JPH0688552A - Exhaust gas reflux system of internal combustion engine - Google Patents

Abstract

(57) [Summary] [Purpose] To recirculate exhaust gas to an internal combustion engine according to load fluctuations. [Structure] An engine 4 is equipped with a supercharger 1 including a turbine 2 and a compressor 3. A bypass line 8 is provided between the exhaust gas line 5 and the air supply line 6. The blower 12 is installed in the bypass line 8. An air extraction line 9 having a control valve 13 is connected to the air supply line 6. An auxiliary turbine 11 that drives the blower 12 is installed in the air extraction line 9. The blower 12 is driven to raise the pressure of the exhaust gas to recirculate it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation system for an internal combustion engine equipped with a supercharger.

[0002]

2. Description of the Related Art As an internal combustion engine equipped with a supercharger (turbocharger), particularly a diesel engine, as shown in FIG. 2 and a compressor 3 connected to the turbine 2 via a turbine shaft and configured to rotate a fan via the turbine shaft by the rotation of the turbine impeller to compress and discharge intake air. The turbocharger 1 is connected to the engine 4 via the exhaust gas line 5 and the intake line 6, and the compressed air from the compressor 3 is connected to the engine 4 via the air supply line 6.
In addition, the exhaust gas from the engine 4 is sent to the turbine 2 via the exhaust gas line, and the turbine 3 is driven by the exhaust gas to operate the compressor 3 to increase the boost pressure to the engine 4. There is something that was made to occur. 7 indicates an intercooler.

In the engine 4 equipped with the above supercharger 1,
Although measures for reducing NOx in exhaust gas are an important issue, until now, if a part of exhaust gas emitted from the turbine 2 of the supercharger 1 and released to the atmosphere is recirculated to the engine 4, NOx in the exhaust gas is reduced. It is known to be effective for reduction.

[0004]

However, the turbine 2
The exhaust gas discharged from the engine is of low pressure, and the load of the engine 4 as an internal combustion engine varies depending on the operating condition. Therefore, the exhaust gas of low pressure is recirculated according to the load variation. Although it is desirable, such an exhaust gas recirculation system has not been established in the past.

Therefore, the present invention makes it possible to easily recirculate low-pressure exhaust gas to the internal combustion engine and to adjust the recirculation amount of exhaust gas in accordance with load fluctuations, thereby reducing NOx. It is intended to provide an exhaust gas recirculation device for an internal combustion engine that is configured as described above.

[0006]

In order to solve the above problems, the present invention provides the above exhaust gas in an internal combustion engine to which a supercharger including a turbine and a compressor is connected via an exhaust gas line and an air supply line. A bypass line for recirculating a part of the exhaust gas is connected between the gas line and the compressor downstream position of the air supply line, and one of the compressed air is provided at a position upstream of the bypass line connection portion of the air supply line. And an auxiliary turbine driven by the air taken out in the air extraction line, and a blower driven by the auxiliary turbine is installed in the bypass line. To do.

Further, it is preferable that a control valve is provided on the downstream side of the air extraction line or the air extraction line connection portion of the air supply line.

[0008]

[Function] When the blower is driven by driving the auxiliary turbine by the air taken out from the air supply line to the air extraction line, the exhaust gas introduced from the exhaust gas line to the bypass line is supplied while being pressurized. It is admitted into the internal combustion engine via the air line. At this time, since the drive of the auxiliary turbine and the blower can be controlled by operating the control valve, the exhaust gas can be recirculated according to the load fluctuation of the internal combustion engine.

Further, by providing a control valve on the downstream side of the air extraction line or the air extraction line connecting portion of the air supply line, the operation according to the load of the internal combustion engine can be performed by operating the control valve.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, in which a supercharger 1 comprising a turbine 2 and a compressor 3 is connected to an engine 4 as an internal combustion engine via an exhaust gas line 5 and an air supply line 6. In the connected configuration, a part of the exhaust gas in the exhaust gas line 5 is provided between the downstream position of the turbine 2 in the exhaust gas line 5 and the downstream position of the intercooler 7 in the air supply line 6. A bypass line 8 for introducing and recirculating air into the air supply line 6 is provided, and a part of the compressed air in the air supply line 6 is taken out from the upstream position of the intercooler 7 to the air supply line 6. 7 is provided with an air extraction line 9 for returning to the downstream position, and the compressed air introduced into the air extraction line 9 is driven in the middle of the air extraction line 9. A turbine 11 is installed, and a blower 12 that is driven by the auxiliary turbine 11 is installed in the middle of the bypass line 8, and a booster (booster turbo) 10 is configured by the auxiliary turbine 11 and the blower 12. Then, the pressure of the exhaust gas in the bypass line 8 is increased by driving the pressure increasing device 10 and then introduced into the air supply line 6. Further, a regulating valve 13 for regulating the flow rate and pressure of the compressed air is attached at a position upstream of the auxiliary turbine 11 in the take-out line 9, and the drive of the booster 10 is controlled by operating the regulating valve 13. Thus, the exhaust gas can be recirculated according to the load change of the engine 4. 1
Reference numerals 4 and 15 denote check valves provided at the downstream ends of the bypass line 8 and the take-out line 9, respectively.

When the engine 4 is operated, the exhaust gas from the engine 4 drives the turbine 2 of the supercharger 1 to drive the compressor 3 to generate supercharging pressure to the engine 4. At this time, a part of the exhaust gas emitted from the turbine 2 is returned to the engine 4 through the bypass line 8 to reduce the NOx of the exhaust gas. That is, since the bypass line 8 is provided between the exhaust gas line 5 at a position downstream of the turbine 2 and the air supply line 6 at a position downstream of the compressor 3, low-pressure exhaust gas after passing through the turbine 2 is exhausted. A part of the gas is about to be introduced into the air supply line 6 through the bypass line 8, but the pressure on the air supply line 6 side is large, and therefore it cannot be recirculated as it is. In this case, in the present invention, a part of the compressed air in the air supply line 6 is taken out from the air take-out line 9 connected to a position downstream of the compressor 3 in the air supply line 6 and returned to the downstream of the intercooler 7. However, since there is a pressure drop in the intercooler 7, the auxiliary turbine 11 is driven, and the auxiliary turbine 11 uses the blower 12 in the bypass line 8.
Together with the booster 10, the auxiliary turbine 11
Since the blower 12 is driven by driving
The exhaust gas in the bypass line 8 is pressurized and guided to the air supply line 6, and is easily returned to the engine 4. In this way, the exhaust gas introduced into the bypass line 8 is pressurized by the blower 12 and is supplied to the air supply line 6
Further, since the check valve 14 is provided at the downstream side of the blower 12 in the bypass line 8, the supply air can be stably recirculated without worrying that the supply air will be returned to the bypass line 8. it can.

In the above, when the engine 4 causes a load fluctuation, the control valve 13 provided in the air extraction line 9 is operated to adjust the flow rate of the compressed air introduced into the auxiliary turbine 11 and the like. As a result, the drive of the booster 10 is controlled, so that the exhaust gas can be recirculated to the engine 4 in accordance with the load fluctuation of the engine 4, and low NOx can be obtained.
Can be realized.

In the above embodiment, the bypass line 8
And the downstream end of the air extraction line 9 are respectively connected to the air supply line 6
Although the case where the downstream side of the intercooler 7 is connected is shown, the downstream end of the air extraction line 9 may be opened to the atmosphere, or the pressure difference between the inlet and the outlet of the intercooler 7 may be controlled. May be controlled, a flow rate control valve 13 may be provided downstream of the air extraction line connection portion of the air supply line 6, and the upstream end of the bypass line 8 may be a turbine of the exhaust gas line 5. Needless to say, it may be connected to a position upstream of 2, and various changes may be made without departing from the scope of the present invention.

[0015]

As described above, according to the exhaust gas recirculation system for an internal combustion engine of the present invention, the exhaust gas recirculation system for an internal combustion engine equipped with a supercharger including a turbine and a compressor is more effective than the compressor for the exhaust gas line and the air supply line. Also connect a bypass line with a blower in the middle between the downstream position,
And since the air extraction line provided with the auxiliary turbine for driving the blower is taken out from the air supply line, a part of low-pressure exhaust gas can be recirculated to the high-pressure side internal combustion engine inlet side, and A control valve is provided downstream of the air extraction line or the air extraction line connection part of the air supply line, and by operating the control valve, exhaust gas can be introduced into the internal combustion engine according to the load of the internal combustion engine. As a result, it has an excellent effect that it can contribute to the reduction of NOx in the exhaust gas.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of an exhaust gas recirculation device for an internal combustion engine of the present invention.

FIG. 2 is a schematic diagram showing an example of an internal combustion engine equipped with a supercharger.

[Explanation of symbols]

 1 Supercharger 2 Turbine 3 Compressor 4 Engine (internal combustion engine) 5 Exhaust gas line 6 Air supply line 8 Bypass line 9 Air extraction line 11 Auxiliary turbine 12 Blower 13 Control valve

Claims (3)

[Claims] 1. An exhaust gas is provided between an exhaust gas line and a compressor downstream position of the air supply line in an internal combustion engine to which a supercharger composed of a turbine and a compressor is connected via an exhaust gas line and an air supply line. A bypass line for recirculating a part of the gas is connected, and an air take-out line for taking out a part of the compressed air is connected to a position upstream of the bypass line connecting portion of the air supply line, and the air take-out is performed. An exhaust gas recirculation system for an internal combustion engine, comprising: an auxiliary turbine driven by air taken out through a line; and a blower driven by the auxiliary turbine installed in the bypass line. 2. The exhaust gas recirculation system for an internal combustion engine according to claim 1, wherein a control valve is provided in the air extraction line. 3. The exhaust gas recirculation system for an internal combustion engine according to claim 1, further comprising a control valve provided downstream of an air extraction line connection portion of the air supply line.