JPH0232855Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an EGR device for a diesel engine.

[Prior Art] In an ignition-type internal combustion engine that has two intake ports in each cylinder, a part of the exhaust gas is guided to one intake port and unburned components are reburned to purify the exhaust gas. However, for example, in 1978
-It is proposed in Publication No. 152552. However, this is applied to two-intake stratified combustion in gasoline engines, and cannot be applied to diesel engines, which have different combustion conditions. In a diesel engine, combustion conditions change due to intake air swirl or turbulence in the intake air that contributes to combustion, and this greatly affects smoke generation, driving noise, and fuel efficiency.

In particular, introducing high-temperature EGR gas in the low-speed range of an engine that is subject to strict 10-mode exhaust regulations reduces the intake amount of fresh air and makes it difficult to obtain sufficient air swirl for combustion. Therefore, the helical intake port is relatively easy to form swirl in the low speed range of the engine and has a high contribution rate to combustion due to micro-mixing.
Introducing EGR gas not only worsens combustion conditions and reduces engine output, resulting in poor fuel efficiency but also smoke.

Furthermore, during acceleration, the excess air ratio decreases and the combustion condition worsens, so it is necessary to reduce the amount of EGR gas introduced, but on the other hand, the concentration of _NOx tends to increase in this state. Therefore, it is difficult to reduce _NOx and ensure good combustion conditions simply by controlling the exhaust gas recirculation rate.

[Problem to be solved by the invention] The purpose of the invention is to avoid hindering the formation of swirl necessary for combustion at low/medium speeds or high loads of the engine.
By introducing EGR gas into the combustion chamber, EGR
An object of the present invention is to provide an EGR device for a diesel engine that avoids deterioration of combustion conditions due to the introduction of gas.

[Means for Solving the Problems] In order to achieve the above object, the configuration of the present invention is to provide an electromagnetic control valve in the middle of the conduit connecting the exhaust manifold to the helical intake port and tangential intake port of each cylinder, and to perform electromagnetic control. A valve connects the exhaust manifold to the tangential intake port at low engine speeds or low loads, and to the helical intake port at high engine speeds or high loads.

[Effect] Since the excess air ratio is large when the engine is under low load,
Even if EGR gas is introduced, the combustion state will not be hindered much. At low engine speeds and low loads, when EGR gas is introduced from the tangential intake port, sufficient swirl and fine turbulence of fresh air necessary for combustion in the low and medium speed range of the engine are introduced into the combustion chamber (cavity).
_NOx is generated in the center of the gas, thereby avoiding deterioration of combustion and reducing NO

At high engine speeds, a strong swirl can be obtained, so if EGR gas is introduced through the helical intake port, which contributes to micro-mixing and swirl generation, relatively dense EGR gas will be distributed in the center of the combustion chamber (cavity), which will cause combustion. helped, NO _X
is reduced.

[Embodiment of the invention] According to the invention, since combustion must be achieved with a swirl that is originally too low at low/medium speeds or low loads of the engine, EGR gas from the helical intake port, which is advantageous for swirl generation, is avoid introducing
A micro-swirl containing only the fresh air necessary for combustion is generated in the center of the combustion chamber (cavity) to prevent deterioration of combustion conditions. On the other hand, when the engine is running at high speed or under high load, the swirl becomes larger than necessary, so EGR gas is introduced only from the helical intake port.
This improves the mixing state of fresh air and EGR gas and improves the _NOx reduction effect.
Of course, in the medium speed range of the engine, EGR is activated from both the tangential intake port and the helical intake port.
Gas may also be introduced.

The present invention will be explained based on examples. As shown in FIG. 1, in a four-valve diesel engine, fuel injection nozzles 18 are arranged for each cylinder along the crankshaft direction in the center of the cylinder head 5, and injection pipes 19 are connected to the fuel injection pump (not shown). Fuel is injected into the combustion chamber through the The upper part of the cylinder head 5 is covered by a head cover 17.

An intake manifold 9 is provided on one side wall of the cylinder head 5. Fresh air is introduced from an air cleaner (not shown) through an intake pipe 12, and a conduit is connected from the intake manifold 9 to a tangential intake port 8a provided in each cylinder. 8 and a conduit 10 that connects to the helical intake port 10a. On the other hand, the combustion gases from each cylinder join together at an exhaust manifold 3 connected to the other side wall of the cylinder head 5, and are discharged to the outside from an exhaust pipe 2.

A conduit 16 is connected to the exhaust manifold 3, the end of which is connected to a solenoid control valve 15, in order to return a portion of the exhaust gas to the intake port for purification. A pair of conduits 13 and 14 are connected to the electromagnetic control valve 15 . Conduit 13 is connected to each conduit 8 via branch pipe 7, and conduit 14 is connected to conduit 10 via branch pipe 6.

The electromagnetic control valve 5 is configured to selectively send the EGR gas in the conduit 16 to the conduit 13 or 14 depending on operating conditions. Therefore, the electromagnetic control valve 15 is operated by the output of the electronic control device 32 based on the signals from the engine load sensor 30 and rotation speed sensor 31. The rotational speed sensor 30 is constituted by a potentiometer disposed on a shaft supporting an acceleration lever of a fuel injection pump operated by an accelerator pedal, for example, and the load is detected from this voltage change. The rotational speed sensor 31 is of an electromagnetic pickup type placed adjacent to the flywheel of the engine, and the rotational speed is detected from the voltage level induced therein.

As shown in FIG. 2, the cylinder head 5 has a
A tangential intake port 8a and a helical intake port 10a that are opened and closed by a pair of intake valves 22.
An exhaust port 3a that is opened and closed by a pair of exhaust valves 24 is provided. The intake port 8a is connected to the aforementioned conduit 8, and the intake port 10a is connected to the conduit 10. In addition, 18
a is a mounting hole for a fuel injection nozzle.

Next, the operation of the device of the present invention will be explained. At low engine speeds and low loads, the amount of rotation of the acceleration lever of the fuel injection pump is small, so the detection signals of the load sensor 30 and rotation speed sensor 31 are small, there is no output signal from the electronic control device 32, and the electromagnetic control valve 1
5 connects the conduit 16 to the conduit 13. A part of the exhaust gas from the exhaust manifold 3, that is, EGR gas, is transferred to the conduit 16, the conduit 13, the branch pipe 7, and the conduit 8.
and enters the tangential intake port 8a.
The EGR gas is well mixed with fresh air from the intake manifold 9 while forming a large swirling flow along the inner circumferential wall of the cylinder 25. On the other hand, in the helical intake port 10a, only the fresh air causes a strong swirl although the radius of rotation is small. This swirl of fresh air at the helical intake port 10a mixes the fuel well with the fresh air, ensuring a good combustion state.

When the detection signal of the rotation speed sensor 30 or the load sensor 31 exceeds a predetermined value or the rate of change exceeds a predetermined value, an output signal is generated from the electronic control device 32, the electromagnetic control valve 15 switches, and the conduit 16 is connected to conduit 14. Therefore, a portion of the exhaust gas from the exhaust manifold 3 flows through the conduit 16 and the electromagnetic control valve 1.
5. The air enters the helical intake port 10a through the conduit 14, the branch pipe 6, and the conduit 10, where it is well mixed with fresh air from the intake manifold 9 while forming a swirl. A swirl with a small turning radius is formed in this helical intake port 10a. On the other hand, only fresh air from the tangential intake port 8a generates a large swirling flow along the inner circumferential wall of the cylinder 25. Thus, under normal load or acceleration, the tangential intake port
By restricting EGR gas, more fresh air is distributed around the outer periphery of the combustion chamber where combustion is difficult, making it possible to reduce _NOx while avoiding deterioration of combustion.

In short, the present invention operates the electromagnetic control valve 15 according to the load or rotational speed of the engine and switches the intake port through which EGR gas is introduced.
By introducing EGR gas from the tangential intake port in low speed and low load ranges, deterioration of combustion conditions due to lack of swirl can be avoided, and at high speed ranges where the engine has excessive swirl and at high loads where the _NOx concentration is high. Now, by introducing EGR gas from the helical intake port,
In addition to promoting the mixing of EGR gas and fresh air,
By distributing fresh air to the inner circumferential wall side of the cylinder 25 where poor combustion is likely to occur, it is possible to prevent a decrease in output and the generation of smoke, and to reduce _NOx .

[Effects of the invention] As mentioned above, the invention provides an electromagnetic control valve in the middle of the conduit that connects the exhaust manifold to the helical intake port and tangential intake port of each cylinder, and uses the electromagnetic control valve to control exhaust gas at low engine speed or low load. Since the manifold is connected to the tangential intake port and the helical intake port when the engine is running at high speed or under high load, if EGR gas is introduced from the tangential intake port at low speed and low load ranges of the engine where it is difficult to obtain sufficient swirl, Sufficient swirl and fine fresh air turbulence necessary for combustion are generated in the center of the combustion chamber (cavity), thereby avoiding deterioration of combustion and reducing NO _x by reburning EGR gas. At low loads, the amount of combustion injection relative to the intake air is small and the excess air ratio is large, so even if EGR gas is introduced, the combustion state will not be disturbed much.

In the medium and high speed range of the engine, the swirl is strong, so
When a certain limit of EGR gas is introduced through the helical intake port, which contributes to micro-mixing and swirl generation, relatively dense EGR gas is distributed in the center of the combustion chamber (cavity), which aids combustion and reduces _NOx . Ru.

[Brief explanation of the drawing]

Figure 1 shows the EGR of the diesel engine according to this invention.
FIG. 2 is a plan view showing a schematic configuration of the device, and FIG. 2 is a cross-sectional view of the same plane. 3: Exhaust manifold, 5: Cylinder head,
6, 7: Branch pipe, 8: Conduit, 9: Intake manifold.

Claims (1)

[Scope of utility model registration request] An electromagnetic control valve is installed in the middle of the conduit that connects the exhaust manifold to the helical intake port and tangential intake port of each cylinder. Diesel engine EGR device characterized by connecting to the helical intake port.