JPH06288220A - Method and equipment for detecting distribution of quantity of granular substance collected of diesel exhaust filter - Google Patents

Abstract

PURPOSE: To locally measure a collected amount of particulate substances by transmitting and receiving a microwave signal through a filter to detect an amount of particulate substances collected on the filter based on a transmission loss, and by displaying a deposit density of the particulate substances. CONSTITUTION: A microwave transmitted from a transmission antenna 20 is passed through a filter 16A, and the microwave damped in response to an amount of particulate substances collected thereby is received by a receiving antenna 30. In a transmitting side, a microwave signal in response to a bias voltage of a bias direct current power source 21 is output by a voltage control oscillator 22, and is input from a diode switch 24 into a reference detector 50 to output a reference signal for expressing expected intensity of the microwave signal. In a receiving side, a received signal of the receiving antenna 30 is input into a signal detector 60 to output a received signal with final intensity. The both signals are input into a comparator 70 and a comparison operation unit 72 in order, and a deposit density of the particulate substances is calculated to be displayed on a display 73.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for detecting the amount of particulate matter collected on a filter, and more particularly to a particulate matter collected by a diesel exhaust filter. And apparatus for detecting the distribution state of

[0002]

2. Description of the Related Art As is well known, in order to purify exhaust gas from diesel engines, it is necessary to prevent atmospheric release of particulate matter (particulates) such as carbon particles (soot), sulfides, and phosphides contained in the exhaust gas. For this purpose, the best method is to install a ceramic honeycomb filter as a trap in the exhaust pipe and collect it.

[0003]

It is known that the honeycomb ceramics filter can change the collection efficiency by adjusting the shape, material and wall thickness and can be monitored from the outside of the filter. Often, the information inside the filter is unknown. For example, regarding the distribution of the amount of particulate matter trapped inside the filter, there was no other effective monitoring means than destroying the filter.

[0004]

The present invention has been made by paying attention to the above-mentioned problems of the prior art, and makes it possible to locally detect the amount of soot trapped inside the filter, and it has been understood until now. The purpose is to monitor the distribution of soot trapping in the filter, which was difficult to achieve.

According to the present invention, which achieves the above object, a method for detecting the distribution state of the collection amount of particulate matter collected by a filter arranged in the exhaust passage of a diesel engine is a method in which a microwave signal of a predetermined constant frequency is paired. Radiating and receiving to the filter via the monopole antenna of, and detecting the transmission loss of the microwave signal passing through the filter to detect the effective dielectric loss factor of the particulate matter collected by the filter. Detecting the amount of trapped particulate matter in the direction of the vertical section of the filter by
Displaying the deposition density of the collected particulate matter.

Further, according to the present invention, the apparatus for detecting the distribution state of the collected amount of the particulate matter collected by the filter arranged in the exhaust passage of the diesel engine radiates the microwave signal of a predetermined constant frequency to the filter. Means for detecting the transmission loss of the microwave signal that has passed through the filter and detecting the effective dielectric loss factor of the particulate matter trapped by the filter, whereby particles in the direction of the vertical cross section of the filter are detected. Means for detecting the amount of trapped particulate matter,
Means for displaying the deposition density of the collected particulate matter.

[0007]

The operating frequency is limited to 150M.
This is because the transmission loss of the signal is low and the soot detection sensitivity is too low at a frequency lower than Hz, and the transmission signal is too high and the reception signal level becomes low at a frequency higher than 300 MHz, so that the system needs to be amplified. This is because it is complicated and expensive.

Furthermore, the deposition of soot on the filter trap changes the dielectric properties of the filter trap. Therefore, by detecting the change in the effective dielectric properties of the filter, the amount of soot deposited on the filter can be detected. The complex permittivity of soot consists of real and imaginary components. The real number component is called the dielectric constant, and the imaginary number component is called the dielectric loss factor. The dielectric loss factor can be detected by measuring the transmission loss of the signal.

When the microwave of a predetermined frequency propagates through the filter, a part of the electric power is absorbed by the particulate matter. Since the amount of absorption corresponds to the amount of particulate matter deposited, that is, the effective dielectric loss factor, the local transmission loss, that is, the local deposit density of particulate matter, is measured by placing a monopole antenna for microwave transmission and reception close to each other. Further, the deposition distribution state of the particulate matter can be known by shifting the position of the antenna inserted in the filter and measuring a large number of points.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an embodiment of a method and apparatus for detecting a particulate matter trapped amount distribution of a diesel exhaust filter according to the present invention.

Inside the filter 16A, a transmitting antenna 20 and a receiving antenna 30 which are a pair of microwave monopole antennas are arranged in parallel with each other toward the upstream side of the exhaust gas as shown in the figure. Transmission antenna 20 from the transmission side
The microwave of the specified frequency is supplied to the filter 1
It is radiated inside 6A. Microwaves pass through the filter 16A in which particulate matter in the exhaust gas called particulates is deposited, the electric power is absorbed according to the amount of particulate matter, and the attenuated microwaves are received by the receiving antenna 30.
Is received by and is detected by the receiving side.

FIG. 2 and FIG. 3 are schematic views of the honeycomb-shaped ceramic filters 16A and 16B, respectively. FIG. 2 shows honeycomb-shaped ceramic filters 16A and 16B.
3 is a side cutaway view of FIG. 3, and FIG. 3 is a sectional view taken along line III-III in FIG.

As can be seen from FIG. 3, a plurality of pipes having a portion (a) having a clogged section and a portion (b) having a vacant section are springed, and the section opposite to the section seen from the figure is as follows: , The opposite side of the tube having the clogged portion (a) has a vacant portion (b) and the opposite side of the tube having the vacant portion (b) has a clogged portion (a) ing.
It is therefore arranged to pass through the walls of the adjacent tubes and out of the adjacent tube, so that the exhaust gas is rubbed as it passes through the walls. Therefore, the collection rate of the particulate matter can be changed by changing the material of the wall, changing the size of the pores (c), changing the wall thickness, and changing the shape (frontage, depth) of the wall. . The arrow d indicates the direction of exhaust gas flow.

First, the circuit configuration on the transmitting side will be described.
The bias DC power supply 21 is a voltage controlled oscillator (VCO) 22.
A predetermined bias voltage is applied to. The voltage controlled oscillator 22 generates a microwave signal having a constant amplitude and a constant frequency according to the bias voltage. In this embodiment, the frequency is selected in the range of 150 to 300 MHz.

The diode switch 24 has two output terminals, one of which is connected to the transmitting antenna 20 and the other of which is connected to the input of the reference detector 50. The diode switch 24 alternately distributes the microwave signal input from the voltage controlled oscillator 22 to the two output terminals according to the pulse of the frequency of 10 KHz from the pulse generator 23. Therefore, from each output terminal of the diode switch 24, the amplitude modulation (A
M) A microwave signal is output.

The reference detector 50 receives the AM microwave signal and receives a reference signal Vr representing the strength of the microwave signal on the transmitting side.
ef is generated. AM detector 5 in reference detector 50
Reference numeral 1 puts a received microwave signal on a DC voltage and causes the amplitude on the positive voltage side to be oscillated. The smoothing circuit converts the DC signal to a DC voltage. Then, the added DC voltage is subtracted and the amplitude is converted to a voltage. That is, the AM microwave signal from the diode switch 24 is demodulated and its level is detected. The detected signal is amplified by the amplifier 52 which gives a predetermined gain, and the reference signal V
It is output to the output terminal 53 as ref. The amplifier 5
No. 2 has its zero level and gain adjustable from the outside.

Next, the receiving side will be described. The AM microwave signal transmitted from the transmitting antenna 20 and passing through the filter 6 is received by the receiving antenna 30. The received signal is given to the signal detector 60 which constitutes a receiving circuit.
The signal is demodulated by the AM detector 61 of the signal detector 60 and its level is detected. The AM detector 61 may have the same configuration as the AM detector 51 on the transmitting side. The detected signal is amplified by the amplifier 62 that gives a predetermined gain, and is output to the output terminal 63 as the reception signal Vout. The amplifier 62 may have the same configuration as the amplifier 52 on the transmission side. Therefore, the reference detector 50 and the signal detector 60 have the same configuration, and by doing so, the temperature characteristics of the detector can be made the same and the accuracy can be improved.

V representing the initial strength of the signal shown in FIG.
ref and Vout representing the final strength of the signal on the receiving side shown in FIG. 5 are each converted into a DC voltage proportional to the amplitude, and are input to the comparator 70 to represent the transmission loss rate. The signal is output to the manual switch 71. The operator manually switches the manual switch 71 so that the comparator 7
The signal from 0 is stored in the determined address memory of the comparison operation device 72 in the next stage. The comparison calculation unit 72 waits until the value when the clean filter 16B is measured and the value when the dirty filter 16A is measured are input, and calculates the local soot accumulation density from the comparison value. , Is displayed on the display 73.

Next, FIG. 6 shows a specific circuit configuration of this embodiment shown in FIG. The DC voltage + V supplied from the DC power supply 21 is divided by the variable resistor 101 and
Varactor diode 10 via 2 and capacitor 103
4 is applied. The varactor diode 104, the capacitors 105 and 106, the resistors 108, 109 and 110, the inductance 107 and the transistor 111 form a Hartley oscillator, which is a voltage controlled oscillator 22.
To work as.

The signal generated by the voltage controlled oscillator 22 is matched by a matching device composed of capacitors 112 and 114 and a resistor 113, and is applied to the diode switch 24. The diode switch 22 includes two diodes 116 and 117.
Are connected to each other with opposite polarities, and the connection point is connected to the output of the pulse generator 23 via the inductance 115. The other terminal of each of the diodes 119 and 117 serves as two branched outputs.

The output of the diode 116 is shifted to a positive potential by the DC voltage + V and the resistor 119, and the capacitor 123
It is applied to the transmitting antenna 20 after being matched by a matching device including a resistor 120 and a resistor 124. On the other hand, the output of the diode 117 is shifted to a positive potential by the DC voltage + V and the resistor 121, and the capacitor 125 and the resistors 122 and 126 are shifted.
After being matched by a matching device composed of and, they are input to the reference detector 50. Since the reference detector 50 has the same configuration as the signal detector 60, the detailed circuit configuration will be described by taking the signal detector 60 as a representative.

AM detector 61 in signal detector 60
Is a high-pass filter including a capacitor 130 and a resistor 131, and capacitors 132 and 137 and a resistor 13
3, 136 and a smoothing circuit formed by two diodes 134 and 135. This AM detector 61 outputs a DC voltage proportional to the amplitude of the microwave signal that is AM-modulated by a pulse.

Two cascaded operational amplifiers 1
43, 145 and resistors 138, 139, 144, 147
And the capacitor 148 form the amplifier 62. Variable resistor 140 and resistors 141, 14 connected to DC voltage + V
2 adjusts the zero level of the amplifier 62. Further, the variable resistor 146 adjusts the gain of the amplifier 62.

The signals Vref and Vout appearing at the terminals 53 and 63 are input to the comparator 70, and the signal representing the power loss is sent to the manual switch 71. That is, the reference signal V
The ref and the received signal Vout are input to the operational amplifier 154 via the resistors 150 and 151, respectively, and the voltage difference between them is commensurate with the amount of amplification determined by the ratio of the resistance value adjusted by the variable resistor 153 and the resistance value of R155. Output signal. Thus, the comparator 70 can be realized by a circuit such as a known differential amplifier. It is also possible to add a circuit that generates an alarm signal or a display signal when the output of the comparator 70 reaches a predetermined level that indicates the combustion timing of soot.

Here, when the operator measures the filter 16A in a clean state and the dirty filter 1
When 6B is measured, if the memory location of the comparison operation device 72 is specified by the manual switch 71, the difference in microwave transmission loss rate is obtained from the comparison of the two signals, and the soot accumulation density is further localized. Is calculated and displayed on the display 73.

In FIG. 1, if the transmitting antenna 20 and the receiving antenna 30 are installed too wide, noise in the entire filter will be picked up. It is preferable that the transmitting antenna 20 and the receiving antenna 30 are inserted on both sides of only one channel.

[0027]

According to the present invention, the soot trapping amount of the filter can be locally measured, and the soot accumulation density distribution detecting device in the filter, which has been difficult until now, can be provided at a low cost. . Furthermore, the soot accumulation density distribution in the filter can be detected without disassembling the filter, which can greatly contribute to the design of the filter and the exhaust flow control.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of particulate matter trapping distribution detection of a diesel exhaust filter according to the present invention.

FIG. 2 is a side cutaway view of a filter used in the present invention.

FIG. 3 is a sectional view taken along the line III-III in FIG.

FIG. 4 is an output waveform diagram of the reference detector shown in FIG.

5 is an output waveform diagram of the signal detector shown in FIG. 1. FIG.

FIG. 6 is a circuit diagram showing a specific circuit configuration of the embodiment of FIG.

[Explanation of symbols]

 16A, 16B filter 20 transmitting antenna 21 bias DC power supply 22 voltage controlled oscillator 23 pulse generator 24 diode switch 30 receiving antenna 50 reference detector 51, 61 AM detector 52, 62 amplifier 53 reference signal output terminal 60 signal detector 63 reception Signal output terminal 70 Comparator 71 Manual switch 72 Comparative operation device 73 Display a Clogged portion b Vacant portion c Pore portion d Direction of exhaust gas flow

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sakae Minagawa 4-14-1 Suehiro, Kumagaya-shi, Saitama Riken Kumagaya Works

Claims (4)

[Claims] 1. A method for detecting a distribution state of a collection amount of particulate matter collected by a filter arranged in an exhaust passage of a diesel engine, wherein a microwave signal having a predetermined constant frequency is used as a pair of monopoles. By radiating and receiving to the filter through an antenna, and detecting the transmission loss of the microwave signal that has passed through the filter to detect the effective dielectric loss factor of the particulate matter collected by the filter. Detecting the amount of trapped particulate matter in the direction of the vertical cross section of the filter, and displaying the deposition density of the trapped particulate matter,
For detecting the distribution of particulate matter trapped in a diesel exhaust filter having a filter. 2. A method for detecting a distribution state of collected amount of particulate matter collected by a filter arranged in an exhaust passage of a diesel engine, wherein a microwave signal having a predetermined constant frequency is used as a pair of monopoles. Radiating / receiving the filter through an antenna, creating a reference signal representing the intensity of the microwave signal before radiation, receiving the microwave signal that has passed through the filter and representing the intensity The step of creating a reception signal, the reference signal and the reception signal are compared to detect the difference between the two, the transmission loss is detected based on the difference, and the particulate matter collected by the filter is effective. Detecting the amount of trapped particulate matter in the vertical cross-sectional direction of the filter by detecting the dielectric loss factor, and displaying the deposition density of the trapped particulate matter,
For detecting the distribution of particulate matter trapped in a diesel exhaust filter having a filter. 3. A device for detecting a distribution state of a collection amount of particulate matter collected by a filter arranged in an exhaust passage of a diesel engine, wherein a pair of monopoles are provided with a microwave signal having a predetermined constant frequency. Means for radiating / receiving to the filter via an antenna, and detecting the transmission loss of the microwave signal passing through the filter to detect the effective dielectric loss factor of the particulate matter collected by the filter. Means for detecting the amount of trapped particulate matter in the direction of the vertical cross section of the filter, means for displaying the deposition density of the trapped particulate matter,
For detecting the amount of particulate matter trapped in a diesel exhaust filter having a filter. 4. A device for detecting a distribution state of a collection amount of particulate matter collected by a filter arranged in an exhaust passage of a diesel engine, wherein a pair of monopoles are provided with a microwave signal having a predetermined constant frequency. Means for radiating / receiving the filter via an antenna, means for creating a reference signal representing the strength of the microwave signal before radiation, and receiving the microwave signal passing through the filter to represent the strength A means for creating a reception signal, the reference signal and the reception signal are compared to detect the difference between the two, the transmission loss is detected based on the difference, and the particulate matter collected by the filter is effective. Means for detecting the amount of particulate matter trapped in the direction of the vertical cross section of the filter by detecting the dielectric loss factor; and means for displaying the deposition density of the trapped particulate matter,
For detecting the amount of particulate matter trapped in a diesel exhaust filter having a filter.