JPS59158265A - Impact type print head - Google Patents

Abstract

PURPOSE:To achieve a high-speed printing with a stable action by covering other electrode surface of a piezo-electric porcelain with a flexible insulation film. CONSTITUTION:A roughly triangular elastic plate 9 and a piezo-electric porcelain 10 of almost the same shape as it with a pair of electrodes on both surfaces thereof and one electrode surface of the piezo-electric porcelain 10 joined with the elastic plate 9 by an adhesive or the like to form a print hammer with a non-symmetrical bimorph type vibrator. A print wire 11 is mounted at one end of the print hammer, namely, the part as free end and the other electrode surface of the piezo-electric porcelain 10 is covered with a flexible insulation film 12. A base plate 13 is arranged on the side of an elastic plate 9 of the print hammer. Then, an upper plate 13 is arranged or formed on the side of the piezo-electric porcelain 10 of the print hammer, a limiter bank 15 at the free end thereof 14 and a spacer 16 between the flexible insulation film 12 and the upper plate 14 respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an electrostrictive-driven impact print head that prints by impacting a print medium with a print wire using the electrostriction effect of piezoelectric ceramics.

[Prior art]

In recent years, impact type dot matrix printers have been widely used as input/output devices for electronic computers, and a wide variety of print heads are currently being developed. Among these, electromagnetic drive type impact print heads utilize electromagnetic energy, and are broadly divided into two types based on their operating principles: electromagnetic attraction type and electromagnetic release type. Since it has the great advantage of being simple, it can be well adapted to the design goals of recent impact printheads, which are smaller size, higher speed, lower power consumption, and higher density of printed dots. This type of impact-type print head has now emerged with a dot repetition frequency of up to 2.5K H7.

Most of the current impact type print heads are of this electromagnetic drive type9, which are highly reliable and have a proven track record in the market. However, as is well known, electromagnetic drive type impact print heads require multiple pairs of armatures, magnetic circuits, excitation coils, etc. Due to their configuration, it is difficult to achieve significant weight reduction and high integration, and in addition, excitation Heat caused by Joule heat generated by the coil and eddy current flowing in the magnetic circuit, and the instability of armature operation due to this heat generation (C), thermal deterioration of excitation coils, etc., and the need to install cooling fins to dissipate heat. It also has many drawbacks.

For these reasons, electrostrictive drive type impact print heads that utilize piezoelectric ceramics have recently begun to attract attention. but,
As is well known, printing hammers with a bimorph configuration require a conventional digrating gap and have the problem that it is extremely difficult to obtain the impact force necessary for printing.To solve this problem, It is necessary to design a printing hammer that has the same initial acceleration of the printing hammer operation as a conventional electromagnetically driven impact printing head and high dot frequency characteristics.

Therefore, from this point of view, as a recent example, Figure 1 (
Electrostrictive drive type printing normal machines as shown in A) and (B) have been proposed. That is, FIG. 1(A) is a side sectional view,
FIG. 1(B) is a front view, in which 1 is a printing hammer with a symmetrical bimorph configuration, 2 and 3 are piezoelectric ceramics that form the printing hammer 1, 4 is a clamping member that supports one end of the printing hammer 1, and 5
is a printing wire attached to the free end of printing hammer 1, 6
7 is a printing ribbon, 7 is a printing medium, and 8 is a platen.

FIG. 2 is a diagram showing the relationship between the movement of the printing wire 5 and time. The principle of operation will be explained with reference to this diagram. First, a voltage is applied to one piezoelectric ceramic 2 of the printing hammer 1 to create piezoelectric distortion. is applied, and after time t1'r a negative potential is applied to the printing hammer 1. At the same time, the electric charge stored in the piezoelectric ceramic 2 is released, and at the same time, a voltage is applied to the other piezoelectric ceramic 3 to increase its potential. Add to the negative potential in the forward direction.

The printing wire 5 is rapidly accelerated by such drive control, and after time t2, the printing wire 5 completely passes the equilibrium point.
After time t5 has elapsed, the tip of the printing wire 5 collides with the printing medium γ wound around the platen 8 via the printing ribbon 6, and pixels are formed on the printing medium γ.

As is clear from the operating principle explained above, in the conventional electrostrictive drive type impact type print head, it is necessary to apply a negative potential to the printing/printing area within the movement period that forms one dot pixel. Therefore, it is very disadvantageous to obtain the high dot frequency required for high-speed printing, and in principle, repeated positive and negative bending stress acts on the two piezoelectric ceramics, so the piezoelectric ceramic becomes particularly brittle under positive stress. There were drawbacks such as the fact that it was easy to destroy the piezoelectric ceramic it held.

Other recently proposed electrostrictive drive type shearing printheads, most of which are the result of increased mechanical compliance of the printing hammer, are currently being used, although efforts have been made to achieve large displacements. In order to obtain the initial acceleration and high dot frequency of the printing hammer comparable to electromagnetic-driven impact printheads on the market, it is thought that there is still room for improvement in the structure of the printing hammer, and therefore By actively utilizing the fact that piezoelectric ceramics are isotropic in all directions perpendicular to the polarization axis of the surface, we have created a small, high-speed movable printing hammer that can obtain large excitation force and displacement. need to be designed.

Furthermore, the design goals for the print head mentioned at the beginning are of course the goals required for this electrostrictive drive type impact type print head, and it is necessary to create a design that corresponds to the magnetic circuit in an electromagnetic drive type impact type print head. Electrostrictive drive-type impact print heads that do not require printing hammers can be highly integrated, and can be expected to be particularly thin. However, to operate this, a voltage of several hundred volts is currently required, and the charge density on the electrode surface of the piezoelectric ceramic to which this voltage is applied becomes extremely high. Therefore, if dust or the like adheres to the surface of the stain electrode due to electrostatic phenomena, it may short-circuit a pair of electrodes or short-circuit between the electrodes of adjacent printing hammers, causing discharge. There were drawbacks such as unstable operation and noise that caused the printer to malfunction. This is a point that must be kept in mind when making electrostrictive drive type shearing print heads smaller, lighter, and thinner.

[Purpose of the invention]

The present invention was made in order to solve the above-mentioned drawbacks of the prior art, and it is possible to reduce the size, weight, and thickness of ktl, and to perform high-speed printing with stable operation. The purpose of this invention is to obtain an impact type print head that does not cause malfunctions.

[Structure of the invention]

In order to achieve the above-mentioned object, the present invention covers one electrode surface of a piezoelectric ceramic whose one electrode surface is bonded to an elastic plate with a flexible insulating film, and which is formed by this elastic plate and the piezoelectric ceramic. A base plate for preventing rebound and reverse warping, which also serves as a clamp for the printing hammer, is arranged on the elastic plate side of the printing hammer, and an upper plate has a limiter bank on the piezoelectric ceramic side for preventing the printing hammer from flying too far. is arranged.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

3(A) is a perspective view of the printing hammer used in the present invention, and FIG. 3(B) is an exploded view thereof. In the figure, 9 is an approximately triangular elastic plate, and 10 is the elastic plate 9. It is a piezoelectric ceramic that is formed in almost the same shape as the piezoelectric ceramic 10 and has a pair of electrodes on both sides.By bonding and fixing one electrode of the piezoelectric ceramic 10 to the elastic plate 9 with an adhesive or the like, an asymmetric bimorph type can be created. A printing hammer is formed by a vibrator.

A printing wire 11 is attached to one end of this printing hammer, that is, a free end, and a piezoelectric ceramic 1
The other electrode surface of 0 is coated with a flexible insulating film 12.

13 is a base plate disposed on the elastic plate 9 side of the printing hammer, and 14 is an upper plate 1-115 disposed on the piezoelectric ceramic 10 side of the printing hammer.
A limiter bank 16 formed at the free end of the flexible insulating film 12 is in contact with the flexible insulating film 12.

To assemble the spacer 0 arranged between the plates 14, place the printing plate 1 having the printing wire 11 and the flexible insulating film 12 on the base plate 13 as described above, and place the spacer 16 on the other end. After overlapping the plates 14'ff and 14'ff, they are fixed together with screws (not shown).

The present invention can be miniaturized by stacking several printing mats with this structure and forming a unit.

It is lightweight and thin in total 9, and achieves high-speed printing with stable operation without causing malfunctions. In other words, as mentioned above, an electrostrictive drive type impact print head At present, the applied voltage required for printing/driving one meter reaches several hundred volts, and therefore, if dust or the like adheres to the pole surface of the piezoelectric ceramic 100'1L due to electrostatic phenomena, the pair of electrodes This may cause a short circuit between the electrodes or the adjacent printing/'% mark', causing discharge.9 As a result, the operation of the printing hammer became unstable9, and the noise caused This may cause problems such as malfunction of the printer, but as described above, in the printing hammer according to the present invention, the other electrode surface of the piezoelectric ceramic 10, that is, the electrode 1] which was exposed in the conventional print head. The above problem is prevented by covering the entire surface with a flexible insulating film 12.

In addition, since the above-mentioned printing /'-77 utilizes the fact that the piezoelectric ceramic 10 crab is isotropic in all directions perpendicular to the polarization axis of its surface, the fixed end force of the printing wire '-11 is The end surface of the printing wire 11g1ll is inserted between the upper plate 14 and the base plate 13 via a spacer 16 which is formed into an arc shape so that the printing wire 11g1ll is clamped at the arcuate end equidistant from the mounting center of the wire 11. It has a fixed structure. The printing hammer thus formed is a piezoelectric ceramic 10
When driven by applying voltage to the electrodes on both sides,
The resulting state of piezoelectric strain is distributed radially in the radial direction, and this distributed piezoelectric strain is caused by the printing wire 11 shown in FIG.
A) It is necessary to effectively and dominantly act on the desired excitation for flight in the direction of the arrow shown in arrow A), and it is small in size and capable of high-speed driving with large excitation force and displacement with delayed initial acceleration. It becomes a hammer.

On the other hand, with the electrostrictive drive printing hammer, it is necessary to set the steady displacement amount when the full DC voltage is applied to be greater than the platen gap, and print within the acceleration range of the printing hammer. Only then can stable, high-quality printing pixels be obtained. However, the platen gap of printers currently in operation equipped with electromagnetically driven impact type print heads is approximately 0.4 to 0.5 mm, and the platen gap of the printers currently in operation is approximately 0.4~0. If the amount of displacement is made to correspond to this amount, the maximum free flight amount of the printing number 1 in response to the stepwise applied voltage at this time theoretically reaches twice as much as 08 to 1. In other words, the maximum free flight distance is 0.8 to 1 m.
This means that unless there is a printing machine with m, it cannot be replaced by an electromagnetically driven printing machine. However, if the maximum free flight amount is set to 08~1 theory, if the printer's platen gap opens wide due to an unexpected situation, the 1-character hammer will fly in a way that is not originally required. The amount of flight increases the stress acting on the piezoelectric ceramic 10, which may exceed its resistance strength and cause the piezoelectric ceramic 10 to break.

Therefore, in the above-mentioned printing hammer, the upper plate 1
4 is provided with a limiter bank 15 to regulate the flight amount,
This prevents the reverse printing hammer from performing unnecessary free flight. In other words, with the printing hammer described above, even if the printer's platen gap opens wide due to an unexpected situation, the free end of the printing hammer will not reach the limiter bank 15.
In this case, free flight exceeding the set flight amount p is prevented, so breakage of the piezoelectric ceramic 10 can be avoided. This is a graph showing the theoretical values and actual measured values of the flight waveform at each part along the length of the printing hammer when the printing hammer is pressed. As you can see, in the part where x/l is small, it deflects once in the opposite direction as it is driven, and then begins to fly in the forward direction. The reason for this is that the tip, or free end, of the printing mark is affected by a reaction force, ie, a transverse acoustic wave, when it flies, and this becomes a factor that slows down the initial acceleration of the printing mark. However, in the case of printing using the electrostrictive drive method, by appropriately designing the shape and changing the bending stiffness along with the location of the printing mark, the above-mentioned bending in the opposite direction and reverse warping can be reduced. However, it is impossible to reduce this to zero from theoretical analysis, and in practice, due to various design constraints, there is a problem that design consideration cannot be given only to countermeasures against counterattacks. be.

Therefore, in the present invention, as described above, the base plate 13 is arranged on the back side of the elastic plate 9 side toe 9 on which the printing plate is formed, and the base plate 13 is brought into surface contact with the printing plate. This shield prevents reverse warping of the printing/printing area and guarantees the initial acceleration of the printing/printing area.

In addition, the base plate 13 also has the following functions. In other words, the print/) mark is the print wire 1
After 1 fully impacts the printing medium (not shown), in addition to the repulsive force from the printing medium, the printing medium itself releases its own elastic energy, so it is gradually accelerated and its kinetic energy reaches its maximum at the equilibrium position. The electromagnetic clapper armature (herein referred to as a printing hammer) uses a collision absorber (printing hammer) as a mechanism to instantly absorb this kinetic energy.
(Dynamic damper) unit, damper unit that uses anti-vibration rubber and anti-vibration alloy, etc. are all used to suppress the rebound of the armature and increase the dot frequency as a result. However, this is a mechanism that can be adopted because the entire armature moves almost as a rigid body, and when the printing material itself is relatively soft, such as in this method, such a mechanism that locally accelerates and brakes is used. It cannot be easily adopted.

Therefore, in the present invention, by employing the base plate 13 that receives the printing marks on its entire surface, it has the function of preventing reverse warping as described above as well as preventing rebound. In other words,
If we consider the system as a vibration system with one degree of freedom, the print mark will return to an equilibrium position between each part, but if we look at it as a real model using a distributed constant system, the print mark will roughly return to its equilibrium position as shown in Figure 4. It returns to the equilibrium position from the other end, that is, the clamp part side (the part where x/l is small) (the actual measured value is the same),
This phenomenon is the reason why the above-mentioned base plate 13 can be used. Since each part of the printing hammer repeatedly returns and rebounds with a certain phase difference, the energy of each part is canceled out very quickly. Renoku Land will disappear.

FIG. 5(A) is a sectional view showing an embodiment of the impact type print head according to the present invention, and FIG. 5(B) is a side view thereof. 1 hammer
A 7-bin head is constructed by stacking two rows of sheets. Here, the print head between each layer is
The dots are assembled in a sequentially shifted manner corresponding to the pitch of each dot of the printed characters, and are integrally fixed via positioning holes 17 with screws or the like (not shown). In addition, in the figure, 18 is a wire guide section provided at the front of the print head.In addition, in this configuration, each of the upper plates 14 other than the top layer also serves as a base plate for other layers, thereby reducing the number of parts. are being reduced.

The impact type print head of the present invention configured as described above can print desired characters, etc. by impacting the print medium with each print wire by selectively driving the print hammers with one print signal. can.

In addition, in the above-mentioned embodiment, a structure was explained in which the printing hammers were stacked in a two-layer arrangement, but in addition to this, it is possible to create a multi-pin structure by arranging a plurality of printing hammers radially on the circumference and stacking them. It is also possible to configure a print head of.

〔Effect of the invention〕

As explained above, the present invention covers the other electrode surface of a piezoelectric ceramic whose one electrode surface is bonded to an elastic plate with a flexible insulating film, which was conventionally exposed. It is possible to eliminate short circuits on the electrode surface due to the adhesion of dust, etc., and it is possible to prevent unstable operation of the printing hammer and malfunction of the printer due to noise.

Further, in the present invention, since the upper plate having the limiter bank is disposed on the piezoelectric ceramic side of the printing hammer having a flexible insulating film as described above, unnecessary flying of the printing hammer can be prevented, and as a result, Breakage of the piezoelectric ceramic becomes less likely to occur.

In addition, the present invention has a structure that actively utilizes the fact that the piezoelectric ceramic is isotropic in all directions perpendicular to the polarization direction of the surface.
In other words, since the printing mark is fixed via a spacer with an arc-shaped end face, a large excitation force and displacement can be obtained with a small printing mark, and the base is attached to the elastic plate side of the printing mark. Since the base plate is placed in the base plate 1, the base plate can serve as a clamp and prevent the printing hammer from rebounding and reversing. This printing hammer using the electrostrictive drive method does not generate heat like the printing hammer using the electromagnetic drive method, so it is possible to perform high-speed printing with stable operation and obtain high printing quality. I can do it.

Further, in the present invention, the printing wire and the asymmetrical bimorph type printing hammer to which the flexible insulating film is attached are laminated and integrated. As a result, it is possible to create an impact-type print head that is smaller, lighter, and thinner, and can print high-density kanji and images, which is currently required in the market.

It can be used as an impact-type print head that is particularly suitable for graphics output.

[Brief explanation of the drawing]

Figure 1 (A) is a side sectional view showing a printing hammer with a symmetrical bimorph configuration, Figure 1 (B) is a front view thereof, and Figure 2 is the printing shown in Figure 1. Movement of the printing wire in the hammer and time. 3(A) is a perspective view of the printing hammer according to the present invention, FIG. 3(B) is an exploded view thereof, and FIG. 4 shows the printing hammer shown in FIG. Figure 5 (A) is a graph showing a comparison between the theoretical value and the measured value of the flight distance of the printing hammer when modeled as a one-dimensional vibration problem.
5 is a sectional view showing an embodiment of the impact type print head according to the present invention, and FIG. 5(B) is a side view thereof. 9... Elastic plate 10... Piezoelectric ceramic 11... Printing wire 12... Flexible insulating film 13... Base plate 14... Upper plate 15... Limiter bank 16... Spacer 17 ...Positioning hole 1
8...Wire guide section patent Applicant: Oki Electric Industry Co., Ltd. Agent, Patent attorney: Takashi Kanakura Nikkaku 1- (A) (B) Kazu 20 Ryu 3 Ciil (B) Procedural amendment (voluntary) November 1988・19th, Mr. Kazuo Wakasugi, Commissioner of the Japan Patent Office■, Indication of the case, Patent Application No. 030923 No. 030923, filed in 1982, Title of the invention: Impact type print head 3, Relationship with the person making the amendment Case Patent applicant address: Tokyo 1-7-12 Toranomon, Minato-ku Name (029) Oki Electric Industry Co., Ltd. Representative Nankai Hashimoto 4, Agent 5 Date of amendment order Initiator 6 Subject of amendment Description “Detailed Description of the Invention” (Oka) 0
7. Contents of the amendment: On page 1, line 46 of the specification, the phrase "commonly known" is amended to read "commonly known". 2. On page 8, line 5 of the specification, the phrase “mix,゛” was replaced with “
First of all,” he corrected. 3. In the fourth line of page 12 of the specification, "resistance strength" is corrected to "flexural strength". 4. On page 12, line 19 of the specification, the word "graph" should be corrected to read "figure."

Claims (1)

[Scope of Claims] 1. A printing hammer using an asymmetric bimorph vibrator is bonded to an elastic plate of a predetermined shape and one electrode surface of a piezoelectric ceramic having approximately the same shape as the elastic plate and having a pair of electrodes on both sides. The printing wire is formed at one end as a free end, and a printing wire is attached to the free end while the other end is fixed.This printing wire is laminated in an arrangement of two sheets per layer, or multiple sheets are placed on the circumference. 1. An impact type print head in which the other electrode surface of the piezoelectric ceramic is covered with a flexible insulating film in the print head arranged and stacked in a radial manner. 2. The impact type print head according to claim 1, characterized in that an upper plate having a limiter bank is disposed on the piezoelectric ceramic side of the printing hammer. 3. The impact type print head according to claim 1, wherein the base plate roller is disposed on the elastic plate side of the printing hammer.