JPH04258501A - Piezoelectric actuator - Google Patents

Abstract

PURPOSE:To obtain a large displacement output at a second piston in a piezoelectric actuator which transmits displacement of a laminated piezoelectric body from a first piston to the second piston. CONSTITUTION:A first to a fourth pistons 4, 5, 7 and 8 are moved back and forth interlockingly with telescopic displacement of a laminated piezoelectric body 6. As the fourth piston 8 makes a second oil chamber 12 communicate to a third oil chamber 14 in the middle of the forward movement, the second piston 5 is further moved forward. As the fourth piston 8 makes the second oil chamber 12 communicate to a reserve tank and the third piston 7 makes the third oil chamber 14 communicate to a reserve tank 16 in the middle of the backward movement, only the second piston 5 is kept in the forward movement state. Thus, by telescopically displacing the laminated piezoelectric body 6 for a plurality of times, a large output is obtained at the second piston 5.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric actuator that converts the displacement of a laminated piezoelectric body into a large output displacement.

0002

2. Description of the Related Art Conventionally, this type of piezoelectric actuator has been disclosed, for example, in Japanese Patent Application Laid-open No. 59-206699. It is configured to expand by an area ratio of , and use this as the output displacement.

0003

[Problems to be Solved by the Invention] However, in such a conventional piezoelectric actuator, the displacement of the laminated piezoelectric body is simply expanded by the area ratio of the two pistons, as described above. There was a limit to the displacement output, and large displacement output could not be obtained.

The present invention has been made in view of the above-mentioned circumstances, and its object is to provide a piezoelectric actuator that can convert the displacement of a laminated piezoelectric body into a large displacement output.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention has a cylinder in which a first piston and a second piston having a smaller cross-sectional area are slidably disposed; In a piezoelectric actuator in which the displacement of a laminated piezoelectric body is transmitted from one piston to a second piston, the displacement is amplified as a displacement output by the second piston,
slidably arranged between the first and second pistons;
and a third piston formed to have the same cross-sectional area as the second piston or a smaller cross-sectional area than the second piston;
and a fourth piston slidably disposed between the second piston and having the same cross-sectional area as the second piston or a smaller cross-sectional area than the second piston; When the fourth piston slides toward the second piston, a valve is provided that communicates a chamber partitioned by the fourth and third pistons with a chamber partitioned by the fourth and second pistons; When the third piston slides toward the first piston, a valve communicates the chamber partitioned by the fourth and third pistons with the reserve tank; when the third piston slides toward the first piston, the second and third pistons communicate with each other. It is characterized by comprising a valve that communicates a chamber partitioned by a fourth piston with a reserve tank.

[0006]

According to the present invention, as a result of the elongation and displacement of the laminated piezoelectric body, the fourth piston slides toward the second piston via the first and third pistons. At this time, the chamber partitioned by the fourth and third pistons and the chamber partitioned by the fourth and second pistons communicate with each other, so that the second piston is further displaced. As a result of the laminated piezoelectric body being shrunk and displaced from this state, the fourth and third pistons slide toward the first piston. At this time, since the chamber partitioned by the fourth and third pistons and the chamber partitioned by the second and third pistons communicate with the reserve tank, only the second piston is maintained in a displaced state, and the other pistons are The piston returns to its original position. Thereby, by expanding and contracting the laminated piezoelectric body multiple times, a large displacement output can be obtained for the second piston.

[0007]

Embodiment An embodiment of the piezoelectric actuator according to the present invention will be described in detail below with reference to FIGS. 1 and 3.

As shown in FIG. 1, this piezoelectric actuator has first and second cylinders 2 and 3 in a housing 1, and the inside of the second cylinder 3 communicates with the inside of the first cylinder 2. Moreover, its inner diameter is smaller than the inner diameter of the first cylinder 2.

A first piston 4 is slidably disposed inside the first cylinder 2, and a second piston 5 is slidably disposed inside the second cylinder 3. is formed to have a smaller cross-sectional area than the first piston 4;
The piston 4 is configured to move back and forth inside the first cylinder 2 by the expansion and contraction of the laminated piezoelectric body 6.

Furthermore, a third piston 7 is provided inside the second cylinder 3, and this third piston 7 is slidably disposed between the first and second pistons 4 and 5. , and is formed to have the same cross-sectional area as the second piston 5. On the other hand, a fourth piston 8 is provided inside the second cylinder 3, and this fourth piston 8 is slidably disposed between the second and third pistons 5 and 7. It is formed to have the same cross-sectional area as the piston 5 of No. 2.

The fourth piston 8 has springs 9, 9 and stoppers 10, 10 on both ends thereof, and is biased to a predetermined position by the springs 10, 10.

By the way, a communication passage 11 is formed in the fourth piston 8, and one end of this communication passage 11 is connected to a chamber (hereinafter referred to as a second oil chamber) partitioned by the third and fourth pistons 7 and 8. ) 12. On the other hand, the other end of the communication path 11 is provided so as to face one end of the port 13 when the fourth piston 8 slides toward the second piston 5; piston 5,
8 (hereinafter referred to as the third oil chamber) 14 is opened. Conversely, when the fourth piston 8 slides toward the first piston 4, the other end of the communication path 11 is provided to face one end of the port 15, and the other end of the port 15 is opened to the reserve tank 16. has been done.

That is, when the fourth piston 8 slides toward the second piston, the second oil chamber 12 and the third
It is configured to have a function as a so-called spool-shaped valve that communicates with the oil chamber 14 and communicates the second oil chamber with the reserve tank 16 when sliding toward the first piston.

[0014] A communication passage 17 is formed in the third piston 7, and one end of this communication passage 17 is connected to the third piston 7.
When the piston 7 slides toward the first piston 4, the port 18 is provided so as to face one end of the port 18.
The other end is opened to the reserve tank 10. on the other hand,
The other end of the communication path 17 is provided so as to face one end of the port 19 when the third piston 7 slides in the same manner as described above.
The other end of the port 19 is opened to the third oil chamber 14 .

That is, when the third piston 7 slides toward the first piston 4, it functions as a so-called spool-shaped valve that communicates the third oil chamber 14 with the reserve tank 10. It is configured to include.

Next, the operation of the piezoelectric actuator constructed as described above will be explained using FIGS. 2 and 3. Note that the chamber partitioned by the first and third pistons 4 and 7 is referred to as a first oil chamber 20 here.

FIG. 2(a) shows the initial state of the piezoelectric actuator, and in this state a voltage is applied to the laminated piezoelectric body 6. As a result, the laminated piezoelectric body 6 begins to extend and displace, and in conjunction with this, the first piston 4 begins to move forward. At the same time, the oil in the first oil chamber 20 is
The piston 7 also moves forward. At this time, since the third piston 7 is formed to have a smaller cross-sectional area than the first piston 4,
The first piston 4 moves further forward than the first piston 4. In addition, the first
The piston 7 moves several tens of μm at most, while the
The piston 7 moves a maximum of ten or more mm.

When the third piston 7 moves forward as described above, the fourth piston 8 moves forward via the oil in the second oil chamber 12;
The second piston 5 moves forward through the oil in the oil chamber 14.

In this way, the first to fourth pistons 4
, 5, 7, and 8 move forward in conjunction with each other, but at this time, each piston moves forward against the spring force on the output shaft 21 side. In addition, when one end of the communication path 11 faces one end of the port 13 during its forward movement as shown in FIG. . As a result, the oil in the second oil chamber 12 flows into the third oil chamber 14 via the communication path 11 and the port 13, so that only the second and third pistons 5 and 7 are interlocked with the first piston 4. Advance. As a result, the second piston 5 advances further until the laminated piezoelectric body 6 is fully extended and the first piston 4 stops advancing (see FIG. 2(c)).

Next, after the laminated piezoelectric body 6 has fully expanded as described above, when the voltage applied to the laminated piezoelectric body 6 is removed, the laminated piezoelectric body 6 is compressed and displaced as shown in FIG. 2(d). At the same time, the fourth piston 8 is pushed back by the spring force on the output shaft 21 side and moves backward. As a result, one end of the port 13 and one end of the communication path 11 become misaligned,
Moreover, the second oil chamber 12 and the third oil chamber 14 are independent.

Thereafter, when the fourth piston 8 further retreats, one end of the communication passage 11 faces one end of the port 15, as shown in FIG. 2(e). As a result, the reserve tank 16 and the second oil chamber 12 are connected via the port 15 and the communication path 11.
As a result, the oil in the reserve tank 16 flows into the second oil chamber 12 via the port 15 and the communication path 11, so that the third piston 7 moves backward in conjunction with the first piston 4. , only the second piston 5 is maintained in an advanced state.

In this way, the first and third pistons 4 and 7 gradually return to their initial states as shown in FIG. While the oil flowing into the oil chamber 12 stops, the fourth piston 8 returns to its initial state.

That is, the above operations bring the first, third, and fourth pistons 4, 7, and 5 into their initial states, and only the second piston 5 maintains its forward state.

Furthermore, if the laminated piezoelectric body 6 is expanded and contracted a plurality of times, the above-mentioned operation is repeated, so that only the second piston 5 continues to move forward, and this second piston 5 A large displacement output can be obtained.

[0025] As the above-described operation is repeated, the second piston 5 (
3(a)), a voltage in the opposite direction to the above applied voltage is applied to the laminated piezoelectric body 6. As a result, the laminated piezoelectric body 6 contracts (see FIG. 3(b)), and in conjunction with this, the third piston 7 moves toward the first piston 4, and during the movement, it contacts one end of the communication path 17. One end of the port 18 faces the other end. As a result, the third oil chamber 14 and the reserve tank 16 communicate with each other, so that the second piston 5 is pushed back from the output shaft 21 side by the spring force and returns to its original position (FIGS. 3(e) and 3(d)). reference).

[0026] In the above embodiment, the third and fourth pistons were formed to have the same cross-sectional area as the second piston, but instead of this, the third and fourth pistons were formed to have the same cross-sectional area as the second piston. It may be formed to have a small cross-sectional area.

[0027]

[Effect of the invention] The piezoelectric actuator according to the present invention has the following features:
As a result of the elongation and displacement of the laminated piezoelectric body as described above, the chamber partitioned by the fourth and third pistons communicates with the chamber partitioned by the fourth and second pistons, and the second piston is further displaced. On the other hand, as a result of the laminated piezoelectric body being compressed and displaced from this state, the chamber partitioned by the fourth and third pistons and the chamber partitioned by the second and third pistons communicate with the reserve tank, and the second piston Since only the piston is maintained in a displaced state, by expanding and contracting the laminated piezoelectric body multiple times, a large displacement output can be obtained for the second piston.

[Brief explanation of the drawing]

FIG. 1 is an explanatory sectional view illustrating main parts of a piezoelectric actuator according to the present invention.

FIG. 2 is an explanatory diagram of the operation of the present piezoelectric actuator.

FIG. 3 is an explanatory diagram of the operation of the present piezoelectric actuator.

[Explanation of symbols]

2 First cylinder 3 Second cylinder 4 First piston 5 Second piston 7 Third piston 11,17 Connection route 12 Second oil chamber 14 3rd oil chamber 15, 18, 19 port 16 Reserve tank

Claims (1)

[Claims] Claim 1: A cylinder having a cylinder in which a first piston and a second piston having a smaller cross-sectional area are slidably disposed,
In the piezoelectric actuator that transmits displacement of the laminated piezoelectric body from the first piston to the second piston, the piezoelectric actuator is arranged so as to be slidable between the first and second pistons, and has the same cross-sectional area or the same cross-sectional area as the second piston. A third piston formed to have a smaller cross-sectional area than the second piston, and a third piston that is slidably disposed between the third and second pistons and has the same cross-sectional area as the second piston or is smaller than the second piston. a fourth piston formed to have a small cross-sectional area; a chamber partitioned by the fourth and third pistons when the fourth piston slides toward the second piston; and a chamber partitioned by the fourth and third pistons; a valve that communicates between a chamber partitioned by the fourth and third pistons and a reserve tank when the fourth piston slides toward the first piston; A piezoelectric actuator comprising a valve that communicates a chamber partitioned by the second and fourth pistons with a reserve tank when the third piston slides toward the first piston.