Vehicle control device

Abstract

To suppress the amount of nitrogen oxide which is generated in cylinders of an engine.SOLUTION: A vehicle includes an engine and a fluid coupling, the engine using hydrogen as fuel, the fluid coupling having a lock-up clutch for transmitting the driving force of the engine via the lock-up clutch to driving wheels. A control device for the vehicle transmits the driving force of the engine via the fluid coupling to the driving wheels, and when the lock-up clutch is not put in a completely engaging state, executes reduction processing. The reduction processing is executed to further reduce the slip ratio of the lock-up clutch when a large amount of nitrogen oxide is discharged from the engine than when a small amount of nitrogen oxide is discharged therefrom.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a vehicle control device. [Background technology]

[0002] The system in Patent Document 1 includes an engine and a control device. The engine uses hydrogen as fuel. The control device performs a process to reduce the amount of nitrogen oxides generated in the engine cylinders. Specifically, when the rotation speed of the engine crankshaft is high, the control device increases the mass of intake air relative to the mass of fuel supplied to the engine cylinders compared to when the rotation speed of the crankshaft is low. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-200805 Summary of the Invention [Problem to be solved by the invention]

[0004] In engines such as those described in Patent Document 1, situations occur in which the rotation speed of the engine crankshaft becomes relatively high. When the rotation speed of the engine crankshaft becomes high, the flow of the fuel and intake air mixture in the cylinder becomes faster, which increases the combustion speed of the mixture. Furthermore, when the combustion speed of the mixture increases, nitrogen oxides are more likely to be generated in the cylinder. Therefore, simply increasing the mass of intake air relative to the mass of fuel supplied to the cylinder may not be enough to suppress the amount of nitrogen oxides. Therefore, there is a need for technology that can suppress the amount of nitrogen oxides in addition to increasing the mass of intake air relative to the mass of fuel supplied to the cylinder. [Means for solving the problem]

[0005] The vehicle control device for solving the above problem is a control device that controls a vehicle equipped with a hydrogen-fueled engine and a fluid coupling having a lock-up clutch that transmits the driving force of the engine to the drive wheels via the lock-up clutch, and when the driving force of the engine is transmitted to the drive wheels via the fluid coupling and the lock-up clutch is not fully engaged, if the amount of nitrogen oxides emitted from the engine is large, the control device executes a reduction process to reduce the slip ratio of the lock-up clutch compared to when the amount of nitrogen oxides is small.

[0006] In the above configuration, when the driving force of the engine is transmitted to the drive wheels via the fluid coupling and the lock-up clutch is not fully engaged, the rotational speed of the input shaft of the fluid coupling is higher than the rotational speed of the output shaft of the fluid coupling. According to the above configuration, when the amount of nitrogen oxides emitted from the engine is large, the slip ratio of the lock-up clutch decreases, thereby reducing the difference in rotational speed between the input shaft and the output shaft of the fluid coupling. This reduces the rotational speed of the engine crankshaft. As a result, the amount of nitrogen oxides generated in the engine cylinders can be reduced. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic configuration diagram of a vehicle. [Figure 2] FIG. 1 is a schematic configuration diagram of an engine. [Figure 3] 10 is a flowchart showing slip ratio change control. DETAILED DESCRIPTION OF THE INVENTION

[0008] <Vehicle Overview> An embodiment of the present invention will now be described with reference to Figures 1 to 3. First, a schematic configuration of a vehicle 100 will be described.

[0009] As shown in Fig. 1, the vehicle 100 includes an engine 10 and a motor generator 30. The engine 10 functions as a drive source for the vehicle 100. The engine 10 uses hydrogen as fuel. The motor generator 30 functions as a drive source for the vehicle 100. Therefore, the vehicle 100 is a so-called hybrid vehicle.

[0010] As shown in FIG. 2, the engine 10 includes a plurality of cylinders 11, an intake passage 12, and an exhaust passage 13. The engine 10 also includes a plurality of pistons 16, a plurality of connecting rods 17, a crankshaft 18, a plurality of intake valves 21, and a plurality of exhaust valves 22. Each cylinder 11 is a space for burning a mixture of fuel and intake air. In this embodiment, the engine 10 includes four cylinders 11. Note that FIG. 2 shows only one representative cylinder 11.

[0011] Piston 16 is located inside cylinder 11. Piston 16 is connected to crankshaft 18 via connecting rod 17. Piston 16 reciprocates inside cylinder 11 as a mixture of fuel and intake air burns in cylinder 11. The reciprocating motion of piston 16 causes crankshaft 18 to rotate.

[0012] The intake passage 12 is connected to the cylinders 11. The intake passage 12 supplies intake air to each cylinder 11 from outside the engine 10. The exhaust passage 13 is connected to the cylinders 11. The exhaust passage 13 discharges exhaust gas from each cylinder 11 to outside the engine 10. The intake valve 21 is located at the downstream end of the intake passage 12. The intake valve 21 opens and closes the downstream end of the intake passage 12 by a driving force from a valve mechanism (not shown). The exhaust valve 22 is located at the upstream end of the exhaust passage 13. The exhaust valve 22 opens and closes the upstream end of the exhaust passage 13 by a driving force from a valve mechanism (not shown).

[0013] The engine 10 includes a throttle valve 23, multiple ignition devices 24, a catalyst 25, multiple port injection valves 26, multiple in-cylinder injection valves 27, and multiple water injection valves 29. The throttle valve 23 is located midway through the intake passage 12. The throttle valve 23 adjusts the amount of intake air flowing through the intake passage 12.

[0014] The tip of the port injection valve 26 is located in the intake passage 12 near the cylinder 11. The port injection valve 26 injects hydrogen as fuel into the intake passage 12, thereby supplying fuel into the cylinder 11 via the intake passage 12. The engine 10 is equipped with four port injection valves 26 corresponding to the four cylinders 11.

[0015] The tip of the in-cylinder injection valve 27 is located inside the cylinder 11. The in-cylinder injection valve 27 supplies fuel to the cylinder 11 by injecting hydrogen as fuel into the cylinder 11. The engine 10 is equipped with four in-cylinder injection valves 27 corresponding to the four cylinders 11.

[0016] The tip of the ignition device 24 is located inside the cylinder 11. The ignition device 24 ignites a mixture of fuel and intake air by spark discharge. The engine 10 is equipped with four ignition devices 24 corresponding to the four cylinders 11. The catalyst 25 is located midway in the exhaust passage 13. The catalyst 25 purifies the exhaust gas flowing through the exhaust passage 13.

[0017] The tip of the water injector 29 is located in the intake passage 12 near the cylinder 11. Water is supplied to the water injector 29 from a water tank (not shown). The water injector 29 injects water into the intake passage 12. When the injected water evaporates, it cools the intake passage 12 and the cylinder 11, thereby cooling the intake air supplied from the intake passage 12 to the cylinder 11 and cooling the intake air inside the cylinder 11. The engine 10 is equipped with four water injectors 29 corresponding to the four cylinders 11.

[0018] The engine 10 is equipped with a water jacket 15. The water jacket 15 is a space for circulating cooling water. The water jacket 15 surrounds the cylinders 11. Cooling water flows through the water jacket 15. The cylinders 11 are cooled by heat exchange with the cooling water in the water jacket 15.

[0019] As shown in FIG. 1, the vehicle 100 includes a power transmission device 40, a differential 51, and a plurality of drive wheels 52. The power transmission device 40 includes a case 41, a damper 42, a connecting shaft 43, a clutch 44, a torque converter 45, and an automatic transmission 46. The case 41 accommodates the damper 42, the connecting shaft 43, the clutch 44, the torque converter 45, and the automatic transmission 46 in addition to the motor generator 30 described above. The motor generator 30 includes a rotor 31 and a stator 32. The stator 32 is fixed to the case 41. The rotor 31 is rotatable relative to the stator 32.

[0020] A first end of the connecting shaft 43 is connected to the crankshaft 18 of the engine 10 via a damper 42. The damper 42 transmits the driving force from the crankshaft 18 to the connecting shaft 43 while suppressing fluctuations in the torque of the crankshaft 18. A second end of the connecting shaft 43 is connected to the rotor 31 of the motor generator 30 via a clutch 44. The connection state of the clutch 44 is switched between an engaged state and a released state depending on the pressure of the oil supplied to the clutch 44.

[0021] The torque converter 45 includes an input shaft 45A, an output shaft 45B, a lock-up clutch 45C, a pump wheel 45D, and a turbine wheel 45E. The input shaft 45A is connected to the rotor 31 of the motor-generator 30. The pump wheel 45D is connected to the input shaft 45A. Therefore, the pump wheel 45D rotates when the input shaft 45A rotates. When the pump wheel 45D rotates, a driving force is transmitted to the turbine wheel 45E via a fluid, causing the turbine wheel 45E to rotate. The turbine wheel 45E is connected to the output shaft 45B. The lock-up clutch 45C can connect the input shaft 45A and the output shaft 45B. The output shaft 45B is connected to the automatic transmission 46. In this embodiment, the torque converter 45 can transmit the driving force of the engine 10 to the drive wheels 52 via the automatic transmission 46 or the like. The torque converter 45 is an example of a fluid coupling.

[0022] The engagement state of the lockup clutch 45C is switched between a fully engaged state, a disengaged state, and a partially engaged state depending on the pressure of the oil supplied to the lockup clutch 45C. The fully engaged state refers to a state in which torque can be transmitted between the input shaft 45A and the output shaft 45B via the lockup clutch 45C, and the input shaft 45A and the output shaft 45B rotate integrally. The disengaged state refers to a state in which torque cannot be transmitted between the input shaft 45A and the output shaft 45B via the lockup clutch 45C. The partially engaged state refers to a state in which torque can be transmitted between the input shaft 45A and the output shaft 45B via the lockup clutch 45C, and a difference in rotational speed between the input shaft 45A and the output shaft 45B is permitted. In the partially engaged state, the slip ratio Z can be controlled. The slip ratio Z will be described later.

[0023] The automatic transmission 46 includes an input shaft 46A and an output shaft 46B. The input shaft 46A is connected to the output shaft 45B of the torque converter 45. The input shaft 46A is connected to the output shaft 46B via a clutch and a gear (not shown). The automatic transmission 46 is capable of changing its gear ratio. Here, the gear ratio is a ratio indicating the number of times the input shaft 46A rotates for one rotation of the output shaft 46B. Therefore, the larger the gear ratio, the faster the input shaft 46A rotates relative to the output shaft 46B. An example of the automatic transmission 46 is a stepped automatic transmission. The output shaft 46B is connected to drive wheels 52 via a differential 51. The differential 51 allows a difference in rotational speed to occur between the left and right drive wheels 52.

[0024] As shown in Fig. 1, vehicle 100 is equipped with a hydraulic device 55. Hydraulic device 55 controls the gear ratio of automatic transmission 46 by adjusting the pressure of oil supplied to automatic transmission 46. Hydraulic device 55 also controls the engagement state of lock-up clutch 45C of torque converter 45 by adjusting the pressure of oil supplied to torque converter 45. Hydraulic device 55 also controls the engagement state of clutch 44 by adjusting the pressure of oil supplied to clutch 44.

[0025] 1, the vehicle 100 includes an inverter 56 and a battery 57. The battery 57 is a secondary battery. The inverter 56 adjusts the amount of electric power exchanged between the motor generator 30 and the battery 57.

[0026] <Vehicle electrical configuration> 1, the vehicle 100 is equipped with an accelerator operation amount sensor 81, a vehicle speed sensor 82, and a crank angle sensor 83. The vehicle 100 also is equipped with a rotor angle sensor 84, a temperature sensor 85, and an air flow meter 86.

[0027] The accelerator operation amount sensor 81 detects the accelerator operation amount ACC, which is the amount of operation of an accelerator pedal (not shown) operated by the driver. The vehicle speed sensor 82 detects the vehicle speed SP, which is the speed of the vehicle 100. The crank angle sensor 83 detects the crank angle SC, which is the angular position of the crankshaft 18. The rotor angle sensor 84 detects the rotor angle SR, which is the angular position of the rotor 31. The temperature sensor 85 detects the catalyst temperature TC, which is the temperature of the catalyst 25. The air flow meter 86 detects the intake air amount GA, which is the amount of intake air flowing through the intake passage 12 per unit time.

[0028] As shown in FIG. 1, vehicle 100 is equipped with a control device 90. Control device 90 obtains a signal indicating accelerator operation amount ACC from accelerator operation amount sensor 81. Control device 90 obtains a signal indicating vehicle speed SP from vehicle speed sensor 82. Control device 90 obtains a signal indicating crank angle SC from crank angle sensor 83. Control device 90 obtains a signal indicating rotor angle SR from rotor angle sensor 84. Control device 90 obtains a signal indicating catalyst temperature TC from temperature sensor 85. Control device 90 obtains a signal indicating intake air amount GA from air flow meter 86. Control device 90 calculates engine rotation speed NE, which is the rotation speed of crankshaft 18, based on crank angle SC. Control device 90 calculates motor rotation speed NM, which is the rotation speed of rotor 31, based on rotor angle SR.

[0029] The control device 90 calculates the vehicle's required driving force, which is a required value of the driving force necessary for the vehicle 100 to travel, based on the accelerator operation amount ACC and the vehicle speed SP. The control device 90 determines the torque distribution between the engine 10 and the motor generator 30 based on the vehicle's required driving force. The control device 90 controls the output of the engine 10 and the power running and regeneration of the motor generator 30 based on the torque distribution between the engine 10 and the motor generator 30.

[0030] The control device 90 controls the engine 10 by outputting control signals to the engine 10. Specifically, it executes various types of control, such as adjusting the opening of the throttle valve 23, adjusting the ignition timing of the ignition device 24, adjusting the amount of fuel injected from the port injection valve 26, adjusting the amount of fuel injected from the direct injection valve 27, and adjusting the amount of water injected from the water injection valve 29. In addition, the control device 90 outputs a control signal to the inverter 56 in order to control the motor generator 30. The control device 90 then controls the motor generator 30 by adjusting the amount of power exchanged between the motor generator 30 and the battery 57 via the inverter 56.

[0031] The control device 90 outputs a control signal to the hydraulic device 55 to control the engagement state of the clutch 44 via the hydraulic device 55. The control device 90 also outputs a control signal to the hydraulic device 55 to control the engagement state of the lock-up clutch 45C of the torque converter 45 via the hydraulic device 55. The control device 90 outputs a control signal to the hydraulic device 55 to control the gear ratio of the automatic transmission 46 via the hydraulic device 55.

[0032] The control device 90 calculates the air-fuel ratio AFR, which indicates the mass of air relative to the mass of fuel supplied to the cylinder 11, based on the fuel injection amount supplied to the cylinder 11 from the port injection valve 26 and the in-cylinder injection valve 27 and the intake air amount GA. In this embodiment, the control device 90 repeatedly calculates the air-fuel ratio AFR at a predetermined control cycle. The air-fuel ratio AFR is expressed by the following equation (1).

[0033] Formula (1): Air-fuel ratio AFR = intake air mass / fuel mass When the vehicle 100 is traveling, the control device 90 selects either the EV mode or the HV mode as the traveling mode of the vehicle 100. Here, the EV mode is a traveling mode in which the engine 10 is stopped while the motor generator 30 is driven to travel the vehicle 100. Therefore, in the EV mode, the vehicle 100 is traveled by the driving force of the motor generator 30. On the other hand, the HV mode is a traveling mode in which the engine 10 is driven in addition to the motor generator 30 to travel the vehicle 100. Therefore, in the HV mode, the vehicle 100 is traveled by the driving force of the engine 10 in addition to the driving force of the motor generator 30.

[0034] The control device 90 selects the EV mode, for example, when the state of charge (SOC) of the battery 57 has a sufficient margin and the required vehicle driving force is small. Examples of when the required vehicle driving force is small include when the vehicle 100 starts moving and when the vehicle 100 is running under a light load with low acceleration. On the other hand, the control device 90 selects the HV mode, for example, when the state of charge (SOC) of the battery 57 does not have a sufficient margin.

[0035] The control device 90 may be configured as a circuit including one or more processors that execute various processes according to a computer program (software). The control device 90 may also be configured as a circuit including one or more dedicated hardware circuits, such as an application-specific integrated circuit (ASIC), that execute at least some of the various processes, or a combination thereof. The processor includes a CPU and memory such as RAM and ROM. The memory stores program code or instructions configured to cause the CPU to execute processes. The memory, i.e., computer-readable medium, includes any medium that can be accessed by a general-purpose or dedicated computer.

[0036] <Slip ratio change control> Next, the slip ratio change control executed by the control device 90 will be described. In this embodiment, the control device 90 repeatedly executes the slip ratio change control when the vehicle 100 is traveling. This slip ratio change control is control for changing the slip ratio Z of the lockup clutch 45C of the torque converter 45. Here, the slip ratio Z is a value related to the magnitude of torque that can be transmitted between the input shaft 45A and the output shaft 45B via the lockup clutch 45C. Note that the lower the slip ratio Z, the greater the force with which the lockup clutch 45C engages. Therefore, when the lockup clutch 45C is fully engaged, the slip ratio Z is the minimum value of "0." On the other hand, when the lockup clutch 45C is released, the slip ratio Z is the maximum value of "100." On the other hand, when the lockup clutch 45C is partially engaged, the slip ratio Z is a value greater than "0" and less than "100."

[0037] 3, when the control device 90 starts slip ratio change control, it executes the process of step S11. In step S11, the control device 90 determines whether or not the EV mode has been selected as the driving mode of the vehicle 100. If the control device 90 determines in step S11 that the HV mode has been selected as the driving mode of the vehicle 100 (S11: NO), the control device 90 proceeds to step S12. In other words, the control device 90 proceeds to step S12 when the driving force of the engine 10 is being transmitted to the drive wheels 52 via the torque converter 45.

[0038] In step S12, the control device 90 determines whether or not warming up of the catalyst 25 has been completed. Specifically, if the control device 90 determines that the catalyst temperature TC is equal to or higher than a predetermined specified temperature, the control device 90 determines that warming up of the catalyst 25 has been completed. On the other hand, if the control device 90 determines that the catalyst temperature TC is lower than the predetermined specified temperature, the control device 90 determines that warming up of the catalyst 25 has not been completed. Here, the specified temperature is, for example, predetermined as a temperature at which the purification function of the catalyst 25 can be fully exerted. In step S12, if the control device 90 determines that warming up of the catalyst 25 has not been completed (S12: NO), the control device 90 proceeds to step S21. Note that if warming up of the catalyst 25 is not completed, the catalyst 25 cannot fully exert its purification function, and therefore the amount of nitrogen oxides emitted from the engine 10 to the outside increases.

[0039] In step S21, the control device 90 determines whether the air-fuel ratio AFR is equal to or less than a predetermined specified rate A. Here, the specified rate A is determined, for example, as follows: First, as a premise, in the engine 10, the lower the air-fuel ratio AFR, the greater the amount of nitrogen oxides generated in the cylinders 11. In other words, the lower the air-fuel ratio AFR, the greater the amount of nitrogen oxides that may be generated in the cylinders 11, to an extent that cannot be purified by the catalyst 25 in a state where warm-up is not complete. Therefore, a threshold value for the air-fuel ratio AFR for performing the processing from step S41 onwards is determined through experiments, simulations, etc. Then, the determined threshold value is set as the specified rate A. In step S21, if the control device 90 determines that the air-fuel ratio AFR is higher than the specified rate A (S21: NO), the control device 90 proceeds to step S31.

[0040] Furthermore, in the above-mentioned step S11, if the control device 90 determines that the EV mode has been selected as the driving mode of the vehicle 100 (S11: YES), the control device 90 proceeds to the process at step S31. Also, in the above-mentioned step S12, if the control device 90 determines that the warm-up of the catalyst 25 has been completed (S12: YES), the control device 90 proceeds to the process at step S31.

[0041] In step S31, the control device 90 calculates a base value of the slip ratio Z based on the running state of the vehicle 100. As a specific example, the control device 90 acquires the engine rotation speed NE, the motor rotation speed NM, the gear ratio of the automatic transmission 46, and the like as the running state of the vehicle 100. The control device 90 then calculates the base value of the slip ratio Z by comparing the engine rotation speed NE, the motor rotation speed NM, the gear ratio of the automatic transmission 46, and the like with a predetermined map. Note that, for example, when the vehicle 100 starts moving, the base value of the slip ratio Z can be a numerical value between a minimum value and a maximum value. Thereafter, the control device 90 proceeds to step S32.

[0042] In step S32, the control device 90 sets the base value of the slip ratio Z calculated in step S31 as the final slip ratio Z. Then, the control device 90 controls the torque converter 45 based on the final slip ratio Z. Thereafter, the control device 90 ends the current slip ratio change control.

[0043] On the other hand, if the control device 90 determines in step S21 that the air-fuel ratio AFR is equal to or less than the specified ratio A (S21: YES), the control device 90 advances the process to step S41.

[0044] In step S41, the control device 90 calculates a base value of the slip ratio Z based on the running state of the vehicle 100. The process of step S41 is the same as the process of step S31 described above. Thereafter, the control device 90 proceeds to step S42.

[0045] In step S42, the control device 90 calculates the coefficient K based on the catalyst temperature TC, the air-fuel ratio AFR, the slip ratio Z, and the engine speed NE. Specifically, the lower the catalyst temperature TC at the start of the process of step S42, the smaller the coefficient K. At this time, the control device 90 reduces the amount of change in the coefficient K as the air-fuel ratio AFR at the start of the process of step S42 increases. That is, for example, even if the catalyst temperature TC is the same, the amount of decrease in the coefficient K when the air-fuel ratio AFR is high is smaller than the amount of decrease in the coefficient K when the air-fuel ratio AFR is low. Furthermore, the control device 90 reduces the amount of change in the coefficient K as the base value of the slip ratio Z at the start of the process of step S42 decreases. That is, for example, even if the catalyst temperature TC is the same, the amount of decrease in the coefficient K when the base value of the slip ratio Z is low is smaller than the amount of decrease in the coefficient K when the base value of the slip ratio Z is high. Furthermore, the control device 90 reduces the amount of change in the coefficient K as the engine speed NE at the start of the process of step S42 decreases. That is, for example, even if the catalyst temperature TC is the same, the amount of decrease in the coefficient K when the engine rotation speed NE is low is smaller than the amount of decrease in the coefficient K when the engine rotation speed NE is high. Here, the coefficient K is a value greater than 0 and less than 1. The control device 90 then multiplies the base value of the slip ratio Z by the coefficient K, and sets the value as the corrected slip ratio Z.

[0046] Due to the above-described method of calculating the coefficient K, in the process of step S42, the lower the catalyst temperature TC, the more the slip ratio Z is reduced. Also, in the process of step S42, the higher the air-fuel ratio AFR, the smaller the amount of reduction in slip ratio Z. Furthermore, in the process of step S42, the lower the base value of slip ratio Z at the time of starting the current process of step S42, the smaller the amount of reduction in slip ratio Z. Also, in the process of step S42, the lower the engine rotation speed NE, the smaller the amount of reduction in slip ratio Z. In this embodiment, the process of step S42 is a reduction process that reduces the slip ratio Z of the lock-up clutch 45C. After step S42, the control device 90 proceeds to step S43.

[0047] In step S43, the control device 90 sets the slip ratio Z after correction in step S42 as the final slip ratio Z. The control device 90 then controls the torque converter 45 based on the final slip ratio Z. Therefore, if the lockup clutch 45C is not fully engaged at the time the processing of step S42 is started, the slip ratio Z of the lockup clutch 45C is reduced by the reduction processing. Note that if the base value of the slip ratio Z is calculated as "0," the value does not change even if it is multiplied by the coefficient K. In other words, even if the processing of step S42 is performed, the lockup clutch 45C remains fully engaged. Thereafter, the control device 90 ends the current slip ratio change control.

[0048] <Operation of this embodiment> 3, in the slip ratio change control, when the HV mode is selected as the driving mode of the vehicle 100 and the warm-up of the catalyst 25 is not complete, the process of step S21 is executed. In other words, when, for example, the purification function of the catalyst 25 cannot be fully exerted and the amount of nitrogen oxides emitted from the engine 10 to the outside increases compared to when the warm-up of the catalyst 25 is complete, the process of step S21 is executed. When it is determined in step S21 that the air-fuel ratio AFR is equal to or less than the specified rate A, the process of step S41 and subsequent steps is executed. In other words, when, for example, the amount of nitrogen oxides generated in the cylinders 11 increases and the amount of nitrogen oxides emitted from the engine 10 to the outside increases compared to when the air-fuel ratio AFR is higher than the specified rate A, the process of step S41 and subsequent steps is executed. Then, in step S42, a reduction process is executed to reduce the slip ratio Z of the lock-up clutch 45C. When the driving force of the engine 10 is transmitted to the drive wheels 52 via the torque converter 45 and the lock-up clutch 45C is not fully engaged, the rotational speed of the input shaft 45A of the torque converter 45 is higher than the rotational speed of the output shaft 45B. Therefore, when the torque that can be transmitted between the input shaft 45A and the output shaft 45B via the lock-up clutch 45C increases due to the reduction process, the difference in rotational speed between the input shaft 45A and the output shaft 45B decreases. As a result, the rotational speed of the input shaft 45A of the torque converter 45 decreases.

[0049] <Effects of this embodiment> (1) As described above, when the rotational speed of the input shaft 45A of the torque converter 45 is reduced by the reduction process, the rotational speed of the crankshaft 18 connected to the input shaft 45A, i.e., the engine rotational speed NE, is reduced. This slows down the flow of the mixture of fuel and intake air in the cylinder 11, thereby slowing down the combustion speed of the mixture. This makes it difficult for nitrogen oxides to be generated in the cylinder 11. As a result, the amount of nitrogen oxides generated in the cylinder 11 can be suppressed.

[0050] (2) In the engine 10, the lower the air-fuel ratio AFR, the greater the amount of fuel relative to the amount of intake air in the cylinder 11, which tends to increase the temperature of the mixture burning in the cylinder 11. As the temperature of the mixture increases in this way, the amount of nitrogen oxides generated in the cylinder 11 increases.

[0051] In this embodiment, the control device 90 executes the reduction process on the condition that the air-fuel ratio AFR is equal to or less than the specified rate A. Therefore, the reduction process is executed only under circumstances where the amount of nitrogen oxides generated in the cylinder 11 increases. This makes it possible to prevent the reduction process from being executed unnecessarily.

[0052] (3) In the engine 10, the lower the catalyst temperature TC, the more likely it is that the purification function of the catalyst 25 will decline. That is, when the catalyst temperature TC is low, it is more necessary to suppress the amount of nitrogen oxides generated in the cylinders 11 than when the catalyst temperature TC is high.

[0053] In this embodiment, the lower the catalyst temperature TC, the more the slip ratio Z is reduced in the reduction process. This allows the engine speed NE to be reduced in situations where there is a high need to suppress the amount of nitrogen oxides generated in the cylinder 11.

[0054] (4) As described above, in the engine 10, the higher the air-fuel ratio AFR, the smaller the amount of nitrogen oxides generated in the cylinder 11. Therefore, when the air-fuel ratio AFR is high, the amount of nitrogen oxides generated in the cylinder 11 is somewhat smaller than when the air-fuel ratio AFR is low. In other words, when the air-fuel ratio AFR is high, there is less need to reduce the slip ratio Z by the reduction process.

[0055] In this embodiment, the higher the air-fuel ratio AFR is, the smaller the reduction amount of the slip ratio Z is. This makes it possible to suppress, for example, vibrations and abnormal noises occurring in the vehicle 100 due to a large change amount of the slip ratio Z caused by the reduction process.

[0056] (5) In the engine 10, when the slip ratio Z is low at the start of the reduction process, the engine speed NE tends to be somewhat lower than when the slip ratio Z is high. In other words, when the slip ratio Z is low at the start of the reduction process, there is little need to reduce the slip ratio Z by the reduction process.

[0057] In this embodiment, in the reduction process, the lower the base value of the slip ratio Z at the start of the current process of step S42, the smaller the reduction amount of the slip ratio Z. This makes it possible to suppress, for example, vibrations and abnormal noises occurring in the vehicle 100 due to a large change in the slip ratio Z caused by the reduction process.

[0058] <Example of change> This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0059] In the above embodiment, the slip ratio change control may be changed. For example, the process of step S21 may be omitted. That is, regardless of whether the air-fuel ratio AFR is equal to or less than the specified ratio A, if a negative determination is made in the process of step S12, the processes from step S41 onward may be executed.

[0060] In the above embodiment, the reduction process in step S42 may be modified. For example, in step S42, the control device 90 may calculate the coefficient K regardless of the catalyst temperature TC at the time when the process of step S42 is started. In this case, the slip ratio Z is determined regardless of the catalyst temperature TC.

[0061] For example, in step S42, the control device 90 may calculate the coefficient K regardless of the air-fuel ratio AFR at the time when the processing of step S42 is started. In this case, the amount of decrease in the slip ratio Z is determined regardless of the air-fuel ratio AFR.

[0062] For example, in step S42, the control device 90 may calculate the coefficient K regardless of the base value of the slip ratio Z at the time when the processing of step S42 is started. In this case, the amount of reduction in the slip ratio Z is determined regardless of the base value of the slip ratio Z.

[0063] For example, in step S42, the control device 90 may calculate the coefficient K regardless of the engine rotation speed NE at the time when the process of step S42 is started. In this case, the amount of decrease in the slip ratio Z is determined regardless of the engine rotation speed NE.

[0064] For example, in step S42, the method of correcting the slip ratio Z is not important. As a specific example, in step S42, the control device 90 may use a value obtained by subtracting a predetermined correction value from the base value of the slip ratio Z as the corrected slip ratio Z. In other words, in the processing of step S42, it is sufficient that the corrected slip ratio Z is a value that is at least smaller than the base value of the slip ratio Z calculated in the processing of step S41.

[0065] In the above embodiment, the configuration of the vehicle 100 may be changed. For example, the motor generator 30, which is the drive source of the vehicle 100, may be omitted. In other words, the present technology can be applied to any vehicle 100 that is equipped with at least the engine 10. [Explanation of symbols]

[0066] Z...slip ratio, 10...engine, 11...cylinder, 12...intake passage, 13...exhaust passage, 15...water jacket, 16...piston, 17...connecting rod, 18...crankshaft, 21...intake valve, 22...exhaust valve, 23...throttle valve, 24...ignition device, 25...catalyst, 26...port injection valve, 27...in-cylinder injection valve, 29...water injection valve, 30...motor generator, 31...rotor, 32...stator, 40...power transmission device, 41...case, 42...damper, 43...connecting shaft, 44...clutch, 45...torque converter, 45A...input shaft, 45B...output shaft, 45C...lock-up clutch, 45D...pump impeller, 45E...turbine impeller, 46...automatic transmission, 46A...input shaft, 46B...output shaft, 51...differential, 52...drive wheels, 55...hydraulic device, 56...inverter, 57...battery, 81...accelerator operation amount sensor, 82...vehicle speed sensor, 83...crank angle sensor, 84...rotor angle sensor, 85...temperature sensor, 86...air flow meter, 90...control device, 100...vehicle,

Claims

1. A hydrogen-fueled engine; a fluid coupling having a lock-up clutch and transmitting the driving force of the engine to the drive wheels via the lock-up clutch; A control device for controlling a vehicle equipped with When the driving force of the engine is transmitted to the drive wheels via the fluid coupling and the lock-up clutch is not in a fully engaged state, and an air-fuel ratio indicating the mass of air relative to the mass of fuel supplied to the cylinders of the engine is equal to or less than a predetermined specified ratio, a reduction process is executed to reduce the slip ratio of the lock-up clutch compared to when the air-fuel ratio is higher than the specified ratio, Even if the driving force of the engine is transmitted to the drive wheels via the fluid coupling and the lock-up clutch is not in a fully engaged state, the reduction process is not executed when the air-fuel ratio is higher than the specified ratio. Vehicle control device.

2. In the reduction process, when the temperature of the catalyst of the engine is low, the slip ratio is reduced compared to when the temperature of the catalyst is high. The vehicle control device according to claim 1 .

3. In the reduction process, when the air-fuel ratio is high, the amount of reduction in the slip ratio is made smaller than when the air-fuel ratio is low. The vehicle control device according to claim 2.

4. In the reduction process, when the slip ratio is low at the time when the reduction process is started, the amount of reduction in the slip ratio is made smaller than when the slip ratio is high. The vehicle control device according to claim 2.

Images