JP2024118754A - Vehicle control device - Google Patents

Abstract

[Problem] To realize the required output of a vehicle when the engine is operated with the air-fuel ratio of the engine at or above a threshold value. [Solution] When operating the engine 20 with the air-fuel ratio of the engine 20 at or above a threshold value, a control device 90 executes a basic process of calculating an engine basic value, which is a basic value of the required output of the engine 20, and an electric motor basic value, which is a basic value of the required output of the MG 40, so that the required output of the vehicle 10 can be obtained under engine operating conditions without air-fuel ratio restrictions, and a modification process of reducing the required output of the engine 20 from the engine basic value to an engine correction value that is equal to or less than the maximum output that the engine 20 can achieve when the engine 20 is operated at a target air-fuel ratio, and increasing the required output of the MG 40 from the electric motor basic value to the electric motor correction value by the amount of the reduction in the required output of the engine 20. [Selected Figure] FIG.

Description

This invention relates to a vehicle control device.

The vehicle disclosed in Patent Document 1 includes an engine, a first electric motor, a torque converter, a second electric motor, drive wheels, and a control device. The first electric motor, the torque converter, and the second electric motor are arranged in this order on a power transmission path from the engine to the drive wheels. The control device calculates the output that the engine should provide to run the vehicle as the required output of the engine. The control device then determines an operating point that satisfies the required torque of the engine, that is, a combination of engine torque and rotation speed. The control device also adjusts the torque of the first electric motor and the torque of the second electric motor, causing the first electric motor, the torque converter, and the second electric motor as a whole to function as a continuously variable transmission.

Patent No. 5522266

Vehicles such as that described in Patent Document 1 may employ an engine that uses hydrogen as fuel. In a hydrogen-fueled engine, water is generated in the cylinders due to the combustion of an air-fuel mixture that contains hydrogen in the cylinders. Therefore, in order to prevent excess water from accumulating in the engine, it is necessary to suppress the amount of water generated in the cylinders. In order to suppress the amount of water generated in the cylinders, it is possible to limit the air-fuel ratio in the cylinders to a predetermined value or higher. However, imposing such a limit on the air-fuel ratio limits the engine output. As a result, there is a risk that the required engine output cannot be met.

A vehicle control device for solving the above problem has as its control object a vehicle that is equipped with an engine that uses hydrogen as fuel and an electric motor located on a power transmission path extending from the engine to drive wheels, and is configured so that the sum of the output of the engine and the output of the electric motor is transmitted to the drive wheels, and is capable of executing lean combustion control for operating the engine with an air-fuel ratio of the engine equal to or greater than a predetermined threshold value, and during execution of the lean combustion control, includes a setting process for setting a target air-fuel ratio of the engine to a value equal to or greater than the threshold value, and a setting process for setting a target air-fuel ratio of the engine to a value equal to or greater than the threshold value under predetermined operating conditions of the engine without restrictions on the air-fuel ratio. A basic process is executed to calculate an engine basic value, which is the basic value of the required output of the engine, and an electric motor basic value, which is the basic value of the required output of the electric motor, so that the required output of the vehicle is obtained, and if the engine basic value is greater than the maximum value of the output that the engine can achieve when the engine is operated at the target air-fuel ratio, a change process is executed to reduce the required output of the engine from the engine basic value to an engine correction value that is equal to or less than the maximum value, and to change the required output of the electric motor to an electric motor correction value that is increased from the electric motor basic value by a value equal to the absolute value of the decrease.

With the above configuration, the vehicle's required output can be achieved even when the engine is operated with an air-fuel ratio equal to or higher than the threshold value.

FIG. 1 is a schematic configuration diagram of a vehicle. 4 is a flowchart showing a procedure of a lean burn control process. 1 is a diagram showing an operating line for each gear in relation to an equal output line. FIG. 1 is a diagram showing operating lines for each air-fuel ratio in relation to isopower lines. FIG. 4 is a diagram illustrating a method for calculating an engine correction value.

One embodiment of a vehicle control device will be described below with reference to the drawings. As shown in FIG. 1, a vehicle 10 includes an engine 20, a motor generator (hereinafter referred to as MG 40), a clutch mechanism 30, a transmission unit 50, a differential 71, and drive wheels 11.

The engine 20 is the driving source of the vehicle 10. The engine 20 has a crankshaft 24. Details of the engine 20 will be described later. The MG 40 is the driving source of the vehicle 10. The MG 40 functions as both an electric motor and a generator. The MG 40 has an output shaft 43 that rotates integrally with the rotor 42. The MG 40 is an example of an electric motor. The clutch mechanism 30 is interposed between the crankshaft 24 and the output shaft 43 of the MG 40. The clutch mechanism 30 is in a connected state in which the crankshaft 24 and the output shaft 43 are connected, or in a disconnected state in which they are disconnected, depending on the hydraulic pressure from a hydraulic mechanism (not shown).

The transmission unit 50 includes a torque converter 51 and a transmission mechanism 56. The torque converter 51 includes a pump impeller 52, a turbine impeller 53, and a lock-up clutch 54. The torque converter 51 is a fluid coupling having a torque amplification function. The pump impeller 52 rotates integrally with the output shaft 43 of the MG 40. The turbine impeller 53 rotates integrally with the input shaft 57 of the transmission mechanism 56. The lock-up clutch 54 directly connects the pump impeller 52 and the turbine impeller 53 in response to the hydraulic pressure from the hydraulic mechanism. In this embodiment, the lock-up clutch 54 is assumed to always directly connect both impellers while the vehicle 10 is traveling. The transmission mechanism 56 is a stepped type in which the gear ratio is switched in multiple stages by switching the gears. The transmission mechanism 56 changes the rotational motion of the input shaft 57 in the transmission mechanism 56 according to the currently selected gear stage and outputs it from the output shaft 58. The gear ratio is the ratio indicating the number of times the input shaft 57 rotates when the output shaft 58 rotates once. The output shaft 58 is connected to the left and right drive wheels 11 via a differential 71.

As described above, in the drive system of the vehicle 10, the MG 40 is located on the power transmission path from the engine 20 to the drive wheels 11. In this drive system, when the clutch mechanism 30 is in the engaged state, the sum of the output of the engine 20 and the output of the MG 40 is transmitted to the drive wheels 11.

The vehicle 10 includes a battery 81 and an inverter 82. The battery 81 is electrically connected to the MG 40 via the inverter 82. The battery 81 supplies power to the MG 40 and stores the power generated by the MG 40. The inverter 82 converts DC to AC. When the MG 40 functions as an electric motor, the torque of the MG 40 (hereinafter referred to as motor torque) is a positive value. When the MG 40 functions as a generator, the motor torque is a negative value.

The engine 20 will now be described in detail. The engine 20 includes a number of cylinders 21, a number of injection valves 22, a number of spark plugs 23, and the crankshaft 24. The cylinders 21 are spaces for burning a mixture of fuel and intake air. An injection valve 22 is provided for each cylinder 21. The injection valve 22 injects hydrogen as fuel for the engine 20. For example, the injection valve 22 directly injects hydrogen into the cylinders 21. An ignition plug 23 is provided for each cylinder 21. The spark plug 23 ignites the mixture in the cylinders 21. The crankshaft 24 rotates with the power generated by the combustion of the mixture in the cylinders 21.

The engine 20 is equipped with an intake passage 25 and a throttle valve 26. The intake passage 25 is a passage for introducing intake air into each cylinder 21. The intake passage 25 is connected to each cylinder 21. The throttle valve 26 is located midway through the intake passage 25. The opening of the throttle valve 26 can be adjusted. The flow rate of intake air in the intake passage 25 changes depending on the opening of the throttle valve 26.

The engine 20 is equipped with an exhaust passage 27 and a catalyst 28. The exhaust passage 27 is a passage for discharging exhaust gas from each cylinder 21. The exhaust passage 27 is connected to each cylinder 21. The catalyst 28 is located midway through the exhaust passage 27. The catalyst 28 purifies NOx contained in the exhaust gas flowing through the exhaust passage 27.

The vehicle 10 is equipped with various sensors. The various sensors include a crank angle sensor 101, a temperature sensor 102, an air flow meter 103, an atmospheric pressure sensor 104, an accelerator sensor 105, a vehicle speed sensor 106, and a battery sensor 107. The crank angle sensor 101 detects the rotation angle of the crankshaft 24. The air flow meter 103 detects the flow rate of intake air in the intake passage 25. The temperature sensor 102 detects the temperature T of the catalyst 28. These three sensors 101 to 103 form part of the engine 20. The atmospheric pressure sensor 104 detects the atmospheric pressure P. The accelerator sensor 105 detects the accelerator opening AC, which is the amount of accelerator pedal operation by the driver of the vehicle 10. The vehicle speed sensor 106 detects the vehicle speed V, which is the traveling speed of the vehicle 10. The battery sensor 107 detects battery information such as the temperature, voltage, and current of the battery 81. Each sensor repeatedly outputs a signal corresponding to the information it detects to the control device 90, which will be described later.

The vehicle 10 is equipped with an operation unit 15 that is operated by the driver when selecting the driving mode of the vehicle 10. The operation unit 15 outputs a signal corresponding to the driving mode selected by the driver to a control device 90 described below. The driving modes of the vehicle 10 include a normal mode and a sports mode that are prepared in advance. The sports mode is a mode that makes the acceleration response of the vehicle 10 when the driver operates the accelerator pedal higher than when the normal mode is selected.

The vehicle 10 includes a control device 90. The control device 90 includes a CPU 91 and a memory 92. The memory 92 stores in advance various programs in which processes to be executed by the CPU 91 are described, and various data required for executing the programs. The CPU 91 sequentially calculates necessary parameters based on signals received from various sensors. For example, the CPU 91 calculates the engine speed, which is the rotation speed of the crankshaft 24, based on the rotation angle of the crankshaft 24. The CPU 91 also calculates the charging rate G, which is the ratio of the remaining capacity to the full charge capacity of the battery 81, based on battery information. The CPU 91 controls the engine 20, the MG 40, the transmission unit 50, the clutch mechanism 30, etc., based on signals received from the operation unit 15 and various sensors, information calculated therefrom, etc. For example, the CPU 91 switches the gear stage of the transmission mechanism 56 based on the accelerator opening AC and the vehicle speed V.

The CPU 91 can cause the vehicle 10 to run on hybrid power or battery power. When the CPU 91 causes the vehicle 10 to run on hybrid power, it controls the engine 20 and the MG 40 after connecting the clutch mechanism 30. When the CPU 91 causes the vehicle 10 to run on battery power, it controls the MG 40 after disconnecting the clutch mechanism 30.

The process performed by the CPU 91 when the vehicle 10 is made to run in hybrid mode will be described in detail. When the vehicle 10 is made to run in hybrid mode, the CPU 91 performs normal control or lean burn control. The CPU 91 selects which of these controls to perform depending on the operating state of the engine 20. The CPU 91 selects lean burn control when a specific condition is met, such as a request to suppress the generation of water in the cylinder 21, and selects normal control when that condition is not met. The normal control is a control that operates the engine 20 without imposing a limit on the air-fuel ratio λ. The lean burn control is a control that operates the engine 20 with the air-fuel ratio λ of the engine 20 set to a value within a predetermined allowable range λR. The lower limit threshold λR1 of the allowable range λR is a value greater than the theoretical air-fuel ratio, i.e., a value on the leaner side than the theoretical air-fuel ratio. Therefore, when the lean burn control is performed, the combustion of the engine 20 becomes lean combustion at an air-fuel ratio λ on the leaner side than the theoretical air-fuel ratio. The lower limit threshold λR1 is determined in advance, for example, through experiments, as a value that can suppress the amount of water generation in the cylinder 21 to an allowable value or less. When lean combustion is performed in the engine 20, the output of the engine 20 is small. In consideration of this, the upper limit threshold λR2 of the allowable range λR is determined in advance, for example, through experiments, as a value that can ensure a certain level of output of the engine 20 even when lean combustion is performed. The CPU 91 can estimate the amount of water remaining in the engine 20 based on the fuel injection amount and the intake air flow rate. When the amount of water exceeds a predetermined reference value, the CPU 91 determines that there is a request to suppress water generation.

When a specific condition is satisfied, the CPU 91 repeats the lean burn control at a predetermined control period. The following describes a series of steps in the lean burn control. As shown in FIG. 2, when the CPU 91 starts the lean burn control, it first executes the process of step S10. In step S10, the CPU 91 calculates the output required to drive the vehicle 10 (hereinafter, referred to as the required output Y of the vehicle 10). The CPU 91 calculates the required output Y of the vehicle 10 based on the vehicle speed V, the accelerator opening AC, the charging rate G of the battery 81, and the like. The control device 90 calculates the required output Y of the vehicle 10 as a larger value as the accelerator opening AC is larger. After calculating the required output Y of the vehicle 10, the CPU 91 proceeds to step S20. As is well known, the output is a parameter that represents the product of the rotation speed and the torque.

In step S20, the CPU 91 calculates the engine basic value E1 and the motor basic value M1. The engine basic value E1 is the basic value of the required output EY of the engine 20. The motor basic value M1 is the basic value of the required output MY of the MG 40. When calculating the engine basic value E1 and the motor basic value M1, the CPU 91 distributes the required output Y of the vehicle 10 calculated in step S10 to the engine basic value E1 and the motor basic value M1. Here, the sum of the engine torque and the motor torque is referred to as the system torque. Also, the engine speed is referred to as the system speed. Note that during hybrid driving, the engine speed and the speed of the output shaft 43 of the MG 40 (hereinafter referred to as the motor speed) are the same. The CPU 91 distributes the required output Y of the vehicle 10 to the engine basic value E1 and the motor basic value M1, for example, as follows. The CPU 91 calculates a combination corresponding to the currently selected gear stage among combinations of the system torque and the system rotation speed that satisfy the required output Y of the vehicle 10 as a reference operating point. When calculating the reference operating point, the CPU 91 uses, for example, a first map as shown in FIG. 3. In the first map, an operating line for each gear stage and a plurality of equal power lines are shown in an orthogonal coordinate system with the system rotation speed as the X-axis and the system torque as the Y-axis. Note that FIG. 3 illustrates two operating lines and two equal power lines. The operating lines show the relationship between the system rotation speed and the system torque at a specific gear stage. As shown by the solid line in FIG. 3, the operating lines have a characteristic that the higher the system rotation speed, the larger the system torque becomes. As shown by the dashed and dotted line in FIG. 3, the equal power lines are inversely proportional curves. The CPU 91 uses the first map to identify an intersection W between the equal power line corresponding to the required output Y calculated in step S10 and the operating line corresponding to the currently selected gear stage. Then, the CPU 91 calculates a combination of the system speed and the system torque at the intersection W as a reference operating point. After calculating the reference operating point, the CPU 91 distributes the system torque at the reference operating point between the required engine torque and the required MG torque. At this time, the CPU 91 sets the following value to the required engine torque without limiting the air-fuel ratio λ of the engine 20. That is, the CPU 91 sets the engine torque at which the fuel efficiency of the engine 20 is optimal at the system speed of the reference operating point to the required engine torque. The CPU 91 sets a value obtained by subtracting the required engine torque from the system torque to the required MG torque. The required MG torque may become negative. The CPU 91 may readjust the torque distribution thus distributed in consideration of the charging rate G of the battery 81. For example, this corresponds to a case where the amount of power generation of the MG 40 is insufficient for the charging request of the battery 81. Due to the readjustment of the torque distribution, the required engine torque may deviate slightly from the value at which the fuel efficiency is optimal at the system speed of the reference operating point. Based on the information obtained through the above processing, the CPU 91 sets the base operating points for the engine 20 and the MG 40. That is, the CPU 91 sets the combination of the required engine torque and the system speed of the reference operating point as the base operating point for the engine 20. The CPU 91 also sets the combination of the required MG torque and the system speed of the reference operating point as the base operating point for the MG 40.

When the CPU 91 calculates the basic operating points of the engine 20 and the MG 40, it calculates the engine basic value E1 and the motor basic value M1. That is, the CPU 91 sets the product of the engine speed and the engine torque, which are the basic operating points of the engine 20, as the engine basic value E1. The CPU 91 also sets the product of the motor speed and the motor torque, which are the basic operating points of the MG 40, as the motor basic value M1. When the CPU 91 calculates the engine basic value E1, it provisionally sets the engine basic value E1 to the required output EY of the engine 20. When the CPU 91 calculates the motor basic value M1, it provisionally sets the motor basic value M1 to the required output MY of the MG 40. After this, as shown in FIG. 2, the CPU 91 advances the process to step S30. Note that the process of step S20 is a basic process. As described above, in this basic process, the condition of optimal or close to optimal fuel economy is set as the operating condition of the engine 20 for calculating the engine basic value E1 and the electric motor basic value M1. The CPU 91 then calculates the engine basic value E1 and the electric motor basic value M1 so that the required output Y of the vehicle 10 is obtained under operating conditions in which there is no air-fuel ratio restriction and the engine 20 has optimal fuel economy. "Best fuel economy" refers to a state in which the torque of the engine 20 per unit amount of fuel is at its maximum.

Now, in step S30, the CPU 91 calculates the target air-fuel ratio λS of the engine 20. In calculating the target air-fuel ratio λS, the CPU 91 first calculates the air-fuel ratio reference value λB. The CPU 91 calculates a value within the above-mentioned allowable range λR as the air-fuel ratio reference value λB. The CPU 91 calculates the air-fuel ratio reference value λB taking into account the water reduction target and emissions of the engine 20. After calculating the air-fuel ratio reference value λB, the CPU 91 corrects this air-fuel ratio reference value λB using the following (Equation 1). The CPU 91 then sets the corrected value as the target air-fuel ratio λS.

(Formula 1) λS=λB×α1×α2×α3×α4
The CPU 91 applies the following positive values to the coefficients α1 to α4 in (Equation 1). The CPU 91 sets the first coefficient α1 to a smaller value as the rate of increase of the accelerator opening AC increases. That is, The CPU 91 sets the target air-fuel ratio λS to a smaller value as the rate of increase of the accelerator opening AC increases. When the sports mode is selected, the CPU 91 sets the target air-fuel ratio λS to a smaller value as compared to when the normal mode is selected. The second coefficient α2 is set to a small value. That is, when the sports mode is selected, the CPU 91 sets the target air-fuel ratio λS to a smaller value than when the normal mode is selected. The lower the atmospheric pressure P, the smaller the third coefficient α3. That is, the CPU 91 sets the target air-fuel ratio λS to a smaller value as the atmospheric pressure P decreases. That is, the CPU 91 sets the target air-fuel ratio λS to a smaller value as the temperature T of the catalyst 28 increases. The CPU 91 sets each coefficient based on the latest information on parameters related to each coefficient, such as the temperature T of the catalyst 28. If the target air-fuel ratio λS is smaller than the lower limit threshold λR1 of the allowable range λR, the CPU 91 replaces the target air-fuel ratio λS calculated using (Equation 1) with the lower limit threshold λR1. is greater than the upper threshold value λR2 of the allowable range λR, the target air-fuel ratio λS is replaced with the upper threshold value λR2 from the value calculated by (Equation 1). , the target air-fuel ratio λS is set to a value within the allowable range λR. After calculating the target air-fuel ratio λS, the CPU 91 advances the process to step S40. The process of step S30 is a setting process.

In step S40, the CPU 91 calculates the maximum output EQ, which is the maximum value of the output that the engine 20 can achieve when the engine 20 is operated at the target air-fuel ratio λS calculated in step S30. As a premise for the processing of this step S40, the second map shown in FIG. 4 will be described. In the second map, an operating line for each air-fuel ratio λ and a plurality of equal output lines are shown in an orthogonal coordinate system with the engine speed on the X-axis and the engine torque on the Y-axis. In FIG. 4, the operating line is shown as a solid line, and the equal output line is shown as a dashed line. The operating line shows the relationship between the engine speed and the engine torque when the engine 20 is operated with the air-fuel ratio λ constant. The four air-fuel ratios λ shown in FIG. 4 have the relationship of "stoichiometric air-fuel ratio < first air-fuel ratio λ1 < second air-fuel ratio λ2 < third air-fuel ratio λ3 < fourth air-fuel ratio λ4". The three equal output lines shown in FIG. 4 have the relationship "first output L1 < second output L2 < third output L3". As shown in FIG. 4, for a certain engine speed, the larger the air-fuel ratio λ, that is, the leaner the air-fuel ratio λ, the smaller the engine torque. In relation to this, the larger the air-fuel ratio λ, the smaller the maximum value of the output that the engine 20 can achieve. Now, in step S40, the CPU 91 uses, for example, the second map shown in FIG. 4 when calculating the above-mentioned maximum output EQ. That is, the CPU 91 identifies an operating line corresponding to the target air-fuel ratio λS, and calculates the maximum value of the output of the engine 20 on this operating line as the maximum output EQ. As shown in FIG. 2, when the CPU 91 calculates the maximum output EQ, the process proceeds to step S50.

In step S50, the CPU 91 determines whether the engine basic value E1 calculated in step S20 is greater than the maximum output EQ calculated in step S40. If the engine basic value E1 is equal to or less than the maximum output EQ (step S50: NO), the CPU 91 advances the process to step S80. On the other hand, if the engine basic value E1 is greater than the maximum output EQ (step S50: YES), the CPU 91 advances the process to step S60.

In step S60, the CPU 91 calculates the engine correction value E2. Specifically, the CPU 91 calculates the value at which the fuel efficiency of the engine 20 is the best among the outputs of the engine 20 that can be realized with the target air-fuel ratio λS as the engine correction value E2. Although not shown in FIG. 4, the second map also shows, for example, iso-fuel efficiency lines as exemplified by the two-dot chain lines in FIG. 5. The iso-fuel efficiency lines are distributed in a concentric circle shape centered on the point at which the fuel efficiency is the best. Note that the distribution of iso-fuel efficiency lines shown in FIG. 5 is an example and does not necessarily match the actual one. The CPU 91 specifies the engine correction value E2 in such a map, for example, as follows. That is, the CPU 91 specifies, on the operating line corresponding to the target air-fuel ratio λS shown by the solid line in FIG. 5, a combination of engine torque and engine speed that provides the best fuel efficiency and satisfies a specified condition as the correction operating point WB. The specified condition is that the product of the engine torque and engine speed is equal to or less than the maximum output EQ calculated in step S40. When the CPU 91 specifies the correction operation point WB, it calculates the product of the engine torque and the engine speed at the correction operation point WB as an engine correction value E2. When the CPU 91 calculates the engine correction value E2, it resets the engine correction value E2 as the required output EY of the engine 20. That is, as illustrated by the arrow N in FIG. 4, the CPU 91 reduces the required output EY of the engine 20 from the engine basic value E1 to the engine correction value E2. The CPU 91 changes the operating point corresponding to the required output EY of the engine 20 from the basic operation point WA to the correction operation point WB. As shown in FIG. 2, after performing the above processing, the CPU 91 advances the processing to step S70. Note that, regarding step S60, when there is no margin in the charging rate G of the battery 81, the CPU 91 adjusts the engine correction value E2 so that the motor correction value M2 described later becomes a value that can be realized at the current charging rate G. Even in this case, the CPU 91 sets the output that can be realized at the target air-fuel ratio λS as the engine correction value E2. That is, the CPU 91 sets the engine correction value E2 to a value equal to or less than the maximum output EQ calculated in step S40. Due to such adjustment, the engine correction value E2 may deviate slightly from the value that provides the best fuel economy among the engine 20 outputs that can be achieved with the target air-fuel ratio λS.

In step S70, the CPU 91 calculates the motor correction value M2. Specifically, the CPU 91 calculates the difference value ΔE by subtracting the engine correction value E2 calculated in step S60 from the engine basic value E1 calculated in step S20. The CPU 91 then adds this difference value ΔE to the motor basic value M1 calculated in step S20. The CPU 91 then sets the obtained value as the motor correction value M2. In this way, the motor correction value M2 is a value that is increased with respect to the motor basic value M1 by the difference value ΔE. When the CPU 91 calculates the motor correction value M2, it resets the motor correction value M2 as the required output MY of the MG40. That is, the CPU 91 changes the required output MY of the MG40 from the motor basic value M1 to the motor correction value M2. When the CPU 91 sets the required output MY of the MG 40, it calculates a combination of motor speed and motor torque that satisfies this required output MY as a correction operation point of the MG 40. The motor speed of this correction operation point is the same as the engine speed of the correction operation point of the engine 20. In addition, the value obtained by dividing the required output MY of the MG 40 by the motor speed of the correction operation point is the motor torque of the correction operation point. After performing the above processing, the CPU 91 advances the processing to step S80. Note that the processing of steps S60 and S70 is a change processing.

In step S80, the CPU 91 controls the engine 20 based on the required output EY of the engine 20 currently set. When the CPU 91 skips the processing of steps S60 and S70 and reaches step S80, it controls the engine 20 at the basic operating point of the engine 20. On the other hand, when the CPU 91 reaches step S80 through the processing of steps S60 and S70, it controls the engine 20 at the corrected operating point of the engine 20. In either case, the CPU 91 controls the engine 20 while adjusting the fuel injection amount, etc. so as to realize the target air-fuel ratio λS. In parallel with controlling the engine 20, the CPU 91 controls the MG 40 based on the required output MY of the MG 40. When the CPU 91 controls the engine 20 at the basic operating point, it controls the MG 40 at the basic operating point. When the CPU 91 controls the engine 20 at the corrected operating point, it controls the MG 40 at the corrected operating point. After executing the process of step S80 for a predetermined period of time, the CPU 91 temporarily ends the series of processes for lean burn control. Then, the CPU 91 executes the process of step S10 again.

This embodiment provides the following advantages.
(1) When the engine 20 is operated with the air-fuel ratio λ of the engine 20 set to a target air-fuel ratio λS equal to or higher than the lower threshold λR1, if the engine basic value E1 cannot be realized, the CPU 91 reduces the required output EY of the engine 20 from the engine basic value E1 to the engine correction value E2. Then, the CPU 91 increases the required output MY of the MG 40 from the electric motor basic value M1 to the electric motor correction value M2 accordingly. By changing both the required output EY of the engine 20 and the required output MY of the MG 40 in this manner, the required output Y of the vehicle 10 can be realized even during execution of lean burn control.

(2) In lean burn control, which limits the air-fuel ratio λ of the engine 20 to equal to or higher than the lower threshold λR1, the torque of the engine 20 and therefore the output power tend to be small. Although the output power of the vehicle 10 is provided by both the engine 20 and the MG 40, it is preferable to maximize the output power of the engine 20 when the user requests acceleration. Therefore, the CPU 91 reduces the target air-fuel ratio λS when the rate of increase in the accelerator opening AC is large. Accordingly, when the rate of increase in the accelerator opening AC is large, the required output power EY of the engine 20 can be set to a large value. This increases the responsiveness of the acceleration of the vehicle 10. Therefore, in the above configuration, acceleration according to the user's request can be realized even during execution of lean burn control.

(3) When the sports mode is selected, the CPU 91 reduces the target air-fuel ratio λS compared to when the normal mode is selected. Therefore, as explained in relation to the accelerator opening AC above, the acceleration responsiveness of the vehicle 10 is increased in the sports mode. In this way, with the above configuration, it is possible to achieve acceleration responsiveness according to the driving mode selected by the user even when lean burn control is being executed.

(4) When the atmospheric pressure P is low, the amount of oxygen contained in the air is reduced, and this reduces the output of the engine 20. Therefore, when the atmospheric pressure P is low, the CPU 91 reduces the target air-fuel ratio λS. This allows the required output EY of the engine 20 to be set as large as possible, even when lean combustion control is performed in an environment where the atmospheric pressure P is low.

(5) In the range of the air-fuel ratio λ where the degree of leanness is relatively large, such as when lean burn control is performed, reducing the air-fuel ratio λ tends to increase the amount of NOx generated. In light of this, the CPU 91 sets the target air-fuel ratio λS to a small value when the temperature T of the catalyst 28 is high and the exhaust purification performance of the catalyst 28 is high. This makes it possible to set the required output EY of the engine 20 as large as possible while suppressing deterioration of emissions.

The above embodiment can be modified as follows: The above embodiment and the following modified examples can be combined with each other to the extent that no technical contradiction occurs.
The engine operating conditions assumed for calculating the engine basic value E1 are not limited to those that provide the best fuel economy. For example, operating conditions that take into account the acceleration response and emissions of the vehicle 10 may be determined in advance. The assumed operating conditions may be changed depending on the driving conditions of the vehicle 10.

- The method of calculating the engine basic value E1 and the electric motor basic value M1 is not limited to the example of the above embodiment. It is sufficient if the engine basic value E1 and the electric motor basic value M1 can be calculated so that the required output Y of the vehicle 10 can be obtained under operating conditions of the engine 20 without air-fuel ratio restrictions.

- Optimizing fuel efficiency is not essential when calculating the engine correction value E2. The engine correction value E2 may be calculated taking other factors into consideration. The engine correction value E2 may be a value equal to or less than the maximum output EQ, which is the maximum value of the output that the engine 20 can achieve when the engine 20 is operated at the target air-fuel ratio λS.

- The method of calculating the engine correction value E2 and the motor correction value M2 is not limited to the example of the above embodiment. It is sufficient to calculate the engine correction value E2 as a value equal to or less than the maximum output EQ, and to calculate the motor correction value M2 by increasing the motor base value M1 by the same value as the absolute value of the reduction from the engine base value E1 to the engine correction value E2.

- The method of determining the first coefficient α1 is not limited to the example of the above embodiment. If the first coefficient α1 is determined so that the target air-fuel ratio λS can be set to a smaller value when the rate of increase of the accelerator opening AC is a first speed, compared to when the rate of increase of the accelerator opening AC is a second speed that is smaller than the first speed, the effect of (2) above can be achieved.

- The method of determining the third coefficient α3 is not limited to the example of the above embodiment. When the atmospheric pressure P is a first pressure, the effect of (4) above can be obtained if the third coefficient α3 is determined so that the target air-fuel ratio λS can be set to a smaller value compared to when the atmospheric pressure P is a second pressure higher than the first pressure.

The method of determining the fourth coefficient α4 is not limited to the example of the above embodiment. If the fourth coefficient α4 is determined so that the target air-fuel ratio λS can be set to a smaller value when the temperature T of the catalyst 28 is a first temperature, compared to when the temperature T is a second temperature that is smaller than the first temperature, the effect of (5) above can be obtained.

- The method of calculating the target air-fuel ratio λS is not limited to the example of the above embodiment. The target air-fuel ratio λS may be calculated based on only some of the parameters of the accelerator opening AC, atmospheric pressure P, catalyst temperature T, and the driving mode of the vehicle 10. For example, one may be selected from the product of the air-fuel ratio reference value λB and the first coefficient α1, the product of the air-fuel ratio reference value λB and the second coefficient α2, the product of the air-fuel ratio reference value λB and the third coefficient α3, and the product of the air-fuel ratio reference value λB and the fourth coefficient α4, and the selected value may be calculated as the target air-fuel ratio λS. The target air-fuel ratio λS may be set regardless of the accelerator opening AC, atmospheric pressure P, catalyst temperature T, and the driving mode of the vehicle 10. The target air-fuel ratio λS may be set to a value within the allowable range λR.

The method of determining the lower limit threshold λR1 is not limited to the example in the above embodiment. The lower limit threshold λR1 may be appropriately determined according to a requirement to be realized, such as suppressing the amount of water generated by the engine 20.
The method of determining the upper threshold λR2 is not limited to the example of the embodiment described above. Furthermore, it is not essential to set the upper threshold λR2. Even if the required output EY of the engine 20 becomes significantly smaller due to the elimination of the upper threshold λR2, the required output Y of the vehicle 10 can be realized by the output of the MG 40 as long as the charging rate G of the battery 81 is sufficient.

The overall configuration of the vehicle 10 is not limited to the example of the above embodiment. A continuously variable transmission may be used in the transmission unit 50. The engine 20 may be any engine that uses hydrogen as fuel.

10...vehicle 11...drive wheels 20...engine 40...MG 90...control device

Claims (5)

A vehicle to be controlled includes an engine that uses hydrogen as fuel, and an electric motor that is located on a power transmission path from the engine to drive wheels, and the sum of the output of the engine and the output of the electric motor is transmitted to the drive wheels,
A lean burn control is executed to operate the engine with an air-fuel ratio equal to or higher than a predetermined threshold value,
During execution of the lean combustion control,
A setting process for setting a target air-fuel ratio of the engine to a value equal to or greater than the threshold value;
A basic process of calculating an engine basic value, which is a basic value of a required output of the engine, and an electric motor basic value, which is a basic value of a required output of the electric motor, so that a required output of the vehicle is obtained under predetermined operating conditions of the engine without any restriction on an air-fuel ratio;
and when the engine basic value is greater than a maximum value of the output that the engine can achieve when the engine is operated at the target air-fuel ratio, a change process is executed to reduce the required output of the engine from the engine basic value to an engine correction value that is equal to or less than the maximum value, and to change the required output of the motor to a motor correction value that is increased from the motor basic value by an amount equal to the absolute value of the decrease. 2. The vehicle control device according to claim 1, wherein in the setting process, when the rate of increase in the accelerator opening is a first speed, the target air-fuel ratio is set to a smaller value than when the rate of increase in the accelerator opening is a second speed that is smaller than the first speed. a normal mode and a sports mode that increases the acceleration responsiveness of the vehicle compared to when the normal mode is selected, are prepared as driving modes of the vehicle;
2. The vehicle control device according to claim 1, wherein in the setting process, when the sports mode is selected, the target air-fuel ratio is set to a smaller value than when the normal mode is selected. The vehicle control device according to claim 1 , wherein in the setting process, when the atmospheric pressure is a first pressure, the target air-fuel ratio is set to a smaller value than when the atmospheric pressure is a second pressure higher than the first pressure. The engine includes a catalyst that purifies exhaust gas flowing through an exhaust passage,
The control device for a vehicle according to claim 1 , wherein in the setting process, when the temperature of the catalyst is a first temperature, the target air-fuel ratio is set to a smaller value than when the temperature is a second temperature that is lower than the first temperature.

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