JPH0373359A - Piezoelectric type actuator - Google Patents

Abstract

PURPOSE:To lengthen the lifetime of an actuator owing to the acquisition of a positive moistureproof effect by lowering the humidity of the periphery of a piezoelectric element. CONSTITUTION:A heating element 11 is installed near a piezoelectric element 2, and supplied with currents by electric wires 12 from a power supply. The heating element 11 is supplied with currents for a fixed time through the electric wires 12 after the power supply is turned ON, and the heating element 11 is heat-generated. Accordingly, since the humidity of the periphery of the piezoelectric element 2 is lowered, the element is not damaged even when a piezoelectric type actuator is operated subsequently, thus lengthening the lifetime of the actuator.

Description

[Detailed Description of the Invention] [Summary] Regarding piezoelectric actuators applied to print heads, etc., the purpose of this invention is to prevent damage to the piezoelectric element due to humidity and extend the life of the actuator. In the piezoelectric actuator used as a piezoelectric actuator, a heating element is provided near the piezoelectric element, or
In the piezoelectric actuator, the piezoelectric element is configured to perform a developing thermal operation for a certain period of time at a predetermined time.

[Industrial application field]

The present invention relates to a piezoelectric actuator applied to print heads and the like.

In recent years, piezoelectric elements have begun to be used as wire drive units in print heads for wire dot printers because of their good high frequency response and low power consumption.

[Conventional technology]

Figure 2 is a side view of a conventional piezoelectric actuator.
In the figure, 1 is a beam and 2 is a piezoelectric element.

The beam 1 is supported by a frame 3 via a leaf spring 4.

The piezoelectric element 2 has a base fixed to the frame 3 and an upper end connected to the vicinity of the base of the beam l. Reference numeral 5 denotes an electric wire that supplies a driving voltage to the piezoelectric element 2.

The piezoelectric actuator having such a configuration operates as follows.

When a voltage is applied to the piezoelectric element 2, the charged piezoelectric element 2 is displaced, and the upper end of the piezoelectric element 2 moves upward by a predetermined amount, causing the beam 1 to move counterclockwise against the force of the leaf spring 4. (direction of arrow). When this piezoelectric actuator is applied to a print head, the print head is constructed by attaching a print wire 6 to the tip of the beam 1, and printing is performed by the print wire 6 when the beam 1 rotates. In this case, the printing wire 6 is given an enlarged displacement to obtain the necessary printing stroke.

Then, at a predetermined time (in the case of a print head, just before printing is completed)
When the voltage application to the piezoelectric element 2 is stopped, the piezoelectric element 2 starts discharging, and the beam 1, which is biased clockwise by the leaf spring 4, returns to its original position as the piezoelectric element 2 returns after completing its discharge. to return to.

In this case, the piezoelectric element 2 is quickly displaced and returned, so if this mechanism is applied to a print head, it is possible to increase the printing speed.

[Problem to be solved by the invention]

When using a piezoelectric actuator having such a configuration 2 effect, attention must be paid to the environment in which it is used. Piezoelectric elements are sensitive to moisture and will be damaged if operated in a humid environment. Therefore, as shown in FIG. 2, a method has been adopted in which the piezoelectric element 2 is coated with a coating 7 made of epoxy resin or the like that does not allow moisture to pass through.

However, this alone is insufficient to insulate the piezoelectric element from moisture, and improvements are required.

The present invention aims to extend the life of an actuator by preventing damage to a piezoelectric element due to humidity.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention provides a piezoelectric actuator using a piezoelectric element as a driving part, in which a heating element is provided near the piezoelectric element.

Further, the above object can also be achieved by configuring a piezoelectric actuator using a piezoelectric element as a drive unit such that the piezoelectric element is caused to perform a thermal operation for a certain period of time at a predetermined time.

[Operation] The operation of this piezoelectric actuator is the same as that of the conventional piezoelectric actuator described above, so a description thereof will be omitted.

In the case of the former configuration (a heating element is provided near the piezoelectric element), the heating element is heated for a certain period of time after the power is turned on, for example.

This reduces the humidity around the element and then activates the actuator.

Furthermore, in the case of the latter configuration, the piezoelectric element is caused to perform the thermal operation for a certain period of time at a predetermined time such as after power is turned on.

This reduces the humidity around the element and then activates the actuator. In this case, the AC voltage applied to the piezoelectric element is desirably at a frequency of about 1000 Hz, and the element will not be damaged at this level.

In either case, element damage due to humidity can be prevented and the life of the actuator can be extended.

〔Example〕

The invention will now be described in detail with reference to FIG.

Figure 1 is a side view showing the piezoelectric actuator of this example.
In the figure, 11 is a heating element. Note that the same reference numerals are given to the same members as in the conventional one.

The heating element 11 is provided near the piezoelectric element 2, and is supplied with current from a power source (not shown) through an electric wire 12.

For example, after the power is turned on, a constant open current is supplied to the heating element 11 through the electric wire 12 to cause the heating element 11 to generate heat. This reduces the humidity around the piezoelectric element 2, so that even if the piezoelectric actuator is operated thereafter, the element will not be damaged, and the life of the actuator can be extended. The operating principle of the piezoelectric actuator is the same as that of the conventional piezoelectric actuator described above, so a description thereof will be omitted.

Although FIG. 1 shows an example in which the periphery of the piezoelectric element 2 is covered with the film 7, the above effect can be obtained regardless of the presence or absence of such a covering. However, by using the coating 7 and the heating element 11 in combination, the moisture-proofing effect becomes more reliable.

Further, the heating element may be attached at any position as long as it is near the piezoelectric element 2, and it goes without saying that it may be wound around the piezoelectric element 2.

In the above description, an example was described in which a heating element separate from the piezoelectric element is provided, but the heating element may be the piezoelectric element itself. In this case, the piezoelectric element 2 is caused to perform a developing thermal operation for a certain period of time at a predetermined time such as after power is turned on, but the applied alternating current voltage is set at a frequency of about 1000 Hz, which will not damage the element itself. In this case as well, effects similar to those described above can be obtained.

[Effects of the Invention] As described above, according to the present invention, by lowering the humidity around the piezoelectric element, a reliable moisture-proofing effect can be obtained, so that the life of the actuator can be extended. It becomes possible.

[Brief explanation of drawings]

FIG. 1 is a side view showing a piezoelectric actuator according to an embodiment of the present invention, and FIG. 2 is a side view showing a conventional piezoelectric actuator. In the figure, 2 is a piezoelectric element, and 11 is a heating element.

Claims (1)

[Claims] 1. A piezoelectric actuator using a piezoelectric element (2) as a driving part, characterized in that a heating element (11) is provided near the piezoelectric element (2). 2. A piezoelectric actuator using a piezoelectric element (2) as a drive unit, characterized in that the piezoelectric element is caused to perform a developing thermal operation for a certain period of time at a predetermined time.