JPS62113567A - Printing head driving method - Google Patents

Abstract

PURPOSE:To restrain a current based on a counter-electromotive force (CEMF) due to mutual interference between magnetic circuits and contrive high-speed printing and energy conservation, by connecting a CEMF-absorbing circuit in series with a diode connected to one end of a driving coil, and connecting an absorbed voltage switching circuit to the CEMF-absorbing circuit. CONSTITUTION:When a current based on a CEMF due to mutual interference between magnetic circuits tends to flow during energization of driving coils L1-L<k>, a transistor TRc3 is not turned ON because a transistor TRc4 in an absorbed voltage switching circuit 2 is in an OFF state. Only when the CEMF generated is higher than the Zener voltage of a Zener diode Dz1, the current based on the CEMF flows through the loop of diodes D1-Dk, the transistor TRc3, the Zener diode Dz1, a transistor TRc1 and the driving coils L1-Ll, whereby the voltage between the emitter and the voltage, and energy arising from the magnetic interference is consumed in the transistor TRc3. During when the driving coils are deenergized, the voltage between the emitter and the collector of the transistor TRc3 is low (substantially 0V).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a print head drive method in a spring-charged wire dot printer, and particularly to a print head drive method that allows dot pins to reciprocate without receiving magnetic interference. .

[Conventional technology]

Wire dot printers are required to be capable of high-speed printing as computer terminals. For this reason, the following printing method is available as a printing method for increasing the printing speed using a print head with limited performance.

In other words, each of the dot bins in one vertical row or two vertical rows in the print head shown in FIG. 2(b) overlaps horizontally adjacent dot bins when printing, as shown in the print pattern diagram shown in FIG. 2(a). Avoid printing at the position.

This doubles the horizontal movement speed of the print head, making it possible to print at twice the speed.

FIG. 3 is a conventional circuit diagram showing a part of the print head drive circuit shown in FIG. 2(b). By having m sets of these drive circuits, a print head having a dot bin of n=k x rn dots can be driven. In FIG. 3, drive coils L1 to Lk cancel the magnetic attraction force of the permanent magnet of the spring-charged print head, and drive the dot bin by the biasing force of the spring. This drive coil L1
One end of ~Lk is a transistor TR, ~TRk, respectively.
The other end is connected to the connector of transistor TRc1.
connected to the connector.

The bases of the transistors TR1 to TRk are connected to the outputs of a group of AND gates AND. One input side of the AND gate AND receives the print head drive signal T2.
are commonly applied, and a data signal is selectively applied to the other input side at a drive timing that prevents each dot bin of the print head from continuously printing in the horizontal direction.

Further, the transistor TRc2 is provided to amplify the print head drive signal T1 and adjust its polarity, and the transistor TRc2 is connected to the collector of the transistor TRc2 through a resistor.
connected to the base of c. The diodes D1 to Dk are
In order to flow the back electromotive current of the drive coils L1 to Lk, which are inductive loads, the transistors are connected between the connectors of the transistors TRI to TRk and the power supply +E, respectively. The diode Dc is
It is connected between the connector of the transistor TRc1 and ground in order to flow the back electromotive current of the drive coils L1 to Lk.

In such a drive circuit, when the drive signal T1 shown in FIG. 4(a) is input, the transistor TR02 and the transistor TRol are turned on. In addition, the drive signal T2 shown in FIG. 4(b) is connected to some AND gates.
is input to one terminal of the
, (d), the output of the AND gate selectively becomes 1''.

As a result, the corresponding transistors TRL to TRk are turned on, and currents as shown by solid lines in FIGS. 4(e) and 4(f) flow through the corresponding drive coils L1 to Lk.

Here, when the drive signal T2 shown in FIG. 4(b) is turned on, the output of the group of analog gates (AND) becomes '0#' and the transistors TR1 to TRk are turned off.

As a result, the energy stored in the drive coils L1 to Lk is transferred to the transistor TRc1 and the drive coils L1 to Lk1.
The back electromotive current flows around the loop of transistors TR1 to TRk and gradually decreases.

Next, when the drive signal T1 shown in FIG. 4(a) becomes '0', the transistors TRo2 and TRol are turned off.

At this time, the energy stored in the drive coils L1 to Lk is transferred to the diode D. 1. The back electromotive current that flows in the direction of the power supply voltage +E through the drive coils L1 to Lk1 and the diodes D1 to Dk and is regenerated and flows through the drive coils L1 to Lk is shown by the solid lines in FIG. 4(e) and (f). It decreases rapidly as shown in . The displacement waveform of the dot bin driven according to the current shown in FIGS. 4(e) and 4(f) is as shown by the solid line in FIG. 4(g).

Therefore, in the drive circuit shown in FIG.
~Dk andri. 1, power supply voltage 1E and drive coil L1~L
By connecting between the two terminals k, the drive coil current can be cut more easily as described above. Moreover, by inputting data so that each dot bin of the print head does not print successively in the horizontal direction, high-speed printing can be performed at twice the speed, and since the back electromotive force is returned to the power supply, the power supply capacity can be reduced.

In particular, in a printer having a relatively large print head or a print head with a small number of dot bins, high-speed printing can be performed using the above-described printing method.

[Problem that the invention seeks to solve]

However, in such a conventional example, when a large number of dot bins are driven, adjacent drive coils 1 to Lk generate leakage magnetic flux, so that the dot bins that were driven at the timing immediately before and are in the process of returning are affected. to the drive coil,
A back electromotive force is generated in a direction that cancels out the leakage magnetic flux.

Therefore, the current flows through the loop of the diode D1 to Dk1 transistor TRc1 and the drive coil L1 to Lk in FIG. 3, and a back electromotive current flows as shown by the broken line in FIG. 4(e).
As shown by the broken line in FIG. 4(g), there is a problem in that the dot pins that are in the process of returning are delayed in returning, which impedes high-speed printing.

In other words, in the conventional example described above, in the case of a printer that is composed of a large number of dot pins and has a small print head, the magnetic circuits corresponding to each dot bin of the print head are arranged close to each other, so that there is no interference between the magnetic circuits. There is a problem in that the return of the driven dot pin is delayed due to magnetic interference, which hinders high-speed printing.

The present invention was made to solve the above problem, and its purpose is to achieve high-speed printing and save energy by suppressing back electromotive current caused by interference between magnetic circuits. There is a particular thing.

[Failure to solve the problem]

In order to achieve the above-mentioned object, the present invention includes a drive coil that respectively drives a large number of dot bins, a first diode connected to one end of the ground side of the drive coil, and a first diode connected to one end of the drive coil. a first transistor that supplies a drive voltage to the one end when a drive signal is input;
a second transistor connected to the other end of the drive coil to flow a drive current to the drive coil when a second drive signal is input; and a second diode connected to the other end of the drive coil. In the print head drive circuit equipped with
The present invention is characterized in that a back electromotive force absorption circuit is connected in series to the second diode, and an absorption voltage switching circuit is connected to the back electromotive force absorption circuit.

[Effect]

The present invention having the above-mentioned characteristics is such that when the first drive signal is input, the first and second transistors are turned on.
Further, when the second drive signal and data signal are input, a current flows through the corresponding drive coil, a magnetic flux is generated, and the dot bin pops out. At this time, a part of the magnetic flux passes through the magnetic circuit of the drive coil arranged close to each other, and a back electromotive voltage is generated in the drive coil, causing a back electromotive current to flow.

However, at this time, the absorption voltage of the reverse electromotive force absorption circuit is set to a high voltage by the absorption voltage switching circuit, so the energy due to the magnetic interference is consumed in the back electromotive force absorption circuit.
The back electromotive current flowing through the drive coil is rapidly reduced and suppressed. This prevents the dot pins from being adversely affected by magnetic interference.

Further, when the first drive signal or the second drive signal is no longer input, the back electromotive force generated in the drive coil is returned to the power source via the first and second diodes. At this time, since the absorption voltage of the back electromotive force absorption circuit is set to a low voltage by the absorption voltage switching circuit, energy loss due to the back electromotive force absorption circuit is reduced, resulting in energy saving.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 5(a) to (a).
The explanation will be based on g).

FIG. 1 is a circuit diagram of an embodiment of the present invention showing a part of a print head drive circuit, and FIGS. 5(a) to 5(g) are time charts of an embodiment of the present invention. When m sets of drive circuits shown in FIG. 1 are assembled, a print head having dot bins of n=kXm dots can be driven as in the conventional example. Incidentally, the same parts as those in the conventional example are given the same reference numerals and the description thereof will be omitted.

In FIG. 1, the back electromotive force absorption circuit 1 includes a transistor TRo5, a Zener diode D21, and a resistor R1 connected between the emitter and base of the transistor TR.
Consists of. The emitter of the transistor TRc5 is commonly connected to the cathodes of the diodes D1 to Dk, and the collector of the transistor TRc3 is connected to the power supply +E and the anode of the Zener diode D21. The cathode of the Zener diode D21 is connected to the transistor TRc.
5 and the absorption voltage switching circuit 2.

The absorption voltage switching circuit 2 is an inverter INV.

Transistor TRc4 and the transistor TE01
It consists of a resistor R2 connected to the collector of. The inverter INV and the transistor TRc11 are provided to adjust the polarity of the print head drive signal T2, amplify this drive signal T2, and switch the absorption voltage of the back electromotive force absorption circuit 1 according to the signal polarity.

The absorption voltage, that is, the voltage between the emitter and the collector of the transistor TRo5 is a high voltage (substantially the Zener voltage vz) when the print head drive signal T2 is on, as will be described later.
), and when it is off, it becomes a low voltage (habo OV), and it takes these two states.

Next, the operation of the above configuration will be explained. First, when the drive signal T1 shown in FIG. 5(a) is input, the transistor TRc
2 and transistor TRc1 are turned on.

Further, the drive signal T2 shown in FIG. 5(b) is applied to the inverter I
When input to NV, its output becomes 0'' and the transistor TRc lI of the absorption voltage switching circuit 2 is turned off.At the same time, the drive signal T2 is input to one terminal of some AND gates, When the data signals shown in Fig. 5(c) and (d) are input to the other terminal,
Selectively, the output of the AND gate AND becomes 61''.

As a result, the corresponding transistors TR, -TRk are turned on, and currents as shown by the solid lines in FIGS. 5(e) and 5(f) flow through the corresponding drive coils L1-Lk.

When current flows through the drive coils L1 to Lk, magnetic flux is generated and the dot pins fly out from the print head. At this time, a part of the generated magnetic flux becomes leakage magnetic flux and passes through the magnetic circuits 1 to Lk of the drive coils arranged close to each other, and a back electromotive force is generated in the drive coils 1 to Lk in a direction that cancels out the leakage magnetic flux. occurs in This energy is transmitted through the diodes D1 to Dk1
Figure 5(e) goes around the loop of transistor TRo5, transistor TRc1, and drive coils L1 to Lk.
It tends to flow as a back electromotive current shown by the broken line in (f).

However, at this time, the transistor T of the absorption voltage switching circuit 2
Since Rc II is in the off state, the transistor TR
However, only when the back electromotive force generated by the magnetic interference is higher than the Zener voltage of the Zener diode Dz1, the back electromotive current flows across the diodes D1 to Dk1 and the emitter of the transistor TRo5. Base, Zener diode Dzl, transistor TRo1
, flows through the loop of drive coils L1 to Lk.

As a result, the absorbed voltage of the back electromotive force absorption circuit 1, that is, the voltage between the emitter of the transistor TRo and the connector, is maintained at the Zener voltage v2 of the high voltage (Zener diode DZL).

Therefore, the energy due to magnetic interference is transferred to the transistor T
The back electromotive current consumed by Ro5 and flowing through the drive coils L1 to Lk rapidly decreases and is suppressed to a very short period of time, and the dot pin is driven as shown in FIG. 5(g) at a timing just before this. Therefore, the dot pin that is in the process of returning is restored within a predetermined repetition period.

Next, it will be explained that the operation of the selectively driven ringing coils 1 to Lk is performed in substantially the same manner as in the conventional example shown in FIG.

First, after the drive signals T1 and T2 shown in FIGS. 5(a) and 5(b) are turned on, when the 1-salt motion signal T2 shown in FIG. 5(b) K becomes "0", the output of the inverter INV becomes "1" and the transistor TRcII is turned on. Still, the output of some AND gates is 1 at the same time.
1011, the transistors TR1 to TRk are turned off, and the energy stored in the drive coils L1 to Lk is transferred to the transistor TRcl and the drive coils L1 to Lk1.
The back electromotive current flows around the loop of the diodes D1 to Dk1 and the transistor TRo5.

At this time, since the transistor TRclI is in the on state, part of the back electromotive current is transferred to the transistor TRc3.
The current flows to the transistor TRo11 via the emitter and base of and the resistor R1. Therefore, the transistor TRc
3 is also turned on, the absorption voltage of the back electromotive force absorption circuit 1, that is, the voltage between the emitter and the collector of the transistor TRo5 becomes a low voltage (about OV), and the drive coil L
The back electromotive current flowing through 1 to Lk is shown in Fig. 4(e), (f
) decreases gradually in the same way as the conventional example.

Next, as shown in FIG. 5(a), when the drive signal T1 becomes "0", the transistor TRc2 and the transistor TR0
2 is turned off, the energy stored in drive coils 1 to Lk is transferred to diodes D1 to Dk, transistor T
It flows into the direction of the power supply +E via Ro5 and is regenerated.

At this time, the voltage between the emitter and the collector of the transistor TRc5 is a low voltage (approximately QV), so there is little energy loss in the transistor TRo, and the drive coil 1
The back electromotive force flowing through ~Lk is shown in Figure 4 (e) and (f).
Almost the same as in the conventional example, it decreases rapidly as shown by the solid lines in FIGS. 5(e) and 5(f). Further, the driven dot bin stably reciprocates within a predetermined period as shown in FIG. 5(b).

Note that in this embodiment, the drive signal T2 is the drive signal T2.
Although the print head driving method in the case where the drive signal T1 is shorter than the drive signal T2 has been described, the same effects as in this embodiment can be obtained even if the drive signal T1 is shorter than the drive signal T2.

However, the loop of the back electromotive current when the drive signal T1 becomes "0"' is different. Further, in the above case, if the absorption voltage switching circuit 2 is eliminated, the negative influence on the dot bin due to magnetic interference can be eliminated almost similarly to the above embodiment, although energy saving is impaired.

〔Effect of the invention〕

As described above, according to the print head driving method according to the present invention, the absorption voltage of the back electromotive force absorption circuit is set to a high voltage by the absorption voltage switching circuit during the power supply period to the drive coil, so that the This has the effect of suppressing back electromotive current due to interference between the magnetic circuits of the coils and allowing the dot bin to reciprocate stably.

4 Furthermore, according to the present invention, during the non-power supply period to the drive coil, the absorption voltage of the back electromotive force absorption circuit is set to a low voltage by the absorption voltage switching circuit, so that heat loss in the back electromotive force absorption circuit is reduced. However, it is possible to prevent the deterioration of the efficiency of regenerating the back electromotive force to the power source, and there is an effect that energy saving can be achieved.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the present invention showing a part of the print head drive circuit, Fig. 2 is an explanatory diagram showing a print head and an example of a print pattern, and Fig. 3 shows a part of the print head drive circuit. FIG. 4 is a time chart of the conventional example, and FIG. 5 is a time chart of an embodiment of the present invention. 1... Back electromotive force absorption circuit 2... Absorption voltage switching circuit TR1~TRkXTRI! l + TR(2,,TRc
3...) Ransistor L1-Lk... Drive coil D1-Dk... Diode Dzl... Zener diode INV... Inverter R1+ R2.
... Resistance patent applicant Oki Electric Industry Co., Ltd. agent Patent attorney Takashi Kanakura Procedural amendment (voluntary) March 28, 1985 Commissioner of the Patent Office Michibe Uga 1, Indication of the case 1985 Patent Application No. 252689 2, Title of the invention Print head driving method 3, Relationship to the amended case Patent applicant address 1-7-12 Toranomon, Minato-ku, Tokyo Name (029) Oki Electric Industry Co., Ltd. 11 ,full name
(6961) Patent Attorney Takashi Kanakura 5. Date of amendment order (voluntary) 6. Subject of amendment ``Claims'' column of the specification. "Detailed Description of the Invention" Column 5 Drawings. 7 Contents of amendment 1. The specification "Claims" is amended as shown in the attached sheet. 2. In the 15th and 16th lines of page 1 of the specification, "... to the connector..." is corrected to "... to the collector...". 3. Correct "connector" in lines 11 and 14 of page 4 of the specification to "collector." 4. “Transistor TR, ~” on page 5, line 11 of the specification
"TRk..." is corrected as "diodes D1 to Dk...". 5. On page 8 of the specification, line 2, “Earth side of...
" is corrected to "The power supply side of...". 6. Replace “first and second” on page 8, line 15 of the specification with “
The first one is corrected. 7. "corresponding to this" and "corresponding to this" on page 8, line 17 of the specification
Insert "the second transistor is turned on and still corresponds" between "driving carp". 8. "From the Zener voltage..." on page 12, line 15 of the specification is corrected to "From the Zener voltage...". 9. [Specification Box] Page 3] Correct "Connector" in line 3 to "Collector". 10 In the second and third lines of page 13 of the specification, "High voltage (mainly Zener diode DZI) is maintained at the Zener voltage v2."
It is held at the Zener voltage V2) of I. ” he corrected. 1. In the third line of page 15 of the specification, "The back electromotive voltage flowing through..." is corrected to "The back electromotive current flowing through..." 12. On page 15, line 9 of the specification, [From issue T2...] is corrected to "From issue T1...". 13 Correct Figure 5 using the attached sheet. Claim 1: A drive coil that moves each of a large number of don't pins, a first diode connected to one end of the power supply side of the drive coil, and a first diode connected to one end of the drive coil.
a first transistor that supplies a drive voltage to the one end when a drive signal is input; a first transistor that is connected to the other end of the drive coil and causes a drive current to flow through the drive coil when a drive signal of No. 2 is input; 2 transistors and a second diode connected to the other end of the drive coil, and when the first drive signal or the second drive signal is no longer input, the In a method for driving a print head of a wire dot printer in which the power is returned to the power source through the first and second diodes for absorbing electromotive force, a back electromotive force absorption circuit is connected in series to the second diode, and the absorption voltage is switched to the back electromotive force absorption circuit. When the circuit is connected, the absorption voltage switching circuit sets the absorption voltage of the back electromotive force absorption circuit to a high voltage when power is being supplied to the drive coil, and the absorption voltage switching circuit sets the absorption voltage of the back electromotive force absorption circuit to a high voltage during the period when power is not being supplied to the drive coil. A print head driving method characterized by setting the absorption voltage of an absorption circuit to a low voltage.

Claims (1)

[Claims] 1. A drive coil that respectively drives a large number of dot pins, a first diode connected to one end of the ground side of the drive coil, and a first diode connected to one end of the drive coil. a first transistor that supplies a drive voltage to the one end when a drive signal is input; a second transistor that is connected to the other end of the drive coil and causes a drive current to flow through the drive coil when a second drive signal is input; transistor, and a second diode connected to the other end of the drive coil, and the back emf generated in the drive coil when the first drive signal or the second drive signal is no longer input. In a wire dot printer print head driving method in which power is returned to the power supply via first and second diodes, a back electromotive force absorption circuit is connected in series to the second diode, and an absorption voltage is connected to the back electromotive force absorption circuit. When the switching circuit is connected, the absorption voltage switching circuit sets the absorption voltage of the back electromotive force absorption circuit to a high voltage during the power supply period to the drive coil, and sets the absorption voltage of the back electromotive force absorption circuit to a high voltage during the power supply period to the drive coil. Therefore, a print head driving method is characterized in that the absorption voltage of the back electromotive force absorption circuit is set to a low voltage.