JPH03153368A - Thermal head - Google Patents

Abstract

PURPOSE:To easily drive two or more heating resistance body blocks on a time shearing base for reducing the number of connection lines between a thermal head and an outside control circuit by providing a shift register on the thermal head to generate block driving signals. CONSTITUTION:Heating resistance bodies R1 - R2048 on which a voltage VH is applied are divided into eight blocks each containing 256 heating resistance bodies, and driven by 32 drivers IC1 - IC32, for example. A shift register SR is to generate STROBE signals for the blocks, and makes signals ST1 - ST8 active as it makes the signals shift sequentially according to the clock signal SCLX. Conventional drivers are used as the drivers IC1 - IC32. B.E.O signals are connected to STROBE signal terminals, and the signals ST1 - ST8 are connected to B.E.O signal terminals.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a thermal head used as a print head of a printer, for example.

(b) Conventional technology Traditionally, line-type thermal heads have a large number of heating resistors, and when printing one line at the same time, a large amount of current flows, requiring a very large-capacity power source. In order to reduce the capacitance, the heating resistor is divided into a plurality of blocks.

FIG. 5 is an example of a block diagram of a thermal head that performs eight-division driving. 2048 heating resistors R1 to R204
8 is driven by 3211 driver IC1 to [C32, but these drivers are 411! It is divided into 8 blocks of I, and each block is 5TROBEL-
8TROBE817) 8117) Block [movement 1<
71/ 8-division driving is performed by a large signal.

FIG. 6 is a basic circuit diagram of one of the drivers tCt to IC32, and is a 64-bit shift register! ! and 64
It consists of a bit latch circuit supervisor 2, an output protection circuit 13, a gate circuit 14, and a 64-bit driver element 15. DAT, which is the output terminal of 64-bit shift register 2
The A OUT terminal 16 is connected to the DATA IN terminal 2 which is the input terminal of the shift register of the next stage driver, and as shown in FIG. 5, 32 64-bit shift registers in 32 drivers are serially connected.

In addition, 17 is a drive voltage VW input terminal, 18 GiB, E
, 0 number terminal, 19 is 5 TROBE signal terminal, 20 is L
ATCII signal terminal, 22 is CLOCl [signal terminal.

FIG. 7 is a timing chart during 8-division driving. The following describes the printing procedure for one line according to FIG. 7. First, data for 2048 dots is sent from the DATA IN terminal 21 to all shift registers in synchronization with the CLOCK signal, and the LATCH signal is activated to print data for the 2048 dots. The print data is latched by the latch circuit 12. Next, after activating the B, E, and O signals to enable the heating resistor to be driven,
Block drive pulse signals 5TROBEI to 5TROBE8 are sequentially activated in a time-division manner for each of the eight divided blocks to drive the heating resistor, thereby printing one line.

Here, eight signal lines of signals 5TROBEI to 5TROBE8 are connected to the outside through connectors.

(c) Problems to be solved by the invention However, in such a conventional thermal head,
There are many signal lines for driving the thermal head from the outside, the dimensions of the connectors and the like that serve as the joining means are large, and the circuit on the control side is also complex and expensive.

This invention was made in consideration of these circumstances,
By simplifying the circuit, it is possible to provide an inexpensive thermal head that is compact in shape and can be easily controlled.

(d) Means for Solving the Problems This invention provides a thermal head that divides a plurality of heating resistors corresponding to printed dots into a plurality of blocks and drives them in a time-division manner, using a block drive pulse signal that sequentially drives each block. This thermal head is characterized by being equipped with a shift register that generates.

This thermal head is usually mounted on a ceramic substrate with 5 (
It is preferable that 10 to 5,000 heat generating resistors are arranged in a straight line and formed so that each of them can output a pixel. The means for energizing the heating resistor usually includes a shift register that inputs serial print data in synchronization with a clock signal and a latch circuit that latches the serial print data using a LATCH signal, and the latched serial print data A driver IC can be used that outputs an energization pattern to the heating resistor according to the waveform of the drive pulse signal.

In this invention, since the cycle of the clock for the shift register for generating the drive pulse signal becomes the drive pulse width of the heating resistor, the printing density can be controlled by changing this cycle. Therefore, if the thermal head of the present invention is provided with a temperature detection element such as a thermistor and the cycle of the clock is changed according to the temperature detection output, the temperature of the thermal head will change and printing with uniform density will be possible. Become.

(E) Operation By equipping the thermal head with a shift register for generating block drive signals, it is possible to easily drive multiple blocks of heating resistors in a time-sharing manner, and the connection between the thermal head and an external control circuit is possible. Fewer lines required.

(f) Example Embodiments of the invention will be described and explained in detail with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention,
Voltage VH is applied. The heating resistors R1 to R204g are divided into 8 blocks of 256 each, and are driven by 32 driving drivers tCt to IC32. The shift register SR is for generating strobe signals 5TI-9T8 for each block, and the shift register SR becomes active while sequentially shifting the signals STI-ST8 in response to the input clock signal 5CLK.

The driver tCt~32 uses the conventional driver shown in FIG. 6, and the B, E, and O signals in FIG. 1 are connected to the 5TROBE signal terminal 19 of the driver, and (STl)~
(ST8) is connected to the B, E, O signal terminals 18 of the driver.

FIG. 2 is a timing chart of 8-division driving in the embodiment shown in FIG. In the initial state, the signal S'I'l
-5T8 and signal 5CIJ are "L", and signals B, E, and 0, which are data inputs of shift register SR, are "H". First, the clock signal SCL input to shift register SR is set to 1. Input only pulses, signal ST
Let I be active, that is, set to "H". Also, signal 5
Immediately after the rise of CLK, the signals B, E, and O, which are data inputs of the shift register SR, are set to "L" to enable all drivers to drive all heating resistors. In order to obtain the time T required for printing, when continuous pulses are input with the clock period of the signal 5CLK being T, the shift register SR
Since the data input signals B, E, and O are at "L", only one bit of the shift register becomes "Ho", and signals STI to ST8 are generated while being shifted sequentially.

As described above, by using the shift register for generating drive pulses, the heating resistor can be easily time-divisionally driven with a small number of signal lines.

Next, with reference to FIGS. 3 and 4, a case will be described in which a 1-bit shift register is incorporated in the driver ICl-IC32 as a shift register for generating block drive pulse signals.

Fig. 4 is a basic circuit diagram of a driver shown in Fig. 6 which further incorporates a 1-bit shift register SRλ for generating drive pulses, and Fig. 3 is a circuit diagram of a thermal head using the driver shown in Fig. 4. It is a block diagram.

In this example, the first driver of each drive block, i.e. drivers IC1, IC5, = IC4n-3
The drive pulses STI to ST8 for each block are generated using a 1-bit shift register SRa for generating block drive pulse signals built in (n=1 to 8). however,
The timing of the block drive pulses is exactly the same as in FIG. In addition, in this case, the driver [C4n-3 (n=
For drivers other than 1 to 8), the 1-bit shift register S for generating block drive pulses shown in FIG.
It is not necessary to use a driver with built-in Ra, and the driver shown in FIG. 6 can be used.

As mentioned above, by adding a shift register,
The block of heating resistors can be driven in a time-division manner by the thermal head using one control signal 5CLf:.

Incidentally, in the above-mentioned embodiment, the description has been given of driving the thermal head in eight divisions, but the present invention is not limited thereto. Further, the number of heating resistors and drivers is not limited to the above.

(G) Effects of the Invention According to the present invention, multiple heat generating resistor blocks can be easily time-divisionally driven using a single control signal using a shift register provided uniquely to the thermal head, thereby controlling the thermal hept. The connection structure between the side circuit and the thermal head is simplified, and a total inexpensive and compact thermal head driving device is provided.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a thermal head showing one embodiment of this invention, FIG. 2 is a timing chart explaining the operation of the embodiment shown in FIG. 1, and FIG. 3 shows another embodiment of this invention. 4 is a circuit diagram showing the main part of Fig. 3, Fig. 5 is a diagram corresponding to Fig. 1 of the conventional example, Fig. 6 is a circuit diagram showing the main part of Fig. 5, and Fig. 7 is a circuit diagram showing the main part of Fig. 3. 6 is a timing chart illustrating the operation of the conventional example shown in FIG. 5. FIG. R1~R204g...Heating resistor, IC1~I
C32...Driver 11...64-bit shift register, 12...64-bit latch circuit, 13...Output protection circuit, 14...
. . . Gate circuit, 15 . . . Driver element, S R1, S Ra . . . Shift register for generating block drive pulse signals. FIG. 2 B, E, O. Hanging diagram

Claims (1)

[Claims] 1. A thermal head that divides a plurality of heating resistors corresponding to printed dots into a plurality of blocks and drives them in a time-division manner, characterized by being equipped with a shift register that generates a block drive pulse signal that sequentially drives each block. thermal head.