Control method for engine with turbocharger and control method for engine with turbocharger

Abstract

To early activate a catalytic converter in an engine with a turbocharger.SOLUTION: A control device 10 for an engine with a turbocharger includes: an engine 1; an exhaust passage 4 in which exhaust gas from the engine flows; a turbocharger 3 having a turbine wheel 35 rotated by a flow of exhaust gas in the exhaust passage; and a catalytic converter 42 located downstream of the turbocharger. The turbocharger includes: a waste gate valve 38 that fully opens a bypass passage 37 while the engine is performing a warming-up operation of the catalytic converter; and a resistance application mechanism (lock mechanism 7) for applying resistance to rotation of the turbine wheel.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The technology disclosed herein relates to a control device for a turbocharged engine and a control method for a turbocharged engine. [Background technology]

[0002] Patent Document 1 describes a conventional control device for a turbocharged engine. The turbocharger of this conventional engine includes a wastegate valve and an actuator that drives the wastegate valve. The wastegate valve opens and closes a bypass passage that bypasses the turbine of the turbocharger. The actuator adjusts the turbocharger's boost pressure in accordance with the engine operating state by changing the opening of the wastegate valve. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-170017 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, if the catalytic converter is inactive after the engine starts, the engine will warm up the catalytic converter. The engine will retard the ignition timing so that the temperature of the engine's exhaust gases increases. During the warm-up of the catalytic converter, the wastegate valve may fully open the bypass passage. Since most of the exhaust gas bypasses the turbine and is supplied to the catalytic converter, the drop in exhaust gas temperature is suppressed. Since high-temperature exhaust gases are supplied to the catalytic converter, the catalytic converter will activate early.

[0005] However, there is a demand for the catalytic converter to be activated more quickly after the engine is started.

[0006] The disclosed technology provides early activation of the catalytic converter in a turbocharged engine. [Means for solving the problem]

[0007] While the engine is warming up the catalytic converter, some of the exhaust gas passes through the turbine even though the wastegate valve is fully open. The exhaust gas passing through the turbine contributes to the work of rotating the turbine wheel, so the temperature of the exhaust gas passing through the turbine is reduced.

[0008] The technology disclosed here is characterized by the fact that the turbocharger applies resistance to the rotation of the turbine wheel while the engine is warming up the catalytic converter, which limits the temperature drop of the exhaust gas passing through the turbine, allowing the catalytic converter to activate more quickly.

[0009] Specifically, the technology disclosed herein relates to a control device for a turbocharged engine. The engine and an exhaust passage connected to the engine and through which exhaust from the engine flows; a turbocharger located in the exhaust passage and having a turbine wheel rotated by the exhaust flow in the exhaust passage; a catalytic converter located downstream of the turbocharger in the exhaust passage and purifying the exhaust gas, The turbocharger has a wastegate valve that fully opens a bypass passage that bypasses the turbine wheel while the engine is warming up the catalytic converter, and a resistance applying mechanism that applies resistance to rotation of the turbine wheel while the engine is warming up the catalytic converter.

[0010] While the engine is warming up the catalytic converter, the wastegate valve fully opens the bypass passage. Because the exhaust gas from the engine passes through the bypass passage, which has a relatively low flow resistance, the temperature drop of the exhaust gas is suppressed. Because high-temperature exhaust gas is supplied to the catalytic converter, the catalytic converter is activated early. During normal operation when the engine is not warming up the catalytic converter, the wastegate valve changes its opening depending on the engine's operating conditions. The boost pressure of the turbocharger is adjusted to a level that corresponds to the engine's operating conditions.

[0011] The turbocharger has a resistance applying mechanism that applies resistance to the rotation of the turbine wheel. While the engine is warming up the catalytic converter, some exhaust passes through the turbine instead of the bypass passage, but the exhaust passing through the turbine inhibits the rotation of the turbine wheel. Because the energy of the exhaust is not converted to the rotation of the turbine wheel, or the conversion is inhibited, the exhaust can pass through the turbine while maintaining a high temperature. Because the temperature of the exhaust supplied to the catalytic converter is high, the catalytic converter activates more quickly.

[0012] The resistance applying mechanism may stop rotation of the turbine wheel while the engine is warming up the catalytic converter.

[0013] When the resistance mechanism stops the rotation of the turbine wheel, the temperature drop of the exhaust gas passing through the turbine is further suppressed. Since the exhaust gas is supplied to the catalytic converter at a higher temperature, the catalytic converter becomes activated more quickly.

[0014] the resistance applying mechanism has a lock pin inserted between blades of the turbine wheel, The resistance applying mechanism may be configured to insert the lock pin between the vanes while the engine is warming up the catalytic converter, and to retract the lock pin from between the vanes when the engine is not warming up the catalytic converter.

[0015] When the lock pin is inserted between the vanes of the turbine wheel, the interference between the lock pin and the vanes prevents the turbine wheel from rotating. The resistance applying mechanism can stop the rotation of the turbine wheel while the engine is warming up the catalytic converter. The resistance applying mechanism advances and retracts the lock pin. The resistance applying mechanism retracts the lock pin from between the vanes when the engine is not warming up the catalytic converter. Because the turbine wheel can rotate, the turbocharger can supercharge the intake air during normal engine operation.

[0016] The resistance applying mechanism having a lock pin can stop the rotation of the turbine wheel with a compact structure.

[0017] The lock pin is fixed to the wastegate valve, The wastegate valve may move between a first position where the bypass passage is fully closed, a second position where the bypass passage is fully open, and a third position where the bypass passage is fully open and the lock pin is inserted between the vanes.

[0018] If a lock pin is fixed to the wastegate valve, the rotation of the turbine wheel can be stopped with an even more compact structure. The bypass passage opening can be adjusted by moving the wastegate valve between a first position, which fully closes the bypass passage, and a second position, which fully opens the bypass passage. A wastegate valve with a fixed lock pin can also be moved to a third position, where the bypass passage is fully open and the lock pin is inserted between the vanes. While the engine is warming up the catalytic converter, if the wastegate valve is in the third position, the wastegate valve fully opens the bypass passage and the lock pin is inserted between the vanes of the turbine wheel. Furthermore, if the engine is not warming up the catalytic converter, if the wastegate valve is moved from the third position, the lock pin will be disengaged from between the vanes of the turbine wheel, allowing the turbine wheel to rotate.

[0019] the turbocharger further includes a compressor wheel fixed to a shaft of the turbine and located in an intake passage of the engine; and a variable vane diffuser through which the intake air compressed by the compressor wheel passes, the variable vane having an opening degree determined by an angle of a variable vane that can be changed between a closed position and an open position, The resistance applying mechanism may change the angle of the variable vane to a lock position where the variable vane interferes with the compressor wheel.

[0020] The variable vane diffuser changes the angle of the variable vanes according to the engine's operating conditions, thereby changing the diffuser opening. By changing the diffuser opening, the turbocharger can maintain high operating efficiency while suppressing surges across a wide range of engine operating speeds, from low to high.

[0021] The variable vanes can also change their angle to a locking position that interferes with the compressor wheel. When the variable vanes stop the rotation of the compressor wheel, the rotation of the turbine wheel also stops. The resistance applying mechanism can stop the rotation of the turbine wheel by locking the compressor wheel. Using the compressor variable vane diffuser as a resistance applying mechanism eliminates the need to add mechanisms to the turbocharger and improves the layout flexibility of the engine system, including the engine, intake passage, exhaust passage, and turbocharger.

[0022] the turbocharger further includes a motor-generator located on a shaft of the turbine and rotating the shaft; The resistance applying mechanism may apply resistance to rotation of the turbine wheel by the motor generator while the engine is warming up the catalytic converter.

[0023] During normal engine operation, the motor-generator can provide assist torque to the turbocharger and generate electricity using the exhaust flow. The resistance applying mechanism operates the motor-generator to generate electricity or keeps the motor-generator stopped from an external load while the engine is warming up the catalytic converter. This applies resistance to the rotation of the turbine wheel or stops the rotation of the turbine wheel when the exhaust gas passes through the turbine. The motor-generator makes it possible to apply resistance to the rotation of the turbine wheel or stop the rotation without affecting the layout of the engine system.

[0024] Another technique disclosed herein relates to a control method for a turbocharged engine, which includes: After the engine is started, while the engine is warming up the catalytic converter, the wastegate valve in the exhaust passage fully opens the bypass passage that bypasses the turbine of the turbocharger, resistance to rotation of a turbine wheel of the turbine is applied while the engine is warming up the catalytic converter; After the engine has finished warming up the catalytic converter, the wastegate valve returns to normal control and the resistance is released.

[0025] After the engine starts, the wastegate valve fully opens the bypass passage while the engine is warming up the catalytic converter. It also applies resistance to the rotation of the turbine wheel. This prevents the exhaust gas from dropping too quickly, allowing hot exhaust gas to be supplied to the catalytic converter, activating it quickly. After the engine has finished warming up the catalytic converter, the wastegate valve returns to normal control and removes resistance to the rotation of the turbine wheel. The turbocharger can supercharge the intake air during normal engine operation. [Effects of the Invention]

[0026] According to the above-described control device for a turbocharged engine and control method for a turbocharged engine, the catalytic converter can be activated early. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 shows a turbocharged engine. [Figure 2] FIG. 2 shows a control system for a turbocharged engine. [Figure 3] Figure 3 shows the torque curve of the engine. [Figure 4] FIG. 4 is a cross-sectional view of a turbine of a turbocharger. [Figure 5] FIG. 5 shows the turbine wheel and the lock pin as viewed from the arrow A in FIG. [Figure 6] FIG. 6 is a flow chart of a method for controlling a turbocharged engine. [Figure 7] FIG. 7 is a cross-sectional view of a turbine of a turbocharger according to a modified example. [Figure 8] FIG. 8 shows a compressor of a turbocharger according to a modified example. [Figure 9] FIG. 9 shows a turbocharger according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0028] Hereinafter, embodiments of a control device for a turbocharged engine and a control method for a turbocharged engine will be described with reference to the drawings. The control device for a turbocharged engine and the control method for a turbocharged engine described here are examples.

[0029] (Overall engine configuration) FIG. 1 shows a turbocharged engine. Engine 1 is mounted on a four-wheeled vehicle. Engine 1 generates driving force for propelling the four-wheeled vehicle. Engine 1 is a reciprocating engine and has multiple cylinders 11. Pistons reciprocate within cylinders 11. Engine 1 in the illustration is an in-line four-cylinder engine, but the type of engine 1 is not limited to a specific type. Engine 1 is a spark-ignition engine. Fuel containing gasoline is supplied to engine 1.

[0030] An intake passage 2 is connected to the engine 1. The intake passage 2 sends intake air to the cylinders 11 of the engine 1. An air cleaner 21 is located upstream of the intake passage 2. The air cleaner 21 filters the intake air to remove foreign matter from the intake air.

[0031] The compressor 31 of the turbocharger 3 is located downstream of the air cleaner 21 in the intake passage 2. The compressor 31 compresses the intake air. The compressor 31 has a compressor wheel 32 and a compressor housing 33 that houses the compressor wheel 32.

[0032] The intercooler 22 is located downstream of the compressor 31 in the intake passage 2. The intercooler 22 cools the intake air compressed by the compressor 31.

[0033] A throttle valve 23 is located downstream of the intercooler 22 in the intake passage 2. The throttle valve 23 adjusts the amount of intake air supplied to the cylinder 11.

[0034] A surge tank 24 is located midway through the intake passage 2. The surge tank 24 is located downstream of the throttle valve 23. The intake passage 2 between the surge tank 24 and the engine 1 is an independent intake passage 25. The independent intake passage 25 connects the surge tank 24 to each cylinder 11 independently of one another. Intake air is introduced from the surge tank 24 through the independent intake passage 25 into each cylinder 11.

[0035] An exhaust passage 4 is connected to the engine 1. The exhaust passage 4 discharges exhaust gas from the cylinders 11 of the engine 1. An upstream portion of the exhaust passage 4 is an independent exhaust passage 41. The independent exhaust passage 41 is independently connected to each cylinder 11 of the engine 1. The exhaust gas discharged from each cylinder 11 is collected after passing through the independent exhaust passage 41.

[0036] The turbine 34 of the turbocharger 3 is located downstream of the independent exhaust passage 41. The turbine 34 has a turbine wheel 35 and a turbine housing 36 that houses the turbine wheel 35. The turbine wheel 35 rotates due to the flow of exhaust gas. The compressor wheel 32 is fixed to a shaft 39 of the turbine wheel 35. The compressor wheel 32 and the turbine wheel 35 rotate together.

[0037] The turbocharger 3 has a bypass passage 37. The bypass passage 37 is a passage that bypasses the turbine 34. The turbocharger 3 also has a wastegate valve 38. The wastegate valve 38 opens and closes the bypass passage 37.

[0038] The structure of the turbocharger 3 will be described in detail later.

[0039] A catalytic converter 42 is located downstream of the turbine 34 in the exhaust passage 4. The catalytic converter 42 purifies the exhaust gas. The catalytic converter 42 may include, for example, a three-way catalyst. The three-way catalyst oxidizes hydrocarbons and carbon monoxide in the exhaust gas to carbon dioxide and reduces nitrogen oxides to nitrogen.

[0040] 2 shows a control device 10 for a turbocharged engine. The engine 1 has an injector 12. The injector 12 injects fuel to be supplied to a cylinder 11, for example, into the cylinder 11. The engine 1 has a spark plug 13. The spark plug 13 ignites the air-fuel mixture in the cylinder 11.

[0041] The control device 10 includes an ECU (Engine Control Unit) 51. The ECU 51 is a controller based on a known microcomputer, and includes a central processing unit (CPU) 52 that executes programs, a memory 53 configured, for example, of a RAM (Random Access Memory) and / or a ROM (Read Only Memory) that stores programs and data, and an I / F circuit 54 that inputs and outputs electrical signals.

[0042] The control device 10 has various sensors. More specifically, the control device 10 has an air flow sensor 61. The air flow sensor 61 is located downstream of the air cleaner 21 in the intake passage 2. The air flow sensor 61 outputs an electric signal corresponding to the flow rate of intake air flowing through the intake passage 2 to the ECU 51.

[0043] The control device 10 has an accelerator opening sensor 62. The accelerator opening sensor 62 is attached to an accelerator pedal and outputs an electric signal corresponding to the driver's operation of the accelerator pedal to the ECU 51.

[0044] The control device 10 has a supercharging pressure sensor 63. The supercharging pressure sensor 63 is located in the surge tank 24. The supercharging pressure sensor 63 outputs an electric signal corresponding to the pressure of the intake air supercharged by the turbocharger 3 to the ECU 51.

[0045] The control device 10 has a crank angle sensor 64. The crank angle sensor 64 is attached to the engine 1. The crank angle sensor 64 outputs an electric signal corresponding to the rotation angle of the crankshaft of the engine 1 to the ECU 51.

[0046] The control device 10 has a first A / F sensor 65 and a second A / F sensor 66. The first A / F sensor 65 is located upstream of the catalytic converter 42 in the exhaust passage 4. The second A / F sensor 66 is located downstream of the catalytic converter 42. The first A / F sensor 65 and the second A / F sensor 66 output electrical signals corresponding to the oxygen concentration of the exhaust gas to the ECU 51.

[0047] The control device 10 has a catalyst temperature sensor 67. The catalyst temperature sensor 67 is attached to the catalytic converter 42. The catalyst temperature sensor 67 outputs an electric signal corresponding to the temperature of the catalytic converter 42 to the ECU 51.

[0048] The control device 10 has a water temperature sensor 68. The water temperature sensor 68 is attached to the engine 1. The water temperature sensor 68 outputs an electric signal corresponding to the temperature of the coolant of the engine 1 to the ECU 51.

[0049] The ECU 51 determines the operating state of the engine 1 based on signals from these sensors 61 to 68. The ECU 51 outputs control signals to the injector 12, the spark plug 13, the throttle valve 23, and / or the wastegate valve 38 according to the operating state of the engine 1. The engine 1 outputs torque corresponding to the driver's operation.

[0050] Figure 3 illustrates a torque curve of the engine 1. The dashed line in Figure 3 illustrates a torque curve of a naturally aspirated engine without a turbocharger 3. As shown by the solid line in Figure 3, the torque of the turbocharged engine 1 is greater than the torque of a naturally aspirated engine due to the boost pressure of the turbocharger 3.

[0051] (Turbocharger structure) Fig. 4 is a cross-sectional view of the turbine 34 of the turbocharger 3. Fig. 5 shows the turbine wheel 35 as seen from the arrow A in Fig. 4. As described above, the turbine 34 has the turbine wheel 35 and the turbine housing 36. The turbine wheel 35 is housed in the turbine housing 36.

[0052] The wastegate valve 38 opens and closes the bypass passage 37. More specifically, the wastegate valve 38 moves between a position shown by a two-dot chain line in FIG. 4 where the bypass passage 37 is fully closed, and a position shown by a solid line in FIG. 4 where the bypass passage 37 is fully open. The wastegate valve 38 rotates around an axis. The opening degree of the wastegate valve 38 is adjusted by an actuator 381. The actuator 381 adjusts the opening degree of the wastegate valve 38 in response to a control signal from the ECU 51. The force that moves the wastegate valve 38 may be electromagnetic force or air pressure.

[0053] The turbocharger 3 has a locking mechanism 7. The locking mechanism 7 stops the rotation of the turbine wheel 35. The locking mechanism 7 is an example of a resistance applying mechanism that applies resistance to the rotation of the turbine wheel 35. As will be described later, after the engine 1 is started, the locking mechanism 7 stops the rotation of the turbine wheel 35 while the catalytic converter 42 is inactive and the engine 1 is performing a warm-up operation of the catalytic converter 42.

[0054] The lock mechanism 7 has a lock pin 71. The lock pin 71 is a rod having a predetermined length, and as shown in FIG. 4 or FIG. 5 , passes through the turbine housing 36 from the outside of the turbine housing 36 to the turbine wheel 35. The lock pin 71 is attached to the turbine housing 36 so as to be able to move back and forth in the axial direction between a first position and a second position, as indicated by the solid arrow in FIG. 4 or FIG. 5 . An actuator 72 moves the lock pin 71 back and forth between the first position and the second position. The actuator 72 moves the lock pin 71 in response to a control signal from the ECU 51. The force that moves the lock pin 71 may be electromagnetic force or air pressure.

[0055] 4 or 5 indicates the first position of the lock pin 71. The tip of the lock pin 71 in the first position is inserted between the blades 351 of the turbine wheel 35. When the lock pin 71 is in the first position, interference between the lock pin 71 and the turbine wheel 35 prevents the turbine wheel 35 from rotating.

[0056] When the lock pin 71 is in the second position, as shown by the dashed line in Figure 4 or 5, the tip of the lock pin 71 retreats from between the blades 351 of the turbine wheel 35. When the lock pin 71 is in the second position, there is no interference between the lock pin 71 and the turbine wheel 35, allowing the turbine wheel 35 to rotate.

[0057] Here, the tip of the lock pin 71 is tapered as shown in Fig. 5. When the lock pin 71 is displaced from the second position to the first position and the tip of the lock pin 71 is inserted between the blades 351 of the turbine wheel 35, even if the tip of the lock pin 71 hits the blade 351, the tapered tip is pushed by the lock pin 71 so as to follow the surface of the blade 351, causing the turbine wheel 35 to rotate. The tip of the lock pin 71 is stably inserted between the blades 351 of the turbine wheel 35.

[0058] (Engine control) After the engine 1 is started by the driver's start operation, if the temperature of the catalytic converter 42 is low and the catalytic converter 42 is inactive, it is necessary to quickly activate the catalytic converter 42. The ECU 51 determines whether the catalytic converter 42 is inactive based on the signal from the catalyst temperature sensor 67 and the signal from the water temperature sensor 68. The ECU 51 may also determine whether the catalytic converter 42 is inactive based on the signal from at least one of the catalyst temperature sensor 67 and the water temperature sensor 68.

[0059] If the catalytic converter 42 is inactive, the engine 1 executes a warm-up operation for the catalytic converter 42. Specifically, the ECU 51 delays the ignition timing of the spark plug 13, for example, until after the top dead center of the compression stroke, thereby increasing exhaust loss. Since high-temperature exhaust gas is discharged from the engine 1 and supplied to the catalytic converter 42, the temperature of the catalytic converter 42 increases, and the catalytic converter 42 is activated early.

[0060] Furthermore, while the engine 1 is warming up the catalytic converter 42, the ECU 51 fully opens the bypass passage 37 by controlling the wastegate valve 38. Since most of the exhaust gas from the engine 1 passes through the bypass passage 37, which has a relatively low passage resistance, the exhaust gas reaches the catalytic converter 42 at a high temperature without losing heat to the turbine wheel 35 and turbine housing 36. This is advantageous for early activation of the catalytic converter 42.

[0061] The ECU 51 also uses the lock mechanism 7 to stop the rotation of the turbine wheel 35 while the engine 1 is warming up the catalytic converter 42. Even when the bypass passage 37 is fully open, some of the exhaust gas passes through the turbine housing 36, which houses the turbine wheel 35. If the turbine wheel 35 were to rotate due to the exhaust gas flowing through the turbine housing 36, the temperature of the exhaust gas would drop. Therefore, the lock mechanism 7 prevents the turbine wheel 35 from rotating by inserting a lock pin 71 between the vanes 351 of the turbine wheel 35. The exhaust gas passing through the turbine housing 36 does not contribute to the work of rotating the turbine wheel 35, so the temperature drop is suppressed. Because the temperature of the exhaust gas supplied to the catalytic converter 42 is further increased, the catalytic converter 42 is activated more quickly.

[0062] FIG. 6 is a flowchart related to engine control after starting the engine 1. The flow in FIG. 6 starts when the driver starts the engine 1 in response to a start operation. In the first step S61, the ECU 51 acquires signals from the sensors 61 to 68. In the following step S62, the ECU 51 determines whether the catalytic converter 42 is inactivated based on the signal from the catalyst temperature sensor 67 and / or the water temperature sensor 68. If the temperature of the catalytic converter 42 is below a predetermined value and / or the temperature of the engine 1 coolant is below a predetermined value, the ECU 51 determines that the catalytic converter 42 is inactivated. If the catalytic converter 42 is not inactivated, the process in FIG. 6 proceeds to step S610, where the ECU 51 executes normal operation of the engine 1. Note that normal operation here refers to operation without warming up the catalytic converter 42.

[0063] If the catalytic converter 42 is inactive, in step S63, the ECU 51 moves the wastegate valve 38 to a position where the bypass passage 37 is fully opened, and then in the subsequent step S64, the lock mechanism 7 is used to lock the turbocharger 3. That is, the lock mechanism 7 inserts the lock pin 71 between the vanes 351 of the turbine wheel 35.

[0064] In step S65, the ECU 51 determines whether or not to cause the engine 1 to warm up the catalytic converter 42. The ECU 51 determines whether or not to cause the catalytic converter 42 to warm up based on signals from the catalyst temperature sensor 67 and / or the water temperature sensor 68. Furthermore, the ECU 51 determines not to cause the catalytic converter 42 to warm up when the driver has started the vehicle by depressing the accelerator pedal.

[0065] If the ECU 51 determines in step S65 that the engine 1 should not perform the warm-up operation of the catalytic converter 42, the process of FIG. 6 proceeds to step S68, which will be described later.

[0066] If the ECU 51 determines in step S65 that the engine 1 should warm up the catalytic converter 42, the ECU 51 causes the engine 1 to perform the warm-up operation in step S66. As described above, the engine 1 operates with the ignition timing of the spark plug 13 retarded. In the following step S67, the ECU 51 determines whether the temperature of the catalytic converter 42 has exceeded a predetermined value TH based on the signal from the catalyst temperature sensor 67. As long as the temperature of the catalytic converter 42 does not exceed the predetermined value TH, the ECU 51 continues the warm-up operation of the engine 1 in steps S65 and S66.

[0067] If the temperature of the catalytic converter 42 exceeds the predetermined value TH, the warm-up operation is terminated. In step S68, the ECU 51 unlocks the turbine wheel 35. Specifically, the lock mechanism 7 retracts the lock pin 71 from between the blades 351 of the turbine wheel 35. The turbine wheel 35 is then able to rotate. In the following step S69, the ECU 51 returns the wastegate valve 38, which was in a position that fully opens the bypass passage 37, to normal control. The ECU 51 adjusts the opening of the wastegate valve 38 to an opening that corresponds to the operating state of the engine 1. Then, in step S610, the ECU 51 operates the engine 1 normally. The engine 1 outputs torque that corresponds to the driving operation of the driver.

[0068] As described above, while the engine 1 is warming up the catalytic converter 42, the wastegate valve 38 fully opens the bypass passage 37, allowing high-temperature exhaust gas to be supplied to the catalytic converter 42. In addition, the lock pin 71 is inserted between the vanes 351 of the turbine wheel 35, preventing the turbine wheel 35 from rotating due to the exhaust gas passing through the turbine 34. Because the energy of the exhaust gas passing through the turbine 34 is not converted into rotation of the turbine wheel 35, the exhaust gas can pass through the turbine 34 while maintaining its high temperature. This further increases the temperature of the exhaust gas supplied to the catalytic converter 42, allowing the catalytic converter to activate earlier.

[0069] The lock mechanism 7 having the lock pin 71 can stop the rotation of the turbine wheel 35 with a compact structure. The lock mechanism 7 can retract the lock pin 71 from between the vanes 351, so that the turbine wheel 35 can rotate when the engine 1 is not performing a warm-up operation of the catalytic converter 42. The turbocharger 3 can supercharge the intake air when the engine 1 is operating normally.

[0070] (Variation 1) 7 shows a modified example of the lock pin. The lock pin 73 is fixed to the wastegate valve 38. The shape of the lock pin 73 is the same as the lock pin 71 described above, except for its length.

[0071] The wastegate valve 38 can move between a position where the bypass passage 37 is fully closed (i.e., first position) and a position where the bypass passage 37 is fully open (i.e., second position), as shown by the two-dot chain line in Fig. 7, and can also move to a third position shown by the solid line in Fig. 7. More specifically, the third position is the opposite position to the first position, with the second position in between. When the wastegate valve 38 is positioned at the third position, the bypass passage 37 is fully open and the lock pin 71 is inserted between the vanes 351. The actuator 381 moves the wastegate valve 38 between the first position, the second position, and the third position.

[0072] Note that engine control is performed in accordance with the flow in Fig. 6. When the wastegate valve 38 is positioned at the third position in step S63 in Fig. 6, the bypass passage 37 is fully opened and at the same time the lock pin 73 is inserted between the vanes 351 of the turbine wheel 35, locking the turbocharger 3. When the wastegate valve 38 moves from the third position in step S68 in Fig. 6, the lock pin 73 is retracted from between the vanes 351 of the turbine wheel 35. The turbocharger 3 is unlocked. When the wastegate valve 38 returns to normal operation in the following step S69, the wastegate valve 38 moves between the first position and the second position.

[0073] Because the lock pin 73 is fixed to the wastegate valve 38, it is possible to stop the rotation of the turbine wheel 35 with an even more compact structure. In addition, because the wastegate valve 38 also serves as the lock mechanism 7, it is possible to omit a lock mechanism and its actuator separate from the wastegate valve 38.

[0074] (Variation 2) The locking mechanism is not limited to a structure that engages with the turbine wheel 35. FIG. 8 shows a modified example of the locking mechanism. The locking mechanism 70 is configured by a variable vane diffuser 310 of the compressor 31 of the turbocharger 3. The variable vane diffuser 310 is a diffuser through which the intake air compressed by the compressor wheel 35 passes. The variable vane diffuser 310 has variable vanes 311 arranged around the periphery of the compressor wheel 32. The multiple variable vanes 311 are positioned at equal angular intervals around the circumferential direction of the compressor wheel 32. The variable vanes 311 can rotate around a support shaft 312 that is parallel to the rotation axis of the compressor wheel 32. An actuator 74 changes the angle of the variable vanes 311.

[0075] The actuator 74 receives a control signal from the ECU 51 and changes the angle of the variable vanes 311. The force that moves the variable vanes 311 may be electromagnetic force or air pressure. The ECU 51 changes the angle of the variable vanes 311 in accordance with the operating state of the engine 1.

[0076] When the angle of the variable vanes 311 changes, the distance between adjacent variable vanes 311 changes. As shown by the solid line in the upper diagram of FIG. 8, when the angle of the variable vanes 311 increases, the distance between adjacent variable vanes 311 increases. As shown by the two-dot chain line, when the angle of the variable vanes 311 decreases, the distance between adjacent variable vanes 311 decreases. The solid line in the upper diagram of FIG. 8 indicates the maximum angle (i.e., the first angle) of the variable vanes 311 during normal operation of the engine 1, and the first angle of the variable vanes 311 corresponds to the open position of the diffuser opening. The two-dot chain line in the upper diagram of FIG. 8 indicates the minimum angle (i.e., the second angle) of the variable vanes 311 during normal operation of the engine 1, and the second angle of the variable vanes 311 corresponds to the closed position of the diffuser opening.

[0077] When the rotation speed of the engine 1 is high, the ECU 51 increases the angle of the variable vanes 311 and increases the opening of the diffuser. When the rotation speed of the engine 1 is low, the ECU 51 decreases the angle of the variable vanes 311 and decreases the opening of the diffuser. The turbocharger 3 can maintain high operating efficiency while suppressing surges over a wide operating range of the engine 1, from low to high rotation speeds.

[0078] The lower diagram in FIG. 8 shows the state in which the variable vane 311 locks the compressor wheel 32. The angle of the variable vane 311 can be set to an angle greater than the first angle (i.e., the third angle). The tip of the variable vane 311 at the third angle interferes with the compressor wheel 32. The interference between the variable vane 311 and the compressor wheel 32 prevents the compressor wheel 32 from rotating. Locking the compressor wheel 32 also prevents the turbine wheel 35 from rotating. While the engine 1 is warming up the catalytic converter 42, the ECU 51 controls the actuator 74 to set the angle of the variable vane 311 to the third angle. Because the compressor wheel 32 is locked, the turbine wheel 35 does not rotate in the exhaust passage 4, even if the exhaust gas passes through the turbine 34. This suppresses a decrease in the exhaust gas temperature. While the compressor wheel 32 is locked, the wastegate valve 38 fully opens the bypass passage 37. Since high-temperature exhaust gas is supplied to the catalytic converter 42, the catalytic converter 42 is activated quickly.

[0079] The engine control is performed according to the flow in Fig. 6. In step S64 in Fig. 6, the compressor wheel 32 is locked by the variable vane 311. In step S68 in Fig. 6, the compressor wheel 32 is released from the lock by the variable vane 311.

[0080] Using the variable vane diffuser 310 of the compressor 31 as the locking mechanism 70 eliminates the need to add a mechanism to the turbocharger 3 and improves the layout flexibility of the engine system including the engine 1, intake passage 2, exhaust passage 4 and turbocharger 3.

[0081] (Variation 3) The locking mechanism is not limited to a structure that applies mechanical resistance to the turbine wheel 35 or the compressor wheel 32. Fig. 9 shows a modified example of the locking mechanism. The locking mechanism 700 has a motor-generator 8. The motor-generator 8 is attached to the shaft 39 of the turbine 34 of the turbocharger 3. A rotor 81 of the motor-generator 8 is fixed to the shaft 39 and rotates integrally with the turbine wheel 35 and the compressor wheel 32. A stator 82 of the motor-generator 8 is located around the rotor 81 and is fixed to a casing 83 of the motor-generator 8.

[0082] The ECU 51 controls the motor generator 8. When the motor generator 8 is driven, the turbocharger 3 can supercharge the intake air even when the exhaust energy is low. The ECU 51 drives the motor generator 8 when, for example, the engine 1 speed is low. This reduces the turbo lag of the turbocharger 3 and achieves the desired boost pressure when the engine 1 speed is low. The ECU 51 also drives the motor generator 8 to generate electricity when, for example, the exhaust energy is sufficiently high. Part of the exhaust energy is converted into electrical energy by the motor generator 8. The motor generator 8 improves the fuel efficiency of the automobile.

[0083] Under the control of the ECU 51, the motor generator 8 is kept stopped from external loads. After the engine 1 starts, the ECU 51 keeps the motor generator 8 stopped while the catalytic converter 42 is inactive and the engine 1 is warming up the catalytic converter 42. Even if the exhaust gas passes through the turbine 34, the turbine wheel 35 is prevented from rotating. A decrease in the temperature of the exhaust gas passing through the turbine housing 36 is suppressed. Note that while the engine 1 is warming up the catalytic converter 42, the bypass passage 37 is fully open under the control of the wastegate valve 38. The catalytic converter 42 is quickly activated.

[0084] The engine control is performed according to the flow shown in Fig. 6. In step S64 in Fig. 6, the ECU 51 holds the motor generator 8 in a stopped state. In step S68 in Fig. 6, the ECU 51 releases the stopped state of the motor generator 8.

[0085] The ECU 51 may operate the motor generator 8 to generate electricity while the engine 1 is warming up the catalytic converter 42. Even if the turbine wheel 35 attempts to rotate due to the exhaust gas passing through the turbine 34, the motor generator 8 can provide resistance to the rotation of the turbine wheel 35. The turbine wheel 35 does not rotate, or its rotation is suppressed. The motor generator 8 is a resistance providing mechanism. Because the turbine wheel 35 does not rotate, or its rotation is suppressed, a decrease in the temperature of the exhaust gas passing through the turbine 34 is suppressed. The catalytic converter 42 is quickly activated.

[0086] The motor generator 8 makes it possible to apply resistance to the rotation of the turbine wheel 35 or to stop the rotation without affecting the layout of the engine system.

[0087] (Other variations) The engine to which the technology disclosed herein can be applied is not limited to a spark ignition engine, but may also be a compression ignition engine. Compression ignition engines are not limited to diesel engines that are supplied with diesel fuel, but also include engines that are supplied with fuel containing gasoline. The engine to which the technology disclosed herein can be applied is not limited to a reciprocating engine, but may also be a rotary piston engine. [Explanation of symbols]

[0088] 1 engine 2 Intake passage 3. Turbocharger 32 Compressor wheel 34 Turbine 35 Turbine wheel 351 Feather 37 Bypass Passage 38 Wastegate valve 39 Shaft 310 Variable Vane Diffuser 311 Variable Vane 4 Exhaust passage 42 Catalytic converter 7 Locking mechanism (resistance mechanism) 71 Lock pin 73 Lock pin 70 Locking mechanism (resistance mechanism) 700 Locking mechanism (resistance mechanism) 8 Motor generator

Claims

1. The engine and an exhaust passage connected to the engine and through which exhaust from the engine flows; a turbocharger located in the exhaust passage and having a turbine wheel rotated by the exhaust flow in the exhaust passage; a catalytic converter located downstream of the turbocharger in the exhaust passage and purifying the exhaust gas, The turbocharger includes a wastegate valve that fully opens a bypass passage that bypasses the turbine wheel while the engine is warming up the catalytic converter, and a resistance applying mechanism that applies resistance to rotation of the turbine wheel while the engine is warming up the catalytic converter. Control device for turbocharged engine.

2. 2. The control device for a turbocharged engine according to claim 1, The resistance applying mechanism stops rotation of the turbine wheel while the engine is warming up the catalytic converter. Control device for turbocharged engine.

3. 3. The control device for a turbocharged engine according to claim 2, the resistance applying mechanism has a lock pin inserted between blades of the turbine wheel, the resistance applying mechanism inserts the lock pin between the vanes while the engine is warming up the catalytic converter, and retracts the lock pin from between the vanes when the engine is not warming up the catalytic converter. Control device for turbocharged engine.

4. 4. The control device for a turbocharged engine according to claim 3, The lock pin is fixed to the wastegate valve, The wastegate valve moves between a first position where the bypass passage is fully closed, a second position where the bypass passage is fully opened, and a third position where the bypass passage is fully opened and the lock pin is inserted between the vanes. Control device for turbocharged engine.

5. 3. The control device for a turbocharged engine according to claim 2, the turbocharger further includes a compressor wheel fixed to a shaft of the turbine and located in an intake passage of the engine; and a variable vane diffuser through which the intake air compressed by the compressor wheel passes, the opening degree of the diffuser being determined by an angle of a variable vane and being changeable between a closed position and an open position, the resistance applying mechanism changes the angle of the variable vane to a lock position where the variable vane interferes with the compressor wheel; Control device for turbocharged engine.

6. The control device for a turbocharged engine according to claim 1 or 2, the turbocharger further includes a motor-generator located on a shaft of the turbine and rotating the shaft; the resistance applying mechanism applies resistance to rotation of the turbine wheel by the motor generator while the engine is warming up the catalytic converter; Control device for turbocharged engine.

7. After the engine is started, while the engine is warming up the catalytic converter, the wastegate valve in the exhaust passage fully opens the bypass passage that bypasses the turbine of the turbocharger, resistance to rotation of a turbine wheel of the turbine is applied while the engine is warming up the catalytic converter; After the engine has finished warming up the catalytic converter, the wastegate valve returns to normal control and the resistance is released. A method for controlling a turbocharged engine.

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