JPS58114976A - Thermal printer - Google Patents

Abstract

PURPOSE:To improve the recording quality by allowing a heat generating element to reach the required temperature instantaneously even after the stoppage of the printing action with a larger current flowing through the heat generating element than that during the normal driving upon the normal arrival of the first drive signal after a certian time of non-drive state. CONSTITUTION:With the closing of a power source, one pulse is fed to a terminal P to open a gate circuit G1 by setting a flip flop circuit F1. A drive signal of a heat generating element TH is fed to a terminal DR and a differential pulse thereof is fed to a one-shot pulse generator W through gate circuit G1 and G3 to turn on a switching circuit S while the output pulse is generated. A drive signal is fed to a transistor Tr via the circuit S so that a large current will be supplied to the element TH to heat it TH instantaneously up to required temperature. This enables the recording of dots in a prescribed size from the beginning without blurring them.

Description

[Detailed description of the invention] The present invention relates to a thermal printer.

Conventional thermal printers have the disadvantage that dots become blurred immediately after printing starts or near the home page, resulting in unclear characters. The main reason for this is that the head cools down when the printing operation is paused or during the head retardation operation, and the heat generation temperature of the heating element is taken away, so that the heating element does not reach the required temperature.

Therefore, the present invention eliminates the above-mentioned drawbacks by causing a larger current to flow than during steady driving upon arrival of the first driving signal after being in a non-driving state for a certain period of time or more.

An embodiment of the present invention will be described below based on the drawings.

In FIG. 1, TH is a heating element, Tr is a drive transistor, R is a current control resistor, and 8 is a switching circuit. OT is a counter that counts the pause time of the drive signal.
．． ν is a 7-rip prop circuit, W is a one-shot pulse generator, GING.

is a gate circuit, d, to d1 are differentiating circuits, and ■ is an inverter.

Next, the operation will be explained. By turning on the power to this device, one pulse is supplied to the terminal P, the flip-flop circuit 11 is set, and the gate circuit G1 is turned on.

Therefore, when the drive signal for the heating element TH is supplied to the terminal DH, its differentiated pulse passes through the JIG and tGa, and is supplied to the pulse generator -W. While the output pulse is being generated, the switching circuit S is turned on, the drive signal is supplied to the transistor D via the switching circuit S, and a large current flows through the heating element TH. Therefore, the heating element TH reaches the required temperature at once, and dots of a specified size can be recorded from the beginning without blurring the dots as in the conventional case.

When the pulse from the pulse generator SW stops, the switching path B is turned off and the differentiating circuit d,
The pulses from the 7 lip-flop circuits 1. or will be reset. If the next drive signal arrives before the heating element TH has completely cooled down, it is supplied to the transistor Tr via the resistor R. Therefore, a steady drive current smaller than the above flows through the heating element TH, and a dot of a specified size is recorded.

By the way, the counter OT is connected to the terminal OL when the drive signal is not supplied.
When the next drive signal arrives within a preset time, it is reset and the heating element TI is driven with the steady drive current.

If the drive signal does not arrive for longer than the set time due to a pause in the printing operation, that is, if the heating element TH has cooled down, an output is generated from the counter OT and the flip-flop circuit is activated. , is set and the gate circuit G is opened. When the drive signal arrives, the counter is set and the differential pulse of the monitor is used to set the counter.
) A pulse is generated from a pulse generator W. Therefore, while this pulse is being generated, a large current flows through the heating element TH, and a dot of a specified size is recorded. By stopping the generation of the pulses, the flip-flop circuit 1. When the counter is set and an output is generated again from the counter 0, steady driving is performed.

The time required for the heat generating element TH to cool down after being driven is set by the counter OT in this way, and this time depends on the ambient temperature. Therefore, the second WJ shows an example of a configuration in which the set time is changed according to the temperature.

In the same figure, PG is a pulse generation circuit consisting of a gate circuit and used to set the time for the cash advance, and generates a pulse when the counter OT measures different times for three types of equipment, for example. be. TM is a detection device that detects the ambient temperature, SL is a selection circuit, and the other configurations are the first
Same as the figure.

The detection device TM divides the ambient temperature into three stages and selects - $14
Five types of pulses from the pulse generation circuit PG are selected at each stage by m+IC. In this way, the set time can be changed depending on the temperature.

As described above, according to the present invention, the heating element instantly reaches the required temperature even after the printing operation is stopped, and the dots are not blurred, making it possible to improve the recording quality.

In addition, a large current is applied only by the first drive signal after the set period of rest, and the rest is driven by a steady drive current.
Current consumption can be suppressed as much as possible.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram showing one embodiment of the present invention, and FIG. 2 is an electric circuit diagram showing another embodiment. TH...Heating element Tr...Drive transistor R
...Resistance S...Switching circuit! ,・
...Flip-flop circuit OT...Counter W...One-shot pulse generator Applicant Kinsha Co., Ltd. Seikosha Agent Patent attorney Mogami Figure 1 Figure 2

Claims (2)

[Claims] (1) During steady driving, a drive circuit drives the heating element by passing a predetermined current through it in response to the arrival of a drive signal; and a control circuit that causes a current larger than the predetermined current to flow through the thermal printer. (2) A drive circuit that drives a heat generating element by passing a predetermined current through it in response to the arrival of a drive signal during steady driving, and a drive circuit that drives the heat generating element by flowing a predetermined current through the heat generating element upon the arrival of a drive signal, and a drive circuit that drives the heat generating element by flowing a predetermined current through the heat generating element upon the arrival of the first drive signal after the heat generating element has been in a non-driving state for a set time or more. A thermal printer comprising: a control circuit that causes a current larger than the predetermined current to flow; and a switching circuit that switches the set time according to a circumferential temperature of 9M.