JPH03216350A - Drive control circuit in thermal head - Google Patents

Abstract

PURPOSE:To perform printing with uniform density by controlling the heating time per block in consideration of the resistance value of heating resistors, a heat accumulation value, and the number of black data. CONSTITUTION:Based on resistance value data of a plurality of heating resistors 13 per block previously measured in a production process, heat accumulation value data per block based on a heat release time from a previous one-line printing, and the number of heating resistors 13 to be heated per block, a time constant determination part 30 determines a time constant in imparting the pulse width of a strobe signal for imparting a drive time to each block of the heating resistors 13. Then, the strobe signals for imparting a drive time to a plurality of heating resistors 13 are outputted. In this manner, for every block of the two or more heating resistors 13, the pulse width of the strobe signal is controlled on the basis of a resistance value dispersion, a heat accumulation value, and the number of black data corresponding to a heating value, and the temperature of the heating resistors is uniformized. Therefore, irregularities in printing density can be reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a drive control circuit for a thermal head incorporated in a facsimile machine, a printer, etc. This invention relates to a circuit for controlling time.

[Conventional technology]

FIG. 2 is a block diagram of a general thermal head, and FIG. 3 is a timing chart for driving this thermal head.

As shown in FIG. 2, the thermal head is composed of a plurality of heating resistor trees R1 to R2048 and one line of registers RES (0 to 31 in the figure) of these heating resistors. The register RES includes the data signal DATA, clock signal CLOCK, latch signal LATCH, and strobe signals STROBE1 to STROBE1 shown in FIG.
8 is input.

One heating resistor corresponds to the 1-bit data signal DATA, and the heating resistor for which the data signal DATA is "1" is energized for a time corresponding to the pulse width of the strobe signals STROBE1 to STROBE8 to generate heat. . Therefore, by changing the width of the strobe signals STROBEI-8, the printing density can be controlled.

Here, FIG. 4 is a block diagram showing a conventional drive control circuit for controlling the pulse widths of strobe signals STROBE1 to STROBE8.

In the drive control circuit shown in the figure, strobe counter 1
The printing time for one line is divided into the number of strobe signals. The multivibrator 2 is activated using the division point of the strobe signal input from the terminal A as a trigger, and is connected to the terminal Cx according to the capacitance of the capacitor C and the resistance value of the thermistor 3 that detects the temperature of the thermal head (not shown). Rx
A pulse signal having a width based on the signal input to the terminal is output from each terminal. Here, the heating time is changed by the resistance value of the thermistor 3 to suppress the amount of heat generated by the heating resistor when the thermal head temperature is high, and to increase the amount of heat generated when the thermal head temperature is low to equalize the printing density. It's for a reason.

The output signal of the strobe counter 1 and the output signal of the terminal Q of the multivibrator 2 are input to an AND circuit 4, and the output thereof is input to a multiplexer (MPX>5). Strobe signals STROBE1 to STROBEN are applied to each block of the register divided into blocks as shown in FIG.

[Invention or problem to be solved]

However, in the conventional thermal head drive control circuit described above, there are variations in the resistance value of the heating resistor in units of blocks, variations in the amount of heat stored in the previous printing, and furthermore, variations in the number of black data in each block. cannot be corrected, resulting in a problem of uneven print density.

Therefore, the present invention has been made to solve the problems of the prior art described above, and its purpose is to take into account the resistance value of the heating resistor, the amount of heat stored, and the number of black data. The purpose of this invention is to provide a drive control circuit for a thermal head that can perform printing with uniform density by controlling the heat generation time for each block. Means for Solving Problem J] A drive control circuit for a thermal head according to the present invention includes: a strobe counter that outputs a trigger signal that gives timing to start driving a plurality of heat generating resistors of a thermal head; a multivibrator that outputs a pulse signal having a pulse width that provides a driving time; and a strobe signal that provides the driving start timing and the driving time to each of the plurality of blocks that partition the plurality of heating resistors. In the thermal head drive control circuit, the thermal head drive control circuit includes a resistance correction register that stores resistance value data for each block of the plurality of heating resistors that has been measured in advance at manufacturing stage zero, and a trigger from the strobe counter. A heat storage correction counter that counts #tI heat amount data stored in the heat generating resistor based on the signal from the heat radiation time required from the time of previous one line printing to the next printing, and stores this heat storage amount data. A register, a black data counter register that counts and holds the number of heat generating resistors for each block, resistance value data of the resistance correction register, and a heat storage correction counter register.
The heat storage amount data of the register and the above black data counter
and a time constant determining unit that provides the multivibrator with a time constant that determines the pulse width of a strobe signal that provides a driving time for each block of the plurality of heating resistors based on the black data of the register. ．． [Function] In the present invention, the heat storage of each block is obtained based on the resistance value data for each block of a plurality of heating resistors that has been measured in advance at the manufacturing stage and the heat dissipation time from the previous printing of one line. The time constant determining section gives a pulse width of a strobe signal that gives a driving time to each block of the plurality of heat generating resistors based on the amount data and the number of heat generating resistors for each block that generates heat (the number of black data). It determines a time constant and outputs a strobe signal that gives drive time to a plurality of heating resistors. In this way, for each block of a plurality of heating resistors, the pulse @ (heating time) of the strobe signal is controlled based on the resistance value variation, the amount of heat storage, and the number of black data corresponding to the amount of heat generation. Uniformity in printing density is reduced by equalizing body temperature.

〔Example〕

The present invention will be explained below based on illustrated embodiments.

FIG. 1 is a block diagram showing an embodiment of a thermal head drive control circuit according to the present invention.

As shown in the figure, the drive control circuit of this example is as follows:
A strobe generating circuit 10 generates strobe signals STROBEI to N that give driving start timing and driving time to the heating resistors of the thermal head, and outputs them to each block (shown in FIG. 2) of the thermal head; Strobe signal STR to strobe generation circuit 10
The strobe pulse width determination circuit 20 provides a time constant for determining the pulse widths of OBE1 to OBEN.

In the strobe generation circuit 10, the strobe counter 11 divides the printing time of one line into the number of strobe signals. In addition, the multivibrator 12 is activated using the division point of the strobe signal input from terminal A as a trigger, and the capacitance of the capacitor (one of 01 to CN) of the strobe pulse width determination step #120 and the thermal head A pulse signal having a width based on the signals input to the terminals Cx and Rx is outputted from the terminal Q in accordance with the resistance value R1 of the thermistor 13 (not shown) that detects the temperature.

The output signal of the strobe counter 11 and the output signal of the terminal Q of the multi-viprator 12 are connected to the AND circuit 1.
4, and its output is input to a multiplexer (MPX>15) as a switching circuit. MPX15, for example, sends strobe signals STROBB1 to STROBBN to each block of registers divided into blocks as shown in FIG. give.

On the other hand, in the strobe pulse width determining circuit 20,
Based on the pre-measured resistance value data for each block of the thermal head, the operation unit 2 stores the resistance value data for each block of the thermal head at the time of shipment of the thermal head.
1 and stored in the RAM 22. When a print request is issued, the CPU 23 reads data from the RAM 22 and sets resistance correction data in the block resistance correction register 25 whose address is specified by the address generation section 24.

Further, FIG. 5 is a timing chart showing the operation of the heat storage correction counter/register 28. As shown in FIG. 5, in the decision time #120, the address generation unit 27
The line trigger Tr output from the strobe counter 11 is input to the heat storage correction counter register 28 whose address is specified by
The time until line printing is performed is counted, and the counter values (L, M, N in FIG. 5) are stored in the register 28 in synchronization with the print start timing. Note that the value of the stored counter represents the heat dissipation time of the heat generating element of each block.

FIG. 6 is a timing chart showing the operation of the black data counter register 29. As shown in the figure, the black data counter register 29 receives a transfer clock signal H and clock transfer data H to the thermal head. Black data is counted in block units along with ATA. That is, this count value represents the number of heating resistors (bit number) that generate heat in each block. The black data counter register 29 is composed of registers for two lines, and can absorb data delays by transferring black data.

30 is a strobe that gives the drive time of each block of a plurality of heating resistors based on the resistance value data of the resistance correction register 25, the heat storage amount data of the heat storage correction counter register 28, and the black data of the black data counter register 29. This is a time constant determination unit that provides the multivibrator with a time constant that determines the pulse width of the signal. The time constant determination unit 30 includes an arithmetic unit 31 that converts the data in the registers 25, 28, and 29 into an N-bit output, an output port 32 that outputs a signal from a port selected based on the N-bit output, and a It is composed of transistors Q1 to QN whose switching is controlled by receiving the output of the output port 32 through a resistor R, and capacitors C1 to CN connected to the transistors Q1 to QN.

Here, FIG. 7 is an explanatory diagram showing the number of input/output pits of the arithmetic unit 31, and this arithmetic unit 31 is composed of a table in which data values from each register are used as addresses.

Therefore, when the switching of the transistors Q1 to QN is controlled by the output of the calculation unit 31 via the output port 32, the time constant of the multivibrator 12 is increased by the transistors Q1 to QN or the activated capacitors 01 to Ci. I can do it.

In addition, this time constant 70 can be described by the following formula.

N Here, T is a constant that the multivibrator 12 has, D
K is the value of the K bit of the arithmetic unit 31, CK is the capacitance of the K-th capacitor, and R1 is the resistance value of the thermistor 13.

Here, FIG. 8 is a timing chart showing the control of this embodiment. The pulse signal (as shown in FIG. 8) having an output width determined by the above time constant becomes the width of each strobe STROBE1 to STROBEN in synchronization with the output of the strobe counter 11.

As described above, in this example, resistance value data for each block of a plurality of heating resistors is measured in advance at the manufacturing stage, and each block is obtained based on the heat dissipation time from the previous printing of one line. Based on the heat storage amount data of the block and the number of heat generating resistors for each block (number of black data), the time constant determination unit 30 generates a strobe signal that gives a driving time to each block of the plurality of heat generating resistors. A time constant that gives a pulse width is determined, and a strobe signal that gives a driving time to a plurality of heating resistors is output. Therefore, for each block of a plurality of heating resistors, resistance variations,
The heating time is controlled based on the amount of heat storage and the amount of heat generated, and unevenness in printing density can be reduced by making the temperature of the heating resistor uniform.

〔Effect of the invention〕

As explained above, according to the present invention, the heating time of each block of a plurality of heat generating resistors is controlled based on the resistance variation, the amount of heat storage, and the amount of heat generated, so that the temperature of the heat generating resistors is controlled. This has the effect that it is possible to achieve uniformity and to perform printing of good quality with little unevenness in printing density.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the thermal head drive control circuit according to the present invention, FIG. 2 is a block diagram of a general thermal head, and FIG.
The figure shows a timing chart when driving the thermal head shown in Figure 2, Figure 4 is a block diagram showing a conventional drive control circuit, and Figure 5 shows a timing chart for driving the thermal head shown in Figure 2.
The figure is a timing chart showing the operation of the heat storage correction counter/register of this embodiment, Figure 6 is a timing chart showing the operation of the black data counter/register of this embodiment, and Figure 7 is the input of the calculation section of this embodiment. FIG. 8 is a timing chart showing the operation of the strobe generating circuit of this embodiment. DESCRIPTION OF SYMBOLS 10... Strope generation circuit 11... Strobe counter 12... Multivibrator 13... Thermistor 15... Multiplexer (MPX) 20... Strobe pulse width determination circuit 21... Operation unit 22... ...RAM 23...CPU 24.27...Address creation unit 25...Block resistance correction register 28...Heat storage correction counter register 29...Black data counter register 30...Time constant determination Section 31...Arithmetic section 32...Output boat Q1-QN...Transistor 01-CN...Capacitor patent consultant

Claims (1)

[Scope of Claims] A strobe counter that outputs a trigger signal that gives drive start timing to a plurality of heat generating resistors of a thermal head, and a multi-function multifunction device that outputs a pulse signal having a pulse width that gives a driving time of the plurality of heat generating resistors. A drive control circuit for a thermal head, comprising: a vibrator; and a switching circuit that outputs a strobe signal that applies the drive start timing and the drive time to each of a plurality of blocks that partition the plurality of heating resistors; a resistance correction register that stores resistance value data for each block of the plurality of heat generating resistors that has been measured in advance in each step; The amount of heat stored in the heat generating resistor is counted based on the heat dissipation time required until then, and a heat storage correction counter/register is used to store this stored heat amount data, and the number of heat generating resistors that generate heat is counted for each block. Based on the black data counter register held in the register, the resistance value data of the resistance correction register, the heat storage amount data of the heat storage correction counter register, and the black data of the black data counter register, the plurality of heating resistors are and a time constant determining section that provides the multivibrator with a time constant that determines the pulse width of a strobe signal that provides the drive time of each block.