JPH0829598B2 - Head control unit for thermal printer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer, and more particularly, to a control circuit for controlling heat generation of a heat generating element.

[Conventional technology]

Conventionally, various methods have been used in thermal printers in order to prevent deterioration of printing quality due to heat accumulation during continuous use of the thermal head. Among them, there is a method of storing the previous data for each dot and determining the energization time as in Japanese Patent Publication No. Sho 55-48631, and these are generally called the history control method. Among these, there are not a few that control their own energization time based not only on their own driving history but also on driving data of adjacent heat generating elements. Representative examples of these are JP-A-60-131262 and JP-A-58-67477.
Etc. are raised.

[Problems to be solved by the invention]

In these conventional examples, when referring to adjacent data,
Generally, a method of sequentially sending data to the drive IC of the thermal head while processing data by the CPU was common. In such a system, even if an attempt is made to operate the thermal printer at high speed, the processing cannot catch up, which is an obstacle to speeding up the thermal printer.

Also, in the serial type thermal printer, the 32 dot font, while the 24 dot font is becoming popular,
48-dot fonts and higher resolution are also active. In order to make the control circuit of the thermal head into a unit or a chip, it must be possible to flexibly cope with such situations.
It costs uselessly.

An object of the present invention is to eliminate such a conventional problem,
It is an object of the present invention to provide a printing control device for a serial type thermal printer which is high speed and has excellent printing quality.

It is another object of the present invention to provide a head control unit that can be added according to the number of heat generating elements of the thermal head and that can control the energization time in consideration of the influence of adjacent data.

[Means for solving problems]

A head control unit of a thermal printer according to the present invention includes a storage circuit for storing current and past drive data of a heating element, and a first control circuit connected to the storage circuit for increasing or decreasing an energization time according to its own drive data of a heating element. It has at least a gate circuit and a second gate circuit for increasing / decreasing energization time according to drive data of adjacent heat generating elements, and further outputs stored information of the ends of the heat generating elements sequentially arranged to another head control unit. Control terminals adjacent to each other when a plurality of head control units are arranged, having an output terminal for extension and an input terminal for extension which uses the output of the end from another head control unit as an input to the second gate circuit. The special feature is that the drive data at the ends of the unit are exchanged with each other, and the respective energization times can be controlled in correspondence with the own drive data and adjacent data. To.

Further, the head control unit has a built-in head drive circuit.

Further, the adjacent data extension input terminal of the head control unit is configured such that the drive data of the adjacent heat generating element is regarded as “none” when the adjacent head control units are not adjacent to each other. .

〔Example〕

FIG. 1 is a schematic diagram showing the configuration of a print control apparatus using a head control unit of a thermal printer according to the present invention.

1 is a thermal head having a plurality of heating elements 1a, 2 is a head drive circuit for driving this thermal head, 3 is a head control unit which is inserted between the CPU 4 and the thermal head 1 and controls the amount of heat generated by the thermal head, CPU4 Also controls the entire thermal printer. Reference numeral 18 is a pulse generation circuit for supplying a pulse having two or more kinds of pulse widths to the head control unit 3, and has a thermistor 14 for detecting the temperature of the thermal head 1 or its ambient temperature.

The CPU 4 is, for example, an 8-bit CPU with a data bus 16 and
It has an address bus 17, ▲ ▼ signals and the like.

The head control unit 3 is composed of a gate array, for example, and is integrated into one chip like the CPU 4. Hereinafter, the head control unit will be abbreviated as an HCU.

The HCU 3 has a data latch circuit which is a kind of memory circuit and has a data input terminal 5 connected to the data bus 16; an address terminal 6 for inputting the lower 2 bits of the address bus 17;
A chip select terminal (▲ ▼ terminal) 7, which is a kind of unit select terminal that knows the designation of the unit according to predetermined address information from U4, a data latch timing input terminal connected to the ▲ ▼ signal of CPU4, and a heating element It has at least a plurality of energization pulse input terminals 9 for determining energization time to the head and a head drive output terminal 10 for outputting a drive signal to each heat generating element of the thermal head 1.

Reference numeral 11 denotes a decoder for generating a predetermined address code assigned to the HCU 3 from the address information of the CPU 4.

Reference numeral 12 is a ROM that stores a control program for the CPU 4, a character generator, and the like, 13 is a RAM, and 15 is a power supply.

FIG. 2 is a detailed circuit diagram showing an embodiment of the head control unit HCU3, and the same components as those in FIG. 1 are designated by the same reference numerals.

The data input terminal 5 can input 8-bit data of D _{0 to} D ₇ in parallel.

21 to 29 shows a data latch circuit to hold 8-bit data, respectively, 21 to 23 of the head drive signals H ₀ to H ₇
24 to 26 hold the data of H _{3 to} H ₁₅ , 27 to 2
9 is latching data of H ₁₆ to H _23, respectively.

The head drive output has, for example, 24 output terminals H _{0 to} H ₂₃ for driving a 24-dot thermal head.

Reference numeral 31 denotes a latch circuit group for holding one dot row of the current head data, 32 denotes one dot row of the previous data of one time before, and 33 denotes one dot row of the past data of two times before. Are shown in FIG.

Reference numeral 30 is an address decoder for storing head data by dividing it by 8 bits according to the address information of the data output of the CPU, and as an example, a data latch circuit according to the lower 2 bits A ₀ , A ₁ of the address data.
21, 24, 27 can be selected. Reference numeral 34 is a gate circuit for converting the pulse input from the energizing pulse input terminal into an energizing section signal. This is unnecessary when the output signal of the pulse generation circuit 18 is originally output as the energization section signal.

At the same time as the head drive data is output from the CPU 4 to the data bus, the ▲ ▼ signal is output.
The terminal is accessed, and data is transferred to each of the data latch circuits 21, 24 and 27 by the information of the lower two bits of the address bus. Then, the already stored data is shifted rightward in FIG. 2, for example, the data of the data latch circuit 21 is shifted to the data latch circuit 22 and sequentially stored as past data.

Although it is possible to access up to four data latch circuits with the information of the lower 2 bits, the number of address input terminals and the number of data latch circuits may be increased according to the number of heat generating elements.

When a predetermined pulse is input to the electric pulse input terminal 9 after the data is set, the heat generating element is energized.

Reference numerals 35 and 36 denote gate circuits G ₀ and G ₁ that combine the latched data and the energization interval signal to generate a heat generation control signal that controls the heat generation amount according to the past history, and each is a _first circuit.
The gate circuit 37 and the second gate circuit 38 of FIG. The first gate circuit 37 increases / decreases the energization time according to the driving result of itself, and the second gate circuit 38 increases / decreases the energization time according to the driving result of the adjacent heat generating element.
G ₁ is a gate circuit excluding both ends of the heat generating element that are sequentially arranged, and G ₀ is a gate circuit of both ends. The second gate circuit 38 in G ₀ includes an AND circuit 38a, a NOR circuit 38b, and an AND circuit 38c.
It is composed of The AND circuit 38a does not check whether or not the adjacent stored information are simultaneously driven.
If only one HCU3 is used, it is essentially unnecessary. However, when the number of heating elements is increased to 32 dots and 48 dots, in order to arrange two or more head control units side by side, the adjacent drive results must be input from another head control unit.

In order to solve the above-mentioned problem, the present invention provides the additional input / output terminals 41 and 42. Since the input terminal 42 is connected to the input of the second gate circuit, referring to the adjacent drive data of the heat generating element at the end of the head control unit,
Used to control energization time.

When a head control unit is added in accordance with the number of heat generating elements of the thermal head, the output terminal 41 of the stored data at the end is provided with the input terminal 42 of the adjacent head control unit.
, And the adjacent output terminal 41 is similarly connected to the input terminal 42 thereof, thereby exchanging data at the end portions with each other and the heat generating elements at the respective end portions provided side by side are connected to one head control unit. It will be controlled in the same manner as the inner heating element.

Reference numeral 42a is a pull-down resistor of the input terminal 42, and is configured so that the drive information when it is not added is regarded as “none”. As a result, when the additional heat generating element is added, there is always no adjacent drive data, so that the drive energy is usually higher than other drive energy corresponding to the print pattern.

The operation of the gate circuit in the latter stage is described as NOR
The circuit 38b compares the current data with the past drive history, and when driven in the past, the AND circuit 38c functions to reduce a predetermined energization section.

FIG. 3 shows the relationship between the input signal of the energizing pulse input terminal 9 and the energizing section signal.

T _{0 to} T ₃ are input waveforms of the energizing pulse input terminal 9 and TW
_{0 ~TW 3} shows the energization section signal, respectively. Each of t _{0 to} t ₃ indicates the pulse width of the energization section signal.

FIG. 4 is an explanatory diagram showing a method of energizing the thermal head by the head control unit of the present invention.

Reference numerals 54, 55 and 56 indicate the data in the latch circuits 21, 22 and 23, respectively, 54 is the present data, 55 is the previous data, and 56 is the two previous data. 51, 52 and 53 have shown the output waveforms of the head driving signal, the of the H ₀ terminal 51, 52 of the H ₂ terminal, 53 denotes an H ₅ terminals.

56 is the data at the start of printing, and in the first energization, all energization sections are added to the heat generating elements. When energized the dot in the previous timing is reduced is t ₃ period indicated by hatched portion, as shown by the output waveform 52 energized the dot in the two previous timing is t _{When two} sections are reduced and three dots are continuously energized, the section of t ₂ + t ₃ is reduced. Furthermore, when both dots are energized in the vertical direction at the timing one before, the t ₁ section is reduced as shown in the output waveform 53. The energization time is determined by the combination of the above cases. With this method, 2 × 2
The configuration is such that it has only to have four energization section signals for eight past cases of × 2 = 8.

The gate circuits G ₀ and G _{1 in} FIG. 2 produce this output signal.

If a small current such as 50 mA or less is sufficient for the current flowing to the heat generating elements of the thermal head, the head drive circuit can be formed in the same package when forming the HCU3 by the gate array.

FIG. 5 is a schematic diagram showing an embodiment of the pulse generating circuit.

An oscillation circuit 60 includes the thermistor 14 described above.
Resistors 61, 62, 66, capacitor 63, transistor 64, inverter 68, zener diode 65, voltage comparator
It is formed by 67 and is connected to the power supply Vc. This output waveform
The cycle S ₀ of 69 has the characteristic that it senses the temperature of the thermal head and is small when the temperature is high and is large when the temperature is low. Reference numeral 70 indicates a frequency dividing circuit, and 71 indicates a gate circuit. The gate circuit 71 outputs each pulse of T _{0 to} T ₃ . As an example, T ₃ = S ₀ × 6, T ₂ = S ₀ × 10, T ₁ = S ₀ × 1
2, the time T ₀ = S ₀ × 22 is formed. By determining the energization time to the thermal head using such a pulse generation circuit, the optimum applied energy is always given to the thermal head, and the applied energy reduced by the past drive history is always correlated with the total energization time at that time. It becomes possible to improve the print quality.

The frequency dividing circuit 70 and the gate circuit 71 in the pulse generating circuit can be integrated into a gate array, and can be further simplified by using a programmable timer.

In the present embodiment, the temperature of the thermal head is fed back during the energization time, but it is also possible to incorporate it in the head power supply and supply the pulse signal from the CPU without using the pulse generation circuit.

FIG. 6 is a schematic diagram of a word processor equipped with a thermal printer using the head control unit of the present invention.
The same parts as those in FIG. 1 are designated by the same reference numerals.

3a is the first HCU, 3b is the second HCU, and the additional terminal 4
By exchanging data mutually using 1 and 42, the heat generation elements 1b and 1c at the ends of the connection portions can perform heat generation control exactly the same as other heat generation elements. Both 11a and 11b are address decoders, but each can write data separately by changing the address information to be responded. A keyboard 19 is for inputting document information such as kanji and graphic information.

In this way, it is possible to easily add more head control units according to the number of heat generating elements of the thermal head.

〔The invention's effect〕

According to the present invention, when the drive energy is controlled by referring to the drive data of the adjacent dots of the heat generating element, the control unit, for example, even if a head control circuit which is an IC chip is added, the control unit is straddled. Since the drive data can be exchanged with, the IC that had to be designed according to the number of heat generating elements in the past can be expanded from the beginning to reduce the development cost and development period. It was possible to eliminate waste and greatly contribute to the cost reduction of the thermal head.

In addition, because the head control unit also provides a configuration that allows the drive data of adjacent dots to be referred to, even if this type of head drive IC is mounted on a thermal print head, adjacent dots can be generated regardless of the number of heating elements. Since the applied energy can be controlled on the basis of the driving data of (1), even if the number of heat generating elements is large, the printing quality can be significantly improved, and the printing speed or the durability can be greatly improved.

Further, since it can be expanded and can be realized with high printing quality, it can be widely applied not only to serial printers but also to parallel printers and the like.

Furthermore, the range of adjacent dots can be easily expanded not only on both sides by the same method, but further improvement in printing quality can be expected.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the configuration of a print control device using a head control unit of a summary printer of the present invention. FIG. 2 is a circuit diagram showing an embodiment of a head control unit according to the present invention. FIG. 3 is an explanatory diagram showing the relationship between the energizing pulse input signal and the energizing section signal of the head control unit according to the present invention. FIG. 4 is an explanatory diagram showing a method of energizing a thermal head by the head control unit of the present invention. FIG. 5 is a schematic diagram of an embodiment of a pulse generation circuit used in the head control unit of the present invention. FIG. 6 is a schematic diagram of a word processor using the head control unit of the present invention 1. The thermal head 3 The head control unit 4 The CPU 16 The pulse generation circuits 41, 42 The expansion input / output terminals

Claims (3)

[Claims] 1. A head control unit of a thermal printer having a storage circuit for storing a drive history of a heat generating element and a gate circuit configured to control the energization time of each of the heat generating elements based on the storage result. A memory circuit for storing current and past drive data of the heat generating element, a first gate circuit connected to the memory circuit for increasing / decreasing energization time according to its own drive data of the heat generating element, and an adjacent heat generating element A second gate circuit for increasing / decreasing the energization time according to the drive data, and an additional output terminal for outputting the memory information of the ends of the heat generating elements sequentially arranged to another head control unit, The head control unit has a plurality of additional input terminals that use the output of the end portion from another head control unit as an input to the second gate circuit. The head control unit of the thermal printer is characterized in that the drive data of the end portions of the adjacent control units are exchanged with each other when they are turned on, and each energization time can be controlled corresponding to the adjacent data together with their own drive data. . 2. A head control unit for a thermal printer according to claim 1, wherein a head drive circuit is built in the head control unit. 3. The adjacent data extension input terminal of the head control unit is configured so that the drive data of the adjacent heat generating element is regarded as “none” when the adjacent head control units are not adjacent to each other. The head control unit of the thermal printer according to claim 1, wherein