JPS62227661A - Thermal head - Google Patents

Abstract

PURPOSE:To prolong the life of each heating element and to improve a printing quality, by providing a resistance element for setting voltage which has the same resistance value as the heating element. CONSTITUTION:Heating elements 21-2N corresponding to the number of dots are embedded in a head substrate 1, and one end of each heating element 21-2N is connected to a common terminal CO of a connector 8 through the intermediary of a flexible member 7, while the other end thereof is connected to a driving circuit 4. Each signal input terminal of the driving circuit 4 corresponding to each heating element 21-2N is connected to each signal terminal 51-5N of the connector 8, while a common terminal of the driving circuit 4 is connected to a terminal CE of the connector 8. Moreover, a resistance element 9 for setting voltage, which is formed of the same material and has the same shape as each heating element, is embedded in the head substrate 1. The opposite ends of this resistance element 9 are connected to terminals CR and CS of the connector 8 through the flexible member 7, respectively. Accordingly, the resistance value of the resistance element 9 is equal to the resistance value of each heating element. When a thermal head thus constructed is connected to a head voltage supply circuit, the resistance element 9 for setting voltage is connected also to the head voltage supply circuit, and the head voltage supply circuit impresses on each heating element 21-2N a head voltage corresponding to an input resistance value.

Description

[Detailed Description of the Invention] [Industrial Application Field] In addition to each heating element for printing dot pattern characters, the present invention also provides a system for maintaining the head voltage applied to each heating element at an optimum value suitable for printing. The present invention relates to a thermal head equipped with a voltage setting resistor.

[Conventional technology]

When using a thermal head used for boom print printing, etc., if the pressure applied to the head is increased above a predetermined voltage value, the amount of heat accumulated in the heating element will increase, affecting printing quality, or in the worst case, It becomes a cause of destruction. Therefore, it is necessary to specify and apply a head voltage according to the resistance of the heating element of each thermal head.

By the way, since the resistance value of the heating element of the thermal head varies during manufacturing, it is divided into several ranks according to each resistance value, and the seventh rank is connected to the connector that connects the thermal head and the head voltage supply circuit. Display in turn. The head voltage supply circuit connected to this connector determines the rank from the above connection and 9 turns, and supplies the most suitable head voltage to the thermal head.

FIG. 6 is a diagram showing a thermal head in which such connections and arm turns are formed. That is, a plate-shaped head substrate 1
N heating elements from the first to the Nth corresponding to the Pt number 2. ~2N is buried, each heating element 2
．． One end of ~2N is commonly connected to the common terminal CO of the connector 3. Each other end of each heating element 21 to 2N is connected to the drive circuit 4, and each heating element 2 of the drive circuit 4
Each signal input terminal corresponding to 1 to 2N is connected to each signal terminal 5I to 5N of the connector 3. Further, a common terminal of the drive circuit 4 is connected to a terminal CF of the connector 3. In addition to the above-mentioned terminals Co, CE, and 5% to 5N, the connector 3 is provided with terminals CJ and C2, and terminals C (7, C
J and C2 are connected on a connector.

Then, depending on the rank of the resistance value of each heating element 21 to 2N at the time of product shipment, the arrangement between each terminal CO, C1, and 02 as shown in F)wfJ7 figures (, ) to (d) is determined! By disconnecting l1t- it is possible to set up four types of connections setter/. When this connector 3t is connected to the connector on the head voltage supply circuit side, the head voltage supply circuit grasps the connection relationship between each terminal CO, CJ, and 02 of the connector 3, and calculates the head voltage value corresponding to the rank. Terminal C
o, applied between CE.

[Problem that the invention seeks to solve]

However, as mentioned above, even with the thermal head in which the connector connected to the head voltage supply circuit is formed in the connection pattern 1 of multiple devices corresponding to the resistance value rank of the heating element, the following problems still exist. . That is, since there is a certain limit on the number of terminals that can be arranged on the connector 3, there is also a certain limit on the connection patterns that can be set, and it is impossible to set the ranks of the resistances of the heating elements in detail. Therefore, even if it happens within the same rank, the resistance difference between the heating element resistance value rut maximum value and the maximum resistance value /J However, there is a large difference in print density when each of these thermal heads is used.If a large difference in print density occurs within the same printer, uniform and good print quality cannot be obtained.

The present invention has been made based on these circumstances, and its purpose is to apply an appropriate head voltage no matter what the resistance value of the heating element is, and to extend the life of each heating element. An object of the present invention is to provide a thermal head that can extend printing time and improve printing quality.

[Means for solving problems]

In the thermal head of the present invention, in addition to a plurality of heating elements whose energization is controlled based on a drive signal input from an external control unit, a head voltage supplied from a head voltage supply circuit to each heating element is suitable for printing. A voltage setting resistor is provided to send the same resistance value as each heating element to the head voltage supply circuit so as to obtain the optimum voltage value.

Further, in another invention, in addition to the above invention, the voltage setting resistor is formed of the same material and the same shape as each heating element.

[For production]

When the thermal head constructed in this manner is connected to the head voltage supply circuit, the voltage setting resistor is also connected to the head voltage supply circuit. As a result, the resistance value of the voltage setting resistor, that is, the resistance value of each heating element is input to the head voltage supply circuit. The head voltage supply circuit then applies a head voltage corresponding to the input resistance value to each heating element of the thermal head.

In yet another invention, in addition to the above effect, the voltage setting resistor is made of the same material and has the same shape as each heating element, so the resistance value of the voltage setting resistor automatically changes to each heating element. O that corresponds to the resistance value of the element [Example] An embodiment of the present invention will be described below with reference to the drawings.
FIG. 2 is an external view of the thermal head. The same parts as in FIG. 6 are given the same reference numerals.

In the thermal head of this embodiment, as shown in FIG. 2, each heating element 2. A flexible part 7 on which signal lines and voltage supply lines are printed and wired is connected to a plate-shaped head substrate 1 in which ~2N'4 is embedded, and the flexible part 7 is further connected to the head [pressure supply circuit]. In FIG. 1, N heating elements 21 to 2N corresponding to the number of dots are embedded in the head substrate 1. ~2N One end wire is connected to the common terminal C of the connector 8 through the flexible part 7.
Connected to O. Each heating element 2. 2N are respectively connected to the drive circuit 4, and each signal input terminal corresponding to each heating element 21 to 2N of the drive circuit 4 is connected to each signal terminal 51 to 5N of the connector 8. Further, the common terminal of the drive circuit 4 is connected to the terminal CE of the connector 8.

Further, a voltage setting resistor 9 formed of the same material and the same shape as each of the heating elements 21 to 2N is embedded in a position adjacent to the Nth heating element 2N on the head substrate 1. Both ends of this voltage setting resistor 9 are connected to each terminal OR of the connector 8 via the flexible part 7.

C8K connected. Therefore, the resistance value RHti of the voltage setting resistor 9 is equal to the resistance value of each heating element 21 to 2N.

FIG. 3 shows a head voltage supply circuit that supplies head voltage vh to the thermal head configured as described above. In the figure, reference numeral 11 denotes a head voltage detection circuit consisting of a series circuit of a resistor R3 and a resistor R4. Connected to one end of 9. The other end of this voltage setting resistor 9 is connected to each heating element 2 through the terminal CR of the connector 8. It is connected to the output terminal (common terminal CO of the connector 8) of the head voltage vh applied to ~2N.

Therefore, the combined resistance formed by the resistance R3゜RH between the output terminal of the head voltage vh and the connection point of the head voltage detection circuit I is FiR3 when the thermal head is not connected; When is R3・RH/(
RJ+RH).

Further, the voltage v3 at the connection point of the head voltage detection circuit 11 is input to the A input terminal of the converter 12. This comparator 12 compares the voltage level of the B input terminal with the voltage level of the A input terminal, and calculates the voltage level of the B input terminal V.
When r is higher than the voltage level V+ at the input terminal, a conductive signal is sent from the output terminal C to the base of the npn transistor Q.

Further, when the DC voltage Vin is input to the VC'll pressure input terminal, VRlii and the constant voltage E is output from the positive output terminal. Output. Reference numeral 13 denotes a reference voltage setting circuit, which sets a reference voltage Vr for adjusting the head voltage vh to be applied to the thermal head 3.
r is sent to the B input terminal of the conzarator 12.

Its configuration consists of a variable resistor RT connected to the VR output terminal of the comparator 12, and a variable resistor RT connected to the VR output terminal of the comparator 12.
Reference numeral 014 is a temperature adjustment circuit consisting of a resistor R5 commonly connected to the B input terminal of 2, and this temperature adjustment circuit J4 is
The reference voltage Vr set by the reference voltage setting circuit 13 is adjusted according to the ambient temperature.
The resistor R7 connected to the B input terminal of No. 2 is connected in series.

Further, the input terminal of the DC voltage Vin is connected to the transistor Q.
The head voltage vh is connected to an output terminal via the collector and emitter of the head voltage vh.

Next, the operation of the thermal head configured as described above is explained in the third section.
This will be explained using the circuit shown in the figure. When the DC voltage Vin is supplied, the variable resistor RTt is first adjusted to set the vJ4Mji reference voltage Vrf to a predetermined value for when the thermal head is not connected. The adjustment reference voltage Vr at this time is as follows, without considering the temperature adjustment circuit 14, and the voltage Vs applied to the input terminal of the comparator 12 is as follows. Therefore, the comparator 12 compares the voltage v1 applied to the A input terminal with the adjustment reference voltage Vr applied to the B input terminal, and until these voltages become the same, the transistor Q
Since the conduction is controlled, the head voltage vh obtained as a result of the conduction control with is Vr=V@. In this way, when vl becomes equal to Vr, transistor Q is turned off and head voltage vh is held constant.

Here, when the connector 8 of the thermal head is connected, the combined resistance between the connection point of the head voltage detection circuit 11 and the output terminal of the head voltage vh is R3·kl/(
R,? +RH). Such a combined resistance value corresponds to the resistance value of each heating element 2° to 2N of each thermal head.Thus, the thermal head 9 has a head voltage vh corresponding to the resistance value of the heating element 21 to 2N. is applied.

Further, the temperature adjustment circuit 14 adjusts the adjustment reference voltage Vr. Composite resistance R of the tab and temperature adjustment circuit 14
01 becomes. Since this combined resistance ROI is connected in parallel to the resistor R5, the combined resistance RO2 is as follows.

Therefore, by substituting this equation (5) into the resistor R5 in equation (1), the adjusted reference voltage Vr can be obtained.

In this embodiment, the voltage setting resistor 9 and the heating elements 21 to 9 of the thermal head are connected via the connector 8.
The resistance value of 2N is identified and a corresponding composite resistance is formed, and the optimum head voltage vht- is determined based on this composite resistance value.
Therefore, by performing the setting operation once using the variable resistor RT, a combined resistance corresponding to the heating element resistance value is formed no matter what heating element resistance value is connected to the thermal head. The optimal head voltage is automatically obtained. Therefore, it is not necessary to adjust the head voltage vh every time the thermal head is replaced, which facilitates handling.

FIG. 4 is a characteristic chart showing the relationship between the resistance value and the power consumption (heat amount) of the heating elements 21 to 2N. The actual f/s force is the characteristic of the thermal head of the embodiment shown in FIG. 1, and the dotted line is the characteristic of the conventional thermal head shown in FIG. As shown in the figure, in the embodiment, even if the resistance of the heating element changes, the power consumption (heat amount) hardly changes. That is, uniform print quality can always be obtained.

Next, we will quantitatively examine this effect. Heat generating elements 2, ~2
When the resistance value of N is divided into conventional ranks, the median value within the rank is Re, the minimum value is Rmin%, the maximum value is R
max □In addition, the minimum value Rmin and the maximum value f
Let the difference between i and max be 2ΔR. In addition, the specified power consumption (specified calorific value) at the median value Re of the resistance value is Wc, and the minimum power consumption corresponding to the minimum value Rmln is Wm1n.
and the maximum power consumption corresponding to the maximum value Rmax is W m
Let it be ax. Then, the ratio of the minimum power consumption and maximum power consumption to the specified power consumption is expressed as Equations (6) and (7).It is understood that the larger the difference in resistance value 2ΔR within the rank, the greater the variation in print density. can.

In the present invention, changes in the resistance values of the heating elements 21 to 2N,
By automatically changing the head voltage vh applied to the heating elements 21 to 2N in response to the change in power consumption, power consumption is maintained at a constant value and the variations shown in equations (6) and (7) are eliminated. .

FIG. 5 is a circuit diagram showing a thermal head according to another embodiment of the present invention. The same parts as in the embodiment of FIG. 1 are given the same reference numerals. In this embodiment, one end of the voltage setting resistor 15 is connected to the terminal C of the connector 8 as in FIG.
The other end is connected to a common terminal Co of the connector 8 in common with each of the heating elements 21 to 2N.

In this way, connect one end of the voltage setting resistor 15 to each heating element 2.
By connecting to the common terminal of I to 2N, the circuit configuration can be simplified, and the number of terminals of the connector 8 can be reduced, or the remaining terminals can be used for other purposes.

[Effects of the Invention] As explained above, according to the present invention, a voltage setting resistor having the same resistance value as each heating element is provided. Therefore, no matter what the resistance value of the heating element is, an appropriate head voltage is always applied to each heating element, and the life of each heating element can be extended and printing quality can be improved.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing a thermal head according to an embodiment of the invention, Fig. 2 is an external view of the embodiment, and Fig. 3 is a Hellard voltage supply circuit for driving the embodiment. A circuit diagram, FIG. 4 is a characteristic diagram for explaining the effects of the same embodiment, FIG. 5 is a circuit diagram showing a thermal head according to another embodiment of the present invention, and FIG. 6 shows a conventional thermal head. The circuit diagram and FIG. 7 are diagrams for explaining the operation of the conventional thermal head. 1...Head board, 21-2N...Heating element, 3,
8... Connector, 7... Flexible part, 4...
Drive circuit, 9.15... Voltage setting resistor, 11...
・Head voltage detection circuit, 12... Condalator, 1
3...Reference voltage setting circuit, J4...Temperature adjustment circuit,
vh...head voltage, co...common terminal. Applicant's agent Patent attorney Takehiko Suzue Figure 5 Cause 6 Figure 7

Claims (3)

[Claims] (1) The plurality of heating elements whose energization is controlled based on the drive signal input from the external control unit and the head voltage supplied from the head voltage supply circuit to each of the heating elements have an optimal voltage value suitable for printing. The thermal head further comprises a voltage setting resistor that sends the same resistance value as each heating element to the head voltage supply circuit. (2) The thermal head according to claim (1), wherein one end of the voltage setting resistor is connected to a common terminal of each of the front heating elements. (3) The plurality of heating elements whose energization is controlled based on the drive signal input from the external control unit and the head voltage supplied from the head voltage supply circuit to each of the heating elements are set to the optimum voltage value suitable for printing. The thermal head further comprises a voltage setting resistor made of the same material and having the same shape as each of the heating elements, which sends the same resistance value as each of the heating elements to the head voltage supply circuit.