JP2684800B2 - Thermal recording device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal recording apparatus that maintains recording density by performing recording pulse control according to the temperature and line speed of a thermal line head.

(Prior Art) In a thermal recording apparatus, the width of a strobe pulse (also referred to as a recording pulse in this specification) input to a logical product means for giving an output to a heating element is changed according to the temperature and line speed of a thermal line head. There is.

In this case, the strobe pulse width is set to be an ideal pulse width (also referred to as an ideal pulse in this specification) in which the density of the recording result becomes a specified density depending on the temperature and line speed of the thermal line head.

In addition, when the strobe pulse width is insufficient due to the line speed, a preheating method of preheating by applying a pulse of a predetermined width to the heating element in advance may be adopted.

(Problems to be Solved by the Invention) However, in the conventional thermal recording apparatus as described above, when the thermal line head is at a high temperature and the line speed is high temperature / high speed, and the thermal line head is at a low temperature, and The strobe pulse width is significantly different when the line speed is low and when the temperature is low.

The relationship between the temperature of the thermal line head and the ideal pulse width is as shown in FIG. 8, for example. When the temperature is high and the speed is high, the thermal line head has a high temperature, so that the size of the recording result of one recording dot is large and the density is high even if the strobe pulse width is short. At low temperature and low speed, the temperature of the thermal line head is low, and the strobe pulse width is long because the cycle period is long because the strobe pulse is not applied due to the low speed. Is limited, the strobe pulse width is insufficient, the size of the recording result of one recording dot is small, and a blank portion occurs between the dots when viewed in the line feed direction.

Explaining this concretely, assuming that the heat sensitive element is divided into, for example, four blocks and strobe pulses are given, and the maximum line speed is 10 msec / line,
The maximum pulse width that can be given to one block is 2.5 msec.
2.4m above the line indicated by the broken line in the figure
Strobe pulse width of sec or more is required. However, since the longest strobe pulse width is set to 2.4 msec, the recording energy applied to the heating element becomes insufficient in the portion beyond the line shown by the broken line in FIG. When the recording energy is insufficient, the dot size of the recording result is small as described above, and when viewed in the line feed direction, the recording is as shown by the hatched portion in FIG. 7 (b),
The recording looks like white spaces between dots.

If the energy is not insufficient, that is, if the strobe pulse width less than the broken line in FIG. 8 is sufficient, the recording energy is large, and the dot size of the recording result is large, as seen in the line feed direction. As shown in a), the recording does not appear as white dots between dots.

That is, when the maximum value of the strobe pulse width is set with reference to a predetermined case such as low temperature / high speed, when the low temperature / low speed is less than the predetermined value, the strobe pulse width becomes insufficient and the density becomes insufficient, resulting in the recording density. However, there was a problem that the concentration did not reach the specified concentration.

(Means for Solving the Problem) A thermal recording apparatus of the present invention includes a thermal line head including a heating element that is heated by being energized by an output from a logical product unit that logically calculates recording data and a strobe pulse, Thermal recording provided with strobe pulse control means for controlling the pulse width of the strobe pulse to a predetermined value or less in accordance with the temperature of the thermal line head or the vicinity thereof and changing the cycle of the strobe pulse according to the line speed. The apparatus is provided with a discriminating means for discriminating the recording energy of the heating element from the line speed and the temperature, and when the discriminating means judges that the recording energy is insufficient, after recording one line, the same line is continuously reproduced again. Application of recording data and strobe pulse for recording to the AND means And a re-recording control unit for controlling the re-recording.

Insufficient recording energy may be determined by the strobe pulse width being a predetermined value.

(Operation) In the thermal recording apparatus of the present invention configured as described above, when it is determined by the determination means that the recording energy is insufficient from the line speed and the temperature of the thermal line head or the temperature in the vicinity thereof, the re-recording means continuously operates on the same line. It is recorded again. Therefore, the recording energy is added again before the recording energy at the first recording disappears, and the same result as the recording energy is equivalently increased, and the size of one recording dot is increased. Therefore, the blank portion generated during one line feed is filled with the same recording dots as the recording dots of the immediately preceding recording, and the blank portion disappears.

(Examples) Hereinafter, the present invention will be described with reference to examples.

FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention,
FIG. 2 is a schematic perspective view of a thermal recording apparatus according to one embodiment of the present invention, FIG. 3 is a circuit diagram of a thermal line head portion in one embodiment of the present invention, and FIG. 4 is a strobe in one embodiment of the present invention. It is a circuit diagram of a pulse generation circuit.

In this embodiment, the number of dots in the line direction is 1728 dots, and 7 ×
The case where the strobe pulse is supplied by dividing into 4 blocks of 3 blocks for every 64 dots and 1 block of 6 × 64 dots is illustrated.

As shown in FIG. 2, the thermal recording apparatus according to the embodiment of the present invention takes out the platen shaft 14 from the platen 12 on both sides and supports the platen shaft 14 with a pair of frames 10 and 10 'so that the platen shaft 14 is supported. It is rotatably supported. The thermal line head 13 faces the platen 12 and is supported by the frames 10 and 10 '. A platen drive wheel 15 is attached to the platen shaft 14. A belt 16 is wound around the platen drive wheel 15 and a motor shaft of a step motor 17 attached to the frame 10. The step motor 17 drives the platen drive wheel 15 via the belt 16. Thermal line head
A heat-sensitive paper 18 that constitutes a heat-sensitive sheet-shaped recording medium is arranged between the platen 12 and the platen 12, and is rotated in the direction perpendicular to the platen shaft 14 by the rotation of the platen 12. In this embodiment, the step motor 17 is composed of a four-phase step motor and is driven by two-phase excitation, and one line is fed in one step.

As shown in Fig. 1, the thermal recording device is a central processing unit (CP
U) 21, a ROM 22 that stores a program, a microcomputer 20 that includes a RAM 23 that temporarily stores recorded data,
The strobe pulse generation circuit 24 which receives the trigger pulse output from the microcomputer 20 and outputs the strobe pulse, and the strobe pulse output from the strobe pulse generation circuit 24 is input by the selection signal output from the microcomputer 20. A multiplexer 25 that outputs a strobe pulse to the block A, B, 5 or D of the thermal line head 13 and recording data for one line read from the RAM 23 at a cycle corresponding to the communication speed and output from the microcomputer 20. A data latch circuit 26 that latches the recording data with a latch pulse output in a cycle corresponding to the communication speed, and outputs the latched recording data to the thermal line head 13.
A motor control circuit 27 that receives a drive control pulse output from the microcomputer 20 and generates a two-phase pulse that drives the step motor 17 is provided.

As shown in FIG. 3, the thermal line head 13 has AND gates 13 ₁ to _{1 1} to which the output of the data latch circuit 26 and the strobe pulse output from the multiplexer 25 are input.
3 _27, and resistors 13 _{31 to} 13 ₅₇ as heating elements, which generate heat by receiving the outputs from the AND gates 13 _{1 to} 13 ₂₇ separately,
It comprises a thermistor 13 ₃₀ for detecting the temperature in the vicinity of the thermal line head 13. In FIG. 2, the AND gates 13 _{1 to} 13 ₂₇ and the resistors 13 _{31 to} 13 ₅₇ are 64 respectively.
The dots are shown collectively. It should be noted that the division into groups A to D is as described above.

In the above thermal line head 13, while the output of the data latch circuit 26 is logic "1" and the strobe pulse output from the multiplexer 25 is logic "1", the corresponding AND gates 13 ₁ , ..., 13 ₂₇ Is producing a logical "1" output and is producing a logical "1" output
The resistors 13 ₃₁ , ..., 13 ₅₇ connected to 13 ₁ , ..., 13 ₂₇ are energized to generate heat. The thermistor 13 ₃₀ detects the temperature in the vicinity of the thermal line head 13 (hereinafter, simply referred to as temperature).

The strobe pulse generation circuit 24 receives the trigger pulse output from the microcomputer 21 as shown in FIG. 4, and is the longest when the maximum line speed is 10 msec as in the conventional case.
A monostable multivibrator 24 ₄ of the set output variable pulse width to generate an output pulse of 2.4 msec, the thermistor 1 output pulse width of the monostable multivibrator 24 ₄
A time constant circuit 24 ₆ for changing the resistance value of 3 ₃₀ is provided. The time constant circuit 24 ₆ has one end pulled up to the power supply voltage and a resistor 24 ₁ in which a thermistor 13 ₃₀ is connected in parallel, a resistor 24 ₂ connected in series with the resistor 24 ₁ , and a resistor 24 ₂
Of the capacitor 24 ₃ connected between one end of the capacitor and the ground, and the potential at the connection point between the resistor 24 ₂ and the capacitor 24 ₃ is output as a variable output pulse width signal to the monostable multivibrator 24 ₄
Supplied to. Monostable multivibrator 24 ₄
The output pulse of is input to the microcomputer 20 for reading.

The strobe pulse generation circuit 24 configured as described above,
The strobe pulse is output from the monostable multivibrator 24 ₄ by the trigger pulse output from the microcomputer 20. On the other hand, monostable multivibrator 24 ₄
The output pulse width of is controlled according to the temperature detected by the thermistor 13 ₃₀ . Further, four trigger pulses output from the microcomputer 20 are continuously output every 2.5 msec, and four trigger pulses are set as one block and are repeated in a cycle according to the line speed except for the case of double strike described later.

The operation of the embodiment of the present invention configured as described above will be described with reference to the waveform chart of FIG. 5 and the flowchart of FIG.

When recording is started, the output pulse width from the strobe pulse generation circuit 24 is read and the thermal line head 13
Calculates the temperature, in calculating the line speed in response to the speed information, the calculation recording energy from the temperature and line speed (Step S _1), a recording energy than in when the operation recording energy is maximum strobe pulse width 2.4msec Check for existence (step
S _2). The check in step S ₂ is made by referring to the table of FIG. 8 stored in the ROM 22. When the strobe pulse width is less than 2.4 msec, it means that the recording energy is not insufficient. In this case,
This is the case where it falls below the broken line in the figure. In this case, a drive control pulse is output from the microcomputer 20 following step S ₂ , and the step motor 17 is driven by one step by the excitation output from the motor control circuit 27 to perform line feed of one line. Further, the switching pulse of the multiplexer 25 is output from the microcomputer 20,
The multiplexer 25 is switched to supply the strobe pulse to the group A of the thermal line head 13. A trigger pulse is supplied to the further strobe pulse generating circuit 24 (step S _3). Pulse width monostable multivibrator 24 receives the trigger pulse at Step S ₃ 2.4 msec
The following strobe pulse is output, and this strobe pulse is transmitted via the multiplexer 25 to the strobe pulse STRA.
Is supplied to the thermal line head 13 (step
S ₄ ). Since the recording energy is not insufficient in step S ₄ , the strobe pulse width becomes 2.4 msec or less according to the temperature detected by the thermistor 13 ₃₀ . Step S switching pulse from the start time of ₃ to the multiplexer 25 from the microcomputer 20 when the elapsed 2.5msec is output, the multiplexer 25 is switched so as to supply a strobe pulse to the B group of the thermal line head 13. A trigger pulse is supplied to the further strobe pulse generating circuit 24 (step S _5). Strobe pulse generator 24 which receives a trigger pulse is output strobe pulse as in step S _4, the strobe pulse is supplied to the thermal line head as the strobe pulse STRB (Step S _6). 2.5m from the execution at the start of the step S ₅
When you sec elapsed, Step S ₃ ~ Step S ₆ and also step S ₇ ~ Step S ₁₀ is performed. Strobe pulse generating circuit 24 in step S ₇ is triggered,
The generated strobe pulse is supplied to the thermal line head 13 as a strobe pulse STRC via the multiplexer 25 (steps S ₇ and S ₈ ). In step S ₉ , as in step S ₅ , a trigger pulse is supplied to the strobe pulse generation circuit 24, and the generated strobe pulse is supplied to the thermal line head 13 as a strobe pulse STRD via the multiplexer 25 (step S 9 ₉ ,
S _10). When passed 2.5msec from the time of execution of step S ₉ waits for the ready for the next line recording is performed from the step S ₁ again (step S _11).

FIG. 5 is a waveform diagram showing the above-mentioned state. That is, the trigger pulse of the strobe pulse generating circuit 24 supplied from the microcomputer 20 is as shown in FIG. The trigger pulse interval is
It is 2.5 msec, and the cycle of each of the four trigger pulses is the same as the line speed. Therefore, when the line speed is 10 msec, the period of each trigger pulse is 10 msec, and a part is as shown by the broken line.

The trigger pulses output in steps S ₄ , S ₆ , S ₈ and S ₁₀ are as shown in FIGS. 5 (b), (c), (d) and (e). 5 (b) to 5 (e)
It is schematically shown as shown in FIG.

The four strobe pulse shown in FIG.
The figure (g) is shown. A to D shown in FIG. 5 (g) and below show strobe pulses STRA to ATRD.

Using the simplification shown in FIG. 5 (g), the strobe pulse when the line speed is 10 msec is as shown in FIG. 5 (h), and similarly, the strobe pulse when the line speed is 20 msec is the fifth strobe pulse. In Figure (i), the line speed is
The strobe pulse at 40 msec is shown in Fig. 5 (j), and the strobe pulse at a line speed of 60 msec is shown in Fig. 5 (j).
This is as shown in FIG. Further, if FIG. 5 (h) is enlarged and shown, it is as shown in FIG. 5 (l).

In FIG. 5 (b) to (l), the temperature in the vicinity of the thermal line head 13, that is, the influence of the temperature of the thermal line head has been neglected for explanation, but when the line speed is 10 msec and the temperature is almost 0 ° C. The lobe pulse is as shown in Fig. 5 (l) and the line speed is 10msec.
When the temperature is approximately 10 ° C, the strobe pulse has a narrow pulse width as shown in Fig. 5 (m). When the line speed is 10 msec and the temperature is approximately 25 ° C, the strobe pulse is as shown in Fig. 5 (n). As shown, the pulse width becomes even narrower.

In addition, if the line speed is 40 msec as an example, when the temperature is about 30 ° C, it becomes narrower as shown in Fig. 5 (q).
When the temperature is about 45 ° C., it becomes narrower as shown in FIG.

When it is determined that the recording energy is insufficient in step S _2, the step S ₃ to S ₆ the same step S ₁₃ to S ₁₆ is performed after step S _2. Steps S ₁₃ ~ S
By executing step _16, the pulse motor 17 is driven one step to perform line feed of one line, and the strobe pulse STRA and strobe pulse ST are applied to the thermal line head.
RB is supplied.

When the elapsed 2.5msec from the execution at the start of the step S _15,
Following step S ₁₆ the switching pulse from the microcomputer 20 to the multiplexer 25 is output, Maruchirekusa 25
Are switched to supply strobe pulses to group C of the thermal line head 13. Further, a trigger pulse is supplied to the strobe pulse generation circuit 24 (step
S ₁₇ ). Step S ₁₇ is the pulse motor in step S ₇ .
Other than 17 step 1 step drive, that is, step
Another is not performed one line of line feed in S ₁₇ is the same as step S _7. Trigger pulse generating circuit 24 which receives a trigger pulse in step S ₁₇ is a step S _14, S
_A strobe pulse is generated similarly to _16, and this strobe pulse is supplied to the thermal line head 13 as a strobe pulse STRC (step S ₁₈ ). Following step S _18, step S ₉ to S ₁₀ and similar steps S ₁₉ to S ₂₀ are executed. The strobe pulse STRD is supplied to the thermal line head 13 by executing steps S _{19 to} S ₂₀ .

From the start of execution of step S ₁₉ following step S ₂₀
When 2.5msec elapsed, the pulse motor 17 from the step S ₁₃
To the exclusion of 1-step driving of the same step S _13A to S _20A as step S ₁₃ to S ₂₀ are executed. Thus, step S _13A to S _20A Following the execution of step S ₁₃ to S ₂₀ is performed, and one line of the line feed is not in step S _13A. Thus subsequent on recording dots recorded by step S ₁₃ to S ₂₀ so that the re-recording is performed. Step S ₁₁ is performed after step S _20A.

In the case where insufficient recording energy when step S ₁₃ to S ₂₀ and step S _13A to S _20A is executed, that is, when the line speed and temperature exceeds a dashed line in FIG. 8, strobe pulse generating circuit 24 outputs a pulse with a pulse width of 2.4 msec, strobe pulse STRA, STRB,
The pulse width of STRC and STRD is 2.4 msec.

Thus, step S ₁₃ to S ₂₀ and step S _13A to S
_{When 20A} is executed, in the case of the example shown in FIG. 8, when the line speed is 20 msec and the temperature is less than about 8 ° C, the line speed is 40 msec and the temperature is less than about 18 ° C,
This is the case when the line speed is 60 msec and the temperature is less than 28 ° C.

Incidentally, conventionally is performed recording is repeated steps S ₃ to S _11, even if the lack of recording energy, the strobe pulse STRA~STRD this time was as shown in FIG. 5 (s).

On the other hand, according to the present embodiment, the strobe pulse STR
The waveforms of A, STRB, STRC, and STRD are as shown in FIG. 5 (p). After strobe pulses STRA to STRD are supplied in two cycles, pulse motor 17 is driven by one step, and then again. The line strobe pulses STRA to ATRD are supplied.

In the present embodiment as described above, to be recorded by the execution of step S _13A to S _20A subsequent to the recording dots recorded by the execution of step S ₁₃ to S _20, step S
It is reheated before the recording energy due to execution of _{13 to} S ₂₀ is completely consumed. As a result, the total recording energy is equivalently increased, and when step _S20A is executed, it is twice hit on the shaded portion in FIG. 7 (b). The recording dots are like the outer frame of FIG. 7B, and there is no space between the recording dots.

In addition, since the double striking is performed only at a low speed of 20 msec / line or more, the rest line processing does not increase and the overall line speed does not decrease.

(Effect of the Invention) As described above, according to the thermal recording apparatus of the present invention, the shortage of the recording energy is determined from the temperature and the line speed in the vicinity of the thermal line head, and when it is determined that the recording energy is insufficient, the same recording data is obtained. Since the recording is performed again, the space between the recording dots in the line feed direction is filled when the recording energy is insufficient, and good recording can be obtained.

Further, since the double striking is performed only at a low speed of 20 msec / line or more, the line speed is not reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of one embodiment of the present invention. FIG. 2 is a schematic perspective view of a thermal recording apparatus according to an embodiment of the present invention. FIG. 3 is a circuit diagram of a thermal line head portion in one embodiment of the present invention. FIG. 4 is a circuit diagram of a strobe pulse generating circuit according to an embodiment of the present invention. FIG. 5 is a waveform diagram for explaining the operation of one embodiment of the present invention. FIG. 6 is a flow chart for explaining the operation of one embodiment of the present invention. FIG. 7 is a schematic diagram showing recording dots used for explaining the operation of one embodiment of the present invention. FIG. 8 is a characteristic diagram showing the relationship between line speed, temperature and strobe pulse width. 12 ... Platen, 13 ... Thermal line head, 13 ₃₀ ...
… Thermistor, 15 …… Drive wheel, 16 …… Belt, 17 …… Pulse motor, 18 …… Thermal paper, 24 …… Strobe pulse generation circuit, 24 ₄ …… Monostable multivibrator, 25 …… Multiplexer, 26… … Data latch circuit, 27 …… Motor control circuit.

Claims (2)

(57) [Claims] 1. A thermal line head having a heating element which is energized by an output from a logical product means for performing a logical product operation of recording data and a strobe pulse to generate heat, and the temperature of the thermal line head or the vicinity thereof. In a thermosensitive recording apparatus comprising a strobe pulse control means for controlling the pulse width of the strobe pulse at a predetermined value or less and changing the cycle of the strobe pulse according to the line speed, the line speed and the temperature A discriminating means for discriminating the shortage of the recording energy of the heating element is provided, and when the discriminating means discriminates the shortage of the recording energy, after recording one line, the recording data and the strobe pulse for performing the same recording again on the same line. And re-recording control means for applying the Thermal recording apparatus. 2. The thermal recording apparatus according to claim 1, wherein the discriminating means is a discriminating means for discriminating that the recording energy is insufficient when the width of the strobe pulse generated by the strobe pulse control means is a predetermined value.