WO2015087159A1

WO2015087159A1 - Controller and control method for internal combustion engine

Info

Publication number: WO2015087159A1
Application number: PCT/IB2014/002930
Authority: WO
Inventors: Masato Shimizu
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2013-12-09
Filing date: 2014-12-08
Publication date: 2015-06-18
Also published as: JP2015113715A

Abstract

A controller for an internal combustion engine that includes a supercharger, the controller includes an electronic control unit. The electronic control unit is configured to adjust engine torque to correspond to a target torque, execute torque reduction control in which the engine torque is temporarily reduced to correspond to the target torque when a torque reduction request is made to reduce toque of the internal combustion engine, and adjust supercharged pressure to correspond to a target supercharged pressure that is set based on an accelerator pedal operation by a driver, during the torque reduction control.

Description

CONTROLLER AND CONTROL METHOD FOR INTERNAL COMBUSTION

ENGINE

BACKGROUND OF THE I VENTION

1. Field of the Invention

[0001] The present invention relates to a controller and a control method for an internal combustion engine that includes a supercharger. 2. Description of Related Art

[0002] An internal combustion engine (an internal combustion engine with a supercharger) has been known that includes a turbocharger driven by internal energy of exhaust gas or a mechanical supercharger driven by power from a crankshaft and the like.

[0003] Output of the internal combustion engine with the supercharger can be increased when intake efficiency is improved. Especially for the turbocharger, when output torque of the internal combustion engine (hereinafter also referred to as engine torque) needs to be reduced and a throttle valve is thus closed, supercharged pressure may not promptly be lowered. This may results in poor responsiveness to torque reduction.

[0004] For example, Japanese Patent Application Publication No. 5-180027 (JP 5-180027 A) discloses a technique of controlling a waste gate valve, so as to lower a supercharged pressure of intake air in the internal combustion engine with the turbocharger when engine torque is reduced by torque reduction control.

SUMMARY OF THE INVENTION

, [0005] According to JP 5-180027 A described above, the supercharger is controlled while a throttle valve is controlled. Thus, the responsiveness to the torque reduction can be improved. Meanwhile, a certain time period is required until the supercharged pressure is increased in the internal combustion engine with the turbocharger. Accordingly, it has been known that, when the internal combustion engine is in a low speed range or in a low torque state, it is difficult to secure sufficient responsiveness to the engine torque. Thus, in the internal combustion engine of JP 5-180027 A described above, responsiveness to the engine torque increase from the torque reduction may degraded.

[0006] In order to improve the responsiveness to the engine torque when the internal combustion engine is in the low speed range or in the low torque state, it is considered to increase the supercharged pressure in advance. However, if the supercharged pressure remains to be increased for a long time even without a request to do so, exhaust resistance is possible increased, and fuel economy is possibly degraded. In addition, it is also considered to increase the supercharged pressure in advance by predicting a torque request by a driver (requested timing and a requested amount). However, it is difficult to determine the timing and a magnitude of the torque request that will be made by the driver.

[0007] The present invention provides a technique of improving responsiveness to an engine torque increase from torque reduction while suppressing degradation of fuel economy by a controller and a control method for an internal combustion engine with asupercharger..

[0008] In the present invention, the controller for the internal combustion engine with the supercharger secures supercharged pressure, with which responsiveness when the engine torque is increased can be improved, in such a situation that the engine torque is temporarily reduced once and the engine torque is increased (recovered) again thereafter.

[0009] A first aspect of the present invention is a controller for an internal combustion engine, the internal combustion engine mcluding a supercharger, the controller includes an electronic control unit. The electronic control unit is configured to: (i) adjust engine torque to correspond to a target torque; (ii) execute torque reduction control in which the target torque is temporarily reduced when a torque reduction request is made to reduce torque of the internal combustion engine is made; and (Hi) adjust supercharged pressure to correspond to a target supercharged pressure that is set based on an accelerator pedal operation by a driver, during the torque reduction control. [0010] According to this configuration, when the torque reduction is requested, the target torque is reduced to correspond to the target torque even when the driver depresses an accelerator pedal. Accordingly, a gear shifting shock and the like during ^• gear shifting can be suppressed.

[0011] Meanwhile, during the torque reduction control, the target supercharged pressure is set on based on the accelerator pedal operation by the driver. Thus, for example, when the driver maintains a depression amount of the accelerator pedal, or when the driver further depresses the accelerator pedal, the supercharged pressure can be maintained to be at least equal to the supercharged pressure before the torque reduction request even during the torque reduction control. In other words, according to this configuration, while an increase of the supercharged pressure in advance is suppressed for a short time (during the torque reduction), it is possible even during the torque reduction control to secure the supercharged pressure that is required to make the engine torque after the torque reduction control promptly correspond to the target torque that is based on an intention of the driver (that is set on the basis of the accelerator pedal operation by the driver).

[0012] _. According to this configuration, when high responsiveness to the increase of the engine torque is not requested (for example, when the driver takes his/her feet off the accelerator pedal during the torque reduction control), the target supercharged pressure is lowered. Thus, it is possible by suppressing unnecessary increase of the supercharged pressure to suppress degradation of fuel economy.

[0013] As described above, according to the above configuration, it is possible to improve responsiveness when the engine torque is increased from the torque reduction while the degradation of the fuel economy is suppressed.

[0014] In the controller, the electronic control unit may be configured to execute the torque reduction control by adjusting an intake air amount into the internal combustion engine and reducing an opening degree of a throttle valve.

[0015] According to this configuration, differing from the torque reduction by an ignition delay, in intake system torque reduction, by which the supercharged pressure is lowered, the supercharged pressure is adjusted so as to correspond to the target supercharged pressure even during the torque reduction control. Accordingly, it is possible to improve the responsiveness to the engine torque increase from the intake system torque reduction. The intake system torque reduction, a degree of the torque reduction of which is larger than in the torque reduction by the ignition delay is adopted. Thus, even when the supercharged pressure is increased in correspondence with the accelerator pedal operation by the driver, a torque reduction amount that corresponds to the target torque can easily be realized.

[0016] In this configuration, the torque reduction control may be executed only by reducing the opening degree of the throttle valve. Alternatively, in order to increase the responsiveness to the torque reduction, the torque reduction control by the ignition delay may be used together.

[0017] In the controller, the supercharger may include a turbine wheel provided in an exhaust passage. The internal combustion engine may include a waste gate valve · provided in a bypass passage that bypasses the turbine wheel, and the bypass passage is connected to an upstream side and a downstream side of the turbine wheel in the exhaust passage.. The electronic control unit may be configured to adjust the supercharged pressure by changing an opening degree of the waste gate valve.

[0018] According to this configuration, when the opening degree of the waste gate valve is reduced, an exhaust amount flowing on the bypass passage side is reduced (the exhaust amount flowing on the turbine wheel side is increased). Thus, the supercharged pressure can easily be increased.

[0019] In the controller, the electronic control unit may be configured to issue the torque reduction request during at least one of the gear shifting, spinning of at least one drive wheel in a four wheel drive vehicle, and vehicle stability control.

[0020] According to this configuration, after the gear shifting shock is reduced, after the spinning of the drive wheel in the four wheel drive vehicle is suppressed to secure a contact property, or after stability of the vehicle is secured in the vehicle stability control (VSC), the engine torque is promptly increased. Thus, accelerating performance can be improved.

[0021] A second aspect of the present invention is a control method for an internal combustion engine, the internal combustion engine including a supercharger, the control method includes: adjusting engine torque to correspond to a target torque; executing torque reduction control in which the target torque is temporarily reduced when a torque reduction request is made to reduce torque of the internal combustion engine; and adjusting supercharged pressure to correspond to a target supercharged pressure that is set based on an accelerator pedal operation by a driver, during the torque reduction control.

[0022] As described above, according to the controller and the control method for the internal combustion engine with the supercharger according to the present invention, the responsiveness to the engine torque increase from the torque reduction can be improved while the degradation of the fuel economy is suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a schematic configuration diagram of a vehicle in which a controller according to an embodiment of the present invention is installed;

FIG. 2 is a schematic configuration diagram of an engine and an intake/exhaust system thereof according to the embodiment;

FIG. 3 is timing charts for schematically illustrating supercharged pressure control during torque reduction according to the embodiment;

FIG. 4 is a flowchart for illustrating operation procedures of the supercharged pressure control according to the embodiment; and

FIG. 5 is timing charts for schematically illustrating supercharged pressure control of a comparative example during the torque reduction. DETAILED DESCRIPTION OF EMBODIMENTS

[0024] A description will hereinafter be made on an embodiment for carrying out the present invention based on the drawings. This embodiment will be described for a case where the present invention is applied to a front-engine, front-wheel-drive (FF) vehicle.

[0025] FIG. 1 is a schematic configuration diagram of a vehicle in which a controller according to this embodiment is installed. As shown in FIG. 1, this vehicle includes an engine 1, a torque converter 30, an automatic transmission 10, a differential gear mechanism 38, drive wheels (front wheels) 40, a power train manager (PTM) 6, an engine electronic control unit (ECU) 9, an electronic controller transmission (ECT)-ECU 7. A description will hereinafter be made on an overall configuration of the engine 1, a power transmission apparatus including the automatic transmission 10, and a control system centered on the PTM 6, the engine ECU 9, and the ECT-ECU 7.

[0026] First, the overall configuration of the engine will be described. FIG. 2 is a schematic configuration diagram of the engine 1 and an intake/exhaust system thereof. FIG. 2 only shows a configuration of one cylinder in the engine 1 for the sake of convenience. The engine 1 is a four-cylinder gasoline engine, for example, and includes: a piston 12 that forms a combustion chamber 11; and a crankshaft 13 as an output shaft. The piston 12 is coupled to the crankshaft 13 via a connecting rod 14, and reciprocal movement of the piston 12 is converted to rotation of the crankshaft 13 by the connecting rod 14.

[0027] A signal rotor 15 has a plurality of projections (teeth) 16 on an outer peripheral surface thereof, and is attached to the crankshaft 13. A crank position sensor 81 is arranged near a side of the signal rotor 15. The crank position sensor 81 is an electromagnetic pick-up, for example, and generates a pulse signal (an output pulse) when the crankshaft 13 rotates. The pulse signal corresponds to the projection 16 of the signal rotor 15.

[0028] A coolant temperature sensor 82 detects an engine coolant temperature (a coolant temperature) Tw, and is arranged in a cylinder block 17. An ignition plug 2 is arranged in the combustion chamber 11. Ignition timing of the ignition plug 2 is adjusted by an igniter 21. The igniter 21 is controlled by the engine ECU 9.

[0029] An intake passage 3 and an exhaust passage 4 are connected to the combustion chamber 11. An intake valve 31 is provided between the intake passage 3 and the combustion chamber 11. An exhaust valve 41 is provided between the exhaust passage 4 and the combustion chamber 11. A communication between the intake passage 3 and the combustion chamber 11 is opened or blocked when the intake valve 31 is driven to be opened or closed. A communication between the exhaust passage 4 and the combustion chamber 11 is opened or blocked when the exhaust valve 41 is driven to be opened or closed. These intake valve 31 and exhaust valve 41 are respectively driven to be opened or closed by rotation of an intake camshaft (not shown) and rotation of an exhaust camshaft 41a. The rotation of the crankshaft 13 is transmitted to the intake camshaft and the exhaust camshaft 41a.

[0030] In the intake passage 3, an air cleaner 32, an airflow meter 83 of hot wire type, an intake temperature sensor 84 (built in the airflow meter 83), an intake pressure sensor 80, and an electronically-controlled throttle valve 33 for adjusting an intake air amount of the engine _.1 are arranged. The throttle valve 33 is driven by a throttle motor 34. An opening degree (a throttle opening degree 0th) of the throttle valve 33 can be controlled electronically and independently of an operation of an accelerator pedal 73 by a driver. The throttle opening degree 0th is detected by a throttle opening degree sensor 85.

[0031] An injector 35 for fuel injection is arranged in the intake passage 3. A fuel pump supplies fuel at a specified pressure from a fuel tank to the injector 35. Then, the fuel is injected into the intake passage 3 in conjunction with opening of the injector 35. Such injected fuel is mixed with the intake air, turns into air-fuel mixture, and is introduced into the combustion chamber 11. The air-fuel mixture that is introduced in the combustion chamber 11 undergoes a compression stroke before being ignited by the ignition plug 2 and combusted. The combustion of the air-fuel mixture in this combustion chamber 11 causes reciprocal motion of the piston 12, and further causes the crankshaft 13 to rotate. [0032] Two three-way catalysts 42, 43 are disposed in the exhaust passage 4. The three-way catalysts 42, 43 each have an 0₂ storage function to store oxygen. The three-way catalysts 42, 43 can each oxidize or reduce HC, CO, and NOx even when an air-fuel ratio is shifted from a theoretical air-fuel ratio to a certain extent. An air-fuel ratio sensor (an A/F sensor) 86 is arranged on an upstream side of the three-way catalyst 42 on an upstream side in the exhaust passage 4, and an oxygen sensor (an 0₂ sensor) 87 is arranged on an upstream side of the three-way catalyst 43 on a downstream side in the exhaust passage 4.

[0033] Furthermore, this engine 1 is provided with a turbocharger 5. The turbocharger 5 includes a turbine wheel 52 and a compressor wheel 53 that are coupled to each other via a turbine shaft 51. The compressor wheel 53 is arranged to face the inside of the intake passage 3, and the turbine wheel 52 is arranged to face the inside of the exhaust passage 4. Accordingly, the turbocharger 5 performs a so-called supercharging operation, in which an exhaust flow (an exhaust pressure) received by the turbine wheel 52 is used to rotate the compressor wheel 53, so as to increase the intake pressure.

[0034] On an upstream side of the throttle valve 33 in the intake passage 3, an intercooler 36 is provided to forcibly cool the intake air, a temperature of which is increased by supercharging in the turbocharger 5. An exhaust bypass passage 47 that bypasses the turbine wheel 52 and is connected to an upstream side and a downstream side of the turbine wheel 52 is provided in the exhaust passage 4. A waste gate valve 48 is provided in this exhaust bypass passage 47. An opening degree of the waste gate valve 48 is controlled by the engine ECU 9. When the waste gate valve 48 is opened, the exhaust gas bypasses the turbine wheel 52 and flows into the exhaust bypass passage 47, and the supercharged pressure is thereby lowered. On the other hand, when the waste gate valve 48 is closed, the exhaust gas flows to the turbine wheel 52 side, and the supercharged pressure is thereby increased.

[0035] The intake passage 3 and the exhaust passage 4 are connected by an EG passage 44. This EGR passage 44 appropriately recirculates some of the exhaust gas into the intake passage 3 and resupplies it to the combustion chamber 11, so as to lower a combustion temperature and thereby reduce a NOx generation amount. The EGR passage 44 is provided with: an EGR valve 45 that is opened and closed in a stepless manner by electronic control and can adjust a flow rate of the exhaust gas that flows through the EGR passage 44; and an EGR cooler 46 that cools the exhaust gas recirculated in the EGR passage 44.

[0036] Next, the power transmission apparatus will be described. The power transmission apparatus installed in the vehicle includes the torque converter 30 and the automatic transmission 10. The torque converter 30 is a fluid transmission device that transmits power generated by the engine 1 to the automatic transmission 10 via a fluid. The torque converter 30 includes a pump impeller (not shown) that is coupled to the crankshaft 13, a turbine runner (not shown), and a stator (not shown). A lock-up clutch (not shown) as a direct coupling clutch is provided between the pump impeller and the turbine runner. When this lock-up clutch is completely engaged, the pump impeller and the turbine runner rotate integrally.

[0037] The automatic transmission 10 has a first planetary gear urrit 18, a second planetary gear unit 19, and a third planetary gear unit 20. The automatic transmission 10 shifts_.rotation of an input shaft (not shown) that is a turbine shaft of the torque converter 30 rotationally driven by the engine 1, and outputs the rotation to the differential gear mechanism 38 from an output rotational member (not shown) for transmitting the power. Accordingly, the output of the engine 1 is transmitted to the pair of drive wheels 40 via the torque converter 30, the automatic transmission 10, the differential gear mechanism 38, and an axle 39.

[0038] The automatic transmission 10 has hydraulic frictional engagement elements, such as a multiplate clutch and a multiplate brake, engagement of each of which is controlled by a hydraulic actuator. These clutch and brake are each switched between an engagement state and a disengagement state by excitation and non-excitation of a linear solenoid valve in a hydraulic control circuit 37 as well as by current control.

[0039] In this automatic transmission 10, when the clutch or the brake is engaged or disengaged into a specified state, any of six forward travel shift stages from first to sixth shift stages (gear stages) is established, or a reverse travel shift stage is set. A shift ratio of the each shift stage is appropriately defined by each of gear ratios (= the number of teeth of a sun gear/the number of teetii of a ring gear) pi, p2, p3 of the first planetary gear unit 18, the second planetary gear unit 19, and the third planetary gear unit 20.

[0040] A rotational speed of the input shaft (a turbine rotational speed) is detected by a turbine rotational speed sensor 70. Meanwhile, a rotational speed of the output rotational member in the automatic transmission 10 is detected by a vehicle speed sensor 58. The current shift stage of the automatic transmission 10 can be determined on the basis of a ratio of the rotational speeds (the output rotational speed/the input rotational speed) that is obtained by output signals from these turbine rotational speed sensor 70 and vehicle speed sensor 58.

[0041] Next, the control system will be described below. In the control system shown in FIG. 1, the PTM 6 that comprehensively controls an entire power train is provided at a higher level of the engine ECU 9. The PTM 6, the engine ECU 9, and the ECT-ECU 7 are configured such that signals can be transmitted and received among them. In addition to a torque request from the driver through an operation of the accelerator pedal 73, the PTM 6 receives, for example, a torque request from the ECT-ECU 7 as well as torque requests from a vehicle stability control (VSC)-ECU, a traction control (TRC)-ECU, a cruise control system (CRC), an antilock brake system (ABS), and the like (not shown). The PTM 6 aggregates various types of the received torque requests, sets target torque of the engine 1 in accordance with properties of the aggregated torque requests, converts the target torque into a digital signal, and supplies a target torque signal as the digital signal to the engine ECU 9.

[0042] As shown in FIG. 1 and FIG. 2, the engine ECU 9 is connected to the intake pressure sensor 80, the crank position sensor 81, the coolant temperature sensor 82, the airflow meter 83, the intake temperature sensor 84, the throttle opening degree sensor 85, the air-fuel ratio sensor 86, the oxygen sensor 87, and an accelerator pedal position sensor 88. [0043] The intake pressure sensor 80 detects the intake pressure in the intake passage 3, and transmits a detection signal to the engine ECU 9. The coolant temperature sensor 82 detects the engine coolant temperature Tw, and transmits a detection signal to the engine ECU 9. The airflow meter 83 detects an amount of the air suctioned into the engine 1, and transmits a detection signal to the engine ECU 9. The intake temperature sensor 84 detects a temperature of the air suctioned into the engine 1 (an intake temperature), and transmits a detection signal to the engine ECU 9. The throttle opening degree sensor 85 detects the opening degree of the throttle valve 33 that is adjusted by the throttle motor 34, and transmits a detection signal to the engine ECU 9. The air-fuel ratio sensor 86 detects an air-fuel ratio of the combusted air-fuel mixture from oxygen concentration in the exhaust gas, and transmits a detection signal to the engine ECU 9. The oxygen sensor 87 detects an air-fuel ratio of the exhaust gas that flows out of the three-way catalyst 42, and transmits a detection signal to the engine ECU 9. The accelerator pedal position sensor 88 detects a depression degree (an accelerator pedal position O_ACC) of the accelerator pedal 73, and transmits a detection signal to the engine ECU 9. The engine ECU 9 calculates an engine speed Ne based on a pulse signal from the crank position sensor. 81.

[0044] Based on the detection signals of these various sensors, the engine ECU 9 executes various types of control for the engine 1. For example, the engine ECU 9 executes well-known ignition timing control of the ignition plug 2, fuel injection control of the injector 35 (air-fuel ratio feedback control based on the each output of the air-fuel ratio sensor 86 and the oxygen sensor 87), drive control of the throttle motor 34, in which the throttle opening degree 0th is controlled on the basis of the actual accelerator pedal position O_ACC from a relation stored in advance, and the like.

[0045] Meanwhile, as shown in FIG. 1, the ECT-ECU 7 is connected to the vehicle speed sensor 58, the turbine rotational speed sensor 70, a position switch 90 of a shift lever .71 , a depression force sensor 91 of a brake pedal 72, and an oil temperature sensor 89. [0046] The vehicle speed sensor 58 detects the rotational speed of the output rotational member of the automatic transmission 10, and transmits a detection signal to the ECT-ECU 7. The turbine rotational speed sensor 70 detects the rotational speed of the input shaft in the automatic transmission 10 (the turbine rotational speed), and transmits a detection signal to the ECT-ECU 7. The position switch 90 detects a position of the shift lever 71, and transmits a detection signal to the ECT-ECU 7. The depression force sensor 91 detects a depression force on the brake pedal 72 (a force that the driver exerts to depress the brake pedal 72), and transmits a detection signal to the ECT-ECU 7. The oil temperature sensor 89 detects a temperature (a hydraulic temperature) of oil that is used for actuation and lubrication of the automatic transmission 10, and transmits a detection signal to the ECT-ECU 7.

[0047] In this embodiment, the ECT-ECU 7 controls the automatic transmission 10 such that any of the shift stages from the first shift stage to the six shift stage is established when the shift lever 71 is operated to a D (drive) position and a D (drive) range is thereby selected. More specifically, the ECT-ECU 7 calculates a vehicle speed V from the output signal of the vehicle speed sensor 58, obtains the accelerator pedal position OACC from the engine ECU 9, and refers to, a shift chart stored in a ROM (not shown) or the like to calculate a target gear stage on the basis of the vehicle speed V and the accelerator pedal position OACC- Then, the ECT-ECU 7 calculates the ratio of the rotational speeds (the output rotational speed/the input rotational speed) obtained from the output signals of the turbine rotational speed sensor 70 and the vehicle speed sensor 58 to determine a current gear stage, compares the current gear stage and the target gear stage to determine whether a shift operation is necessary.

[0048] If the gear shifting is not necessary as a result of this determination, the ECT-ECU 7 outputs a solenoid control signal that is used to maintain the current gear stage to the hydraulic control circuit 37. On the other hand, if the current gear stage differs from the target gear stage, the ECT-ECU 7 executes the shift control to output a solenoid control signal that is used to set the target gear stage to the hydraulic control circuit 37. [0049] A description will hereinafter be made on torque control and supercharged pressure control during a normal time. During the normal time (that is, when torque reduction, which will be described below, is not requested), the PTM 6 uses a predetermined map (or a function expression) to set target torque Tet on the basis of the depression degree of me accelerator pedal 73 by the driver (the accelerator pedal position QACC), and outputs the set target torque Tet to the engine ECU 9. Then, the engine ECU 9 executes the torque control as follows. The engine ECU 9 sets a target throttle opening degree Gtht by using data of the target throttle opening degree Gtht, the data being prepared in advance by an experiment and using the engine speed Ne and the target torque Tet as variables, for example. Then, the engine ECU 9 drives the throttle motor 34 such that the target throttle opening degree Gtht and the actual throttle opening degree Gth correspond to each other, and adjusts output torque Te of the engine 1.

[0050] In conjunction with the above, the engine ECU 9 executes the supercharged pressure control, in which an opening degree of the waste gate valve 48 is controlled such that a target supercharged pressure Pt that is set in accordance with (on the basis of) the target torque Tet and an actual supercharged pressure P correspond to each other. More specifically, the ROM (not shown) of the engine ECU 9 stores a target supercharged pressure map, for which a supercharged pressure (a target supercharged pressure) that is required to achieve the target torque Tet is measured for each driving condition with the target torque Tet being used as a parameter, and in which, based on a measurement result, a relation between the target torque Tet and the target supercharged pressure Pt is defined. The engine ECU 9 refers to such a target supercharged pressure map, and calculates the target supercharged pressure Pt from the target torque Tet, which is set on the basis of the accelerator pedal position GACC- Then, the engine ECU 9 compares the actual supercharged pressure P (the intake pressure detected by the intake pressure sensor 80) with the target supercharged pressure Pt, and controls the opening degree of the waste gate valve 48 such that the actual supercharged pressure P and the target supercharged pressure Pt correspond to each other. [0051] Next, torque reduction control during gear shifting will be described. As described above, the ECT-ECU 7 executes the gear shifting operation when the current gear stage differs from the target gear stage. When the gear is shifted in the automatic transmission 10, a shock on gear shifting may occur due to an abrupt change in the torque that is transmitted to the automatic transmission 10. In more detail, the gear shifting in the automatic transmission 10 undergoes a process from a torque phase to an inertia phase and then terminated, the torque phase being a phase in a first half of the gear shifting in which a rotational speed of each of rotational members in the automatic transmission 10 is not changed for the gear shifting and in which the input rotational speed and the output rotational speed are defined by the gear ratio, and the inertia phase being a phase in a latter half of the gear shifting in which the rotational speed of each of the rotational members is changed for a change of the gear ratio. Then, a gear shifting shock occurs when rotary inertia torque (inertia torque) of the engine 1 during a change of the engine speed Ne is superimposed on the output torque Te of the engine 1 and transmitted to the input shaft of the automatic transmission 10.

[0052] Thus, in order to reduce the gear shifting shock by reducing an influence of the rotary inertia torque of the engine 1, the controller (the PTM 6, the ECT-ECU 7, and the engine ECU 9) of this embodiment is configured to execute torque reduction control in which the output torque Te of the engine 1 is temporarily reduced in the inertia phase where the rotational speed is changed.

[0053] More specifically, the ECT-ECU 7 is configured to calculate a target torque reduction amount Ted on the basis of a driving state of the vehicle when the ECT-ECU 7 compares the current gear stage with the target gear stage and determines that the gear shifting operation is necessary. In more detail, the ECT-ECU 7 refers to a map stored in the ROM, for example, and calculates the target torque reduction amount Ted on the basis of the output torque Te of the engine 1 that is converted from the intake air amount detected by the airflow meter 83 and the output speed that is obtained from the output signal of the vehicle speed sensor 58. Then, the ECT-ECU 7 subtracts the target torque reduction amount Ted from the output torque Te of the engine 1 to calculate target torque during the gear shifting Tect (an absolute value), and outputs this target torque during the gear shifting Tect as a torque request to the PTM 6.

[0054] At this time, the PTM 6 receives not only the torque request from the ECT-ECU 7 but also a torque request from the driver through a depressing operation of the accelerator pedal 73. As described above, the PTM6 determines performance to be prioritized in the engine 1 in accordance with the property of the torque request. In this case, the PTM6 prioritizes the torque request from the ECT-ECU 7, and outputs the target torque during the gear shifting Tect to the engine ECU 9.

[0055] Once receiving a command from the PTM 6, the engine ECU 9 drives the throttle motor 34 to reduce the throttle opening degree 0th. Then, the engine ECU 9 temporarily reduces the output torque Te of the engine 1 such that the output torque Te of the engine 1 corresponds to the target torque during the gear sWfting Tect.

[0056] In addition to the reduction of the throttle opening degree 0th, ignition timing of the ignition plug 2 is delayed to temporarily reduce the output torque Te of the engine 1. In such a case, the ECT-ECU 7 calculates target torque during the gear shifting for an ignition delay, which is different from the target torque during the gear shifting Tect, and outputs the target torque during the gear shifting for the ignition delay to the PTM 6. In this case, the engine ECU9 that receives a command from the PTM 6 controls the igniter 21 and delays the ignition timing.

[0057] When {the rotational speed of the input shaft of the automatic transmission 10 - (the rotational speed of the output rotational member of the automatic transmission 10 x the gear ratio of the automatic transmission 10)} becomes smaller than a specified threshold and the torque reduction is terminated, the PTM 6 sets the target torque Tet on the basis of the torque request from the driver through the depressing operation of the accelerator pedal 73, and outputs the target torque Tet to the engine ECU 9. Once receiving a command from the PTM 6, the engine ECU 9 drives the throttle motor 34 to increase the throttle opening degree 0th. Then, the engine ECU 9 increases the output torque Te of the engine 1 such that the output torque Te of the engine 1 corresponds to the target torque Tet. ,

16

[0058] A description will be made on the supercharged pressure control during the torque reduction with reference to FIG. 5. FIG. 5 is tirning charts for schematically illustrating the supercharged pressure control of a comparative example during the torque reduction, (a) of FIG. 5 shows the target torque (the target torque during the gear shifting Tect) that is output from the PTM 6 to the engine ECU 9, (b) of FIG. 5 shows the target throttle opening degree 9tht that is set in the engine ECU 9 (a solid line) and the actual throttle opening degree 9th (a broken line), (c) of FIG. 5 shows the target supercharged pressure Pt that is set in the engine ECU 9 (a solid line) and the actual supercharged pressure P (a broken line), and (d) of FIG. 5 shows the output torque Te of the engine 1 to be realized.

[0059] When a torque reduction request is issued by the ECT-ECU 7, the PTM 6 outputs the target torque during the gear shifting Tect such as one shown in (a) of FIG. 5 to the engine ECU 9. The engine ECU 9 uses data of the target throttle opening degree 9tht that is prepared in advance by an experiment and that uses the engine speed Ne and the target torque during the gear shifting Tect as variables, so as to set the target throttle opening degree 9tht such as one shown in (b) of FIG. 5. Based on the target throttle .opening degree 9th, the engine. ECU 9. drives the throttle motor 34 and controls the throttle valve 33 to a closed side.

[0060] If the torque reduction is performed in this state, possible necessity for increasing the supercharged pressure P is low. Rather, the high supercharged pressure degrades the responsiveness to the torque reduction. Accordingly, the engine ECU 9 refers to the target supercharged pressure map, and sets the target supercharged pressure Pt such as one shown in (c) of FIG. 5 with the target torque during the gear shifting Tect being the target torque Tet on the target supercharged pressure map. Then, the engine ECU 9 compares the supercharged pressure P detected by the intake pressure sensor 80 with the target supercharged pressure Pt. If the supercharged pressure P is higher than the target supercharged pressure Pt, the engine ECU 9 controls the waste gate valve 48 to an open side, so as to lead the exhaust gas to flow through the exhaust bypass passage 47 and lower the supercharged pressure P. In this way, the engine ECU 9 improves the responsiveness to the torque reduction.

[0061] As described above, in the supercharged pressure control of the comparative example, the responsiveness to the torque reduction can be improved not only by controlling the throttle valve 33 but also by controlling the supercharged pressure P. Meanwhile, a certain time period is required for the supercharged pressure P that has been lowered to be increased again. Thus, it has been known that it is difficult in the engine 1 with the turbocharger 5 to secure sufficient engine torque responsiveness in the low speed range or in the low torque state. For this reason, in the supercharged pressure control of the comparative example, responsiveness to the engine torque increase from the torque reduction is possibly degraded. In other words, the throttle valve 33 is controlled to the open side (see (b) of FIG. 5) after the termination of the torque reduction. However, there is a delay in the increase of the supercharged pressure P (see (c) of FIG. 5). Thus, as shown in (d) of FIG. 5, the increase (recovery) of the output torque Te of the engine is possibly delayed.

[0062] In order to handle this delay of the increase of the output torque Te, it is considered to increase the supercharged pressure P in advance so that the engine torque responsiveness is increased in the low torque state. However, if the supercharged pressure P remains to be increased for a long time period even without a request to do so, there is a possibility that the exhaust resistance is increased and the fuel economy is degraded. It is also considered to increase the supercharged pressure P in advance by predicting the torque request (request timing and a request amount) by the driver. However, it is difficult to determine the timing and a level of the torque request that will be made by the driver.

[0063] In this embodiment, in a situation where the output torque Te of the engine

1 (the engine torque) is temporarily reduced and where the engine torque is increased (recovered) again, such supercharged pressure is secured that can improve the responsiveness to the engine torque increase. That is, the target torque is temporarily reduced and the output torque Te (the engine torque) is adjusted to correspond to the target torque. More specifically, when the torque reduction request is issued by the ECT-ECU.7, the PTM 6 and the engine ECU 9 executes the torque reduction control, in which the output torque Te of the engine 1 is temporarily reduced such that the output torque Te of the engine 1 corresponds to the target torque during the gear shifting Tect (first target torque) that is set not on the basis of the depression degree of the accelerator pedal 73 by the driver (the accelerator pedal position OACC)- Meanwhile, the PTM 6 and the engine ECU 9 are configured to execute the supercharged pressure control during the torque reduction control such that the supercharged pressure P corresponds to target supercharged pressure Pet that is set on the basis of the accelerator pedal operation by the driver. More specifically, the PTM 6 and the engine ECU 9 are configured to execute the supercharged pressure control for adjusting the supercharged pressure P such that the supercharged pressure P corresponds to the target supercharged pressure Pet. Here, the target supercharged pressure Pet is set in accordance with target torque for the supercharged pressure control Tept (second target torque), and the target torque for the supercharged pressure control Tept is set on the basis of the depression degree of the accelerator pedal 73 (the accelerator pedal position OACC) by the driver.

[0064] „ In more ..detail, when the torque reduction request is issued by the ECT-ECU 7, the PTM 6 outputs the target torque during the gear shifting Tect to the engine ECU 9 as described above. In addition, the PTM 6 sets the target torque for the supercharged pressure control Tept that is independent of the target torque during the gear shifting Tect, and outputs this target torque for the supercharged pressure control Tept to the engine ECU 9. This target torque for the supercharged pressure control Tept is a target value that is, for example, based on the depression degree of the accelerator pedal 73 (the accelerator pedal position OACC) by the driver during the torque reduction control and is calculated by using a predetermined map (or a function expression) in order to maintain the supercharged pressure even during the torque reduction control. Then, the engine ECU 9 refers to the target supercharged pressure map, calculates the target supercharged pressure Pt with the target torque for the supercharged pressure control Tept being the target torque Tet on the target supercharged pressure map, and sets the target supercharged pressure Pt as the target supercharged pressure Pet during the torque reduction control. For example, when the driver maintains the depression degree of the accelerator pedal 73 before the torque reduction request, or when the driver further depresses the accelerator pedal 73, the target supercharged pressure Pet is set to be at least equal to the target supercharged pressure before the torque reduction request. The engine ECU 9 controls the waste gate valve 48 to the closed side such that the target supercharged pressure Pet, which is set to be at least equal to the target supercharged pressure before the torque reduction request, corresponds to the actual supercharged pressure P, and mamtains (or increases) the supercharged pressure P in order to prepare for the engine torque increase after the termination of the torque reduction. Accordingly, in this embodiment, it is possible to secure the supercharged pressure P during the torque reduction control, the supercharged pressure P being required for engine torque Te after the torque reduction control to promptly correspond to the target torque Tet that is based on the intention of the driver (that is set on the basis of the accelerator pedal operation by the driver).

[0065] Meanwhile, when high responsiveness to the engine torque increase is not requested, that is, for example, when the driver takes his/her foot off the accelerator pedal 73 during the torque reduction control, the target supercharged pressure Pet is lowered. Thus, it is possible by suppressing the unnecessary increase of the supercharged pressure P to prevent degradation of the fuel economy.

[0066] As described above, in this embodiment, the supercharged pressure P is increased in advance only in a limited situation, that is, during the torque reduction upon upsMfting in which the accelerator pedal 73 is depressed. Accordingly, the degradation of the fuel economy can be suppressed, and the supercharged pressure P is increased during the torque reduction control. Thus, it is possible to improve responsiveness to the engine torque increase (recovery) from the torque reduction.

[0067] FIG. 3 is timing charts for schematically illustrating the supercharged pressure control of this embodiment during the torque reduction, (a) of FIG. 3 shows the target torque during the gear shifting Tect (a solid line) that is output from the PTM 6 to the engine ECU 9 and the target torque for the supercharged pressure control Tept (a broken line), (b) of FIG. 3 shows the target throttle opening degree Otht (a solid line) set in the engine ECU 9 and the actual throttle opening degree 9th (a broken line), (c) of FIG. 3 shows the target supercharged pressure Pet (a broken line) that is set in the engine ECU 9 and the actual supercharged pressure P (a solid line), and (d) of FIG. 3 shows the output torque Te of the engine 1 to be realized.

[0068] During upshifting in which the accelerator pedal 73 is depressed, when the torque reduction request is issued by the ECT-ECU 7, the PTM 6 outputs the target torque during the gear shifting Tect (the solid line) such as one shown in (a) of FIG. 3 to the engine ECU 9, and also outputs the target torque for the supercharged pressure control Tept (the broken line) that is different from the target torque during the gear shifting Tect and is set on the basis of the accelerator pedal position OACC to the engine ECU 9. The engine ECU 9 uses data of the target throttle opening degree Otht with the engine speed Ne and the target torque during the gear shifting Tect being the variables, so as to set the target throttle opening degree Otht such as one shown in (b) of FIG. 3, the engine speed Ne and the target torque during the gear shifting Tect being prepared by an experiment in advance. Based on this, the engine ECU 9 drives the throttle motor 34 and controls the throttle valve 33 to the closed side. . , .

[0069] The engine ECU 9 refers to the target supercharged pressure map and calculates the target supercharged pressure Pet such as one shown in (c) of FIG. 3 with the target torque for the supercharged pressure control Tept being the target torque Tet on the target supercharged pressure map. Based on this, the engine ECU 9 controls the opening degree of the waste gate valve 48. More specifically, the engine ECU 9 controls the waste gate valve 48 to the closed side and lets the exhaust gas flow through the turbine wheel 52 side, so as to maintain the high supercharged pressure P. Noted that, when the supercharged pressure P is maintained, compared to a case where the supercharged pressure P is lowered, the intake air amount is increased even at the same throttle opening degree 0th. Thus, the engine ECU 9 takes into account of a relative increasing amount of the supercharged pressure P to correct the target throttle opening degree Otht. [0070] According to this embodiment, during upshifting in which the accelerator pedal 73 is depressed, the output torque Te of the engine 1 is reduced by an amount that corresponds to the inertia torque. Accordingly, the gear shifting shock can be reduced. In addition, when the supercharged pressure P is maintained to be high during the torque reduction control, as shown in (d) of FIG. 3, the output torque (the realized torque) Te of the engine 1 after the termination of the torque reduction can promptly correspond to the target torque Tet.

[0071] Next, a description will be made on a procedure of the supercharged pressure control according to this embodiment along the flowchart in FIG. 4.

[0072] First, in step SI, the PTM 6, the ECT-ECU 7, and the engine ECU 9 obtain parameters related to a driving state of the vehicle, such as the accelerator pedal position B_ACC (detected by the accelerator pedal position sensor 88), the vehicle speed V (detected by the vehicle speed sensor 58, the rotational speed of the input shaft (detected by the turbine rotational speed sensor 70), the intake air amount (detected by the airflow meter 83), and the engine speed Ne (calculated on the basis of the signal from the crank position sensor 81).

. [0073] In next step. S2, based on the accelerator, pedal position 0ACC obtained in step SI, the PTM 6 sets the target torque Tet. In next step S3, the engine ECU 9 refers to the target supercharged pressure map and sets the target supercharged pressure Pt on the basis of the target torque Tet set in step S2.

[0074] In next step S4, the PTM 6 determines whether the torque reduction request is issued by the ECT-ECU 7. If a determination of this step S4 is NO, it is during the normal time, and the process proceeds to step S7. Then, the engine ECU 9 executes the torque control based on the target torque Tet and the supercharged pressure control based on the target supercharged pressure Pt, and the process returns thereafter. More specifically, the engine ECU 9 sets the target throttle opening degree Otht on the basis of the engine speed Ne and the target torque Tet. Then, based on this, the engine ECU 9 drives the throttle motor 34 to adjust the throttle opening degree 9th, and controls the opening degree of the waste gate valve 48 on the basis of the target supercharged pressure Pt, so as to increase or lower the supercharged pressure P.

[0075] On the other hand, if the determination of step S4 is YES, the process proceeds to step S5. Then, the ECT-ECU 7 subtracts the target torque reduction amount Ted from the output torque Te of the engine 1 to set the target torque during the gear sMfting Tect, and the process proceeds to step S6 thereafter.

[0076] If the deteraiination of step S4 is YES, the target torque Tet set in step S2 corresponds to the target torque that is set on the basis of the depression degree of the accelerator pedal 73 by the driver during the torque reduction control. Accordingly, the target torque Tet set in step S2 becomes the target torque for the supercharged pressure control Tept. Thus, if the determination of step S4 is YES, the target supercharged pressure Pt set in step S3 becomes the target supercharged pressure Pet during the torque reduction control.

[0077] In next step S6, the engine, ECU 9 executes the torque reduction control that is based on the target torque during the gear shifting Tect set in step S5 and the supercharged pressure control that is based on the target supercharged pressure Pt (= the target supercharged pressure Pet) set in step S3, and the process returns thereafter. More specifically, the engine ECU 9 sets the target throttle opening degree Otht on the basis of the engine speed Ne and the target torque during the gear shifting Tect. Based on this, the engine ECU 9 drives the throttle motor 34 to reduce the output torque Te of the engine 1. The engine ECU 9 controls the waste gate valve 48 to the closed side on the basis of the target supercharged pressure Pt, so as to increase (or maintain) the supercharged pressure P.

[0078] Next, modified examples of this embodiment will be described. In the above-described embodiment, when the torque reduction request is issued by the ECT-ECU 7, two types of the target torque, one for the torque control and the other for the supercharged pressure control, are set. Instead of this, during spinning of at least one drive wheel in a four-wheel-drive vehicle, two types of the target torque, one for the torque control (first) and for the supercharged pressure control (second), may be set, and the supercharged pressure control may be executed such that the supercharged pressure P corresponds to the target supercharged pressure Pet, which is set on the basis of the accelerator pedal operation by the driver.

[0079] Although not shown, for example, it is set such that a wheel speed sensor for detecting a rotational state of the wheel is attached to each of the four drive wheels 40 in the four-wheel-drive vehicle and that a detection result from the wheel speed sensor is transmitted to the TRC-ECU. Then, the vehicle speed V, which is detected by the vehicle speed sensor 58, is compared with the detection result from the wheel speed sensor. The TRC-ECU is configured such that, when the wheel speed is at least equal to a specific threshold with respect to the vehicle speed V, it is determined that the wheel is spinning and the TRC-ECU outputs the torque request to the PTM 6. According to this first modified example, when the drive wheel 40 spins in the four-wheel-drive vehicle, the output torque Te of the engine 1 is reduced. Accordingly, it is possible to suppress the spinning of the drive wheel 40 to secure a contact property. In addition, after the contact property is secured, the output torque Te of the engine 1 can promptly be increased.

[0080] In another modified example, when vehicle stability control (VSC) is executed, in other, words, when the, torque reduction request is issued by VSC-ECU, two types of the target torque, one for the torque control and the other for the supercharged pressure control, may be set, and the supercharged pressure control may be executed such that the supercharged pressure P corresponds to the target supercharged pressure Pet that is set on the basis of the accelerator pedal operation by the driver.

[0081] For the VSC, control can be applied in which optimum values of a brake oil pressure in each of the wheels, the requested torque, and the like are automatically set to secure stability of the vehicle when a sensor detects a state in which sideslips of the front and rear wheels are likely to occur. For example, it is adapted such that, when the torque reduction request is issued by the VSC-ECU to the PTM 6, two types of the target torque, one for the torque control and the other for the supercharged pressure control, are set. Accordingly, when the sideslip of the vehicle, which tends to occur during cornering on a slippery road surface, for example, is detected, the stability of the vehicle can be secured by reducing the output torque Te of the engine 1. In addition, after the stability of the vehicle is secured, the torque can promptly be increased.

[0082] The present invention is not limited to the above embodiment, but can be implemented in various modes without departing from the spirit and main characteristics thereof.

[0083] In the above embodiment, the description has been made on a case where the present invention is applied to the FF layout vehicle. However, the present invention is not limited thereto. The present invention may be applied to a front-engine, rear-wheel-drive vehicle.

[0084] In the above embodiment, the description has been made on a case where the present invention is applied to the torque reduction control in the stepped automatic transmission 10. However, the present invention is not limited thereto. The present invention may be applied to torque reduction control in a manual transmission or a continuously variable transmission (CVT), for example.

[0085] The above embodiment is configured such that the controller is provided for each function to be controlled, such as the engine ECU 9 for controlling the engine 1 and the ECT-ECU. 7 for. controlling the automatic transmission 10. However, the configuration of the controller is not limited thereto. For example, it may be configured that one controller is provided as an ECU.

[0086] In the above embodiment, the turbocharger 5 is a turbocharger with the waste gate valve 48. However, the turbocharger 5 is not limited thereto. For example, the turbocharger 5 may be a turbocharger in which the turbine wheel 52 includes a variable nozzle vane. In this case, the supercharged pressure P can easily be increased by changing an opening degree of the nozzle vane.

[0087] In the above embodiment, the present invention is applied to the engine 1 that includes the turbocharger 5. However, the present invention is not limited thereto. For example, the present invention may be applied to an engine that includes a mechanical supercharger, and the supercharged pressure P may be maintained to be high by engaging an electromagnetic clutch even during torque reduction. [0088J In the flowchart in the above embodiment, the case is estimated where both of the target torque Tet and the target torque for the supercharged pressure control Tept are set only on the basis of the accelerator pedal position OACC- However, the present invention is not limited thereto. For example, other parameters may be taken into consideration in addition to the accelerator pedal position OACC during the torque reduction control, and the target torque for the supercharged pressure control Tept may thereby be set. In this case, when the torque reduction request is issued, the target torque for the supercharged pressure control Tept is set separate from the target torque Tet in step S2, and the target supercharged pressure Pet is set separate from the target supercharged pressure Pt in step S3.

[0089] In the above embodiment, the target torque for the supercharged pressure control Tept is set on the basis of the depression degree of the accelerator pedal 73 by the driver, and the target supercharged pressure Pet is set in accordance with the target torque for the supercharged pressure control Tept. However, the target supercharged pressure Pet may be set directly from the depression degree of the accelerator pedal 73 by the driver or through a parameter other than the torque by using a predetermined map or the like, for example.

[0090] As described above, the above-described embodiment is merely illustrative in any respect, and thus should not be narrowly construed. Furthermore, all changes and modifications that fall within the scope of the claims and equivalents thereof fall within the scope of the present invention.

[0091] According to the present invention, responsiveness to the engine torque increase from the torque reduction can be improved while degradation of the fuel economy is suppressed. Therefore, the present invention is beneficial for a controller of an internal combustion engine with a supercharger.

Claims

1. A controller for an internal combustion engine, the internal combustion engine including a supercharger, the controller comprising:

an electronic control unit configured to:

(i) adjust engine torque to correspond to a target torque;

(ii) execute torque reduction control in which the target torque is temporarily reduced when a torque reduction request is made to reduce torque of the internal combustion engine; and

(iii) adjust supercharged pressure to correspond to a target supercharged pressure that is set based on an accelerator pedal operation by a driver, during the torque reduction control.

2. The controller according to claim 1 wherein the electronic control unit is configured to execute the torque reduction control by adjusting an intake air amount into the internal combustion engine and reducing an opening degree of a throttle valve.

3. The controller according to claim 1 or 2 wherein

the supercharger includes a turbine wheel provided in an exhaust passage,

the internal combustion engine includes a waste gate valve provided in a bypass passage that bypasses the turbine wheel, and the bypass passage is connected to an upstream side and a downstream side of the turbine wheel in the exhaust passage, and

the electronic control unit is configured to adjust the supercharged pressure by changing an opening degree of the waste gate valve.

4. The controller according to any one of claims 1 to 3 wherein the electronic control unit is configured to issue the torque reduction request during at least one of gear shifting, spinning of at least one drive wheel in a four wheel drive vehicle, or vehicle stability control.

5. A control method for an internal combustion engine, the internal combustion engine including a supercharger, the control method comprising:

adjusting engine torque to correspond to a target torque;

executing torque reduction control in which the engine torque is temporarily reduced to correspond to the target torque when a torque reduction request is made to reduce torque of the internal combustion engine; and

adjusting supercharged pressure to correspond to a target supercharged pressure that is set based on an accelerator pedal operation by a driver, during the torque reduction control.