JPH0252904B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a printing element driving device in a parallel head recording device using heat-generating printing elements.

(b) Prior Art A recording device in which a large number of heat-generating printing elements are arranged in a line and operated in parallel is used as a high-speed printing device in facsimile machines, etc., but when this type of recording device is generally used as a recording device, particularly as a recorder in a measuring machine, When drawing the vertical coordinate line Y as shown in FIG. 1, the following problem occurred. The heat-generating printing element generates, for example, 33 mA and 15 V per head when activated.
However, in the case of writing the vertical axis coordinate line in a recorder, all the elements of the parallel head are activated at the same time, so if the number of heads is, for example, 1280 (A4 size),
A large current of 42A will temporarily flow.
In the case of normal printing or recording of graphics, such simultaneous operation of all the heads, or a state close to it, does not occur, so a particularly large-capacity power supply for driving the parallel heads is not required. However, in the case of a recorder that records the output of a measuring device, it is necessary to consider the case where all the heads operate simultaneously as mentioned above, so a power supply with a capacity that can provide an instantaneous power of about 15V and 42A must be used. It didn't happen. However, even in a recorder, all the heads operate simultaneously for a very small portion of the total operating time, and usually only about 1% of all heads operate at most. Therefore, the instantaneous output (5
I couldn't help but feel that the 15V, 44A power supply was excessive and uneconomical.

C. OBJECTIVES: The present invention provides a drive circuit for a parallel head recording device that can cope with the simultaneous operation of all heads of a parallel head or nearly so with a relatively small capacity power supply device.

D. Configuration When a parallel head recording device is powered on by giving an on or off data signal to each print head in one recording cycle, the heads to which an on signal has been given are energized. A predetermined pattern is recorded by repeating one recording cycle as described above, but the printing element driving device of the present invention divides all the heads into a plurality of blocks and delays each block little by little in one recording cycle. The first block is first energized, the required current value is detected, and if that value is below a predetermined level, the second block is energized and the total current at that time is detected. When the total current reaches the predetermined level, the start of energization is delayed in block units, such as starting energization to the third block, and when the total current reaches the predetermined level, the energization of the following blocks is postponed, and then the third block is started. The feature is that the remaining blocks are energized after the first energized block is energized.

E. Example A parallel head recording device consisting of 1280 elements.
Divide this into 10 blocks. Each block has 128 heads. The current when all heads of one block operate simultaneously is 4.2A. This 4.2A is set as the reference current level. The required energization time for each print head in one recording cycle is 2 msec. First, the operation of this embodiment device will be briefly described. In the recording operation, after energization for 2 msec in one recording cycle, there is a cooling period of about 2 msec, and then the next recording cycle begins. The schedule of such recording operations is the same as in the conventional system. The feature of the present invention is that in one recording cycle, a strobe signal is sequentially applied to each block at intervals of 1 μs to start energizing, and only the first block starts being energized, and the blocks are driven within 1 μs from the start of energization. The current value is detected and compared with a reference level, and if it is less than the reference level, the second block is energized. Thereafter, similar operations are performed for the second, third to tenth blocks. The capacity of the power supply is 8.4A. Normally, even if all 10 blocks are energized, the drive current rarely exceeds 8.4A. The energization is delayed by 1 μs for each block to check the current, and the 10th block starts energizing from the start point of one recording cycle.
There is a delay of 9 microseconds, but the energization time for one head is 2
Since it is milliseconds, the delay of 9 microseconds can be ignored. Now the operating current of the first block is 2A, and the second block is
If 3A, since 2<4.2, the current is applied to the second block, and since the combined operating current of the first and second blocks is 5A, which is more than 4.2A, the third block and below are energized to the first and second blocks. Power will not be turned on until the end. When all the heads operate simultaneously, as shown in the vertical axis coordinate line of the recorder, the power is applied to two blocks at a time, and the
Finish filling in the vertical axis at . At this time, the end of one cycle of recording operation is 2 ms x 10 = 20 ms and 9 μs,
It can be seen as approximately 20 msec.

FIG. 2 is a circuit diagram of this embodiment. 1 is a power supply, 2 is a resistor for detecting the operating current of the recording head, and 3 is a parallel head consisting of 1280 heads. The operating current is converted into a voltage value by the voltage drop across the resistor 2, amplified by the amplifier 4, and then compared with the voltage Vs of the constant voltage source 6 by the comparator 5.
When the operating current exceeds the reference value of 4.2A, the comparator 5 outputs a high level signal. 8 is a shift register, and 7 is a control circuit that controls this shift register. 91, 92...90 are one-shot circuits that control the 1st to 10th bits of shift register 8.
They correspond to Q1 to Q10, and are triggered when the corresponding bit becomes "1" to output a pulse with a width of 2 msec. This pulse is applied to the corresponding block of the parallel head 3 as a strobe signal. 91 is the first block B1 of the parallel head
Similarly, 92 corresponds to B2 and below, and 90 corresponds to the 10th block BO. 1 is a clock pulse oscillator. An ON or OFF data signal is applied from the latch circuit 11 to each element of the parallel head 3, and when a strobe signal is applied, the elements to which the ON signal is applied are energized. The latch circuit 11 latches the active input data signal by a latch signal a sent from a central processing circuit (not shown). The shift register control circuit 7 receives the latch signal a and sends a preset signal d to the 0th bit QO of the shift register 8 to set it. Thereafter, the clock pulse generated by the clock pulse oscillator 10 is sent to the shift register as a shift pulse. Therefore, when the latch signal a is sent from the central processing circuit, data "1" is preset to the 0th bit of the shift register 8, and this data "1" is sequentially shifted to Q1, Q2, and so on, and then sent to the function circuit 91, 92... are triggered one after another, and each block B1,
A strobe signal is sequentially applied to B2, . The sum of the currents of these energized elements is detected by the resistor 2, and is compared with a reference value by the comparator 5. If the detected current exceeds the reference value, the comparator 5 Output becomes high. When this high signal b is applied to the control circuit 7, the control circuit 7 sends a shift pulse to the shift register 8, and therefore stops. In this way, the current supplied to the parallel head 3 at one time can be suppressed to twice the reference value at most. Each triggered one-shot circuit 91,92
When all the output pulses of... have finished falling, the current supplied to the parallel head 3 becomes O, and the output of the comparator 5 becomes low. Then, the control circuit 7 starts sending shift pulses to the shift register 8 again, and a strobe signal is sequentially applied to each of the remaining blocks, and in the same manner as described above, each block is energized until the total current exceeds the reference level. This kind of operation means that the data “1” is the 10th shift register 8.
This continues until bit Q10 is reached and the 10th block is energized, and when the end of energization of the 10th block is detected by the central processing unit by the fall of the output pulse of the one-shot circuit 90, the central processing unit After a cooling period, the latch signal a is output again. Recording progresses in this manner.

FIG. 3 is a time chart explaining the above operation. Using this time chart, the operation of the apparatus of this embodiment will be summarized and described again. When the latch signal a is issued from the central processing circuit, the latch circuit 11 latches the data and transfers the data to the parallel head 3.
The control circuit 7 applies the preset pulse d to the shift register 8 at the falling timing of the signal a.
to the Oth bit QO and start sending shift pulse C to the shift register. Due to this shift pulse, the data “1” read into the Oth bit QO is
The strobe signals STB1, STB2, . . . with a width of 2 msec are sequentially output from the one-shot circuits 91, 92, .
In this figure, when the sixth block is energized, the output b of the comparator 5 becomes high, and the shift pulse is interrupted. At the fall of the strobe signal STB6 of the sixth block, the head drive current becomes O, the output b of the comparator 5 returns to O, and the supply of shift pulses to the shift register is restarted, and the strobe signals STB7,
STB8... is applied. clock pulse is
The frequency is 1MHz, and it takes 5 μs from the start of recording to the start of energization of the 6th block, then 2 ms elapse, and energization of the 7th block and below starts again, and 3 μs until the start of energization of the 10th block. It took another 2 msec to complete, making a total of 4 msec and 9 μsec to complete one recording cycle.

F. Effects The recording device of the present invention has the above-described configuration, and divides a large number of parallel heat-generating printing elements into a plurality of blocks, and starts energizing with a slight delay for each block.
When the current value exceeds a predetermined value, the start of energization of the subsequent blocks is temporarily stopped, and the energization of the remaining blocks is started after waiting for the block that started energizing first to finish energizing. So,
Even in cases where many print heads are given an on-data signal, which would otherwise require a very large drive current, the energization is divided, so
The power supply can be of small capacity and is economical, and since the current is not divided and supplied unconditionally but only when necessary, the recording speed is hardly reduced.

[Brief explanation of drawings]

Fig. 1 is a plan view showing an example of recording measurement data by a recorder, Fig. 2 is a block diagram showing an embodiment of the present invention, and Fig. 3 is a time chart for explaining the operation of the embodiment. be. 1... Power supply, 2... Current value detection resistor, 3... Parallel head, 5... Comparator, 8... Shift register, 91 to 92... One shot circuit,
10...Clock pulse oscillator.

Claims (1)

[Claims] 1. A parallel head in which a large number of heat-generating printing elements are arranged in a line, a strobe signal generating means for dividing the parallel head into a plurality of blocks and applying a strobe signal to each division, and means for sequentially operating the means; A means for detecting the current value input to the parallel head, a means for comparing the detected current value with a reference value, and a means for detecting the current value supplied to the parallel head by the means exceeding the reference value. and means for stopping the operation of the means for sequentially operating the strobe signal generating means.