JPS6139859B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a liquid ejecting device, and more particularly to a liquid ejecting device that ejects ink from an injection recording section in an electronic recording device, for example. Recently, electronic recording devices are often used in place of conventional mechanical recording devices. Compared to mechanical recording devices, electronic recording devices (a) have an inherently faster recording mechanism and are capable of high-speed recording; (b) Since no mechanical impact force is applied to the recording paper, noise during recording is extremely low. (c) Compared to mechanical recording devices that often print matrix characters,
Since characters are formed and printed using a dot matrix, there are few restrictions on the font, number of characters, and character size of printed characters, and there is high flexibility in printing images. (d) It is possible to downsize parts and reduce the number of parts;
Therefore, mass production and cost reduction can be achieved. When classified by recording method, electrostatic recording, discharge recording, electrophotographic recording, thermosensitive recording, electrolytic recording, inkjet recording, ink mist recording, etc. have been put into practical use. However, electronic recording devices generally require recording paper that has been specially treated to suit each recording method, and among the electronic recording methods, only inkjet recording and ink mist recording methods are capable of recording on plain paper. It's just that. Many specially treated recording papers are expensive to produce, have an unnatural surface, some produce a bad odor during recording, and few have excellent storage stability after recording. In this sense, inkjet recording and ink mist recording have the ability to solve the above-mentioned problems, and can be said to be one of the promising high-speed plain paper recording methods. In addition, as a recent trend, the demand for kanji printing using dot matrix is increasing, but in order to increase the number of dots required to form one character and improve the printing quality, it is necessary to increase the dot diameter that constitutes the smallest unit. It becomes necessary to miniaturize. For this reason, 1
There has been a desire for a printing mechanism that can generate minute recording dots at high speed, with individual positioning control possible. The inkjet recording method, which allows high-speed recording on plain paper and allows individual control of recording particles, is limited in its range. ) Utilizes the phenomenon of ink leakage caused by electrostatic fields. (A-2) This method utilizes the phenomenon of uniform ink particle formation caused by an electrostatic field. (B) Continuously pressurized injection jet (B-1) Jet that deflects the pressurized jet stream by deflecting the nozzle (galvanometer type). (B-2) One that controls the amount of charge on the droplet and deflects it using an electrostatic field (charge amount control type). (C) Impact pressure injection type inkjet (C-1) One side of the ink pressurizing chamber is composed of a circular bimorph oscillator, and has a double structure with the ink injection chamber. As an example of this, JP-A-48-
Some of these are described in Japanese Patent Publication No. 9622 and Japanese Patent Publication No. 53-45698. (C-2) One side of the ink pressurizing chamber is composed of rectangular bimorph oscillators, and a plurality of rectangular bimorph oscillators are arranged. Examples of this include those described in Japanese Patent Application Laid-Open No. 47-2006 and Japanese Patent Publication No. 53-12138. (C-3) The ink pressurizing chamber is composed of a cylindrical piezoelectric body,
and respiratory vibrations (radial expansion and contraction)
This directly causes the inner wall of the ink pressurizing chamber to contract and expand. As an example of this,
Some of them are described in Japanese Patent Application Publication No. 6308, Japanese Patent Publication No. 51-39495, Japanese Patent Application Publication No. 52-28321, and Japanese Patent Application Publication No. 52-49035. Among the above-mentioned inkjet recording methods, the method (B-2) is capable of high-speed and high-quality recording. In this method, the ejection frequency of synchronized ink droplets ejected from the nozzle is 50kHz~
Many droplets that can be used for direct dot recording are in practical use at frequencies between 100 kHz and uncharged droplets are inserted between recording droplets to alleviate the electrostatic interference between charged droplets. Since the actual droplet recording frequency is less than 1/2 of the nozzle jetting frequency, the practical upper limit has been 25kHz to 50kHz. In addition, in this method, it is necessary to apply static pressure and constantly eject ink to charge the droplets at the same time as when they break up from the liquid column into droplets. In general, the splitting time varies depending on the viscosity of the ink, the voltage applied to the vibrating piezoelectric body, the particles present in the ink, etc. The charge correction circuit for preventing charge induction makes this system complicated and expensive. Furthermore, since ink droplets are ejected even during non-printing periods, the ink collection gutter and other ink circulation system
The physical properties of the ink change due to the incorporation of fine particles into the ink and the evaporation of moisture or solvent, which, together with the complexity of the ink supply device and the ink property control device, makes it difficult to improve the overall reliability of the printing press. ing. On the other hand, the impact pressurized inkjet (C) jets the ink droplets directly used for printing at the required timing, and any of the methods (C-1) to (C -3), the contraction and expansion of the internal volume of the ink pressurizing chamber is the principle for ejecting ink droplets. When the ink pressurizing chamber contracts, the liquid pressure increases, and if the ink is incompressible, an amount of ink equal to the contracted volume is released from the ink ejection port (orifice).
and move to the ink supply port. At this time, the acceleration force of the droplet necessary to jet from the orifice,
If a force greater than the relaxation of the viscous frictional force accompanying the movement of the liquid and the surface tension acting on the growth of the liquid column acts from the ink pressurizing chamber, droplets are ejected. However, in reality, a large proportion of energy is consumed other than the ejection kinetic energy of the droplets, so the amount of volumetric contraction of the ink pressurizing chamber must be sufficiently large. For this reason, the inner wall of the ink chamber is covered with a bimorph oscillator (piezoelectric ceramic and an elastic body such as metal).
There are many examples in which the system is configured using a method that utilizes flexural vibration, and the patent applications (C-1) and (C-2) mentioned above fall under this system. A bimorph vibrator is made by pasting together two pieces of piezoelectric ceramic that contract in the length direction (radial direction), or by pasting together a metal plate and a piezoelectric ceramic.When one side stretches, the other contracts, resulting in bending vibration as a whole. It is something that causes The natural resonant frequency of a circular bimorph is given by the following equation (1), for example, when the physical properties (Young's modulus E, density ρ, Poisson's ratio υ) of the material constituting the piezoelectric body are constant. If so, the natural resonant frequency that determines the highest vibration response frequency is inversely proportional to the square of the radius r of the bimorph and proportional to the overall thickness t.

[Table] The vibration area of the bimorph oscillator that makes up one side of the ink pressurizing chamber is πr ² , but in order to increase the ink ejection repetition rate, the value of r ² must be small and t
The value of must be increased. At this time, since the volume change of the ink pressurizing chamber is proportional to the product of the average amplitude of the vibrator and the vibration area, there is a paradox in that the response frequency cannot be improved unless the volume change is sacrificed. FIG. 1 is a diagram showing relational expressions such as the support method, displacement when the shape and dimensions are given, and resonance frequency in the case of a rectangular bimorph vibrator. FIG. 2 is a diagram showing the determination of the resonant frequency when the length (lmm) and thickness (tmm) of the support at both ends are given. The natural resonant frequency of a rectangular bimorph oscillator, like that of a circular bimorph oscillator, depends on the length of the bimorph.
It is inversely proportional to the square of (l) and proportional to the total thickness t. The resonant frequency of this rectangular bimorph resonator can be determined by the following equation (2). Next, the amount of volume change caused by the fundamental vibration of each bimorph oscillator will be analyzed. FIG. 3 is an illustrative diagram for explaining a circumferentially supported circular bimorph, which is the background of the present invention. As shown in FIG. 3, when a voltage is applied to the piezoelectric ceramic of a circumferentially supported circular bimorph and a uniform pressure P is applied, the amount of deflection ω(r) is
If the center is the coordinate origin, it is given by the following equation (3). ω(r)=P/64D(a- ^r2 )(5+υ/1+ ^υa2-
r ² ) ...(3) where k = 5 + υ / 1 + υ D = Et ³ /12 (1 - υ) ² a: radius of circular bimorph t: thickness of circular bimorph υ: Poisson's ratio of bimorph material E: of bimorph material Young's modulus D: Stiffness of bending The volume change △V of a circular part with radius r from the center is △V=2πr△rω(r), and when performing circular integral from radius r=0 to radius r=a, V =∫ ^r=a _r=0 △V=2πP/64D∫ ^r=a _r=0 r(a ² −r ² )(ka ² −r ² ) dr =2πP/64(1−υ)(2υ+14)( t ² /h) ³ ...(4). On the other hand, the resonant frequency f _p is calculated from equation (1) above. Therefore, by substituting this equation (5) into the above equation (4), V=2πP/64(1−υ)(2υ+14)(k _p /f _p
) ³ ...(6) becomes. From this equation (6), it can be seen that the volume change amount of the circular bimorph resonator is inversely proportional to the cube of the resonance frequency f _p . FIG. 4 is an illustrative diagram for explaining a rectangular bimorph supported at both ends, which is the background of the present invention. As shown in Figure 2, when calculating the amount of volume change for a rectangular bimorph supported at both ends, the length l, width b
When a uniform pressure P is applied, the amount of deflection ω(x) at a distance x from the support point is given by the following equation (7). ω(t)=Pl ⁴ /24EI(x/l-2x ³ /l ³
+x ⁴ /l ⁴ )...(7) Also, the volume change is: △V=b∫ ^x=l _x=0 ω(x)dx=Pbl ⁵ /5×2
4×EI...(8) I=bt ^3/12 ...(9) t: Thickness of bimorph Substituting the above equation (9) into equation (8), △V=P/10E(l ⁵ /t ³ ) ...(10) Also, from equation (2), the resonant frequency f _p is Therefore, by substituting this resonant frequency f _p into equation (10), △V=P/10El(k' _p /f _p ) ³ ...(11) Therefore, in the case of a rectangular bimorph, the rectangular length l is also If it is kept constant, the amount of volume change will be inversely proportional to the cube of the resonance frequency. FIG. 5 is an external perspective view of a hollow cylindrical bimorph resonator, which is the background of the present invention. With reference to FIG. 5, when we consider the volume change and resonance frequency of the breathing movement in the hollow cylinder, we find that the wall thickness t,
When a uniform pressure P acts on the inside of the thin-walled cylinder 3 having an inner diameter r and a length l, the inner diameter increases as shown in equation (12). Therefore, the volume change is becomes. On the other hand, the resonant frequency in respiratory vibration is
Given by equation (14), Therefore, by substituting equation (14) into equation (13) and expressing the amount of volume change in terms of the resonance frequency, equation (15) is obtained.
It becomes like the formula. △V=2πP/Et(1-υ/2)l(k _p ″/f _p )
³ ...(15) From this result, it can be seen that the breathing vibration of the cylinder is also inversely proportional to the cube of the resonance frequency. FIG. 6 is an external perspective view showing a hollow cylindrical vibrator to which the present invention is applied. In the axial vibration of a hollow cylinder, which is the main component of this invention, when the inner diameter r, length l, and axial pressure P act on both end faces of the cylinder, the volume change inside the cylinder is as follows: △V=πr ² ( 1-2υ)△l = πkEP(1-2υ)r ² l ...(16). On the other hand, the axial resonance frequency f _p is Then, by substituting equation (17) into equation (16), we get △V=πkPE(1-2υ)r ² (k _p /f _p ) (18). Therefore, the amount of volume change in this method is only inversely proportional to the first power of the resonance frequency, and since ^r2 acts as a proportional term with respect to the inner diameter r, the volume change can be increased without lowering the resonance frequency by increasing the inner diameter r. can be made larger. As mentioned above, the amount of change in container volume and the resonant frequency that determines the response frequency depending on the structure of the ink pressurizing chamber are summarized by vibration mode as shown in Attached Table 1. The ink pressurizing chamber for intermittent ejection, which has been commonly used in the past, has a part or all of its inner wall made up of (A) circular bimorph oscillators. (B) Consists of rectangular bimorph oscillators. (C) Consisting of a radial constriction cylinder. If the physical constants of the constituent materials (υ: Poisson's ratio, E: Young's modulus, ρ: density) and external force (P) are constant, the amount of volume change can be calculated using the theoretical formula shown in Attached Table 1. It varies depending on the geometry, ie length (l), radius (r), and thickness (t).
An increase in length (l) and radius (r) increases volume, and an increase in thickness (t) decreases volume. On the other hand, the resonance frequency of the ink pressurizing chamber, which limits the maximum repetition frequency of droplet ejection, is also determined by the geometric shape l,
It is a function of r and t; an increase in l and r will lower the response frequency, and an increase in x will increase the frequency. In other words, the amount of change in volume of the ink pressurizing chamber, which is most relevant to the mechanism of ejecting droplets from the nozzle, and the maximum response frequency are in a contradictory relationship.
It is essentially impossible to improve the response frequency without reducing the amount of volume change. resonance frequency f
With respect to _p , in (A), it is proportional to 1/f ³ _p , in (B), it is proportional to 1/l·f ³ _p , and in (C), it is proportional to l/f ³ _p . That is, when the resonance frequency is doubled, tripled, or quadrupled, the amount of volume change is significantly reduced to 1/8, 1/27, or 1/64. Therefore, the amount of change in volume that attempts to increase the response frequency is reduced, and a conventional ink pressurizing chamber, which cannot eject ink at a high frequency, has the problem of not being able to perform high-speed inkjet printing. Ta. Therefore, a main object of the present invention is to provide a liquid ejecting device that can independently set the amount of change in volume of a pressurizing chamber and the resonance frequency, and has a high response frequency. To summarize the invention, the present invention is a liquid injection device that injects liquid by changing the volume of a liquid pressurizing chamber, which comprises a hollow cylindrical elastic body with flanges formed at both ends thereof, and the inside of which is filled with liquid. A liquid pressurizing chamber is formed for the purpose of the elastic body, and a liquid injection port is formed at one end of the elastic body so as to communicate with the liquid pressurizing chamber.
By forming a liquid supply port at the other end and holding the piezoelectric ceramic in the shape of a hollow cylinder whose inner diameter is larger than the outer diameter of the elastic body by the flanges at both ends of the elastic body, the thickness of the piezoelectric ceramic can be reduced. It is designed so that the volume of the liquid pressurizing chamber can be changed by vibration. The above objects and other objects and features of the present invention will become more apparent from the detailed description given below with reference to the drawings. As shown in FIG. 6, the basic structure of the ink pressurizing chamber of the liquid ejecting apparatus of the present invention is an elastic hollow cylinder, and the cylinder is expanded and contracted in the axial direction by an external force in the axial direction. If the tensile stress in the axial direction of the ink pressurizing chamber shown in FIG. 4 is P, the axial change △l=kEPl, the radial change -
When deformation occurs due to r=υkEPr (υ is Poisson's ratio of the elastic body) and elongation occurs in the axial direction, the internal volume change △V becomes positive, and as shown in equation (16) above, △V=πPkE (1−2υ)r ² l. Generally, since Poisson's ratio υ=0.3 to 0.4, (1-2υ)=0.4 to 0.2, and the volume increase due to inner diameter contraction does not cancel out. It can be seen that the volume change amount ΔV is proportional to the external force P, the cylinder axis length l, the elastic modulus of the material, and the cross-section of the cylinder. The first resonance frequency, which is a guideline for the upper limit of the response frequency, uses the longitudinal vibration mode in the axial direction of the cylinder, so from equation (17) above, Therefore, in order to increase the resonant frequency, the resonant frequency f _p is inversely proportional to the axial dimension l, so l should be made smaller. The amount of volume change in this case is expressed by the resonance frequency from equation (18) as △V=πkPE(1-2υ)r ² (k _p /f _p ), which is inversely proportional to the first power of f _p , but the inner diameter r
remains in the equation in the form of a square, so the volume change can be increased by selecting the inner diameter without changing the resonance frequency. As a specific example, when increasing the resonant frequency by 2, 3, or 4 times, if the inner diameter r is set to √2 times, √3 times, and √4 times, respectively,
The amount of volume change can be made the same. As described above, the present invention has the feature that the resonant frequency can be increased without sacrificing volume change.
A vibration state of the ink pressurizing chamber suitable for high-speed intermittent ejection can be obtained. Now, the vibration states of three conventional types of ink pressurizing chambers and the characteristics of the vibration state according to the present invention have been explained from the viewpoint of volume change and resonance frequency. However, when used as an actual pressurizing chamber, Liquid ink is filled inside it. However, piezoelectric ceramics, which are commonly used electromechanical transducers, must not come into direct contact with ink. This is because the piezoelectric ceramic is porous and absorbs ink, resulting in a decrease in insulation and other changes in properties, as well as electrolysis of the ink. Therefore, a pressurized chamber made of ink and a corrosion-resistant material must be provided in conjunction with the piezoelectric ceramic. Therefore, in both the above-mentioned methods (A) and (B), the bimorph vibrator is formed of a double structure of piezoelectric ceramic and a metal plate, and the metal plate surface is usually in contact with the ink. In addition, in the above-mentioned method (C), an elastic cylinder such as a glass tube or a metal tube is inserted inside the cylindrical piezoelectric ceramic.
This is the ink pressurizing chamber. In this invention as well, the ink pressurizing chamber is made of, for example, corrosion-resistant metal or glass, and the external force in the axial direction is obtained by longitudinal vibration or pressure vibration of piezoelectric ceramic. FIG. 7 is a longitudinal sectional view showing an elastic cylinder for an ink pressurizing chamber according to an embodiment of the present invention arranged in the center of an annular piezoelectric ceramic. In FIG. 7, the liquid pressurizing chamber 5 is formed into a hollow cylindrical shape by an elastic metal material 51 such as stainless steel (SUS). The piezoelectric ceramic 52 is formed into a hollow cylindrical shape having an inner diameter larger than the outer diameter of the hollow cylindrical elastic body 51 . The piezoelectric ceramic 52 has flanges 5 formed at both ends of the elastic body 51 and engaged with the elastic body 51 by screws.
3 and 54 to be tightened and fixed. At this time, as a reaction to the mechanical pressure that tightens the piezoelectric ceramic 52, a tensile force is applied to the elastic body 51, and the ink is applied to the piezoelectric ceramic 52 according to the polarity of the electrical pulse centered around this bias tensile force. Contraction and tension forces are superimposed on the chamber 55. The cylinder internal volume change △V at this time is the ink chamber 5
This results in a volume change of 5. FIG. 8 is a longitudinal sectional view showing a cylindrical piezoelectric ceramic arranged inside an ink pressurizing chamber according to another embodiment of the present invention. In FIG. 8, both end surfaces of the cylindrical piezoelectric ceramic 61 are the inner end surface of the volume-changing elastic cylinder 62 and the outer container 6 facing the inner end surface.
It is held between a protruding portion 631 formed on the inner surface of 3. The other side of the elastic cylinder 62 is fixed to the outer container 63 by a threaded portion 64 formed on the projection 631. The outer container 63 is formed to cover the elastic cylinder 62 with a predetermined gap therebetween. And external container 6
The gap space 65 between the elastic cylinder 62 and the elastic cylinder 62 becomes the internal volume of the ink pressurizing chamber. In this configuration, the ink pressurizing chamber internal volume 65 is the internal volume of the external container 63 and the elastic cylinder 62.
, and the expansion of the elastic cylinder 62 reduces the internal volume 65 of the ink pressurizing chamber. A tensile force is applied to the elastic cylinder 62 as a reaction to the compressive force of the piezoelectric ceramic 61 inside the elastic cylinder 62, and the elastic cylinder 62 stretches and contracts around this bias tensile force in response to the polarity of the electrical pulse applied to the piezoelectric ceramic 61. Forces are superimposed. The piezoelectric ceramic used as the electromechanical transducer in FIGS. 7 and 8 described above utilizes longitudinal vibration or thickness vibration, and the amount of expansion and contraction of the piezoelectric ceramic is △l=d ₃₃ ·V _l ... ...(19) d ₃₃ : Piezoelectric constant in longitudinal or thickness vibration V _l : Applied voltage in longitudinal or thickness direction. FIG. 9 is a diagram for explaining a piezoelectric ceramic having a single layer structure to which an embodiment of the present invention is applied; in particular, FIG. 9a is an external perspective view of a cylindrical piezoelectric ceramic; 9b is an external perspective view of a cylindrical piezoelectric ceramic, and FIG. 9c is a diagram showing a drive circuit for driving the piezoelectric ceramic. The piezoelectric ceramic having a single-layer structure in the form of a cylinder or a column as shown in FIGS _.
The amount of expansion/contraction Δl is determined by . FIG. 10 shows N to which an embodiment of the present invention is applied.
These are diagrams for explaining piezoelectric ceramics having a layered structure. In particular, Fig. 10a shows an N-layer of annular piezoelectric ceramic, and Fig. 10b shows an N-layer of a cylindrical piezoelectric ceramic. Yes, Figure 10c
1 is a diagram showing a drive circuit for driving the piezoelectric ceramic having the above-mentioned N-layer structure. In this divided N-layer structure as shown in Fig. 10, by connecting the electrodes in parallel as shown in Fig. 10c, the total amount of expansion and contraction is △l = Nd ₃₃ V _l ... (20), N times the amount of expansion and contraction can be obtained with the same voltage. However, in piezoelectric ceramics manufactured from the same material, the load capacity seen from the drive circuit increases by a factor of ^N2 . Now, the resonant frequency of a piezoelectric ceramic made of a single elastic body as shown in FIGS. It has a composite structure of piezoelectric ceramic as a source and an elastic body as an ink pressurizing chamber. In particular, the mass effect of the piezoelectric ceramic fixing flanges 53 and 54 shown in FIG. Due to the mass effect of a mechanism such as an orifice plate (not shown), the resonance frequency is no longer in a simple form as in equation (17), and strictly speaking, it is necessary to perform a complex vibration analysis. FIG. 11 is a longitudinal sectional view of a composite vibrating body to which an embodiment of the present invention is applied. The composite vibrating body shown in FIG. 11 includes two annular piezoelectric ceramics 93,
94, and these piezoelectric ceramics 93, 9
4 are tightened by flange nuts 95,96. In FIG. 11, when the dimensions of each part are defined as shown, the axial resonance conditional expression is as follows. Z ₁ tanγ ₁ l ₁ −Z ₂ cotγ ₂ l ₂ /2 −Z ₃ cotγ ₃ l ₂ /2 = 0 ... (21) Z ₁ = ρ ₁ C ₁ S ₁ = ρ ₁ C ₁ (D ₅ /2 ) ² π……(22) Z ₂ =ρ ₂ C ₂ S ₂ =ρ ₂ C ₂ {(D ₄ /2) ² −(D ₃ /2) ² }π……(23) Z ₃ =ρ ₃ C ₃ S ₃ = ρ ₁ C ₁ {(D ₂ /2) ² − (D ₁ /2) ² }π ...(24) γ ₁ = ω/C ₁ , γ ₂ = ω/C ₂ , γ ₃ =ω/ _C3 ...
(25) ω=2πf _p However, C ₁ , C ₂ , C ₃ are shown in Fig. 13 (95, 91),
(93,94), (92) The sound speed in the medium ρ ₁ , ρ ₂ , ρ ₃ is the density of the same medium f _p is the axial resonance frequency As a result, the resonance frequency is the piezoelectric ceramic axial dimension l ₂ , the cylinder The shape is almost determined by the axial dimension _l1 of the pressurizing chamber, and material constants such as density, sound velocity, cross-sectional area, etc. have a secondary effect. Therefore, to determine the upper limit of the expansion/contraction response frequency of the ink pressurizing chamber,
It is sufficient to determine the dimensions of l ₁ and l ₂ , and in general, the smaller this value is, the higher the resonant frequency will be. FIGS. 12 and 13 are diagrams showing specific examples of the composite vibrating body shown in FIG. 11. In FIGS. 12 and 13, two annular piezoelectric ceramics 102 and 103 are fastened and fixed by an ink pressurizing chamber elastic bolt part 101 and a nut part 104. The dimensions of the pressurizing chambers having the various resonance frequencies shown in FIGS. 12 and 13 are expressed using the symbols for the dimensions shown in FIG. 11, as shown in Table 2 below. And piezoelectric ceramics 102, 10
3, the bolt portion 101, and the nut portion 104 by selecting their respective axial lengths as shown in the figure, it is possible to cause resonance at the frequency shown in the figure.

[Table] Furthermore, when the material constants at this time correspond to the component names in FIG. 11, the following Table 3 is obtained.

[Table] A vibrator having such a structure can be regarded as a modification of the basic form of a so-called Langevin-type vibrator. FIG. 14 is an external view showing an example of a Langevin type vibrator. The Langevin type vibrator invented by Mr. Langevin shown in FIG.
3, and the piezoelectric ceramic 122 and the elastic body are bonded with an adhesive with high tensile strength. In general, piezoelectric ceramics are located where stress distribution is high, and elastic bodies are located where strain distribution is high. For this reason, when this type of vibrator is stretched in the axial direction, tensile stress is applied to the adhesive, which often causes problems such as the adhesive coming off. The bolted Langevin type resonator was devised as a structure that can withstand this tensile stress. FIG. 15 is a diagram showing a bolted Langevin type vibrator. As shown in FIG. 15, one elastic body 131 has a bolt-shaped structure, and the other elastic body 1
34 has a nut structure. And this 2
Bolt threaded portion 1 between two elastic bodies 131 and 134
33 is provided, and the piezoelectric ceramic 132 is tightened by an elastic body 131 having a bolt and an elastic body 134 having a nut. Therefore, tensile stress is applied to the piezoelectric ceramic 132, and tensile stress is applied to the bolt threads, so that the elastic bodies 131, 134 and the piezoelectric ceramic 1
32 becomes unnecessary. Piezoelectric ceramic 13
In the case of the bonded Langevin vibrator shown in FIG. 12, the amount of static distortion of the Langevin vibrator when a voltage is directly applied to the piezoelectric ceramic 122 is d ₃₃ × applied voltage, where d ₃₃ is the piezoelectric constant of the piezoelectric ceramic 122. is equal to However, in the case of the Langivin vibrator shown in FIG. 13, work must be done to overcome the tensile elastic deformation of the threaded portion of the nut 134 passing through the center. Therefore, with the same applied voltage, the amount of static distortion is reduced for the bonded Langevin vibrator. FIG. 16 is a characteristic diagram showing the relationship between the applied voltage and the amount of distortion of the Langivin vibrator. In the example shown in FIG. 16, the amount of static strain of the bolted Langevin vibrator is approximately 1/2 that of the bonded Langevin vibrator. Furthermore, in the case of one method of the ink pressurizing chamber of the present invention, which utilizes a change in the internal volume of an elastic cylinder, the basic structure shown in FIG. This corresponds to the threaded portion 133 that has been partially machined. However, most of the general uses of bolted Langivin transducers are for example as an oscillation source for ultrasonic transmitters in sonar or as an excitation source for ultrasonic cleaners, and in rare cases, liquid fuel There is a vibrator for powder atomization. The gist of this invention, the application of internal volume change for pressurizing ink as a driving force generation source, has never been seen before, and is therefore an element of novelty in this invention. FIG. 17 is a diagram showing the frequency characteristics of the amount of axial expansion and contraction of the ink pressurizing chamber in one embodiment of the present invention. Judging from this characteristic, generally the first resonant frequency f
With respect to _p , from 1/ _2fp to 1/ _3fp , a substantially flat frequency characteristic is exhibited, and the amount of distortion increases in proportion to the applied voltage. Therefore, if the occupied frequency band of the applied waveform is less than (×1/2 to ×1/3) of the mechanical natural resonance frequency of the ink pressurizing chamber, forced volume deformation vibration corresponding to the applied waveform is generated. be able to. Here, when an impact voltage is applied to an ink pressurizing device composed of an elastic container made of metal or the like and a piezoelectric ceramic, and ink droplets are ejected from an orifice by contraction of the internal volume of the ink pressurizing chamber, the most The important points are as follows. (1) The amount of change in volume of the ink pressurizing chamber must correspond completely proportionally to the applied electrical signal. (2) Sufficient volume change is ensured for ink droplets to be ejected from the orifice. (3) Ink acts as an incompressible fluid. (1) The natural resonance frequency of the entire ink pressurizing mechanism must be set high so that it can respond up to the target ink ejection repetition frequency. Furthermore, even at the same repetition frequency, the applied waveform must occupy a smaller frequency band, and an isolated sine wave is preferable to a rectangular wave with rapid rises and falls. Also,
Apply a shock waveform to obtain a single ejected droplet;
Even if a volume change is caused in the ink pressurizing chamber and then the electric signal is released, the volume change vibration of the ink pressurizing chamber rarely stops completely, and residual vibration continues with a natural vibration period of this diameter. . When the volume change due to this residual vibration is not negligible compared to the volume change due to forced vibration when an electric signal is applied, a satellite droplet is generated following the target ejected droplet. The generation of satellite droplets is closely related to residual vibration, and it is necessary to select an applied waveform with less residual vibration. The internal volume vibration waveform of the piezoelectric ceramic of the ink pressurizing chamber shown in FIG. 11, which is a typical mechanism of the present invention, with respect to the applied voltage waveform was measured. FIG. 18 is a diagram showing an internal volume vibration waveform with respect to a voltage waveform applied to the piezoelectric ceramic of the ink pressurizing chamber according to an embodiment of the present invention. In FIG. 18, a to e indicate the falling characteristics of the applied voltage applied to the piezoelectric ceramic, and a' to e' indicate the vibration in the axial direction of the ink pressurizing chamber when the applied voltage is applied to the piezoelectric ceramic. This shows the residual vibration when transitioning from the expanded state to the contracted state. The fall time of the applied voltage is determined by the product C _p R _D of the piezoelectric ceramic capacitance C _p and the drive circuit series resistance R _D , so the series resistance R _D is 10Ω, 100Ω, 1kΩ, 10kΩ.
The fall time was controlled by changing the resistance to Ω and 100kΩ. It can be seen from FIG. 18 that if the fall time of the applied voltage is short and the waveform becomes steep, the applied waveform and the vibration waveform will have less correspondence, and the residual vibration at the natural period will continue. FIG. 19 is a diagram showing a vibration waveform in the axial direction of the ink pressurizing chamber when a vertical sinusoidal wave is applied to the piezoelectric ceramic of the ink pressurizing chamber. In this Figure 19, a to i represent the repetition frequency of the isolated sine wave.
Fixed to 2kHz, time width of one wavelength of sine wave to 3kHz
or shows the applied voltage waveform equivalent to a 30kHz waveform,
a' to i' indicate the response vibration waveforms of the piezoelectric ceramic at the applied voltage. The ink pressurizing chamber is initially in an equilibrium state, expanding at the + period of the sine wave and contracting at the - period. When the duration of this vertical sine wave is long, the vibration waveform corresponds proportionally to the applied voltage waveform, but when the duration becomes short, the residual vibration component grows, and when the duration is shortened further, the forced vibration due to the applied voltage waveform increases. The residual free vibrations also grow larger. As mentioned above, if it is used in a region where the applied voltage and the amount of change in the volume of the ink pressurizing chamber do not completely correspond, the liquid jet will be split due to residual vibration, resulting in the generation of satellite droplets, a decrease in the droplet diameter, and the separation of main and satellite droplets. Differences in vibration phase can lead to a decrease in injection speed, etc., and these must be avoided. Next, an important point is the amount of change in volume of the ink pressurizing chamber, which must be secured to be sufficient to cover the droplets ejected from the orifice and the volume of ink flowing back into the ink supply path. Here, No. (16)
From the formula, △V=πkEP(1-2υ)γ ² l, so (1) Increase the external force (∝P) for ink chamber contraction and expansion. In other words, the voltage applied to the piezoelectric ceramic,
It is proportional to the force coefficient A, the axial cross-sectional area S, and the piezoelectric constant _d33 . (2) Increase the internal volume of the ink pressurizing chamber. That is, it is proportional to the ink chamber cross-sectional area πr ² and the axial length l. (3) It is proportional to the material constant of the ink pressurizing chamber, that is, Young's modulus E, 1-2υ (υ is Poisson's ratio). A feature of the present invention is that the above (1) to (3) can be selected without lowering the natural resonance frequency as described above. Next, the other condition most closely related to stabilizing the performance of a liquid ejecting device is the physical properties of the ink used. Among these, there are (1) viscosity, (2) surface tension, (3) content of insoluble fine particles in the ink, and (4) volumetric compression ratio of the ink. , item (4) is the most important. originally,
Water-based ink and oil-based ink contain a certain percentage of bubbles and dissolved air, and when assembling the ink fluid system such as the ink supply system, ink pressure chamber, and ink jet orifice as a liquid ejecting device, there may be a small amount of air bubbles on the wall of the fluid system. These air bubbles act as an equivalent air chamber, which acts to alleviate the pressure increase when the internal volume of the ink chamber contracts. Furthermore, when the internal volume expands, dissolved gas, ink pressurizing chambers, and air bubbles attached within the liquid system act as cavitation nuclei, which also acts to alleviate the pressure decrease. In such a case, ink droplets are not ejected from the orifice, or even if ink droplets are ejected, the voltage sensitivity response frequency range becomes poor. Therefore, in order to remove air bubbles and dissolved gases from the ink used, it is necessary to degas it using a vacuum pump or to add a degassing agent (for example, sulfite) having the ability to adsorb dissolved gases to the ink. In addition, the ink supply port, ink pressurization chamber,
When a fluid system such as an injection orifice is assembled and filled with ink, the entire fluid system must be evacuated to remove air bubbles attached to the walls of the channel. FIG. 20 is an illustrative diagram for explaining changes in pressure in the ink ejection mechanism. The liquid ejecting device shown in FIG. 20 is composed of an ink pressurizing chamber 181, an ink ejection port 182 including an ink ejection orifice and an ink outlet path, and an ink supply port 183 into which ink flows from an ink storage tank (not shown). .
In this resting equilibrium state of the liquid ejecting device 18, the pressure outside the orifice (atmospheric pressure) is P ₀ and the ink pressurizing chamber 18 is
When the pressure inside the ink supply port 182 is P ₂ and the pressure at the inlet of the ink supply port 183 is P ₃ , a balance is maintained by the surface tension acting at the orifice and the resistance of the pipes of the ink ejection port 182 and the ink supply port 183. . The pressure distribution at this time is considered to be as shown in FIG. 20b.
Next, the inner volume of the ink pressurizing chamber 181 shrinks −△Q ₂
occurs, the pressure in the ink pressurizing chamber 181 increases by ΔP, and its internal pressure becomes P ₂ +ΔP. At this time, ΔQ ₁ flows out from the outlet of the ink ejection port, and ΔQ ₃ flows out to the inlet side of the ink supply port 183. The pressure distribution at this time is considered to be as shown in FIG. 20c, and the following equations 27 to (29) hold true regarding the flow. △Q ₂ = △Q ₁ + △Q ₃ ... (27) △Q ₁ = △P + (P ₂ - P ₀ ) / R ₁ ... (28) △Q ₃ = △P - (P ₃ - _{P 2} )/R ₃ ...(29) holds true. However, R ₁ is the total pipe resistance of C ₁ R ₂ is the total pipe resistance of C ₃ Pipe resistance generally varies depending on the structure, and as a specific example of this method, for a capillary, R ₁ = 128 μl/πd ⁴ ρ... ...(30) d: Capillary inner diameter, μ: Liquid viscosity coefficient, ρ: Liquid density, l: Capillary length For short tube orifices Therefore, the pipe resistance is nonlinear. In addition, the specific structure of the ink supply pipe is (1) a single pipe with a uniform cross-sectional area, (2) one with a porous body (filter), and (3) a valve whose pipe resistance varies depending on the direction of flow. There are some that have this. In both cases, ink flows out through the outlet of the ink ejection port _C1 due to the contraction of the internal volume of the ink pressurizing chamber _C2 , but even for the same volume change △ _Q2 , the structure of the ink supply port C3 _changes . Therefore, the appearance of the jet, the shape of the droplets, the presence or absence of satellite droplets, etc. differ.
The pipe resistance of C ₃ is (1) the same as type 30 for a single pipe. (2) For porous bodies (filters), from Darcy's formula, R ₃ = μl ₃ /kS ₃ ... (31) S ₃ : Cross-sectional area of porous bodies, l ₃ : Thickness of porous bodies,
μ: viscosity coefficient of fluid, k: permeability of porous body In addition, when fluid becomes turbulent in a porous body, inertial force acts, △P-(P ₃ - P ₂ )/l ₃ = μ/K( △ _Q3 / _S3 )
+ρ/B(△ _Q3 / _S3 )...(32) _R3 =△P-( _P3 - _P2 )/△ _Q3 ...(33). However, K and B are constants determined by the internal structure of the porous body. Next, considering the forces acting on the fluid, the ink ejection port C ₁ and the ink pressurizing chamber C ₂
^At _{the boundary of _} ^_ _{_ _ _ _}
…(34) holds true. The first term on the right side is the inertial force accompanying the accelerated movement of the ink in the ejection port, and the second term on the right side is the viscous frictional force of the ink. At the boundary between the ink supply port C ₃ and the ink pressurizing chamber C ₃ π(d ₃ /2) ² {△P−(P ₃ −P ₂ )}= ρ(d ₃ /2) ² πl ₃ dυ ₃ /dt+8πμl ₃ υ ₃ …
…(35) holds similarly. However, at the ink supply port,
In general, d ₃ ≫d ₁ and υ ₃ ≪υ ₁ , so the (35th)
The viscous friction term on the right side of the equation is smaller than the inertial force term. Generally, when ink is ejected from an ink ejection port by pressurized contraction, the larger R ₃ is and the smaller υ ₃ is, the higher the ejection sensitivity is. Next, the state in which the ink pressurizing chamber 181, which has been deflated after ink ejection has been completed, is in an expansion process will be analyzed.
There are three types of expansion: (1) Direct return to resting equilibrium state. At this time, the internal pressure of the ink pressurizing chamber 181 becomes P ₂ , and this stroke becomes △Q ₁ =0 △Q ₂ >0 △Q ₃ <0, and ink is supplied from the supply port 183 at a flow rate equal to the ejection amount. be done. (2) Ink pressurizing chamber 181 further than the static equilibrium state
(see Figure 20d), P ₀ <P ₂ -△P<P ₃ Nozzle external pressure P ₀ <P ₂ -△P. At this time,
△Q ₁ = 0, but the values of △Q ₂ and △Q ₃ are
It becomes larger compared to (1). That is, since the difference between the pressure and the pressure at the ink supply port 183 becomes larger, the ink supply speed becomes faster. Furthermore, since the pressure in the ink pressurizing chamber 181 does not drop below the nozzle external pressure, ink near the ink ejection port 182 will not flow backward and air from outside will not be taken in. (3) The ink pressurizing chamber 181 is further expanded than the static equilibrium state.
expands and becomes lower than the nozzle external pressure (second
(See Figure 0) P ₀ > P ₂ - △P < P ₃ At this time, the internal pressure of the ink pressurizing chamber 181 is lower than the nozzle external pressure, so △Q ₁ <0 △Q ₂ >0 △Q ₃ <0 Therefore, ink corresponding to the stroke of the expanding body flows in from the ink supply port 183 and the ink ejection port 182. Generally, the orifice after ink is ejected is in contact with air, so the ink ejection port 182
At the same time, the ink remaining in the ink chamber 181 is caused to flow backward, and at the same time, air from the outside is taken in and bubbles are generated in the ink pressurizing chamber 181. However, since the pressure difference between the ink supply port and the ink supply port is large,
The amount of ink flowing in from the ink outlet 181 also increases, but if this inflow velocity is lower than the inflow velocity from the ink ejection port 181, the above-mentioned result will occur.
This is a condition that must be avoided in liquid injection devices. When air bubbles enter the ink pressurizing chamber 181, when the ink pressurizing chamber 181 contracts, only the air bubbles with a high volume change rate contract, and the ink pressurizing chamber 1
The liquid pressure of the ink No. 81 does not increase. That is,
Air bubbles act as pressure buffers and should be avoided in all other fluid control equipment. FIG. 21 and FIG. 22 are external views showing a specific embodiment of a single gun type ink ejecting device. Second
In FIG. 1, a piezoelectric body 191 has an annular shape and serves as a source of external force for expansion and contraction of an ink pressurizing chamber 196. Two or more pieces of this piezoelectric body 191 are provided so that their same polarized surfaces face each other and are in close contact with each other. It is tightened. Electrodes 201, 202
are each formed of a washer-like thin metal plate, one of which is inserted between the two piezoelectric bodies 191, 191, and the other is between the piezoelectric body 191 and the ink chamber nut portion 19.
It is inserted at the joint surface with 3. Note that the electrode 202 may be inserted between the piezoelectric body 191 and the ink chamber bolt portion 192. Ink pressurization chamber 19
Reference numeral 6 indicates a hollowed-out central axis of the bolt portion 192 and the nut portion 193, and a cylindrical ink chamber 1.
It has 96. A male thread (not shown) is formed at the rear end of this bolt shaft, and meshes with a nut portion 193 formed with a female thread of the same diameter.
The expansion and contraction in the axial direction of the ink pressurizing chamber is performed by the elastic body (thin cylinder) 203 located inside the annular piezoelectric bodies 191, 191, and by tightening the bolt part 192 and nut part 193. Initial stress is given. When a voltage with the same polarity as the polarization of the piezoelectric body 191 is applied to the electrodes 201 and 202, the piezoelectric body 19
1 expands due to thickness vibration and applies a tensile force in the axial direction to the hollow cylinder of the ink chamber 196. electrode 201,
When a voltage having a polarity opposite to that of the piezoelectric body 191 is applied to the piezoelectric body 202, the piezoelectric body 191 contracts in the axial direction due to the initial stress of the hollow cylinder. In FIGS. 21 and 22, an orifice plate 194 having an orifice 195 serving as an ink ejection port is attached to the end face of the bolt portion 192 of the ink pressurizing chamber 19. Further, the ink supply port is constructed by press-fitting a joint 197 into the inner surface of the central cylinder of the nut portion 193. A conduit 198 as a supply port is formed in this joint 197, and an ink supply pipe (not shown) is connected to this conduit 198. In addition, this conduit 19
Generally, the cross-sectional area of the orifice 195 is extremely large compared to the inner diameter of the orifice 195. The configuration of the ink pressurizing chamber shown in FIG. 22 is almost the same as that shown in FIG. is formed. Further, in the ink pressurizing chamber shown in FIG. 22, a metal fiber sintered filter 200 is inserted into the joint 197 in order to control the pipe resistance on the ink supply port side. By appropriately selecting the transmittance, axial thickness, and cross-sectional area, the target pipe resistance is determined. The expansion speed of the ink pressurizing chamber shown in FIGS. 21 and 22 is approximately determined by the axial dimension of the ink pressurizing chamber, as described in the section on mathematical analysis of vibration, but strictly speaking, the expansion speed of the ink pressurizing chamber shown in FIG. It can be found from equation (21) to equation (26). Note that for the annular piezoelectric body 191 having the same thickness dimension, the axial dimension of the bolt part 192 of the ink pressurizing chamber, the nut part 19
The longer the axial dimension of 3, the lower the resonant frequency, and the shorter the axial dimension, the higher the resonant frequency. Therefore, in order to improve the response frequency characteristics of this single gun type injection device, the axial dimensions other than the piezoelectric body 191 should be eliminated as much as possible. Here, among the types in which the ink pressurizing chamber and the ink ejection port are integrated, the relationship between the typical structural dimensions of the prototype, the voltage applied to the piezoelectric body, and the amount of change in the ink chamber volume at that time is shown in Attached Table 2. . This Attached Table 2 shows the voltage applied to the piezoelectric body necessary to obtain the desired ejected droplet diameter, but it is assumed that the voltage sensitivity of the strain in the axial direction of the ink pressurizing chamber is higher than that of the piezoelectric body. 1/2 and prevents ink from flowing back into the ink supply port when the ink pressurizing chamber contracts. Therefore, the voltage applied to the piezoelectric body required for actual droplet ejection is slightly higher than the value in Appendix 2. FIG. 23 is a cross-sectional view of a base plate in a multi-type liquid ejecting device according to another embodiment of the present invention, viewed from the ink pressurizing chamber side. Figure 24 is the 23rd
25 is a plan view of the etching plate, and FIG. 26 is a plan view of the orifice plate. Next, the multi-type liquid injection device will be explained with reference to FIGS. 23 to 26. The base plate 21 is formed into a disk shape, and for example, six ink pressurizing chambers 22 are arranged concentrically thereon. Ink supply joints 23 are provided in association with these ink pressurizing chambers 22. These ink pressure chambers 22 and ink supply joints 23 are, for example, vinyl tubes 24.
Each is connected by... Further, an ink supply path 3 is provided in a circumferential manner inside the base plate 21.
0 is formed, and this ink supply path 30 communicates each ink supply joint 23 . . . with an ink supply port 29 that receives ink sent from an external ink tank. As shown in FIG. 24, the ink pressurizing chamber 22 includes a cylindrical ink pressurizing chamber flange 221, an elastic body 222 for expanding and contracting the cylindrical ink pressurizing chamber, and this elastic body 22.
an ink chamber interior 223 in which the inside of the ink chamber 223 is hollowed out;
A check valve mounting space 224 communicating with the ink chamber interior 223, an ink supply port 225, a check valve mounting holder 226, and two annular piezoelectric bodies 2
27, 227, and a piezoelectric body electrode 228 for applying a voltage to the piezoelectric bodies 227, 227. A thread is formed on the outer periphery of one end of the elastic body 222, and this thread meshes with a thread in a through hole 211 formed in the base plate 21. Also,
A thread is also formed in the portion of the elastic body 222 to which the flange 221 is attached, and this threaded portion and the threaded portion of the flange 221 mesh with each other. That is,
By tightening the flange 221, the piezoelectric body 2
27,227 are fixed. Note that the check valve installation space 224 may be provided with a porous filter for setting the flow pipe resistance to an appropriate value or a check valve whose pipe resistance varies depending on the time of supply and discharge. In FIG. 25, the etching plate 25 is formed into a disk shape that is substantially the same as the base plate 21, and has ink guide portions 251 extending radially from the center thereof. These ink lead-out portions 251 . . . guide ink pressurized by the ink pressurizing chamber 22 to an orifice 261 formed in an orifice plate 26, which will be described later. In addition, the etching plate 25 includes
This etching plate 25 and base plate 2
1 and the orifice plate 26 with bolts 271..., 281
... are drilled respectively. In FIG. 26, the orifice plate 26 is connected to the base plate 21 and the etching plate 2.
5, and six orifices 261... are bored in the center thereof. Further, this orifice plate 26 is also provided with bolt mounting holes 272 . . . , 282 . When assembling the above-described base plate 21, etching plate 25, and orifice plate 26, insert the bolts 27 into the respective mounting holes 212,
271, 272, and the bolts 28 are inserted into the respective mounting holes 213, 281, 282. Next, the flow of ink will be explained. first,
Ink flows from an ink storage tank (not shown) through a supply pipe into an ink supply port 29 formed in the base plate 21 under static pressure. The ink that has flowed into the ink supply port 29 flows to each ink supply joint 23 . . . via an ink supply path 30 formed in the base plate 21 . Each ink supply joint 23 and the ink pressurizing chamber 22 are communicated with each other by a highly elastic pipe 24 with low gas permeability, and connected to a pressurizing chamber ink supply port 225 . The ink in the ink pressurizing chamber 22 is supplied to the piezoelectric body 227,
The pressure inside the ink chamber 223 increases due to the contraction of the ink 227, and a part of the ink flows back into the ink supply port 225.
The other parts are the ink outlet part 2 of the etching plate 25.
51 to the orifice 261 of the orifice plate 26. Then, several drops of ink are ejected from the orifice 261. Further, after the droplets are ejected from the orifice 261, the internal volume of the ink pressurizing chamber 22 expands, and the orifice 261
At the same time that the ink meniscus faces from the end surface of the ink pressurizing chamber 22, ink is supplied through the ink supply port 225 of the ink pressurizing chamber 22. As described above, according to this embodiment, by integrally forming a plurality of ink pressurizing chambers, when printing each dot in a dot matrix shape, for example, the corresponding ink can be ejected from each orifice 261. can be done. As described above, according to this embodiment, the internal volume of the ink pressurizing chamber is changed using the thickness vibration of the piezoelectric ceramic to eject the ink droplets. The effects of the device are as follows. (1) When trying to increase the ink ejection response frequency using conventional pressurization methods (circular bimorph, rectangular bimorph, cylindrical breathing vibration), the amount of volume change in the ink pressurizing chamber rapidly decreases, resulting in a substantially faster response. Although it was not possible to realize a liquid injection device,
In this example, the thickness vibration of the piezoelectric ceramic is directly used to expand and contract the elastic cylinder in the axial direction, thereby changing the internal volume of the ink chamber. Therefore, the ink jetting repetition frequency can be increased without reducing the amount of volume change. It can be made higher. Specifically, in the conventional method, the ejection repetition frequency was limited to 20kHz with one orifice, but the ejection repetition frequency of the liquid injection device according to the present invention is
Now possible up to 100kHz. (2) The amount of change in the volume of the ink pressurizing chamber is determined by the material constants and shape of the elastic body that constitutes the ink pressurizing chamber, the material constants and shape of the piezoelectric body, and the applied voltage. It is not affected by the amount of ink occupied or the amount of residual gas in the room. Therefore, changes in the performance of the ejecting device due to changes in the physical properties of the ink can be reduced. (3) Since the time required for volume change is very short compared to other methods, the droplet ejection speed is fast and the distance between the nozzle and the recording paper can be set large. (4) Since the elastic body for the ink pressurizing chamber and the piezoelectric body are fixed with screws without using adhesive or the like, assembly, disassembly, and repair can be made extremely easy. As described above, according to the present invention, since the volume of the ink pressurizing chamber is changed by the thickness vibration of the piezoelectric ceramic, the volume change amount and the resonance frequency can be set independently.
A liquid ejecting device that can increase the response frequency and is suitable for high-speed printing can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing relational expressions such as the support method, displacement when the shape and dimensions are given, and resonance frequency in the case of a rectangular bimorph vibrator. FIG. 2 is a diagram showing how to determine the resonant frequency when the length and thickness are given when both ends are supported. FIG. 3 is an illustrative diagram for explaining a circumferentially supported circular bimorph, which is the background of the present invention. FIG. 4 is an illustrative diagram for explaining a rectangular bimorph supported at both ends, which is the background of the present invention. FIG. 5 is an external perspective view of a hollow cylindrical respiratory oscillator, which is the background of the present invention. FIG. 6 is an external perspective view showing a hollow cylindrical axial vibrator to which the present invention is applied. FIG. 7 is a longitudinal sectional view showing an elastic cylinder for an ink pressurizing chamber according to an embodiment of the present invention arranged in the center of an annular piezoelectric ceramic. FIG. 8 is a longitudinal sectional view showing a cylindrical piezoelectric ceramic arranged inside an ink pressurizing chamber according to another embodiment of the present invention. FIG. 9 is a diagram for explaining a single-layer structure piezoelectric ceramic included in one embodiment of the present invention. FIG. 10 is a diagram for explaining a piezoelectric ceramic having an N-layer structure included in an embodiment of the present invention. FIG. 11 is a longitudinal sectional view of the composite vibrator. FIG. 12 and FIG. 13 are diagrams for explaining the specific shape of the ink pressurizing chamber and the resonance frequency at that time. FIG. 14 is an external view showing an example of a Langivin resonator. FIG. 15 is an external view showing another example of the Langivin resonator. FIG. 16 is a characteristic diagram showing the relationship between the applied voltage and the amount of strain of the Langivin vibrator. FIG. 17 is a diagram showing the frequency characteristics of the amount of axial expansion and contraction of the ink pressurizing chamber in one embodiment of the present invention. FIG. 18 is a diagram showing the internal volume vibration waveform with respect to the voltage waveform applied to the piezoelectric body of the ink pressurizing chamber. FIG. 19 is a diagram showing vibrations in the axial direction of the ink pressurizing chamber when an arcing sinusoidal wave is applied to the piezoelectric body of the ink pressurizing chamber. FIG. 20 is an illustrative diagram for explaining changes in pressure in the ink ejection mechanism. FIG. 21 and FIG. 22 are external views showing a specific embodiment of a single gun type liquid injection device. Second
FIG. 3 is a plan view of a base plate in a multi-type liquid ejecting device according to another embodiment of the present invention, viewed from the ink pressurizing chamber side. FIG. 24 is a longitudinal sectional view of the main part taken along line A-A' in FIG. 23. FIG. 25 is a plan view of the etching plate included in the multi-type liquid injection device. FIG. 26 is a plan view of an orifice plate included in the multi-type liquid injection device. In the figure, 52, 61, 92, 93, 191
is a piezoelectric ceramic, 5, 6, 22 are ink pressurizing chambers, 55, 65, 196, 223 are ink chambers, 6
3 is an external container; 51, 62, and 92 are elastic bodies; 5
3, 54, 95, 96, 192, 193 are flange parts, 195, 261 are orifices, 197, 2
25 is an ink supply port, 251 is an ink outlet, 2
3 is an ink supply joint, 30 is an ink supply path, 21 is a base plate, 25 is an etching plate, and 26 is an orifice plate.

【table】

【table】

【table】

Claims (1)

[Claims] 1. A liquid ejecting device that ejects liquid by changing the volume of a liquid pressurizing chamber, wherein the liquid pressurizing chamber has flange portions at both ends, and the liquid pressurizing chamber is filled with liquid. a hollow cylindrical elastic body formed; a liquid injection port formed at one end of the elastic body so as to communicate with the liquid pressurizing chamber; the other end of the elastic body communicating with the liquid pressurizing chamber. a liquid supply port formed in the elastic body, and a piezoelectric ceramic formed in the shape of a hollow cylinder, the inner diameter of which is larger than the outer diameter of the elastic body, and whose both ends are held by flanges at both ends of the elastic body. , liquid injection device. 2. A plurality of the liquid pressurizing chambers are formed on a base, and a liquid supply path that commonly communicates with the liquid supply port of each liquid pressurizing chamber is formed on the base.
A liquid ejecting device according to claim 1. 3. In a liquid ejection device that ejects liquid by changing the volume of a liquid pressurizing chamber, the liquid pressurizing chamber is formed into a hollow cylindrical shape by an elastic body, and further includes a liquid injection port communicating with the liquid pressurizing chamber. a piezoelectric ceramic provided inside the liquid pressurizing chamber, whose thickness vibration follows the axial direction of the cylindrical shape of the liquid pressurizing chamber, and a piezoelectric ceramic provided at a predetermined gap from the outer wall of the liquid pressurizing chamber. an external container that covers the liquid pressurizing chamber, and a gap between the liquid pressurizing chamber and the external container,
When the liquid is filled and the piezoelectric ceramic causes the thickness vibration, the piezoelectric ceramic expands and contracts the liquid pressurizing chamber in the axial direction, thereby causing the liquid to be ejected from the liquid injection port. liquid injection device. 4. The liquid ejecting device according to claim 3, wherein the piezoelectric ceramic is sandwiched between one inner end surface of the elastic body and an inner end surface of the outer container that faces the inner one end surface. 5. The liquid ejecting device according to claim 3 or 4, wherein the liquid pressurizing chamber further includes a liquid supply port for supplying the liquid. 6. A plurality of the liquid pressurizing chambers are formed on a base, and a liquid supply path that commonly communicates with the liquid supply port of each liquid pressurizing chamber is formed on the base.
A liquid ejecting device according to any one of claims 3 to 5.