JPH04307260A - Printing control apparatus - Google Patents

Abstract

PURPOSE:To prevent the deterioration of printing quality due to the temp. rise of a printing head and to impart stable printing quality in the printing control apparatus of an impact type printing apparatus. CONSTITUTION:A resistor R1 is inserted in series to the drive coil S1 of a solenoid ejecting the printing wire of a printing head. The current of the drive coil S1 is detected by detecting the voltage generated across both terminals of the resistor R1. On the basis of this detected output, a CPU 1 detects that the temp. of the drive coil rises and the internal resistance of said coil is increased to stop the operation of a transistor Tr1 controlling printing for a certain period. Since the temp. rise of the drive coil causing the deterioration of printing quality can be certainly detected, proper control is performed and printing quality can be stabilized.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a print control device for an impact printing device such as a dot matrix printer using a wire dot print head.

0002

BACKGROUND OF THE INVENTION In recent years, there have been remarkable advances in printer speeds, lower power consumption, higher efficiency, and lower costs.

[0003] The print control device of an impact type printing device using a conventional wire dot type print head has a posistor built into the print head in order to suppress the heat generation of the print head. The resistance value was detected and printing was controlled. A conventional printing control device will be explained below. FIG. 3(a) is a circuit diagram of a conventional print control device that drives a print head, where S1 is a drive coil for protruding a print wire (not shown in the figure) of the print head, and Tr1 is a drive coil S1. ZD1 is a Zener diode that absorbs the back electromotive force generated from the drive coil S1, and D
1 indicates that the transistor Tr1 is in a conductive state (hereinafter referred to as ON), and when the drive coil S1 is excited, current is prevented from flowing, and when the transistor Tr1 is in a cutoff state (hereinafter referred to as OFF) ) is a diode that allows current to flow through the Zener diode 2D1.

[0004] A posister (not shown) for detecting the temperature of the print head is built into the print head in which the drive coil is built-in. A print control device is used in which a central processing unit 2 (hereinafter referred to as CPU) detects the resistance value of this POSISTOR and responds to changes in the temperature of the print head.

The operation of the conventional printing control device configured as described above will be explained below. In the timing chart of Figure (b), at time t1, the transistor TR
When the base point P of the transistor Tr1 reaches +5V (hereinafter abbreviated as H level), the transistor Tr1 turns on.
A voltage V shown in FIG. 3(b) is applied to the drive coil S1, a current is supplied from the drive power supply Vcc to the drive coil S1, and the current flowing through the drive coil S1 is as shown by the current I in FIG. 3(b). Increase gradually. Next, after a certain period of time has passed, point P becomes 0V (hereinafter referred to as L level) at time t2, transistor Tr1 is turned off, and the current in drive coil S1 flows through diode D1 and Zener diode ZD to current I. decrease rapidly as shown. As the current I repeatedly flows through the drive coil S1, the temperature of the drive coil S1 increases, and at the same time, the resistance value of the POSISTOR in the print head increases. The CPU 2 detects the resistance value of the POSISTOR and stops printing. At the same time, the temperature of the drive coil S1 within the print head also decreases, and the resistance value of the POSISTOR within the print head also decreases. The CPU 2 detects that the resistance value of the POSISTOR has become small, starts printing, and repeats the same operation to keep the upper limit of the temperature of the drive coil in the print head constant.

[0006]

[Problems to be Solved by the Invention] However, in the conventional configuration described above, the heat transfer efficiency of the drive coil is low due to the large mounting area of the POSISTOR in the print head, and the temperature of the drive coil in the print head exceeds the expected value. However, there was a problem in that the printing quality significantly deteriorated.

[0007] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a print control device that detects a temperature rise in a print head and does not cause a deterioration in print quality.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the printing control device of the present invention controls the printing head in an impact printing device by detecting the coil current of a solenoid that causes the printing wire of the printing head to protrude. This is performed by a current detecting means for detecting the current and a printing control means for controlling a solenoid driving means based on the output of the current detecting means.

[0009]

[Operation] In the printing control device of the present invention having the above configuration, the current detection means detects the coil current of the solenoid of the print head, so that it is possible to detect a change in the resistance value of the coil due to a rise in the temperature of the coil. . The print head for impact-type printing devices uses a solenoid inside the print head to protrude a print wire, and prints by impacting dots with this print wire.The temperature rise in this print head is due to the temperature rise in this solenoid. The majority of this is due to Therefore, detecting the temperature rise of this solenoid coil is the best way to directly detect the temperature rise of the print head. In addition, since the cause of print quality deterioration due to temperature rise is a change in the impact force of the printing wire due to a change in the resistance value of this solenoid coil, the current change due to the change in the resistance value of this coil is detected, and the print head is The method of controlling the drive is the most reliable way to improve print quality.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram of a printing control device according to an embodiment of the present invention. Components having the same functions as those of the conventional printer are designated by the same reference numerals and their explanations will be omitted. CPU
1, unlike the conventional one, the solenoid drive coil S1
An input terminal is provided for inputting the voltage generated across the resistor R1 connected in series with the resistor R1.

Note that the drive coil S1 is a transistor Tr.
1 constitutes a drive means for the solenoid, and a current detection means is constituted by detecting the current of the drive coil S1 by a resistor R1, and control according to this output is performed by C.
The PU1 constitutes a print control means.

The operation of the printing control device of this embodiment configured as described above will be explained below. Figure 2
As shown in FIG. 2, the signal at point A becomes H level at time t1, transistor Tr1 is turned on, and current is supplied to drive coil S1. The current I flowing through the drive coil S1 gradually increases as shown by the waveform I1 in FIG. 2, and this results in a printing operation by the print head. After a certain period of time T has elapsed, the signal at point A becomes L level, transistor Tr1 turns off, and the current due to the back electromotive force of drive coil S1 flows through diode D1, Zener diode ZD1, and resistor R1, and rapidly decreases as shown in waveform I1. . Furthermore, in synchronization with the fall of the signal A, the CPU 1 detects the voltage at point B generated by the current flowing through the resistor R1.

When this series of operations is repeated, the temperature of the drive coil S1 gradually increases, the resistance value of the drive coil S1 gradually increases, and as a result, the temperature of the drive coil S1 gradually increases.
The current gradually decreases as shown by waveform I2 in FIG. Therefore, when the voltage generated across the resistor R1 becomes smaller and becomes smaller than the set voltage corresponding to the upper limit of the temperature of the drive coil S1, the CPU 1 holds the signal at point A at the L level, turning off the transistor Tr1 and turning off the drive coil. No current flows through S1. In Fig. 2, drive coil S1
It is shown as the voltage IS corresponding to the set voltage at the current I of . Since the current I2 has become lower than the set current IS, it means that the current in the drive coil S1 has been cut off. Therefore, the temperature of the drive coil S1 gradually decreases, and the resistance value of the drive coil S1 decreases correspondingly. Next, after a certain period of time has elapsed, the CPU 1 sets the signal at point A to H level, thereby turning on the transistor Tr1 and causing current to flow through the drive coil S1 again. In this way, the voltage generated in the resistor R1 is detected, and when it becomes larger than the set voltage corresponding to the upper limit value of the temperature of the drive coil, a series of control operations are performed to hold the signal at point A at L again, and the temperature of the drive coil S1 is increased. The upper limit value of is maintained, and deterioration of print quality is prevented. In addition,
Although the set voltage or set current for setting the upper limit of the temperature of the drive coil S1 has been described using its peak value, it is of course possible to control using its average value.

[0014]

Effects of the Invention As is clear from the above description, the present invention detects the current flowing through the solenoid to directly detect changes in the current flowing through the solenoid in response to changes in the temperature of the solenoid. Since the temperature of the drive coil can be detected as expected, it is possible to realize a print control device that can perform print control with stable print quality without quality deterioration due to a decrease in the impact force of the print head.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a printing control device according to an embodiment of the present invention.

[Fig. 2] Timing chart for explaining the operation of the printing control device of the same embodiment.

[Figure 3] (a) is a block diagram of a conventional printing control device (b)
) is a timing chart showing the operation of the conventional printing control device.

[Explanation of symbols]

1 Central processing unit Tr1 transistor S1 Drive coil R1 resistance

Claims (1)

[Claims] 1. A solenoid for protruding a print wire of a print head, a drive means for driving the solenoid, a current detection means for detecting a current value flowing through the solenoid by the drive means, and an output of the current detection means. and a print control means for controlling the drive means accordingly, and when the print control means detects by the current detection means that a current value flowing through the solenoid has become equal to or less than a predetermined value, the drive means controls the solenoid. A printing control device designed to stop the drive of the printer.