JP2002052752A - Method of adjusting resistance value of thermal head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of adjusting a resistance value by pulse trimming capable of surely executing adjustment of a resistance value of a heating resistor of a thermal head. SOLUTION: There is disclosed the method of adjusting the resistance value of the thermal head wherein a trimming voltage applied to the thermal head having multiple heating resistors 5' arranged in a line is gradually raised, thereby adjusting the resistance value of each of the heating resistors 5'. A minimum resistance value Rmin which is the minimum resistance value in the resistance values greater than a target resistance value R01 in all the heating resistors 5' of the thermal head is sought and the amount of raising of the trimming voltage is adjusted based on the magnitude of the minimum resistance value Rmin. Particularly, the adjustment of the resistance values is executed in such a manner that the raising amount of the trimming voltage is switched in three steps corresponding to the magnitude of the minimum resistance value Rmin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to trimming control by pulse trimming for adjusting the resistance of a heating resistor of a thermal head.

[0002]

2. Description of the Related Art Conventionally, a thermal head used in an output device for performing printing using a thermal paper or a thermal ribbon is provided by linearly disposing a resistor as a heating element on an insulating substrate such as a ceramic substrate. A current is applied only to a required section of the resistor to generate heat, and the thermal paper or ribbon reacts to perform printing.

At this time, the resistance value is adjusted in advance so that the heat value does not vary in each section of the resistor, so that the thermal paper or the thermal ribbon reacts uniformly as a whole.

As shown in the schematic diagram of FIG. 2, the thermal head referred to here has a large number of linear common electrode bodies 2 arranged in parallel on an insulating substrate 1 such as a ceramic substrate using a wiring paste in advance. A common part 3 having a comb-like shape provided at predetermined intervals and a linear independent electrode body 4 disposed between the common electrode bodies 2 are printed and fired to form a wiring pattern. A resistor paste produced by mixing ruthenium oxide as a resistance material or silicon dioxide as a sintering agent is linearly printed across the common electrode 2 and the independent electrode 4 and fired. This is a resistor 5.

That is, the common electrode body 2 and the independent electrode body 4 are alternately arranged at predetermined intervals along the direction in which the resistor 5 is provided. The resistor 3 is separated by 3. Among them, a resistor 5 between two adjacent common electrode bodies 2
The portion constitutes one heating resistor 5 ′, and the independent electrode body 4 is disposed substantially at the center of the heating resistor 5 ′. That is, the heating resistor 5 ′ is connected in one direction to form the resistor 5.

The resistance value is adjusted by trimming by applying a pulse voltage so that each of the heating resistors 5 'has a required resistance value. In the resistance value adjustment, the common portion 3 is dropped to GND by a relay, and a trimming current is applied to the heating resistor 5 ′ from the independent electrode body 4 through the relay. 'The resistance value is reduced by destroying the sintered material inside, so that it approaches the target resistance value.

[0007] Switching of energization to the independent electrode body 4 is performed as shown in FIG.
As shown in the schematic diagram, the switching is performed by a switching element 6 of a thermal head control element connected to each independent electrode body 4 by a required wiring, and by switching a relay 7 provided in the switching element 6. I have.

After the trimming current is applied, the resistance value is measured when the temperature of the single resistor 5 decreases. If the resistance value has reached the target resistance value, the resistance value adjustment is terminated. If the resistance value has not reached the target resistance value, the voltage value of the trimming voltage applied from the independent electrode body 4 is appropriately increased. Then, the trimming current is supplied again, and as shown in FIG.
The resistance value is adjusted by repeatedly applying the trimming current while increasing the voltage value of the trimming voltage until the resistance value of the single resistor 5 ′ approaches the target resistance value.

[0009]

However, in the above-described resistance adjustment by trimming, if the resistance does not reach the target resistance, the trimming is simply repeated by appropriately increasing the trimming voltage. Therefore, the resistance may be erroneously trimmed to a value that is significantly lower than the target resistance value, and the variation in the resistance value of each heating resistor after the resistance value adjustment cannot be suppressed. There is a problem that it is difficult to converge within the resistance value standard of the head.

[0010]

In order to solve the above problems, according to the present invention, trimming is performed while sequentially increasing a trimming voltage applied to a thermal head formed by arranging a large number of heating resistors in a line. In the resistance adjustment method of the thermal head for adjusting the resistance value of each heating resistor, the minimum resistance value which is the smallest of the resistance values larger than the target resistance value among all the heating resistors of the thermal head. And to provide a method for adjusting the resistance value of the thermal head that adjusts the amount of increase in the trimming voltage based on the magnitude of the minimum resistance value.

In particular, a first set resistance value which is a resistance value larger than the target resistance value and a second set resistance value which is a resistance value larger than the first set resistance value are set in advance, and the thermal head is set. Among all the heating resistors, a minimum resistance value which is the smallest among the resistance values larger than the target resistance value is found, and when the minimum resistance value is smaller than the first set resistance value, the amount of increase of the trimming voltage is determined. The first voltage rise value is the minimum resistance value of the first voltage rise value.
When the resistance value is equal to or more than the set resistance value and smaller than the second set resistance value, the amount of increase in the trimming voltage is defined as a second voltage increase value. Is set as the third voltage rise value.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a method for adjusting a resistance value of a thermal head according to the present invention, a thermal head is determined based on the resistance value of a heating resistor having a minimum resistance value among heating resistors to be trimmed. To determine the voltage increase value of the trimming voltage to be applied.

Therefore, as a result of the trimming, it is possible to prevent the resistance value of the heating resistor from falling significantly below the target resistance value.

In particular, a first set resistance value that is larger than the target resistance value and a second set resistance value that is larger than the first set resistance value are set in advance, Among the total heating resistors of the head, a minimum resistance value is found among resistance values larger than the target resistance value, and when the minimum resistance value is smaller than the first set resistance value, the amount of increase of the trimming voltage is determined. When the minimum resistance value is equal to or larger than the first set resistance value and smaller than the second set resistance value, the amount of increase in the trimming voltage is set as the second voltage rise value, and the minimum resistance value is set to the second set resistance. If it is not less than the value, the amount of increase in the trimming voltage is set as the third voltage increase value.

By adjusting the resistance value while switching the amount of increase of the trimming voltage in three stages, trimming can be performed in a short time while suppressing the variation in the resistance value of each heating resistor.

Hereinafter, the present invention will be described in detail with reference to examples.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As described in the section of "Prior Art", a thermal head to which the resistance adjusting method according to the present invention is applied is, as shown in a schematic diagram in FIG. On the first electrode 1, a common electrode body 2 and an independent electrode body 4 are printed using a wiring paste, and a wiring pattern is formed by baking the common electrode body 2 and the independent electrode body 4. The body paste is printed in a line shape and fired to form the resistor 5 to form a thermal head. In particular, the portion of the resistor 5 between two adjacent common electrode bodies 2 constitutes one heating resistor 5 '.

Further, one end of all the common electrode bodies 2 is connected to form a common part 3. When the heating resistor 5 ′ is trimmed, the common part 3 is dropped to GND, and the trimming voltage is applied from the independent electrode body 4. Is applied.

That is, the independent electrode body 4 is connected to the switching element 6 of the thermal head control element by a required wiring, and the relay 7 provided in the switching element 6 is switched, so that the heating element is connected to the independent electrode body 4 by the heating element. The application of the trimming voltage to the body 5 'is switched.

The resistance adjusting apparatus for performing the resistance adjusting method according to the present invention includes a voltage applying section for applying a trimming voltage to the thermal head, and a thermal head control element for supplying power to the heating resistor 5 '. An element control unit for controlling the switching element 6, a current measuring unit for measuring a current value to calculate a resistance value of the heating resistor 5 ', and a voltage applying unit for them.
It comprises an element control section and a central control section for controlling the current measurement section.

A data storage area is provided in the central control unit so that the resistance value of each heating resistor 5 'calculated from the current value measured by the current measuring unit can be stored. And
It is configured to find the minimum resistance value _Rmin that is the minimum among the resistance values larger than the preset target resistance value _R01 from among the stored resistance values of the heating resistor 5 ′.

Furthermore, the central control unit provided with a trimming voltage setting region, first sets a target resistance R _{0 1,} a first set resistance value R ₁ is the resistance value greater than the target resistance value R ₀₁ , and setting the second set and the resistance value R ₂ is the resistance value larger than the first set resistance value R _1.

[0023] Then, the first set resistance value R ₁ and the second set resistance value R ₂ which is set at the minimum resistance value R _min is the increased amount of trimming voltage when the first set resistance value R ₁ is smaller than A certain first voltage rise value V ₁ and a second voltage rise value which is the amount of increase in the trimming voltage when the minimum resistance value R _min is greater than or equal to the first set resistance value R _{1 and} smaller than the second set resistance value R _2. and V _2, the minimum resistance R _min is set and the third voltage rise value V ₃ is increased amount of trimming voltage in the case of the second set resistance value R ₂ or more.

Actually, the setting is not performed by using the resistance value, but by using the calculated resistivity R% defined by the following equation.

[0025]

(Equation 1)

[0026] R _min = Calculation resistivity R%, calculated as R ₁ first calculates resistivity R% 1, R _min = calculated resistivity was calculated as R ₂ R
% Is referred to as a second calculated resistivity R% 2.

That is, in the trimming voltage setting area of the central control unit, a target resistance value _R01 , a first calculated resistivity R% 1, and a second calculated resistivity R% 2 are set, and further, R% < a first voltage rise value V ₁ is an increase amount of trimming voltage for R% 1,
R% 1 ≦ R% <the second voltage rise value V ₂ is the amount of increase in the trimming voltage for R% 2, the third voltage rise value is an increase amount of trimming voltage for R% 2 ≦ R% It has set up and V _3.

The calculation of the calculated resistivity R% is performed by the central control unit. By using the calculated resistivity R%, the setting operation of the resistance value adjusting device can be easily performed for the thermal heads having different resistance values for each product type. In this embodiment, R% 1 = 10, R % 2 = 20, V 1 = 10V, V 2 = 25V, V 3 = 50V
And

After the above settings are made, a thermal head for which the resistance value adjustment is performed is set in the resistance value adjustment device. Each independent electrode body 4 of the set thermal head is connected to a voltage application unit of the resistance value adjusting device, so that a current for measuring a resistance value or a voltage for trimming can be applied to the independent electrode body 4.

The switching element 6 of the thermal head control element is connected to the element control section 9 of the resistance adjusting device, and the switching element 6 of the thermal head control element has a relay 7 and a switching transistor for measuring and trimming the resistance value. 8 can be transmitted.

Further, each independent electrode body 4 of the thermal head
And the current measuring section of the resistance value adjusting device, and by measuring the current value of each heating resistor 5 ', the resistance value can be calculated.

Thereafter, first, a current for measuring the resistance value is supplied to the independent electrode body 4 to measure the initial resistance value of each heating resistor 5 ', and the relay 7 and the switching transistor 8 are turned on and off. While measuring the voltage value of each heating resistor 5 ', the resistance value is calculated from the measured voltage value and stored in the data storage area.

A trimming initial voltage value V ₀ is determined from the stored resistance values, and the determined trimming initial voltage value V ₀ is applied to the common unit 3, and each heating resistor is switched while the relay 7 is turned on and off. Trim the body 5 '. A lower voltage value is selected as the trimming initial voltage value V _0, and the resistance value of the heating resistor 5 ′ is set to the target resistance value R ₀₁ by repeating trimming.

After the trimming, after the temperature of each heating resistor 5 ′ is sufficiently lowered, a constant current for resistance measurement is applied to the independent electrode 4 to turn on / off the relay 7 and the switching transistor 8. Each heating resistor while switching off
The voltage value of 5 ′ is measured, the resistance value is calculated from the measured voltage value, and stored in the data storage area.

Then, among the stored resistance values, the minimum resistance value among the resistance values larger than the target resistance value _R01 is found, and the minimum resistance value is set as the minimum resistance value _Rmin .

Next, the calculated resistivity R% calculated from the minimum resistance value _Rmin , the first calculated resistivity R% 1, and the second calculated resistivity R%
The amount of increase of the trimming voltage is determined by comparing the magnitude with% 2, and the trimming voltage for adjusting the resistance value applied to the common unit 3 is determined.
Set V '. That is, if R% <R% 1, V ′ = V ₀ + V ₁
And then, R% 1 ≦ R% <if R% 2 V '= a _{V 0 + V 2, R%} 2 ≦ R%
In this case, V ′ = V ₀ + V ₃ .

Thereafter, the independent electrode body 4 is
The trimming voltage V ′ for resistance adjustment is applied to
While heating is switched on and off, each heating resistor 5 'is trimmed.

After the trimming, after the temperature of each heating resistor 5 ′ has been sufficiently lowered, a constant current for resistance measurement is applied to the independent electrode 4 again to turn on the relay 7 and the switching transistor 8. Measure the voltage value of each heating resistor 5 'while switching off, calculate the resistance value from the measured voltage value, and store it in the data storage area.

Then, among the stored resistance values, a minimum resistance value among the resistance values larger than the target resistance value _R01 is found, and the minimum resistance value is set as a minimum resistance value _Rmin .

Next, the calculated resistivity R% calculated from the minimum resistance value _Rmin , the first calculated resistivity R% 1, and the second calculated resistivity R%
The amount of increase in the trimming voltage is determined by comparing the magnitude with% 2, and a new trimming voltage V ′ for adjusting the resistance value to be applied to the common section 3 is set. That is, if R% <R% 1, V '+ V
₁ is the new trimming voltage for resistance adjustment V ', R% 1 ≦ R%
<If R% 2 V '+ a V ₂ new resistance value adjusting trimming voltage V' and, if R% 2 ≦ R% V ' + a V ₃ new resistance value adjusting trimming voltage V' and, the new The trimming is performed by applying a resistance value adjusting trimming voltage V ′ to the common unit 3.

[0041] By repeating this, it is possible to approximate as shown in FIG. 1, the resistance value of the heat generating resistor 5 'to the target resistance R _01.

The resistance value of the heating resistor 5 'is equal to the target resistance value _R01.
When the temperature falls below the above range, the heating resistor 5 'is not trimmed. That is, when finding the minimum resistance value among the resistance values larger than the target resistance value R ₀₁ from among the resistance values stored in the data storage area, the target resistance value R ₀₁
Detecting the heating resistor 5 'with a smaller resistance value,
The element control section of the resistance value adjusting device is set so that the heating resistor 5 'is not trimmed, and the thermal head control element 6 is not grounded to the independent electrode body 4 connected to the heating resistor 5'. I have to.

Therefore, all the heating resistors of the thermal head
The resistance value of 5 ′ can be adjusted to a resistance value slightly lower than the target resistance value _R01, and variation in the resistance value of each heating resistor 5 ′ can be suppressed. The target resistance value _R01 itself is
It is set to a value that takes that into account.

Further, since the amount of increase in the trimming voltage is determined based on the minimum resistance value _Rmin , it is possible to prevent the trimmed heating resistor 5 'from dropping significantly below the target resistance value _R01. The resistance value can be adjusted within the standard width.

[0045]

According to the present invention, among the total heating resistors of the thermal head, the minimum resistance value that is the smallest among the resistance values larger than the target resistance value is found, and the minimum resistance value is determined. By adjusting the amount of increase in the trimming voltage based on the resistance value, it is possible to prevent the resistance value of the heating resistor from falling significantly below the target resistance value, and to reduce the variation in the resistance value of each heating resistor. It can be suppressed and adjusted within the standard range of the resistance value.

In particular, a first set resistance value which is a resistance value larger than the target resistance value and a second set resistance value which is a resistance value larger than the first set resistance value are set in advance, and the thermal head is set. Among all the heating resistors, a minimum resistance value which is the smallest among the resistance values larger than the target resistance value is found, and when the minimum resistance value is smaller than the first set resistance value, the amount of increase of the trimming voltage is determined. The first voltage rise value is the minimum resistance value of the first voltage rise value.
When the resistance value is equal to or more than the set resistance value and smaller than the second set resistance value, the amount of increase in the trimming voltage is defined as a second voltage increase value. Is used as the third voltage rise value, the resistance value is adjusted while switching the amount of increase of the trimming voltage in three stages, thereby suppressing variation in the resistance value of each heating resistor and performing reliable trimming in a short time. It can be performed.

[Brief description of the drawings]

FIG. 1 is a graph showing an adjustment state of a resistance value in a conventional trimming method.

FIG. 2 is a schematic explanatory view of a thermal head to which a resistance value adjustment is performed according to the present invention.

FIG. 3 is a graph showing a state of adjustment of a resistance value in a conventional trimming method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 Common electrode body 3 Common part 4 Independent electrode body 5 Resistor 5 'Heating resistor 6 Switching element 7 Relay 8 Switching transistor 9 Element control part

Claims (2)

[Claims] 1. A method of performing trimming while sequentially increasing a trimming voltage applied to a thermal head formed by arranging a large number of heating resistors (5 ') in a line, thereby forming each heating resistor.
In the method of adjusting the resistance value of the thermal head (5 '), among the total heating resistors (5') of the thermal head, the minimum among the resistance values larger than the target resistance value ( _R01 ) found a minimum resistance value of becomes (R _min), the minimum resistance value (R _min) of the resistance value adjusting method for a thermal head and adjusts the amount of increase in the trimming voltage based on the size. 2. Trimming is performed while sequentially increasing a trimming voltage applied to a thermal head formed by arranging a large number of heating resistors (5 ') in a line, thereby forming each heating resistor.
In the method of adjusting the resistance value of the thermal head of (5 ′), the first resistance value that is larger than the target resistance value (R ₀₁ ) is determined in advance.
A set resistance value (R ₁ ) and a second set resistance value (R ₂ ) that is a resistance value larger than the first set resistance value (R ₁ ) are set, and the total heating resistor (5 '), The minimum resistance value that is the smallest among the resistance values larger than the target resistance value (R ₀₁ )
(R _min ), and when the minimum resistance value (R _min ) is smaller than the first set resistance value (R ₁ ), the amount of increase in the trimming voltage is set to the first voltage rise value (V ₁ ). When the value (R _min ) is equal to or more than the first set resistance value (R ₁ ) and smaller than the second set resistance value (R ₂ ), the amount of increase of the trimming voltage is set to a second voltage increase value (V ₂ ), minimum resistance value (R _min) is a second set resistance value (R ₂₎ greater than or equal the resistance of the thermal head, characterized by that the amount of increase in the trimming voltage third voltage rise value (V ₃₎ in the case of Adjustment method.