JP2005039984A - Oscillation generator and liquid ejector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oscillation generator and a liquid ejector from which heat can be removed sufficiently while reducing the size. <P>SOLUTION: The oscillation generator comprises a piezoelectric displacement element, and a cooler for cooling the piezoelectric displacement element using a thermoelectric conversion element preferably disposed contiguously to the piezoelectric displacement element. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a vibration generator and a liquid discharge device, and more particularly, vibration generation using a piezoelectric actuator used in, for example, a fuel jet ink ejector, an inkjet printer print head, an oscillator, an ultrasonic motor, an ultrasonic vibrator, and the like. The present invention relates to a liquid ejecting apparatus suitably used as a printing head equipped with an apparatus and an actuator using a spreading vibration mode, an extension vibration mode, or a thickness longitudinal vibration mode.

  Conventionally, products using piezoelectric ceramics include, for example, piezoelectric actuators, filters, piezoelectric resonators (including oscillators), ultrasonic vibrators, ultrasonic motors, piezoelectric sensors, pressure pumps, and the like.

Among these, since the response speed of the piezoelectric actuator to electrical signals is as high as 10 ⁻⁶ seconds, it can be used as a piezoelectric actuator for positioning an XY stage of a semiconductor manufacturing apparatus, a piezoelectric actuator used for a print head of an inkjet printer, Applied.

  A print head using an ink jet system includes a piezoelectric displacement element made of perovskite ceramics including Pb such as PZT, and uses a displacement of the piezoelectric displacement element when a drive voltage is applied to the piezoelectric displacement element from both sides. Liquid droplets are discharged from the liquid discharge port.

  In this piezoelectric ceramic, the temperature of the piezoelectric ceramic layer rises due to internal frictional heat, electrical heat generation, or the like due to deformation of the piezoelectric displacement element. When the temperature of the piezoelectric ceramic layer increases, the displacement characteristics deteriorate, and the pressure generated by the piezoelectric actuator also decreases.

  Therefore, it has been proposed to cool the pressure air and supply the cooling air to the piezoelectric actuator to cool the piezoelectric actuator to prevent the deterioration of the displacement characteristics (see, for example, Patent Document 2).

Further, it has been proposed to bond a metal having a high thermal conductivity such as copper to a piezoelectric actuator and remove the heat generated by the piezoelectric actuator through the metal (for example, see Patent Document 3).
JP 11-34321 A JP 2002-532049 A JP 2002-532658 A

  However, in the piezoelectric actuator described in Patent Document 2, it is necessary to produce pressurized air, and there is a problem that the apparatus is enlarged including the heat insulation of the cooling air transport pipe. It was inappropriate.

  In addition, the piezoelectric actuator described in Patent Document 3 uses heat conduction to remove heat. However, a piezoelectric actuator in which piezoelectric displacement elements are integrated at a high density or a piezoelectric actuator that generates a large amount of heat is insufficient to remove heat. Thus, there is a problem that the temperature of the piezoelectric actuator rises.

  Accordingly, an object of the present invention is to provide a vibration generating apparatus and a liquid discharge apparatus that can sufficiently remove heat and can be reduced in size.

  In order to cool the piezoelectric displacement element, the present invention is provided with a cooling means using a thermoelectric conversion element, and in particular, by providing the thermoelectric conversion element on the same surface as the piezoelectric displacement element, the heat generated by the piezoelectric displacement element is sufficiently reduced. It is based on the novel knowledge that it can be removed and the depolarization of the piezoelectric displacement element can be prevented. As a result, it is difficult to depolarize, has high durability, and can be downsized. A liquid ejecting apparatus can be provided.

  That is, the vibration generator of the present invention is a vibration generator using a piezoelectric displacement element, and includes a cooling means using a thermoelectric conversion element to cool the piezoelectric displacement element. It is.

  In particular, it is preferable that the thermoelectric conversion element is provided adjacent to the piezoelectric displacement element. Furthermore, it is preferable that the thermoelectric conversion element is provided on the same surface as the piezoelectric displacement element. By these, more efficient cooling can be performed.

  Moreover, it is preferable that the said cooling device is equipped with the heat sink.

  Furthermore, the thermoelectric conversion element is preferably bonded to the piezoelectric displacement element via an adhesive layer, and the adhesive layer is preferably a high thermal conductive adhesive or a high thermal conductive brazing material.

  Furthermore, it is preferable that the piezoelectric displacement element is a laminated body of an internal electrode and a piezoelectric ceramic layer.

  The piezoelectric displacement element includes a surface individual electrode, an internal electrode, and a piezoelectric ceramic layer sandwiched between the internal electrode and the surface individual electrode, and the piezoelectric displacement element is provided on the diaphragm. Preferably it is.

  Furthermore, it is preferable that the internal electrode of the piezoelectric displacement element and one electrode of the thermoelectric conversion element have the same potential.

  The piezoelectric displacement element preferably has a plurality of displacement regions.

  Furthermore, it is preferable that a means for detecting the temperature of the piezoelectric displacement element is provided.

  The liquid ejection device of the present invention is characterized in that the vibration generating device is provided on the surface of a flow path member including a liquid supply port, a liquid pressurizing chamber, and a liquid ejection port. Is.

  In the vibration generator of the present invention, the piezoelectric displacement element is cooled by a cooling device using a thermoelectric conversion element, so that the piezoelectric actuator can be efficiently cooled simply by supplying electric power, and the occurrence of depolarization of the piezoelectric ceramic layer is remarkable. And can be downsized.

  In particular, since the piezoelectric actuator can be directly cooled by providing a thermoelectric conversion module bonded to the surface of the piezoelectric actuator at a position adjacent to the piezoelectric displacement element, efficient cooling is possible.

  In addition, since the liquid ejection characteristics of the present invention are stable, the liquid ejection device can be driven without repolarization for a long period of time, and can be suitably used particularly for printers and printing machines using an inkjet system. .

  A vibration generator and a liquid ejection device according to an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1A is a cross-sectional view of the vibration generator and the liquid ejection device of the present embodiment, and FIG. 1B is a plan view thereof. As shown in FIGS. 1A and 1B, this liquid ejection device has a structure in which a vibration generating device including a piezoelectric actuator 1 is provided on a flow path member 3.

  For example, as shown in FIG. 1A, the piezoelectric actuator 1 includes a common electrode 5, a piezoelectric ceramic layer 4 that is a part involved in vibration, and individual surfaces provided on the surface of the diaphragm 2. The electrodes 6 are sequentially formed. A plurality of piezoelectric displacement elements 7 each having a piezoelectric ceramic layer 4 sandwiched between a common electrode 5 and a surface individual electrode 6 are provided on the diaphragm 2. With such a configuration, it is possible to reduce the thickness of the piezoelectric ceramic layer 4 and increase the amount of displacement.

  The diaphragm 2 is preferably provided to hold the piezoelectric displacement element 7 and protect the piezoelectric displacement element 7 from mechanical vibration and impact. The piezoelectric ceramic layer 4 and the common electrode 5 exist on the vibration substrate 2 across the plurality of piezoelectric displacement elements 7, but the piezoelectric ceramic layer 4 and the common electrode 5 included in the piezoelectric displacement element 7 have a displacement region. It corresponds only to the portion shown in the range 7a, and does not mean the entire piezoelectric ceramic layer 4 or the entire common electrode 5.

  A plurality of liquid pressurizing chambers 3a are arranged in parallel in the flow path member 3, and a partition wall 3b is formed as a wall that partitions the liquid pressurizing chamber 3a. The piezoelectric actuator 1 and the flow path member 3 are bonded so that the individual surface electrode 6 is disposed immediately above the opening of the liquid pressurizing chamber 3a. Although not shown, it goes without saying that the flow path member 3 is provided with a liquid supply port, and this liquid supply port is connected to the liquid pressurizing chamber 3a.

  When a driving voltage is applied between the common electrode 5 and the individual surface electrode 6, the piezoelectric ceramic layer 4 sandwiched between the common electrode 5 and the individual surface electrode 6 is deformed, and the piezoelectric displacement element 7 is displaced. With this displacement, the diaphragm 2 integrated with the piezoelectric displacement element 7 is also displaced in the same direction as the piezoelectric displacement element 7, and the displacement region 7a is displaced. As a result, the volume of the liquid pressurizing chamber 3a is changed. Therefore, the liquid in the liquid pressurizing chamber 3a is discharged from the liquid discharge port 8 with the pressure generated at that time.

  The piezoelectric actuator 1 in which a plurality of such piezoelectric displacement elements 7 are provided on the surface of the diaphragm 2 controls each piezoelectric displacement element 7 independently and causes vibration in a minute region. It has a structure suitable for a print head that discharges ink to a specific fine region.

  However, heat is generated with the displacement of the piezoelectric displacement element 7 and the temperature of the piezoelectric ceramic layer 4 rises. The piezoelectric ceramic layer 4 has been subjected to polarization treatment in advance, but depolarization progresses as the temperature rises, and the displacement characteristics gradually deteriorate. Therefore, it is important to dissipate this heat.

  According to the present invention, it is important to include a cooling device for cooling the piezoelectric displacement element 7 in order to scatter heat generated in the piezoelectric displacement element 7. As a result, the influence of heat generated in the piezoelectric actuator 1 can be removed, and depolarization of the piezoelectric ceramic layer can be suppressed. Therefore, it is possible to realize a vibration generator that is hardly depolarized and has excellent durability.

  It is also important to use a thermoelectric conversion element composed of a Peltier element for the cooling device. In the thermoelectric conversion element, one end face has a low temperature and the other end face has a high temperature, so that the piezoelectric displacement element 7 can be efficiently cooled by abutting the low temperature face on the piezoelectric actuator 1 and the thermoelectric conversion is performed. When the element is used, cooling can be performed without hindering the downsizing of the vibration generator.

  As a cooling means, a thermoelectric conversion element may be directly mounted on the piezoelectric actuator 1, but it is preferable to use it as a thermoelectric module in which a plurality of thermoelectric conversion elements are sandwiched between a pair of substrates. By using it as a thermoelectric module, it is possible to increase the cooling efficiency, easily mount it, and increase the cooling efficiency.

  FIG. 2 illustrates the thermoelectric conversion module 9b shown in FIG. 1B in detail. As shown in FIG. 2, the thermoelectric conversion module 9b includes an N-type P-type Peltier element 103a and a P-type Peltier element 103b on the lower substrate 101 so that wiring is simplified and suitable for miniaturization. The N-type and the P-type are alternately placed and arranged so as to be electrically in series. These Peltier elements 103 are sandwiched between the lower substrate 101 and the upper substrate 102.

  It is desirable to arrange the Peltier elements 103 in series as described above, since the current flowing through the Peltier elements 103 is small and self-heating due to Joule heat is small. If the Peltier device 103 itself generates a large amount of heat, the device may be complicated to remove it.

  Wiring conductors 104 and 105 are provided on the surface of the lower substrate 101 and the surface of the upper substrate 102 to electrically connect the Peltier elements 103. Then, power is supplied to the N-type 103a and P-type 103b Peltier elements 103 from the outside via the connection terminals 107, and one substrate (lower substrate 01) is cooled to form a cooling surface, while the other substrate is formed. (The upper substrate (102) generates heat to form a heat generating surface.

  In FIG. 2, only a part of the upper substrate 102 is displayed to show the internal structure. Moreover, although FIG. 2 showed the long-shaped thermoelectric module, it cannot be overemphasized that the shape is not restricted to a long shape, and can be made into desired shapes, such as a square, a rectangle, a polygon, and a circle. Furthermore, as a ring shape, it can be arranged on the outer periphery of the displacement element, handling at the time of connection is easy, and cooling efficiency can be further increased.

  In particular, it is preferable to place a thermoelectric conversion element adjacent to the piezoelectric displacement element 7 that generates heat, and to arrange them on the same surface. That is, the more the thermoelectric conversion element 10 is provided near the piezoelectric displacement element 7, the easier it is to keep the piezoelectric displacement element 7 at a low temperature and the depolarization can be reliably suppressed.

  Specifically, as shown in FIG. 1, it is preferable to provide the thermoelectric conversion element 9 adjacent to the piezoelectric displacement element 7 on the surface of the piezoelectric actuator 1. Moreover, as shown in FIG. 3, it can also be provided on the same plane so as to be adjacent to the piezoelectric actuator 11 on the surface of the flow path member 13 having the liquid pressurizing chamber 13a and the partition wall 13b. At this time, it goes without saying that the cooling surface 19a is joined so as to be in contact with the flow path member 13, and the high temperature surface 19b is arranged so as to be in contact with the atmosphere.

  Thus, even if the thermoelectric conversion element 19 is provided on the surface of the flow path member 13, the same effect as that obtained when the piezoelectric displacement element 17 is adjacent to the piezoelectric actuator 11 can be expected.

  However, it is necessary to provide the cooling surface 19 a of the thermoelectric conversion element 19 so as to contact the flow path member 13, and it is not preferable to contact the heat generation surface 19 b with the flow path member 13. For example, when the thermoelectric conversion element 19 is disposed between the piezoelectric actuator 11 and the flow path member 13, cooling and heat generation occur inside the print head. However, since the heat generation amount is larger than the cooling amount as a whole, The applied thermal stress is increased and cracks are likely to occur, and when the temperature of the flow path member 13 becomes high, the viscosity of the liquid such as ink changes, and the discharge state of the liquid may change and the image quality may deteriorate. Such an arrangement should be avoided.

  In the vibration generator of the present invention, as shown in FIGS. 1A and 1B, the thermoelectric conversion modules 9a and 9b, which are cooling devices, are directly attached to the surface of the piezoelectric ceramic layer 4, that is, the surface of the piezoelectric actuator 1. You can also. In this way, the cooling efficiency can be further increased by direct cooling.

  Further, like the thermoelectric conversion module 9 b, it is preferable that the shape thereof is a long shape and is provided in a wide area along the peripheral portion of the piezoelectric actuator 1. Thus, cooling efficiency can be improved by occupying a large area.

  In the above configuration, since the thermoelectric conversion module is formed on the same surface as the surface on which the piezoelectric displacement element 7 is provided, the cooling efficiency is high, the temperature of the piezoelectric actuator 1 can be kept low, and the piezoelectric piezoelectric element is polarized. Depolarization of the ceramic layer can be suppressed, and deterioration of the displacement characteristics of the piezoelectric displacement element can be prevented. In addition, the power supplied to the thermoelectric conversion element can be reduced.

  The thermoelectric conversion module 9 is bonded so as to be in contact with the piezoelectric actuator 1, and is particularly preferably provided at the edge of the surface of the piezoelectric actuator 1. Since the thermoelectric conversion module directly cools the piezoelectric actuator, efficient cooling can be performed. Further, by providing the edge portion, even if the piezoelectric displacement elements are formed with high density, the apparatus can be downsized without obstructing the discharge of the liquid.

  The thermoelectric conversion element may be constantly energized to continue cooling the piezoelectric displacement element, but it detects the temperature of the piezoelectric displacement element or its vicinity and energizes the thermoelectric conversion element when the temperature exceeds a specific temperature. The piezoelectric displacement element may be cooled. Thus, when the means for detecting the temperature of the piezoelectric displacement element is provided, power consumption can be suppressed while preventing depolarization.

  As a temperature detecting means, a thermocouple may be attached to the piezoelectric displacement element 7 or the vicinity thereof, or the capacitance is detected inside the piezoelectric actuator, and the temperature is detected using the temperature dependence of the capacitance. Good, and other methods may be used.

Further, in order to efficiently transfer heat from the piezoelectric actuator to the thermoelectric conversion module, the thermoelectric conversion module is preferably joined to the piezoelectric actuator with a high heat conductive adhesive or a high heat conductive brazing material. Specifically, it is desirable to contain conductive metal powder such as Ag and a glass component and melt at about 400 to 600 ° C. For example, 70 to 98% by mass of Ag powder and ₂ to 30% by mass of a glass component composed of PbO—SiO ₂ —B ₂ O ₃ can be formed. Alternatively, the bonding can be performed through a thin adhesive layer made of an epoxy resin, a polyamide resin, a polyimide resin, a silicon resin, particularly a silicon resin having high thermal conductivity.

  According to the present invention, the thickness of the actuator 1 indicates the thickness from the surface individual electrode 6 to the diaphragm 2 (including the surface individual electrode 6 and the diaphragm 2), and is preferably 100 μm or less. By using such a thin layer, a large displacement can be obtained, and high-efficiency driving can be realized with a low driving voltage. Therefore, particularly in response to the demand for higher speed and higher accuracy accompanying the recent improvement in the performance of color printers, the present invention can meet the demand by setting the thickness to 100 μm or less. It can contribute to the improvement of the performance of the print head using it.

  In order to further enhance the characteristics as the actuator 1, the upper limit value of the thickness of the piezoelectric actuator 1 is particularly preferably 80 μm or less, more preferably 65 μm or less, and more preferably 50 μm or less. In addition, the lower limit value of the thickness of the piezoelectric actuator 1 is preferably 30 μm, more preferably 40 μm in order to have sufficient mechanical strength and prevent breakage during handling and operation.

  As the thermoelectric conversion module, as shown in FIGS. 1A and 1B, a small thermoelectric conversion module 9a may be provided at a specific location on the surface of the piezoelectric actuator 1, but the outer periphery, that is, the outside of the piezoelectric displacement element. In addition, it is preferable to use a long thermoelectric module 9b in which Peltier elements are arranged along the side. And as shown in FIG.4 (b), it is still more preferable to provide a thermoelectric conversion module in 2 sides which oppose. With such a configuration, heat removal can be performed efficiently.

  Further, as shown in FIGS. 4A and 4B, thermoelectric conversion modules 29 a and 29 b using Peltier elements are replaced with a piezoelectric displacement element 27 including a common electrode 25, a piezoelectric ceramic layer 24, and a surface individual electrode 26. It is preferable to arrange | position along the outer periphery of the piezoelectric actuator 21 surface outside. Moreover, the heat generated from the thermoelectric conversion module 29 can be more efficiently removed by attaching the heat radiating plate 30 so as to integrate these thermoelectric conversion modules 29a and 29b.

  According to FIG. 4B, the thermoelectric conversion module 29 includes a ring-shaped heat dissipation plate 30, and is arranged on the outer periphery of the surface individual electrode 26 forming the displacement element 27, so that handling at the time of connection is easy. Even if the displacement region 27a is displaced and heat is generated, more efficient cooling can be performed.

  Since the heat generated by the piezoelectric displacement element 27 is efficiently removed by the thermoelectric conversion module 29, a heat transport layer (not shown) for moving the heat from a central part to an end part in a part of the piezoelectric actuator 21. Is preferably provided.

For example, a member having high thermal conductivity can be provided in at least a part of the diaphragm, and in particular, ceramics such as AlN, SiC, Si ₃ N ₄ having high thermal conductivity as a high thermal conductive layer, copper, It is preferably made of a metal or alloy containing silver and having a thickness of 3 μm or more, particularly 5 μm or more, and more preferably 10 μm or more.

  Further, as shown in FIG. 5, in order to increase the amount of displacement, a piezoelectric displacement element 37 composed of a plurality of piezoelectric ceramic layers 34 a-i sandwiched between a plurality of electrodes 35 a-e and 36 a-e is provided. Even when the piezoelectric actuator 31 is provided on the flow path member 33 including the liquid pressurizing chamber 33a and the partition wall 33b and the displacement region 37a vibrates, the thermoelectric conversion module 40 using a Peltier element as a cooling device. Is provided on the surface of the piezoelectric actuator 31 so as to be adjacent to the piezoelectric displacement element 37, a similar effect can be expected.

  According to the present invention, the upper support substrate and the lower support substrate have a structure for sandwiching a plurality of Peltier elements, the upper support substrate generates heat, and the lower support substrate is cooled. The piezoelectric actuator can be directly cooled by bonding so as to contact the surface of the actuator. Therefore, since the piezoelectric actuator can be sufficiently cooled and maintained at a low temperature, depolarization of the piezoelectric actuator can be prevented. In addition, a highly reliable piezoelectric actuator can be realized without causing a major obstacle to miniaturization of the piezoelectric actuator.

  A liquid discharge apparatus according to the present invention includes the above-described pressure generation device provided in a flow path member including a liquid supply port, a liquid pressurization chamber, and a liquid discharge port. An ink jet printer, a printing apparatus, It can be suitably used for a printing machine. Further, it can also be suitably used as a liquid pump that transports, conveys, and ejects a small amount of liquid.

The structure of the vibration generator of this invention is shown, (a) is a schematic sectional drawing, (b) is a top view. It is a perspective view which shows the structure of the thermoelectric module used for the vibration generator of this invention. It is a schematic sectional drawing which shows the other structure of the vibration generator of this invention. FIG. 4 shows still another structure of the vibration generator of the present invention, in which (a) is a schematic sectional view and (b) is a plan view. It is a schematic sectional drawing which shows other structure of the vibration generator of this invention.

Explanation of symbols

1, 11, 21, 31... Piezoelectric actuators 2, 12, 22, 32... Diaphragms 3, 13, 23, 33 ... Flow path members 3 a, 13 a, 23 a, 33 a. Chambers 3b, 13b, 23b, 33b ... partition walls 4, 14, 24, 34a-i ... piezoelectric ceramic layers 5, 15, 25 ... common electrodes 6, 16, 26 ... surface individual electrodes 7, 17, 27, 37... Piezoelectric displacement elements 7a, 17a, 27a, 37a ... Displacement regions 8, 18, 28, 38 ... Liquid discharge ports 9, 19, 29, 39 ... Thermoelectric conversion module 9a 9b, 19a, 19b, 29a, 29b, thermoelectric conversion module

Claims (12)

A vibration generator using a piezoelectric displacement element, comprising a cooling means using a thermoelectric conversion element for cooling the piezoelectric displacement element. The vibration generating apparatus according to claim 1, wherein the thermoelectric conversion element is provided adjacent to the piezoelectric displacement element. The vibration generator according to claim 1, wherein the thermoelectric conversion element is provided on the same surface as the piezoelectric displacement element. The vibration generator according to claim 1, wherein the cooling device includes a heat sink. The thermoelectric conversion element is bonded to the piezoelectric displacement element via an adhesive layer, and the adhesive layer is a high thermal conductive adhesive or a high thermal conductive brazing material. A vibration generator according to claim 1. The vibration generating apparatus according to claim 1, wherein the piezoelectric displacement element is a laminated body of an internal electrode and a piezoelectric ceramic layer. The piezoelectric displacement element is composed of a surface individual electrode, an internal electrode, and a piezoelectric ceramic layer sandwiched between the internal electrode and the surface individual electrode, and the piezoelectric displacement element is provided on a diaphragm. The vibration generator according to any one of claims 1 to 6. The vibration generator according to claim 6 or 7, wherein the internal electrode of the piezoelectric displacement element and one electrode of the thermoelectric conversion element have the same potential. The vibration generating apparatus according to claim 1, wherein the piezoelectric displacement element has a plurality of displacement regions. The vibration generating apparatus according to claim 1, wherein the piezoelectric displacement element has a plurality of displacement regions on the same plane. The vibration generator according to any one of claims 6 to 9, further comprising means for detecting a temperature of the piezoelectric displacement element. A liquid characterized in that the vibration generator according to any one of claims 1 to 11 is provided on a surface of a flow path member having a liquid supply port, a liquid pressurizing chamber, and a liquid discharge port. Discharge device.

Images