JP2001162854A - Thermal printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent influence of thermal accumulation due to a condition of a thermal printer and to secure high quality printing. SOLUTION: This thermal printer comprises a heat radiating time calculating means that obtains a temperature and a driving voltage of a thermal head by using a temperature detecting means and a voltage detecting means, and calculates a radiating time period from supplying of energy at the previous dot line printing to starting of printing at the present dot line wherein the accumulated heat is radiating with respect to an energizing pulse time calculated by an energizing time calculating means based on the inputs. The thermal printer further comprises an energizing time correcting means that executes controlling wherein a correction factor is reduced as the heat radiating time period is reduced and then executes the correction of the energizing pulse time and a thermal head driving means that performs the printing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer. More specifically, the present invention relates to a thermal printer provided with a control device for performing high-quality printing.

[0002]

2. Description of the Related Art A thermal printer heats heat-sensitive paper by supplying energy to a heating element corresponding to a dot to be printed on a thermal head in which heating elements for one dot line are arranged. And printing is performed. At this time, the ultimate temperature of the heating element changes depending on the amount of energy given to the heating element.
Since the dot coloring area changes, the print density changes. Therefore, the energy supplied to the thermal head is controlled to prevent the print quality from being degraded due to the print density difference. Normal energy control is performed by the time of a drive pulse for supplying a current to the thermal head.

The energy required to heat the thermal head to a temperature required for coloring the thermal paper is lower as the temperature of the thermal head before heating is higher. Therefore, the energy supply time depends on the temperature state of the thermal head. Needs to be controlled. Also, in order to supply the same energy, the required energy supply time becomes longer as the drive voltage is lower, and it is necessary to perform control based on the drive voltage value.

FIG. 2 is a block diagram showing an example of a conventional control of the energizing pulse time. A thermistor is installed on the thermal head 21 as a temperature detecting device, and the temperature state of the thermal head is determined from data obtained from the temperature detecting means 2.
2 to detect. In addition, a drive voltage for supplying energy to the thermal head is detected by the voltage detection unit 23.

On the basis of the conditions detected by these state detecting means, the energizing time calculating means 24 calculates an energizing pulse time at which the print quality is optimized. Next, consider the effect of heat storage. When dot line printing is performed, immediately after energy is supplied to the printed dots, heat is accumulated in the vicinity of the heating element, so that the temperature is higher than the temperature of the entire thermal head. For this reason, if dot line printing is performed continuously, the current dot line printing is performed with the heat accumulated during the previous dot line printing accumulated. The temperature becomes higher than a certain temperature, which causes a decrease in print quality. Further, the influence of the heat storage becomes more conspicuous as the time interval between the printing of the previous dot line and the printing of the current dot line becomes shorter.

Conventionally, in order to prevent the print quality from deteriorating due to the heat storage of the thermal head, the printing interval between the previous dot line and the current dot line is set by a thermal head driving means 25.
The energizing time correction means 26 controls the energizing pulse time calculated from the temperature of the thermal head and the power supply voltage so that the energizing pulse time is corrected in accordance with the printing interval. The energization pulse time was controlled.

[0007]

The effect of the heat accumulation in the previous dot line printing on the next dot line printing depends on the energizing pulse time and the printing interval in the previous dot line. The energization pulse time for driving the dot line thermal head was corrected. However, since the energization pulse time calculated by the energization time calculation means varies depending on the temperature of the thermal head and the drive voltage, for example, when the drive voltage greatly changes, the calculated energization pulse time also fluctuates. The effect of heat storage on dot line printing also varies. In the conventional method, the energizing time of the next dot line is corrected by the printing interval, so even if the influence of heat storage is different, the same correction works if the printing interval is the same. Such fluctuations in the conditions of the thermal printer have affected the print quality.

[0008]

In order to solve the above-mentioned problems, in the present invention, the temperature of the thermal head and the drive voltage are obtained by the temperature detecting means and the voltage detecting means, and are calculated from the input by the conduction time calculating means. A heat radiation time calculating means for calculating a heat radiation time during which accumulated heat is radiated from after the energy supply of the previous dot line printing to the start of the current dot line printing with respect to the energizing pulse time; and Energization time correction means for correcting the energization pulse time using a correction coefficient that decreases in accordance with the decrease of
A thermal printer device for printing by a thermal head driving unit that supplies a head driving pulse for the corrected energizing pulse time determined by the energizing time correction unit to the thermal head is provided.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the block diagram of FIG. In FIG. 1, a temperature detecting means 1
2. The functions of the voltage detecting means 13 and the energizing time calculating means 14 are the same as in the conventional case. The heat radiation time calculation means 17 calculates the heat radiation time from the supply of energy to the previous dot line to the start of the current dot line printing. Memory 18
Is stored in advance with a correction coefficient capable of performing a correction to optimize the printing quality in each heat radiation time.

In this embodiment, an 8-bit timer counter built in a microprocessor is used as a heat radiation time calculating means. One count is 0.1 [ms],
The correction coefficient when the heat radiation time was 25.6 [ms] or more was set to 1. To ensure optimal print quality, if the drive time of the head drive pulse is long and the heat radiation time is short in the same print cycle, the drive time of the next head drive pulse will be shortened to reduce the energy supplied to the head. Need to be smaller. The relationship between the heat release time and the energizing pulse time at which the printing quality is optimal was obtained by experiment, and the correction coefficient = 1
− (1 / exp ((radiation time [ms] / 5) +0.2)
8)), a correction coefficient for the heat radiation time corresponding to each value of the timer counter in this equation is obtained and stored in the memory 18 in the form of a correction coefficient table. However, the memory 18 can be omitted by directly calculating and obtaining the correction coefficient from the characteristic equation.

A part of the energizing time calculating means 14, the heat radiation time calculating means 17, the memory 18, the energizing time correcting means 16, the temperature detecting means 12, the voltage detecting means 13, and the thermal head driving means 15 is a general one chip. It is composed of a microprocessor. The microprocessor multiplies the calculated energization pulse time by a correction coefficient,
The corrected energization pulse time is calculated. The head drive pulse is output to the thermal head 11 by using a 16-bit timer counter built in the microprocessor to generate a pulse for the corrected energizing pulse time.

Next, the operation of the apparatus having the above configuration will be described. First, at a certain point, a head drive pulse is output, and one dot line is printed. The energization time calculation means 14 is provided from the temperature detection means 12 to the thermal head 1.
1 and the driving voltage of the thermal head 11 from the voltage detecting means 13, and the energizing pulse time of the next head driving pulse to be output is calculated based on these. On the other hand, the heat radiation time calculation means 17 recognizes the point in time when the output of the previous head drive pulse is completed, and further inputs the time until the next head drive pulse is output from the thermal head drive means 15 to calculate the heat radiation time. It calculates and outputs this to the energization time correction means 16. Energizing time correction means 16
Is obtained by multiplying the energization pulse time calculated by the energization time calculation unit 14 with reference to the memory 18 by a correction coefficient according to the heat radiation time based on the data on the heat radiation time input from the heat radiation time calculation unit 17. Determine the next energizing pulse time. The thermal head driving means 15 drives the thermal head 11 according to the energizing pulse time to perform printing.

As described above, according to the present invention, the energizing pulse time of the drive pulse to be output next time is corrected in accordance with the heat radiation time to prevent the influence of heat storage.

[0014]

According to the present invention, there is provided a thermal printer which controls a correction coefficient for an energizing pulse time calculated from a temperature of a thermal head and a power supply voltage based on a heat radiation time after printing a previous dot line. As a result, there is an effect that printing quality is prevented from deteriorating due to the effect of heat storage, and high-quality printing can be performed irrespective of conditions such as temperature and voltage of the thermal head.

[Brief description of the drawings]

FIG. 1 is a block diagram of a system according to the present invention.

FIG. 2 is a block diagram of a conventional system configuration.

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 thermal head 12 temperature detecting means 13 voltage detecting means 14 energizing time calculating means 15 thermal head driving means 16 energizing time correcting means 17 heat dissipation time calculating means 18 memory

Claims (3)

[Claims] 1. A thermal head having a heating element for one dot line, temperature detecting means for detecting the temperature of the thermal head, voltage detecting means for detecting a drive voltage supplied to the thermal head, and the temperature Energizing time calculating means for calculating a time of an energizing pulse for supplying energy to the thermal head based on data from the detecting means and the voltage detecting means, and energizing for correcting the energizing pulse time outputted from the energizing time calculating means In a thermal printer apparatus comprising: a time correction unit; and a thermal head driving unit that outputs a head driving pulse to drive the thermal head based on the corrected energization pulse time corrected by the energization time correction unit. The dot line to be printed this time from the point when the energy supply to the line is completed A heat-dissipation time calculating unit for calculating a heat-dissipation time until the start of energy supply to the heat-dissipation time correction unit. A thermal printer device for determining a time. 2. The thermal printer device according to claim 1, wherein said energization time correction means performs a correction to reduce a correction coefficient with a decrease in said heat radiation time to shorten said energization pulse time. 3. The thermal printer according to claim 1, wherein said energization time correction means determines the corrected energization pulse time with reference to a correction coefficient table having a correction coefficient corresponding to the heat radiation time. apparatus.