METHOD OF POLING PIEZOELECTRIC ACTUATOR
A method of poling a piezoelectric actuator, which can improve the uniformity of a plurality of piezoelectric actuators. In the method, a plurality of piezoelectric actuators are prepared for poling. Then, at least two preliminary poling processes are performed on the prepared piezoelectric actuators under different preliminary voltages and displacements of the piezoelectric actuators subjected to each of the at least two poling processes are measured. A relationship between a voltage and a displacement for each of the piezoelectric actuators is established. Poling voltages are calculated so that the piezoelectric actuators can have the same target displacement. Formal poling is performed on the piezoelectric actuators under the calculated poling voltages. The displacements of the piezoelectric actuators, which have completed the formal poling, are measured.
1 . A method of poling piezoelectric actuators, the method comprising:
preparing a plurality of piezoelectric actuators;
performing at least two preliminary poling processes on the plurality of prepared piezoelectric actuators such that each preliminary poling process is under a different poling condition and measuring at least one piezoelectric characteristic of each of the plurality of piezoelectric actuators subjected to each of the at least two preliminary poling processes;
establishing a relationship between a poling condition and a piezoelectric characteristic for each of the plurality of piezoelectric actuators;
calculating a poling condition for each prepared piezoelectric actuator so that the plurality of piezoelectric actuators have substantially the same target piezoelectric characteristic;
performing formal poling on each of the plurality of piezoelectric actuators under the calculated poling conditions; and
measuring at least one piezoelectric characteristic of each of the plurality of piezoelectric actuators which have completed the formal poling.
2 . The method of claim 1 , wherein the preparing the plurality of piezoelectric actuators operation comprises:
preparing a device which includes a plurality of piezoelectric actuators to be poled.
3 . The method of claim 2 , wherein the device is at least one of an inkjet head, a micropump, or a fluidics system.
4 . The method of claim 1 , wherein when the measuring the at least one piezoelectric characteristic of each of the piezoelectric actuators operation results in a value that exceeds a target uniformity value then an additional method of measuring is performed, comprising:
performing at least two additional preliminary poling processes on each of the piezoelectric actuators under a different poling condition for each additional preliminary poling process and measuring at least one piezoelectric characteristic of each piezoelectric actuator;
establishing a new relationship between a poling condition and a piezoelectric characteristic for each of the plurality of piezoelectric actuators;
calculating a new poling condition so that the piezoelectric actuators can have substantially an identical target piezoelectric characteristic;
performing formal poling on each piezoelectric actuator under each newly calculated poling condition; and
measuring at least one piezoelectric characteristic of each of the piezoelectric actuators which have completed the formal poling under each newly calculated poling condition.
5 . The method of claim 4 , wherein a poling condition in the performing at least two additional preliminary poling processes operation is different from a poling condition of claim 1 .
6 . The method of claim 1 , wherein each poling condition is a voltage level, and each piezoelectric characteristic is a displacement.
7 . The method of claim 6 , wherein the performing at least two preliminary poling processes operation comprises:
performing a first preliminary poling on each piezoelectric actuator under a first preliminary voltage;
performing a first displacement measurement to measure the displacement of each piezoelectric actuator which has completed the first preliminary poling;
performing a second preliminary poling on each piezoelectric actuator under a second preliminary voltage; and
performing a second displacement measurement to measure the displacement of each piezoelectric actuator which has completed the second preliminary poling.
8 . The method of claim 7 , wherein the second preliminary voltage is greater than the first preliminary voltage.
9 . The method of claim 7 , wherein the first preliminary poling is performed under a condition where the first preliminary voltage is uniformly applied to the plurality of piezoelectric actuators, and the second preliminary poling is performed under a condition where the second preliminary voltage is uniformly applied to the plurality of piezoelectric actuators.
10 . The method of claim 7 , wherein each first displacement measurement and each second displacement measurement is to measure the displacement of each piezoelectric actuator and is performed under a condition where the same driving voltage is applied to the plurality of piezoelectric actuators.
11 . The method of claim 7 , wherein the performing at least two preliminary poling processes operation further comprises:
performing a third preliminary poling on the plurality of piezoelectric actuators under a third preliminary voltage; and
performing a third displacement measurement to measure the displacement of each piezoelectric actuator which has completed the third preliminary poling.
12 . The method of claim 11 , wherein the third preliminary voltage is greater than the second preliminary voltage, and the second preliminary voltage is greater than the first preliminary voltage.
13 . The method of claim 6 , the establishing a relationship between a poling condition and a piezoelectric characteristic comprises:
establishing a relationship between a voltage and a displacement value for each of the plurality of piezoelectric actuators by using each voltage applied to the plurality of piezoelectric actuators and the displacement of each piezoelectric actuator measured in the performing at least two preliminary poling processes operation.
14 . The method of claim 6 , wherein the calculating a poling condition operation comprises:
calculating a poling voltage to be applied to the plurality of piezoelectric actuators so that the plurality of piezoelectric actuators have substantially the same target displacement value by using the relationships established in the establishing a relationship between a poling condition and a piezoelectric characteristic operation.
15 . The method of claim 14 , wherein each calculated poling voltage to be applied to the plurality of piezoelectric actuators is different.
16 . The method of claim 6 , wherein the performing formal poling operation comprises:
performing a formal poling by applying each poling voltage calculated in the calculating a poling condition operation to the plurality of piezoelectric actuators.
17 . The method of claim 6 , wherein in the measuring at least one piezoelectric characteristic operation the measuring at least one piezoelectric characteristic comprises:
measuring the displacement of each piezoelectric actuator under a condition where the same driving voltage is applied to the plurality of piezoelectric actuators.
18 . The method of claim 1 , wherein the preparing a plurality of piezoelectric actuators comprises:
preparing a plurality of devices each including at least one piezoelectric actuator to be poled.
19 . A method of poling a piezoelectric device, comprising:
applying a first voltage and then a second voltage which is greater than the first voltage to the piezoelectric device;
measuring a first and a second displacement of the device caused by the respective applications of the first and the second applied voltages;
determining a linear relationship between the first and second applied voltages and the measured first and second displacements of the piezoelectric device; and
applying a predetermined poling voltage to the piezoelectric device to achieve a predetermined displacement of the piezoelectric device, where the predetermined poling voltage is a function of the determined linear relationship.
20 . The method of claim 19 , wherein the piezoelectric device is a piezoelectric actuator.
21 . The method of claim 19 , further comprising:
applying at least one additional voltage to the piezoelectric device which is greater than the first and second voltages; and
measuring an additional displacement of the piezoelectric device caused by application of the at least one additional applied voltage.
22 . The method of claim 21 , wherein the determining the linear relationship includes a defined linear relationship between the first and second applied voltages and the measured first and second displacements of the piezoelectric device and between each additional applied voltage and a unique displacement of the piezoelectric device associated with each additional applied voltage.
23 . A method to achieve a desired displacement of a piezoelectric actuator, comprising:
applying a plurality of increasingly greater voltages to the actuator;
measuring a unique displacement of the actuator for each of the applied plurality of increasingly greater voltages;
defining a relationship between the applied plurality of increasingly greater voltages and each measured unique displacement of the actuator; and
applying a poling voltage to the actuator to achieve a predetermined displacement of the actuator such that the poling voltage is a function of the defined relationship.
24 . The method of claim 23 , wherein a polarity of a current associated with each of the applied plurality of increasingly greater voltages is the same.
25 . The method of claim 23 , wherein the defined relationship is a linear relationship.