JP2001003816A - Egr (exhaust gas recirculation) device with egr gas cooler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an EGR(exhaust gas recirculation) device with an EGR gas cooler capable of preventing the cooling of the EGR gas with a simple structure in a cooling-off period. SOLUTION: An EGR gas cooler 11 is positioned at an upper part of a turbo- charger 2. The EGR gas cooler 11 is connected to a cooling water flow passage of the turbo-charger 2. In the stop of an engine, the cooling water used for cooling the turbo-charger 2 is boiled, and the bubbles are generated. The bubbles are sent into the EGR gas cooler 11. A cutoff valve 12 is mounted on a cooling water outlet part of the EGR gas cooler 11 to store the bubbles inside thereof and to discharge the cooling water. The cutoff valve 12 is opened after the warming-up.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an EGR device with an EGR gas cooling device. More specifically, it is possible to avoid excessive cooling of the EGR gas with a simpler configuration.
The present invention relates to an EGR device with a GR gas cooling device.

[0002]

2. Description of the Related Art Recently, nitrogen oxides (NO _x ) contained in exhaust gas from internal combustion engines have been subject to exhaust gas regulations.
There is. As a method for reducing the NO _x, EGR (Exhaus
t GasRecirculation: Exhaust gas recirculation) is effective. EGR
Then, a part of the exhaust gas (EGR gas) is returned to the intake system. Therefore, the temperature of the EGR gas becomes high during the operation of the engine, and the heat may deteriorate the durability of the EGR control valve. Further, with the expansion of the high temperature EGR gas, the relative mass flow rate of the EGR gas to the fresh air in the combustion mixture decreases. Therefore, an EGR gas cooling device is provided in the middle of the EGR passage to cool the EGR gas, thereby increasing the relative mass flow rate.

However, when the engine is cold immediately after starting the engine, E
In addition to the low GR gas temperature, the EGR in the EGR gas cooling device
When the passage is at a low temperature and the EGR gas cooling device is operated in this state, that is, when the EGR gas is cooled, the cooling of the EGR gas is excessively performed, the combustion temperature is extremely lowered, and the operability is deteriorated. There's a problem. Also, in this state,
A large amount of SOF (Soluble Organic Fraction) generates a large amount of carbon and promotes the adhesion of carbon, blocking passages and condensing moisture containing highly corrosive components such as sulfur oxides and eroding the engine. Or

Therefore, in the EGR device with an EGR gas cooling device disclosed in Japanese Patent Application Laid-Open No. Hei 10-238418, the cooling water is removed from the EGR gas cooling device at the time of cooling immediately after the start of the engine, so that the EGR gas is excessively cooled. Cooling is avoided.

[0005]

However, in this case, since the outside air is filled in the EGR gas cooling device in which the cooling water is removed by gravity or by mechanical work, the cooled cooling is excluded. Requires special reserve tanks or additional pumps to contain water.
As another method, there is a method in which a branch path that bypasses the EGR gas cooling device is formed in the EGR passage. This one is
By recirculating the EGR gas through the branch path at the time of cooling, excessive cooling of the EGR gas is avoided. Thus, all require special components, and the device is large-scale. This is also disadvantageous in terms of cost.

In view of such circumstances, an object of the present invention is to provide an EG
EGR that avoids excessive cooling of R gas with a simpler configuration
It is to provide an EGR device with a gas cooling device.

[0007]

According to the present invention, an EGR gas cooling device for cooling the EGR gas with engine cooling water is provided in an EGR passage for recirculating the EGR gas from an exhaust system to an intake system. In the EGR device for an internal combustion engine provided, the cooling water circulation part of the EGR gas cooling device is provided in a portion of the engine cooling system where the cooling water boils when the engine is stopped to generate bubbles, It was connected so as to be guided into the EGR gas cooling device. And, from the time of engine stop to a predetermined time after restart,
The EGR gas cooling device is configured to keep the bubbles.

[0008] With this configuration, the cooling water is removed from the inside of the EGR gas cooling device by the introduced bubbles, and the EGR gas cooling device is filled with steam until a predetermined time after the restart. In the invention according to claim 2, the cooling water inlet portion of the EGR gas cooling device is connected to the bubble generation location. Further, a shut-off valve is provided at a cooling water outlet of the EGR gas cooling device. By closing the shut-off valve from a time when the engine stops to a predetermined time after restarting, the air bubbles are kept in the EGR gas cooling device.

According to the third aspect of the present invention, the necessity of EGR gas cooling is determined based on the engine temperature, and the shut-off valve is opened after the engine temperature reaches a predetermined value after restarting. It is preferable that the predetermined value is a value capable of determining completion of warm-up of the engine.

According to a fourth aspect of the present invention, a flow control valve capable of controlling a flow rate of cooling water flowing through the EGR gas cooling device is provided as the shutoff valve. After the EGR gas cooling is started by the flow control valve, the flow rate of the cooling water is increased or decreased based on the engine temperature.

[0011] In the invention according to claim 5, the engine temperature is a cooling water temperature. In the invention according to claim 6, the engine temperature is an EGR gas temperature. In the invention according to claim 7, an EGR control valve opening correction means for correcting the opening of the EGR control valve provided in the EGR passage based on the EGR gas temperature is provided. That is, E set for each operation area
The correction based on the actual EGR gas temperature is performed on the EGR control valve opening corresponding to the required GR gas flow rate. Specifically, it is preferable to make correction so that the EGR control valve opening increases as the EGR gas temperature increases.

In the invention according to claim 8, the location where the bubbles are generated is a cooling water outlet of the turbocharger. The EGR
The cooling water flowing part of the gas cooling device and the cooling water outlet of the turbocharger are connected to each other so that air bubbles generated by boiling of the cooling water that has cooled the turbocharger when the engine is stopped are generated in the EGR gas cooling device. Connect to be guided to

[0013]

According to the first aspect of the present invention, since the cooling water in the EGR gas cooling device is eliminated by bubbles generated by boiling of the engine cooling water, a special reserve tank or an additional pump is provided. There is no need to provide such a device.
For this reason, it is possible to avoid excessive cooling of the EGR gas with a simpler configuration, and to prevent deterioration in drivability due to an extremely low combustion temperature. In addition, since the EGR gas temperature increases, the amount of SOF generated is reduced, so that the adhesion of carbon can be suppressed, and the generation of condensed components that cause erosion of the engine can be prevented.

According to the second aspect of the present invention, since the cooling water inlet of the EGR gas cooling device is connected to the bubble generating portion, the introduction of bubbles after the engine is stopped is smoothly performed by the inertia of the cooling water. . Further, by providing the shutoff valve at the cooling water outlet, the introduced bubbles can be reliably retained in the EGR gas cooling device.

According to the third aspect of the present invention, the necessity of the EGR gas cooling can be determined based on the engine temperature, so that the optimal opening timing of the shutoff valve can be easily set. Under the operating condition of a low engine temperature at which the EGR gas is not cooled, the shut-off valve is closed, and the inside of the EGR gas cooling device is filled with bubbles (water vapor). In this state, E
Since the temperature of the EGR gas passage in the GR gas cooling device becomes high, the amount of deposited carbon can be suppressed by burning attached carbon.

According to the fourth aspect of the present invention, after the cooling water is circulated and the EGR gas cooling is started, the flow rate of the cooling water can be increased or decreased based on the engine temperature. Performance can be variably controlled. Therefore, optimum cooling efficiency can be obtained.

According to the fifth or sixth aspect of the invention, the EGR is performed based on the cooling water temperature or the EGR gas temperature.
Excessive cooling of the EGR gas can be more reliably avoided by accurately determining the necessity of gas cooling. In particular, EGR
According to the gas temperature, more accurate determination is possible. When a flow control valve is used, the cooling efficiency of the EGR gas cooling device can be further optimized.

According to the seventh aspect of the invention, EGR control corresponding to a change in mass flow rate due to expansion of the EGR gas can be performed. By correcting so that the EGR control valve opening increases as the EGR gas temperature increases, the decrease in the mass flow rate of the EGR gas due to expansion can be compensated, and the EGR rate can be controlled more precisely.

According to the eighth aspect of the present invention, the turbocharger is constantly exposed to the exhaust heat during operation of the engine and becomes high in temperature. Therefore, when the engine is stopped, the cooling water that has cooled the cooling water boils. Is introduced into the EGR gas cooling device, thereby making it possible to easily obtain a sufficient amount of air bubbles to remove the cooling water.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a hardware configuration according to an embodiment of the present invention.

After the air introduced into the intake system is dust-removed by the air cleaner 1, the air is passed through the intake passage.
It is compressed and supercharged by a compressor 2A constituting the turbocharger 2. The high-temperature compressed air is cooled by an intercooler 3 interposed in an intake passage on the downstream side of the compressor 2A, passes through an intake throttle valve 4, and is passed through an intake manifold 5 to an internal combustion engine (diesel engine). And (6) distributed to each combustion chamber.

The internal combustion engine 6 compresses intake air in a compression stroke, and discharges generated exhaust gas to an exhaust system after combustion in an expansion stroke. The discharged exhaust gas is collected by an exhaust manifold 7 constituting an exhaust system, and a part (EGR gas) is returned to an intake system by an EGR device. Here, the EGR device includes an EGR passage 8, an EGR
The control valve 9 and the intake throttle valve 4 are included.

The EGR passage 8 connects an EGR gas outlet 7ex provided in the exhaust manifold 7 and an EGR gas inlet 10in provided in the collector 10. An EGR control valve 9 is interposed in the EGR passage 8.

The EGR control valve 9 operates the actuator in response to an electric signal from an electronic control unit 31 which will be described later, and controls the EGR gas flow rate by freely controlling the valve opening.

The intake throttle valve 4 is located upstream of the collector 10, and controls the pressure difference between the exhaust pressure and the intake pressure by adjusting the pressure in the collector 10. The EGR rate is controlled by controlling the EGR control valve opening at the same time.

Exhaust gas other than the exhaust gas recirculated as EGR gas passes through the exhaust manifold 7, and then drives the turbine 2B constituting the turbocharger 2 to rotate.
Thereafter, the harmful components contained in the catalytic converter and the like are purified, and after silencing, are released into the atmosphere.

The EGR gas expanded at high temperature is EG
This may cause the durability of the R control valve 9 to deteriorate and the drivability to deteriorate. Therefore, an EGR gas cooling device 11 that cools the EGR gas is provided in the EGR passage 8. EG
These problems are avoided by recirculating the EGR gas cooled by the R gas cooling device 11 to the collector 10 constituting the intake system.

The EGR gas cooling by the EGR gas cooling device 11 is performed by heat exchange between the engine cooling water flowing inside the cooling device and the EGR gas. The EGR gas cooling device 11 may be any known water-cooled heat exchanger. In addition, the engine cooling water is introduced into the cooling water flow section of the EGR gas cooling device 11 from a bubble generation point in the engine cooling system. Here, the bubble generation location refers to a location where the engine is heated by combustion heat or exhaust heat during operation of the engine, and when the engine stops, cooling water boils to generate bubbles (water vapor). In the present embodiment, as the bubble generation location,
An example is shown in which the cooling water outlet 2ex of the turbocharger 2 (turbine 2B), which is constantly exposed to exhaust heat and becomes hot during engine operation, is selected. Of course, the location where the bubbles are generated is not limited by the present embodiment.

The cooling water pumped by a water pump (not shown) circulates through an engine cooling system through a cooling water pipe 21 indicated by hatching in the figure. The cooling water sent to 21a by the water pump cools the turbocharger 2, and a part of the cooling water is sent from 21b to other components.
On the other hand, the EGR gas cooling device 11
After cooling the EGR gas, the cooling water introduced into the cooling water exits the EGR gas cooling device 11 from the cooling water outlet 11ex. The cooling water discharged from the cooling water outlet 11ex can be used for a room heater or the like from 21c. In addition, in the cooling water outlet 11ex,
A shutoff valve (open / close valve or flow control valve) 12 is interposed. The shutoff valve 12 is controlled to open and close by an electric signal from an electronic control unit 31 described later.

The electronic control unit 31 receives the cooling water temperature T
water temperature sensor 41 capable of detecting w, EGR gas temperature Tegr
In addition to the input of the detection signal from the gas temperature sensor 42 capable of detecting the engine speed, various signals indicating the engine speed Ne and the load Tq are input, and the control described later is executed for the shutoff valve 12 and the EGR control valve 9. You.

Next, control of the shutoff valve 12 according to the present invention will be described. FIG. 2 shows the configuration of the EGR gas cooling device 11 from the side. The two-dot chain line shown in the figure indicates the flow of the exhaust gas.

Here, attention should be paid to the positional relationship between the EGR gas cooling device 11 and the turbocharger 2 where bubbles are generated. In the present embodiment, the turbocharger 2 is an EGR
It is arranged below the gas cooling device 11. The purpose of this arrangement will be clear from the description below.

That is, when the EGR gas is cooled during the operation of the engine, the shut-off valve 12 is opened. Cooling water (H2Oli
q) fills the inside of the EGR gas cooling device 11 as shown by oblique lines and circulates through the engine cooling system as described above (FIG. 2).
A). On the other hand, from the time the engine is stopped until a predetermined time after the restart, the internal combustion engine 6 is in a cold state, the EGR gas is at a low temperature, and the EGR passage in the EGR gas cooling device 11 is also at a low temperature. Cooling the EGR gas may cause deterioration of drivability and erosion of the engine. Therefore, control for removing the cooling water from the EGR gas cooling device 11 is performed.

Specifically, after the engine stops, the shut-off valve 12 is closed (FIG. 2B). From the above description, bubbles (H2Ogas) due to boiling of the cooling water from the cooling water outlet 2ex of the turbocharger 2
Occurs. The generated air bubbles are guided into the EGR gas cooling device 11 located above. Since the shutoff valve 12 is closed, the air bubbles remain in the EGR gas cooling device 11,
Eliminate internal cooling water. In order to facilitate the introduction of bubbles, the cooling water inlet 11 in is provided below the EGR gas cooling device 11.

After the restart, the shutoff valve 12 is kept closed until a predetermined time. In the present embodiment, this predetermined time is the time when the warm-up of the engine is completed. Thus, the EGR gas cooling device 1
By filling the inside with steam, the EGR gas cooling is not performed at the time of cooling, and the EGR gas temperature can be increased, so that problems such as a decrease in drivability, an increase in the amount of SOF generated, and generation of condensed components are avoided. can do. In addition, since the temperature of the EGR gas passage in the EGR gas cooling device 11 can be increased, the amount of carbon deposited can be limited by burning attached carbon.

After a predetermined time, the shut-off valve 12 is opened again. The bubbles are discharged, and the EGR gas cooling is restarted. In order to discharge air bubbles smoothly, the cooling water outlet
It is provided above the R gas cooling device 11 and has a shut-off valve 1
2 is interposed above the EGR gas cooling device 11.

The EGR gas cooling device 11 according to the present embodiment
Indicates that the EGR at the time of cold operation is performed by removing the internal cooling water by bubbles introduced from a bubble generation portion located therebelow.
It is characterized in that excessive cooling of the gas is avoided. Therefore,
The flow direction of the cooling water does not matter as long as the bubble generation location is located below the EGR gas cooling device 11 and the air bubbles can be guided when the engine is stopped. That is, the cooling water may be configured to flow from the cooling water outlet 11ex to the cooling water inlet 11in.

When the EGR gas cooling device 11 is provided with an air vent passage, a shut-off valve is also provided in the air vent passage, and the shut-off valve is closed from a time when the engine is stopped until a predetermined time after restarting. With such a configuration, both the cooling water inlet 11in and the cooling water outlet 11ex can be provided below the EGR gas cooling device 11, and the layout is improved.

Next, control when the shut-off valve 12 is an open / close valve will be described with reference to FIG. In S11 (Step 11, the same applies hereinafter), the stop of the internal combustion engine 6 is determined. When stopped, the shutoff valve 12 is closed in S12. According to the above description, bubbles are accumulated in the EGR gas cooling device 11 from this point. If not stopped, the process proceeds to S13.

In S13, the restart of the internal combustion engine 6 is determined. If it has not been restarted, this routine returns. When restarted, a cooling water temperature Tw as an engine temperature is read in S14. In S15, the read cooling water temperature Tw becomes a predetermined value Tw0 (for example, 40
６０60 ° C.) or more. Predetermined value Tw0
Is the cooling water temperature at which completion of warm-up of the engine can be determined.

If the cooling water temperature Tw is lower than the predetermined value Tw0, the shutoff valve 12 is kept closed (S16), and the routine returns. At this time, the EGR gas cooling device 1
The air bubbles in 1 are retained and all the cooling water from the turbocharger 2 is circulated to other components. On the other hand, the cooling water temperature Tw
Is greater than or equal to the predetermined value Tw0, the shut-off valve 12 is opened (S17), and then this routine returns. The held bubbles are released from the cooling water outlet 11ex, the cooling water flows, and the EGR gas cooling is started.

The control shown in S11 to S17 can also be performed by the EGR gas temperature Tegr as the engine temperature (instead of the cooling water temperature Tw). That is, the EGR gas temperature Tegr is read in S14, it is determined whether or not the EGR gas temperature Tegr read in S15 is equal to or higher than a predetermined value Tegr0 capable of determining completion of warm-up. If this condition is satisfied, the process proceeds to S17. The shut-off valve 12 may be configured to be opened. According to this configuration, the necessity of the EGR gas cooling can be more accurately determined as compared with the case where the cooling water temperature Tw is used, and an accurate valve opening timing can be set.

Next, control when the shut-off valve 12 is a flow control valve will be described with reference to FIG. When the flow control valve 12 is used, the EG after the start of EGR gas cooling
The heat exchange performance of the R gas cooling device 11 can be variably controlled.

The control performed in S21 to S26 is as follows.
When the above-mentioned on-off valve is used (S11 to S16)
Is the same as When the cooling water temperature Tw becomes equal to or higher than the predetermined value Tw0 (for example, 40 to 60 ° C.) in S25, the process proceeds to S27, and the flow control valve opening θw is set based on the cooling water temperature Tw as the engine temperature. In S28, the flow control valve 12 is opened according to the set valve opening θw. The setting of the valve opening degree θw is based on, for example, a flowchart shown in FIG.

At S31, the cooling water temperature Tw is set to the set value Tw1.
(For example, 80 ° C.). If it is higher than the set value Tw1, in step S32, the flow control valve opening degree θw
Is updated to a value larger than the previous valve opening degree θw by a constant Δθ, and the routine returns. On the other hand, if it is equal to or smaller than the predetermined value Tw1, the routine returns after the valve opening θw is updated to a value smaller than the previous valve opening θw by a constant Δθ in S33.

The control similar to S31 to S33 is performed by EG
It can also be performed based on the R gas temperature Tegr. That is,
In S31, it is determined whether or not the EGR gas temperature Tegr is higher than the set value Tegr1.
In step S32, the flow control valve opening θw is updated to a value larger than the previous valve opening θw by a constant Δθ, and the routine returns. On the other hand, if it is equal to or smaller than the set value Tegr1, in S33, the valve opening θw is changed to the previous valve opening. The routine is returned after updating the opening degree θw to a value smaller by the constant Δθ.

Further, the flow control valve opening θw is adjusted so that the cooling water flow rate corresponding to the EGR gas flow rate is corrected based on the engine temperature (so that the cooling water flow rate increases as the engine temperature increases). Then, it may be set.

Next, control of the EGR device with the EGR gas cooling device according to the present embodiment will be described with reference to FIG. In this example, a flow control valve is used as the shut-off valve 12, and the processes of S21 to S28 are incorporated.

When it is determined in S41 that the internal combustion engine 6 has been stopped, in S42, the EGR control valve 9 and the flow control valve 12 are fully closed, and a restart is awaited. If not stopped,
Proceed to S43.

When restart is determined in S43, S
The control after 44 is performed. On the other hand, if it is not restarted, this routine returns as it is. In S44, the engine speed Ne, the load Tq, and the cooling water temperature Tw are obtained from various sensors.
, A signal indicating the EGR gas temperature Tegr is input. S4
In step 5, the operation region is determined based on the input Ne and Tq, and the EGR control valve opening θegr corresponding to the required EGR gas flow rate set for each operation region is calculated. The valve opening θ
egr may be a value obtained by performing a correction based on the cooling water temperature Tw or a correction at the time of acceleration.

In S46, it is determined whether or not the EGR gas temperature Tegr as the engine temperature is equal to or higher than a predetermined value Tegr0 which can determine the completion of the warm-up of the internal combustion engine 6. If it is lower than the predetermined value Tegr0, the flow proceeds to S50 while keeping the flow control valve 12 closed in S47. On the other hand, if it is equal to or greater than the predetermined value Tegr0, the flow control valve opening degree θw is set in S48 based on the EGR gas temperature Tegr. The setting of the valve opening degree θw is based on S27 (S31 to S33) in the flowchart shown in FIG.

Note that the control in S46 and S48 can be performed based on the cooling water temperature Tw as described above. In S49, the flow control valve 12 is opened according to the set flow control valve opening degree θw.

At S50, the EGR calculated at S45 is obtained.
The control valve opening degree θegr is corrected based on the EGR gas temperature Tegr. That is, the decrease in the mass flow rate due to the expansion of the EGR gas is compensated for. This correction is based on the flowchart shown in FIG.

In S61, it is determined whether or not the EGR gas temperature Tegr is within a predetermined range (for example, is equal to or lower than a predetermined lower limit value Tset). Within a predetermined range (lower limit value Tset
If the following is satisfied, the EGR control valve opening correction value Kegr is set to the initial value Kegr0 (for example, 0) in S62, and then the process proceeds to S62.
At 66, the EGR control valve opening degree θegr is corrected to a correction value Kegr.
The value is updated by adding (initial value Kegr0), and the routine returns. Here, if the lower limit value Tset is set to the predetermined value Tegr0, it is possible to perform a control without performing the correction at the time of a cold restart and at the time of a hot restart when the cooling water temperature Tw is high and the EGR gas temperature Tegr is low.

Out of predetermined range (greater than lower limit value Tset)
If so, the process proceeds to S63, where the relationship with the set value Tegr2 is grasped. If the EGR gas temperature Tegr is higher than the set value Tegr2, the correction value Kegr is increased in S64, for example, by increasing the previous EGR control valve opening correction value Kegr by a constant ΔK, and the EGR control valve opening θegr in S66. Is updated to a value obtained by adding the increased correction value Kegr, and the routine returns.

On the other hand, the EGR gas temperature Tegr is set to the set value Teg.
If it is equal to or less than r2, in S65, for example, the previous EGR
The correction value Kegr is reduced by decreasing the control valve opening correction value Kegr by the constant ΔK. Similarly, in S66, the EGR control valve opening θegr is reduced by the reduced correction value Kegr.
Is updated to the value added and the routine returns.

Here, S61 to S66 constitute the EGR control valve opening correction means. In S51, the EGR control valve 9 is determined based on the EGR control valve opening θegr corrected in S50.
Is opened. Thereafter, the routine returns, and the same control is repeated.

As described above, according to the present invention, the cooling water in the EGR gas cooling device 11 is eliminated by the bubbles generated by the boiling of the engine cooling water.
Excessive cooling of the gas can be avoided with a simpler configuration. Further, based on the engine temperature, the EGR gas cooling device 1
By making the heat exchange performance and the EGR gas flow rate variably controllable, the EGR gas temperature can be controlled optimally,
The mass flow rate of the EGR gas can be precisely controlled.

In this embodiment, an example in which a diesel engine is used as the internal combustion engine 6 has been described. However, the present invention is not limited to this, and a gasoline engine may be used.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention.

FIG. 2 is a diagram illustrating the operation of an EGR gas cooling device.

FIG. 3 is a flowchart showing control of a shutoff valve.

FIG. 4 is a flowchart showing control of a flow control valve;

FIG. 5 is a flowchart showing setting of a flow control valve opening degree;

FIG. 6 is a flowchart showing control of an EGR device with an EGR gas cooling device according to an embodiment of the present invention.

FIG. 7 is a flowchart showing correction of an EGR control valve opening degree;

[Explanation of symbols]

 2 Supercharger 4 Intake throttle valve 5 Intake manifold 6 Internal combustion engine 7 Exhaust manifold 8 EGR passage 9 EGR control valve 10 Collector 11 EGR gas cooling device 12 Shutoff valve 21 Cooling water pipe 31 Electronic control unit 41 Water temperature sensor 42 Gas temperature sensor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 21/08 311 F02D 21/08 311B F-term (Reference) 3G062 AA05 BA00 CA01 EA10 ED08 GA08 GA10 GA21 3G092 AA02 AA17 AA18 DB03 DC03 DC09 DF00 DF08 DG07 EA08 EA17 EA28 EA29 FA00 FA36 GA01 GA10 HD07X HD07Z HE08Z

Claims (8)

[Claims] An EGR device for an internal combustion engine, wherein an EGR gas cooling device that cools the EGR gas with engine cooling water is provided in an EGR passage that recirculates the EGR gas from an exhaust system to an intake system. A cooling water circulation unit connected to a bubble generating portion of the engine cooling system where the cooling water boils when the engine is stopped and bubbles are generated, such that the bubbles are guided into the EGR gas cooling device when the engine is stopped; An EGR device with an EGR gas cooling device, wherein the air bubbles are retained in the EGR gas cooling device from a time when the engine is stopped until a predetermined time after a restart. 2. A cooling water inlet portion of the EGR gas cooling device is connected to the bubble generating portion, and a cooling water outlet portion of the EGR gas cooling device is provided with a shut-off valve that closes from a time when an engine stops until the predetermined time. The EGR device with an EGR gas cooling device according to claim 1, wherein: 3. The E according to claim 2, wherein the shut-off valve is opened after the engine temperature reaches a predetermined value after the restart.
EGR device with GR cooling device. 4. The flow control valve according to claim 2, wherein the shut-off valve is a flow control valve capable of controlling a flow rate of cooling water flowing through the EGR gas cooling device based on an engine temperature. EGR device with EGR gas cooling device. 5. The EGR device with an EGR gas cooling device according to claim 3, wherein the engine temperature is a cooling water temperature. 6. The EGR device with an EGR gas cooling device according to claim 3, wherein the engine temperature is an EGR gas temperature. 7. An EGR control valve opening correction means for correcting an opening of an EGR control valve provided in the EGR passage on the basis of an EGR gas temperature.
The EGR device with an EGR gas cooling device according to claim 6. 8. The EGR device with an EGR gas cooling device according to claim 1, wherein the bubble generation point is a cooling water outlet of a turbocharger.