JPH06262795A - Thermal printer - Google Patents

Abstract

PURPOSE:To obtain sufficient printing density even when a first sheet after standby state is printed by supplying a voltage to a thermal head resistor when a temperature of the head is low. CONSTITUTION:When a drive controller 3 judges that a temperature detected by a thermistor 5 is low in a printer standby state after a power source is turned ON, the-controller 3 switches a voltage switching circuit 4 to 5V side [contact 4a side] of a voltage value necessary for a lowest available current of a power source 1, and a lower voltage as compared with the time of printing is applied to a heat generating resistor of a thermal head 2. Thus, a current is supplied to the resistor to raise a temperature of the head 2 to be stabilized. Thus, even at the time of printing immediately after a standby state, an image of a stable density can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer such as a thermal transfer system.

[0002]

2. Description of the Related Art In a conventional thermal transfer printer, the voltage value of a power source for driving a thermal head is one kind of voltage value except for a slight voltage adjustment according to the color of an ink film. It was configured to be applied.

[0003]

However, in the thermal transfer printer, the temperature of the thermal head is low except when printing continuously, and the first head after a long standby state is used.
When printing the first sheet, there is a problem that a sufficient thermal head temperature, that is, a sufficient print density cannot be obtained.

On the other hand, the thermal transfer printer uses a so-called multi-output type power source capable of obtaining a plurality of output voltages for driving a mechanical system and for data calculation processing, in addition to the power source for driving the thermal head. In order to stabilize the output voltage, most of the multi-output type power supplies require a current consumption of at least the minimum operating current for a 5V output or the like which is generally used for data arithmetic control processing.

However, thermal transfer printers often do not meet the minimum operating current required by the power source as a current value of 5 V for data arithmetic control processing. Therefore, a dummy resistor having a large wattage is provided to make up for the shortage of current. There was a waste of having to supplement.

In particular, since the commercially available standard type switching power supply is designed to be used for various general products other than the thermal printer, for the thermal transfer printer, the output current of the mechanical system drive voltage and the calculation are calculated. Many of the output currents of the processing voltage have a poor balance, which causes the waste as described above.

The present invention has been made in view of the above problems, and by effectively utilizing a useless current value, it is possible to prevent the temperature of the thermal head from decreasing during standby of the thermal printer, and to reduce the temperature after the standby state. It is an object of the present invention to obtain a sufficient print density even when the first first sheet of is printed.

[0008]

In order to achieve this object, the thermal printer according to the present invention requires a first voltage which requires a current consumption of at least a minimum value as an output current and a current consumption of at least a minimum value. Power source for outputting a second voltage not controlled, voltage switching means for supplying the thermal head resistor by switching between the first voltage and the second voltage of the power source, temperature detecting means for detecting the temperature of the thermal head, and temperature detecting means. And a drive control means for switching the voltage switching means so as to supply the first voltage to the thermal head resistor when it is determined from the output of the above that the temperature of the thermal head is low.

[0009]

In the thermal printer having the above construction, when the drive control means determines from the output of the temperature detection means that the temperature of the thermal head is low, the voltage switching means is switched to apply the voltage to the thermal head resistor. By supplying the heat, the temperature of the thermal head is increased and stabilized, thereby preventing the temperature of the thermal head from decreasing during standby of the thermal printer.

Further, since the first voltage required to consume a current equal to or more than the minimum value is supplied to the thermal head resistor, it is possible to effectively use the current which has been wasted in the past and to save energy. Can be planned.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block connection diagram showing an embodiment of a thermal printer according to the present invention.

In FIG. 1, reference numeral 1 denotes a multi-output type power supply, and in order to stabilize the output voltage, + 5V output of the multi-outputs is required to have a current consumption of a minimum value or more. The power supply 1 supplies electric power to the thermal head 2, the drive control circuit 3, and a mechanical system (not shown), and supplies electric power to the dummy resistor 9 and the dummy resistor 10 in order to secure current consumption of at least the minimum value. We are supplying. The power supply to the dummy resistor 9 is switched on / off by the switching circuit 8. Further, in order to switch and supply the voltage to the thermal head 2, + 5V of the power source 1 is supplied.
The output is always applied to the terminal 4a.

A thermal head 2 is connected to the drive control circuit 3 via a bus line 5 for a print signal. Reference numeral 3 denotes a drive control circuit that performs arithmetic control processing and drive control, and transmits a print signal to the drive control circuit 3 via the bus line 5 to perform print control. Further, the voltage switching circuit 4 is controlled to be switched to switch the voltage applied to the thermal head resistor (not shown) of the thermal head 2. The voltage applied to the thermal head resistor is the thermal head 2
Applied between the Vcc terminal and the GND terminal.

Reference numeral 4 denotes a voltage switching circuit for switching the voltage supplied from the power source 1 to the thermal head 2 and is composed of a relay. The switching operation of the voltage switching circuit 4 is controlled by the drive control circuit 3. Reference numeral 5 is a bus line for a thermal head drive control signal. A thermistor 6 is attached to the surface of the thermal head 2 to detect the temperature of the thermal head 2. Reference numeral 7 denotes a thermal head driving power source that generates a voltage to be applied to a thermal head resistor (not shown) and supplies the voltage to the thermal head 2.
The output voltage is set to + 24V. The voltage of + 24V is constantly applied to the terminal 4b. 8 is a power source 1
Is a switching circuit used as a switching switch for switching on / off the power supply to the dummy resistor 9 and is composed of a relay. 9 and 10 are dummy resistors.

Next, the operation will be described.

In the printer standby state after the power is turned on,
When the drive control circuit 3 determines that the temperature detected by the thermistor 6 is low, the drive control circuit 3 controls the voltage switching circuit 4 to the 5V side (contact 4a), which is the voltage value that requires the minimum operating current of the power supply 1. Side), thermal head 2
A voltage lower than that at the time of printing is applied to the heating resistor (not shown). In this way, a current is passed through the heating resistor to raise the temperature of the thermal head 2 and stabilize it.
The applied voltage (5V) at this time is the voltage (24V) during printing.
Since the voltage is sufficiently lower than V), the heating resistor of the head is not burned by the idle heat generation.

The drive control circuit 3 sets the voltage switching circuit 4 to 5V.
At the same time as switching to the contact side (contact 4a side), the switching circuit 8 is switched to the contact 8a side to turn off the energization to the dummy resistor 9. This is to prevent the current from flowing through the dummy resistor 9 having the same resistance value as the resistor of the thermal head 2 while the current is flowing through the heating resistor of the thermal head 2. Note that the resistor 10 in FIG. 1 consumes a current together with the dummy resistor 9 in order to secure the minimum current value used by the power source 1, and is necessary when the dummy resistor 9 is insufficient. is there.

When printing is started, the voltage switching circuit 4 is switched to the 24V side (contact 4b side) by the drive control circuit 3, and a normal printing operation is performed.

When the temperature of the thermal head 2 rises too much, the drive control circuit 3 suspends the transmission of the print signal transmitted via the bus line 5 to suppress the temperature rise of the thermal head 2. , The voltage switching circuit 4 is switched to the 24V side (contact 4b side). Further, the switching circuit 8 is switched to the contact 8b side to turn on the energization of the dummy resistor 9, and a current is passed through the dummy resistor 9 to secure the minimum use current of the power source 1.

Although the voltage switching circuit 4 and the switching circuit 8 are relays in the above-described embodiments, the same effect can be obtained by using a semiconductor element such as a switching transistor or FET.

[0022]

As described above, according to the thermal printer of the present invention, when the drive control means determines from the output of the temperature detection means that the temperature of the thermal head is low,
The voltage switching means is switched to supply a voltage to the thermal head resistor to stabilize and increase the temperature of the thermal head, which prevents the thermal head temperature from dropping when the thermal printer is on standby. Even in the state, it is possible to automatically prevent the temperature of the thermal head from decreasing, and it is possible to obtain an image having a stable density even in the printing immediately after the standby state.

Further, since the first voltage, which requires a current consumption of the minimum value or more, is supplied to the thermal head resistor, it is possible to effectively use the current which has been wasted in the past and to save energy. It is possible to plan.

[Brief description of drawings]

FIG. 1 is a block connection diagram showing an embodiment of a thermal printer according to the present invention.

[Explanation of symbols]

 1 power supply 2 thermal head 3 drive control circuit 4 voltage switching circuit 4a contact 4b contact 5 bus line 6 thermistor 7 thermal head drive power supply 8 switching circuit 8a contact 8b contact 9 dummy resistor 10 dummy resistor

Claims (3)

[Claims] 1. A power supply that outputs a first voltage that requires a current consumption of at least a minimum value as an output current, and a second voltage that does not require a current consumption of at least a minimum value, and a first voltage of the power supply to a thermal head resistor. In the case where it is determined from the output of the temperature detecting means that the temperature of the thermal head is low, a voltage switching means for switching and supplying the first voltage and the second voltage, a temperature detecting means for detecting the temperature of the thermal head, A drive control means for switching the voltage switching means so as to supply a first voltage to the thermal head resistor. 2. The drive control means applies a first voltage to the thermal head resistor when it determines from the output of the temperature detection means that the temperature of the thermal head is low only when the printer is in a standby state. 2. The thermal printer according to claim 1, wherein the voltage switching means is switched to supply the voltage. 3. The thermal printer according to claim 1, wherein the first voltage has a voltage value sufficiently lower than a voltage applied to the thermal head during printing.