JPH04197654A - Electrification printer - Google Patents

Abstract

PURPOSE:To enable inferiority of a printing head to be easily detected with a simple circuit and by simple control by a method wherein a constant current driving circuit is used as a driving circuit for a printing head, and variation in voltage according to variation in resistance of load resistance in printing is monitored. CONSTITUTION:A peak hold circuit 16 is cleared by a clear signal before printing, and printing is started. When printing of one line is ended, a start pulse is sent to a A/D converter 17 and maximum voltage of the peak hold circuit 16 is taken into a CPU 2. A CPU 2 compares a data of a preliminarily set (Vh-Vz) with the taken into data to check presence of abnormalities of conversion on printing. Further, an abovementioned executed example is not always limited but it may be preferably made possible also that a maximum value is stored in a register or a memory by using A/D conversion in a peak detection circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Industrial Application Field) The present invention relates to an energized printer in which printing is performed by heating the ribbon by passing an electric current from the print head to the ribbon.

(Prior Art) An electric printer generates heat in the base material of the ribbon by passing an electric current from the print head to the ribbon, thereby transferring ink to the paper surface. For this reason, the self-diagnosis of the print head is based on the resistance between the print head drive circuit and the return electrode when either a small current that does not cause ink transfer or a very short current is applied to each print head bin. Print head electrode breakage is detected by measuring .

(Problem to be Solved by the Invention) Conventionally, in order to check the printing by applying power to each pin one by one, in addition to the print head drive circuit, a signal selection circuit corresponding to the number of pins of the print head and a very short pulse or low current were used. It was necessary to have a generation circuit.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an energized printer that can easily detect print head defects using a simple circuit and simple control.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a printing method in an electric printer in which printing is performed by heating the ribbon by passing an electric current from the print head to the ribbon. A constant current drive circuit that supplies a signal current to the head, a maximum voltage detection means that detects the maximum value of the voltage corresponding to the resistance change of the load resistance of this constant current drive circuit, and a maximum voltage detection means that detects the voltage detected by the maximum voltage detection means. The present invention is characterized by comprising a defective print head detection means for detecting a defect in the print head based on the maximum value.

(Function) In the present invention, a constant current drive circuit is used as a print head drive circuit, and a defect in the print head is detected by monitoring a change in voltage according to a change in resistance of a load resistor during printing. That is, if a pin of the print head breaks somewhere, the print head cannot perform proper printing and is replaced with a new one, thereby detecting that the print head is defective somewhere.

(Example) Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is an example of a printer diagram of an energized printer. The printed character code sent by the R5232C signal of the data input/output standard specification from the terminal device 1 is input to the CPU 2 of the one-touch microcomputer, and the address signal of this CPU 2 sends the character code to the character font RO via the chip selector 3.
Call the pattern data from M4, and read the pattern data from this ROM4.
The pattern data called from is input to the shift register 5 via the CPU 2. The data output from this shift register 5 is output to a constant current drive circuit 6, and the signal current from this constant current drive circuit 6 is input as an on/off signal to each pin of the print head of a defective print head detection circuit 7. be done. At the same time, the CPU 2 controls the head feed pulse motor 9 via the driver 8 and also controls the paper feed pulse motor 11 via the driver 10 to print characters and figures. 12 is program R
OM, 13 is a data RAM.

FIG. 2 is a block diagram of the shift register 5, constant current drive circuit 6, and defective print head detection circuit 7. An on/off signal for the print head 14 is supplied by each constant current drive circuit 6 to the print head 14 . For energized printers,
Load resistance R of constant current drive circuit 6 (print head equivalent resistance R
,,R2,...,R,) is the sum of the contact resistance between the print head 14 and the ribbon, the resistance of the ribbon base material, and the contact resistance between the ribbon and the return electrode. If the print head 14 becomes dirty, the load resistance R of the constant current drive circuit 6 increases.
The constant current drive circuit 6 attempts to maintain a constant current by increasing the voltage. That is, in the constant current drive circuit 6 of FIG.
If the power supply voltage is vh, the Zener voltage of the Zener diode D2 is Vz, and the emitter resistance of the transistor Tr2 is RE, then the current I flowing through one pin of the print head 14 is expressed as 1-Vz/RE, or the load resistance R is When the voltage increases, the maximum value of the voltage applied to both ends of the load resistance R is (Vh - Z), and the maximum value of the load resistance R at that time is Rmax - (Vh - Vz) *RE /Vz. The constant current drive circuit 6 only operates normally up to this value. There is dust or dirt on the pins of the print head 14.
Print head] If pin 4 is damaged, load resistance R
is a very large value.

Then, the voltage across the load resistor R (transistor Tr2
collector voltage) becomes (Vh - Vz) volts. The maximum value of this voltage is extracted from all the pins of the print head 14 through an OR circuit 15 consisting of diodes D1 to D, and is held by a peak hold circuit 16.
The data is digitized by the converter 17 and taken into the CPU 2 to determine if the electrodes of the print head are broken. In FIG. 3, Tr is a transistor and r is a resistor.

In actual control, before printing, the peak hold circuit 16 is cleared with a clear signal and printing is started.

After printing one line, send a start pulse to the A/D converter 17 and set the maximum voltage of the peak hold circuit 16 to the CPU.
Incorporate into 2. The CPU 2 compares the previously set data (Vh-Vz) with the captured data to check whether there is any abnormality in the print head.

Note that the present invention is not limited to the above embodiment, and the peak detection circuit may use A/D conversion to store the maximum value as a digital value in a register or memory.

Further, print head defects may be detected by measuring the voltage of the constant current drive circuit.

[Effects of the Invention] As explained above, according to the present invention, by using a constant current drive circuit as the print head drive circuit and monitoring the change in voltage according to the resistance change of the load resistor during printing,
With a simple circuit and simple control, it is possible to easily detect print head defects in energized printers.

In addition, when the resistance value becomes high due to ribbon dregs etc. adhering to the print head, a warning message saying "Please clean the print head" is issued.

[Brief explanation of the drawing]

FIG. 1 is a configuration explanatory diagram showing one embodiment of the present invention, FIG. 2 is a configuration explanatory diagram showing an example of a defective print head detection circuit according to the present invention, and FIG. 3 is a configuration explanatory diagram showing an example of a defective print head detection circuit according to the present invention. FIG. 2 is a configuration explanatory diagram showing an example. 2. CPU, 5. Shift register, 6. Constant current drive circuit, 7. Defective print head detection circuit, 15. OR circuit, 16. Peak hold circuit, 17. A/D converter. Applicant's agent Patent attorney Takehiko Suzu

Claims (1)

[Scope of Claims] In an electric printer in which printing is performed by heating the ribbon by passing current from the print head to the ribbon, there is provided a constant current drive circuit that supplies a signal current to the print head, and a load of this constant current drive circuit. A maximum voltage detection means for detecting the maximum value of voltage corresponding to a resistance change of the resistor, and a defective print head detection means for detecting a defective print head from the maximum value of the voltage detected by the maximum voltage detection means. An energized printer featuring: