JP2594398B2 - Thermal recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal recording apparatus used for a facsimile apparatus and the like.

[0002]

2. Description of the Related Art Recently, facsimile apparatuses for transmitting images and the like using a line have been installed not only in a workplace but also in a general home. For recording a received image of the facsimile apparatus, a low-noise, high-reliability thermal recording apparatus using a thermal head which is excellent in high speed and high resolution is widely used. Various recording methods are used in this thermal recording apparatus. Among these methods, the method of recording one line on recording paper with one disturbance is the fastest. However, the thermal recording apparatus according to this method records one line to be recorded by one driving. Therefore, when all the pixels of one line are black pixels, the driving current of all the recording elements of the one line is simultaneously increased. Power supply, that is, a power supply having a very large capacity. However, the ratio of black pixels in almost all lines of transmitted documents and the like is not more than ten percent,
Moreover, there are cases where the number of black pixels in the line is extremely small. Therefore, the use of a large-capacity power supply is extremely uneconomical and leads to an increase in the cost of the apparatus itself.

Therefore, if the number of black pixels contained in one transmitted line is equal to or less than a fixed value K, one line is recorded at one time, and if the number of black pixels exceeds the fixed value K,
One line is divided so that the number of black pixels is equal to or less than K, and recording is performed by dividing the number of times. A so-called constant bit recording method has been proposed.

[0004]

However, in the thermal recording apparatus using the constant bit recording method, the recording time of one line varies according to the number of black pixels, that is, each recording element (heating element) is driven. Although the time is the same, the driving timing of the printing elements differs according to the number of black pixels, so that as the number of times of one-line division increases, the difference in heat storage between the individual printing elements increases. Accordingly, this causes a density difference in a recorded black pixel portion due to a difference in heat storage between the individual recording elements, and in particular, a remarkable density difference occurs as the number of divisions of a line increases, that is, a problem occurs in that an entire recorded image becomes uneven. there were.

The present invention solves the above-mentioned conventional problems. When driving and recording by a constant bit recording method, a complicated circuit,
An object of the present invention is to provide a thermosensitive recording apparatus which does not require control and can change a driving time of a recording element according to the number of divisions of one line to obtain a recorded image without density unevenness.

[0006]

In order to achieve the above object, a thermal recording apparatus according to the present invention comprises: a recording element corresponding to the number of pixels for one line; a storage circuit for storing an image signal for one line; The image signal from the storage circuit is temporarily stored, and
A latch circuit for transferring to the recording element, a thermal recording apparatus comprising; and a driving circuit for selectively driving the recording elements in accordance with the number of black pixels of the stored image signal, to the memory circuit Black pixel counting means for sequentially counting the number of black pixels of the image signal to be transferred for each predetermined value, division recording number determination means for determining the number of division recording times for one line based on the counting result of the black pixel counting means, A drive time setting means for setting the drive time for driving the printing element to gradually increase in accordance with the increase in the number of divided recordings; and and output means recording interval stepwise one line and outputs a one-line recording end signal to increase Te, the recording end signal
When the image signal of the next line is transferred to the storage circuit after output
In both cases, the image signal stored in the storage circuit is
To the switching circuit and set by the driving time setting means.
Driving time of the recording element and the number of division recording times determination means
Stored in the latch circuit with the number of divided recordings determined in
Control means for recording an image signal using the recording element
Those having a structure called.

[0007]

According to the present invention, a recording element corresponding to the number of pixels for one line, a storage circuit for storing an image signal for one line, and an image signal from the storage circuit are temporarily stored.
A thermal recording apparatus comprising: a latch circuit for transferring data to a recording element; and a driving circuit for selectively driving the recording element in accordance with the number of black pixels of the stored image signal. together with decide to increase gradually in accordance with the division recording frequency, stepwise output recording end signal so that the recording period for one line is increased according to the increase of the divided recording times, after the output of the recording end signal Remember next line
The image data transferred to the circuit and stored in the memory circuit
Signal to the latch circuit and set by the drive time setting means.
Drive time of divided printing elements and means for determining the number of divided recordings
Stored in the latch circuit with the number of divided recordings determined in
The recorded image signal is recorded using a recording element .

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of a thermal recording apparatus according to one embodiment of the present invention. In the figure,
Reference numeral 1 denotes a transfer clock (hereinafter, TCK) for transferring an image signal.
2) is a signal input terminal for inputting an image signal (hereinafter abbreviated as PIX), and 3 is 1
A signal input terminal for inputting a line recording cycle signal (hereinafter abbreviated as LINE), a signal output terminal 4 for outputting a one-line recording end signal (hereinafter abbreviated as FIN), and a signal output terminal 5 for P
A signal input terminal for inputting, for example, a signal (hereinafter abbreviated as TNSO) which becomes high level “H” during the transfer of IX;
6 counts the number of black pixels in the PIX1 line, and every time this number exceeds a predetermined value, a pulse, for example, a carry (OV below carry) signal is output.
R), a black pixel counter, 7 is a transfer pixel counter for counting the number of transferred PIXs in one line, and 8 is an OVR from the black pixel counter 6 and a transfer pixel counter. 7, a batch recording block detection unit for inputting information on the number of PIXs transferred from the unit 7 and determining a division method necessary for recording one line. Reference numeral 9 denotes data from the batch recording block detection unit (partition information of one line). ), And a recording block selector 10 for selecting a block to be recorded based on the data, counts OVR from the black pixel counter, and determines the number of divisions for performing one-line recording, that is, the number of divisions counter ( The BDT) 11 counts the number of outputs of an applied pulse width signal (hereinafter abbreviated as ENB), which will be described later, for one-line recording by the BDT. The number of ENB outputs that outputs a trigger signal (hereinafter abbreviated as TRIG) if the values do not match, and outputs a one-line recording end signal (hereinafter abbreviated as FIN) if they do not match. The counter 12 is variable in accordance with the BDT from the division number counter 10 and the TRI from the ENB output number counter 11 is changed.
The drive time determining means for outputting the ENB synchronized with G, that is, the applied pulse width generating section 13 has the TNSO at the low level "L", that is, the state in which the image signal is not being transferred.
At the output timing of IN, the thermal head 1 described later
5 strobe signal (hereinafter referred to as STB) for latching the PIX temporarily stored in the shift register 5 in the latch circuit.
, An AND gate for selecting one of ENB1 to ENBN based on the signal from the recording block selecting unit 9 and ENB in one-line recording, a shift register, a latch circuit, an AND gate, This is a thermal head unit equipped with a driver and the like.

Next, the operation of the thermal recording apparatus of the present invention will be described in the second.
A description will be given based on the timing chart in FIG. First, L
In synchronization with the rise of INE, PIX, TCK, TNSO
Enter. Here, the first line of the PIX does not need to be divided, the second line needs to be divided into two, and the third line needs to be divided into three.
Black pixels corresponding to each are distributed. When this PIX is transferred to the thermal head unit 15, the previous line that has already been transferred to the shift register is latched by the latch circuit, and recording starts at the rising edge of LINE on the next line.

At this time, based on the data already detected by the black pixel counter 6 and the transfer pixel counter 7, the collective recording block detecting section 8 calculates the data of the recording block in which the previous line is collectively recorded. The black pixel counter 6 outputs a pulse signal (hereinafter abbreviated as OVR) each time the number of black pixels, which is the detected data, exceeds a preset value. That is, when it is necessary to record one line by dividing it into n lines, n-1 OVRs are output. Then, the batch recording block detecting section 8 receives the OVR, detects the data from the transfer pixel counter 7, and transfers the PIX transferred thereto.
A method for dividing one line is determined. At the same time, this OV
BDT (in this example, data in which the number of divisions is 0, 1, 2, 3, etc.) is output from the division number counter 10 to which R is input. The ENB output number counter 11 receiving the BDT presets the number of divisions, and generates a TRIG that causes the applied pulse width generation unit 12 to output ENB. Further, the applied pulse width generation unit 12 which inputs this BDT
Determines the pulse width according to the number of divisions and outputs ENB in synchronization with TRIG. The pulse width of the ENB increases as the number of divisions increases. Therefore, in this example, the pulse width of ENB has a relationship of TA <TB <TC. In other words, this makes it possible to vary the applied pulse width according to the number of divisions of one line. At this time, this E
The collective recording block detection unit 8 to which the NB is input determines the division method of one line, and outputs the data of the block to be collectively recorded to the recording block selecting unit 9. Here, the data of the block is decoded by the recording block selecting unit 9, and the ENB 1 in which the ENB is selected via the AND gate 14 is selected.
ＥＮENBN are applied to the thermal head unit 15. At this time, the ENB is such that the greater the number of divisions, the greater the pulse width (T
A, TB, TC). In addition, E which inputs this ENB
The NB output number counter 11 has a preset value (BDT).
Is continuously output every time ENB output ends until
G is output. That is, a number of pulses corresponding to the number of divisions are output. When the preset width and the number of outputs of ENB match, and a one-line recording end signal FIN is output, the strobe generating unit 13 that detects this FIN and the external TNSO low level transfers the next line to be recorded to the thermal head. The latch circuit of the section 15 outputs the STB to be latched. The above operation is sequentially repeated to record one page. LINE is handshake with FIN.
ke), the output of the FIN is detected and then input to the signal input terminal 3. That is, a high-level signal is input to the signal input terminal 3. The timing chart of FIG. 2 shows the case of simultaneous driving, two-division driving, and three-division driving of one line. However, even when the number of divisions of one line increases, the recording operation is performed at the same timing as described above. I can do it.

On the other hand, the sub-scan feed of the recording paper is performed by generating a predetermined driving current by a stepping motor driver (not shown) in synchronization with the rising of the LINE, and rotating the stepping motor.

[0013]

According to the present invention, according to the number of times of divisional recording of one line, the drive time (recording time for the recording element) can be reduced without using a complicated circuit and control so that the influence of the heat storage difference between the recording elements is eliminated. Since the energization time can be made variable, the density of the recorded image does not become uneven even with the constant bit recording method, and an effect of obtaining a high quality image can be obtained. Furthermore, by outputting a recording end signal so that the recording cycle of one line increases stepwise in accordance with the increase in the number of division recordings, the transfer of the next line is started after the output of this signal,
The image signal stored in the storage circuit is transferred to the latch circuit.
In addition, by performing the recording, it is possible to simplify the timing control between the start of the recording and the start of the transmission due to the difference in the recording time for each line when performing the divided recording.

[Brief description of the drawings]

FIG. 1 is a block diagram of a thermal recording apparatus showing one embodiment of the present invention.

FIG. 2 is an operation timing chart of the thermal recording apparatus shown in FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 TCK signal input terminal 2 PIX signal input terminal 3 LINE signal input terminal 4 FIN signal output terminal 5 TNSO signal input terminal 6 Black pixel counter (number of black pixels detecting means) 7 Transfer pixel counter 8 Batch recording block detection unit 9 Recording block selection Unit 10 division number counter (division recording number determination unit) 11 ENB output number counter 12 applied pulse width generation unit (drive time determination unit) 13 strobe generation unit 14 AND gate 15 thermal head unit

Claims (1)

(57) [Claims] 1. A recording element corresponding to the number of pixels for one line, a storage circuit for storing an image signal for one line, the SL
Temporarily stores the image signal from the storage circuit and transfers it to the recording element
A latch circuit for, a thermal recording apparatus comprising; and a driving circuit for selectively driving the recording elements in accordance with the number of black pixels of the stored image signals, image to be transferred to said storage circuit Black pixel counting means for sequentially counting the number of black pixels of a signal for each predetermined value; division recording number determination means for determining the number of division recording times for one line based on the counting result of the black pixel counting means; Is set so that the drive time for driving the printing element is gradually increased in accordance with the increase in
A drive time setting means, and output means recording interval stepwise one line in accordance with an increase in the divided recording number of times determined by the divided recording number determination means outputs a one-line recording end signal so as to increase the After the recording end signal is output, the next
Image signal to the memory circuit, and
Transfers the image signal stored in the memory circuit to the latch circuit
Drive of the printing element set by the drive time setting means.
Moving time, and determined by the division recording number determination means.
The image signal stored in the latch circuit is divided by the number of divided recordings.
Control means for performing recording using the recording element.
And a thermal recording device.