Acoustical inspection method for inspecting the ceramic coating of catalytic converter monolith substrates

• US 4,653,327 A
• Filed: 05/14/1986
• Issued: 03/31/1987
• Est. Priority Date: 04/10/1986
• Status: Expired due to Fees

• Current Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Original Assignee: General Motors Corporation (Motors Liquidation Co. GUC Trust)
• Inventors: Varterasian, John H., Blaser, Dwight A.
• Primary Examiner(s): Birmiel, Howard A.
• Application Number:
  US06/863,146
• Time in Patent Office: 321 Days
• Field of Search: 73/118.1, 73/579, 73/582, 73/596, 181/0.5
• US Class Current: 73/579
• CPC Class Codes: G01H 17/00 Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves, not provided for in the preceding groups see provisionally also G01H1/00
• CPC Class Codes: G01N 2291/02854 Length, thickness
• CPC Class Codes: G01N 29/075 by measuring or comparing phase angle measuring frequencies or phase angles per se G01R23/00, G01R25/00

Abstract

An acoustic inspection method is disclosed for determining in a catalytic converter monolith substrate whether a ceramic coating was applied in a predetermined amount and uniformly to the surface of exhaust gas passages extending therethrough and whether the ceramic coating is blocking any of the passages. The method includes mounting the substrate in an acoustically sealed structure so as to form a throat communicating a speaker at an entrance end of the coated passages with an empty resonator cavity at an exit end of the coated passages and thereby form a Helmholtz resonator. The speaker is then driven to produce a continuous sound wave through the coated passages into the resonator cavity at a predetermined frequency approximately the natural frequency of the resonator to thereby produce oscillatory sound waves through the coated passages at the same frequency. The substrate is then reversely mounted and the previous step is repeated. The phase angles of the sound waves at the entrance and exit ends of the coated substrate passages are then compared with respect to those of a reference sound wave of the same frequency passed in like manner through a reference substrate known to have the desired quantity and uniformity of coating on the passages and no blockage. Whether or not the passages of the substrate being inspected have the prescribed quantity and uniformity of coating and any blockage is then detected on the basis of the occurrence of a prescribed difference in the phase angles.

Claims

1. An acoustic inspection method for determining in a catalytic converter monolith substrate whether a ceramic coating was applied in a predetermined amount to the surface of exhaust gas passages extending therethrough and whether the ceramic coating is blocking any of the passages, comprising the steps of:

(a) mounting a catalytic converter monolith substrate with ceramic coated exhaust gas passages extending therethrough in an acoustically sealed structure so as to form a throat communicating a speaker at an entrance end of the coated passages with an empty resonator cavity at an exit end of the coated passages and thereby form a Helmholtz resonator,

(b) driving the speaker to produce a continuous sound wave through the coated passages into the resonator cavity at a predetermined frequency and thereby produce oscillatory sound waves through the coated passages at the same frequency,

(c) comparing the phase angles of the sound waves at the entrance and exit ends of the coated substrate passages and with respect to those of a reference sound wave of the same frequency passed in like manner through a reference substrate known to have the desired quantity of coating on the passages and no blockage, and

(d) detecting whether or not the passages of the substrate being inspected have the prescribed quantity and any blockage on the basis that the occurrence of a prescribed difference in the phase angles infers a deviation in the total flow area of the passages and thereby a deviation from the desired coating as to amount and lack of blockage.

2. An acoustic inspection method for determining in a catalytic converter monolith substrate whether a ceramic coating was applied in a predetermined amount to the surface of exhaust gas passages extending therethrough and whether the ceramic coating is blocking any of the passages, comprising the steps of:

(a) mounting a catalytic converter monolith substrate with ceramic coated exhaust gas passages extending therethrough in an acoustically sealed structure so as to form a throat communicating a speaker at an entrance end of the coated passages with an empty resonator cavity at an exit end of the coated passages and thereby form a Helmholtz resonator,

(b) driving the speaker to produce a continuous sound wave through the coated passages into the resonator cavity at a predetermined frequency approximately the natural frequency of the resonator and thereby produce oscillatory sound waves through the coated passages at the same frequency,

(c) comparing the phase angles of the sound waves at the entrance and exit ends of the coated substrate passages and with respect to those of a reference sound wave of the same frequency passed in like manner through a reference substrate known to have the desired quantity of coating on the passages and no blockage, and

(d) detecting whether or not the passages of the substrate being inspected have the prescribed quantity and any blockage on the basis that the occurrence of a prescribed difference in the phase angles infers a deviation in the total flow area of the passages and thereby a deviation from the desired coating as to amount and lack of blockage.

3. An acoustic inspection method for determining in a catalytic converter monolith substrate whether a ceramic coating was applied uniformly to the surface of exhaust gas passages extending therethrough, comprising the steps of:

(a) mounting a catalytic converter monolith substrate with ceramic coated exhaust gas passages extending therethrough in an acoustically sealed structure so as to form a throat communicating a speaker at an entrance end of the coated passages with an empty resonator cavity at an exit end of the coated passages and thereby form a Helmholtz resonator,

(b) driving the speaker to produce a continuous sound wave through the coated passages into the resonator cavity at a predetermined frequency and thereby produce oscillatory sound waves through the coated passages at the same frequency,

(c) reversing the mounting of the substrate so that the entrance end is now near the resonator cavity and the exit end is now near the speaker and then repeating step (b),

(d) comparing the phase angles of the sound waves at the entrance and exit ends of the coated substrate passages and with respect to those of a reference sound wave of the same frequency passed in like manner through a reference substrate known to have the desired quantity and uniformity of coating on the passages and no blockage, and

(e) detecting whether or not the passages of the substrate being inspected have the prescribed uniformity of coating on the basis that a prescribed difference in the phase angles with reversal of the substrate mounting infers a deviation in the total flow areas at the entrance and exit ends and thereby a deviation from the desired coating as to uniformity along the length of the passages.

4. An acoustic inspection method for determining in a catalytic converter monolith substrate whether a ceramic coating was applied uniformly to the surface of exhaust gas passages extending therethrough, comprising the steps of:

(a) mounting a catalytic converter monolith substrate with ceramic coated exhaust gas passages extending therethrough in an acoustically sealed structure so as to form a throat communicating a speaker at an entrance end of the coated passages with an empty resonator cavity at an exit end of the coated passages and thereby form a Helmholtz resonator,

(b) driving the speaker to produce a continuous sound wave through the coated passages into the resonator cavity at a predetermined frequency approximately the natural frequency of the resonator and thereby produce oscillatory sound waves through the coated passages at the same frequency,

(c) reversing the mounting of the substrate so that the entrance end is now near the resonator cavity and the exit end is now near the speaker and then repeating step (b),

(d) comparing the phase angles of the sound waves at the entrance and exit ends of the coated substrate passages and with respect to those of a reference sound wave of the same frequency passed in like manner through a reference substrate known to have the desired quantity and uniformity of coating on the passages and no blockage, and

(e) detecting whether or not the passages of the substrate being inspected have the prescribed uniformity of coating on the basis that a prescribed difference in the phase angles with reversal of the substrate mounting infers a deviation in the total flow areas at the entrance and exit ends and thereby a deviation from the desired coating as to uniformity along the length of the passages.

5. An acoustic inspection method for determining in a catalytic converter monolith substrate whether a ceramic coating was applied in a predetermined amount and uniformly to the surface of exhaust gas passages extending therethrough and whether the ceramic coating is blocking any of the passages, comprising the steps of:

(a) mounting a catalytic converter monolithic substrate with ceramic coated exhaust gas passages extending therethrough in an acoustically sealed structure so as to form a throat communicating a speaker at an entrance end of the coated passages with an empty resonator cavity at an exit end of the coated passages and thereby form a Helmholtz resonator,

(b) driving the speaker to produce a continuous sound wave through the coated passages into the resonator cavity at a predetermined frequency and thereby produce oscillatory sound waves through the coated passages at the same frequency,

(c) reversing the mounting of the substrate so that the entrance end is now near the resonator cavity and the exit end is now near the speaker and then repeating step (b),

(d) comparing the phase angles of the sound waves at the entrance and exit ends of the coated substrate passages and with respect to those of a reference sound wave of the same frequency passed in like manner through a reference substrate known to have the desired quantity and uniformity of coating on the passages and no blockage, and

(e) detecting whether or not the passages of the substrate being inspected have the prescribed quantity and uniformity of coating and any blockage on the basis that the occurrence of a prescribed difference in the phase angles without reversal of the substrate mounting infers a deviation in the total flow area of the passages and thereby a deviation from the desired coating as to amount and lack of blockage and that a prescribed difference in the phase angles with reversal of the substrate mounting infers a deviation in the total flow areas at the entrance and exit ends and thereby a deviation from the desired coating as to uniformity along the length of the passages.

6. An acoustic inspection method for determining in a catalytic converter monolith substrate whether a ceramic coating was applied in a predetermined amount and uniformly to the surface of exhaust gas passages extending therethrough and whether the ceramic coating is blocking any of the passages, comprising the steps of:

(a) mounting a catalytic converter monolithic substrate with ceramic coated exhaust gas passages extending therethrough in an acoustically sealed structure so as to form a throat communicating a speaker at an entrance end of the coated passages with an empty resonator cavity at an exit end of the coated passages and thereby form a Helmholtz resonator,

(b) driving the speaker to produce a continuous sound wave through the coated passages into the resonator cavity at a predetermined frequency approximately the natural frequency of the resonator and thereby produce oscillatory sound waves through the coated passages at the same frequency,

(c) reversing the mounting of the substrate so that the entrance end is now near the resonator cavity and the exit end is now near the speaker and then repeating step (b),

(d) comparing the phase angles of the sound waves at the entrance and exit ends of the coated substrate passages and with respect to those of a reference sound wave of the same frequency passed in like manner through a reference substrate known to have the desired quantity and uniformity of coating on the passages and no blockage, and

(e) detecting whether or not the passages of the substrate being inspected have the prescribed quantity and uniformity of coating and any blockage on the basis that the occurrence of a prescribed difference in the phase angles without reversal of the substrate mounting infers a deviation in the total flow area of the passages and thereby a deviation from the desired coating as to amount and lack of blockage and that a prescribed difference in the phase angles with reversal of the substrate mounting infers a deviation in the total flow areas at the entrance and exit ends and thereby a deviation from the desired coating as to uniformity along the length of the passages.