JPS61122579A - Testing method of thermal head - Google Patents

Abstract

PURPOSE:To detect the position of abnormality immediately if the abnormality is found by checking an IC for a shift register and respective signals successively according to a check sequence. CONSTITUTION:Only an IC power source for the shift register is turned on firstly to turn on a clock, whose signal is fed back to check the clock. At this time, if abnormality is found, signals 3-5 are turned off instantaneously. Similarly, a latch, a stroker, etc., are checked. Then, test data is sent and checked. Lastly, a power source 9 for leak checking is turned on to set data in an all-black state, thereby making a leak check, etc. The level of a voltage drop by an abnormality detection resistance 8, on the other hand, is checked by an abnormal level detecting circuit 6 to make a leak check. Further, a microcomputer 7 decides whether the feedback signal is pulses synchronizing with the stroker. When results of said checks are normal, a print test is taken and when not, the signals 3-5 are turned off and the abnormal position is displayed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermal head testing method for detecting abnormalities in a thermal head to be tested in advance during an operation test of the thermal head.

[Conventional technology]

As a conventional method for testing this type of thermal head, for example, a method for testing a thermal head disclosed in Japanese Patent Application Laid-Open No. 54-80139 has been proposed.

FIG. 3 is a block diagram showing a thermal head testing device used in a conventional thermal head testing method.

In the figure, 1 is a thermal head to be tested, 2 is a drive signal generation circuit for driving the thermal head 1, 3,
4.5 is a signal generated by the drive signal generation circuit 2.

In the thermal head testing device having the above configuration, each signal 3, 4.5 generated by the drive signal generation circuit 2
The operation of the thermal head 1 is tested by driving the thermal head 1t to be tested and actually printing a test pattern (not shown).

[Problem that the invention seeks to solve]

In the conventional thermal head testing method as described above, each signal 3, 4, . If there is a short circuit or disconnection between s, there is a risk of destroying the 7-foot resistor and heating element (both not shown), and there is also a risk of damaging the thermal head testing device itself. There were problems such as.

This invention was made in order to solve such problems, and the abnormality is detected before the test pattern is actually printed, and the thermal head to be tested and the thermal head testing device are protected. The purpose is to obtain a testing method for thermal heads.

[Means for solving problems]

What is the testing method for the thermal head according to this invention?

Before actually printing the test pattern, check the shift register IC and each signal in sequence.
If there is an abnormality, each signal is instantly turned off and the abnormal location is displayed.

[Effect]

In the thermal head testing method of this invention
Before actually printing the test pattern, the shift register IC is checked and each signal is checked according to a predetermined check sequence, for example, by a microcomputer. Perform detection.

〔Example〕

FIG. 1 is a block diagram showing a thermal head testing device used in a thermal head testing method according to an embodiment of the present invention. The same parts as in FIG. Detailed explanation will be omitted. In the figure,
6 is an abnormal level detection circuit for each signal 3, 4.5, 7 is a microcomputer, 8 is an abnormality detection resistor, and 9 is a leak check power supply.

FIG. 2 is a flowchart showing a check sequence by a microcomputer in the thermal head testing method of FIG. 1.

Next, a method for testing a thermal head according to the present invention using the thermal head testing apparatus shown in FIG. 1 will be described. Before actually printing the test pattern, perform a check sequence as shown in Figure 2.First, turn on only the IC power supply for the shift register (not shown) to turn on the clock, and then use the feedback of this clock signal to start the shift register. Check. At this time, if there is any abnormality, all signals 3, 4.5 are turned off instantly. Similarly, check latches, strobes, etc. Next, test data is sent and this test data is checked. Finally, turn on the leak check power supply 9 and clear the data in all black (H
level) and perform a leak check and strobe check.

A leak check is performed by checking the level of voltage drop caused by the abnormality detection resistor 8 using the abnormality level detection circuit 6. Also, the microcomputer 7 determines whether the feedback signal is a pulse synchronized with the strobe.

A strobe check can be performed. If all of the above checking steps are normal, the process proceeds to 1 normal printing test. By the way, if there is an abnormality, all signals 3, 4,
5 to 0FFL to display the abnormal location.

In the nose embodiment, a 3-5 tate buffer and a relay are used for switching each signal 3, 4.5, but other switching elements may be used.

Further, in the above embodiment, the abnormal level detection circuit 6 is
In addition to detecting the level of voltage drop by the abnormality detection resistor 8, it may be possible to add functions such as determining pulse width and synchronization.

〔Effect of the invention〕

As described above, in the thermal head testing method, before actually printing a test pattern,
Since the shift register IC and each signal are checked sequentially according to the check resistance, if there is an abnormality, each signal can be instantly turned off and the abnormal location can be displayed. This provides an excellent effect in that the thermal head to be tested and the thermal head testing device can be reliably and safely protected.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a thermal head testing device used in a thermal head testing method according to an embodiment of the present invention, and FIG. 2 shows a microcomputer-based check in the thermal head testing method shown in FIG. A flowchart showing the sequence, and FIG. 3 is a block diagram showing a thermal head testing device used in a conventional thermal head testing method. In the figure, 1... Thermal head, 2... Drive signal generation circuit, 3, 4.5... Signal, 6... Abnormal level detection circuit, 7... Microcomputer, 8...
Resistor for abnormality detection, 9...Power source for leak check. In each figure, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] In a thermal head equipped with a shift register, an abnormality is detected by checking the shift register IC and each signal before a printing test using a thermal head testing device, and the thermal head to be tested and the thermal head are tested. A thermal head testing method characterized by protecting a testing device.