JP4563301B2 - 4-cycle engine with internal EGR system - Google Patents

Description

  The present invention is mainly applied to a four-cycle diesel engine and a four-cycle gas engine, and an intake valve is sub-lifted by a minute amount away from a main lift during an intake stroke during an exhaust stroke, and a part of the combustion gas in the combustion chamber is taken into an intake passage. Is a four-cycle engine with an internal EGR system that mixes the intake gas into intake air and returns the combustion gas to the combustion chamber when the intake valve is opened by the main lift of the intake valve, and cools the gas in the intake passage including the internal EGR gas. The present invention relates to a 4-cycle engine with an internal EGR system provided with a passage cooling means.

  In a 4-cycle diesel engine, 4-cycle gas engine, etc., the intake valve is separated from the main lift during the intake stroke by a small amount during the exhaust stroke, and a part of the combustion gas in the combustion chamber is sent to the intake passage and mixed into the intake air There is provided a four-cycle engine having an intake sublift type internal EGR system that recirculates the combustion gas to a combustion chamber when the intake valve is opened by a main lift of the intake valve.

FIG. 5 is a plan view showing the arrangement of the intake device around the engine in a 4-cylinder 4-cycle diesel engine to which the intake sublift internal EGR system is applied.
In FIG. 5, reference numeral 100 denotes an engine (four-cycle diesel engine). In this example, a four-cylinder four-cycle diesel engine is shown, and 1 is a cylinder of the engine 100.
Reference numeral 5 denotes an intake port formed in the cylinder head 20 of the engine 100, 2 denotes an intake valve that opens and closes each intake port 5, and 7 denotes an intake branch pipe connected to each intake port 5. Reference numeral 4 denotes an intake manifold to which the intake branch pipes 7 for 4 cylinders are connected.
Reference numeral 6 denotes an exhaust port formed in the cylinder head 20 of the engine 1, 3 denotes an exhaust valve that opens and closes each exhaust port 6, and 9 denotes an exhaust branch pipe connected to each exhaust port 6. Reference numeral 8 denotes an exhaust manifold to which the exhaust branch pipes 9 for 4 cylinders are connected.

FIG. 4 is an intake / exhaust timing diagram in # 1 and # 2 of the intake sublift internal EGR system applied to the 4-cylinder 4-cycle diesel engine as shown in FIG.
In FIG. 4, In is the main lift of the intake valve 2, Is is the sub-lift of the intake valve 2, Ex is the lift (main lift) of the exhaust valve 3, and in the intake sub-lift internal EGR system, for example, in the # 1 cylinder During the exhaust stroke when the exhaust valve 3 is performing the main lift Ex, the intake valve 2 is moved away from the main lift In during the intake stroke (advanced) to make a small amount of sublift Is, and the combustion gas in the combustion chamber of the cylinder 1 The internal EGR gas which is a part of the intake air is sent to the intake passage such as the intake port 5, the intake branch pipe 7, the intake manifold 4, and mixed with the intake air in the intake passage, and this internal EGR gas is generated by the main lift In of the intake valve 2. When the valve is opened, it is recirculated into the combustion chamber.

As one of the technologies related to the engine provided with such an internal EGR system, there is a technology provided in Patent Document 1 (Japanese Patent Laid-Open No. 7-133726).
In the technique of Patent Document 1, an intake control valve that opens and closes the intake passage to change the intake passage area is installed in the intake passage, and the intake valve is opened before the intake control valve immediately before the end of the exhaust stroke. The combustion gas (EGR gas) is pushed into the intake passage, which is under negative pressure, as the piston rises, and the intake air mixed with EGR gas is recirculated into the combustion chamber during the intake stroke. In addition, the internal EGR amount is controlled to a desired value by controlling the pressure (negative pressure) between the intake control valve and the intake valve by controlling the opening and closing according to engine operating conditions such as engine load and engine speed. .

JP-A-7-133726

  Among the four-cycle engines having the internal EGR system, in particular, in the engine having the intake valve sub-lift type internal EGR system as shown in FIG. 4, the exhaust valve 3 in FIG. 4 to FIG. During the exhaust stroke, the intake valve 2 is advanced with respect to the main lift In during the intake stroke to cause a small amount of sublift Is, and the internal EGR gas in the combustion chamber is supplied to the intake port 5, the intake branch pipe 7, the intake manifold 4, etc. After being fed into the intake passage and mixed with the intake air in the intake passage, the internal EGR gas is recirculated into the combustion chamber when the intake valve 2 is opened by the main lift In.

For this reason, high-temperature combustion gas is introduced into the combustion chamber when it is opened by the main lift In of the intake valve 2 after the high-temperature combustion gas is sent to the intake passage as internal EGR gas and mixed into the intake air. As a result, the intake air temperature rises.
Therefore, in an engine equipped with such an intake valve sub-lift type internal EGR system, an increase in intake air temperature as described above causes a decrease in engine output and an increase in intake air temperature due to a decrease in intake air flow rate (weight flow rate). Problems such as an increase in the heat load around the combustion chamber due to an increase in the in-cylinder combustion temperature and a decrease in NOx reduction effect in the internal EGR due to an increase in the in-cylinder combustion temperature occur.
The technique provided in Patent Document 1 (Japanese Patent Application Laid-Open No. 7-133726) allows the intake valve to be sub-lifted by a minute amount away from the main lift during the intake stroke during the exhaust stroke, and the combustion gas in the combustion chamber Only a four-cycle engine having an internal EGR system in which a part of the engine is fed into the intake passage and mixed into the intake air and the combustion gas is returned to the combustion chamber when the intake valve is opened by the main lift of the intake valve is disclosed. No means for solving the problems associated with the rise in intake air temperature as described above is shown.

  In view of the problems of the prior art, the present invention suppresses an increase in intake air temperature associated with internal EGR, and causes a decrease in engine output due to a decrease in intake air flow and an increase in in-cylinder combustion temperature accompanying the increase in intake air temperature. An object of the present invention is to provide a four-cycle engine with an internal EGR system that prevents an increase in the heat load around the combustion chamber due to the above and a decrease in NOx reduction effect due to an increase in the in-cylinder combustion temperature.

The present invention achieves such an object. An intake port formed in each cylinder head of an engine having a plurality of cylinders, an intake valve that opens and closes each intake port, and each cylinder connected to each intake port. An intake manifold having a plurality of intake branch pipes,
Wherein the intake valve of each cylinder, part of the combustion gas in the combustion chamber by a small amount Saburifuto apart from the main lift during intake stroke during the exhaust stroke (hereinafter referred internal EGR gas), through the intake manifold In a four-cycle engine having an internal EGR (exhaust gas recirculation) system that feeds into the intake port of each cylinder head and mixes with intake air, and returns the combustion gas to the combustion chamber when the intake valve is opened by the main lift,
A cooling tube inserted into the intake port of each cylinder head is provided from the intake manifold via the intake branch pipe, and a coolant is allowed to flow through the cooling tube to pass through the intake branch pipe. The intake gas including the internal EGR gas sent to the intake port of each cylinder head is cooled , and the cooling tube is attached to a two-part intake manifold .

According to this invention, the cooling liquid is allowed to flow through the intake tube comprising the cooling tube or the cooling jacket to constitute the intake passage cooling means, and the intake passage cooling means passes through the intake branch pipe to each cylinder head. Since the intake gas including the internal EGR gas sent to the intake port is cooled , the temperature is raised by the internal EGR gas sent into the intake passage by sub-lifting the intake valve during the exhaust stroke. By cooling the intake air in the intake passage by the intake passage cooling means, it is possible to suppress an increase in intake air temperature due to mixing of internal EGR gas.
As a result, the engine load decreases due to a decrease in the intake air flow rate due to the increase in the intake air temperature due to the mixing of the internal EGR gas, and the heat load around the combustion chamber due to the increase in the in-cylinder combustion temperature due to the increase in the intake air temperature. And the occurrence of problems such as a decrease in NOx reduction effect due to an increase in the in-cylinder combustion temperature accompanying an increase in the intake air temperature, the required engine output is maintained, and the durability of the combustion chamber components is improved. It is possible to provide a 4-cycle engine with an internal EGR system that can improve and further achieve the required NOx reduction effect.

According to this invention , the cooling tube can be inserted deep into the intake port to the vicinity of the intake valve of each cylinder to cool the gas in the intake passage, and the thin cooling tube can be freely bent according to the shape of the intake passage. As a result, the intake air cooling effect is greatly increased, and the intake air temperature rise preventing effect is also increased.
In addition, since the cooling tube can be installed by being attached to the intake manifold and inserted into the intake branch pipe and the intake port, it can be installed on the existing cylinder head without modifying the cylinder head.

According to the present invention, with the above-described configuration , the engine output decreases due to the intake flow rate decreasing due to the increase in intake air temperature due to mixing of internal EGR gas, and the in-cylinder combustion temperature increases as the intake air temperature increases. Can prevent the occurrence of problems such as an increase in the heat load around the combustion chamber due to combustion and a decrease in NOx reduction effect due to an increase in in-cylinder combustion temperature accompanying an increase in intake air temperature, while maintaining the required engine output and combustion It is possible to provide a four-cycle engine with an internal EGR system that improves the durability of the chamber constituent members and further provides the required NOx reduction effect.

  Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this example are not intended to limit the scope of the present invention only to specific examples unless otherwise specified. Only.

FIG. 1 is a plan view showing a layout around an engine of a 4-cycle engine with an internal EGR system having an intake passage cooling means according to a first embodiment of the present invention, and FIG. 2 is a diagram of the intake passage cooling means in the embodiment. FIG. 2A is an enlarged cross-sectional view of a Z portion in FIG. 1, and FIG. 2B is a cross-sectional view taken along line AA in FIG.
1 and 2, reference numeral 100 denotes an engine (a four-cycle diesel engine). In this embodiment, a four-cylinder four-cycle diesel engine is shown, and 1 is a cylinder of the engine 100.
Reference numeral 5 denotes an intake port formed in each cylinder head 20 of the engine 100, 2 denotes an intake valve that opens and closes each intake port 5, and 7 denotes an intake branch pipe connected to each intake port 5. Reference numeral 4 denotes an intake manifold to which the intake branch pipes 7 for 4 cylinders are connected.
Reference numeral 6 denotes an exhaust port formed in each cylinder head 20 of the engine 1, 3 denotes an exhaust valve for opening and closing each exhaust port 6, and 9 denotes an exhaust branch pipe connected to each exhaust port 6. Reference numeral 8 denotes an exhaust manifold to which the exhaust branch pipes 9 for 4 cylinders are connected.

Reference numeral 10 denotes a cooling tube through which cooling water flows. The cooling tube intake port penetrates the intake manifold 4 in the longitudinal direction and is bent for each cylinder and enters the intake branch 7 and the intake port 5. The insertion portion 10a is provided so as to be able to cool down to the deep part of the intake port 5.
Since the long cooling tube 10 as described above is inserted from the intake manifold 4 to the deep part of the intake port 5 of each cylinder, the intake manifold 4 has a main body 42 on the intake branch 7 side as shown in FIG. The lid portion 41 is divided into two parts. After the cooling tube 10 is inserted, it is tightened fluid-tightly with a plurality of bolts 43.

By configuring as described above, the cooling tube 10 can be inserted deeply into the intake port 5 to the vicinity of the intake valve 2 of each cylinder 1 to cool the gas in the intake branch 7 and the intake port 5, and the thin wall The cooling tube 10 can be freely bent according to the shape of the intake passage (the intake branch 7 and the intake port 5), so that the intake air cooling effect becomes extremely large and the intake temperature rise prevention effect is also increased.
Further, since the cooling tube 10 can be installed by being attached to the two intake manifolds 41 and 42 and inserted into the intake branch pipe 7 and the intake port 5, the cylinder head 20 is modified to the existing cylinder head 20. It can be installed without

In the first embodiment, intake air (air) pumped from a compressor of a supercharger (not shown) passes through the intake manifold 4, passes through the intake branch pipes 7, the intake ports 5, and the intake valves 2 in the cylinder 1. To be introduced.
The exhaust gas from the cylinders 1 is stored in the exhaust manifold 8 through the exhaust valves 3, the exhaust ports 6 and the exhaust branch pipes 9 every time the exhaust valves 3 are opened. The turbocharger is fed to the turbocharger that does not drive the turbocharger.
The cooling water for intake air cools the intake air in each intake branch pipe 7 and intake port 5 by flowing through the cooling tube intake port insertion portion 10a of each cylinder 1 from the cooling tube 10 in the intake manifold 4 in order. Then, it is sent to the outside through the cooling tube 10 in the intake manifold 4.

FIG. 3 is a plan configuration diagram (corresponding to FIG. 1) showing an arrangement around the engine of a 4-cycle engine with an internal EGR system provided with an intake passage cooling means according to a second embodiment of the present invention.
In the second embodiment, a cooling jacket 23 that covers the outer periphery of the intake branch pipe 7 of each cylinder 1 and through which cooling water flows is provided.
A cooling water main pipe 20 is provided in the intake manifold 4 so as to penetrate in the longitudinal direction. An inlet branch pipe 21 and an outlet branch pipe 23 of each cylinder 1 are connected to the cooling water main pipe 20. The inlet branch pipe 21 and the outlet branch pipe 23 of each cylinder 1 are opened at both ends of the cooling jacket 23 so that the cooling water flows uniformly in the cooling jacket 23.

In the second embodiment, the intake cooling water branches from the cooling water main pipe 20 in the intake manifold 4 for each cylinder, enters the cooling jacket 23 from the inlet branch pipe 21, and takes the intake air inside the cooling jacket 23. The intake air flowing through the branch pipe 7 is cooled and flows out through the outlet branch pipe 23 to the outlet side of the cooling water main pipe 20.
According to the second embodiment, the cooling water circulation flow rate of the cooling jacket 23 can be increased. Therefore, the intake air cooling effect can be increased by increasing the cooling liquid circulation flow rate.

According to the first and second embodiments described above, the inside of the intake passage including the internal EGR gas that is supplied to the intake passage by flowing the cooling water through the intake passage composed of the intake branch 7 and the intake port. Since the intake passage cooling means such as the cooling tube 10 and the cooling jacket 23 for cooling the gas are provided, the temperature is raised by the internal EGR gas sent into the intake passage by sub-lifting the intake valve 2 during the exhaust stroke. By cooling the intake air in the intake passage by the intake passage cooling means, it is possible to suppress an increase in intake air temperature due to mixing of internal EGR gas.
As a result, the engine load decreases due to a decrease in the intake air flow rate due to the increase in the intake air temperature due to the mixing of the internal EGR gas, and the heat load around the combustion chamber due to the increase in the in-cylinder combustion temperature accompanying the increase in the intake air temperature. It is possible to prevent the occurrence of problems such as a decrease in NOx reduction effect due to an increase in combustion temperature and an increase in in-cylinder combustion temperature accompanying an increase in intake air temperature.

  According to the present invention, an increase in the intake air temperature associated with the internal EGR is suppressed, and an increase in the intake air temperature causes a decrease in engine output due to a decrease in intake air flow rate, and an increase in in-cylinder combustion temperature. It is possible to provide a four-cycle engine with an internal EGR system that prevents an increase in heat load and a decrease in NOx reduction effect due to an increase in in-cylinder combustion temperature.

1 is a plan configuration diagram showing an arrangement around an engine of a 4-cycle engine with an internal EGR system provided with an intake passage cooling means according to a first embodiment of the present invention. The details of the intake passage cooling means in the embodiment are shown (A) is an enlarged sectional view of a Z portion in FIG. 1, and (B) is a sectional view taken along the line AA in (A). FIG. 5 is a plan configuration diagram (corresponding to FIG. 1) showing an arrangement around an engine of a four-cycle engine with an internal EGR system provided with an intake passage cooling means according to a second embodiment of the present invention. It is an intake and exhaust timing diagram in # 1 and # 2 of an intake sublift type internal EGR system applied to a 4-cylinder 4-cycle diesel engine. It is a plane block diagram which shows arrangement | positioning around the engine of the intake device in the 4 cylinder 4 cycle diesel engine to which the conventional intake sublift type internal EGR system is applied.

Explanation of symbols

1 Cylinder 2 Intake Valve 3 Exhaust Valve 4 Intake Manifold 5 Intake Port 6 Exhaust Port 7 Intake Branch Pipe 8 Exhaust Manifold 9 Exhaust Branch Pipe 10 Cooling Tube 10a Cooling Pipe Intake Port Insertion Port

Claims (1)

An intake port formed in each cylinder head of an engine having a plurality of cylinders, an intake valve for opening and closing each intake port, and an intake manifold having intake branch pipes for each cylinder connected to each intake port ,
Wherein the intake valve of each cylinder, part of the combustion gas in the combustion chamber by a small amount Saburifuto apart from the main lift during intake stroke during the exhaust stroke (hereinafter referred internal EGR gas), through the intake manifold wherein is mixed into feed inlet to the intake port of each cylinder head, the four-stroke engine with internal EG R system for recirculating combustion gas into the combustion chamber when the valve is opened by the main lift of the intake valve,
A cooling tube inserted into the intake port of each cylinder head is provided from the intake manifold via the intake branch pipe, and a coolant is passed through the cooling tube to pass through the intake branch pipe. A four-cycle engine with an internal EGR system , wherein the intake gas including the internal EGR gas sent to the intake port of each cylinder head is cooled , and the cooling tube is attached to a two-part intake manifold. .

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