JPH02299865A - Thermal printer control device - Google Patents

Abstract

PURPOSE:To permit simple real-time control by detecting a current amount flowing through a thermal head and controlling the energy given to a thermal element based on the value and allowing for the characteristics of the thermal head. CONSTITUTION:Printing data is transmitted to a transistor array 2 passing through a data bus 6 by CPU 3. Consequently, thermal elements on a thermal head 1 are driven to perform printing. In this case, a signal detected by a resistor for detection 5 provided in the common electrode part of the transistor array 2 is amplified by amplification resistors 8, 9 of an operation amplifier 4. Then the amplified signal is converted from analog mode to digital mode using an AD converter and the converted signal is read in the CPU 3. This value is a function of current value for the current supplied to the thermal head 1, and the current calorific value generated at the thermal head 1 is estimated using the function. After this, a calculation is performed along the characteristics of the thermal head 1 based on the value which is read in the CPU 3, and the energy to be given to the thermal head 1 after the initial energy supply is controlled.

Description

[Detailed description of the invention] [Industrial usage Wjf] The present invention relates to a control device for a thermal printer.

[Prior Art] Conventionally, heat storage in a thermal head is controlled by detecting the temperature with a thermistor mounted on the thermal head or by counting the number of printed dots and applying energy to the heating element according to the number of printed dots. Ta.

[The problem that the invention attempts to solve! ] However, the above-mentioned conventional technology has the following problems.

In other words, mounting a thermistor on the thermal head requires a step to mount the thermistor, and there is a difference between the detected temperature and the actual temperature of the thermal head. Thermistors have a delay in response to temperature changes, and there are variations in the mounting position of the thermistor and in the characteristics of the thermistor itself, resulting in differences in the detected values.

In addition, counting the number of printed dots and performing detailed control in real time places a heavy burden on the software, and if the printing speed of a thermal printer is high, the processing may not be able to be completed in time in some cases. Furthermore, in order to see the cumulative effect of the number of printed dots, a large amount of memory is required to store the number of counted dots.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the thermal printer control device of the present invention includes means for detecting the amount of current flowing through the heating element on the thermal head, and a means for detecting the amount of current flowing through the heating element on the thermal head. It has means for configuring a function that performs calculations according to certain characteristics, and means for varying the energy given to the heating element in accordance with the output signal of the calculation circuit.

[Function] According to the above configuration of the present invention, it is possible to know the amount of current flowing through the thermal head, and from this value it is possible to estimate the amount of heat currently generated on the thermal head. By changing the energy given to the heating element on the thermal head based on the characteristics of the thermal head, more straightforward and real-time control can be achieved.

[Embodiment] FIG. 1 is a schematic diagram of an embodiment of the present invention. C.P.
Print data is sent by U3 to the transistor array 2 through the data bus 6, and printing is performed by driving each heating element on the thermal head 1. At this time, a detection resistor 5 is installed in the common electrode part of the transistor array 2, No. 13 is taken out from there, amplified by an operational amplifier 4 using an amplification resistor 8.9, and AD converted by an AD converter 7. Load it with This value can be considered as a function of the amount of current flowing through the thermal head 1, and the amount of heat currently generated in the thermal head 1 can be estimated from this value.

The CPU 3 performs calculations based on the read values in accordance with the characteristics of the thermal head 1, and controls the next energization energy to be applied to the thermal head 1. Here, the energization pulse width is used as a parameter for changing the energization energy, but the head voltage may be used instead.

Furthermore, the resistance component of the common electrode portion of the transistor array 2 may be used as the detection resistor 5.

FIG. 2 is a diagram showing the characteristics of the feedback control shown in FIG. 1. From this characteristic diagram, the thermal head 1 is made to obtain an appropriate energizing energy for the detected voltage from the A/D converter 7.

For example, if the detected voltage is Vl, the energizing energy E1 is given on this characteristic curve. Further, when a large number of dots are energized and the detected voltage becomes V2, energizing energy E2 is applied. Here, the energizing energy is given by changing the energizing pulse width when the head voltage is constant.
The energization pulse width has a value proportional to the energization energies E1 and E2 shown in FIG.

FIG. 3 is a diagram showing the position from which the current amount signal in FIG. 1 is taken out from the position of the common electrode section of the thermal head 1. This is done by installing a detection resistor 10 on the common electrode part of the thermal head 1, extracting a signal for detecting the amount of current from there, and using an operational amplifier 4 with a differential amplification resistor 11.12.1.
3.14, differential amplification is performed, AD conversion is performed by the AD converter 7, and the data is read by the CPU 3.

Here, the resistance component of the common electrode portion of the thermal head 1 may be used as the detection resistor 10.

FIG. 4 is a diagram in which the heat generation and heat dissipation characteristics of the thermal head 1 are incorporated into the charging and discharging characteristics on the circuit.

The detection signal of the thermal head 1 amplified by the operational amplifier 4 is connected to a charging resistor 17, a discharging resistor 18, and a capacitor 16, which have charging and discharging characteristics that correlate with the heat generation and heat dissipation characteristics of the thermal head 1. By giving this, the temperature characteristics of the thermal head 1 can be simulated on the circuit. Here, the diode 15 prevents the voltage charged in the capacitor 16 from discharging toward the operational amplifier 4.

By reading the voltage charged in the capacitor 16 through the AD converter 7 with the CPU 3, the current thermal head 1 can be determined.
Since the temperature can be estimated, it is possible to control the temperature according to that value.

FIG. 5 is a diagram in which the energy supply to the thermal head 1 is stopped when the estimated temperature of the thermal head 1 reaches a certain value in FIG. 4.

A comparator 21 compares the charged IE voltage of the capacitor 16 and a reference voltage formed by reference resistors 19 and 20. When a large amount of current flows through the thermal head 1 and the charging voltage becomes higher than the reference voltage, the transistor 22 is turned off and the energy supply to the thermal head 1 is stopped. By adjusting this reference voltage, it is possible to stop the energy supply when the thermal head 1 reaches a certain estimated temperature.

By reading the output of the comparator 21 with the CPU 3,
The output of print data to the transistor array 2 may be stopped.

FIG. 6 shows how the AD converter 7 in FIG. 4 is connected to the pulse generator 2.
3.

The pulse generator 23 generates a pulse having characteristics based on the input charging voltage of the capacitor 16.

The pulse width or number of pulses of this output pulse is determined by the CPU3.
By reading the capacitor 1 without using an AD converter,
You can know the charging voltage of 6.

FIG. 7 is a diagram obtained by adding the influence of ambient temperature to FIG. 4.

The thermistor 26 is placed at a position such as on the mechanical body or circuit board of the thermal printer where the internal temperature can be detected. The thermistor 26 is connected to the capacitor 16 along with correction resistors 24 and 25, and has characteristics that correlate with the influence of ambient temperature on the heat generation and heat radiation characteristics of the thermal head 1.

In this way, the voltage input to the AD converter 7 can be adjusted to match the actual thermal head 1, taking into account the ambient temperature.
Since it can be correlated with the heat generation and heat dissipation characteristics of
More effective temperature control becomes possible.

[Effects of the Invention] As described above, according to the present invention, temperature control is performed by detecting the driving current of the thermal head and applying energy corresponding to the detected value to the heating element on the thermal head.
This has the effect of making real-time temperature control easier.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the basic functions of the present invention. FIG. 2 is a characteristic diagram of energy control according to the present invention. FIG. 3 is a circuit diagram showing another signal detection position of the present invention. FIG. 4 is a circuit diagram showing another characteristic of the present invention. FIG. 5 is a circuit diagram showing the energy stopping means of the present invention. FIG. 6 is a circuit diagram showing another function of the present invention. FIG. 7 is a circuit diagram showing another characteristic of the present invention. 1... Thermal head 2... Transistor array 3... CPU 4... Operational amplifier 5.10... Detection resistor 6... Data bus 7... AD converter 8.9... Amplification resistor 11.1.2, 13.14... Differential amplification resistor 15.
...Diode 16...Capacitor 17...Charging resistor 18...Discharging resistor 19.20...Reference resistor 21...Comparator 22...Transistor 23...Pulse generator 24. 25...Correction resistor 26...Thermistor or above Applicant: Seiko Epson Co., Ltd. Representative Patent Attorney Kizobe Suzuki (and 1 other person) Figure 1 0 So1 ゞ2 years old tIC Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] In a thermal printer that performs printing using a thermal head having a plurality of heating elements mounted on a heat-resistant insulating substrate, there is provided a means for detecting the amount of current applied to the heating elements, and a means for calculating the detected amount of current. . A thermal printer control device, comprising means for varying the energy given to the heating element in accordance with the output signal of the arithmetic circuit.