JPS5922048B2 - Exhaust gas recirculation device for exhaust turbocharged engines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an engine equipped with a supercharger driven by an exhaust gas turbine, that is, an exhaust gas turbo supercharger, in which a part of the exhaust gas is reduced for the purpose of reducing NOx' in the exhaust gas. This relates to a device that recirculates water to the intake system.

Exhaust gas turbo superchargers have the advantage of being able to make use of the energy contained in the exhaust gas from the engine to increase engine output. , it is impossible to reflux and mix a part of the exhaust gas into the supercharged air as it is.

Recently, it has been proposed to install a venturi in the supercharging passage from the blower compressor to the engine to generate a pressure lower than the exhaust pressure, and to recirculate the exhaust gas using this venturi pressure. Providing a venturi in the supercharging passage not only complicates the structure of the supercharging passage, but also increases the flow resistance of supercharging air in high load and high rotation ranges due to the venturi. Since a recirculation passage connecting the system and the intake system is required, the structure of the entire system is complicated, and additions require an increase in space.

The present invention solves the above problem by using a hollow shaft as the shaft that directly connects the exhaust turbine and the blower compressor in the turbo supercharger, and recirculating the exhaust gas to the intake side through the hollow shaft. At the same time, it promotes an increase in the humidity of the turbocharger oil during a cold start of the engine, allows exhaust gas containing few solid particles such as Garbon to recirculate, and improves afterburn and exhaust system when the engine suddenly decelerates. This also prevents parts from overheating. Another invention, in addition to the above invention, is that the rotation of the hollow shaft positively ensures the recirculation of exhaust gas.

Next, an example of the present invention will be explained with reference to the drawings, in which 1 is an engine having an intake manifold 2 and an exhaust manifold 3, 4 is an exhaust turbine 5 and a blower-compressor 6.
7 is a muffler or a catalytic converter that discharges exhaust gas into the atmosphere, and the intake manifold 2 is equipped with a carburetor 8 with a throttle valve 9 (another embodiment In this case, instead of a carburetor, fuel can be supplied to each cylinder of the engine using a fuel injection nozzle.)
, is connected to the discharge side of the blower-compressor 6 via a supercharging passage 10, and the suction side of the blower-compressor 6 is connected to an air cleaner 12 via an atmospheric suction passage 11.

Further, the exhaust side of the exhaust turbine 5 is connected to the muffler 7 via an exhaust pipe 13, and the inlet side of the exhaust turbine 5 is connected to the exhaust manifold 3 via an exhaust passage 14.

The shaft 15 of the turbocharger 4 is formed into a hollow shaft having an exhaust gas recirculation passage 16 at its center, and one end of the shaft 15 is made to look into the exhaust port 1γ of the exhaust turbine 5, so that the recirculation is carried out to that location. A shaft sealing member 20 which opens the passage 16, has the other end of the shaft 15 looking into the suction port 18 of the blower compressor 6, and has an orifice 19 bored in the other end in the radial direction.
The reflux passage 16 in the shaft 15 is connected to the suction port 18 of the blower-compressor 6 through an orifice 19.

Further, the shape of the tip of the shaft sealing member may be arbitrarily selected, such as a pointed shape.

In addition, the reference numeral 21 in the figure is a supply passage for supplying secondary air to the exhaust manifold 3 to purify CO, HC, etc. in the exhaust gas, and 24 is a warm oil pipe branched from the warm oil system of the engine 1. After the hot oil from the pipe 24 enters the bearing 25 of the turbocharger 4 and warms it,
A pipe line 26 is connected to an oil pan (not shown) in the engine 1.
and return via an oil cooler (not shown).

Reference numeral 22 in the figure is an exhaust gas switching valve provided in a bypass passage 23 that connects the exhaust passage 14 and the exhaust pipe 13 or the muffler 7 so as to bypass the exhaust turbine 5. When the rotation speed is exceeded and supercharging occurs, the switching valve 22 is activated to allow part of the exhaust gas to flow directly to the muffler, thereby preventing supercharging.

In this configuration, exhaust gas discharged from the engine during operation of the engine is transferred from the exhaust passage 14 to the exhaust turbine 5.
The intake air from the air cleaner 12 is transferred to the blower-compressor 6 by rotating the exhaust turbine 5 and rotationally driving the blower-compressor 6 which is directly connected to the exhaust turbine 5 through the shaft 15.
is compressed and supercharged to the engine.

In this turbocharged state, the pressure Pl at the suction port 18 of the blower-compressor 6 becomes lower than the exhaust pressure P2 at the exhaust port 17 of the exhaust turbine 5 due to the suction action of the blower-compressor. The exhaust gas flows to the intake port 18 side through the recirculation passage 16 and orifice 19 in the shaft 15, is mixed equally with the intake air in the blower-compressor 6, and is recirculated to the intake system. , in this case the outlet 17 of the exhaust turbine 5
The exhaust gas flows while swirling at high speed due to the high-speed rotation of the exhaust turbine 5, and solid particles such as carbon in the exhaust gas are blown away in the circumferential direction by the centrifugal force caused by this high-speed swirling action, and the solid particles are concentrated in the center. Since the exhaust gas is in a state where there are few solid particles such as carbon, it can be recirculated to the intake system.

Further, the pressure P1 at the intake port 18 of the blower-compressor 6 decreases in inverse proportion to the amount of intake air which increases in proportion to the engine load, while
The exhaust pressure P2 at 1 increases in proportion to the amount of exhaust gas, that is, the amount of intake air, which increases in proportion to the engine load, and the pressure difference between the two pressures PI and P2 increases in proportion to the engine load. Therefore, the amount of exhaust gas recirculated to the intake system increases in proportion to the amount of intake air, that is, the engine load.

In this way, the increase in the amount of recirculated exhaust gas in the high load range of the engine can suppress the occurrence of knocking caused by the increase in the maximum compression pressure of the engine due to turbocharging.

The maximum value of the recirculated exhaust gas amount can be regulated arbitrarily by the orifice 19.Then, when the throttle valve 9 is suddenly closed from the turbocharged state to decelerate, the exhaust gas amount is drastically reduced, but the turbocharger 4 continues to rotate due to inertia, the pressure P2 at the discharge port 11 suddenly decreases, while the flow of intake air to the blower-compressor 6 rapidly decreases, causing P2 to decrease to Pl.
Since the air in the suction passage 11 flows back through the recirculation passage 16 to the discharge port 17 side.

This backflow of intake air into the exhaust system during sudden deceleration is caused by the incomplete combustion of the engine during sudden deceleration, and the mixture is released into the exhaust system, causing afterburn that occurs within the exhaust system. This prevents overheating of exhaust system components such as the muffler 7 provided in the exhaust system, and also prevents clogging by blowing off carbon that adheres in the recirculation passage 16 to the backflow air.

FIG. 3 shows another embodiment of the invention, in which the inner wall surface of the recirculation passage 16 in the shaft 15 that directly connects the exhaust turbine 5 and the blower-compressor 6 in the turbocharger 4 is marked with the direction of rotation of the shaft 15. This is provided with spiral fins 27 in opposite directions.

That is, the fins 27 provided on the inner wall surface of the recirculation passage 16 in the shaft 15 have the effect of blowing the exhaust gas from the exhaust port 17 toward the intake port 18 side by the rotation of the shaft 15. The recirculation is actively carried out by the combination of the pressure difference between P1 and P2 and the blowing action of the fins 21, so that exhaust gas recirculation can be effectively achieved in the partial negative region where the rotation is low. In place of this fin 27, the reflux passage 1
A spiral groove may be provided on the inner wall surface of the turbocharger.As described above, in the present invention, the shaft that directly connects the exhaust turbine and the blower compressor in the turbocharger is formed into a hollow shaft and connected to the intake system. Because it recirculates the exhaust gas of
There is no need to complicate the structure of the supercharging passage from the blower-compressor or to provide a recirculation passage at "i't+Mm" as in the conventional case, and the structure is simplified and the installation space can be reduced.

Furthermore, since the exhaust gas recirculated to the intake system according to the present invention has few solid particles such as carbon, it is possible to prevent the deposition of carbon and other substances on passages, carburetors, fuel injection nozzles, throttle valves, etc. in the intake system. Moreover, since the recirculated exhaust gas passes through the shaft of the turbocharger and warms the shaft bearing, the temperature of the lubricating oil for the turbocharger quickly rises during a cold start. This improves the temperature of the bearing in a short time, and prevents seizure of the bearing.

Furthermore, the present invention allows intake air to flow back into the exhaust system through the recirculation passage in the shaft of the turbocharger during sudden engine deceleration, thereby cleaning the recirculation passage and preventing afterburn and exhaust system parts. Overheating can be reliably prevented.

Furthermore, in addition to the above-mentioned invention, the other invention is capable of actively recirculating exhaust gas to the intake system, so it is possible to reliably achieve recirculation in a partial load range, and also to improve the recirculation of exhaust gas into the intake system. This has the effect of making the internal reflux passage thinner and preventing the shaft from becoming larger in diameter.

[Brief explanation of the drawing]

FIG. 1 is a diagram of an embodiment of the present invention, FIG. 2 is an enlarged sectional view of the turbo supercharger in FIG. 1, and FIG. 3 is a sectional view of another example of the turbo supercharger. 1...Engine, 4...Turbocharger, 5...Exhaust turbine, 6...Blower-compressor, 15... Shaft, 10...Supercharging passage, 14...Exhaust passage, 17...Exhaust turbine outlet, 18...Blower-compressor inlet, 16 ...Exhaust gas recirculation passage.

Claims (1)

[Claims] 1. In an engine equipped with an exhaust gas turbocharger,
The shaft that directly connects the exhaust turbine and the blower compressor in the turbocharger is formed into a hollow shaft having an exhaust gas recirculation passage therein, and one end of the exhaust gas recirculation passage in the hollow shaft is connected to the exhaust gas of the exhaust turbine. 1. An exhaust gas recirculation device for an exhaust turbocharged engine, characterized in that one end of the recirculation passage is opened into the mouth, and the other end of the recirculation passage is opened at a portion of the blower-compressor where the pressure is low. 2 In an engine equipped with an exhaust gas turbocharger,
The shaft that directly connects the exhaust turbine and the blower compressor in the turbocharger is formed into a hollow shaft having an exhaust gas recirculation passage therein, and one end of the exhaust gas recirculation passage of the hollow shaft is connected to the exhaust port of the exhaust turbine. On the other hand, the other end of the recirculation passage is opened at a portion of the blower compressor where the pressure is low and is □, and the inner surface of the exhaust gas recirculation passage is provided with spiral fins or An exhaust gas recirculation device for an exhaust turbocharged engine characterized by providing a groove.