JPS63145073A - Printing head control device - Google Patents

Abstract

PURPOSE:To prevent deterioration in follow-up performance or duplication capabilities by prolonging an energization time for a printing head at lower temperatures than a thermal protection operating temperature. CONSTITUTION:A first operating point A on a high temperature side and a second operating point B on a low temperature side are detected respectively by means of resistance variations following an increase in thermister temperatures. A thermal protection circuit 13 operates at the time when the first operating point has been detected, applying thermal protection to the action of a printing head. A printing head drive control circuit 14 operates when the second operating point has been detected to prolong an energization time for the printing head. Consequently, a faulty follow-up action or deterioration of copying capability due to a decrease in printing pressure at the time of temperature of the printing head being risen is prevented. At the same time, the degradation of the printing head also can be prevented because of the shortening of a time in which the printing head is exposed to a high temperature area.

Description

[Detailed Description of the Invention] [Summary] The present invention is a serial printer in which when the temperature of the print head increases, the resistance value of the built-in coil wire increases, the current value decreases, and the impact force decreases to follow it. The purpose of this technology is to solve the problem of deterioration in printing performance and copying performance, and the purpose is to extend the time during which electricity is applied to the print head at a predetermined temperature lower than the thermal protection operating temperature.

[Industrial application field]

The present invention relates to a control device for a print head of a serial printer.

In serial printers, when printing continues for a long time, the temperature of the print head rises due to the heat generated by the head itself.
If this temperature exceeds the heat resistance temperature of the parts used, the parts will be destroyed. Therefore, we set a predetermined temperature below this heat-resistant temperature,
When the temperature of the print head reaches this predetermined temperature, either stop printing until it reaches a certain temperature, or apply thermal protection such as lowering the printing duty (for example, printing in 3 parts per line) or reducing the printing speed. This prevents parts from breaking.

[Conventional technology]

A block diagram of a conventional print head driving procedure is shown in FIG.

As is clear from this figure, the print head is provided with a thermal sensor 1. When this thermal sensor 1 detects a predetermined temperature, a signal is sent to a thermal protection circuit 3 via a detection circuit 2, thereby thermally protecting the operation of the print head.

[Problem that the invention seeks to solve]

However, although such a conventional structure can prevent component damage, if the temperature of the print head rises below the above-mentioned predetermined temperature, the resistance value of the wire of the head built-in coil increases, causing the current value to decrease, resulting in shock damage. The force (printing pressure) is lower and the followability is improved.

Copy ability decreases.

[Means for solving the problems] The present invention provides a print head control device that can solve the above problems. , detection means for detecting a first operating point on the high temperature side and a second operating point on the lower temperature side, respectively, by a change in resistance as the temperature of the thermistor increases; and the detection means detects the first operating point. thermal protection means that operates when the detection means detects a second operating point to thermally protect the operation of the print head; and a print head drive that operates when the detection means detects a second operating point to extend the energization time for the print head. A control means is provided.

[Effect]

When the temperature of the thermistor provided in the print head increases together with the head, the detection means detects a first operating point on the high temperature side and a second operating point on the low temperature side due to a change in resistance of the thermistor as the temperature rises.

When the temperature of the print head increases and the second operating point is detected, the energization time to the print head is extended, thereby compensating for the drop in printing pressure at high temperatures and increasing the temperature of the first operating point.
The time it takes to reach the operating point becomes shorter.

When the temperature of the print head further increases and reaches the first operating point, thermal protection is applied to the operation of the print head to prevent further temperature rise.

〔Example〕

The present invention will now be described in detail with reference to FIGS. 1-3.

FIG. 1 is a block diagram of a print head control device according to the present invention, in which 11 is a thermistor provided in the print head, 12 is a detection circuit (detection means), and 13 is a thermal protection circuit (thermal protection means). , 14 is a print head drive control circuit (print head drive control means). The temperature of the thermistor 11 increases along with the print head, which increases in temperature during operation, and the detection circuit 12 detects a first operating point on the high temperature side and a second operating point on the lower temperature side due to a resistance change as the temperature of the thermistor 11 increases. Detect each. The thermal protection circuit 13 operates when the first operating point is detected to apply thermal protection to the operation of the print head, and the print head drive control circuit 14 operates when the second operating point is detected. Extend the time the print head is energized.

By the way, when the print head is at a low temperature, the waveform of the current applied to the print head during printing is as shown by the solid line in FIG. 2. (a) is the energization end point.

Further, the waveform of the current applied to the print head whose temperature has increased due to long-term use decreases as shown by the thin dotted line. This is because the resistance value of the coil wire built into the print head increases due to temperature rise.This decrease in current value causes a decrease in printing energy (printing pressure), leading to poor tracking and copying performance. A decline defect was occurring.

However, in the case of the present invention, when the second operating point is reached, the print head drive control circuit 14 extends the energization time as shown by the large dotted line in FIG. be done. (b) is the end point of energization at the time of extension. Furthermore, by extending the energization time, the time to reach the first operating point is reduced. FIG. 3 is a graph explaining this, where the solid line shows the conventional case and the large dotted line shows the present invention. As is clear from this figure, the second
By extending the energization time when the operating point is reached, the time required for the temperature of the print head to rise to the first operating point is shortened, and the curve between the second operating point and the first operating point has a steep rise. Become. As a result, the time of exposure to high temperature ranges is shortened, making it possible to prevent deterioration. When the temperature of the print head reaches the first operating point, the thermal protection circuit 13
Thermal protection is applied to the operation of the print head. As thermal protection, a method can be considered in which printing is performed by dividing one line in the line direction by raising the temperature to a first operating point, thereby reducing the frequency of energization in one magnet.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to prevent tracking failure and copy performance deterioration due to a drop in printing pressure when the temperature of the gutter increases during printing, and to prevent deterioration by shortening the time that the print head is exposed to a high temperature range. It becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a control device for a print head according to an embodiment of the present invention, FIG. 2 is a waveform diagram of a current applied to the print head, and FIG. 3 is a graph showing temperature changes in the print head. FIG. 4 is a block diagram showing a conventional print head drive procedure. In the figure, 11 is a thermistor, 12 is a detection circuit (detection means), 13 is a thermal protection circuit (thermal protection means), and 14 is a print head drive control circuit. (Print head drive control means). Figure 1: Graph showing the change in printing spatula whiteness of the example of this defense Figure 3:

Claims (1)

[Claims] In a serial printer equipped with a print head, the print head is provided with a thermistor, and a resistance change of the thermistor as the temperature rises enables a first operating point on a high temperature side and a second operating point on a lower temperature side. a detecting means for detecting each of the second operating points; a thermal protect means for operating when the detecting means detects the first operating point to apply thermal protection to the operation of the print head; 1. A print head control device comprising: print head drive control means that is activated when an operating point of said print head is detected to extend the current supply time to said print head.