JPS6356072B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a printing method for a thermal printer.

Conventionally, when operating a thermal printer using a power source with large voltage fluctuations such as a dry battery, it is necessary to control the amount of time the thermal head is energized or to stabilize the power supply voltage in order to obtain prints with a constant density. Controlling the supplied energy is being done. However, all of these methods have complicated circuits, are difficult to control using only digital circuits, and require adjustment, which has been a major obstacle to lowering the cost of the device. .

The present invention eliminates such drawbacks and realizes a thermal printer that can easily obtain a constant density using a timing signal obtained from the motor rotation system and a print inhibit pulse generated by a digital circuit. It is.

The present invention will be explained in detail below with reference to the drawings.

FIG. 1 schematically shows an embodiment of a printing circuit according to the printing method of a thermal printer of the present invention, and FIG. 2 is a diagram showing the timing of its operation.

1 is a thermal head, and 2 is a motor. Both are connected via a mechanism such as a cam or a feed screw, and the thermal head 1 is configured to perform reciprocating motion by the rotation of the motor 2. 3 is a timing generator connected to the motor 2;
A timing signal a is generated in synchronization with the rotation of the motor 2. Reference numeral 4 denotes a print inhibit pulse generation circuit consisting of a monomulti circuit or a timer circuit using a counter, which generates a print inhibit pulse b triggered by the timing signal a. Reference numeral 5 denotes a print control circuit, which is composed of a data buffer memory, a character generator, etc., and controls a data conversion circuit 6 that converts input data into print data c according to the timing signal a, and also controls a motor drive transistor. Performs ON-OFF control of T _r .

Furthermore, the print data c is gated by the print prohibition pulse b in the output gate circuit 7, and the next timing signal a starts from the end of the print prohibition pulse b.
The thermal head 1 is energized during the rising edge of .

That is, the time obtained by subtracting the pulse width of the print inhibit pulse b from the period of the timing signal a becomes the energization time for each dot of the thermal head.

In the above configuration, since the motor 2 is only ON-OFF controlled by the drive transistor _Tr , the rotation speed changes according to the power supply voltage, and the period of the timing signal a also changes.

On the other hand, since the voltage printed on the thermal head 1 also changes depending on the power supply voltage, in order to obtain a print with a constant density, a current application time is required depending on the voltage.

FIG. 3 shows the cycle of the timing signal a and the energization time of the thermal head using voltage as a parameter. As is clear from this, it can be seen that the difference between the timing signal period and the energization time is almost constant. Therefore, by keeping the pulse width of the print inhibit pulse shown in Figure 2 constant, even when the power supply voltage fluctuates,
Since the necessary energization time for the head is obtained, it is possible to print at a constant density.

In addition, in the print inhibit pulse generation circuit 4, by adding a switching circuit so that the time constant of the monomulti circuit that determines the pulse width or the count number of the counter can be arbitrarily set, the sensitivity of the thermal paper can be changed. Alternatively, it becomes possible to obtain a print density according to one's preference.

Next, FIG. 4a shows an embodiment in which the print inhibit pulse is changed depending on the number of dots to be printed. 8 is a print dot number detection circuit whose input is connected to print data and whose output is connected to a print inhibit pulse generation circuit. FIG. 4b is a detailed circuit diagram of the print inhibit pulse generating circuit, which is composed of a flip-flop circuit 41, a counter 42, a decoding circuit 43, and a switching circuit 44. The Q output of the flip-flop 41 becomes "H" at the rising edge of the timing signal a connected to the clock input terminal, and is output as a print inhibit pulse b. At the same time, the counter 42 is released from reset and counts clock pulses. The output of the counter 42 is decoded through a decoder 43, and when a preset count is reached, the output is input to the switching circuit 44. This count number is set in several stages depending on the number of dots to be printed. The switching circuit 44 selects the count number according to the dot number detection signal and resets the flip-flop 41. When the number of print dots is small, increase the count and lengthen the print inhibit pulse. Also, when the number of print dots is large, the count number is decreased to shorten the print inhibit pulse. With such a configuration, it is possible to always obtain uniform printing even in the case of a power supply having a large internal resistance, even if there is a rapid voltage fluctuation due to the number of printed dots during printing.

As described above, according to the present invention, by utilizing the voltage dependence of the motor and the thermal head, the printing circuit has a very simple configuration and can control the printing density entirely by digital circuits. can be realized, and the cost of the circuit can be significantly reduced.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the overall configuration of the printing method of a thermal printer according to the present invention, FIG. 2 is a timing diagram thereof, and FIG. 3 shows timing signal cycles and energization of the thermal head. FIG. 4a and FIG. 4b are block diagrams showing other embodiments of the printing method of the thermal printer according to the present invention. 1...Thermal head, 2...Motor, 3...
Timing generator, 4... Print inhibit pulse generation circuit,... Timing signal,... Print inhibit pulse,... Print data,... Energizing pulse.

Claims (1)

[Scope of Claims] 1. In a printer that prints while moving a thermal head by rotation of a motor, in order to generate a timing signal to synchronize the rotation of the motor and the timing of printing, a timing generator connected to the motor; A print prohibition pulse triggered by a timing signal closes the print signal while the print prohibition pulse is being output, and the print signal is closed between the end of output of the print prohibition pulse and the output of the next timing signal. A printing method for a thermal printer characterized in that the thermal printer outputs electricity to energize the thermal head. 2. The printing method for a thermal printer according to claim 1, wherein the pulse width of the print inhibit pulse can be set arbitrarily. 3. The printing method for a thermal printer according to claim 1, wherein the pulse width of the print inhibit pulse is automatically changed according to print data.