JPH0269249A - Printing head driving circuit of printer - Google Patents

Abstract

PURPOSE:To apply always uniform impact energy to all wires by a method wherein a pulse width conversion circuit is provided between a current switching circuit for turning on and off current flowing to a wire driving coil and a control part, and driving current to each inputted one pin is varied considering turning around of magnetic flux from another coil. CONSTITUTION:A pulse width conversion circuit 2 varying a pulse width of a driving current is inserted between a current switching circuit 3 which turns on and off current driving a printing head 4 and a control part 1 controlling the current switching circuit 3. A printing data inputted to a printing head driving circuit 5 from the control part 1 is converted to an optimum current pulse width for each coil with the pulse width conversion circuit 2. The current switching circuit 3 switches current flowing to a coil of the printing head 4 by an output of the pulse width conversion circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a print head drive circuit for a printer, and in particular to a print head drive circuit for a printer, in which a current is passed through a coil as in a wire dot printer.
The present invention relates to a print head drive circuit for a printer that operates a wire to print using electromagnetic energy.

(Prior Art) Conventionally, in this type of print head drive circuit, the waveform and amount of current flowing through the coil that drives each wire are equal, and therefore the impact energy applied to each wire is equal, and the wire 1
I don't have to change the pins at all.

(Problems to be Solved by the Invention) The above-described conventional print head drive circuit has the drawback that the magnetic flux of the coil that is about to impact changes due to the influence of the magnetic flux that wraps around from the adjacent coil, so the printing force also changes. .

For example, as shown in Figure 4, when coils A1B and C are simultaneously excited so that their magnetic fluxes are in the same direction, the magnetic flux φb produced by coil B in the figure is
Since the magnetic fluxes φ3 and φb circulating from C and C cancel each other out, the attractive force of the coil B becomes weaker.

The purpose of the present invention is to eliminate such drawbacks, to eliminate the influence of the magnetic flux of the adjacent coil at that time for each pin of the printing head pin, and to always make the printing pressure of every head pin the same. An object of the present invention is to provide a print head drive circuit for a printer.

(Means for Solving the Problems) In order to achieve the above object, the print head drive circuit of the printer of the present invention includes a print head drive circuit 5 having a plurality of print drive coils in the print head 4. a switching circuit 3 that turns on and off the current flowing to the
Between the control unit 10 that controls the switching circuit 3, for each single pin excited by the coil, the pulse width of one drive current flowing through each coil is changed to compensate for the influence of the magnetic flux of the adjacent coil. Drive current pulse width conversion circuit 2
The configuration is such that .

(Example) Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention.

As shown in FIG. 1, this embodiment includes a current switching circuit 3 that turns on and off the current that drives the print head 4;
A pulse width conversion circuit 2 that changes the pulse width of the drive current is inserted between the control section 1 that controls the current switching circuit 3.

In FIG. 1, from a control section 1 to a print head and a drive circuit 5,
The input print data is converted by the pulse width conversion circuit 2 into the optimum current pulse width for each coil.

Current switching circuit 3 is activated by the output of the pulse width conversion circuit.
switches the current flowing through the coil of the print head 4.

Next, the operation of the pulse width conversion circuit 2 and its effects will be explained using an example.

Figure 2 shows an example of a print head of a dot printer.
Figure 3 shows each coil L, , L, of the print head in Figure 2.
...L, the input waveform P1 to the pulse width conversion circuit 2. P, ...P7 and output waveform S,
, S, ...Sl, and current waveforms I, , I, ..., which flow through each coil, are shown.
P in figure (a), 8. ,I.

corresponds to coil L in Fig. 2, and the same applies to (b), (C), (d), and (e) in the same figure.
, (f) and (g) are the carp “Ll” in Fig. 2, respectively.
* LRt "4 +" IL@, corresponding to L block.

For example, the coils L, , L, of the print head shown in FIG.
. . . When driving L, P, , P in FIG.

When P is input as a parallel input to the pulse width conversion circuit 2, S, , S, ...S in Fig. 3 are obtained.

A pulse with a waveform of Current flows through each of the coils L, , L, . . . in Fig. 2.

Then, as shown in FIG. 3(b), inputs P, , P to the coils L1 on both sides of the coil L.

When both are in the off state, a current such as
, flows to.

On the other hand, as shown in FIG. 3(e), the coil L.

When the inputs P4P to the coils L and L on both sides of the coil are on, the output waveform S of the pulse width conversion circuit 2 has a pulse width much larger than the pulse width S for the coil L. The flowing current is also thick (,
The energy input to the coil is maximum.

In addition, when only the input P to one adjacent coil L is on, like coil L4JPLa, N P
3 r "4 1 Output S4 for P60 input is S
2 and 8. The pulse width is between .

Similarly, output S for inputs K P s , P s , P t.

has a pulse width between S and S. Therefore, the current I4. flowing into the coil L4'PLe. I.

is less than II and more than L, so the energy input to the coil L and spear is medium.

In this way, when adjacent coils are excited at the same time, the drive current is increased to compensate for the decrease in magnetic flux due to the influence of the adjacent coils, and the energy input to the wire is kept constant.

(Effects of the Invention) As explained above, the present invention provides a pulse width conversion circuit between the control unit and the current switching circuit that turns on and off the current flowing through the wire and the actual working coil, and drives the input pin by pin. Considering the current and the wraparound of magnetic flux from other coils,
This has the effect of constantly applying uniform impact energy to all wires.

Therefore, when printing with the printer used in this embodiment, every part of the printed dots or lines has a uniform density and looks beautiful.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is an explanatory diagram showing an example of the state of the coil incorporated in the print head of FIG. 1. Figure 3 shows the coils L, , L, ...L in Figure 2.
FIG. 2 is an explanatory diagram showing an example of a current waveform of a main part of the embodiment of FIG. 1 corresponding to . FIG. 4 is an explanatory diagram showing a state of excitation by a coil of a conventional print head. 1...Control unit 2...Pulse width conversion circuit 3...Current switching circuit 4...Print head 5...Print head drive circuit L, Ll, L, L, L ,,L,... Wire drive coil patent applicant NEC Corporation

Claims (1)

[Claims] In a print head drive circuit that has a plurality of print drive coils in the print head, an excitation circuit is provided between a switching circuit that turns on and off the current flowing through the coils and a control section that controls the switching circuit. A print head drive for a printer characterized by inserting a drive current pulse width conversion circuit that changes the pulse width of the drive current flowing through each coil for each single pin to compensate for the influence of magnetic flux of adjacent coils. circuit.