JPH04208470A - Impact dot printer - Google Patents

Abstract

PURPOSE:To print with a high grade by a method wherein the number of driven times of a print wire is counted at a count circuit, the number of driven times is replaced by an abrasion loss at a part influencing a crater quantity of the print wire of a print head, and a feedback circuit drive time for energizing an exciting coil is set in accordance with the frequency. CONSTITUTION:When a print wire 2 of a head 21 is driven by a head driver 22, it is counted at a count circuit 23 through a control circuit 20. When the counted value becomes a set number of times, a drive time table means 25 is controlled through the control circuit 20 and a feedback circuit drive time for driving an exciting coil 13 is switched to a time table which becomes longer than before. Then, a proper coil drive time is reset for a distance between a tip of the print wire 2 and a print medium which are widening due to abrasion, and a decreasing printing force is reinforced so that a high printing grade can be maintained again. Thus, substantially the same printing force is given during a guaranteed life and a high grade printing can be carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an impact dot printer that performs printing by impact driving a printing wire.

<Conventional technology> Conventionally, impact printers, which drive a print wire to impact a print medium via an ink ribbon and print using that force, have a high degree of freedom in the print medium, and are relatively inexpensive. It is used in many fields, including output devices such as processing systems.

Impact printers include a wire dot printing type, a plunger type, a spring charge type, and a clapper type.

Among these, the spring-charged type has an armature to which the printing wire is fixed, which is swingably supported by an impact leaf spring, and this armature is previously attached to the impact leaf spring by a permanent magnet against the elastic force of the spring. The core is attracted to the core, and when printing, a coil wound around the core is energized to generate magnetic flux in the opposite direction to the permanent magnet, thereby opening the armchair. There is a demand for higher speeds, and this spring-charged wire dot print head, which has good high-speed response, is being widely used.

FIG. 3 is a longitudinal sectional side view of essential parts showing an example of a conventional wire dot printing lead.

In the figure, this print head is a spring-charged print head with an annular base frame 1 made of magnetic material.
is formed based on the base frame l, and multiple (9 to 24 are common, but only one is shown in the figure) on this base frame l.
A printing wire 2 is arranged. Further, on the base frame 1, there are provided yokes 3, each having an annular shape. Permanent magnet 4
and yoke 5 are sequentially stacked and fixedly connected together with screws (not shown). Further, one end of an impact leaf spring 6 corresponding to each of the plurality of printing wires 2 is fixed on the yoke 5 via a spacer yoke 7, and in addition, an armature yoke 8 and an impact leaf spring 6 are fixed on the upper side of the impact leaf spring 6. A guide frame 3 is provided. The other end of the impact leaf spring 6 is a free end that protrudes toward the center, and one end of the armature 9 is fixed to the upper surface of the tip. On the other hand, a printing wire 2 is fixed to the tip portion on the other end side of the armature 9 in a state of protruding upward in the figure. Also, on the base frame 2, there is a lower side of each impact leaf spring 6! A core 10 made of a magnetic material such as iron (Fe)-cobalt (Co) alloy is attached thereto. In addition, an excitation coil 13 is wound around the outer peripheral surface of the core 10, and the excitation coil 13 and the core 10 form an excitation magnet 14. This excitation coil 13 is soldered onto a printed circuit board 16 that is attached to the lower surface of the base frame 1 via an insulating rubber packing 15. In addition, on the bottom side of the base frame 1,
The cap 11 is attached to cover the printed circuit board 16, and the clamper 12 is further integrated into the circumferential surface of the entire print head.

In this print head, the free end of the impact plate spring 6 is able to swing vertically around the fixed part with the armature yoke 8, and this swing is caused by the movement of the permanent magnet 4 and the excitation magnet 14. done under control. That is, when the current to the excitation coil 13 is cut off and the excitation magnet 14 is off, only the magnetic flux of the permanent magnet 4 works effectively, and the magnetic flux of the permanent magnet 4 at this time is transferred to the yoke 5. Spacer yoke 7, armature yoke 8. Armature9. It flows through the core 10° base frame 1 and returns to the permanent magnet 4 again. At this time, the impact plate spring 6 is bent to attract the armature 9 toward the core 10 and maintain this state. As a result, the printing wire 2 is drawn into the guide frame 3 and held in a non-printing state. Note that FIG. 3 shows this state.

On the other hand, when a current is applied to the excitation coil 13 and the excitation magnet 14 is turned on, the magnetic flux of the excitation magnet 14 is transferred to the core 10. Armature9. Armature yoke8. Spacer yoke 7, yoke 5° permanent magnet 4. base frame 1
In the route through which the magnetic flux returns to the core 10, it flows in the opposite direction to the magnetic flux of the permanent magnet 4, canceling out the magnetic flux of the permanent magnet 4.

Then, the adsorption force on the side of the core 10 that was holding the impact leaf spring 6 by bending is canceled out and released, and the impact leaf spring 6 is released. Then, until then, the tip side of the impact leaf spring 6 becomes the impact leaf spring 6.
The repulsive force causes the armature 9 to rotate upward in the direction of arrow A in the figure. Further, the printing wire 2 is instantaneously projected by this rotation, and the projected printing wire 2 impacts the printing medium on the platen via an ink ribbon (not shown), thereby performing printing. Further, once the impact leaf spring 6 is released together with the armature 9, the power to the excitation coil 13 is cut off again, and the impact leaf spring 6 is connected to the core 1 with the printing wire 2 that has finished impacting the printing medium.
It is held on the 0 side.

Therefore, if this operation is selected for each of a plurality of print wires 2 and performed while moving the print head in the row direction,
Characters and graphic patterns made up of dots can now be printed on printing paper.

Next, in FIG. 4, the excitation coil 13 is energized and the excitation magnet 14 is
This figure shows a drive circuit for driving switching transistors Tr2. Tr3 and diodes DI, D2, which form a feedback circuit for preventing back electromotive force. It is composed of D3, a power supply 15, and the like. One terminal of each excitation coil 13 corresponding to each of the plurality of printing wires 2 is connected to the transistor Tr.
connected to i. Further, a voltage is supplied from the power supply 15 to this transistor Tri. On the other hand, the other terminal of each excitation coil 13 is connected to the transistors Tr2, Tr3, . . . to be selected respectively;
connected to earth.

FIG. 5 shows an example of a drive current waveform flowing through the drive circuit shown in FIG. 4. Therefore, the operation of the drive circuit shown in FIG. 4 will be explained below together with the waveforms shown in FIG.

First, in this drive circuit, in FIG.
Therefore, a current is passed through the transistor Tri for a time L1 in synchronization with the drive cycle of the printing wire 2, and the transistor Tri is turned on every drive cycle. On the other hand, in the same figure, a current is passed from the drive B to the transistor Tr2 (or Tr3.--) corresponding to the selected excitation coil 13 for a time (tl+t2), and the symbol T1 in FIG.
An open current flows in the section. Then, when the transistor Tri is turned off, the exciting coil 13. Transistor Tr2. Diode D3. In the loop of the excitation coil 13, an open current indicated by the symbol 12 in FIG. 5 flows through the transistor Tr.
2 is turned off, the excitation coil 13. Diode Dl,
Power supply 15, diode D3. An open current indicated by reference numeral 13 in FIG. 5 flows in the loop of the excitation coil 13. However, ′
The power supply capacity here is sufficient as long as it can supply energy for the time t1 when the transistor Tri is on.

<Problems to be Solved by the Invention> However, as printing speeds have increased in recent years, the wire drive frequency has increased, and as a result, as shown in FIG. 6, the wire drive period S shown in FIG. There was a problem in that the difference from the wire reciprocating time (TA) shown in FIG. Also, when dot printing is performed by the printing wire 2, the eighth
As shown in the enlarged figure, when the bottom surface of the impact plate spring 7, which is formed by fixing the armature 9 holding the printing wire 2, collides with the core 10, the tip portion 10a of the core 10 is worn out by this collision energy. , this wear appears as a dent amount δ of the printing wire 2. That is, as shown in FIG. 7, it can be seen that the amount of depression δ increases in proportion to the number of times the print head is driven. Also, due to the denting of the printing wire 2, the stroke from the tip of the printing wire 2 to the platen (wire flight waveform) is longer than that shown by the dotted line in FIG. The wire arrival time to the platen (TF) and the wire reciprocating time (TA) increase near the end of the printer's life, and at the same time the wire arrival time to the platen (TF) and the wire reciprocating time (TA) also increase as shown by the dotted line compared to the state at the beginning of printer use, which is shown by the solid line in Figure 6(b). This increases when the product is near the end of its life after many years of use. This is also increased by the increased rattling of the carriage in which the wire dot printhead is mounted. This causes problems such as a decrease in printing power or drop-out of dots (dotting), resulting in a decrease in print quality.

Therefore, if an attempt is made to prevent a decrease in printing force by lengthening the coil driving time from the beginning, the magnetic flux generated from the excitation coil 13 becomes difficult to cut. Also, along with this, printing
The return of the roller 2 becomes slow, making it impossible to follow repeated movements. Additionally, there were other problems such as the printing wire getting caught on the ink ribbon and causing malfunctions.

The present invention has been made in view of the above-mentioned problems, and its purpose is to provide an impact dot printer that can always obtain high printing quality without being affected by the amount of denting of the printing wire caused by use.

Means for Solving the Problems> In order to achieve the above object, the impact dot printer according to the present invention includes a count circuit that counts the number of times the printing wire is driven, and a feedback circuit that powers the excitation coil for demagnetization. The drive time table means includes at least two different types of time tables, and a control circuit that switches the time table to be used according to the number of drives detected by the counter circuit.

According to this, the number of times the printing wire is driven is counted by a counting circuit, and this number of driving times is replaced as the amount of wear on the part of the print head that affects the amount of denting of the printing wire, and the current flow to the excitation coil is controlled. Feedback circuit driving time can be set. Therefore, by adjusting the driving time according to the frequency of use, it is possible to maintain substantially the same printing power throughout the guaranteed life and perform high-quality printing.

<Example> Hereinafter, an example of the present invention will be described in detail using the drawings.

FIG. 1 is a block diagram of an impact dot printer according to an embodiment of the present invention. In this example, the mechanical configuration and drive circuit of the wire dot print head are as follows:
The conventional structure shown in FIGS. 3 and 4 can be used as is. Therefore, in the following description, the same reference numerals as those in FIGS. 3 and 4 refer to the same elements as in FIGS. 3 and 4.

In FIG. 1, this printer has a control circuit (
CPU) 20, a head driver 22 that drives the print wire 2 in the print head 21, and a count circuit 23.
, a reset circuit 24, and a drive time table means 2.
5 is set.

More specifically, as the print head 21, for example, the third
The print head shown in the figure is used as is, and the wire print head drive circuit shown in FIG. 4 is used as the head driver 22 as is.

The count circuit 23 calculates the number of times the print wire 2 of the print head 21 is driven by the head driver 22 and the control circuit 20
Supported by and counting.

The reset circuit 24 can reset the value counted by the count circuit 23 in response to an instruction from the control circuit 20, and is activated when the print head 21 is replaced at the end of its life.

The drive time table means 25 calculates the value counted by the count circuit 23, for example, every 150,000 times, when the excitation coil 13
By switching this time table, it is possible to supplement the printing force of the printing wire 2 due to drive wear and set the appropriate coil drive time to always obtain a constant printing pressure. It has become.

Therefore, in the impact dot printer configured as described above, when the print wire 2 of the head 21 is driven by the head driver 22, this is counted by the count circuit 23 via the control circuit 20. Further, when this count value reaches 150,000 times, the drive time table means 25 is controlled via the control circuit 20, and the time table is switched to a time table in which the feedback circuit drive time for driving the excitation coil 13 is longer than before. It will be done. Then, the coil driving time is reset to be appropriate for the distance between the tip of the printing wire 2 and the printing medium, which is being worn out and expanding. This compensates for the printing power that had been decreasing, making it possible to maintain high printing quality again. In this case, since the distance between the printing wire 2 and the printing medium is larger than the distance set during the initial assembly adjustment, the printing wire 2 will not be caught on the ink ribbon, and the diodes Di, D2.
Since only the driving time of the feedback circuit section (see FIG. 5) including D3 and the like is lengthened, there is no increase in the load on the power supply 15.

Note that the above time table is switched every 150,000 times, but the standard number of times to switch, that is, the frequency, is not limited to 150,000 times, but first is the 100 millionth time, then 100 million times, and then the 100 millionth time. It is also possible to sequentially switch at the 500 millionth, 200 million, 250,000, 300 million, and so on. When the print head 21 is replaced at the end of its life, the reset circuit 24 resets the count value in the count circuit 23 and starts counting again from the beginning.

In addition, there are generally 9 to 24 printing wires 2 counted by the counting circuit 23, and the number of times they are driven is not uniform. Now, the number of times the center bin 2a is driven, where the distance 1 between the tip of the printing wire 2 and the platen 31 is the smallest, is counted.

<Effects of the Invention> As explained above, according to the impact dot printer according to the present invention, the number of times the print wire is driven is counted by the counting circuit, and the number of times the print wire is driven is counted by the part of the print head that affects the amount of indentation of the print wire. Since the drive time of the feedback circuit for energizing the excitation coil is set according to the frequency, high-quality printing can be performed with substantially the same printing force throughout the guaranteed life.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the structure of an impact printer according to an embodiment of the present invention, Fig. 2 is a diagram for explaining printing wires to be counted when a round brine type platen is used, and Fig. 3 4 is a longitudinal cross-sectional side view of essential parts showing an example of a general wire dot print head, FIG. 4 is a drive circuit diagram of a general wire dot print head, and FIG. Figure 6 is a diagram showing the waveform, Figure 6 is a diagram explaining the relationship between the wire drive cycle and wire reciprocating time, Figure 7 is a diagram showing the relationship between the number of times the printing wire is driven and the amount of dent in the printing wire, and Figure 8 is a diagram showing the relationship between the number of times the printing wire is driven and the amount of indentation of the printing wire. FIG. 3 is a diagram for explaining the reason why a print wire is indented by driving the print wire. 2... Printing wire, 4... Permanent magnet, 6... Leaf spring for impact, 9... Armature, 13... Excitation coil, 14
... Excitation magnet, 20 ... Control circuit, 21 ... Print head, 23 ... Count circuit, 25 ... Drive time table means. Patent applicant Oki Electric Industry Co., Ltd. Agent
Patent Attorney Funabashi Kuni Rule 2: fPf phi V 2VJP'f'Het Fig. 2 I Base frame Fig. 3 ll - Pf fig.

Claims (1)

[Claims] A permanent magnet attracts an armature to which a printing wire is fixed via an impact leaf spring, energizes an excitation coil to cancel the magnetic flux of the permanent magnet, and releases the impact leaf spring. The impact dot printer that causes an impact motion of the printing wire has at least two types of time tables having different driving times: a count circuit that counts the number of times the printing wire is driven, and a feedback circuit for energizing the excitation coil. A wire dot print head, comprising: drive time table means; and a control circuit that switches the time table to be used according to the number of drives detected by the counter circuit.