JPH07108572B2 - Printing control device for thermal printer - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer, and sometimes to a method for driving a heat generating element thereof.

[Conventional technology]

Conventionally, in thermal printers, in order to prevent deterioration of print quality due to heat accumulation during continuous use of the thermal head,
Various methods have been used. 55
For example, the method of storing the previous data for each dot to determine the energization time, such as −48631, and the method of changing the energization time according to the driving cycle, as in Japanese Patent Publication No. 57-18507, are used. These are generally called history control methods. Further, there is also proposed a preheating control as in the case of Shokai 61-158476, in which preheating is performed just before the next driving data is present and reduction is combined with past driving history.

[Problems to be solved by the invention]

In these conventional examples, generally, a method of sequentially transmitting data to a drive IC of a thermal head while performing data processing by a 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.

An object of the present invention is to eliminate such conventional problems and to provide a print control device for a thermal printer which is high-speed and has excellent print quality.

Another object of the present invention is to provide a print control device for a thermal printer, which optimally controls heat generation according to the type of printing paper or the type of ink ribbon.

[Means for solving problems]

A print control device for a thermal printer according to the present invention includes an energization width control means for determining a total energization time serving as a reference of an energization time for a heat generating element of a thermal head, and a self drive of an arbitrary heat generating element stored in a storage circuit. The control means for reducing the ON time when the next drive data is ON according to the result and the drive result of the adjacent heat generating element, and the extent to which dots are not formed when the next drive data is OFF due to both drive results. Control means for applying a preheating pulse of, and the type of the printing object involving the thermal head, or
A control unit that has a detection unit that detects the type of the transfer ink ribbon, and that can change the ratio of reducing the on-time to the total energization time or the ratio of the preheating pulse or the presence or absence of the preheating pulse according to the detection result of the detection unit. A print control device for a thermal printer, comprising:

〔Example〕

FIG. 1 is a schematic diagram showing the configuration of a print control device for a thermal printer according to the present invention.

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

The CPU4 is, for example, an 8-bit CPU, and has a data bus 16, an address bus 17, a ▲ ▼ signal, and a pulse generation circuit control terminal.
It has 4a, 4b, 4c and the like.

Reference numeral 19 denotes a switch which is a kind of detection means for detecting the type of the ink ribbon cassette 20 and is a micro switch installed on a carriage or the like in which the ribbon cassette of the printer body is mounted. The presence or absence of the ribbon cassette, the type of the ink ribbon, etc. are detected by a hole (not shown) installed in the ink ribbon cassette 20.

The head heat generation control circuit unit 3 is composed of a gate array, for example, and is integrated into one chip like the CPU 4.
Hereinafter, the head heat generation control circuit 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, a P-address input terminal 6 for inputting the lower 2 bits of the address bus 17, and predetermined address information from the CPU 4. According to the above, the chip select terminal (▲ ▼ terminal) 7, which is a kind of unit select unit for knowing the designation of the unit, the data latch timing input terminal connected to the ▲ ▼ signal of the CPU 4, and the energizing time to the heat generating element are determined. At least a plurality of energization pulse input terminals 9 and a head drive output terminal 10 for outputting a drive signal to each heat generating element of the thermal head 1 are provided.

Reference numeral 11 is a decoder for creating 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 heat generation control circuit unit HCU3, and the same parts 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.

Reference numerals 21 to 29 denote data latch circuits holding 8-bit data, 21 to 23 hold head driving signal data H _{0 to} H ₇ , and 24 to 26 data H _{8 to} H ₁₅ . 27 ~ 29
It is latched 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 is a latch circuit group that holds one dot row of the next head data, 32 is one dot row of the past data one time before, and 33 is one dot row of the past data two times before. 2 shows a latch circuit group that holds the respective.

Reference numeral 30 is an address decoder for storing the head data by dividing it into 8-bit data according to the address information of the CPU data output.
Data latch circuit 2 depending on the bit information of bits A ₀ and A _1.
1, 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 16 is originally output as the energization section signal.

At the same time when the head drive data is output from the CPU4 to the data bus, the ▲ ▼ signal is output, the ▲ ▼ terminal is accessed by the address information previously defined on the memory map of the CPU4, and the lower 2 bits of the address bus information is used. Data is transferred to each of the data latch circuits 21, 24 and 27. Then the data already stored is
In the right direction of FIG. 2, for example, the data of the data latch circuit 21 is shifted to the data latch circuit 22 and sequentially held 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 energization pulse input terminal 9 after the data is set, the heating element is energized.

Reference numeral 35 is a gate circuit that combines the latched data and the energization interval signal to produce a heat generation control signal that controls the heat generation amount according to the past history.

The gates 37a, b, c, d, and e constitute control means for reducing a predetermined time from the total energization time when the next data is on according to the self-driving result of any heating element, and 38a, b, c. According to the driving result of the adjacent heat generating element, the control means is similarly configured to reduce the predetermined time when the next driving data is ON, and the driving result does not reduce the next energization time by 36a, b, c. Then, the control means is configured to preheat the heat generating element to the extent that dots are not formed when the next drive data is off.

Reference numeral 40 is an OR gate, which integrates various energization sections based on the history result to create an energization time to the heat generating element. H ₀ ~ H ₂₃
Shows a head drive output terminal having an output terminal number of 24 bits as an example.

Reference numeral 41 is an AND gate for controlling the presence or absence of preheating control, and preheating is controlled by a preheating control terminal 42. This is because the printing characteristics of thermal paper and thermal transfer ink ribbon are generally different, so that it is necessary to adjust to the best print quality depending on the presence or absence of preheating. Preheating is not necessary and the ink ribbon requires preheating in order to improve the reproducibility of the edge portion of the dot at the print start portion.

43 is a preheat amount control terminal for varying the ratio of the total energization time of the preheating, t ₁ period or t ₂ by the level of the terminal
Preheating of the section is selected via the gate circuits 43a, 43b, 43c, 43d. This is to control the dot reproducibility optimally by changing the temperature for warming the head depending on whether the ink ribbon is wax type or lysine type. Generally, in lysine type, the higher the head temperature, the better the wax temperature. In the system, it is possible to achieve beautiful dot reproducibility with high gloss if it is not too high. Furthermore, in order to improve the color reproducibility of the color ink ribbons when they are repeatedly applied, the finish is better if the head temperature is not set too high. The preheat amount control terminal is used in such a case.

Reference numeral 44 is an expansion terminal that allows the HCU3 to be expanded when the heating element becomes 32 bits or 48 bits, and exchanges the stored information of the latch circuit corresponding to the dot at the end of one unit.

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 the input waveforms of the energizing pulse input terminal 9, TW ₀ to
TW ₃ shows the energization section signals 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 of the print control apparatus according to the present invention.

Reference numerals 51, 52, and 53 respectively represent data in the memory circuits 31, 32, and 33, in which 1 represents ON and 0 represents OFF, and 51 represents the next 52
Indicates the data of the previous time, and 53 indicates the data of the second time. 54 to 58 show the output waveform of the head drive signal,
54 is the H ₀ terminal, 55 is the H ₂ terminal, 56 is the H ₅ terminal, and 57 is
58 of the H ₇ terminal shows an output waveform of the H ₁₀ terminal.

In FIG. 4, 53 is shown as data at the start of printing. Energization The dots that are energized for the first time are energized in all energization periods. The entire energization time is applied, and the dots that are energized are t ₁
The section is added as a preheating palace. In this preheating pulse, the heat-sensitive paper is colored only by raising the substrate temperature of the thermal head, or the energization time is set to a level at which the ink of the ink ribbon is not melted to form dots, and in the present embodiment, the adjacent heat generation is performed. The same energization period as the time to be reduced according to the driving result of the element is used. The preheating pulse time is not limited to this and may be set separately.

The method proposed in JP-A-61-158476 is a method of preheating only when the energization is scheduled for the next time, but in this method there is insufficient preheating in the heating element that has a sufficient down time, The temperature of the entire substrate of the thermal head may be overcooled. Therefore, in the present embodiment, even for heat generating elements that are not on-data, the effect of keeping the temperature of the heat generating elements arranged in a row in the thermal head uniform by always preheating in synchronization with the energization timing is provided. It is possible to eliminate uneven density.

Further, by using the print control device according to the present invention, several tens of timings of this preheating pulse are added before the start of printing to raise the substrate temperature of the thermal head so that the print density at the right end and the left end of one line is completely eliminated in the serial printer. Can be matched to. At this time, all the drive data may be set to 0, which is off data, and the data may be transmitted at the same timing as printing.

Next, the case where there is past drive data will be described. If the energization data of its own heat generating element is on at the timing one before, it is indicated by the shaded area, and the predetermined time in the t ₃ section is reduced (shown in the output waveform 54), and there is drive data at the timing two before. And the predetermined time in the t ₂ section is reduced (shown in the output waveform 57), and when this is continuous, the t ₃ + t ₂ section is reduced (shown in the output waveform 54). When the energization data of both heat generating elements adjacent to an arbitrary heat generating element is ON in the previous drive result, the t ₁ section is reduced (shown in output waveform 56). When all the data to be compared to be reduced are ON data and the current data of its own is ON, energization is turned ON only in the t ₀ section. Conversely, if some or all of the data being compared is the result of not reducing the current on-time and the current data is off, the preheat pulse t ₁
Is given, and conversely, when some or all of the driving results result in reducing the current pulse width, the preheating pulse is not added (shown in output waveform 55). That is, if it is determined that an arbitrary heat generating element is locally heated and there is preheating, no preheating is performed. According to the experiment, in the past two driving results, when even one of the data to be compared is the result that the current on-time should be reduced, if the current data is off, it is not preheated, and conversely all If the data is the result of not reducing the current on-time and the current data is off, the method of preheating was most effective. Gate circuit of FIG.
35 is based on this.

The energization time is determined by a combination of past drive histories.
This method has a configuration in which it is sufficient to have four energization section signals for eight past cases of 2 × 2 × 2 = 8.

FIG. 5 is an explanatory diagram showing a comparison between a case where a preheating pulse is applied at the start of printing and a conventional example, showing changes in the surface temperature of the heating element and the substrate temperature of the thermal head. FIG. FIG. 5 (b) shows a conventional example when a preheating pulse is applied. 81 and 83 indicate drive pulses, 8
The dotted lines at 5 and 86 indicate the substrate temperature, and 82 and 84 indicate the preheat pulse.

In the conventional example, the substrate temperature rises at the same time as the start of printing and maintains a substantially predetermined temperature in relation to heat dissipation, but when printing is interrupted, the substrate temperature 85 rapidly cools.

However, when the printing control apparatus according to the present embodiment is used, first, the substrate temperature 86 is raised by the preheating pulse 82 and the driving pulse is
After adding 83, it is possible to keep the substrate temperature 86 at a predetermined level because the preheating pulse 84 is continuously applied even during a pause in one line, and to reduce the print density after printing is interrupted in one line. It is possible to always print at a predetermined density without any trouble.

FIG. 6 is a kind of pulse generation circuit of the energization width control means for determining the total energization time which is the reference of the energization time of the heat generating element of the printing control apparatus according to the present invention.

In this embodiment, the pulse generation circuit is not limited to the total energization time,
The predetermined time to be reduced and the preheating time are also determined according to the driving history.

60 is an oscillation circuit including the thermistor 14 described above, and resistors 61, 62, 66, a capacitor 63, transistors 64, 69,
It is composed of an inverter 70, zener diodes 65 and 67, and a voltage comparator 68, and is connected to a power supply Vc. The cycle S ₀ of the waveform 71 in this output has a 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. The transistor 69 is for varying the cycle of the oscillation circuit, and is controlled by the pulse width switching terminal 74 used when switching the energizing time to the head according to the change of the printing speed of the thermal printer and the type of recording paper. Reference numeral 72 is a frequency dividing circuit, and 73 is a gate circuit. The gate circuit 73 outputs each pulse of T _{0 to} T ₃ . As an example, T ₃ = S ₀ × 6, T ₂ = S ₀ × 10 or = S ₀ × 8, T ₁ = S ₀ × 12,
A time of T ₀ = S ₀ × 22 is formed.

That is, it is possible to always obtain an output waveform having a pulse width obtained by multiplying the total energization time by each substantially constant ratio. By determining the energization time of the thermal head using such a pulse generation circuit, the applied energy that is optimal for the ambient temperature of the thermal head and the temperature of the heat sink is always applied to the heat generating element, and the applied energy is reduced by the past drive history. The energy also always correlates with the total energization time at that time, and the preheating energy can also match the thermal head temperature at that time.
Even when the total energization time is switched by inputting the pulse width switching terminal, it can be used without changing the ratio. Reference numeral 75 is a variable reduction ratio terminal for varying the ratio of the energization time to be reduced during history control, and is a reduction ratio variable terminal for selecting the optimal control for the difference in ink ribbon characteristics. Reference numeral 76 denotes a reset terminal of the frequency dividing circuit 72, which is a synchronous input terminal that is reset at each energization cycle and drives the heat generating element in synchronization with the energization timing.

The pulse width switching terminal 74, the reduction ratio variable terminal 75, and the synchronous input terminal 76 are controlled by the CPU 4 and are connected to the pulse generation circuit control terminals 4a, 4b, 4c of FIG. 1, respectively, which are suitable for printing paper and ink ribbon. It is set and used in the condition.

〔The invention's effect〕

According to the present invention, data processing by past driving history
Since it is not necessary to do it in U, high-speed processing of the CPU is possible,
It is possible to increase the printing speed of the thermal printer.

Also, the head heat generation control circuit unit is formed by a gate array, etc., and it is integrated into one chip. It is very easy because it is allocated to the memory map of the CPU and directly connected to the data bus and address bus to write the data directly from the CPU. With this simple structure, complicated processing is possible.

Furthermore, by teaching the preheating pulse during the printing cycle, the temperature of the thermal head can be maintained almost constant, the thermal head can always be driven under optimal printing conditions, and printing quality can be improved. Since it is not necessary to apply the applied energy, it is possible to suppress the peak temperature and increase the durability of the thermal head.

In recent years, types of recording media such as paper and ink ribbon have increased, and it is necessary to optimally control heat generation of the thermal head for these types. The present invention is extremely convenient to cope with such diversification.

INDUSTRIAL APPLICABILITY The present invention can be widely applied to not only those using a serial type thermal head but also those using a line type thermal head, and the effect is remarkable.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the configuration of a print control device for a thermal printer of the present invention. FIG. 2 is a circuit diagram showing an embodiment of the head heat generation control circuit unit of 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 heat generation control circuit unit of the present invention. FIG. 4 is an explanatory diagram showing the method of energizing the thermal head of the print control device according to the present invention. FIG. 5 is an explanatory diagram showing changes in the surface temperature of the heat generating element and the substrate temperature of the thermal head. FIG. 6 is a circuit diagram of an example of a kind of pulse generation circuit of the energization width control means of the print control device according to the present invention. 1 ... Thermal head 3 ... Head heat generation control circuit unit 4 ... CPU 18 ... Energization width control means

Claims (1)

[Claims] 1. A thermal printer for printing using a thermal head having a plurality of heat generating elements, comprising a memory circuit for storing at least the past two driving data of the thermal head, and the stored driving data. In a print control device of a thermal printer for determining an energization time to the heat generating element based on the result, an energization width control means for determining a total energization time which is a reference of the energization time to the heat generating element, and a storage in the storage circuit. Control means for reducing the on-time when the next drive data is on, depending on the self-drive result of the arbitrary heat-generating element and the drive result of the adjacent heat-generating element,
A control unit that applies a preheating pulse to the extent that dots are not formed when the next drive data is off based on the drive results of both of them, and the type of the print target that involves the thermal head or the type of the ink ribbon for transfer is detected. And a control unit capable of changing the ratio of reducing the ON time to the total energization time or the ratio of the preheating pulse or the presence or absence of the preheating pulse according to the detection result of the detection unit. Print control device.