JPH0750912B2 - Thermal recording device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a thermal recording apparatus.

2. Description of the Related Art Many thermal recording devices have a plurality of heating elements arranged in a line.
The heating elements are selectively energized in accordance with an image signal input signal to perform recording line by line.

However, in such a thermal recording apparatus, when the recording is started or when the recording interval is set to some extent, or when all white lines continue, the density of the image of the line to be recorded next is lowered. Therefore, there is a problem that an image having a uniform density cannot be obtained.

This problem occurs because, as shown in FIG. 4, the temperature of the heating element decreases when there is some time before the next recording, and the temperature of the heating element does not rise sufficiently when the next recording is performed.

In order to increase the temperature rise of the heating element, a method of increasing the energy to be applied to the heating element can be considered. However, with this method, the energy that can be applied to the thermal head at one time cannot exceed a certain value.
The heating element is destroyed. Therefore, the temperature of the heating element cannot be raised sufficiently.

The present invention solves the above-mentioned conventional problems, when recording is started or when recording intervals are set to some extent, or when all white lines continue, without reducing the recording density of the line to be recorded next, Another object of the present invention is to provide a heat-sensitive recording apparatus capable of obtaining an image of uniform density without causing an unnecessary increase in density when there is a black signal.

Means for Solving the Problems In order to achieve the above object, the present invention inputs a transfer interval of image signals and the number of all white lines to be reset when there is a line including a black signal, and sets these values. Based on this, an arithmetic circuit that calculates the time from energizing the heating element of the thermal head to the next energizing, and if this calculated value exceeds the reference value, the thermal recording is performed so that the line to be recorded next is repeatedly recorded An energization control circuit for controlling energization of the heating element of the head is provided.

It is more effective if the energization control circuit has a recording counter that counts the number of times of repetitive recording, and controls energization to the thermal head according to the value of the recording counter.

Operation When the recording is started or when the recording interval is set to some extent, or when all white lines continue, the calculated value of the arithmetic circuit exceeds the reference value. At this time, the energization control circuit controls the energization of the heating element of the thermal head to record the line to be recorded next a plurality of times.

Embodiment FIG. 1 is a schematic configuration diagram showing a thermal recording apparatus according to an embodiment of the present invention. In the figure, 1 is a terminal for outputting a transfer request signal a for requesting transfer of an image signal to an external circuit (not shown), 2 is a terminal for inputting an effective section signal b indicating an effective section of the image signal, and 3 is A terminal 4 for inputting the clock signal c of the image signal transferred from the external circuit, a terminal 4 for inputting the image signal d transferred from the external circuit, and a terminal 5 for inputting the reference value 1 input to the comparator 10. A terminal, 6 is a circuit for controlling the time for energizing the heating element of the thermal head 11, 7 is a timer for measuring the transfer interval of image signals, 8 is a counter for counting the lines in which the image signals are all white, and 9 is An arithmetic circuit for calculating the time from energization of the heating element to the next energization based on the values of the timer 7 and the all-white counter 8, and 10 is a comparison for comparing the value of the arithmetic result k of the arithmetic circuit 9 with the reference value 1. Device 11 has a memory circuit with a memory capacity of 1 line, Energizing the heating element according to 憶 been image signal, a thermal head for recording, 12 is a control unit for said circuit.

The operation of the heat-sensitive recording apparatus configured as described above will be described below.

First, the control unit 12 turns on the image signal transfer request signal a to the external circuit. When the image signal transfer request signal a is turned on, the external circuit turns on the valid section signal b of the image signal and starts the transfer of the image signal clock signal c and the image signal d synchronized with the clock signal c. The control unit 12 turns off the image signal request signal a when the valid section signal b is turned on. The thermal head 11 samples the transferred image signal d with the clock signal c and stores it.

The all-white line counter 8 detects the white signal of the image signal d,
When the image signal d is white on one line, the count value i
Is incremented by 1, and 1 is sequentially added according to the number of all white lines. If even one of the image signals d of one line contains a black signal, the count value i up to now is i.
To clear.

When the external circuit transfers the image signal d for one line, the effective section signal d is turned off. When the valid section signal b is turned off, the timer 7 starts counting in time, and measures the time until the valid section signal b is turned off again.

Next, the control unit 12 outputs the pulse signal e to the energization control circuit 6. The energization control circuit 6 outputs an energization signal f when the pulse signal e is input. The thermal head 11 energizes the heating element corresponding to the black signal of the stored image signal while the energization signal f is on. Further, the control unit 12 detects that the energization signal f is off and knows that the energization of the thermal head has ended.

Then, at the start of recording, the control unit 12 detects that the energization of the thermal head has ended, and then the pulse signal e
Is output and recorded in the same manner as the above operation. This operation is repeated N times, and recording is repeated N times.

After that, the control unit 12 sends the image signal transfer request signal a to the external circuit.
Is turned on to wait for the transfer of the image signal d.

When the transfer of the image signal for one line from the external circuit is completed,
Similarly to the above, the control unit 12 outputs and records the pulse signal e.

Then, the arithmetic circuit 9 inputs the count value j of the timer 7 (the time from the end of the transfer of the image signal of the previous line to the end of the transfer of the current line) and the count value i of the all-white line counter 8, and actually the thermal head 11 The energization interval k for energizing is calculated by the equation (1).

k = j + (i × t) (1) where t is the sum of the image signal transfer time and the energization time.

The comparator 10 has an energization interval k calculated by the arithmetic circuit 9 and a reference value 1
When the energization interval k exceeds the reference value 1, the signal m is turned on as shown in FIG.

After that, when an image signal including a black signal is input, the image signal is recorded. After this recording is completed, the control unit
In No. 12, since the signal m is on, the pulse signal e is repeatedly output N times and recording is repeated N times, as at the start of recording. After that, the image signal transfer request signal a is turned on. Also,
If the signal m is off, repetitive recording is not performed and the image signal transfer request signal a is turned on.

By repeating the above operation, the transferred image signals are sequentially recorded.

FIG. 2 is a detailed diagram showing an energization control circuit of a thermal recording apparatus according to another embodiment of the present invention. In the figure, 13 is a counter that counts the pulse signal e, 14 is a circuit that changes the energization time according to the counter value g of the counter 13 when the pulse signal e is input, and generates an energization signal f, and 15 is A terminal for inputting the clear signal h of the counter, 16 for inputting the pulse signal e output by the control unit 12, and 17 for the thermal head 11
This is a terminal for outputting an energization signal f to.

Next, the operation will be described.

When performing repeated recording N times, the control unit 12 first outputs the counter clear signal h and clears the count value g of the counter 13, and then outputs the pulse signal e, the counter 13 outputs the count value g. Is set to 1, and 1 is sequentially added according to the pulse signal e. The energization time generation circuit 14 also generates an energization time f according to the count value g. When the energization is completed, the control unit 12 outputs the repetitive pulse signal e to repeatedly record.

In the above operation, when recording is repeated N times, the energization time is controlled according to the number of recordings.

In this embodiment, the energization energy is controlled during the energization time, but the voltage during energization may be controlled.

EFFECTS OF THE INVENTION According to the present invention, when recording is started or when recording intervals are set to some extent, or when all white lines continue, by recording a line to be recorded next a plurality of times, it is possible to reduce the temperature of the heating element. If the black signal is raised, unnecessary density rise can be prevented and the recording density can be kept constant. Also, if the energizing energy is controlled according to the number of recordings, the temperature of the heating element will decrease. It is possible to more accurately set the amount of increase in the recording density and keep the recording density more uniform.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a thermal recording apparatus according to an embodiment of the present invention, FIG. 2 is a detailed view of an energization control circuit of a thermal recording apparatus of another embodiment of the present invention, and FIG. 3 is FIG. 2 is a signal waveform diagram in the apparatus shown in FIG. 2, and FIG. 4 is a characteristic diagram showing the state of the heating element temperature in the conventional thermal recording apparatus. 8 ... energization control device, 7 ... timer, 8 ... all white line counter, 9 ... arithmetic circuit, 10 ... comparator, 11 ... thermal head, 12 ... control unit, 13 ... counter, 14 ...... Energization time generation circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hidenori Hayashi Inventor Hidenori 2-3-3 Shimomeguro, Meguro-ku, Tokyo Within Matsushita Densen Co., Ltd. (72) Inventor Takashi Saito 1-2356 Takeshi, Yokosuka-shi, Kanagawa Nippon Telegraph and Telephone (51) References JP 59-17769 (JP, A) JP 60-174668 (JP, A)

Claims (2)

[Claims] 1. A timer for counting a recording interval from a current line to a next line of an input image signal, an all-white line counter for sequentially counting all white lines of the input image signal, and a black portion in the input image signal. Reset means for resetting the count value of the all-white line counter when a signal is included, and the output value of each of the timer and the all-white line counter are energized to the heating element of the thermal head and then energized next. And an energization control means for controlling energization to the heating element of the thermal head so as to repeatedly record the next line a plurality of times when the calculated value of the arithmetic means exceeds a reference value. Thermal recording device equipped. 2. The energization control means has a recording counter for counting the number of repetitive recordings, and the energization of the thermal head is controlled according to the value of the recording counter. Thermal recording device.