JPS6050980B2 - 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.

Exhaust gas turbochargers have the advantage of being able to effectively utilize the energy contained in the exhaust gas from the engine to generate engine output. Since the pressure of the exhaust gas is higher than that of the exhaust gas from the exhaust gas, part of the exhaust gas cannot be refluxed and mixed into the supercharged air as it is. So recently, in the evening...
Nohe n, Yu Guanxuan ΔTwo Exhaust L Providing a ventilator in the feed passage increases the flow resistance of supercharging air, which not only reduces the output, but also causes the above-mentioned problems in low load and low rotation ranges where the amount of exhaust gas is small and the turbocharger rotation is low. Since the flow rate of intake air passing through the ventilator is slow, exhaust gas cannot be recirculated.The present invention has two systems for recirculating exhaust gas,
When turbocharging is operating in a high load and high rotation range, the pressure on the suction side of the turbocharger's blower-compressor is reduced, while in a low load and low rotation range, the throttle valve The exhaust gas is recirculated through a port located slightly upstream of the closed position of the exhaust gas, thereby ensuring that exhaust gas can be recirculated throughout the entire operating range of the engine.

Next, an example of the present invention will be explained with reference to the drawings. In Fig. J, 1 is an engine having an intake manifold 2 and an intake manifold 3, 4 is an exhaust turbo supercharger that directly connects an exhaust turbine 5 and a blower-compressor 6, and 7 is an engine having an intake manifold 2 and an intake manifold 3. 1 and 2 respectively indicate a muffler or a catalytic converter that discharges exhaust gas into the atmosphere, and the intake manifold 2 is provided with a fuel injection device 8 for each cylinder in the engine 1.

In addition, the collecting part 9 of the intake manifold 2 is equipped with a throttle valve 10 to increase or decrease the amount of air to the engine 1 (in this case, in other embodiments, a carburetor is installed in the collecting part instead of the fuel injection device). ), and gathering part 9
is connected to the discharge side of the blower compressor 6 through a supercharging passage 11, and the suction side of the blower compressor 6 is connected to the air cleaner 1 through an air suction passage 12 with an air flow meter 14.
Connected to 3. Further, the exhaust side of the exhaust turbine 5 is connected to the muffler 7 via an exhaust pipe 15, and the inlet side of the exhaust turbine 5 is connected to the exhaust manifold 3 via an exhaust passage 16. Reference numeral 17 in the figure indicates a low-load exhaust gas recirculation passage, one end of which connects to the exhaust passage 16 to the exhaust turbine 5, and the other end of which connects to a portion slightly upstream of the closed position of the throttle valve 10 in the gathering portion 9. Boat 18 installed in
The recirculation passage 17 is provided with a recirculation control valve 19 and an orifice 20 that are opened when the pressure of the intake manifold 2 increases toward the negative pressure side. In addition, the reference numeral 21 in the figure indicates a high-load exhaust gas recirculation passage, one end of which is connected to the exhaust passage 16 to the exhaust turbine 5, and the other end is connected to the suction side of the blower compressor or to the center of the back side of the blade of the blower compressor. A reflux control valve 22 and an orifice 23 are connected to the parts where the pressure becomes low in the reflux passage 21, and are configured to open when the pressure of the intake manifold 2 increases to the atmospheric pressure side.
It is made up of the following. Note that the reference numeral 24 in the figure indicates the supercharging passage 11 and the suction passage. 12 bypassing the blower compressor, the passage 24 is provided with a blow-off valve 25 that opens during deceleration by rapidly closing the throttle valve 9, and reference numeral 26 connects the exhaust passage 16 and the muffler. 7 or the exhaust pipe 15 by bypassing the exhaust turbine 5. An exhaust bypass passage 26 is provided with a wastegate valve 26 that opens when supercharging exceeds the engine's critical rotational speed.
7 is provided.

In this configuration, exhaust gas discharged from the engine during engine operation enters the exhaust turbine 5 through the exhaust passage 16, rotates the exhaust turbine 5, and rotationally drives the blower compressor 6 directly connected thereto. Now throttle valve 9
In the high load/high rotation range where the engine is fully open or close to fully open, the amount of exhaust gas is large and the turbo supercharger 4 is sufficiently rotated, and the supercharging pressure from the turbo supercharger increases, resulting in so-called turbo supercharging. When the supply state is reached, the control valve 22 in the high-load recirculation passage 21 opens, and the pressure at the suction port of the blower compressor 6 becomes lower than the exhaust gas pressure due to the suction action of the blower compressor. The exhaust gas in the exhaust passage 16 flows through the high-load recirculation passage 21 to the suction side of the blower compressor, where it is mixed equally with the intake air, and the exhaust gas is recirculated to the intake system. In this case, the pressure on the suction side of the blower compressor 6 decreases in inverse proportion to the amount of intake air, which increases in proportion to the engine load and rotation speed, while the exhaust gas pressure increases as the engine load and rotation speed increase. Exhaust in proportion to. As the amount of gas increases, it will increase in proportion to the amount of intake air, and the pressure difference between the two pressures will increase in proportion to the engine load and rotation speed, so the exhaust gas recirculated to the intake system will increase. The amount increases in proportion to the amount of intake air, that is, the load and rotation of the engine. In this way, the increase in the amount of recirculated exhaust gas in the high load/high rotation range of the engine can suppress the occurrence of knocking caused by the increase in the engine's maximum compression pressure due to turbocharging. Then, in a low load/low rotation range when the throttle valve 10 is throttled down, the rotation of the turbocharger 4 slows down as the amount of intake air decreases, and so-called turbocharging cannot be performed. In this state, the pressure on the downstream side of the throttle valve 10 becomes negative pressure, and the control valve 22 in the high load recirculation passage 21 closes and the control valve 19 in the low load recirculation passage 17 opens, while the throttle valve 10 Since the pressure at 18 points on the boat becomes negative pressure and becomes lower than the exhaust pressure in the exhaust passage 16, the exhaust gas in the exhaust passage 16 passes through the low-load recirculation passage 17 and returns to the intake air. It is returned to the system and mixed with the intake air to the engine.

In the idling state with the throttle valve 10 closed, the boat 18 is located upstream of the throttle valve 10, so the recirculation of exhaust gas to the intake side is stopped. When the throttle valve 10 is suddenly closed from the turbocharging state to rapidly decelerate, the pressure in the intake manifold 2 increases to the negative pressure side, and the control valve 19 in the low-load recirculation passage 17 opens, while the turbocharger The supercharging pressure rapidly increases due to the inertial rotation of the supercharger 4, and the supercharging air in the supercharging passage 11 flows backward through the low-load recirculation passage 17 and flows into the exhaust system.

This backflow of intake air into the exhaust system during sudden deceleration prevents a sudden increase in supercharging pressure in the same way as the blow-off valve 25, thereby avoiding a drop in turbocharger rotation, and preventing the engine from accelerating the next time. In addition to improving the follow-up performance of the turbo supercharger, incomplete combustion of the engine during sudden deceleration causes the mixer to be discharged unburned into the exhaust system, reducing afterburn and exhaust gas that occur in the exhaust system. Overheating of system parts can be prevented, and carbon and the like adhering to the inside of the reflux passage 17 can be blown away and cleaned by the backflow air. As described above, the present invention provides a high-load recirculation passage for high-load and high-speed rotations, and a low-load recirculation passage for low-load and low-speed rotations. This system recirculates exhaust gas to each boat located slightly upstream from the closed position of the throttle valve, and recirculates exhaust gas over the entire operating range of a turbocharged engine, making it possible to reliably reduce NOx. have an effect.

Moreover, the low-load recirculation passage connected to the port slightly upstream of the closed position of the throttle valve can reduce the rotational drop of the turbocharger that occurs during engine deceleration, thereby reducing the rotational drop during the next acceleration. In addition to improving followability,
It is possible to prevent afterburn and overheating of exhaust system parts that occur when the engine decelerates, and it also has the effect of cleaning the low-load recirculation passage, where carbon is likely to adhere, while the engine is decelerating.

[Brief explanation of the drawing]

The drawings illustrate embodiments of the invention. DESCRIPTION OF SYMBOLS 1... Engine, 4... Turbo supercharger, 5... Exhaust valve, - pin, 6... Blower compressor, 10... Throttle valve, 11... Supercharging passage, 16... ...Exhaust passage, 17,21...Exhaust gas recirculation passage, 18...Boat, 19,22...Control valve.

Claims (1)

[Claims] 1. In an exhaust gas recirculation device having two recirculation passages for recirculating part of the exhaust gas to the intake system in an engine equipped with an exhaust gas turbocharger, one of the recirculation passages for high load is connected to the exhaust gas. An exhaust turbo characterized in that a part of a blower compressor of a gas turbo supercharger where the pressure is low is connected to a port provided at a part slightly upstream of a closed position of a throttle valve, and the other low-load recirculation passage is connected to a port provided at a part slightly upstream of a closed position of a throttle valve. Exhaust gas recirculation device for supercharged engines.