Ultrasonic cleaning method and ultrasonic cleaning apparatus
View Patent ↗An ultrasonic cleaning method for cleaning an object in a liquid in which a gas is dissolved includes preparing the liquid in which the gas is dissolved. The object is cleaned while applying ultrasonic waves to the liquid so that a ratio determined by dividing a vibration strength of the liquid at a fourth-order frequency of the ultrasonic waves by a vibration strength of the liquid at a fundamental frequency of the ultrasonic waves is larger than 0.8/1000.
1. An ultrasonic cleaning method for cleaning an object in a liquid in which a gas is dissolved, the method comprising:
irradiating the liquid in which the gas is dissolved with ultrasonic waves using an irradiation unit;
measuring a first strength of acoustic waves of the liquid, at a fourth-order frequency of ultrasonic waves, and a second strength of the acoustic waves of the liquid, at a fundamental frequency of ultrasonic waves, as a second strength;
calculating a ratio between the first strength and the second strength, by dividing the first strength by the second strength;
adjusting the liquid by changing a dissolved gas concentration, optionally while stirring the liquid, so that the ratio determined in the calculating is larger than 0.8/1000; and
cleaning the object while applying ultrasonic waves to the liquid so that the ratio is larger than 0.8/1000.
2. The ultrasonic cleaning method recited in claim 1 , wherein the step of cleaning the object includes applying the ultrasonic waves to the liquid so that a third strength of acoustic waves of the liquid, at a fifth-order frequency of the ultrasonic waves is larger, than the first strength.
3. The ultrasonic cleaning method recited in claim 1 , wherein in the step of cleaning the object, the liquid is adjusted, based on the first strength, so that a state where bubbles containing the gas continue to be generated in the liquid is realized.
4. The ultrasonic cleaning method recited in claim 1 , wherein sonoluminescence occurs during the cleaning of the object.
5. The ultrasonic cleaning method recited in claim 1 , wherein the gas is nitrogen and the dissolved gas concentration of the liquid is 5 ppm or more.
6. The ultrasonic cleaning method recited in claim 1 , further comprising:
preparing the liquid in which the gas is dissolved.
7. The ultrasonic cleaning method recited in claim 1 , further comprising, during the adjusting:
stirring the liquid.
8. The ultrasonic cleaning method recited in claim 1 , wherein the ratio is larger than 3/1000.
9. The ultrasonic cleaning method recited in claim 1 , wherein the ratio is larger than 5/1000.
10. The ultrasonic cleaning method recited in claim 1 , wherein the ratio is larger than 10/1000.
11. The ultrasonic cleaning method recited in claim 1 , wherein the ratio is larger than 50/1000.
12. The ultrasonic cleaning method recited in claim 1 , wherein the ratio is in a range of from larger than 0.8/1000 to 50/1000.
13. The ultrasonic cleaning method recited in claim 1 , wherein the gas is nitrogen.
14. The ultrasonic cleaning method recited in claim 1 , wherein the dissolved gas concentration of the liquid is 5 ppm or more.
15. The ultrasonic cleaning method recited in claim 1 , wherein the dissolved gas concentration of the liquid is in a range of from 5 ppm to 15.7 ppm.
16. The ultrasonic cleaning method recited in claim 1 , wherein the gas is nitrogen and the dissolved gas concentration of the liquid is in a range of from 5 ppm to 15.7 ppm.