JP2018033235A - Piezoelectric actuator - Google Patents

Abstract

A piezoelectric actuator that suppresses the development of cracks at the interface between a welded portion and a base material and stably obtains a desired amount of displacement for a long period of time. SOLUTION: A piezoelectric actuator includes a piezoelectric element, and a case having a cylindrical body 21 and a lid body 22, which accommodates the piezoelectric element so as to sandwich the piezoelectric element from above and below. 22 is inserted, and the cylindrical body 21 and the lid body 22 are joined by the welding part 3, and a part of the welding part 3 enters from the side surface of the lid body 22 toward the inside of the lid body 22, and the welding is performed. When the boundary between the portion 3 and the lid body 22 is viewed in a vertical cross section, there is a corner portion 5 provided so as to enter the welded portion 3 at the boundary. [Selection drawing] Fig. 4

Description

  The present disclosure relates to a piezoelectric actuator used in a mass flow controller, an XY table precision positioning device, and the like.

  There is known a piezoelectric actuator including a piezoelectric element and a case having a cylindrical body and a lid that are housed inside so as to sandwich the piezoelectric element from above and below (see, for example, Patent Documents 1 and 2). This piezoelectric actuator is manufactured, for example, by joining the inner surface near the upper end of the cylindrical body to the side surface of the lid body by laser welding or resistance welding in a state where a compressive load is applied to the piezoelectric element.

JP 2010-258025 A JP 2010-192832 A

  In a piezoelectric actuator sealed with a metal case, tensile stress is repeatedly applied to the weld due to displacement during driving. Here, since the strength of the interface between the welded portion and the base material of the lid is weaker than that of the base material itself, cracks may develop along this interface. When this crack progresses, the load applied to the piezoelectric element becomes per one piece, and furthermore, the applied load may decrease and the displacement amount may decrease.

  The present disclosure has been made in view of the above circumstances, and provides a piezoelectric actuator that can suppress the progress of cracks at the interface between a weld and a base material and can stably obtain a desired displacement for a long period of time. With the goal.

  A piezoelectric actuator of the present disclosure includes a piezoelectric element and a case having a cylinder and a lid that are housed inside so as to sandwich the piezoelectric element from above and below, and the lid from the one end side opening of the cylinder. Inserted, and the tubular body and the lid body are joined by a welded portion, and a part of the welded portion enters from the side surface of the lid body toward the inside of the lid body, When the boundary with the lid body is viewed in a cross section cut in the vertical direction, the boundary has corners provided so as to enter the welded portion.

  According to the piezoelectric actuator of the present disclosure, it is possible to suppress the extension of cracks generated at the interface between the welded portion and the lid (base material), to prevent a decrease in the displacement amount, and to achieve a desired displacement amount. Can be obtained stably over a long period of time.

It is a schematic perspective view which shows an example of a piezoelectric actuator. It is a schematic sectional drawing of the piezoelectric actuator cut | disconnected by the AA line shown in FIG. FIG. 3 is a schematic perspective view of the piezoelectric element shown in FIG. 2. It is an enlarged view of an example of the area | region B shown in FIG. It is a principal part expanded sectional view of the other example of a piezoelectric actuator. It is a principal part expanded sectional view of the other example of a piezoelectric actuator. It is a principal part expanded sectional view of the other example of a piezoelectric actuator. It is a principal part expanded sectional view of the other example of a piezoelectric actuator. It is a principal part expanded sectional view of the other example of a piezoelectric actuator.

  Hereinafter, an example of the piezoelectric actuator of the present embodiment will be described with reference to the drawings.

  1 is a schematic perspective view showing an example of the piezoelectric actuator 10, FIG. 2 is a schematic sectional view of the piezoelectric actuator cut along the line AA shown in FIG. 1, and FIG. 3 is a schematic perspective view of the piezoelectric element shown in FIG. 4 is an enlarged view of an example of the region B shown in FIG.

  The piezoelectric actuator 10 shown in FIGS. 1 to 4 includes a piezoelectric element 1 and a case 2 having a cylinder body 21 and a lid body 22 accommodated inside the piezoelectric element 1 so as to sandwich the piezoelectric element 1 from above and below. The lid body 22 is inserted from the one end side opening, and the cylindrical body 21 and the lid body 22 are joined by the welded portion 3. Specifically, the side surface of the lid body 22 and the inner surface of the upper end portion of the cylindrical body 21 are joined by welding. And when a part of welding part 3 has entered toward the inside of lid body 22 from the side of lid body 22, when it sees in the section which cut the boundary of welding part 3 and lid body 22 in the up-and-down direction, At the boundary, there is a corner portion 5 provided so as to enter the welded portion 3. In other words, the boundary line between the welded portion 3 and the lid body 22 has a convex corner 5 on the welded portion 3 side.

  As shown in FIG. 3, the piezoelectric element 1 constituting the piezoelectric actuator 10 is laminated at, for example, an active part in which a plurality of piezoelectric layers 11 and internal electrode layers 12 are alternately laminated, and both ends of the active part in the lamination direction. The multilayer piezoelectric element includes a multilayer body 13 having an inactive portion made of the piezoelectric layer 11. Here, the active part is a part where the piezoelectric layer expands or contracts in the stacking direction during driving, and the inactive part is a part where the piezoelectric layer 11 does not extend or contract in the stacking direction during driving.

  The laminated body 13 constituting the piezoelectric element 1 is formed in a rectangular parallelepiped shape having a length of 4 to 7 mm, a width of 4 to 7 mm, and a height of about 20 to 50 mm, for example. In addition, although the laminated body 13 shown in FIG. 3 is a quadrangular prism shape, a hexagonal prism shape, an octagonal prism shape, etc. may be sufficient, for example.

The piezoelectric layer 11 constituting the multilayer body 13 is made of piezoelectric ceramics having piezoelectric characteristics, and the piezoelectric ceramics has an average particle diameter of, for example, 1.6 to 2.8 μm. As the piezoelectric ceramic, for example, a perovskite oxide made of lead zirconate titanate (PbZrO ₃ —PbTiO ₃ ), lithium niobate (LiNbO ₃ ), lithium tantalate (LiTaO ₃ ), or the like can be used.

  Moreover, the internal electrode layer 12 which comprises the laminated body 13 has metals, such as silver, silver-palladium, silver-platinum, copper, as a main component, for example. For example, positive electrodes and negative electrodes are alternately arranged in the stacking direction. The positive electrode is drawn out on one side surface of the laminate 13 and the negative electrode is drawn out on the other side surface. With this configuration, a drive voltage can be applied to the piezoelectric layer 11 sandwiched between the internal electrode layers 12 adjacent in the stacking direction in the active portion.

  The laminate 13 may include a metal layer that is a layer for relaxing stress and does not function as an internal electrode layer.

  External electrodes 14 are provided on a pair of opposing side surfaces of the laminate 13 from which the positive electrode or negative electrode of the internal electrode layer 12 is drawn, and are electrically connected to the drawn internal electrode layer 12. The external electrode 14 is a metallized layer made of a sintered body of silver and glass, for example.

On the other hand, the positive electrode and the negative electrode of the internal electrode layer 12 are exposed on the other pair of opposite side surfaces of the laminate 13, and a coating layer 15 made of an insulator is provided on this side surface if necessary. . By providing the covering layer 15, it is possible to prevent creeping discharge between both electrodes that occurs when a high voltage is applied during driving. Examples of the insulator to be the covering layer 15 include a ceramic material. In particular, the insulating layer 15 can follow the driving deformation (expansion / contraction) of the laminated body 13 when the piezoelectric actuator 10 is driven, and the covering layer 15 is peeled off to cause creeping discharge. A material that can be deformed by stress can be used without fear. Specifically, stress occurs when locally phase transformation to volume change to deformable partially stabilized _{zirconia, Ln 1-X Si X AlO} 3 + 0.5X (Ln is, Sn, Y, La, Ce, A ceramic material such as Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb, at least one selected from x = 0.01 to 0.3), Alternatively, piezoelectric materials such as barium titanate and lead zirconate titanate, in which the distance between ions in the crystal lattice changes so as to relieve the generated stress, can be mentioned. The covering layer 15 is formed, for example, by forming it into an ink form, applying it to the side surface of the laminate 13 by dipping or screen printing, and sintering.

  The piezoelectric actuator 10 also includes a case 2 that accommodates the piezoelectric element 1 so as to sandwich the piezoelectric element 1 from above and below. The case 2 has a cylindrical body 21 and a lid body 22. More specifically, it includes a base body 23, a cylinder body 21 having a lower end portion joined to the upper surface of the base body 23, and a lid body 22 joined to the upper end portion of the cylinder body 21. The lower end surface of the piezoelectric element 1 is in contact with the upper surface of the base body 23, and the upper end surface of the piezoelectric element 1 is in contact with the lower surface of the lid body 22.

  The base | substrate 23, the cylinder 21, and the cover body 22 consist of metals, such as SUS304 and SUS316L, for example.

  The cylindrical body 21 has a cylindrical portion extending vertically and a flange portion connected to the lower end of the cylindrical portion. The cylindrical body 21 is formed, for example, in a bellows shape by making a seamless tube with a predetermined shape and then rolling or hydrostatic pressing. The cylinder 21 has a predetermined spring constant so that the expansion and contraction of the piezoelectric element 1 (laminated body 13) can be followed, and the spring constant is adjusted by the thickness, groove shape, and number of grooves. For example, the thickness of the cylinder 21 is 0.1 to 0.5 mm, for example. The cylindrical portion extending vertically from the cylindrical body 21 to the one end side opening (upper end side opening) is cylindrical, but the other end side opening (lower end side opening) of the cylindrical body 21 extends radially outward. It is a so-called trumpet shape. Thus, since the other end side opening of the cylinder 21 is a trumpet shape, the cylinder 21 has a structure having a flange portion. The cylinder 21 may have an inclined portion that is inclined inward from the outer surface near the upper end to the upper end.

  Further, the lid body 22 is formed to have the same outer diameter as the inner diameter of the opening on the one end side of the cylindrical body 21. The lid body 22 is fitted from one end side opening of the cylinder body 21, and its side surface (outer periphery) is joined by welding to the inner wall near the one end side opening of the cylinder body 21 (near the upper end). At this time, a part of the welded portion 3 formed by welding the cylindrical body 21 and the lid body 22 enters from the side surface of the lid body 22 toward the inside of the lid body 22. In addition, the welding part 3 here is the site | part which the lid body 22 and the cylinder 21 reacted by welding. Here, a part of the welded portion 3 shown in FIG. 4 is different from the lid body 22 (base material), and a part of the welded portion 3 and the lid body 22 (base material) are distinguished. Moreover, although the site | part which the cover body 22 and the cylinder 21 reacted by welding has also entered the inside of the cylinder 21, only the part which entered the inside of the lid 22 is welded part 3 in FIG. As part of

  Moreover, the base | substrate 23 is a disk-shaped thing, and the peripheral part is thinner than another site | part in the example shown to a figure. And the peripheral part of the base | substrate 23 and the collar part of the cylinder 21 are joined by welding, for example so that a compressive load may be applied to the piezoelectric element 1. FIG.

  Note that two through holes into which the lead pins 43 can be inserted are formed in the base 23, and the lead pins 43 are inserted through the through holes. And the clearance gap of a through-hole is filled with the soft glass 44, for example, and the lead pin 43 is being fixed. A lead wire 41 is connected to the tip of the lead pin 43, and the lead wire 41 is attached to the external electrode 14 with solder 42, and the drive voltage is applied to the piezoelectric element 1 via the lead pin 43 and the lead wire 41. Is applied.

  As shown in FIG. 4, a part of the welded portion 3 enters from the side surface of the lid body 22 toward the inside of the lid body 22, and moves up and down the boundary between the welded portion 3 and the lid body 22 (base material). When viewed in a cross section cut in the direction, there is a corner portion 5 provided at the boundary so as to enter the welded portion 3. In other words, a part of the welded portion 3 that enters from the side surface of the lid body 22 toward the inside of the lid body 22 has a shape having at least two peaks (projections) or a shape having a step. Here, when a part of the welded portion 3 has a shape having two peaks (protrusions), the valley portion between the peaks (projections) and the peaks (projections) is the corners 5. Become. Further, when a part of the welded portion 3 has a stepped shape, the stepped portion becomes the corner portion 5. In addition, angle (theta) 1 of the corner | angular part 5 shown in FIG. 4 is an obtuse angle.

  According to such a configuration, even if a crack occurs along the boundary between the welded portion 3 and the lid body 22 (base material), the progress direction of the crack abruptly changes at the corner portion 5, which is a large resistance. It is possible to stop the progress of cracks. That is, the progress of cracks generated at the interface between the welded portion 3 and the lid 22 (base material) can be suppressed. Therefore, it is possible to prevent a decrease in the amount of displacement accompanying the progress of cracks, and a desired amount of displacement can be obtained stably over a long period of time.

  Further, as shown in FIG. 5, when the boundary between the welded portion 3 and the lid body 22 (base material) is viewed in a cross-section cut in the vertical direction, the welded portion 3 is arranged in an upper stage and the lid body 22 There are a first convex portion 31 that enters the inside of the lid body 22 from the side surface, and a second convex portion 32 that is arranged in the lower stage and enters the inside of the lid body 22 from the side surface of the lid body 22. 5 may be configured to be provided at an acute angle between the first convex portion 31 and the second convex portion 32. In the configuration shown in FIG. 4, the angle θ1 of the corner portion 5 is an obtuse angle, whereas in the configuration shown in FIG. 5, the angle θ1 of the corner portion 5 is an acute angle. According to such a configuration, since the change in the crack propagation direction at the corner portion 5 is large, this becomes a larger resistance and can further prevent the crack from progressing. Accordingly, it is possible to further prevent a decrease in the amount of displacement accompanying the progress of the crack. In addition, as angle (theta) 1 when the corner | angular part 5 is an acute angle, it sets to 20 to 85 degree | times, for example.

  Further, as shown in FIG. 6, the second convex portion 32 rather than the first convex portion 31 when the boundary between the welded portion 3 and the lid body 22 (base material) is viewed in a cross section cut in the vertical direction. It is also possible to adopt a configuration in which is deeper. In other words, the depth D2 from the side surface of the lid 22 of the second convex portion 32 is greater than the depth D1 from the side surface of the lid 22 of the first convex portion 31 (D1 <D2).

  If cracks occur at the boundary between the welded portion 3 and the lid 22 (base material), stress is applied to the boundary between the first convex portion 31 and the lid 22 (base material) located on the upper side of the welded portion 3. Since it is easy to add, it is anticipated that a crack will occur at the boundary between the first convex portion 31 and the lid 22 (base material). At this time, it is expected that a stress that moves the cylinder 21 in the upper right direction in FIG. 6 (stress that peels off the cylinder 21) is generated. On the other hand, by setting it as said structure, the 2nd convex part 32 gets caught and it can suppress a crack progress while reducing stress. Therefore, it is possible to more reliably prevent a decrease in the displacement amount accompanying the progress of the crack. The depth D2 of the deepest penetration position of the second convex portion 32 is, for example, 1.1 to 3.0 times the depth D1 of the deepest penetration depth of the first convex portion 31. Is set.

  Further, as shown in FIG. 7, when the boundary between the welded portion 3 and the lid body 22 (base material) is viewed in a cross section cut in the vertical direction, the second convex portion 32 rather than the first convex portion 31. It is possible to have a wider configuration. In other words, the width W2 of the second protrusion 32 is larger than the width W1 of the first protrusion 31 (W1 <W2). According to this configuration, a crack is generated at the boundary between the first convex portion 31 and the lid body 22 (base material), and the crack extends beyond the corner portion 5 to form the second convex portion 32 and the lid body 22 (base material). Even if there is a case where the material extends to the boundary with the material, since the distance between the second convex portion 32 and the lid 22 (the base material) is long, the propulsive force that the crack progresses is weakened. be able to. Accordingly, it is possible to further suppress the decrease in the displacement amount accompanying the progress of the crack. Note that the width W2 of the second protrusion 32 is set to a width 1.1 to 3.0 times the width W1 of the first protrusion 31, for example.

  Further, as shown in FIG. 8, the second convex portion 32 is more than the first convex portion 31 when the boundary between the welded portion 3 and the lid 22 (base material) is viewed in a cross section cut in the vertical direction. It is also possible to have a configuration in which the second protrusion 32 is wider than the first protrusion 31. In other words, the depth D2 from the side surface of the lid body 22 of the second convex portion 32 is larger than the depth D1 from the side surface of the lid body 22 of the first convex portion 31 (D1 <D2). The width W2 of the second protrusion 32 is larger than the width W1 of the first protrusion 31 (W1 <W2). As a result, it is possible to more reliably prevent the displacement from being reduced as the crack progresses.

  Further, as shown in FIG. 9, the surface of the second convex portion 32 and the side surface of the lid body 22 when the boundary between the welded portion 3 and the lid body 22 (base material) is cut in a vertical direction. It is also possible to adopt a configuration in which the angle θ2 at which the angle intersects is an acute angle. In other words, the angle θ2 formed by the boundary line of the second convex portion 32 and the lid body 22 and the side surface of the lid body 22 is an acute angle. According to this configuration, since the angle θ2 is an acute angle, the lower portion of the second convex portion 32 has a shape that swells downward, and with respect to the stress that peels the cylindrical body 21 from the side surface of the lid body 22, It gets caught and suppresses peeling. Note that the angle θ2 when the angle between the boundary line of the second protrusion 32 and the lid body 22 and the side surface of the lid body 22 is an acute angle is, for example, 40 degrees to 85 degrees.

  In the example shown in FIG. 9, there is a gap between the lid body 22 and the cylinder body 21 below the welded portion 3, and the boundary line between the second convex portion 32 and the lid body 22 is the lid body 22. The angle θ3 formed between the extended line extending from the boundary line and the inner surface of the cylindrical body 21 is an acute angle. According to this configuration, the lower side of the welded portion 3 is easily deformed, and the load concentrated on the upper side of the welded portion 3 is distributed to the lower side. Therefore, the occurrence of cracks itself is suppressed, and a decrease in displacement due to this can be eliminated.

  Next, a method for manufacturing the piezoelectric actuator according to the present embodiment will be described.

First, a ceramic green sheet to be the piezoelectric layer 11 is produced. Specifically, a ceramic slurry is prepared by mixing a calcined powder of piezoelectric ceramic, a binder made of an organic polymer such as acrylic or butyral, and a plasticizer. And a ceramic green sheet is produced from this ceramic slurry by using tape forming methods, such as a well-known doctor blade method and a calender roll method. As the piezoelectric ceramic, any material having piezoelectric characteristics may be used. For example, a perovskite oxide made of PbZrO ₃ —PbTiO ₃ may be used. As the plasticizer, dibutyl phthalate (DBP), dioctyl phthalate (DOP), or the like can be used.

Next, a conductive paste to be the internal electrode layer 12 is produced. Specifically, a conductive paste is prepared by adding and mixing a binder and a plasticizer to a silver-palladium alloy metal powder. This conductive paste is printed on the ceramic green sheet using a screen printing method, and then a plurality of ceramic green sheets on which the conductive paste is printed are stacked, and the conductive paste is formed at both ends in the stacking direction. A multilayer molded body is obtained by laminating a plurality of ceramic green sheets that are not printed. After debinding the laminated molded body at a predetermined temperature, the laminated body 13 is obtained by firing at 900 to 1200 ° C.

  Next, an oxide ink is printed by screen printing on a pair of side surfaces from which both internal electrode layers (positive electrode and negative electrode) are led out of the side surfaces of the laminate 13, and then fired at 900 to 1200 ° C. 15 is formed. The oxide ink disperses the powder of the oxide in a solution of a solvent, a dispersant, a plasticizer, and a binder, and then pulverizes the powder by passing three rolls several times. It is produced by dispersing powder.

  Next, the external electrode 14 made of a metallized layer is formed. First, a silver glass-containing conductive paste is prepared by adding a binder to silver particles and glass powder, and printing is performed by a screen printing method on a pair of opposing side surfaces of the laminate from which the positive electrode or negative electrode of the internal electrode layer 12 is derived, Baking is performed at a temperature of about 500 to 800 ° C. Thus, the external electrode 14 made of a metallized layer is formed to complete the piezoelectric element 1.

  Next, the external electrode 14 and the lead wire 41 are soldered. Further, a base body 23 (lower lid) having a shape as shown in FIG. 2 formed by forming a through hole by drilling is prepared, and lead pins 43 are inserted into the two through holes formed in the base body 23, respectively. At the same time, soft glass 44 is filled and fixed in the gap, and the lower end of the piezoelectric element 1 is bonded to the upper surface of the base 23 with an adhesive. Then, the lead wire 41 soldered to the external electrode 14 of the piezoelectric element 1 with the solder 42 and the lead pin 43 attached to the base 23 are connected by solder.

  Next, a bellows shape is formed on the seamless cylindrical cylinder 21 made of, for example, SUS304 by rolling. Here, one end side (upper end side) of the cylindrical body 21 is opened, and a flange portion is formed on the other end side (lower end side). Moreover, the thickness of a groove part and a curvature radius can be changed by changing a metal mold | die shape at the time of a rolling process.

  A lid 22 made of SUS304 is fitted into the opening so as to close the opening on one end side (upper end side) of the cylindrical body 21, and is welded by, for example, laser welding.

  At this time, in order to provide the corner portion 5 having the angle θ1 as shown in FIG. 4, laser irradiation is performed twice as a condition of laser welding of the cylindrical body 21 and the lid body 22. For example, welding is performed by making the second laser output smaller than the first laser output, or slightly shifting the second laser irradiation position from the first laser irradiation position.

  Here, in order to configure the corner portion 5 as shown in FIG. 5 such that the angle θ1 is provided between the first convex portion 31 and the second convex portion 32 at an acute angle, the cylindrical body 21 and the lid As a condition of laser welding with the body 22, two laser irradiations with different outputs are performed. At this time, the focus of the laser was narrowed down, and control was performed so that the fusion depth at the laser center position became the deepest so that the center output of the focus became more than twice the intensity at the outer peripheral position of the irradiation area. Above, welding is performed by setting the distance between the second laser focus center position and the first laser focus center position to be larger than the irradiation radius of any laser.

  In order to make the depth D2 of the second convex portion 32 larger than the depth D1 of the first convex portion 31 as shown in FIG. 6, laser welding of the cylindrical body 21 and the lid 22 is performed. As a condition, laser irradiation is performed twice with different outputs. At this time, welding is performed by making the intensity of the laser focus center position forming the second protrusion 32 larger than the intensity of the laser focus center position forming the first protrusion 31.

  In order to make the width W2 of the second convex portion 32 larger than the width W1 of the first convex portion 31 as shown in FIG. As a result, two laser irradiations with different outputs are performed. At this time, welding is performed by increasing the intensity of the laser focal center position forming the second convex portion 32 to be greater than the intensity of the laser focal center position forming the first convex portion 31 and increasing the laser irradiation radius. I do.

  Further, in order to make the angle θ2 formed between the boundary line of the second convex portion 32 and the lid body 22 and the side surface of the lid body 22 as shown in FIG. As laser welding conditions, two laser irradiations with different outputs are performed. At this time, the intensity of the laser focal center position forming the second convex part 32 is made larger than the intensity of the laser focal center position forming the first convex part 31, and the laser forming the second convex part 32 The center of the laser is irradiated so that the irradiation direction of the laser beam is obliquely upward to obliquely downward, the laser focus is narrowed down, and the center output of the focus is more than twice the intensity at the outer peripheral position of the irradiation area. Welding is performed after controlling the melt depth at the position to be the deepest.

  The lid 22 is heated by the laser irradiation. If the temperature of the lid 22 before the laser irradiation is high, the melting depth becomes deep. If the temperature of the lid 22 before the irradiation is different, the lid 22 melts. Since there is a problem that the depth is non-uniform, it is not necessary to continuously perform the laser irradiation for forming the first convex portion 31 and the laser irradiation for forming the second convex portion 32. It is important to perform the next irradiation after cooling to the temperature.

  Next, the cylindrical body 21 and the lid body 22 are put on the piezoelectric element 1 bonded to the base 23, the cylindrical body 21 is pulled with a predetermined load, and a load is applied to the piezoelectric element 1. In this state, the flange portion of the cylindrical body 21 and the base body 23 are welded by, for example, resistance welding.

  Finally, the piezoelectric actuator 10 of this embodiment is completed by applying a direct current electric field of 0.1 to 3 kV / mm to the lead pins 43 attached to the base 23 to polarize the laminated body 13. Then, by connecting the lead pin 43 and an external power source and applying a voltage to the piezoelectric layer 11, each piezoelectric layer 11 can be largely displaced by the inverse piezoelectric effect.

DESCRIPTION OF SYMBOLS 10 ... Piezoelectric actuator 1 ... Piezoelectric element 11 ... Piezoelectric layer 12 ... Internal electrode layer 13 ... Laminated body 14 ... External electrode
DESCRIPTION OF SYMBOLS 15 ... Cover layer 2 ... Case 21 ... Cylindrical body 22 ... Cover body 23 ... Base | substrate 3 ... Welding part 31 ... 1st convex part 32 ... 2nd Convex part 41 ... lead wire 42 ... solder 43 ... lead pin 44 ... soft glass 5 ... corner part

Claims (5)

  A piezoelectric element and a case having a cylindrical body and a lid housed inside so as to sandwich the piezoelectric element from above and below, the lid body being inserted from one end side opening of the cylindrical body, The cylindrical body and the lid are joined, and a part of the welded portion enters from the side surface of the lid toward the inside of the lid, and the boundary between the welded portion and the lid is defined. A piezoelectric actuator characterized in that, when viewed in a cross-section cut in the vertical direction, the boundary has a corner provided to enter the weld.   When the boundary between the welded portion and the lid body is viewed in a cross section cut in the vertical direction, the welded portion is arranged in an upper stage and enters the inside of the lid body from the side surface of the lid body. And a second protrusion that is arranged in a lower stage and enters from the side surface of the lid toward the inside of the lid, and the corners are the first and second protrusions. The piezoelectric actuator according to claim 1, wherein the piezoelectric actuator is provided at an acute angle therebetween.   The second protrusion is deeper than the first protrusion when the boundary between the weld and the lid is viewed in a cross-section cut in the vertical direction. The piezoelectric actuator according to claim 1 or 2.   2. The second convex portion is wider than the first convex portion when viewed in a cross-section cut in the vertical direction at the boundary between the welded portion and the lid. The piezoelectric actuator according to claim 3.   When the boundary between the welded portion and the lid body is seen in a cross section cut in the vertical direction, the angle at which the surface of the second convex portion and the side surface of the lid body intersect is an acute angle. The piezoelectric actuator according to any one of claims 1 to 4.