JP2002371921A - Egr cooler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an EGR cooler capable of preventing a clogging by avoiding the adhesion of particulate matter in EGR gas to an EGR gas passage irrespective of the temperature of the EGR cooler by charging the particulate matters in the EGR gas passing the EGR cooler and charging the surface of the EGR gas passage at the heat exchanging portion of the EGR cooler to the same polarity as that of the particulate matters to electrically repel the particulate matters each other. SOLUTION: In this EGR cooler 1 disposed in the EGR device of an engine to cool the EGR gas G, a particulate matter charging means 30 for charging particulate matters PM in the exhaust gas G is installed on the upstream side of the EGR gas passage 21 at the heat exchanging portion 20 of the EGR cooler 1, and a passage charging means 40 for charging the surface 21f of the EGR gas passage 21 at the heat exchanging portion 20 to the same polarity as that of the charged particulate matters PM is installed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an EGR cooler provided in an EGR device for suppressing generation of nitrogen oxides by recirculating a part of exhaust gas of an engine.

[0002]

2. Description of the Related Art One of the measures against exhaust gas from a diesel engine or the like is to reduce the combustion temperature by lowering the combustion temperature by recirculating a part of the exhaust gas to the intake air in order to reduce the emission of NOx in the exhaust gas. , EGR to suppress NOx generation
(Exhaust gas recirculation: Exhaust gas recirculation) is available and widely used.

In this EGR device, an EGR passage is provided between an exhaust passage and an intake passage of an engine to divide and recirculate EGR gas from exhaust gas, and a flow rate of the EGR gas is adjusted by an EGR valve disposed in the EGR passage. While performing EGR. In an engine such as a diesel engine, EG indicating a supply ratio of exhaust gas to fresh air is used.
When the R rate is increased, the effect of suppressing NOx increases.

[0004] However, if the EGR gas expanded at a high temperature is directly recirculated to the intake side, the filling rate of the EGR gas and fresh air into the cylinder decreases.
Since the amount of EGR decreases and the NOx suppressing effect decreases, and the amount of fresh air required for fuel also decreases, good combustion cannot be obtained.

To avoid this, a water-cooled type EGR cooler or the like is provided in the middle of the EGR passage to cool the EGR gas to reduce its volume before supplying it to the intake passage. By cooling the EGR gas with this EGR cooler to reduce the gas volume, the amount of EGR gas supplied into the cylinder is increased, and the combustion temperature is lowered by the low temperature EGR gas to efficiently reduce NOx in the exhaust gas. Reduce. Further, the efficiency of sucking air into the cylinder is improved to maintain good combustion of the engine.

[0006] Since high temperature and highly corrosive exhaust gas flows through the EGR cooler, stainless steel (SUS) excellent in corrosion resistance and heat resistance is often used. Since the thermal conductivity is poor, the EGR gas passage is narrowed or fins are provided on the EGR gas passage side in order to increase the heat transfer area and increase the cooling efficiency.

[0007]

However, not only NOx but also NOx is contained in exhaust gas from diesel engines and the like.
Since particulate matter (particulates: PM) containing carbon as a main component is contained and cooled in the EGR gas passage in the heat exchange part, the particulate matter adheres to the heat exchange part and causes the EGR cooler to be cooled. As the accumulated amount of passing exhaust gas increases, clogging progresses in the heat exchange portion, and EG
The cooling of the R gas and the passage of the EGR gas are hindered. As a result, the cooling efficiency of the EGR gas decreases, and the amount of the EGR gas also decreases, which causes a problem that the amount of exhausted NOx increases.

In order to avoid this, Japanese Patent Laid-Open No. 11-12 / 1999
In the exhaust gas recirculation apparatus disclosed in Japanese Patent No. 5153, a combustion means such as a combustion burner for burning carbon adhered to a large number of small tubes is provided at an exhaust gas inlet of an EGR cooler. By burning off the adhered carbon, the flow of exhaust gas is made appropriate,
This prevents a decrease in the cooling performance of the GR cooler.

However, in this exhaust gas recirculation device, even if it is temporary, the burner is burned to burn the deposited carbon, and the temperature of the EGR cooler is increased.
As the cooling efficiency decreases, a combustion burner, a fuel tank, a fuel pipe, and an air pipe are required as fuel means.
There is a problem that the structure and control of the R cooler are complicated.

In the method for preventing foreign matter from adhering in an exhaust gas recirculation combustion system disclosed in Japanese Patent Application Laid-Open No. 2000-146465, an oxidation catalyst is carried on a pipe upstream of an EGR cooler or a portion of the EGR cooler that comes into contact with EGR gas. By oxidizing and burning the SOF component that performs the bonding function such as carbon particles, the bonding function is eliminated,
The carbon particles and the like are dried by the heat of combustion to be separated and blown off, thereby preventing soot and carbon from adhering and accumulating.

However, in the method using the oxidation catalyst, the amount of the EGR gas is small, and the gas passage in the EGR cooler is cooled, so that the temperature of the oxidation catalyst is easily lowered, and it is difficult to activate the catalyst. There's a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and there is provided an EGR apparatus for branching a part of exhaust gas from an exhaust passage of a diesel engine, cooling the exhaust gas through an EGR cooler, and introducing the cooled exhaust gas into an intake passage. Charge the particulate matter in the EGR gas before entering the heat exchange portion of the EGR cooler, and charge the EGR gas in the heat exchange portion of the EGR cooler.
By charging the gas passage surface to the same polarity as the charged particulate matter and repelling the particulate matter, it is possible to prevent clogging regardless of the temperature of the heat exchange part.
To provide an R cooler.

[0013]

An EGR cooler for achieving the above object is configured as follows.

1) E provided in the EGR device of the engine
In an EGR cooler for cooling GR gas, a particulate matter charging means for charging particulate matter in exhaust gas is provided upstream of an EGR gas passage in a heat exchange portion of the EGR cooler, and the EGR cooler in the heat exchange portion is provided. It is formed by providing a passage charging means for charging the passage surface of the gas passage to the same polarity as the charged particulate matter.

With this configuration, the particulate matter in the exhaust gas is charged, and the surface of the exhaust gas passage in the heat exchange portion of the EGR cooler is charged to the same polarity.
Since they repel each other, particulate matter can be prevented from adhering to the surface of the exhaust gas passage, and clogging can be prevented regardless of the temperature of the EGR cooler.

In the above EGR cooler, a particulate matter discharging means for discharging the charged particulate matter is provided in or downstream of the EGR gas passage of the heat exchange portion. According to this configuration, it is possible to prevent the charged particulate matter from leaving the EGR cooler while being charged and adhering to the EGR passage or the intake passage.

2) In the above-mentioned EGR cooler, the particulate matter charging means is formed by a combination of a positive electrode and a negative electrode opposed to each other across a passage on the upstream side of the EGR gas passage in the heat exchange portion. A passage charging means is formed by electrically connecting the surface of the passage to a negative electrode of a DC power supply and electrically connecting the particulate matter discharging means to the EGR gas passage of the heat exchange portion. It is formed by inserting an electrode connected to the electrode. With this configuration, it is possible to prevent clogging of the EGR cooler with a relatively simple configuration.

Further, in the above EGR cooler, the electrode inserted into the EGR gas passage of the heat exchange portion is connected to a negative electrode of the DC power supply to which the electrode is connected via a switch, and the switch is turned on. Thus, the electrode is formed so as to be energized and heated. With this configuration, the particulate matter attached to the electrode can be easily removed by burning.

When an oxidation catalyst is supported on the positive electrode, the burning and removal of particulate matter can be promoted, and the burning and removal of particulate matter can be performed efficiently.

3) Alternatively, in the EGR cooler, the particulate matter charging means may be provided in a mesh-like or porous state connected to a negative electrode of a DC power supply in a path on the upstream side of the EGR gas passage in the heat exchange portion. The passage charging means is formed by electrically insulating the passage surface and connecting to the negative electrode of the DC power supply,
The particulate matter discharging means is connected to the EG of the heat exchange portion.
A mesh-like or porous, gas-permeable second conductor connected to the positive electrode is provided and formed in a passage downstream of the R gas passage. Also with this configuration, it is possible to prevent clogging of the EGR cooler with a relatively simple configuration.

Further, in the above-mentioned EGR cooler, the second conductor is connected to a negative electrode of the DC power source to which the second conductor is connected via a switch, and the switch is turned on to thereby switch the second conductor. It is formed and configured so that it can be heated by energizing the body. With this configuration, the particulate matter attached to the electrode can be easily removed by burning.

Further, when an oxidation catalyst is carried on the second conductor, burning and removal of particulate matter can be promoted,
The particulate matter can be burned and removed efficiently.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an EGR cooler according to the present invention will be described with reference to the drawings.

FIG. 1 is a schematic sectional view showing the structure of an EGR cooler according to a first embodiment of the present invention.
FIG. 3 is a cross-sectional view illustrating a configuration of an exhaust gas passage of a heat exchange portion of an EGR cooler. FIG. 3 is a schematic sectional view showing a structure of an EGR cooler according to a second embodiment of the present invention.

First, the EGR cooler according to the first embodiment will be described.

As shown in FIG. 1, the EGR cooler 1 of the first embodiment is provided with tube sheets 12, 13 near both ends inside a main body (casing) 11, and the tube sheets 12, 1 are provided.
3, the interior of the main body 11 is partitioned, a gas supply chamber 14 is provided on the inlet side (upstream side), and a gas discharge chamber 15 is provided on the outlet side.
Are formed by disposing a plurality of cooling pipes (heat exchanger tubes) 16 that form the exhaust gas passage 21 of the heat exchange part 20 through which the air flows.

On the cooling water side, a cooling water supply pipe 17 is provided near the gas supply chamber 14 and a cooling water discharge pipe 18 is provided near the gas discharge chamber 15 so as to communicate with a water jacket of an engine (not shown). The cooling water W is configured to circulate.

The particulate matter charging means 30 for charging the particulate matter PM in the exhaust gas G is supplied to the gas supply chamber 14 which is a passage on the upstream side of the EGR gas passage 21 of the heat exchange portion 20 of the EGR cooler 1. Is provided. The particulate matter charging means 30 includes a positive electrode 31 and a negative electrode 32 which are electrically insulated from the main body 11 with the gas supply chamber 14 interposed therebetween. Switch 34
And are formed by applying a high voltage to the positive electrode 31 and the negative electrode 32.

Then, a passage charging means 40 is provided in the EGR gas passage 21 of the heat exchange part 20. The passage charging means 40 electrically insulates the passage surface 21f, which is the surface of the cooling pipe 16 on the EGR gas passage side, with an insulating film 16s or the like, and connects to the negative electrode of the second DC power supply 42 via the second switch 44. To form a connection. With this configuration, the passage surface 21f is charged to the same negative polarity as the charged particulate matter PM.

Further, a round rod or a plate-like electrode 51 is inserted into each EGR gas passage 21 of the heat exchange section 20 to connect the downstream side to the positive electrode of the second DC power supply 42 and the upstream side to the second side. A negative electrode of the power supply 42 is connected via a third switch 52, and a particulate matter discharging means 50 is provided.

Next, the operation and effect of the EGR cooler 1 will be described.

When the EGR gas G is passing through the EGR cooler 1 by performing the EGR, the first switch 34 and the second switch 44 are turned on, and the EGR gas G is not performed.
Is turned off when does not pass through the EGR cooler 1. As a result, only during the EGR, a high voltage is applied to the positive electrode 31 and the negative electrode 32, and the charging of the passage surface 21f and the voltage to the positive electrode 51 are applied.

The exhaust gas G entering the EGR cooler 1
The gas passes between the positive electrode 31 and the negative electrode 32 to which a high voltage is applied in the gas supply chamber 14 on the upstream side of the EGR gas passage 21 of the heat exchange portion 20 of the EGR cooler 10, and the exhaust gas is discharged by corona discharge or the like. The particulate matter PM in G is negatively (negatively) charged.

The negatively charged particulate matter PM
Is passed through the EGR gas passage 21 of the heat exchange part 20, but since the passage surface 21f of the EGR gas passage 21 is negatively charged, the exhaust gas G repels each other and the charged particulate matter PM The positive electrode 5 disposed at the center of the EGR gas passage 21 without adhering to the passage surface 21f
1 attracts and loses charge by contact, and adheres to or passes through the positive electrode 51. Then, the particulate matter PM that has passed through the EGR gas passage 21 goes out of the EGR cooler 1 and enters the cylinder together with fresh air to be reburned. This allows
Regardless of the temperature of the EGR cooler 1, the particulate matter PM can be prevented from adhering to the passage surface 21f, so that clogging can be prevented.

When the amount of the particulate matter PM attached to the positive electrode 51 increases, the third switch 52 is turned on to form a circuit, and a current is supplied to the positive electrode 51 for heating. The particulate matter P attached to the positive electrode 51 by this heating
M is burned off. The burning and removal of the particulate matter PM
Since it is performed in the center of the exhaust gas passage 21, the influence of the cooling water is small and the combustion can be efficiently removed.

When an oxidation catalyst is carried on the positive electrode 51, the burning and removal of the particulate matter PM can be promoted, and the burning and removal of the particulate matter PM can be efficiently performed.

Next, an EGR cooler according to a second embodiment will be described.

As shown in FIG. 3, in the EGR cooler 1A of the second embodiment, the EGR cooler 1A of the second embodiment
The particulate matter charging means 30A is formed similarly to the GR cooler 1, but charges the particulate matter PM in the exhaust gas G.
Is a gas supply chamber 14A serving as a passage on the upstream side of the EGR gas passage 21A of the heat exchange portion 20A of the EGR cooler 10A.
The mesh-shaped or porous air-permeable first conductor 35
A is provided and connected to the negative electrode of the first DC power supply 33A via the first switch 34A.

Further, the passage charging means 40A of the EGR gas passage 21A of the heat exchange portion 20A is connected to the EGR gas passage 21A of the heat exchange portion 20A.
The passage surface 21Af of the GR gas passage 21A is
A is electrically insulated by A or the like, and is formed by connecting to the negative electrode of the second DC power supply 42A via the second switch 44A. The positive electrode side of the fourth DC power supply 42A is connected to the first DC power supply 33A.
Of the passage surface 21 from the conductor 35A.
Af is made electrically negative (negative).

The particulate matter discharging means 50A is connected to the gas discharge chamber 15A on the downstream side of the EGR gas passage 21A of the heat exchange section 20A to the positive electrode of the first DC power supply 33A via the third switch 52A. It is formed by providing a mesh-shaped or porous air-permeable second conductor 55A.

With this configuration, the EGR cooler 1
The exhaust gas G entering A passes between the first conductors 35A provided in the gas supply chamber 14A on the upstream side of the EGR gas passage 21A of the heat exchange portion 20A of the EGR cooler 1A. Is negatively charged.

The negatively charged particulate matter PM
Is passed through the EGR gas passage 21A of the heat exchange portion 20A. Since the passage surface 21Af of the EGR gas passage 21A is negatively charged with the same polarity as the particulate matter PM, the exhaust gas G repels each other. However, the particulate matter PM does not adhere to the passage surface 21Af and the EGR gas passage 21
A, and enters the downstream gas discharge chamber 15A.

In the gas discharge chamber 15A, the negatively charged particulate matter PM is attracted to the positively charged second conductor 55A and comes into contact therewith, loses charge and becomes electrically neutral.
Attach to or pass through the second conductor 55A. Then, the passed particulate matter PM goes out of the EGR cooler 1A, enters the cylinder together with fresh air, and reburns. Thereby, regardless of the temperature of the EGR cooler 1A, clogging by the particulate matter PM can be prevented.

When the amount of the particulate matter PM attached to the second conductor 55A increases, the third switch 52A
Is turned on to form a circuit, and a current is passed through the second conductor 55A to heat it. This heating burns and removes the particulate matter PM attached to the second conductor 55A. Since the combustion removal of the particulate matter PM is performed in the gas discharge chamber 15A downstream of the exhaust gas passage 21A, it is hardly affected by the cooling water, and the combustion removal can be performed efficiently.

When an oxidation catalyst is carried on the second conductor 55A, the burning and removal of the particulate matter PM can be promoted, and the particulate matter PM can be efficiently burned and removed.

[0046]

As described above, the EGR of the present invention is
According to the cooler, in an EGR device that branches a part of the exhaust gas from an exhaust passage of a diesel engine, cools the exhaust gas through an EGR cooler, and introduces the exhaust gas into an intake passage, the particulate matter in the exhaust gas is charged and the EGR cooler is charged. The passage surface of the exhaust gas passage in the heat exchange portion is charged to the same polarity as the charged particulate matter and is electrically repelled, thereby preventing the adhesion of the particulate matter to the passage surface of the exhaust gas passage. it can.

Therefore, clogging can be prevented irrespective of the temperature of the EGR cooler, and the EG can be continuously and efficiently used.
R can be performed.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a structure of an EGR cooler according to a first embodiment of the present invention.

FIG. 2 is a schematic sectional view showing a configuration of an exhaust gas passage of a heat exchange portion of the EGR cooler of FIG.

FIG. 3 is a schematic sectional view showing a structure of an EGR cooler according to a second embodiment of the present invention.

[Explanation of symbols]

 1, 1A EGR cooler 14, 14A Gas supply chamber (upstream passage) 15, 15A Gas exhaust chamber (downstream passage) 20, 20A Heat exchange portion 21, 21A EGR gas passage 21f, 21Af passage surface of heat exchange portion 30, 30A Particulate matter charging means 31 Positive electrode 32 Negative electrode 33A, 42A DC power supply 35A First conductor 40, 40A Passage charging means 42 DC power supply 50, 50A Particulate matter discharging means (51 Electrode 52, 52A Switch 55A Second conductive material Body G EGR gas PM Particulate matter

Claims (6)

[Claims] 1. An EG disposed in an EGR device of an engine.
In an EGR cooler for cooling R gas, a particulate matter charging means for charging particulate matter in exhaust gas is provided upstream of an EGR gas passage in a heat exchange part of the EGR cooler, and the EGR cooler in the heat exchange part is provided. EGR characterized in that a passage charging means for charging the surface of the gas passage to the same polarity as the charged particulate matter is provided.
Cooler. 2. An EGR cooler according to claim 1, further comprising a particulate matter discharging means for discharging the charged particulate matter in the EGR gas passage or downstream of the heat exchange portion. . 3. The particulate matter charging means is formed by a combination of a positive electrode and a negative electrode opposed to each other across a passage on the upstream side of the EGR gas passage of the heat exchange portion, and the passage charging means is provided on the surface of the passage. Is electrically insulated and connected to the negative electrode of the DC power supply, and the particulate matter discharging means is inserted through the EGR gas passage of the heat exchange portion through the electrode connected to the positive electrode of the DC power supply. The EGR cooler according to claim 1, wherein the EGR cooler is formed. 4. The electrode inserted into the EGR gas passage of the heat exchange portion is connected to a negative electrode of the DC power supply to which the electrode is connected via a switch, and the switch is turned on to thereby switch the electrode. 4. The EGR cooler according to claim 3, wherein the EGR cooler is formed so as to be able to heat by energizing the EGR. 5. A mesh-shaped or porous gas-permeable first conductor connected to a negative electrode of a DC power supply, wherein the particulate matter charging means is provided in a passage on the upstream side of the EGR gas passage in the heat exchange portion. The passage charging means is formed by connecting the surface of the passage electrically insulated to the negative electrode of a DC power supply, and the particulate matter discharging means is formed of the EGR gas in the heat exchange portion. 3. The EGR cooler according to claim 1, wherein a mesh-shaped or porous second conductive body connected to the positive electrode is provided in a passage downstream of the passage. 6. The second conductor is connected to a negative electrode of the DC power supply to which the second conductor is connected via a switch, and when the switch is turned on, the second conductor is energized and heated. The EGR cooler according to claim 5, wherein the EGR cooler is formed so as to be capable of being formed.