JPH04269557A - Pulse trimming device of thermal printing head - Google Patents

Abstract

PURPOSE:To execute pulse trimming regulation for resistance values of respective heating elements Ra, Rb, Rc, Rd, Re, Rf formed on a surface of an insulation substrate of a thermal printing head simultaneously for a plurality of the heating elements and by high precision. CONSTITUTION:In a pulse trimming device consisting of voltage pulse application circuits 4a, 4b, 4c, 4d to be applied to each of a plurality of heating elements Ra, Rb, Rc, Rd, Re, Rf of a thermal printing head, short circuits 13a, 13b, 13c, 13d, 13e, 13f which short-circuit selectively both ends of said heating element are provided to a plurality of heating elements Ra, Rb, Rc, Rd, Re, Rf respectively.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse trimming device for trimming and adjusting the resistance value of each heating resistor in a thermal print head to a substantially constant value using voltage pulses.

0002

2. Description of the Related Art In general, a thermal print head generates heat by energizing any one of its many heat generating resistors by energizing the heat generating resistor.
Since printing is performed, if the resistance values of the heating resistors are uneven, uneven printing will occur. Therefore, recently, for example, JP-A-61-15
As described in Publication No. 4006, focusing on the fact that when a high voltage pulse is applied to a film-type resistor formed on the surface of an insulating substrate, the resistance value of the resistor changes. By applying a high voltage pulse to each heating resistor in the thermal print head, the resistance value of each heating resistor is adjusted to a substantially constant value by pulse trimming adjustment. It is.

0003

[Problem to be Solved by the Invention] However, in this case, applying voltage pulses to a plurality of heat generating resistors at the same time only changes the resistance value of each heat generating resistor at the same time. The difference in resistance between resistors,
In other words, variations cannot be corrected. Therefore, when adjusting the resistance values of each heating resistor by pulse trimming so that they are approximately constant, the resistance value of one heating resistor is adjusted by pulse trimming by applying a voltage pulse, and then the resistance value of the heating resistor of the next heating resistor is adjusted by pulse trimming by applying a voltage pulse. As in applying voltage pulses to the body to perform pulse trimming adjustments,
Since the pulse trimming adjustment to keep the resistance value approximately constant must be performed for each heat generating resistor one by one, it takes a considerable amount of time to perform the pulse trimming adjustment for all the heat generating resistors in the thermal print head. However, there is a problem in that the cost will increase significantly. Moreover, when a voltage pulse is applied to one heating resistor, the voltage pulse also flows to the heating resistor adjacent to the heating resistor, and the resistance value changes. There is also a problem in that the accuracy of adjusting the resistance values to a constant value is low, or in other words, there is a large variation in the resistance values of each heating resistor. The technical object of the present invention is to provide a pulse trimming device that eliminates these problems.

0004

[Means for Solving the Problem] In order to achieve this technical problem, the present invention includes a voltage pulse application circuit that applies a trimming voltage pulse to each of a plurality of heating resistors in a thermal print head. In the pulse trimming device, a short circuit for selectively shorting both ends of the heat generating resistor is provided for each of the plurality of heat generating resistors.

[0005]

[Operation] In this configuration, when a trimming voltage pulse is applied to each of the plural heating resistors in the thermal print head with each short circuit cut off,
The resistance values of each of the heating resistors are simultaneously adjusted by pulse trimming. Therefore, the resistance value of each heating resistor is measured, and if the resistance value does not reach a predetermined value, the trimming voltage pulse is repeatedly applied to each heating resistor. For a heating resistor whose resistance value has been adjusted to a predetermined value, that is, a heating resistor for which pulse trimming adjustment has been completed, short-circuit both ends of the heating resistor for which pulse trimming adjustment has been completed. This causes a short circuit. Then, the trimming voltage pulse is not applied to the heating resistor for which the pulse trimming adjustment has been completed, but the trimming voltage pulse is applied to the other heating resistor for which the pulse trimming adjustment has not been completed. Therefore, without changing the resistance value of the heat generating resistor for which the pulse trimming adjustment has been completed, the pulse trimming adjustment can be made so that the resistance value of the other heat generating resistors approaches a predetermined value, and by repeating this,
It is possible to adjust the resistance values of all the heating resistors in the thermal print head by pulse trimming so that the resistance values are approximately constant.

[0006]

Therefore, according to the present invention, it is possible to perform pulse trimming adjustment for a plurality of heat generating resistors at the same time so that the resistance value of each heat generating resistor in the thermal print head is kept at a substantially constant value. like,
Compared to performing pulse trimming adjustment for each heating resistor one by one, the time required to perform pulse trimming adjustment for all heating resistors in a thermal print head can be definitely shortened and costs can be significantly reduced. be. Moreover, when the resistance values of multiple heat generating resistors are simultaneously adjusted by pulse trimming, the short circuit can reliably prevent the resistance value of the heat generating resistors for which pulse trimming adjustment has already been completed from changing. Variations in the resistance values of the resistors are reduced, and the accuracy of aligning the resistance values of each heating resistor to a constant value can be greatly improved.

[0007]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a first embodiment, and in this figure, reference numeral A indicates an insulating substrate in a thermal print head, and on the surface of this insulating substrate A, a large number of film-type heating resistors Ra, Rb, Rc, Rd, and Re are formed in a line.

Reference numeral 1 indicates a pulse trimming device;
The pulse trimming device 1 includes each heating resistor Ra,
Four probes 2a, 2b detachably contact one end of a plurality of (four in this embodiment) heating resistors Ra, Rb, Rc, and Rd among Rb, Rc, Rd, and Re.
, 2c, 2d, and each probe 2a, 2d.
b, 2c, 2d to voltage pulse application circuits 4a, 4b, 4c, 4d on the positive side of a DC power source 3 such as a battery.
These voltage pulse application circuits 4a, 4 are connected via
In b, 4c, 4d, capacitors 5a, 5b, 5c, 5d, resistors 6a, 6b, 6c, 6 for generating voltage pulses.
d and changeover switches 7a, 7b, 7c, and 7d, respectively.

The pulse trimming device 1 also includes:
Probes 8a, 8b, 8c detachably contact the other ends of the heating resistors Ra, Rb, Rc, and Rd.
, 8d, and each probe 8a, 8b, 8c, 8
d are connected to the negative side of the DC power supply 3 via circuits 10a, 10b, 10c, and 10d each having switches 9a, 9b, 9c, and 9d.

Furthermore, the pulse trimming device 1 includes:
a short-circuiting probe 11a that detachably contacts the other end of each heating resistor Ra, Rb, Rc, and Rd;
11b, 11c, and 11d are provided, and these shorting probes 11a, 11b, 11c, and 11d are connected via shorting circuits 13a, 13b, 13c, and 13d each having selection switches 12a, 12b, 12c, and 12d. , to the one of the probes 2a, 2b, 2c, 2d or the voltage pulse application circuits 4a, 4b, 4c, 4d.

[0011] The reference numeral 14 indicates a resistance value measuring device,
The resistance value measuring device 14 includes one of the probes 2a,
Switches 15a, 15b, 15 from 2b, 2c, 2d
Circuits 16a, 16b, 16c, 16 with c, 15d
d, and each of the other probes 8a, 8b, 8c, 8d
10a, 10b, 10c, and 10d are connected to each other to measure the resistance values of the heat generating resistors Ra, Rb, Rc, and Rd, respectively. When measuring the resistance value of each of the heating resistors Ra, Rb, Rc, and Rd, the resistance value of the first heating resistor Ra is determined by turning ON only the switch 9a and switch 15a for the first heating resistor Ra. The resistance value of the second heating resistor Rb is
Switch 9b and switch 15 for heating resistor Rb
This is done by turning on only b.

In this configuration, the one probe 2a, 2b, 2c, 2d and the other probe 8
a, 8b, 8c, 8d, and each of the shorting probes 1
1a, 11b, 11c, and 11d are brought into contact with each of the heating resistors Ra, Rb, Rc, and Rd, and in this state, each of the voltage pulse application circuits 4a, 4b, 4c, 4
Each changeover switch 7a, 7b, 7c, 7d in d
By connecting them to the resistors 6a, 6b, 6c, and 6d, the respective capacitors 5a, 5b, 5c, and 5d are charged.

Next, each short circuit 13a, 13b, 13
Each switch 12a, 12b, 12c in c, 13d
, 12d is turned off, while each of the other probes 8
Switches 9a, 9b, 9 in a, 8b, 8c, 8d
With c and 9d turned on, each of the changeover switches 7
a, 7b, 7c, 7d, respectively one of the probes 2a,
By switching to the 2b, 2c, and 2d sides, a trimming voltage pulse is applied to each of the heating resistors Ra, Rb, Rc, and Rd.
The resistance values of each of Rb, Rc, and Rd are simultaneously adjusted by pulse trimming.

[0014] Therefore, each of the heating resistors Ra, Rb, R
The resistance value of each of the heating resistors Ra, Rb, and Rd is measured by the resistance value measuring device 14.
When the resistance value of the first heating resistor Ra among Rc and Rd is a predetermined value, the switch 12a in the short circuit 13a for the first heating resistor Ra is turned off.
N, and when the resistance value of the third heating resistor Rc is a predetermined value, the switch 12 in the short circuit 13c for the third heating resistor Rc
For the heat generating resistor that has undergone pulse trimming adjustment, short-circuit both ends of the heat generating resistor that has completed the pulse trimming adjustment, as shown in FIG. The application of voltage pulses is repeated. Then, since the voltage pulse for trimming is not applied to the heating resistor for which the pulse trimming adjustment has been completed as described above, the remaining resistance value of the heating resistor for which the pulse trimming adjustment has been completed remains unchanged. By repeating this process, pulse trimming adjustment can be performed for the other four heat generating resistors Ra, Rb, Rc, R.
This can be done simultaneously for d.

When the pulse trimming adjustment for the four heating resistors Ra, Rb, Rc, and Rd is completed as described above, the entire pulse trimming device 1 is
The process moves to the next four heating resistors on the insulating substrate A of the thermal print head and repeats the above process.

FIG. 2 shows a second embodiment which is a modification of the first embodiment. In this second embodiment, each shorting probe 11a in the first embodiment is
, 11b, 11c, and 11d, and these are used also as the other probes 8a, 8b, 8c, and 8d, and the switches 9a, 9b, 9c, and 9d for the other probes 8a, 8b, 8c, and 8d are replaced. attached circuits 10a, 10b, 10
c, 10d, and one probe 2a, 2b, 2c, 2
d or each of the voltage pulse application circuits 4a, 4b, 4c, 4
switches 12a, 12b, 12c, 12d between
The probes are connected via short circuits 13a, 13b, 13c, and 13d, which have the same effect as described above, and the number of probes can be made smaller than in the first embodiment.

FIG. 3 shows a third embodiment, in which six heating resistors Ra, Rb, Rc,
In the case of simultaneous pulse trimming adjustment of Rd, Re, and Rf, the first heating resistor Ra and the second heating resistor Rb
One probe 2a and one voltage pulse application circuit 4a are connected to both of the third heating resistor Rc and the fourth heating resistor Rc.
one probe 2b and one voltage pulse application circuit 4b for both the fifth heating resistor Re and the sixth heating resistor Rf, and one probe 2c and one voltage pulse application circuit for both the fifth heating resistor Re and the sixth heating resistor Rf. 4c, respectively, while short-circuiting probes 11a, 11b, 11c, 11 are applied to the other ends of the heating resistors Ra, Rb, Rc, Rd, Re, Rf.
d and each of the voltage pulse application circuits 4a, 4b, 4
switches 12a, 12b,
Short circuit 13 with 12c, 12d, 12e, 12f
By connecting them through a, 13b, 13c, 13d, 13e, and 13f, one voltage pulse application circuit can perform pulse trimming adjustment of the two heating resistors. According to this configuration, the number of voltage pulse application circuits can be made smaller than in the first and second embodiments.

FIG. 4 shows a fourth embodiment, which is a modification of the third embodiment.
Each short circuit probe 11a, 1 in the third embodiment
1b, 11c, and 11d, and use these as the other probes 8a, 8b, 8c, and 8d, and switch 9a for each of the other probes 8a, 8b, 8c, and 8d.
, 9b, 9c, 9d.
c, 10d and one of the probes 2a, 2b, 2c or each of the voltage pulse application circuits 4a, 4b, 4c,
Switches 12a, 12b, 12c, 12d, 12e, 1
Short circuit 13a, 13b, 13c, 13d with 2f
, 13e, 13f, and the number of probes can be made smaller than in the case of the third embodiment.

In each of the above embodiments, each short circuit 13a
, 13b, 13c, 13d, 13e, 13f are switches 12a, 12b, 12c, 1.
Although the case where 2d, 12e, and 12f are used is shown, the present invention is not limited to this, and other selection means may be applied.
Furthermore, it goes without saying that one voltage pulse application circuit may be configured to apply voltage pulses to three or more heat generating resistors.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention.

FIG. 3 is a circuit diagram showing a third embodiment of the present invention.

FIG. 4 is a circuit diagram showing a fourth embodiment of the present invention.

[Explanation of symbols]

A Thermal print head insulating substrate Ra, Rb, Rc, Rd, Re, Rf
Heat generating resistor 1
Pulse trimming devices 2a, 2b, 2c, 2d
One probe 3
DC power supply 4a, 4b, 4
c, 4d Voltage pulse application circuits 5a, 5b, 5c, 5d
Capacitors 6a, 6b, 6c, 6d
Resistors 7a, 7b, 7c, 7d
Changeover switch 8a, 8b, 8c, 8d
The other probes 9a, 9b, 9c, 9d
Switches 10a, 10b, 10c, 10d
Circuits 11a, 11b, 11c, 11d
Short circuit probes 12a, 12b, 12c, 12d, 12e, 12f
Short circuit switches 13a, 13b, 13c, 13d, 13e, 13f
short circuit 14
resistance value measuring device

Claims (1)

[Claims] 1. A pulse trimming device comprising a voltage pulse application circuit that applies a trimming voltage pulse to each of a plurality of heat generating resistors in a thermal print head, wherein both ends of the heat generating resistor are selectively A pulse trimming device for a thermal print head, characterized in that a short circuit for shorting is provided for each of the plurality of heating resistors.