JP7020380B2 - Supercharging system - Google Patents

Description

This disclosure relates to a supercharging system, and particularly to a supercharging system having a plurality of superchargers connected in parallel.

As a supercharging system for supercharging the intake air of an engine, for example, a configuration having a plurality of superchargers connected in parallel is known. For example, in a supercharging system having two superchargers connected in parallel, a supercharging mode in which one of the two superchargers is used to supercharge the intake air of the engine (hereinafter referred to as a single supercharging mode). It is also described) and a supercharging mode in which the intake air of the engine is supercharged using both superchargers (hereinafter, also referred to as a twin supercharging mode) is switched.

When executing such switching control, a step in the boost pressure may occur. In order to reduce this step in the supercharging pressure, there is a supercharging system including a motor for assisting the start of the second turbocharger (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2008-255902

However, in the supercharging system of Patent Document 1, it costs a lot to mount the motor, it is necessary to secure a space for mounting the motor, and mounting the motor increases the weight of the vehicle.

This disclosure has been made to solve the above-mentioned problems, and the purpose of the disclosure is to reduce the step of the supercharging pressure without adding a device for assisting the start of the supercharger. To provide a pay system.

The supercharging system according to this disclosure includes a first turbine driven by exhaust discharged from the engine and a first variable nozzle mechanism that adjusts the flow velocity of the exhaust flowing into the first turbine according to the opening degree, and is sucked into the engine. Includes a first turbocharger that supercharges the air, a second turbocharger driven by the exhaust discharged from the engine, and a second variable nozzle mechanism that adjusts the flow velocity of the exhaust flowing into the second turbine according to the opening degree. From the second supercharger that supercharges the air sucked into the engine and the first supercharging mode in which the supercharged air in the first supercharger is supplied to the engine, the first supercharger is supercharged. It is provided with a control device for switching to the second supercharging mode in which the supercharged air and the supercharged air in the second supercharger are supplied to the engine. Before switching from the first supercharging mode to the second supercharging mode, the control device supplies the exhaust to the second supercharger and transfers the air supercharged by the second supercharger to the first supercharger. The run-up operation to be supplied is executed, and when the supercharging pressure of the second supercharger reaches the supercharging pressure of the first supercharger during the run-up operation, the mode is switched to the second supercharging mode and the run-up operation is started. In this case, the second variable nozzle mechanism is controlled so that the opening degree of the second variable nozzle mechanism is smaller than the opening degree of the first variable nozzle mechanism.

Preferably, the control device makes the opening degree of the second variable nozzle mechanism the same as the opening degree of the first variable nozzle mechanism when the increase in the boost pressure of the second supercharger is stagnant during the run-up operation. The second variable nozzle mechanism is controlled.

Preferably, the control device has an opening degree of the first variable nozzle mechanism that maximizes the turbine efficiency of the first turbocharger and an opening degree that maximizes the turbine work of the first turbocharger during the run-up operation. The first variable nozzle mechanism is controlled so as to have a predetermined opening degree between.

More preferably, the control device calculates the limit opening of the first variable nozzle mechanism when the pressure of the exhaust gas discharged from the engine reaches the limit pressure, and when the predetermined opening exceeds the calculated limit opening, The first variable nozzle mechanism is controlled so that the opening degree of the first variable nozzle mechanism becomes the limiting opening degree.

According to this disclosure, it is possible to provide a supercharging system capable of reducing a step in the supercharging pressure without adding a device for assisting the start of the supercharger.

It is a figure which shows an example of the schematic structure of the engine in this embodiment. It is a figure for demonstrating the operation of the supercharging system in the single supercharging mode. It is a figure for demonstrating the operation of the supercharging system in the approach mode. It is a figure for demonstrating the operation of the supercharging system in the twin supercharging mode. It is a flowchart which shows an example of the process executed by a control device. It is a figure for demonstrating the calculation of the limit opening degree using an estimation model. It is a figure for demonstrating the calculation of the base opening degree of the variable nozzle mechanism of a primary supercharger. It is a figure which shows the change between the pressure in the exhaust manifold and the command opening degree shown by the control signal VN1. It is a figure for demonstrating the case where the 2nd supercharging pressure of a secondary supercharger is stagnant. It is a figure for demonstrating the change of supercharging pressure in this embodiment. It is a figure for demonstrating the change of the conventional supercharging pressure.

Hereinafter, embodiments of this disclosure will be described with reference to the drawings. In the following description, the same parts are designated by the same reference numerals. Their names and functions are the same. Therefore, detailed explanations about them are not repeated.

<About the configuration of the supercharging system>
FIG. 1 is a diagram showing an example of a schematic configuration of an engine 1 in this embodiment. With reference to FIG. 1, the engine 1 is mounted on the vehicle, for example, as a drive source for traveling. In this embodiment, the case where the engine 1 is a diesel engine will be described as an example, but the engine 1 may be, for example, a gasoline engine.

The engine 1 includes banks 10A and 10B, an air cleaner 20, an intercooler 25, intake manifolds 28A and 28B, a primary turbocharger 30, a secondary turbocharger 40, and an exhaust manifold 50A and 50B (hereinafter referred to as "exhaust manifolds"). Also referred to as), an exhaust treatment device 81, and a control device 200.

A plurality of cylinders 12A are formed in the bank 10A. A plurality of cylinders 12B are formed in the bank 10B. A piston (not shown) is housed in each of the cylinders 12A and 12B, and a combustion chamber (a space for burning fuel) is formed by the top of the piston and the inner wall of the cylinder. The volume of the combustion chamber is changed by sliding the piston in each of the cylinders 12A and 12B. An injector (not shown) is provided in each of the cylinders 12A and 12B, and during the operation of the engine 1, the timing and amount of fuel set by the control device 200 are injected into the cylinders 12A and 12B. .. The injection amount and timing of the fuel injected from each injector are set by the control device 200, for example, from the engine speed NE, the intake air amount Qin, the accelerator pedal depression amount, the vehicle speed, and the like.

The pistons of the cylinders 12A and 12B are connected to a common crankshaft (not shown) via a connecting rod. By burning fuel in each cylinder 12A, 12B in a predetermined order, the piston slides in each cylinder 12A, 12B, and the vertical movement of the piston is converted into the rotational movement of the crankshaft via the connecting rod. ..

The primary turbocharger 30 is a turbocharger including a compressor 31 and a turbine 32. The compressor 31 of the primary turbocharger 30 is provided in the intake passage of the engine 1 (that is, the passage from the air cleaner 20 to the intake manifolds 28A and 28B). The turbine 32 of the primary turbocharger 30 is provided in the exhaust passage of the engine 1 (that is, the passage from the exhaust manifolds 50A and 50B to the exhaust treatment device 81).

The compressor wheel 33 is rotatably housed in the compressor 31. A turbine wheel 34 and a variable nozzle mechanism 35 are provided in the turbine 32. The turbine wheel 34 is rotatably housed in the turbine 32. The compressor wheel 33 and the turbine wheel 34 are connected by a rotating shaft 36 and rotate integrally. The compressor wheel 33 is rotationally driven by the exhaust energy (exhaust energy) supplied to the turbine wheel 34.

The variable nozzle mechanism 35 changes the flow velocity of the exhaust gas that operates the turbine 32. The variable nozzle mechanism 35 is arranged on the outer peripheral side of the turbine wheel 34, and by rotating each of the plurality of nozzle vanes (not shown) and the plurality of nozzle vanes that guide the exhaust gas supplied from the exhaust inlet to the turbine wheel 34. It includes a drive device (not shown) that changes the gap between adjacent nozzle vanes (this gap is referred to as the VN opening in the following description). The variable nozzle mechanism 35 changes the VN opening degree by rotating the nozzle vane using the drive device in response to the control signal VN1 from the control device 200, for example.

The secondary turbocharger 40 is a turbocharger including a compressor 41 and a turbine 42. In this embodiment, the secondary turbocharger 40 has the same structure and size as the primary turbocharger 30. The compressor 41 of the secondary supercharger 40 is provided in parallel with the compressor 31 in the intake passage of the engine 1 to supercharge the intake air of the engine 1. The turbine 42 of the secondary turbocharger 40 is provided in parallel with the turbine 32 in the exhaust passage of the engine 1.

The compressor wheel 43 is rotatably housed in the compressor 41. A turbine wheel 44 and a variable nozzle mechanism 45 are provided in the turbine 42. The turbine wheel 44 is rotatably housed in the turbine 42. The compressor wheel 43 and the turbine wheel 44 are connected by a rotating shaft 46 and rotate integrally. The compressor wheel 43 is rotationally driven by the exhaust energy supplied to the turbine wheel 44.

Since the variable nozzle mechanism 45 has the same configuration as the variable nozzle mechanism 35, the detailed description thereof will not be repeated. The variable nozzle mechanism 45 changes the VN opening degree by rotating the nozzle vane using the drive device in response to the control signal VN2 from the control device 200, for example.

The air cleaner 20 removes foreign matter from the air sucked from the intake port (not shown). One end of the intake pipe 23 is connected to the air cleaner 20. The other end of the intake pipe 23 is branched and connected to one end of the intake pipe 21 and one end of the intake pipe 22.

The other end of the intake pipe 21 is connected to the intake inlet of the compressor 31 of the primary turbocharger 30. One end of the intake pipe 37 is connected to the intake outlet of the compressor 31 of the primary turbocharger 30. The other end of the intake pipe 37 is connected to the intercooler 25. The compressor 31 supercharges the air sucked through the intake pipe 21 by the rotation of the compressor wheel 33 and supplies the air to the intake pipe 37.

The other end of the intake pipe 22 is connected to the intake inlet of the compressor 41 of the secondary turbocharger 40. One end of the intake pipe 47 is connected to the intake outlet of the compressor 41 of the secondary turbocharger 40. The other end of the intake pipe 47 is connected to a connecting portion P3 in the middle of the intake pipe 37. The compressor 41 supercharges the air sucked through the intake pipe 22 by the rotation of the compressor wheel 43 and supplies the air to the intake pipe 47.

A first control valve 62 is provided in the middle of the intake pipe 47. The first control valve 62 is, for example, a normally-off VSV (negative pressure switching valve) that is ON (open) / OFF (closed) controlled according to the control signal CV1 from the control device 200.

Further, one end of the return pipe 48 is connected to the connection portion P4 located on the upstream side (compressor 41 side) of the first control valve 62 in the intake pipe 47. Further, the other end of the return pipe 48 is connected to the intake pipe 21. The return pipe 48 is a passage for returning at least a part of the air flowing through the intake pipe 47 to the upstream side of the compressor 31 of the primary turbocharger 30. The air that has returned to the intake pipe 21 through the return pipe 48 is supplied to the compressor 31.

A second control valve 64 is provided in the middle of the return pipe 48. The second control valve 64 is, for example, a normally-off solenoid valve (solenoid valve) that is ON (open) / OFF (closed) controlled according to the control signal CV2 from the control device 200.

The air supercharged by the compressor 31 and the air supercharged by the compressor 41 and passed through the first control valve 62 are supplied to the connection portion P3. These air merge at the connection portion P3 and flow into the intercooler 25.

The intercooler 25 is configured to cool the inflowing air. The intercooler 25 is, for example, an air-cooled or water-cooled heat exchanger. The intercooler 25 is provided with two intake air outlets. One end of the intake pipe 27A is connected to one outlet of the intercooler 25. The other end of the intake pipe 27A is connected to the intake manifold 28A. One end of the intake pipe 27B is connected to the other outlet of the intercooler 25. The other end of the intake pipe 27B is connected to the intake manifold 28B.

The intake manifolds 28A and 28B are connected to the intake ports (not shown) of the cylinders 12A and 12B in the banks 10A and 10B, respectively. On the other hand, the exhaust manifolds 50A and 50B are connected to the exhaust ports (not shown) of the cylinders 12A and 12B in the banks 10A and 10B, respectively.

Exhaust gas (gas after combustion) discharged from the combustion chambers of the cylinders 12A and 12B to the outside of the cylinder through the exhaust port is discharged to the outside via the exhaust passage of the engine 1. The exhaust passage includes an exhaust manifold 50A, 50B, an exhaust pipe 51A, 51B, a connection portion P1, an exhaust pipe 52A, 52B, 53A, 53B, and a connection portion P2. One end of the exhaust pipe 51A is connected to the exhaust manifold 50A. One end of the exhaust pipe 51B is connected to the exhaust manifold 50B. The other end of the exhaust pipe 51A and the other end of the exhaust pipe 51B merge once at the connection portion P1, then branch off and are connected to one end of the exhaust pipe 52A and one end of the exhaust pipe 52B.

The other end of the exhaust pipe 52A is connected to the exhaust inlet of the turbine 32. One end of the exhaust pipe 53A is connected to the exhaust outlet of the turbine 32. The other end of the exhaust pipe 52B is connected to the exhaust inlet of the turbine 42. One end of the exhaust pipe 53B is connected to the exhaust outlet of the turbine 42.

A third control valve 66 is provided in the middle of the exhaust pipe 52B. The third control valve 66 is, for example, a normally-on VSV (negative pressure switching valve) that is ON (open) / OFF (closed) controlled according to the control signal CV3 from the control device 200.

The other end of the exhaust pipe 53A and the other end of the exhaust pipe 53B merge at the connection portion P2 and are connected to the exhaust treatment device 81. The exhaust treatment device 81 is composed of, for example, an SCR catalyst, an oxidation catalyst, a PM removal filter, or the like, and purifies the exhaust gas flowing from the exhaust pipe 53A and the exhaust pipe 53B.

The operation of the engine 1 is controlled by the control device 200. The control device 200 includes a CPU (Central Processing Unit) that performs various processes, a memory that includes a ROM (Read Only Memory) that stores programs and data, a RAM (Random Access Memory) that stores the processing results of the CPU, and the like. Includes input / output ports (neither shown) for exchanging information with the outside. Various sensors (for example, an air flow meter 102, a first pressure sensor 106, a second pressure sensor 108, etc.) are connected to the input port. Devices to be controlled (for example, a plurality of injectors, variable nozzle mechanisms 35 and 45, first control valve 62, second control valve 64, third control valve 66, etc.) are connected to the output port.

The control device 200 controls various devices so that the engine 1 is in a desired operating state based on the signals from each sensor and the device, and the map and the program stored in the memory. It should be noted that various controls are not limited to processing by software, but can also be processed by dedicated hardware (electronic circuit). Further, the control device 200 has a built-in timer circuit (not shown) for measuring the time.

The air flow meter 102 detects the intake air amount Qin. The air flow meter 102 transmits a signal indicating the detected intake air amount Qin to the control device 200.

The engine speed sensor 104 detects the engine speed NE. The engine rotation speed sensor 104 transmits a signal indicating the detected engine rotation speed NE to the control device 200.

The first pressure sensor 106 detects the pressure (hereinafter, referred to as the first boost pressure) Pp at the connection portion P3 of the intake pipe 37. The first pressure sensor 106 transmits a signal indicating the detected first boost pressure Pp to the control device 200.

The second pressure sensor 108 detects the pressure at the connection portion P4 of the intake pipe 47 (hereinafter, referred to as the second boost pressure Ps). The second pressure sensor 108 transmits a signal indicating the second boost pressure Ps to the control device 200.

In this embodiment, the "supercharging system" is configured by the primary supercharger 30, the secondary supercharger 40, and the control device 200.

The control device 200 has a single supercharging mode in which supercharging is performed only by the primary supercharger 30 (primary turbo) by controlling the first control valve 62, the second control valve 64, and the third control valve 66, and the primary. It is configured to be able to execute switching control for switching from one of the twin supercharging modes in which supercharging is performed by both the supercharger 30 (primary turbo) and the secondary supercharger 40 (secondary turbo) to the other. Further, when switching from the single supercharging mode to the twin supercharging mode, the control device 200 executes the operation in the approach mode in which the supercharging pressure by the secondary supercharger 40 is increased to a certain level or more from the single supercharging mode. After that, the supercharging mode is switched to the twin supercharging mode.

Hereinafter, the operation of the supercharging system in each of the single supercharging mode, the approaching mode, and the twin supercharging mode will be described with reference to FIGS. 2, 3, and 4.

<About single supercharging mode>
The control device 200 operates the supercharging system in the single supercharging mode when a predetermined execution condition is satisfied. The predetermined execution condition includes, for example, a condition that the operating state of the engine 1 based on the engine speed NE and the intake air amount Qin is a low load operating state. When the supercharging mode is the single supercharging mode, the control device 200 closes (offs) the first control valve 62, the second control valve 64, and the third control valve 66.

FIG. 2 is a diagram for explaining the operation of the supercharging system in the single supercharging mode. As shown by the arrows in FIG. 2, the exhaust gas flowing through the exhaust manifolds 50A and 50B flows to the turbine 32 of the primary turbocharger 30 via the exhaust pipe 52A, and flows to the exhaust treatment device 81 via the exhaust pipe 53A. It flows. The exhaust supplied to the turbine 32 rotates the turbine wheel 34, and the compressor wheel 33 rotates with the rotation of the turbine wheel 34.

The air sucked from the air cleaner 20 flows to the compressor 31 via the intake pipe 23 and the intake pipe 21. The intake air discharged from the compressor 31 flows to the intercooler 25 via the intake pipe 37. The intake air flowing through the intercooler 25 branches into the intake pipes 27A and 27B and flows into each of the intake manifolds 28A and 28B.

<About run-up mode>
The control device 200 switches from the single supercharging mode to the twin supercharging mode, for example, when the supercharging mode is the single supercharging mode and the rotation speed of the primary supercharger 30 exceeds the threshold value. Determine that there is a request.

When there is a request for switching from the single supercharging mode to the twin supercharging mode, the control device 200 executes the run-up mode before switching to the twin supercharging mode. That is, the control device 200 puts both the second control valve 64 and the third control valve 66 in the open state (on state) and puts the first control valve 62 in the closed state (off state).

FIG. 3 is a diagram for explaining the operation of the supercharging system in the run-up mode. As shown by the arrow in FIG. 3, the exhaust gas flowing through the exhaust manifolds 50A and 50B once merges at the connection portion P1 and then branches into the exhaust pipes 52A and 52B, and the turbines of the primary supercharger 30 and the secondary supercharger 40. It flows to both 32 and 42, and flows to the exhaust treatment device 81 via the exhaust pipes 53A and 53B.

The exhaust supplied to the turbine 32 rotates the turbine wheel 34, and the compressor wheel 33 rotates with the rotation of the turbine wheel 34. The exhaust supplied to the turbine 42 rotates the turbine wheel 44, and the compressor wheel 43 rotates with the rotation of the turbine wheel 44.

The air sucked from the air cleaner 20 branches from the intake pipe 23 to the intake pipes 21 and 22, and flows to both the compressors 31 and 41. The intake air discharged from the compressor 31 flows to the intercooler 25 via the intake pipe 37. The intake air discharged from the compressor 41 flows from the intake pipe 47 to the reflux pipe 48 via the connection portion P4, and flows from the reflux pipe 48 to the compressor 31 via the intake pipe 21.

The intake air flowing through the intercooler 25 branches into the intake pipes 27A and 27B and flows into each of the intake manifolds 28A and 28B. In the run-up mode, the rotation speed of the secondary supercharger 40 is increased while supercharging the intake air flowing through the intercooler 25 by the primary supercharger 30. As the rotation speed of the secondary supercharger 40 increases, the pressure of the intake air discharged from the compressor 41 of the secondary supercharger 40 increases.

<About twin supercharging mode>
The control device 200 operates the supercharging system in the twin supercharging mode at the timing when the supercharging capacity of the secondary supercharger 40 becomes sufficiently high in the run-up mode. When the supercharging mode is the twin supercharging mode, the control device 200 sets the first control valve 62 in the open state (on state) and the second control valve 64 in the closed state (off state).

FIG. 4 is a diagram for explaining the operation of the supercharging system in the twin supercharging mode. In the run-up mode, the intake air discharged from the compressor 41 of the secondary supercharger 40 flows from the middle of the intake pipe 47 to the intake pipe 21 via the return pipe 48, whereas in the twin supercharge mode. In, as shown by the arrow in FIG. 4, the intake air discharged from the compressor 41 of the secondary turbocharger 40 flows from the intake pipe 47 to the intercooler 25 via the intake pipe 37.

The exhaust and intake flows other than the above are the same as the exhaust and intake flows in the run-up mode. Therefore, the detailed explanation will not be repeated.

FIG. 11 is a diagram for explaining a change in the conventional boost pressure. With reference to FIG. 11, the solid line shows the second supercharging pressure Ps of the secondary turbocharger 40, and the broken line shows the first supercharging pressure Pp of the primary turbocharger 30. When switching directly from the single supercharging mode to the twin supercharging mode without switching to the run-up mode described above, the mode is switched to the twin supercharging mode after the first supercharging pressure Pp of the primary supercharger 30 rises in the single supercharging mode. At that time, as the second supercharging pressure Ps of the secondary supercharger 40 rises sharply, the first supercharging pressure Pp of the primary supercharger 30 drops sharply. Therefore, the step of the boost pressure of the first boost pressure Pp becomes large. As a result, for example, the drivability deteriorates due to the sluggishness of the increase in the supercharging pressure, or the reliability of the supercharger deteriorates because the supercharger is burdened by a relatively large fluctuation of the supercharging pressure, for example.

In order to reduce this step in the supercharging pressure, it is conceivable to provide a motor for assisting the start of the second secondary supercharger 40 in the supercharging system. However, in such a supercharging system, the cost for mounting the motor is high, it is necessary to secure a space for mounting the motor, and mounting the motor increases the weight of the vehicle.

Therefore, in this embodiment, the control device 200 is supercharged by the secondary supercharger 40 while supplying air to the secondary supercharger 40 before switching from the single supercharging mode to the twin supercharging mode. When the operation in the run-up mode in which air is supplied to the primary supercharger 30 is executed and the supercharging pressure of the secondary supercharger 40 reaches the supercharging pressure of the primary supercharger 30 during the operation in the run-up mode. When switching to the twin supercharging mode and starting the operation in the run-up mode, the variable nozzle mechanism 45 is controlled so that the opening degree of the variable nozzle mechanism 45 is smaller than the opening degree of the variable nozzle mechanism 35.

This makes it possible to reduce the step in the supercharging pressure without adding a device that assists in starting the secondary turbocharger 40. As a result, drivability and reliability of the turbocharger are improved.

FIG. 5 is a flowchart showing an example of processing executed by the control device. This process is repeatedly called and executed by the control device 200 from the main process at predetermined control cycles. With reference to FIG. 5, the control device 200 determines whether or not the supercharging mode flag has a value indicating the single supercharging mode (step S101). The supercharging mode flag is a flag indicating the currently controlled supercharging mode, and is a value indicating one of the single supercharging mode, the twin supercharging mode, and the run-up mode as the controlled supercharging mode. Can be taken.

If it is determined that the supercharging mode flag does not indicate the single supercharging mode (NO in step S101), the control device 200 advances the process to be executed to the process of step S111.

On the other hand, when it is determined that the supercharging mode flag indicates the single supercharging mode (YES in step S101), the control device 200 determines whether or not there is a request for switching to the twin supercharging mode (step S102). For example, as described above, when the rotation speed of the primary supercharger 30 exceeds the threshold value, it is determined that there is a request for switching to the twin supercharge mode. If it is determined that there is no switching request (NO in step S102), the control device 200 advances the process to be executed to the process of step S111.

On the other hand, if it is determined that there is a switching request (YES in step S102), the control device 200 rewrites the supercharging mode flag to a value indicating the approach mode (step S103). Next, the control device 200 calculates the limited opening degree VN1th output as the command opening degree by the control signal VN1 of the variable nozzle mechanism 35 by the estimation model of the limited opening degree (step S104).

FIG. 6 is a diagram for explaining the calculation of the limited opening degree using the estimation model of the limited opening degree. With reference to FIG. 6, first, the target effective opening area μA is calculated using the nozzle formula shown by the following mathematical formula (1).

A: actual opening area, μA: target effective opening area, m: intake air amount Ga + mass flow rate Gf of injected fuel, R: gas constant, T4: exhaust manifold internal temperature, P6: exhaust manifold back pressure, P4: exhaust manifold Internal pressure, a, b: a predetermined constant for each value of P6 / P4.

The limit exhaust manifold internal pressure P4th input as the exhaust manifold internal pressure P4 in the formula (1) is predetermined as a value at which the oil seal of the valve stem of the exhaust valve does not blow through or the exhaust valve does not open. The intake air amount Ga, the exhaust manifold internal temperature T4, and the back pressure P6 are specified according to the detection signals from the air flow meter 102, the temperature sensor 114, and the pressure sensor 116, respectively. The mass flow rate Gf of the injected fuel is calculated from the fuel injection amount calculated by the control device 200 for fuel injection.

Next, the limited opening VN1th is calculated from the calculated target effective opening area μA by using the opening characteristic map showing the relationship between the VN opening and the effective opening area.

Returning to FIG. 5, the control device 200 determines whether or not the base opening degree VN1b of the variable nozzle mechanism 35 is larger than the VN1th (step S105).

FIG. 7 is a diagram for explaining the calculation of the base opening degree of the variable nozzle mechanism 35 of the primary turbocharger 30. With reference to FIG. 7, the solid line shows the turbine work and the broken line shows the turbine efficiency. In the variable nozzle mechanism 35, as the opening degree indicated by the control signal VN1 changes from the open side to the closed side, the turbine of the primary turbocharger 30 increases with the expansion ratio of the exhaust gas up to the peak. The work increases, but after reaching the peak, the turbine work of the primary turbocharger 30 decreases as the amount of exhaust gas passing through the primary turbocharger 30 decreases as it further changes to the closed side. descend. Further, the turbine efficiency of the primary turbocharger 30 has a peak at a certain opening degree due to the characteristics of the primary turbocharger 30.

The opening degree between the opening degree at which the turbine work peaks and the opening degree at which the turbine efficiency peaks is defined as the base opening degree VN1b. For example, the central opening degree between the opening degree at which the turbine work peaks and the opening degree at which the turbine efficiency peaks is defined as the base opening degree VN1b.

When the command opening indicated by the control signals VN1 and VN2 is controlled on the closed side in the run-up mode as in this embodiment, the exhaust flow path area becomes smaller, while the boost pressure of the primary supercharger 30 increases. Since the step is small, the exhaust manifold internal pressure P4 tends to increase. The limit exhaust manifold internal pressure P4th is provided so that the oil seal of the valve stem of the exhaust valve does not blow through or the exhaust valve opens, but there is a concern that the exhaust manifold internal pressure P4 will exceed the limited exhaust manifold internal pressure P4th. be.

FIG. 8 is a diagram showing changes between the pressure inside the exhaust manifold and the command opening degree indicated by the control signal VN1. With reference to FIG. 8, when the command opening indicated by the control signal VN1 is not limited and the command opening is set to the base opening VN1b, the exhaust manifold internal pressure P4 exceeds the limited exhaust manifold internal pressure P4th during the run-up mode. It may end up.

Therefore, when the command opening exceeds the limit opening VN1th, the command opening is set to the limit degree VN1th. Thereby, the exhaust manifold internal pressure P4 can be prevented from exceeding the limiting exhaust manifold internal pressure P4th.

Returning to FIG. 5, when it is determined that VN1b is not larger than VN1th (NO in step S105), the control device 200 outputs the control signal VN1 with the command opening degree in the control signal VN1 as the base opening degree VN1b. (Step S106).

On the other hand, when it is determined that VN1b is larger than VN1th (YES in step S105), the control device 200 outputs a control signal VN1 with the command opening as the limiting opening VN1th to the variable nozzle mechanism 35 of the primary turbocharger 30. (Step S107).

After step S106 or step S107, the control device 200 sets the command opening as the opening VN2b of the control fully closed (the opening area is not 0), which is the minimum opening in control. VN2 is output to the variable nozzle mechanism 45 of the secondary turbocharger 40 (step S108).

Cpg: constant pressure specific heat (0.26), K: specific heat ratio of exhaust gas (1.33), G4: amount of gas passing through the supercharger, T4: temperature inside the exhaust mani, P4: pressure inside the exhaust gas, P6: exhaust passage Back pressure.

Cpa: constant temperature specific heat (0.24), k: specific heat ratio of air (1.4), Ga: intake air amount, T1: intake air temperature, P3: intake pressure after supercharger, P2: supercharger The front intake pressure.

The formulas (2) to (4) shown above are the physical formulas of the turbocharger. As shown in steps S107 and S108, in this embodiment, in the approach mode, the opening degree of the variable nozzle mechanism 45 of the secondary supercharger 40 is larger than the opening degree of the variable nozzle mechanism 35 of the primary turbocharger 30. Is used on the closed side. Therefore, it is possible to suppress a decrease in the amount of gas passing through the supercharger G4 of the primary supercharger 30 due to the increase in the pressure loss on the side of the secondary supercharger 40 as compared with the case of using it on the open side. Further, since the decrease in the exhaust manifold internal pressure P4 can be suppressed as compared with the case of using it on the opening side, the decrease in the expansion ratio P4 / P6 can be suppressed. As a result, according to the mathematical formula (2), it is possible to suppress a decrease in the turbine work of the primary turbocharger 30, and it is possible to suppress a decrease in the compressor work. Further, according to the mathematical formula (3), it is possible to suppress a decrease in the intake pressure P3 after the supercharger of the primary supercharger 30 = the first supercharge pressure Pp.

Next, the control device 200 uses the control signal CV2 of the second control valve 64 as a signal for opening the second control valve 64 (step S109), and controls the control signal CV3 of the third control valve 66 to the third control. It is a signal to open the valve 66 (step S110).

The control device 200 determines whether or not the supercharging mode flag is a value indicating the approaching mode (step S111). If it is determined that the run-up mode is not set (NO in step S111), the control device 200 returns the process to be executed to the caller of the run-up mode process.

On the other hand, when it is determined that the run-up mode is set (YES in step S111), the control device 200 determines whether or not the second supercharging pressure Ps of the secondary supercharger 40 is stagnant (step S112). For example, whether or not the second supercharging pressure Ps is stagnant is determined by whether or not the time derivative value of the second supercharging pressure Ps is smaller than a predetermined value that can be determined to be stagnant.

When it is determined that the second boost pressure Ps is stagnant (YES in step S112), the command opening in the control signal VN2 of the variable nozzle mechanism 45 is changed to the same opening as the command opening in the control signal VN1. Then, the control signal VN2 is output (step S113).

FIG. 9 is a diagram for explaining a case where the second supercharging pressure Ps of the secondary supercharger 40 is stagnant. With reference to FIG. 9, the solid line shows the second supercharging pressure Ps of the secondary turbocharger 40, and the broken line shows the first supercharging pressure Pp of the primary turbocharger 30. If the first supercharging pressure Pp is high before switching to the run-up mode, the second supercharging pressure Ps does not catch up with the first supercharging pressure Pp and stagnates as shown by the two-dot chain line in FIG. It may end up. In such a case, by increasing the opening degree of the variable nozzle mechanism 45 of the secondary supercharger 40, the second supercharging pressure Ps catches up with the first supercharging pressure Pp as shown in FIG. 2 The stagnation of the supercharging pressure Ps can be eliminated. In this case, in this embodiment, the opening degree of the variable nozzle mechanism 45 of the secondary turbocharger 40 is increased to the same opening degree as the opening degree of the variable nozzle mechanism 35 of the primary turbocharger 30.

Returning to FIG. 5, when it is determined that the second supercharging pressure Ps is not stagnant (NO in step S112), or after step S113, the control device 200 controls the second supercharging of the secondary supercharger 40. It is determined whether or not the pressure Ps becomes equal to the first supercharging pressure Pp of the primary turbocharger 30 (step S114). If it is determined that they are not equal (NO in step S114), the control device 200 returns the process to be executed to the caller of this run-up mode process.

On the other hand, when it is determined that the second supercharging pressure Ps becomes equal to the first supercharging pressure Pp (YES in step S114), the supercharging mode flag is changed to a value indicating the twin supercharging mode (step S115). The control signal CV1 of the first control valve 62 is used as a signal for opening the first control valve 62 (step S116), and the control signal CV2 of the second control valve 64 is used as a signal for closing the second control valve 64. (Step S117). After that, the control device 200 returns the process to be executed to the caller of the run-up mode process.

FIG. 10 is a diagram for explaining a change in boost pressure in this embodiment. With reference to FIG. 10, the solid line is the second supercharging pressure Ps of the secondary turbocharger 40, the broken line is the first supercharging pressure Pp of the primary turbocharger 30, and the two-dot chain line is the conventional first supercharging pressure Pp. And the second supercharging pressure Ps are shown. By executing the control shown in FIG. 5, a run-up mode is provided between the single supercharging mode and the twin supercharging mode, so that the first supercharging of the conventional primary turbocharger 30 shown in FIG. 11 is provided. It is possible to reduce the step of the first supercharging pressure Pp as compared with the step of the pressure Pp.

[Modification example]
(1) In the above-described embodiment, the primary supercharger 30 and the secondary supercharger 40 are provided in the intake passage of the engine 1, but the primary supercharger 30 is provided in the intake passage of the engine 1. In addition to the 30 and the secondary turbocharger 40, for example, an EGR (Exhaust Gas Recirculation) gas inlet of an intake throttle valve or an exhaust gas recirculation device may be provided.

(2) In the above-described embodiment, the engine 1 has been described as an example of a V-type 6-cylinder engine, but may be, for example, an engine having another cylinder layout (for example, in-line type or horizontal type).

(3) In the above-described embodiment, it has been described that it is determined whether or not there is a request for switching from the single supercharging mode to the twin supercharging mode based on the rotation speed of the primary supercharger 30. Whether or not there is a request to switch from the single supercharging mode to the twin supercharging mode from the viewpoint of drivability such as the efficiency of the primary supercharger 30 and the operating state (for example, acceleration state) of the vehicle in addition to the rotation speed of 30. May be determined.

(4) In the above-described embodiment, the supercharging system has been described as having two superchargers, but it may have three or more superchargers.

(5) In the above-described embodiment, the first pressure sensor 106 has been described as detecting the pressure in the intake pipe 37, but at least the first boost pressure Pp of the compressor 31 of the primary supercharger 30 is detected. If possible, for example, the pressure in the intake pipe 27A may be detected, or the pressure in the intake pipe 27B may be detected.

(6) In the above-described embodiment, the control device 200 has been described as switching the supercharging mode to the twin supercharging mode when the second supercharging pressure Ps reaches the first supercharging pressure Pp. The second supercharging pressure Ps may reach the first supercharging pressure Pp. For example, the control device 200 may use the control device 200 at a predetermined timing after the second supercharging pressure Ps reaches the first supercharging pressure Pp. The supercharging mode may be switched to the twin supercharging mode.

(7) In the above-described embodiment, as shown in step S112 of FIG. 5, whether or not the second supercharging pressure Ps is stagnant is determined by the time derivative value of the second supercharging pressure Ps being stagnant. It is now judged by whether or not it is smaller than the predetermined value that can be judged. However, not limited to this, whether or not the second boost pressure Ps is stagnant is determined by whether or not the period after switching to the run-up mode is longer than a predetermined period that can be determined to be stagnant. Alternatively, it may be determined whether or not the time derivative value of Pp-Ps is smaller than a predetermined value that can be determined to be stagnant, or the time derivative of the first boost pressure Pp may be determined. The value may be determined based on whether or not the value is smaller than a predetermined value that can be determined to be stagnant.

(8) In the above-described embodiment, as shown in step S113 of FIG. 5, the opening degree of the variable nozzle mechanism 45 of the secondary turbocharger 40 is set to the opening degree of the variable nozzle mechanism 35 of the primary turbocharger 30. I tried to increase it to the same opening as. However, the present invention is not limited to this, and the opening degree of the variable nozzle mechanism 45 of the secondary supercharger 40 may be increased, and the opening degree of the variable nozzle mechanism 45 of the secondary supercharger 40 and the variable nozzle mechanism of the primary supercharger 30 may be increased. It may be increased to a predetermined opening degree between the opening degree of 35.

(9) Disclosure of a supercharging system including a primary supercharger 30, a secondary supercharger 40, and a control device 200, disclosure of an internal combustion engine such as an engine 1, internal combustion of an engine 1 or the like, according to the above-described embodiment. It can be regarded as disclosure of a control device such as an engine ECU 100, disclosure of a control method by such a control device, or disclosure of an internal combustion engine system including such an internal combustion engine and a control device.

[effect]
(1) As shown in FIGS. 1 to 4, the supercharging system is a variable nozzle mechanism that adjusts the flow velocity of the turbocharger 32 driven by the exhaust gas discharged from the engine 1 and the exhaust gas flowing into the turbocharger 32 according to the opening degree. The primary supercharger 30, which includes 35 and supercharges the air sucked into the engine 1, the turbine 42 driven by the exhaust discharged from the engine 1, and the flow velocity of the exhaust flowing into the turbine 42 are adjusted by the opening degree. From a single supercharging mode that includes a variable nozzle mechanism 45 for supercharging the air sucked into the engine 1 and a single supercharging mode in which the supercharged air in the primary supercharger 30 is supplied to the engine 1. A control device 200 for switching between the supercharged air in the primary supercharger 30 and the twin supercharged mode in which the supercharged air in the secondary supercharger 40 is supplied to the engine 1 is provided.

As shown in FIG. 5, the control device 200 supplies exhaust gas to the secondary supercharger 40 and supercharges the air by the secondary supercharger 40 before switching from the single supercharging mode to the twin supercharging mode. Is executed in the run-up mode in which the primary turbocharger 30 is supplied to the primary turbocharger 30. As shown in steps S114 to S117 of FIG. 5, the second supercharging pressure Ps of the secondary supercharger 40 reached the first supercharging pressure Pp of the primary supercharger 30 during the operation in the approach mode. In case of switching to twin supercharging mode. As shown in steps S106 to S108 of FIG. 5, when the operation in the approach mode is started, the opening degree of the variable nozzle mechanism 45 of the secondary turbocharger 40 is changed to the variable nozzle mechanism 35 of the primary turbocharger 30. The variable nozzle mechanism 45 is controlled so as to be smaller than the opening degree of.

This makes it possible to reduce the step in the supercharging pressure without adding a device that assists in starting the secondary turbocharger 40. As a result, drivability and reliability of the turbocharger are improved.

(2) When the increase of the second supercharging pressure Ps of the secondary supercharger 40 is stagnant while the control device 200 is operating in the approach mode, the opening degree of the variable nozzle mechanism 45 of the secondary supercharger 40 is the primary. The variable nozzle mechanism 45 is controlled so as to have the same opening degree as the variable nozzle mechanism 35 of the turbocharger 30. As a result, by reducing the opening degree of the variable nozzle mechanism 45 of the secondary turbocharger 40, even when the rise of the second supercharging pressure Ps is stagnant, the stagnation can be eliminated.

(3) In the control device 200, during operation in the run-up mode, the base opening VN1b of the variable nozzle mechanism 35 of the primary supercharger 30 has the opening degree at which the turbine efficiency of the primary supercharger 30 is maximized and the primary supercharging. The variable nozzle mechanism 35 of the primary turbocharger 30 is controlled so that the opening degree is at the center of the opening degree at which the turbine work of the machine 30 is best. As a result, even when the opening degree of the variable nozzle mechanism 45 of the secondary supercharger 40 is controlled to be smaller than the opening degree of the variable nozzle mechanism 35 of the primary supercharger 30, the primary supercharger 30 Turbine efficiency and turbine work can be set to high values in a well-balanced manner.

(4) The control device 200 calculates the limit opening VN1th of the variable nozzle mechanism 35 of the primary supercharger 30 when the pressure of the exhaust gas discharged from the engine 1 reaches the limit exhaust manifold internal pressure P4th, and the calculated limit. When the base opening degree VN1b exceeds the opening degree VN1th, the variable nozzle mechanism 35 is controlled so that the opening degree of the variable nozzle mechanism 35 becomes the limiting opening degree VN1th. Thereby, the exhaust manifold internal pressure P4 can be prevented from exceeding the limiting exhaust manifold internal pressure P4th.

It is also planned that the embodiments disclosed this time will be implemented in combination as appropriate. And it should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present disclosure is set forth by the claims rather than the description of the embodiments described above, and is intended to include all modifications within the meaning and scope of the claims.

1 engine, 10A, 10B bank, 12A, 12B cylinder, 20 air cleaner, 21,22,23,27A, 27B, 37,47 intake pipe, 25 intercooler, 28A, 28B intake manifold, 30 primary supercharger, 31, 41 Compressor, 32,42 Turbine, 33,43 Compressor Wheel, 34,44 Turbine Wheel, 35,45 Variable Nozzle Mechanism, 36,46 Rotating Shaft, 40 Secondary Supercharger, 48 Recirculation Pipe, 50A, 50B Exhaust Manifold, 51A , 51B, 52A, 52B, 53A, 53B Exhaust pipe, 62 1st control valve, 64 2nd control valve, 66 3rd control valve, 81 Exhaust treatment device, 102 Air flow meter, 104 Engine rotation speed sensor, 106 1st pressure Sensor, 108 second pressure sensor, 114 temperature sensor, 116 pressure sensor, 200 control device.

Claims (4)

It includes a first turbine driven by exhaust gas discharged from the engine and a first variable nozzle mechanism that adjusts the flow velocity of the exhaust gas flowing into the first turbine according to the opening degree, and supercharges the air sucked into the engine. The first supercharger and
A second turbine driven by the exhaust gas discharged from the engine and a second variable nozzle mechanism for adjusting the flow velocity of the exhaust gas flowing into the second turbine according to the opening degree are included, and the air sucked into the engine is supercharged. The second supercharger to do
From the first supercharging mode in which the supercharged air in the first supercharger is supplied to the engine, the supercharged air in the first supercharger and the second supercharger are supercharged. It is equipped with a control device that switches to a second supercharging mode in which air is supplied to the engine.
The control device is
Before switching from the first supercharging mode to the second supercharging mode, the first supercharger uses the air supercharged by the second supercharger while supplying exhaust gas to the second supercharger. Perform a run-up operation to supply to
When the supercharging pressure of the second supercharger reaches the supercharging pressure of the first supercharger during the run-up operation, the mode is switched to the second supercharging mode.
A supercharging system that controls the second variable nozzle mechanism so that the opening degree of the second variable nozzle mechanism becomes smaller than the opening degree of the first variable nozzle mechanism when the run-up operation is started. In the control device, when the increase in the boost pressure of the second turbocharger is stagnant during the run-up operation, the opening degree of the second variable nozzle mechanism is the same as the opening degree of the first variable nozzle mechanism. The supercharging system according to claim 1, wherein the second variable nozzle mechanism is controlled so as to be. In the control device, during the run-up operation, the opening degree of the first variable nozzle mechanism becomes the opening degree at which the turbine efficiency of the first supercharger becomes the best and the turbine work of the first supercharger becomes the best. The supercharging system according to claim 1, wherein the first variable nozzle mechanism is controlled so as to have a predetermined opening degree between the opening degree and the opening degree. The control device is
The limit opening of the first variable nozzle mechanism when the pressure of the exhaust gas discharged from the engine reaches the limit pressure is calculated.
The supercharging according to claim 3, wherein when the predetermined opening exceeds the calculated limited opening, the first variable nozzle mechanism is controlled so that the opening of the first variable nozzle mechanism becomes the limited opening. system.

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