JPH0195059A - Method for driving dot printing head - Google Patents

Abstract

PURPOSE:To enable dot pins to be driven at the minimum energy without catch of dot pins on a ribbon, by detecting the moment when the tip of a dot pin reaches printing paper for every dot pin, and by independently controlling the timing for each dot pin to return to the origin. CONSTITUTION:A detection board 45 is fitted with a piezoelectric element at a position nearly above an end of armature 37 opposite to the end where dot pins are secured. When dot pins 38 impinge on the printing paper, the piezoelement emits output A. When output C resulting from comparison with it is applied to flip flop 74 LS107, this element is reset by drive signal D and emits output E showing low level to high level. When the output of an impact detection circuit outputted on the reaching of dot pins to the printing paper shows low level, coil current flows. Therefore, the timing for dot pins to return to the origin is controlled for every dot pin, and the catch of pins on the ribbon can be eliminated. As the result, power necessary pin drive can be reduced as much as possible.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for driving a dot print head, and more specifically, to a method for driving a dot print head.
This invention relates to a method for driving a dot print head in a serial dot printer.

(Prior art) A serial dot printer receives character and graphic information from information equipment, prints dots while moving the dot print head using a space motor, performs a line feed using a line feed motor, and repeats this process. It is used for the purpose of outputting information.

Conventionally, so-called open type dot print heads for serial dot printers, such as a spring charge type or a clapper type, have been known.

Figure 2 shows one dot bin unit and the central axis (not shown) of a conventional spring-charged dot print head (hereinafter sometimes simply referred to as a spring I'l'+' release head).
A cross-sectional view taken along a plane including . In the figure, 33 is a base, and on the outer edge of the base 33 there is a magnet 31 and a base plate 3.
2. The spacer 40 and the yoke 39 are stacked, and the yoke 39
The fixed end of the leaf spring 36 is held between the yoke 39 and the spacer 40, and the base of the guide 41 is superimposed on the yoke 39, and these are fixed together by a clamp 42. An armature 37 is supported at the free end of the leaf spring 36, and a dot pin 37 is fixed to the tip of the armature 37, and the tip of the dot pin 38 projects from the guide 41 at the center of the head. It is located in Further, a core 34 is provided at the center of the base 33, and a coil 35 is wound around the outer periphery of the core 34, and both form an electromagnet. When the coil 35 is not energized, the leaf spring 36 to which the armature 37 is attached is attracted to the core 34 due to the magnetic attraction force caused by the magnetic flux of the magnet 31, and the dot pin 38 is attached to the guide 4.
It is in a state where it does not protrude beyond the tip of 1, that is, it is at the origin. When the coil 35 is energized to cancel the magnetic flux generated by the magnet 31 and passing through the core 34, the armature 37 is released from the core 34, and the strain energy stored in the leaf spring 36 is released. In this way, the leaf spring 36
is restored, and the tip of the dot pin 38 fixed to the armature 37 projects forward of the guide 41 to perform printing. A plurality of these printing elements are arranged radially to form a dot printing head.

Among the various functions of a serial dot printer, dot printing control greatly affects printing quality, printing speed, etc., and is extremely important in improving its performance.

Next, we will discuss the third method for driving the spring release type head.
This will be explained with reference to the figures and FIG. FIG. 3 is a block diagram showing an example of a conventional method of controlling a spring release type head. In the figure, 6 is a command circuit composed of a CPU, etc., 7 is a drive time generation circuit for driving the dot pins, 8 is a dot pin drive circuit, and 9 is a cross section of which is shown in FIG. Showing dot print heads, #1, #2, #
3...#n, for example, #1 indicates the first bin of the dot print head, #n indicates the nth bin, and the others have the same meanings (same in other drawings).

FIG. 4 is a diagram showing an example of a timing chart of dot print head control signals, in which a is a timing signal, b is a drive signal, C is a print pattern signal, and d is a timing chart of dot print head control signals.
is the charge/discharge circuit output, e is the drive time T+ signal, f is the drive time T2 signal, and g is the drive current for driving the head bin 38 (same in other drawings).

First, in response to a timing signal (a) from the command circuit 6, a print pattern signal (C) corresponding to each dot pin of the dot print head to be printed at that time is output.

Further, the drive signal (b) output from the command circuit 6 at the same time as the print pattern signal (C) drives the drive time generation circuit 8, and the coil 35 is activated to release the dot pins attracted to the core 34. A drive time T1 signal (e) that determines the time for energization and a drive time T2 signal (f) that determines the time to maintain the self-current and prevent the dot pin from being re-attracted are generated.

As the drive time generating circuit 7, for example, one shown in FIG. 5 is used. To explain its operation, first, a drive signal (b) is input to the inverter 10. At the rising edge of this signal (b), the charge stored in the capacitor C is discharged. At the falling edge of the drive signal (b), the capacitor C is connected to the drive voltage Vcc and the resistor R1.
is charged with electric charge. This charge/discharge signal is the charge/discharge circuit output (d) shown in FIG. This charge/discharge circuit output (d) is then input to comparators 11 and 12. The other input of the comparator has a resistor R shown in the figure.
4 and Rs, and a voltage obtained by dividing +5■ by R2 and R3, so-called slice levels L1 and L2, are respectively applied. This slice level L or L2 is the charging/discharging circuit output (d)
The drive time T1 signal (e) or drive time T2 signal (f) is generated by the rise and fall of the drive time T1 signal (e) or the drive time T2 signal (f). These drive time TI and T2 signals and the above print pattern signal (C)
is input to the drive circuit 7 to drive the dot print head 9.

As the drive circuit 8, for example, one shown in FIG. 6 is used. To explain its operation, Drive Time T+
The transistors TRn and I are turned on by the signal (e), and at the same time, the drive time T2 signal (f) and the print pattern signal (C
), the transistors T Rr to TRn
The one connected to the coil 35 corresponding to the drive pin turns on, and the current becomes, for example, ■ce-TRn+1-L, =T
R, -ov. Next, the transistor T Rn
il is turned off and the current flows from Ll-TR1 → D1-Ll,
Finally, TRI is also turned off and 0V-DI-L I-Dn+
1-112 I)-V cc. The current waveform at this time is the drive current (g) shown in FIG.

(Problems to be Solved by the Invention) However, in the conventional dot print head driving method, each dot pin #1, which is driven simultaneously as described above,
#2, #3...#n drive time T1 signal (e)
Since the drive time T2 signal (f) and drive time T2 signal (f) are common to all printers, the following problems arise when trying to improve the print quality and throughput of a serial printer. This point will be explained using FIG. 7.

FIG. 7 shows the drive current (g) and the flight waveform of the dot pin 38 when it is applied to the coil 35, together with the drive time T1 signal (e) and T2 signal (f). In the figure, ■ indicates a suitable flight waveform, and shows a case where, after the dot pin 38 reaches the printing paper P, it is immediately attracted by the core 34, stored in the guide 41, and returned to the origin.

However, the dot pins 38... have different printing times, so in the conventional drive method, even the dot pins, which take the longest printing time for boat fishing and take time to return to the origin, can print sufficiently. A method of increasing the drive time TI or drive time T2 has been adopted.

Therefore, as shown in Figure 7-0, with dot pins that start printing quickly, even though the tip of the dot pin has reached the printing paper P, other dot pins that print relatively slowly can finish printing. As a result, the leading edge of the ribbon remains near the printing paper P even after printing, which tends to cause the ribbon to get caught.Also, since the drive time T1 or drive time T2 is set longer, There is a problem in that extra energy is required to be supplied, and the amount of heat generated also increases, making it impossible to improve throughput.

(Means for Solving the Problems) The present invention is a method for driving an impact type dot print head, in which a piezoelectric element provided in each dot head detects the moment when the tip of a dot pin reaches printing paper for each dot pin. This is a dot print head driving method characterized by detecting and individually controlling the timing of each dot pin's return to its origin.

(Function) The spring release type head according to the present invention includes an armature 3 as a member that transmits the movement of the plate spring 36 to the dot pin 38.
7 is used (see Figure 9 below). The operation of this armature 37 will be explained using FIG. 8. In Figure 8,
37a, the leaf spring 36 is attracted to the core 34 and the dot pin 3
8 is at the origin (before printing starts), 37b is the dot pin 38 just before printing, and 37c is the dot pin 3
8 is in the state immediately after printing, each armature 37
Indicates the location of As is clear from FIG. 8, the armature 37 is rotated approximately around the zero point shown in the figure by the leaf spring 36 during the period from 37a to 37b. However, immediately after printing, the center of rotation momentarily moves to point M shown in the figure, and the rear end S of the armature 37 protrudes upward in the figure compared to when the center is at point 0.

The piezoelectric element used in the present invention has the function of detecting the impact caused by the protrusion of the rear end S of the armature 37 and converting it into an electrical signal.

(Example) Next, the present invention will be explained with reference to drawings showing embodiments.

The dot print head used in the present invention has the same configuration as the conventional spring-release type shown in FIG. A piezoelectric element is attached. FIG. 9 shows a cross-sectional view of the dot print head used in the present invention taken along a plane including one unit of dot bin and the central axis (not shown), and in the figure, 45 is a detection board provided with a piezoelectric element. It is.

The detection board 45 is sandwiched between a film-like ring sheet 46 and a guide 41 on the yoke 39.
A piezoelectric element is attached to the upper end of the armature 37 opposite to where the dot pin is fixed. As the piezoelectric element, for example, a piezo element can be used. FIG. 10 shows a perspective view looking down on the detection board 45 with the guide 41 in FIG. 9 removed, and in the figure, 47 indicates a piezo element. Detection board 45
consists of a thin plate ring portion 45a and a number of tongue pieces 46b corresponding to the number of dot pins projecting from the ring portion 45a for each dot pin in the direction of the dot pins. Further, this tongue piece 46b is provided with a U-shaped cavity 46c, and a small tongue piece 4 is provided in the tongue piece 46b in the opposite direction to the direction in which the tongue piece 46b extends.
6d is formed. A piezo element 47 is attached to the surface near the tip of this tongue piece 46d.

In this way, since the piezo element 47 is installed in a buffering manner by the double tongue piece, the piezo element 47 has a structure that is not easily affected by vibrations or shocks other than itself.

Next, a method for driving a spring release type head according to the present invention will be explained with reference to FIGS. 1 and 11. FIG. 1 is a block diagram showing an example of a method for controlling a spring release type head according to the present invention. In the figure, 1 is a command circuit, 2 is a drive time generating circuit, 3 is a drive circuit, 4 is a dot print head having the configuration shown in FIG. 9, and 5 is an impact detection circuit. Further, FIG. 11 is a drawing showing an example of a timing chart of the dot print head control signal, and among the symbols in the figure, i indicates the impact detection circuit output, and other symbols have the same meanings as in FIG. 4. .

First, the command circuit 1 outputs a print pattern signal (C) corresponding to each dot pin in response to the timing signal (a). At the same time, the drive signal (b) is input to the drive time generation circuit 2 shown in FIG. 1, and a drive time T1 signal (e) and a drive time T2 signal (f) are generated. The control process in this area is similar to that of the prior art, and as the drive time generating circuit 2, for example, the one shown in FIG. 5 mentioned above can be used. Then, this drive time T1 signal (e) and drive time T2 signal (
The dot print head 4 is driven by the drive circuit 3 using the print pattern signal (C) and the impact detection circuit output (i).

As the impact detection circuit 5, for example, one shown in FIG. 12 is used. The timing chart (13th
When the dot pins 38 collide with the printing paper, an output (2A) is produced from the piezoelectric element attached to each dot pin. This output (A
) is amplified by an amplifier, it becomes the waveform of (B). When this waveform is compared with a reference voltage, a pulse as shown in (C) is output. Next, when this output (C) is applied to the flip-flop 74LS107, the impact detection circuit output (i
) is obtained as the flip-flop output (E). Note that the flip-flop output (E) is reset by the drive signal (D), and the output (E) changes from low level to high level.

Further, as the drive circuit 14, for example, one shown in FIG. 14 is used. To explain its operation, transistors TRn and I are turned on by the drive time T1 signal (e), and at the same time, by the AND output of the drive time T2 signal (f), the impact detection circuit output (i), and the printing pattern signal (C), The transistors TRI to TR connected to the coils 35 corresponding to the drive bins are turned on.

At this time, for example, if the first bin of the dot pins is driven, the current is vcc-TRn+1-L1→TRl
It flows like -0V. Next, transistors TRn and l are turned off, current flows from -TRI -DI to L1, and when the impact detection circuit output (i), which is output when the dot pin reaches the printing paper, becomes a low level, transistors TR, can be cut. The current waveform at this time is the drive current (g) shown in FIG. Although the drive time 'r2 (f) may not be provided in this circuit, it is used for protection when the dot pin does not reach the printing paper.

(Effects of the Invention) Since the dot print head driving method of the present invention has the above configuration, the dot pins are not caught on the ribbon, and the dot pins can be driven with minimum energy. can.

This point will be explained with reference to FIG. Figure 15 shows
Drive current (g) when driven by the method of the present invention
・Dot pin 3 when this is energized to coil 35
The flight waveform of No. 8 is the drive time T1 signal (e) and drive time T2 signal (f), which are control pulses of the drive circuit.
) and the impact detection circuit output (i), etc., and should be compared with FIG. 7 according to the prior art. As shown by the waveforms ■ and ■ in the figure, according to the method of the present invention, the timing of the return of the dot pin to the origin is independent of the printing time of the dot pin, and is controlled by the dot pin. In principle, it is possible to eliminate the dot pin from getting caught on the ribbon, and the power required to drive the dot pin can be reduced as much as possible.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a control circuit according to the present invention, Fig. 2 is a sectional view of a conventional spring release type head, Fig. 3 is a block diagram of a conventional control circuit, and Fig. 4 is a timing diagram of a conventional control circuit. Chart, Figure 5 is a detailed diagram of the drive time generation circuit,
FIG. 6 is a detailed diagram of a conventional drive circuit, FIG. 7 is a diagram showing the flight waveform and drive current of a conventional dot pin, FIG. 8 is a diagram showing the operation of an armature, and FIG. 9 is a diagram of a spring according to the present invention. 10 is a partial perspective view of the spring-released head according to the present invention, FIG. 11 is a timing chart of the control circuit according to the present invention, and FIG. 12 is details of the impact detection circuit according to the present invention. 13 is a timing chart of the impact detection circuit according to the present invention, FIG. 14 is a detailed diagram of the drive circuit according to the present invention, and FIG. 15 is a diagram showing the flight waveform and drive current of the dot pin according to the present invention. It is. 1... Command circuit, 2... Drive time generation circuit,
3... Drive circuit, 4... Dot print head, 5
...Impact detection circuit, 31...Magnet, 3
4... Core, 35... Coil, 36... Leaf spring,
37... Armature, 37a... Armature state before printing starts, 37b
... Armature state immediately before printing, 37c... Armature state immediately after printing, 38... Dot pin,
45...Detection board, 47...Piezo element. Patent Applicant: Oki Electric Industry Co., Ltd.Professor of i-flag circuit according to the present inventor No. 9 1!2!1 Cross-sectional view of conventional spring release type head Figure 2 Tonbu tile generation cycle 'Live circuit Qllllll Figure 6 9 showing the flight waveform and drive tit of the conventional dot pin
Fig. 7 shows the operation of the armature Fig. 8 A sectional view of a spring-released type heel with 13 series of A1 blades FIG. 14(e) Drive time T, signal FIG. 15 is a diagram showing the flight waveform of time 1 for a dot and drive tJR according to the present invention.

Claims (1)

[Claims] In a method for driving an impact-type dot print head, a piezoelectric element provided in each dot print head detects the moment when the tip of a dot pin reaches the printing paper for each dot pin, and A method for driving a dot print head, characterized by independently controlling the timing of each return to its origin.