JP2001221106A - Circulated gas cooling system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an EGR gas cooling system capable of cooling EGR gas by a simple structure by providing minimum possible special components for cooling the EGR gas. SOLUTION: Circulated gas is cooled by arranging a circulated gas pipe passage 6 branching off from an exhaust manifold 2 and communicating with an intake manifold 3 through control valve 5 across a flow passage of cooling air by a cooling fan 10, or cooled with cooling water by penetrating a thermostat housing 4 attached to a cylinder head 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recirculation system for an exhaust gas recirculation system (hereinafter, referred to as an "EGR system") that communicates from an exhaust passage of an internal combustion engine to an intake passage to recirculate a part of exhaust gas to the intake passage. The present invention relates to a gas (hereinafter, referred to as “EGR gas”) cooling mechanism.

[0002]

2. Description of the Related Art In order to improve the properties of exhaust gas of an internal combustion engine, in particular, to reduce nitrogen oxides (hereinafter referred to as NOx), the exhaust gas is communicated from an exhaust passage to an intake passage, and part of the exhaust gas is returned to the intake passage. An EGR device for performing this is known. In addition, this E
In the GR device, a technique for cooling the EGR gas by interposing a cooler to further improve the exhaust gas is also known.

For example, Japanese Patent Application Laid-Open No. 7-42628 discloses a technique for incorporating an EGR cooler in a cylinder block, and Japanese Patent Application Laid-Open No. 7-180620 discloses cooling an EGR gas with cooling water passing through a heater pipe. Japanese Patent Application Laid-Open No. 6-229328 discloses an intake air control device and E
EGR is provided by providing a cooling water passage connected in series with a GR device.
Techniques for cooling gas are disclosed.

Further, Japanese Patent Application Laid-Open No. Hei 7-243354 discloses a technique for preventing corrosion by providing a piezoelectric element in an EGR cooler and driving it at a high frequency. And the like have been disclosed in which the EGR pipe connecting the.

However, in these techniques, a special EGR cooler is provided for cooling the EGR gas, and the cooler becomes a complicated device for guiding cooling water from a cooling device of the engine, or the entire mechanism is provided. However, there is a problem that the size and weight are increased.

[0006]

SUMMARY OF THE INVENTION The present invention has been proposed to solve the problems of the prior art described above,
An object of the present invention is to provide an EGR gas cooling mechanism that can cool an EGR gas with a simple configuration without providing special components as much as possible for cooling the gas.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a recirculation gas cooling means in an exhaust gas recirculation system for communicating a part of exhaust gas to an intake passage by communicating from an exhaust passage of an internal combustion engine to an intake passage. A recirculation gas pipe branching from the inlet and communicating with the intake manifold via a control valve is disposed at a position to be cooled by air flowing in from the outside.

Here, it is preferable that the reflux gas pipe is disposed so as to cross the flow path of the cooling air so as to be cooled by the cooling fan.

According to the present invention having such a configuration, the reflux gas pipe is disposed at a position to be cooled by air flowing in from the outside, and more specifically, to be cooled by a cooling fan. Is arranged so as to traverse the flow path of the cooling air.
The EGR gas is sufficiently cooled without the GR cooler.

Therefore, according to the present invention, there is no need to provide an EGR cooler without increasing the amount of generated NOx, reduce the number of components, and reduce the weight of the internal combustion engine (or a vehicle or other machine on which it is mounted). Is achieved.
In connection with this, since the EGR cooler can be omitted, the degree of freedom in layout at the place where the internal combustion engine is installed increases.

In practicing the present invention, the location of the reflux gas pipe is not limited to the position "traversing the flow path of the cooling air so as to be cooled by the cooling fan". For example, the recirculation gas pipe can be arranged in front of a radiator provided (or outside) with respect to the cooling fan.

It is preferable to improve the cooling effect by providing a fin in the reflux gas pipe or using a bellows pipe (corrugated tube).

According to the present invention, there is provided a recirculation gas cooling means in an exhaust gas recirculation device for communicating a part of exhaust gas to an intake passage by communicating from an exhaust passage of an internal combustion engine to an intake passage. A recirculation gas line communicating with the intake manifold via a valve is configured to penetrate through a thermostat housing attached to the cylinder head and be cooled by cooling water.

According to the present invention having the above-described structure, the reflux gas pipe is configured to penetrate through the inside of the thermostat housing attached to the cylinder head and to be cooled by the cooling water. The EGR cooler can be omitted without increasing the generation amount.

In addition to this, according to the present invention, the high temperature E
Even if the cooling water boils due to the GR gas, since the reflux gas pipe is disposed so as to penetrate the thermostat housing, the steam can be discharged very smoothly. Therefore, safety is also improved. Here, it is preferable that the reflux gas passage penetrating through the inside of the thermostat housing is provided on the upstream side of the thermostat.

The engine to which the present invention is applied includes N
Engines with low Ox generation (low NOx engines),
An engine having a low EGR gas mixing ratio is preferable.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2, an exhaust manifold 2 is mounted on one side of the cylinder head 1 in the left-right direction (a direction perpendicular to the crankshaft), and an intake manifold 3 is mounted on the other side.

In the exhaust manifold 2 which is an exhaust passage,
One end of the EGR pipe 6 is attached, and the EGR pipe 6 extends forward and is bent forward of the cylinder head 1, behind a radiator (not shown in FIGS. 1 and 2) cooling fan 10. To the opposite side across the left and right direction, further bent and the other end is an intake manifold 3 which is an intake passage.
Is connected to an EGR valve attached to the EGR valve.

1 and 2, reference numeral 11 denotes a fan shroud. In FIG. 2, the fan 10
Are not shown.

According to the embodiment shown in FIGS. 1 and 2, a part of the exhaust gas branches off from the exhaust manifold 2 under the control of the EGR valve 5 which is a control valve, is guided to the EGR pipe 6, and the fan 10 It is cooled by the cooling air passing rearward and is returned to the intake manifold 2.

As shown in FIG. 3, it is preferable to provide a cooling fin 6a in the EGR pipe 6A because the cooling effect is improved.

Alternatively, as shown in FIG. 4, a corrugated tube may be used for the EGR tube 6B. The use of a corrugated tube is preferable because it has a cooling effect similar to that of the cooling fins, as well as flexibility against thermal expansion or vibration.

Next, in another embodiment shown in FIGS. 5 and 6, the EGR pipe 7 (8) is
And is cooled by the cooling water in the housing. In FIG. 5, the front of the engine (indicated by the cylinder block 21 and the cylinder head 1) (left side in FIG. 5)
Is provided with a radiator 23. Radiator 23
After cooling the cylinder block 21 and the cylinder head 1 via the piping 30 with the water pump 27 interposed therebetween, the cooling water returned to the radiator 23 via the thermostat housing 4 containing the thermostat 12.

Here, an EGR pipe 7 (8) is arranged in the thermostat housing 4 in a direction perpendicular to the paper surface of FIG. And this EGR pipe 7 (8)
As in the embodiment shown in FIG. 4, the cooling air passes through the rear of the fan 10 and is cooled by cooling air. In FIG. 5, reference numeral 25 denotes a cooling water bypass pipe, reference numeral 28 denotes a first air ventilation pipe, and reference numeral 29 denotes a second air ventilation pipe.
1 shows an air ventilation tube of the present invention.

FIG. 6 shows the positional relationship between the thermostat housing 4 and the EGR pipe in more detail. In FIG. 6, an exhaust manifold 2 (FIG. 6) is mounted on one side in the left-right direction of a cylinder head (not shown in FIG. 6), and an intake manifold 3 (FIG. 6) is mounted on the other side. A thermostat housing 4 is attached to the front side. As an EGR pipe, a first EGR pipe 7A connected to the exhaust manifold 2 is connected to the thermostat housing 4, penetrates the thermostat housing 4, and is provided by the second EGR pipe 7B from the opposite side through the intake manifold. 3 is connected to an EGR valve (control valve) 5 attached to the apparatus.

As shown in FIG. 7, an EGR cooling pipe 8 is inserted into the through portion of the thermostat housing 4 on the upstream side (cylinder head side) of the thermostat 12. In the embodiment shown in FIG. 7, the cooling tube 8 is provided in the thermostat housing 4 by casting.
In the embodiment shown in FIG. 8, a separate cooling pipe 8A is inserted and fixed by fastening means (not shown).

According to the embodiment described with reference to FIGS.
The EGR gas branches from the exhaust manifold 2 and is guided to the thermostat housing 4 by the first EGR pipe 7A,
The cooling water is cooled by cooling water in a cooling pipe 8 (A) in the thermostat housing 4, guided to the EGR valve 5 by a second EGR pipe 7 B, and controlled by the EGR valve 5 to flow back into the intake manifold 2. .

In the thermostat housing 4, when the temperature of the cooling water is lower than a predetermined value, the thermostat 12 closes, and the cooling water A that has left the cylinder head 1 is bypassed to a bypass pipe 25 as shown by an arrow C. At a water temperature equal to or higher than a predetermined value, the thermostat 12 opens and flows to the radiator (23) as indicated by an arrow B. Therefore, by inserting the cooling pipe 8 (A) upstream of the thermostat 12, the EGR gas is cooled by a stable water temperature,
More stable control is possible.

Further, the EG through which high-temperature EGR gas flows
Even when cooling water is in contact with the R pipe 7 (8) and boils to generate steam, the steam is transferred to the water sub tank 24 through the first and second air ventilation pipes 28 and 29 shown in FIG. Can be discharged from the side to the outside. Therefore, even if the cooling water boils, the pressure in the thermostat housing 4 does not extremely increase, and safety is maintained.

In addition, the EGR pipe 7 (8) is cooled by the cooling water in the thermostat housing 4, and the cooling water is immediately returned to the radiator 23.
Therefore, even if the EGR pipe 7 (8) is cooled, the cooling performance of the cylinder head 1 and the cylinder block 21 is not adversely affected.

Next, the first embodiment (FIGS. 1 to 4)
FIG. 10 shows experimental results on the cooling effect of the EGR gas according to the second embodiment (FIGS. 5 to 9).
In FIG. 10, the vertical axis shows the measured value of the EGR gas temperature, and the horizontal axis shows the measurement points. As shown in FIG. 6, S1 is the outlet of the exhaust manifold 2, and S2 is the EGR pipe. 7, and S3 is an EGR valve 5 inlet.
A broken line (reference A) indicates a conventional example in which the EGR pipe does not pass through the cooling air flow path, and a solid line (reference B) indicates that the EGR pipe 6
In the first embodiment, which crosses the cooling air flow path according to the first embodiment, and a chain line (reference numeral C) indicates that the EGR pipe 7 is
Shows the respective results of the second embodiment cooled through. As can be seen from the figure, passing the EGR tube through the cooling air flow shows a cooling effect of about 100 ° C, and cooling through the thermostat housing ° C shows a further cooling effect of about 50 ° C.

[0032]

The present invention is configured as described above,
The following effects are obtained. (1) EGR gas can be easily and easily cooled without using a complicated device such as an EGR cooler (EGR cooler). (2) Therefore, the number of parts can be reduced and the weight can be reduced without increasing the amount of generated NOx. (3) Since the EGR cooler can be omitted, a spatial margin around the engine is formed, and the degree of freedom in layout is increased. (4) In the configuration in which the EGR gas pipe branching from the exhaust manifold and communicating with the intake manifold passes through the inside of the thermostat housing attached to the cylinder head, the steam generated even when the cooling water boils is transferred to the water sub-tank. Since it is possible to escape to the outside via the outside, abnormal pressure increase in the thermostat housing can be prevented and safety can be improved. (5) Since the EGR pipe is cooled in the thermostat housing at the engine outlet, the heating does not adversely affect the cooling performance of the cylinder block and the cylinder head.

[Brief description of the drawings]

FIG. 1 is a top view showing a first embodiment of the present invention.

FIG. 2 is a front view of the embodiment shown in FIG.

FIG. 3 is a plan view showing another embodiment of the EGR tube.

FIG. 4 is a plan view showing still another embodiment of the EGR tube.

FIG. 5 is a block diagram showing a second embodiment of the present invention.

FIG. 6 is a perspective view of the embodiment shown in FIG. 5;

FIG. 7 is a sectional view showing a thermostat housing part of FIG. 5;

FIG. 8 is a sectional view showing an embodiment of an EGR cooling pipe of a thermostat housing part.

FIG. 9 is a sectional view showing another embodiment of the EGR cooling pipe of the thermostat housing part.

FIG. 10 is a graph showing experimental results of an EGR gas cooling effect of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Cylinder head 2 ... Exhaust manifold 3 ... Intake manifold 4 ... Thermostat housing 5 ... EGR valve 6, 6A, 6B, 7A, 7B ... EGR pipe 8, 8A ... EGR cooling pipe 10 ... fan 12 ... thermostat

Claims (3)

[Claims] 1. A recirculation gas cooling mechanism in an exhaust gas recirculation device that communicates from an exhaust passage of an internal combustion engine to an intake passage and recirculates a part of the exhaust gas to the intake passage, branches from an exhaust manifold through a control valve. A recirculation gas cooling mechanism, wherein a recirculation gas pipe communicating with an intake manifold is disposed at a position to be cooled by air flowing in from the outside. 2. The recirculation gas cooling mechanism according to claim 1, wherein the recirculation gas pipe is disposed so as to cross a flow path of the cooling air so as to be cooled by a cooling fan. 3. A recirculation gas cooling mechanism in an exhaust gas recirculation device that communicates from an exhaust passage of an internal combustion engine to an intake passage and recirculates a part of the exhaust gas to the intake passage, branches off from an exhaust manifold via a control valve. A recirculation gas cooling mechanism, wherein a recirculation gas pipe communicating with an intake manifold penetrates through a thermostat housing attached to a cylinder head and is cooled by cooling water.