JP2008070235A - Device and method for detecting defect of particle collection filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and method capable of discovering a defect linked to a defect of a particle collection filter, accurately by a simple method. <P>SOLUTION: The device includes the particle collection filter formed by sealing one end of each circulation hole alternately in a zigzag way on the end face of a structure having many circulation holes penetrating in the axial direction partitioned by a bulkhead, a sound wave generation means disposed on one end face side of the particle collection filter, and a sound wave detection means disposed on the other end face side of the particle collection filter. The defect detection method using the device is also provided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a defect detection device and a defect detection method for a combustion exhaust particulate collection filter contained in exhaust gas discharged from automobiles, construction machines, industrial stationary engines, combustion equipment, and the like.

  A fine particle collection filter (DPF) having a porous wall honeycomb structure in which both ends are alternately plugged is used as a filter. This particulate collection filter needs to detect the defect for the following reasons.

  First, when manufacturing the DPF, it is necessary to confirm that the DPF has sufficient filter characteristics and is free of harmful defects. Secondly, when using the DPF, it is desirable to quickly know the detection on the vehicle when a defect that causes the filter function to deteriorate due to some damage is reached.

  For the former, a method of actually flowing fine particles and measuring the permeation amount or observing defects (Patent Document 1) is used.

Regarding the latter, a method is known in which the pressure loss between the inlet and outlet is measured and detected by a change in pressure loss when an abnormal defect occurs (Patent Document 2). Alternatively, a method of measuring the fine particle concentration on the outlet side has been attempted.
JP 2000-193582 A JP 60-47937 A

  In the measurement of actually flowing fine particles, there is a problem that a fine particle generation device, a fine particle measurement device, or a leakage observation device becomes large. There is also a problem that post-processing such as burning and removing fine particles after inspection is necessary. Furthermore, there is a problem that defects cannot be detected with high accuracy due to variations in conditions and variations in measurement.

  On the other hand, in the method of detecting the occurrence of a defect during use by the change in pressure difference, the detection sensitivity is low, and it is impossible to detect leakage of 1.5 times the regulation value required in on-board diagnosis (OBD).

  The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide an apparatus and a method for accurately detecting a defect of a particulate collection filter by a simple method. There is.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors achieve the above-described problems by inputting sound waves from one end face of the particulate collection filter and measuring the intensity of sound waves passing through the other end face. As a result, the present invention has been completed.

  That is, according to the present invention, the following defect detection device and defect detection method for a particulate collection filter are provided.

[1] On the end face of a structure having a large number of flow holes penetrating in the axial direction partitioned by the partition walls, one end of each flow hole is staggered so as to be staggered. A particulate filter, a sound wave generating means disposed on one end face side of the particulate collection filter, and a sound wave detecting means disposed on the other end face side of the particulate collection filter. Collection filter defect detection device.

[2] The defect detection device for a particulate collection filter according to [1], wherein the particulate collection filter is disposed in an exhaust gas flow path of an internal combustion engine.

[3] In the end face of the structure having a large number of flow holes penetrating in the axial direction partitioned by the partition walls, one end of each flow hole is staggered so as to be staggered. The particulate collection filter for detecting a defect of the particulate collection filter from the attenuation rate of the acoustic wave by measuring the intensity of the acoustic wave that is input from one end surface side of the collection filter and passing through the other end surface side Defect detection method.

[4] The defect detection method for a particulate collection filter according to [3], wherein the particulate collection filter is disposed in an exhaust gas flow path of an internal combustion engine.

[5] The defect detection method for a particulate collection filter according to the above [3] or [4], in which high-frequency sound waves are input from the one end face side.

[6] The defect detection method for a particulate collection filter according to any one of [3] to [5], wherein a part of engine exhaust sound is used as the high-frequency sound wave.

  According to the defect detection apparatus and detection method for the particulate collection filter of the present invention, it is possible to easily detect the defect of the particulate collection filter with high accuracy.

  BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the present invention will be described below, but the present invention is not limited to the following embodiment, and is based on the ordinary knowledge of those skilled in the art without departing from the gist of the present invention. It should be understood that modifications and improvements as appropriate to the following embodiments also fall within the scope of the present invention.

  The principle of the present invention will be described with reference to FIGS. 3 and 4 which are principle diagrams of the present invention. As shown in FIG. 3, when the sound wave 6 is emitted to the partition wall 8 of the particulate collection filter (DPF), the sound wave 6 is attenuated by the partition wall 8. On the other hand, as shown in FIG. 4, if there is a defect 9 in the partition wall 8 of the particulate collection filter, a part of the sound wave 6 emitted toward the partition wall 8 passes through the defect 9. As compared with FIG. 3, the attenuation rate of the sound wave 6 is lowered. The present invention quantifies this decrease in the attenuation rate and attempts to detect a defect in the particulate collection filter from the change in the attenuation rate.

  A more specific description will be given with reference to a schematic view (FIG. 1) of a defect detection device for a particulate collection filter disposed in an exhaust pipe of an internal combustion engine according to an embodiment of the present invention. In FIG. 1, a particulate collection filter (DPF) 1 is a test object, and is disposed between the upstream exhaust pipe 4 and the downstream exhaust pipe 5. The gas flow flows from the upstream exhaust pipe 4 through the particulate collection filter 1 to the downstream exhaust pipe 5. At this time, the fine particles in the exhaust gas flowing through the upstream side exhaust pipe 4 are collected by the fine particle collecting filter 1. Here, if there is a defect such as a hole (pinhole) in the partition wall in the particulate collection filter, the particulate passes through the particulate collection filter 1 and flows into the downstream exhaust pipe 5.

  In FIG. 1, a sound wave 6 having a specific frequency is generated from a speaker 2 as a sound wave generating means, passes through an upstream exhaust pipe 4, and enters a particulate collection filter 1. The sound wave 6 is attenuated by the particulate collection filter 1 and then proceeds to the downstream exhaust pipe 5 as a sound wave 7 having a specific frequency. The attenuated sound wave 7 is detected by the microphone 3 as sound wave detecting means.

  The sound wave 6 generated from the speaker 2 as the sound wave generation means and the attenuated sound wave 7 detected by the speaker 3 as the sound wave detection means are electrically compared to determine the attenuation rate. Defects in the particulate collection filter 1 are detected based on this attenuation rate.

  In the present specification, the particulate collection filter refers to a structure (honeycomb structure) having a large number of flow holes (cells) penetrating in the axial direction partitioned by partition walls at one end of each flow hole. It refers to what is alternately plugged so as to form a shape.

  In the present invention, the material of the particulate collection filter is not particularly limited, but is made of silicon carbide, cordierite, alumina titanate, sialon, mullite, silicon nitride, zirconium phosphate, zirconia, titania, alumina, silica, or a combination thereof. What is comprised from the material which has ceramics or a sintered metal as a main component is suitable.

  As a cause of the defect of the particulate collection filter, a hole of a partition wall (pinhole), a crack (one having an opening), and a cavity due to melting damage are considered. These defects are undesirable because they cause a reduction in the collection efficiency of the particulate collection filter. Further, if there is a defect in the particulate collection filter, the sound wave easily passes and the attenuation rate of the sound wave decreases.

  In the present specification, the sound wave generation means may be any means that can inject sound waves of a specific frequency to one end face of the particulate collection filter that is the test object. Specifically, a speaker or an ultrasonic transducer that converts an electric signal into a sound wave can be exemplified, but the present invention is not limited thereto.

  The sound wave generation means may be disposed so that sound waves can be input to the upstream end face of the gas flow in the particulate collection filter, or may be disposed so that sound waves can be input to the downstream end face.

  A high-frequency sound wave can be used as the sound wave having a specific frequency. Specifically, it is preferably set to a specific frequency between 5 kHz and 100 kHz, and more preferably set to a specific frequency between 8 kHz and 20 kHz. The reason for the preference is that the engine exhaust sound includes frequency components in this range, and the characteristic of the filter that collects fine particles with high collection efficiency is the characteristic of blocking sound waves in this frequency range.

  The setting of the specific frequency varies depending on the pore distribution characteristics of the filter base material, and a frequency that is easily cut off by the filter is selected as appropriate.

  An engine can also be employed as the sound wave generation means. When the engine is driven, engine exhaust noise is inevitably generated, and as described above, engine exhaust noise is a sound wave having a frequency that is blocked by a filter that collects fine particles with high collection efficiency. This is because it contains ingredients. However, other sound wave generation means may be installed on one end face side of the DPF without using the engine.

  In this case, it is preferable to generate a sound wave having a specific frequency. However, even a sound wave generating unit having a wide frequency band may include a specific frequency detected by the sound wave detecting unit. .

  In the present specification, the sound wave detecting means may be any means that can detect sound waves of a specific frequency generated by the sound wave generating means. Specifically, a microphone can be exemplified, but not limited thereto. The sound wave detection means is disposed on the end surface opposite to the sound wave generation means with respect to the particulate collection filter. Specifically, when the sound wave generating means is disposed on the upstream end surface side of the gas flow in the particulate collection filter, the acoustic wave detection means is provided on the downstream end face side of the gas flow in the particulate collection filter. It arranges in. Conversely, when the sound wave generating means is disposed on the end face downstream of the gas flow in the particle collecting filter, the sound wave detecting means is disposed on the end face upstream of the gas flow in the particle collecting filter. Set up.

  As a characteristic of the sound wave detection means, a DPF is obtained by a method of providing a characteristic of electrically converting a sound wave of only a specific frequency or by providing a circuit for measuring the intensity of a specific frequency in the electric signal of the sound wave detection means. It is preferable to measure the intensity of the sound wave of a specific frequency on the downstream side of the first frequency.

  The sound wave generating means and the sound wave detecting means are provided with a branch pipe that is branched from a part of the upstream and downstream exhaust pipes of the DPF and is thinner than the engine exhaust pipe, and has a length of 200 mm or more as a length at which the temperature is sufficiently lowered. It is preferable to install it at its tip. At this time, it is possible to increase the detection sensitivity at a specific frequency by causing the air column vibration to occur at a specific frequency in the length of the branch pipe of the sound wave detection means. It is also possible to adjust the sensitivity of the sound wave detection means by providing a throttle part such as an orifice in the middle of the branch pipe.

  The above is a method of use as a means for detecting damage to a filter that is attached to an exhaust system of a diesel engine and collects fine particles. This method is also used as a defect inspection method at the time of manufacturing a filter. Can be used.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.

  A sound wave generating means and a microphone composed of a transmitter having a frequency of 1 kHz to 20 kHz were installed on the upstream side of the DPF, and a sound wave detecting means composed of a microphone was disposed on the downstream side. The intensity of sound waves was measured for DPFs with different degrees of defects on the upstream side and the downstream side. The defect of the DPF was modeled by removing the plugging of the DPF end face. DPFs with 0%, 10%, 15%, and 30% of plugging were made and used as experimental objects. For these DPFs, the number ratio of the upstream and downstream particles when installed in the engine exhaust system was measured by SMPS manufactured by TSI, and the particle collection efficiency of the DPF was measured. The engine conditions were a 2-liter displacement diesel engine with operating speed of 2000 rpm and torque of 50 Nm. Table 1 shows the measurement results at a frequency of 12 kHz.

  Based on the results in Table 1, FIG. 2 is a graph in which the vertical axis plots the intensity ratio of 12 kHz sound waves before and after the particulate collection filter, and the horizontal axis plots the particulate (PM) collection efficiency.

  From FIG. 2, there is a strong correlation between the intensity of the sound wave at the outlet side 12 kHz and the collection efficiency of the filter, and if the intensity of the 12 kHz sound wave is measured at the downstream side of the filter, the degree of filter defects and the degree of particulate leakage can be detected. I understand.

  The present invention can be used to detect defects in particulate collection filters.

It is the schematic diagram which has arrange | positioned the detection apparatus which is one Embodiment of this invention in the exhaust pipe of the internal combustion engine. It is a graph which shows the relationship between the attenuation rate by the DPF of the sound wave of 12 kHz, and the particulate collection efficiency of DPF. It is a schematic diagram which shows the principle of this invention. It is another schematic diagram which shows the principle of this invention.

Explanation of symbols

1: particulate collection filter, 2: speaker, 3: microphone, 4: upstream exhaust pipe, 5: downstream exhaust pipe, 6: sound wave, 7: attenuated sound wave, 8: DPF wall, 9: defect

Claims (6)

A particulate collection filter in which one end of each flow hole is alternately plugged in an end face of a structure having a large number of flow holes penetrating in the axial direction partitioned by a partition; ,
A sound wave generating means disposed on one end face side of the particulate collection filter;
A sound wave detecting means disposed on the other end face side of the particulate collection filter;
A defect detection apparatus for the particulate collection filter, comprising:   The defect detection apparatus for a particulate collection filter according to claim 1, wherein the particulate collection filter is disposed in an exhaust gas flow path of an internal combustion engine. In the end face of the structure having a large number of flow holes penetrating in the axial direction partitioned by the partition walls, one end of each flow hole is staggered so as to be staggered. ,
Throw sound waves from one end face side,
Measure the intensity of the sound wave passing to the other end face side,
A defect detection method for the particle collection filter, wherein a defect of the particle collection filter is detected from the attenuation rate of the sound wave.   The defect detection method for a particulate collection filter according to claim 3, wherein the particulate collection filter is disposed in an exhaust gas flow path of an internal combustion engine.   The defect detection method of the particulate collection filter according to claim 3 or 4, wherein high-frequency sound waves are input from the one end face side.   The defect detection method for a particulate collection filter according to any one of claims 3 to 5, wherein a part of engine exhaust sound is used as the high frequency sound wave.