JP2012136957A - Internal combustion engine and egr method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine capable of preventing the corrosion and stain of an intercooler due to EGR gas, and suppressing the discharge of white smoke in exhaust gas at the cold start of the internal combustion engine, and an EGR method and control method therefor.SOLUTION: An internal combustion engine 1, 1A is provided with a compressor 3a of a discharge turbo supercharger 13, an intercooler 14 and externally driven supercharger 15 in order from the upstream side in a suction passage 11 of the internal combustion engine 1, 1A, with a turbine 13b of the discharge turbo supercharger 13 in a discharge passage 12, and with a bypass passage 16 having a flow rate adjustment valve 16a for bypassing the externally driven supercharger 15, wherein EGR gas Ge which is a part of exhaust gas G is supplied to the upstream side of the externally driven supercharger 15 from the upstream side of the turbine 13b.

Description

  The present invention relates to an internal combustion engine including an externally driven supercharger and an exhaust turbocharger, and to an EGR method thereof. More specifically, the internal combustion engine can prevent corrosion and fouling of an intercooler due to EGR gas. The present invention relates to an internal combustion engine capable of preventing white smoke from being discharged into exhaust gas during a cold start, and an EGR method thereof.

  In internal combustion engines such as diesel engines, high supercharging and high EGR using supercharging technology are effective and important for reducing fuel consumption and improving exhaust gas. Various supercharging technologies such as an exhaust turbocharger have been developed.

  However, when using an exhaust turbo-type supercharger, it is difficult to eliminate the turbocharge delay called turbo lag, and there is a limit to improving torque response in transient operating conditions such as sudden acceleration of an internal combustion engine and measures against exhaust gas. There is. Due to the delay in supercharging, the amount of air necessary for combustion in the cylinder is insufficient and black smoke is generated, or the introduction of EGR gas becomes difficult in order to secure the minimum amount of air necessary for combustion. In some cases, NOx is generated instantaneously.

  In order to improve the supercharging delay in this transient operation condition, an externally driven supercharger that does not use an exhaust turbine and is driven by a mechanical type or an electric type is employed. Examples of the externally driven supercharger include a positive displacement type and a centrifugal type supercharger.

  Many externally driven superchargers have excellent transient supercharging characteristics due to their characteristics. However, since the operation can easily make the intake pressure higher than the exhaust pressure, the prior art as shown in FIG. In the high pressure (HI-EGR) type EGR gas introduction method that introduces EGR gas to the downstream side of the externally driven supercharger 15, the EGR gas cannot be taken into the intake side. In order to solve this, a low pressure (LP-EGR) type EGR gas introduction method for introducing EGR gas upstream of the externally driven supercharger 15 as shown in FIG. 8 is employed.

  In this low pressure type EGR gas introduction method, EGR gas, which is part of exhaust gas, flows into an intercooler (intake intermediate cooler). In this intercooler, the gas (intake air or intake air and EGR gas) passing using the traveling wind is cooled and the temperature thereof is greatly reduced, so that water condenses inside the intercooler. Therefore, when the EGR gas flows into the intercooler, the components in the EGR gas react with the condensed water in the interior to generate an acidic substance, and the intercooler is corroded, or the solid substance in the EGR gas ( Soot) accumulates inside the intercooler and causes clogging.

  As a countermeasure against the accumulation of carbon particles in the intercooler, a filter for capturing carbon particles is provided in a passage bypassing the mechanical supercharger (for example, refer to Patent Document 1), or as a countermeasure against condensation of moisture in the EGR gas. The intake passage in the range from the EGR passage connecting portion on the upstream side of the mechanical supercharger to the mechanical supercharger is inclined or curved so that the height becomes lower toward the downstream side, and the mechanical supercharger is at the lowest portion Arrangement is made such that the inner bottom wall of the casing of the main body is positioned (see, for example, Patent Document 2). However, it is very difficult to avoid corrosion in the intercooler unless the components in the exhaust gas are changed or removed.

  In addition, when a high pressure ratio operation, that is, a high supercharging operation is performed with a mechanical supercharger alone, the required driving force required during the high supercharging operation becomes very large, which greatly affects fuel consumption. And it is not a good idea because high pressure ratio operation is difficult due to structural problems. In response to this, it has been proposed to combine a mechanical supercharger and an exhaust turbocharger in a diesel engine that requires high supercharging operation (see, for example, Patent Document 3).

  Moreover, there are the following problems at the time of cold start. Immediately after this cold start, the temperature of the exhaust system is lowered, so that there is a lot of exhaust gas cooling loss, and the amount of heat supplied to the turbine is reduced accordingly, and the exhaust temperature is lowered. Further, since the temperature of the lubricating oil is also lowered, the viscosity of the lubricating oil is increased, and the operation efficiency and the operation amount are greatly reduced due to the increase of friction in the supercharger. As a result, the supercharging pressure and the transient response obtained by the supercharger are significantly reduced. Further, at the time of cold start, exhaust gas countermeasures due to an increase in EGR gas cannot be taken sufficiently, and the exhaust gas characteristics are significantly deteriorated.

  For exhaust gas countermeasures and warm-up acceleration countermeasures during cold start, measures are taken to reduce heat capacity by reducing the thickness of exhaust system parts and heat insulation measures by using a double exhaust pipe. Has been. However, it is difficult to fundamentally solve these cold start problems by measures such as reducing the heat capacity of the exhaust system and keeping warm.

Japanese Patent Application Laid-Open No. 07-332166 Japanese Patent Laid-Open No. 08-177646 JP 07-91265 A

  The present invention has been made in view of the above situation, and an object of the present invention is to provide an internal combustion engine including an externally driven supercharger and an exhaust turbocharger, and an EGR method using an intercooler using EGR gas. It is an object of the present invention to provide an internal combustion engine and an EGR method thereof that can prevent corrosion and fouling of the engine and prevent white smoke from being discharged into the exhaust gas when the internal combustion engine is cold started.

  In order to achieve the above object, an internal combustion engine of the present invention comprises, in an intake passage of an internal combustion engine, a compressor, an intercooler, and an externally driven supercharger in order from the upstream side, and an exhaust passage. And an exhaust passage on the upstream side of the turbine in the internal combustion engine having a bypass passage that has a flow rate adjusting valve and bypasses the externally driven supercharger. An intake passage is connected downstream of the intercooler and upstream of the externally driven supercharger.

  In addition, this externally driven supercharger refers to a supercharger that obtains a driving force from other power without obtaining a rotational driving force from the energy of exhaust gas, like an exhaust turbo-type supercharger, As this externally driven supercharger, there are a mechanical supercharger driven by the output of the internal combustion engine, an electric supercharger driven by electric power generated by the output of the internal combustion engine, etc. Each has a capacity type and a centrifugal type.

  According to this configuration, since EGR gas does not pass through the intercooler (intake intercooler), it is possible to prevent corrosion and fouling such as generation of condensed water and accumulation of solid substances in the intercooler due to EGR gas.

  In addition, an externally driven supercharger can be arranged in the immediate vicinity of the internal combustion engine body to reduce the length of the intake system piping from the externally driven supercharger to the internal combustion engine body. Since the heat capacity can be reduced, warm-up is promoted, and as a result, the cold operation time of the internal combustion engine is shortened, so that the amount of white smoke discharged into the exhaust gas during cold start can be reduced. .

  Further, in the internal combustion engine, when the exhaust turbo supercharger control device has a warm-up index temperature indicating a warm-up state of the internal combustion engine equal to or lower than a predetermined determination temperature, the exhaust turbo supercharger When it is configured to increase the amount of exhaust gas that bypasses the turbine and perform control to reduce the operation of the exhaust turbocharger, the amount of supercharging operation by the externally driven supercharger is increased, The temperature of the gas sucked into the cylinder can be increased, and warm-up can be further promoted. Moreover, since the exhaust energy recovery amount in this turbine can be reduced by reducing the operation of the exhaust turbocharger, the turbine outlet temperature can be raised, and as a result, connected to the downstream The warm-up of the catalyst system can be promoted at the same time.

  The warm-up indicator temperature includes the temperature of the engine cooling water, the exhaust gas temperature, the catalyst temperature of the exhaust gas treatment device provided in the exhaust passage, and the amount of exhaust gas that bypasses the turbine of the exhaust turbocharger. As a method of increasing the exhaust gas pressure, an opening degree of a VGT (variable capacity turbo) turbine blade (opening area), an opening degree of a wastegate valve, or an opening of an exhaust bypass valve corresponding to these is used. There is a way to increase the degree.

  In the above internal combustion engine, a second intercooler is provided on the downstream side of the externally driven supercharger, and a second bypass passage having a bypass valve and bypassing the second intercooler is provided. Provide and configure. This second intercooler has a smaller capacity than an intercooler arranged on the upstream side of the externally driven supercharger, and an air-cooled intake air cooling device capable of minimizing the piping system and the volume of the cooler, or A water-cooled intake air cooling device such as an existing EGR cooler that does not need to take measures against EGR gas contamination is preferable.

  And the EGR method of the internal combustion engine of the present invention for achieving the above-described object is a compressor, an intercooler, and an externally driven supercharger of an exhaust turbocharger in order from the upstream side to the intake passage of the internal combustion engine. In the EGR method for an internal combustion engine, the exhaust gas turbocharger turbine is provided in an exhaust passage, and a bypass passage that has a flow rate adjusting valve and bypasses the externally driven supercharger is provided. Is supplied from the upstream side of the turbine to the upstream side of the externally driven supercharger.

  According to this method, since the EGR gas does not pass through the intercooler, it is possible to prevent corrosion and fouling such as generation of condensed water and accumulation of solid substances in the intercooler due to the EGR gas.

  According to the internal combustion engine and the EGR method thereof according to the present invention, the effects of preventing corrosion and fouling in the intercooler, and suppressing the generation of white smoke by promoting warm-up by an external supercharger at the time of cold start of the internal combustion engine. Can play.

  That is, since the EGR gas does not pass through the intercooler, it is possible to avoid corrosion and fouling of the intercooler due to components in the EGR gas. Therefore, countermeasures against contamination by EGR gas need only be implemented for the externally driven supercharger. Therefore, it is possible to achieve both the EGR introduction countermeasure and the EGR contamination countermeasure in the external drive supercharger, and the cost can be greatly reduced.

  In addition, an externally driven supercharger can be arranged in the immediate vicinity of the internal combustion engine body to reduce the length of the intake system piping from the externally driven supercharger to the internal combustion engine body. Since the heat capacity can be reduced, warm-up is promoted, and as a result, the cold operation time of the internal combustion engine is shortened, so that the amount of white smoke discharged into the exhaust gas during cold start can be reduced. .

It is a figure showing composition of an internal-combustion engine of a 1st embodiment concerning the present invention. It is a figure which shows the structure of the internal combustion engine of 2nd Embodiment which concerns on this invention. It is a figure which shows the improvement simulation result of a transient supercharging characteristic. It is a figure which shows the evaluation value of the temperature rising effect with respect to intake temperature. It is a figure which shows the evaluation value of the temperature rising effect with respect to compression end temperature. It is a figure which shows the evaluation value of the temperature rising effect with respect to exhaust temperature. It is a figure which shows the EGR gas introduction method of the high pressure system of the internal combustion engine provided with the mechanical supercharger in a prior art. It is a figure which shows the EGR gas introduction method of the low pressure system of the internal combustion engine provided with the mechanical supercharger in a prior art.

  Hereinafter, an internal combustion engine according to an embodiment of the present invention and an EGR method thereof will be described with reference to the drawings.

  As shown in FIG. 1, an internal combustion engine (hereinafter referred to as an engine) 1 according to a first embodiment of the present invention exhausts exhaust air in order from an upstream side into an intake passage 11 connected to an intake manifold 10a of an engine body 10. The turbocharger 13 includes a compressor 13a, an intercooler (intake intermediate cooler) 14, an externally driven supercharger 15, and an exhaust turbocharger in an exhaust passage 12 connected to an exhaust manifold 10b. 13 turbines 13b are provided.

  Further, a bypass passage 16 that bypasses the externally driven supercharger 15 is provided, and a flow rate adjustment valve 16 a is arranged in the bypass passage 16 so that the flow rate of the intake air A that passes through the bypass passage 16 can be adjusted. Further, the EGR passage 17 is provided by connecting the exhaust passage 12 upstream of the turbine 13b and the intake passage 11 downstream of the intercooler 14 and upstream of the branch point 16b of the bypass passage 16, The EGR passage 17 is provided with an EGR cooler 17a and an EGR valve 17b.

  In the exhaust turbocharger 13, the turbine 13b is rotationally driven by exhaust gas passing through the turbine 13b, and the compressor 13b connected to the rotating shaft of the turbine 13b rotates to compress the intake air A to a high pressure. To pay. In order to control the rotation of the turbine 13b of the exhaust turbocharger 13, although not shown, the opening degree of a turbine blade such as a VGT (variable capacity turbo) for bypassing a part of the exhaust gas G (not shown) Opening area), waste gate valves, and exhaust bypass passages and exhaust bypass valves corresponding to these. The exhaust turbo supercharger 13 may be constituted by a multi-stage supercharge system including not only one exhaust turbo supercharger but also a plurality of exhaust turbo superchargers.

  The externally driven supercharger 15 is a supercharger that obtains a driving force from other power without obtaining a rotational driving force from the energy of the exhaust gas G, like the exhaust turbocharger 13. Examples of the drive supercharger 15 include a mechanical supercharger driven by the output of the engine 1 and an electric supercharger driven by the electric power generated by the output of the engine 1. There are capacity type and centrifugal type respectively.

  When a mechanical supercharger is employed, the mechanical supercharger 15 and the output shaft of the engine main body 10 are driven by being connected to the output shaft of the engine main body 10 via a normal gear or a belt (not shown). If necessary, the speed increasing ratio may be made variable using a continuously variable transmission or the like, or the speed increasing ratio may be made constant without providing these transmissions. A clutch (not shown) is provided between the mechanical supercharger 15 and the output shaft of the engine 10 so that the mechanical supercharger 15 can be turned ON / OFF. When an electric supercharger is used, the electric motor of the electric supercharger 15 is driven by electricity generated by the generator on the engine side.

  Then, the rotation control of the exhaust turbocharger 13, the ON / OFF operation of the externally driven supercharger 15 and the speed increase ratio control (when a transmission is provided), the ON / OFF operation of the flow rate adjustment valve 16 a and the valve A control device (not shown) for controlling the opening adjustment, the ON / OFF operation of the EGR valve 17b, the valve opening adjustment, and the like is provided. This control device is usually configured to be incorporated in a control device called an ECU (Engine Control Unit) that controls the overall operation of the engine 10.

  Next, as shown in FIG. 2, the internal combustion engine 1 </ b> A according to the second embodiment of the present invention has a second intercooler (the second intercooler) in addition to the configuration of the internal combustion engine 1 according to the first embodiment. The intake intermediate cooling device 20) is arranged in the intake pipe 11a from the externally driven supercharger 15 to the intake manifold 10a. The second intercooler 20 preferably has a smaller capacity than the intercooler 14 and has a configuration in which the piping system and the cooler volume are minimized. Further, the second intercooler 20 is provided with a second bypass passage 21 and a second bypass valve 21a so that the second intercooler 20 can be bypassed in accordance with a warm-up state or the like. The air-fuel mixture (intake air + EGR gas: A + (Ge)) can be flowed. Other configurations are the same as the configuration of the internal combustion engine 1 of the first embodiment.

  The EGR method in the engine 1, 1A having these configurations is performed by supplying EGR gas Ge, which is a part of the exhaust gas G, from the upstream side of the turbine 13b to the upstream side of the externally driven supercharger 15.

  Next, a control method in the engine 1, 1A having the above-described configuration will be described. In the engines 1 and 1A, when the warm-up index temperature indicating the warm-up state of the engines 1 and 1A is equal to or lower than a predetermined determination temperature, the amount of exhaust gas that bypasses the turbine 13b of the exhaust turbocharger 13 is increased. Thus, the operation of the exhaust turbocharger 13 is reduced.

  As a method for increasing the amount of exhaust gas that bypasses the turbine 13b of the exhaust turbocharger 13, the opening degree of the turbine blade of the exhaust turbocharger 13, the opening degree of the wastegate valve, or the like There is a method of increasing the opening degree of the exhaust bypass valve.

  According to the engine 1, 1 </ b> A having the above-described configuration and the EGR method thereof, the EGR gas Ge does not pass through the intercooler 14. And can prevent fouling. Furthermore, since the supercharging pressure can be secured by the externally driven supercharger 15 without worrying about the contamination of the intercooler 14 due to the EGR gas Ge, the amount of EGR gas and the EGR rate can be increased. The exhaust gas G can be improved.

  In the engines 1 and 1A, the externally driven supercharger 15 is disposed in the immediate vicinity of the engine main body 10 to reduce the length of the intake system piping 11a from the externally driven supercharger 15 to the engine main body 10. As a result, the heat capacity of the intake pipe 11a can be reduced, so that warm-up can be promoted and the cold operation time of the engine 1, 1A can be shortened, and the white in the exhaust gas G at the cold start can be reduced. Smoke emission can be suppressed. Further, since the internal volume of the intake system pipe 11a can be reduced as the length of the intake system pipe 11a is reduced, the supercharging response associated with the operation of the externally driven supercharger 15 can be enhanced.

  Further, since the intercooler 14 is not disposed downstream of the externally driven supercharger 15 or with the second bypass passage 21 in which countermeasures against EGR gas fouling are taken, the second intercooler 20 having a small capacity is provided. Even in the case of being arranged, by using the second bypass passage 21, the intake air increased by the supercharging operation by the externally driven supercharger 15 can be supplied to the cylinder as it is, so that the temperature of the intake air entering the cylinder is increased. It becomes possible to make it.

  Further, according to this control method, since the operation of the exhaust turbocharger 13 is lowered during the cold operation at the cold start, the work amount of the supercharging operation by the externally driven supercharger 15 is increased. Thus, the intake air temperature can be positively increased, and the temperature of the gas A (or A + Ge) sucked into the cylinder of the engine body 10 can be increased. As a result, the compression end temperature in the cylinder rises, so that generation of CO and HC can be suppressed.

  Further, since the drive energy of the externally driven supercharger 15 is finally obtained from the shaft output of the engine 1 or 1A, increasing the work of the externally driven supercharger 15 increases the fuel injection amount. It means that exhaust temperature and exhaust energy increase at the same time. Therefore, exhaust temperature can be raised and warm-up can be promoted.

  In addition to this, at the time of cold start, since the consumption of the thermal energy of the exhaust gas G in the turbine 13b is reduced by lowering the operation of the exhaust turbocharger 13, the exhaust in the downstream of the turbine 13b. A decrease in the temperature of the gas G can be prevented. Therefore, early activation of the catalyst system can be expected.

  FIG. 3 shows the characteristics of the change in the intake system volume with respect to the externally driven supercharger 15 on the transient performance in the arrangement of the conventional intercooler 14 in FIGS. 7 and 8 and the arrangement of the intercooler 14 in FIG. The results of simulation calculation of “degree of improvement in transient supercharging characteristics” for evaluation are shown. FIG. 3 shows the case where the mechanical supercharger is started by increasing the fuel injection amount from 0 (zero) seconds on the horizontal axis in FIG. 3 under the condition of constant engine speed and 0% EGR. Indicates the supercharging pressure. Example A in the case of using an externally driven supercharger 15 in addition to the exhaust turbocharger 13 of the present invention is a conventional example B in the case of using only the externally driven supercharger 15 of FIGS. It can be seen that the supercharging pressure increases more quickly than.

  4 to 6 show evaluation values of the temperature rise effect with respect to the intake air temperature, the compression end temperature, and the exhaust gas temperature in the internal combustion engine 1 having the configuration shown in FIG. This evaluation value is a constant condition of 50% engine speed, 50% load, and EGR 0%. Example C is the turbine blade 100b opening degree of the turbine 13b of the turbocharger 13, and further the wastegate. Is fully opened and the mechanical supercharger 15 is operated to perform supercharging, and Example D illustrates the case where the mechanical supercharger is operated with 100% opening of the turbine blade of the turbine 13b and supercharged. E shows a case where the turbocharger 13 is used only for supercharging.

  INDUSTRIAL APPLICABILITY The internal combustion engine, the EGR method and the control method thereof according to the present invention can prevent corrosion and fouling of the intercooler due to EGR gas, and suppress the discharge of white smoke into the exhaust gas when the internal combustion engine is cold started Therefore, it can be used as an internal combustion engine mounted on an automobile, its EGR method and its control method.

1, 1A, 1X, 1Y engine (internal combustion engine)
10 Engine Body 11 Intake Passage 12 Exhaust Passage 13 Exhaust Turbo Supercharger 14 Intercooler (Intake Intercooler)
15 Externally driven supercharger 16 Bypass passage 16a Flow rate adjusting valve 17 EGR passage 20 Second intercooler (second intake intermediate cooler)
21 Second bypass passage 21a Second bypass valve A Intake G Exhaust gas Ge EGR gas

Claims (4)

  A compressor, an intercooler, and an externally driven supercharger are provided in the intake passage of the internal combustion engine in order from the upstream side, and an exhaust drive turbocharger turbine is provided in the exhaust passage, and a flow rate adjusting valve. In the internal combustion engine having a bypass passage that bypasses the externally driven supercharger, the exhaust passage on the upstream side of the turbine, the downstream side of the intercooler, and the externally driven supercharger An internal combustion engine having an EGR passage connecting an intake passage upstream of the engine.   When the warm-up indicator temperature indicating the warm-up state of the internal combustion engine is equal to or lower than a predetermined determination temperature, the exhaust turbo-supercharger control device determines an exhaust gas amount that bypasses the turbine of the exhaust turbo-supercharger. 2. The internal combustion engine according to claim 1, wherein control is performed to increase and decrease the operation of the exhaust turbocharger.   A second intercooler is provided downstream of the externally driven supercharger, and a second bypass passage having a bypass valve and bypassing the second intercooler is provided. Item 3. The internal combustion engine according to Item 1 or 2.   A compressor, an intercooler, and an externally driven supercharger of an exhaust turbocharger are provided in order from the upstream side in the intake passage of the internal combustion engine, and the exhaust turbocharger turbine is provided in the exhaust passage, and a flow rate adjusting valve. And supplying an EGR gas from the upstream side of the turbine to the upstream side of the externally driven supercharger. A feature of the EGR method for an internal combustion engine.

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