JP2008041983A - Piezoelectric actuator - Google Patents

Abstract

To provide a piezoelectric actuator that can align a piezoelectric element in a storage case with a simple structure and is excellent in durability and reliability.
A piezoelectric actuator 1 houses a laminated piezoelectric element 10 in a cylindrical storage case 20 and a housing 30 provided with an external electrode 31 for power supply, at one open end 201 of the storage case 20. Joined to. An alignment member 40 for aligning the piezoelectric element 10 is provided between the piezoelectric element 10 and the housing 30. The alignment member 40 has an alignment spherical surface portion 401 that exhibits a convex spherical surface, and the housing 30 has an alignment spherical surface receiving portion 301 that exhibits a concave spherical surface that fits with the alignment spherical surface portion 401 of the alignment member 40. have. The alignment spherical surface portion 401 of the alignment member 40 is in sliding contact with the alignment spherical surface receiving portion 301 of the housing 30.
[Selection] Figure 1

Description

  The present invention relates to a piezoelectric actuator using a laminated piezoelectric element.

  2. Description of the Related Art In recent years, fuel injectors for automobiles using piezoelectric actuators have been developed from the viewpoint of measures such as automobile fuel consumption and exhaust gas. Since this piezoelectric actuator is incorporated in an injector and used in a harsh environment, a compact structure and high durability are required.

As the piezoelectric actuator, there is known a piezoelectric actuator in which a stacked piezoelectric element is hermetically housed in a housing case.
For example, Patent Document 1 proposes a structure of a piezoelectric actuator in which a housing case and a housing having an external electrode for supplying electric power to a piezoelectric element are joined by welding in order to realize a reduction in the structure. However, although the above-described structure can achieve downsizing, the following problems arise. That is, the storage case and the housing are joined by press-fitting a part of the housing into the storage case, and then welding the two together to form a joint. Bad attachment occurs. Therefore, the piezoelectric element in the storage case is eccentric, and an eccentric load is applied during driving. Thereby, when driven for a long time, the piezoelectric element is cracked and the durability is lowered.

Patent Documents 2 to 4 propose a structure of a piezoelectric actuator that does not weld the storage case and the housing. However, with the above structure, it is difficult to achieve downsizing. For example, Patent Document 4 shows a structure in which a small ball is incorporated as a mechanism for correcting the inclination of the storage case. In such a structure, the strength is insufficient unless the portion that receives the ball is strengthened, but space is required to increase the strength, and miniaturization cannot be realized.
Therefore, there is a demand for a piezoelectric actuator that is capable of aligning the piezoelectric elements in the storage case while having a compact structure, and that is excellent in durability and reliability.

JP 2004-319967 A JP 2004-353488 A JP 2000-170629 A Japanese Patent Laid-Open No. 10-288121

  The present invention has been made in view of such conventional problems, and is intended to provide a piezoelectric actuator that can easily align a piezoelectric element in a storage case with a simple structure and has excellent durability and reliability. It is what.

The present invention relates to a piezoelectric actuator in which a stacked piezoelectric element is stored in a cylindrical storage case, and a housing including an external electrode for supplying power is joined to one opening end of the storage case.
An alignment member for aligning the piezoelectric element is provided between the piezoelectric element and the housing, and the alignment member has an alignment spherical surface portion that exhibits a convex or concave spherical surface, The housing has an aligning spherical surface receiving portion that has a concave or convex spherical surface that fits with the aligning spherical surface portion of the aligning member, and the aligning spherical surface portion of the aligning member is The piezoelectric actuator is in sliding contact with the aligning spherical receiving portion (claim 1).

  In the piezoelectric actuator of the present invention, an alignment member is provided between the piezoelectric element and the housing. The aligning spherical surface portion of the aligning member is slidably in contact with the aligning spherical surface receiving portion of the housing, and both have a concave and convex spherical surfaces that fit together. That is, the alignment member can be displaced along the spherical surface within the spherical surface of the alignment spherical receiving portion of the housing.

  Therefore, when the piezoelectric actuator is assembled, even if the storage case is inclined with respect to the housing due to welding of the storage case and the housing, the position of the alignment member is adjusted according to the inclination of the storage case. Can be easily adjusted on the spherical surface of the alignment spherical receiving portion of the housing, and the alignment member can be arranged in a state of being aligned with the axis of the storage case. If the piezoelectric element is arranged coaxially with the alignment member via the alignment member in the housing, the axes of the storage case and the piezoelectric element can be easily aligned, and the storage The piezoelectric element in the case can be accurately aligned.

  Thereby, the piezoelectric actuator can easily align the piezoelectric element, and can prevent an assembly failure such as eccentricity of the piezoelectric element with respect to the storage case. In addition, it is possible to suppress a problem that an uneven load is applied to the piezoelectric element during driving, and the piezoelectric element is cracked or the like due to long-time use. Therefore, the piezoelectric actuator has high durability and reliability.

  The piezoelectric element expands in the axial direction when driven, and a large stress is generated in the extending direction. However, in the piezoelectric actuator of the present invention, the alignment member and the housing arranged in the extending direction of the piezoelectric element are in sliding contact with each other on the spherical surfaces fitted together as described above. Therefore, the stress generated during driving can be dispersed and alleviated by the spherical surface, deformation at the contact portion between the alignment member and the housing can be suppressed, and the piezoelectric element can be driven stably. Thereby, durability and reliability of the piezoelectric actuator can be improved.

  Thus, the piezoelectric actuator of the present invention can align the piezoelectric elements in the storage case with a simple structure, and is excellent in durability and reliability.

In the present invention, it is preferable that the alignment spherical surface portion of the alignment member has a convex spherical surface.
That is, in this case, the centering spherical surface receiving portion of the housing has a concave spherical surface. Thereby, the position of the alignment member can be adjusted more easily. Further, during driving, the stress generated at the contact portion between the alignment member and the housing can be further dispersed and relaxed.

Moreover, it is preferable that the said alignment spherical surface part of the said alignment member is exhibiting the spherical surface whose curvature radius is 4-20 mm (Claim 3).
When the radius of curvature is less than 4 mm, the alignment member and the housing have a smaller area for receiving stress generated during driving. Therefore, the contact force between the two cannot sufficiently receive the driving force of the piezoelectric element, and deformation or the like may occur. Moreover, when it exceeds 20 mm, there exists a possibility that the position of the said alignment member cannot be adjusted accurately.

Further, a driving member for outputting a driving force accompanying the piezoelectric displacement of the piezoelectric element to the outside is joined to the other opening end of the case,
A transmission member for transmitting the driving force of the piezoelectric element to the drive member is provided between the piezoelectric element and the drive member, and the transmission member has a transmission spherical surface portion that has a convex spherical surface. The drive member includes a transmission spherical surface receiving portion that has a concave spherical surface that fits with the transmission spherical surface portion of the transmission member, and the transmission spherical surface portion of the transmission member is the transmission spherical surface reception of the drive member. It is preferable that it is in sliding contact with the part (claim 4).

  The transmission spherical surface portion of the transmission member is in sliding contact with the transmission spherical surface receiving portion of the driving member, and both of them have a convex spherical surface and a concave spherical surface. That is, the transmission member can be displaced along the spherical surface within the range of the spherical surface of the transmission spherical surface receiving portion of the drive member. The relationship between the transmission member and the drive member is the same as the relationship between the alignment member and the housing already described above. Therefore, when the piezoelectric actuator is assembled, the piezoelectric element can be accurately aligned at the other opening end of the storage case. Thus, by providing a structure for aligning the piezoelectric element at both ends of the storage case, it is possible to further improve the alignment accuracy of the piezoelectric element and further prevent assembly failure. . The durability and reliability of the piezoelectric actuator can be further improved.

  Further, the transmission spherical surface portion of the transmission member has a convex spherical surface. Since the transmission member has a role of transmitting the driving force of the piezoelectric element to the driving member, the driving spherical surface has a convex spherical surface, so that the driving force is efficiently transmitted. It can be transmitted to the drive member.

Moreover, it is preferable that the said transmission spherical surface part of the said transmission member is exhibiting the spherical surface whose curvature radius is 1.5-8 mm (Claim 5).
When the curvature radius is less than 1.5 mm, the transmission member has a small area for transmitting the driving force of the piezoelectric element. Therefore, there is a possibility that the driving force cannot be sufficiently transmitted to the driving member. Moreover, when it exceeds 8 mm, there exists a possibility that the position of the said transmission member cannot be adjusted accurately.

In the piezoelectric actuator, it is preferable that a space in which each of the alignment member and the transmission member is displaced in a direction in which the alignment member and the transmission member are displaced for alignment of the piezoelectric element is provided.
If there is no space for displacement, adjustment of the positions of the alignment member and the transmission member may be insufficient, and the effect of aligning the piezoelectric element may not be exhibited sufficiently.

The alignment spherical surface portion of the alignment member and the transmission spherical surface portion of the transmission member are preferably coated with a heat resistant resin such as Teflon (registered trademark), polyimide, or silicone.
In this case, the positions of the alignment member and the transmission member can be adjusted more smoothly. Moreover, the effect that the contact part of the said alignment member and the said housing and the contact part of the said transmission member and the said drive member is protected is also acquired.

The piezoelectric actuator is preferably an actuator built in an injector for fuel injection of an internal combustion engine.
The injector is used under severe conditions of high temperature and high humidity. Therefore, durability and reliability can be improved by using the excellent piezoelectric actuator described above, and the performance of the entire injector can be improved.

(Example 1)
A piezoelectric actuator according to an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the piezoelectric actuator 1 of the present example houses a stacked piezoelectric element 10 in a cylindrical storage case 20, and a housing 30 having an external electrode 31 for power supply is provided on one side of the storage case 20. It joins to the opening edge part 201 of this.
An alignment member 40 for aligning the piezoelectric element 10 is provided between the piezoelectric element 10 and the housing 30. The alignment member 40 has an alignment spherical surface portion 401 that exhibits a convex spherical surface, and the housing 30 has an alignment spherical surface receiving portion 301 that exhibits a concave spherical surface that fits with the alignment spherical surface portion 401 of the alignment member 40. have. The alignment spherical surface portion 401 of the alignment member 40 is in sliding contact with the alignment spherical surface receiving portion 301 of the housing 30.
This will be described in detail below.

  As shown in FIG. 1, the piezoelectric actuator 1 stores a piezoelectric element 10 in a storage case 20. The piezoelectric element 10 has a ceramic laminated body 11, and the ceramic laminated body 11 is a unit body 110 (FIG. 10) formed by alternately laminating piezoelectric layers 12 made of a piezoelectric material and conductive internal electrode layers 13. 5)). The unit bodies 110 are bonded to each other with an adhesive 117 made of an epoxy resin having an insulating property.

  As shown in FIG. 5, the unit body 110 is formed by alternately laminating the piezoelectric layers 12 and the internal electrode layers 13 as described above. The unit body 110 has a barrel shape in cross section, and a pair of electrode joint surfaces 111 and 112 facing each other are formed on the outer peripheral surface. That is, the ceramic laminate 11 formed by laminating a plurality of unit bodies 110 has a barrel shape in cross section similar to the unit body 110, and a pair of electrode joint surfaces 111 and 112 facing each other on the outer peripheral surface. Is formed. The cross-sectional shapes of the unit body 110 and the ceramic laminate 11 are not limited to the barrel shape of the present example, and may be various shapes such as a quadrangle and an octagon.

  As shown in FIG. 1, side electrodes 14 are provided on the electrode bonding surfaces 111 and 112 of the ceramic laminate 11, respectively. Each side electrode 14 is electrically connected to every other internal electrode layer 13 in the stacking direction of the ceramic laminate 11, and the internal electrode layer 13 electrically connected to one side electrode 14 is In this state, the other side electrode 14 is electrically insulated. That is, the ceramic laminate 11 of this example has a so-called electrode holding structure (partial electrode structure). The entire outer peripheral surface of the ceramic laminate 11 is covered with a molding material 15 made of a silicone resin having insulation properties.

The piezoelectric layer 12 is made of a piezoelectric ceramic made of lead zirconate titanate (PZT). The internal electrode layer 13 is made of an Ag / Pd alloy.
The side electrode 14 is configured by embedding a mesh-like expander metal obtained by processing a metal plate in a conductive adhesive in which an Ag filler is dispersed in an epoxy resin.

  Further, as shown in the same figure, an alignment member 40 composed of two members, a ring member 41 and a holding member 42, is provided on one end surface 118 of the ceramic laminate 11. The holding member 42 made of alumina is bonded to the end face 118 of the ceramic laminate 11. Further, the ring member 41 made of SUS304 is slidably in contact with the housing 30.

  The other end surface 119 of the ceramic laminate 11 is provided with a joining member 18 and a transmission member 19 for transmitting a driving force of the piezoelectric element 10 to a driving member 22 described later. The joining member 18 made of alumina is joined to the end face 119 of the ceramic laminate 11. Further, the transmission member 19 made of SUS304 and the driving member 22 for outputting the driving force of the piezoelectric element 10 to the outside are joined at the transmission member welding portion 199 by laser welding.

  As shown in the figure, the housing 30 has a pair of external electrodes 31 arranged on a substantially cylindrical member made of SUS304. The external electrode 31 is electrically connected to the side electrode 14 and the external electrode connection portion 319 and is disposed through the holding member 40 and the housing 30. A gap between the external electrode 31 and the housing 30 is sealed with a rubber bush seal 33 made of heat-resistant rubber. The housing 30 is provided with a seal ring 34 for sealing when the housing 30 is assembled in an injector or the like.

Further, the housing 30 has an insertion portion 32 that is inserted into the storage case 20, and the insertion portion 32 is inserted so as to seal one open end 201 of the storage case 20. The opening end portion 201 of the storage case 20 and the insertion portion 32 of the housing 30 are joined by laser welding at the housing welding portion 309.
Further, the other opening end 202 of the storage case 20 and the drive member 22 are joined by laser welding at the drive member welding portion 229.

Here, the alignment member 40 will be described in detail with reference to FIGS. 2 and 3.
As shown in FIGS. 2 and 3, the alignment member 40 is composed of two members, the ring member 41 and the holding member 42 as described above.
As shown in FIG. 3A, the ring member 41 having a ring shape is provided with a through hole 411 for allowing the external electrode 31 to pass therethrough. Further, an aligning spherical surface portion 401 having a convex spherical surface is provided. As shown in FIG. 3B, the holding member 42 having a substantially columnar shape is provided with an escape groove 421 for arranging the external electrode 31.

As shown in FIG. 2, the housing 30 is provided with an aligning spherical surface receiving portion 301 having a concave spherical surface that fits with the aligning spherical surface portion 401 of the ring member 41. The alignment spherical surface portion 401 of the ring member 41 is slidably in contact with the alignment spherical surface receiving portion 301 of the housing 30. A space 35 is provided between the outer peripheral surface 412 of the ring member 41 and the housing 30.
Further, the alignment member 40 has the external electrode 31 penetrated through the through hole 411 of the ring member 41 and the escape groove 421 of the holding member 42.

In addition, the curvature radius of the spherical surface of the alignment spherical surface portion 401 of the ring member 41 and the alignment spherical surface receiving portion 301 of the housing 30 is 6 mm.
Further, the alignment spherical surface portion 401 of the ring member 41 is coated with Teflon (registered trademark) resin having excellent heat resistance. As the resin to be coated, polyimide resin, silicone resin, and the like can be used in addition to the above.

Next, a method for manufacturing the piezoelectric actuator 1 of this example will be briefly described.
First, a process for manufacturing the piezoelectric element 10 is performed.
A ceramic raw material powder made of lead zirconate titanate (PZT) to be a piezoelectric material is prepared, and a slurry is prepared by adding a solvent, a binder, a plasticizer, a dispersant, and the like. And the said slurry is apply | coated on a carrier film with a doctor blade method, and the green sheet (not shown) of fixed thickness is shape | molded.
In addition to the doctor blade method used in this example, an extrusion molding method and various other methods can be used as the green sheet molding method.

Next, an electrode material 130 made of a pasty Ag / Pd alloy is applied to a portion where the internal electrode layer 13 is formed on the formed green sheet. Then, as shown in FIG. 4, a sheet piece 120 having a desired size is cut out from the green sheet. At this time, the sheet piece 120 is formed with a holding portion 131 which is a portion where the electrode material 130 is not applied.
As the electrode material 130, a pasty Ag / Pd alloy was used.

Next, as shown in FIG. 4, the sheet pieces 120 are laminated so that the positions of the holding portions 131 are alternated to form an intermediate laminated body (not shown). And after degreasing | defatting an intermediate | middle laminated body, it bakes by hold | maintaining for 2 hours at the maximum temperature of 1060 degreeC.
Thereby, as shown in FIG. 5, the unit body 110 formed by alternately laminating the piezoelectric layers 12 and the internal electrode layers 13 is produced.

Next, the produced plurality of unit bodies 110 are adhered by an adhesive 117 made of an epoxy resin, and the ceramic laminate 11 is produced. And after apply | coating a conductive adhesive to the electrode joining surfaces 111 and 112 of the ceramic laminated body 11 and arrange | positioning a mesh-like expander metal, a conductive adhesive is heat-hardened and an expander metal is joined.
Thereby, as shown in FIG. 1, the piezoelectric element 10 in which the side electrode 14 formed by embedding the expander metal in the conductive adhesive is formed on the electrode bonding surfaces 111 and 112 of the ceramic laminate 11 is manufactured.

Next, a process of assembling the housing 30 to the piezoelectric element 10 and storing the piezoelectric element 10 in the storage case 20 is performed (see FIG. 1).
The holding member 42 and the bonding member 18 are bonded to the end surfaces 118 and 119 of the ceramic laminate 11 in the piezoelectric element 10 by an adhesive, respectively. Then, the side electrode 14 of the piezoelectric element 10 and the external electrode 31 of the housing 30 are welded, and both are joined at the external electrode connection portion 319. At this time, the external electrode 31 is passed through the through hole 411 of the ring member 41 and the escape groove 421 of the holding member 42. The gap between the external electrode 31 and the housing 30 is sealed with a rubber bush seal 33.

  Thereafter, the ring member 41 is disposed between the holding member 42 and the housing 30. Then, the piezoelectric element 10 and the housing 30 are assembled in a state where the alignment spherical surface portion 401 of the ring member 41 and the alignment spherical surface receiving portion 301 of the housing 30 are in contact with each other. At this time, the alignment spherical surface portion 401 of the ring member 41 is slidably in contact with the alignment spherical surface receiving portion 301 of the housing 30.

  Next, a molding material 15 is applied so as to cover the entire piezoelectric element 10 and is cured by heating. Then, the piezoelectric element 10 is stored in the storage case 20 from the open end 201 of the storage case 20. Further, the insertion portion 32 of the housing 30 is press-fitted so as to seal the opening end portion 201 of the storage case 20. Thereafter, the opening end portion 201 of the storage case 20 and the insertion portion 32 of the housing 30 are laser welded, and both are joined at the housing welding portion 309.

  At this time, if the storage case 20 is inclined with respect to the housing 30, the position of the alignment member 40 is adjusted on the spherical surface of the alignment spherical receiving portion 301 of the housing 30 in accordance with the inclination of the storage case 20. The axes of the storage case 20 and the alignment member 40 are aligned. Thereby, the axis | shaft of the storage case 20 and the piezoelectric element 10 can be match | combined, and the piezoelectric element 10 in the storage case 20 can be aligned.

Next, the drive member 22 is disposed on the joining member 18 via the transmission member 19. And the transmission member 19 and the drive member 22 are laser-welded, and both are joined in the transmission member welding part 199. Further, the driving member 22 and the opening end portion 202 of the storage case 20 are laser welded, and both are joined at the driving member welding portion 229. As a result, the inside of the storage case 20 is sealed.
Thus, the piezoelectric actuator 1 shown in FIG. 1 is completed.

Next, the effect of the piezoelectric actuator 1 of this example is demonstrated. For convenience of explanation of the effects, the holding member 40 is handled as an integral member in which the ring member 41 and the holding member 42 are combined.
In the piezoelectric actuator 1 of this example, an alignment member 40 is provided between the piezoelectric element 10 and the housing 30. The aligning spherical surface portion 401 of the aligning member 40 is slidably in contact with the aligning spherical surface receiving portion 301 of the housing 30, and both have a convex spherical surface and a concave spherical surface that fit together. That is, the alignment member 40 can be displaced along the spherical surface within the spherical surface of the alignment spherical receiving portion 301 of the housing 30.

  Therefore, as shown in FIG. 6, even when the storage case 20 is inclined with respect to the housing 30 due to welding of the storage case 20 and the housing 30 when the piezoelectric actuator 1 is assembled, according to the inclination of the storage case 20, The position of the alignment member 40 can be easily adjusted on the spherical surface of the alignment spherical receiving portion 301 of the housing 30, and the alignment member 40 can be disposed with the axis of the storage case 20 aligned. If the piezoelectric element 10 is disposed coaxially with the alignment member 40 via the alignment member 40 in the housing 30, the axes of the storage case 20 and the piezoelectric element 10 can be easily aligned. The piezoelectric element 10 in 20 can be accurately aligned.

  Accordingly, the piezoelectric actuator 1 can easily align the piezoelectric element 10, and can prevent an assembly failure such as eccentricity of the piezoelectric element 10 with respect to the storage case 20. In addition, it is possible to suppress a problem that an unbalanced load is applied to the piezoelectric element 10 at the time of driving, and the piezoelectric element 10 is cracked due to long-time use. Therefore, the piezoelectric actuator 1 has high durability.

  The piezoelectric element 10 expands in the axial direction when driven, and a large stress is generated in the extending direction. However, in the piezoelectric actuator 1 of this example, the alignment member 40 and the housing 30 disposed in the extending direction of the piezoelectric element 10 are in sliding contact with the spherical surfaces that are fitted to each other as described above. Therefore, the stress generated during driving can be dispersed and alleviated by this spherical surface, and deformation at the contact portion (aligning spherical surface portion 401, alignment spherical surface receiving portion 301) between the alignment member 40 and the housing 30 is suppressed. The piezoelectric element 10 can be driven stably. Thereby, the durability of the piezoelectric actuator 1 can be improved.

In this example, the alignment spherical surface portion 401 of the alignment member 40 has a convex spherical surface. The centering spherical surface receiving portion 301 of the housing 30 has a concave spherical surface. Thereby, the position of the alignment member 40 can be adjusted more easily. Further, the stress generated at the contact portion between the alignment member 40 and the housing 30 during driving can be further dispersed and relaxed.
The alignment spherical surface portion 401 of the alignment member 40 has a spherical surface with a curvature radius of 6 mm. Therefore, the position of the alignment member 40 can be adjusted with higher accuracy, and the alignment accuracy of the piezoelectric element 10 can be increased.

A space 35 is provided in the direction in which the holding member 40 is displaced for alignment of the piezoelectric element 10. Therefore, the position of the alignment member 40 can be sufficiently adjusted, and the effect of aligning the piezoelectric element 10 can be sufficiently exhibited.
Further, the alignment spherical surface portion 401 of the alignment member 40 is coated with Teflon (registered trademark) resin, which is a heat resistant resin. Therefore, the position of the alignment member 40 can be adjusted more smoothly. Moreover, the effect that the contact part of the alignment member 40 and the housing 30 is protected is also acquired.

  Thus, the piezoelectric actuator 1 of the present example can easily align the piezoelectric element 10 in the storage case 20 with a simple structure, and is excellent in durability and reliability.

(Example 2)
This example is an example in which the shape of the ring member 41 in the alignment member 40 is changed in the piezoelectric actuator 1 of the first embodiment.
As shown in FIGS. 7 and 8, the alignment member 40 of this example includes two members, a holding member 41 and a ring member 42. As shown in FIG. 8A, the ring member 41 is provided with an aligning spherical surface portion 401 having a concave spherical surface on the surface that contacts the housing 30. Further, the holding member 42 has the same shape as that of the first embodiment as shown in FIG.

Further, as shown in FIG. 7, the housing 30 is provided with an alignment spherical surface receiving portion 301 having a convex spherical surface that fits with the alignment spherical surface portion 401 of the ring member 41. The alignment spherical surface portion 401 of the ring member 41 is slidably in contact with the alignment spherical surface receiving portion 301 of the housing 30.
The other configuration is the same as that of the first embodiment, and has the same operation and effect.

(Example 3)
This example is an example in which the alignment member 40 is constituted by one member in the piezoelectric actuator 1 of the first embodiment.
The alignment member 40 of this example is composed of one member as shown in FIGS. As shown in FIG. 10, the alignment member 40 is provided with a relief groove 402 for arranging the external electrode 31. In addition, a centering spherical surface portion 401 having a convex spherical surface is provided on the surface in contact with the housing 30.

Further, as shown in FIG. 9, the housing 30 is provided with an alignment spherical surface receiving portion 301 that exhibits a concave spherical surface that fits with the alignment spherical surface portion 401 of the alignment member 40. The alignment spherical surface portion 401 of the alignment member 40 is slidably in contact with the alignment spherical surface receiving portion 301 of the housing 30.
Other configurations are the same as those in the first embodiment.

In this case, the number of parts can be reduced by changing the alignment member 40 from two members to one member. Thereby, alignment of the piezoelectric element 10 and assembly work of the piezoelectric actuator 1 can be facilitated.
The other functions and effects are the same as those of the first embodiment.

Example 4
In this example, in the piezoelectric actuator 1 according to the first embodiment, a structure for aligning the piezoelectric element 10 is also provided on the opening end 202 side of the storage case 20.
As shown in FIG. 11, the transmission member 19 of this example is provided with a transmission spherical surface portion 191 having a convex spherical surface. Further, the drive member 22 is provided with a transmission spherical surface receiving portion 221 that has a concave spherical surface that fits with the transmission spherical surface portion 191 of the transmission member 19. The transmission spherical surface portion 191 of the transmission member 19 is slidably in contact with the transmission spherical surface receiving portion 221 of the drive member 22.
In addition, the curvature radius of the spherical surface of the transmission spherical surface portion 191 of the transmission member 19 and the transmission spherical surface receiving portion 221 of the drive member 22 is 3 mm.
Other configurations are the same as those in the first embodiment.

  In this case, the transmission member 19 can be displaced along the spherical surface within the range of the spherical surface of the transmission spherical surface receiving portion 221 of the drive member 22. The relationship between the transmission member 19 and the drive member 22 is the same as the relationship between the alignment member 40 and the housing 30 already described above. Therefore, when the piezoelectric actuator 1 is assembled, the piezoelectric element 10 can be accurately aligned also at the opening end 202 of the storage case 20. Thus, by having the structure which aligns the both ends of the piezoelectric element 10, the precision of the alignment of the piezoelectric element 10 can further be improved, and the assembly | attachment defect can be prevented further. The durability of the piezoelectric actuator 1 can be further improved.

The transmission spherical surface portion 191 of the transmission member 19 has a spherical surface with a curvature radius of 3 mm. Therefore, the position of the transmission member 19 can be adjusted with higher accuracy, and the alignment accuracy of the piezoelectric element 10 can be increased.
The other functions and effects are the same as those of the first embodiment.

  The transmission spherical surface portion 191 of the transmission member 19 may be coated with a heat resistant resin such as Teflon (registered trademark), polyimide, or silicone. In this case, the position of the transmission member 19 can be adjusted more smoothly. Moreover, the effect of protecting the contact part of the transmission member 19 and the drive member 22 is also acquired.

(Example 5)
In this example, the piezoelectric actuator 1 of the first embodiment is used for an injector 6.
The injector 6 of this example is applied to a common rail injection system of a diesel engine as shown in FIG.
As shown in the figure, the injector 6 has an upper housing 62 in which the multilayer piezoelectric element 1 as a drive unit is accommodated, and a lower housing 63 that is fixed to the lower end and in which an injection nozzle portion 64 is formed. is doing.

The upper housing 62 is substantially cylindrical, and the laminated piezoelectric element 1 is inserted and fixed in a vertical hole 621 that is eccentric with respect to the central axis.
A high-pressure fuel passage 622 is provided in parallel to the side of the vertical hole 621, and an upper end portion thereof communicates with an external common rail (not shown) through a fuel introduction pipe 623 protruding to the upper side of the upper housing 62. .

A fuel lead-out pipe 625 communicating with the drain passage 624 protrudes from the upper portion of the upper housing 62, and the fuel flowing out from the fuel lead-out pipe 625 is returned to a fuel tank (not shown).
The drain passage 624 passes through a gap 60 between the vertical hole 621 and the drive unit (piezoelectric actuator) 1, and further, a three-way valve, which will be described later, by a passage (not shown) extending downward from the gap 60 in the upper and lower housings 62 and 63. It communicates with 651.

  The injection nozzle section 64 has a nozzle needle 641 that slides in the vertical direction in the piston body 631, and an injection hole 643 that is opened and closed by the nozzle needle 641 and injects high-pressure fuel supplied from a fuel reservoir 642 into each cylinder of the engine. I have. The fuel reservoir 642 is provided around the middle portion of the nozzle needle 641, and the lower end portion of the high-pressure fuel passage 622 is opened here. The nozzle needle 641 receives the fuel pressure in the valve opening direction from the fuel reservoir 642 and receives the fuel pressure in the valve closing direction from the back pressure chamber 644 provided facing the upper end surface, and the pressure in the back pressure chamber 644 is reduced. When lowered, the nozzle needle 641 is lifted, the nozzle hole 643 is opened, and fuel is injected.

  The pressure in the back pressure chamber 644 is increased or decreased by the three-way valve 651. The three-way valve 651 is configured to selectively communicate with the back pressure chamber 644 and the high pressure fuel passage 622 or the drain passage 624. Here, a ball-shaped valve body that opens and closes a port communicating with the high-pressure fuel passage 622 or the drain passage 624 is provided. The valve body is driven by the drive unit 1 through a large-diameter piston 652, a hydraulic chamber 653, and a small-diameter piston 654 disposed below the valve body.

  In this example, the piezoelectric actuator 1 of the present invention is used as a drive source in the injector 6 having the above configuration. As described above, the piezoelectric actuator 1 has excellent durability and reliability. Therefore, the performance of the injector 6 as a whole can be improved.

In Example 1, it is explanatory drawing which shows the structure of a piezoelectric actuator. In Example 1, it is an enlarged view which shows the shape and contact part of an alignment member and a housing. In Example 1, (a) Explanatory drawing which shows a ring member, (b) Explanatory drawing which shows a holding member. In Example 1, it is explanatory drawing which shows the process of laminating | stacking a sheet | seat. In Embodiment 1, it is explanatory drawing which shows a unit body. In Example 1, it is explanatory drawing which shows the structure of the piezoelectric actuator in which the storage case inclined. In Example 2, it is explanatory drawing which shows the example of the other shape of the alignment member. In Example 2, (a) explanatory drawing which shows a ring member, (b) explanatory drawing which shows a holding member. In Example 3, it is explanatory drawing which shows the example of the other shape of the alignment member. In Example 3, it is explanatory drawing which shows the alignment member. In Example 4, it is an enlarged view which shows the shape and contact part of a transmission member and a drive member. In Example 5, it is explanatory drawing which shows the structure of an injector.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piezoelectric actuator 10 Piezoelectric element 20 Storage case 201, 202 Open end 30 Housing 301 Alignment spherical receiving part 31 External electrode 40 Holding member 401 Alignment spherical part 6 Injector

Claims (6)

In a piezoelectric actuator formed by housing a laminated piezoelectric element in a cylindrical storage case and joining a housing provided with an external electrode for power supply to one opening end of the storage case,
An alignment member for aligning the piezoelectric element is provided between the piezoelectric element and the housing, and the alignment member has an alignment spherical surface portion that exhibits a convex or concave spherical surface, The housing has an aligning spherical surface receiving portion that has a concave or convex spherical surface that fits with the aligning spherical surface portion of the aligning member, and the aligning spherical surface portion of the aligning member is A piezoelectric actuator characterized by being in sliding contact with the aligning spherical surface receiving portion.   The piezoelectric actuator according to claim 1, wherein the alignment spherical surface portion of the alignment member has a convex spherical surface.   3. The piezoelectric actuator according to claim 1, wherein the alignment spherical surface portion of the alignment member has a spherical surface with a radius of curvature of 4 to 20 mm. In any 1 paragraph of Claims 1-3, the drive member for outputting the driving force accompanying the piezoelectric displacement of the above-mentioned piezoelectric element outside is joined to the other opening end of the above-mentioned storage case,
A transmission member for transmitting the driving force of the piezoelectric element to the drive member is provided between the piezoelectric element and the drive member, and the transmission member has a transmission spherical surface portion that has a convex spherical surface. The drive member includes a transmission spherical surface receiving portion that has a concave spherical surface that fits with the transmission spherical surface portion of the transmission member, and the transmission spherical surface portion of the transmission member is the transmission spherical surface reception of the drive member. A piezoelectric actuator characterized by being in sliding contact with a portion.   5. The piezoelectric actuator according to claim 4, wherein the transmission spherical surface portion of the transmission member has a spherical surface with a radius of curvature of 1.5 to 8 mm.   6. The piezoelectric actuator according to claim 1, wherein the piezoelectric actuator is an actuator built in a fuel injection injector of an internal combustion engine.

Images