JP3988351B2 - Inkjet recording head and image recording apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ink jet recording head that discharges ink from a nozzle opening due to pressure fluctuation in a pressure generating chamber, and an image recording apparatus such as an ink jet printer including the ink jet recording head.
[0002]
[Prior art]
As an ink jet recording apparatus, an ink jet printer, an ink jet plotter, and the like are well known. Some ink jet recording heads (hereinafter referred to as recording heads) used in such ink jet recording apparatuses use piezoelectric vibrators as electromechanical transducers.
As shown in FIG. 5A, the recording head 50 includes a piezoelectric vibrator unit in which a plurality of piezoelectric vibrators 51 are unitized, a case 52 in which the piezoelectric vibrator units can be housed and fixed, And a flow path unit 53 joined to the front end surface of the case 52. The flow path unit 53 is configured by joining a nozzle plate 55 to one surface of a flow path forming plate 54 and joining a diaphragm 56 to the other surface.
[0003]
In the nozzle plate 55, a plurality of nozzle openings 57 are formed in a row. The flow path forming plate 54 includes a plurality of pressure generation chambers 58 communicating with the nozzle openings 57, a common ink chamber 59 for storing ink to be supplied to the pressure generation chambers 58, and the common ink chamber 59. The ink supply ports 60 and the like communicating with the respective pressure generation chambers 58 are defined by partition walls. The diaphragm 56 is formed, for example, by etching a composite plate obtained by laminating a resin film 62 on a stainless steel plate 61, and the thick portion 56a is formed by leaving the stainless steel rod 61 in an island shape. In addition, a thin portion 56b of only the resin film 62 is formed around the thick portion 56a. Then, the piezoelectric vibrator unit is fixed to the case 52 such that the free end of the piezoelectric vibrator 51 is in contact with the thick portion 56a.
[0004]
The recording head 50 configured as described above supplies the ink in the common ink chamber 59 into each pressure generating chamber 58 through the ink supply port 60, and the diaphragm 56 is bent by the expansion and contraction of the piezoelectric vibrator 51 to thereby pressurize the diaphragm 56. Pressure fluctuations are generated in the generation chamber 58, and ink droplets are ejected from the nozzle openings 57 by the pressure fluctuations.
[0005]
[Problems to be solved by the invention]
By the way, in this type of recording head, when the ink droplets are ejected, the natural vibration of the Helmholtz resonance frequency is excited in the ink in the pressure generating chamber. There is a risk of shifting to energy of vibration in a direction orthogonal to the longitudinal direction. When energy transfer occurs, there is no damper element for stopping the lateral vibration of the vibrator in the recording head, so that the lateral vibration lasts for a long time. Furthermore, the energy of the transverse vibration acts on the ink in the pressure chamber due to the transverse vibration of the piezoelectric vibrator for a long time, etc., and after ejecting the ink droplet, the meniscus (the ink exposed at the nozzle opening) The vibration of the free surface (indicated by reference numeral 63 in FIG. 5) does not easily converge.
Here, if the next ink droplet is ejected in a state where the vibration of the meniscus is not sufficiently converged, ink mist may be generated, causing image quality defects. For this reason, it is necessary to wait until the vibration of the meniscus sufficiently converges, which is one factor that hinders high-frequency driving.
[0006]
Further, when the excited lateral vibration is large or is sustained for a longer time than necessary, a pressure wave α that reciprocates in the pressure generating chamber 58 is also generated. The pressure wave α behaves as if the inside of the pressure generating chamber 58 is an acoustic tube, and repeats reflection reciprocation between the nozzle opening 57 and the ink supply port 60. As a result, as indicated by a solid line in FIG. 5B, when the ink pressure on the nozzle opening 57 side is high in the pressure generating chamber 58, the ink pressure on the ink supply port 60 side is low, and as indicated by the dotted line. In addition, when the ink pressure on the nozzle opening 57 side is low, a pressure deviation occurs in which the ink pressure on the ink supply port 60 side increases. This uneven ink pressure also contributes to the generation of ink mist.
[0007]
In view of the above problems, an object of the present invention is an ink jet recording head capable of preventing excessive continuation of lateral vibration in a piezoelectric vibrator and improving responsiveness of ink droplet ejection, and an image recording apparatus provided with the same Is to provide.
[0008]
[Means for Solving the Problems]
The present invention has been proposed in order to achieve the above object. According to the first aspect of the present invention, there is provided a nozzle plate having a plurality of nozzle openings, and an empty portion serving as a pressure generating chamber corresponding to the nozzle openings. A plurality of side-by-side channel forming plates, a vibration plate joined to the channel forming plate to form part of the inner wall of the pressure generating chamber, and one end in the longitudinal direction that is elongated in the vertical direction and the other An ink-jet having an electromechanical transducer element whose free end portion can vibrate in the longitudinal direction, and deforming the diaphragm by the longitudinal vibration of the free end portion of the electromechanical transducer element so as to vary the volume of the pressure generating chamber In the recording head,
The diaphragm includes an island portion whose periphery is composed only of an elastic film in a portion corresponding to the pressure generation chamber, and the tip of the free end portion of the electromechanical transducer is brought into contact with the island portion,
In the ink jet recording head, the vibration period of the natural vibration excited by the ink in the pressure generating chamber is shorter than the transverse vibration primary mode period of the free end portion of the electromechanical transducer.
[0009]
Here, the “electromechanical conversion element” is an element that causes mechanical deformation by application of a drive signal, and corresponds to, for example, a piezoelectric vibrator.
[0011]
As for the thing of Claim 2, an island part is a block shape long and thin in the direction orthogonal to the row direction of a nozzle opening,
2. The ink jet recording head according to claim 1, wherein the direction of the transverse vibration of the electromechanical transducer coincides with the longitudinal direction of the island portion.
[0012]
According to the third aspect of the present invention, the center of the electromechanical transducer element and the center of the island portion in the longitudinal direction of the island portion are aligned, and the tip portion of the electromechanical transducer element is brought into contact with the island portion in this state. An ink jet recording head according to claim 1 or 2, wherein
[0013]
According to a fourth aspect of the present invention, the vibration period of the pressure vibration reflected and reciprocated inside the pressure generation chamber is longer than the vibration period of the natural vibration excited by the ink. An ink jet recording head according to any one of the above.
[0014]
The ink jet recording according to any one of claims 1 to 4, wherein the pressure generating chamber is a chamber elongated in a direction orthogonal to the direction in which the nozzle openings are arranged. Head.
[0015]
The structure described in claim 6 is characterized in that one end of the electromechanical transducer is joined to the fixed plate, and the free end protrudes from the edge of the fixed plate. The ink jet recording head described in 1.
[0016]
A seventh aspect of the present invention is the ink jet recording head according to any one of the first to sixth aspects, wherein the electromechanical conversion element is formed in a comb-teeth shape elongated in the vertical direction.
[0017]
The invention according to claim 8 is configured to supply a drive voltage simultaneously over the entire free end when the electromechanical transducer is driven. The ink jet recording head described in 1.
[0018]
A ninth aspect of the present invention is the ink jet recording head according to any one of the first to eighth aspects, wherein the electromechanical transducer is a lateral effect type piezoelectric vibrator.
[0019]
A tenth aspect of the present invention is the ink jet recording head according to any one of the first to eighth aspects, wherein the electromechanical transducer is a longitudinal effect type piezoelectric vibrator.
[0020]
According to an eleventh aspect of the present invention, the piezoelectric vibrator is a laminated piezoelectric vibrator configured by alternately laminating piezoelectric bodies and internal electrodes. Inkjet recording head.
[0021]
According to a twelfth aspect of the present invention, there is provided an image recording apparatus comprising the ink jet recording head according to any one of the first to eleventh aspects.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, an ink jet printer 31 (hereinafter referred to as a printer 31), which is a typical image recording apparatus, will be described with reference to FIG.
[0023]
The illustrated printer 31 includes a carriage 33 to which the recording head 2 is attached and holds an ink cartridge 32. The carriage 33 is movably attached to a guide member 35 installed on the housing 34, and is reciprocated along the guide member 35 (that is, along the main scanning direction) by a head scanning mechanism. .
[0024]
The head scanning mechanism includes a pulse motor 36 provided at one end of the case 34, a drive pulley 37 connected to the rotation shaft of the pulse motor 36, and an idle pulley 38 provided at the other end of the case 34. And a timing belt 39 that is spanned between the drive pulley 37 and the idle pulley 38 and connected to the carriage 33, a printer controller (not shown) that controls the rotation of the pulse motor 36, and the like. It is. In other words, this head scanning mechanism operates the pulse motor 36 to reciprocate the carriage 33, that is, the recording head 2, in the width direction of the recording paper 40 which is a kind of print recording medium. In addition, the printer 31 includes a paper feeding mechanism that feeds the recording paper 40 in the sub-scanning direction orthogonal to the main scanning direction. This paper feed mechanism is composed of a paper feed motor 41, a paper feed roller 42, and the like. The printer controller controls the recording head 2, the pulse motor 36, the paper feed motor 41, and the like based on the print data transmitted from the host computer, and performs the main scanning of the recording head 2 and is linked to the main scanning. Then, the recording paper 40 is sequentially sent out.
[0025]
Next, the recording head 2 will be described in detail. FIG. 1 is a cross-sectional view of an embodiment of an ink jet recording head 2, and FIG. 2 is a schematic view showing a main part of the recording head 2 shown in FIG. 1. In the recording head 2 of the present embodiment, the piezoelectric vibrator 1 is used as an electromechanical conversion element.
[0026]
As shown in FIG. 1, the illustrated recording head 2 includes a plurality of piezoelectric vibrators 1..., A fixed plate 7, a flexible cable 6, and the like, and a piezoelectric vibrator unit. A case 3 that can be stored and a flow path unit 5 that is joined to the front end surface of the case 3 are provided.
[0027]
The case 3 is a block-shaped member made of synthetic resin in which a storage chamber 4 having an open front end and a rear end is formed. A piezoelectric vibrator unit is stored and fixed in the storage chamber 4. The piezoelectric vibrator unit has a posture in which the comb-like tip 1 a of the piezoelectric vibrator 1 faces the opening on the tip side, and the fixing plate 7 is bonded to the wall surface of the storage chamber 4.
[0028]
The piezoelectric vibrator 1 has a comb-like shape elongated in the vertical direction, and is formed, for example, by being cut into needles having an extremely narrow width of about 50 μm to 100 μm. The illustrated piezoelectric vibrator 1 is a laminated piezoelectric vibrator configured by alternately laminating piezoelectric bodies 1c and internal electrodes 1d, and can expand and contract (i.e., vibrate) in a vertical direction perpendicular to the electric field direction. This is a lateral effect (d31 effect) type piezoelectric vibrator. Each of the piezoelectric vibrators 1... Has a base end portion joined to the fixed plate 7, and a cantilever in which the free end portion 1 b of the piezoelectric vibrator 1 protrudes outward from the edge of the fixed plate 7. It is attached in the state. In addition, the comb-shaped tips 1a of each piezoelectric vibrator 1 are abutted and fixed to island portions 22 which are predetermined portions of the flow path unit 5, respectively, and the flexible cable 6 is opposite to the fixed plate 7. It is electrically connected to the piezoelectric vibrator 1 on the side surface of the base end portion of the vibrator.
[0029]
The internal electrode 1d is composed of a common internal electrode having a constant potential and individual internal electrodes whose potential varies with the supply of a driving voltage. The common internal electrodes and the individual internal electrodes are alternately stacked with the piezoelectric body 1c interposed therebetween. ing. The potential of the individual internal electrode varies in units of piezoelectric vibrators, and the common internal electrode is set to the same potential in all the piezoelectric vibrators 1. The overlapping region of these common internal electrodes and individual internal electrodes is formed over substantially the entire region of the free end portion 1b in the longitudinal direction of the vibrator.
For this reason, when a driving voltage is applied to the individual electrode of the piezoelectric vibrator 1 to be driven, this driving voltage is supplied simultaneously over substantially the entire free end 1 b of the piezoelectric vibrator 1. Thereby, a uniform electric field acts on the free end 1b in the electrode stacking direction at a time, and the free end 1b expands or contracts in the longitudinal direction. In this way, by simultaneously applying a uniform electric field over the entire length of the free end 1b, the free end 1b can be excited in the primary mode.
[0030]
The flow path unit 5 has the nozzle plate 9 disposed on one surface side of the flow path forming plate 8 with the flow path forming plate 8 interposed therebetween, and the vibration plate 10 on the other surface opposite to the nozzle plate 9. It is configured by arranging and laminating on the side.
[0031]
The nozzle plate 9 is a thin plate made of stainless steel in which a plurality of nozzle openings 11 are opened in a row at a pitch corresponding to the dot formation density. In this embodiment, 96 nozzle openings 11 are opened at a pitch of 180 dpi, and a nozzle row is constituted by these nozzle openings 11. Then, the nozzle rows are formed in a plurality of rows corresponding to the colors of ink that can be ejected.
[0032]
As shown in FIG. 2, a plurality of flow path forming plates 8 are formed in a state in which empty portions that become pressure generation chambers 13 are partitioned by partition walls so as to correspond to the respective nozzle openings 11 of the nozzle plate 9, and the ink supply ports 14 and the common ink chamber 15 are formed in a plate-like member. The pressure generation chamber 13 is a chamber that is elongated in a direction orthogonal to the direction in which the nozzle openings 11 are arranged (nozzle row direction), and a part of the pressure generation chamber 13 is substantially parallel in cross section through the thickness direction of the flow path forming plate 8. It is constituted by a quadrangular through hole 16, and the remaining part is constituted by a flat concave chamber partitioned by a dam portion 17. The dam portion 17 is formed in the flow path from the common ink chamber 15 to the pressure generation chamber 13, and the ink supply port 14 is formed by the dam portion 17 in the form of a narrowed portion having a narrow flow path width.
The through hole 16, the pressure generating chamber 13, the ink supply port 14, and the common ink chamber 15 of the flow path forming plate 8 are formed by etching a silicon wafer.
[0033]
In the present embodiment, the through hole 16 is formed at one end of the pressure generation chamber 13, that is, at a position farthest from the common ink chamber 15 in the pressure generation chamber 13. An ink supply port 14 is connected to the other end of the pressure generating chamber 13, and the nozzle opening 11 is disposed in the vicinity of the end opposite to the ink supply port 14.
The common ink chamber 15 is a chamber for supplying the ink stored in the ink cartridge 32 to each pressure generating chamber 13, and an ink supply pipe 19 through which the ink from the ink cartridge 32 passes substantially at the center in the longitudinal direction. Communicate.
[0034]
The vibration plate 10 is laminated on the other surface of the flow path forming plate 8 and the sealing plate that seals one opening surface of the pressure generating chamber 13, and seals one opening surface of the common ink chamber 15. It also has a double structure in which a resin film 21 such as PPS (polyphenylene sulfide) is laminated on the stainless steel plate 20. Since the sealing plate and the elastic film are made of the same material, the portion that functions as the sealing plate, that is, the stainless steel plate 20 corresponding to the pressure generation chamber 13 is etched to etch the tip of the piezoelectric vibrator 1. A thick wall portion (island portion 22) for abutting and fixing the film is formed, and a portion functioning as an elastic film, that is, a portion corresponding to the common ink chamber 15 is removed by etching to remove the film. Only the portion 21 (elastic film) is used. The island portion 22 has an elongated block shape in a direction perpendicular to the direction in which the nozzle openings 11 are arranged, like the planar shape of the pressure generating chamber 13, and the longitudinal center of the island portion 22 and the axis of the piezoelectric vibrator 1 (illustrated). In the example of FIG. 5, the piezoelectric material is attached in a state in which it is aligned with the center in the piezoelectric material stacking direction.
[0035]
In the recording head 2 having the above-described configuration, by extending the piezoelectric vibrator 1 in the vibrator longitudinal direction (that is, the longitudinal direction), the island portion 22 is pressed toward the nozzle plate 9, and the film portion around the island portion 22. The (elastic film) 21 is deformed and the pressure generating chamber 13 contracts. Further, when the piezoelectric vibrator 1 is contracted in the vibrator longitudinal direction, the pressure generating chamber 13 is expanded by the elasticity of the film portion 21. Then, by controlling the expansion / contraction of the pressure generating chamber 13, the ink pressure in the pressure generating chamber 13 varies and ink droplets are ejected from the nozzle openings 11.
[0036]
The vibration system in the recording head 2 configured as described above can be represented by an equivalent circuit shown in FIG. In FIG. 3, symbol M is an inertance [Kg / m ⁴ ] which is the mass of the medium per unit length, Ma is an inertance in the piezoelectric vibrator 1, Mn is an inertance in the nozzle opening 11, and Ms is an ink supply port. 14 is inertance. Symbol R is resistance [N · s / m ⁵ ] which is an internal loss of the medium, Ra is resistance in the piezoelectric vibrator 1, Rn is resistance in the nozzle opening 11, and Rs is resistance in the ink supply port 14. Symbol C is a compliance [m ⁵ / N] which is a volume change per unit pressure, Cc is a compliance between the partition wall forming the pressure generating chamber 13 and the diaphragm 10, Ca is a compliance in the piezoelectric vibrator 1, Cn is the compliance of the nozzle plate 9. The symbol P is a pressure generated by the piezoelectric vibrator 1 over time, in other words, a voltage pulse applied to the piezoelectric vibrator 1 converted into an equivalent pressure.
[0037]
The natural frequency fc of the natural vibration excited by the ink in the pressure generation chamber 13 can be expressed by the following equation (1) using the above Mn, Ms, and Cc.
[0038]
fc = 1 / 2π × √ [(Mn + Ms) / (Mn · Ms · Cc)] (1)
[0039]
Further, the vibration period (Helmholtz resonance frequency) Tc of the natural vibration of the ink can be expressed by the following equation (2) using the above natural frequency fc. The natural vibration period Tc of the ink is a factor that affects the ink speed and the ink amount.
[0040]
Tc = 1 / fc (2)
[0041]
In the present embodiment, the vibration period Tc of the natural vibration excited in the pressure generating chamber 13 is set to be shorter than the transverse vibration primary mode period of the piezoelectric vibrator 1, thereby exciting the natural vibration period Tc. The transverse vibration (specifically, the vibration in the longitudinal direction of the island portion 22) of the piezoelectric vibrator 1 is prevented.
[0042]
Here, if the natural frequency of the transverse vibration of the piezoelectric vibrator 1 is fh, fh can be expressed as the following equation (3).
[0043]
fh = λ ² / 2πL ² × √ [(Eh · I) / (A · ρ)] (3)
[0044]
In this formula (3), L is the length [m] of the free end 1b of the piezoelectric vibrator 1, Eh is the longitudinal elastic modulus [N / m ² ] of the material of the piezoelectric vibrator 1, and I is the piezoelectric vibrator 1. the second moment [m ^4], a is the cross-sectional area of the piezoelectric vibrator 1 [m ^2], [rho is the piezoelectric vibrator 1 material density K [kg / m ^3], lambda is determined by the boundary conditions and the vibration mode It is a dimensionless coefficient. Since the piezoelectric vibrator 1 can be regarded as a support end with one end being a fixed plate and the other end being in contact with the island portion 22, the primary mode count λ is 3.927.
[0045]
Further, the primary mode period Th of the transverse vibration in the piezoelectric vibrator 1 can be expressed as the following equation (4) using the natural frequency fh.
[0046]
Th = 1 / fh (4)
[0047]
Therefore, in the present embodiment, the conditions of each component are defined based on the above formulas (1) to (4), and the natural vibration period Tc of the ink is the primary mode period Th of the transverse vibration in the piezoelectric vibrator 1. It is configured to be shorter. In other words, the primary mode period Th of the transverse vibration is configured to be longer than the natural vibration period Tc of the ink.
[0048]
With this configuration, there is no vibration between the natural vibration of the ink excited in the pressure generation chamber 13 by the ejection of the ink droplet and the lateral vibration of the piezoelectric vibrator 1 (specifically, the free end 1b). A shift in period occurs. For this reason, the natural vibration of the ink and the transverse vibration of the piezoelectric vibrator 1 do not resonate, and the energy of the natural vibration of the ink hardly shifts to the energy of the transverse vibration of the piezoelectric vibrator 1. Accordingly, it is possible to prevent a problem that the lateral vibration of the piezoelectric vibrator 1 continues for a long time. As a result, the vibration of the meniscus 23 can be quickly converged and the responsiveness of ink droplet ejection can be improved.
[0049]
Further, since the primary mode period Th of the transverse vibration is set to be longer than the natural vibration period Tc of the ink, the reciprocating reflection between the nozzle opening 11 and the ink supply port 14 is caused by the transverse vibration of the piezoelectric vibrator 1. Even if the pressure wave in the pressure generation chamber 13 is repeatedly generated, the movement period of the pressure wave depends on the transverse vibration period of the piezoelectric vibrator 1 and is longer than the natural vibration period Tc of the ink. For this reason, it becomes difficult to synchronize the ejection timing of the ink droplets performed at the timing defined by the natural vibration period Tc of the ink and the movement period of the pressure wave, and problems such as ink mist due to the pressure wave are prevented. Can be prevented.
[0050]
Further, since the piezoelectric vibrator 1 and the island portion 22 are brought into contact with each other with the longitudinal center of the island portion 22 and the axis of the piezoelectric vibrator 1 being substantially coincident with each other, the reaction force from the diaphragm 10 is related. The island part longitudinal direction one end side and the island part longitudinal direction other end side become equal. Thereby, during the longitudinal vibration of the piezoelectric vibrator 1, it is possible to prevent excitation of lateral vibration caused by an unbalance of reaction force from the diaphragm 10.
[0051]
Further, when the piezoelectric vibrator 1 is driven, as described above, a uniform electric field is applied over the entire longitudinal direction of the free end 1b to positively excite the longitudinal vibration primary mode of the piezoelectric vibrator 1. Thus, the excitation of the transverse vibration of the piezoelectric vibrator 1 during driving can be prevented. Therefore, also in this respect, the vibration of the meniscus 23 can be quickly converged, and the responsiveness of ink droplet ejection can be improved.
[0052]
In the present embodiment, the lateral effect (d31 effect) type piezoelectric vibrator 1 is exemplified as the electromechanical transducer, but the electromechanical transducer is not limited thereto. For example, the present invention can be applied to a longitudinal effect (d33 effect) type piezoelectric vibrator in which a piezoelectric body and an internal electrode are laminated in the vibrator longitudinal direction (that is, the longitudinal direction of the piezoelectric vibrator 1) and can vibrate in the electric field direction.
[0053]
Furthermore, the electromechanical conversion element is not limited to a piezoelectric vibrator, and may be any element that causes mechanical deformation upon application of a drive signal.
[0054]
【The invention's effect】
As described above, the present invention has the following effects.
That is, since the vibration period of the natural vibration excited by the ink in the pressure generation chamber is shorter than the transverse vibration primary mode period of the free terminal portion of the electromechanical transducer, it is excited in the pressure generation chamber by the ejection of ink droplets. In addition, a vibration period shift occurs between the natural vibration of the ink and the lateral vibration of the electromechanical transducer. For this reason, the natural vibration of the ink and the transverse vibration of the electromechanical conversion element do not resonate, and it becomes difficult for the energy of the natural vibration of the ink to shift to the energy of the transverse vibration of the electromechanical conversion element.
Therefore, the lateral vibration in the electromechanical transducer is not maintained for a longer time than necessary, and the meniscus vibration can be quickly converged. As a result, the responsiveness of ink droplet ejection can be improved.
[0055]
In addition, since the transverse mode of the primary mode of the electromechanical transducer is set to be longer than the natural oscillation cycle of the ink, a pressure wave that repeats reciprocation in the pressure generating chamber is generated by the transverse oscillation of the electromechanical transducer. Even so, since the moving period of the pressure wave depends on the transverse vibration period of the electromechanical transducer, it is longer than the natural vibration period of the ink. Accordingly, it becomes difficult to synchronize the ejection timing of the ink droplets performed at the timing defined by the natural vibration period of the ink and the movement period of the pressure wave, and prevent problems such as ink mist due to the pressure wave. be able to.
[0056]
In addition, when the center of the electromechanical conversion element and the center of the island are aligned with respect to the longitudinal direction of the island, and the tip of the piezoelectric vibrator is brought into contact with the island in this state, the reaction from the diaphragm The force is equalized at one end side in the island portion longitudinal direction and the other end side in the island portion longitudinal direction. Thereby, at the time of the longitudinal vibration of the electromechanical transducer, it is possible to prevent the excitation of the transverse vibration of the electromechanical transducer due to the unbalance of the reaction force.
[0057]
In addition, when the vibration period of the pressure vibration reflected and reciprocated inside the pressure generation chamber is longer than the vibration period of the natural vibration excited by the ink, the ink droplet ejection timing and the pressure wave movement period are It becomes difficult to synchronize, and problems such as ink mist caused by the pressure wave can be prevented.
[0058]
Further, when the electromechanical conversion element is driven, when the drive voltage is supplied simultaneously over the entire free end, the longitudinal vibration primary mode is more strongly excited at the free end. For this reason, excitation of the transverse vibration of the electromechanical transducer during driving can be prevented. Accordingly, it is possible to further improve the responsiveness in ejecting ink droplets.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an ink jet recording head.
FIG. 2 is a schematic diagram illustrating a main part of a recording head.
FIG. 3 is an explanatory diagram showing a vibration system in the recording head by an equivalent circuit.
FIG. 4 is a perspective view illustrating a configuration of an ink jet printer.
FIGS. 5A and 5B are diagrams for explaining the prior art. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Piezoelectric vibrator 2 Inkjet recording head 3 Case 4 Storage chamber 5 Channel unit 6 Flexible cable 7 Fixed plate 8 Channel formation plate 9 Nozzle plate 10 Vibration plate 11 Nozzle opening 13 Pressure generation chamber 14 Ink supply port 15 Common ink chamber 16 Through-hole 17 Weir part 19 Ink supply pipe 20 Stainless steel plate 21 Resin film part (elastic film)
22 Island part 23 Meniscus 31 Inkjet recording device

Claims (12)

A nozzle plate having a plurality of nozzle openings, a flow path forming plate formed by arranging a plurality of empty portions corresponding to the nozzle openings, with a partition wall interposed therebetween, and a pressure generating chamber bonded to the flow path forming plate. A diaphragm constituting a part of the inner wall, and an electromechanical conversion element that is elongated in the vertical direction and has one end fixed in the longitudinal direction and capable of vibrating in the vertical direction at the other free end. In the ink jet recording head in which the diaphragm is deformed by the longitudinal vibration of the free end to change the volume of the pressure generating chamber,
The diaphragm includes an island portion whose periphery is composed only of an elastic film in a portion corresponding to the pressure generation chamber, and the tip of the free end portion of the electromechanical transducer is brought into contact with the island portion,
An ink jet recording head characterized in that a vibration period of natural vibration excited by ink in the pressure generation chamber is shorter than a transverse vibration primary mode period of a free end portion of an electromechanical transducer. The island portion is in the form of a block elongated in a direction orthogonal to the direction in which the nozzle openings are arranged,
2. The ink jet recording head according to claim 1, wherein a direction of transverse vibration of the electromechanical transducer is coincident with a longitudinal direction of the island portion.   The center of the electromechanical transducer element and the center of the island portion in the longitudinal direction of the island portion are aligned, and the tip portion of the electromechanical transducer element is brought into contact with the island portion in this state. Item 3. The ink jet recording head according to Item 2.   The inkjet recording according to any one of claims 1 to 3, wherein a vibration period of pressure vibration reflected and reciprocated in the pressure generation chamber is longer than a vibration period of natural vibration excited by ink. head.   5. The ink jet recording head according to claim 1, wherein the pressure generating chamber is a chamber elongated in a direction orthogonal to a direction in which the nozzle openings are arranged.   6. The ink jet recording head according to claim 1, wherein one end of the electromechanical conversion element is joined to a fixed plate, and a free end portion protrudes from an edge of the fixed plate.   The ink jet recording head according to any one of claims 1 to 6, wherein the electromechanical transducer is formed in a comb shape elongated in a vertical direction.   8. The ink jet recording head according to claim 1, wherein a driving voltage is supplied simultaneously over the entire free end when the electromechanical transducer is driven.   9. The ink jet recording head according to claim 1, wherein the electromechanical transducer is a lateral effect type piezoelectric vibrator.   The ink jet recording head according to any one of claims 1 to 8, wherein the electromechanical transducer is a longitudinal effect type piezoelectric vibrator.   11. The ink jet recording head according to claim 9, wherein the piezoelectric vibrator is a laminated piezoelectric vibrator configured by alternately laminating piezoelectric bodies and internal electrodes.   An image recording apparatus comprising the ink jet recording head according to claim 1.

Images