JP3867464B2 - EGR device for engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an engine EGR device that recirculates part of exhaust gas discharged from an engine to intake air.
[0002]
[Prior art]
Multi-cylinder water-cooled engine mounted in an automobile, for the reduction of NO _X, by introducing a part of the exhaust gas to the suction side have been made to lower the combustion temperature and slow combustion.
[0003]
The EGR device refers to a device that recirculates a part of the exhaust gas to the suction side. Usually, the device includes an exhaust passage on one side of the cylinder head that sandwiches the cylinder row, for example, a part of the exhaust manifold, Is an EGR passage arranged between the intake passage on the opposite side, for example, the EGR valve attached to the intake manifold, so as to straddle the upper side of the rocker cover and the cylinder head, specifically, the upper side in the center of the entire length of the engine. A connected structure is used, and EGR gas is introduced to the intake side through an EGR valve.
[0004]
[Problems to be solved by the invention]
However, since the exhaust gas introduced from the EGR valve into the intake passage is hot, the gas concentration per unit volume decreases, and a desired EGR amount cannot be introduced, and the intake gas heat rises due to the heat of the exhaust gas. Therefore, there is a problem that the intake efficiency is likely to decrease.
[0005]
The intercooler is disposed in front, the vertical engine leads to turbocharged through intercooler with turbocharger to the intake passage, under the influence of the point of the EGR passage which passes through the upper rocker cover and Cylinders head The mounting position of the EGR valve is likely to be forced downstream of the intake manifold. For this reason, the exhaust gas tends to be introduced from the downstream side of the intake manifold. However, as the exhaust gas is introduced from the downstream side of the intake manifold, the intake and mixing cannot be performed well. Therefore, there is a problem that intake air having a different EGR gas concentration is easily guided to each cylinder of the engine. Moreover, the structure in which the EGR passage straddles the upper side of the rocker cover is difficult to perform engine maintenance and repair work by removing the rocker cover, and requires a considerable length of pipe formed by the EGR passage. There were also problems that could be complicated.
[0007]
The present invention has been made by paying attention to the above circumstances, and the object of the present invention is an EGR passage with a short overall length, which enhances demounting workability at the top of the engine and further suppresses an increase in intake air temperature, An object of the present invention is to provide an engine EGR device that can supply intake air with a uniform EGR gas concentration to each cylinder.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the engine EGR device according to claim 1 is provided with a case containing a thermostat for controlling the cooling water temperature at the front of the cylinder head , and further supercharged with the energy of the exhaust gas. Assuming a turbocharged vertical engine that can supply intake air to the intake passage through the front intercooler, a part of the exhaust gas is separated from the exhaust passage on one side of the engine and the lower part of the thermostat case An EGR passage that leads to an intake passage on the other side of the engine through a gas passage formed integrally with the engine is formed, and the outlet side of the EGR passage is guided from the other side of the engine to the one side of the engine through the front of the engine. The structure is connected to a point on the upstream side.
[0009]
As a result, the EGR gas (exhaust gas) is cooled by the engine coolant flowing in the thermostat case and then introduced into the intake passage of the engine, so that the EGR amount is increased and the intake air of the engine is increased. Efficiency is increased.
[0011]
Be teeth, the outlet side of the EGR passage, not the upper engine by the engine front having the intercooler, goes around from the exhaust passage of the engine to the opposite side of the intake passage is connected to a portion close to the intercooler intake passage.
[0012]
Therefore, mixing of the EGR gas and the intake air is sufficiently performed by effectively utilizing the entire length of the intake passage, and intake air having a uniform EGR gas concentration is supplied to each cylinder of the engine. In addition, the outlet of the EGR passage is connected to the upstream portion of the intake passage that is piped to extend toward the intercooler (the front side of the engine), that is, a point close to the intercooler. Is simplified. In addition, since the EGR passage is disposed in front of the engine so as to open the upper side of the engine, it is easy to attach and detach components such as a rocker cover and a cylinder head, and provides excellent detachability to the engine. .
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described based on an embodiment shown in FIGS.
[0014]
FIG. 1 is a plan view of the front side of an engine, for example, a vertical water-cooled diesel engine (engine laid out in the longitudinal direction of the vehicle body) using a turbocharger mounted on a truck, and FIG. 1 is a side view of the upper part of the engine as viewed from line A to A in FIG. 1. In FIG. 1, 1 is an engine body of a diesel engine in which a cooling fan 1a and a radiator 1b are disposed in front, and 20 is the engine body 1. FIG. 1 shows a turbocharger (not shown in detail) attached to FIG.
[0015]
The engine body 1 drives a crankcase 3 (a part of which is shown in FIG. 2) in which a plurality of cylinders 2 are housed in the longitudinal direction of the engine, and an intake / exhaust valve and the valve attached to the upper part of the crankcase 3 A cylinder head 4 in which devices such as a valve operating system such as a camshaft and an injector (both not shown) are housed, a rocker case (not shown) attached to the top of the cylinder head 4, and a rocker that closes the opening of the rocker case And a cover 5. The intake / exhaust valves, injectors, and pistons (not shown) that reciprocate in the cylinder 2 are used to output power by repeatedly performing intake, compression, explosion, and exhaust strokes in each cylinder 2. . An intake manifold 7 connected to an intake passage, for example, an inlet pipe 6, for introducing intake air to each cylinder 2 is attached to one side of the cylinder head 4 that sandwiches two rows of cylinders. On the other side of the opposite side, an exhaust passage for discharging the combustion gas of each cylinder 2, for example, an exhaust manifold 8 is attached. The inlet pipe 6 is formed to extend forward of the engine.
[0016]
Further, for example, two thermostats 10 are attached to the front portion of the engine body 1, for example, the front portion of the cylinder head 4. The thermostat 10 is housed in a case in which cooling water flows, for example, a box-shaped upper and lower split type case 11 formed of an aluminum material, and is configured as one part. One side surface of the case 11 is attached so as to be in close contact with the front surface of the cylinder head 4. The case 11 has an external discharge port 12 in the upper part, an inlet 13 communicating with an outlet (not shown) of a water jacket formed inside the cylinder head 4 on the side close to the cylinder head 4, and a lower part Further, a bypass port (not shown) communicating with a bypass path of an engine axial force driven water pump 14 (shown only in FIG. 2) attached to the front portion of the crankcase 3 is provided. The external discharge port 12 of the case 11 is connected to the inlet (not shown) of the radiator 1b via a radiator hose (not shown). When the cooling water in the water jacket is hot due to the switching operation (exit control) of the bypass port or the external discharge port 12 according to the cooling water temperature performed by the thermostat 10, the flow of the cooling water passes through the radiator 1b. In other words, when the cooling water is at a low temperature, the flow is changed to a flow passing through the bypass path of the water pump (flow not passing through the radiator 1b).
[0017]
The turbocharger 20 is attached to the outlet of the exhaust manifold 8. The turbocharger 20 has a turbine which is rotated by the energy of exhaust gas discharged from the exhaust manifold 8 (not shown) between this and compressors connected coaxially (not shown). The inlet of the intake pipe 22a is connected to an air cleaner (not shown), and the outlet pipe 22 of the compressor housing is connected to the inlet of, for example, an air-cooled intercooler 23 disposed in front of the engine, that is, in front of the cooling fan 1a. ing. Reference numeral 23a denotes an inlet pipe connecting the outlet pipe 22 of the compressor housing and the inlet of the intercooler 23. The outlet of the intercooler 23 is connected to the inlet 6a of the inlet pipe 6 extending toward the intercooler 23 via the outlet pipe 23b, and the intake air supercharged by the turbocharger 20 is connected by the intercooler 23. After cooling, it is supplied to the intake side of the diesel engine.
[0018]
Further, an EGR device 25 is attached to the engine body 1 to return the exhaust gas discharged into the exhaust manifold, for example, the exhaust manifold 8 to the manifold on the intake side of the engine body 1 as EGR gas.
[0019]
The EGR device 25 is designed to increase intake efficiency, to reduce the pipe length, to improve the detachability of the upper parts of the engine such as the rocker cover 5, and to intake air with a uniform EGR gas concentration to each cylinder 2. The structure that has been devised to supply is adopted.
[0020]
That is, in this structure, the shortest EGR passage 26 using the case 11 of the thermostat 10 through which the cooling water flows is used, and the intake passage is provided as much as possible while realizing piping from the exhaust side to the intake side across the two rows of cylinders. A structure in which EGR gas is introduced on the upstream side is used.
[0021]
Explaining this structure, the case 11 of the thermostat 10 has, for example, a substantially inverted L-shaped gas passage 27 extending along the width direction of the engine body 1 as shown in FIGS. 3 (a) and 3 (b). It is integrally formed. A flange portion 27a formed at the end of the gas passage 27 facing the exhaust side of the engine body 1 is separated from the lower portion of the collecting portion of the exhaust manifold 7 and extends to the front of the engine, that is, an EGR pipe 29. Is connected to the end of the. A flange portion 27b formed at the end of the gas passage 27 facing the intake side of the engine body 1 is attached to the most upstream side of the inlet pipe 6 via an EGR passage, that is, an EGR pipe 30 extending to the intake passage side. It is connected to a certain EGR valve 31. The EGR pipe 29, the gas passage 27 of the case 11, and the EGR pipe 30 separate from the exhaust manifold 8 of the engine, then wrap around the front of the engine body 1 and connect on the upstream side of the inlet pipe 6. An EGR passage 26 is formed. That is, the case 11 is structured to form a part of the EGR passage 26.
[0022]
In such an EGR device 25, when the EGR valve 31 is operated at a desired opening degree during engine operation, a part of the exhaust gas discharged into the exhaust manifold 8 is EGR as shown by a two-dot chain line in FIG. It is led out from the EGR pipe 29 as gas and goes to the gas path 27 in the case 11 of the thermostat 10 mounted on the front part of the engine.
[0023]
At this time, since the case 11 of the thermostat 10 is formed of a thermally conductive member, that is, an aluminum material, the gas path 27 plays a role of an EGR cooler, and is an engine cooling water. The EGR gas passing through is cooled. The EGR gas is guided from the EGR valve 31 into the inlet pipe 6 through the EGR pipe 30.
[0024]
That is, the EGR gas is supplied from the intake manifold 7 to each cylinder 2 while being mixed with the intake air flowing through the inlet pipe 6.
[0025]
At this time, since the EGR gas introduced into the inlet pipe 6 is cooled by the engine coolant flowing through the case 11 of the thermostat 10, the volume of the EGR gas can be reduced and the rise in the intake air temperature can be suppressed. As a result, the amount of EGR can be increased.
[0026]
As a result, the diesel engine can be operated in which intake is performed with a high EGR amount and high intake efficiency.
[0027]
Further, a structure in which the EGR passage 26 is piped through the front of the engine body 1 with the case 11 of the thermostat 10 as a part of the EGR passage 26 and a turbocharged water-cooled engine having an intercooler 23 in front of the engine body 1 are combined. Thus, the outlet of the EGR passage 26 can be connected to the upstream portion of the inlet pipe 6, that is, the intake passage portion near the inlet 6 a close to the intercooler 23 with the shortest path, and the entire length of the intake passage is effectively utilized, that is, the inlet The EGR gas and the intake air can be sufficiently mixed before reaching each cylinder 2 by fully utilizing the collecting portion 7a of the pipe 6 and the intake manifold 7. Thereby, intake air with a uniform EGR gas concentration can be supplied to each cylinder 2 of the engine body 1. Moreover, since the EGR passage 26 is the shortest route, the periphery of the engine can be simplified. In addition, since the EGR passage 26 is disposed in front of the engine so as to open the upper side of the engine body 1, it is easy to attach and detach parts on the engine such as the rocker cover 5 and the cylinder head 4, which is superior to the engine body 1. Desorption workability can be brought about.
[0028]
The present invention is not limited to the above-described embodiment, and various modifications may be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the gas path is formed in the case that houses two thermostats. However, the present invention is not limited to this, and the gas path may be formed in a case that houses one thermostat or two or more thermostats. Moreover, for example, although applied to the diesel engine in embodiment, you may apply to other engines.
[0029]
【The invention's effect】
As described above, according to the first aspect of the present invention, the EGR gas is introduced into the intake passage after being cooled by the engine coolant flowing in the thermostat case. The volume can be reduced and the rise in intake air temperature caused by EGR gas can be suppressed, and the EGR operation of the engine with the increased EGR amount and the intake efficiency can be performed.
[0030]
Also, the exit side of the EGR passage is the shortest route through the front of the engine and can be connected to the intake passage near the intercooler from the engine exhaust passage to the opposite intake passage. Therefore, EGR gas and intake air can be sufficiently mixed before reaching each cylinder, and intake air with a uniform EGR gas concentration can be supplied to each cylinder of the engine. Moreover, since the EGR passage is the shortest route, the engine periphery can be simplified. In addition, since the EGR passage is disposed in front of the engine so as to open the upper side of the engine, it is easy to attach and detach parts such as a rocker cover and a cylinder head on the upper part of the engine, thereby providing excellent detachment workability to the engine. There is an effect that can be .
[Brief description of the drawings]
FIG. 1 is a plan view showing an EGR device according to an embodiment of the present invention together with an engine equipped with the EGR device.
FIG. 2 is a front view of the upper part of the engine as seen from line A to A in FIG.
FIG. 3 is a view for explaining the structure of a thermostat case having a gas passage attached to the front portion of the engine.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Engine main body 1b ... Radiator 2 ... Cylinder 4 ... Cylinder head 6, 7 ... Inlet pipe, intake manifold (intake path)
8 ... Exhaust manifold (exhaust passage)
DESCRIPTION OF SYMBOLS 10 ... Thermostat 11 ... Case 20 ... Turbocharger 23 ... Intercooler 25 ... EGR device 26 ... EGR passage 27 ... Gas passage 29, 30 ... EGR pipe 31 ... EGR valve.

Claims (1)

A case in which a thermostat for controlling the cooling water temperature is housed in the front part of the cylinder head is mounted, and a vertically mounted engine having an intake passage on one side of the cylinder head sandwiching the cylinder and an exhaust passage on the other side,
An intercooler disposed in front of the engine;
A turbocharger that supplies intake air supercharged by the energy of the exhaust gas of the engine to the intake passage through the intercooler;
An EGR passage that is separated from the exhaust passage and guides a part of the exhaust gas to the intake passage of the engine through a gas passage formed integrally with a lower portion of the thermostat case;
An EGR device for an engine, characterized in that an outlet side of the EGR passage is led from the other side of the engine to one side of the engine through the front of the engine and connected to a point on the upstream side of the intake passage.

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