JPH09324707A - Egr device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To aim at elimination of mist and small dew drops generated by dew formation from moisture included inside of EGR(exhaust gas recirculation) gas by arranging, in a piping system connecting gas cooling device and the intake valve of an engine in which EGR gas passes, at least one of more than one mist separators or dew eliminators. SOLUTION: A mist separator 51 or a dew eliminator 52 is provided immediately behind the EGR gas flow outlet 40 of an EGR gas cooler 30. A mist separator 51' or dew eliminator 52' is provided immediately behind an intetrcooler for the purpose of a mixture consisting of air and fuel introduced through an air filter A and EGR gas added to this mixture. And also it is possible to use, in immediate front of the air intake valve of an engine E, a single or plural mist separators 51" or dew eliminators 52". Thereby, EGR gas which is allowed to pass the inside of a tubular body 34 and cooled removes any mist or small dew drops generated by dew formation of moisture included in the gas in an EGR piping 50 so as to restrain performance deterioration caused by corrosion of parts.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a cooled EGR.
The present invention relates to an EGR device that prevents corrosive substances from being generated due to dew condensation of water in a gas in an EGR pipe, thereby improving durability with respect to components of an EGR gas circulation system and smoothing engine operation. It is a thing.

[0002]

2. Description of the Related Art A method of extracting a part of exhaust gas from an exhaust system, returning the exhaust gas to an intake system of an engine, and adding the exhaust gas to an air-fuel mixture is based on an EGR (Exhaust Gas Recircucu).
ration: exhaust gas recirculation). EGR is NO
x, suppression of pump loss, reduction of heat radiation loss to coolant due to lowering of combustion gas temperature, increase of specific heat ratio by change of working gas amount and composition, and improvement of cycle efficiency accompanying this. Therefore, it is an effective method to improve the thermal efficiency of the engine.

However, when the temperature of the EGR gas rises, the thermal action deteriorates the durability of the EGR valve and the like, which may lead to premature damage, and it is necessary to make the EGR valve a water-cooled structure to prevent it. It is known that there is. In order to avoid such a situation, E
A device for cooling GR gas is used, and a multi-tube heat exchanger is mainly used as this device, but a fin-tube heat exchanger is used, or a multi-tube heat exchanger and a fin tube are used. There is also a case where a type heat exchanger is used together.

A multi-tube heat exchanger used in this case has an end cap 14 having an EGR gas inflow port 14a or an EGR gas outflow port 14b on one side or both sides as shown in FIG. A body tube 11 is connected and fixed to a head member (hub) 16 which is partitioned by a partition wall 15 and additionally has a cooling medium inlet 16a. Inside the body tube 11, a large number of heat transfer tubes 12 are provided. The head member 16 is fixedly arranged in the mounting hole provided in the partition wall 15 of
Cooling medium inlet 16a, cooling medium outlet 1
A branch pipe 17 such as a rubber hose is connected to the nipple 18 screwed to the 6b, and the heat transfer pipe 12 is introduced by the engine coolant introduced or discharged from the branch pipe 17.
It is known that the EGR gas flowing inside is cooled (see Japanese Utility Model Publication No. 57-309).

However, the multi-tube heat exchanger has a problem in that a large flow resistance is generated because the flow of the engine cooling liquid or the like is sharply bent at the cooling medium inlet 16a, and a large number of heat transfer tubes 12 are fixed. Since both the head member 16 and the partition wall 15 are made of cast or forged, the weight of the heat exchanger body becomes excessive, and the nipple 18 for connecting the upper branch pipe 17 is screwed to the cooling medium outlet 16b. Machining connection holes and partitioning multiple heat transfer tubes 12 1
Since the work of fixing and arranging to the No. 5 is required, there is a problem that the number of assembling steps is increased and the workability is deteriorated. Further, a brazing work is adopted as a joining means of the many heat transfer tubes 12 to the partition wall 15. Therefore, the heat transfer tube 12 and the partition wall 15 have different wall thicknesses, and thus have different heat capacities, which results in poor reliability in maintaining the strength of the brazing work portion, which may cause brazing failure.

The present applicant has proposed Japanese Patent Application No. 7-267691 to solve the above-mentioned difficulties. This device is shown in FIG.
As shown in FIG. 2, a plurality of heat transfer tubes 12 are fixedly arranged on the tube sheet 3 fixed to the inner wall of the body tube 11 at both ends of the body tube 11, and the EGR gas inlets 14 a and the EGR gas inlet ports 14 a and EGR are formed at the ends of the body tube 11. A multi-tube EGR gas cooling device provided with a gas outlet port (14b), further including a cooling medium inlet port (6a) in the barrel tube (1) itself by burring molding outward.
And an EGR gas cooling apparatus having a structure in which branch pipes 7a and 7b are directly brazed or welded to the cooling medium inlet 6a and the cooling medium outlet 6b provided by the burring molding. .

Although the EGR gas cooling device proposed in Japanese Patent Application No. 7-267691 has been effective in improving the above-mentioned problems, it passes through the pipes constituting the heat transfer pipe group and cools with the cooling medium. The EGR gas cooled by the exchange was recirculated to the intake system of the engine as it was without any treatment thereafter. Now, the EGR gas recirculated from the exhaust system of the engine to the intake system of the engine via the EGR gas cooling device contains the sulfur dioxide gas and the nitrous acid gas which are the composition of the exhaust gas. On the other hand, when the EGR gas is cooled, the water content in the EGR gas is condensed to form mist or small droplets. As a result, the EGR gas cooled by the EGR gas cooling device becomes a mist or a small droplet due to the condensation of water in the gas, and the sulfurous acid gas or the nitrous acid gas in the EGR gas is mixed into the mist or the small droplet. As a result, sulfurous acid or nitrous acid is produced. The sulfurous acid or nitrous acid generated in this way corrodes the inner peripheral surface of the EGR pipe and engine parts such as the cylinder, piston ring, and intake valve, and results in a lack of smooth engine operation. .

[0008]

SUMMARY OF THE INVENTION The present invention overcomes the above drawbacks by making minor changes to the components,
In the R device, the EG cooled by the EGR gas cooling device
It is possible to prevent the moisture in the R gas from condensing in the passage to form a corrosive substance, thereby improving the durability of the EGR gas circulation system components against corrosion and ensuring smooth engine operation. (EN) It is an object of the present invention to provide an EGR device in which even if a leak occurs in an EGR cooling device and engine cooling water leaks into an EGR piping system, it does not reach a combustion chamber of an engine.

[0009]

In order to solve the above problems, the present invention is directed to an EGR device in which a part of exhaust gas is taken out as EGR gas from an exhaust system, returned to the intake system of an engine, and added to an air-fuel mixture. In the above, in the EGR gas cooling device for exchanging heat with the cooling medium for cooling the EGR gas and the piping system through which the EGR gas is connected, which connects between the intake valve of the engine,
It is characterized by an EGR device provided with at least one of one or more mist separators or a drip removing device.
In this case, at least one of the mist separator and the drip removal device is preferably provided with an auto drain or a water sensor.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to an EG as shown in FIG.
The exhaust gas of the engine E is partially taken out from the exhaust system and the EGR gas cooling device 30
The air is returned to the intake system of the engine via the air filter A, is added to the mixture of air and fuel introduced from the air filter A, and is circulated to the intake valve via the intercooler I if necessary. EGR pipe 50 connecting at least one mist separator and / or drip removal device to the EGR pipe 50
By using the GR device, it is possible to prevent the corrosion deterioration phenomenon of the components due to the circulation of the corrosion product generated from the cooled EGR gas within the pipe diameter through which the EGR gas passes and to ensure smooth engine operation. It is a thing.

The present invention will now be described in detail below with reference to the accompanying drawings. FIG. 1 is a block diagram showing an outline of an EGR device of the present invention, FIG. 2 is a schematic view of an embodiment of the present invention, and FIG. FIG. 4 is a schematic view of another embodiment of the present invention.

The EGR device according to the present invention is provided with an EGR gas cooling device 30, which is made of sheet metal and fixed to both ends of an inner wall 32 of a body tube 31, as shown in FIG. A heat transfer tube group consisting of a plurality of tube bodies 34 is fixedly arranged in the tube body 34, and the tube body 34 has a plurality of through holes 37 in a support plate 36 whose outer peripheral portions 35 are fixed to the inner wall 32 of the body tube 31 at a plurality of locations. End caps 38 ′ provided with EGR gas inlets 39 and EGR gas outlets 40 are fixed to the outside of both ends of the body tube 31, and a cooling medium flow is attached to the body tube 31. An inlet 41 and a cooling medium outlet 42 are provided, and a branch pipe 43 is joined to the cooling medium inlet 41 and the cooling medium outlet 42. On the other hand, the EGR pipe 5 that connects the EGR gas outlet 40 of the EGR gas cooling device 30 and the intake system of the engine E
0 is a conventionally known plate type or cyclone
Type mist separator 51 and drip removal device (not shown)
Or a refrigerant type (freezing type) drip removing device 52 is provided in addition to the mist separator 51 as shown in FIG.

If the mist separator 51 or the drip removing device 52 is provided near the EGR gas outlet 40 of the EGR gas cooling device 30, mist or small droplets will be generated from the EGR gas cooled by the EGR gas cooling device. Is preferable because it can be removed before it is generated in the EGR pipe 50 or immediately after it is generated, and an auto drain 54 is provided at the bottom of the mist separator 51 or the drip removal device 52.
It is preferable to discharge the mist or droplets in which the sulfurous acid gas, the nitrous acid gas, etc. are dissolved to the outside. Furthermore, EGR piping 50
It is more preferable to provide a plurality of cooling fins 53 on the outer peripheral surface thereof in order to utilize as a fin tube type heat exchanger because the heat exchange efficiency is improved.

In this case, both the mist separator 51 and the drip removing device 52 may be arranged in combination as shown in FIG. 3 and as described above, or, as shown in FIG. 1, the EGR of the EGR gas cooling device 30. Immediately after the gas outlet 40, a mixture of air and fuel introduced from a mist separator 51 or a drip removal device 52, an air filter A and EGR added to the mixture.
The mist separator 51 'or drip removal device 52' immediately after the intercooler I for gas and the mist separator 51 '' or drip removal device 5 immediately before the intake valve of the engine E.
It is also possible to use one or a plurality of 2 "in combination, and it is preferable to use a plurality of or 2" in combination in order to ensure the effect of the mist separator or the drip removing device.

With the above construction, when the EGR gas cooling device 30 is operated, the E gas cooled by passing through the tube body 34 forming the heat transfer tube group and exchanging heat with the cooling medium is cooled.
GR gas removes mist and droplets generated by condensation of water in the EGR pipe 50, so that sulfur dioxide, nitrite gas, etc. are dissolved to form corrosion products such as sulfurous acid, nitrous acid, etc. Can be recirculated in the system without causing As a result, the performance deterioration due to corrosion of various parts constituting the EGR gas recirculation system was significantly suppressed.

Further, even if a leak occurs in the EGR gas cooling device 30, the engine cooling water leaked by the provision of the mist separator 51 and the drip removing device 52 is discharged without reaching the intake system piping, especially the intake manifold. If necessary, the water sensor 55 is incorporated in the auto drain 54 to provide a signal according to various situations (for example, when the drain interval becomes short, the EGR gas cooling device 30 may be leaked due to corrosion or the like. Therefore, by issuing a warning to the driver), control according to the situation becomes possible.

[0017]

As described above, the EG according to the present invention is used.
Since the R device is provided with one or more mist separators and / or a drip removing device in a piping system through which EGR that connects between the EGR gas cooling device and the intake valve of the engine, the R device is cooled by the EGR gas cooling device. The mist and droplets generated by the condensation of water in the generated EGR gas are removed, so that sulfurous acid gas, nitrous acid gas, etc. will not dissolve and the corrosion products such as sulfurous acid, nitrous acid, etc. will not occur Can be recycled. As a result, the performance deterioration due to the corrosion of various components forming the EGR gas circulation system is significantly suppressed, and the operation of the engine becomes smooth. In the unlikely event of E
Even if a leak occurs in the GR gas cooling device, major trouble can be prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing an outline of an EGR device of the present invention.

FIG. 2 is a schematic view of an embodiment of the present invention.

FIG. 3 is a schematic view of another embodiment of the present invention.

FIG. 4 is a partially cutaway plan view of a conventional example.

FIG. 5 is a partially cutaway plan view of another conventional example.

[Explanation of symbols]

 E Engine 30 EGR Gas Cooling Device 31 Body Tube 32 Inner Wall 33 Tube Sheet 34 Tubular Body 36 Support Plate 37 Through Hole 38 End Cap 39 EGR Gas Inlet 40 EGR Gas Outlet 41 Cooling Medium Inlet 42 Cooling Medium Outlet 50 EGR Piping 51, 51 ', 51 "Mist separator 52, 52', 52" Drip removal device 53 Cooling fin 54 Auto drain 55 Water sensor

Claims (3)

[Claims] 1. An EGR gas for cooling an EGR gas by exchanging heat with a cooling medium in an EGR device for extracting a part of the exhaust gas as EGR gas from the exhaust system, returning the exhaust gas to the intake system of the engine again, and adding the mixture gas. 1 for the piping system through which EGR gas that connects between the cooling device and the intake valve of the engine passes
An EGR device comprising at least one of at least one mist separator and a drip removal device. 2. The EGR device according to claim 1, wherein at least one of the mist separator and the drip removing device is provided with an auto drain. 3. The EGR device according to claim 1, wherein a water sensor is arranged in at least one of the mist separator and the drip removing device.