Hybrid vehicles

Abstract

To improve lean imbalance detection accuracy to address it more appropriately.SOLUTION: A hybrid vehicle calculates the sum of an inertia torque and a resonance influence torque when counters have the same value with each other as an engine output torque; based on an amount of fluctuation in the output torque, determines whether a lean imbalance has occurred, in which a fuel injection amount of any one cylinder is less than a fuel injection amount of the other cylinders; and when determining that the lean imbalance has occurred, increases a target injection amount of the one cylinder compared to the target injection amount of the other cylinders.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to hybrid vehicles. [Background technology]

[0002] A conventional technique of this type is a control device for an internal combustion engine in which each cylinder is provided with a fuel injection valve, the control device comprising a rotation measurement means, an inter-cylinder rotation difference calculation means, an injection amount correction means, an inter-cylinder rotation difference averaging means, and a torque adjustment means (see, for example, Patent Document 1). Here, the rotation measurement means measures the rotation speed for each cylinder between a predetermined crank angle. The inter-cylinder rotation difference calculation means calculates the difference in rotation speed between the current firing cylinder and the previous firing cylinder from the measured rotation speed. After a cold start, the injection amount correction means adjusts the average injection amount of the fuel injection valves for all cylinders according to the calculated difference in rotation speed between the cylinders. The inter-cylinder rotation difference averaging means averages the calculated differences in rotation speed between the cylinders for each cylinder. The torque adjustment means adjusts the torque of each cylinder so that the average of the calculated differences in rotation speed between the cylinders approaches zero. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-281236 Summary of the Invention [Problem to be solved by the invention]

[0004] When an engine crankshaft is connected to a motor via a torsional element, the torsional resonance of the torsional element can affect the torque fluctuations (behavior) of the engine, resulting in a torque affected by the torsional resonance on the output side of the torsional element. Therefore, it is necessary to calculate engine torque while eliminating the effects of the torsional resonance. When a first control device that controls the engine receives information about the torsional angle of the torsional element via communication from a second control device that controls the motor and calculates the torsional resonance component, communication delays can reduce the accuracy of the calculation of the torsional resonance component and the accuracy of the calculation of engine torque. This can reduce the accuracy of detecting lean imbalance, in which the fuel injection amount of one cylinder is lower than the fuel injection amount of the other cylinders, and can make it difficult to take adequate measures when lean imbalance occurs.

[0005] The hybrid vehicle of the present disclosure has a primary objective of improving the accuracy of lean imbalance detection and dealing with the issue more appropriately. [Means for solving the problem]

[0006] The hybrid vehicle of the present disclosure employs the following measures to achieve the above-mentioned main object.

[0007] A hybrid vehicle disclosed herein is a hybrid vehicle including an engine having a fuel injection valve for each cylinder, a motor, a torsion element having an input side connected to a crankshaft of the engine and an output side connected to a rotor of the motor, a first sensor that detects a crank angle of the crankshaft, a second sensor that detects a rotational position of the rotor, a first control device that controls the engine based on the crank angle, and a second control device that controls the motor based on the rotational position, wherein the first control device controls the fuel injection valves for each cylinder so that fuel is injected from the fuel injection valves based on a target injection amount, and the first control device transmits a counter that switches every time the crank angle rotates by a predetermined angle to the second control device, and calculates a rotational angular velocity of the engine based on the crank angle every time the counter switches. and calculates an inertia torque of the engine based on the rotational angular velocity of the engine, and the second control device calculates, each time the counter is switched, the rotational angular velocity of the motor based on the rotational position, and calculates a resonance-affected torque on the output side of the torsion element based on torsional resonance of the torsion element based on the rotational angular velocity of the motor, and transmits the calculated torque to the first control device, and the first control device calculates the sum of the inertia torque and the resonance-affected torque when the counters have the same value as each other as the output torque of the engine, and determines whether a lean imbalance has occurred, in which the fuel injection amount of one cylinder is less than the fuel injection amount of the other cylinder, based on the amount of fluctuation in the output torque, and when it is determined that a lean imbalance has occurred, increases the target injection amount of one of the cylinders compared to the target injection amount of the other cylinder.

[0008] In the hybrid vehicle of the present invention, the first control device calculates the sum of the inertia torque and the resonance-affected torque when the counters are equal to each other as the engine output torque. The first control device determines whether a lean imbalance has occurred, where the fuel injection amount of one cylinder is smaller than the fuel injection amount of the other cylinders, based on the fluctuation in the output torque. If a lean imbalance has occurred, the first control device increases the target injection amount of that cylinder (the lean cylinder with the smaller fuel injection amount) compared to the target injection amounts of the other cylinders. Therefore, since the engine output torque is calculated using the synchronized inertia torque and the resonance-affected torque, the accuracy of calculating the engine output torque can be improved. Furthermore, since the determination of whether a lean imbalance has occurred is based on the fluctuation in the output torque, the accuracy of detecting when a lean imbalance has occurred can be improved. Furthermore, since the target injection amount of one cylinder (the lean cylinder) is increased compared to the target injection amount of the other cylinders, the difference in fuel injection amount (air-fuel ratio difference) between the cylinders can be suppressed. That is, the accuracy of detecting lean imbalance can be improved, and the lean imbalance can be dealt with more appropriately.

[0009] In the hybrid vehicle of the present invention, the first control device may calculate, for each cylinder, an average output torque that is an average of the output torque during at least a portion of an expansion stroke, and calculate a fluctuation amount of the output torque by subtracting the average output torque of a cylinder that ignites a predetermined time earlier than the target cylinder from the average output torque of the target cylinder. In this case, when the lean imbalance occurs, the first control device may increase the target injection amount of any one of the cylinders compared to the target injection amount of the other cylinders, the more the fluctuation amount of the output torque or the average amount of the fluctuation amount of the output torque is on the negative side. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram of a hybrid vehicle 20 according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram of an engine 22. [Figure 3]4 is an explanatory diagram for explaining the calculation process of the output torque Te of the engine 22. FIG. [Figure 4] 10 is a flowchart illustrating an example of a diagnostic process. [Figure 5] FIG. 4 is an explanatory diagram showing an example of an increasing correction coefficient map. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of the present disclosure will be described with reference to the drawings. FIG. 1 is a schematic diagram of a hybrid vehicle 20 according to this embodiment, and FIG. 2 is a schematic diagram of an engine 22. As shown in FIG. 1, the hybrid vehicle 20 according to this embodiment includes the engine 22, an engine electronic control unit (engine ECU) 24, a planetary gear 30, motors MG1 and MG2, inverters 41 and 42, a motor electronic control unit (motor ECU) 40, a battery 50, a battery electronic control unit (battery ECU) 52, and a hybrid vehicle electronic control unit (HVECU) 70. The engine ECU 24, the motor ECU 40, the battery ECU 52, and the HVECU 70 can communicate with each other via a shared communication line (CAN bus) 90. The engine ECU 24 and the motor ECU 40 can communicate with each other via a dedicated communication line (local bus) 92. Note that communication via the dedicated communication line 92 has a sufficiently reduced communication delay compared to communication via the shared communication line 90.

[0012] The engine 22 is configured as a four-cylinder internal combustion engine that uses fuel such as gasoline or diesel and outputs power through four strokes: intake, compression, expansion (explosive combustion), and exhaust. As shown in Fig. 2, the engine 22 has, for each cylinder, an in-cylinder injection valve 127 that injects fuel into a combustion chamber 129, and an ignition plug 130. The in-cylinder injection valve 127 is disposed approximately in the center of the top of the combustion chamber 129, and injects the fuel in a spray form. The ignition plug 130 is disposed near the in-cylinder injection valve 127 so that it can ignite the fuel sprayed in a spray form from the in-cylinder injection valve 127. The engine 22 draws air purified by an air cleaner 122 into an intake pipe 123, passes it through a throttle valve 124 and a surge tank 125, and then draws it into a combustion chamber 129 via an intake valve 128. Fuel is injected one or more times from an in-cylinder injection valve 127 during the intake stroke or compression stroke, and is ignited by a spark plug 130 to cause explosive combustion. The reciprocating motion of a piston 132, which is pushed down by the energy produced by this explosive combustion, is converted into the rotational motion of the crankshaft 23. Exhaust gas discharged from the combustion chamber 129 into an exhaust pipe 134 via an exhaust valve 133, is then discharged into the outside air via a purification device 135. The purification device 135 has a purification catalyst (three-way catalyst) 135a that purifies harmful components in the exhaust, such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx).

[0013] The engine ECU 24 includes a microcomputer having a CPU, ROM, RAM, flash memory, input / output ports, and communication ports. The engine ECU 24 receives inputs of the crank angle θcr of the crankshaft 23 from a crank position sensor 140 and the coolant temperature Tw of the engine 22 from a water temperature sensor 142. The engine ECU 24 also receives inputs of the cam angles θci and θco of the intake camshaft that opens and closes the intake valve 128 and the exhaust camshaft that opens and closes the exhaust valve 133 from a cam position sensor 144, and the throttle opening TH of the throttle valve 124 from a throttle position sensor 124a. The engine ECU 24 also receives inputs of the intake air amount Qa from an air flow meter 123a, the intake air temperature Ta from a temperature sensor 123t, and the surge pressure Ps from a pressure sensor 125a. The engine ECU 24 also receives inputs of the air-fuel ratios AF1 and AF2 of the exhaust pipe 134 upstream and downstream of the purifier 135 from air-fuel ratio sensors 137 and 138. The engine ECU 24 outputs control signals to the throttle valve 124, the in-cylinder injection valve 127, and the spark plug 130. The engine ECU 24 calculates the rotation speed Ne, the rotation angular velocity ωe, and the load factor KL. The rotation speed Ne and the rotation angular velocity ωe are calculated based on the crank angle θcr. The load factor KL is calculated based on the intake air amount Qa and the rotation speed Ne.

[0014] 1, the sun gear is connected to the rotor of the motor MG1 via a sun gear shaft 31, the ring gear is connected to a drive shaft 37 which is coupled to drive wheels 39a, 39b via a differential gear 38, and the carrier is connected to the crankshaft 23 of the engine 22 via a carrier shaft 32 and a damper 28. The damper 28 has an input element connected to the crankshaft 23, an output element connected to the carrier shaft 32, and a plurality of elastic bodies (springs) arranged between the input element and the output element.

[0015] The motors MG1 and MG2 are configured as, for example, synchronous generator motors. As described above, the rotor of the motor MG1 is connected to the sun gear of the planetary gear 30 via the sun gear shaft 31, and the rotor of the motor MG2 is connected to the drive shaft 37. The inverters 41 and 42 are connected to the battery 50 via a power line 54. The motors MG1 and MG2 are rotationally driven by the motor ECU 40 controlling the switching of multiple switching elements of the inverters 41 and 42.

[0016] The motor ECU 40 includes a microcomputer similar to the engine ECU 24. The motor ECU 40 receives inputs such as rotational positions θm1, θm2 of the rotors of the motors MG1, MG2 from rotational position sensors 43a, 44a and phase currents Iu, 1v1, Iu2, Iv2 of the respective phases of the motors MG1, MG2 from current sensors 43u, 43v, 44u, 44v. The motor ECU 40 outputs control signals to the inverters 41, 42 via output ports. The motor ECU 40 calculates rotational speeds Nm1, Nm2 and rotational angular velocities ωm1, ωm2 of the motors MG1, MG2 based on the rotational positions θm1, θm2.

[0017] The battery 50 is configured as, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery, and as described above, is connected to the inverters 41, 42 via the power line 54. The battery 50 is managed by the battery ECU 52. The battery ECU 52 includes a microcomputer, similar to the engine ECU 24. The battery ECU 52 receives inputs such as the voltage Vb of the battery 50 from a voltage sensor and the current Ib of the battery 50 from a current sensor. The battery ECU 52 calculates the state of charge (SOC) of the battery 50 based on the integrated value of the current Ib.

[0018] The HVECU 70 includes a microcomputer, similar to the engine ECU 24. The HVECU 70 receives inputs such as a start signal from a start switch 80, the operating position (shift position SP) of a shift lever 81 from a shift position sensor 82, the depression amount (accelerator opening Acc) of an accelerator pedal 83 from an accelerator pedal position sensor 84, the depression amount (brake pedal position BP) of a brake pedal 85 from a brake pedal position sensor 86, and a vehicle speed V from a vehicle speed sensor 87.

[0019] In the hybrid vehicle 20 of this embodiment, the engine 22 and the motors MG1 and MG2 are controlled to travel in a hybrid driving mode (HV driving mode) or an electric driving mode (EV driving mode) through cooperative control between the HVECU 70, the engine ECU 24, and the motor ECU 40. The HV driving mode is a mode in which the vehicle travels with the engine 22 operating, and the EV driving mode is a mode in which the vehicle travels with the engine 22 stopped.

[0020] In the HV traveling mode, the HVECU 70 first sets a required torque Tr* of the drive shaft 37 based on the accelerator pedal position Acc and the vehicle speed V, and then calculates a required power Pr* required for traveling by multiplying the set required torque Tr* by the drive shaft rotation speed Nd (motor MG2 rotation speed Nm2). Next, the HVECU 70 calculates a target power Pe* of the engine 22 based on the required power Pr* and the battery 50's required charging and discharging power Pb*, and sets the target rotation speed Ne* and target torque Te* of the engine 22 and torque commands Tm1* and Tm2* of the motors MG1 and MG2 so that the calculated target power Pe* is output from the engine 22 and the required torque Tr* is output to the drive shaft 37. The HVECU 70 then transmits the target rotation speed Ne* and target torque Te* of the engine 22 to the engine ECU 24, and transmits the torque commands Tm1* and Tm2* of the motors MG1 and MG2 to the motor ECU 40. The engine ECU 24 performs operation control (intake air amount control, fuel injection control, ignition control, etc.) of the engine 22 so that the engine 22 is operated based on the target rotational speed Ne* and the target torque Te*. In the intake air amount control, a target air amount Qa* is set based on the target torque Te* of the engine 22, a target throttle opening TH* is set so that the intake air amount Qa becomes the target air amount Qa*, and the throttle valve 124 is controlled so that the throttle opening TH of the throttle valve 124 becomes the target throttle opening TH*. In the fuel injection control, a target injection amount Qf* is set based on the intake air amount Qa so that the air-fuel ratio AF1 becomes the target air-fuel ratio AF* (e.g., the stoichiometric air-fuel ratio), a target injection time τf* is set based on the target injection amount Qf*, and the direct injection valve 127 is controlled so that fuel is injected from the direct injection valve 127 for the target injection time τf*. In the ignition control, a target ignition timing Tf* is set based on the rotation speed Ne and load factor KL of the engine 22, and the spark plug 130 is controlled so that ignition occurs at the target ignition timing Tf*. The motor ECU 40 controls the switching of multiple switching elements of the inverters 41 and 42 so that the motors MG1 and MG2 are driven by torque commands Tm1* and Tm2*.

[0021] In the EV driving mode, the HVECU 70 sets the required torque Tr* in the same manner as in the HV driving mode, sets the torque command Tm1* of the motor MG1 to the value 0, and sets the torque command Tm2* of the motor MG2 so that the required torque Tr* is output to the drive shaft 37. The torque commands Tm1* and Tm2* of the motors MG1 and MG2 are sent to the motor ECU 40. The control of the inverters 41 and 42 by the motor ECU 40 has been described above.

[0022] Next, we will explain the operation of the hybrid vehicle 20 of this embodiment, particularly the calculation process of the output torque Te of the engine 22 and the diagnosis process of lean imbalance of the engine 22. Here, lean imbalance means that the fuel injection amount of one of the cylinders of the engine 22 is less than the fuel injection amount of the other cylinders, that is, the air-fuel ratio of one of the cylinders is leaner than the air-fuel ratio of the other cylinders.

[0023] First, the calculation process of the output torque Te of the engine 22 will be described. FIG. 3 is an explanatory diagram for explaining the calculation process of the output torque Te of the engine 22. As described above, the engine ECU 24 and the motor ECU 40 can communicate with each other via the shared communication line 90 and the dedicated communication line 92. The processing of the motor ECU 40 will be described. The motor ECU 40 executes a motor torque calculation process M21, a motor rotation speed calculation process M22, a motor rotation angular velocity calculation process M23, a carrier shaft rotation angular velocity calculation process M24, and a resonance influence torque calculation process M25. In this embodiment, each of the processes M21 to M25 is executed each time the crank counter Ccr is switched. The crank counter Ccr, as will be described in detail later, is set by the engine ECU 24 and transmitted to the motor ECU 40 via the dedicated communication line 92. In the following description, [Ccr] means a value corresponding to the crank counter Ccr. Note that [Ccr] is not shown in FIG. 3.

[0024] The motor torque calculation process M21 is a process for calculating the output torque Tm1 [Ccr] of the motor MG1. The motor ECU 40 coordinate-transforms the U-phase and V-phase currents Iu and Iv of the motor MG1 from the current sensors 43u and 43v into d-axis and q-axis currents Id and Iq using the rotational position θm1 of the rotor of the motor MG1 from the rotational position sensor 43a, and calculates the output torque Tm1 [Ccr] of the motor MG1 based on the obtained d-axis and q-axis currents Id and Iq. The motor rotation speed calculation process M22 is a process for calculating the rotation speeds Nm1 [Ccr] and Nm2 [Ccr] of the motors MG1 and MG2. The motor ECU 40 calculates the rotation speeds Nm1 [Ccr] and Nm2 [Ccr] of the motors MG1 and MG2 based on the rotational positions θm1 and θm2 of the rotors of the motors MG1 and MG2 from the rotational position sensors 43a and 44a.

[0025] The motor rotational angular velocity calculation process M23 is a process for calculating the rotational angular velocity ωm1 [Ccr] of the motor MG1. The motor ECU 40 converts the rotational speed Nm1 [Ccr] of the motor MG1 calculated in the motor rotational speed calculation process M22 into the rotational angular velocity ωm1 [Ccr] of the motor MG1. The carrier shaft rotational angular velocity calculation process M24 is a process for calculating the rotational angular velocity ωm1 [Ccr] of the carrier shaft 32. The motor ECU 40 calculates the rotational speed Nc [Ccr] of the carrier shaft 32 according to equation (1) using the rotational speeds Nm1 [Ccr] and Nm2 [Ccr] of the motors MG1 and MG2 calculated in the motor rotational speed calculation process M22, and converts the calculated rotational speed Nc [Ccr] into the rotational angular velocity ωc [Ccr]. In equation (1), "ρ" is the gear ratio of the planetary gear 30 (number of teeth of the sun gear / number of teeth of the ring gear).

[0026] Nc[Ccr]=(ρ·Nm1[Ccr]+Nm2[Ccr]) / (1+ρ) (1)

[0027] The resonance influence torque calculation process M25 is a process for calculating the torque of the carrier shaft 32 based on the torsional resonance of the damper 28 (resonance influence torque Tdmp [Ccr]) and transmitting it to the engine ECU 24. In the hybrid vehicle 20, the crankshaft 23 of the engine 22 is connected to the carrier shaft 32 via the damper 28, and therefore the torque of the carrier shaft 32 based on the torsional resonance of the damper 28 (resonance influence torque) can affect fluctuations in the rotation speed and torque of the engine 22. The motor ECU 40 calculates the resonance influence torque Tdmp[Ccr] according to equation (2) using the output torque Tm1[Ccr] of the motor MG1 calculated in the motor torque calculation process M21, the rotational angular velocity ωm1[Ccr] of the motor MG1 calculated in the motor rotational angular velocity calculation process M23, and the rotational angular velocity ωc[Ccr] of the carrier shaft 32 calculated in the carrier shaft rotational angular velocity calculation process M24, and transmits the calculated resonance influence torque Tdmp[Ccr] to the engine ECU 24 via the shared communication line 90. In equation (2), "Ic" is the moment of inertia of the carrier shaft 32, and "Im1" is the moment of inertia of the motor MG1. Equation (2) can be derived from equation (3), which shows the torque relationship of the sun gear shaft 31.

[0028] Tdmp[Ccr]=Ic·dωc[Ccr] / dt+(1+ρ) / ρ·(Im1·dωm1[Ccr] / dt-Tm1[Ccr]) (2) ρ / (1+ρ)·Ic·dωc+Im1·dωm1 / dt=Tm1+ρ / (1+ρ)·Tdmp (3)

[0029] Next, a description will be given of the processing of the engine ECU 24. The engine ECU 24 executes crank counter update processing M11, engine rotation angular velocity calculation processing M12, inertia torque calculation processing M13, and engine torque calculation processing M14. In this embodiment, each of the processing M12 to M13 is executed every time the crank counter Ccr is switched.

[0030] The crank counter update process M11 is a process for updating the crank counter Ccr. The engine ECU 24 counts up the crank counter Ccr each time the crank angle θcr of the crankshaft 23 of the engine 22, which is received from the crank position sensor 140, rotates by a predetermined angle Δθcr (e.g., 30 degrees or 45 degrees), and resets the crank counter Ccr to a value of 0 for each cycle (two rotations) of the engine 22. The engine rotation angular velocity calculation process M12 is a process for calculating the rotation angular velocity ωe[Ccr] of the engine 22. The engine ECU 24 calculates the rotation speed Ne[Ccr] of the engine 22 based on the crank angle θcr of the crankshaft 23 of the engine 22, which is received from the crank position sensor 140, and converts the calculated rotation speed Ne[Ccr] into the rotation angular velocity ωe[Ccr] of the engine 22. The inertia torque calculation process M13 is a process for calculating the inertia torque Tei[Ccr] of the engine 22. The engine ECU 24 calculates the inertia torque Tei [Ccr] of the engine 22 according to equation (4) using the rotational angular velocity ωe [Ccr] of the engine 22 calculated in the engine rotational angular velocity calculation process M12. In equation (4), "Ie" is the moment of inertia of the engine 22. Equation (4) can be derived from equation (5) which shows the relationship of the torque of the crankshaft 23.

[0031] Tei[Ccr]=Ie·dωe[Ccr] / dt (4) Ie·dωe / dt=Te-Tdmp=Tei (5)

[0032] The engine torque calculation process M14 is a process for calculating the output torque Te[Ccr] of the engine 22. The engine ECU 24 selects the inertia torque Tei[Ccr] and the resonance influence torque Tdmp[Ccr] when the crank counter Ccr has the same value (for example, the latest value) from the inertia torque Tei[Ccr] of the engine 22 for each crank counter Ccr calculated in the inertia torque calculation process M13 and the resonance influence torque Tdmp[Ccr] for each crank counter Ccr received from the motor ECU 40, and calculates the sum of the two as the output torque Te[Ccr] of the engine 22.

[0033] In this way, the sum of the synchronized inertia torque Tei [Ccr] and the resonance influence torque Tdmp [Ccr] of the engine 22 is calculated as the output torque Te [Ccr] of the engine 22, thereby improving the calculation accuracy of the output torque Te [Ccr] of the engine 22. The output torque Te [Ccr] corresponds to the crank counter Ccr and, ultimately, the crank angle θcr of the engine 22. Furthermore, because the crank counter Ccr is transmitted from the engine ECU 24 to the motor ECU 40 via the dedicated communication line 92, it is possible to reduce the discrepancy between the execution timing of the processes M12 to M13 by the engine ECU 24 and the execution timing of the processes M21 to M25 by the motor ECU 40, compared to when the crank counter Ccr is transmitted via the shared communication line 90. Furthermore, because the resonance influence torque Tdmp is calculated by the motor ECU 40 and used to calculate the output torque Te of the engine 22, it is possible to appropriately eliminate the influence of the tolerance of the damper 28.

[0034] Next, a process for diagnosing a lean imbalance in the engine 22 will be described. FIG. 4 is a flowchart showing an example of the process for diagnosing the lean imbalance executed by the engine ECU 24. This process for diagnosing is repeatedly executed when a value greater than 1 is not set for a boost correction coefficient k[i], which will be described later. When this process for diagnosing is executed, the engine ECU 24 first inputs the average output torque Teav(Teav[i]) of the ignition cylinder (target cylinder) to be diagnosed and the average output torque Teav(Teav2) of the ignition cylinder two prior to the ignition of the target cylinder (two prior cylinders) (step S100). Here, "i" is the cylinder number of the target cylinder. In this embodiment, a four-cylinder engine 22 is used, so "i" is any one of 1 to 4. The average output torque Teav may be calculated as the average value of the output torque Te in the latter half of the expansion stroke of the ignition cylinder (the section from the position 90 degrees from the compression top dead center to the bottom dead center), or may be calculated as the average value of the output torque Te in the entire expansion stroke of the ignition cylinder (the section from the compression top dead center to the bottom dead center). The output torque Te is obtained in accordance with the crank angle θcr (crank counter Ccr) as described above.

[0035] Next, the average output torque Teav2 of the two pre-ignition cylinders is subtracted from the average output torque Teav[i] of the target cylinder to calculate the inter-cylinder output torque variation ΔTe[i] (step S110), and the calculated inter-cylinder output torque variation ΔTe[i] is compared with a negative threshold ΔTeref (step S120). Here, the threshold ΔTeref is a threshold used to determine whether a lean imbalance occurs in the engine 22, specifically, whether the fuel injection amount of the target cylinder is smaller than the fuel injection amount of the two pre-ignition cylinders (i.e., whether the air-fuel ratio of the target cylinder is leaner than the air-fuel ratio of the two pre-ignition cylinders). The process of step S120 takes into account the fact that when the fuel injection amount of the target cylinder is smaller than the fuel injection amount of the two pre-ignition cylinders, the output torque Te0 of the target cylinder becomes somewhat smaller than the output torque Te2 of the two pre-ignition cylinders.

[0036] If, in step S120, the variation ΔTe[i] in the output torque between cylinders is greater than the threshold ΔTeref, it is determined that the fuel injection amount of the target cylinder is not smaller than the fuel injection amount of the two pre-ignition cylinders (including cases where it is smaller by within an error range), and the diagnostic process ends. In this case, the number of lean imbalance detections Nli[i], the cumulative variation ΔTesum[i] in the output torque between cylinders, and the average variation RτTeav[i] are reset to the initial value of 0, and the increase correction coefficient k[i] is also reset to the initial value of 0. Note that each parameter is set to the initial value of 0 when the engine 22 is started.

[0037] If the variation ΔTe[i] in the output torque between cylinders is equal to or less than the threshold ΔTeref in step S120, it is determined that the fuel injection amount of the target cylinder is somewhat smaller than the fuel injection amount of the two pre-ignition cylinders. As described above, the accuracy of calculating the output torque Te of the engine 22 can be improved, and therefore, by comparing the variation ΔTe[i] in the output torque between cylinders based on the output torque Te with the threshold ΔTeref, it is possible to improve the accuracy of determining whether the fuel injection amount of the target cylinder is somewhat smaller than the fuel injection amount of the two pre-ignition cylinders.

[0038] In this case, the number of times lean imbalance has been detected Nli[i] is counted up by 1 (step S130), and the amount of fluctuation in output torque between cylinders ΔTe[i] is added to the previous value of the integrated amount of fluctuation in output torque between cylinders ΔTesum[i] to calculate the integrated amount of fluctuation in output torque between cylinders ΔTesum[i] (step S140). Next, the number of times lean imbalance has been detected Nli[i] is compared with a predetermined number of times Nli1 (step S150). Here, the predetermined number of times Nli1 is set to approximately 50 to 150. If the number of times lean imbalance has been detected Nli[i] is less than the predetermined number of times Nli1, this diagnostic process is terminated.

[0039] If the number of lean imbalance detections Nli[i] is equal to or greater than the predetermined number Nli1 in step S150, the integrated variation amount ΔTesum[i] of the output torque between the cylinders is divided by the predetermined number Nli1 to calculate the average variation amount ΔTeav[i] of the output torque between the cylinders (step S160). Next, based on the average variation amount ΔTeav[i] of the output torque between the cylinders, the increase correction coefficient k[i] of the fuel injection amount of the target cylinder is set to a value greater than 1 (step S170), and the diagnostic process ends. After setting the increase correction coefficient k[i] of the target cylinder in this way, in subsequent fuel injection control, the target injection amount Qf* (target injection time τf*) of the target cylinder is multiplied by the increase correction coefficient k[i] compared to the other cylinders. This makes it possible to suppress discrepancies in the fuel injection amount (air-fuel ratio discrepancies) between the cylinders. This effect is particularly noticeable when emissions are likely to be affected, such as during warm-up of the exhaust gas purification catalyst 135a.

[0040] Here, the boost correction coefficient k[i] can be set, for example, by applying the average fluctuation amount ΔTeav[i] of the output torque between the cylinders to a boost correction coefficient map. The boost correction coefficient map is determined in advance through experiments, analysis, and machine learning as the relationship between the average fluctuation amount ΔTeav[i] of the output torque between the cylinders and the boost correction coefficient k[i]. FIG. 5 is an explanatory diagram showing an example of the boost correction coefficient map. As shown in the figure, the boost correction coefficient k[i] is set to be larger as the average fluctuation amount ΔTeav[i] of the output torque between the cylinders is smaller (more negative), that is, as the fuel injection amount of the target cylinder is not smaller than the fuel injection amount of the two pre-ignition cylinders. Therefore, in fuel injection control, the target injection amount Qf* (target injection time τf*) of the target cylinder is set to be larger compared to the other cylinders as the average fluctuation amount ΔTeav[i] of the output torque between the cylinders is smaller. This makes it possible to more appropriately suppress the difference in fuel injection amount (air-fuel ratio difference) between cylinders.

[0041] In the hybrid vehicle 20 of this embodiment described above, the engine ECU 24 selects the inertia torque Tei[Ccr] and the resonance influence torque Tdmp[Ccr] when the crank counter Ccr is the same from the inertia torque Tei[Ccr] of the engine 22 for each crank counter Ccr and the resonance influence torque Tdmp[Ccr] for each crank counter Ccr, and calculates the sum of the two as the output torque Te[Ccr] of the engine 22. This improves the calculation accuracy of the output torque Te of the engine 22. Then, the ECU 24 compares the inter-cylinder output torque variation ΔTe[i] based on the output torque Te with a threshold ΔTeref. This improves the accuracy of determining whether the fuel injection amount of the target cylinder is somewhat smaller than the fuel injection amount of the two pre-ignition cylinders. Furthermore, at this time, the target injection amount Qf* (target injection time τf*) of the target cylinder is increased compared to the other cylinders. This reduces the difference in fuel injection amount (air-fuel ratio) between the cylinders.

[0042] In the above-described embodiment, the motor ECU 40 calculates the resonance influence torque Tdmp[Ccr] according to the above-described equation (2) using the output torque Tm1[Ccr] of the motor MG1, the rotational angular velocity ωm1[Ccr] of the motor MG1, and the rotational angular velocity ωc[Ccr] of the carrier shaft 32. However, the resonance influence torque Tdmp[Ccr] may be calculated without using the rotational angular velocity ωc[Ccr] of the carrier shaft 32, that is, without using the first term on the right-hand side of equation (2).

[0043] In the above-described embodiment, the engine ECU 24 calculates the inter-cylinder output torque fluctuation amount ΔTe[i] by subtracting the average output torque Teav2 of the two pre-ignition cylinders from the average output torque Teav[i] of the target cylinder. However, the inter-cylinder output torque fluctuation amount ΔTe[i] may also be calculated by subtracting the average output torque Teav1 of the one pre-ignition cylinder from the average output torque Teav[i] of the target cylinder.

[0044] In the above-described embodiment, the engine ECU 24 sets the increase correction coefficient k[i] of the fuel injection amount of the target cylinder based on the average variation amount ΔTeav[i] of the output torque between the cylinders. However, the increase correction coefficient k[i] may also be set based on the maximum value of the variation amount ΔTe[i] of the output torque between the cylinders for a predetermined number of times Nli1. Also, instead of the processing of steps S130 to S170, the increase correction coefficient k[i] may be set to a constant value or may be set based on the variation amount ΔTe[i] of the output torque between the cylinders.

[0045] In the above-described embodiment, a four-cylinder engine is used as the engine 22. However, a six-cylinder or eight-cylinder engine may also be used.

[0046] In the above-described embodiment, the crankshaft 23 of the engine 22 and the rotor of the motor MG1 are connected via the damper 28, the carrier shaft 32, the planetary gear 30, and the sun gear shaft 31. However, any configuration may be used as long as the crankshaft of the engine and the rotor of the motor are connected via a torsion element.

[0047] The correspondence between the main elements of the embodiment and the main elements of the invention described in the "Means for Solving the Problem" section will be described below. In the embodiment, the engine 22 corresponds to the "engine," the motor MG1 corresponds to the "motor," the damper 28 corresponds to the "torsion element," the crank position sensor 140 corresponds to the "first sensor," the rotational position sensor 43a corresponds to the "second sensor," the engine ECU 24 corresponds to the "first control device," and the motor ECU 40 corresponds to the "second control device."

[0048] The above describes embodiments for implementing the present disclosure, but the present disclosure is not limited to these embodiments and can, of course, be implemented in various forms within the scope that does not deviate from the gist of the present disclosure. [Explanation of symbols]

[0049] 20 hybrid vehicle, 22 engine, 23 crankshaft, 24 engine ECU, 28 damper, 30 planetary gear, 31 sun gear shaft, 32 carrier shaft, 40 motor ECU, 41, 42 inverter, 43a, 44a rotational position sensor, 43u, 43v, 44u, 44v current sensor, 90 shared communication line, 92 dedicated communication line, 127 in-cylinder injection valve, 140 crank position sensor, MG1 motor.

Claims

1. A hybrid vehicle comprising: an engine having a fuel injection valve for each cylinder; a motor; a torsion element having an input side connected to a crankshaft of the engine and an output side connected to a rotor of the motor; a first sensor that detects a crank angle of the crankshaft; a second sensor that detects a rotational position of the rotor; a first control device that controls the engine based on the crank angle; and a second control device that controls the motor based on the rotational position, the first control device controls the fuel injection valve so as to inject fuel from the fuel injection valve based on a target injection amount for each cylinder; the first control device transmits to the second control device a counter that is switched every time the crank angle rotates by a predetermined angle, and calculates a rotational angular velocity of the engine based on the crank angle and an inertia torque of the engine based on the rotational angular velocity of the engine every time the counter is switched; the second control device calculates a rotational angular velocity of the motor based on the rotational position and a resonance-affected torque on the output side of the torsion element based on torsional resonance of the torsion element based on the rotational angular velocity of the motor each time the counter is switched, and transmits the calculated torque to the first control device; the first control device calculates the sum of the inertia torque and the resonance influence torque when the counters have the same value as each other as the output torque of the engine, determines whether or not a lean imbalance has occurred in which the fuel injection amount of any one of the cylinders is smaller than the fuel injection amount of any other cylinder based on the amount of fluctuation in the output torque, and increases the target injection amount of any one of the cylinders compared to the target injection amount of the other cylinder when it is determined that the lean imbalance has occurred. Hybrid car.

2. The hybrid vehicle according to claim 1, the first control device calculates an average output torque, which is an average of the output torque of at least a part of an expansion stroke, for each of the cylinders, and calculates a fluctuation amount of the output torque by subtracting the average output torque of a cylinder that is ignited a predetermined time before the target cylinder from the average output torque of the target cylinder. Hybrid car.

3. 3. The hybrid vehicle according to claim 2, When the lean imbalance occurs, the first control device increases the target injection amount of any one of the cylinders compared to the target injection amount of the other cylinder as the amount of fluctuation in the output torque or the average value of the amount of fluctuation in the output torque increases on the negative side. Hybrid car.

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