JPS6391266A - Thermal recorder - Google Patents

Abstract

PURPOSE:To improve the recording quality, by providing a means for correcting the temperature data outputted from an A/D converter correspondingly to the number of heating elements to be applied simultaneously with pulses and a means for varying the width of said pule correspondingly to the corrected temperature data. CONSTITUTION:When the temperature of a thermal line head 1 increases, the time interval for producing an enable signal ENB corresponding to single gradation is shortened. Consequently, the time interval for applying voltage across a heating element is shortened to reduce the calorific value. In the reverse case, the time interval for producing the enable signal ENB is lengthened to lengthen the time interval for applying voltage across the heating element, thereby increasing the heat to be produced to maintain proper coloring quantity. Furthermore, when the output from a counter 20 is high, production of heat from the thermal line head 1 is increased and temperature rise of the head 1 is expected, whereby the values of the temperature data are reduced to shorten the time interval for applying voltage across the heating element, thus reducing production of heat and maintaining proper coloring quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to printers and printers that record on paper images having gradations displayed on a cathode ray tube display or the like or images having gradations read out by a scanner or the like. The present invention relates to a thermal recording device used in facsimile.

Conventional technology FIG. 5 is a functional block diagram of a conventional thermal recording device.
1 is a thermal line head that is equipped with a plurality of heating elements (omitted in the figure) and performs recording with gradation by changing the number of pulses applied to each heating element; 2 is a thermal line head 1 is a temperature sensor that detects the temperature; 3 is an analog-to-digital converter (3) that converts the analog data output from temperature sensor 2 into a digital value;
Hereinafter, it will be abbreviated as an A/D converter. ), 4 is a conversion means for outputting temperature data according to the data output from the A/D converter 3, and 5 is an enable signal control means for adjusting the width of the applied pulse applied to the thermal line head 1.

FIG. 6 is a circuit block diagram of a conventional thermal recording device.
6 is a power supply; 7 is a control signal output means for outputting a control signal to the thermal line to the RAD 1; 8 is a processing means for supplying image data to the control signal output means 7; Memory 10 (hereinafter abbreviated as RAM) and read-only memory 1
1 (hereinafter abbreviated as ROM) and an internal interface 12. Image data is in RAM10
Each pixel is stored as 6-bit data corresponding to 64 gradations.

FIG. 7 is a block diagram showing the configuration of the thermal line head 1, in which 13 is a heating element group, 14 is a shift register, 15 is a latch, and 16 is a drive circuit. The heating element group 13 is composed of n heating element elements, and the drive circuit 16 is composed of two MOS transistors (omitted in the figure, hereinafter abbreviated as Msj). One Msi drives m/9 heating elements.

FIG. 10 is a circuit block diagram of the enable signal control means 5, in which 17 is a counter, 18 is a flip-flop, 1
9 is a clock generator.

Regarding the conventional thermal recording device configured as described above,
The operation will be explained below.

First, the processing means 8 outputs one line of image data. In Fig. 8, the heating elements D1 to D5 are 40 and 20, respectively.
, 10.5.0 gradation recording is performed for one line of image data. As shown in FIG. 9, the image data corresponding to one line outputted from the processing means 8 is
The control signal output means 7 converts it into a serial data signal 5DATA for one gradation corresponding to n heating elements. The control signal output means 7 has a counter (not shown in the figure) and a comparator (not shown in the figure). The value of this force 1 kunta is compared with the image data for each heating element element using a comparator, and the serial data signal is applied so that the drive pulse is applied every time until the image data becomes equal to this value. 5DATA
form. In other words, in the case of the data shown in FIG. 8, from the first to the fifth time the pulse is 11110, and from the sixth to the tenth time it is 11100, and the larger the number of gradations, the more the pulse continues to be applied until the end.

Serial data signal 5DAT corresponding to recording of one gradation
A is transferred to the shift register 14 in synchronization with the data clock signal DCLK. Serial data signal 5D
When the ATA transfer is completed, it is latched into the latch 15 by the strobe signal STB. The drive circuit 16 inputs the data signal of the latch 15 and selectively drives the heating element group 13. If 64 gradations are to be recorded here and now, data will be transferred to the shift register 64 times, and the heating element group will be driven 64 times.

Next, temperature compensation for a conventional thermosensitive recording device will be explained below.

In recording one gradation, the drive circuit 16 is controlled by the enable signal ENB. The drive circuit 16 is
When the enable signal ENB is OV (hereinafter abbreviated as L level), it becomes inactive, and when it is +5V (hereinafter abbreviated as H level), it becomes active, and corresponds to the temperature data for one gradation. Increase or decrease the length of the applied pulse.

First, the temperature sensor 2 outputs an analog signal according to the temperature of the thermal line head l, and the A/D converter 3
Digitized by. This data is read into the microprocessor 9 via the internal interface 12.

This data is converted into temperature data and input to the enable signal control means 5. The conversion method is ROMI in advance.
This is done by referring to the conversion table written in I. The enable signal control circuit 5 increases or decreases the pulse width of the applied pulse corresponding to one gradation for each drive circuit 16 based on this temperature data.

FIG. 11 is a timing chart of pulse width modulation,
The temperature data output from the processing means 8 is set as an initial value in the counter 17 at the time when the strobe signal STB is generated. This strobe signal STB is input to the clock terminal CK of the flip-flop 18, and the enable signal ENB becomes H level, making the thermal line head 1 operable.

On the other hand, the temperature data initially set in the counter 17 is incremented by the output of the clock generator 19. When this value reaches O, a pollo signal B is output from the counter 17. This signal is input to the clear terminal CLR of the flip-flop 18. Therefore, the enable signal ENI'3 goes to I level and puts the thermal line head 1 into a non-operating state. By changing the operating time in this way, the pulse width corresponding to one gradation is changed.

In Fig. 11, m indicates the number of clocks corresponding to the length of the applied pulse when the maximum correction is performed when the temperature of the thermal line head 1 is low, and the time for the maximum of m pulses. is the time required to record one gradation.

The Y-ple signal E N I3, which is the output of the enable signal control circuit 11 described above, is applied to the thermal line by rad 1.
sent to.

When the temperature of the thermal line head 1 increases due to the above-described configuration, the enable signal E corresponding to one gradation level increases.
In order to shorten the length where NB is generated, the voltage application time to the heating element is shortened, and as a result, the amount of heat generated is reduced.
Appropriate exothermic temperature can be obtained. In the opposite case, the length of time during which the enable signal ENB is generated is increased, so that the voltage application time to the heating element becomes longer, and as a result, the amount of heat generated increases and an appropriate heat generation temperature is obtained.

Problems to be Solved by the Invention However, in the above-mentioned conventional configuration, the output length of the enable signal is adjusted only for each recording of one line. However, there was a problem that sufficient temperature compensation could not be performed. This is because there is a large temperature difference between the heating element and the temperature sensor if you suddenly start recording near black with a large number of gradations after recording something close to white with a small number of gradations. As a result, the reaction of the temperature sensor is delayed, making this problem more noticeable.

Means for Solving the Problems The present invention provides a correction means for correcting the temperature data output from the analog-to-digital converter in accordance with the number of heating elements to which application pulses are simultaneously applied; Change the pulse width of the applied pulse according to the data → J
It is equipped with processing means for temperature compensation of the multi-head.

Effect: With the above configuration, each time an application pulse is applied, more detailed control is performed in anticipation of a rise in temperature.

Embodiment FIG. 1 is a functional block diagram of a thermal recording apparatus according to an embodiment of the present invention, in which ▪ is a thermal line head, 2 is a temperature sensor, 3 is an A/D:r converter, and 5 is an enable signal control means. These are the same configurations as the conventional example. 20 is a counter that counts the number of heating elements to which applied pulses are applied in recording corresponding to one gradation; 21 is a conversion table based on the output of the A/D converter 3 and the count value of the counter 20; This is a conversion means for calculating temperature data.

FIG. 2 is a circuit diagram of the thermal recording apparatus of this embodiment, in which 6 is a power supply, 7 is a control signal output means, and 8 is a processing means, which includes a microprocessor 9 and a RAM 10. R
It consists of an OMI 1 and an internal interface 12, which have the same structure as the conventional example.

FIG. 3 is a circuit block diagram of the enable signal control means 5, in which 17 is a counter, 18 is a flip-flop, and 19 is a circuit block diagram of the enable signal control means 5.
is a clock generator, which has the same configuration as the conventional example.

FIG. 4 is a block diagram showing the configuration of the thermal line head 1, in which 13 is a heating element group, 14 is a shift register, 15 is a latch, and 16 is a drive circuit, which have the same configuration as the conventional example. .

The operation of the thermal recording apparatus of this embodiment configured as follows will be described below.

As in the conventional example, the processing means 8 first processes (5
One line of image data of 6-bit data = 10- for reproducing a 4-gradation image is output. Also, as in the conventional example, the temperature sensor 2 outputs an analog signal corresponding to the temperature of the thermal line head 1,
The data is digitized by the D converter 3. As shown in Table 1, this data is 216 when the temperature is 64.degree. C. and 72.0.degree. C., and this value is read by the microprocessor 9 via the internal interface 12 and stored.

As in the conventional example, the control signal output means 7 forms a serial data signal 5DATA which is a recording corresponding to one gradation, that is, an application pulse applied to the heating element at one time. ,
In other words, this serial data signal SDΔTA drives all the heating elements for recording 1' gradation or higher the first time, 2nd gradation or higher for the second time, and 3rd gradation or higher for the third time. Only the heating element that performs recording with a large number of gradations is driven. This serial data signal 5DATA is then transferred to the shift register 14 in synchronization with the clock signal 5CLK. At this time, the counter 20 counts this data to calculate the number of heat generating elements that generate heat during this recording, and outputs the counted value KEI to the processing means 8. The processing means 8 creates correction data based on the conversion table shown in Table 2, which is stored in the ROMII in advance. Table 2 shows that thermal line head 1 is 5
This corresponds to the case of having 11 heating element elements. Then, this correction data and the value output from the A/D converter 3 are added, temperature data is created by referring to Table 1 again, and is output to the enable signal control means 5. As in the conventional example, the enable signal control means 5 increases or decreases the pulse width of the applied pulse corresponding to one gradation for each drive circuit 16 based on this temperature data.

With the above configuration, as in the conventional example, when the temperature of the thermal line head 1 increases, the length of the enable signal ENB corresponding to one gradation is shortened.
The voltage application time to the heating element becomes shorter, and as a result, the amount of heat generated decreases.In the opposite case, the length of time during which the enable signal ENB is generated is lengthened. As a result, the amount of heat generated increases and the amount of color produced is maintained at an appropriate level.In addition, in this embodiment, when the output of the counter 20 is large, the amount of heat generated from the thermal line head 1 increases, and the amount of heat generated from the thermal line increases. Assuming that the temperature of the head 1 is rising, the value of the temperature data is reduced, so the voltage application time to the heating element is shortened, and as a result, the amount of heat generated is reduced and the amount of color development is maintained at -14=appropriate.

Effects of the Invention The present invention provides a correction means for correcting temperature data output from an analog-to-digital converter in accordance with the number of heating elements to which application pulses are simultaneously applied; This device is equipped with a processing means that compensates for the temperature of the thermal head by changing the pulse width of the thermal head, and each time an applied pulse is applied, the pulse width of the applied pulse is increased or decreased in anticipation of a rise in temperature. It is possible to perform detailed control that cannot be handled by a temperature sensor alone, prevent density unevenness, reproduce images with a predetermined number of gradations, and obtain high recording quality.

[Brief explanation of the drawing]

Fig. 1 is a functional block diagram of a thermal recording device according to an embodiment of the present invention, Fig. 2 is an open circuit block diagram, Fig. 3 is a block diagram of the same main part, and Fig. 4 is a block diagram of the same main circuit. The circuit block diagram of the thermal line head, Fig. 5 is the functional block diagram of the conventional thermal recording device, Fig. 6 is the same circuit block diagram, Fig. 7 is the circuit block diagram of the same thermal line head, and Fig. 8 is the same data. Figure 9 is the same timing chart.
FIG. 10 is a circuit diagram of the main part, and FIG. 11 is a timing chart of the same. 1...Thermal line head 2...Temperature sensor 3...A/D converter 5...Enable signal control means 20...Counter 21...Conversion means Name of agent Patent attorney Toshio Nakao Idiot 1 Figure 7 Figure 8, -□□ Figure 9 ENB-11111, -111''-11 Figure 11

Claims (1)

[Claims] The thermal head includes a thermal head having a plurality of heating elements, and the thermal head is configured to simultaneously apply application pulses to the heating elements selected according to recorded data, and a temperature sensor that detects the temperature of the thermal head, and an analogue of the output of the temperature sensor. an analog-to-digital converter that converts a signal into a digital signal and outputs it; and a correction means for correcting temperature data output from the analog-to-digital converter in accordance with the number of heating elements to which applied pulses are simultaneously applied.
A thermal recording apparatus characterized by comprising processing means for compensating the temperature of the thermal head by changing the pulse width of an applied pulse in accordance with the corrected temperature data.