JP2926947B2 - Piezoelectric actuator and optical switch device using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a piezoelectric actuator capable of high-speed and high-precision displacement and an optical switch device using the actuator, and capable of suppressing vibration of a piezoelectric plate and operating at high speed and high accuracy. In addition to obtaining a simple actuator and realizing an optical switch using this actuator, the length of the piezoelectric plate is 1, the distance from the tip of the piezoelectric plate to the mounting position of the stopper is x, When the diameter is a, the stopper is attached at a position of a / 2 or more and x / l <0.2 from the front end of the piezoelectric plate with respect to the center thereof.

[Industrial applications]

The present invention relates to a piezoelectric actuator capable of high-speed and high-precision displacement, and an optical switch device using the actuator.

In recent years, actuators that can obtain high-speed and high-precision displacement have been desired especially for application to optical switch devices in optical transmission systems such as optical LANs.

In particular, for application to an optical switch, an actuator having a speed of about 10 ms and an accuracy of about ± 1 μm is required.

[Conventional technology]

2. Description of the Related Art Conventionally, a piezoelectric actuator using a bending displacement of a piezoelectric plate that changes according to an applied voltage has been used.

There is a piezoelectric actuator provided with stoppers on both sides of the piezoelectric plate in order to suppress free vibration generated when the piezoelectric plate operates.

In an optical switch using the actuator, a primary optical fiber is installed on the piezoelectric plate, and a plurality of secondary optical fibers are installed on the optical switch device body. The optical switch applies a voltage to the piezoelectric plate to cause a bending displacement to move the primary optical fiber. The switching operation is performed by aligning the optical axis with one of the secondary side optical fibers.

[Problems to be Solved by the Invention] However, when an attempt is made to operate the piezoelectric actuator provided with the stopper at high speed, the free vibration can be suppressed. However, when the piezoelectric plate collides with the stopper, the secondary vibration is reduced. Chattering vibration such as resonance occurred. The chattering vibration cannot be suppressed by the stopper, so that the actuator must be operated at a low speed.

To achieve high speed and high accuracy, within 20 ms, preferably
An operation with a speed of 10 ms or less and an accuracy of about ± 1 μm is required, and for that purpose, vibration must be suppressed.

Therefore, an object of the present invention is to obtain an actuator that can operate at high speed and high accuracy by suppressing vibration of a piezoelectric plate, and to realize an optical switch using the actuator.

[Means for solving the problem]

 FIG. 1 is a diagram illustrating the principle of the present invention.

When a voltage is applied to the electrodes 5 provided on both sides of the piezoelectric plate 1, bending displacement occurs in the piezoelectric plate 1.

In the present invention, the stoppers 2 are provided on both sides of the piezoelectric plate 1, the length of the piezoelectric plate 1 is l, the distance from the tip of the piezoelectric plate 1 to the position where the stopper 2 is provided is x, and the diameter of the stopper is a. In this case, the stopper 2 is provided at a position where a / 2 or more and x / l <0.2 from the tip of the piezoelectric plate 1 with respect to the center of the stopper 2 as a reference.

[Action]

A voltage is applied to the electrode 5 provided on the piezoelectric plate 1, and the piezoelectric plate 1 undergoes bending displacement. At this time, free time is generated in the piezoelectric plate 1 and a certain time is required until the piezoelectric plate 1 stops. However, the piezoelectric plate 1 has a stopper 2 provided at a position opposed to both side surfaces thereof. The free vibration can be suppressed by causing a collision. Here, the stopper mounting position is at least a / 2 from the tip of the piezoelectric plate 1 and x / l <
By setting the value to 0.2, the vibration suppression time can be significantly reduced.

〔Example〕

FIG. 2 shows an embodiment according to the present invention. In FIG. 2, 1 is a bimorph, 2 is a stopper, 3 is a load mass, 4 is a fixed base, 5 is an electrode, and 6 is a terminal. Hereinafter, description will be made with reference to FIG.

FIG. 2 shows a piezoelectric actuator using a piezoelectric bimorph made of lead zirconate titanate (PZT) as a piezoelectric plate. One end of the bimorph 1 is fixed by a fixing base 4. Gold is deposited on the surface of the bimorph 1, and this gold is used as the electrode 5. When a voltage is applied to the electrode 5, a bending displacement occurs in the bimorph 1 accordingly.

A stopper 2 is provided at a position facing both side surfaces of the bimorph 1. The stopper has a function of determining the position of the bimorph 1 and suppressing vibration of the bimorph 1.

Epoxy resin is applied to the tip of the stopper 2. This is to take insulation from the electrode 5 on the surface of the bimorph 1.

Further, the stopper 2 applies a load to the bimorph 1. The stopper 2 is mounted 20 to 30 μm inside the position where the bimorph 1 should be. That is,
The bimorph 1 is not just in contact with the stopper 2 but in the same state as being pressed inward by 20 to 30 μm. This is equivalent to about 100 mg when converted to power.
By applying the load, the influence of external vibration applied to the bimorph 1 can be eliminated.

A load mass 3 is provided on the upper part of the bimorph 1.
The load mass 3 is desirably made of a material having an insulating property because the electrode 5 is provided on the surface of the bimorph 1.

The relationship between the time from the voltage application and the vibration of the bimorph 1 is examined. FIG. 3 is a graph showing the relationship between the time from voltage application and the vibration of the bimorph 1. 3A shows the case where the stopper 2 and the load mass 3 are not provided, FIG. 3B shows the case where only the stopper 2 is provided, and FIG.
The graphs in the case where both are present are shown. At this time, the bimorph length is 29 mm, and the stopper position is provided at 3 mm from the bimorph tip. If the length of the bimorph 1 is 1 and the distance from the tip of the bimorph 1 to the stopper mounting position is x, x / l in this case is approximately 0.1.
Here, the mounting position of the stopper 2 is determined based on the center of the stopper 2. This is the same in the following.

Comparing FIG. 3A and FIG. 3B, it can be seen that FIG. 3B, that is, the one provided with the stopper 2 has a shorter time required for vibration damping. This is because the free vibration of the bimorph 1 is suppressed by the stopper 2 of the bimorph 1. The load applied to the bimorph 1 by the stopper 2 also contributes to suppressing vibration. However, since there is chattering vibration generated when the bimorph 1 and the stopper 2 collide, the time until the stop is still long.

Next, FIG. 3C will be compared with the aforementioned FIGS. 3A and 3B. In this case, it can be seen that in the case of FIG. 3C in which the stopper 2 and the load mass 3 are provided, the vibration of the bimorph 1 is attenuated much faster than the other two. That is,
This shows that the load mass 3 has an effect of absorbing chattering vibration. At this time, the stopper 2 applies a preliminary load to the piezoelectric plate 1, and this load has an effect of suppressing vibration more effectively.

Subsequently, the relationship between the length of the bimorph 1 and the distance x from the tip of the bimorph 1 to the mounting position of the stopper 2 as x / l, ie, the mounting position of the stopper, and the vibration damping time are examined. Was. FIG. 4 is a graph showing the measurement results. In FIG. 4, the horizontal axis represents x / l, and the vertical axis represents the vibration decay time. The broken line shows the measurement results when the load mass 3 is not provided, and the solid line shows the measurement results when the load mass 3 is provided at 20 mg. Length of bimorph 1
= 30 mm, width t = 0.2 mm, and width 5 mm.

When the shape of the bimorph 1 is as described above, as shown in FIG. 4, when the load mass 3 is present and when it is not present, the x / l is smaller, that is, the stopper 2 is provided near the tip of the bimorph piezoelectric plate 1. The vibration damping time becomes exponentially shorter as the distance is set. Comparing the case where x / l is 0.2 or more and the case where x / l is less than 0.2, it is understood that the case where the value of x / l is less than 0.2 has a shorter vibration damping time. Therefore, if the mounting position of the stopper 2 is set in the range of x / l <0.2, the effect of reducing the vibration damping time can be obtained.

At this time, the stopper 2 is just the tip of the bimorph 1,
That is, x / l = 0 may be used. It is conceivable that the tip of the bimorph 1 may be damaged by the collision of the stopper 2, but this problem can be solved by providing a cover for protecting the tip of the bimorph 1 with, for example, a metal piece. However, there may be a case where an error such as a dimension occurs, and the stopper 2 does not completely collide and the vibration is not suppressed. Therefore, it is desirable that the entire surface of the stopper 2 completely collides with the bimorph 1. For this reason, when the diameter of the stopper 2 is a, a good effect can be obtained by setting the lower limit of the stopper mounting position to a / 2 from the tip of the bimorph 1. Using specific numerical values, when the diameter of the stopper 2 is 1 mm, the lower limit of the stopper mounting position is 0.5 mm from the tip of the bimorph 1.

Also, comparing the case where the load mass is provided and the case where the load mass is not provided, even in this case, the vibration of the bimorph 1 can be more effectively attenuated when the load mass is provided in the bimorph 1.

The relationship between the mounting position of the stopper 2 and the vibration decay time when the length, thickness, etc. of the bimorph 1 is changed is shown in FIG. Shows almost the same tendency. As an example, when l = 25mm, t = 0.2mm, width 5mm, and load mass 20mg, the damping vibration time is 13ms when x / l = 0.3, and the vibration damping time is 40ms when x / l = 0.5. The curve of the vibration decay time shows the same change as in FIG. The graph is shown in FIG.

In other cases, l = 20mm, t = 0.2mm, width 5mm, load mass 20
In the case of mg, a curve similar to that of FIG. Similarly, l = 20 mm, t = 0.
3mm, width 5mm, load mass 20mg, x / l = 0.2, vibration damping time 4ms, l = 40mm, t = 0.2mm, load mass 20mg, x / l = 0.2, vibration damping time 22ms, l = 40mm, t = 0.
In the case of 3 mm, width of 5 mm, and load mass of 20 mg, the vibration damping time is 19 ms at x / l = 0.2, and each draws the same curve as FIG. These curves are also shown in the graph of FIG.

Therefore, the vibration damping time of the bimorph 1 can be reduced most effectively by setting the mounting position of the stopper 2 at a / 2 or more and x / l <0.2 from the tip of the bimorph 1 with respect to the center thereof. You can do it.

The size of the bimorph 1 is 20 to
It is desirable to be in the range of 40 mm. If l is 20 mm or less, the voltage for operating the bimorph 1 must be increased, and if l is 40 mm or more, it is too large. Further, the thickness t is desirably in the range of 0.2 to 0.3 mm. If it is 0.3 mm or more, a large operating voltage is required, and if it is 0.2 mm or less, it becomes unstable and weak against external vibration.

FIG. 6 shows an optical switch device to which the piezoelectric actuator according to the present invention is applied. FIG. 7 is a three-view drawing of the optical switch device according to the present embodiment. FIG. 8 is an enlarged view of a mounting portion of the optical fibers 7, 8, and 9. 6 to 8, 1 is a bimorph, 2, 2 'are stoppers, 3
Is a load mass, 4 is a fixed base, 5 is an electrode, 6 is a terminal, 7 is a first optical fiber, 8 is a second optical fiber, 9 is a third optical fiber, and 10 and 11 are optical switch device bodies. A cover 12 is an optical switch body, 13 is a first fiber guide, and 14 is a second fiber guide. In FIG. 6, one cover 11 is omitted for easy viewing. Hereinafter, description will be made with reference to FIGS.

One end of the bimorph 1 is fixed by a fixing base 4. A first fiber guide having a load mass 3 made of silicon and a V-shaped groove 15 is provided above the bimorph 1.
13 are installed. V of the first fiber guide 13
The first optical fiber 7 is installed in the groove 15. The stoppers 2 and 2 'are provided on the covers 10 and 11, respectively.

When a voltage is applied to the electrode 5 and the bimorph 1 operates, the first optical fiber 7 is directly moved. The optical switch body 11 also has a second fiber guide 14 having V-shaped grooves 16 and 17, and the V-groove 1 of the second fiber guide 14 is provided.
The second and third optical fibers 8 and 9 are installed in 6, 17 respectively.

Normally, the first optical fiber 7 is arranged so that the optical axis coincides with the second optical fiber 8. When a voltage is applied to the electrode 5 and the bimorph 1 operates, the first optical fiber 7 installed on the bimorph 1 moves, and the light between the first optical fiber 7 and the third optical fiber 9 is changed. They are arranged so that their axes coincide. As described above, by moving the first optical fiber 7 by the bending displacement of the bimorph 1, the optical path is changed and switching is performed.

The stoppers 2, 2 'are provided on the covers 10, 11 of the switch body. Needless to say, the stopper mounting position is at least a / 2 from the tip of the bimorph 1 and x / l <0.2. Epoxy resin is applied to the tips of the stoppers 2, 2 '. This is to obtain electrical insulation with the bimorph 1. The distance between stoppers 2 and 2 'is 170-200
μm.

Also in the present optical switch device, the stoppers 2, 2 'are attached to the inside of the stop device of the bimorph 1 by about 20 to 30 [mu] m, and a load is applied to the bimorph 1. Thanks to this load, even if external vibration is applied to the switch body, it is possible to eliminate the influence on the device.

By adopting such a configuration, high-speed operation of about 10 ms can be performed, and positioning of the fiber can be performed with high accuracy of about ± 1 μm due to little vibration. Further, since a load is applied to the bimorph 1 by the stoppers 2 and 2 ', the influence of external vibration can be eliminated.

(Other Embodiments) (1) FIG. 9 shows an optical switch device having a plurality of optical fibers on a bimorph 1. In FIG.
Reference numerals 18, 19, 20, 21, and 22 denote optical fibers, 23 denotes a first fiber guide, and 24 denotes a second fiber guide. The same parts as those in the other drawings are denoted by the same reference numerals. FIG. 10 shows an arrangement state of optical fibers and an optical path of the optical switch device according to FIG.

The first fiber guide 23 is provided above the bimorph 1. On the other hand, the second fiber guide 24 is provided in the optical switch device main body 12. First fiber guide 23
Are provided with three V-shaped grooves 25, 26, and 27, and similarly, the second fiber guide 24 is also provided with three V-shaped grooves 28, 29, and 30. A load mass 3 for absorbing chattering vibration is provided above the bimorph 1.
The switch body cover 10 is provided with a stopper 2. The stopper 2 is according to the present invention, and its mounting position is a / 2 or more and x / l <0.2. In FIG. 10, the main body cover 11 is omitted for easy viewing, but the stopper 2 is also provided on the main body cover 11 similarly to the optical switch device shown in FIG. 'Is provided.

The V-shaped grooves 25, 26, and 27 are provided with one end of an optical fiber 18, an optical fiber 19, and an optical fiber 20 on the primary side, respectively. The other ends of the secondary side optical fiber 20, the optical fiber 21, and the optical fiber 22 are provided in the V-shaped grooves 28, 29, and 30, respectively. The optical fiber 21 and the optical fiber 22 input an optical signal to the present optical switch device, and the optical fiber 18 and the optical fiber 19 output an optical signal from the present optical switch device.

The cross sections of the respective optical fibers are arranged so as to face each other. The installation condition of the optical fiber
10 Shown in FIGS. FIG. 10A shows the arrangement of the optical fibers and the state of the optical path when a voltage is applied to the bimorph 1.
FIG. 10B shows the arrangement of the optical fibers and the state of the optical path when no voltage is applied to the bimorph 1. In each figure, (a) shows an arrangement of optical fibers, and (b) shows an optical path. The reference numerals attached to (b) represent the optical fibers of the respective numbers.

The arrangement of the optical fibers shown in FIGS. 10A and B will be described. The primary optical fiber is installed at 31 and the secondary optical fiber is installed at 32.
In this case, the optical fibers 19 and 21 extend from the 31 side, and the optical fibers 18 and 22 extend from the 32 side. One end of the optical fiber 20 is a first fiber guide.
At 23, the other end is connected to a second fiber guide 24 to serve as a bypass.

When a voltage is applied to the bimorph 1, the optical fiber
18 and optical fiber 21, and optical fiber 19 and optical fiber 22
Have the same optical axis. When no voltage is applied to the bimorph 1, one end of the optical fiber 18 and the optical fiber 20 on the second fiber guide 24 side, the optical fiber
The optical axis of the optical fiber 22 coincides with one end of the optical fiber 19, the optical fiber 21, and one end of the optical fiber 20 on the first fiber guide 23 side.

By such an operation, the optical path changes as shown in FIGS. 10A and 10B. When a voltage is applied, light input from the side 31 through the optical fiber 21 is
The light output to the side and input from the 32 side through the optical fiber 22 is output to the 31 side through the optical fiber 19.

When the bimorph 1 does not operate, the light input from the 31 through the optical fiber 21 is output to the 31 again through the optical fiber 19. On the other hand, light input from the 32 through the optical fiber 22 enters one end of the optical fiber 20 on the first fiber guide 23 side, enters the optical fiber 18 from one end of the optical fiber 20 on the second fiber guide 24 side, and again. Output to the 32 side.

Even when the piezoelectric actuator according to the present invention is used for an optical switch device that performs such an operation, vibration generated when the bimorph 1 operates and chattering vibration generated when the bimorph 1 collides with the stoppers 2 and 2 ′ are reduced. It is possible to suppress. Therefore, it is possible to simultaneously change a plurality of optical paths with high speed and high accuracy.

The number and arrangement method of the optical fibers are not limited to the contents described in the present embodiment.

(2) When a piezoelectric bimorph in which the metal plate 33 shown in FIG. 11A is sandwiched by a plurality of ceramics 34 and 35 is used, the occurrence of hysteresis shown in FIG. 11B becomes a problem. Due to this hysteresis, high-precision positioning is difficult.

The piezoelectric plate using the domain-inverted lithium niobate (LiNbO ₃ ) 36 shown in FIG. 12A has no hysteresis.
Therefore, it is very convenient for an actuator used for a device requiring high accuracy such as an optical switch. By using this LiNbO ₃ , the actuator of the present invention can position the fiber with higher accuracy.

〔The invention's effect〕

As described above, when the present invention is used, the vibration of the piezoelectric plate is suppressed, and a piezoelectric actuator that can operate at higher speed and higher accuracy than before can be realized, and an optical switch that can perform high-speed switching is also realized. It becomes possible.

[Brief description of the drawings]

1 is a diagram illustrating the principle of the present invention, FIG. 2 is an embodiment according to the present invention, FIG. 3A is vibration of a piezoelectric plate when there is no stopper / load mass, and FIG. 3B is when only a stopper is provided. FIG. 3C shows the vibration of the piezoelectric plate when both the stopper and the load mass are provided, and FIG. 4 shows the change in the vibration decay time of the piezoelectric plate of the present embodiment when the stopper mounting position is changed. FIG. 5 is a diagram showing a change in vibration decay time of piezoelectric plates having different dimensions when the stopper mounting position is changed, FIG. 6 is a perspective view of an optical switch device using a piezoelectric actuator according to one embodiment, and FIG. FIG. 8 is a perspective view of an optical switch device using a piezoelectric actuator according to one embodiment, FIG. 8 is a mounting portion of an optical fiber in the optical switch device, FIG. 9 is an optical switch device according to another embodiment, and FIG. Voltage is applied FIG. 10B shows the arrangement of the optical fibers and the state of the optical path when no voltage is applied to the bimorph, FIG. 11A shows the ceramic piezoelectric plate, and FIG. FIG. 12A shows the voltage-displacement characteristics of the plate, and FIG. 12A shows the voltage-displacement characteristics of the lithium niobate piezoelectric plate. In all the drawings, the same parts are denoted by the same reference numerals. In the figure, 1 is a piezoelectric plate, 2 is a stopper, 3 is a load mass, 5 is an electrode, 7, 8, and 9 are optical fibers.

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noboru Wakatsuki 1015 Ueodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Within Fujitsu Limited (58) Field surveyed (Int. Cl. ⁶ , DB name) H01L 41/00- 41/26

Claims (5)

(57) [Claims] 1. A piezoelectric plate (1) that generates a bending displacement in accordance with an applied voltage, and positions the piezoelectric plate (1), and suppresses free vibration generated during operation of the piezoelectric plate (1). And a stopper (2) provided at a position facing both side surfaces of the piezoelectric plate (1), wherein the length of the piezoelectric plate (1) is 1 and the length of the piezoelectric plate (1) is from the tip of the piezoelectric plate (1). The distance to the mounting position of the stopper (2) is x,
When the diameter of the stopper is a, the stopper (2) is attached at a position of a / 2 or more and x / l <0.2 from the tip of the piezoelectric plate (1) with respect to the center thereof. A piezoelectric actuator. 2. A load mass (3) installed on the piezoelectric plate (1) for suppressing chattering vibration generated when the piezoelectric plate (1) collides with the stopper (2). The piezoelectric actuator according to claim 1. 3. The piezoelectric actuator according to claim 1, wherein the piezoelectric plate is made of domain-inverted lithium niobate. 4. A first fiber guide (13) provided on the piezoelectric plate (1), a first optical fiber (7) installed on the first fiber guide (13), A second fiber guide (14) provided on the switch device main body (12); and a second fiber guide (14) on the second fiber guide (14), facing the first fiber (6). 4. An optical switch device using a piezoelectric actuator according to claim 1, comprising a plurality of optical fibers (8, 9) provided so as to have the same optical axis as the optical fiber (6). . 5. The first fiber guide (13) has a plurality of primary optical fibers (18, 19, 20), and the primary optical fibers (18, 19, 20) are second fibers. A plurality of secondary optical fibers (2
0,21,22) and the secondary side optical fiber (20,21,2).
The piezoelectric plate (1) is disposed so as to have the same optical axis as each of 2), and the primary side optical fiber (18, 19, 20)
5. The optical switch device according to claim 4, wherein the switching of a plurality of optical paths is performed simultaneously by driving the optical switch.