JP2008167548A - Piezoelectric actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric actuator excellent in durability and reliability, to prevent crack, breakage, and the like in a displacement transmission member and maintain displacement characteristics even after a long-term use. <P>SOLUTION: The piezoelectric actuator 1 includes: a housing case 2 having a cylindrical barrel portion 21 housing a piezoelectric element 10 and a driving member 22 closing one end of the barrel portion 21; and a displacement transmission member 19 that is provided between the piezoelectric element 10 and the driving member 22 and transmits driving force from the piezoelectric element 10 to the driving member 22. The driving member 22 has a flat contact receiving surface 221, and a flat end face 191 of the displacement transmission member 19 is abutted against the contact receiving surface 221. The end face 191 of the displacement transmission member 19 has a chamfered portion 194 obtained by chamfering its peripheral end portion 192, and the chamfered amount C of the chamfered portion 194 is 0.1 to 0.8 mm. <P>COPYRIGHT: (C)2008,JPO&INPIT

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.
The piezoelectric actuator includes, for example, a storage case including a cylindrical body portion that houses a stacked piezoelectric element, and a drive member that closes one end of the body portion, There is a configuration in which a displacement transmitting member that transmits a driving force generated by piezoelectric displacement of a piezoelectric element to the driving member is provided between the driving member (see Patent Document 1).

In such a piezoelectric actuator, normally, in order to transmit displacement efficiently, the flat surfaces of the driving member and the displacement transmitting member are brought into contact with each other, and both are brought into contact with each other.
However, there is no problem when the two flat surfaces are in contact with each other in a parallel state, but when the contacts are not in a parallel state due to misalignment or the like, a problem occurs in the displacement transmission member. That is, when the displacement is transmitted from the displacement transmitting member to the driving member, stress concentration occurs on the contact surface of the displacement transmitting member with the driving member. In particular, when the outer peripheral end portion of the contact surface is a right angle or an acute angle, the outer peripheral end portion mainly comes into contact with the drive member and displacement is transmitted, so that stress concentration occurs in that portion. As a result, problems such as cracking and breakage occur in the displacement transmitting member due to repeated driving of the piezoelectric element.

  For this reason, there is a demand for a piezoelectric actuator with excellent durability and reliability that can suppress the occurrence of cracking or breakage of the displacement transmission member even during long-term use and maintain the displacement characteristics. It is rare.

JP 2003-97418 A

  The present invention has been made in view of such conventional problems, and can suppress the occurrence of cracks and breakage of the displacement transmission member even during long-term use, and can maintain the displacement characteristics. It is intended to provide a piezoelectric actuator with excellent performance and reliability.

The present invention includes a storage case including a cylindrical body portion that houses a laminated piezoelectric element, a drive member that closes one end of the body portion, the piezoelectric element, and the drive member. A piezoelectric actuator having a displacement transmitting member provided between the displacement transmitting member and transmitting the driving force of the piezoelectric element to the driving member;
The drive member has a flat contact receiving surface, and a flat distal end surface of the displacement transmitting member is in contact with the contact receiving surface,
The distal end surface of the displacement transmitting member has a chamfered portion at an outer peripheral end portion thereof, and a chamfering amount of the chamfered portion is 0.1 to 0.8 mm. 1).

  In the piezoelectric actuator of the present invention, the contact receiving surface of the drive member and the tip end surface of the displacement transmitting member are in contact with each other. That is, the drive member and the displacement transmission member are in contact with each other by their flat surfaces. And the said front end surface of the said displacement transmission member has a chamfering part in the outer peripheral edge part. Therefore, it is possible to suppress the occurrence of problems such as cracks and breakage in the displacement transmission member.

  That is, in the present invention, the chamfered portion is formed by chamfering the outer peripheral end portion of the tip end surface, which is a surface for transmitting the driving force due to the piezoelectric displacement of the piezoelectric element from the displacement transmitting member to the driving member. Is provided. Therefore, for example, even when the contact receiving surface and the tip surface are not in contact in a parallel state due to a positional deviation or the like, the tip surface is not subjected to chamfering as compared with the conventional case where the tip surface is not chamfered. Stress concentrated on the outer peripheral edge is dispersed. Thereby, the stress concentration in the said front end surface of the said displacement transmission member can be suppressed. And even if it is used for a long time, it can suppress that malfunctions, such as a crack and breakage, arise in the said displacement transmission member.

  Furthermore, in the present invention, the chamfering amount of the chamfered portion is in the range of 0.1 to 0.8 mm. By obtaining the chamfering amount within the above range, the above effect can be obtained while sufficiently securing displacement characteristics such as a displacement transmission amount transmitted from the piezoelectric element to the drive member via the displacement transmission member. Can do.

  As described above, the piezoelectric actuator of the present invention can suppress the occurrence of cracking / breakage of the displacement transmitting member even during long-term use, and can maintain the displacement characteristics, and has excellent durability and reliability. It will be.

In the present invention, when the chamfering amount of the chamfered portion is less than 0.1 mm, there is a possibility that the effect of suppressing the stress concentration on the distal end surface of the displacement transmitting member cannot be sufficiently obtained. In particular, the tendency becomes more prominent as the driving force due to the displacement of the piezoelectric element increases. On the other hand, when it exceeds 0.8 mm, there is a possibility that a sufficient displacement transmission amount cannot be obtained.
The chamfering amount here is the distance from the outer peripheral end before chamfering to the outer peripheral end after chamfering on the distal end surface of the displacement transmitting member.

Further, the chamfered portion may be configured to be chamfered so that the angle of the outer peripheral end portion of the distal end surface of the displacement transmitting member is greater than 90 ° and less than 180 ° (Claim 2). .
In this case, the effect of suppressing the stress concentration on the distal end surface of the displacement transmitting member can be effectively exhibited.
In addition, in the case of the said structure, the said chamfering part can be provided in inclination flat form so that the angle of the said corner | angular part may become the said range, for example.

Further, the chamfered portion may be configured by chamfering an outer peripheral end portion of the distal end surface of the displacement transmitting member into an R shape having a certain curvature (Claim 3). That is, the chamfered portion can be provided in a curved shape having a certain curvature.
Even when the chamfered portion has an R shape, the effect of suppressing the stress concentration on the distal end surface of the displacement transmitting member can be sufficiently obtained.

The displacement transmitting member is preferably made of ceramic. In particular, the displacement transmitting member is preferably made of alumina.
In this case, since the Young's modulus is high, the loss of displacement transmitted from the piezoelectric element to the drive member via the displacement transmission member can be reduced.

In addition, the body portion of the storage case may include a stretchable portion that can be elastically stretched in the axial direction according to the driving of the piezoelectric element.
In this case, a bellows-type piezoelectric actuator using a bellows or the like as the expansion / contraction part can be obtained. Of course, even in such a configuration, it is possible to sufficiently obtain the effect of suppressing stress concentration on the distal end surface of the displacement transmitting member.

Moreover, it can be set as the structure which has a diaphragm film | membrane part which can be elastically deformed according to the drive of the said piezoelectric element between the said trunk | drum and the said drive member in the said storage case.
In this case, a diaphragm type piezoelectric actuator can be obtained. Of course, even in such a configuration, it is possible to sufficiently obtain the effect of suppressing stress concentration on the distal end surface of the displacement transmitting member.

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 this example includes a cylindrical body portion 21 that houses a stacked piezoelectric element 10 and a drive member 22 that closes one end of the body portion 21. The storage case 2 is provided, and a displacement transmission member 19 is provided between the piezoelectric element 10 and the driving member 22 and transmits the driving force of the piezoelectric element 10 to the driving member 22.
The drive member 22 has a flat contact receiving surface 221, and the flat distal end surface 191 of the displacement transmitting member 19 is in contact with the contact receiving surface 221. The distal end surface 191 of the displacement transmitting member 19 has a chamfered portion 194 at the outer peripheral end 192, and the chamfered amount C of the chamfered portion 194 is in the range of 0.1 to 0.8 mm.
This will be described in detail below.

As shown in FIG. 1, the multilayer piezoelectric element 10 has a ceramic laminate 11 in which piezoelectric layers 12 and internal electrode layers 13 are alternately laminated. The ceramic laminate 11 has a rectangular cross section, and a pair of side electrode forming surfaces 111 and 112 facing each other are formed on the outer peripheral surface of the ceramic laminate 11.
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.

Further, the side electrode plate 16 is formed on the side electrode forming surfaces 111 and 112 of the ceramic laminate 11 via a conductive adhesive in which an Ag filler is contained in an epoxy resin on a baked silver obtained by baking an Ag paste. The side electrode 14 which joined is provided.
In addition, as the side electrode plate 16, a mesh-like expanded metal obtained by processing a metal plate was used.

In addition, each side electrode 14 is electrically connected to every other internal electrode layer 13 in the stacking direction of the ceramic laminate 11 and is electrically connected to one side electrode 14. 13 is electrically insulated from the other side electrode 14. That is, the ceramic laminate 11 of this example has a so-called partial electrode structure.
The entire outer peripheral surface of the ceramic laminate 11 is covered with a molding material (not shown) made of an insulating silicone resin.

As shown in the figure, a connecting member 18 made of a hermetic seal is joined to one end face of the ceramic laminate 11 in the lamination direction. The connecting member 18 has an external electrode 20 that guides the side electrode 14 to the outside, and the side electrode 14 and the external electrode 20 are joined by laser welding.
The other end face of the ceramic laminate 11 is provided with a displacement transmission member 19 made of alumina and for transmitting the driving force generated by the piezoelectric displacement of the piezoelectric element 10 to the driving member 22 of the storage case 2. The displacement transmission member 19 is in contact with the drive member 22.

Moreover, as shown in the figure, the metal storage case 2 has a barrel portion 21 that has a substantially cylindrical shape and a drive member 22 that constitutes the bottom portion. The trunk | drum 21 and the drive member 22 are joined by laser welding.
In addition, at the end of the body portion 21 on the drive member 22 side, an expansion / contraction portion 211 that can be expanded and contracted in the axial direction according to the driving of the piezoelectric element 10 is provided. The stretchable portion 211 is a metal bellows having a large diameter and a small diameter alternately.

  Moreover, the opening end 201 of the storage case 2 is sealed by the connecting member 18, and the storage case 2 is sealed. The opening end 201 of the storage case 2 and the connection member 18 are joined by laser welding.

Here, the drive member 22 and the displacement transmission member 19 that are in contact with each other will be described in detail.
As shown in FIG. 1, the displacement transmission member 19 has a flat front end surface 191. On the other hand, the drive member 22 also has a flat contact receiving surface 221. And the displacement transmission member 19 and the drive member 22 are maintaining the contact state by making the front end surface 191 and the contact receiving surface 221 contact.

  Further, as shown in FIGS. 2A and 2B, the outer peripheral end 192 of the distal end surface 191 of the displacement transmitting member 19 is chamfered, and a chamfered portion 194 is formed in the chamfered portion. . The chamfered portion 194 is provided in an inclined flat shape over the entire circumference from the outer peripheral corner portion 195 of the displacement transmitting member 19 to the corner portion 193 of the distal end surface 191.

  Further, as shown in FIG. 2B, the cross-sectional shape of the displacement transmitting member 19 has a circular shape with a diameter of 6 mm, and the tip end surface 191 also has a circular shape with a diameter of 5 mm. The chamfering amount C in this example is 0.5 mm. In addition, the angle α of the corner portion 193 of the outer peripheral end 192 of the front end surface 191 is 135 °.

The chamfering amount C here is a radial distance from the outer peripheral end of the displacement transmitting member 19 to the outer peripheral end of the distal end surface 191. In this example, the distance in the radial direction is from the outer peripheral corner portion 195 of the displacement transmitting member 19 to the corner portion 193 of the distal end surface 191. The chamfering amount in the axial direction is also 0.5 mm, which is the same as the chamfering amount C in the radial direction.
Further, as the cross-sectional shape of the displacement transmitting member 19, various shapes such as a quadrangle and an octagon can be adopted.

Next, a method for manufacturing the piezoelectric actuator 1 will be briefly described.
First, a ceramic raw material powder made of lead zirconate titanate (PZT) serving as 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 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, as shown in FIG. 3, an electrode material 130 is applied in advance to a portion where the internal electrode layer 13 is formed on the green sheet 120, and a sheet piece 100 having a desired size is cut out from the green sheet 120. The sheet piece 100 is formed with a holding portion 131 to which the electrode material 130 is not applied. As the electrode material 130, an Ag / Pd alloy paste was used.

Next, as shown in FIG. 4, the sheet pieces 100 are laminated to form an intermediate laminate 110. At this time, the sheet pieces 100 are stacked so that the positions of the holding portions 131 formed on the sheet pieces 100 are alternated.
And after baking the formed intermediate laminated body 110, it bakes. Thereby, the ceramic laminated body 11 formed by alternately laminating the piezoelectric layers 12 and the internal electrode layers 13 is formed.

  Then. Ag paste is applied on the side electrode forming surfaces 111 and 112 of the ceramic laminate 11. Then, the applied Ag paste is baked to form baked silver. Then, the side electrode plate 16 is disposed on the baked silver by applying a conductive adhesive. Thereafter, the conductive adhesive is heated and cured, and the side electrode plate 16 is joined. Thereby, the side electrode 14 is formed on the side electrode forming surfaces 111 and 112.

Next, a connection member 18 made of a hermetic seal is joined to one end face of the ceramic laminate 11 in the lamination direction, and a displacement transmission member 19 made of alumina is joined to the other end face. At this time, the side electrode 14 and the external electrode 20 which the joining member 18 has are joined by laser welding.
And the opening end 201 of the storage case 2 which joined the piezoelectric element 10 which joined the connection member 18 and the displacement transmission member 19 to the both end surfaces of the ceramic laminated body 11, and the trunk | drum 21 and the drive member 22 by laser welding. Store from. At this time, the contact receiving surface 221 of the drive member 22 of the storage case 2 and the distal end surface 191 of the displacement transmitting member 19 are in contact with each other.

Next, the opening end 201 of the storage case 2 and the connecting member 18 are joined by laser welding. Thereby, the opening end 201 of the storage case 2 is sealed by the connecting member 18, and the inside of the storage case 2 is sealed.
Thus, the piezoelectric actuator 1 shown in FIG. 1 is manufactured.

The effect in the piezoelectric actuator 1 of this example is demonstrated.
In the piezoelectric actuator 1 of this example, the contact receiving surface 221 of the driving member 22 and the tip end surface 191 of the displacement transmitting member 19 are in contact. That is, the drive member 22 and the displacement transmission member 19 are in contact with each other by their flat surfaces. The distal end surface 191 of the displacement transmitting member 19 has a chamfered portion 194 formed by chamfering the outer peripheral end portion 192 thereof. Therefore, it is possible to suppress the occurrence of problems such as cracks and breakage in the displacement transmission member 19.

  That is, in this example, the chamfered portion is formed by chamfering the outer peripheral end portion 192 of the distal end surface 191 as a surface for transmitting the driving force due to the piezoelectric displacement of the piezoelectric element 10 from the displacement transmitting member 19 to the driving member 22. 194 is provided. For this reason, for example, even when the contact receiving surface 221 and the tip surface 191 are not in contact in parallel due to a positional deviation or the like, compared to the conventional case where the outer peripheral end 192 of the tip surface 191 is not chamfered, the displacement is transmitted. The stress concentrated on the outer peripheral end 192 of the front end surface 191 is dispersed. Thereby, stress concentration on the distal end surface 191 of the displacement transmitting member 19 can be suppressed. And even if it is used for a long time, it can suppress that troubles, such as a crack and breakage, arise in the displacement transmission member 19.

  Furthermore, in this example, the chamfering amount C of the chamfered portion 194 is in the range of 0.1 to 0.8 mm. By setting the chamfering amount C in the above range, the above effect can be obtained while sufficiently securing displacement characteristics such as a displacement transmission amount transmitted from the piezoelectric element 10 to the drive member 22 via the displacement transmission member 19. Can do.

  Further, in this example, the chamfered portion 194 is chamfered so that the angle α of the corner portion 193 of the outer peripheral end portion 192 on the distal end surface 191 of the displacement transmitting member 19 is in the range of more than 90 ° and less than 180 °. Therefore, the effect of suppressing the stress concentration on the distal end surface 191 of the displacement transmitting member 19 can be effectively exhibited.

  As described above, the piezoelectric actuator of the present invention can suppress the occurrence of cracking / breakage of the displacement transmitting member even during long-term use, and can maintain the displacement characteristics, and has excellent durability and reliability. It will be.

Further, in this example, the chamfered portion 194 on the distal end surface 191 of the displacement transmitting member 19 can be variously changed by changing the chamfering amount C and the angle α of the corner portion 193 as shown in FIGS. It can be made into a form.
Further, as shown in FIGS. 6A and 6B, the chamfered portion 194 can be formed in an R shape having a certain curvature.

  The piezoelectric actuator 1 of this example is a bellows type piezoelectric actuator provided with an expansion / contraction portion 23 made of a metal bellows that can expand and contract according to the driving of the piezoelectric element 10, but as shown in FIG. A diaphragm type piezoelectric actuator in which a diaphragm film portion 29 that can be elastically deformed in accordance with the driving of the piezoelectric element 10 between the body portion 21 and the driving member 22 may be employed. In this case, the same effect as described above can be obtained.

(Example 2)
In this example, the relationship between the chamfering amount of the displacement transmitting member and the load resistance is evaluated.
In this example, what changed the chamfering amount of the displacement transmission member in the range of 0-1.5 mm was prepared, and load resistance was measured about each. In addition, as a displacement transmission member, the same material as Example 1 was used.

  In measuring the load resistance of the displacement transmitting member, as shown in FIG. 8, a displacement transmitting member 19 having a size of 6 mm × 6 mm × 18 mm was prepared and chamfered so as to have a desired chamfering amount C. Next, the displacement transmission member 19 was accommodated in the storage case 2 constituted only by the drive member 22 and the expansion / contraction part 211 of the trunk portion 21, and the drive member 22 and the displacement transmission member 19 were brought into contact with each other. At this time, the shim 31 was sandwiched under the driving member 22, and an inclination angle of 2 ° was provided between the contact receiving surface 221 and the tip surface 191. Then, a load F was applied to the displacement transmission member 19 in the axial direction, and a load F (load resistance) at the time when the displacement transmission member 19 was cracked or damaged was measured.

Next, the measurement results are shown in FIG. In the figure, the vertical axis represents the load resistance F (kN) and the horizontal axis represents the chamfering amount C (mm). In addition, the case where cracks or breakage occurred is indicated by X, and the case where no breakage or breakage occurred is indicated by ○.
As can be seen from the figure, as the chamfering amount C increases, the displacement transmitting member 19 is less likely to be cracked or damaged. The effect is particularly prominent when the chamfering amount C is 0.1 mm or more. Therefore, it can be seen that the chamfering amount C of the displacement transmitting member 19 is preferably 0.1 mm or more.

(Example 3)
In this example, the relationship between the chamfering amount of the displacement transmitting member and the displacement loss amount is evaluated.
In this example, the displacement loss amount when the chamfering amount of the displacement transmitting member is changed in the range of 0 to 2 mm was obtained by calculation. The displacement transmitting member is the same material as in Example 1.

  In calculating the displacement loss amount of the displacement transmitting member, as shown in FIG. 10A, the shape of the 6 × 6 × 18 mm displacement transmitting member 19 having the chamfered portion 194 with the chamfering amount C is shown in FIG. The model as shown in b) was simplified and the large diameter portion was designated as the large diameter portion 19A (cross sectional area SA), and the small diameter portion was designated as the small diameter portion 19B (cross sectional area SB).

Here, the strain amounts εA and εB of the large-diameter portion 19A and the small-diameter portion 19B when the load F is applied in the axial direction to the displacement transmission member 19 are Hook's law (strain ε = stress σ / Young's modulus E). Was calculated by the following formulas (1) and (2). Then, the total strain amount εΣ, which is the sum of the strain amounts εA and εB of the large diameter portion 19A and the small diameter portion 19B, is obtained by the following equation (3), and this is used as the displacement loss amount. The applied load F is 500 N, and the Young's modulus E is 360000 MPa (alumina).
Distortion amount of the displacement transmission member 19A: εB = (load F / cross-sectional area SA) / (Young's modulus E)) × (full length L−chamfering amount C) (1)
Distortion amount of the displacement transmitting member 19B: εB = (Load F / Cross sectional area SB) / (Young's modulus E)) × (Total length L−Chamfering amount C) (2)
Distortion amount of the displacement transmission member 19 as a whole: εΣ = εA + εB (3)

Next, a calculation result is shown in FIG. In this figure, the vertical axis represents the displacement loss amount (mm), and the horizontal axis represents the chamfering amount C (mm).
As can be seen from the figure, the amount of displacement loss increases gradually as the chamfer amount C increases. This is because the displacement transmission amount is related to the size of the cross-sectional area of the displacement transmission member 19. That is, as the chamfering amount C increases, the cross-sectional area of the displacement transmission member 19 decreases. As a result, the displacement transmission amount is reduced and the displacement loss amount is increased. In particular, the amount of displacement loss increases when the chamfering amount C exceeds 0.8 mm, and there is a possibility that sufficient displacement characteristics cannot be obtained. Therefore, it can be seen that the chamfering amount C of the displacement transmitting member 19 is preferably 0.8 mm or less.

Example 4
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 includes an upper housing 62 in which the piezoelectric actuator 1 serving as a drive unit is accommodated, and a lower housing 63 that is fixed to the lower end of the injector 6 and in which an injection nozzle portion 64 is formed. Yes.

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 piezoelectric actuator 1 serving as a drive unit, 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 Example 1 is used as a drive source in the injector 6 having the above-described 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.

FIG. 3 is an explanatory diagram illustrating a structure of a piezoelectric actuator in the first embodiment. In Example 1, (a) Explanatory drawing of the front-end | tip part of a displacement transmission member, (b) Explanatory drawing which shows a front-end | tip surface. FIG. 3 is an explanatory diagram illustrating a process of laminating sheets in Example 1. FIG. 3 is an explanatory view showing an intermediate laminate (ceramic laminate) in Example 1. Explanatory drawing which shows the example of the other shape of (a), (b) chamfering part in Example 1. FIG. Explanatory drawing which shows the example of the other shape of (a), (b) chamfering part in Example 1. FIG. FIG. 3 is an explanatory diagram illustrating a structure of a diaphragm type piezoelectric actuator in the first embodiment. Explanatory drawing which shows the measuring method of the load resistance of the displacement transmission member in Example 2. FIG. Explanatory drawing which shows the relationship between the amount of chamfering and load resistance in Example 2. FIG. Explanatory drawing which shows the measuring method of the displacement loss amount of the displacement transmission member in Example 3. FIG. Explanatory drawing which shows the relationship between the amount of chamfering and the amount of displacement loss in Example 3. FIG. Explanatory drawing which shows the structure of the injector in Example 4. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piezoelectric actuator 10 Piezoelectric element 19 Displacement transmission member 191 Tip end surface 192 Outer peripheral end 194 Chamfer 2 Storage case 21 Body 22 Drive member 221 Contact receiving surface

Claims (8)

Provided between the piezoelectric element and the drive member, a storage case having a cylindrical barrel portion that houses the laminated piezoelectric element, and a drive member that closes one end of the barrel portion. A piezoelectric actuator having a displacement transmitting member that transmits a driving force of the piezoelectric element to the driving member;
The drive member has a flat contact receiving surface, and a flat distal end surface of the displacement transmitting member is in contact with the contact receiving surface,
The piezoelectric actuator according to claim 1, wherein the distal end surface of the displacement transmitting member has a chamfered portion at an outer peripheral end thereof, and a chamfering amount of the chamfered portion is 0.1 to 0.8 mm.   2. The piezoelectric actuator according to claim 1, wherein the chamfered portion is chamfered so that an angle of an outer peripheral end portion of the distal end surface of the displacement transmitting member is greater than 90 ° and less than 180 °.   2. The piezoelectric actuator according to claim 1, wherein the chamfered portion is formed by chamfering an outer peripheral end portion of the distal end surface of the displacement transmitting member into an R shape having a certain curvature.   The piezoelectric actuator according to claim 1, wherein the displacement transmission member is made of ceramic.   5. The piezoelectric actuator according to claim 4, wherein the displacement transmission member is made of alumina.   6. The piezoelectric actuator according to claim 1, wherein the body portion of the storage case includes an expansion / contraction portion that can elastically expand and contract in an axial direction in accordance with driving of the piezoelectric element.   7. The diaphragm film part according to claim 1, further comprising a diaphragm film part that is elastically deformable in accordance with driving of the piezoelectric element between the trunk part of the storage case and the driving member. A characteristic piezoelectric actuator.   The piezoelectric actuator according to claim 1, wherein the piezoelectric actuator is an actuator built in an injector for fuel injection of an internal combustion engine.

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