JPH04308768A - Impact dot head - Google Patents

Abstract

PURPOSE:To obtain an impact dot head capable of compensating the magnetic attraction force immediately after the start of the supply of a current and capable of performing high speed printing by arranging a piezoelectric element between a damper holder and a damper and supplying a current to the piezoelectric element for an extremely short time at the time of the start of the supply of a current to a coil to impart minute displacement to a lever. CONSTITUTION:In an impact dot head having a lever 16 driving a wiper 8, the damper 17 supporting a lever 16 in a contact state at the time of non- printing and the damper holder 5 supporting the damper 17, a piezoelectric element 19 is arranged between the damper 17 and the damper holder 5.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impact dot head.

0002

[Prior Art] Generally, when printing, an impact dot head rotates a lever by energizing a coil wound around the core and uses magnetic attraction force to drive a wire fixed to or in contact with the tip of the lever. , the end of the wire collides with the ink ribbon on the printing paper surface to form dots. By the way, the current flowing through the coil gradually increases from the start of energization due to the influence of the inductance of the coil, so the lever cannot rotate at the same time as energization starts, but operates with a time delay. Furthermore, the lever requires a long acceleration time to obtain the kinetic energy necessary for printing due to the lever's own moment of inertia, which has been an obstacle to achieving high-speed printing. For this reason, in impact dot heads that require high-speed printing, the number of turns in the coil is minimized to suppress inductance and the current rises quickly, and the lever is made thinner to reduce weight.

0003

[Problem to be solved by the invention] However, since the generated electromagnetic force is proportional to the product of the current flowing through the coil and the number of turns of the coil, in order to obtain the specified printing force, the current value must be increased by the amount of the number of turns of the coil. This increases power consumption and requires a large-capacity power supply. Furthermore, the heat generated in the coil is proportional to the square of the current value, so when the print head is continuously driven, it tends to reach high temperatures, and to protect the head, the printing speed must be reduced or printing may be temporarily stopped when the temperature is high. , the throughput will drop.

[0004] In addition, even if the lever is to be made lighter and faster, it must be strong enough to withstand the impact force during printing, and if the strength is insufficient, the lever may break due to fatigue during long-term use. It becomes impossible to print. Furthermore, since the lever constitutes a part of the magnetic circuit, making the cross-sectional area of the lever too small increases magnetic resistance, leading to a decrease in magnetic attraction, which is contradictory to increasing speed.

For the above reasons, conventional impact dot heads have had the problem that it is extremely difficult to increase the speed. The present invention solves these conventional problems and provides an impact dot head that is capable of high-speed printing while maintaining high efficiency and reliability without increasing power consumption or reducing lever strength. It's there.

[0006]

[Means for Solving the Problems] In order to solve the above problems, the impact dot head of the present invention includes a lever that drives a wire, a damper that abuts and supports the lever when not printing, and a damper holder that supports the damper. The impact dot head has a feature that a piezoelectric element is disposed between the damper and the damper holder.

[0007]

[Embodiment] An embodiment of the present invention will be explained based on the drawings. FIG. 1 is a sectional view of the impact dot head of the present invention. A tip guide 6 is attached to the nose 1, and the tip guide 6 arranges the wires 8 at predetermined positions. A guide holder 18 is inserted into the nose 1, and the guide holder 1
8 holds the intermediate guide A7. Nose 1
A printed wiring board 10 is disposed between the frame 2 and the frame 2 with an insulating member 9 interposed therebetween. The frame 2 has a cylindrical shape, and a plurality of cores 14 are erected in parallel with each other from the bottom surface thereof. These cores 14 have coils 20
is inserted and connected to the printed wiring board 10. The inner ring part 11 of the frame 2 has an intermediate guide B1.
A spring holder 13 is attached with the spring holder 2 interposed therebetween. The spring holder 13 is equipped with the same number of return springs 15 as the cores 14, and at the same time, the vicinity of the wire 8 fixed portion of the lever 16 is guided by the slit portion of the spring holder 13. Next, a side yoke A3 and a side yoke B4 are attached to the upper surface of the frame 2, and a lever 16 facing the core 14 is attached to the side yoke A3 and side yoke B4. The wires 8 are fixed to the tips of these levers 16, and are urged in the return direction by the return springs 15. Further, a damper holder 5 is attached so as to be in contact with the upper surface of the spring holder 13, and this damper holder 5
A damper 17 is attached to the center portion of the housing via a piezoelectric element 19. The tip of the lever 16 is in contact with this damper 17.

In such a configuration, the coil 20 connected to the printed wiring board 10 is selectively energized according to the print signal, and the magnetic flux excited by the coil 20 is distributed to the frame core portion 14, the frame 2, the yoke A3, and the yoke. B4
, through a loop that passes through the lever 16 and returns to the frame core portion 14 . As a result, a magnetic attraction force is exerted between the frame core portion 14 and the lever 16, causing the lever 16 to advance.
A wire 8 fixed to the tip of the wire 6 applies an impact force to the printing paper to form dots.

Incidentally, the impact dot head of the present invention energizes the piezoelectric element 19 for a very short time at the same time as the coil 20 starts energizing, displaces the piezoelectric element 19, and causes the lever 16 and the wire 8 to protrude through the damper 17. It was made to make a slight displacement in the direction. Although the displacement amount is generally small as a characteristic of a piezoelectric element, a large force can be obtained with little time delay from the start of energization, so it is possible to compensate for the lack of magnetic attraction force immediately after the coil 20 is energized. In this way, the lever 16 is given an initial velocity by the piezoelectric element 19, and the lever 16 leaves the damper 17, and is then accelerated by the magnetic attraction force and applies an impact force to the printing paper to form a dot. Therefore, by energizing the piezoelectric element 19 at the same time as the coil 20 is energized as described above, it is possible to speed up the rise of the wire without increasing the energization to the coil 20 or reducing the weight of the lever. An impact dot head for printing was realized.

FIG. 2 is a diagram showing a wire displacement waveform when the piezoelectric element 19 using the longitudinal strain effect having the shape shown in FIG. 3 is incorporated into the impact dot head shown in FIG. 1, and the piezoelectric element 19 is not driven. Compared to the wire displacement (indicated by a broken line) when the piezoelectric element 19 is driven, the wire displacement (indicated by a solid line) when Ta2=
It took 350μsec, but Ta1=250μ
sec, and for the wire return time Tb2=
It took 600μsec, but Tb1=500μ
It was shortened to sec.

As a result, the responsable frequency is
9 The frequency that was 1.3kHz when not driven is now 1.3kHz when piezoelectric element 1 is not driven
By driving 9, the frequency became 1.5 kHz, and a remarkable effect was recognized in achieving high printing speed. Regarding power consumption, when comparing the input energy when the piezoelectric element is not driven and the voltage applied to the coil 20 is increased to obtain a response frequency of 1.5kHz, the input energy is lower when the piezoelectric element is not driven. However, by driving the piezoelectric element 19 as in the present invention, 1.5 kHz was required.
When the response frequency of z was obtained, the total input energy of the piezoelectric element 19 and the coil 20 could be suppressed to 4.5 mJ. Therefore, it was possible to realize an impact dot head that does not require an increase in power supply capacity as the speed increases, unlike conventional print heads, and reduces throughput reduction due to heat generated during continuous printing.

Here, the results shown in FIG. 4 were obtained regarding the length of the pulse for driving the piezoelectric element 19 and the rise time Ta of the wire 8. As shown in the figure, the energization pulse length of the coil 20 is Pw1, and the energization pulse length of the piezoelectric element 19 is Pw2.
When Pw2<0.01Pw1, the piezoelectric element force does not act sufficiently, so there is no difference in the rise time Ta of the wire 8 compared to when the piezoelectric element is not driven (Pw1=0). Further, in the range of Pw2>0.3Pw1, the rise time Ta is not shortened even if Pw2 is increased. This indicates that the piezoelectric element 19 continues to be displaced even after the lever 16 has protruded due to the magnetic attraction force. Therefore,
The effective Pw2 for shortening the rise time of the wire 8 by the piezoelectric element 19 is 0.01Pw1<Pw2<
It has been found that it is appropriate to use it within the range of 0.3Pw2.

FIG. 6 shows a plurality of levers 1 as a second embodiment.
6 a plurality of piezoelectric elements 19 and dampers 2 corresponding to each
An example in which 0 is provided will be shown. The first embodiment shown in FIG. 3 has a simpler structure than the second embodiment shown in FIG. The piezoelectric element 19 must be constantly operated periodically. Therefore, as shown in FIG. 5, the lever 16 in the non-printing state is also displaced by the piezoelectric element 19. Since the displacement of the lever 16 by the piezoelectric element 19 is sufficiently smaller than the stroke of the lever 16 during printing operation, the lever 16 in a non-printing state may jump out due to the displacement of the piezoelectric element 19, and the tip of the wire 8 may reach the paper surface, resulting in incorrect printing. Although this is not the case, since the lever 16 is vibrated even during non-printing, sliding wear is accelerated. On the other hand, in the second embodiment shown in FIG. 6, since each lever 16 is independent, multiple signal lines are required to conduct electricity to the piezoelectric element 19, and although the structure and control circuit are complicated, It is only necessary to drive the piezoelectric element 19 corresponding to each lever 16 during operation, and since the lever 16 in a non-printing state is not vibrated, there is no sliding wear due to vibration during non-printing, and durability is improved. Although the above-mentioned embodiment is an example that utilizes the longitudinal strain effect of the piezoelectric element, piezoelectric elements may be stacked and used depending on the amount of displacement. Furthermore, a similar effect may be obtained by using a bimorph type piezoelectric element or the like.

[0014] The above explanation has been given using a direct attraction type impact dot head as an example, but a spring charge type impact dot head using a permanent magnet can also be applied by applying a minute displacement to a lever using a piezoelectric element, thereby increasing the magnetism of the permanent magnet. It is clear that the present invention is applicable because the opening current applied to the coil to release the attraction force can be kept small.

[0015]

[Effects of the Invention] As explained above, according to the present invention, a piezoelectric element is disposed between a damper holder and a damper, and when the coil starts to be energized, the piezoelectric element is energized for a very short time to give a minute displacement to the lever. By compensating for the lack of magnetic attraction immediately after power is turned on, the impact dot head is capable of high-speed printing while maintaining high efficiency and reliability without increasing power consumption or reducing lever strength. realizable.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of an impact dot head of the present invention.

FIG. 2 is a diagram showing the displacement of the wire and piezoelectric element of the impact dot head of the present invention.

FIG. 3 is an exploded perspective view of the damper section of the impact dot head of the present invention.

FIG. 4 is a diagram showing the wire rise time characteristics of the impact dot head of the present invention.

FIG. 5 is a diagram showing the displacement of the wire and piezoelectric element of the impact dot head of the present invention.

FIG. 6 is an exploded perspective view of the damper portion of the impact dot head of the present invention.

[Explanation of symbols]

1 Nose 2 Frame 3 Side yoke A 4 Side yoke B 5 Damper holder 6 Tip guide 7 Intermediate guide A 8 Wire 9 Insulating material 10 Printed wiring board 11 Frame inner ring part 12 Intermediate guide B 13 Spring holder 14 Frame core part 15 Return spring 16 Lever 17 Damper 18 Guide holder 19 Piezoelectric element 20 Coil

Claims (1)

[Claims] 1. An impact dot head having a lever that drives a wire, a damper that abuts and supports the lever when not printing, and a damper holder that supports the damper, wherein a piezoelectric element is disposed between the damper and the damper holder. The impact dot head is characterized by: