JPH0453009Y2 - - Google Patents

Description

[Detailed description of the invention] <Industrial field of application> The invention is designed to bend in one direction when voltage is applied, and is used as a drive source for various devices such as dot printers, parts feeders, and polarizing mirrors for laser beams. The present invention relates to a piezoelectric drive body using a piezoelectric laminate.

<Prior art> A piezoelectric actuator that uses one or two piezoelectric elements and applies voltage to electrode layers formed on the upper and lower surfaces of the piezoelectric element to cause a bending action at its free end is called a unimorph or bimorph. , is publicly known.

Such a piezoelectric driver is used in a cantilever supported or both end supported format, and the amount of displacement varies greatly depending on the polarization direction of the piezoelectric element.

In other words, in the case of a piezoelectric driver using a piezoelectric element polarized in the thickness direction, in the case of cantilever support, the displacement amount δ of the free end is the free length l, the total thickness t, the applied voltage V, and the piezoelectric constant d ₃₁ When, δ=3/2(l/t) ²・V・d ₃₁

In addition, in the previous equation, the displacement of a piezoelectric driver using a piezoelectric element polarized in the length direction is determined by the piezoelectric constant
It is sufficient to change d ₃₁ to a piezoelectric constant d ₃₃ , which is expressed as δ=3/2(l/t) ² ·V·d ₃₃ .

By the way, this piezoelectric constant d ₃₃ is 2 of the piezoelectric constant d ₃₁
~3 times the value. From this, it is understood that a piezoelectric drive body with a larger displacement can be obtained by using a piezoelectric element polarized in the length direction.

Therefore, in order to increase the amplitude by using the mode of piezoelectric constant d ₃₃ , multiple piezoelectric layers are laminated via internal electrodes with their polarization directions alternately different, and each internal electrode is placed on both sides of the piezoelectric layer. Piezoelectric lamination is performed by forming external electrodes that are electrically connected alternately to the electrodes, applying voltage from the external electrodes in parallel to each piezoelectric layer between the internal electrodes, and matching the direction of expansion and contraction with the direction of polarization. A piezoelectric drive body has been proposed in which the piezoelectric laminate is arranged on one or both sides of a support plate.

<Problems to be solved by the invention> By the way, in such a configuration, when a voltage is applied to the piezoelectric layer to cause the laminate to expand and contract, the external electrodes do not have elasticity, so they hinder the expansion and contraction of the laminate. acts as a resistance to

In addition, the external electrodes must be electrically connected alternately to each internal electrode, so only one end of the internal electrodes is exposed alternately to the side surface of the laminate so that the required internal electrodes are connected to the external electrodes. Otherwise, it is necessary to bulge the external electrode at the end of the unnecessary internal electrode to maintain non-contact, which causes various difficulties in molding.

The object of the present invention is to provide a piezoelectric drive body that does not have the above-mentioned conventional drawbacks.

<Means for Solving the Problems> The present invention includes a piezoelectric laminate formed by laminating a plurality of piezoelectric layers with internal electrodes interposed therebetween while alternating their polarization directions, and the internal electrodes on both sides. The device is characterized by comprising an insulating support plate formed with external electrodes that are alternately electrically contacted.

<Function> The external electrode was removed from the piezoelectric laminate that expands and contracts, and was formed on the support plate side. Therefore, the resistance to the stretching force due to the external electrodes is removed.

<Example> A first example of the present invention will be described with reference to FIGS. 1 and 2.

A is a piezoelectric drive body with a unimorph structure in which a piezoelectric laminate 1 of the same shape is adhered to an insulating support plate 2 made of a high-strength ceramic plate such as alumina, partially stabilized zirconia, or phosphorus oxide. show.

Here, the piezoelectric laminate 1 has a plurality of internal electrodes 6a and 6b disposed across a rectangular piezoelectric ceramic base material 5 made of lead zirconate titanate, etc.
A piezoelectric layer 7 is formed between a and 6b. This base material 5 and internal electrodes 6a, 6b are integrally fired. Therefore, for the internal electrodes 6a and 6b, materials that can be fired integrally with the piezoelectric ceramic base material 5 are selected, such as silver-palladium alloy, molybdenum, etc. whose melting point is higher than the firing temperature.
Manganese, platinum, etc. may be provided.

External electrodes 1 are provided on both sides of the support plate 2.
0a and 10b are formed. External electrode 10a, 1
0b, the exposed end of the internal electrode 6a is the external electrode 10a.
The exposed end of the internal electrode 6b is connected to the external electrode 1.
0b, and in order to enable this alternating connection, connection lengths 1 are provided on the external electrodes 10a and 10b and extend to the internal electrodes 6a and 6b every other time.
1 is formed into a comb-teeth shape. The connection fee 11
are extended to both upper surfaces of the support plate 2 in order to ensure the connection, and the extensions are connected to the connection end 12.
In addition, connection ends 13 are formed on the lower surfaces of required ends of the internal electrodes 6a and 6b to electrically connect with the internal electrodes 6a and 6b, and the connections are made when the piezoelectric laminate 1 and the support plate 2 are joined. The end 12 and the connecting end 13 are brought into surface contact.

Thereby, the electrodes 6a, 10a, the electrodes 6b,
It is electrically connected to 10b. Required lead wires 14, 14 are connected to the external electrodes 10a, 10b at optimal positions, and by applying a DC voltage, the piezoelectric layer 7 is polarized alternately in different directions. .

Furthermore, after this polarization, the electrodes 6a, 10a
By applying a required alternating voltage to the piezoelectric layer 7 via the electrodes 6b and 10b, the piezoelectric driving body A is caused to expand and contract.

In FIG. 3, a bimorph type piezoelectric drive body B is constructed using two piezoelectric laminates 20a and 20b.

In this case, the support plate 2 made of a ceramic plate
1a, 21b are interposed in piezoelectric laminates 20a, 20b, and external electrodes 23a, 23b, 2 are provided on both sides of each.
4a and 24b are formed. This external electrode 23a,
23b and the external electrodes 24a, 24b are in a bonded state and are not in contact with each other.

And external electrodes 23a, 23b of support plate 21a
are the internal electrodes 22a, 22b of the piezoelectric laminate 20a.
A connection gap 25 is formed which is alternately connected to the connection gap 25. Similarly, the external electrodes 24a and 24b of the support plate 21b are
Connection margins 27 are formed to alternately connect to the internal electrodes 26a and 26b of the piezoelectric laminate 20b.

In the above configuration, the upper and lower piezoelectric laminates 20a,
By applying a circuit configuration with different expansion and contraction timings to the external electrodes 20b, an alternating voltage of a predetermined frequency is applied to the external electrodes 23a, 23b, 24a, 24.
b, each piezoelectric laminate 20a, 20b expands and contracts at opposite timings corresponding to the frequency.
This results in bending vibration toward the extension side.

Therefore, the piezoelectric actuators A and B are most suitable for use as a drive source that requires large torque, such as dot printers, feeders, polarizing mirrors for laser beams, magnetic heads for VTRs, fine movement control devices, and the like.

<Effects of the Invention> As described above, in the present invention, when constructing a piezoelectric laminate that expands and contracts in a mode with a piezoelectric constant d ₃₃ , the external electrode is removed from the piezoelectric laminate and formed on the support plate side. Therefore, the resistance caused by the external electrodes to the expansion and contraction of the piezoelectric laminate is removed, the piezoelectric laminate can be expanded and contracted efficiently, and the driving force is improved. In addition, one end of the internal electrodes may be exposed alternately on the side surface of the laminate so that only the required internal electrodes are connected to the external electrode, or the external electrode may be bulged at the end of the internal electrode other than the required internal electrode. This eliminates the need for configurations such as maintaining contact, and has the advantage of facilitating manufacturing.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view of a unimorph piezoelectric driver A of the present invention, FIG. 2 is a side view, and FIG. 3 is a perspective view of a bimorph piezoelectric driver B of the present invention. A, B...Piezoelectric drive body, 1...Piezoelectric laminate, 2
... Support plate, 6a, 6b ... Internal electrode, 7 ... Piezoelectric layer, 10a, 10b ... External electrode, 11 ... Connection allowance, 12 ... Connection end, 13 ... Connection end, 20
a, 20b...piezoelectric laminate, 22a, 22b...
Internal electrodes, 23a, 23b, 24a, 24b...
External electrodes, 25a, 25b...Connection cost.

Claims (1)

[Scope of utility model registration request] An insulating piezoelectric laminate consisting of a plurality of piezoelectric layers laminated via internal electrodes while alternating their polarization directions, and external electrodes formed on both sides to be electrically connected alternately to the internal electrodes. A piezoelectric drive body comprising a support plate.