JPS6056259B2 - 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 the exhaust gas is reduced in order to reduce NOx in the exhaust gas. This relates to a device that partially recirculates the air to the intake system.

It is known that a part of exhaust gas is recirculated to the intake system in a turbocharged engine, but conventional exhaust gas recirculation devices only have the purpose of recirculating exhaust gas to the intake system, so the throttle In order to prevent an abnormal rise in boost pressure when the valve is suddenly closed, it cannot be used in combination with a system that guides some of the supercharged air to the exhaust system. In this case, the system and the exhaust gas recirculation device must be provided separately, which not only complicates the structure but also increases the installation space.

Ta. The present invention replaces the recirculation passage that recirculates exhaust gas in the low to medium load range, which is frequently used in turbocharged engines, with a passage that guides supercharged air to the exhaust system during sudden engine deceleration and in the high load range. The above-mentioned drawbacks can be solved by using the same function.

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 turbo supercharger directly connected to an exhaust turbine 5 and a blower-compressor 6; 7 each indicates a muffler or a catalytic converter that releases exhaust gas to the atmosphere;
The intake manifold 2 is provided with a fuel injection device 8 for each cylinder in the engine 1.

In addition, the gathering part 9 of the intake manifold 2 is provided with a throttle valve 10 for increasing or decreasing the amount of air to the engine 1 (in this case, in other embodiments, the fuel injection device 8
(Instead, a vaporizer may be provided), and the gathering portion 9 is connected to the discharge side of the blower-compressor 6 via the supercharging passage 11, and the suction side of the blower-compressor 6 is connected to an air flow meter. It is connected to an air cleaner 14 via an air intake passage 13 with 12. Further, the exhaust side of the exhaust turbine 5 is connected to the muffler 7 via the exhaust pipe 15.
The inlet sides of each are connected to the exhaust manifold 3 via an exhaust passage 16. Reference numeral 17 in the figure indicates an exhaust gas recirculation passage, one end of which is connected to the exhaust passage 16 to the exhaust turbine 5, and the other end of which is connected to the throttle valve 1 in the collecting portion 9.
The chambers 19 are connected to the boats 18 provided slightly upstream from the closed position of 0, and provided in the recirculation passage 17.
The valve seat 21 is composed of a valve seat 21 with a boat 20 and a valve body 23 that is biased against the valve seat 21 by a spring 22, and is configured to open only in the direction from the boat 18 of the collecting section 9 to the exhaust passage 16. A backflow valve 24 is provided in the reflux passage 17 by providing an orifice 25 in the valve body 23 of the backflow valve 24, or by providing an orifice in the valve seat 21 instead of the valve body 23. 24 and an orifice 25 are provided in parallel, and the valve body of the reverse valve may itself be a plate-shaped member having elasticity.

In the drawing, reference numeral 26 indicates a supply passage for supplying secondary air to the exhaust manifold 3, and 27 indicates an exhaust passage 16 and an exhaust pipe 15 or a muffler 7 so as to bypass the exhaust turbine 5.
An exhaust gas switching valve installed in the detour passage 28 connecting the
When the supercharging of the engine exceeds the engine's critical rotational speed and becomes supercharging, the switching valve 27 opens 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 16 to the exhaust turbine 5.
By rotating the exhaust turbine 5 and rotationally driving the blower compressor 6 directly connected to the exhaust turbine 5, the intake air from the air cleaner 14 is compressed by the blower compressor 6 and sent to the engine through the supercharging passage 11. be provided.

In the idling state with the throttle valve 10 closed, the boat 18 of the recirculation passage 17 is connected to the throttle valve 1.
Although the turbo supercharger 4 is not in a supercharging state, the pressure in the boat 18 is low and there is almost no difference between it and the exhaust pressure in the exhaust passage 16. Although there is no recirculation of exhaust gas from the passage 17 to the intake system and no backflow of air to the exhaust system, if the throttle valve 10 is opened as the load increases, the throttle valve 10 will open at 18 points in the boat of the recirculation passage 16. Since the pressure at 18 points on the boat becomes negative and lower than the exhaust pressure in the exhaust passage 16, the exhaust gas flows into the exhaust passage 16 through the recirculation passage 1.
7, the flow rate is regulated and controlled by the orifice 25, and then returned to the intake system and mixed with the intake air to the engine.

Next, in a high load range where the throttle valve 10 is fully open or close to fully open, the amount of exhaust gas is large and the turbocharger is sufficiently rotated, and the supercharging pressure by the turbocharger becomes high. Since the pressure at 18 locations on the boat becomes higher than the pressure in the exhaust passage 16, a portion of the supercharged air from the blower compressor flows back through the recirculation passage 17 and the orifice 25 into the exhaust passage 16, and is contained in the exhaust gas. It acts as a so-called secondary air purifying CO and HC. Furthermore, when the throttle valve 10 is suddenly closed from a turbocharged state to suddenly reduce the amount of exhaust gas, the amount of exhaust gas decreases sharply, but the turbocharger continues to rotate due to inertia, and the supercharging pressure in the supercharging passage 11 rapidly increases. .
Then, due to this high boost pressure, the reverse valve 2 of the recirculation passage 17
The valve body 23 at 4 opens against the spring 22, and a large amount of supercharged air flows back toward the exhaust passage 16, preventing an abnormal increase in supercharging pressure when the throttle valve is suddenly closed. , a large amount of air is supplied to the exhaust system. Note that the recirculation passage 17 is provided with a temperature sensing valve 2 that opens when the temperature of the engine increases, such as the engine cooling water temperature or the lubricating oil temperature.
9, the recirculation passage 17 may be cut off during warm-up operation of the engine, and the recirculation passage 17 may be activated after the warm-up operation is completed.

As described above, according to the present invention, the recirculation of exhaust gas to the intake system in the low to medium load range where the engine is frequently used,
Supplying secondary air to the exhaust system in high load ranges and releasing supercharged air to the exhaust system when the throttle valve is suddenly closed.
Since a single recirculation passage is used for both functions, the structure is significantly simplified, the installation space is reduced, and the miniaturization of turbocharged engines can be promoted.
Furthermore, by quickly closing the throttle valve and releasing supercharged air to the exhaust system during sudden deceleration, abnormal increases in supercharging pressure can be prevented, and sudden increases in load on the blower compressor can also be prevented from flowing into the exhaust system. This can be reduced by releasing a large amount of supercharged air, and a sudden drop in rotation of the turbocharger can be prevented. Therefore, during the next acceleration after a sudden engine deceleration, the turbocharger will quickly reach the specified speed. rotation, which improves the follow-up performance of the turbocharger and, in turn, the acceleration performance of the engine.

In addition, due to the supply of a large amount of air to the exhaust system during sudden deceleration of the engine, afterburn occurs in the exhaust system due to the release of unburned gas due to incomplete combustion during sudden deceleration, and exhaust system parts such as mufflers. It is possible to prevent overheating of the reflux passage, and also to remove and clean solid particles such as carbon deposited in the reflux passage by the air flowing back in the reflux passage.

[Brief explanation of the drawing]

The drawings are diagrams showing embodiments of the invention. DESCRIPTION OF SYMBOLS 1... Engine, 4... Turbo supercharger, 5... Exhaust turbine, 6... Blower compressor, 11... Supercharging passage, 16... Exhaust passage, 10... Throttle valve,
17...Exhaust gas recirculation passage, 18...Boat, 24
...Reverse valve, 25... Orifice.

Claims (1)

[Claims] 1 In an engine equipped with an exhaust gas turbocharger,
A recirculation passage that recirculates a portion of the exhaust gas to the intake system is connected to a port located slightly upstream from the closed position of the throttle valve. 1. An exhaust gas recirculation device for an exhaust turbocharged engine, characterized in that it is provided with a check valve that opens in the direction of .