JP2003254170A - Exhaust gas recirculation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas recirculating device capable of preventing the exhaust gas recirculation passage from being deposited by SOF and/or soot by oxidating the SOF to be removed, suppressing a temperature rise of the recirculation gas, and supplying a major potion of gas-form CO and HC in the exhaust gas to the combustion chambers. <P>SOLUTION: An SOF adsorptive oxidating catalyst capable of adsorbing SOF in the gas being recirculated and oxidating selectively is installed at least either of in the upstream and inside of a cooling device 3 for the exhaust gas recirculation passage. The catalyst adsorbs SOF at 200-400°C and oxidates it and removes selectively, while it does not oxidate the gas-form CO and HC under 400°C, and oxidation of SO<SB>2</SB>is also suppressed. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation device for supplying exhaust gas in an exhaust passage of an internal combustion engine to an intake passage via a cooling device.

[0002]

2. Description of the Related Art For example, in a diesel combustion engine,
In order to suppress the emission of NO _x , the exhaust passage and the intake passage are connected by an exhaust gas recirculation (hereinafter referred to as EGR) passage.
The exhaust gas is recirculated into the intake passage through the EGR passage. In this case, since the recirculated gas has a relatively high specific heat and therefore can absorb a large amount of heat, the EGR rate (recirculated gas amount / recirculated gas amount /
The combustion temperature in the combustion engine decreases as the (recirculation gas amount + intake air amount) increases. NO as the combustion temperature decreases
_Since the amount of _x produced decreases, the higher the EGR rate, the more NO _x
It is possible to suppress the discharge amount of.

However, when the EGR rate exceeds a certain limit, there is a phenomenon in which the amount of soot generated, that is, smoke increases rapidly. Therefore, it is conventionally thought that the amount of smoke generated will increase infinitely as the EGR rate further increases, and therefore smoke will start to increase rapidly.
The EGR rate is considered to be the maximum allowable EGR rate limit. Therefore, the EGR rate has traditionally been set within a range that does not exceed this maximum allowable limit. The maximum allowable limit of this EGR rate is approximately 30% to 50%, although it depends on the type of combustion engine and fuel.

However, even if the EGR rate is determined so as to suppress the generation of NO _x and smoke as much as possible, there is a limit to the suppression of these, and in reality, a certain amount of NO
It is inevitable that _x and smoke are discharged. Therefore, as a result of extensive studies to further suppress NO _x and smoke emissions, there is a peak in the relationship between the EGR rate and the amount of smoke generated, and the peak is exceeded.
It was clarified that the amount of smoke generated decreased sharply when the GR rate was further increased. For example, it becomes clear that almost no smoke occurs when the EGR rate is set to 70% or more during idling operation, or when the EGR rate is set to 55% or more when the recirculated gas is forcibly cooled. It was also clarified that the amount of _x produced was extremely small.

This means that when the temperature at the time of combustion is below a certain temperature, the growth of hydrocarbons (hereinafter referred to as HC) is stopped at a stage before reaching soot, and the temperature at the time of combustion is above a certain temperature. It means that HC will grow to soot at a stretch. Also, since the temperature during combustion is greatly affected by the endothermic action of the gas around the fuel, the temperature during combustion can be controlled by adjusting the amount of endothermic gas around the fuel according to the amount of heat generated during fuel combustion. You can

Therefore, it is desirable to control the temperature at the time of combustion so that the growth of HC is stopped at a stage before the soot is reached by adjusting the amount of heat absorbed by the gas around the fuel. On the other hand, HC, which has stopped growing in the middle of soot, is called a soluble organic substance (hereinafter referred to as SOF), but this SOF is easily removed by post-treatment using an oxidation catalyst. can do. As a system utilizing such a system, Japanese Patent Laid-Open No. 11-036923 discloses that exhaust gas discharged into an exhaust manifold is supplied to an intake passage as a recirculation gas to increase the amount of inert gas around the fuel. As a result, the temperature during combustion is suppressed below the temperature at which soot is generated, and the exhaust gas from the combustion chamber is passed through the oxidation catalyst.
An internal combustion engine that oxidizes and removes OF and discharges it is disclosed.

However, in the system disclosed in Japanese Unexamined Patent Publication No. 11-036923, since the exhaust gas before passing through the oxidation catalyst is recirculated, a large amount of unburned HC and SOF are contained in the recirculated gas. However, there was a problem that it was deposited and accumulated in the EGR passage.

Therefore, Japanese Patent Laid-Open No. 2000-8964 discloses an internal combustion engine in which an oxidation catalyst is arranged upstream of an EGR cooler arranged in the EGR passage for cooling the recirculation gas. Further, JP 2000-038962 A discloses an EGR cooler in which an oxidation catalyst is arranged. In this way, the unburned HC and SOF contained in the recirculated gas can be oxidized and removed, and the adhesion and deposition of the unburned HC and SOF in the EGR passage can be suppressed.

However, in the EGR device in which the oxidation catalyst is arranged, the temperature of the recirculation gas rises due to the combustion heat of the oxidation reaction, and the EGR efficiency described below decreases.
In addition, the gaseous state of the recirculated gas that can contribute to the engine output
Since CO and HC are also oxidized, there is also a problem that fuel efficiency is reduced. Furthermore, there is a torque step due to the thermal deterioration of the catalyst and the fluctuation of the oxidizing power due to the fluctuation of the incoming gas temperature, and the sulfate generated by the oxidation of SO ₂ in the recirculated gas corrodes the EGR passage and deteriorates the emission. There was also a problem.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is possible to prevent SOF and soot from accumulating in the EGR passage by oxidizing and removing SOF and to control the temperature of the recirculated gas. It is an object of the present invention to provide an EGR device that can suppress the rise, supply most of the gaseous CO and HC in exhaust gas to the combustion chamber, and can also prevent the formation of sulfate.

[0011]

The features of the EGR device of the present invention for solving the above problems are that an EGR passage connecting an exhaust passage and an intake passage of an internal combustion engine and an EGR passage arranged in the EGR passage and supplied from the exhaust passage. An EGR device comprising a cooling device for cooling the recirculated gas, which cools the recirculated gas by the cooling device and supplies it to the intake passage, at least one of the upstream side of the cooling device in the EGR passage and the inside of the cooling device. , Having a SOF adsorption oxidation catalyst that can selectively oxidize SOF in the recirculated gas.

In the above EGR device, the temperature detection means for detecting the temperature of the recirculated gas flowing into the SOF adsorption oxidation catalyst and the flow rate of the recirculated gas according to the temperature of the recirculated gas detected by the temperature detection means are set. It is desirable to further include a flow rate adjusting means for adjusting.

Further, it is desirable that the SOF adsorption oxidation catalyst comprises a base metal supported on a porous oxide carrier.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION According to the EGR device of the present invention, at least one of the upstream side of the cooling device in the EGR passage and the inside of the cooling device adsorbs SOF in the recirculated gas to selectively oxidize SOF. It has an oxidation catalyst. This SOF adsorption oxidation catalyst adsorbs and selectively oxidizes and removes SOF at 200 to 400 ° C, but its oxidizing power is weaker than that of general oxidation catalysts, and gaseous CO and HC are mostly oxidized below 400 ° C. Without passing through the SOF adsorption oxidation catalyst. Therefore, the amount of SOF contained in the recirculated gas can be greatly reduced, so
It is possible to prevent the accumulation of soot and the soot that adheres to the SOF and accumulates. Further, since the recirculated gas supplied to the combustion chamber contains a sufficient amount of gaseous CO and HC, it is possible to prevent a problem that may hinder the engine output.

Since the SOF adsorption oxidation catalyst slowly oxidizes the adsorbed SOF, the amount of heat generated by the oxidation is extremely small and the bed temperature hardly rises. Therefore, since it is not exposed to a temperature higher than the temperature of the gas entering the catalyst, thermal deterioration of the catalyst is prevented, fluctuations in oxidizing power are small, and problems such as torque fluctuations do not occur. And since the temperature rise of the recirculation gas hardly occurs, the EGR efficiency is improved. The EGR efficiency is a value calculated by the following formula, and the higher the value, the lesser the NO _x emissions.

[0016] Furthermore, since the SOF adsorption oxidation catalyst does not oxidize SO ₂ at 200 to 400 ℃, the formation of sulfate is suppressed and the corrosion of the EGR passage and the deterioration of emission are prevented.

As the SOF adsorption oxidation catalyst, it is preferable to support almost no precious metal or not, and it is preferable to support the base metal on the porous oxide carrier.
This enables SOF to be adsorbed and selectively oxidized and removed at 200 to 400 ℃.

Examples of the porous oxide include ZrO ₂ , Al ₂ O ₃ and Ti.
O ₂ , SiO ₂ , CeO ₂ , zeolite and the like are exemplified, and the carrier can be composed of a single product or a mixture thereof.
Above all, it is preferable to contain at least zeolite having an excellent SOF adsorption capacity. Zeolite also adsorbs gaseous HC, but since gaseous HC is released from the zeolite at temperatures above 150 ° C, there are almost no problems such as engine output reduction.

For example, CeO _{2 and the} like have an oxidizing ability by themselves, so that they can be used as an SOF adsorption oxidation catalyst without supporting a base metal. However, in order to optimize the oxidation efficiency, it is preferable to support the base metal on the carrier. The base metals are Fe, Cu, Ni, Mn, Co, V, Mo.
Etc. are exemplified, and it is desirable to carry in a supported amount of 1 to 10% by weight. If the supported amount is less than this range, the oxidizing activity is too low to be practical, and if the supported amount is more than this range, the oxidizing activity may be saturated and adverse effects may occur.

It is desirable that noble metal should not be supported because it has too large an oxidation activity and generates a large amount of heat to lower the EGR efficiency. Even if it is carried, if it is Pt, it is 0.
05% by weight or less, Rh should be 0.1% by weight or less.

The cooling device cools the recirculated gas, and an EGR cooler such as a conventionally used intercooler can be used.

This SOF adsorption oxidation catalyst can be arranged in the EGR passage on the upstream side of the cooling device, for example, as a shape coated on a honeycomb substrate or as a pellet shape. As the honeycomb base material, a metal honeycomb base material composed of a flat plate and a corrugated plate, a ceramic monolith base material, or the like can be used. For example, Fe with a plate thickness of 30 μm
-When using a metal honeycomb substrate formed of -Cr-Al, etc., damage is unlikely to occur even under use conditions under which a strong mechanical impact acts, so there is a problem that interferes with the operation of the internal combustion engine. Absent.

When a monolith substrate is used, it is preferable to use one having a large number of cells and a small wall thickness, such as a cell thickness of 600 cells / in ² and a wall thickness of 75 μm. By doing so, even if the space for arrangement in the EGR passage is small, a large surface area of the catalyst can be secured and a high SOF purification efficiency can be secured. Further, for example, a monolith substrate having a porosity of about 50% and an average pore diameter of about 25 μm is used.
It is also preferable to form the coat layer from a fine slurry having an average particle diameter of 1 μm or less. By doing so, both the surface and the inside of the monolith substrate serve as the SOF collection field and reaction field, so the SOF purification rate is further improved. Further, since the coat thickness on the cell wall surface becomes thin, pressure loss at the catalyst is reduced and clogging is less likely to occur.

It is also preferable to dispose an SOF adsorption oxidation catalyst inside the cooling device. For example, the cooling device may have a honeycomb structure or a laminated structure, and the coat layer may be formed on the surface of the slurry containing the SOF adsorption oxidation catalyst powder. By doing so, the pressure loss of the recirculated gas can be reduced and the EGR efficiency can be improved as compared with the case where the SOF adsorption oxidation catalyst is arranged separately from the cooling device. Since the SOF adsorption oxidation catalyst hardly raises the bed temperature due to the oxidation of SOF, it hardly affects the cooling efficiency of the recirculated gas.

The SOF adsorption oxidation catalyst gradually oxidizes gaseous CO, HC and SO ₂ at a high temperature of 400 ° C. or higher. Therefore, the temperature of the recirculated gas rises due to the heat generation, and the EGR efficiency decreases.

Therefore, temperature detecting means for detecting the temperature of the recirculated gas flowing into the SOF adsorption oxidation catalyst, and flow rate adjusting means for adjusting the flow rate of the recirculated gas according to the temperature of the recirculated gas detected by the temperature detecting means. It is desirable to further include When the recirculated gas is detected to be 400 ° C or higher, if the flow rate adjusting means adjusts the flow rate of the recirculated gas to be low or zero, the formation of sulfate can be prevented and the corrosion of the EGR passage can be prevented.

As the temperature detecting means for detecting the temperature of the recirculated gas flowing into the SOF adsorption oxidation catalyst, a temperature sensor for directly detecting the temperature of the recirculated gas may be used, or an engine speed and torque may be detected. It is also possible to estimate the temperature of the exhaust gas from these. In addition, as a flow rate adjusting means for adjusting the flow rate of the recirculated gas, the EGR that has been used conventionally
A valve or the like can be used. Then, in order to adjust the flow rate of the recirculated gas according to the temperature of the recirculated gas, the signal from the temperature detecting means may be input to the computer, and the drive of the flow rate adjusting means may be controlled by the output signal according to the value. .

[0028]

EXAMPLES The present invention will be specifically described below with reference to test examples, examples and comparative examples.

(Test example) Fe in which Fe was previously supported on ZrO ₂
100 g of ZrO ₂ catalyst powder and Fe / Fe in which CeO ₂ was preloaded
20 g of CeO ₂ powder and 20 g of mordenite powder were mixed to prepare a catalyst powder. TiO ₂ sol as a binder,
A slurry was prepared by mixing with ZrO ₂ sol and water, wash coated on a 250 cc metal honeycomb substrate, and dried.
It was calcined at 500 ° C. for 1 hour to obtain a first catalyst. The coating amount is 135 g per liter of the honeycomb substrate, and Fe is supported in an amount of 0.1 mol per liter of the honeycomb substrate.

On the other hand, using Fe / ZrO ₂ catalyst powder carrying the Fe to ZrO _2, to prepare a second catalyst coated in the same manner as described above. In the second catalyst, Fe per liter of honeycomb substrate
It is loaded with 0.1 mol. Further, the catalyst powder used in the first catalyst was further loaded with Pt to prepare a catalyst powder, which was coated in the same manner as above to prepare a third catalyst. In the third catalyst, Fe
Is loaded in an amount of 0.1 mol per liter of the honeycomb substrate, and Pt is loaded in an amount of 0.5 g per liter of the honeycomb substrate.

Each of these catalysts was mounted on an exhaust system of a diesel engine having a displacement of 2 L, and PM (particulate), HC and CO purification rates were measured when operating at each temperature under the condition of 2000 rpm. The relationship between the temperature of the gas containing the catalyst and each purification rate is shown in FIGS. The HC purification rate was measured under the temperature-decreasing conditions for the first catalyst and the second catalyst, and under the temperature-increasing condition for the third catalyst.

Further, with respect to the first catalyst, the purification rates of SOF, HC and CO were measured when operating at each temperature under a steady condition of 1200 rpm, and the results are shown in FIG.

In FIG. 1, a negative PM purification rate means that SO _{2 in} the exhaust gas was oxidized to produce sulfate, and when the amount of PM removed by oxidation and the amount of sulfate produced were balanced. The PM purification rate becomes 0%. From Fig. 1, the temperature at which the PM purification rate becomes 0% is
The first and second catalysts are in the high temperature range of 500 ° C or higher, while the third catalyst carries Pt, which is low at 380 ° C.

That is, with the first and second catalysts, 450
Almost no sulfate is produced in the low temperature range below ℃. As is clear from FIGS. 2 to 3, the first catalyst and the second catalyst have lower HC and CO oxidation activities in the low temperature range of 400 ° C. or lower than the third catalyst. Further, as is clear from FIG. 4, although the first catalyst exhibits a high SOF oxidizing ability in the range of 200 to 400 ° C., the oxidizing ability of HC and CO is low. Therefore, the first catalyst and the second catalyst are suitable as the SOF adsorption oxidation catalyst according to the present invention.

(Embodiment 1) FIG. 5 shows a schematic configuration diagram of a diesel engine equipped with the EGR device of this embodiment. The exhaust port of the engine body 1 is an exhaust manifold 10 and an exhaust pipe.
It is connected to the catalytic converter 2 via 11. The catalytic converter 2 is further connected to the EGR cooler 3, and the EGR cooler 3 is connected to the intake port 5 via the EGR valve 4. The exhaust pipe 11, the catalytic converter 2, the EGR cooler 3, and the EGR valve 4 form an EGR passage.

As shown in FIG. 6, the EGR cooler 3 is composed of a metal honeycomb body in which flat plates 30 and corrugated plates 31 made of metal foil are alternately laminated, and a cooling water passage (not shown) is formed on the outer periphery.

The exhaust manifold 10 is also connected to the turbocharger 6. Then, the air flowing in from the intake pipe 7 passes through the air cleaner 70 from the turbocharger 6 and is supplied to the intake port 5. At the intake port 5, the recirculated gas supplied from the EGR passage and the air are mixed to the engine body 1. Supplied.

In the catalytic converter 2, an SOF adsorption oxidation catalyst manufactured by the following manufacturing method is arranged.

[0039] and Fe / ZrO ₂ which Fe is previously supported on ZrO ₂ catalyst powder 100 g, Fe / CeO ₂ powder Fe in CeO ₂ is pre-supported 20
g and 20 g of mordenite powder were mixed to prepare a catalyst powder. This was mixed with TiO ₂ sol as a binder, ZrO ₂ sol and water to prepare a slurry, and the number of cells was 400 / in ² ,
250cc ceramic honeycomb monolith substrate with 100μm wall thickness square cells was wash-coated and dried
It was calcined at 500 ° C for 1 hour to obtain an SOF adsorption oxidation catalyst. The coating amount is 135 g per liter of the monolith substrate.

(Comparative Example 1) Al ₂ O ₃ powder 100 g, CeO ₂ --ZrO
₂ powder 40 g, La ₂ O ₃ powder 20g were mixed to prepare a slurry by mixing with Al ₂ O ₃ sol and water as a binder. Then, a coat layer was formed on the same monolith substrate as in Example 1 in the same manner. The coat layer is 215 g per liter of monolith substrate. Then, Pt was supported on the coat layer using an aqueous solution of dinitrodiammine platinum to prepare an oxidation catalyst.
The amount of Pt carried is 6 g per liter of the monolith substrate. An EGR device of Comparative Example 1 was prepared in the same manner as in Example 1 except that this oxidation catalyst was placed in the catalytic converter 2 instead of the SOF adsorption oxidation catalyst of Example 1.

(Comparative Example 2) The amount of Pt carried was changed to the monolith substrate 1
An oxidation catalyst was prepared in the same manner as in Comparative Example 1 except that the amount was 0.5 g per liter, and this oxidation catalyst was placed in the catalytic converter 2 instead of the SOF adsorption oxidation catalyst of Example 1. An EGR device of Comparative Example 2 was prepared in the same manner as in.

<Evaluation> EGR of Example 1 and Comparative Examples 1 and 2
Regarding the equipment, the engine body is 1600 rpm × 20 Nm, and E
Driven under low temperature combustion conditions with the GR valve 4 fully open, the purification rates of SOF, HC and CO were measured from the difference in concentration in the recirculated gas at the inlet and outlet sides of the catalytic converter 2. The results are shown in FIGS.
Are shown respectively.

The temperature of the recirculated gas was measured at the inlet of the catalytic converter 2, the catalyst bed, the inlet of the EGR cooler 3 and the outlet of the EGR cooler 3, and the results are shown in FIG.

From FIGS. 7 to 9, in the EGR device of Example 1, S
It can be seen that the purification rate of OF is comparable to that of each comparative example, and that it has almost the same SOF oxidizing ability as that of Comparative example 2 carrying 0.5 g / L of Pt. Moreover, the purification rates of HC and CO are significantly lower than those of the comparative examples. As is clear from FIG. 10, Example 1
In the EGR device, the temperature of the recirculated gas is low, and the temperature does not rise even when passing through the catalytic converter 2. This is HC
It is considered that CO and CO are hardly oxidized.

Next, with respect to the EGR device of Example 1, the pressure loss before and after the EGR cooler 3 was measured in the case of a new product and after the engine body 1 was driven in a predetermined actual vehicle running pattern, and the results are shown in FIG. . From Fig. 11, it can be seen that even after the operation equivalent to traveling 300,000 km, the increase in pressure loss was 12 kPa or less, which was slight, and the accumulation in the EGR passage was suppressed. This is because SOF was purified.

(Embodiment 2) The EGR device of this embodiment is the same as that of the embodiment 1, and further, as shown in FIG. 12, a rotation speed sensor 80 for detecting the engine speed and an engine torque are detected. The control device 8 includes a torque sensor 81 and a computer 82.

In this EGR device, when the detection signals of the rotation speed sensor 80 and the torque sensor 81 are input to the control device 8, the control device 8 refers to the map stored in the ROM 83 and flows into the catalytic converter 2. Estimate the actual recirculation gas temperature. When the recirculation gas temperature is 400 ° C or lower, the EGR valve 4 is opened by a predetermined amount, but the recirculation gas temperature is 400
If it is estimated that the temperature exceeds ℃, fully close the EGR valve 4.

As a result, the formation of sulfate by the SOF adsorption oxidation catalyst is prevented, so that the corrosion of the EGR passage can be prevented.

(Embodiment 3) FIG. 13 shows an EGR apparatus of the third embodiment. In this EGR device, the catalytic converter 2 was not used, but the coat layer 33 made of the catalyst powder used for the first catalyst of the test example or the SOF adsorption oxidation catalyst of the first example was formed in the EGR cooler 3 The configuration is the same as that of 1.

As shown in FIG. 14, the EGR cooler 3 is composed of a metal honeycomb body in which flat plates 30 and corrugated plates 31 made of the same metal foil as in Example 1 are alternately laminated, and a cooling water passage (not shown) is provided on the outer periphery. Has been formed. On the wall surface of the cell 32, a coat layer 33 made of a catalyst powder used for the first catalyst of the test example or the SOF adsorption oxidation catalyst of the first example is formed with a thickness of 50 μm.

According to this EGR device, the coat layer 33 has the same effects as the catalytic converter 2 of the first embodiment. Since the catalytic converter 2 is not provided, the pressure loss of the recirculated gas can be reduced as compared with the first embodiment.
GR efficiency is improved. Further, since the catalyst bed temperature in the coat layer 33 hardly rises, the cooling efficiency of the recirculated gas does not decrease, and the accumulation in the EGR passage can be prevented.

(Embodiment 4) FIG. 15 shows an EGR device of the fourth embodiment. This EGR device has the same configuration as that of the first embodiment except that the strainer 9 is arranged on the downstream side of the EGR cooler 3. The strainer 9 is made of a metal mesh having a pore size of 100 μm or more. Soot in the recirculation gas can pass, but particles having a particle size of 100 μm or more can be strainer 9.
To be collected by.

According to the EGR device of this embodiment,
The same effect as the EGR device is achieved, and even if the monolith substrate or coat layer of the SOF adsorption oxidation catalyst is damaged by strong vibration or exhaust pulsation,
The debris can be collected by the strainer 9. Therefore, these fragments can be prevented from entering the engine body 1, and the engine body 1 can be prevented from being damaged.

[0054]

According to the EGR device of the present invention, S
By oxidizing and removing OF, it is possible to prevent the accumulation of SOF and soot in the EGR passage, suppress the temperature rise of the recirculated gas, and improve the EGR efficiency. In addition, most of the gaseous CO and HC in the exhaust gas can be supplied to the combustion chamber, which improves engine output and also prevents the formation of sulfate, thus preventing corrosion of the EGR passage.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the temperature of gas entering a catalyst and the PM purification rate.

FIG. 2 is a graph showing the relationship between the temperature of gas entering the catalyst and the HC purification rate.

FIG. 3 is a graph showing the relationship between the temperature of gas entering the catalyst and the CO purification rate.

[Fig. 4] Temperature of gas entering the first catalyst and SOF, HC and CO
It is a graph which shows the relationship with the purification rate of.

FIG. 5 is an explanatory diagram showing a schematic configuration of an internal combustion engine having the EGR device of the first embodiment.

FIG. 6 is an enlarged cross-sectional view of a main part of the EGR cooler used in the EGR device of the first embodiment.

FIG. 7 is a graph showing SOF purification rates in the EGR devices of Examples and Comparative Examples.

FIG. 8 is a graph showing the HC purification rates in the EGR devices of Examples and Comparative Examples.

FIG. 9 is a graph showing CO purification rates in the EGR devices of Examples and Comparative Examples.

FIG. 10 is a graph showing the temperature of the recirculated gas in each part of the EGR devices of Examples and Comparative Examples.

FIG. 11 is a graph showing pressure loss before and after an EGR cooler in the EGR device of Example 1.

FIG. 12 is an explanatory diagram showing a schematic configuration of an internal combustion engine having an EGR device according to a second embodiment.

FIG. 13 is an explanatory diagram showing a schematic configuration of an internal combustion engine having an EGR device according to a third embodiment.

FIG. 14 is an enlarged cross-sectional view of a main part of an EGR cooler used in the EGR device of Example 3.

FIG. 15 is an explanatory diagram showing a schematic configuration of an internal combustion engine having an EGR device according to a fourth embodiment.

[Explanation of symbols]

1: Engine body 2: Catalytic converter 3: E
GR cooler 4: EGR valve 5: Intake port 10: Exhaust manifold 11: Exhaust pipe 70: Air cleaner

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takekazu Ito             1 Toyota Town, Toyota City, Aichi Prefecture Toyota Auto             Car Co., Ltd. (72) Inventor Daisuke Oki             7800 Chihama, Daito Town, Ogasa County, Shizuoka Prefecture Stock Association             Inside the company caterer F term (reference) 3G062 AA01 AA05 EA04 EA10 ED01                       ED04 ED08 ED09 ED10 FA02                       FA05 FA06 FA23 GA05 GA06                       GA10

Claims (3)

[Claims] 1. An exhaust gas recirculation passage that connects an exhaust passage and an intake passage of an internal combustion engine, and a cooling device that is disposed in the exhaust gas recirculation passage and cools the recirculated gas supplied from the exhaust passage. An exhaust gas recirculation device that cools the recirculated gas by the cooling device and supplies it to the intake passage, wherein the exhaust gas recirculation passage has at least one of an upstream side of the cooling device and an inside of the cooling device. An exhaust gas recirculation device having an SOF adsorption oxidation catalyst capable of adsorbing a soluble organic substance in the recirculation gas and selectively oxidizing it. 2. A temperature detecting means for detecting the temperature of the recirculated gas flowing into the SOF adsorption oxidation catalyst, and a flow rate of the recirculated gas according to the temperature of the recirculated gas detected by the temperature detecting means. The exhaust gas recirculation apparatus according to claim 1, further comprising: a flow rate adjusting unit that adjusts. 3. The exhaust gas recirculation apparatus according to claim 1, wherein the SOF adsorption oxidation catalyst comprises a base metal supported on a porous oxide carrier.