JP2008157150A - Internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal combustion engine suppressing an exhaust gas sensor from getting wet while improving early activation of an exhaust emission control catalyst in warming up. <P>SOLUTION: This internal combustion engine 10 is provided with an exhaust valve 70 shutting off one of a main passage 44 running inclusive of a turbine wheel 64c and a bypass passage 50 bypassing the turbine wheel 64c. An ECU controls the exhaust valve 70 to shut off the main passage 44 until the ECU 80 determines that the exhaust emission control catalyst 55 is activated and a turbine 64 is warmed up. Thereby, when the main passage 44 is shut off, the exhaust emission control catalyst 55 is excellently activated by high-temperature exhaust gas from the bypass passage 50 bypassing the turbine wheel 64c. After that, when the main passage 44 is opened, warming up of the turbine 64 is completed and condensed water is not produced. Thereby, the exhaust gas sensor 76 located on the downstream side of the turbine 64 is suppressed from getting wet. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an internal combustion engine with a turbocharger, and more particularly to an internal combustion engine in which an exhaust sensor and an exhaust purification catalyst are provided on the downstream side of a turbine of the turbocharger.

  In an internal combustion engine with a turbocharger, an exhaust purification catalyst is usually provided downstream of the turbocharger turbine. In such an internal combustion engine, a turbine having a larger heat capacity than that of other exhaust system components is provided in an exhaust passage from the cylinder to the exhaust purification catalyst.

  For this reason, in the internal combustion engine with a turbocharger, when the internal combustion engine is warmed up, such as during a cold start, the heat of the exhaust gas discharged from the cylinder is taken away by the turbine. Therefore, an internal combustion engine with a turbocharger tends to have a lower temperature of a gas flowing through an exhaust purification catalyst when warming up than an internal combustion engine without a turbocharger, because of the presence of a turbine. It takes time until the purification catalyst is activated.

  In order to take measures against this, in Patent Document 1 below, in addition to the main exhaust passage from the cylinder to the exhaust purification catalyst, a sub exhaust passage that bypasses the turbine and a valve that closes one of these exhaust passages are provided. Technology has been proposed. By controlling the opening and closing of the valve, the exhaust gas is guided to the bypass passage when warming up, and the temperature of the exhaust gas flowing through the exhaust purification catalyst is raised, thereby shortening the time required until the exhaust purification catalyst is activated.

JP 2004-339842 A

  By the way, in an internal combustion engine provided with an exhaust purification catalyst, an exhaust sensor for detecting a specific component such as oxygen in the exhaust gas is usually provided upstream of the exhaust purification catalyst. Such an exhaust sensor may lose its function when exposed to water. The exhaust sensor is generally provided on the downstream side of a portion where exhaust gases from the cylinders merge in the exhaust passage. Therefore, in the case of an internal combustion engine with a turbocharger, the exhaust sensor is generally disposed between the turbine and the exhaust purification catalyst.

  In the technique described in Patent Document 1 described above, since a valve that closes one of the exhaust passages is provided at the branch portion between the main exhaust passage and the sub exhaust passage, the valve blocks the main exhaust passage. The turbine is not exposed to the exhaust gas from the cylinder and is in a low temperature state.

  For this reason, in the technique described in Patent Document 1, when the main exhaust passage is opened after the warm-up of the exhaust purification catalyst is completed, water vapor in the exhaust gas condenses at low temperature turbine components (for example, a turbine wheel). Sometimes. The water condensed in the turbine in this way (hereinafter referred to as condensed water) is carried further downstream by the exhaust gas.

  Therefore, when the technique described in Patent Document 1 is applied to an internal combustion engine including an exhaust purification catalyst and an exhaust sensor, if the main exhaust passage is opened after the exhaust purification catalyst is activated downstream of the turbine, There is a possibility that the exhaust sensor on the downstream side may be flooded with water condensed by the turbine.

  The present invention has been made in view of the above, and an exhaust purification catalyst at the time of warm-up is an internal combustion engine provided with an exhaust sensor and an exhaust purification catalyst on the downstream side of the turbine of the turbocharger. An object of the present invention is to provide an internal combustion engine that suppresses water exposure of an exhaust sensor while improving early activation of the engine.

  In order to achieve the above object, an internal combustion engine according to the present invention is an internal combustion engine that includes a turbocharger, and is provided with an exhaust sensor and an exhaust purification catalyst downstream of the turbine of the turbocharger. A main passage that the exhaust gas flows through the turbine wheel of the turbine toward the exhaust purification catalyst, a bypass passage that the exhaust gas bypasses the turbine wheel of the turbine and goes to the exhaust purification catalyst, a downstream side of the turbine wheel in the main passage, An exhaust valve capable of shutting off one of the bypass passages, and a control means for controlling to shut off the main passage by the exhaust valve until activation of the exhaust purification catalyst and warming up of the turbine are completed, To do.

  In the internal combustion engine according to the present invention, the control means includes catalyst activation determination means for determining whether or not the exhaust purification catalyst has been activated, and turbine warm-up determination means for determining whether or not the turbine has been warmed up. The main passage may be controlled to be shut off until it is determined that the exhaust purification catalyst is activated and it is determined that the turbine is warmed up.

  In the internal combustion engine according to the present invention, the exhaust sensor may be provided in a portion of the exhaust pipe downstream of the exhaust valve that blocks the main passage and on the main passage side.

  The internal combustion engine according to the present invention further includes intake air amount detection means for detecting the intake air amount, and the turbine warm-up determination means is a time integral value of the intake air amount after the internal combustion engine starts to start. It can be determined that the turbine is warmed up when the integrated air amount is equal to or greater than a predetermined determination value.

  In the internal combustion engine according to the present invention, the determination value is set to a value at which the water vapor in the exhaust gas does not condense in the turbine even when the exhaust valve opens the main passage and the exhaust gas flows through the turbine wheel. Can be.

  In the internal combustion engine according to the present invention, the determination value may be set according to a coolant temperature at the start of the start.

  According to the present invention, when the main passage that flows through the turbine wheel and goes to the exhaust purification catalyst is blocked, the exhaust gas from the bypass passage that bypasses the turbine wheel is exhausted at a high temperature without taking heat away from the turbine. Since it reaches the purification catalyst, the early activation of the exhaust purification catalyst 55 can be improved. After that, when the main passage is opened, since the turbine has already been warmed up and no condensed water is generated in the turbine, the exhaust sensor provided downstream of the turbine is prevented from getting wet. can do.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same.

  First, a schematic configuration of the internal combustion engine according to the present embodiment will be described with reference to FIG. FIG. 1 is a schematic diagram showing a schematic configuration of an internal combustion engine. In FIG. 1, only the main part related to the present invention is schematically shown for the internal combustion engine.

  As shown in FIG. 1, the internal combustion engine 10 includes a turbocharger 60 that compresses air taken in by kinetic energy of exhaust gas discharged from the cylinder 12. The internal combustion engine 10 is mounted on a vehicle as a prime mover. Further, the internal combustion engine 10 has an electronic control unit 80 (hereinafter referred to as ECU) as a control means for controlling various components provided in the internal combustion engine 10.

  The internal combustion engine 10 is provided with a cylinder block and a piston (not shown), a crankshaft 18 and a cylinder head 20 as engine body system parts in which a cylinder 12 is formed. A cylinder bore (not shown) is formed in the cylinder block, and the piston reciprocates in the cylinder bore. The piston is in sliding contact with the inner wall surface of the cylinder bore (hereinafter referred to as the cylinder wall). A cylinder head 20 is coupled to the cylinder block so as to close the cylinder bore so as to face the piston.

  A space surrounded by the cylinder head 20, the piston, and the cylinder wall of the cylinder block is a “cylinder”. The cylinder block is provided with a coolant temperature sensor that detects the temperature of coolant circulating in the engine body (hereinafter referred to as coolant temperature), and sends a signal related to the coolant temperature to the ECU 80. Yes.

  An intake port 24 and an exhaust port 26 are formed in the cylinder head 20 corresponding to each cylinder 12. Corresponding to the intake port 24 and the exhaust port 26, an intake valve and an exhaust valve (not shown) are provided. These intake valves and exhaust valves are configured to be openable and closable at a predetermined timing according to the rotational angle position of the crankshaft 18.

  When the crankshaft 18 rotates, the piston reciprocates and air is sucked into the cylinder 12. Further, the cylinder 12 is supplied with fuel by a fuel injection device (not shown) to form a mixture of air and fuel. The air-fuel mixture thus formed is hereinafter referred to as an in-cylinder air-fuel mixture. In-cylinder mixture is ignited in the cylinder 12 by an ignition device (not shown). The reciprocating motion of the piston caused by the ignition and combustion of the in-cylinder air-fuel mixture is converted into a rotational motion and output from the crankshaft 18. The internal combustion engine 10 is provided with a crank angle sensor 19 that detects the rotational angle position of the crankshaft 18, and sends a signal related to the detected rotational angle position to the ECU 80.

  The internal combustion engine 10 includes, as intake system components for introducing air from outside air to the cylinder 12, an outside air duct 32 that introduces air from outside air, an air cleaner 33 that removes dust from the intake air, and a flow rate of intake air (hereinafter referred to as “intake air”). An air flow meter 34 that measures the intake air amount), a throttle valve 36 that adjusts the intake air amount, and an intake manifold 38 that is a branch pipe that distributes the intake air to each cylinder 12 are provided.

  The intake manifold 38 is connected to the cylinder head 20, and its branch passage 39 communicates with the intake port 24. A surge chamber 37 (resonance chamber) communicating with the branch passage 39 is formed on the upstream side of the branch passage 39. Further, the intake manifold 38 is provided with a supercharging pressure sensor (not shown) for detecting an intake pressure in the surge chamber 37 (hereinafter referred to as supercharging pressure), and a signal related to the supercharging pressure is sent to the ECU 80. Is being sent to.

  An intake pipe 30 is connected to the upstream side of the intake manifold 38, and the surge chamber 37 communicates with a passage 30 a formed in the intake pipe 30. A compressor 62 of a turbocharger 60 described later is connected to the upstream side of the intake pipe 30, and an intake pipe 31 is connected to the upstream side of the compressor 62. An air flow meter 34 is disposed in a passage 31 a formed in the intake pipe 31. The upstream side of the intake pipe 31 is connected to an air cleaner 33, and the passage 31 a communicates with the outside air duct 32 via the air cleaner.

  The air introduced from the outside air duct 32 passes through the air cleaner 33, the amount of intake air is measured by the air flow meter 34, and is compressed by the compressor 62 of the turbocharger 60. The compressed air flows to the throttle valve 36. The air whose flow rate is adjusted by the throttle valve 36 flows into the surge chamber (resonance chamber) 37 of the intake manifold 38, is distributed from the branch passage 39 to each cylinder 12, and flows into the cylinder 12 through the intake port 24. The air flow meter 34 sends a signal related to the intake air amount measured in the passage 31a to the ECU 80. The throttle valve 36 is controlled by the ECU 80 and can adjust the amount of intake air flowing into the cylinder 12.

  The “intake passage” means a passage formed by the intake system parts and the intake pipe described above, through which the air introduced from the outside air duct 32 flows into the cylinder 12 and will be described below. Are referred to as “intake passages”. In this embodiment, the intake passage includes not only the surge chamber 37 and branch passage 39 of the intake manifold 38 but also the intake port 24 of the cylinder head 20.

  Further, in the internal combustion engine 10, in order to exhaust the exhaust gas from the cylinder 12 to the outside air, the exhaust purification catalyst 55 that reduces harmful components in the exhaust gas and the exhaust gas from the cylinder 12 are guided to the exhaust purification catalyst 55. An exhaust pipe 40 is provided. The exhaust pipe 40 has an upstream side connected to the cylinder head 20 and a downstream side connected to the exhaust purification catalyst 55. A turbine 64 of the turbocharger 60 is provided in the middle of the exhaust pipe 40.

  Here, the configuration of the turbocharger 60 will be described. The turbocharger 60 includes a compressor 62 provided between the intake pipe 30 and the intake pipe 31 and a turbine 64 provided in the middle of the exhaust pipe 40. The compressor 62 accommodates a compressor wheel 62 c that compresses air by rotating in the compressor 62, and the turbine 64 accommodates a turbine wheel 64 c that is rotationally driven by an exhaust gas flow. The compressor wheel 62c and the turbine wheel 64c are integrally coupled. In the turbocharger 60, the turbine wheel 64c and the compressor wheel 62c are rotationally driven by the kinetic energy of the exhaust gas flowing into the turbine 64 from the main passage 44, compressing the air in the compressor 62, and the intake pipe 30 To the passage 30a.

  In the exhaust pipe 40, a manifold passage 41 for joining the exhaust gases from the cylinders 12 and the exhaust gas from the manifold passage 41 are guided to the exhaust purification catalyst 55 via the turbine wheel 64 c of the turbocharger 60. A main passage 44 is provided.

  A branch portion 41 a is provided in the manifold passage 41 corresponding to each cylinder 12, and the branch portion 41 a communicates with the exhaust port 26. On the downstream side of the branch portion 41 a of the manifold passage 41, a merging portion 41 c where exhaust gases from the cylinders 12 merge is provided. The manifold passage 41 joins the exhaust gas from the cylinder 12 at the joining portion 41 c of the manifold passage 41. The junction portion 41 c of the manifold passage 41 communicates with the main passage 44.

  The main passage 44 communicates with the merging portion 41 c of the manifold passage 41 on the upstream side, and an exhaust purification catalyst 55 is provided on the downstream side. A turbine wheel 64 c of the turbine 64 is disposed in the middle of the main passage 44. The main passage 44 causes the exhaust gas merged in the manifold passage 41 to flow to the turbine wheel 64 c in the turbine 64. The main passage 44 causes the exhaust gas flowing through the turbine wheel 64 c to flow toward the exhaust purification catalyst 55.

  That is, the “main passage” 44 means a flow path of exhaust gas from the exhaust gas that has joined from the manifold passage 41 to the exhaust purification catalyst 55 through the turbine wheel 64 c of the turbine 64. . A flow path of the exhaust gas flowing through the main passage 44 is indicated by a two-dot chain line arrow A in the figure. In the present embodiment, the main passage 44 includes a passage that flows through the turbine wheel 64 c in the housing of the turbine 64.

  The exhaust pipe 40 is provided with a bypass passage 50 so that the exhaust gas from the manifold passage 41 can be guided to the exhaust purification catalyst 55 by bypassing the turbine wheel 64c of the turbocharger 60. Yes.

  The upstream side of the bypass passage 50 communicates with a portion 44 a on the upstream side of the turbine wheel 64 c in the main passage 44. On the other hand, the downstream side of the bypass passage 50 communicates with a portion 44 c downstream of the turbine wheel 64 c in the main passage 44. The bypass passage 50 is configured such that after exhaust gas is introduced from the upstream portion 44a of the main passage 44 and the turbine wheel 64c of the turbine 64 is bypassed, it can be merged with the main passage 44 again at the downstream portion 44c. Has been. A flow path of the exhaust gas flow through the bypass passage 50 is indicated by a one-dot chain arrow B in the figure. The bypass passage 50 can divert the exhaust gas flowing through the main passage 44 to the exhaust purification catalyst 55 without causing it to flow to the turbine wheel 64 c in the turbine 64.

  In the main passage 44, the exhaust gas flow from the bypass passage 50 toward the exhaust purification catalyst 55 mainly passes through the portion 52 on the downstream side of the bypass passage 50, and the exhaust toward the exhaust purification catalyst 55 from the turbine wheel 64 c. It is an area where the gas flow hardly passes.

  Further, the exhaust pipe 40 is provided with an exhaust valve 70 that can block one of the downstream side of the turbine wheel 64 c in the main passage 44 and the bypass passage 50. The exhaust valve 70 is a so-called cantilever valve, and includes a valve body 70a and a rotating shaft 70c that rotatably supports one end of the valve body 70a. The rotary shaft 70c is rotationally driven by an actuator (not shown). The driving of the actuator is controlled by the ECU 80. In the exhaust valve 70, the rotary shaft 70 c is rotationally driven, so that the valve body 70 a can block either the downstream side of the turbine wheel 64 c in the main passage 44 and the bypass passage 50. .

  The exhaust valve 70 is provided on the downstream side of the turbine wheel 64 c in the turbine 64, and the rotation shaft 70 c is disposed between the bypass passage 50 and the main passage 44. The exhaust valve 70 can block the bypass passage 50 by moving the valve body 70a to the bypass passage 50 side to the position indicated by the one-dot chain line in the drawing. When the valve body 70a of the exhaust valve 70 blocks the bypass passage 50, the main passage 44 is opened. At this time, the exhaust gas from the cylinder 12 flows to the turbine wheel 64c of the turbine 64, drives the turbine wheel 64c, and then travels toward the exhaust purification catalyst 55. That is, when the exhaust valve 70 blocks the bypass passage 50, the exhaust gas flow path A (hereinafter referred to as the main path) from the cylinder 12 to the exhaust purification catalyst 55 passes through the turbine wheel 64c.

  In addition, the exhaust valve 70 can block the main passage 44 on the downstream side of the turbine wheel 64c by moving the valve body 70a to the main passage 44 side to the position indicated by a two-dot chain line in the drawing. When the valve body 70a of the exhaust valve 70 blocks the main passage 44, the bypass passage 50 is opened. At this time, the exhaust gas from the cylinder flows to the exhaust purification catalyst 55 after flowing through the bypass passage 50 so as to bypass the turbine wheel 64 c of the turbine 64. That is, when the exhaust valve 70 blocks the main passage 44 on the downstream side of the turbine wheel 64c, an exhaust gas flow path B (hereinafter referred to as a bypass path) from the cylinder 12 to the exhaust purification catalyst 55 bypasses the turbine wheel 64c. Will be.

  In addition, the exhaust pipe 40 is provided with an exhaust sensor 76 that detects a specific component in the exhaust gas directed to the exhaust purification catalyst 55. Examples of the exhaust sensor 76 include an A / F sensor that detects the oxygen concentration in the exhaust gas, and a NOx sensor that detects the concentration of nitrogen oxide in the exhaust gas.

  The exhaust sensor 76 is disposed upstream of the exhaust purification catalyst 55 in the exhaust pipe 40. Specifically, the exhaust sensor 76 is disposed at a portion immediately downstream of the exhaust valve 70 and is disposed at a portion on the main passage 44 side. In addition, the exhaust sensor 76 is a portion where the exhaust gas flowing from the bypass passage 50 to the exhaust purification catalyst 55 is not as much as possible when the exhaust valve 70 blocks the main passage 44 and opens the bypass passage 50, that is, the bypass passage. The exhaust gas flow that flows from 50 to the exhaust purification catalyst 55 is disposed at a position as far as possible from the flow path B of the exhaust gas flow. Further, the exhaust sensor 76 is disposed at a position where the exhaust gas flow through the main passage 44 is in a good state when the exhaust valve 70 blocks the bypass passage 50 and opens the main passage 44.

  Further, the internal combustion engine 10 is provided with an ECU 80 as a control means for controlling this. The ECU 80 includes a signal related to the rotational angle position of the crankshaft 18 from the crank angle sensor 19, a signal related to the intake air amount from the air flow meter 34, a signal related to supercharging pressure from an intake pressure sensor (not shown), and A signal related to the coolant temperature is received from the coolant temperature sensor that does not. Based on these signals, the ECU 80 determines the rotational angle position of the crankshaft 18 (hereinafter referred to as crank angle), the rotational speed of the crankshaft 18 of the internal combustion engine 10 (hereinafter referred to as engine rotational speed), and the intake air amount. The supercharging pressure, the output torque required for the internal combustion engine 10 (hereinafter referred to as engine load), and the like can be calculated. Based on these calculated control variables, the ECU 80 can control the throttle valve 36, a fuel injection device and an ignition device (not shown), and an actuator of the exhaust valve 70.

  In the internal combustion engine 10 configured as described above, the ECU 80 as the control means controls the exhaust valve 70 via the actuator, so that the downstream of the turbine wheel 64c in the main passage 44 according to the operating state of the internal combustion engine 10. One of the side and the bypass passage 50 can be shut off. That is, whether the ECU 80 guides the exhaust gas from the cylinder 12 to the exhaust purification catalyst 55 after passing through the turbine wheel 64c of the turbocharger 60 or to the exhaust purification catalyst 55 without passing through the turbine wheel 64c. Can be selected. That is, the ECU 80 selects an exhaust gas path from the cylinder 12 to the exhaust purification catalyst 55 from any one of a path A passing through the turbine wheel 64c of the turbine 64 and a path B bypassing the turbine wheel 64c. can do.

  When the warm-up of the internal combustion engine 10 is completed, the ECU 80 controls the exhaust valve 70 to block the bypass passage 50 when the supercharging pressure is equal to or lower than a predetermined pressure. As a result, exhaust gas from the cylinder 12 is caused to flow through the turbine wheel 64c and the compressor wheel 62c is driven to rotate, thereby increasing the supercharging pressure and improving the volumetric efficiency of the air filled in the cylinder 12. . On the other hand, when the supercharging pressure exceeds a predetermined pressure, the exhaust valve 70 is controlled to shut off the main passage 44 on the downstream side of the turbine wheel 64c. As a result, the exhaust gas from the cylinder 12 bypasses the turbine wheel 64c and travels toward the exhaust purification catalyst 55, thereby preventing the supercharging pressure from rising excessively. Thus, the internal combustion engine 10 according to the present embodiment can cause the exhaust valve 70 to function as a so-called “waste gate valve” by the ECU 80 controlling the opening and closing of the exhaust valve 70 in accordance with the supercharging pressure. .

  By the way, when the internal combustion engine 10 is not warmed up, such as during a cold start, the exhaust purification catalyst 55 that is at a low temperature is not activated, so as to reduce harmful components in the exhaust gas such as hydrocarbons. Therefore, it is necessary to activate the exhaust purification catalyst 55 as early as possible by supplying high temperature exhaust gas to the exhaust purification catalyst 55 and raising the temperature. In addition, since the exhaust pipe 40 and the turbine 64 (turbine wheel 64c) are in a cold state at the time of cold start, water vapor contained in the exhaust gas condenses on the surfaces of these components to generate condensed water. It is necessary to prevent the exhaust sensor from getting wet with such condensed water.

  Therefore, in the internal combustion engine according to the present embodiment, the control means (ECU) controls to shut off the main passage until it is determined that the exhaust purification catalyst is activated and the turbine is warmed up. By doing so, the early activation of the exhaust purification catalyst is made good, and the moisture of the exhaust sensor is suppressed. The exhaust valve control executed by the control means (ECU) of the internal combustion engine according to the present embodiment will be described with reference to FIGS. FIG. 2 is a flowchart of exhaust valve control executed by the ECU.

  As shown in FIGS. 1 and 2, first, the ECU 80 receives a signal related to the intake air amount from the air flow meter 34 and a signal related to the coolant temperature from the coolant temperature sensor. The ECU 80 acquires the coolant temperature at the start of starting the internal combustion engine 10. Further, the ECU 80 calculates a time integration value (hereinafter referred to as an integrated air amount) of the intake air amount from the start of the internal combustion engine 10 based on the intake air amount. The amount of air is acquired (S100).

  In step S102, the ECU 80 determines whether the activation of the exhaust purification catalyst 55 has been completed. Specifically, it is determined whether or not the integrated air amount from the start of the internal combustion engine 10 is equal to or greater than a predetermined determination value C.

  The determination value C relating to the activation of the exhaust purification catalyst 55 is set according to the coolant temperature at the start of the start. The determination value C is set to such a value that the exhaust purification catalyst 55 rises in temperature by receiving the heat of the exhaust gas discharged in accordance with the intake air amount after the internal combustion engine 10 starts to be activated, and the activation is completed. Has been. The relationship between the coolant temperature at the start of the start of the internal combustion engine 10 and the judgment value C of the integrated air amount related to the activation of the exhaust purification catalyst 55 has been obtained in advance by a conformance experiment or the like, and as a control constant (map) It is stored in a ROM (not shown) of the ECU 80.

  In step S102, when it is determined that the activation of the exhaust purification catalyst 55 is not completed (No), that is, when it is determined that the integrated air amount is lower than the predetermined determination value C, the ECU 80 starts the start. Therefore, it is determined that the amount of exhaust gas supplied to the exhaust purification catalyst 55 is small and the exhaust purification catalyst has not yet been activated at a low temperature, and the exhaust valve 70 is controlled to block the main passage 44 (S104). Then, the process returns to step S100.

  In this way, the internal combustion engine 10 guides the exhaust gas from the cylinder 12 to the exhaust purification catalyst 55 by bypassing the turbine wheel 64c of the turbine 64 from the bypass passage 50. The exhaust purification catalyst 55 is supplied with a relatively high temperature exhaust gas in the path B that bypasses the turbine wheel 64c. As a result, the internal combustion engine 10 warms up and raises the temperature of the exhaust purification catalyst 55.

  On the other hand, when it is determined in step S102 that the activation of the exhaust purification catalyst 55 is completed (Yes), that is, it is determined that the integrated air amount from the start of the start is equal to or greater than a predetermined determination value C. If this is the case, the ECU 80 proceeds to step S106 and determines whether or not the turbine has been warmed up. Specifically, it is determined whether or not the integrated air amount from the start of start is greater than or equal to a predetermined determination value D.

  Note that the determination value D relating to the warm-up of the turbine 64 is set according to the coolant temperature at the start of startup. The determination value D is determined by the temperature of the turbine 64 including the turbine wheel 64c being raised by the heat of the exhaust gas discharged in an amount corresponding to the amount of intake air after the start is started, and the exhaust by the opening of the main passage 44. Even when the gas flows through the turbine 64, the temperature is set such that the water vapor in the exhaust gas does not condense in the turbine 64, that is, no condensed water is generated in the turbine 64. In other words, the determination value D is set to a temperature at which the components in the turbine 64 are equal to or higher than the dew point temperature of the water vapor in the exhaust gas. The relationship between the coolant temperature at the start of the start and the judgment value D of the integrated air amount related to the warming up of the turbine 64 is obtained in advance by a conformance experiment or the like and is stored in the ROM of the ECU 80 as a control constant (map). ing. The determination value D related to warming up of the turbine 64 is larger than the determination value C related to activation of the exhaust purification catalyst 55.

  In step S106, when it is determined that the turbine 64 has not been warmed up (No), that is, when it is determined that the integrated air amount falls below the preset determination value D, the ECU 80 causes the main passage 44 to When the exhaust gas flows through the turbine 64 due to the opening, it is determined that the water vapor in the exhaust gas condenses in the turbine 64 and that condensed water is generated, and the exhaust valve 70 is controlled to block the main passage 44 ( S104). Then, the process returns to step S100.

  Thus, the internal combustion engine 10 directs the exhaust gas from the cylinder 12 toward the exhaust purification catalyst 55 from the bypass passage 50 even after the activation of the exhaust purification catalyst 55 is completed. Detour. Thereby, it is suppressed that the water vapor | steam in exhaust gas condenses within the turbine 64, and condensed water arises here.

  In the state where the main passage 44 is blocked on the downstream side of the turbine wheel 64c, the exhaust gas does not flow in the turbine 64 so as to pass through the turbine wheel 64c, but the exhaust gas from the upstream portion 44a stays. ing. In the upstream portion 44a, the exhaust gas flowing from the junction 41c of the manifold passage 41 toward the bypass passage 50 flows and is at a relatively high temperature. The components (turbine wheel 64c and the like) in the turbine 64 rise in temperature by receiving heat from the exhaust gas flowing in from the upstream portion 44a and staying in the turbine 64.

  On the other hand, if it is determined in step S106 that the warm-up of the turbine 64 has been completed (Yes), that is, if the integrated air amount is greater than or equal to the predetermined determination value D, the ECU 80 proceeds to step S108, and the exhaust gas The exhaust valve 70 is controlled to open the main passage 44 by determining that the components in the turbine 64 have sufficiently heated so that the water vapor therein does not condense in the turbine 64. Then, the process returns to step S100.

  In this way, the internal combustion engine 10 opens the main passage 44 after the turbine 64 has been warmed up. At this time, since the temperature of the components in the turbine 64 has sufficiently increased, even if the exhaust gas from the cylinder 12 flows so as to pass through the turbine wheel 64c, no condensed water is generated in the turbine 64. It can suppress that the exhaust sensor 76 provided in the downstream of the wheel 64c gets wet.

  As described above, in this embodiment, the exhaust valve 70 capable of blocking one of the main passage 44 flowing through the turbine wheel 64c and the bypass passage 50 bypassing the turbine wheel 64c is provided on the downstream side of the turbine wheel 64c. The ECU 80 as the control means controls the exhaust passage 70 to block the main passage 44 until the activation of the exhaust purification catalyst 55 and the warming up of the turbine 64 are completed.

  Thus, when the main passage 44 is shut off, the exhaust gas from the bypass passage 50 that bypasses the turbine wheel 64c reaches the exhaust purification catalyst 55 at a high temperature without being deprived of heat by the turbine 64. The early activation of the purification catalyst 55 can be improved. Thereafter, when the main passage 44 is opened, the warm-up of the turbine 64 has already been completed, and no condensed water is generated in the turbine 64, so that the exhaust sensor 76 on the downstream side of the turbine 64 gets wet. This can be suppressed.

  In the present embodiment, an exhaust valve 70 capable of blocking one of the main passage 44 flowing through the turbine wheel 64c and the bypass passage 50 bypassing the turbine wheel 64c is provided on the exhaust pipe 40 downstream of the turbine wheel 64c. The ECU 80 as the control means controls the exhaust valve 70 so as to shut off the main passage 44 until it is determined that the exhaust purification catalyst 55 is activated and the turbine 64 is warmed up. It was. Thus, when the main passage 44 is shut off, high-temperature exhaust gas that has not been deprived of heat by the turbine 64 is supplied from the bypass passage 50 to the exhaust gas purification catalyst 55, and when the main passage 44 is opened, the turbine The internal combustion engine 10 that does not generate condensed water in the 64 can be realized by the exhaust valve 70 and the ECU 80.

  Further, in the present embodiment, the exhaust sensor 76 is provided in the exhaust pipe 40 on the downstream side of the exhaust valve 70 and on the main passage 44 side. It is possible to suppress the exhaust sensor 76 from being exposed to the exhaust gas flow flowing through the bypass passage 50 as much as possible until the turbine 64 is warmed up. Thereby, it is possible to effectively prevent the exhaust sensor 76 from being flooded by the exhaust gas flow from the bypass passage 50 toward the exhaust purification catalyst 55 until the turbine 64 is warmed up.

  In this embodiment, the air flow meter 34 is provided as a means for detecting the intake air amount, and the ECU 80 as a means for determining the warm-up of the turbine is the time of the intake air amount after the internal combustion engine 10 starts to start. It is determined that the turbine 64 has been warmed up when the integrated air amount that is an integral value exceeds a preset determination value D. It is possible to determine whether or not the turbine 64 has been warmed up without providing the turbine 64 with a temperature sensor or the like.

  In this embodiment, the determination value D is set to a value at which the water vapor in the exhaust gas does not condense in the turbine 64 even when the exhaust valve 70 opens the main passage 44 and the exhaust gas flows through the turbine wheel 64c. Therefore, when the main passage 44 is opened, the exhaust sensor 76 can be more reliably prevented from getting wet.

  Further, in this embodiment, the determination value D is set according to the coolant temperature at the start of the start. Therefore, it is determined whether or not the turbine 64 is warmed up when the internal combustion engine is started. This can be performed with high accuracy according to the environmental conditions.

  In this embodiment, it is determined whether or not the turbine 64 has been warmed up based on whether or not the integrated air amount after the internal combustion engine 10 has started is greater than or equal to a predetermined determination value D. However, the method for determining the warm-up of the turbine 64 is not limited to this. For example, it may be determined that the turbine 64 has been warmed up when a predetermined time has elapsed since the start of the internal combustion engine 10.

  Further, in this embodiment, it is determined whether or not the exhaust purification catalyst 55 is activated, whether or not the integrated air amount from the start of the internal combustion engine 10 is greater than or equal to a predetermined determination value D. However, the method for determining the activation of the exhaust purification catalyst 55 is not limited to this. For example, it may be determined that the exhaust purification catalyst 55 has been warmed up when a predetermined time has elapsed since the start of the internal combustion engine 10 was started.

  In this embodiment, the exhaust valve 70 is a so-called cantilever valve in which one end of the valve body 70a is rotatably supported by the rotary shaft 70c. However, the configuration of the exhaust valve is limited to this. It is not a thing. It is only necessary to block either the downstream side of the turbine wheel 64c in the main passage 44 or the bypass passage 50. For example, a slidable valve element is provided on both the main passage 44 side and the bypass passage 50 side, and this is used as an actuator or the like. It is good also as what drives by.

  As described above, the internal combustion engine according to the present invention is useful for an internal combustion engine with a turbocharger that includes an exhaust sensor and an exhaust purification catalyst on the downstream side of the turbine of the turbocharger, and in particular, a turbine having a large heat capacity. Is suitable for an internal combustion engine with a turbocharger.

1 is a diagram schematically illustrating a schematic configuration of an internal combustion engine according to a first embodiment. 2 is a flowchart of exhaust valve control executed by a control means (ECU) of the internal combustion engine according to the first embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Cylinder 18 Crankshaft 30,31 Intake piping 33 Air cleaner 34 Air flow meter 36 Throttle valve 38 Intake manifold 40 Exhaust pipe 44 Main passage 50 Bypass passage 55 Exhaust purification catalyst 60 Turbocharger 62 Compressor 62c Compressor wheel 64 Turbine 64c Turbine wheel 70 Exhaust valve 76 Exhaust sensor 80 Electronic control unit (ECU, control means) for internal combustion engine

Claims (6)

An internal combustion engine comprising a turbocharger, wherein an exhaust sensor and an exhaust purification catalyst are provided downstream from the turbine of the turbocharger,
A main passage through which exhaust gas flows through the turbine wheel of the turbine toward the exhaust purification catalyst,
A bypass passage for exhaust gas to bypass the turbine wheel of the turbine and to the exhaust purification catalyst;
An exhaust valve that can shut off one of the bypass passages on the downstream side of the turbine wheel in the main passage;
Until the activation of the exhaust purification catalyst and the warm-up of the turbine are completed, control means for controlling the main passage to be shut off by the exhaust valve,
An internal combustion engine comprising: The internal combustion engine according to claim 1,
The control means includes
Catalyst activation determination means for determining whether or not the exhaust purification catalyst is activated;
Turbine warm-up determination means for determining whether the turbine has been warmed up;
Have
An internal combustion engine that controls to shut off the main passage until it is determined that the exhaust purification catalyst is activated and the turbine is determined to be warmed up. The internal combustion engine according to claim 1 or 2,
The internal combustion engine, wherein the exhaust sensor is provided in a portion of the exhaust pipe downstream of the exhaust valve that blocks the main passage and on the main passage side. The internal combustion engine according to claim 2 or 3,
Intake air amount detection means for detecting the intake air amount,
The turbine warm-up determination means warms up the turbine when an integrated air amount that is a time integral value of the intake air amount after the internal combustion engine starts is equal to or greater than a predetermined determination value. An internal combustion engine characterized by determining that An internal combustion engine according to claim 4,
The determination value is set to a value at which water vapor in the exhaust gas does not condense in the turbine even if the exhaust valve opens the main passage and the exhaust gas flows through the turbine wheel. organ. An internal combustion engine according to claim 4,
The internal combustion engine, wherein the determination value is set in accordance with a coolant temperature at the start of starting.

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