JP2010024878A - Control device for internal combustion engine - Google Patents

Abstract

In a two-stage turbo system, an apparatus for improving the responsiveness of a high-pressure turbo when switching from an operation mode in which the rotation speed of the high-pressure turbo is low to an operation mode in which the rotation speed of the high-pressure turbo is high is provided.
A control device for an internal combustion engine (1) includes a low-pressure turbo (13). A high-pressure turbo 14 connected in series with the low-pressure turbo 13 is provided. An exhaust bypass valve 32 is provided on a low-pressure turbine bypass passage 75 that bypasses the low-pressure turbine 13 a of the low-pressure turbo 13. In the intermediate operation mode before switching from the low rotation operation mode in which the rotation speed of the high pressure turbo 14 is low to the high rotation operation mode in which the rotation speed of the high pressure turbo 14 is higher than that in the low rotation operation mode, the exhaust bypass valve 32 is in the high pressure turbo 14 The high pressure turbine 14a is opened and closed to increase the pressure difference between the inlet pressure and the outlet pressure.
[Selection] Figure 6

Description

  The present invention relates to an internal combustion engine having a low-pressure turbo and a high-pressure turbo connected in series, and in particular, the response of a high-pressure turbo when switching from an operation mode in which the rotation speed of the high-pressure turbo is low to an operation mode in which the rotation speed of the high-pressure turbo is high. It is related with the apparatus which improves.

As in Patent Document 1, an internal combustion engine having a low-pressure turbo and a high-pressure turbo connected in series and constituting a two-stage turbo system has been proposed. In the two-stage turbo system, the operation mode is switched according to the operation state of the internal combustion engine, and the turbo used for supercharging is selectively used. For example, when the exhaust flow rate is low, the high-pressure turbo is used as the main turbo in an operation mode with a high rotation speed of the high-pressure turbo, and when the exhaust flow rate is high, the operation mode is low with a low-pressure rotation speed of the high-pressure turbo. Turbo is used as the main turbo.
JP 2007-77900 A

  It is necessary to improve the responsiveness when the operation mode is switched, that is, when the turbo starts. For example, when switching from an operation mode in which the rotation speed of the high-pressure turbo is low to an operation mode in which the rotation speed of the high-pressure turbo is high, the rotation speed of the high-pressure turbo is changed to the rotation speed necessary for supercharging corresponding to the operation mode after switching. Although it is desirable to shorten the time for raising, in the conventional two-stage turbo system such as Patent Document 1, the time is not sufficiently shortened and high responsiveness is not ensured.

  Accordingly, an object of the present invention is to provide an apparatus that improves the response of a high-pressure turbo when switching from an operation mode in which the rotation speed of the high-pressure turbo is low to an operation mode in which the rotation speed of the high-pressure turbo is high in a two-stage turbo system. That is.

  An internal combustion engine control apparatus according to the present invention includes a low-pressure turbo, a high-pressure turbo connected in series with the low-pressure turbo, and an exhaust bypass valve provided on a low-pressure turbine bypass passage that bypasses the low-pressure turbine of the low-pressure turbo. In the intermediate operation mode before switching from the low-rotation operation mode in which the rotation speed of the high-pressure turbo is low to the high rotation operation mode in which the rotation speed of the high-pressure turbo is higher than that in the low-rotation operation mode, the exhaust bypass valve is a high-pressure turbo high-pressure turbine Is opened or closed to increase the pressure difference between the inlet pressure and the outlet pressure.

  By setting the exhaust bypass valve to an open / close state different from the normal operation mode, increasing the pressure difference between the inlet pressure and the outlet pressure of the high pressure turbine and making the high pressure turbo easy to rotate, the rotational speed of the high pressure turbo can be reduced. In addition, it is possible to shorten the time required to increase the number of revolutions required for supercharging corresponding to the high-speed operation mode, and it is possible to improve the responsiveness when the high-pressure turbo starts up.

  Preferably, in the intermediate operation mode, the exhaust bypass valve is changed from a small opening degree in the low rotation operation mode to a large opening state, and in the high rotation operation mode, the exhaust bypass valve is in a state in which the opening degree is large in the intermediate operation mode. To a small opening.

  When the exhaust bypass valve opens, that is, when the exhaust bypass valve is in a large state, exhaust gas is likely to be discharged through the low-pressure turbine bypass passage. The outlet pressure of the high-pressure turbine is lower than For this reason, compared with the case where such opening / closing control is not performed, the pressure difference with the inlet pressure of the high pressure turbine in a high pressure state becomes large, and the high pressure turbine is easily rotated. Further, since the exhaust gas is not converted into kinetic energy by the low-pressure turbine, it becomes possible to supply the exhaust gas to the exhaust gas purification catalyst at a high temperature.

  More preferably, it further includes an exhaust control valve provided on a high-pressure turbine bypass passage that bypasses the high-pressure turbine, and in the intermediate operation mode and the high-speed operation mode, the exhaust control valve has a large opening in the low-speed operation mode. To a small opening.

  Since the exhaust control valve closes, that is, the exhaust control valve becomes small, the exhaust gas concentrates on the inlet side of the high-pressure turbine, so the exhaust control valve is open and the exhaust gas is high pressure The inlet pressure of the high-pressure turbine is higher than when it is easy to flow through the turbine bypass passage. For this reason, compared with the case where such opening / closing control is not performed, the pressure difference with the outlet pressure of the high pressure turbine in a low pressure state becomes large, and the high pressure turbine is easily rotated.

  In addition, it preferably further includes an intake bypass valve provided on a high-pressure compressor bypass passage that bypasses the high-pressure compressor of the high-pressure turbo, and the intake bypass valve is opened in the low-speed operation mode in the intermediate operation mode and the high-speed operation mode. From a state with a high degree to a state with a small opening.

  When the intake bypass valve closes, that is, when the intake bypass valve becomes small, intake air concentrates on the inlet side of the high-pressure compressor, so the intake bypass valve is open and the intake air is high pressure. Compared with the case where it is easy to flow through the compressor bypass passage, the air is likely to flow through the high-pressure compressor, that is, the high-pressure turbo is likely to rotate.

  Preferably, the turbine side of the high-pressure turbo has a variable vane whose opening degree is adjusted according to the operation state, and the opening degree of the variable vane is set smaller than that in the low-speed operation mode in the intermediate operation mode. Is done.

  By reducing the opening degree of the variable vane provided in the housing of the high-pressure turbine, the high-pressure turbine rotates at a higher speed than when the opening / closing control is not performed.

  Preferably, an EGR valve provided on an EGR passage for returning a part of the exhaust gas to the intake side is further provided. In the intermediate operation mode, the opening degree of the EGR valve is set smaller than that in the low rotation operation mode. Is done.

  By reducing the opening of the EGR valve, the exhaust gas is less likely to flow through the EGR passage, and the exhaust gas is concentrated on the inlet side of the high-pressure turbine, so the inlet pressure of the high-pressure turbine increases. For this reason, compared with the case where such opening / closing control is not performed, the pressure difference with the outlet pressure of the high pressure turbine in a low pressure state becomes large, and the high pressure turbine is easily rotated.

  Preferably, the turbine side of the low-pressure turbo has a variable vane whose opening degree is adjusted according to the operation state, and the opening degree of the variable vane is set larger than that in the low-speed operation mode in the intermediate operation mode. Is done.

  By increasing the opening degree of the variable vane provided in the housing of the low-pressure turbine, the exhaust gas easily flows into the low-pressure turbine, the exhaust gas is easily discharged, and the outlet pressure of the high-pressure turbine upstream of the exhaust is lowered. For this reason, compared with the case where such opening / closing control is not performed, the pressure difference with the inlet pressure of the high pressure turbine in a high pressure state becomes large, and the high pressure turbine is easily rotated.

  As described above, according to the present invention, in a two-stage turbo system, an apparatus for improving the response of a high-pressure turbo when switching from an operation mode in which the rotation speed of the high-pressure turbo is low to an operation mode in which the rotation speed of the high-pressure turbo is high. Can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The internal combustion engine 1 includes a control unit 5, a low pressure turbo 13, a high pressure turbo 14, an engine body 30, a low pressure compressor inlet side intake passage 51, a low pressure compressor outlet side intake passage (high pressure compressor inlet side intake passage) 52, and a high pressure compressor outlet side intake air. Passage 53, high pressure compressor bypass passage 54, high pressure turbine inlet side exhaust passage 71, high pressure turbine outlet side exhaust passage (low pressure turbine inlet side exhaust passage) 72, low pressure turbine outlet side exhaust passage 73, high pressure turbine bypass passage 74, low pressure turbine bypass A passage 75 and an EGR passage 76 are provided.

  The control unit 5 includes a CPU, a ROM that stores a control program, and a RAM that stores various data. The control unit 5 receives signals from various sensors, and outputs control signals to the exhaust bypass valve 32 and the like to generate an internal combustion engine. It controls each part of the vehicle including the engine 1. In particular, in the present embodiment, the control unit 5 improves the responsiveness of the high-pressure turbo 14 when the high-pressure turbo 14 is switched to the operation mode in addition to the opening / closing control of the exhaust bypass valve 32 and the like corresponding to the operation mode. In other words, in order to shorten the time for the rotation speed of the high-pressure turbine 14a to reach the rotation speed required for supercharging corresponding to the operation mode after switching, an intermediate operation mode is provided, and the inlet pressure of the high-pressure turbine 14a The opening / closing state of the exhaust bypass valve 32 and the like is controlled so that the pressure difference from the outlet pressure is increased and the high-pressure turbo 14 is easily rotated.

  During operation of the internal combustion engine 1, air is sucked into the combustion chambers of the cylinders of the engine body 30 through the low-pressure compressor inlet side intake passage 51 and the like (see dotted arrows in FIGS. 1 to 4). The fuel injected from the injector forms an air-fuel mixture with the sucked air. A crankshaft (not shown) rotates by the reciprocating motion of the piston according to the explosive force caused by the combustion of the air-fuel mixture. Exhaust gas generated by the combustion is discharged through the high-pressure turbine inlet side exhaust passage 71 and the like (see broken line arrows in FIGS. 1 to 4). However, part of the exhaust gas returns to the intake side via the EGR passage 76.

  Next, the configuration of each part of the internal combustion engine 1 will be described focusing on the low pressure turbo 13 and the high pressure turbo 14. The low-pressure turbo 13 and the high-pressure turbo 14 are connected in series, that is, a high-pressure turbo 14 is installed upstream of the low-pressure turbo 13 in the exhaust path.

  The low pressure turbo 13 includes a low pressure turbine 13a and a low pressure compressor 13b, and the high pressure turbo 14 includes a high pressure turbine 14a and a high pressure compressor 14b. The high-pressure turbo 14 is a variable nozzle turbo having a variable vane on the turbine side, and the opening degree of the variable vane is adjusted according to the operating state of the internal combustion engine 1.

  The inlet side of the low pressure compressor 13 b is connected to the low pressure compressor inlet side intake passage 51. The low pressure compressor inlet side intake passage 51 is provided with an air cleaner and an air flow meter (both not shown). The outlet side of the low-pressure compressor 13b is connected to the low-pressure compressor outlet side intake passage 52. The inlet side of the high pressure compressor 14 b is connected to the low pressure compressor outlet side intake passage 52. The outlet side of the high pressure compressor 14 b is connected to a high pressure compressor outlet side intake passage 53 that communicates with an intake manifold (not shown) of the engine body 30.

  Further, a high-pressure compressor bypass passage 54 is provided that communicates the low-pressure compressor outlet side intake passage 52 and the high-pressure turbine outlet side intake passage 53 and bypasses the high-pressure compressor 14b. An intake bypass valve 17 is provided in the high-pressure compressor bypass passage 54. When the intake bypass valve 17 is open, most of the air from the low-pressure compressor 13b flows to the engine body 30 via the high-pressure compressor bypass passage 54, and a part of the air passes through the high-pressure compressor 14b. The main body 30 flows. The amount of air flowing into the high-pressure compressor 14b is adjusted according to the opening degree of the intake bypass valve 17. An intercooler (not shown) and a throttle valve (electronically controlled throttle) 25 are provided downstream of the connection point between the high-pressure compressor outlet side intake passage 53 and the high-pressure compressor bypass passage 54.

  The inlet side of the high pressure turbine 14 a is connected to a high pressure turbine inlet side exhaust passage 71 that communicates with an exhaust manifold (not shown) of the engine body 30. The outlet side of the high pressure turbine 14 a is connected to the high pressure turbine outlet side exhaust passage 72. The inlet side of the low pressure turbine 13 a is connected to the high pressure turbine outlet side exhaust passage 72. The outlet side of the low pressure turbine 13a is connected to a low pressure turbine outlet side exhaust passage 73 that communicates with an exhaust gas purification catalyst (not shown).

  In addition, a high pressure turbine bypass passage 74 is provided that communicates the high pressure turbine inlet side exhaust passage 71 and the high pressure turbine outlet side exhaust passage 72 and bypasses the high pressure turbine 14a. The high pressure turbine outlet side exhaust passage 72 and the low pressure turbine outlet are provided. A low-pressure turbine bypass passage 75 that communicates with the side exhaust passage 73 and bypasses the low-pressure turbine 13a is provided. A connection point on the high pressure turbine outlet side exhaust passage 72 of the high pressure turbine bypass passage 74 is disposed upstream of a connection point on the high pressure turbine outlet side exhaust passage 72 of the low pressure turbine bypass passage 75. The high pressure turbine bypass passage 74 is provided with the exhaust control valve 31, and the low pressure turbine bypass passage 75 is provided with the exhaust bypass valve 32.

  When the exhaust control valve 31 is in an open state, most of the exhaust gas from the engine body 30 flows to the high pressure turbine outlet side exhaust passage 72 via the high pressure turbine bypass passage 74, and a part thereof is the high pressure turbine 14a. To the high pressure turbine outlet side exhaust passage 72. The amount of exhaust gas flowing into the high-pressure turbine 14a is adjusted according to the opening degree of the exhaust control valve 31. When the exhaust bypass valve 32 is in the open state, most of the exhaust gas from the high pressure turbine outlet side exhaust passage 72 flows to the low pressure turbine outlet side exhaust passage 73 via the low pressure turbine bypass passage 75 and is partially Flows into the low-pressure turbine outlet side exhaust passage 73 via the low-pressure turbine 13a. The amount of exhaust gas flowing into the low-pressure turbine 13a is adjusted according to the opening degree of the exhaust bypass valve 32.

  In addition, an EGR passage 76 that communicates the high-pressure turbine inlet-side exhaust passage 71 and the high-pressure compressor outlet-side intake passage 53 and returns part of the exhaust gas discharged from the engine body 30 to the intake side is provided. The EGR passage 76 is provided with an EGR valve 39 that adjusts the amount of return exhaust gas. The opening degree of the EGR valve 39 is adjusted according to the operating state of the internal combustion engine 1.

  Next, the opening / closing states of the valves in the first to fourth operation modes set according to the operation state of the internal combustion engine 1 derived from the engine speed and the like will be described.

  In the two-stage turbo system in the present embodiment, the turbo used for supercharging is selectively used in the first to fourth operation modes corresponding to the operation state of the internal combustion engine 1 derived from the engine speed or the like. When the exhaust flow rate from the engine main body 30 is extremely small, supercharging is performed by the low-pressure turbo 13 and the high-pressure turbo 14 with the rotation speed of the high-pressure turbo 14 being extremely high (see the first operation mode, FIG. 1). In this case, the high pressure turbo 14 becomes the main turbo and supercharging is performed. When the exhaust gas flow rate from the engine main body 30 is small, supercharging is performed by the low pressure turbo 13 and the high pressure turbo 14 while the rotation speed of the high pressure turbo 14 is high (second operation mode, see FIG. 2). In this case, the rotation speed of the high-pressure turbo 14 is lower than that in the first operation mode, and supercharging is performed with the low-pressure turbo 13 serving as the main turbo. When the exhaust flow rate from the engine body 30 is large, supercharging is performed by the low-pressure turbo 13 (third operation mode, see FIG. 3). In this case, the rotation speed of the high-pressure turbo 14 is lower than that in the second operation mode, and supercharging by the high-pressure turbo 14 is hardly performed. When the exhaust flow rate from the engine body 30 is extremely large, supercharging is performed by the low-pressure turbo 13 with some exhaust gas bypassing the low-pressure turbo 13 (see the fourth operation mode, see FIG. 4). Also in this case, the rotational speed of the high-pressure turbo 14 is low as in the third operation mode, and supercharging by the high-pressure turbo 14 is hardly performed. FIG. 5 shows the relationship between the first to fourth operation modes, the engine speed, and the torque in the full load performance graph.

  When operating in the first operation mode, the intake bypass valve 17, the exhaust control valve 31, and the exhaust bypass valve 32 are closed (see FIG. 1). The air sucked through the air cleaner enters the engine body 30 via the low pressure compressor inlet side intake passage 51, the low pressure compressor 13b, the low pressure compressor outlet side intake passage 52, the high pressure compressor 14b, and the high pressure compressor outlet side intake passage 53. (Refer to the thick dotted line in FIG. 1). Exhaust gas from the engine body 30 passes to the exhaust gas purification catalyst via the high pressure turbine inlet side exhaust passage 71, the high pressure turbine 14a, the high pressure turbine outlet side exhaust passage 72, the low pressure turbine 13a, and the low pressure turbine outlet side exhaust passage 73. It is discharged (see thick broken line in FIG. 1). In this case, the air from the low-pressure compressor 13b flows into the high-pressure compressor 14b without bypassing, and the exhaust gas from the engine body 30 flows into the high-pressure turbine 14a without bypassing. Supercharging is performed at a higher pressure ratio than in the mode. On the other hand, since the exhaust flow rate is extremely small, the low-pressure turbine 13a does not rotate at high speed, and the low-pressure compressor 13b performs supercharging at a lower pressure ratio than in the second operation mode.

  When operating in the second operation mode, the exhaust control valve 31 is opened, and the intake bypass valve 17 and the exhaust bypass valve 32 are closed (see FIG. 2). The opening degree of the exhaust control valve 31 is adjusted according to the operating state of the internal combustion engine 1. The air sucked through the air cleaner enters the engine body 30 via the low pressure compressor inlet side intake passage 51, the low pressure compressor 13b, the low pressure compressor outlet side intake passage 52, the high pressure compressor 14b, and the high pressure compressor outlet side intake passage 53. (Refer to the thick dotted line in FIG. 2). Exhaust gas from the engine body 30 is purified through the high pressure turbine inlet side exhaust passage 71, the high pressure turbine bypass passage 74, the high pressure turbine outlet side exhaust passage 72, the low pressure turbine 13a, and the low pressure turbine outlet side exhaust passage 73. It is discharged to the catalyst (see thick broken line in FIG. 2). Further, a part of the exhaust gas is exhausted through a route passing through the high-pressure turbine 13a (see a thin broken line in FIG. 2). In this case, the air from the low-pressure compressor 13b flows into the high-pressure compressor 14b without bypassing, and a part of the exhaust gas from the engine body 30 flows into the high-pressure turbine 14a without bypassing. Pay is done. However, since most of the exhaust gas from the engine body 30 bypasses the high-pressure turbine 14a, the rotation speed of the high-pressure turbo 14 is lower than that in the first operation mode, and the high-pressure compressor 14b has a lower pressure than that in the first operation mode. Supercharging is performed at a ratio. On the other hand, since more exhaust gas flows into the low-pressure turbine 13a than in the first operation mode, the low-pressure compressor 13b performs supercharging at a higher pressure ratio than in the first operation mode.

  When operating in the third operation mode, the intake bypass valve 17 and the exhaust control valve 31 are opened, and the exhaust bypass valve 32 is closed (see FIG. 3). The opening degree of the intake bypass valve 17 and the exhaust control valve 31 is adjusted according to the operating state of the internal combustion engine 1. The air sucked through the air cleaner passes through the low pressure compressor inlet side intake passage 51, the low pressure compressor 13 b, the low pressure compressor outlet side intake passage 52, the high pressure compressor bypass passage 54, and the high pressure compressor outlet side intake passage 53. 30 (see the thick dotted line in FIG. 3). A part of the intake air is supplied to the engine main body 30 through a path passing through the high-pressure compressor 14b (see a thin dotted line in FIG. 3). Exhaust gas from the engine body 30 is purified through the high pressure turbine inlet side exhaust passage 71, the high pressure turbine bypass passage 74, the high pressure turbine outlet side exhaust passage 72, the low pressure turbine 13a, and the low pressure turbine outlet side exhaust passage 73. It is discharged to the catalyst (see thick broken line in FIG. 3). Further, a part of the exhaust gas is discharged through a route passing through the high-pressure turbine 13a (see a thin broken line in FIG. 3). In this case, most of the exhaust gas bypasses the high-pressure turbine 14a, and most of the air from the low-pressure compressor 13b bypasses the high-pressure compressor 14b, so that supercharging by the high-pressure turbo 14 is hardly performed. On the other hand, since the exhaust flow rate is large and more exhaust gas flows into the low-pressure turbine 13a than in the second operation mode, the low-pressure compressor 13b is supercharged at a higher pressure ratio than in the second operation mode.

  When operating in the fourth operation mode, the intake bypass valve 17, the exhaust control valve 31, and the exhaust bypass valve 32 are opened (see FIG. 4). The opening degrees of the intake bypass valve 17, the exhaust control valve 31, and the exhaust bypass valve 32 are adjusted according to the operating state of the internal combustion engine 1. The air sucked through the air cleaner passes through the low pressure compressor inlet side intake passage 51, the low pressure compressor 13 b, the low pressure compressor outlet side intake passage 52, the high pressure compressor bypass passage 54, and the high pressure compressor outlet side intake passage 53. 30 (see the thick dotted line in FIG. 4). A part of the intake air is supplied to the engine main body 30 through a path passing through the high-pressure compressor 14b (see the thin dotted line in FIG. 4). Exhaust gas from the engine main body 30 is exhausted through a high pressure turbine inlet side exhaust passage 71, a high pressure turbine bypass passage 74, a high pressure turbine outlet side exhaust passage 72, a low pressure turbine bypass passage 75, and a low pressure turbine outlet side exhaust passage 73. It is discharged to the gas purification catalyst (see thick broken line in FIG. 4). Further, a part of the exhaust gas is exhausted through a route passing through the high-pressure turbine 13a (see a thin broken line in FIG. 4). A part of the exhaust gas is discharged through a path passing through the low-pressure turbine 13a (see the thin broken line in FIG. 4). In this case, most of the exhaust gas bypasses the high-pressure turbine 14a, and most of the air from the low-pressure compressor 13b bypasses the high-pressure compressor 14b, so that supercharging by the high-pressure turbo 14 is hardly performed. On the other hand, although most of the exhaust gas bypasses the low-pressure turbine 13a, the exhaust flow rate is extremely large and more exhaust gas flows into the low-pressure turbine 13a than in the second operation mode. Supercharging is performed at a higher pressure ratio.

  In the present embodiment, when the high-pressure turbo 14 is switched from the operation mode in which the rotational speed is low to the high operation mode, before the exhaust bypass valve 32 or the like is opened or closed corresponding to the operation mode in the high rotational speed, An operation mode is provided, and the exhaust bypass valve 32 and the like increase the pressure difference between the inlet pressure and the outlet pressure of the high-pressure turbine 14a to make the high-pressure turbo 14 easy to rotate and improve the response of the high-pressure turbo 14. Is opened and closed. Specifically, when switching from the second operation mode to the first operation mode, the exhaust bypass valve 32 and the like are in the first intermediate operation mode (see FIG. 6) before being opened and closed corresponding to the first operation mode. ), And then the open / close state corresponding to the first operation mode. When switching from the third operation mode to the second operation mode, the exhaust bypass valve 32 and the like are opened / closed corresponding to the second intermediate operation mode (see FIG. 7) before being opened / closed corresponding to the second operation mode. Then, an open / close state corresponding to the second operation mode is set. When switching from the third operation mode to the first operation mode, the exhaust bypass valve 32 and the like are opened / closed corresponding to the third intermediate operation mode (see FIG. 8) before being opened / closed corresponding to the first operation mode. After that, an open / close state corresponding to the first operation mode is set.

  In the first intermediate operation mode, the intake bypass valve 17 is maintained in the closed state, the exhaust control valve 31 is changed from the open state to the closed state, and the exhaust bypass valve 32 is changed from the closed state to the open state. When the exhaust control valve 31 is closed, the exhaust gas from the engine body 30 is concentrated on the inlet side of the high-pressure turbine 14a except for the amount of exhaust gas flowing through the EGR passage 76, so that the exhaust control valve 31 is in the open state. The inlet pressure of the high-pressure turbine 14a is higher than Further, since the exhaust bypass valve 32 is opened, the exhaust gas in the high-pressure turbine outlet side exhaust passage 72 is easily discharged to the low-pressure turbine outlet side exhaust passage 73, so that the exhaust bypass valve 32 is in a closed state. In comparison, the outlet pressure of the high-pressure turbine 14a is lowered. Therefore, the pressure difference between the inlet pressure and the outlet pressure of the high-pressure turbine 14a becomes larger than when the opening / closing control is not performed, and the high-pressure turbine 14a is easily rotated. When it is easy to rotate, it becomes possible to shorten the time until the high-pressure turbo 14 is in a high-speed rotation state sufficient to perform supercharging corresponding to the first operation mode, and the responsiveness when the high-pressure turbo 14 starts up. Can be improved. After the high-pressure turbo 14 enters a high-speed rotation state sufficient for supercharging corresponding to the first operation mode, the first operation mode is set. That is, the intake bypass valve 17 is maintained in the closed state, the exhaust control valve 31 is maintained in the closed state, and the exhaust bypass valve 32 is changed from the open state to the closed state.

  In the second intermediate operation mode, the intake bypass valve 17 is changed from the open state to the closed state, the exhaust control valve 31 is maintained in the open state, and the exhaust bypass valve 32 is changed from the closed state to the open state. When the intake bypass valve 17 is closed, the air from the low pressure compressor 13b is concentrated on the inlet side of the high pressure compressor 14b, so that the air is not supplied to the high pressure compressor 14b compared to when the intake bypass valve 17 is in the open state. The state is easy to flow, that is, the high-pressure turbo 14 is likely to rotate. Further, since the exhaust bypass valve 32 is opened, the exhaust gas in the high-pressure turbine outlet side exhaust passage 72 is easily discharged to the low-pressure turbine outlet side exhaust passage 73, so that the exhaust bypass valve 32 is in a closed state. In comparison, the outlet pressure of the high-pressure turbine 14a is lowered. Therefore, the pressure difference between the inlet pressure and the outlet pressure of the high-pressure turbine 14a becomes larger than when the opening / closing control is not performed, and the high-pressure turbine 14a is easily rotated. If it is easy to rotate, it becomes possible to shorten the time until the high-pressure turbo 14 is in a high-speed rotation state sufficient to perform supercharging corresponding to the second operation mode, and the responsiveness when the high-pressure turbo 14 starts up. Can be improved. After the high-pressure turbo 14 enters a high-speed rotation state sufficient to perform supercharging corresponding to the second operation mode, the second operation mode is set. That is, the intake bypass valve 17 is maintained in the closed state, the exhaust control valve 31 is maintained in the open state, and the exhaust bypass valve 32 is changed from the open state to the closed state.

  In the third intermediate operation mode, the intake bypass valve 17 is changed from the open state to the closed state, the exhaust control valve 31 is changed from the open state to the closed state, and the exhaust bypass valve 32 is changed from the closed state to the open state. Is done. When the intake bypass valve 17 is closed, the air from the low pressure compressor 13b is concentrated on the inlet side of the high pressure compressor 14b, so that the air is not supplied to the high pressure compressor 14b compared to when the intake bypass valve 17 is in the open state. The state is easy to flow, that is, the high-pressure turbo 14 is likely to rotate. Further, since the exhaust control valve 31 is closed, the exhaust gas from the engine body 30 is concentrated on the inlet side of the high-pressure turbine 14a except for the amount flowing through the EGR passage 76, so that the exhaust control valve 31 is opened. The inlet pressure of the high-pressure turbine 14a is higher than in some cases. Further, since the exhaust bypass valve 32 is opened, the exhaust gas in the high-pressure turbine outlet side exhaust passage 72 is easily discharged to the low-pressure turbine outlet side exhaust passage 73, so that the exhaust bypass valve 32 is in a closed state. In comparison, the outlet pressure of the high-pressure turbine 14a is lowered. Therefore, the pressure difference between the inlet pressure and the outlet pressure of the high-pressure turbine 14a becomes larger than when the opening / closing control is not performed, and the high-pressure turbine 14a is easily rotated. When it is easy to rotate, it becomes possible to shorten the time until the high-pressure turbo 14 is in a high-speed rotation state sufficient to perform supercharging corresponding to the first operation mode, and the responsiveness when the high-pressure turbo 14 starts up. Can be improved. After the high-pressure turbo 14 enters a high-speed rotation state sufficient for supercharging corresponding to the first operation mode, the first operation mode is set. That is, the intake bypass valve 17 is maintained in the closed state, the exhaust control valve 31 is maintained in the closed state, and the exhaust bypass valve 32 is changed from the open state to the closed state.

  In the first to third intermediate operation modes, the determination as to whether or not the high-pressure turbo 14 has reached a high-speed rotation state sufficient to perform supercharging corresponding to the operation mode after switching is made in the first to third intermediate operation modes. Is performed based on a comparison between an elapsed time from the start of opening / closing control of the exhaust bypass valve 32 corresponding to the above and a time threshold (about 1 to 2 seconds) calculated in advance by experiments or the like. Alternatively, a separate sensor may be provided, which may be performed based on a comparison between the rotation speed of the high-pressure turbo 14 and a rotation speed threshold value or a comparison between the outlet pressure of the high-pressure compressor 14b and the pressure threshold value.

  In the first to third intermediate operation modes, since the exhaust bypass valve 32 is opened, most of the exhaust gas is discharged without being converted into kinetic energy by the low-pressure turbine 13a. For this reason, it becomes possible to supply exhaust gas to the exhaust gas purification catalyst arranged downstream in a high temperature state. Thereby, it becomes easy to maintain a state where the temperature of the exhaust gas purification catalyst is high, that is, a temperature state where the exhaust gas purification action is possible.

  In addition, the time for the exhaust bypass valve 32 and the like to be opened and closed corresponding to the first to third intermediate operation modes is a short time (temporary time) of about 1 to 2 seconds. Therefore, although it differs from the open / closed state of the exhaust bypass valve 32 and the like corresponding to the normal operation mode (first to fourth operation modes), the open / close control of the exhaust bypass valve 32 and the like has little adverse effect on the internal combustion engine 1.

  Further, while the exhaust bypass valve 32 and the like are opened and closed corresponding to the first to third intermediate operation modes, the EGR valve 39 and the housing of the high pressure turbine 14a are provided in order to further rotate the high pressure turbine 14a. You may add the opening degree adjustment of the variable vane. Specifically, by reducing the opening of the EGR valve 39, the exhaust gas hardly flows into the EGR passage 76, and the exhaust gas from the engine body 30 is concentrated on the inlet side of the high-pressure turbine 14a, so that the high-pressure turbine 14a Increase the inlet pressure. Moreover, the opening degree of the variable vane provided in the housing of the high-pressure turbine 14a is reduced.

  When the turbine side of the low-pressure turbo 13 is a variable nozzle turbo having a variable vane, the high-pressure turbine 14a is further set when the exhaust bypass valve 32 and the like are opened and closed corresponding to the first to third intermediate operation modes. In order to facilitate rotation, the opening adjustment of the variable vane provided in the housing of the low-pressure turbine 13a may be added. Specifically, by increasing the opening of the variable vane of the low-pressure turbine 13a, the exhaust gas easily flows into the low-pressure turbine 13a, and the exhaust gas in the high-pressure turbine outlet-side exhaust passage 72 enters the low-pressure turbine outlet-side exhaust passage 73. The outlet pressure of the high-pressure turbine 14a located upstream of the exhaust is lowered by facilitating the discharge.

FIG. 3 is a configuration diagram of an internal combustion engine in which an exhaust control valve and the like in the present embodiment are in an open / closed state corresponding to a first operation mode. FIG. 3 is a configuration diagram of an internal combustion engine in which an exhaust control valve and the like are in an open / closed state corresponding to a second operation mode. FIG. 6 is a configuration diagram of an internal combustion engine in which an exhaust control valve and the like are in an open / closed state corresponding to a third operation mode. FIG. 6 is a configuration diagram of an internal combustion engine in which an exhaust control valve and the like are in an open / closed state corresponding to a fourth operation mode. It is a graph which shows engine full load performance. FIG. 3 is a configuration diagram of an internal combustion engine in which an exhaust control valve or the like is in an open / closed state corresponding to a first intermediate operation mode. FIG. 3 is a configuration diagram of an internal combustion engine in which an exhaust control valve or the like is in an open / closed state corresponding to a second intermediate operation mode. FIG. 5 is a configuration diagram of an internal combustion engine in which an exhaust control valve or the like is in an open / closed state corresponding to a third intermediate operation mode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 5 Control part 13 Low pressure turbo 13a Low pressure turbine 13b Low pressure compressor 14 High pressure turbo 14a High pressure turbine 14b High pressure compressor 17 Intake bypass valve 25 Throttle valve 30 Engine body 31 Exhaust control valve 32 Exhaust bypass valve 39 EGR valve 51 Low pressure compressor inlet side Intake passage 52 Low pressure compressor outlet side intake passage 53 High pressure compressor outlet side intake passage 54 High pressure compressor bypass passage 71 High pressure turbine inlet side exhaust passage 72 High pressure turbine outlet side exhaust passage 73 Low pressure turbine outlet side exhaust passage 74 High pressure turbine bypass passage 75 Low pressure turbine Bypass passage 76 EGR passage

Claims (7)

Low pressure turbo,
A high pressure turbo connected in series with the low pressure turbo;
An exhaust bypass valve provided on a low-pressure turbine bypass passage that bypasses the low-pressure turbine of the low-pressure turbo,
In the intermediate operation mode before switching from the low rotation operation mode in which the rotation speed of the high pressure turbo is low to the high rotation operation mode in which the rotation speed of the high pressure turbo is higher than that in the low rotation operation mode, the exhaust bypass valve is in the high pressure operation mode. A control device for an internal combustion engine with a supercharger, wherein the control device is opened and closed to increase a pressure difference between an inlet pressure and an outlet pressure of a turbo high-pressure turbine. In the intermediate operation mode, the exhaust bypass valve is changed from a small opening state to a large opening state in the low rotation operation mode,
2. The control device according to claim 1, wherein in the high-speed operation mode, the exhaust bypass valve is changed from a state with a large opening to a state with a small opening in the intermediate operation mode. An exhaust control valve provided on a high-pressure turbine bypass passage that bypasses the high-pressure turbine;
3. The control according to claim 2, wherein, in the intermediate operation mode and the high rotation operation mode, the exhaust control valve is changed from a large opening state to a small opening state in the low rotation operation mode. apparatus. An intake bypass valve provided on a high-pressure compressor bypass passage that bypasses the high-pressure compressor of the high-pressure turbo,
3. The control according to claim 2, wherein in the intermediate operation mode and the high rotation operation mode, the intake bypass valve is changed from a large opening state to a small opening state in the low rotation operation mode. apparatus. The turbine side of the high-pressure turbo has a variable vane whose opening degree is adjusted according to the operating state,
2. The control device according to claim 1, wherein in the intermediate operation mode, the opening degree of the variable vane is set smaller than that in the low rotation operation mode. An EGR valve provided on the EGR passage for returning a part of the exhaust gas to the intake side;
2. The control device according to claim 1, wherein in the intermediate operation mode, an opening degree of the EGR valve is set smaller than that in the low rotation operation mode. The turbine side of the low-pressure turbo has a variable vane whose opening is adjusted according to the operating state,
2. The control device according to claim 1, wherein in the intermediate operation mode, the opening degree of the variable vane is set larger than that in the low rotation operation mode.

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