JPS58187371A - Controlling circuit for printing density - Google Patents

Abstract

PURPOSE:To enable to obtain an optimum printing density without generating any excessive heat at a driving element, by driving a hammer magnet by a logical product of a driving signal for a printing hammer and a row of printing density controlling pulses, in an impact printer. CONSTITUTION:When selection signals are selected in accordance with the thickness or the number of sheets of a printing paper used in a line printer, for example, when IMP1 is selected to be L while IMP2 is selected to be H, an inverted output of the raw of density controlling pulses generated by an oscillator OSC1 is outputted from an NAND circuit (which is connected to OSC1) through an AND circuit A, and a transistor Qn is turned ON or OFF by the logical product of the inverted output and a hammer-driving pulse (a), whereby an amount of printing energy according to the selection signals is given to the hammer. In this case, when both of the selection signals IMP1, IMP2 are selected to be L, outputs from the NAND circuit and the AND circuit A become H, and the hammer performs a printing action with the maximum energy. Accordingly, the optimum printing density can be obtained without generating any excess heat from the driving element.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a printing hammer drive circuit for an impact printer;
In particular, it relates to a print density control circuit.

The printing paper used in impact printers is of various thicknesses, or paper that can be inserted with carbon paper to copy the prickles at the same time.

For this reason, the printing machine and its drive circuit are designed and manufactured to have a printing power that allows clear printing even on the maximum thickness of printing paper allowed for use.

Therefore, when printing on a thin sheet of printing paper, problems such as smearing due to the printing force of the printing paper and a reduction in the life of the ink ribbon are likely to occur.

Various mechanical and electrical methods have been used to overcome this drawback.

As for the mechanical method, contact the printing hammer with some kind of cushioning material and press the printing energy key. The goal is to reduce

However, this method has difficulties such as wear of the buffer material and maintaining uniformity over all digits.

Also, as an electrical method, a transistor is used as a driving element and the printing voltage (or current or power) is controlled by actively operating the transistor to control the voltage or current or both of the hammer magnet. It's a method. but,
In this case, there is a drawback that heat is generated because the transistor is actively operated.

Further, as another electrical method, there is a method of controlling the printing force by operating the drive element in a saturated state and controlling the power supply voltage of the magnet.

However, in this case, there is a drawback that switching the voltage requires a considerable amount of time.

As an electrical print density control method, the present invention controls the print density by intermittently driving the drive circuit in a saturation region operation by multiplying the print density control pulse train and the hammer drive 1LIJ pulse by N times. The present invention provides a circuit that can significantly reduce heat generation and time delay, which are disadvantages of the conventional circuit.

According to the present invention, a pulse train obtained by a generator having an 0N-OFF ratio corresponding to the thickness and number of sheets of paper used in the printer and a circuit for selecting the generator is superimposed with a drive signal for the hammer. Thus, by intermittent operation of the hammer magnet drive circuit to which the back electromotive force absorption circuit is added, a circuit capable of controlling (selecting) the printing energy of the hammer is obtained.

In the present invention, the magnet that drives the printing hammer generates a back electromotive force when the element that drives the magnet is 0FFI, but when this back electromotive force is sent to an absorption circuit other than the drive element, the current is This is because the current does not decrease instantaneously but lasts for a certain period of time, so the driving element can be controlled intermittently to reach the required current.

Next, embodiments of the present invention will be described with reference to the drawings.

Referring to Figure 1, printing density selection command color number IMF-1
, IMP2. ..., oscillators 08C1, 08C2, etc. with corresponding 0N-OFF ratios, AND and NAND circuits that superimpose these non-zero driving pulses, a transistor Qn that drives the hammer magnet Ln, and the hammer magnet. L1 and back electromotive force absorption circuit “Zrr
and wrap around.

FIG. 2A shows the case where the maximum print value IMAX is reached. IMPI, IMP2. . . . are all 101, the output of all NAND circuits is 111, and the output of AND circuit A is also +11. At this time, when the hammer drive pulse is input, the transistor Qn enters a saturated operating state, and the magnet LnK power supply voltage VD is applied during T1. Then, the IL of the hammer magnet 11 reaches the IMAX as shown in the figure, and the hammer receives the force of the hammer magnet and performs a printing operation.

FIG. 2 shows the case where BFi and printing current IIMPI are used.

The selection signal is set to IMPI +111MP according to the printing paper of a certain thickness or number of sheets used in the line printer.
Let 2... be l□+. At this time, since IMP l is l□1, the NAND circuit connected to 08C1
It outputs an inverted output of 1 output, and all other NAND circuit outputs become + 1 +. And the output of AND circuit A is 0
An inverted version of the 801 output can be obtained. At this time, when the hammer drive pulse is input, the transistor Qn becomes 080
It performs intermittent saturation operation by turning ON when the output of 1 is l o lo and OFF' when the output is +11. Then, when the output of 08C1 is 101, the current It flowing through the hammer magnet Ln flows through the transistor Qn and rises for a period of T3, and when the output of 08C1 is l11, it absorbs the back electromotive force for a period of 1゛2. It flows into the circuit and descends. This process is repeated to reach MPI, and printing energy corresponding to the selection signal IMPI is applied to the hammer.

Figure 2 CFi shows the case where a printing current of 11 MP2 is obtained.

Select signal IMP according to printing paper different from Fig. 2B.
2 is lI' and all others are l□+. At this time, 08C
The output of the NAND circuit connected to 2 is an inverted signal of the output of 08C2, and as shown in the figure, a magnet current IL that rises for a period of T and falls for a period of 1', which is different from the case of INIPl, is obtained. and reaches IIMP2.

As a result, a selection signal I different from IMAX, IIMPI
The printing energy corresponding to iP2 is given to the hammer.As explained above, the present invention selects the type, hammer #, and Mta flow depending on the printing paper used in the printer, and controls the printing energy of the printing hammer. This has the effect of achieving smooth printing density without excessive heat generation from the drive element.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing an embodiment of the present invention.
This is a schematic diagram of the operation of the embodiment shown in FIG. 1.

Claims (1)

[Claims] A print density control circuit that drives a hammer magnet by logically ANDing a print hammer drive signal of an impact printer and a print density control pulse train.