Control device for internal combustion engine

Abstract

To reduce emissions of nitrogen oxide.SOLUTION: A vehicle includes a control device for controlling, as a control target, an internal combustion engine that uses hydrogen as fuel. The control device can execute first processing to third processing. In the first processing, the control device calculates required output required for the internal combustion engine on the basis of an operation amount of an accelerator pedal. In the second processing, the control device sets combinations of engine torque of the internal combustion engine and engine speed of the internal combustion engine that can attain the required output as operating points of the internal combustion engine, and sets an operating point that obtains best fuel economy out of the plurality of operating points as an optimal fuel economy point. In the second processing, the control device sets an operating point in which a difference from the optimal fuel economy point becomes minimum as a reference operating point of the internal combustion engine. In the third processing, the control device sets an operating point in which the engine torque is higher compared to the reference operating point and the engine speed is lower compared to the reference operating point out of the operating points as a target operating point of the internal combustion engine, when the engine speed at the reference operating point is specified speed or higher.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a control device for an internal combustion engine. [Background technology]

[0002] Patent Document 1 discloses an internal combustion engine fueled by hydrogen and a control device for controlling the internal combustion engine. The control device of Patent Document 1 executes a process to increase the target air-fuel ratio when the engine speed of the internal combustion engine is high, compared to when the engine speed is low. In other words, the control device operates the internal combustion engine in a lean fuel state when the engine speed is high. This slows the combustion rate of hydrogen when the engine speed of the internal combustion engine is high, compared to when the process is not executed. As a result, the combustion rate of the combustion gas is prevented from becoming excessively high, and nitrogen oxide emissions are also reduced. [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 an internal combustion engine such as that disclosed in Patent Document 1, the higher the engine speed, the less likely it is that nitrogen oxide emissions will be reduced even if the air-fuel ratio is increased. In other words, simply adjusting the air-fuel ratio as in the technology disclosed in Patent Document 1 may not be enough to suppress nitrogen oxide emissions when the engine speed is high. Therefore, for internal combustion engines that use hydrogen as fuel, there is a demand for a technology for suppressing nitrogen oxide emissions that does not rely on adjusting the air-fuel ratio. [Means for solving the problem]

[0005] In order to solve the above problems, the present invention is a control device for an internal combustion engine that uses hydrogen as fuel, and is capable of executing the following steps: a first process of calculating a required output required of the internal combustion engine based on the amount of operation of an accelerator pedal; a second process of setting an operating point of the internal combustion engine that is a combination of engine torque and engine speed of the internal combustion engine that can achieve the required output, and an operating point among multiple operating points that provides the best fuel efficiency as an optimal fuel efficiency point, and then setting the operating point that is the smallest difference from the optimal fuel efficiency point as a reference operating point of the internal combustion engine; and a third process of setting, when the engine speed at the reference operating point is equal to or higher than a specified speed, an operating point among the operating points where the engine torque is greater than that of the reference operating point and the engine speed is smaller than that of the reference operating point as a target operating point of the internal combustion engine.

[0006] According to the above configuration, when the engine speed at the reference operating point is equal to or higher than a specified speed, an operating point with a lower engine speed than the reference operating point is set as the target operating point. Setting the target operating point in this manner limits the degree of increase in engine speed in response to an increase in the required output. This prevents the internal combustion engine from operating in an operating state with an excessively high engine speed, i.e., an operating state in which nitrogen oxides are likely to be emitted due to the combustion of hydrogen. As a result, nitrogen oxide emissions can be reduced without adjusting the air-fuel ratio. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram of a vehicle. [Figure 2] FIG. 2 is a schematic diagram of an internal combustion engine. [Figure 3] FIG. 3 is a map showing the operating points. [Figure 4] FIG. 4 is a flowchart of the target operating point setting control executed by the control device. DETAILED DESCRIPTION OF THE INVENTION

[0008] <Vehicle mechanical configuration> An embodiment of the present invention will now be described with reference to the accompanying drawings. First, the mechanical configuration of a vehicle to which a control device of the present invention is applied will be described.

[0009] As shown in FIG. 1, a vehicle 500 includes an internal combustion engine 10, a power split mechanism 40, a reduction mechanism 50, a first motor generator 61, and a second motor generator 62. The internal combustion engine 10 has a crankshaft 11 as an output shaft. The crankshaft 11 is connected to a power split mechanism 40. The power split mechanism 40 is a planetary gear mechanism having a sun gear 41, a carrier 42, a plurality of pinion gears 43, a ring gear 44, and a ring gear shaft 45.

[0010] The sun gear 41, which is an external gear, and the ring gear 44, which is an internal gear, are positioned coaxially. The sun gear 41 is rotatable. The ring gear 44 is rotatable. The sun gear 41 is connected to the ring gear 44 via multiple pinion gears 43. That is, the pinion gears 43 mesh with both the sun gear 41 and the ring gear 44. The carrier 42 supports the pinion gear 43 in a rotatable state. The carrier 42 also supports the pinion gear 43 so that it can revolve. That is, the pinion gear 43 revolves around the sun gear 41. The carrier 42 also rotates coaxially with the sun gear 41 in accordance with the revolution of the pinion gear 43. The carrier 42 is connected to the crankshaft 11. The sun gear 41 is connected to a rotating shaft 61A of the first motor generator 61. The ring gear 44 is connected to a ring gear shaft 45.

[0011] When the torque of the internal combustion engine 10 is input to the carrier 42, the torque of the internal combustion engine 10 is distributed to the sun gear 41 side and the ring gear 44 side. Then, when the torque of the internal combustion engine 10 transmitted via the sun gear 41 is input to the rotating shaft 61A of the first motor generator 61, the first motor generator 61 functions as a generator.

[0012] On the other hand, when the first motor generator 61 is made to function as an electric motor, the torque of the first motor generator 61 is input to the sun gear 41. Then, the torque of the first motor generator 61 input to the sun gear 41 is distributed to the carrier 42 side and the ring gear 44 side. Then, when the torque of the first motor generator 61 transmitted via the carrier 42 is input to the crankshaft 11 of the internal combustion engine 10, the crankshaft 11 of the internal combustion engine 10 rotates. In other words, the first motor generator 61 is able to rotate the crankshaft 11 by transmitting the torque of the first motor generator 61 to the crankshaft 11.

[0013] In this way, the power split mechanism 40 is a planetary gear mechanism that can distribute the torque of the internal combustion engine 10, the torque of the first motor generator 61, and the torque of the second motor generator 62 among one another. In addition, by controlling the rotational resistance of the first motor generator 61, the power split mechanism 40 also functions as a continuously variable transmission that changes the speed of the torque of the internal combustion engine 10 and outputs it to the ring gear shaft 45.

[0014] As shown in Fig. 1, the vehicle 500 includes a transmission mechanism 66, a differential 67, and a plurality of drive wheels 68. The transmission mechanism 66 is connected to the ring gear shaft 45. The transmission mechanism 66 includes, for example, a reduction gear mechanism. The transmission mechanism 66 is connected to the drive wheels 68 via the differential 67. The differential 67 allows a difference in rotational speed to occur between the left and right drive wheels 68.

[0015] The ring gear shaft 45 is connected to the reduction mechanism 50. The reduction mechanism 50 is a planetary gear mechanism having a sun gear 51, a carrier 52, multiple pinion gears 53, a ring gear 54, and a case 55. The sun gear 51, which is an external gear, and the ring gear 54, which is an internal gear, are positioned coaxially. The sun gear 51 is connected to the ring gear 54 via multiple pinion gears 53. The carrier 52 supports the pinion gear 53 in a rotatable state. The carrier 52 is fixed to a case 55 of the reduction mechanism 50. In other words, the carrier 52 is non-rotatable. Therefore, the pinion gear 53 is prevented from revolving due to the carrier 52. The ring gear 54 is connected to the ring gear shaft 45. The sun gear 51 is connected to a rotating shaft 62A of a second motor-generator 62. In other words, the ring gear 44 of the power split mechanism 40 is connected to the rotary shaft 62A of the second motor generator 62 via the ring gear shaft 45 and the reduction mechanism 50.

[0016] Second motor generator 62 functions as a generator when decelerating vehicle 500, thereby making it possible to generate a regenerative braking force in vehicle 500 according to the amount of power generated by second motor generator 62.

[0017] On the other hand, when the second motor generator 62 is made to function as an electric motor, the torque of the second motor generator 62 is input to the drive wheels 68 via the reduction mechanism 50, the ring gear shaft 45, the transmission mechanism 66, and the differential 67. Then, the torque of the second motor generator 62 causes the drive wheels 68 to rotate.

[0018] <Vehicle electrical configuration> 1, the vehicle 500 includes a first inverter 71, a second inverter 72, and a battery 73. The first inverter 71 adjusts the amount of electric power exchanged between the first motor generator 61 and the battery 73. The second inverter 72 adjusts the amount of electric power exchanged between the second motor generator 62 and the battery 73.

[0019] <Specific configuration of the internal combustion engine> As shown in Fig. 2, the vehicle 500 is equipped with an internal combustion engine 10. The internal combustion engine 10 uses hydrogen as fuel. The internal combustion engine 10 has four cylinders 12, four pistons 13, four connecting rods 14, and the above-mentioned crankshaft 11. Note that Fig. 1 shows only one of the four sets of cylinders 12, pistons 13, and connecting rods 14.

[0020] Each cylinder 12 is a space for burning a mixture of fuel and intake air. A piston 13 reciprocates within each cylinder 12 as the mixture burns. The piston 13 is connected to the crankshaft 11 via a connecting rod 14. The connecting rod 14 converts the reciprocating motion of the piston 13 into the rotational motion of the crankshaft 11.

[0021] As shown in Figure 2, the internal combustion engine 10 includes an intake passage 21 and an exhaust passage 22. The intake passage 21 is a passage through which intake air flows. The intake passage 21 is connected to each cylinder 12. The exhaust passage 22 is a passage through which exhaust air flows. The exhaust passage 22 is connected to each cylinder 12.

[0022] The internal combustion engine 10 has a plurality of intake valves 21A and a plurality of exhaust valves 22A. Note that FIG. 1 illustrates only one of the plurality of intake valves 21A and one of the plurality of exhaust valves 22A. An intake valve 21A is provided for each cylinder 12. The intake valve 21A is located at a connection between the intake passage 21 and the cylinder 12. Operation of the intake valve 21A opens and closes an opening of the intake passage 21 on the cylinder 12 side. An exhaust valve 22A is provided for each cylinder 12. The exhaust valve 22A is located at a connection between the exhaust passage 22 and the cylinder 12. Operation of the exhaust valve 22A opens and closes an opening of the exhaust passage 22 on the cylinder 12 side.

[0023] The internal combustion engine 10 has an intercooler 24 and a throttle valve 23. The intercooler 24 is located midway through the intake passage 21. The intercooler 24 cools the intake air. The throttle valve 23 is located downstream of the intercooler 24 in the intake passage 21. The opening of the throttle valve 23 is adjustable. The throttle valve 23 adjusts the amount of intake air flowing into the cylinder 12 depending on its opening.

[0024] The internal combustion engine 10 has four spark plugs 15. Note that FIG. 1 shows only one of the four spark plugs 15. A spark plug 15 is provided for each cylinder 12. The tip of each spark plug 15 is located inside the cylinder 12. The spark plug 15 ignites the air-fuel mixture inside the cylinder 12.

[0025] The internal combustion engine 10 has four in-cylinder injection valves 16. Each in-cylinder injection valve 16 is connected to a hydrogen tank (not shown). Note that FIG. 1 shows only one of the four in-cylinder injection valves 16. An in-cylinder injection valve 16 is provided for each cylinder 12. The in-cylinder injection valve 16 injects hydrogen as fuel directly into the cylinder 12 without passing through the intake passage 21.

[0026] The internal combustion engine 10 has four water injectors 17. Each water injector 17 is connected to a water tank (not shown). Note that FIG. 1 shows only one of the four water injectors 17. The water injector 17 is located downstream of the throttle valve 23 in the intake passage 21. A water injector 17 is provided for each cylinder 12. The water injector 17 injects water into the intake passage 21. The water injected from the water injector 17 flows into the cylinder 12 together with the intake air. The water evaporates in the cylinder 12, thereby lowering the temperature inside the cylinder 12 to an appropriate temperature.

[0027] The internal combustion engine 10 has a catalyst 25. The catalyst 25 is located midway through the exhaust passage 22. The catalyst 25 purifies the exhaust gas flowing through the exhaust passage 22. The internal combustion engine 10 has a turbocharger 30. The turbocharger 30 is provided across the intake passage 21 and the exhaust passage 22. The turbocharger 30 has a compressor wheel 31, a turbine wheel 32, a bypass passage 33, and a wastegate valve 34. The compressor wheel 31 is located upstream of the intercooler 24 in the intake passage 21. The turbine wheel 32 is located upstream of the catalyst 25 in the exhaust passage 22. The turbine wheel 32 rotates in accordance with the flow of exhaust gas. The compressor wheel 31 rotates integrally with the turbine wheel 32. At this time, the compressor wheel 31 compresses and sends out the intake air. In other words, the rotation of the compressor wheel 31 supercharges the intake air. The bypass passage 33 connects the upstream portion and downstream portion of the exhaust passage 22 as viewed from the turbine wheel 32. In other words, the bypass passage 33 is a passage that bypasses the turbine wheel 32. The wastegate valve 34 is located at the downstream end of the bypass passage 33. The opening degree of the wastegate valve 34 is adjustable. When the opening degree of the wastegate valve 34 changes, the amount of exhaust gas flowing through the bypass passage 33 changes.

[0028] As shown in FIG. 2, the vehicle 500 includes an air flow meter 81, a crank angle sensor 82, and a catalyst temperature sensor 83. The air flow meter 81 is located in the intake passage 21. Specifically, the air flow meter 81 is located upstream of the throttle valve 23 in the intake passage 21 and downstream of the intercooler 24. The air flow meter 81 detects the amount of air GA flowing into the internal combustion engine 10. The crank angle sensor 82 is located near the crankshaft 11. The crank angle sensor 82 detects the crank angle AC, which is the angular position of the crankshaft 11. The catalyst temperature sensor 83 is located in the exhaust passage 22. Specifically, the catalyst temperature sensor 83 is located downstream of the catalyst 25 in the exhaust passage 22. The catalyst temperature sensor 83 detects the temperature of the exhaust gas flowing out from the catalyst 25 as a catalyst temperature TMP. The air flow meter 81, the crank angle sensor 82, and the catalyst temperature sensor 83 each output a signal according to the detected information.

[0029] Vehicle 500 also has accelerator pedal 90 and accelerator sensor 84. Accelerator pedal 90 is a foot pedal that is depressed by the driver. Accelerator sensor 84 detects the amount of operation of accelerator pedal 90 as accelerator operation amount ACCP. Accelerator sensor 84 outputs a signal corresponding to the detected information.

[0030] <About the control device> 1, a vehicle 500 includes a control device 100. The control device 100 controls an internal combustion engine 10, a first motor generator 61, and a second motor generator 62.

[0031] The vehicle 500 is equipped with a control device 100. The control device 100 obtains a signal indicating an air amount GA from an air flow meter 81. The control device 100 obtains a signal indicating a crank angle AC from a crank angle sensor 82. The control device 100 obtains a signal indicating a catalyst temperature TMP from a catalyst temperature sensor 83. The control device 100 obtains a signal indicating an accelerator operation amount ACCP from an accelerator sensor 84.

[0032] The control device 100 calculates the excess air ratio λ based on the air amount GA. The excess air ratio λ is calculated as the ratio of the air amount GA to the theoretical amount of air required to theoretically completely combust fuel. The control device 100 calculates the engine speed NE, which is the rotation speed of the crankshaft 11, based on the crank angle AC.

[0033] The control device 100 is capable of executing the following first to third processes as part of the target operating point setting control described later. In the first process, the control device 100 calculates a required output R required of the internal combustion engine 10 based on the accelerator operation amount ACCP. Specifically, the control device 100 calculates the required output R to be a larger value as the accelerator operation amount ACCP increases.

[0034] In the second process, the control device 100 first calculates a combination of engine torque TR and engine speed NE that can achieve a required output R as an operating point DP of the internal combustion engine 10. Here, as shown in FIG. 3 , there are multiple operating points DP that satisfy a specific required output R. Specifically, the required output R is strongly correlated with the product of the engine torque TR and the engine speed NE. Therefore, as the engine speed NE increases, the engine torque TR decreases, and conversely, as the engine speed NE decreases, the engine torque TR increases. For this reason, in a two-dimensional coordinate map represented by the engine torque TR and the engine speed NE, a set of operating points DP that satisfy a specific required output R is represented linearly, as shown as "constant output lines" in FIG. 3 .

[0035] Next, in the second process, the control device 100 identifies the operating point DP that provides the best fuel economy from among multiple operating points DP that satisfy the required output R as the optimal fuel economy point. As described above, the power split device 40 functions as a continuously variable transmission by controlling the rotational resistance of the first motor-generator 61. Therefore, the control device 100 can change the engine speed NE substantially continuously. Therefore, the control device 100 sets the operating point DP that has zero difference from the optimal fuel economy point, i.e., the optimal fuel economy point, as the reference operating point DP1 of the internal combustion engine 10. Note that the "best fuel economy" refers to a state in which the output energy of the internal combustion engine 10 per unit amount of fuel is maximized.

[0036] In the third process, the control device 100 first determines whether the engine speed NE at the reference operating point DP1 is equal to or greater than a predetermined specified rotation speed NE1. If the determination is affirmative, the control device 100 sets, as a target operating point ADP for the internal combustion engine 10, an operating point DP at which the engine speed NE is smaller than the reference operating point DP1, among the operating points DP represented linearly on the two-dimensional coordinate map. In other words, the control device 100 sets, as the target operating point ADP, an operating point DP at which the engine torque TR is larger than the reference operating point DP1. The specified rotation speed NE1 is determined in advance by performing tests, simulations, etc., as the engine rotation speed NE at which the amount of nitrogen oxides emitted when the internal combustion engine 10 is operated can exceed an allowable level.

[0037] The control device 100 sets the target operating point ADP based on the engine speed NE, catalyst temperature TMP, and excess air factor λ at the start of the third process. Specifically, the control device 100 sets the target operating point ADP so that the engine speed NE decreases as the engine speed NE increases at the start of the third process. The control device 100 also sets the target operating point ADP so that the engine speed NE decreases as the catalyst temperature TMP at the start of the third process decreases. The control device 100 also sets the target operating point ADP so that the engine speed NE decreases as the excess air factor λ at the start of the third process decreases.

[0038] <Control flow for target operating point setting control> When the internal combustion engine 10 of the vehicle 500 is running, the control device 100 repeatedly executes the following target operating point setting control.

[0039] As shown in Fig. 4, when the control device 100 executes the target operating point setting control, it first executes the processing of step S11. In step S11, the control device 100 acquires the engine speed NE. Specifically, the control device 100 acquires a signal indicating the crank angle AC from the crank angle sensor 82. Then, the control device 100 calculates the engine speed NE based on the change in the crank angle AC per unit time. Thereafter, the processing of the control device 100 proceeds to step S12.

[0040] In step S12, the control device 100 acquires the catalyst temperature TMP. Specifically, the control device 100 acquires a signal indicating the catalyst temperature TMP from the catalyst temperature sensor 83. Thereafter, the processing of the control device 100 proceeds to step S13.

[0041] In step S13, the control device 100 acquires the excess air ratio λ. Specifically, the control device 100 acquires a signal indicating the air amount GA from the air flow meter 81. Then, the control device 100 calculates the excess air ratio λ based on the air amount GA. Thereafter, the processing of the control device 100 proceeds to step S14.

[0042] In step S14, the control device 100 calculates the required output R. Specifically, the control device 100 acquires a signal indicating the accelerator operation amount ACCP from the accelerator sensor 84. Then, the control device 100 calculates the required output R based on the accelerator operation amount ACCP. Note that step S14 is the first process. Thereafter, the process of the control device 100 proceeds to step S15.

[0043] In step S15, the control device 100 sets a reference operating point DP1. Specifically, as described above, the control device 100 sets the operating point DP that provides the best fuel economy among the operating points DP that satisfy the required output R as the reference operating point DP1. As described above, in this embodiment, the control device 100 sets the optimal fuel economy point as the reference operating point DP1. Note that step S15 is the second process. Thereafter, the process of the control device 100 proceeds to step S16.

[0044] In step S16, the control device 100 determines whether the engine speed NE at the reference operating point DP1 is equal to or greater than a specified speed NE1. If this determination is affirmative, the process of the control device 100 proceeds to step S17.

[0045] In step S17, the control device 100 determines whether the catalyst temperature TMP acquired in step S12 is less than a predetermined specified temperature T1. The specified temperature T1 is predetermined as a threshold value related to the purification capacity of the catalyst 25. For example, if the catalyst temperature TMP is less than the specified temperature T1, the purification capacity of the catalyst 25 is low and the amount of nitrogen oxides emitted will be correspondingly large. Therefore, the specified temperature T1 is determined in advance by conducting tests and simulations, for example, as the minimum temperature at which the catalyst 25 can exhibit sufficient purification capacity. If this determination is affirmative, the processing of the control device 100 proceeds to step S18.

[0046] In step S18, the control device 100 determines whether the excess air ratio λ acquired in step S13 is less than a predetermined specified excess air ratio A. The specified excess air ratio A is predetermined as a threshold for nitrogen oxide emissions. For example, if the excess air ratio λ is less than the specified excess air ratio A, combustion is performed in a fuel-rich state relative to the stoichiometric air-fuel ratio, resulting in a higher combustion temperature. As a result, the amount of nitrogen oxides generated during combustion increases accordingly. Therefore, the specified excess air ratio A is determined in advance by conducting tests and simulations, for example, as the minimum excess air ratio that keeps the amount of nitrogen oxides at an allowable level. If this determination is positive, the processing of the control device 100 proceeds to step S19.

[0047] In step S19, the control device 100 sets the operating point DP at which the engine speed NE is smaller than the reference operating point DP1 as the target operating point ADP. Specifically, as described above, the control device 100 sets the target operating point ADP based on the engine speed NE, the catalyst temperature TMP, and the excess air factor λ. Note that the processing of steps S16 and S19 is the third processing. Thereafter, the control device 100 ends the target operating point setting control.

[0048] On the other hand, if the determination in step S16 is negative, the process of the control device 100 proceeds to step S20. Also, if the determination in step S17 is negative, or if the determination in step S18 is negative, the process of the control device 100 proceeds to step S20. In step S20, the control device 100 selects the reference operating point DP1 as the target operating point ADP. Thereafter, the control device 100 ends the target operating point setting control.

[0049] <Operation of this embodiment> In the internal combustion engine 10 that uses hydrogen as fuel, when the engine speed NE is high, the combustion speed is faster than when the engine speed NE is low. Therefore, when the engine speed NE is high, the amount of nitrogen oxide emissions is likely to be greater than when the engine speed NE is low.

[0050] On the other hand, the leaner the fuel, the slower the combustion speed, and therefore the less nitrogen oxides are generated. However, the higher the engine speed NE, the less likely it is that nitrogen oxide emissions will decrease even if the air-fuel ratio is increased. Specifically, regardless of the engine speed NE, increasing the air-fuel ratio tends to decrease nitrogen oxide emissions. On the other hand, if the air-fuel ratio is increased to the same extent, when the engine speed NE is high, nitrogen oxide emissions are less likely to decrease compared to when the engine speed NE is low.

[0051] In this embodiment, the control device 100 executes target operating point setting control when the internal combustion engine 10 is operating. Here, it is assumed that the engine speed NE at an operating point DP that satisfies a certain required output R is equal to or greater than a specified speed NE1. In this case, the control device 100 sets, as the target operating point ADP, an operating point DP whose engine speed NE is smaller than the reference operating point DP1, among the operating points DP.

[0052] <Effects of this embodiment> (1) According to the above embodiment, when the engine speed NE at the reference operating point DP1 is equal to or greater than the specified speed NE1, the degree of increase in the engine speed NE in response to an increase in the required output R is suppressed. Therefore, it is possible to prevent the internal combustion engine 10 from operating in an operating state where the engine speed NE is excessively high, i.e., an operating state in which nitrogen oxides are likely to be emitted due to the combustion of hydrogen. Therefore, it is possible to reduce the amount of nitrogen oxide emissions without adjusting the air-fuel ratio.

[0053] (2) The higher the engine speed NE, the faster the combustion rate in the internal combustion engine 10. Therefore, the higher the engine speed NE, the more likely it is that nitrogen oxide emissions will increase. In the above embodiment, the control device 100 sets the target operating point ADP so that the engine speed NE decreases as the engine speed NE at the start of the third process increases. This makes it possible to more effectively reduce nitrogen oxide emissions when the engine speed NE is in a state where nitrogen oxides are likely to be generated.

[0054] (3) The lower the catalyst temperature TMP, the lower the exhaust purification capability of the catalyst 25. Therefore, the lower the catalyst temperature TMP, the more likely it is that nitrogen oxide emissions will increase. In the above embodiment, the control device 100 sets the target operating point ADP so that the engine speed NE decreases as the catalyst temperature TMP at the start of the third process decreases. This makes it possible to more effectively reduce nitrogen oxide emissions when the catalyst temperature TMP is in a state where nitrogen oxides are likely to be generated.

[0055] (4) The smaller the excess air ratio λ, the faster the combustion speed in the internal combustion engine 10. Therefore, the smaller the excess air ratio λ, the more likely nitrogen oxide emissions are to increase. In the above embodiment, the control device 100 sets the target operating point ADP so that the engine speed NE decreases as the excess air ratio λ at the start of the third process decreases. This allows for a further reduction in nitrogen oxide emissions when the excess air ratio λ is in a state where nitrogen oxides are likely to be generated.

[0056] (5) In the above embodiment, when the catalyst temperature TMP is equal to or higher than the specified temperature T1, the base operating point DP1 is set as the target operating point ADP. Similarly, when the excess air ratio λ is equal to or higher than the specified excess air ratio A, the base operating point DP1 is set as the target operating point ADP. In these cases, nitrogen oxides are less likely to be generated during hydrogen combustion. Therefore, in these cases, by setting the base operating point DP1 as the target operating point ADP, it is possible to prevent a deterioration in fuel economy.

[0057] <Example of change> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0058] In the above embodiment, the configuration of the vehicle 500 is not limited to the example of the above embodiment. For example, the vehicle 500 may be configured to include a stepped transmission such as a transmission. However, a stepped transmission cannot continuously change the gear ratio. Furthermore, regardless of whether the transmission is stepped or continuous, there are cases where the gear ratio must be set to a specific gear ratio due to a balance with other controls. In such cases, it is not always possible to achieve an engine speed NE that matches the optimal fuel economy point. In such cases, the control device 100 sets an operating point DP that is minimally different from the optimal fuel economy point as the reference operating point DP1 of the internal combustion engine 10. Here, an example of the "operating point DP that is minimally different from the optimal fuel economy point" is the operating point DP that is minimal in difference between the optimal fuel economy point and the engine speed NE. Furthermore, an example of the "operating point DP that is minimally different from the optimal fuel economy point" is the operating point DP that is minimal in difference between the optimal fuel economy point and the optimal fuel economy point, or the operating point DP that is minimal in distance from the optimal fuel economy point on a two-dimensional coordinate map such as that shown in FIG. 3.

[0059] In the above embodiment, the detailed configuration of the internal combustion engine 10 is not limited to the example of the above embodiment. For example, the internal combustion engine 10 may further include a port injection valve that injects fuel into the intake passage 21.

[0060] In the above embodiment, the control device 100 may calculate the required output R in the first process by taking into account other parameters in addition to the accelerator operation amount ACCP. For example, in the first process, the control device 100 may calculate the required output R based on the vehicle speed in addition to the accelerator operation amount ACCP. Furthermore, the control device 100 may calculate the required output R based on multiple parameters.

[0061] In the above embodiment, the control device 100 may omit the processes of steps S17 and S18 in the target operating point setting control. That is, when the engine speed NE at the reference operating point DP1 is equal to or higher than the specified engine speed NE1, the control device 100 may perform the process of step S19 regardless of the magnitudes of the catalyst temperature TMP and the excess air ratio λ.

[0062] In the above embodiment, the control device 100 may set the target operating point ADP to an operating point DP at an engine speed NE that is lower by a certain fixed value than the engine speed NE at the reference operating point DP1. That is, the control device 100 does not have to set the target operating point ADP based on the three parameters of the engine speed NE, catalyst temperature TMP, and excess air factor λ. Furthermore, the control device 100 may set the target operating point ADP based on some of the parameters of the engine speed NE, catalyst temperature TMP, and excess air factor λ, or may calculate the target operating point ADP based on other parameters. [Explanation of symbols]

[0063] ADP: Target operating point DP...operating point DP1: Reference operating point NE: Engine RPM NE1...Regulated RPM R…Request output TR: Engine torque 10...Internal combustion engine 90...Accelerator pedal 100...Control device

Claims

[Claim 1] A control device for controlling an internal combustion engine that uses hydrogen as fuel and has a catalyst in an exhaust passage for purifying exhaust gas, a first process of calculating a required output of the internal combustion engine based on an operation amount of an accelerator pedal; a second process of setting an operating point of the internal combustion engine that is a combination of engine torque and engine speed of the internal combustion engine that can realize the required output, and an operating point among the plurality of operating points that provides the best fuel economy as an optimal fuel economy point, and then setting the operating point that is the smallest in difference from the optimal fuel economy point as a reference operating point of the internal combustion engine; a third process for setting, when the engine speed at the reference operating point is equal to or higher than a specified speed, one of the operating points at which the engine torque is greater than that at the reference operating point and the engine speed is smaller than that at the reference operating point as a target operating point of the internal combustion engine; is executable, In the third process, the target operating point is set so that the engine speed decreases as the catalyst temperature at the start of the third process decreases, and the engine speed decreases as the excess air ratio of the internal combustion engine at the start of the third process decreases. Control device for internal combustion engines.

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