JPH1182186A - Cooling device for recirculating exhaust in internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve exhaust property during high load operation of an engine. SOLUTION: An internal combustion engine 10 is provided with an EGR pipe 14 taking out a part of exhaust from an exhaust passage 12 and leading exhaust to an inlet part of an intake manifold 13. An intermediate part of the EGR pipe 14 is formed in double pipe structure consisting of the EGR pipe 14 and an outer pipe 18 covering the EGR pipe 14. A main cooling water passage closed at both end parts is formed between the EGR pipe 14 and the outer pipe 18. The EGR pipe 14 on the upperstream and downstream of the main cooling water passage 19 is formed in double pipe structure consisting of the EGR pipe 14 and outer pips 20 covering the EGR pipe 14, and auxiliary cooling water passages 21 closed at both end parts are formed between the EGR pipe 14 and the outer pipes 20, respectively. A cooling water lead-in pipe on the downstream of EGR gas, and a cooling water lead-in pipe 18 on the upperstream of EGR gas are respectively connected to the outer pipe 18 constituting the main cooling water passage 19 that is, the flow direction of cooling water in the main cooling water passage 19 is reverse to the flow direction of EGR gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for cooling exhaust gas recirculation gas in an internal combustion engine, and more particularly to a technique for improving the exhaust gas properties by lowering the temperature of the exhaust gas recirculation gas.

[0002]

2. Description of the Related Art Conventionally, an EGR (Exhaust Gas) for reducing nitrogen oxides (NOx) generated from an internal combustion engine by extracting a part of exhaust gas from an exhaust system and recirculating the exhaust gas to an intake system to lower a combustion temperature. Recirculation (exhaust gas recirculation) devices are known. Further, in the EGR device, it has been experimentally revealed that as the temperature of exhaust gas (hereinafter, referred to as “EGR gas”) recirculated to the intake system is lowered, nitrogen oxides discharged from the internal combustion engine are reduced. .

Therefore, in order to lower the temperature of the EGR gas and improve the exhaust properties, for example, as shown in FIG.
EG that connects the intake passage 2 and the exhaust passage 3 of the internal combustion engine 1
A part of the R pipe 4 has a double structure of the EGR pipe 4 and the outer pipe 5 covering the EGR pipe 4 to form a cooling water passage 6 having both ends closed between the EGR pipe 4 and the outer pipe 5. , Cooling water passage 6
An EGR gas cooling device has been proposed in which a cooling water inlet pipe 7 and an outlet pipe 8 are connected to both ends of the EGR gas, respectively, so that the EGR pipe 4 is directly cooled with the cooling water to lower the temperature of the EGR gas. (See Japanese Patent Application Laid-Open No. 8-261072).

[0004]

However, in such an EGR gas cooling device, a single cooling water passage 6 is provided.
When the internal combustion engine 1 is operated under a high load and a large amount of EGR is required, the EGR gas amount is increased and the EGR gas temperature is reduced. The cooling water flowing through the cooling water passage 6 may boil due to the high temperature, and there is a possibility that the cooling water deteriorates and the cooling efficiency is reduced due to the generation of bubbles.

Accordingly, the present invention has been made in view of the above-mentioned conventional problems, and thus, by preventing the boiling of cooling water during high-load operation of an engine, a reduction in cooling capacity is suppressed, and an internal combustion engine with improved exhaust characteristics is provided. An object of the present invention is to provide a cooling device for exhaust gas recirculation gas in an engine.

[0006]

According to a first aspect of the present invention, there is provided a cooling apparatus for exhaust gas recirculation gas in an internal combustion engine, wherein the exhaust passage and the intake passage of the internal combustion engine communicate with each other.
A plurality of independent cooling water passages are provided along the exhaust recirculation passage around the exhaust recirculation passage for recirculating a part of the exhaust gas to the intake system, and the exhaust water is recirculated by the cooling water flowing through each cooling water passage. The circulation passage is cooled to cool the exhaust gas recirculation gas.

With this configuration, the exhaust gas recirculated to the intake system via the exhaust gas recirculation passage is cooled by the cooling water flowing through the cooling water passage, and the nitrogen oxides (NOx) in the exhaust gas are cooled. Is reduced. In this case, since a plurality of cooling water passages are provided along the exhaust gas recirculation passage, the amount of heat received by the cooling water flowing through each cooling water passage is reduced,
The temperature rise of the cooling water is suppressed, and the boiling of the cooling water hardly occurs.

According to a second aspect of the present invention, a part of a pipe constituting the exhaust gas recirculation passage is formed of an inner pipe and an outer pipe which cover the inner pipe. The cooling water passage was formed between the inner pipe and the outer pipe. According to this configuration, since the cooling water passage has an inner / outer double pipe structure of the inner pipe through which the exhaust gas recirculation gas flows and the outer pipe covering the inner pipe, it is easy to form the cooling water passage. Done.

According to a third aspect of the present invention, the cooling water supply system of each of the cooling water passages has an independent configuration for each of the cooling water passages. According to this configuration, since the cooling water flowing through each cooling water passage flows through the independent cooling water supply system, by appropriately setting the flow rate of the cooling water for each cooling water passage, the cooling water Is effectively suppressed.

According to a fourth aspect of the present invention, the cooling water in each of the cooling water passages flows in a direction opposite to an exhaust gas recirculation gas flowing in the exhaust gas recirculation passage. According to such a configuration, the cooling water in each cooling water passage flows in the opposite direction to the exhaust gas recirculation gas, that is, from the downstream having a lower temperature to the upstream having a higher temperature. Boiling is suppressed.

According to a fifth aspect of the present invention, at least one of the plurality of cooling water passages is provided with another cooling water passage so as to reduce the amount of heat received from exhaust gas recirculation gas flowing through the exhaust gas recirculation passage. A sub-cooling water passage is formed shorter in the axial direction of the exhaust gas recirculation passage than the water passage, and the sub-cooling water passage is located upstream of the other cooling water passages.

According to this configuration, the sub-cooling water passage is located upstream of the other cooling water passages, so that the temperature boundary layer at the upstream is developed, and the heat passage rate of the other cooling water passages is reduced. Suppress temperature rise of cooling water. In this case, since the sub cooling water passage is formed so that the amount of heat received from the exhaust gas recirculation gas is reduced, the temperature rise of the cooling water flowing through the sub cooling water passage is suppressed, and the boiling of the cooling water is suppressed. Is done.

According to a sixth aspect of the present invention, a cooling water inlet pipe and a cooling water outlet pipe are connected to the sub cooling water passage in a substantially straight line orthogonal to the sub cooling water passage. The introduced cooling water is configured to be led out of the cooling water outlet pipe around the periphery of the exhaust gas recirculation passage. According to this configuration, the cooling water flowing through the sub-cooling water passage is introduced through the cooling water introduction pipe, and then is discharged around the periphery of the exhaust gas recirculation passage from the cooling water discharge pipe. Therefore, the flow resistance of the cooling water is reduced, and it is not necessary to increase the capacity of the water pump or the like to increase the flow rate of the cooling water flowing through the sub cooling water passage.

According to a seventh aspect of the present invention, the cooling water supply system of the sub-cooling water passage includes a heat exchange means for exchanging heat with the surrounding atmosphere to cool the cooling water, and a circulating means for circulating the cooling water. , Including. According to such a configuration, the cooling water flowing through the sub-cooling water passage is reduced to near the ambient temperature by the heat exchange means, so that the cooling capacity of the exhaust gas recirculation gas is greatly improved.

According to an eighth aspect of the present invention, a temperature detecting means for detecting a temperature of the internal combustion engine, a storage means for storing cooling water flowing through the sub cooling water passage, and a cooling system for the sub cooling water passage are switched. Switching means, wherein the switching means causes the cooling water to flow through the sub-cooling water passage when the detected temperature of the internal combustion engine is equal to or higher than a predetermined temperature, and the detected temperature of the internal combustion engine is When the temperature is lower than the predetermined temperature, control for storing the cooling water flowing through the sub cooling water passage in the storage means is performed.

With this configuration, when the engine is cold, that is, when the temperature of the internal combustion engine is lower than the predetermined temperature, the cooling water flowing through the sub cooling water passage is stored in the storage means, and the cooling capacity is reduced. Subcooling of the recirculated gas is prevented. According to a ninth aspect of the present invention, in the cooling system for exhaust gas recirculation gas in the internal combustion engine, the exhaust gas recirculation passage for recirculating a part of the exhaust gas of the internal combustion engine to the intake system is cooled and the exhaust gas recirculation passage is circulated. A plurality of cooling systems for cooling the exhaust gas recirculation gas are provided independently along the exhaust gas recirculation passage.

According to this structure, the exhaust gas recirculated to the intake system through the exhaust gas recirculation passage is cooled,
Nitrogen oxides (NOx) in the exhaust gas are reduced. In this case, since a plurality of cooling systems for cooling the exhaust gas recirculation passage are provided independently, the amount of heat received from the exhaust gas recirculation gas in each cooling system is reduced.For example, the exhaust gas recirculation passage is cooled by cooling water. In such a case, the temperature rise of the cooling water is suppressed, and the boiling of the cooling water hardly occurs.

[0018]

As described above, according to the first aspect of the present invention, the boiling of the cooling water flowing through the cooling water passage is suppressed, and the deterioration of the cooling water and the reduction of the cooling capacity are prevented. Even during high-load operation of the engine, it is possible to improve the exhaust properties. According to the second aspect of the present invention, since the cooling water passage is easily formed, it is possible to suppress an increase in cost. .

According to the third aspect of the invention, it is possible to effectively suppress the temperature rise of the cooling water. According to the fourth aspect of the invention, the boiling of the cooling water in the cooling water passage is suppressed, so that the cooling capacity can be improved.
According to the fifth aspect of the present invention, the provision of the sub cooling water passage suppresses a rise in the temperature of the cooling water flowing through the other cooling water passage, so that the cooling water flowing through the other cooling water passage boils. Can be effectively suppressed.

According to the sixth aspect of the present invention, the flow resistance of the cooling water is reduced, and it is not necessary to increase the capacity of the water pump or the like in order to increase the flow rate of the cooling water flowing through the sub cooling water passage. In addition, cost increase can be suppressed. According to the seventh aspect of the present invention, since the temperature of the cooling water is reduced to near the atmospheric temperature by the heat exchange means, the cooling capacity of the exhaust flowing through the exhaust recirculation passage can be greatly improved.

According to the eighth aspect of the present invention, since the exhaust gas recirculation gas flowing through the exhaust gas recirculation passage is prevented from being supercooled, it is possible to prevent the deterioration of the exhaust properties at the time of cold. According to the ninth aspect of the invention, it is possible to improve the exhaust properties even during the high load operation of the engine.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the attached drawings. FIG. 1 shows a configuration of an embodiment of an EGR gas cooling device according to the present invention. Internal combustion engine 1
0, the exhaust passage 12 connected to the exhaust manifold 11
An EGR pipe 14 (inner pipe) for taking out a part of the exhaust gas from the exhaust manifold and introducing the exhaust gas to the inlet of the intake manifold 13 is attached. EGR valve 15 that changes pressure
Is interposed. The opening of the EGR valve 15 is changed by an actuator 17 that is driven and controlled by a control unit 16 containing a microcomputer. Then, the EGR amount is calculated in accordance with the engine operating state detected by the various sensors, and the actuator 17 is driven based on the calculated EGR amount to drive E.
The EGR amount is controlled by changing the opening of the GR tube 14.

An intermediate portion of the EGR tube 14 has an inner / outer double tube structure including the EGR tube 14 and an outer tube 18 covering the EGR tube 14, and both ends are disposed between the EGR tube 14 and the outer tube 18. A closed main cooling water passage 19 is formed. The EGR pipes 14 upstream and downstream of the main cooling water passage 19 are respectively
It has an inner / outer double pipe structure including an EGR pipe 14 and an outer pipe 20 that covers the EGR pipe 14, and sub cooling water passages 21 whose both ends are closed are formed between the EGR pipe 14 and the outer pipe 20. ing. The main coolant length L ₁ along the EGR pipe 14 of the passage 19 and the relationship between the length L ₂ along the EGR pipe 14 of the secondary cooling water passage 21, L _1> L _2, i.e., sub-cooling Water passage 2
Found the following first length L ₂ is set to be smaller.

The outer pipe 18 constituting the main cooling water passage 19 is connected to a cooling water introducing pipe 18a downstream of the EGR gas and a cooling water outlet pipe 18b upstream of the EGR gas. That is, the flowing direction of the cooling water in the main cooling water passage 19 is opposite to the flowing direction of the EGR gas. On the other hand, the cooling water inlet pipe 20a and the cooling water outlet pipe are connected to the outer pipe 20 constituting the sub cooling water passage 21 so that the cooling water introduced here is discharged around the periphery of the EGR pipe 14. 20b is connected. That is, the cooling water inlet pipe 20a and the cooling water outlet pipe 20b are arranged substantially in a straight line,
By being connected to the outer tube 20, the flow resistance of the cooling water is minimized. The flow rate of the cooling water flowing through the sub cooling water passage 21 is set to be larger than that of the cooling water flowing through the main cooling water passage 19.

Next, the operation of the cooling device for the EGR gas having the above configuration will be described. FIG. 2 shows a heat transfer rate diagram of a cooling water passage having an inner / outer double pipe structure for cooling EGR gas with cooling water, and FIG. 2 (a) shows a conventional cooling water passage, and FIG.
(b) shows experimental data of the cooling water passage of the present invention. In FIG. 2 (a) showing a conventional heat transmittance diagram,
The location where the heat transfer rate is maximum is the inlet of the EGR gas where the temperature boundary layer has not developed, where a large amount of heat is released from the EGR gas to the cooling water. Therefore, boiling of the cooling water is most likely to occur at the inlet of the EGR gas.

In the present embodiment, as shown in FIG. 1, the flow direction of the cooling water in the main cooling water passage 19 is opposite to the flowing direction of the EGR gas, that is, from the downstream side where the temperature of the EGR gas is low to the upstream side. The cooling water is not easily boiled at the inlet of the EGR gas. Further, by providing the sub cooling water passage 21 having a small contact area with the EGR gas upstream and downstream of the main cooling water passage 19,
The temperature boundary layer is developed, and the heat transfer rate in the main cooling water passage 19 is reduced. Further, the flow rate of the cooling water flowing through the sub cooling water passage 21 is increased, and
By returning the cooling water flowing through 1 to a radiator (not shown) for cooling the cooling water of the internal combustion engine 10, the boiling of the cooling water in the sub cooling water passage 21 is also suppressed.

For this reason, the cooling water in the main cooling water passage 19 and the sub-cooling water passage 21 is maintained at a temperature not higher than the boiling temperature as shown in FIG. The EGR gas can be cooled, and the exhaust properties can be improved. In addition, since the cooling water flowing through the sub-cooling water passage 21 is led out around the EGR pipe 14, the cooling water flow resistance is small, and the cooling water flow rate is increased. There is no need to increase the capacity of the water pump or the like. That is, cost increase can be suppressed.

FIG. 3 shows the configuration of another embodiment of the EGR gas cooling device according to the present invention. In this embodiment,
Unlike the first embodiment, the cooling water supply system of the main cooling water passage 19 and the cooling water supply system of the sub cooling water passage 21 are different systems. That is, the cooling water supply system of the main cooling water passage 19 is configured to cool the EGR pipe 14 to cool the rising temperature of the cooling water by the radiator 22, whereas the cooling water supply system of the sub cooling water passage 21 The system includes a small air-cooled heat exchanger 23 (heat exchange means) for cooling the cooling water, a circulation pump 24 for circulating the cooling water, and upstream and downstream of the circulation pump 24 (circulation means). Provided electromagnetic three-way valves 25 and 26 and a tank 2 for storing cooling water
7 (storage means). Three-way valve 25,
The reference numeral 26 indicates that the cooling water flowing through the sub cooling water passage 21 is drained into the tank 27 or the cooling water is returned from the tank 27 to the sub cooling water passage 21 according to an instruction from the control unit 16 (not shown) (see FIG. 1). Or

Here, the operation control of the three-way valves 25 and 26 is as follows.
The coolant temperature of the radiator 22 representing the temperature of the internal combustion engine 10 is detected by a water temperature sensor or the like (temperature detecting means), and the control unit 16 is controlled based on the detected coolant temperature.
Is executed by software.
That is, when the detected cooling water temperature is equal to or higher than the predetermined temperature, the cooling water is circulated through the sub cooling water passage 21, and when the detected cooling water temperature is lower than the predetermined temperature, the cooling water is drained and stored in the tank 27. .

The three-way valves 25 and 26 and the program stored in the control unit 16 constitute switching means. According to such a configuration, at the time of the normal operation in which the warm-up of the engine is completed, the cooling water in the sub-cooling water passage 21 that has cooled the EGR gas is cooled by the heat exchanger 23, regardless of the cooling water temperature of the internal combustion engine. , Its temperature drops to near ambient temperature. Therefore, the cooling capacity of the EGR gas is greatly improved.

On the other hand, when the cooling water temperature is low, such as when the engine is started, if the EGR gas is excessively cooled, white smoke and SOF (Soluble Organic Fraction) are generated in the exhaust gas. By operating the three-way valves 25 and 26, the cooling water is drained into the tank 27 to reduce the cooling capacity of the EGR gas, thereby preventing the EGR gas from being excessively cooled. Therefore, in addition to the effects of the first embodiment, it is possible to further improve the exhaust properties when the engine is cold.

In the embodiment described above, one main cooling water passage 19 and two sub cooling water passages 21 are provided, but one or more main cooling water passages 19 are provided. May be provided at least one upstream of the main cooling water passage 19. With the configuration in which a plurality of main cooling water passages 19 are provided, the amount of heat received from the EGR gas in each main cooling water passage is reduced, and the cooling water is more difficult to boil.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention.

FIGS. 2A and 2B illustrate the operation and effects of the present invention, wherein FIG. 2A is a conventional characteristic diagram, and FIG.

FIG. 3 is a partial configuration diagram showing another embodiment of the present invention.

FIG. 4 is a configuration diagram of a conventional EGR gas cooling device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Internal combustion engine 11 Exhaust manifold 12 Exhaust passage 13 Intake manifold 14 EGR pipe 16 Control unit 18 Outer pipe 19 Main cooling water passage 20 Outer pipe 21 Sub cooling water passage 23 Air-cooled heat exchanger 24 Circulation pump 25, 26 Three-way valve 27 tank

Claims (9)

[Claims] An exhaust passage and an intake passage of an internal combustion engine communicate with each other, and a plurality of independent exhaust passages are provided along the exhaust recirculation passage around an exhaust recirculation passage for recirculating a part of exhaust gas to an intake system. An exhaust gas recirculation gas cooling device for an internal combustion engine, comprising: a cooling water passage; and cooling the exhaust gas recirculation passage by cooling water flowing through each cooling water passage. 2. A part of a pipe constituting the exhaust gas recirculation passage has an inner / outer double pipe structure of an inner pipe through which exhaust gas recirculation gas flows, and an outer pipe covering the inner pipe. 2. The cooling device for exhaust gas recirculation gas in an internal combustion engine according to claim 1, wherein said cooling water passage is formed between a pipe and an outer pipe. 3. The exhaust gas recirculation gas for an internal combustion engine according to claim 1, wherein a cooling water supply system of each of the cooling water passages has an independent configuration for each of the cooling water passages. Cooling system. 4. The cooling system according to claim 1, wherein the cooling water in each of the cooling water passages flows in a direction opposite to an exhaust gas recirculation gas flowing in the exhaust gas recirculation passage. An apparatus for cooling exhaust gas recirculation gas in an internal combustion engine according to any one of the preceding claims. 5. At least one of said plurality of cooling water passages.
One auxiliary cooling water passage formed shorter in the axial direction of the exhaust recirculation passage than the other cooling water passages so that the amount of heat received from the exhaust recirculation gas flowing in the exhaust recirculation passage is reduced. Wherein the sub-cooling water passage is located upstream of other cooling water passages.
The cooling device for exhaust gas recirculation gas in an internal combustion engine according to any one of claims 1 to 4. 6. A cooling water inlet pipe and a cooling water outlet pipe are connected to the sub cooling water passage substantially in a straight line orthogonal to the sub cooling water passage. 6. The cooling system for exhaust gas recirculation gas in an internal combustion engine according to claim 5, wherein the cooling device is configured to extend around a periphery of the exhaust gas recirculation passage and to be led out from a cooling water discharge pipe. 7. The cooling water supply system of the sub cooling water passage includes heat exchange means for exchanging heat with the surrounding atmosphere to cool the cooling water, and circulating means for circulating the cooling water. The cooling device for exhaust gas recirculation gas in an internal combustion engine according to claim 5 or 6, wherein 8. A cooling system comprising: a temperature detecting means for detecting a temperature of an internal combustion engine; a storage means for storing cooling water flowing through the sub cooling water passage; and a switching means for switching a cooling system of the sub cooling water passage. The switching means, when the detected temperature of the internal combustion engine is equal to or higher than a predetermined temperature, allows the cooling water to flow through the sub-cooling water passage,
8. The exhaust gas recirculation in an internal combustion engine according to claim 7, wherein when the detected temperature of the internal combustion engine is lower than a predetermined temperature, control for storing the cooling water flowing through the sub-cooling water passage in the storage means is performed. Gas cooling device. 9. A cooling system for cooling an exhaust gas recirculation passage for recirculating a part of exhaust gas of an internal combustion engine to an intake system and cooling an exhaust gas recirculated gas flowing through the exhaust gas recirculation passage. A cooling device for exhaust gas recirculation gas in an internal combustion engine, wherein a plurality of cooling devices are provided independently along a passage.