web-shaped mount at a constant interval is transported by a paper transport unit such as a platen and a predetermined printing is performed on the label in the transport process. Widespread. As a print head in such a label printer,
Thermal printer heads are often used because they are suitable for printing bar codes. In particular, in the case of a label attached to a product or its packaging during the distribution process of the product, the printed content of the label helps to stimulate the consumer's willingness to purchase. Therefore, there is a strong demand for a label printer for printing and issuing such a label as a print head, for example, a thermal printer head which provides a printing quality that is superior to a dot printer head in extraordinary order.

[0003] On the other hand, the thermal printer head has a problem of disconnection of each heating element because of the structure in which printing is performed by selectively heating a large number of heating elements. When the heating element is disconnected, dots are missing at a portion corresponding to the heating element, and it becomes impossible to maintain high printing quality, which is a characteristic of the thermal printer head. This problem is extremely serious. is there. For example, when a barcode is printed using a broken heating element, in some cases, the barcode cannot be read by a scanner or the like due to a defective barcode shape due to missing dots. Therefore, conventionally, in a label printer using a thermal printer head, for example, it is common to check the disconnection of the heating element every batch processing. For example, the disconnection of the heating element is checked once every 100 labels printed and issued.

Here, the disconnection check of the heating element is performed by energizing the heating element to be checked, taking in the output voltage of the heating element after a lapse of a predetermined time, and comparing the output voltage with a reference voltage value stored in a memory in advance. This is done by:
That is, in the conventional disconnection check, the resistance value increases when the heating element is disconnected, and the idea is to detect this and determine whether there is a disconnection. Then, such processing is sequentially performed for each heating element, and such processing is performed for all heating elements, thereby completing one disconnection check.

[0005]

In the conventional disconnection check method, the timing for taking in the output voltage of the heating element to be compared with the reference voltage is about 5 ms after the heating element is energized.
c is the time that has elapsed. The reason for waiting until about 5 msec elapses is that this time is required until the output voltage is stabilized. Therefore, in order to perform a correct disconnection check, a standby time of about 5 msec is required for one heating element. Therefore, assuming that the number of heating elements is, for example, 832, 5 (msec) × 832
According to the calculation formula of (number), about 4.16 sec is required. In addition, since a data transfer time, an output voltage capturing time, and the like are required in addition to the above, more time is actually required. However, as mentioned above,
The disconnection check of the heating element is executed, for example, every time one batch of labels, typically 100 labels are printed and issued. Therefore, if a disconnection check process of about 4.16 sec is required every time, a large number of labels are required. If issued, the loss time will not be ignored.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thermal printer capable of shortening a time required for checking a disconnection of a heating element.

[0007]

According to the first aspect of the present invention,
In a thermal printer that prints and issues predetermined items on paper using a thermal printer head, a reference that captures the output value of the heating element immediately after applying an energizing signal to each heating element of the thermal printer head and temporarily stores it in a memory as a reference value. A value setting unit, and a comparison unit that obtains a comparison result by comparing an output value of a corresponding heating element after a lapse of a predetermined time period in which an energization signal is continuously applied with a reference value temporarily captured in a memory as a comparison value, Disconnection determining means for determining whether the value of the comparison result obtained by the comparing means exceeds a predetermined allowable value.

Therefore, by comparing the reference value with the comparison value, the actual change in the output value of the heating element is monitored, and the disconnection determination is performed by the disconnection determining means based on the change in the output value of the heating element. . At this time, since the actual change in the output value of the heating element is monitored, even if the time between the capture of the reference value and the capture of the comparison value is short,
A correct decision is made.

According to a second aspect of the present invention, in a thermal printer for printing and issuing predetermined items on paper using a thermal printer head, an energizing signal is applied to each heating element of the thermal printer head to output an output value of the heating element. Then, the presence or absence of disconnection of the heating element is determined based on the fluctuation of the output value.

Therefore, the fluctuation of the output value of the heating element is
The actual output value change of the heating element can be monitored because the actual output value change of the heating element is monitored based on the actual output value of the heating element obtained by applying the energization signal to the heating element. The disconnection determination is performed by the disconnection determination means based on such a change in the output value of the heating element. At this time, since the actual output value change of the heating element is monitored,
The correct decision is made even if the time for data collection is short.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the drawings. This embodiment is an example of application to a label printer. This label printer employs a thermal transfer method using a thermal printer head 1 (hereinafter abbreviated as a thermal head) as a print head. Since the mechanism is the same as that of a general thermal printer, the description is omitted.

FIG. 1 is a block diagram showing the electrical connection of each part. A pulse motor 2 is used as a drive source for transporting label paper (not shown). The pulse motor 2 and the thermal head 1 are a control unit including a CPU 4, a ROM 5, and a RAM 6 (memory) connected via a bus line 3. Is driven and controlled. That is, the CPU 4
Performs various arithmetic processing in accordance with an operation program written in the ROM 5 to centrally control each unit. Typically, the thermal head 1 and the pulse motor 2 are drive-controlled to print a label (not shown) and print the label after printing. Issue. More specifically, the control unit mainly composed of the CPU 4
Print data is received from an external computer or the like (not shown) via the communication I / F 7 connected to the bus line 3, and the received print data is developed in a drawing area (not shown) in the image memory in the RAM 6. . At this time, the communication I
The code data received via / F7 is the code data. Based on this code data, the character stored in the mask ROM 8 connected to the bus line 3 is called, and this character is developed in the drawing area. . Then, the control unit mainly composed of the CPU 4 outputs a print signal to the thermal head driver 9 based on the print data developed in the drawing area, and outputs a drive signal to the motor driver 10. The output of the printing signal and the driving signal is performed synchronously. As a result, the pulse motor 2 is driven to convey the label paper, and the thermal head driver 9 selectively energizes a number of heating elements (not shown) of the thermal head 1, thereby printing the label in a heat-sensitive manner. Done.

At the time of such a printing operation, output signals of the transmission sensor 11 and the reflection sensor 12 arranged in the label paper conveyance path are taken into the bus line 3 via the sensor circuit 13 having an A / D converter. CPU4
Sent to A control unit mainly composed of the CPU 4 executes setting of a label feed amount, detection of a jam, and the like based on output signals from the transmission sensor 11 and the reflection sensor 12.

Further, when a cover (not shown) of the label printer is opened, the head open switch 14 is opened.
Operates, and its analog output is taken into the bus line 3 via the switch circuit 15 of the A / D converter configuration,
It is sent to CPU4. Thus, the printing operation by the drive control of the thermal head 1 and the pulse motor 2 is interrupted.

Here, a process for checking the disconnection of the heating element of the thermal head 1 will be described. 2 and 3 are flowcharts showing a disconnection check process, FIG. 4 is a timing chart at the time of a disconnection check, FIG. 5 is a graph showing a temporal change of an output voltage in a normal heating element, and FIG. 6 is a heating element having a disconnection 5 is a graph showing the change over time of the output voltage at.

First, the first heating element is energized for disconnection check. As a process of the control unit mainly constituted by the CPU 4 for this purpose, data transmission for driving the corresponding heating element is performed to the thermal head driver 9 (step S1). The transmitted data is latched by a latch circuit (not shown) incorporated in the thermal head driver 9 (step S2), and the latch is released with the transmission of the enable signal to drive the corresponding heating element (step S3). At the same time, the timer starts (step S4). Immediately thereafter, as shown in FIG. 4, an interrupt signal or an input signal is input to take out the output voltage of the corresponding heating element, which is A / D converted by the thermal head driver 9 and sent to the CPU 4 (step S5; reference value). Setting means). By this processing, a reference value is obtained. Then, when the timer elapses a predetermined time (step S6), the interrupt processing is again executed, and the output voltage of the corresponding heating element is taken out. The output voltage is A / D converted by the thermal head driver 9 and recognized by the CPU 4 ( Step S7). By this processing, a comparison value is obtained. Here, the reference value and the comparison value are temporarily stored in the register area of the RAM 6 in steps S5 and S7. Then, in the subsequent step S8, a calculation process in the CPU 4 for subtracting the comparison value from the reference value is executed (comparing means). As a result of the calculation, it is determined whether or not the difference between the reference value and the comparison value is less than the allowable value of 1 V (step S9; disconnection determining means). Time 2
When msec has elapsed (step S10), the enable signal is terminated (step S11), and the process is continued until the same process is completed for all the heating elements (step S12).

Next, when it is determined in step S9 that the difference between the reference value and the comparison value is equal to or more than the allowable value of 1 V, when the time measured by the timer elapses 2 msec (step S9).
13) Terminate the enable signal (step S14)
An enable signal is sent to the thermal head driver 9 again (step S15). As a result, the latch is opened and the corresponding heating element is driven, and at the same time, the timer starts (step S16). Thereafter, when the timer elapses a predetermined time (step S17), as shown in FIG. 4, an interruption process or interruption is performed, and the output voltage of the corresponding heating element is taken out. Sent to the CPU 4 (step S1
8). By this processing, the comparison value is obtained again. Then, the CPU 4 executes an arithmetic process of subtracting the obtained comparison value from the reference value temporarily stored in the register area of the RAM 6 (step S19; comparison means), and as a result of the calculation, the reference value and the comparison value are compared. Is determined to be less than the allowable value of 2V (step S20; disconnection determining means). If the difference does not exceed the allowable value of 2V, the time measured by the timer has elapsed by 1 msec (step S2).
1) The enable signal is terminated (step S22), and the process proceeds to step S12.

Next, if it is determined in step S20 that the difference between the reference value and the comparison value is equal to or more than the allowable value of 2 V, the enable signal is terminated when the time measured by the timer has elapsed by 1 msec (step S23). S2
4), the enable signal is again sent to the thermal head driver 9
(Step S25). As a result, the latch is opened and the corresponding heating element is driven, and at the same time, the timer starts (step S26). Thereafter, when a predetermined time elapses (step S27), as shown in FIG. 4, an interrupt process or interruption is performed, and the output voltage of the corresponding heating element is taken out. Sent to the CPU 4 (step S
28). By this processing, the comparison value is obtained again. Therefore, it is determined whether the obtained comparison value is 1 V or less (step S29). If the determination result indicates that the comparison value is larger than 1 V, the process proceeds to step S21. On the other hand, when the comparison value is 1 V or less, information that the corresponding heating element is disconnected is written into the RAM 6 (step S30), and the process proceeds to step S21.

That is, in the present embodiment, as the first stage processing, the output voltage of the heating element to be checked for disconnection is taken in to obtain a reference value (step S5). Is obtained again (step S7), and it is determined whether or not the difference between the reference value and the comparative value is within a predetermined allowable value (step S9), thereby determining whether there is a disconnection. If there is a possibility of disconnection, the process proceeds to the second step, in which the output voltage of the heating element to be checked for the presence or absence of disconnection is re-acquired to obtain a comparison value (step S18). Is determined to be within a predetermined tolerance (step S2).
0), thereby determining whether there is a disconnection. This is because when the connection state of the heating element is normal, its output voltage is substantially constant irrespective of aging (see FIG. 5).
If the heating element is disconnected, the output voltage of the heating element gradually decreases (see FIG. 6). Therefore, in steps S9 and S18, a change in the output voltage of the heating element is monitored, and based on the result, the presence or absence of a disconnected state is determined. Is determined.
If there is a possibility of disconnection in the second-stage processing, the process proceeds to the third-stage processing, and it is determined whether the output voltage value of the heating element is 1 V or more (step S29). To determine if there is a disconnection. Therefore,
In the first stage processing and the second stage processing, the actual output value change of the heating element is monitored by comparing the reference value and the comparison value, and based on such output value change of the heating element. The disconnection determination is performed. At this time, since the actual change in the output value of the heating element is monitored, a correct determination can be made even if the time between when the reference value is captured and when the comparison value is captured is short. Specifically, in the case of the present embodiment, the time required to perform a disconnection check for one heating element is about 3 msec for a normal heating element.
It ends with the following.

[0020]

According to the first aspect of the present invention, the output value of the heating element immediately after the application of the conduction signal to each heating element of the thermal printer head is taken in, temporarily stored in a memory as a reference value, and the conduction signal is continued. The output value of the corresponding heating element after the given predetermined time has elapsed is taken as a comparison value and compared with a reference value temporarily stored in a memory to obtain a comparison result, and whether the value of the comparison result exceeds a predetermined allowable value. By judging whether or not the heating element is disconnected,
By comparing the reference value and the comparison value, the actual output value change of the heating element can be monitored, and therefore,
A correct determination result can be obtained even if the time between when the reference value is captured and when the comparison value is captured is short. Therefore, the time required for the disconnection check can be greatly reduced.

According to a second aspect of the present invention, an energization signal is applied to each of the heating elements of the thermal printer head to capture the output value of the heating element, and the presence or absence of a disconnection of the heating element is determined based on the change in the output value. Therefore, the variation of the output value of the heating element is obtained based on the actual output value of the heating element obtained by applying an energization signal to the heating element, and is obtained as a change value of the reference value. A change in the actual output value of the element can be monitored, and thus a correct determination result can be obtained in a short time. Therefore, the time required for the disconnection check can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an electrical connection of each unit according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a disconnection check process.

FIG. 3 is a flowchart illustrating a disconnection check process.

FIG. 4 is a timing chart at the time of disconnection check when there is a possibility that the heating element is disconnected.

FIG. 5 is a graph showing a change over time of an output voltage in a normal heating element.

FIG. 6 is a graph showing a change over time of an output voltage in a heating element in which a disconnection has occurred.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Thermal printer head (thermal head) 6 Memory S5 Reference value setting means S8, 19 Comparison means S9, 20 Disconnection determination means

Claims (2)

[Claims] 1. A thermal printer which prints and issues predetermined items on paper using a thermal printer head, wherein an output value of the heating element immediately after an energizing signal is applied to each heating element of the thermal printer head is taken in and a reference value is taken. A reference value setting means for temporarily storing in the memory as the reference value, and taking the output value of the corresponding heating element after a lapse of a predetermined time continuously applying the energization signal as a comparison value and comparing the output value with the reference value temporarily stored in the memory. A thermal printer, comprising: a comparison unit that obtains a comparison result by performing the operation; and a disconnection determination unit that determines whether a value of the comparison result obtained by the comparison unit exceeds a predetermined allowable value. 2. A thermal printer which prints and issues predetermined items on paper using a thermal printer head, wherein an energizing signal is applied to each heating element of the thermal printer head to capture an output value of the heating element. A thermal printer, wherein the presence or absence of disconnection of the heating element is determined based on a change in the value.