JPH01249367A - Thermal recording apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention uses a thermal recording head provided with a predetermined number of heating elements, and periodically energizes the heating elements of the head selectively according to recording data. This invention relates to a thermal recording device that performs dot recording by generating heat.

[Prior Art] In this type of thermal recording device, the recording density changes depending on the temperature of the thermal recording head (hereinafter abbreviated as thermal head); when the temperature is high, the density becomes thicker, and when the temperature is low, the density becomes thinner. Conventionally, in order to make the recording density uniform, the power applied to the heating element of the thermal head to generate heat is controlled by the temperature of the thermal head, and when the temperature is high, the applied power is reduced, and when the temperature is low, the applied power is A method is being used to increase the amount of electricity. One way to control the applied power in this case is to control the energization time of the heat generating element, specifically the enable signal output from the thermal head control circuit to the thermal head in order to activate the application of heat voltage to the heat generating element. A method of controlling the pulse width of the signal is employed.

[Problems to be Solved by the Invention] In the conventional thermal recording apparatus of this type, the period of selectively energizing each heating element of the thermal head, that is, the period of one line of dot recording by driving all the heating elements (
(hereinafter referred to as one line period) is kept constant. However, in this case, when controlling the energization time of the heating element according to the temperature of the thermal head, the energization time (if a large number of heating elements are divided into multiple blocks and each block is energized sequentially, the total energization time of all blocks) If it becomes longer than the above-mentioned fixed one-line period, recording in the next period will not be performed well, resulting in so-called line omissions and deterioration of recording quality. Therefore, the energization time must be within one line period.

Figure 7 shows this situation, and one line period is 2.4 m in a thermal recording device using a thermal head in which all heating elements are divided into four blocks and energized sequentially.
s is the energization time depending on the temperature Tp of the thermal head (pulse width W of the enable signal) when controlling the energization time of each heating element according to the temperature of the thermal head as described above.
) shows an example of the settings. Thermal head temperature T
p indicates the temperature of the surrounding area, not the head itself.

In the case of Fig. 7, the temperature Tp of the thermal head is 25°C to 60°C.
Within the range of ℃, the pulse width is set according to the temperature Tp,
The lower the temperature Tp, the longer the pulse width W is set. However, when the temperature Tp is 25°C, the pulse width W is 600μs.
Therefore, the total energization time for all four blocks is 600μm×
Since 4=2.4 ms is the same as one line period, the pulse width is kept constant at 600 μs when the temperature is 25° C. or lower.

However, if the energization time of each heating element of the thermal head is controlled by such settings, if the temperature of the thermal head is considerably lower than 25° C. at the beginning of recording, the energization time will not be sufficient and the recorded density will be low. Moreover, there is a drawback that the recording of several pages immediately after the start of recording is of low density and difficult to see.

In order to avoid this, it is conceivable to always make one line period longer in anticipation of the long pulse width required immediately after the start of recording, but if this is done, the recording speed will decrease at a rate.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a thermal recording apparatus which can eliminate these drawbacks, perform high-quality recording with an appropriate uniform density from the beginning of recording, and is also capable of high-speed recording.

[Means for Solving the Problems] In order to solve the above problems, according to the present invention, in a thermal recording device of the type described in the section of the industrial application field, the heating element of the thermal head is adjusted according to the temperature of the thermal head. A configuration is adopted in which a control means is provided to variably control the time period for one energization of the heating elements, and to variably control the cycle of energization of each heating element in accordance with the energization time.

[Function] According to such a configuration, the period of energization of each heating element is controlled according to the energization time of the heating element, so the energization time is not limited by the period and is controlled according to the temperature of the head. , recording can always be performed with uniform density. Furthermore, by appropriately controlling the energization cycle without making it unnecessarily long, high-speed recording can be performed.

[Embodiments] Hereinafter, details of embodiments of the present invention will be described with reference to the attached drawings.

FIG. 2 schematically shows the mechanical configuration of a recording mechanism section of a thermal printer that constitutes a recording output section of a facsimile machine, for example, as an embodiment of the present invention.

In FIG. 2, reference numeral 8 denotes a recording sheet made of thermal paper, which is wound around a roll 8a, and is pulled out from the roll 8a and guided onto a platen 9 that serves as a recording table and a paper feed roller. Thermal head 6 is placed on platen 9.
is provided, and the platen 9 is biased by the spring 10.
It is designed to come into pressure contact with the upper recording paper 8. A predetermined number of heating elements 6a are arranged in a line with a length approximately corresponding to the width of the recording paper 8 in a portion of the thermal head 6 that comes into pressure contact with the recording paper 8.

Then, a predetermined number of heating elements 6a are selectively driven to generate heat according to the recording data, so that the heated portion of the recording paper 9 develops color, and one line of dot recording is performed. When one line of recording is completed, the platen 9 is rotated as shown by arrow a by the drive of the paper feed motor 11, and the recording paper 8 is rotated as shown by arrow a.
Send one line of pitch as shown by the arrow. By repeating this process, recording is performed one line at a time.

Here, it is assumed that the heating element 6a of the thermal head 6 is divided into four blocks, which are successively energized and driven to generate heat. Although not shown in the figure, the thermal head 6 also includes a buffer circuit that converts and latches the recording data (dot pattern image data) that is input serially one line at a time from serial to parallel, as will be described later, and a buffer circuit that converts and latches the recording data (dot pattern image data) that is input serially one line at a time, and the heating element 6a. Four blocks are sequentially selected and each of the heating elements 6a of one block is selectively applied to each bit of 1/4 data corresponding to each block of one line of data buffered in the buffer circuit. It is assumed that a block selection drive circuit is provided which energizes and drives the block selection drive circuit to generate heat.

Furthermore, as will be described later, each heating element 6
A temperature sensor 7 consisting of a thermistor or the like for detecting the temperature around the thermal head 6 is provided near the thermal head 6 in order to control the time for one time of energization to a.

Next, the configuration of a control system related to the control of the thermal head 6 is shown in FIG.

In FIG. 1, reference numeral 1 denotes a CPU (central processing unit) consisting of a microprocessor element, etc., which controls the entire printer. CPU is ROM (read only memory)
According to a control program stored in 2, a RAM (random access memory) 3 is used as a working area etc. to process data and control the entire printer.

The CPUI includes a recording data manual section 4 for inputting recording data to the thermal head 6 as a configuration that replaces the control of the thermal head 6, and a thermal head control circuit (hereinafter referred to as "thermal head control circuit") that directly controls the thermal head 6 according to instructions from the CPUI. A head control circuit (hereinafter referred to as a head control circuit) 5 is connected. Further, the aforementioned temperature sensor 7 is connected to the A/D converter 12 via the head control circuit 5.

The recording data input unit 4 is configured as an image reading unit including an image reading sensor such as a COD (not shown) and a document conveyance system, or as an image memory. Then, the recording data input unit 4 manually inputs recording data as serial data for one line to the head control circuit 5 at a predetermined timing according to the control of the CPUI, and the data is sent to the thermal head from the head control circuit 5 as serial data SIN. given to 6.

The head control circuit 5 is composed of a human output boat element, and outputs the serial data SIN inputted from the recording data input section 4 to the thermal head 6, and also transfers the same data to a shift register that constitutes a buffer circuit of the thermal head 6. It outputs a clock signal CLK to be input to the terminal. It also outputs a strobe signal STB, which causes the buffer circuit to latch the serial data SIN input into the shift register, at a timing corresponding to a command from the CPU 1. Immediately after outputting the strobe signal STB, the head control circuit 5 sequentially selects each of the four blocks of the heating elements 6a of the thermal head 6 and sequentially drives them in accordance with 1/4 of each line of serial data SIN. enable signals ENI to EN4 are output to the block selection drive circuit of the thermal head 6. Enable [number EN1 to EN4 pulse width W is the thermal head 6
The heating element 6a is energized once, and
This pulse width lW is controlled by a CPU command.

Each of the above signals is input to the thermal head 6 at the timing shown in FIG. 3 during recording. That is, first, the clock signal CLK is input together with the serial data SIN, and then the serial data SIN is input to the thermal head 6.
The buffer circuit is manually operated. Then the strobe signal S
Serial data SIN is latched into the buffer circuit by inputting TB. Furthermore, enable signals ENI to EN4
are sequentially input to the block selection circuit of the thermal head 6, and thereby four blocks of heating elements 6a of the thermal head 6 are sequentially selected, and for each of the heating elements 6a of each block! On the line! The current is selectively energized according to each bit data of the /4 data. One line is recorded by driving four blocks.

Note that the pulse widths of the enable signals ENI to EN4 indicated by the symbols Wo to Wl in FIG.
This is the time for one energization for each. Also, the code T
The period of the strobe signal STB indicated by A to T corresponds to one line period, which is the recording period of one line mentioned above. This one line period is the same as each period of enable signals ENI to EN4. That is, it is the same as the period of selective energization of each heating element 6a.

By the way, in the printer of this embodiment, the enable signal E N
It is assumed that the pulse width W of 1 to EN4 is variably controlled according to the temperature of the thermal head 6. In this case, regarding the setting of the pulse width W according to the temperature of the thermal head 6, there is no restriction in relation to one line period, such as 600 μs for all temperatures below 25° C., as in the conventional example shown in FIG. For example, assume that settings are made as shown in FIG. That is, as shown in FIG. 5, even if the temperature Tp of the thermal head is 25 DEG C. or lower, the pulse width W is set to be larger as the temperature becomes lower, so that a sufficient recording density can be obtained. The setting data shown in FIG. 5 is tabulated as shown in FIG. 6 and stored in the ROM 2 shown in FIG. 1, and the CPUI uses this to control the pulse width W.

However, if the one-line period T is kept constant as in the prior art, if it is set short, the above-mentioned line omission will occur, and if it is set long, the recording speed will decrease. Therefore, in this embodiment, the one line period T is variably controlled in accordance with the pulse width W, which is variably controlled in accordance with the temperature of the thermal head 6.

Here, as an example, the normal one line period TA is 2.5 m.
5 and 6 depending on the temperature of the thermal head 6.
4 times the pulse width W set according to the relationship shown in the figure, that is, the energization time for all four blocks of heating elements 6a is 2.5 ms.
If the line period exceeds 2.5ms,
It is assumed that the energization time is extended to a value longer than the energization time for all four blocks.

Such control is performed by the CPU of FIG. 1 in the procedure shown in FIG. 4 as follows. Incidentally, FIG. 4 shows the procedure of control processing related to the thermal head 6 of the CPU for each recording of one line, and a control program corresponding to this is stored in the ROM 2.

First, the CPUI measures the temperature of the thermal head 6 in step S1 in FIG. 4 before starting the recording operation for one line. This converts the detection signal of the temperature sensor 7 into the A/D converter 12.
This is done by taking in measurement data from the head control circuit 5, which is A/D converted and input to the head control circuit 5 as an input/output board, and analyzing it.

Next, in step S2, the CPU reads the pulse width W of the enable signal corresponding to the head temperature measured in step S1 from the table shown in FIG. 6 stored in the ROMZ, and determines the read data as the pulse width W.

Next, in step S3, it is determined whether 4 times the pulse width W determined in step S2 is smaller than the normal one line period TA=2.5ms, and if it is smaller, in step S4
The line period T is set to the normal one line period TA.

On the other hand, if it is larger than the one-line period TA, 4W+α is determined as the period T in step S5. Note that α should be set appropriately according to the specifications of the thermal printer, for example 1.
The time is approximately 00 μs.

After step S4 or S5, the process proceeds to step S6, in which the head control circuit 5 is instructed to output the serial data SIN and the clock signal CLK to the thermal head 6, input the serial data SIN to the buffer circuit of the head, and further output the strobe signal. Output STB and latch serial data. Note that, simultaneously with the output of the strobe signal STB, a timer (not shown) provided as hardware or configured by software starts measuring one line period T.

Next, in step S7, the head control circuit 5 is instructed to
Enable signal E with pulse width W determined in step S2.
NI to EN4 are sequentially output, and four blocks of heating elements 6a of the thermal head 6 are sequentially driven to record one line.

Next, in a loop of step S8, the count of the above-mentioned timer is checked and one line period T is waited for to elapse, and when it has elapsed, the process returns to step S1 and the following processing is repeated.

Through such processing, when the temperature of the thermal head 6 is, for example, 25° C., the pulse width W of the enable signals ENI to EN4, that is, the one-time energization time of each heating element 6a is
From the table in the figure, it is set to 600 μs. Also 600μ5
Since X4=2.4μs<2.5μs, one line period T is the normal period TA=2.5 as shown on the left side of FIG.
μs.

On the other hand, assuming that the temperature of the thermal head 6 is, for example, 10° C., the pulse width W is set to 800 μs from the table of FIG. And 800μs×4=3.2ms>2.5m
s, one line period T = 3.2ms + a,
When a=100 μs, the time is set to 3.3 ms. Note that when the one-line period T is made longer than the standard period TA in this way, the CPU 1 controls the recording data input section 4 to match this and delays the timing of the manual input of recording data for the next line.

As described above, according to this embodiment, the period of energization (one line period) of each heating element 6a is controlled according to the energization time (pulse width W) of the heating element 6a of the thermal head 6, and the period of energization (one line period) of the heating element 6a of the thermal head 6 is controlled. The upper limit of the energization time is not limited in relation to the energization cycle as in the case of . Even if the temperature of the thermal head 6 is lower than 25°C, the current supply time is set longer as the temperature decreases, so sufficient recording density can be obtained, and regardless of the temperature of the thermal head 6, high-quality recording can be performed with an appropriate uniform density from the beginning of recording. can be done.

In addition, the one-line period T is extended only when the temperature of the thermal head 6 is low, and is shortened to the normal period TA when the temperature is high, allowing high-speed recording without unnecessarily reducing the overall recording speed. can be done.

By the way, in the process of the above embodiment, if 4 times the pulse width W exceeds the normal 1-line period TA, the 1-line period T is
W+α was set variably according to the pulse width W each time, but one line period T was set to 4 W + a = 3.0, for example.
If it is within the range of ms to 3.5ms, set it to 3.5ms, and set 3.
．． An appropriate value may be set for each range, such as 4.0 ms in the case of 5 mS to 4.0 ms.

Furthermore, if four times the pulse width W is sufficiently shorter than the normal one-line period TA, it is also possible to make the one-line period T shorter than the normal period TA accordingly.

[Effects of the Invention] As is clear from the above description, according to the present invention, a thermal recording head provided with a predetermined number of heating elements is used, and each of the heating elements is periodically selected according to recording data. In a thermal recording device that performs dot recording by energizing and generating heat, the time for one energization of the heating element is variably controlled according to the temperature of the head, and the energization of each heating element is controlled according to the energization time. Since we have adopted a configuration that includes a control means to variably control the cycle of the

It is possible to perform high-quality recording at a uniform density from the beginning of recording without having to withstand the temperature of the multihead, and it also has the excellent effect of being able to perform recording at high speed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the structure of a control system related to controlling the thermal head of a thermal printer according to an embodiment of the present invention, FIG. 2 is an explanatory diagram schematically showing the structure of the recording mechanism section of the printer, and FIG. The figure is a timing chart of each signal input to the thermal head during recording with the same printer.
The figure is a flowchart showing the control processing procedure for recording for each line by the CPU in Figure 1, and Figure 5 shows the relationship between the temperature of the thermal head of the printer and the pulse width of the enable signal set accordingly. Figure 6 is a data table of the pulse width according to the temperature of the thermal head corresponding to Figure 5, and Figure 7 shows the temperature of the thermal head in a conventional printer and the settings set accordingly. FIG. 3 is a diagram showing the relationship between the enable signal and the pulse width. 1 ・CPU 2 ・ROM3...RA
M 4...Record data input section 5...Thermal head control circuit 6...Thermal head 6a...Heating element 7...Temperature sensor 8...
Recording paper 9...Platen 6 inches - full head, t' hko@SugiKobushiuchinnaitsu 2nd figure 4th figure 6'

Claims (1)

[Claims] 1) A thermal recording head equipped with a predetermined number of heating elements, and performing dot recording by selectively energizing each of the heating elements periodically in accordance with recording data to generate heat. In the recording apparatus, variably controls the time for one time of energizing the heating element according to the temperature of the head;
A thermal recording apparatus further comprising a control means for variably controlling the period of energization of each heating element according to the energization time. 2) The control means makes the cycle of energization of each heating element constant when the energization time of the heating element is shorter than a predetermined time;
2. The thermal recording apparatus according to claim 1, wherein when the energization time exceeds the predetermined time, the energization period of each heating element is extended beyond the predetermined period.