JP3849916B2 - Exhaust pressure measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust pressure measuring device.
[0002]
[Prior art]
Particulate matter (particulate matter) discharged from a diesel engine is mainly composed of soot made of carbonaceous matter and SOF content (Soluble Organic Fraction) made of high-boiling hydrocarbon components. As shown in FIG. 2, an exhaust pipe 3 through which exhaust gas 2 from the diesel engine 1 flows is used as a measure for reducing this kind of particulates. The exhaust pipe 3 has a composition containing a small amount of sulfate (misty sulfuric acid component). It is considered that the particulate filter 4 is provided in the middle of the above.
[0003]
As shown in FIG. 3, the particulate filter 4 has a porous honeycomb structure made of ceramic such as cordierite, and the inlets of the respective flow paths 5 partitioned in a lattice pattern are alternately sealed. As for the flow path 5 that is not sealed, the outlet is sealed, and only the exhaust gas 2 that has permeated through the porous thin wall 6 defining each flow path 5 is discharged downstream. Thus, the particulates are collected on the inner surface of the porous thin wall 6.
[0004]
In such a particulate filter 4, it is necessary to regenerate the particulate filter 4 by appropriately burning and removing the particulate before the exhaust resistance increases due to clogging. In this case, since there is little opportunity to obtain an exhaust temperature high enough to cause the particulates to self-combust, for example, an oxidation catalyst formed by adding an appropriate amount of rare earth elements such as cerium to a material in which platinum is supported on alumina. It has been studied to adopt a catalyst regeneration type particulate filter 4 that is integrally supported on the curative filter 4 or that an oxidation catalyst is disposed separately from the particulate filter 4.
[0005]
That is, if such a catalyst regeneration type particulate filter 4 is employed, the oxidation reaction of the collected particulates is promoted to lower the ignition temperature, and the particulates are burned and removed even at an exhaust temperature lower than the conventional one. Is possible.
[0006]
However, even when such a catalyst regeneration type particulate filter 4 is employed, the oxidation catalyst attached to the particulate filter 4 has an active temperature region, and is at least about 200 ° C. or higher. Since the temperature is required, if the operating condition at the exhaust temperature that falls below this temperature (especially, the region where the exhaust temperature falls below about 200 ° C extends to the light load operating range), the oxidation catalyst becomes active. Therefore, there is still a possibility that the particulate filter 4 is not well burned and removed, and the particulate filter 4 is clogged.
[0007]
For this reason, some means for forcibly increasing the exhaust temperature is taken to perform good combustion removal of the particulates collected by the particulate filter 4, thereby regenerating the particulate filter 4. However, when putting such means for raising the exhaust temperature into practical use, means for detecting in advance that the particulate filter 4 is in an over-collected state is indispensable. It is.
[0008]
In general, when detecting that the particulate filter 4 is becoming over-collected, a pressure sensor 7 is connected to the exhaust pipe 3 upstream of the particulate filter 4 as indicated by a two-dot chain line in FIG. It is considered that the pressure of the exhaust gas 2 is detected by directly installing the exhaust gas 2 and the collection state of the particulate filter 4 is estimated based on the detected pressure of the exhaust gas 2.
[0009]
[Problems to be solved by the invention]
However, even if the pressure sensor 7 is installed and the pressure of the exhaust gas 2 is detected in this way, the exhaust gas 2 of the diesel engine contains soot or a small amount of sulfate (mist-like sulfuric acid component) which is one composition of particulates. ) Is included, the detection port of the pressure sensor 7 is clogged by the soot and accurate pressure detection cannot be performed, or the pressure sensor 7 is corroded due to the condensation of sulfate, making it unusable in a short period of time. There was concern.
[0010]
The present invention has been made in view of the above circumstances, and has a long-life exhaust pressure that can accurately measure exhaust gas pressure by avoiding clogging due to pressure sensor flaws and corrosion due to condensation of sulfate. The object is to provide a measuring device.
[0011]
[Means for Solving the Problems]
The present invention is an exhaust pressure measuring device for measuring the pressure of exhaust gas flowing in an exhaust pipe, and a pressure sensor arranged outside the exhaust pipe is used as a pressure measurement location of the exhaust pipe and a pressurized air supply source. connected via an electromagnetic three-way valve to be switched selectively connecting passage against, at the time of non-measurement of the pressure of the exhaust gas from the pressurized air supply source to the flow path from the three-way solenoid valve down to a pressure sensor The pressurized air can be stored by switching the electromagnetic three-way valve .
[0012]
Therefore, in the present invention, when the pressure of the exhaust gas is not measured, the flow path between the pressurized air supply source and the pressure sensor is connected by the electromagnetic three-way valve and the pressure sensor is disconnected from the pressure measurement location side. since a state where pressurized air has been accumulated from the source of pressurized air to the flow path from the electromagnetic three-way valve up to the pressure sensor, when you want to measure the pressure of the exhaust gas by the pressure sensor, three-way solenoid When the valve is switched and the pressure sensor is opened to the pressure measurement location side, the pressurized air accumulated in the flow path from the electromagnetic three-way valve to the pressure sensor is expelled to the pressure measurement location side. The exhaust gas in the flow path from the electromagnetic three-way valve to the pressure measurement location is discharged to the exhaust pipe side along with soot etc. due to the release of pressurized air, and there is no concern about clogging by soot or corrosion due to condensation of sulfate Pressure in harsh environment It is possible to perform the pressure measurement of the exhaust gas by the capacitor.
[0013]
And after completing the pressure measurement of the exhaust gas with such a pressure sensor in an extremely short time, the electromagnetic three-way valve is switched again to return to the original state, and the pressure sensor is kept disconnected from the pressure measurement location side. Then, since the flow path from the electromagnetic three-way valve to the pressure measurement point is in a clogged state, intrusion of exhaust gas from the exhaust pipe side is prevented as much as possible, and exhaust gas gradually enters. Even in this case, the electromagnetic three-way valve reliably prevents the exhaust gas from reaching the pressure sensor.
[0014]
In the present invention, an air tank for an air brake mounted on a large vehicle may be used as a pressurized air supply source, and in this way, existing facilities can be effectively used without providing a new pressurized air supply source. It can be used.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0016]
FIG. 1 shows an example of an embodiment of the present invention. In this embodiment, the present invention is applied to a large vehicle such as a large truck or a bus equipped with an air tank 8 for an air brake. Thus, the pressure sensor 7 disposed outside the exhaust pipe 3 is selectively switched between the inlet side (pressure measurement location) of the particulate filter 4 in the exhaust pipe 3 and the existing air tank 8. The structure is such that it is connected via an electromagnetic three-way valve 9 so as to obtain.
[0017]
Here, the electromagnetic three-way valve 9 has three ports 10, 11, and 12, and one of these ports 10 is connected to the air tank 8 by a communication pipe 14 through an air dryer 13 with a filter or the like. The port 11 is connected to the pressure extraction pipe 15 on the inlet side of the particulate filter 4 by a communication pipe 16, and the port 12 is connected to the pressure sensor 7 by a communication pipe 17. .
[0018]
A movable iron core 18 is loosely fitted in the port 10 of the electromagnetic three-way valve 9 so as to be movable along the axial center direction of the port 10, and a valve body 19 provided at one end of the movable iron core 18. Can selectively close either the port 10 or the port 11, and when one of the port 10 or the port 11 is closed by the valve body 19, the other of the port 10 and the port 11 is Is communicated with the port 12.
[0019]
Further, a solenoid 20 is provided around the movable iron core 18 so as to surround the movable iron core 18, and when the solenoid 20 is excited by flowing a current, the movable iron core 18 is energized by an electromagnetic force. The solenoid 21 is pulled in against the compression force 21.
[0020]
That is, when the solenoid 20 is de-energized, as shown in the figure, the valve body 19 is seated on the port 11 to close the port 11 and the port 10 and the port 12 are communicated. Is excited, the valve body 19 floats from the port 11, closes the port 10, and the port 11 and the port 12 communicate with each other.
[0021]
Thus, when the pressure of the exhaust gas 2 is not measured, the solenoid 20 of the electromagnetic three-way valve 9 is de-energized to close the port 11 and connect the port 10 and the port 12, whereby the air tank 8 and the pressure sensor 7 are connected. When the pressure sensor 7 is disconnected with respect to the inlet side of the particulate filter 4, the communication pipe 17 extending from the electromagnetic three-way valve 9 to the pressure sensor 7 is connected to about 5 from the air tank 8. ^{~9kg / cm 2 (≒ 5 ×} 9.8 × 10 4 Pa~9 × 9.8 × 10 4 Pa) of the pressurized air 22 is in a state of being accumulated.
[0022]
Next, when it is desired to measure the pressure of the exhaust gas 2 by the pressure sensor 7, the solenoid 20 of the electromagnetic three-way valve 9 is excited to close the port 10 and to connect the port 11 and the port 12. When the pressure sensor 7 is switched and opened to the inlet side of the particulate filter 4, the pressurized air 22 accumulated in the communication pipe 17 is released to the inlet side of the particulate filter 4. The exhaust gas 2 in the communication pipe 16 from the electromagnetic three-way valve 9 to the entrance side of the particulate filter 4 is scavenged to the exhaust pipe 3 side along with soot, etc. due to the release of the soot The pressure of the exhaust gas 2 can be measured by the pressure sensor 7 in a clean environment where there is no concern about corrosion.
[0023]
Here, when the exhaust gas 2 in the communication pipe 16 is surely scavenged to the exhaust pipe 3 side together with soot or the like by the pressurized air 22 accumulated in the communication pipe 17, the following formula [Equation 1]
kP ₀ <π / 4 · (D _b ² · b) / (D _a ² · a + D _b ² · b) · P ₁
a: Length D _a of the flow path from the pressure measurement position to the electromagnetic three-way valve _a : Inner diameter of the flow path from the pressure measurement position to the electromagnetic three-way valve b: Length of the flow path D _b from the pressure sensor to the electromagnetic three-way valve: Of course, the inner diameter k of the flow path from the pressure sensor to the electromagnetic three-way valve is a coefficient of 1 or more: P ₀ : Exhaust gas pressure P ₁ : Various dimensional relationships need to be considered so as to satisfy the pressure of pressurized air. is there.
[0024]
For example, as a relatively simple method, when a, D _a , and D _b are determined, if the length of the connecting pipe 17 is appropriately selected and the value of b is adjusted, the pressurized air Thus, it is possible to realize a reliable scavenging of the communication pipe 16 by 22.
[0025]
After the pressure measurement of the exhaust gas 2 by the pressure sensor 7 is completed in a very short time, the electromagnetic three-way valve 9 is switched again to return to the original state, and the pressure sensor 7 is inserted into the particulate filter 4. If the connection pipe 16 is held in a disconnected state, the inflow of the exhaust gas 2 from the exhaust pipe 3 side is prevented as much as possible, and the exhaust gas 2 gradually enters. Even in this case, the electromagnetic three-way valve 9 reliably prevents the exhaust gas 2 from reaching the pressure sensor 7.
[0026]
Therefore, according to the above embodiment, the exhaust gas 2 in the communication pipe 16 extending from the electromagnetic three-way valve 9 to the inlet side of the particulate filter 4 is scavenged together with soot and the like by the pressurized air 22 in a clean environment. The pressure sensor 7 can measure the pressure of the exhaust gas 2, and when the pressure of the exhaust gas 2 is not measured, the pressure sensor 7 is disconnected from the inlet side of the particulate filter 4 by the electromagnetic three-way valve 9. Since it can be protected, it is possible to avoid clogging of the pressure sensor 7 due to fouling and corrosion due to dew condensation of sulfate, so that the pressure of the exhaust gas 2 can be accurately measured and the pressure sensor 7 The service life can be greatly extended compared to the conventional one.
[0027]
Further, in this embodiment, the air tank 8 for air brake is used as a pressurized air supply source, so that the existing equipment can be effectively used without newly providing a pressurized air supply source. A long-life exhaust pressure measuring device capable of accurately measuring the pressure of the gas 2 can be implemented at low cost.
[0028]
The exhaust pressure measuring device of the present invention is not limited to the above-described embodiment. The pressure measurement location of the exhaust pipe is not limited to the inlet side of the particulate filter, and the pressurized air supply source be may be employed other than the existing air tank, others, can of course be modified in various ways without departing from the gist of the present invention.
[0029]
【The invention's effect】
According to the exhaust pressure measuring device of the present invention described above, various excellent effects as described below can be obtained.
[0030]
(I) According to the invention described in claim 1 of the present invention, the exhaust gas in the flow path from the electromagnetic three-way valve to the pressure measurement location is scavenged together with soot and the like with pressurized air to be clean. It is possible to measure the pressure of the exhaust gas with the pressure sensor in the environment, and when the exhaust gas pressure is not measured, the pressure sensor can be protected from the pressure measurement location side by the electromagnetic three-way valve . In addition, it is possible to avoid clogging due to pressure sensor fouling and corrosion due to condensation of sulfate, which makes it possible to accurately measure the exhaust gas pressure and greatly extend the service life of the pressure sensor compared to the past. it can.
[0031]
(II) According to the invention described in claim 2 of the present invention, the existing equipment can be effectively used without newly providing a pressurized air supply source, and the pressure of the exhaust gas can be accurately measured. However, it is possible to implement an exhaust pressure measuring device with a long service life at a low cost.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of an embodiment of the present invention.
FIG. 2 is a schematic view showing a conventional example.
3 is a cross-sectional view showing details of the particulate filter shown in FIG. 2;
[Explanation of symbols]
2 Exhaust gas 3 Exhaust pipe 7 Pressure sensor 8 Air tank (Pressurized air supply source)
9 Electromagnetic three-way valve 17 Communication pipe (flow path)
22 Pressurized air

Claims (2)

An exhaust pressure measuring device for measuring the pressure of exhaust gas flowing in an exhaust pipe, wherein a pressure sensor disposed outside the exhaust pipe is selectively used with respect to a pressure measurement location of the exhaust pipe and a pressurized air supply source. Connected via an electromagnetic three-way valve so that the connection flow path can be switched, and pressurized air from a pressurized air supply source is supplied to the flow path from the electromagnetic three-way valve to the pressure sensor when the exhaust gas pressure is not measured. An exhaust pressure measuring device configured to store pressure by switching the electromagnetic three-way valve .   The exhaust pressure measuring device according to claim 1, wherein an air tank for an air brake mounted on a large vehicle is used as a pressurized air supply source.

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