JP2005058933A - Liquid jetting apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid jetting apparatus from which a large quantity of minute liquid droplets can be jetted by arranging a plurality of piezoelectric/electrostrictive elements in a chamber and driving these elements at different timings without deteriorating the durability of these elements. <P>SOLUTION: This liquid jetting apparatus 10 is provided with the chamber 10-3 and two piezoelectric/electrostrictive elements 11, 12 arranged in the chamber 10-3. Liquid is introduced into the chamber 10-3 and jetted from a liquid jetting hole 10-3a. A driving voltage signal is imparted to each of the elements 11, 12 in a cycle T1. A phase when the driving voltage signal is imparted to one of the elements 11, 12 is shifted only by T1/2 from the phase when the driving voltage signal is imparted to the other of the elements 12, 11. The liquid is jetted while being formed into minute particles by operating the elements 11, 12. The cycle of the pressure fluctuation in the chamber 10-3 becomes T1/2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a liquid ejecting apparatus that ejects liquid while atomizing it.

As shown in FIG. 28, this type of conventionally known liquid ejecting apparatus includes a chamber 303 having a volume changed by a piezoelectric / electrostrictive element 301 and a liquid ejecting nozzle 302, and a hollow cylindrical liquid. An introduction hole 304 and a liquid supply passage 305 are provided. The liquid is supplied into the liquid supply passage 305 and then introduced into the chamber 303 through the liquid introduction hole 304. Then, the liquid is pressurized by the operation of the piezoelectric / electrostrictive element 301 in the chamber 303 and ejected from the liquid ejecting nozzle 304 (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 5-317400 (paragraph numbers 0003-0004, FIG. 5)

  In such an apparatus, in order to atomize a larger amount of liquid droplets, a large number of nozzles for ejecting liquid are provided in the chamber to increase the flow rate of the ejected liquid and increase the driving frequency of the piezoelectric / electrostrictive element 301. There must be. However, if the drive frequency of the piezoelectric / electrostrictive element 301 is increased too much, there is a problem that the durability of the piezoelectric / electrostrictive element 301 is lowered.

  One of the objects of the present invention is to arrange a plurality of piezoelectric / electrostrictive elements in a chamber and drive these piezoelectric / electrostrictive elements at different timings, thereby improving the durability of the piezoelectric / electrostrictive elements. An object of the present invention is to provide a liquid ejecting apparatus capable of ejecting a large amount of fine droplets without being lowered.

  The liquid ejecting apparatus of the present invention has a chamber having a plurality of liquid ejecting nozzles and configured by a plurality of walls, and is connected to the chamber and allows the liquid to flow and introduce the liquid into the chamber. A liquid introduction passage and a pressure wave applied to the liquid introduced into the chamber through the liquid introduction passage and / or applied to at least one of a plurality of walls constituting the chamber; And a piezoelectric / electrostrictive element for reducing and increasing the volume of the chamber, and ejecting liquid in the chamber into the external space through the liquid ejecting nozzle while forming fine particles by the operation of the piezoelectric / electrostrictive element. The liquid ejecting apparatus includes a plurality of the piezoelectric / electrostrictive elements, and the plurality of piezoelectric / electrostrictive elements apply the pressure wave at different timings. It is characterized in driven it to perform increase reduction of the volume of the beauty / or the chamber. The piezoelectric / electrostrictive element is a concept including not only a piezoelectric body but also an electrostrictive body.

  According to this, a plurality of piezoelectric / electrostrictive elements apply pressure waves to the liquid in the chamber, and / or a plurality of piezoelectric / electrostrictive elements increase and decrease the volume of the chamber. The liquid is sprayed while being atomized. In addition, since the plurality of piezoelectric / electrostrictive elements are driven to apply the pressure wave and / or increase / decrease the volume of the chamber at different timings, the driving frequency of one piezoelectric / electrostrictive element is small. However, the frequency of the pressure fluctuation of the liquid in the chamber can be increased. Accordingly, it is possible to avoid a decrease in durability of the piezoelectric / electrostrictive element.

  In this case, the chamber includes a liquid ejecting nozzle forming wall that is a wall in which the plurality of liquid ejecting nozzles are formed, and a liquid ejecting nozzle facing wall that is a wall facing the liquid ejecting nozzle forming wall. It is preferable that at least two of the plurality of piezoelectric / electrostrictive elements are disposed on the liquid jet nozzle facing wall.

  Pressure fluctuations caused by the respective piezoelectric / electrostrictive elements arranged at different positions on the liquid jet nozzle facing wall are propagated to each of the plurality of liquid jet nozzles. The traveling direction of the pressure fluctuation wave is different between the pressure fluctuation from one piezoelectric / electrostrictive element and the pressure fluctuation from another piezoelectric / electrostrictive element disposed on the liquid jet nozzle facing wall. . As a result, the droplet ejection direction by driving one piezoelectric / electrostrictive element is slightly different from the droplet ejection direction by driving another piezoelectric / electrostrictive element. As a result, it is possible to reduce the frequency with which the droplets ejected before and after a certain liquid ejecting nozzle are recombined in the ejecting space. Therefore, the particle size of the ejected droplets can be kept minute.

  Further, the liquid ejecting nozzle forming wall and the liquid ejecting nozzle facing wall are parallel to each other, and when viewed from a direction orthogonal to the liquid ejecting nozzle facing wall, the outer shape of the liquid ejecting nozzle forming wall Two piezoelectric / electrostrictive elements having the same shape as each other, wherein the liquid jet nozzle facing wall has the same outer shape, and the liquid jet nozzle facing wall has a line-symmetric outer shape with respect to a predetermined straight line Is preferably arranged on the liquid jet nozzle facing wall so as to be line-symmetric with respect to the predetermined straight line.

  According to this, even when the liquid jet nozzle facing wall is deformed by the heat generated by the piezoelectric / electrostrictive element, the deformation of the liquid jet nozzle facing wall is axisymmetric. Accordingly, the angles of the two piezoelectric / electrostrictive elements with respect to the liquid injection nozzle forming wall are substantially the same. In other words, even when the liquid jet nozzle facing wall is deformed, the angle of the two piezoelectric / electrostrictive elements with respect to the liquid jet nozzle forming wall does not change greatly. Therefore, since the liquid having substantially the same pressure fluctuation reaches each of the plurality of liquid ejecting nozzles before and after the deformation of the liquid ejecting nozzle facing wall, it is possible to reduce the particle size variation of the ejected liquid droplets. it can. Further, since the angle between the two piezoelectric / electrostrictive elements does not change greatly, the injection direction does not vary.

  The chamber includes a liquid ejecting nozzle forming wall that is a wall on which the plurality of liquid ejecting nozzles are formed, and a liquid ejecting nozzle facing wall that is a wall facing the liquid ejecting nozzle forming wall, At least one of the plurality of piezoelectric / electrostrictive elements is disposed on the liquid jet nozzle facing wall, and at least one other of the plurality of piezoelectric / electrostrictive elements is formed with the liquid jet nozzle. It is also suitable to be arranged on the wall.

  According to this, by driving the piezoelectric / electrostrictive element provided on the liquid ejecting nozzle forming wall, the angle of the liquid ejecting nozzle forming wall (accordingly, the angle of the liquid ejecting nozzle) is changed. . Accordingly, the droplet ejection direction associated with the driving of the piezoelectric / electrostrictive element disposed on the liquid ejecting nozzle facing wall and the liquid associated with the driving of the piezoelectric / electrostrictive element disposed on the liquid ejecting nozzle forming wall. The direction is different from the droplet ejection direction. As a result, it is possible to reduce the frequency with which the droplets ejected before and after a certain liquid ejecting nozzle are recombined in the ejecting space. Therefore, the particle size of the ejected droplets can be kept minute.

  In any one of the liquid ejecting apparatuses, each of the plurality of piezoelectric / electrostrictive elements is driven so as to apply the pressure wave and / or change the volume of the chamber with the same period T. At the same time, when the number of the piezoelectric / electrostrictive elements is N, it is preferable that the phases are mutually driven by a time (T / N) obtained by dividing the period T by the number N.

According to this, since the maximum value of the pressure of the liquid in the chamber appears periodically with a period (T / N), the distance between the droplets ejected from the same liquid ejecting nozzle before and after in time is reduced. It becomes uniform. As a result, it is possible to reduce the frequency with which the droplets ejected before and after a certain liquid ejecting nozzle are recombined in the ejecting space. Therefore, the particle size of the ejected droplets can be kept minute.

  Hereinafter, embodiments of a liquid ejecting apparatus (a liquid spraying apparatus, a liquid supply apparatus, and a droplet discharge apparatus) according to the present invention will be described with reference to the drawings.

(First embodiment)
The liquid ejecting apparatus 10 according to the first embodiment of the present invention is applied to, for example, an internal combustion engine as a mechanical device that requires finely divided liquid (fuel) as shown in the schematic configuration diagram of FIG. It is used as an electronic fuel injection control device.

  The electronic fuel injection control device is atomized into a fuel injection space (liquid injection space) 31 formed by an intake pipe (or intake port) 30 of the internal combustion engine and the like toward the back surface of the intake valve 32 of the internal combustion engine. Liquid (eg, liquid fuel such as gasoline, hereinafter may be simply referred to as “fuel”). The electronic fuel injection control device includes a liquid injection device 10 having a piezoelectric / electrostrictive element that functions as an actuator, a pressure pump (fuel pump) 21 as a pressurizing means, and a fuel supply pipe (liquid supply pipe, fuel pipe). 22, a pressure regulator 23, an electromagnetic open / close discharge valve (discharge valve, open / close valve) 24, a fuel tank (liquid storage tank) 25, and an electric control device 40. The pressure pump 21 and the pressure regulator 23 are interposed in the fuel supply pipe 22.

  The pressurizing pump 21 includes an introduction portion 21 a that communicates with the bottom of the fuel tank 25 via a fuel supply pipe 22 and a discharge portion 21 b that is connected to the pressure regulator 23 via the fuel supply pipe 22. . The pressurizing pump 21 introduces and pressurizes the fuel in the fuel tank 25 from the introduction part 21a, and discharges the pressurized fuel from the discharge part 21b. In the pressurizing pump 21, even if the piezoelectric / electrostrictive element of the liquid ejecting apparatus 10 is not operated, the fuel is supplied through the pressure regulator 23, the electromagnetic open / close discharge valve 24, and the liquid ejecting apparatus 10. The fuel is pressurized to a pressure higher than the pressure that can be injected into the injection space 31 (this pressure is referred to as “pressure pump discharge pressure”).

  The pressure regulator 23 is given pressure in the intake pipe 30 by a pipe (not shown). The pressure regulator 23 depressurizes (or regulates) the pressure of the fuel pressurized by the pressurizing pump 21 based on the pressure in the intake pipe 30. As a result, the pressure of the fuel in the liquid supply pipe 22 between the pressure regulator 23 and the electromagnetic open / close discharge valve 24 is higher than the pressure in the intake pipe 30 by a predetermined (constant) pressure (this pressure is “adjusted”). Pressure "). Accordingly, when the electromagnetic open / close discharge valve 24 is opened for a predetermined time, a fuel amount approximately proportional to the predetermined time is injected into the intake pipe 30 regardless of the pressure in the intake pipe 30.

  The electromagnetic open / close discharge valve 24 is a well-known fuel injector (electromagnetic injection valve) that has been widely used in electronic fuel injection control devices for internal combustion engines. FIG. 2 is a front view of the electromagnetic open / close discharge valve 24, and shows a front end portion of the electromagnetic open / close discharge valve 24 taken along a plane including the center line of the electromagnetic open / close discharge valve 24.

  The electromagnetic open / close discharge valve 24 includes a liquid introduction port 24a that is connected to the liquid supply pipe 22 and communicates with the pressure regulator 23, an outer cylinder portion 24c that forms a liquid passage 24b that communicates with the liquid introduction port 24a, and an electromagnetic type An on-off valve (needle valve) 24d that operates as an on-off valve, a discharge hole 24e that is formed at the tip of the outer cylinder portion 24c and that is opened and closed by the tip of the on-off valve 24d, and an electromagnetic mechanism (not shown) that drives the on-off valve 24d It has. The liquid passage 24b of the electromagnetic open / close discharge valve 24 is connected to the liquid ejecting apparatus 10 through the discharge hole 24e. As a result, the electromagnetic open / close discharge valve 24 is supplied with the pressurized fuel supplied from the pressure pump 21 via the pressure regulator 23 when the liquid passage 24b (discharge hole 24e) is opened by the open / close valve 24d. The liquid is supplied to the liquid ejecting apparatus 10 through the liquid passage 24b and the discharge hole 24e.

  The liquid ejecting apparatus 10 includes a chamber in which a piezoelectric / electrostrictive element is formed at least on a wall surface thereof to atomize a liquid (fuel injected toward the back surface of the intake valve 32) to be injected into the fuel injection space 31, and the piezoelectric / Ejecting device having a liquid ejecting hole (liquid ejecting nozzle) formed on a wall different from the wall on which the electrostrictive element is formed, and is shown in detail in FIGS.

  The liquid ejecting apparatus 10 has a substantially rectangular parallelepiped shape in which each side extends parallel to the X, Y, and Z axes orthogonal to each other. As shown in FIGS. 4 and 5, the liquid ejecting apparatus 10 includes a plurality of metal thin plates (hereinafter, referred to as “metal plates”) 10 a to 10 c that are sequentially stacked, and an outer surface (Z It is composed of two piezoelectric / electrostrictive elements 11 and 12 fixed to a plane along the XY plane in the positive axial direction.

  The material of the metal plates 10a to 10c is stainless steel (SUS304 or SUS316) in this example. The metal plate 10c is extremely thin and forms a diaphragm that can be easily deformed and restored (deformable). In addition, the material of the metal plate which concerns on other embodiment mentioned later is the same as that of the metal plates 10a-10c.

  The liquid ejecting apparatus 10 includes a liquid introduction port 10-1, a liquid supply passage 10-2, a chamber 10-3, and a liquid introduction passage portion 10-4 that communicates the liquid supply passage 10-2 and the chamber 10-3. And.

  The liquid inlet 10-1 is a circular through hole formed in the metal plate 10c. The liquid inlet 10-1 is provided at the center in the Y-axis direction of the metal plate 10c and in the vicinity of the end portion in the negative X-axis direction. As shown in FIG. 4, a discharge hole 24 e of an electromagnetic open / close discharge valve 24 is fluid-tightly connected to the liquid introduction port 10-1 by a sleeve 25.

  The liquid supply passage 10-2 is a space defined by an upper surface of the metal plate 10a, a side wall surface that forms a through hole provided in the metal plate 10b, and a lower surface of the metal plate 10c. As shown in FIG. 3, the planar shape of the liquid supply passage 10-2 (the shape viewed from the positive direction of the Z axis) is a top portion P that coincides with the arc of the liquid inlet 10-1, and the top portion P extends to the X axis. It is a substantially isosceles triangle having a base T extending along the Y axis at a position separated by a predetermined distance in the positive direction.

  The chamber 10-3 includes an upper surface of the metal plate 10a, a side wall surface that forms a through-hole provided in the metal plate 10b at a predetermined distance in the X-axis positive direction with respect to the liquid supply passage 10-2, It is a space defined by the lower surface of the plate 10c. The planar shape of the chamber 10-3 is a substantially rectangular shape having a long side LH and a short side SH along the Y axis and the X axis, respectively, as shown in FIG. The length of the long side LH is slightly longer than the length of the bottom side T of the liquid supply passage 10-2. The positions of the pair of short sides SH are located on the outer side in the Y-axis direction (the Y-axis positive direction outer side and the Y-axis negative direction outer side) from both ends of the base T.

  In the metal plate 10a which is one wall (lower wall) constituting the chamber 10-3, a plurality of (in this example, 15 × 6 = 90 in total) through holes are formed as liquid ejection holes (for liquid ejection). Nozzle) 10-3a. Each liquid ejection hole 10-3a is a cylindrical space having a diameter d on the bottom surface having an axis in the Z-axis direction. Accordingly, a plurality of circular injection holes having a diameter d are formed on the lower surface of the metal plate 10a.

  The plurality of liquid ejection holes 10-3a are arranged in a square lattice pattern. That is, the center points of the plurality of liquid ejection holes 10-3a are arranged on a line parallel to the plurality of X axes arranged at a certain distance and a plurality of Y axes arranged at the same certain distance. It coincides with the intersection with parallel lines. In this specification, the term “liquid injection nozzle” refers to a “liquid injection nozzle whose cross-sectional area is changed in the direction of flow for the purpose of increasing the flow speed by converting the fluid's pressure and heat energy into kinetic energy. In addition to the “flow channel”, a hollow cylindrical liquid injection through-hole provided in the wall constituting the chamber 10-3 like the liquid injection hole 10-3a (ie, the cross-sectional area in the flow direction is It is also used as a term including “an unaltered flow path)”.

  The liquid introduction passage portion 10-4 is defined by a top surface of a substantially central portion in the X-axis direction of the metal plate 10b, a side wall surface erected from both ends of the top surface in the Y-axis direction, and a bottom surface of the metal plate 10c. It is the space which comprises the hollow space (namely, slit). This slit is also called a liquid introduction passage.

  As shown in FIG. 3, the planar shape of the slit of the liquid introduction passage portion 10-4 is a substantially rectangular shape having a long side LI and a short side SI along the Y axis and the X axis, respectively. The long side LI on the X-axis negative direction side coincides with the bottom side T of the liquid supply passage 10-2. Accordingly, the starting points of the pair of short sides SI coincide with both end portions of the base T.

  The piezoelectric / electrostrictive element 11 as an actuator is fixed to the upper surface of the metal plate 10c. The planar shape of the piezoelectric / electrostrictive element 11 is substantially square as shown in FIG. One side of this square is shorter than the short side SH of the chamber 10-3. The piezoelectric / electrostrictive element 11 is disposed inside the chamber 10-3 in a plan view and on the Y axis negative direction side of the center of the chamber 10-3 in the Y axis direction. Each side of the square forming the outer shape of the piezoelectric / electrostrictive element 11 is parallel to either the short side SH or the long side LH of the chamber 10-3.

  The piezoelectric / electrostrictive element 11 is a “lateral effect type laminated piezoelectric actuator” formed by alternately laminating layered piezoelectric / electrostrictive films and layered electrodes. When a predetermined potential difference is applied between the pair of comb-shaped electrodes 11a and 11b (when a driving voltage is applied), the piezoelectric / electrostrictive element 11 is a metal plate immediately below the piezoelectric / electrostrictive element 11. 10c is bent and deformed in the negative direction of the Z axis, a pressure wave is applied to the liquid in the chamber 10-3, and / or the volume of the chamber 10-3 is reduced. The electrode 11b is grounded.

  The piezoelectric / electrostrictive element 12 has the same configuration as the piezoelectric / electrostrictive element 11. The piezoelectric / electrostrictive element 12 is also fixed to the upper surface of the metal plate 10c as shown in FIGS. The piezoelectric / electrostrictive element 12 is disposed inside the chamber 10-3 in a plan view and on the Y axis positive direction side of the center of the chamber 10-3 in the Y axis direction. Each side of the square forming the outer shape of the piezoelectric / electrostrictive element 12 is parallel to either the short side SH or the long side LH of the chamber 10-3.

  The piezoelectric / electrostrictive element 11 and the piezoelectric / electrostrictive element 12 are line-symmetric with respect to the center line CL of the chamber 10-3 extending in the X-axis direction through the center in the Y-axis direction of the chamber 10-3 in plan view. It is arranged to be.

  When a predetermined potential difference is applied between the pair of comb-like electrodes 12a and 12b (when a driving voltage is applied), the piezoelectric / electrostrictive element 12 is a metal plate immediately below the piezoelectric / electrostrictive element 12. 10c is bent and deformed in the negative direction of the Z axis, a pressure wave is applied to the liquid in the chamber 10-3, and / or the volume of the chamber 10-3 is reduced. The electrode 12b is grounded.

  Thus, the upper wall of the chamber 10-3 is deformed by the operation of the piezoelectric / electrostrictive elements 11 and 12. When the volume of the chamber 10-3 is reduced, the liquid in the chamber 10-3 is pressurized by this volume reduction.

  The electric control device 40 is a circuit including a microcomputer, and is connected to sensors such as an engine rotation speed sensor 41 and an intake pipe pressure sensor 42 as shown in FIG. The electric control device 40 inputs the engine rotation speed and the intake pipe pressure from these sensors to determine the fuel amount and injection start timing required for the internal combustion engine, and electromagnetically responds to the determined fuel amount and injection start timing. A discharge valve drive signal INJ is supplied to the electromagnetic mechanism of the open / close type discharge valve 24. Further, the electric control device 40 sends a piezoelectric element driving voltage signal DV1 and a piezoelectric element driving voltage signal DV2 described later to the electrode 11a of the piezoelectric / electrostrictive element 11 and the electrode 12a of the piezoelectric / electrostrictive element 12, respectively. It has become.

  Next, an outline of the operation of the liquid ejecting apparatus 10 configured as described above will be described. When the electric control device 40 outputs the discharge valve drive signal INJ at a predetermined timing, the fuel is supplied from the discharge hole 24e of the electromagnetic open / close discharge valve 24 to the liquid supply passage 10 via the liquid injection port 10-1 of the liquid injection device 10. -2. Thereafter, the fuel is introduced into the chamber 10-3 through the slit of the liquid introduction passage 10-4 (through the slit in the X-axis direction). Then, the liquid introduced into the chamber 10-3 is pushed out (injected) into the intake pipe 30 via the liquid injection hole 10-3a (an injection port of the liquid injection hole).

  At this time, vibration energy (pressure fluctuation) due to the operation of the piezoelectric / electrostrictive element 11 or the piezoelectric / electrostrictive element 12 is applied to the injected fuel in the chamber 10-3. Therefore, as shown in FIG. 6, a constricted portion is generated in the injected fuel, and the fuel is detached from the constricted portion at the tip end portion. As a result, uniform and finely pulverized fuel is injected into the fuel injection space 31 of the intake pipe 30. The above is the outline of the operation of the liquid ejecting apparatus 10.

  Next, the detailed operation of the liquid ejecting apparatus 10 will be described with reference to FIGS. 7 and 8. The electrical control device 40 outputs the discharge valve drive signal INJ at a predetermined timing, and outputs the piezoelectric element drive voltage signals DV1 and DV2 shown in FIG. 7 to the electrode 11a of the piezoelectric / electrostrictive element 11 and the piezoelectric / electrostrictive. Each is applied to the electrode 12a of the element 12. Each of the piezoelectric element drive voltage signals DV1 and DV2 is a signal that repeatedly changes to a trapezoidal shape with a period T1 (seconds). The phase of the piezoelectric element driving voltage signal DV1 and the phase of the piezoelectric element driving voltage signal DV2 are different from each other by ½ period.

  As shown in FIG. 7, when the piezoelectric element drive voltage signal DV1 applied to the piezoelectric / electrostrictive element 11 starts to increase from 0 (V) to VA (V) at time t1, it is shown in FIG. As described above, the piezoelectric / electrostrictive element 11 deforms the Y-axis negative direction side of the metal plate 10c, which is the upper wall of the chamber 10-3, in the Z-axis negative direction. Thereafter, the piezoelectric element drive voltage signal DV1 returns to 0 (V) after maintaining the constant time VA (V). As described above, the pressure of the liquid (fuel) in the chamber 10-3 increases and then decreases. As a result, the liquid ejected from the liquid ejection hole 10-3a is atomized.

  At this time, the ejection direction of the liquid droplets ejected from the liquid ejection hole 10-3a (the liquid ejection hole 10-3a on the Y axis negative direction side of the chamber 10-3) located immediately below the piezoelectric / electrostrictive element 11 is , And the axial direction (Z-axis direction) of the liquid injection hole 10-3a. This is because the traveling direction of the pressure wave or pressure vibration caused by the operation of the piezoelectric / electrostrictive element 11 substantially coincides with the direction of the axis of the liquid injection hole 10-3a on the Y axis negative direction side of the chamber 10-3. It is thought that it is because.

  On the other hand, the ejection direction of the liquid droplets ejected from the liquid ejection hole 10-3a that is not located directly below the piezoelectric / electrostrictive element 11 is a direction having components in the Z-axis negative direction and the Y-axis positive direction (in FIG. 9). Diagonally to the right). In other words, the liquid ejecting direction of the liquid ejected from the liquid ejecting hole 10-3a on the Y axis positive direction side of the chamber 10-3 is the liquid ejecting hole 10-3a and the piezoelectric / electrostrictive element 11 existing at the position. The direction is substantially parallel to the straight line connecting the two. This is the direction in which the traveling direction of the pressure wave or pressure vibration caused by the operation of the piezoelectric / electrostrictive element 11 intersects the axis of the liquid injection hole 10-3a on the Y axis positive direction side of the chamber 10-3. This is probably because of this.

  Next, at time t2 when T1 / 2 (seconds) has elapsed from time t1, the piezoelectric element drive voltage signal DV2 applied to the piezoelectric / electrostrictive element 12 increases from 0 (V) to VA (V). Start. Thereby, as shown in FIG. 9, the piezoelectric / electrostrictive element 12 deforms the Y axis positive direction side of the metal plate 10c, which is the upper wall of the chamber 10-3, in the Z axis negative direction. Thereafter, the piezoelectric element drive voltage signal DV2 returns to 0 (V) after maintaining the constant time VA (V). As described above, the pressure of the liquid (fuel) in the chamber 10-3 increases and then decreases. As a result, the liquid ejected from the liquid ejection hole 10-3a is atomized.

  At this time, the ejection direction of the liquid droplets ejected from the liquid ejection hole 10-3a (liquid ejection hole 10-3a on the Y axis positive direction side of the chamber 10-3) located immediately below the piezoelectric / electrostrictive element 12 is , And the axial direction (Z-axis direction) of the liquid injection hole 10-3a. This is because the traveling direction of the pressure wave or pressure vibration caused by the operation of the piezoelectric / electrostrictive element 12 substantially coincides with the direction of the axis of the liquid injection hole 10-3a on the Y axis positive direction side of the chamber 10-3. It is thought that it is because.

  On the other hand, the ejection direction of the droplet ejected from the liquid ejection hole 10-3a that is not located directly below the piezoelectric / electrostrictive element 12 is a direction having components in the negative Z-axis direction and the negative Y-axis direction (in FIG. 9). Diagonally to the left). In other words, the ejection direction of the liquid ejected from the liquid ejection hole 10-3a on the Y axis negative direction side of the chamber 10-3 is the liquid ejection hole 10-3a and the piezoelectric / electrostrictive element 12 present at that position. The direction is substantially parallel to the straight line connecting the two. This is because the traveling direction of the pressure wave or pressure vibration caused by the operation of the piezoelectric / electrostrictive element 12 intersects the axis of the liquid injection hole 10-3a on the Y axis negative direction side of the chamber 10-3. This is probably because of this.

  As a result, as shown in FIG. 9, the jetting directions of the liquid droplets jetted back and forth through a certain liquid jet hole 10-3a are different, so that the piezoelectric / electrostrictive elements 11, 12 Are simultaneously ejected (with a period T1 / 2), and droplets ejected from the same liquid ejection hole before and after the time are ejected into the ejection space, as in an apparatus in which the ejection directions are always the same (see FIG. 10). It is possible to reduce the frequency of recombination in the inside, thereby increasing the droplet diameter. Therefore, the liquid ejecting apparatus 10 can keep the particle size of the ejected droplets minute.

  Thereafter, when T1 (seconds) elapses from time t1, the piezoelectric element drive voltage signal DV1 changes to a trapezoid again. Further, when T1 (seconds) elapses from time t2, the piezoelectric element driving voltage signal DV2 changes to a trapezoid again. Thereafter, the same operation is repeated. As a result, the pressure of the liquid in the chamber 10-3 changes with a period T1 / 2 (second). That is, the pressure of the liquid in the chamber 10-3 changes at a frequency 2 · f that is twice the driving frequency f of the piezoelectric element driving voltage signals DV1 and DV2. As a result, even when the flow rate of the ejected liquid increases, the ejected liquid is reliably atomized.

  As described above, the liquid ejecting apparatus 10 according to the first embodiment has a plurality of liquid ejecting nozzles 10-3a and is connected to the chamber 10-3 including a plurality of walls and the chamber. In addition, a liquid introduction passage portion 10-4 for introducing the liquid into the chamber by allowing the liquid to flow therethrough, and at least one wall (chamber 10- configured by the metal plate 10c) constituting the chamber. 3 and the piezoelectric / electrostrictive element 11 for applying a pressure wave to the liquid introduced into the chamber through the liquid introduction passage and / or increasing / decreasing the volume of the chamber. , 12, and the liquid in the chamber is sprayed into the external space through the liquid jet nozzle while being atomized by the operation of the piezoelectric / electrostrictive element The injection device 10 includes a plurality of piezoelectric / electrostrictive elements such as the piezoelectric / electrostrictive elements 11 and 12, and the plurality of piezoelectric / electrostrictive elements apply the pressure wave at different timings. And / or an apparatus driven to increase or decrease the volume of the chamber.

  According to this, the piezoelectric / electrostrictive elements 11 and 12 which are a plurality of piezoelectric / electrostrictive elements apply pressure waves to the liquid in the chamber 10-3 and / or the plurality of piezoelectric / electrostrictive elements 11. 12 increase or decrease the volume of the chamber. Thereby, the liquid in the chamber 10-3 is ejected while being atomized. The plurality of piezoelectric / electrostrictive elements 11 and 12 are driven to apply the pressure wave and / or increase / decrease the volume of the chamber at different timings according to the piezoelectric element driving voltage signals DV1 and DV2. Therefore, even if the driving frequency of one piezoelectric / electrostrictive element is small (that is, even if the driving period is T1), the frequency of the pressure fluctuation of the liquid in the chamber is increased (that is, the pressure fluctuation period is T1 / 2). As a result, a large amount of liquid can be atomized and ejected while avoiding a decrease in durability of the piezoelectric / electrostrictive elements 11 and 12.

  Further, the chamber 10-3 includes a liquid ejection nozzle forming wall (metal plate 10a), which is a wall in which a plurality of liquid ejection nozzles (liquid ejection holes) 10-3a are formed, and the liquid ejection nozzle formation wall. A piezoelectric / electrostrictive element 11 and a piezoelectric / electrostrictive element, which are at least two of the plurality of piezoelectric / electrostrictive elements. The element 12 is disposed on the liquid jet nozzle facing wall (metal plate 10c).

  Therefore, pressure fluctuations caused by the piezoelectric / electrostrictive elements 11 and 12 disposed at different positions are propagated to each of the plurality of liquid ejection holes 10-3a. The traveling direction of the pressure fluctuation wave is different between the pressure fluctuation from the piezoelectric / electrostrictive element 11 and the pressure fluctuation from the piezoelectric / electrostrictive element 12. As a result, the droplet ejection direction by driving one piezoelectric / electrostrictive element 11 is slightly different from the droplet ejection direction by driving another piezoelectric / electrostrictive element 12. As a result, it is possible to reduce the frequency with which the droplets ejected before and after a certain liquid ejecting nozzle are recombined in the ejecting space. Therefore, the particle size of the ejected droplets can be kept minute.

  The liquid jet nozzle forming wall (metal plate 10a) and the liquid jet nozzle facing wall (metal plate 10c) are parallel to each other (parallel to the XY plane). When viewed from an orthogonal direction (Z-axis direction), the outer shape of the liquid ejecting nozzle forming wall and the outer shape of the liquid ejecting nozzle facing wall coincide with each other, and the liquid ejecting nozzle facing wall is a predetermined straight line (center line). CL) and the two piezoelectric / electrostrictive elements 11 and 12 having the same shape as each other are arranged on the predetermined wall (center line CL) on the liquid jetting nozzle facing wall. It arrange | positions so that it may become line symmetrical with respect to it.

  According to this, even when the liquid jet nozzle facing wall (metal plate 10c) is deformed by the heat generation of the piezoelectric / electrostrictive elements 11, 12, the deformation of the liquid jet nozzle facing wall is axisymmetric. Accordingly, the angles of the two piezoelectric / electrostrictive elements 11 and 12 with respect to the liquid injection nozzle forming wall (metal plate 10a) are substantially the same. In other words, even when the liquid jet nozzle facing wall is deformed, the angle of the two piezoelectric / electrostrictive elements 11 and 12 with respect to the liquid jet nozzle forming wall does not change greatly. Accordingly, since the liquid having substantially the same pressure fluctuation arrives at each of the plurality of liquid ejecting nozzles (liquid ejecting holes 10-3a) before and after the deformation of the liquid ejecting nozzle facing wall, Variation in particle size can be reduced. Furthermore, since the angle of the two piezoelectric / electrostrictive elements 11 and 12 does not change greatly, the droplet ejection direction does not vary.

(Second Embodiment)
Next, a liquid ejecting apparatus 50 according to a second embodiment of the invention will be described with reference to FIGS. The liquid ejecting apparatus 50 is different from the liquid ejecting apparatus 10 only in that the piezoelectric / electrostrictive elements 11 and 12 of the liquid ejecting apparatus 10 according to the first embodiment are replaced with piezoelectric / electrostrictive elements 13 and 14. . Therefore, the following description will focus on such differences.

  The piezoelectric / electrostrictive element 13 is fixed to the upper surface of the metal plate 10 c in the same manner as the piezoelectric / electrostrictive elements 11 and 12. The planar shape of the piezoelectric / electrostrictive element 13 is substantially rectangular as shown in FIG. 11, and is slightly smaller than the planar shape of the chamber 10-3. The piezoelectric / electrostrictive element 13 is disposed inside the chamber 10-3 in plan view. The long side and short side of the rectangle forming the outer shape of the piezoelectric / electrostrictive element 13 are parallel to the long side and short side of the chamber 10-3, respectively.

  The piezoelectric / electrostrictive element 13 is a “lateral effect type multilayer piezoelectric actuator” similar to the piezoelectric / electrostrictive element 11. When a predetermined potential difference is applied between the pair of comb-like electrodes 13a and 13b (when a drive voltage is applied), the piezoelectric / electrostrictive element 13 has a metal plate immediately below the piezoelectric / electrostrictive element 13. 10c is bent and deformed in the negative direction of the Z axis, a pressure wave is applied to the liquid in the chamber 10-3, and / or the volume of the chamber 10-3 is reduced. The electrode 13b is grounded.

  The piezoelectric / electrostrictive element 14 has a substantially rectangular parallelepiped shape having sides extending along the X-axis, Y-axis, and Z-axis directions, as shown in FIGS. 12 and 13. The length of the piezoelectric / electrostrictive element 14 in the X-axis direction is about 1/3 of the length of the piezoelectric / electrostrictive element 13 in the X-axis direction. The length of the piezoelectric / electrostrictive element 14 in the Y-axis direction is about ½ of the length of the piezoelectric / electrostrictive element 13 in the Y-axis direction. The piezoelectric / electrostrictive element 14 is located at the position between the chamber 10-3 and the liquid introduction passage portion 10-4 (the X axis negative direction end of the chamber 10-3) from the central portion in the Y axis direction of the chamber 10-3. Below the position of the Y-axis negative direction end, it is fixed to the lower surface of the metal plate 10a.

  The piezoelectric / electrostrictive element 14 is a “lateral effect type laminated piezoelectric actuator” similar to the piezoelectric / electrostrictive element 11. When a predetermined potential difference is applied between the pair of comb-like electrodes 14a and 14b (when a drive voltage is applied), the piezoelectric / electrostrictive element 14 has a metal plate immediately above the piezoelectric / electrostrictive element 14. 10a is bent and deformed in the positive direction of the Z axis, a pressure wave is applied to the liquid in the chamber 10-3, and / or the volume of the chamber 10-3 is reduced. The electrode 14b is grounded.

  Next, the operation of the liquid ejecting apparatus 50 will be described with reference to FIGS. 14 to 16. The electric control device 40 outputs the discharge valve drive signal INJ at a predetermined timing, and outputs the piezoelectric element drive voltage signals DV1 and DV2 shown in FIG. 14 to the electrode 13a of the piezoelectric / electrostrictive element 13 and the piezoelectric / electrostrictive. Each is applied to the electrode 14a of the element 14. Each of the piezoelectric element drive voltage signals DV1 and DV2 is a signal that repeatedly changes to a trapezoidal shape with a period T1 (seconds). The phase of the piezoelectric element driving voltage signal DV1 and the phase of the piezoelectric element driving voltage signal DV2 are different from each other by ½ period.

  As shown in FIG. 14, when the piezoelectric element drive voltage signal DV1 applied to the piezoelectric / electrostrictive element 14 starts to increase from 0 (V) to VA (V) at time t1, it is shown in FIG. As described above, the piezoelectric / electrostrictive element 13 deforms the metal plate 10c, which is the upper wall of the chamber 10-3, in the negative Z-axis direction. Thereafter, the piezoelectric element drive voltage signal DV1 returns to 0 (V) after maintaining the constant time VA (V). As described above, the pressure of the liquid (fuel) in the chamber 10-3 increases and then decreases. As a result, the liquid is ejected in the negative Z-axis direction from the liquid ejection hole 10-3a while being atomized.

  Next, at time t2 when T1 / 2 (seconds) has elapsed from time t1, the piezoelectric element drive voltage signal DV2 applied to the piezoelectric / electrostrictive element 14 increases from 0 (V) to VA (V). Start. Thereby, as shown in FIG. 16, the piezoelectric / electrostrictive element 14 deforms the vicinity of the piezoelectric / electrostrictive element 14 fixing portion of the metal plate 10a in the positive direction of the Z-axis. Thereafter, the piezoelectric element drive voltage signal DV2 returns to 0 (V) after maintaining the constant time VA (V). As described above, the pressure of the liquid (fuel) in the chamber 10-3 increases and then decreases. As a result, the liquid ejected from the liquid ejection hole 10-3a is atomized.

  At this time, since the metal plate 10a is deformed into a wave shape, the axis of the liquid injection hole 10-3a is not parallel to the Z axis. As a result, the ejection direction of the liquid ejected from the liquid ejection hole 10-3a is different from the Z-axis negative direction.

  As a result, as shown in FIG. 16, the ejection directions of the liquid droplets ejected back and forth through a certain liquid ejection hole 10-3 a are different, so that the liquid droplets are in the ejection space. The frequency with which the droplet diameter increases due to recombination can be reduced. Therefore, the particle size of the ejected droplets can be kept minute.

  As described above, in the liquid ejecting apparatus 50 according to the second embodiment, at least one of the plurality of piezoelectric / electrostrictive elements (piezoelectric / electrostrictive element 13) is the liquid ejecting nozzle facing wall (metal). Plate 10c), and at least one of the plurality of piezoelectric / electrostrictive elements (piezoelectric / electrostrictive element 14) is provided on the liquid injection nozzle forming wall (metal plate 10a). .

  Accordingly, when the piezoelectric / electrostrictive element 14 is driven, the angle of the liquid ejecting nozzle forming wall (metal plate 10a) (accordingly, the angle of the liquid ejecting nozzle, that is, the axial direction of the liquid ejecting hole 10-3a). Is changed. Thereby, the ejection direction of the droplet accompanying the driving of the piezoelectric / electrostrictive element 14 is different from the ejection direction of the droplet accompanying the driving of the piezoelectric / electrostrictive element 13. As a result, it is possible to reduce the frequency with which the liquid droplets jetted back and forth through a certain liquid jet nozzle (liquid jet hole 10-3a) recombine in the jet space. Therefore, the particle size of the ejected droplets can be kept minute.

(Third embodiment)
Next, a liquid ejecting apparatus 60 according to a third embodiment of the invention will be described. The liquid ejecting apparatus 60 differs from the liquid ejecting apparatus 10 only in that the liquid ejecting apparatus 10 according to the first embodiment further includes a piezoelectric / electrostrictive element 15. Therefore, the following description will be made with reference to FIGS.

  The piezoelectric / electrostrictive element 15 has a substantially rectangular parallelepiped shape having sides extending along the X-axis, Y-axis, and Z-axis directions. The length of the piezoelectric / electrostrictive element 15 in the X-axis direction is about 1/3 of the length of the piezoelectric / electrostrictive element 11 in the X-axis direction. The length of the piezoelectric / electrostrictive element 15 in the Y-axis direction is about twice the length of the piezoelectric / electrostrictive element 11 in the Y-axis direction. The piezoelectric / electrostrictive element 15 has a metal plate 10a below the chamber 10-3 at a position between the chamber 10-3 and the liquid introduction passage portion 10-4 (X-axis negative direction end of the chamber 10-3). It is fixed to the lower surface of the.

  When a potential difference is applied between the electrodes 15a and 15b (when a drive voltage is applied), the piezoelectric / electrostrictive element 15 is directly connected to the piezoelectric / electrostrictive element 15 in the same manner as the piezoelectric / electrostrictive element 14. The upper metal plate 10a is bent and deformed in the positive direction of the Z axis, a pressure wave is applied to the liquid in the chamber 10-3, and / or the volume of the chamber 10-3 is increased or decreased. It has become. Moreover, the piezoelectric / electrostrictive element 15 changes the axis of the liquid injection hole 10-3a as a result of bending and deforming the metal plate 10a. The electrode 15b is grounded.

  Next, the operation of the liquid ejecting apparatus 60 will be described with reference to FIG. The electrical control device 40 outputs the discharge valve drive signal INJ at a predetermined timing, and outputs the piezoelectric element drive voltage signals DV1, DV2, and DV3 shown in FIG. 20 to the electrode 11a of the piezoelectric / electrostrictive element 11, the piezoelectric / The voltage is applied to the electrode 12a of the electrostrictive element 12 and the electrode 15a of the piezoelectric / electrostrictive element 15, respectively.

  Each of the piezoelectric element driving voltage signals DV1 to DV3 is a signal that repeatedly changes to a trapezoidal shape with a period T1 (seconds). The phase of the piezoelectric element driving voltage signal DV2 is delayed from the phase of the piezoelectric element driving voltage signal DV1 by 1/3 period (T1 / 3 (second)). The phase of the piezoelectric element driving voltage signal DV3 is further delayed by 1/3 period (T1 / 3 (second)) than the phase of the piezoelectric element driving voltage signal DV2. Thereby, the pressure of the liquid in the chamber 10-3 increases or decreases with a period of T1 / 3 (second).

  Therefore, even if the driving frequency of one piezoelectric / electrostrictive element is small (that is, even if the driving cycle is T1), the frequency of the pressure fluctuation of the liquid in the chamber is increased (that is, the driving cycle is set to T1 / 3). And). As a result, a decrease in durability of the piezoelectric / electrostrictive elements 11, 12 and 15 can be avoided.

  As described above, in the liquid ejecting apparatus including N piezoelectric / electrostrictive elements in one chamber, each of the plurality of piezoelectric / electrostrictive elements is applied with the pressure wave and / or the It is preferable to drive the chamber so as to change the volume, and to drive the chambers so that the phases are different from each other by a time (T / N) obtained by dividing the period T by the number N. This is because the pressure of the liquid in the chamber can be changed at a frequency N times the frequency of the piezoelectric element drive voltage signal.

(Fourth embodiment)
Next, a liquid ejecting apparatus 70 according to a fourth embodiment of the invention will be described. The liquid ejecting apparatus 70 includes metal plates 10d, 10e, and 10c, and includes a chamber 10-5 that is different from the chamber 10-3, and the piezoelectric / electrostrictive elements 16 and 12 instead of the piezoelectric / electrostrictive elements 11 and 12. 17 differs from the liquid ejecting apparatus 10 only in that it includes 17. Therefore, the following description will be made with reference to FIGS.

  The chamber 10-5 is provided with a rectangular parallelepiped partition 10-5b in the center of the same space as the chamber 10-3. The partition portion 10-5b is formed of a metal plate 10e. The partition part 10-5b extends in the X-axis direction from the liquid introduction passage part 10-4 formed in the metal plate 10e in the upper part of the chamber 10-5 to the X-axis positive direction end part of the chamber 10-5. As a result, a space having a lower height than the height of the chamber 10-5 in the portion where the partition 10-5b does not exist is formed below the partition 10-5b.

  The liquid injection hole 10-5a is formed in a metal plate 10d that replaces the metal plate 10a. The liquid ejection holes 10-5a are arranged in a square lattice pattern, similarly to the liquid ejection holes 10-3a. However, the liquid injection hole 10-5a is formed only in a region immediately below the partition portion 10-5a.

  The piezoelectric / electrostrictive element 16 is different from the piezoelectric / electrostrictive element 11 only in that it has a slightly smaller outer shape than the piezoelectric / electrostrictive element 11. The piezoelectric / electrostrictive element 16 is fixed to the upper surface of the metal plate 10c so as to be positioned on the Y axis negative direction side with respect to the partition portion 10-5a of the chamber 10-5. Each side of the square forming the outer shape of the piezoelectric / electrostrictive element 16 is parallel to either the short side or the long side of the chamber 10-5.

  The piezoelectric / electrostrictive element 17 has the same configuration as the piezoelectric / electrostrictive element 16. The piezoelectric / electrostrictive element 17 is fixed to the upper surface of the metal plate 10c so as to be positioned on the Y axis positive direction side with respect to the partition portion 10-5a of the chamber 10-5. Each side of the square forming the outer shape of the piezoelectric / electrostrictive element 17 is parallel to either the short side or the long side of the chamber 10-5.

  The piezoelectric / electrostrictive element 16 and the piezoelectric / electrostrictive element 17 have a center line (line 7-7) of the chamber 10-5 extending in the X-axis direction through the center in the Y-axis direction of the chamber 10-5 in plan view. Are arranged in line symmetry. The drive voltage signal DV1 is applied to the piezoelectric / electrostrictive element 16 similarly to the piezoelectric / electrostrictive element 11, and the drive voltage signal DV2 is applied to the piezoelectric / electrostrictive element 17 similarly to the piezoelectric / electrostrictive element 12. It is like that.

  According to the liquid ejecting apparatus 70 configured as described above, the pressure wave applied to the liquid in the chamber 10-5 by the operation of the piezoelectric / electrostrictive element 16 and the piezoelectric / electrostrictive element 17 or the volume of the chamber 10-5. The pressure fluctuation of the liquid due to the increase / decrease of the liquid reaches each liquid ejection hole 10-5a while having a large angle with respect to the axis of each liquid ejection hole 10-5a. As a result, the direction of the liquid droplet ejected from the liquid ejection hole 10-5a is the ejection (particulate formation) by the operation of the piezoelectric / electrostrictive element 16, and the ejection (particulate formation) by the operation of the piezoelectric / electrostrictive element 17. ) Will be much different. In other words, since the ejected droplets are more diffused, the frequency with which the droplets recombine in the ejection space can be reduced.

  Here, experimental conditions and results performed on the liquid ejecting apparatus according to the present invention will be described. Note that the liquid ejecting apparatus that is the subject of the experiment has the same configuration as the liquid ejecting apparatus 10 of the first embodiment. However, the number and size of the piezoelectric / electrostrictive elements were as follows.

(Experimental conditions)
(1) The diameter of the liquid injection hole was φ30 μm.
(2) The number of liquid injection holes was 288, and the liquid injection holes were arranged at intervals of 0.15 mm in a lattice shape.
(3) The size of the chamber was 2 × 6 mm and the thickness was 0.2 mm.
(4) The thickness of the vibration plate (liquid injection hole facing wall, metal plate 10c) was set to 0.01 mm.
(5) The thickness of the liquid injection hole forming wall (metal plate 10a) was 0.03 mm.
(6) The slit of the liquid introduction passage 10-4 has a thickness of 0.03 mm, a width of 5.8 mm, and a length of 2 mm.

(7) The size of the piezoelectric / electrostrictive element is 1.8 × 5.8 mm when there is one piezoelectric / electrostrictive element, 1.8 mm × 2.8 mm when there are two, and 1.8 mm when there are three. × 1.9 mm, 4 mm 1.8 mm × 1.2 mm, 10 mm 1.8 mm × 0.4 mm.
(8) The frequency of the piezoelectric element driving voltage signal applied to each piezoelectric / electrostrictive element was 70 kHz (period T), the voltage was 12 V, and the waveform was a rectangular wave. For comparison, a piezoelectric element driving voltage signal having a frequency of 140 kHz, a voltage of 12 V, and a waveform of a rectangular wave when a single piezoelectric / electrostrictive element is provided.
(9) When there were n piezoelectric / electrostrictive elements, the phases of the piezoelectric element driving voltage signals were different from each other by (T / n) periods. As a result, when there were two piezoelectric / electrostrictive elements, the pressure fluctuation period of the chamber was 140 kHz, three was 210 kHz, four was 280 kHz, and ten was 700 kHz. For comparison, an experiment was conducted in which the pressure fluctuation frequency of the chamber was set to 70 kHz when there were two piezoelectric / electrostrictive elements.

(10) The pressure of the liquid introduced into the chamber was 0.3 MPa, and the flow rate was 130 cc / min.
(11) In order to measure the diameter of the ejected droplets, the liquid used was a dry sol belt.

(Experimental result)
Next, the experimental results will be described. Table 1 shows the results of experiments on the durability of the liquid ejecting apparatus. As can be understood from Table 1, the liquid ejecting apparatus of the present invention in which a plurality of piezoelectric / electrostrictive elements are provided in the chamber and the pressure in the chamber is varied by shifting the phase of the piezoelectric element driving voltage signal is provided in the chamber. Even when the pressure fluctuation frequency was set to a high frequency (140 kHz), it was not damaged and was more durable than a liquid ejecting apparatus having only one piezoelectric / electrostrictive element. Further, although not shown in Table 1, the liquid ejecting apparatus was not damaged in each of the three, four, and ten piezoelectric / electrostrictive elements.

  FIG. 24 is a graph showing the relationship between the number of piezoelectric / electrostrictive elements and the measured value of the diameter of the ejected droplets. As is apparent from this graph, it was confirmed that when the number of piezoelectric / electrostrictive elements was 2 to 4, the droplets were finely divided.

  Note that when the number of piezoelectric / electrostrictive elements was 10, the diameter of the droplets increased. This is considered due to the frequency response of the liquid. Therefore, although the reason is not clear, it is considered preferable that the number of piezoelectric / electrostrictive elements is several (for example, 2 to 4).

  Furthermore, in the liquid ejecting apparatus 10 according to the first embodiment in which two piezoelectric / electrostrictive elements are installed, the two piezoelectric / electrostrictive elements are driven at opposite phases and 70 kHz, and the liquid ejected at that time is driven. When the droplet ejection direction was confirmed by a high-speed camera, the droplet ejection direction when one piezoelectric / electrostrictive element was driven and the droplet ejection direction when another piezoelectric / electrostrictive element was driven The angle difference with respect to was 1 °. Further, in the liquid ejecting apparatus 50 of the second embodiment, when a similar experiment was performed, the ejection direction of the droplet when one piezoelectric / electrostrictive element was driven and the other piezoelectric / electrostrictive element were driven. The angle difference from the droplet ejection direction was 0.5 °.

  As described above, the liquid ejecting apparatus according to each embodiment of the present invention includes a plurality of piezoelectric / electrostrictive elements for one chamber, and each of the piezoelectric / electrostrictive elements has the same period. Driven to apply pressure waves to the liquid in the chamber and / or change the volume of the chamber with T, and assuming that the number of piezoelectric / electrostrictive elements is N, the period T is divided by the number N. Driven so that the phases are different from each other by time (T / N) (that is, at different timings). According to this, a large amount of fine droplets can be ejected without reducing the durability of the piezoelectric / electrostrictive element.

  In addition, this invention is not limited to the said embodiment, A various modification can be employ | adopted within the scope of the present invention. For example, in the liquid ejecting apparatus 10 shown in FIGS. 3 to 5, a plurality of piezoelectric / electrostrictive elements 11 are disposed on the wall facing the liquid ejecting nozzle. However, as shown in FIG. Wall that does not face the liquid ejection nozzle forming wall 10f on which the nozzle 10-3a is formed (a wall that constitutes the chamber 10-3 and is not parallel to the liquid ejection nozzle formation wall 10f) A plurality of piezoelectric / electrostrictive elements 11 may be provided in 10 g.

  Furthermore, as shown in FIG. 26, a wall not facing the liquid ejection nozzle forming wall 10f (a wall that is one of the walls constituting the chamber 10-3 and not parallel to the liquid ejection nozzle forming wall 10f). ) The piezoelectric / electrostrictive element 11 may be disposed at 10 g and 10 h, respectively. According to this, a plurality of piezoelectric / electrostrictive elements 11 are disposed in the chamber 10-3. In addition, the angle formed by the droplet ejection direction from each liquid ejection hole 10-3a accompanying the operation of the piezoelectric / electrostrictive 11 disposed on the wall 10g and the axis of each liquid ejection hole 10-3a, and the wall The angle formed by the droplet ejection direction from each liquid ejection hole 10-3a accompanying the operation of the piezoelectric / electrostrictive 11 disposed at 10h and the axis of each liquid ejection hole 10-3a is made equal. Can do. Therefore, such a liquid ejecting apparatus can be used for a wide range of applications.

  In addition, in the liquid ejecting apparatus 50 according to the third embodiment shown in FIGS. 11 to 13, the piezoelectric / electrostrictive element 13 and the piezoelectric / electrostrictive element are formed on the liquid ejecting nozzle forming wall and the liquid ejecting nozzle facing wall. One 14 was arranged for each. On the other hand, as shown in FIG. 27, liquid ejection is performed in accordance with required specifications (for example, a flow rate is small but a request to change the ejection direction more greatly and maintain the droplet diameter to be minute). A plurality of piezoelectric / electrostrictive elements 11 may be disposed on the nozzle forming wall 10i. According to this, since the region where the liquid injection hole 10-3a can be formed becomes small, the flow rate of the liquid that can be ejected is slightly reduced, but the operation of one piezoelectric / electrostrictive element and the other piezoelectric / electrostrictive element Since the angle of the axis of the liquid ejection hole 10-3a can be greatly varied depending on the time of operation, the droplet ejection direction can be greatly changed.

  Further, the liquid injection device of the above embodiment has been applied to a gasoline internal combustion engine of a type in which fuel is injected into the intake pipe (intake port) 30. However, the liquid injection device according to the present invention is directly applied to the cylinder. It can also be applied to a so-called “direct injection gasoline internal combustion engine” for injection. Furthermore, it is also effective to use the liquid injection device according to the present invention as a direct injection injector for a diesel engine.

  Furthermore, the liquid injection holes of the respective embodiments according to the present invention have the cross-sectional area gradually reduced in the flow direction (liquid injection direction) for the purpose of increasing the flow speed by converting the pressure of the liquid into kinetic energy. A so-called tapered nozzle may be used.

FIG. 1 is a diagram showing an outline of an electronic fuel injection control device using a liquid injection device according to a first embodiment of the present invention. It is a front view of the electromagnetic opening-and-closing type discharge valve shown in FIG. FIG. 2 is a plan view of the liquid ejecting apparatus illustrated in FIG. 1. FIG. 5 is a cross-sectional view of the liquid ejecting apparatus cut along a plane along line 1-1 in FIG. 3 and an enlarged front view of the electromagnetic on-off type discharge valve shown in FIG. 2. FIG. 4 is a cross-sectional view of the liquid ejecting apparatus cut along a plane along line 2-2 in FIG. 3. It is the figure which showed the state of the liquid ejected from the liquid ejecting apparatus shown in FIG. FIG. 4 is a time chart showing changes in a piezoelectric element driving voltage signal applied to a piezoelectric / electrostrictive element of the liquid ejecting apparatus shown in FIG. 3 and a pressure of a liquid in a chamber. It is the schematic for demonstrating the action | operation of the liquid ejecting apparatus shown in FIG. It is the schematic for demonstrating the action | operation of the liquid ejecting apparatus shown in FIG. FIG. 4 is a schematic diagram for explaining an operation of a comparative example of the liquid ejecting apparatus illustrated in FIG. 3. FIG. 6 is a plan view of a liquid ejecting apparatus according to a second embodiment of the invention. FIG. 13 is a cross-sectional view of the liquid ejecting apparatus cut along a plane along line 3-3 in FIG. 11. FIG. 4 is a cross-sectional view of the liquid ejecting apparatus taken along a plane along line 4-4 in FIG. 12 is a time chart showing changes in piezoelectric element driving voltage signal applied to the piezoelectric / electrostrictive element of the liquid ejecting apparatus shown in FIG. 11 and the pressure of the liquid in the chamber. It is the schematic for demonstrating the action | operation of the liquid ejecting apparatus shown in FIG. It is the schematic for demonstrating the action | operation of the liquid ejecting apparatus shown in FIG. FIG. 10 is a plan view of a liquid ejecting apparatus according to a third embodiment of the invention. It is sectional drawing which cut | disconnected the liquid ejecting apparatus in the plane in alignment with line 5-5 in FIG. FIG. 18 is a cross-sectional view of the liquid ejecting apparatus taken along a plane along line 6-6 in FIG. FIG. 18 is a time chart showing a change in a piezoelectric element driving voltage signal applied to a piezoelectric / electrostrictive element of the liquid ejecting apparatus shown in FIG. 17 and a pressure of a liquid in a chamber. FIG. 10 is a plan view of a liquid ejecting apparatus according to a fourth embodiment of the invention. FIG. 22 is a cross-sectional view of the liquid ejecting apparatus taken along a plane along line 7-7 in FIG. 21. FIG. 22 is a cross-sectional view of the liquid ejecting apparatus taken along a plane along line 8-8 in FIG. 21. 6 is a graph showing experimental results of the liquid ejecting apparatus according to the present invention. FIG. 10 is a schematic cross-sectional view illustrating a modified example of the liquid ejecting apparatus according to the invention. FIG. 10 is a schematic cross-sectional view illustrating another modification of the liquid ejecting apparatus according to the invention. FIG. 10 is a schematic cross-sectional view illustrating another modification of the liquid ejecting apparatus according to the invention. It is sectional drawing of the conventional liquid ejecting apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Liquid injection apparatus, 10-3 ... Chamber, 10-3a ... Liquid injection hole, 10-2 ... Liquid supply channel, 10-1 ... Liquid introduction port, 10-4 ... Liquid introduction channel, 10a-10c ... Metal plate 11, 12 ... Piezoelectric / electrostrictive element, 21 ... Pressurizing pump, 24 ... Same electromagnetic open / close discharge valve, 40 ... Electric control device.

Claims (5)

A chamber having a plurality of nozzles for ejecting liquid and configured by a plurality of walls;
A liquid introduction passage section connected to the chamber and for introducing the liquid into the chamber by flowing the liquid;
The pressure wave is applied to the liquid introduced into the chamber through the liquid introduction passage and / or the volume of the chamber is reduced while being installed on at least one of the plurality of walls constituting the chamber. A piezoelectric / electrostrictive element that performs the increase,
A liquid ejecting apparatus that ejects liquid in the chamber into an external space through the liquid ejecting nozzle while being atomized by the operation of the piezoelectric / electrostrictive element;
A plurality of the piezoelectric / electrostrictive elements are provided, and the plurality of piezoelectric / electrostrictive elements are driven to apply the pressure wave and / or increase or decrease the volume of the chamber at different timings. A liquid ejecting apparatus. The liquid ejecting apparatus according to claim 1,
The chamber includes a liquid ejecting nozzle forming wall that is a wall on which the plurality of liquid ejecting nozzles are formed, and a liquid ejecting nozzle facing wall that is a wall facing the liquid ejecting nozzle forming wall. Configured,
The liquid ejecting apparatus, wherein at least two of the plurality of piezoelectric / electrostrictive elements are disposed on the liquid ejecting nozzle facing wall. The liquid ejecting apparatus according to claim 2,
The liquid ejecting nozzle forming wall and the liquid ejecting nozzle facing wall are parallel to each other, and when viewed from a direction orthogonal to the liquid ejecting nozzle facing wall, the outer shape of the liquid ejecting nozzle forming wall and the same liquid The outer shape of the jetting nozzle facing wall is matched, and the liquid jetting nozzle facing wall is configured to have a line-symmetric outer shape with respect to a predetermined line
A liquid ejecting apparatus in which two piezoelectric / electrostrictive elements having the same shape are arranged symmetrically with respect to the predetermined straight line on the liquid ejecting nozzle facing wall. The liquid ejecting apparatus according to claim 1,
The chamber includes a liquid ejecting nozzle forming wall that is a wall on which the plurality of liquid ejecting nozzles are formed, and a liquid ejecting nozzle facing wall that is a wall facing the liquid ejecting nozzle forming wall,
At least one of the plurality of piezoelectric / electrostrictive elements is disposed on the liquid jet nozzle facing wall, and at least one other of the plurality of piezoelectric / electrostrictive elements is formed with the liquid jet nozzle. A liquid ejecting apparatus disposed on a wall. The liquid ejecting apparatus according to any one of Claims 1 to 4,
Each of the plurality of piezoelectric / electrostrictive elements is driven so as to apply the pressure wave and / or change the volume of the chamber with the same period T, and the number of the piezoelectric / electrostrictive elements is determined. A liquid ejecting apparatus that is driven so that phases are different from each other by a time (T / N) obtained by dividing the period T by the number N, where N.

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