JP6419056B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to control of an internal combustion engine capable of switching between a twin turbo mode using a first supercharger and a second supercharger and a single turbo mode using only a first supercharger.

  2. Description of the Related Art Conventionally, an internal combustion engine that can switch between a twin turbo mode using a first supercharger and a second supercharger and a single turbo mode using only a first supercharger is known.

  Japanese Patent Laying-Open No. 2010-209870 (Patent Document 1) discloses a control device for an internal combustion engine that suppresses a drop in supercharging pressure that occurs when a control mode is switched between a single turbo mode and a twin turbo mode.

  As a supercharger, a variable nozzle turbo that controls the flow rate of exhaust gas to the turbine by providing a plurality of vanes around the turbine and adjusting the vane opening is known.

JP 2010-209870 A

  By the way, in an internal combustion engine in which a first supercharger and a second supercharger are provided in each of two banks such as a V-type engine, in order to switch a control mode between a single turbo mode and a twin turbo mode, There is a case where a switching valve for changing the flow path of the exhaust is provided in an exhaust passage connected to one of the two banks. In this case, the pressure loss in one exhaust passage provided with the switching valve may be larger than the pressure loss in the other exhaust passage. As a result, when operating the internal combustion engine in the twin turbo mode, the rotational speed of one turbocharger provided with a switching valve in the exhaust passage is lower than the rotational speed of the other turbocharger, and surge is generated. May occur.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an internal combustion engine that suppresses the occurrence of a surge during supercharging using a first supercharger and a second supercharger. Is to provide.

  An internal combustion engine according to an aspect of the present invention includes an engine block having a first bank and a second bank, and a first turbine that adjusts the flow rate of exhaust gas to the first turbine, the first compressor, and the first turbine by the vane opening. The first turbocharger including the first variable nozzle mechanism and driving the first turbine by the exhaust gas discharged from the first bank; and the vane flow rate of the exhaust gas to the second turbine, the second compressor, and the second turbine. A second variable nozzle mechanism that adjusts according to the degree of opening, and a second supercharger that drives the second turbine by exhaust gas discharged from the second bank; and exhaust gas discharged from the first bank Provided in the second exhaust passage, a connection passage connecting the first exhaust passage that circulates to the feeder and the second exhaust passage that circulates the exhaust gas discharged from the second bank to the second supercharger, Second A switching valve for blocking the flow of exhaust gas from the tank to the second supercharger, the vane opening of the first variable nozzle mechanism, the vane opening of the second variable nozzle mechanism, and the operation of the switching valve. And a control device for controlling. When operating both the first supercharger and the second supercharger, the control device sets the vane opening degree of the second variable nozzle mechanism to be larger than the vane opening degree of the first variable nozzle mechanism. 2 Controls the opening of the variable nozzle mechanism.

  In this case, when both the first supercharger and the second supercharger are operated, the vane opening degree of the second variable nozzle mechanism is larger than the vane opening degree of the first variable nozzle mechanism. 2 The vane opening degree of the variable nozzle mechanism is controlled. By increasing the vane opening degree of the second variable nozzle mechanism, the pressure loss in the second turbine can be reduced, and the exhaust gas can easily flow. Thereby, the fall of the flow volume of the exhaust gas to a 2nd supercharger can be suppressed. Therefore, since it can operate | move so that the rotation speed of a 1st supercharger and a 2nd supercharger may become comparable, it can suppress that a surge generate | occur | produces in a 2nd supercharger.

  Preferably, the control device determines a vane opening degree of the first variable nozzle mechanism based on a rotational speed and a load of the internal combustion engine, and the determined vane opening degree of the first variable nozzle mechanism depends on the state of the internal combustion engine. The value increased by the increased amount is determined as the vane opening degree of the second variable nozzle mechanism.

  In this case, compared with the case where the vane opening degree of the first variable nozzle mechanism and the vane opening degree of the second variable nozzle mechanism are separately controlled based on the supercharging pressure or the like, in the control of the vane opening degree. Occurrence of hunting due to response delay can be suppressed.

  According to the present invention, when both the first supercharger and the second supercharger are operated, the vane opening degree of the second variable nozzle mechanism is larger than the vane opening degree of the first variable nozzle mechanism. 2 The vane opening degree of the variable nozzle mechanism is controlled. By increasing the vane opening degree of the second variable nozzle mechanism, the pressure loss in the second turbine can be reduced, and the exhaust gas can easily flow. Thereby, the fall of the flow volume of the exhaust gas to a 2nd supercharger can be suppressed. Therefore, since it can operate | move so that the rotation speed of a 1st supercharger and a 2nd supercharger may become comparable, it can suppress that a surge generate | occur | produces in a 2nd supercharger. Therefore, it is possible to provide an internal combustion engine that suppresses the occurrence of surge during supercharging using the first supercharger and the second supercharger.

It is a figure which shows the structure of the internal combustion engine which concerns on this Embodiment. It is a functional block diagram of the control apparatus in this Embodiment. It is a figure for demonstrating the determination method of a target supercharging pressure. It is a figure which shows the relationship between an engine speed and the offset amount of a VN opening degree. It is a timing chart for demonstrating operation | movement of each switching valve at the time of transfer of control mode. It is a flowchart which shows the control processing performed with the control apparatus in this Embodiment. It is a timing chart for demonstrating the change of the control mode according to the change of the target supercharging pressure. It is a timing chart for demonstrating the change of the VN opening degree in a 1st supercharger and a 2nd supercharger.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  FIG. 1 shows a schematic configuration of the engine 10. In the present embodiment, engine 10 is an internal combustion engine having two banks. The engine 10 may be, for example, a V-type engine or a horizontally opposed engine. The engine 10 may be a gasoline engine or a diesel engine.

  As shown in FIG. 1, the engine 10 includes a first bank 12, a second bank 14, a first fuel injection device 17, a second fuel injection device 19, a first intake manifold 20, and a second intake manifold. 22, a first exhaust manifold 24, a second exhaust manifold 26, a first supercharger 50, a second supercharger 52, a connection passage 30, and a control device 200.

  The first bank 12 and the second bank 14 are provided in the engine block of the engine 10. The first bank 12 is provided with one or more circular holes as the cylinders 16. A cylinder head in which an intake port and an exhaust port are formed is provided at the top of the cylinder 16 of the first bank 12. A first fuel injection device 17 is provided at the intake port. The first fuel injection device 17 injects fuel into the intake port based on the control signal of the control device 200. The first fuel injection device 17 may be provided so that fuel can be directly injected into the cylinder 16.

  The second bank 14 is provided with one or more circular holes as cylinders 18. A cylinder head in which an intake port and an exhaust port are formed is provided at the top of the cylinder 18 of the second bank 14. A second fuel injection device 19 is provided at the intake port. The second fuel injection device 19 injects fuel into the intake port based on the control signal of the control device 200. The second fuel injection device 19 may be provided so that fuel can be directly injected into the cylinder 18.

  A first intake manifold 20 is connected to the intake port of the first bank 12. A first exhaust manifold 24 is connected to the exhaust port of the first bank 12. A second intake manifold 22 is connected to the intake port of the second bank 14. A second exhaust manifold 26 is connected to the exhaust port of the second bank 14. The first exhaust manifold 24 and the second exhaust manifold 26 are connected so as to communicate with each other through a connection passage 30.

  The first exhaust manifold 24 is connected to one end of the exhaust passage 37. A first supercharger 50 is connected to the other end of the exhaust passage 37. The first supercharger 50 includes a compressor 50a, a turbine 50b, and a variable nozzle mechanism 50c.

  One end of the intake passage 32 is connected to the intake port of the compressor 50a. One end of the intake passage 33 is connected to the discharge port of the compressor 50a. The other end of the intake passage 32 is connected to an air cleaner via a throttle valve. A compressor wheel is accommodated in the housing of the compressor 50a.

  The other end of the exhaust passage 37 is connected to the suction port of the turbine 50b. One end of the exhaust passage 38 is connected to the discharge port of the turbine 50b. A turbine wheel is accommodated in the housing of the turbine 50b. The compressor wheel and the turbine wheel are connected by a connecting shaft and rotate integrally. Therefore, the compressor wheel is rotationally driven by the exhaust energy of the exhaust gas supplied to the turbine wheel. As the compressor wheel is driven to rotate, the intake air flowing through the intake passage 32 is compressed. The air compressed in the compressor 50 a is supplied to the intake passage 33.

  The variable nozzle mechanism 50c is disposed at an exhaust inflow portion around the rotation axis of the turbine wheel, and includes a plurality of vanes that guide exhaust gas supplied from the first exhaust manifold 24 to the turbine wheel, and each of the plurality of vanes. And an actuator that changes a gap between adjacent vanes (in the following description, this gap is described as a VN opening or a vane opening). The actuator is an electric motor or a hydraulic actuator, and changes the VN opening of the variable nozzle mechanism 50c in accordance with a control signal from the control device 200.

  By changing the VN opening of the variable nozzle mechanism 50c, the flow path of the exhaust gas in the exhaust inflow portion is narrowed or expanded. Thereby, the flow velocity of the exhaust gas sprayed on the turbine wheel can be changed.

  The second exhaust manifold 26 is connected to one end of the exhaust passage 39. A second supercharger 52 is connected to the other end of the exhaust passage 39. The second supercharger 52 includes a compressor 52a, a turbine 52b, and a variable nozzle mechanism 52c.

  One end of the intake passage 34 is connected to the intake port of the compressor 52a. One end of the intake passage 35 is connected to the discharge port of the compressor 52a. The other end of the intake passage 34 joins the intake passage 32 and is connected to an air cleaner via a throttle valve. A compressor wheel is accommodated in the housing of the compressor 52a.

  The other end of the exhaust passage 39 is connected to the suction port of the turbine 52b. One end of the exhaust passage 40 is connected to the discharge port of the turbine 52b. A turbine wheel is accommodated in the housing of the turbine 52b. The compressor wheel and the turbine wheel are connected by a connecting shaft and rotate integrally. Therefore, the compressor wheel is rotationally driven by the exhaust energy of the exhaust gas supplied to the turbine wheel. As the compressor wheel is driven to rotate, the intake air passing through the intake passage 34 is compressed. The air compressed in the compressor 52 a is supplied to the intake passage 35.

  The other end of the intake passage 33 and the other end of the intake passage 35 are connected to one end of the intake passage 36. The other end of the intake passage 36 is branched and connected to each of the first intake manifold 20 and the second intake manifold 22.

  The exhaust passage 39 is provided with an ECV (Exhaust Control Valve) 60. In the ECV 60, the one end and the other end of the exhaust passage 39 are brought into a communication state by opening the valve body according to a control signal from the control device 200, or the valve body is in the closed state. To shut off. When the one end and the other end of the exhaust passage 39 are in communication with each other, the exhaust gas in the second exhaust manifold 26 flows through the exhaust passage 40 via the turbine 52b and passes through the turbine wheel of the turbine 52b. Rotate.

  On the other hand, when one end of the exhaust passage 39 is cut off from the other end, the exhaust gas in the second exhaust manifold 26 cannot pass through the exhaust passage 39, and therefore the first passage via the connection passage 30. It distribute | circulates to the exhaust manifold 24 and rotates the turbine wheel of the turbine 50b.

  The intake passage 35 is provided with an ACV (Air Control Valve) 64. The ACV 64 is connected between the one end and the other end of the intake passage 35 according to a control signal from the control device 200 when the valve body is opened, or the valve body is closed. To shut off. When the one end and the other end of the intake passage 35 are in communication with each other, the compressed air from the compressor 52a can flow.

  On the other hand, when the gap between one end and the other end of the intake passage 35 is cut off, the flow of compressed air from the compressor 52a is cut off.

  A bypass passage 42 is provided between the intake passage 34 and the intake passage 35 to allow air to flow between the intake passage 34 and the intake passage 35 without passing through the compressor 52a. In the middle of the bypass passage 42, an IBV (Intake Bypass Valve) 62 is provided. The IBV 62 opens the valve body between the one end and the other end of the bypass passage 42 according to a control signal from the control device 200 to make it open, or makes the valve body close. To shut off. When the one end and the other end of the bypass passage 42 are in communication with each other, air can flow between the intake passage 34 and the intake passage 35. Therefore, for example, when the ACV 64 is in a state of blocking between the one end and the other end of the intake passage 35, the air supplied from the compressor 52a to the intake passage 35 does not pass through the intake passage 35, and the bypass passage 42 It is possible to circulate through the intake passage 34 via the. Therefore, when the control mode to be described later is switched, the flow of air through the bypass passage 42 is prevented so that the supercharging is not performed until the rotation speed of the turbine wheel of the second supercharger 52 rises to an appropriate value. Can be formed.

  On the other hand, when the gap between one end and the other end of the bypass passage 42 is cut off, the compressed air is supplied to the intake passage 35 from the compressor 52a. Therefore, for example, when the ACV 64 communicates between one end and the other end of the intake passage 35, the air supplied from the compressor 52a to the intake passage 35 passes through the intake passage 35 and the intake passage 36. It is supplied to each of the first intake manifold 20 and the second intake manifold 22.

  An engine speed sensor 206 is provided on the crankshaft of the engine 10. The engine speed sensor 206 detects the rotational speed of the crankshaft (hereinafter referred to as engine speed) Ne. The engine speed sensor 206 transmits a signal indicating the detected engine speed Ne to the control device 200.

  A supercharging pressure sensor 208 is provided at a position where the other end passage of the intake passage 36 branches. The supercharging pressure sensor 208 detects the pressure (supercharging pressure) Pb in the intake passage 36. The supercharging pressure sensor 208 transmits a signal indicating the detected supercharging pressure Pb to the control device 200.

  The control device 200 receives signals indicating the state of the engine 10 such as the engine speed Ne received from the engine speed sensor 206 and the boost pressure Pb received from the boost pressure sensor 208, and receives the received engine 10. The operation of the first fuel injection device 17, the second fuel injection device 19, the first supercharger 50, the second supercharger 52, the ECV 60, the IBV 62, and the ACV 64 is controlled based on a signal indicating the state of the above.

  Specifically, the control device 200 selects one of the single turbo mode and the twin turbo mode based on the load of the engine 10 and the engine speed Ne, and sets the selected control mode. Accordingly, the operations of the first supercharger 50, the second supercharger 52, the ECV 60, the IBV 62, and the ACV 64 are controlled.

  The single turbo mode is a control mode in which supercharging is performed using only the first supercharger 50. The twin turbo mode is a control mode in which supercharging is performed using both the first supercharger 50 and the second supercharger 52.

  For example, when the single turbo mode is selected, the control device 200 controls the ECV 60 so that the gap between the one end and the other end of the exhaust passage 39 is cut off, and the one end and the other end of the bypass passage 42 are The IBV 62 is controlled so as to be in a communication state, and the ACV 64 is controlled so that a gap between one end and the other end of the intake passage 35 is in a disconnected state.

  By controlling the ECV 60, the IBV 62, and the ACV 64 in the single turbo mode as described above, the exhaust gas discharged from the second bank 14 to the second exhaust manifold 26 passes through the connection passage 30 to the first The exhaust manifold 24 is distributed. Therefore, the exhaust gas discharged from both the first bank 12 and the second bank 14 is supplied to the turbine 50b of the first supercharger 50.

  The compressor 50 a of the first supercharger 50 compresses the air from the intake passage 32 by the rotation of the turbine wheel of the turbine 50 b and supplies the compressed air to the intake passage 33. The air supplied to the intake passage 33 is supplied to each of the first intake manifold 20 and the second intake manifold 22 via the intake passage 36.

  On the other hand, the one end and the other end of the bypass passage 42 are in a communicating state. Therefore, the air supplied from the compressor 52 a to the intake passage 35 can be circulated to the intake passage 34 via the bypass passage 42.

  On the other hand, for example, when twin turbo mode is selected, control device 200 controls EVC 60 so that the one end and the other end of exhaust passage 39 are in communication with each other, and one end and the other end of bypass passage 42 are connected. The IBV 62 is controlled so as to be in a disconnected state with respect to the end, and the ACV 64 is controlled so that a communication state is established between one end and the other end of the intake passage 35.

  By controlling the ECV 60, the IBV 62, and the ACV 64 in the twin turbo mode as described above, the exhaust gas discharged from the second bank 14 to the second exhaust manifold 26 passes through the exhaust passage 39 to the turbine 52b. To rotate the turbine wheel of the turbine 52b. As a result, the compressor wheel of the compressor 52 a rotates, and the air from the intake passage 34 is compressed and supplied to the intake passage 35.

  On the other hand, the exhaust gas discharged from the first bank 12 to the first exhaust manifold 24 is supplied to the turbine 50b and rotates the turbine wheel of the turbine 50b. As a result, the compressor wheel of the compressor 50 a rotates, and the air from the intake passage 32 is compressed and supplied to the intake passage 33.

  The air supplied to each of the intake passage 33 and the intake passage 35 joins at one end of the intake passage 36 and then branches again at the other end of the intake passage 36, so that the first intake manifold 20 and the second intake manifold 22 Supplied to each.

  In the engine 10 having the above-described configuration, in order to switch the control mode between the single turbo mode and the twin turbo mode as described above and change the exhaust flow path, the ECV 60 that is a switching valve is exhausted. It is necessary to provide in the passage 39. However, when the ECV 60 is provided in the exhaust passage 39, the pressure loss may be greater in the exhaust passage 39 than in the exhaust passage 37. Therefore, the rotational speed of the turbine wheel of the second supercharger 52 connected to the exhaust passage 39 may be lower than the rotational speed of the turbine wheel of the first supercharger 50. As a result, in the intake passage 33 and the intake passage 35, the supercharging pressure is increased by the operation of the first supercharger 50, while the second supercharger 52 is appropriate due to the decrease in the exhaust flow rate of the exhaust passage 39. There is a case where a so-called surge that cannot be supercharged occurs.

  Therefore, in the present embodiment, when the control device 200 operates both the first supercharger 50 and the second supercharger 52, the VN opening degree of the variable nozzle mechanism 52c is the VN of the variable nozzle mechanism 50c. It is assumed that the VN opening degree of the variable nozzle mechanism 52c is controlled to be larger than the opening degree.

  If it does in this way, pressure loss in turbine 52b can be reduced and it will become easy to distribute exhaust gas from turbine 52b to exhaust passage 40. Therefore, it is possible to suppress a decrease in the flow rate of the exhaust gas to the second supercharger 52 and suppress the occurrence of a surge in the second supercharger 52.

  FIG. 2 shows a functional block diagram of a control device 200 that controls the operation of the engine 10 according to the present embodiment. Control device 200 includes a target boost pressure calculation unit 250, a target boost pressure determination unit 252, a VN opening determination unit 254, a VN opening control unit 256, and a switching valve control unit 258. In addition, these structures may be implement | achieved by software, such as a program, and may be implement | achieved by hardware.

  The target boost pressure calculation unit 250 calculates the first target boost pressure Pbts for the single turbo mode based on the engine speed Ne and the load (specifically, the fuel injection amount Af). The target supercharging pressure calculation unit 250 calculates the first target supercharging pressure Pbts using, for example, a map showing the relationship among the engine speed Ne, the fuel injection amount Af, and the first target supercharging pressure Pbts.

  The target boost pressure calculation unit 250 further calculates a second target boost pressure Pbtt for the twin turbo mode based on the engine speed Ne and the fuel injection amount Af. The target supercharging pressure calculation unit 250 calculates the second target supercharging pressure Pbtt using, for example, a map showing the relationship among the engine speed Ne, the fuel injection amount Af, and the second target supercharging pressure Pbtt.

  Note that the target boost pressure calculation unit 250 determines the fuel injection amount Af based on, for example, the accelerator opening, the throttle opening, and the intake air amount.

  The target supercharging pressure determining unit 252 compares the first target supercharging pressure Pbts and the second target supercharging pressure Pbtt, and determines the larger one as the target supercharging pressure Pbt. For example, FIG. 3 shows a change between the first target boost pressure Pbts and the second target boost pressure Pbtt. The horizontal axis in FIG. 3 indicates time, and the vertical axis in FIG. 3 indicates supercharging pressure.

  As shown in FIG. 3, in the period before time T (0), the first target boost pressure Pbts (broken line in FIG. 3) is higher than the second target boost pressure Pbtt (thin solid line in FIG. 3). large. Therefore, in the period, the first target boost pressure Pbts is determined as the target boost pressure Pbt (thick solid line in FIG. 3).

  On the other hand, in the period after time T (0), the second target boost pressure Pbtt is greater than the first target boost pressure Pbts. Therefore, in the period, the second target boost pressure Pbtt is determined as the target boost pressure Pbt.

  Returning to FIG. 2, the VN opening determination unit 254 determines the VN opening D (1) of the variable nozzle mechanism 50c and the VN opening D (2) of the variable nozzle mechanism 52c. In the present embodiment, the VN opening determination unit 254 determines the VN opening D (1) of the variable nozzle mechanism 50c when the first target boost pressure Pbts is determined as the target boost pressure Pbt. Then, the determined same VN opening is determined as the VN opening D (2) of the variable nozzle mechanism 52c.

  The VN opening determination unit 254 is, for example, the difference between the base opening based on the engine speed Ne and the fuel injection amount Af, and the actual boost pressure Pbr detected by the boost pressure sensor 208 and the target boost pressure Pbt. VN opening D (1) is calculated by adding a feedback correction value based on (for example, a correction value by PID control). The VN opening determination unit 254 determines the base opening using, for example, a map showing the relationship among the engine speed Ne, the fuel injection amount Af, and the base opening. The map is adapted by, for example, experiments.

  In the map, the engine speed Ne and the base opening are set such that, for example, the base opening increases as the engine speed Ne increases, and the base opening decreases as the engine speed Ne decreases. In the map, the fuel injection amount Af and the base opening are set such that, for example, the base opening increases as the fuel injection amount Af increases, and the base opening decreases as the fuel injection amount Af decreases. . In the map, in a region where the engine speed Ne is low, a region where the base opening becomes a constant value regardless of the fuel injection amount Af may be set.

  In the present embodiment, when the second target boost pressure Pbtt is determined as the target boost pressure Pbt, the VN opening determination unit 254 determines the VN opening D (1) of the variable nozzle mechanism 50c and the VN The offset amount C from the opening degree D (1) is determined, and the VN opening degree D (2) of the variable nozzle mechanism 52c is determined by adding the offset amount C to the determined VN opening degree D (1). .

  For example, as described above, the VN opening determination unit 254 includes a base opening based on the engine speed Ne and the fuel injection amount Af, the actual boost pressure Pbr detected by the boost pressure sensor 208, and the target boost pressure. The VN opening degree D (1) is calculated by adding the feedback correction value based on the difference from Pbt. The VN opening determination unit 254 determines the base opening using, for example, a map. Since the map is as described above, detailed description thereof will not be repeated.

  The VN opening determination unit 254 further determines an offset amount C from the VN opening D (1) based on the engine speed Ne.

  For example, as shown in FIG. 4, the VN opening determination unit 254 uses an map indicating the relationship between the engine speed Ne and the offset amount C to offset the variable nozzle mechanism 52c from the VN opening D (1). C is determined. The map is adapted by, for example, experiments.

  The horizontal axis in FIG. 4 indicates the engine speed Ne, and the vertical axis in FIG. As shown in FIG. 4, when the engine speed Ne is Ne (0), the offset amount C is set to zero. When the engine speed Ne is Ne (1) larger than Ne (0), the offset amount C is set to C (1). When the engine speed Ne is Ne (3) larger than Ne (1), the offset amount C is C (0) smaller than C (1).

  The map shown in FIG. 4 is an example, and is not particularly limited to the map shown in FIG. The offset amounts C (0) and C (1) indicate the amount of increase from the VN opening D (1) of the variable nozzle mechanism 52c.

  The VN opening determining unit 254 determines a value obtained by adding the offset amount C to the determined VN opening D (1) of the variable nozzle mechanism 50c as the VN opening D (2) of the variable nozzle mechanism 52c.

  The VN opening degree control unit 256 generates the VN control signal (1) so as to be the VN opening degree D (1) determined by the VN opening degree determination unit 254, and varies the generated VN control signal (1). It transmits to the drive circuit of the actuator of the nozzle mechanism 50c. The actuator of the variable nozzle mechanism 50c is driven by the drive circuit. Further, the VN opening degree control unit 256 generates the VN control signal (2) so as to be the VN opening degree D (2) determined by the VN opening degree determination unit 254, and the generated VN control signal (2). Is transmitted to the actuator drive circuit of the variable nozzle mechanism 52c. The actuator of the variable nozzle mechanism 52c is driven by the drive circuit.

  For example, when the first target supercharging pressure Pbts is higher than the second target supercharging pressure Pbtt, the switching valve control unit 258 selects the single turbo mode. When the second target boost pressure Pbtt is higher than the first target boost pressure Pbts, the switching valve control unit 258 selects the twin turbo mode.

  When the second target boost pressure Pbtt becomes higher than the first target boost pressure Pbts during the selection of the single turbo mode, the switching valve control unit 258 switches the mode from the single turbo mode to the twin turbo mode. After passing, the control mode is shifted to the twin turbo mode.

  If the first target boost pressure Pbts becomes higher than the second target boost pressure Pbtt during the selection of the twin turbo mode, the switching valve control unit 258 switches the mode from the twin turbo mode to the single turbo mode. After passing through, the control mode is shifted to the single turbo mode.

  The switching valve control unit 258 controls the operation of the ECV 60, IBV 62, and ACV 64 according to the control mode. Specifically, the switching valve control unit 258 generates an ECV control signal for controlling the ECV 60 according to the control mode, an IBV control signal for controlling the IBV 62, and an ACV control signal for controlling the ACV 64. The generated ECV control signal, the IBV control signal, and the ACV control signal are transmitted to the respective drive circuits of ECV60, IBV62, and ACV64. ECV60, IBV62, and ACV64 are driven by each drive circuit.

  Hereinafter, an example of the control of the ECV 60, the IBV 62, and the ACV 64 according to the control mode that is executed by the switching valve control unit 258 will be described with reference to FIG. As shown in FIG. 5, during the selection of the single turbo mode, the switching valve control unit 258 controls each switching valve so that both the ECV 60 and the ACV 64 are closed and the IBV 62 is opened.

  For example, when the second target boost pressure Pbtt becomes higher than the first target boost pressure Pbts at time T (1), the switching valve control unit 258 switches from the single turbo mode to the twin turbo mode. Select. In this case, the switching valve control unit 258 switches the ECV 60 from the closed state to the open state, and maintains the closed state of the ACV 64 and the open state of the IBV 62. When the ECV 60 is in the open state, exhaust gas flows from the second exhaust manifold through the exhaust passage 39 to the turbine 52b, so that the turbine wheel of the turbine 52b rotates. At this time, the air compressed in the compressor 52 a is circulated to the intake passage 34 via the bypass passage 42.

  At time T (2), the switching valve control unit 258 switches the ACV 64 from the closed state to the open state and switches the IBV 62 from the open state when the rotational speed of the turbine wheel increases to an appropriate rotational speed for supercharging. By switching to the closed state, transition to the twin turbo mode is made. At this time, the air compressed in the compressor 52 a is supplied to the intake passage 35. That is, supercharging is performed using the first supercharger 50 and the second supercharger 52.

  When the first target boost pressure Pbts becomes higher than the second target boost pressure Pbtt at time T (3), the switching valve control unit 258 switches the mode from the twin turbo mode to the single turbo mode. select. In this case, the switching valve control unit 258 switches the IBV 62 from the closed state to the open state, and maintains the ECV 60 open state and the ACV 64 open state. When the IBV 62 is opened, the air supplied from the compressor 52a to the intake passage 35 can flow through the bypass passage 42.

  At time T (4), the switching valve control unit 258 shifts to the single turbo mode by switching the ACV 64 from the open state to the closed state. When the ACV 64 is in a closed state, a gap between one end and the other end of the intake passage 35 is cut off.

  At time T (5), the switching valve control unit 258 switches the ECV 60 from the open state to the closed state. Thereby, the exhaust gas discharged from the second bank 14 to the second exhaust manifold 26 flows through the connection passage 30 and the first exhaust manifold 24 to the turbine 50 b. That is, supercharging is performed using the first supercharger 50.

  With reference to FIG. 6, the control process performed by the control apparatus 200 mounted in the engine 10 according to the present embodiment will be described.

  In step (hereinafter, step is described as S) 100, control device 200 calculates first target boost pressure Pbts and second target boost pressure Pbtt.

  In S102, control device 200 determines whether or not first target boost pressure Pbts is greater than second target boost pressure Pbtt. When it is determined that first target boost pressure Pbts is greater than second target boost pressure Pbtt (YES in S102), the process proceeds to S104. If not (NO in S102), the process proceeds to S108.

  In S104, control device 200 determines first target boost pressure Pbts as target boost pressure Pbt. In S106, control device 200 determines VN opening degree D (1) in variable nozzle mechanism 50c of first supercharger 50. In addition, the control apparatus 200 determines the VN opening degree D (2) in the variable nozzle mechanism 52c of the 2nd supercharger 52 to the same value as the VN opening degree D (1).

  In S108, control device 200 determines second target boost pressure Pbtt as target boost pressure Pbt. In S110, control device 200 determines VN opening degree D (1) in variable nozzle mechanism 50c of first supercharger 50. In S112, control device 200 determines offset amount C based on engine speed Ne. In S114, the control device 200 adds the determined offset amount C to the VN opening D (1) in the variable nozzle mechanism 50c of the first supercharger 50 to add the variable nozzle mechanism of the second supercharger 52. The VN opening degree D (2) at 52c is determined. In S116, control device 200 controls first supercharger 50 and second supercharger 52 so that the determined VN opening degree is obtained. In S118, control device 200 executes control of the switching valve according to the control mode.

  The operation of control apparatus 200 for engine 10 according to the present embodiment based on the above-described structure and flowchart will be described with reference to FIGS. 7 and 8. For example, it is assumed that a vehicle on which the engine 10 is mounted travels.

  The horizontal axis in FIG. 7 represents time, and the vertical axis in FIG. 7 represents the control mode, the engine speed Ne, the fuel injection amount Af, and the supercharging pressure Pb. The horizontal axis in FIG. 8 indicates time, and the vertical axis in FIG. 8 indicates the VN opening.

  As shown in FIG. 7, for example, the single turbo mode is selected, and the engine speed Ne, the fuel injection amount Af, and the supercharging pressure Pb are the engine speed, fuel injection amount, and supercharging pressure corresponding to the idle state, respectively. Assume a case.

  When the driver depresses the accelerator pedal at time T (6), the engine speed Ne and the fuel injection amount Af increase, and the vehicle starts. At this time, the first target boost pressure Pbts and the second target boost pressure Pbtt are calculated based on the engine speed Ne and the fuel injection amount Af (S100).

  When first target boost pressure Pbts is higher than second target boost pressure Pbtts (YES in S102), first target boost pressure Pbts is determined as target boost pressure Pbt (S104). Therefore, a feedback correction value based on the difference between the actual boost pressure Pbr and the target boost pressure Pbt is added to the base opening based on the engine speed Ne and the fuel injection amount Af, and the VN opening of the variable nozzle mechanism 50c. D (1) is determined (S106). The variable nozzle mechanism 50c of the first supercharger 50 is controlled so that the determined VN opening degree D (1) is obtained (S116).

  When the first target boost pressure Pbts is higher than the second target boost pressure Pbtt, the single turbo mode is selected as the control mode. Therefore, as described with reference to FIG. 5, both ECV 60 and ACV 64 are closed, and IBV 62 is opened (S118).

  When second target boost pressure Pbtt becomes higher than first target boost pressure Pbts at time T (7) (NO in S102), second target boost pressure Pbtt is equal to target boost pressure Pbt. (S108). Therefore, the value obtained by adding the feedback correction value based on the difference between the actual boost pressure Pbr and the target boost pressure Pbt to the base opening based on the engine speed Ne and the fuel injection amount Af is the variable nozzle mechanism 50c. VN opening degree D (1) is determined (S110). Then, the offset amount C is determined based on the engine speed Ne (S112). A value obtained by adding the offset amount C to the VN opening D (1) is determined as the VN opening D (2) of the variable nozzle mechanism 52c (S114). The VN opening degree of the variable nozzle mechanism 50c of the first supercharger 50 is controlled so that the determined VN opening degree D (1) is obtained, and the first VN opening degree D (2) is obtained. The VN opening of the variable nozzle mechanism 52c of the two supercharger 52 is controlled (S116).

  When the second target supercharging pressure Pbtt is higher than the first target supercharging pressure Pbts, the transition mode from the single turbo mode to the twin turbo mode is selected as the control mode, and the switching valve control is executed (S118). ). That is, in the transition mode from the single turbo mode to the twin turbo mode, the ECV 60 is switched from the closed state to the open state as described with reference to FIG. When the ECV 60 is switched to the open state, exhaust gas flows from the second exhaust manifold 26 to the turbine 52b, so that the turbine wheel of the turbine 52b starts to rotate.

  Since the ACV 64 is in the closed state and the IBV 62 is in the open state, the air compressed in the compressor 52 a is circulated from the intake passage 35 to the intake passage 34 via the bypass passage 42.

  At times T (7) to (8), as shown in FIG. 7, the engine speed Ne increases with time. Therefore, the offset amount C increases with the passage of time, and as shown by the solid and broken lines in FIG. 8, the VN opening of the variable nozzle mechanism 50c and the VN opening of the variable nozzle mechanism 52c are , It will diverge.

  At time T (8), the control mode is shifted to the twin turbo mode at the timing when the rotation speed of the second supercharger 52 becomes an appropriate rotation speed. Therefore, as described with reference to FIG. 5, the IBV 62 is switched from the open state to the closed state, and the ACV 64 is switched from the closed state to the open state.

  From time T (8) to time (9), the VN opening D (2) of the variable nozzle mechanism 52c shown by the broken line in FIG. 8 is equal to the VN opening D (1) of the variable nozzle mechanism 50c shown by the solid line in FIG. ) Larger than the offset amount C.

  When the VN opening degree D (2) becomes larger than the VN opening degree D (1), the pressure loss in the turbine 52b is lower than the pressure loss in the turbine 50b. As a result, the exhaust flow rate in the turbine 52b is approximately the same as the exhaust flow rate in the turbine 50b. Therefore, the rotation speed of the 1st supercharger 50 and the rotation speed of the 2nd supercharger 52 become comparable. Thereby, generation | occurrence | production of the surge in the 2nd supercharger 52 is suppressed.

  Returning to FIG. 7, when the first target boost pressure Pbts becomes higher than the second target boost pressure Pbtts at time T (9) (YES in S102), the first target boost pressure Pbts. Is determined as the target boost pressure Pbt (S104). Therefore, the VN opening D (1) of the variable nozzle mechanism 50c is determined (S106). The variable nozzle mechanism 50c of the first supercharger 50 is controlled so that the determined VN opening degree D (1) is obtained (S116).

  When the first target boost pressure Pbts is higher than the second target boost pressure Pbtt, the transition mode from the twin turbo mode to the single turbo mode is selected as the control mode, and the switching valve control is executed (S118). ). In the transition mode from the twin turbo mode to the single turbo mode, as described with reference to FIG. 5, the IBV 62 is switched from the closed state to the open state. By switching the IBV 62 from the closed state to the open state, the air compressed in the compressor 52 a can circulate from the intake passage 35 to the intake passage 34 via the bypass passage 42.

  From time T (9) to (10), as shown in FIG. 7, the engine speed Ne decreases with time. Therefore, the offset amount C decreases with the passage of time, and the VN opening D (1) of the variable nozzle mechanism 50c and the VN opening of the variable nozzle mechanism 52c are opened as shown by the solid line and the broken line in FIG. The degree is getting closer.

  At time T (10), the ACV 64 is switched from the open state to the closed state, and shifts to the single turbo mode. Thereafter, the ECV 60 is switched from the open state to the closed state.

  As described above, according to engine 10 according to the present embodiment, when both first supercharger 50 and second supercharger 52 are operated, the VN opening degree of variable nozzle mechanism 52c is variable nozzle mechanism. The VN opening of the variable nozzle mechanism 52c is controlled to be larger than the VN opening of 50c. By increasing the VN opening of the variable nozzle mechanism 52c, the pressure loss in the turbine 52b can be reduced, and the exhaust gas can easily flow from the turbine 52b to the exhaust passage 40. Thereby, the fall of the flow volume of the exhaust gas to the 2nd supercharger 52 can be suppressed. Therefore, since it can operate | move so that the rotation speed of the 1st supercharger 50 and the 2nd supercharger 52 may become comparable, it can suppress that a surge generate | occur | produces in the 2nd supercharger 52. . Therefore, it is possible to provide an internal combustion engine that suppresses the occurrence of surge during supercharging using the first supercharger and the second supercharger.

  Further, the VN opening of the variable nozzle mechanism 50c is determined based on the engine speed Ne and the fuel injection amount Af, and the determined VN opening of the variable nozzle mechanism 50c is increased by an increase corresponding to the state of the engine 10. The determined value is determined as the VN opening degree of the variable nozzle mechanism 52c. Thereby, compared with the case where the VN opening degree of the variable nozzle mechanism 50c and the VN opening degree of the variable nozzle mechanism 52c are controlled separately based on the supercharging pressure or the like, it is caused by a response delay in the control of the VN opening degree. It is possible to suppress the occurrence of hunting.

Hereinafter, modified examples will be described.
In the above-described embodiment, the control mode is changed depending on the magnitude of the first target boost pressure and the second target boost pressure. However, the first target boost pressure and the second target boost pressure Hysteresis may be set for comparison.

  In the above-described embodiment, the offset amount C has been described as being determined based on the engine speed Ne. For example, the offset amount C is determined based on the engine speed Ne and the load (that is, the fuel injection amount Af). Also good. In this case, for example, the value of the offset amount C may be increased as the fuel injection amount A is increased.

  In the above-described embodiment, the switching valve control is executed after the VN opening degree control is executed. However, the switching is performed based on the comparison result between the first target boost pressure and the second target boost pressure. The valve control only needs to be executed, and is not limited to the execution after the VN opening degree control is executed.

  In the above-described embodiment, in the single turbo mode, the VN opening D (2) of the variable nozzle mechanism 52c has been described as having the same value as the VN opening D (1) of the variable nozzle mechanism 50c. In particular, it is not limited to the same value as the VN opening degree D (1) of the variable nozzle mechanism 50c. For example, the VN opening D (2) of the variable nozzle mechanism 52c in the single turbo mode may be a predetermined opening, or the same opening as the VN opening of the current variable nozzle mechanism 52c. Also good.

In addition, you may implement combining the above-mentioned modification, all or one part.
The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  10 engine, 12, 14 bank, 16, 18 cylinder, 17, 19 fuel injection device, 20, 22 intake manifold, 24, 26 exhaust manifold, 30 connection passage, 32, 33, 34, 35, 36 intake passage, 37, 38, 39, 40 Exhaust passage, 42 Bypass passage, 50, 52 Supercharger, 50a, 52a Compressor, 50b, 52b Turbine, 50c, 52c Variable nozzle mechanism, 200 Control device, 206 Engine speed sensor, 208 Supercharging pressure Sensor, 250 supercharging pressure calculation unit, 252 supercharging pressure determination unit, 254 opening determination unit, 256 opening control unit, 258 switching valve control unit.

Claims (2)

An engine block having a first bank and a second bank;
A first variable nozzle mechanism that adjusts a flow rate of exhaust gas to the first turbine by a vane opening degree, and the first turbine is driven by exhaust gas discharged from the first bank. A first supercharger to be driven;
A second variable nozzle mechanism that adjusts a flow rate of exhaust gas to the second turbine by a vane opening degree, and the second turbine is configured by exhaust gas discharged from the second bank. A second supercharger to be driven;
A first exhaust passage through which exhaust gas discharged from the first bank flows to the first supercharger, and a second exhaust passage through which exhaust gas discharged from the second bank flows to the second supercharger A connecting passage connecting the
A switching valve provided in the second exhaust passage for blocking the flow of exhaust gas from the second bank to the second supercharger;
A control device that controls the vane opening of the first variable nozzle mechanism, the vane opening of the second variable nozzle mechanism, and the operation of the switching valve;
When the control device operates both the first supercharger and the second supercharger, the vane opening degree of the second variable nozzle mechanism is larger than the vane opening degree of the first variable nozzle mechanism. An internal combustion engine that controls the opening of the second variable nozzle mechanism to be large.   The control device determines a vane opening degree of the first variable nozzle mechanism based on a rotational speed and a load of the internal combustion engine, and determines the determined vane opening degree of the first variable nozzle mechanism in a state of the internal combustion engine. 2. The internal combustion engine according to claim 1, wherein a value increased by an increase corresponding to the second variable nozzle mechanism is determined as a vane opening degree of the second variable nozzle mechanism.

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