JPH04255365A - Thermal head printing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is a thermal printer that prints black and white image data by moving a thermal head and thermal paper relative to each other, or by moving a head block composed of a thermal head and a thermal transfer ribbon relative to plain paper. This invention relates to a head type printing device.

0002

2. Description of the Related Art A conventional thermal head printing device is constructed as shown in FIG. Although this figure shows an example of an 8-dot thermal head with heating elements e1 to e8, an actual thermal head has a large number of heating elements, such as 256 dots or 384 dots. A black and white image per line is input as a serial signal to the pattern input IN, and the shift pulse S shifts the inside of the shift register SR from left to right in FIG. The black and white pattern is temporarily held at the position. It is transferred to latch memory M by latch signal LO and held until the next latch instruction is given to latch memory M. Then, at an appropriate timing until the next latch instruction, the strobe pulse P
When given, at that timing, electricity is applied from the power supply +E to the heat generating element located at the black pattern position among the heat generating elements e1 to e8, via the gates G1 to G8 and the amplifiers A1 to A8, according to the contents of the latch memory M. The area in contact with the driven heating element changes color to black due to the thermal properties of the thermal paper, recording a black image.

In those using a thermal transfer ribbon, a black image is recorded by thermally transferring ink from the thermal transfer ribbon onto plain paper using heat from a heating element. FIG. 5 shows the relationship between pattern input IN, strobe pulse P, and latch signal LO. Here, as shown in FIG. 5(a), the Nth line and the (N+
In the example of the 1)th line, L1 represents the serial signal period for one line, and W1 represents the pulse width of the strobe pulse P that defines the energization period to the heating element.

0004

As described above, when the number of black images per line is large, the number of elements that are energized and heated at one time increases, and the load on the power supply +E increases. If the regulation of the power supply +E is poor, the voltage will drop as the load increases. Additionally, as the load current increases, the voltage drop due to the electrical resistance of the wiring to the heat generating element increases, causing the effective voltage actually applied to the heat generating element to drop, resulting in a problem with the recording of a black image becoming fainter. .

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermal head printing device that can prevent black images from being recorded too faintly.

[0006]

[Means for Solving the Problems] The thermal head type printing device of the present invention has each heating element of the thermal head.
It is configured to be driven only during a strobe pulse period based on black-and-white image data represented by a plurality of dots per line, and includes a counter unit that counts the number of black images in the black-and-white image data for each line, and a count value of the counter unit. The present invention is characterized in that a strobe pulse generating section is provided that outputs the strobe pulse whose pulse width is longer as the pulse width increases.

[0007]

According to this configuration, the greater the number of black images per line, the longer the pulse width of the strobe pulse. In other words, as the number of heating elements that are energized at once increases, the energization period becomes longer, thereby compensating for a decrease in input energy due to a decrease in the effective voltage applied to the heating elements.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. It should be noted that the same reference numerals are given to the parts having the same functions as those shown in FIGS. 4 and 5 showing the conventional example.

The thermal head type printing device of the present invention is constructed as shown in FIG. The strobe pulse P applied to the thermal head 1, which is composed of a large number of heating elements, a shift register SR necessary to drive them, a latch memory M, a gate, and an amplifier, is generated from a strobe pulse generator 2. ing. The strobe pulse generator 2 generates a strobe pulse as the number of black images increases, as shown in FIG. The pulse width is controlled to be long.

Specifically, as shown in FIG. 3(a),
The number of black images in the Nth line, where the number of black images is small, is counted by the counter unit 3, and the counted value CNT for one line is temporarily stored in the latch 4 by the latch signal LO shown in FIG. 3(c). The strobe pulse generator 2 generates a strobe pulse P having a pulse width W1 shown in FIG. The voltage is applied to the thermal head 1. The heating element at the position corresponding to the black image of the thermal head 1 is driven by the power supply +E over a period of pulse width W1. The contents of the counter section 3 are cleared for counting the next line.

In the case of the (N+1)th line in which the number of black images is greater than the Nth line, the count CNT temporarily held in the latch 4 by the latch signal LO is large, and the pulse width W1 is The strobe pulse P, which is wider than the strobe pulse P, is generated from the strobe pulse generator 2, and even if the voltage of the power supply +E decreases due to the large number of heating elements that are energized at once, the strobe pulse P that is wider than the The heating element is driven for a period as long as (W2-W1), and the decrease in input energy due to the voltage actually applied to the heating element being lower than the driving voltage of the Nth line is compensated for. The compensation is automatically performed, and a uniform recording density can be obtained between the Nth line and the (N+1)th line.

In the above embodiment, the case of black and white binary recording was explained as an example, but printing is performed by moving a head block composed of a thermal head and a thermal transfer ribbon relative to plain paper. In this type, it is possible to record in colors other than black by selecting the color of the thermal transfer ribbon, and the description of "number of black images" in the claims limits the color of recording to black. It's not a thing.

[0013]

As described above, according to the present invention, there is provided a counter section that counts the number of black images in monochrome image data for each line, and a strobe pulse whose pulse width is longer as the count value of the counter section is larger. Since a strobe pulse generator is provided, the more heat-generating elements are energized at once, the longer the energization period becomes, compensating for the decrease in input energy due to the decrease in the effective voltage applied to the heat-generating elements. This eliminates the drop in recording density that occurs when the effective voltage actually applied to the heating element decreases due to the influence of power supply regulation and the voltage drop due to the electrical resistance of the wiring to the heating element. Uniform recording density can be obtained regardless of the number of heating elements energized.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a thermal head type printing device of the present invention.

FIG. 2 is a characteristic diagram of a strobe pulse generating section of the device.

FIG. 3 is a waveform diagram showing the relationship between one line image data input to the device and strobe pulses.

FIG. 4 is a configuration diagram of a conventional thermal head printing device.

FIG. 5 is a waveform diagram showing the relationship between conventional one-line image data and strobe pulses.

[Explanation of symbols]

e1 to e8 Heat generating element IN pattern input S
Shift pulse SR Shift register LO Latch signal M Latch memory +E
Power supply P Strobe pulse 1
Thermal head 2
Strobe pulse generator 3
Counter section 4 latch

Claims (1)

[Claims] 1. Each heating element of the thermal head is configured to be driven for a strobe pulse period based on black-and-white image data represented by a plurality of dots per line, and the number of black images in the black-and-white image data for each line is determined. A thermal head type printing device comprising: a counter unit that counts the number of pulses; and a strobe pulse generating unit that outputs the strobe pulse whose pulse width is longer as the count value of the counter unit is larger.