JP2002303200A - Exhaust gas pressure measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas pressure measuring apparatus with long service life capable of accurately measuring the pressure of exhaust gas by avoiding the clogging of a pressure sensor with soot and corrosion of sulfate due to condensation. SOLUTION: In this exhaust gas pressure measuring apparatus for measuring the pressure of the exhaust gas 2 flowing in an exhaust pipe 3, the pressure sensor 7 disposed on the outside of the exhaust pipe 3 is connected to the input side (pressure measuring position) of a particulate filter 4 in the exhaust pipe 3 and an air tank 8 (compressed air supply source) through a solenoid three-way valve 9 (passage selector means) so that a connection flow passage can be selectively switched over. Thus the compressed air 22 from the air tank 8 can be properly accumulated in a communication pipe 17 (passage) ranging from the solenoid three-way valve 9 to the pressure sensor 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust pressure measuring device.

[0002]

2. Description of the Related Art Particulate matter (particulate matter) emitted from a diesel engine is:
Soot composed of carbonaceous material and SO composed of high-boiling hydrocarbon components
F (Soluble Organic Fraction: Soluble Organic Component) as a main component, and also contains a small amount of sulfate (mist-like sulfuric acid component). As a measure to reduce this kind of particulates, FIG. As shown in FIG. 1, an exhaust pipe 3 through which exhaust gas 2 from a diesel engine 1 flows
It is considered that a particulate filter 4 is provided in the middle of the process.

As shown in FIG. 3, the particulate filter 4 has a porous honeycomb structure made of a ceramic such as cordierite or the like, and the inlets of the respective flow paths 5 partitioned in a grid are alternately plugged. The outlets of the flow passages 5 whose inlets are not plugged are plugged, and only the exhaust gas 2 that has passed through the porous thin wall 6 that defines each flow passage 5 is located on the downstream side. And the particulates are collected on the inner surface of the porous thin wall 6.

In such a particulate filter 4, it is necessary to appropriately burn and remove the particulate before the exhaust resistance increases due to clogging, and to regenerate the particulate filter 4. In the operating state of the above, since there is little chance of obtaining an exhaust temperature high enough to cause the particulates to self-combust, for example, an oxidation is performed by adding an appropriate amount of a rare earth element such as cerium to alumina carrying platinum. It has been studied to employ a catalyst regeneration type particulate filter 4 in which a catalyst is integrally supported on the particulate filter 4 or an oxidation catalyst is separately provided in a stage preceding the particulate filter 4.

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 even at a lower exhaust gas temperature than before. It can be removed.

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 range, and is at least about 200 ° C. Since the above exhaust temperature is required, the operating state at an exhaust temperature lower than this is required (especially when the exhaust temperature is less than about 2 in the light load operation region).
If the area below 00 ° C. is extended, the oxidation catalyst will not be activated and the particulates will not be burned and removed properly, which may cause the particulate filter 4 to be clogged. Still remains.

For this reason, by taking some means for forcibly raising the exhaust gas temperature, the particulate matter collected by the particulate filter 4 is favorably burned and removed, thereby regenerating the particulate filter 4. However, when such means for raising the exhaust gas temperature are put to practical use, means for detecting in advance that the particulate filter 4 is in an over-collection state is considered. Is essential.

In general, when detecting that the particulate filter 4 is in an over-collecting state, as shown 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 pressure sensor 7 and the trapping state of the particulate filter 4 is estimated based on the detected pressure of the exhaust gas 2.

[0009]

However, even if the pressure sensor 7 is installed to detect the pressure of the exhaust gas 2 as described above, the exhaust gas 2 of the diesel engine still contains
Since it contains soot and a trace amount of sulfate (mist-like sulfuric acid component), which is a component of particulates, the detection port of the pressure sensor 7 is blocked by soot and accurate pressure detection cannot be performed. There was a concern that the sensor 7 would be corroded and unusable in a short time.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has a service life that enables accurate measurement of exhaust gas pressure by avoiding clogging of a pressure sensor with soot and corrosion due to sulfate condensation. It is intended to provide a long exhaust pressure measuring device.

[0011]

SUMMARY OF THE INVENTION The present invention relates to an exhaust pressure measuring device for measuring the pressure of exhaust gas flowing through an exhaust pipe, wherein a pressure sensor disposed outside the exhaust pipe measures the pressure of the exhaust pipe. A connection is made via flow path switching means so that the connection flow path can be selectively switched between the location and the pressurized air supply source, and pressurized air is supplied to the flow path from the flow path switching means to the pressure sensor. It is characterized in that it is configured so that pressurized air from a source can be appropriately stored.

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 flow path switching means, and the pressure sensor is disconnected from the pressure measurement point side. In this state, the pressure from the pressurized air supply source is accumulated in the flow path from the flow path switching means to the pressure sensor, so the pressure sensor measures the exhaust gas pressure. When it is desired to switch the flow path switching means and open the pressure sensor to the pressure measurement point side, the pressurized air stored in the flow path from the flow path switching means to the pressure sensor vigorously violates the pressure measurement point. Released to the side,
Due to the release of the pressurized air, the exhaust gas in the flow path from the flow path switching means to the pressure measurement point is scavenged to the exhaust pipe side together with the soot and the like, and there is a fear of clogging with the soot and corrosion due to dew condensation of the sulfate. It is possible to measure the pressure of the exhaust gas by the pressure sensor in a clean environment without any pressure.

After the exhaust gas pressure measurement by such a pressure sensor is completed within a very short time, the flow path switching means is switched again to return to the original state, and the pressure sensor is moved to the pressure measurement point side. When the disconnection state is maintained, the inflow of exhaust gas from the exhaust pipe side is prevented as much as possible because the flow path from the flow path switching means to the pressure measurement point is in a state of being blocked, and the exhaust gas Even if the gas gradually enters, exhaust gas can be reliably prevented from reaching the pressure sensor by the flow path switching means.

Further, 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. In this case, an existing pressurized air supply source can be provided without newly providing a pressurized air supply source. Effective utilization of the equipment can be achieved.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of an embodiment of the present invention. In this embodiment, an example in which 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 is illustrated. As shown in the figure, a pressure sensor 7 disposed outside the exhaust pipe 3 is selectively connected to the inlet side of the particulate filter 4 in the exhaust pipe 3 (pressure measurement point) and the existing air tank 8. The structure is connected via an electromagnetic three-way valve 9 (flow path switching means) so that the path can be switched.

Here, the electromagnetic three-way valve 9 has three ports 10, 11, and 12, one of which is connected to the air tank 8 via 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. Have been.

A movable core 18 is loosely fitted in the port 10 of the electromagnetic three-way valve 9 so as to be movable along the axial direction of the port 10.
The valve body 19 provided at one end of the port 10 and the port 1
1 can be selectively closed, and when one of the ports 10 and 11 is closed by the valve body 19, the other of the ports 10 and 11 communicates with the port 12. It is supposed to.

Further, a solenoid 20 is provided around the movable iron core 18 so as to surround the movable iron core 18. When a current is applied to the solenoid 20 to excite it, the movable iron core 18 is moved by an electromagnetic force. The spring 20 is drawn toward the solenoid 20 against the compression force of the biasing spring 21.

That is, when the solenoid 20 is not energized, as shown in FIG.
When the solenoid 20 is energized by closing the port 11 while the port 11 is closed and the ports 10 and 12 are communicated with each other, the valve body 19 floats from the port 11 to close the port 10 and 12 is communicated.

Thus, when the pressure of the exhaust gas 2 is not measured,
Port 1 with solenoid 20 of solenoid three-way valve 9 de-energized
1 is closed and port 10 and port 12 are communicated.
Therefore, the flow path between the air tank 8 and the pressure sensor 7 is
Connect the pressure sensor 7 to the particulate filter 4
When the cut-off state is set for the inlet side of the
Connect the air tank 8 to the connecting pipe 17 up to the pressure sensor 7
About 5-9 kg / cm ^Two(≒ 5 × 9.8 × 10^FourPa ~
9 x 9.8 x 10^FourPa) pressurized air 22 is stored
State.

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 make the port 11 and the port 12 communicate with each other. When the flow path is switched to open the pressure sensor 7 to the inlet side of the particulate filter 4, the pressurized air 22 stored in the communication pipe 17 is vigorously discharged to the inlet side of the particulate filter 4, and The release of the compressed air 22 causes the electromagnetic three-way valve 9
The exhaust gas 2 in the communication pipe 16 from the air to the inlet side of the particulate filter 4 is scavenged to the exhaust pipe 3 together with soot and the like, so that there is no fear of clogging with soot or corrosion due to dew condensation of sulfate. The pressure of the exhaust gas 2 can be measured by the pressure sensor 7 under the environment.

Here, when the exhaust gas 2 in the communication pipe 16 is surely scavenged to the exhaust pipe 3 side together with soot by the pressurized air 22 accumulated in the communication pipe 17, the following equation is used.

KP ₀ <π / 4 · (D _b ² · b) / (D _a ² · a +
^{_{D b 2 · b) · P}} 1 a: from the pressure measuring portion electromagnetic length D _a of the flow path to the three-way valve: to electromagnetic three-way valve from the pressure sensor: the inner diameter of the flow path from pressure measuring point to three-way solenoid valve b Length of flow path D _b : inner diameter of flow path from pressure sensor to solenoid three-way valve k: coefficient of 1 or more P ₀ : pressure of exhaust gas P ₁ : pressure of pressurized air Of course, it is necessary to consider.

For example, relatively simple methods include a,
When D _a and D _b are determined, if the value of b is adjusted by appropriately selecting the length of the communication pipe 17, reliable scavenging of the communication pipe 16 by the pressurized air 22 is realized. It becomes possible.

After the pressure measurement of the exhaust gas 2 by the pressure sensor 7 is completed within a very short time,
When the electromagnetic three-way valve 9 is switched again to return to the original state and the pressure sensor 7 is kept disconnected from the input side of the particulate filter 4, the exhaust pipe is closed because the connecting pipe 16 is in a state of being clogged. Intrusion of the exhaust gas 2 from the side 3 is prevented as much as possible, and even when the exhaust gas 2 gradually enters, the electromagnetic three-way valve 9 reliably prevents the exhaust gas 2 from reaching the pressure sensor 7. become.

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 of the particulate filter 4 is scavenged by the pressurized air 22 together with soot and the like to be cleaned. Exhaust gas 2 by pressure sensor 7 in various environments
And when the pressure of the exhaust gas 2 is not measured, the pressure sensor 7 can be protected by the electromagnetic three-way valve 9 from the input side of the particulate filter 4 in a disconnected state. It is possible to prevent clogging of the sensor 7 with soot and corrosion due to dew condensation of the sulfate beforehand, whereby the pressure of the exhaust gas 2 can be accurately measured and the life of the pressure sensor 7 can be greatly extended as compared with the conventional case. Can be.

In this embodiment, the air tank 8 for the air brake is used as a pressurized air supply source.
Exhaust pressure measuring device with a long service life that can accurately measure the pressure of exhaust gas 2 can be used at a low cost because existing equipment can be used effectively without newly providing a pressurized air supply source. can do.

It should be noted that the exhaust pressure measuring device of the present invention is not limited to the above-described embodiment, and that the pressure measuring point of the exhaust pipe is not limited to the inlet side of the particulate filter. A source other than the existing air tank may be used as the supply source.Furthermore, the flow path switching means may use valves other than an electromagnetic three-way valve by various driving methods using air pressure or the like. Needless to say, the flow path switching means may be constituted by the valve described above, and various changes may be made without departing from the spirit of the present invention.

[0029]

According to the exhaust pressure measuring apparatus of the present invention described above, various excellent effects as described below can be obtained.

(I) According to the first aspect of the present invention, the exhaust gas in the flow path from the flow path switching means to the pressure measurement point is scavenged with pressurized air together with soot and the like. The pressure sensor can measure the pressure of the exhaust gas in a clean environment, and when the pressure of the exhaust gas is not measured, the pressure sensor is protected by the flow path switching means from the pressure measurement point as disconnected. Therefore, it is possible to prevent clogging of the pressure sensor with soot and corrosion due to dew condensation of the sulfate beforehand, whereby the pressure of the exhaust gas can be accurately measured and the life of the pressure sensor is longer than before. Can be extended significantly.

(II) According to the second aspect of the present invention, existing equipment can be effectively used without newly providing a pressurized air supply source, and the pressure of exhaust gas can be accurately adjusted. An exhaust pressure measuring device having a long life and capable of measuring can be implemented at low cost.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of an embodiment for implementing the present invention.

FIG. 2 is a schematic view showing a conventional example.

FIG. 3 is a sectional view showing details of a particulate filter of 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 (flow path switching means) 17 Communication pipe (flow path) 22 Pressurized air

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takashi Dobashi 3-1-1, Hinodai, Hino-shi, Tokyo Inside Hino Motors Co., Ltd. (72) Kiyoshi Hirano 3-1-1, Hinodai, Hino-shi, Tokyo Hino (72) Inventor Takemichi Kawakami 3-1-1 Hinodai, Hino-shi, Tokyo Hino Motors Co., Ltd. (72) Toshiaki Osaki 3-1-1 Hinodai, Hino-shi, Tokyo Hino Motors, Ltd. F term (reference) 3G084 AA01 BA13 BA24 DA10 3G090 AA02 BA01 CA01 DA02 EA04

Claims (2)

[Claims] An exhaust pressure measuring device for measuring the pressure of exhaust gas flowing through an exhaust pipe, comprising: a pressure sensor disposed outside the exhaust pipe; a pressure measuring point of the exhaust pipe; a pressurized air supply source; Connected to the flow path switching means so that the connection flow path can be selectively switched, and pressurized air from a pressurized air supply source is appropriately supplied to the flow path from the flow path switching means to the pressure sensor. An exhaust pressure measuring device characterized by being configured to be able to accumulate pressure. 2. The exhaust pressure measuring device according to claim 1, wherein an air tank for an air brake mounted on a heavy-duty vehicle is used as a pressurized air supply source.