JP2005147030A - Exhaust gas reflux device for engine with supercharger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas reflux device for an engine with a supercharger capable of performing EGR sufficiently and enlarging an operation region for performing EGR even when there is the operation region in which intake pressure becomes higher than exhaust pressure such as, in particular, a low speed high load region in the supercharging engine. <P>SOLUTION: In this exhaust gas reflux device for the engine with the supercharger provided with an EGR passage 7 for leading a part of exhaust gas into an intake passage 6 as EGR gas from an exhaust passage 3 and the supercharger 4 for supercharging intake air, an EGR booster 8 for feeding EGR gas into the intake passage under pressure by utilizing intake pressure is provided in the EGR passage, and the intake passage is divided into a first passage 6a provided with a turbine of the EGR booster and a second passage 6b provided with a variable throttle valve 19 for controlling flow rate of high pressure intake air led into the turbine on the downstream side of the supercharger. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

    The present invention relates to an exhaust gas recirculation device for a supercharged engine.

  In an engine provided with a supercharger, there is an operation region (particularly, a low speed and high load region) in which the supply air pressure becomes higher than the exhaust pressure, and therefore EGR cannot be performed sufficiently. There is also a pulse EGR type that performs EGR using intake and exhaust pressure pulsation, but the effect is small when the intake pulsation is small. On the other hand, some use inertia (resonance) supercharging to increase intake pulsation, but the intake system becomes bulky. Further, in the internal EGR system, the temperature of the EGR gas is high, so that the NOx reduction effect cannot be obtained sufficiently.

  As an exhaust gas recirculation device of the prior art, for example, there is one disclosed in Patent Document 1. As shown in FIG. 4, this exhaust gas recirculation apparatus exhausts an engine 51, an intake passage 56 that guides intake air to the engine 51, an exhaust passage 53 that guides exhaust gas from the engine 51, and a part of exhaust gas as EGR gas. An EGR passage 57 that leads from the passage 53 to the intake passage 56 and a supercharger 54 that supercharges intake air are provided.

  The EGR passage 57 is provided with an exhaust recirculation air supply device 59 that sucks EGR gas from the exhaust passage 53 downstream of the muffler 58 and pressure-feeds it to the intake passage 56 via the exhaust recirculation valve 52. The exhaust gas recirculation gas supply device 59 is driven by the exhaust pressure of the exhaust gas flowing through the exhaust passage 53.

By adopting such a configuration, EGR is going to be performed without hindrance.
Japanese Patent Application Laid-Open No. 07-91325

  In the exhaust gas recirculation device using such an exhaust gas recirculation device, since the EGR gas is sucked from the most downstream side of the exhaust passage, the EGR pressure is sufficient with respect to the supply air pressure even if the exhaust gas recirculation gas supply device increases the pressure. It is not high, and sufficient EGR cannot be performed particularly in a high supercharged engine.

  An object of the present invention is to provide an exhaust gas recirculation device for an engine with a supercharger that solves the above-described problems and can sufficiently perform EGR in a high supercharged engine.

  In order to achieve the above object, a first aspect of the present invention is a supercharger comprising: an EGR passage that leads a part of exhaust gas from the exhaust passage to the intake passage as EGR gas; and a supercharger that supercharges intake air. In the exhaust gas recirculation apparatus for an engine with an engine, an EGR booster that pumps EGR gas into the intake passage using intake pressure is provided in the EGR passage, and the intake passage is connected to the EGR booster downstream of the supercharger. The first passage is provided with a turbine, and the second passage is provided with a variable throttle valve for controlling the flow rate of high-pressure intake air that is led to the turbine.

  According to a second aspect, in the first aspect, a control means is provided for opening the variable throttle valve when increasing the EGR rate, and throttleting the variable throttle valve when decreasing the EGR rate.

  According to a third aspect, in the first aspect, a venturi that draws EGR gas is provided in the intake passage, and the EGR passage communicates with the venturi.

  In a fourth aspect based on the first aspect, an EGR cooler that cools EGR gas is provided in the EGR passage.

  In a fifth aspect based on the first aspect, an intake air cooler for cooling intake air is provided in the intake passage.

According to a sixth invention, in the first invention, instead of the variable throttle valve, the EGR booster is configured to change the angle by rotating the nozzle blade, and by controlling the angle of the nozzle blade. The flow rate of high-pressure intake air that is led to the turbine is controlled.
The EGR booster is configured to rotate the nozzle blade to change its angle, and controls the supercharging pressure of the EGR booster by controlling the angle of the nozzle blade.

  According to a seventh invention, in the first invention, the supercharger is divided into two stages to supercharge intake air, and an intercooler is provided in the supercharged air.

  According to a first aspect of the present invention, in an exhaust gas recirculation device for a supercharged engine, comprising: an EGR passage that guides a part of exhaust gas from the exhaust passage to the intake passage as EGR gas; and a supercharger that supercharges intake air. The EGR passage is provided with an EGR booster that pumps EGR gas into the intake passage using intake pressure, and the intake passage is provided downstream of the supercharger with the turbine of the EGR booster interposed therebetween. By dividing the passage into one passage and a second passage having a variable throttle valve for controlling the flow rate of high-pressure intake air leading to the turbine, the supply air pressure can be increased particularly in a low-speed high-load region in a high-supercharged engine. Even when there is an operation region in which the exhaust pressure is higher than that, sufficient EGR can be performed, and the operation region in which EGR can be performed can be expanded.

  According to a second aspect of the present invention, in the first aspect of the present invention, by providing a control means for opening the variable throttle valve when increasing the EGR rate and opening the variable throttle valve when decreasing the EGR rate, supercharging of the EGR booster is provided. The pressure can be controlled, and the EGR rate can be easily controlled.

  According to the third invention, a venturi for drawing EGR gas is provided in the intake passage, and the EGR passage communicated with the venturi allows the EGR gas pumped from the EGR booster to be drawn into the flow of intake air. EGR can be performed using both the EGR booster's pumping force and the venturi's suction force, and the operating range where the supply pressure is higher than the exhaust pressure, especially in the low-speed, high-load region, in high-supercharged engines Even if there is, sufficient EGR can be performed, and the operation range in which EGR can be performed can be expanded.

  According to the fourth invention, the EGR gas can be cooled by providing an EGR cooler for cooling the EGR gas in the EGR passage.

  According to the fifth invention, the intake air can be cooled by providing the intake air cooler for cooling the intake air in the intake passage.

  According to a sixth invention, in the first invention, instead of the variable throttle valve, the EGR booster is configured to change the angle by rotating the nozzle blade, and to control the angle of the nozzle blade. Thus, by controlling the flow rate of the high-pressure intake air led to the turbine, the supercharging pressure of the EGR booster can be controlled and the EGR rate can be controlled.

  According to a seventh invention, in the first invention, the supercharger is divided into two stages, a low pressure stage and a high pressure stage, to supercharge the supply air, and the supercharging of the low pressure stage and the high pressure stage is configured. By providing an intercooler between the machines, the supercharging amount of the supercharger can be increased.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows a first embodiment of the exhaust gas recirculation apparatus of the present invention.

  The engine 1 is a six-cylinder engine having six cylinders, and includes an intake passage 6 that guides intake air to each cylinder and an exhaust passage 3 that guides exhaust gas from each cylinder.

  The exhaust passage 3 and the intake passage 6 are respectively provided with a turbine 40 and a compressor 41 of the supercharger 4 so as to supercharge intake air using the energy of the exhaust gas.

  The exhaust passage 3 is provided with a muffler 22 that silences the exhaust sound.

  The intake passage 6 and the exhaust passage 3 are communicated by an EGR passage 7, and a part of the exhaust gas is recirculated from the exhaust passage 3 to the intake passage 6 as EGR gas.

  The intake passage 6 is provided with a venturi 9 that speeds up the intake air flow by narrowing the intake passage 6. An EGR passage 7 is communicated with the venturi 9 preferably at its narrowest portion, and EGR gas is drawn into the intake air flow by the ejector effect.

  The EGR passage 7 is provided with an EGR booster 8 that increases the pressure of EGR gas. The EGR booster 8 includes a turbine 8a and a compressor 8b. The turbine 8 a is disposed between the supercharger 4 and the venturi 9 in the intake passage 6, and rotates using high-pressure air pressurized by the supercharger 4. The compressor 8b is driven by using the rotational force of the turbine 8a, and pumps EGR gas to the venturi 9. Since the EGR booster 8 is driven by high-pressure air from the supercharger 4, no external power source such as an electric motor or a hydraulic motor is required.

  An EGR cooler 11 that lowers the temperature of the EGR gas is provided downstream of the EGR booster 8 in the EGR passage 7. The EGR cooler 11 recirculates more EGR gas by lowering the temperature of the EGR gas and increasing the density of the EGR gas.

  The intake passage 6 is divided downstream of the supercharger 4 into a first passage 6a and a second passage 6b.

  A turbine 8a of an EGR booster 8 is interposed in the first passage 6a, and high-pressure intake air flowing through the first passage rotates the turbine 8a.

  The second passage 6b is provided with a variable throttle valve 19 that controls the flow rate of the high-pressure air flowing through the first passage 6a. The variable throttle valve 19 is configured to change the opening degree by rotating the valve body by an actuator. The controller 20, which is a control means, controls the flow rate of the intake air flowing through the second passage 6b by controlling the opening of the variable throttle valve 19 to throttle or open the second passage 6b. Thereby, the supercharging pressure of the EGR booster 8 can be controlled, and the EGR rate can be controlled.

  An intake air cooler 60 is provided in the intake passage 6 downstream of the turbine 8 a of the EGR booster 8. As a result, the intake air temperature, which has been lowered by the expansion by the turbine 8a of the EGR booster 8, can be further cooled.

  Here, the effect of this embodiment is demonstrated.

  The EGR gas guided to the EGR passage 7 is pumped to the venturi 9 by the EGR booster 8, and the EGR gas pumped by the venturi 9 is drawn into the intake air flow by the ejector effect. Thereby, EGR can be performed using both the pumping force of the EGR booster 8 and the suction force of the venturi 9. Therefore, in the high supercharged engine 1, even when there is an operation region where the supply air pressure is higher than the exhaust pressure, particularly in a low speed and high load region, sufficient EGR can be performed and the operation region where EGR can be performed is expanded. can do.

  The high-pressure intake air that is guided to the turbine 8a in the first passage 6a is increased or decreased by the opening degree of the variable throttle valve 19 interposed in the second passage 6b. For example, when the variable throttle valve 19 is throttled, the intake flow rate flowing to the turbine 8a increases, and the EGR amount by the compressor 8b increases. On the contrary, when the variable throttle valve 19 is opened, the intake flow rate flowing to the turbine 8a is reduced, and the EGR amount by the compressor 8b is reduced. Therefore, the EGR rate can be controlled by controlling the supercharging pressure of the EGR booster 8 by controlling the opening of the variable throttle valve 19.

  FIG. 2 shows a second embodiment of the exhaust gas recirculation device of the present invention.

  The same components as those in the first embodiment are denoted by the same reference numerals.

  In this embodiment, the turbine 8a of the EGR booster 8 is composed of a nozzle blade and a turbine blade, and the angle is changed by rotating the nozzle blade by an actuator. The controller 20 which is a control means controls the load of the variable nozzle turbine 8 a by controlling the angle of the nozzle blades, and controls the supercharging pressure of the EGR booster 8.

  Therefore, in the second embodiment, there is no need to provide the variable throttle valve 19 provided in the first embodiment. Further, it is not necessary to divide the intake passage 6 into the first passage 6a and the second passage 6b. Other configurations are the same as those of the first embodiment.

  FIG. 2 shows a third embodiment of the exhaust gas recirculation apparatus of the present invention.

  The same components as those in the first embodiment are denoted by the same reference numerals.

  In this embodiment, the supercharger 4 is composed of a two-stage turbocharger 4 that supercharges intake air in two stages.

  In the first stage of the two-stage turbocharger 4, a first turbine 40 a is provided in the exhaust passage 3, and the first turbine 40 a rotates using the exhaust pressure in the exhaust passage 3. A first compressor 41a is provided in the intake passage 6, and the first compressor 41a is driven by the first turbine 40a to supercharge intake air.

  In the second stage of the two-stage turbocharger 4, a second turbine 40 b is provided in the exhaust passage 3, and the second turbine 40 b rotates using the exhaust pressure in the exhaust passage 3. A second compressor 41b is provided in the intake passage 6, and the second compressor 41b is driven by the second turbine 40b to further supercharge the intake air supercharged by the first compressor 41a.

  The second turbine 40b is provided with a bypass passage 45 in which an adjustment valve 43 is interposed, and the flow rate of exhaust gas led to the second turbine 40b is adjusted by adjusting the opening degree of the adjustment valve 43. The second compressor 41b is provided with a bypass passage 46 in which an adjustment valve 44 is interposed, and the flow rate of exhaust gas led to the second compressor 41b is adjusted by adjusting the opening degree of the adjustment valve 44.

  Between the first and second compressors 41 a and 41 b on the intake passage 6, an intercooler 42 for cooling the intake air that has been supercharged by the first compressor 41 a and has reached a high temperature is provided.

  Other configurations are the same as those of the first embodiment.

  By using the supercharger 4 as the two-stage turbocharger 4, it is possible to increase the supercharging pressure of the intake air. Even if the boost pressure of intake air is increased, sufficient EGR can be performed.

  Although the present invention has been described in certain terms with regard to structural and methodological features, the means disclosed herein include preferred forms of practicing the invention, and the invention is illustrated and described. It should be understood that the invention is not limited to specific features. Accordingly, the present invention includes any forms or modifications within the scope of the claims as appropriately interpreted in accordance with the principle of equality.

  The present invention can be applied to an exhaust gas recirculation device for a supercharged engine.

It is a block diagram which shows the exhaust gas recirculation apparatus of 1st Embodiment. It is a block diagram which shows the exhaust gas recirculation apparatus of 2nd Embodiment. It is a block diagram which shows the exhaust gas recirculation apparatus of 3rd Embodiment. It is a block diagram which shows the exhaust-gas recirculation apparatus of a prior art.

Explanation of symbols

1 Engine 3 Exhaust Passage 4 Supercharger 6 Intake Passage 6a First Passage 6b Second Passage 7 EGR Passage 8 EGR Booster 9 Venturi 11 EGR Cooler 19 Variable Throttle Valve 20 Controller 22 Muffler

Claims (7)

In an exhaust gas recirculation device for a supercharged engine comprising: an EGR passage for leading a part of exhaust gas from the exhaust passage to the intake passage as EGR gas; and a supercharger for supercharging intake air.
The EGR passage is provided with an EGR booster that pumps EGR gas into the intake passage using intake pressure,
On the downstream side of the supercharger, the intake passage is provided with a first passage through which the turbine of the EGR booster is interposed, and a second passage through which a variable throttle valve for controlling the flow rate of high-pressure intake air leading to the turbine is provided. Divided into,
An exhaust gas recirculation device for an engine with a supercharger.   2. The exhaust gas recirculation device for a supercharged engine according to claim 1, further comprising a control means for restricting the variable throttle valve when increasing an EGR rate and opening the variable throttle valve when decreasing an EGR rate. .   The exhaust gas recirculation device for a supercharged engine according to claim 1, wherein a venturi for drawing EGR gas is provided in the intake passage, and the EGR passage is communicated with the venturi.   The exhaust gas recirculation apparatus for an engine with a supercharger according to claim 1, wherein an EGR cooler for cooling EGR gas is provided in the EGR passage.   The exhaust gas recirculation apparatus for a supercharged engine according to claim 1, wherein an intake air cooler for cooling intake air is provided in the intake passage.   Instead of the variable throttle valve, the EGR booster is configured to change the angle by rotating the nozzle blade, and the flow rate of the high-pressure intake air led to the turbine is controlled by controlling the angle of the nozzle blade. The exhaust gas recirculation device for a supercharged engine according to claim 1.   The supercharger is divided into two stages, a low pressure stage and a high pressure stage, so as to supercharge the supply air, and an intercooler is provided between the low pressure stage and the high pressure stage supercharger. The exhaust gas recirculation device for a supercharged engine according to claim 1.

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