JPH0321105B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a piezoelectric bimorph device, and more particularly to a piezoelectric actuator that uses bending deformation of a piezoelectric bimorph element as a drive source for minute movements of various devices.

[Conventional technology]

The relationship between the deformation and force of a piezoelectric bimorph element under a constant input voltage condition is that the force decreases linearly as the deformation increases, and the force becomes 0 at the time of maximum deformation. Therefore, for example, if a piezoelectric relay is constructed in such a way that the force of the free end of a bimorph element is used to open and close an electrical contact, the force that closes the contact is extremely weak.
Operation is unstable and lacks practicality. Therefore, as an improvement measure, a method has been proposed in which the weak force of the bimorph element is compensated for by the attractive force of a permanent magnet at the time of maximum deformation.
In this case, stable operation of this system is impossible unless a certain balance is maintained between the attractive force of the permanent magnet, the generated force of the bimorph element, and the amount of deformation.

[Problem that the invention seeks to solve]

However, it is extremely difficult to adjust the force generated by each bimorph element without changing the voltage, and conventionally this type of adjustment has had the disadvantage of requiring extremely time and effort.

The present invention aims to eliminate such drawbacks, and aims to provide a piezoelectric bimorph device in which the operation of the piezoelectric bimorph element can be easily adjusted, and drive conditions can be easily adjusted.

[Means for solving problems]

The present invention has a configuration in which a permanent magnet is used to reinforce force during deformation of a piezoelectric bimorph element, and a rigid body is provided near the center of the piezoelectric bimorph element so as to be movable in a direction perpendicular to the surface of the bimorph element. The piezoelectric bimorph element is characterized in that it can be adjusted so that the tip of the rigid body touches the surface of the piezoelectric bimorph element at a slight distance when the element is deformed to its maximum and is attracted to the permanent magnet.

[Effect]

According to such a configuration, the operating conditions of the piezoelectric bimorph element can be adjusted by adjusting the constraint conditions that the permanent magnet exerts on the piezoelectric bimorph element by adjusting the position of the rigid body.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 shows the basic configuration of the present invention.

One end of the piezoelectric bimorph element 1 is clamped and fixed by a fixed support part 5, and a ferromagnetic piece 2 such as an iron piece is fixed to the free end. In addition, in the figure, a permanent magnet 3 is fixedly arranged at a position corresponding to the ferromagnetic piece 2 when the ferromagnetic piece 2 is maximally deformed downward. Thereby, when the bimorph element 1 is deformed, the weak force of the bimorph element 1 can be compensated for by the attractive force of the magnet 3. Further, a rigid rod 4 is disposed below the intermediate portion of the bimorph element 1 so as to be movable in a direction perpendicular to the plate surface of the bimorph element 1. This location is
The tip of the rigid body 4 is set to be in contact with the surface of the bimorph element 1 at a slightly distant position when the bimorph element 1 is deformed to the maximum as shown in the figure. With this configuration, the downward force at the point of action at the free end of the bimorph element 1 has a constant value even at this position because of the reinforcement of the permanent magnet 4. Next, when trying to bend the tip of the bimorph element 1 upward in the figure by reversing the voltage applied to the bimorph element 1, it is easy to bend the tip of the bimorph element 1 if the force generated by the bimorph element is sufficiently large compared to the attractive force of the permanent magnet. The tip of the bimorph element can escape the restraint of the permanent magnet and deform upward. However, if the generated force of the bimorph element is poor, the tip of the bimorph element remains restrained by the permanent magnet and cannot freely deform upward.

Figure 4a shows the case where the tip of the rod 4 is sufficiently separated from the surface of the bimorph element 1 and a voltage is applied to deform it in the direction of the arrow from the state of Figure 3, where the force generated by the bimorph element 1 is small. Since the tip of the bimorph element 1 remains attracted to the permanent magnet 3, the center of the bimorph element 1 swells downward, and the force at the tip becomes even smaller. FIG. 4b shows a case where the rod 4 is close to or in contact with the center of the bimorph element 1 and applies a constant pressure upward to the bimorph element 1. At this time, the fourth
The center cannot bulge downward as shown in Figure a, and the force at the tip does not decrease. Therefore, even if the difference between the force generated by the bimorph element 1 and the attraction force of the permanent magnet 3 is very small, the rod 4 can stop the downward bulge by simply approaching or touching the center of the bimorph element 1.
becomes able to separate from the restraint of the permanent magnet 3. If the difference between the force and the force of the permanent magnet 3 is even larger, the rod 4 contacts the center of the bimorph element 1 and applies pressure, thereby substantially weakening the restraining force of the permanent magnet 3. As a result, the tip of the bimorph element 1 can be easily separated from the permanent magnet 3 as shown in FIG.

FIG. 1 shows a specific example of a piezoelectric bimorph device according to the invention. Here, a case will be described in which the piezoelectric bimorph element 1 is used as a piezoelectric relay by opening and closing the contacts of the relay. The bimorph element 1 having the same configuration as that shown in FIG. 3 is housed in a case 9 made of resin.
The case 9 consists of a case body 91 and a lid 92. As shown in FIG. 2, the fixed end of the bimorph element 1 is connected to one end of the case body 91 and the lid 9.
It is fixed by being sandwiched between one end edge of 2. Two contacts 10a and 10b are provided on the other end wall of the case body 91.
is inserted, and the bimorph element 1 is arranged so as to open and close contacts 10a and 10b at its free end. Various electric circuits (not shown) are connected to the contacts 10 and 10b. The rod 4 is partially threaded and is screwed through a female screw hole formed in the lower wall of the case body 91, so that its position can be easily adjusted. Therefore, even if the force generated by the bimorph element is small, the driving conditions for the bimorph device can be easily and accurately adjusted.

Incidentally, the bimorph element is not limited to the one described in the embodiment, that is, the one in which an intermediate metal plate is sandwiched between two ceramic thin plates with electrodes formed on both the front and back sides. For example, as shown in FIG. 5, an intermediate metal plate 7 made of a ferromagnetic material may be sandwiched between two piezoelectric ceramic plates 6 having electrodes formed on both the front and back surfaces. According to this piezoelectric bimorph element, the ferromagnetic piece 2 of the above embodiment is unnecessary.

〔Effect of the invention〕

As described above, according to the present invention, in a configuration in which a permanent magnet is used to reinforce the force of a piezoelectric bimorph element during deformation, the balance between the attraction force of the permanent magnet and the generated force of the bimorph element can be easily adjusted. It has become possible to provide a bimorph device that can obtain stable operation even if the force generated by the bimorph element is small.

[Brief explanation of the drawing]

Fig. 1 shows an embodiment of the present invention in an exploded perspective view, Fig. 2 is a vertical sectional view of the device shown in Fig. 1, Fig. 3 is a diagram showing the basic configuration of the invention, and Figs. 4 a and b. , c are views for explaining the operation of the configuration shown in FIG. 3, and FIG. 5 is an exploded perspective view of another example of the bimorph element used in the present invention. In the figure, 1 is a piezoelectric bimorph element, 2 is a ferromagnetic piece, 3 is a permanent magnet, 4 is a rigid rod, 5 is a fixed support, 6 is a ceramic thin plate, 7 is an intermediate metal plate,
9 is a case, and 10a and 10b are contacts.

Claims (1)

[Claims] 1. A configuration in which a ferromagnetic material is provided in the piezoelectric bimorph element, a permanent magnet is disposed near the ferromagnetic material, and the attractive force of the permanent magnet is used as force reinforcement when the piezoelectric bimorph element is deformed, A rigid body is provided near the center of the piezoelectric bimorph element so as to be movable in a direction perpendicular to the surface of the piezoelectric bimorph element, and when the piezoelectric bimorph element is deformed to the maximum and is attracted to the permanent magnet, A piezoelectric bimorph device, characterized in that the driving conditions of the piezoelectric bimorph element can be adjusted by adjusting the tip of the rigid body so that it is in contact with the surface or slightly separated from the surface.