Control method of vehicle and control device of vehicle

Abstract

The vehicle includes: an internal combustion engine (7) capable of operating as an electric motor using a generator (6); an exhaust catalyst device (24) for purifying the exhaust from the internal combustion engine (7); and an A / F sensor (47) located upstream of the exhaust catalyst device (24) to detect the air-fuel ratio. Fuel injection in the internal combustion engine (7) is stopped when the impact on exhaust performance downstream of the exhaust catalyst device (24) is minimal even if the oxygen storage in the exhaust catalyst device (24) increases. The internal combustion engine (7) is then operated as an electric motor, and air-fuel ratio learning is performed based on the detection value of the A / F sensor (47). This allows the internal combustion engine (7) to operate as an electric motor without deteriorating exhaust performance. Furthermore, air-fuel ratio learning is performed without deteriorating exhaust performance.

Description

Technical Field

[0001] This invention relates to a vehicle control method and a vehicle control device. Background Technology

[0002] For example, Patent Document 1 discloses the following motoring technology.

[0003] That is, after the internal combustion engine stops, the crankshaft is rotated using the power of an electric motor until the exhaust gas remaining in each cylinder is completely discharged from the combustion chamber.

[0004] In Patent Document 1, even when the oxygen storage of the catalyst used for exhaust purification located in the exhaust passage is low, the electric motor is operated when the internal combustion engine is stopped. Therefore, when the internal combustion engine is started again, the oxygen storage of the catalyst increases, and exhaust performance may deteriorate.

[0005] That is, there is room for further improvement in suppressing the deterioration of exhaust performance when the internal combustion engine is operated by an electric motor.

[0006] Patent Document 1: Japanese Patent Application Publication No. 2004-19519 Summary of the Invention

[0007] Regarding the vehicle of the present invention, when the impact on exhaust performance is minimal even if oxygen flows into the exhaust purification catalyst, the fuel injection of the internal combustion engine is stopped, and the internal combustion engine is operated by an electric motor to perform air-fuel ratio learning based on the detection value of the air-fuel ratio sensor.

[0008] According to the present invention, an internal combustion engine can be operated as an electric motor without causing a deterioration in exhaust performance. Furthermore, air-fuel ratio learning can be performed without causing a deterioration in exhaust performance. Attached Figure Description

[0009] Figure 1 This is an explanatory diagram schematically illustrating the system structure of a hybrid vehicle to which the present invention is applied.

[0010] Figure 2 It is an illustrative diagram that schematically represents the system structure of an internal combustion engine.

[0011] Figure 3 This is an explanatory diagram showing the relationship between air-fuel ratio learning and exhaust performance.

[0012] Figure 4 This is a flowchart illustrating the control process for learning the air-fuel ratio in the first embodiment.

[0013] Figure 5 This is a flowchart illustrating the control process for learning the air-fuel ratio in the second embodiment.

[0014] Figure 6 This is a flowchart illustrating the control process for learning the air-fuel ratio in the third embodiment.

[0015] Figure 7 This is a flowchart illustrating the control process for learning the air-fuel ratio in the fourth embodiment.

[0016] Figure 8 This is a flowchart illustrating the control process for learning the air-fuel ratio in the fifth embodiment.

[0017] Figure 9 This is a flowchart illustrating the control process for learning the air-fuel ratio in the sixth embodiment.

[0018] Figure 10 This is a flowchart illustrating the control process for learning the air-fuel ratio in the 7th embodiment.

[0019] Figure 11 This is a flowchart illustrating the control process for learning the air-fuel ratio in the 8th embodiment.

[0020] Figure 12 This is a flowchart illustrating the control process for learning the air-fuel ratio in the 9th embodiment. Detailed Implementation

[0021] An embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

[0022] Figure 1 This is an explanatory diagram schematically illustrating the system structure of a hybrid vehicle to which the present invention is applied.

[0023] The hybrid vehicle has: a drive wheel 1; a drive motor 2 that drives the drive wheel 1 to rotate; an inverter 3 that supplies AC power to the drive motor 2; and a battery 4 and a power generation unit 5 that supply power to the inverter 3.

[0024] The drive motor 2 is used as the drive source to rotate the drive wheel 1 of the vehicle.

[0025] The drive motor 2 is equivalent to an electric motor, for example, it is composed of a synchronous motor that uses permanent magnets for the rotor.

[0026] The drive motor 2 is the vehicle's power source, powered by AC power from the inverter 3. Additionally, the drive motor 2 functions as a generator when the vehicle decelerates. That is, the drive motor 2 can use the regenerative energy generated during vehicle deceleration as electricity to charge the battery 4 via the inverter 3.

[0027] Inverter 3 is a power conversion circuit that converts the electricity generated by the generator unit 5 and the drive motor 2 into DC power and supplies it to the battery 4. In addition, inverter 3 is also a power conversion circuit that converts the DC power output from the battery 4 into AC power and supplies it to the drive motor 2.

[0028] Battery 4 is a secondary battery capable of being charged using the power generated by the power generation unit 5 and the drive motor 2 as DC power. The power charged by battery 4 is supplied to the drive motor 2 via inverter 3.

[0029] The power generation unit 5 is generally composed of the following components: a generator 6, which serves as a generator motor; an internal combustion engine 7, which drives the generator 6 for power generation; and a reducer 8, which is disposed between the generator 6 and the internal combustion engine 7 to connect the two.

[0030] That is, the hybrid vehicle of the present invention operates the internal combustion engine 7 to drive the generator 6.

[0031] The power generation unit 5 is capable of operating (working and stopping) independently of the drive motor 2.

[0032] The generator 6 is, for example, a synchronous motor with permanent magnets used for the rotor.

[0033] The generator 6 converts the rotational energy generated in the internal combustion engine 7 into electrical energy, which is then supplied to the battery 4 and the drive motor 2 via the inverter 3. In addition, the generator 6 also functions as a starter motor when the internal combustion engine 7 is started.

[0034] The reducer 8, equivalent to a gear train, has multiple gears (not shown) that transmit the rotation of the internal combustion engine 7 to the generator 6 at a predetermined reduction ratio (speed ratio). Furthermore, when the generator 6 is used as a starter motor for the internal combustion engine 7, the reducer 8 transmits the rotation of the generator 6 to the internal combustion engine 7. Additionally, the internal combustion engine 7 can operate using the generator 6 while the vehicle is in motion. Generator operation refers to driving the generator 6 to rotate the crankshaft of the internal combustion engine 7.

[0035] Figure 2 This is an explanatory diagram schematically representing the system structure of the internal combustion engine 7.

[0036] The internal combustion engine 7 is a so-called reciprocating internal combustion engine that converts the reciprocating linear motion of the piston 11 into the rotational motion of the crankshaft (not shown) and extracts it as power. The internal combustion engine 7 is configured to change the air-fuel ratio. In addition, the internal combustion engine 7 can be started using a dedicated starter motor, which is different from the generator 6.

[0037] The internal combustion engine 7 has an intake passage 12 and an exhaust passage 13. The intake passage 12 is connected to the combustion chamber 15 via an intake valve 14. The exhaust passage 13 is connected to the combustion chamber 15 via an exhaust valve 16.

[0038] The internal combustion engine 7 has a fuel injection valve 17 that injects fuel (gasoline) directly into the combustion chamber 15. The fuel injected from the fuel injection valve 17 is ignited by a spark plug 19 within the combustion chamber 15. Furthermore, the internal combustion engine 7 can inject fuel into the intake ports of each cylinder.

[0039] The air intake passage 12 is provided with: an air filter 20, which captures foreign objects in the intake air; an air flow meter 21, which detects the amount of intake air; and an electrically operated throttle valve 23, which controls the opening degree according to the control signal from the control unit 22.

[0040] Air flow meter 21 is located upstream of throttle valve 23. Air flow meter 21 has a built-in temperature sensor that can detect the intake air temperature at the intake inlet. Air filter 20 is located upstream of air flow meter 21.

[0041] An exhaust catalyst device 24, consisting of a three-way catalyst or the like, is installed in the exhaust passage 13 as an exhaust purification catalyst.

[0042] Furthermore, the internal combustion engine 7 has an exhaust turbine type turbocharger (turbocharger) 28, namely, a compressor 26 disposed on the intake passage 12 and an exhaust turbine 27 disposed on the exhaust passage 13, which are coaxially mounted. The compressor 26 is disposed upstream of the throttle valve 23 and downstream of the air flow meter 21. The exhaust turbine 27 is disposed upstream of the exhaust catalyst device 24.

[0043] A recirculation passage 29 is connected to the intake passage 12. One end of the recirculation passage 29 is connected to the intake passage 12 upstream of the compressor 26, and the other end is connected to the intake passage 12 downstream of the compressor 26.

[0044] An electrically operated recirculation valve 30 is provided in the recirculation passage 29, capable of releasing boost pressure from the downstream side of the compressor 26 to the upstream side of the compressor 26. Furthermore, as the recirculation valve 30, a so-called check valve that opens only when the pressure on the downstream side of the compressor 26 is greater than or equal to a specified pressure can also be used.

[0045] Additionally, an intercooler 31 is provided on the downstream side of the compressor 26 in the intake passage 12 to improve filling efficiency by cooling the intake air compressed (pressurized) by the compressor 26. The intercooler 31 is located further downstream than the downstream end of the recirculation passage 29 and further upstream than the throttle valve 23.

[0046] An exhaust bypass passage 32 is connected to the exhaust passage 13, bypassing the exhaust turbine 27 and connecting the upstream and downstream sides of the exhaust turbine 27. The downstream end of the exhaust bypass passage 32 is connected to the exhaust passage 13 at a position upstream of the exhaust catalyst device 24. An electrically operated wastegate valve 33 is provided in the exhaust bypass passage 32 to control the exhaust flow rate within the exhaust bypass passage 32. The wastegate valve 33 allows a portion of the exhaust gas directed to the exhaust turbine 27 to bypass to the downstream side of the exhaust turbine 27, thereby controlling the boost pressure of the internal combustion engine 7.

[0047] also, Figure 1 34 in the figure is the main pipe section of the intake passage 12. Regarding the intake passage 12, if the internal combustion engine 7 is a multi-cylinder internal combustion engine, the part further downstream than the main pipe section 34 serves as the intake manifold and branches to each cylinder.

[0048] As the moving valve mechanism of the intake valve 14, the internal combustion engine 7 has an intake-side variable valve mechanism 41 that can change the valve timing (opening and closing timing) of the intake valve 14.

[0049] The intake-side variable valve mechanism 41 is a phase-variable mechanism that continuously advances or lags the phase of the center angle of the intake valve 14's lift (relative to the phase of the crankshaft, not shown). The phase-variable mechanism is, for example, a structure known according to Japanese Patent Application Publication No. 2002-89303, which causes the phase of the intake camshaft 42, which drives the opening and closing of the intake valve 14, to lag or advance relative to the crankshaft (not shown).

[0050] Furthermore, the valve mechanism of the exhaust valve 16 is a typical direct-acting valve mechanism. That is, the phase of the exhaust valve 16's operating head angle and center head angle remains constant.

[0051] The intake-side variable valve mechanism 41 is, for example, hydraulically driven and controlled according to a control signal from the control unit 22. That is, the control unit 22 acts as a control unit that controls the intake-side variable valve mechanism 41. Furthermore, the valve timing of the intake valve 14 can be variably controlled using the control unit 22. By changing the closing timing of the intake valve 14, the intake-side variable valve mechanism 41 can change the amount of air in the cylinder.

[0052] The intake-side variable valve mechanism 41 can be a structure that allows for independent changes to the opening and closing timing of the intake valve 14. Furthermore, the intake-side variable valve mechanism 41 is not limited to a hydraulically driven structure; it can also be electrically driven by a motor or the like.

[0053] Furthermore, the intake-side variable valve mechanism 41 can be a variable head and operating angle mechanism capable of changing the head and operating angle of the intake valve 14. The variable head and operating angle mechanism is, for example, a structure known from Japanese Patent Application Publication No. 2002-89303, which allows the head and operating angle of the intake valve 14 to increase and decrease simultaneously and continuously.

[0054] In addition, the intake-side variable valve mechanism 41 can be composed of the following components: a phase variable mechanism that causes the phase of the center angle of the intake valve 14 to be continuously advanced or delayed; and a head operating angle variable mechanism that can change the head amount and operating angle of the intake valve 14.

[0055] The control unit 22 is a well-known electronic computer with a CPU, ROM, RAM and input / output interfaces.

[0056] In addition to the detection signal from the air flow meter 21, the control unit 22 also receives detection signals from various sensors, including an intake-side camshaft position sensor 43 for detecting the valve timing of the intake valve 14, a vehicle speed sensor 44 for detecting the vehicle speed, a crankshaft angle sensor 45 for detecting the crankshaft angle, an accelerator pedal opening sensor 46 for detecting the amount of pressure applied to the accelerator pedal, an A / F sensor 47 for detecting the air-fuel ratio, an oxygen sensor 48, a pressure sensor 49 for detecting the pressure acting on the A / F sensor 47, and a humidity sensor 50 for detecting the humidity of the intake air.

[0057] The intake-side camshaft position sensor 43 detects the phase of the intake camshaft 42 relative to the crankshaft.

[0058] The vehicle speed sensor 44 is equivalent to the vehicle speed detection unit.

[0059] The crankshaft angle sensor 45 can detect the rotational speed of the internal combustion engine 7.

[0060] In addition to detecting the accelerator opening degree, which is the amount of operation of the accelerator pedal, the accelerator opening degree sensor 46 can also detect the accelerator change rate, which is the operating speed of the accelerator pedal. That is, the accelerator opening degree sensor 46 is equivalent to an accelerator operation amount detection unit.

[0061] The A / F sensor 47 is a so-called wide-range air-fuel ratio sensor with an output characteristic that is approximately linear with respect to the exhaust air-fuel ratio. It is disposed in the exhaust passage 13 upstream of the exhaust catalyst device 24. Specifically, the A / F sensor 47 is located upstream of the exhaust catalyst device 24 and downstream of the exhaust bypass passage 32.

[0062] The output voltage varies in an ON / OFF manner within a narrow range near the stoichiometric air-fuel ratio. The oxygen sensor 48 is a sensor that detects only the richness or leanness of the air-fuel ratio and is located in the exhaust passage 13 downstream of the exhaust catalyst device 24.

[0063] Pressure sensor 49 is disposed, for example, in the exhaust passage 13 upstream of exhaust catalyst device 24. Specifically, pressure sensor 49 is located further upstream of exhaust catalyst device 24 and further downstream of the downstream end of exhaust bypass passage 32. Pressure sensor 49 is configured to be adjacent to the upstream side of A / F sensor 47. Alternatively, pressure sensor 49 may be disposed in intake passage 12.

[0064] The humidity sensor 50 is disposed, for example, in the intake passage 12 downstream of the intercooler 31. That is, the humidity sensor 50 is located upstream of the exhaust catalyst device 24. Alternatively, the humidity sensor 50 may be disposed in the exhaust passage 13 upstream of the exhaust catalyst device 24.

[0065] Furthermore, the control unit 22 optimizes the injection quantity and timing of fuel injected from the fuel injection valve 17, the ignition timing of the internal combustion engine 7 (spark plug 19), and the intake air volume based on detection signals from various sensors, and controls the air-fuel ratio of the internal combustion engine 7.

[0066] The control unit 22 calculates the requested load (load of internal combustion engine 7) of internal combustion engine 7 using the detection value of accelerator opening sensor 46.

[0067] In addition, the control unit 22 can detect the ratio of the remaining charge to the charging capacity of the battery 4, i.e., the State of Charge (SOC).

[0068] Furthermore, the control unit 22 calculates the oxygen storage capacity of the exhaust catalyst device 24 using the detection values ​​of the A / F sensor 47 and the oxygen sensor 48. For example, the oxygen storage capacity of the exhaust catalyst device 24 can be calculated using a calculation method known from sources such as Japanese Patent Application Publication No. 2013-100821.

[0069] The hybrid vehicle described in the above embodiment is a so-called series hybrid vehicle that uses electricity from a generator 6 driven by an internal combustion engine 7 and electricity from a battery 4 to drive a drive motor 2. In the series hybrid vehicle, if the state of charge (SOC) of the battery 4 decreases during driving, the internal combustion engine 7 is driven to charge the battery 4. Furthermore, in the series hybrid vehicle, if a predetermined stopping condition, such as the SOC of the battery 4 being greater than or equal to a predetermined value, is met during driving, the internal combustion engine 7, which is driven to charge the battery 4, is stopped.

[0070] The internal combustion engine 7 can control the target air-fuel ratio to be leaner than the stoichiometric air-fuel ratio. To achieve this lean combustion with high precision, the A / F sensor 47 is preferably designed with high detection accuracy.

[0071] Therefore, regarding the control unit 22, if the prescribed air-fuel ratio learning conditions are met, the internal combustion engine 7 is started to operate as an electric motor while fuel injection from the fuel injection valve 17 is stopped. This allows for the learning (storage) of the air-fuel ratio by using the detection signal (detection value) from the A / F sensor 47 at this time as a learning value (air-fuel ratio learning value) corresponding to the oxygen concentration in the air. In other words, the control unit 22 is equivalent to a control unit that performs air-fuel ratio learning.

[0072] Here, if the internal combustion engine 7 is operated as an electric motor while the fuel injection from the fuel injection valve 17 is stopped, air (oxygen) flows into the exhaust catalyst device 24 located downstream of the A / F sensor 47, and the oxygen storage capacity of the exhaust catalyst device 24 may increase.

[0073] Regarding the exhaust catalyst device 24, the more oxygen is stored, the more it becomes an oxidizing atmosphere, resulting in a lower NOx purification rate.

[0074] For example, if the oxygen storage capacity of the exhaust catalyst device 24 is greater than a reference value (e.g., approximately 100%), even if the motor is operated to supply fresh gas to the exhaust catalyst device 24, the oxygen storage capacity of the exhaust catalyst device 24 will not change. Therefore, when the oxygen storage capacity of the exhaust catalyst device 24 is greater than the reference value, the presence or absence of motor operation will not affect whether the NOx purification rate deteriorates after combustion recovery in the internal combustion engine 7. Here, the maximum oxygen storage capacity that can be accumulated in the exhaust catalyst device 24 is set to 100%.

[0075] When the oxygen storage in the exhaust catalyst device 24 is low, if the motor is operated to supply fresh gas to the exhaust catalyst device 24, the oxygen storage in the exhaust catalyst device 24 will increase. Therefore, when the oxygen storage in the exhaust catalyst device 24 is low, if the motor is operated, the NOx purification rate after combustion recovery in the internal combustion engine 7 will deteriorate.

[0076] That is, if the oxygen storage capacity of the exhaust catalyst device 24 increases, the NOx purification rate in the exhaust catalyst device 24 will decrease when the internal combustion engine 7 is started, and the exhaust performance may deteriorate.

[0077] Therefore, when the effect of oxygen flowing into the exhaust catalyst device 24 on the exhaust performance of the downstream side of the exhaust catalyst device 24 is small, the control unit 22 determines that the air-fuel ratio learning condition is met and performs air-fuel ratio learning.

[0078] In detail, when the internal combustion engine 7 stops, if the oxygen storage of the exhaust catalyst device 24 is greater than or equal to a preset reference value (e.g., approximately 100%), the control unit 22 of the first embodiment stops the fuel injection of the internal combustion engine 7 and performs air-fuel ratio learning after the motor of the internal combustion engine 7 has been running for a predetermined time.

[0079] Figure 3 This is an explanatory graph showing the relationship between air-fuel ratio learning and exhaust performance. The rich-side A / F fluctuation at the base air-fuel ratio (e.g., 33.5) is set to "0".

[0080] Regarding the fuel cut-off learning that performs air-fuel ratio learning when fuel injection in the internal combustion engine 7 stops, the fluctuation of the rich side of the A / F sensor 47 is increased due to the influence of unburned fuel in the cylinder, resulting in increased engine emissions (EOE) and worse exhaust performance.

[0081] On the other hand, during motor operation learning when the internal combustion engine 7 is running as an electric motor, the air-fuel ratio can be learned, and the unburned fuel in the cylinder can be scavenged sufficiently, thus suppressing the influence of unburned fuel in the cylinder and suppressing the increase in the rich side fluctuation of the A / F sensor 47.

[0082] During motor operation learning, the amount of unburned fuel remaining around the A / F sensor 47 can be reduced, and compared with learning during fuel cut-off, the increase in emissions from the internal combustion engine 7, namely engine emissions (EOE), can be suppressed.

[0083] That is, the control unit 22 of the first embodiment can perform air-fuel ratio learning without causing a deterioration in exhaust performance. In addition, it can enable the internal combustion engine 7 to operate as an electric motor without causing a deterioration in exhaust performance.

[0084] Figure 4 This is a flowchart illustrating the control process for learning the air-fuel ratio in the first embodiment.

[0085] During the operation of the internal combustion engine 7 in lean-fuel operation (where the air-fuel ratio is leaner than the stoichiometric air-fuel ratio), the oxygen storage level of the exhaust catalyst device 24 is monitored using the A / F sensor 47 and the oxygen sensor 48 (step S11). If the oxygen storage level of the exhaust catalyst device 24 is greater than or equal to a preset reference value when the internal combustion engine 7 is stopped, the internal combustion engine 7 is started by electric motor operation for a preset predetermined time (steps S12, S13, and S14). After the electric motor operation of the internal combustion engine 7 ends, air-fuel ratio learning is performed (step S15).

[0086] Other embodiments of the present invention will now be described. Furthermore, structural elements identical to those in the first embodiment described above will be labeled with the same reference numerals, and repeated descriptions will be omitted.

[0087] The second embodiment of the present invention will be described. In this second embodiment, the control unit 22, in the same manner as in the first embodiment, determines that the air-fuel ratio learning condition is met and performs air-fuel ratio learning when the impact on the exhaust performance downstream of the exhaust catalyst device 24 is small even if oxygen flows into the exhaust catalyst device 24.

[0088] Furthermore, regarding the control unit 22 of the second embodiment, in lean operation where the air-fuel ratio of the internal combustion engine 7 is leaner than the theoretical air-fuel ratio, if the oxygen storage of the exhaust catalyst device 24 is greater than or equal to a preset reference value, and if the impact on exhaust performance is small even if the oxygen storage increases, then the fuel injection of the internal combustion engine 7 is stopped, and the internal combustion engine 7 is put into motor operation and air-fuel ratio learning is performed.

[0089] This second embodiment can also achieve roughly the same effects as the first embodiment described above.

[0090] Figure 5 This is a flowchart illustrating the control process for learning the air-fuel ratio in the second embodiment.

[0091] If, during operation of the internal combustion engine 7 in a lean-fuel operation (where the air-fuel ratio is leaner than the stoichiometric air-fuel ratio), the oxygen storage in the exhaust catalyst device 24 is greater than or equal to a preset reference value, then the internal combustion engine 7 is stopped (steps S21, S22, and S23). The internal combustion engine 7 is then operated by an electric motor for a preset time, and air-fuel ratio learning is performed after the electric motor operation of the internal combustion engine 7 ends (steps S24 and S25).

[0092] The third embodiment of the present invention will be described. In this third embodiment, the control unit 22 is the same as in the first embodiment described above, and determines that the air-fuel ratio learning condition is met and performs air-fuel ratio learning when the impact on the exhaust performance of the downstream side of the exhaust catalyst device 24 is small even if oxygen flows into the exhaust catalyst device 24.

[0093] Furthermore, the control unit 22 of the third embodiment calculates the oxygen storage capacity of the exhaust catalyst device 24 using the detection value of the air flow meter 21.

[0094] For example, the oxygen storage capacity of the exhaust catalyst device 24 can be calculated based on the detection values ​​of the air flow meter 21 and the A / F sensor 47. Specifically, the calculation can be performed using, for example, a calculation method known from Japanese Patent Application Publication No. 2002-70611.

[0095] In this third embodiment, the same effect as that of the first embodiment described above can also be achieved.

[0096] Figure 6 This is a flowchart illustrating the control process for learning the air-fuel ratio in the third embodiment.

[0097] If, during operation of the internal combustion engine 7 in a lean-fuel operation (where the air-fuel ratio is leaner than the stoichiometric air-fuel ratio), the oxygen storage in the exhaust catalyst device 24 is greater than or equal to a preset reference value, then the internal combustion engine 7 is stopped (steps S31, S32, and S33). The internal combustion engine 7 is then operated by an electric motor for a preset time, and air-fuel ratio learning is performed after the electric motor operation of the internal combustion engine 7 ends (steps S34 and S35).

[0098] In addition, the oxygen storage capacity of the exhaust catalyst device 24 can be calculated using the detection values ​​of the A / F sensor 47, the oxygen sensor 48, and the air flow meter 21.

[0099] The accuracy of the oxygen storage calculated in this case is improved compared to the oxygen storage calculated using the detection values ​​of the A / F sensor 47 and the oxygen sensor 48 without using the detection value of the air flow meter 21.

[0100] The fourth embodiment of the present invention will be described. In this fourth embodiment, the control unit 22 is the same as in the first embodiment described above, and determines that the air-fuel ratio learning condition is met and performs air-fuel ratio learning when the impact on the exhaust performance of the downstream side of the exhaust catalyst device 24 is small even if oxygen flows into the exhaust catalyst device 24.

[0101] Furthermore, regarding the control unit 22 of the fourth embodiment, if the air-fuel ratio of the internal combustion engine 7 is leaner than the theoretical air-fuel ratio and the lean operation continues for a predetermined time, the fuel injection of the internal combustion engine 7 is stopped, the internal combustion engine 7 is put into motor operation, and air-fuel ratio learning is performed.

[0102] When operating in lean conditions for a specified period of time, the oxygen storage capacity of the exhaust catalyst device 24 can be considered to be greater than or equal to a preset reference value (e.g., approximately 100%).

[0103] In this fourth embodiment, the same effect as that of the first embodiment described above can also be achieved.

[0104] Figure 7 This is a flowchart illustrating the control process for learning the air-fuel ratio in the fourth embodiment.

[0105] If the air-fuel ratio is leaner than the stoichiometric air-fuel ratio for a specified period of time, the internal combustion engine 7 is stopped (steps S41 and S42). The internal combustion engine 7 is then operated by an electric motor for a predetermined period of time. After the electric motor operation of the internal combustion engine 7 ends, air-fuel ratio learning is performed (steps S43 and S44).

[0106] The fifth embodiment of the present invention will be described. In this fifth embodiment, the control unit 22 is the same as in the first embodiment described above, and determines that the air-fuel ratio learning condition is met and performs air-fuel ratio learning when the impact on the exhaust performance of the downstream side of the exhaust catalyst device 24 is small even if oxygen flows into the exhaust catalyst device 24.

[0107] Furthermore, regarding the control unit 22 of the fifth embodiment, if the predetermined stopping condition for stopping the internal combustion engine 7 during vehicle operation is met, the internal combustion engine 7 is made to operate the electric motor, and air-fuel ratio learning is performed after the electric motor operation ends.

[0108] The specified stopping conditions for stopping the running internal combustion engine 7 while the vehicle is in motion include, for example, the situation where the SOC of the battery 4 is greater than or equal to a specified value, as described above.

[0109] In this fifth embodiment, the same effect as that of the first embodiment described above can also be achieved.

[0110] Furthermore, in the fifth embodiment, air-fuel ratio learning can be performed even while the vehicle is in motion. Therefore, the opportunity for air-fuel ratio learning can be increased. Additionally, while the vehicle is in motion, road noise, wind noise, and the sound of the motor operating are less likely to propagate to the vehicle occupants, thus not affecting comfort.

[0111] Figure 8 This is a flowchart illustrating the control process for learning the air-fuel ratio in the fifth embodiment.

[0112] If the stopping condition of the internal combustion engine 7 is met while the vehicle is in motion, the internal combustion engine 7 is stopped (steps S51, S52, S53, S54). The internal combustion engine 7 is then operated by an electric motor for a predetermined time. After the electric motor operation of the internal combustion engine 7 ends, air-fuel ratio learning is performed (steps S55, S56).

[0113] The sixth embodiment of the present invention will be described. In this sixth embodiment, the control unit 22 is the same as in the first embodiment described above, and determines that the air-fuel ratio learning condition is met and performs air-fuel ratio learning when the impact on the exhaust performance of the downstream side of the exhaust catalyst device 24 is small even if oxygen flows into the exhaust catalyst device 24.

[0114] Furthermore, regarding the control unit 22 of the sixth embodiment, if the predetermined stopping condition for stopping the internal combustion engine 7 during vehicle operation is met, the internal combustion engine 7 is started to operate as an electric motor, and air-fuel ratio learning is performed during the operation of the electric motor of the internal combustion engine 7.

[0115] Furthermore, the pressure value acting on the A / F sensor 47 is preset (stored) in the control unit 22 of the sixth embodiment for each operating condition. Moreover, the control unit 22 corrects the detection value of the A / F sensor 47 for the air-fuel ratio learning value based on this pressure value.

[0116] The higher the set pressure value, the lower the detection value of the A / F sensor 47 will be corrected (towards the rarefied side).

[0117] In this sixth embodiment, the same effect as that of the first embodiment described above can also be achieved.

[0118] Furthermore, the detection value of the A / F sensor 47 is affected by the pressure acting on the A / F sensor 47. Therefore, by correcting the detection value of the A / F sensor 47 based on the pressure, the air-fuel ratio can be learned with high accuracy.

[0119] Figure 9 This is a flowchart illustrating the control process for learning the air-fuel ratio in the sixth embodiment.

[0120] If the stopping condition of the internal combustion engine 7 is met while the vehicle is in motion, the internal combustion engine 7 is stopped (steps S61, S62, S63, S64). The internal combustion engine 7 is then operated by an electric motor for a predetermined time (step S65). During the electric motor operation of the internal combustion engine 7, air-fuel ratio learning is performed, and the learned air-fuel ratio value is corrected according to the pressure acting on the A / F sensor 47 (steps S66, S67, S68).

[0121] The seventh embodiment of the present invention will be described. In this seventh embodiment, the control unit 22 is the same as in the first embodiment described above, and determines that the air-fuel ratio learning condition is met and performs air-fuel ratio learning when the impact on the exhaust performance of the downstream side of the exhaust catalyst device 24 is small even if oxygen flows into the exhaust catalyst device 24.

[0122] Furthermore, regarding the control unit 22 of the seventh embodiment, if the predetermined stopping condition for stopping the internal combustion engine 7 during vehicle operation is met, the internal combustion engine 7 is started to operate as an electric motor, and air-fuel ratio learning is performed during the operation of the electric motor of the internal combustion engine 7.

[0123] In addition, the control unit 22 of the seventh embodiment uses the detection value of the humidity sensor 50 to correct the detection value of the A / F sensor 47, which is the air-fuel ratio learning value.

[0124] The higher the humidity detected by the humidity sensor 50, the lower the detected value of the A / F sensor 47 will be corrected (towards the thinner side).

[0125] In this seventh embodiment, the same effect as that of the first embodiment described above can also be achieved.

[0126] Furthermore, the detection value of the A / F sensor 47 is affected by humidity. Therefore, by correcting the detection value of the A / F sensor 47 based on the humidity detected by the humidity sensor 50, the air-fuel ratio can be learned with high accuracy.

[0127] Figure 10 This is a flowchart illustrating the control process for learning the air-fuel ratio in the 7th embodiment.

[0128] If the stopping condition of the internal combustion engine 7 is met while the vehicle is in motion, the internal combustion engine 7 is stopped (steps S71, S72, S73, S74). The internal combustion engine 7 is then operated by an electric motor for a predetermined time (step S75). During the electric motor operation of the internal combustion engine 7, air-fuel ratio learning is performed, and the learned air-fuel ratio value is corrected based on the humidity detected by the humidity sensor 50 (steps S76, S77, S78).

[0129] The eighth embodiment of the present invention will be described. In this eighth embodiment, the control unit 22 is the same as in the first embodiment described above, and determines that the air-fuel ratio learning condition is met and performs air-fuel ratio learning when the impact on the exhaust performance of the downstream side of the exhaust catalyst device 24 is small even if oxygen flows into the exhaust catalyst device 24.

[0130] Furthermore, regarding the control unit 22 of the eighth embodiment, if the predetermined stopping condition for stopping the internal combustion engine 7 during vehicle operation is met, the internal combustion engine 7 is started to operate as an electric motor, and air-fuel ratio learning is performed during the operation of the electric motor of the internal combustion engine 7.

[0131] In addition, the control unit 22 of the eighth embodiment uses the detection value of the pressure sensor 49 to correct the detection value of the A / F sensor 47 of the air-fuel ratio learning value.

[0132] The higher the pressure detected by the pressure sensor 49, the lower the detected value of the A / F sensor 47 will be corrected (towards the rarefied side).

[0133] In this eighth embodiment, the same effect as that of the first embodiment described above can also be achieved.

[0134] Furthermore, the detection value of the A / F sensor 47 is affected by the pressure acting on it. Therefore, by correcting the detection value of the A / F sensor 47 based on the detection value of the pressure sensor 49, high-precision air-fuel ratio learning can be achieved.

[0135] Figure 11 This is a flowchart illustrating the control process for learning the air-fuel ratio in the 8th embodiment.

[0136] If the stopping condition of the internal combustion engine 7 is met while the vehicle is in motion, the internal combustion engine 7 is stopped (steps S81, S82, S83, S84). The internal combustion engine 7 is then operated by an electric motor for a predetermined time (step S85). During the electric motor operation of the internal combustion engine 7, air-fuel ratio learning is performed, and the learned air-fuel ratio value is corrected based on the pressure detected by the pressure sensor 49 (steps S86, S87, S88).

[0137] The ninth embodiment of the present invention will be described. In this ninth embodiment, the control unit 22 is the same as in the first embodiment described above, and determines that the air-fuel ratio learning condition is met and performs air-fuel ratio learning when the impact on the exhaust performance of the downstream side of the exhaust catalyst device 24 is small even if oxygen flows into the exhaust catalyst device 24.

[0138] Furthermore, regarding the control unit 22 of the 9th embodiment, when vehicle driving begins based on the driver's key switch operation, if the catalyst temperature of the exhaust catalyst device 24 has not reached the prescribed activation temperature, the internal combustion engine 7 is started to operate as an electric motor, and air-fuel ratio learning is performed after the electric motor operation ends.

[0139] If the catalyst temperature of the exhaust catalyst device 24 does not reach the specified activation temperature, the exhaust purification function of the exhaust catalyst device 24 will not be realized, and therefore the exhaust performance will remain unchanged even if the motor is running.

[0140] In this ninth embodiment, the same effect as that of the first embodiment described above can also be achieved.

[0141] Figure 12 This is a flowchart illustrating the control process for learning the air-fuel ratio in the 9th embodiment.

[0142] If the catalyst temperature of the exhaust catalyst device 24 is less than or equal to the predetermined activation temperature when vehicle driving begins based on the driver's key switch operation, the internal combustion engine 7 is operated by an electric motor for a predetermined time (steps S91, S92, and S93). Furthermore, air-fuel ratio learning is performed after the electric motor operation of the internal combustion engine 7 ends (step S94).

[0143] The specific embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments and various modifications can be made without departing from its spirit.

[0144] For example, when the oxygen storage in the exhaust catalyst device 24 is greater than or equal to a preset reference value, and the impact of oxygen flowing into the exhaust catalyst device 24 on the exhaust performance of the downstream side of the exhaust catalyst device 24 is small, or when the catalyst temperature of the exhaust catalyst device 24 has not reached the activation temperature, the fuel injection of the internal combustion engine 7 can be stopped, and the internal combustion engine 7 can be started to run as an electric motor. After the electric motor operation ends, the air-fuel ratio learning is performed.

[0145] In addition, when the oxygen storage of the exhaust catalyst device 24 is greater than or equal to a preset reference value, and the impact of oxygen flowing into the exhaust catalyst device 24 on the exhaust performance of the downstream side of the exhaust catalyst device 24 is small, or when the catalyst temperature of the exhaust catalyst device 24 has not reached the activation temperature, the fuel injection of the internal combustion engine 7 can be stopped, and the internal combustion engine 7 can be started to run as an electric motor. During the operation of the electric motor, the air-fuel ratio learning is performed.

[0146] When the internal combustion engine 7 is running, the opening of the throttle valve 23 and the exhaust valve 33 of the turbocharger 28 can be set to be fully open. As a result, the amount of fresh gas (air without unburned fuel) passing through the A / F sensor 47 increases, which can promote the scavenging of unburned fuel near the A / F sensor 47 and enable air-fuel ratio learning to be performed as quickly and accurately as possible.

[0147] When the internal combustion engine 7 is running, the throttle valve 23, the exhaust valve 33, the intake-side variable valve mechanism 41, and the speed of the internal combustion engine 7 can be controlled to reduce the pressure impact on the A / F sensor 47 and thus control the amount of air flowing in the A / F sensor 47. This improves the accuracy of the A / F sensor 47's detection value and further enhances the accuracy of air-fuel ratio learning.

[0148] Furthermore, the above embodiments can be appropriately combined within the scope of achieving consistency.

[0149] The above embodiments relate to vehicle control methods and vehicle control devices.

Claims

1. A method for controlling a vehicle, the vehicle having: An internal combustion engine is capable of operating by using a generator-electric motor; An exhaust purification catalyst that purifies the exhaust gas from the aforementioned internal combustion engine; and An air-fuel ratio sensor, located upstream of the aforementioned exhaust gas purification catalyst, is capable of detecting the air-fuel ratio. Determine whether the oxygen storage capacity of the aforementioned exhaust purification catalyst is greater than a preset benchmark value. In response to the determination that the oxygen storage capacity of the exhaust purification catalyst is greater than the preset reference value, a first process is implemented, wherein the first process includes: stopping fuel injection in the internal combustion engine; using the generator motor to operate the internal combustion engine; and performing air-fuel ratio learning by learning the detection value of the air-fuel ratio sensor. In response to the determination that the oxygen storage capacity of the exhaust purification catalyst is not greater than the preset benchmark value, the first process is not performed.

2. The vehicle control method according to claim 1, wherein, When the internal combustion engine stops, and when the oxygen storage capacity of the exhaust purification catalyst is greater than the preset reference value, While maintaining the state of stopping fuel injection in the aforementioned internal combustion engine, the aforementioned internal combustion engine is operated by an electric motor to perform the aforementioned air-fuel ratio learning.

3. The vehicle control method according to claim 1 or 2, wherein, In the lean-fuel operation of the aforementioned internal combustion engine, where the air-fuel ratio is leaner than the stoichiometric air-fuel ratio, if the oxygen storage capacity of the aforementioned exhaust purification catalyst is greater than the aforementioned preset benchmark value, then... This stops the fuel injection of the internal combustion engine and causes the internal combustion engine to operate as an electric motor, thus implementing the air-fuel ratio learning process.

4. The vehicle control method according to claim 1 or 2, wherein, The oxygen storage capacity of the exhaust purification catalyst is calculated using at least one of the detection values ​​of the air-fuel ratio sensor, the oxygen sensor located downstream of the exhaust purification catalyst, and the air flow meter installed in the intake passage of the internal combustion engine.

5. The vehicle control method according to claim 1, wherein, If the air-fuel ratio of the aforementioned internal combustion engine is leaner than the theoretical air-fuel ratio and this lean operation continues for a specified period of time, then the fuel injection of the aforementioned internal combustion engine is stopped, and the aforementioned internal combustion engine is put into electric motor operation to implement the aforementioned air-fuel ratio learning.

6. The vehicle control method according to claim 1 or 2, wherein, If the prescribed stopping conditions for stopping the internal combustion engine are met while the vehicle is in motion, the internal combustion engine is started by an electric motor to perform the air-fuel ratio learning.

7. The vehicle control method according to claim 1 or 2, wherein, The above air-fuel ratio learning is performed after the motor has finished running or during the motor's operation.

8. The vehicle control method according to claim 1, wherein, When the vehicle starts driving based on the driver's key switch operation, if the catalyst temperature of the exhaust purification catalyst has not reached the specified activation temperature, the internal combustion engine is started to run as an electric motor. After the electric motor stops running or during the electric motor operation, the air-fuel ratio learning is performed.

9. The vehicle control method according to claim 1 or 2, wherein, The air-fuel ratio learning value is corrected based on the pressure value applied to the air-fuel ratio sensor.

10. The vehicle control method according to claim 1 or 2, wherein, The vehicle is equipped with a humidity sensor that detects the humidity of the air drawn into the internal combustion engine. During air-fuel ratio learning, the air-fuel ratio learning value is corrected using the detection value from the humidity sensor.

11. The vehicle control method according to claim 1 or 2, wherein, The vehicle has: A throttle valve that controls the amount of air intake into the aforementioned internal combustion engine; and An exhaust turbine-type supercharger, which pressurizes the intake air of the aforementioned internal combustion engine. When the motor of the aforementioned internal combustion engine is running, the opening degree of the aforementioned throttle valve and the aforementioned turbocharger exhaust valve is set to be fully open.

12. The vehicle control method according to claim 1 or 2, wherein, The vehicle has: A throttle valve controls the amount of air intake for the aforementioned internal combustion engine; An exhaust turbine-type supercharger that boosts the intake air of the aforementioned internal combustion engine; and A variable valve mechanism is provided, which enables the valve timing of the intake valve of the aforementioned internal combustion engine to be variable. When the motor of the aforementioned internal combustion engine is running, the amount of air flowing through the aforementioned air-fuel ratio sensor is controlled by controlling the throttle valve, the exhaust valve of the aforementioned turbocharger, the aforementioned variable valve mechanism, and the speed of the aforementioned internal combustion engine.

13. A vehicle control device, wherein, The vehicle has: An internal combustion engine is able to operate by using a generator-electric motor while the vehicle is in motion; Exhaust purification catalyst, which purifies the exhaust gas from the aforementioned internal combustion engine; An air-fuel ratio sensor, located upstream of the aforementioned exhaust gas purification catalyst, is capable of detecting the air-fuel ratio; and The control unit is composed of: Determine whether the oxygen storage capacity of the aforementioned exhaust purification catalyst is greater than a preset benchmark value. In response to the determination that the oxygen storage capacity of the exhaust purification catalyst is greater than the preset reference value, a first process is implemented, wherein the first process includes: stopping fuel injection in the internal combustion engine; using the generator motor to operate the internal combustion engine; and performing air-fuel ratio learning by learning the detection value of the air-fuel ratio sensor. In response to the determination that the oxygen storage capacity of the exhaust purification catalyst is not greater than the preset benchmark value, the first process is not performed.

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