JP3659561B2 - Thermal printer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thermal printer that performs printing using a thermal head.
[0002]
[Prior art]
A conventional image forming apparatus includes a thermal printer that performs printing with a thermal head in which a plurality of printing elements using heating resistors are arranged. The thermal head energizes the heating resistance of the printing element corresponding to the location to be printed to generate heat, and the ink of the ink ribbon is dissolved by the heat of the printing element or the thermal paper is heated to perform printing.
[0003]
FIG. 3 shows the electrical connection between the control block of a conventional thermal printer and the thermal head portion provided with the thermal head. As shown in FIG. 3, the head power supply voltage, the print data, and the enable signal A are output from the control block 1 to the thermal head unit 2. The enable signal A is controlled to be either H or L, and when the enable signal A is active L, the thermal head unit 2 is energized with the heating resistor of the printing element corresponding to the print data.
[0004]
In such a conventional thermal printer, energization control to the heating resistor is performed by an enable signal A of 1 pulse per line. As shown in FIGS. 4 and 5, when the enable signal A changes from H to L, energization to the heating resistor is started, and when the enable signal A changes from L to H, energization to the heating resistor is ended. With such energization control, the temperature change of the thermal head unit 2 has one peak in one line cycle.
[0005]
Here, assuming that the upper limit of the heat resistance temperature of the ink ribbon is T1, the temperature required to melt and transfer the ink is T2, and the time is t, if the peak is too low as shown in FIG. The time during which the temperature of T2 is maintained at T2 or higher is less than t. In this case, printing failure occurs due to insufficient heat. On the other hand, if the peak is too high as shown in FIG. 5, the ink ribbon is deformed by heat, and printing failure still occurs.
[0006]
As a proposal for eliminating such inconvenience, there is an invention described in Japanese Patent Laid-Open No. 10-181063. In this publication, there is a technique in which intermittent energization is performed by supplying an intermittent enable signal so that the temperature of the thermal head unit 2 is maintained within an appropriate range of T1 to T2 when energizing the heating resistor. It is disclosed (see FIG. 6). In order to control the energization as described above, a simple block diagram shown in FIG. 7 will explain the conversion means for converting the enable signal A output from the control block 1 to the thermal head unit 2 into an intermittent enable signal B. 3 is provided between the control block 1 and the thermal head unit 2.
[0007]
According to this technology, since the temperature of the printing element can be controlled within a temperature range that takes into consideration the melting point of the ink and the heat resistance temperature of the ink ribbon, not only can the printing defect due to insufficient heat quantity or deformation of the ink ribbon be prevented, but also Long life can be expected by preventing overheating.
[0008]
[Problems to be solved by the invention]
By the way, conventionally, as shown in FIG. 3, the thermal printer performs the disconnection check by outputting not the print data but the data for the disconnection check. In the disconnection check, it is necessary to energize continuously for a predetermined time required for the check. (However, the voltage at the time of check is considerably lower than that at the time of printing.)
However, in the invention described in Japanese Patent Application Laid-Open No. 10-181063, as shown in FIG. 7, all the enable signals A output from the control block 1 by the converting means 3 are intermittent enable signals B shown in FIG. Since it is converted, the thermal printer as it is described in this publication has a disadvantage that it is always energized intermittently and the disconnection check cannot be performed.
[0009]
SUMMARY OF THE INVENTION An object of the present invention is to enable temperature control of a thermal head and to perform a disconnection check.
[0010]
[Means for Solving the Problems]
The thermal printer according to the present invention includes a thermal head in which a plurality of printing elements each having a heating resistor are arranged, a thermal head unit having a driver for driving the thermal head , and print data and disconnection check data in the driver of the thermal head unit. The data supply means that selectively supplies one of the above and the head power supply voltage that differs between the time of printing and the check of disconnection so that the voltage is lower when checking the disconnection than when printing. Supplying power to the driver of the thermal head unit, basic control signal supplying unit for supplying a basic enable signal for determining the energization timing of the heating resistor to the driver of the thermal head unit, and the basic control signal supplying unit pulsed intermittent converting enable the foundation enable signal but which has been supplied Conversion means for converting a signal, the power supply means with reference to the head power supply voltage value supplied to the thermal head unit, if is a relatively low the head power voltage value selects the basic enable signal, If a relatively high the head voltage value and selecting means for supplying select the conversion enable signal to the thermal head driver.
[0011]
Therefore, since the form of the enable signal can be selected based on the voltage value selected depending on whether printing or disconnection check, the temperature of the thermal head is controlled by intermittent energization during printing, and continuous energization can be performed during disconnection check.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a thermal printer according to the present invention will be described with reference to FIGS. First, FIG. 1 is a block diagram schematically showing electrical connection of a control system of the thermal printer of the present embodiment.
[0013]
The thermal printer includes a control block 11 and a thermal head unit 12. The thermal head unit 12 includes a thermal head and a driver that controls the thermal head. A control block 11 that executes various arithmetic processes and centrally controls each unit includes a CPU, a ROM, a RAM, and a power source. The ROM is a medium storing an operation program, and the CPU controls each unit according to the operation program. The RAM temporarily stores various variable information. Also, a partial area of the RAM is used as a print buffer or as various counter areas.
[0014]
The control block 11 is data supply means, and supplies print data and disconnection check data to the thermal head unit 12. The control block 11 is power supply means, and a suitable head power supply voltage selected by the control block 11 is supplied to the thermal head 12. Further, the control block 11 is a basic control signal supply means and outputs an enable signal A as a basic enable signal.
[0015]
Here, the enable signal A is branched into two, one being input to the selector 14 via the conversion means 13 and the other being directly input to the selector 14. The conversion means 13 converts the enable signal A into a pulse-like intermittent enable signal B as a conversion enable signal. Therefore, both the enable signal A and the enable signal B are input to the selector 14.
[0016]
The head power supply voltage is input to the thermal head unit 12, and the head power supply voltage is also input to the comparison unit 15. A reference voltage (15 V) is also input to the comparison means 15. Then, the comparison means 15 compares this reference voltage with the head power supply voltage (27V at the time of printing, 5V at the time of disconnection check), and notifies the selector 14 of whether the head power supply voltage is higher or lower than the reference voltage. To do.
[0017]
The selector 14 determines that the print data is being output from the control block 11 to the thermal head unit 12 when the head power supply voltage is higher than the reference voltage based on the notification content from the comparison unit 15, and the thermal head The enable signal B is output to the unit 12. When the head power supply voltage is lower than the reference voltage, it is determined that disconnection check data is being output from the control block 11 to the thermal head unit 12, and an enable signal A is output to the thermal head unit 12.
[0018]
Here, the selector 14 and the comparison means 15 constitute a selection means 16.
[0019]
In such a configuration, in the thermal printer of the present embodiment, when the control block 11 supplies print data to the thermal head unit 12 and supplies a head voltage power supply of 27 V, the reference voltage in the comparison unit 15 and Based on the comparison result, the enable signal B (see FIG. 2) is selected by the selector 14, so that a current flows intermittently through the thermal head unit 12. In this case, from the start of energization, energization is continuously performed for time t0, and thereafter, energization is intermittently performed for time t. Time t0 is a head power supply voltage of 27 V, and is required to raise the temperature of the printing element to a temperature higher than the temperature T2 required to melt and transfer the ink and lower than the upper limit T1 of the heat resistance temperature of the ink ribbon. It's time. The time t is the time required to melt and transfer the ink at a temperature higher than T2 and lower than T1. As a result, the temperature of the printing element can be controlled within a temperature range that takes into consideration the melting point of the ink and the heat resistant temperature of the ink ribbon. Life expectancy can also be expected.
[0020]
When the control block 11 outputs disconnection check data to the thermal head unit 12 and applies a 5 V head power supply voltage, an enable signal is output from the selector 14 based on the comparison result with the reference voltage in the comparison unit 15. A (refer to FIG. 2) is selected, and as a result, a current flows through the thermal head unit 12 continuously. In this case, since the voltage is low, the amount of power supplied to the thermal head unit 12 is small, so the thermal head does not rise to a temperature that melts the ink on the ink ribbon.
[0021]
According to this embodiment, it is possible to control the temperature of the thermal head by intermittently energizing the thermal head during printing, and also to enable continuous energization at a low voltage, thus preventing printing defects. As a result, the print quality can be improved, the life of the thermal head can be extended, and disconnection can be checked. In addition, since whether the enable signal supplied to the thermal head unit is intermittent or continuous is selected according to the head power supply voltage supplied to the thermal head unit, the circuit is not complicated.
[0022]
In this embodiment, the head power supply voltage during printing is 27 V, the head power supply voltage during disconnection check is 5 V, and the reference voltage is 15 V between them. (Head power supply voltage during printing)> (reference voltage)> (head power supply voltage during disconnection check).
[0023]
【The invention's effect】
In the present invention, the basic enable signal for determining the energization timing of the heating resistor suitable for the disconnection check based on the voltage value selected by the disconnection check or printing, or the energization of the heating resistor suitable for printing converted from the basic enable signal Since the conversion enable signal for determining the timing can be selected and supplied to the thermal head unit, the temperature of the thermal head can be controlled by intermittent energization during printing, and the energization can be performed continuously during disconnection check. Therefore, it is possible to control the temperature of the thermal head to improve the print quality, to prolong the life of the thermal head, and to enable a disconnection check.
[Brief description of the drawings]
FIG. 1 is a block diagram schematically showing electrical connection of a control system of a thermal printer according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram showing a basic enable signal and a conversion enable signal.
FIG. 3 is a block diagram schematically showing electrical connection of a control system provided in a conventional thermal printer.
FIG. 4 is a graph showing the relationship between the enable signal and the temperature of the thermal head in a conventional thermal printer as a function of time.
FIG. 5 is a graph showing the relationship between the enable signal and the temperature of the thermal head in a conventional thermal printer over time.
FIG. 6 is a graph showing the relationship between the enable signal and the temperature of the thermal head in the thermal printer described in the official gazette over time.
FIG. 7 is a block diagram schematically showing electrical connection of a control system of a thermal printer described in the published publication.
[Explanation of symbols]
11 Data supply means, power supply means, basic control signal supply means 12 thermal head unit 13 conversion means 16 selection means A basic enable signal B conversion enable signal

Claims (1)

A thermal head in which a plurality of printing elements each having a heating resistor are arranged, and a thermal head portion including a driver for driving the thermal head;
Data supply means for selectively supplying either print data or disconnection check data to the driver of the thermal head unit;
A power supply means for supplying a different head power supply voltage to the driver of the thermal head unit between the time of printing and the time of checking the disconnection so that the voltage at the time of the disconnection check is lower than that at the time of printing; and
Basic control signal supply means for supplying a basic enable signal for determining energization timing of the heating resistor to the driver of the thermal head unit ;
Conversion means for converting the basic enable signal supplied by the basic control signal supply means into a pulsed intermittent conversion enable signal;
The power supply means refers to a head power supply voltage value supplied to the thermal head unit, and if the head power supply voltage value is relatively low, the basic enable signal is selected and the relatively high head voltage value is selected. and selection means for supplying to said thermal head portion of the driver by selecting the conversion enable signal if it is,
Thermal printer equipped with.

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