Vehicle control device

Abstract

To further improve emission when starting an internal combustion engine.SOLUTION: A vehicular control apparatus is for starting an internal combustion engine in response to establishment of a predetermined start condition and stopping operation of the internal combustion engine in response to establishment of a predetermined stop condition. The vehicular control apparatus performs: setting a fuel injection mode at a first injection mode in which a fuel is prevented from attaching to an internal wall surface of a combustion chamber during processing to start the internal combustion engine; setting the fuel injection mode at a second injection mode different from the first injection mode after completing the start processing; allowing the fuel injection mode to be maintained in the first injection mode until a predetermined extension allowance time elapses since the start of the start processing, under a condition that a temperature of the internal combustion engine falls within a predefined low temperature zone, and setting the extension allowance time longer at an initial start of the internal combustion engine than when the internal combustion engine is intermittently started.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a control device for a vehicle equipped with an internal combustion engine. [Background technology]

[0002] Conventionally, a combustion control device for a direct injection type internal combustion engine equipped with a fuel injection valve that directly injects fuel into a combustion chamber is known that selectively switches between a compression stroke injection mode in which fuel is injected during the compression stroke and an intake stroke injection mode in which fuel is injected during the intake stroke based on the operating state of the internal combustion engine (see, for example, Patent Document 1). This combustion control device switches the fuel injection mode from the compression stroke injection mode to the intake stroke injection mode when the fuel injection amount integrated value and the fuel injection count integrated value reach or exceed threshold values ​​set for each after the internal combustion engine has started to start. In addition, the combustion control device sets the threshold value based on at least one of the cooling water temperature at the start of the start, the fuel pressure supplied to the fuel injection valve, and the engine stop time. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-061332 A Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, by selecting the compression stroke injection mode in which the fuel is less likely to hit the combustion chamber wall surface until the combustion chamber wall surface is sufficiently warmed up, and by selecting the intake stroke injection mode in which the injected fuel has a longer time to vaporize after the combustion chamber wall surface is warmed up, it is possible to reduce HC emissions. However, even if the fuel injection mode is switched from the compression stroke injection mode to the intake stroke injection mode based on the integrated value of the fuel injection amount and the number of fuel injections as in the above conventional combustion control device, there is a risk that emissions will deteriorate depending on the timing at which the internal combustion engine start process is executed.

[0005] Therefore, a main object of the present disclosure is to further improve emissions when starting an internal combustion engine. [Means for solving the problem]

[0006] The vehicle control device disclosed herein is a vehicle control device that starts an internal combustion engine in response to the satisfaction of predetermined start conditions and stops the operation of the internal combustion engine in response to the satisfaction of predetermined stop conditions, and includes a fuel injection mode setting means that sets a fuel injection mode to a first injection mode that suppresses adhesion of fuel to the inner wall surface of the combustion chamber during the start process of the internal combustion engine, and sets the fuel injection mode to a second injection mode different from the first injection mode after the start process is completed, and the fuel injection mode setting means allows the fuel injection mode to be maintained in the first injection mode after the start process is completed until a predetermined allowable extension time has elapsed since the start of the start process, provided that the temperature of the internal combustion engine is within a predetermined low temperature range, and makes the allowable extension time longer at the initial start of the internal combustion engine than at the time of intermittent start of the internal combustion engine.

[0007] According to this vehicle control device, when the temperature of the internal combustion engine is within a predetermined low temperature range, the fuel injection mode can be continuously maintained in the first injection mode that suppresses the adhesion of fuel to the inner wall surface of the combustion chamber after the start of the internal combustion engine is completed, so that it is possible to suppress the disturbance of the air-fuel ratio in the combustion chamber and the increase in the number of particulate matter (fine particles) in the exhaust gas after the start is completed. Furthermore, by making the extension allowable time longer at the initial start of the internal combustion engine than at the intermittent start, it is possible to effectively suppress the adhesion of fuel to the inner wall surface of the combustion chamber at the initial start, which tends to take more time to warm up the internal combustion engine than at the intermittent start, and to suppress the fuel injection mode from being maintained in the first injection mode longer than necessary at the intermittent start. As a result, it is possible to further improve the emissions when starting the internal combustion engine.

[0008] In addition, when rich control for making the air-fuel ratio in the combustion chamber rich is executed after completion of the start process, the fuel injection mode setting means may maintain the fuel injection mode in the first injection mode until the rich control is terminated.

[0009] This makes it possible to reduce NOx when starting the internal combustion engine, thereby further improving emissions.

[0010] Furthermore, the internal combustion engine may include an in-cylinder injection valve that directly injects fuel into the combustion chamber, the first injection mode may be a compression stroke injection mode in which fuel is injected from the in-cylinder injection valve into the combustion chamber during a compression stroke, and the second injection mode may be an intake stroke injection mode in which fuel is injected from the in-cylinder injection valve into the combustion chamber during an intake stroke.

[0011] The vehicle may be a hybrid vehicle equipped with an electric motor capable of outputting power for running. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic configuration diagram showing a vehicle controlled by a control device of the present disclosure. [Diagram 2] 2 is a schematic diagram showing the configuration of an internal combustion engine mounted on the vehicle of FIG. 1. [Diagram 3] 4 is a flowchart showing a fuel injection mode setting routine executed by the vehicle control device of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Next, an embodiment of the present disclosure will be described with reference to the drawings.

[0014] 1 is a schematic diagram showing a hybrid vehicle 1 as a vehicle controlled by a control device of the present disclosure. The hybrid vehicle 1 shown in the figure includes an engine (internal combustion engine) 10, a motor generator MG, a power transmission device 30, and a hydraulic clutch K0. The hybrid vehicle 1 further includes a high-voltage battery (high-voltage electricity storage device) 40, a low-voltage battery (low-voltage electricity storage device) 50 as an auxiliary battery, a power control device (hereinafter referred to as "PCU") 60 that drives the motor generator MG, a motor electronic control unit (hereinafter referred to as "MGECU") 70 that controls the PCU 60, and an electronic control unit (hereinafter referred to as "main ECU") 80 as a control device of the present disclosure that controls the engine 10 and the power transmission device 30.

[0015] As shown in FIG. 2, engine 10 is a multi-cylinder gasoline engine (e.g., a V-type 6-cylinder engine) that converts the reciprocating motion of pistons 13, which accompanies the combustion of a mixture of hydrocarbon fuel and air in multiple combustion chambers (cylinders) 12 formed in engine block 11, into the rotational motion of a crankshaft (output shaft) 14. In addition to engine block 11, multiple combustion chambers 12, pistons 13, and crankshaft 14, engine 10 includes an air cleaner 15, an intake pipe 16, an electronically controlled throttle valve 17, an intake manifold 18 having a surge tank and multiple intake ports, multiple intake valves 19i that open and close the corresponding intake ports, exhaust valves 19e that open and close the corresponding exhaust ports, multiple port injection valves 20p that inject fuel into the corresponding intake ports, multiple in-cylinder injection valves 20d that directly inject fuel into the corresponding combustion chambers 12, multiple ignition plugs 21, and an exhaust pipe 22 that forms an exhaust passage.

[0016] The engine 10 also includes an upstream purification device 23 and a downstream purification device 24, each of which is incorporated in the exhaust pipe 22, as exhaust gas purification devices. The upstream purification device 23 includes a NOx storage type exhaust gas purification catalyst (three-way catalyst) that purifies harmful components such as CO (carbon monoxide), HC, and NOx in the exhaust gas from each combustion chamber 12 of the engine 10. The downstream purification device 24 includes a particulate filter (GPF) that collects particulate matter (fine particles) in the exhaust gas, and is disposed downstream of the upstream purification device 23. In this embodiment, the particulate filter is a porous filter that supports a NOx storage type exhaust gas purification catalyst (three-way catalyst). That is, the downstream purification device 24 is configured as a four-way catalyst that has the purification function of a three-way catalyst and the collection function of particulate matter.

[0017] Furthermore, the engine 10 includes a coolant circulation passage 25 for cooling the engine block 11 etc., an electric pump 26, and a radiator 27. The electric pump 26 circulates coolant (LLC) through the coolant circulation passage 25. The radiator 27 cools the coolant that has absorbed heat from the engine block 11 etc. by heat exchange with air from traveling wind or an electric fan (not shown). A water temperature sensor 25t is also provided in the coolant circulation passage 25. The water temperature sensor 25t detects the water temperature Tw of the coolant that has absorbed heat from (flowed out of) the engine block 11.

[0018] In addition, the engine 10 includes a supercharger 28 that compresses intake air by utilizing the energy of exhaust gas, and a liquid-cooled intercooler 29 that cools the air compressed by the supercharger 28. The supercharger 28 is a turbocharger, and includes a turbine wheel 28t, a compressor wheel 28c, a turbine shaft 28s that integrally connects the turbine wheel 28t and the compressor wheel 28c, a wastegate valve 28w, and a blow-off valve 28b, as shown in FIG. 2. The turbine wheel 28t is rotatably disposed in a turbine housing formed in the exhaust pipe 22 so as to be located upstream of the upstream purification device 23. The compressor wheel 28c is rotatably disposed in a compressor housing formed in the intake pipe 16 so as to be located between the air cleaner 15 and the throttle valve 17.

[0019] 1, the engine 10 also includes a starter (engine starting device) ST that is used to crank the engine 10 mainly in an extremely low temperature environment, and an alternator A that is driven by the engine 10 to generate electric power. Furthermore, a crankshaft 14 of the engine 10 is connected to an input member of a damper mechanism D (e.g., a flywheel damper).

[0020] The motor generator MG is a synchronous generator motor (three-phase AC motor) including a rotor with a permanent magnet embedded therein and a stator around which a three-phase coil is wound, and exchanges electric power with the high-voltage battery 40 via the PCU 60. The motor generator MG operates as an electric motor that is driven by electric power from the high-voltage battery 40 to generate drive torque, and outputs regenerative braking torque when braking the hybrid vehicle 1. The motor generator MG also operates as a generator that generates electric power using at least a portion of the power from the engine 10 that is operated under load. As shown in FIG. 1, the rotor of the motor generator MG is fixed to a transmission shaft TS.

[0021] The power transmission device 30 includes a torque converter (fluid transmission) 31 having a torque amplification function, a lock-up clutch 32, a mechanical oil pump 33, an electric oil pump 34, a transmission (automatic transmission) 35, a hydraulic control device 36 that adjusts the pressure of hydraulic oil, etc. The torque converter 31 includes a pump impeller connected to the transmission shaft TS via a front cover (input member), a turbine runner connected to an input shaft 35i of the transmission 35, and a stator that amplifies the torque by rectifying the flow of hydraulic oil from the turbine runner to the pump impeller. The lock-up clutch 32 is a multiple-plate or single-plate friction hydraulic clutch that connects the front cover and the input shaft 35i of the transmission 35 and releases the connection between them.

[0022] The transmission 35 is, for example, a 4-10 speed type multi-speed transmission including an input shaft 35i, an output shaft 35o, a plurality of planetary gears, and a plurality of clutches and brakes (engagement elements for gear shifting). The transmission 35 changes the speed of the power transmitted from the transmission shaft TS to the input shaft 35i via either the torque converter 31 or the lock-up clutch 32 in a plurality of stages, and outputs the power from the output shaft 35o to the left and right wheels (drive wheels) W via the differential gear DF ​​and the drive shaft DS. The hydraulic control device 36 includes a valve body in which a plurality of oil passages are formed, a plurality of regulator valves, a plurality of linear solenoid valves, and the like. The hydraulic control device 36 adjusts the pressure of the hydraulic oil (hydraulic pressure) from at least one of the mechanical oil pump 33 and the electric oil pump 34, and supplies it to the torque converter 31, the lock-up clutch 32, the clutches and brakes of the transmission 35, and the like.

[0023] The clutch K0 connects and disconnects the output member of the damper mechanism D, i.e., the crankshaft 14 of the engine 10, to the transmission shaft TS, i.e., the rotor of the motor generator MG, in response to the hydraulic pressure supplied from the hydraulic control device 36. In this embodiment, the clutch K0 is a normally open hydraulic clutch that is released as the engagement hydraulic pressure supplied from the hydraulic control device 36 decreases and is engaged as the engagement hydraulic pressure increases. When the clutch K0 is engaged, the engine 10 (crankshaft 14) is connected to the motor generator MG via the clutch K0. As a result, the engine 10 is connected to the left and right wheels W via the damper mechanism D, the clutch K0, the transmission shaft TS (motor generator MG), the power transmission device 30, and the like. The clutch K0 may be disposed inside the rotor of the motor generator MG, or may be disposed axially between the damper mechanism D and the motor generator MG.

[0024] The high-voltage battery 40 is, for example, a lithium-ion secondary battery or a nickel-hydrogen secondary battery having a rated output voltage of about 200-300 V. However, the high-voltage battery 40 may be a capacitor, or may include both a secondary battery and a capacitor. The low-voltage battery 50 is, for example, a lead-acid battery having a rated output voltage of 12 V, and is charged by power from the alternator A. The low-voltage battery 50 supplies power to auxiliary equipment such as the starter ST of the engine 10, the electric oil pump 34, and the hydraulic control device 36, and electronic devices such as various ECUs.

[0025] The PCU 60 includes an inverter that drives the motor generator MG, a boost converter, a DC / DC converter, etc. (none of which are shown), and is connected to the high-voltage battery 40 and the low-voltage battery 50 via a system main relay SMR. The inverter includes, for example, six transistors as switching elements and six diodes connected in parallel in the reverse direction to these transistors. The boost converter boosts the voltage from the high-voltage battery 40 and supplies it to the inverter, and also reduces the voltage from the inverter and supplies it to the high-voltage battery 40. The DC / DC converter reduces the power from the high-voltage battery 40 or the inverter and supplies it to a low-voltage system, i.e., the low-voltage battery 50 and various auxiliaries.

[0026] The MGECU 70 includes a microcomputer having a CPU, ROM, RAM, input / output interface, etc. (not shown), various drive circuits, various logic ICs, etc., and is connected to the main ECU 80 via a shared communication line and a dedicated communication line. The MGECU 70 acquires command values ​​from the main ECU 80, pre-boost voltages and post-boost voltages of the boost converter, the rotational position of the rotor of the motor generator MG, i.e., the transmission shaft TS, detected by a rotational position sensor (resolver) (not shown), and a phase current applied to the motor generator MG. The MGECU 70 controls the switching of the inverter and the boost converter based on this information. In addition, the MGECU 70 calculates the rotation speed Nm (rpm) of the rotor (transmission shaft TS) of the motor generator MG based on the detection value of the rotational position sensor at predetermined time intervals (for example, several msec), and calculates the angular velocity ωm and angular acceleration αm of the rotor.

[0027] The main ECU 80 includes a microcomputer having a CPU, ROM, RAM, input / output interfaces, etc. (not shown), various drive circuits, various logic ICs, etc. The main ECU 80 acquires a signal from a start switch (IG switch), an accelerator opening Acc (amount of depression of the accelerator pedal) detected by an accelerator pedal position sensor (not shown), a vehicle speed V detected by a vehicle speed sensor (not shown), a gear ratio γ of the transmission 35 corresponding to the accelerator opening Acc and the vehicle speed V, a rotation speed Nm of the motor generator MG from the MGECU 70, etc.

[0028] 1, the crank angle sensor 14a, the air flow meter 16a, the pressure sensor 16p and the temperature sensor 16t provided upstream of the compressor wheel 28c of the intake pipe 16, the boost pressure sensor 16c, the throttle opening sensor 17o, the intake pressure sensor 18p and the temperature sensor 18t provided in the intake manifold 18 (surge tank), the upstream air-fuel ratio sensor 22f, the downstream air-fuel ratio sensor 22r, the exhaust gas temperature sensor 22t, the water temperature sensor 25t, and an outside air temperature sensor and an atmospheric pressure sensor (not shown). Furthermore, the main ECU 80 obtains the SOC, the target charge / discharge power Pb*, the allowable charge power Win, the allowable discharge power Wout, and the like of the high-voltage battery 40 calculated by a power management device (power management ECU) (not shown) connected via a shared communication line and a dedicated communication line. Based on this information, the main ECU 80 controls the engine 10, the power transmission device 30, and the clutch K0 (hydraulic control device 36), and sets a torque command value Tm* to the motor generator MG.

[0029] In the hybrid vehicle 1 configured as described above, when the system is stopped and the mechanical oil pump 33 and the electric oil pump 34 are not generating oil pressure (parked), the normally open clutch K0 is released, thereby disconnecting the engine 10 from the transmission shaft TS, i.e., the motor generator MG. After the system is started, the hybrid vehicle 1 basically starts moving using torque (power) from the motor generator MG that is output to the power transmission device 30 as the drive system via the transmission shaft TS with the clutch K0 released.

[0030] After the system of the hybrid vehicle 1 is started, the main ECU 80 derives a required torque Tr* (including a required braking torque) to be output to the output shaft 35o of the transmission 35 corresponding to the accelerator opening Acc and the vehicle speed V, and sets a required running power Pd* required for running the hybrid vehicle 1 based on the required torque Tr* and the rotation speed of the output shaft 35o. When the operation of the engine 10 is stopped, the main ECU 80 sets the target power Pe*, target rotation speed Ne*, and target torque Te* of the engine 10 to "0", and sets a torque command value Tm* within the range of the allowable charging power Win and the allowable discharging power Wout so that a torque corresponding to the required torque Tr* is output from the motor generator MG to the output shaft 35o. The torque command value Tm* is transmitted from the main ECU 80 to the MGECU 70, and the MGECU 70 controls the switching of the inverter and the boost converter of the PCU 60 based on the torque command value Tm*.

[0031] Furthermore, while the hybrid vehicle 1 is stopped (including parked) or traveling by power from the motor generator MG, the main ECU 80 judges whether or not predetermined engine start conditions related to the required torque Tr*, the required running power Pd*, the target charge / discharge power Pb* of the high-voltage battery 40, the allowable discharge power Wout, and the like are satisfied. When the main ECU 80 judges that the engine start conditions are satisfied, it executes a start process in a manner corresponding to the traveling state of the hybrid vehicle 1 to start the engine 10 and engage the clutch K0. When the start process of the engine 10 is completed and the clutch K0 is fully engaged, the main ECU 80 sets the target power Pe*, the target rotation speed Ne*, and the target torque Te* of the engine 10 based on the required running power Pd*, the target charge / discharge power Pb* of the high-voltage battery 40, and the like so that the engine 10 is operated efficiently. Furthermore, the main ECU 80 sets a torque command value Tm* to the motor generator MG according to the required torque Tr*, and the like within the range of the allowable charge power Win and the allowable discharge power Wout. This allows the engine 10 to be operated at an operating point near the optimum fuel economy line, while the high-voltage battery 40 is charged with electric power generated by the motor generator MG according to the SOC of the high-voltage battery 40, and the motor generator MG is driven with electric power from the high-voltage battery 40 to output torque from both the engine 10 and the motor generator MG to the wheels W. Therefore, in the hybrid vehicle 1, it is possible to ensure good power performance while improving the fuel economy of the engine 10.

[0032] During operation of the engine 10, the main ECU 80 determines whether or not a predetermined engine stop condition is satisfied in relation to the vehicle speed V, the required torque Tr*, the required running power Pd*, the target charge / discharge power Pb*, the allowable discharge power Wout, and the like. When the main ECU 80 determines that the engine stop condition is satisfied, it executes a process for stopping the operation of the engine 10 and releases the clutch K0. This makes it possible to intermittently stop the engine 10 according to the state of the hybrid vehicle 1, thereby improving the fuel efficiency of the engine 10 and further improving the energy efficiency of the hybrid vehicle 1. Furthermore, when an engine start condition is satisfied after the operation of the engine 10 is stopped in response to the satisfaction of the engine stop condition, the engine 10 is started again.

[0033] Furthermore, while executing the start process of the engine 10 in response to the establishment of the engine start condition, the main ECU 80 sets the fuel injection mode to a compression stroke injection mode (first injection mode) and controls each in-cylinder injection valve 20d to inject fuel into each combustion chamber 12 at least once during the compression stroke (at least the last time in the case of split injection). This ensures good startability by burning a rich mixture (stratified combustion) near the ignition plug 21, and makes it possible to suppress adhesion of unburned fuel to the inner wall surface of each combustion chamber 12, thereby suppressing disturbance of the air-fuel ratio and an increase in the number (PN) of particulate matter (fine particles) in the exhaust gas. Furthermore, when the start process of the engine 10 is completed, the main ECU 80 sets the fuel injection mode to an intake stroke injection mode (second injection mode) and controls at least each in-cylinder injection valve 20d to inject fuel during the intake stroke. This ensures sufficient time for the fuel to vaporize after fuel injection, allowing a homogeneous mixture to be burned (homogeneous combustion) in each combustion chamber 12, making it possible to effectively reduce HC emissions.

[0034] However, if the fuel injection mode is uniformly switched from the compression stroke injection mode to the intake stroke injection mode upon completion of starting the engine 10, it may not be possible to sufficiently suppress the increase in the number of particulate matter in the exhaust gas and the amount of HC emissions. In light of this, in the hybrid vehicle 1, upon completion of the starting process of the engine 10, the main ECU 80 repeatedly executes a fuel injection mode setting routine shown in Fig. 3 at predetermined time intervals (very short time intervals) in order to properly set the fuel injection mode and further improve emissions.

[0035] At the start of the routine of FIG. 3, the main ECU 80 acquires information necessary for setting the fuel injection mode after the completion of the start process, such as the rotation speed Ne of the engine 10 (crankshaft 14), the load factor KL, the water temperature Tw of the cooling water of the engine 10, the elapsed time tp from the start process of the engine 10, the post-start increase value Δq of the fuel injection amount, the value of the start type flag Fcl, and the value of the rich control flag Frich (step S100). The rotation speed Ne of the engine 10 is calculated separately at predetermined time intervals by the main ECU 80 based on the output value (crank position) of the crank angle sensor 14a. The load factor KL is the ratio of the volume of air actually taken in during one cycle to the stroke volume per cycle of the engine 10, and is calculated separately at predetermined time intervals by the main ECU 80 based on the intake air volume detected by the air flow meter 16a and the rotation speed Ne. The water temperature Tw of the cooling water is detected by the water temperature sensor 25t.

[0036] The elapsed time tp is the time elapsed from when the engine 10 starts to be started and the engine speed Ne reaches a predetermined engine speed (for example, 400-500 rpm), and is measured separately by a timer (not shown). The post-start increase value Δq of the fuel injection amount is an increase in the amount of fuel that is separately set according to the water temperature Tw, etc., in order to ensure torque against the friction of the engine 10, and is gradually reduced over time. The value of the post-start increase value Δq and the manner of reduction are different when the engine 10 is started for the first time after the start switch of the hybrid vehicle 1 is turned on (initial start) and when the started engine 10 is stopped in response to the establishment of an engine stop condition and then started again (intermittent start). The start type flag Fcl is set to "0" when the engine 10 is started for the first time, and is set to "1" when the engine 10 is started intermittently. The rich control flag Frich is set to "0" when rich control is not being executed to enrich the air-fuel ratio in each combustion chamber 12 so that the upstream purification device 23 and the downstream purification device 24 do not become oxygen-excessive atmospheres in order to effectively reduce NOx in the upstream purification device 23 and the downstream purification device 24 when the engine 10 is started, and is set to "1" when the rich control is being executed.

[0037] After the process of step S100, the main ECU 80 judges whether the water temperature Tw acquired in step S100 is less than a predetermined threshold value Tref (step S110). The threshold value Tref is a temperature at which the warm-up of the engine 10 can be considered to be completed, and is set to a value of, for example, about 80°C to 90°C. When it is determined that the water temperature Tw is included in a low temperature range less than the threshold value Tref (step S110: YES), the main ECU 80 sets an allowable extension time tx, which is a threshold value for judging whether or not to permit switching of the fuel injection mode, based on the value of the start type flag Fcl acquired in step S100 (step S120). The allowable extension time tx is a time at which the air-fuel ratio in each combustion chamber 12 can be considered to be sufficiently stable in a state in which the amount of fuel is increased after the start of the engine 10. In this embodiment, at the initial start of the engine 10 when the start type flag Fcl is set to "0", the allowable extension time tx is set to a predetermined relatively long time (for example, about 10 seconds). On the other hand, during intermittent start of the engine 10 in which the start type flag Fcl is set to "1", the permissible extension time tx is set to a time (eg, about 2 seconds) shorter than the value during initial start.

[0038] Next, the main ECU 80 judges whether the elapsed time tp is less than the extension allowable time tx (step S130), and when it is judged that the elapsed time tp is less than the extension allowable time tx (step S130: YES), it judges whether the rich control flag Frich is "0" (step S140). When it is judged that the rich control flag Frich is "0" and the rich control is not being executed (step S140: YES), the main ECU 80 sets an increase threshold value Δqref to be compared with the post-start increase value Δq based on the value of the start type flag Fcl acquired in step S100 (step S150). The increase threshold value Δqref indicates the amount of increase in fuel when it can be considered that the disturbance of the air-fuel ratio in each combustion chamber 12 has disappeared in a state in which the amount of fuel has been increased after the start of the engine 10. In this embodiment, at the initial start of the engine 10, in which the start type flag Fcl is set to "0", the increase threshold value Δqref is set to a first value (constant value) that has been adapted in advance, and at the intermittent start of the engine 10, in which the start type flag Fcl is set to "1", the increase threshold value Δqref is set to a second value (constant value) that is different from the first value.

[0039] After setting the boost threshold value Δqref, the main ECU 80 judges whether the post-start boost value Δq acquired in step S100 exceeds the boost threshold value Δqref (step S160), and when it is judged that the post-start boost value Δq exceeds the boost threshold value Δqref (step S160: YES), the main ECU 80 sets an upper limit load rate KLmax to be compared with the load rate KL based on the rotation speed Ne of the engine 10 acquired in step S100 (step S170). The upper limit load rate KLmax corresponds to the maximum value of the load rate that can suppress the deterioration of the emission under the compression stroke injection mode, and is set to a predetermined constant value when the rotation speed Ne is relatively low, and is set to a smaller value as the rotation speed Ne becomes higher when the rotation speed Ne is included in a predetermined high rotation range.

[0040] Furthermore, the main ECU 80 judges whether the load rate KL acquired in step S100 is equal to or greater than a predetermined lower limit load rate KLmin and equal to or less than an upper limit load rate KLmax set in step S170 (step S180). The lower limit load rate KLmin is a load rate corresponding to the minimum amount of intake air that can ensure the stability of combustion in each combustion chamber 12. If the main ECU 80 judges that the load rate KL acquired in step S100 is equal to or greater than a predetermined lower limit load rate KLmin and equal to or less than the upper limit load rate KLmax set in step S170 (step S180: YES), the main ECU 80 sets (maintains) the fuel injection mode to the compression stroke injection mode (step S190) even if the start process of the engine 10 is completed, and executes the process from step S100 onwards in response to the arrival of the next execution timing. In this manner, when the fuel injection mode is set to the compression stroke injection mode in step S190, even after the start-up process of the engine 10 is completed, the fuel injection mode is extended and set (maintained) in the compression stroke injection mode without being switched to the intake stroke injection mode.

[0041] On the other hand, when it is determined in step S110 that the water temperature Tw is included in a temperature range equal to or higher than the threshold value Tref (step S110: NO), the main ECU 80 sets (changes) the fuel injection mode to the intake stroke injection mode (step S200) and ends the routine of Fig. 3. When it is determined in step S130 that the elapsed time tp is equal to or higher than the permissible extension time tx (step S130: NO), the main ECU 80 sets (changes) the fuel injection mode to the intake stroke injection mode (step S200) and ends the routine of Fig. 3. That is, after the start process of the engine 10 is completed, the fuel injection mode is allowed to be maintained in the compression stroke injection mode until the permissible extension time tx has elapsed since the start process began, on condition that the water temperature Tw is included in a low temperature range lower than the threshold value Tref.

[0042] Furthermore, when it is determined in step S140 that the rich control flag Frich is "1" and the rich control is being executed (step S140: YES), the main ECU 80 skips the processing of steps S150-S180 and sets (maintains) the fuel injection mode to the compression stroke injection mode (step S190). As a result, the fuel injection mode is maintained in the compression stroke injection mode from the start to the end of the rich control in response to the initial start or intermittent start of the engine 10. As a result, it is possible to suppress the disturbance of the air-fuel ratio in each combustion chamber 12 while the rich control is being executed and to suppress the upstream purification device 23 and the downstream purification device 24 from becoming an oxygen-excessive atmosphere, so that it is possible to reduce NOx and further improve the emission. Note that the rich control is usually completed by the time the extended permission time corresponding to the value of the start type flag Fcl has elapsed after the start processing of the engine 10 has started (after the rotation speed Ne has reached a predetermined rotation speed).

[0043] Also, when it is determined in step S160 that the post-start increase value Δq is equal to or less than the increase threshold value Δqref (step S160: NO), the main ECU 80 sets (changes) the fuel injection mode to the intake stroke injection mode (step S200) and ends the routine of FIG. 3. This allows the fuel injection mode to be shifted to the intake stroke injection mode at a stage where it can be considered that the air-fuel ratio in each combustion chamber 12 has been cleared in a state where the fuel amount has been increased after the engine 10 has been started, so that it is possible to further improve emissions. Furthermore, when it is determined in step S180 that the load rate KL is less than the lower limit load rate KLmin or exceeds the upper limit load rate KLmax (step S180: NO), the main ECU 80 sets (changes) the fuel injection mode to the intake stroke injection mode (step S200) and ends the routine of FIG. 3. This makes it possible to switch the fuel injection mode from the compression stroke injection mode to the intake stroke injection mode when there is a risk that the stability of combustion in each combustion chamber 12 cannot be ensured or that emissions may deteriorate. In this embodiment, when the fuel injection mode is maintained in the compression stroke injection mode after the start process of the engine 10 is completed, the fuel injection start timing, the target fuel pressure, the ratio of the injection amount in the split injection, and the like are set according to dedicated constraints (maps, etc.) that are individually adapted for both the initial start and the intermittent start.

[0044] As described above, the main ECU 80, which is a control device of the vehicle disclosed herein, starts the engine 10 in response to the establishment of a predetermined start condition while the vehicle is stopped or running, and stops the operation of the engine 10 in response to the establishment of a predetermined stop condition. The main ECU 80 also functions as a fuel injection mode setting means for setting the fuel injection mode to a compression stroke injection mode (first injection mode) that suppresses the adhesion of fuel to the inner wall surface of each combustion chamber 12 during the start processing of the engine 10, and for setting the fuel injection mode to an intake stroke injection mode after the start processing is completed. Furthermore, the main ECU 80 allows the fuel injection mode to be maintained in the first injection mode after the start processing is completed until a predetermined allowable extension time tx has elapsed since the start processing began, on the condition that the water temperature Tw indicating the temperature of the engine 10 is included in a low temperature range below a threshold value Tref (step S110), and also makes the allowable extension time tx longer at the initial start of the engine 10 than at the time of intermittent start of the engine 10 (steps S120, S130).

[0045] That is, in the hybrid vehicle 1, when the water temperature Tw of the engine 10 is included in the above-mentioned low temperature range, the fuel injection mode can be continuously maintained in the compression stroke injection mode that suppresses the adhesion of fuel to the inner wall surface of each combustion chamber 12 after the start of the engine 10 is completed (steps S110, S190), so that it is possible to suppress the disturbance of the air-fuel ratio in each combustion chamber 12 after the start is completed and the increase in the number of particulate matter (fine particles) in the exhaust gas. Furthermore, by making the extension allowable time tx longer at the initial start of the engine 10 than at the intermittent start (step S120), it is possible to effectively suppress the adhesion of fuel to the inner wall surface of each combustion chamber 12 at the initial start when it tends to take more time to warm up the engine 10 than at the intermittent start, and it is possible to suppress the fuel injection mode from being maintained in the compression stroke injection mode for longer than necessary at the intermittent start. As a result, it is possible to further improve the emissions when starting the engine 10.

[0046] Furthermore, when rich control for making the air-fuel ratio in each combustion chamber 12 rich is being executed after the start process of the engine 10 is completed, the main ECU 80 maintains the fuel injection mode in the compression stroke injection mode until the rich control ends (steps S140, S190). This makes it possible to reduce NOx when starting the engine 10 and further improve emissions.

[0047] The engine 10 of the hybrid vehicle 1 may be a diesel engine, an LPG engine, a biofuel engine, or the like. The hybrid vehicle 1 may be a four-wheel drive vehicle including a transfer that can distribute and transmit torque from the output shaft 35o of the transmission 35 to the differential gear DF ​​and another differential gear. The transmission 35 may be a mechanical continuously variable transmission, a dual clutch transmission, or the like. A clutch that connects and disconnects the rotor of the motor generator MG and the transmission shaft TS may be disposed between them (see the two-dot chain line in FIG. 1). The alternator A may be omitted from the hybrid vehicle 1. The functions of the main ECU 80 may be distributed to a plurality of electronic control devices, such as an engine ECU and a transmission ECU. The vehicle to which the control device of the present disclosure is applied is not limited to a hybrid vehicle, but may be a vehicle that includes only an engine as a power generation source for running and in which so-called idle stop control is executed.

[0048] The invention of the present disclosure is not limited to the above embodiment, and various modifications can be made within the scope of the present disclosure. Furthermore, the above embodiment is merely a specific form of the invention described in the Summary of the Invention, and does not limit the elements of the invention described in the Summary of the Invention. [Industrial Applicability]

[0049] The invention of the present disclosure can be used in the internal combustion engine and vehicle manufacturing industries, etc. [Explanation of symbols]

[0050] 1 Hybrid vehicle, 10 Engine, 12 Combustion chamber (cylinder), 20d In-cylinder injection valve, 20p Port injection valve, 30 Power transmission device, 40 High voltage battery, 50 Low voltage battery, 70 Motor electronic control unit (MGECU), 80 Electronic control device (main ECU), MG motor generator.

Claims

[Claim 1] A control device for a vehicle that starts an internal combustion engine in response to the satisfaction of a predetermined start condition and stops operation of the internal combustion engine in response to the satisfaction of a predetermined stop condition, a fuel injection mode setting means for setting a fuel injection mode to a first injection mode that suppresses adhesion of fuel to an inner wall surface of a combustion chamber during a start process of the internal combustion engine, and for setting the fuel injection mode to a second injection mode different from the first injection mode after completion of the start process, The fuel injection mode setting means allows the fuel injection mode to be maintained in the first injection mode after completion of the start-up process until a predetermined permissible extension time has elapsed since the start-up process began, on the condition that the temperature of the internal combustion engine is within a predetermined low temperature range, and at the initial start of the internal combustion engine, makes the permissible extension time longer than at the time of intermittent start of the internal combustion engine, and when rich control that makes the air-fuel ratio in the combustion chamber rich is executed after completion of the start-up process, maintains the fuel injection mode in the first injection mode until the rich control ends.

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