Control device for internal combustion engine

Abstract

To reduce NOx emissions while satisfying a target output.SOLUTION: A first operating condition is set to such a condition of a fuel injection amount of a fuel injection valve and an opening degree of a throttle valve that an air excess ratio in a cylinder becomes greater than or equal to a prescribed value set as a value greater than 1.2 while satisfying a target output of an internal combustion engine. A second operating condition is set to such a condition of the fuel injection amount and the opening degree of the throttle valve that the air excess ratio in the cylinder becomes 1 or less while satisfying the target output of the internal combustion engine. A controller of the internal combustion engine executes acquisition processing for acquiring the first operating condition and the second operating condition that correspond to the target output (step S10, step S20), and selection processing for selecting either of the first operating condition and the second operating condition according to the operating situation of the internal combustion engine (step S30, step S40, step S50).SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] The internal combustion engine disclosed in Patent Document 1 has a fuel injection valve and a throttle valve. The fuel injection valve injects fuel. The throttle valve adjusts the amount of intake air. A control device for the internal combustion engine controls the internal combustion engine while varying the target air-fuel ratio. In this case, the control device controls the internal combustion engine so that the same output is obtained for the same accelerator operation amount even when the target air-fuel ratio is changed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 2644732 Summary of the Invention [Problem to be solved by the invention]

[0004] In an internal combustion engine fueled by hydrogen gas, it is desirable to reduce the NOx contained in the exhaust. In an internal combustion engine fueled by hydrogen gas, when various air-fuel ratios are set depending on the situation as in Patent Document 1, the NOx contained in the exhaust may increase depending on the air-fuel ratio. Therefore, a technology that can reduce NOx while achieving a target output is desired. [Means for solving the problem]

[0005] A control device for an internal combustion engine to solve the above problem has as its control target an internal combustion engine having cylinders, fuel injection valves that supply hydrogen gas into the cylinders, and a throttle valve that adjusts the amount of intake air, and when a first operating condition is a condition of a fuel injection amount of the fuel injection valve and an opening degree of the throttle valve that satisfies a target output of the internal combustion engine while causing the excess air ratio in the cylinder to be equal to or greater than a predetermined specified value greater than 1.2, and a second operating condition is a condition of the fuel injection amount and the opening degree that satisfies the target output while causing the excess air ratio in the cylinder to be equal to or less than 1, the control device executes an acquisition process to acquire the first operating condition and the second operating condition that correspond to the target output, and a selection process to select either the first operating condition or the second operating condition acquired in the acquisition process depending on the operating status of the internal combustion engine.

[0006] In the above configuration, the internal combustion engine is controlled to avoid an excess air ratio range where NOx emissions increase, thereby reducing NOx emissions while still achieving the target output. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic diagram of an internal combustion engine. [Figure 2] FIG. 2 is a diagram showing the relationship between the excess air ratio and the amount of NOx produced. [Figure 3] 10 is a flowchart showing a procedure for specific control. [Figure 4] 10 is a time chart showing an example of the transition of each parameter related to specific control. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment of a control device for an internal combustion engine will be described below with reference to the drawings. <General configuration of an internal combustion engine> The vehicle 500 has an internal combustion engine 10. The internal combustion engine 10 is a driving source of the vehicle 500. The internal combustion engine 10 has an engine body 10A, a plurality of cylinders 11, a plurality of pistons 12, a plurality of connecting rods 13, and a crankshaft 14. Note that FIG. 1 shows only one of the plurality of cylinders 11. The same applies to the pistons 12 and connecting rods 13. A piston 12 and a connecting rod 13 are provided for each cylinder 11. The number of cylinders 11 is, for example, four.

[0009] Cylinder 11 is a space defined in engine body 10A. Cylinder 11 is a space for burning a mixture of fuel and intake air. Piston 12 is located inside cylinder 11. Piston 12 reciprocates inside cylinder 11. Piston 12 is connected to crankshaft 14 via connecting rod 13. Crankshaft 14 rotates in response to the reciprocating motion of piston 12. Crankshaft 14 is an output shaft of internal combustion engine 10. Crankshaft 14 is connected to drive wheels 502 via an automatic transmission 501, a differential, etc.

[0010] The internal combustion engine 10 has a plurality of fuel injection valves 18. Note that FIG. 1 shows only one of the plurality of fuel injection valves 18. A fuel injection valve 18 is provided for each cylinder 11. The fuel injection valve 18 injects hydrogen gas as fuel. The fuel injection valve 18 supplies fuel directly into the cylinder 11 without passing through an intake passage 15, which will be described later.

[0011] The internal combustion engine 10 has a plurality of spark plugs 19. Note that FIG. 1 shows only one of the plurality of spark plugs 19. A spark plug 19 is provided for each cylinder 11. The tip of the spark plug 19 is located inside the cylinder 11. The spark plug 19 ignites the air-fuel mixture inside the cylinder 11.

[0012] The internal combustion engine 10 has an intake passage 15 and a throttle valve 16. The intake passage 15 is a passage for introducing intake air into each cylinder 11. The intake passage 15 is connected to each cylinder 11. The throttle valve 16 is located midway through the intake passage 15. The opening of the throttle valve 16 is adjustable. The throttle opening D of the throttle valve 16 can be changed from fully closed, which is the minimum opening, to fully open, which is the maximum opening. The amount of intake air G changes depending on the throttle opening D. In other words, the throttle valve 16 adjusts the amount of intake air G.

[0013] The internal combustion engine 10 has an exhaust passage 21, an oxidation catalyst 22, a urea water injector 23, and a selective catalytic reduction catalyst (hereinafter referred to as an SCR catalyst 24). The exhaust passage 21 is a passage for discharging exhaust gas from each cylinder 11. The exhaust passage 21 is connected to each cylinder 11. The oxidation catalyst 22 is located midway through the exhaust passage 21. The oxidation catalyst 22 oxidizes components contained in the exhaust gas. The urea water injector 23 is located downstream of the oxidation catalyst 22 in the exhaust passage 21. The urea water injector 23 injects urea water into the exhaust passage 21. The SCR catalyst 24 is located downstream of the urea water injector 23 in the exhaust passage 21. The SCR catalyst 24 reduces NOx (nitrogen oxides) contained in the exhaust gas to nitrogen and water, using ammonia gas derived from the urea water injected by the urea water injector 23 as a reducing agent. That is, the SCR catalyst 24 purifies the NOx in the exhaust gas.

[0014] The internal combustion engine 10 has a crank position sensor 61, an air flow meter 62, an air-fuel ratio sensor 63, and a temperature sensor 64. The crank position sensor 61 is located near the crankshaft 14. The crank position sensor 61 detects the rotational position R of the crankshaft 14. The air flow meter 62 is located upstream of the throttle valve 16 in the intake passage 15. The air flow meter 62 detects the intake air amount G. The air-fuel ratio sensor 63 is located upstream of the oxidation catalyst 22 in the exhaust passage 21. The air-fuel ratio sensor 63 detects the air-fuel ratio A of the exhaust gas discharged from the cylinder 11. In this embodiment, the air-fuel ratio A detected by the air-fuel ratio sensor 63 is treated as the air-fuel ratio A in the cylinder 11. The temperature sensor 64 is located between the oxidation catalyst 22 and the urea water injector 23. The temperature sensor 64 detects the temperature M of the exhaust gas flowing between the oxidation catalyst 22 and the urea water injector 23.

[0015] The vehicle 500 has an ignition switch 70, a vehicle speed sensor 71, and an accelerator sensor 72. The ignition switch 70 is a switch that the occupant uses to instruct the start of the internal combustion engine 10. The ignition switch 70 is turned on or off in response to an operation by the occupant. The vehicle speed sensor 71 detects the traveling speed of the vehicle 500 as a vehicle speed V. The accelerator sensor 72 detects the operation amount of the accelerator pedal in the vehicle 500 as an accelerator operation amount C.

[0016] <Outline of the control device> The vehicle 500 includes a control device 100. The control device 100 may be configured as one or more processors that execute various processes according to computer programs (software). The control device 100 may also be configured as one or more dedicated hardware circuits, such as application-specific integrated circuits (ASICs), that execute at least some of the various processes, or as a circuit including a combination thereof. The processor includes a CPU 111 and memory 112, such as RAM and ROM. The memory 112 stores program code or instructions configured to cause the CPU 111 to execute processes. The memory 112, i.e., a computer-readable medium, includes any available medium accessible by a general-purpose or dedicated computer. The memory 112 includes an electrically rewritable non-volatile memory. The control device 100 realizes various controls and processes, described below, by the CPU 111 executing the programs stored in the memory 112.

[0017] The control device 100 receives a signal from the ignition switch 70. Furthermore, while the ignition switch 70 is on, the control device 100 repeatedly receives detection signals from various sensors in the vehicle 500. Specifically, the control device 100 receives detection signals for the following parameters:

[0018] Vehicle speed V detected by vehicle speed sensor 71 Accelerator operation amount C detected by accelerator sensor 72 The rotational position R of the crankshaft 14 detected by the crank position sensor 61 The intake air volume G detected by the air flow meter 62 The air-fuel ratio A detected by the air-fuel ratio sensor 63 The temperature of the exhaust gas detected by the temperature sensor 64 is M The control device 100 controls the internal combustion engine 10. While the ignition switch 70 is on, the control device 100 repeatedly calculates a target output PQ, which is a target value of the output P of the internal combustion engine 10, based on the vehicle speed V and the accelerator operation amount C. The target output PQ is the output P of the internal combustion engine 10 required to generate the driving force of the vehicle 500 requested by the occupant through operation of the accelerator pedal. After calculating the target output PQ, the control device 100 operates various controllable devices such as the throttle valve 16, the fuel injection valve 18, and the spark plug 19 so that the actual output P of the internal combustion engine 10 matches the target output PQ. Note that the output P of the internal combustion engine 10 is the product of the engine torque TK, which is the torque of the internal combustion engine 10, and the engine rotation speed NE, which is the rotation speed of the crankshaft 14. Strictly speaking, when controlling the internal combustion engine 10, the control device 100 calculates a target value of the engine torque TK and a target value of the engine rotation speed NE based on the target output PQ. At this time, the control device 100 calculates an optimal combination of engine torque TK and engine speed NE by taking into consideration, for example, exhaust performance and fuel economy. Then, the control device 100 operates each of the target devices so that the calculated target value of engine torque TK matches the actual engine torque TK, and so that the calculated target value of engine speed NE matches the actual engine speed NE. Note that, in the following, a detailed explanation of how the respective target values ​​of engine torque TK and engine speed NE are calculated will be omitted.

[0019] The control device 100 repeatedly calculates various parameters related to the state of the internal combustion engine 10. For example, the control device 100 calculates the engine rotation speed NE based on the rotational position R of the crankshaft 14. The control device 100 also calculates the temperature of the SCR catalyst 24 based on the exhaust temperature M. The control device 100 also calculates the excess air ratio λ in the cylinder 11 based on the air-fuel ratio A in the cylinder 11. The excess air ratio λ represents the ratio of the actual air-fuel ratio A to the stoichiometric air-fuel ratio AS. In other words, when the excess air ratio λ is "1.0", the combustion in the internal combustion engine 10 is stoichiometric combustion at the stoichiometric air-fuel ratio AS. When the excess air ratio λ is greater than "1.0", the combustion in the internal combustion engine 10 is lean combustion at an air-fuel ratio A that is leaner than the stoichiometric air-fuel ratio AS. When the excess air ratio λ is less than "1.0", the combustion in the internal combustion engine 10 is rich combustion at an air-fuel ratio A that is richer than the stoichiometric air-fuel ratio AS.

[0020] <Specific control overview> In the internal combustion engine 10, NOx is generated during the combustion reaction of hydrogen gas. When the SCR catalyst 24 is at or above its activation temperature, the SCR catalyst 24 purifies the NOx generated by the combustion, thereby reducing the amount of NOx emitted into the outside air. However, after the internal combustion engine 10 starts, the SCR catalyst 24 is unable to fully demonstrate its NOx purification capability during the period until the SCR catalyst 24 has completely warmed up. The control device 100 can execute specific control targeted at the warm-up period of the SCR catalyst 24.

[0021] The control device 100 is capable of executing a first acquisition process, a second acquisition process, and a selection process as part of the specific control. In the first acquisition process, the control device 100 calculates a first operating condition according to the target output PQ. The first operating condition is a condition of the fuel injection amount F of the fuel injection valve 18, the throttle opening D, and the ignition timing Y of the spark plug 19 such that the target output PQ of the internal combustion engine 10 is satisfied while the excess air ratio λ in the cylinder 11 is equal to or greater than a first set value U1. The first set value U1 will be described later. Note that calculating the first operating condition corresponds to acquiring the first operating condition. Also, the first set value U1 corresponds to a specified value.

[0022] In the second acquisition process, the control device 100 calculates a second operating condition according to the target output PQ. The second operating condition is a condition of the fuel injection amount F, the throttle opening D, and the ignition timing Y that satisfies the target output PQ of the internal combustion engine 10 while keeping the excess air ratio λ in the cylinder 11 equal to or less than a second set value U2. Note that calculating the second operating condition corresponds to acquiring the second operating condition.

[0023] In the selection process, the control device 100 selects either the first operating condition calculated in the first acquisition process or the second operating condition calculated in the second acquisition process, depending on the operating state of the internal combustion engine 10. In this embodiment, the control device 100 selects the first operating condition when the target output PQ is equal to or less than a predetermined judgment value PN, and selects the second operating condition when the target output PQ is greater than the judgment value PN.

[0024] The control device 100 stores the first set value U1, the second set value U2, and the determination value PN in advance. <Regarding the first and second setting values> The first set value U1 and the second set value U2 are determined in relation to the amount of NOx generated by the combustion of hydrogen gas. As shown in FIG. 2, the amount of NOx generated in the internal combustion engine 10 increases or decreases depending on the excess air ratio λ. Note that the NOx generation amount in FIG. 2 represents the weight ratio of NOx in the exhaust gas. The amount of NOx generated changes with the excess air ratio λ as follows. Now, assume that the excess air ratio λ is a first positive value less than "1.0." As the excess air ratio λ increases from the first value toward "1.0," the amount of NOx generated gradually increases. When the excess air ratio λ further increases beyond "1.0," the amount of NOx generated changes from increasing to decreasing when the excess air ratio λ exceeds "1.2." As the excess air ratio λ further increases, the amount of NOx generated gradually decreases. Thus, the amount of NOx generated is maximized when the excess air ratio λ is near "1.2." Hereinafter, the excess air ratio λ at which the amount of NOx generated is maximized is referred to as the maximum excess air ratio.

[0025] The upper limit of the NOx generation amount permitted when the temperature of the SCR catalyst 24 has not yet reached its activation temperature and the engine is in an unwarmed state is referred to as the upper limit NOx amount. The upper limit NOx amount is predetermined so that the amount of NOx emitted into the outside air satisfies the regulations. It has been found through experiments or simulations that, within the range of excess air ratio λ greater than the maximum excess ratio, when the excess air ratio λ is equal to or greater than a first predetermined value, the NOx generation amount will be equal to or less than the upper limit NOx amount. In other words, the first predetermined value can be considered the minimum value of excess air ratios λ greater than the maximum excess ratio that can keep the NOx generation amount equal to or less than the upper limit NOx amount. In consideration of the maximum excess ratio, the first predetermined value is set to a value greater than "1.2". A first set value U1 related to the first operating condition is predetermined to be greater than this first predetermined value. The first set value U1 is, for example, "2.5".

[0026] It has been found through experiments or simulations that, within a range of excess air ratio λ smaller than the maximum excess ratio, when the excess air ratio λ is equal to or smaller than a second predetermined value, the amount of NOx generated will be equal to or smaller than the upper limit NOx amount. In other words, the second predetermined value can be said to be the maximum value at which the amount of NOx generated can be equal to or smaller than the upper limit NOx amount, among excess air ratios λ smaller than the maximum excess ratio. A second set value U2 related to the second operating condition is predetermined as a value smaller than the second predetermined value. The second set value U2 is set to a value smaller than "1.0". The second set value U2 is, for example, "0.9". In this embodiment, the amount of NOx generated when the excess air ratio λ is the second set value U2 is greater than the amount of NOx generated when the excess air ratio λ is the first set value U1.

[0027] <About the judgment value> The setting of the first set value U1 causes the internal combustion engine 10 to perform lean combustion under the first operating condition. On the other hand, the setting of the second set value U2 causes the internal combustion engine 10 to perform rich combustion under the second operating condition. In relation to this, a larger output P can be achieved under the second operating condition than under the first operating condition. The determination value PN, which is used as a threshold value for determination in the selection process, is determined in advance, for example, through experiments or simulations, as a value slightly smaller than the maximum value of the output P that can be achieved by the internal combustion engine 10 when the excess air ratio λ is set to the first set value U1.

[0028] <Specific processing procedures for specific control> When the ignition switch 70 is turned on, the control device 100 repeatedly executes the specific control on the condition that the temperature of the SCR catalyst 24 is equal to or lower than the activation temperature. When the temperature of the SCR catalyst 24 reaches the activation temperature, the control device 100 ends the specific control at that point. After ending the specific control, the control device 100 transitions to normal control of the internal combustion engine 10. The control device 100 stores the activation temperature of the SCR catalyst 24 in advance.

[0029] As shown in FIG. 3, when the control device 100 starts specific control, it first executes the process of step S10. In step S10, the control device 100 refers to the current target output PQ. Then, the control device 100 calculates the fuel injection amount F, throttle opening D, and ignition timing Y required to make the excess air ratio λ in the cylinder 11 equal to or greater than a first set value U1 while satisfying the target output PQ. The values ​​of each parameter calculated by the control device 100 in step S10 correspond to first operating conditions, which are conditions for the fuel injection amount F, throttle opening D, and ignition timing Y that make the excess air ratio λ equal to or greater than the first set value U1 while satisfying the target output PQ. The fuel injection amount F, throttle opening D, and ignition timing Y vary depending on the target output PQ. That is, in step S10, the control device 100 calculates the first operating conditions according to the target output PQ. Note that the fuel injection amount F may be calculated for each fuel injection valve 18.

[0030] When calculating the first operating condition, the control device 100 calculates the throttle opening D as being fully open among the three parameters of the fuel injection amount F, the throttle opening D, and the ignition timing Y. Then, the control device 100 calculates the fuel injection amount F and the ignition timing Y required to achieve the target output PQ. At this time, the control device 100 calculates a combination of the fuel injection amount F and the ignition timing Y such that the air excess ratio λ becomes as large as possible, on the premise that the air excess ratio λ becomes equal to or greater than a first set value U1. In other words, the control device 100 prioritizes reducing the amount of NOx generated. The control device 100 calculates the optimal combination of each parameter, for example, by using various maps stored in advance.

[0031] Regarding the processing of step S10, if the current target output PQ is greater than the judgment value PN, the control device 100 sets provisional values ​​for each of the fuel injection amount F, the throttle opening D, and the ignition timing Y. The provisional values ​​indicate that no valid values ​​exist. After executing the processing of step S10, the control device 100 proceeds to the processing of step S20. The processing of step S10 is the first acquisition processing.

[0032] In step S20, the control device 100 calculates the fuel injection amount F, throttle opening D, and ignition timing Y required to keep the excess air ratio λ in the cylinder 11 equal to or less than the second set value U2 while satisfying the target output PQ referenced in step S10. The parameter values ​​calculated by the control device 100 in step S20 correspond to the second operating conditions, which are the conditions for the fuel injection amount F, throttle opening D, and ignition timing Y that keep the excess air ratio λ equal to or less than the second set value U2 while satisfying the target output PQ. As described above, the fuel injection amount F, throttle opening D, and ignition timing Y vary depending on the target output PQ. That is, in step S20, the control device 100 calculates the second operating conditions according to the target output PQ. Here, the control device 100 calculates a combination of the fuel injection amount F, throttle opening D, and ignition timing Y that can achieve the target output PQ so that the excess air ratio λ is as small as possible within a range where the excess air ratio λ is equal to or greater than the allowable value and equal to or less than the second set value U2. At this time, the control device 100 calculates the values ​​of these parameters so that the throttle opening D is smaller than full open. The above-mentioned allowable values ​​are predetermined, for example, from the viewpoint of preventing pre-ignition. Pre-ignition is a phenomenon in which the air-fuel mixture is ignited before ignition by the spark plug 19. After executing the process of step S20, the control device 100 proceeds to the process of step S30. The process of step S20 is the second acquisition process.

[0033] In step S30, the control device 100 determines whether the target output PQ referenced in step S10 is equal to or less than the judgment value PN. If the target output PQ is equal to or less than the judgment value PN (step S30: YES), the control device 100 selects the first operating condition as the operating condition for controlling the internal combustion engine 10. Then, the control device 100 proceeds to step S40.

[0034] In step S40, the control device 100 controls the internal combustion engine 10 under the first operating condition. That is, the control device 100 controls each spark plug 19 so that ignition occurs at the ignition timing Y calculated in step S10. The control device 100 also controls each fuel injection valve 18 so that the fuel injection amount F calculated in step S10 is injected. The control device 100 also controls the throttle valve 16 so that the throttle opening degree D calculated in step S10 becomes equal to the throttle opening degree D. The control device 100 controls the internal combustion engine 10 based on the first operating condition for a predetermined control period. Thereafter, the control device 100 temporarily ends the series of processes for the specific control. Then, the control device 100 executes the process of step S10 again.

[0035] On the other hand, in step S30, if the target output PQ is greater than the determination value PN (step S30: NO), the control device 100 selects the second operating condition as the operating condition for controlling the internal combustion engine 10. Then, the control device 100 advances the process to step S50.

[0036] In step S50, the control device 100 controls the internal combustion engine 10 under the second operating condition. That is, the control device 100 controls each target device based on the ignition timing Y, throttle opening D, and fuel injection amount F calculated in step S20. As in step S40, the control device 100 continues the processing of step S50 for a predetermined control period. Thereafter, the control device 100 temporarily ends the specific control. Then, the control device 100 executes the processing of step S10 again. Note that the processing of steps S30, S40, and S50 is a selection processing.

[0037] <Operation of the embodiment> As shown in FIG. 4, it is assumed that the ignition switch 70 is turned on at time T1. Then, it is assumed that the internal combustion engine 10 is started at time T1. Now, it is assumed that the target output PQ of the internal combustion engine 10 is equal to or less than the determination value PN (step S30: YES) from time T1 to time T2. In this case, the control device 100 controls the internal combustion engine 10 under the first operating condition (step S40). That is, as shown in FIG. 4(b), the control device 100 controls the internal combustion engine 10 by setting the excess air ratio λ to a first set value U1 or more. As a result, the control device 100 controls the internal combustion engine 10 while avoiding the region of the excess air ratio λ where the amount of NOx generated becomes large. By controlling the internal combustion engine 10 while avoiding the excess air ratio λ where the amount of NOx generated becomes large, the amount of NOx generated is maintained low, as shown in FIG. 4(c). Note that, as shown in FIG. 4(b), the control device 100 fully opens the throttle opening D under the first operating condition. This allows a large amount of high-temperature exhaust gas to reach the SCR catalyst 24. Therefore, the SCR catalyst 24 is more likely to warm up.

[0038] Now, let us assume that at time T2, the target output PQ of the internal combustion engine 10 becomes greater than the determination value PN (step S30: NO). At this time, it is assumed that the warm-up of the SCR catalyst 24 has not yet been completed. In this case, the control device 100 controls the internal combustion engine 10 under the second operating condition (step S50). That is, as shown in FIG. 4(b), the control device 100 controls the internal combustion engine 10 by setting the excess air ratio λ to a second set value U2 or less. As a result, the control device 100 controls the internal combustion engine 10 while avoiding the region of the excess air ratio λ where the amount of NOx generated becomes large.

[0039] Here, when reducing the excess air ratio λ to achieve the target output PQ after time T2, let us assume that the excess air ratio λ is set to approximately 1.2, as shown by the two-dot chain line in (b) of Figure 4. In this case, the amount of NOx generated becomes excessively large, as shown by the two-dot chain line in (c) of Figure 4.

[0040] In contrast, when the internal combustion engine 10 is controlled under the second operating condition as in this embodiment, the amount of NOx generated can be maintained low even after time T2, as shown by the solid line in FIG. 4(c). As already explained, the second set value U2, which is the limit value for the excess air ratio λ under the second operating condition, generates a larger amount of NOx than the first set value U1, which is the limit value for the excess air ratio λ under the first operating condition. In relation to this, when the internal combustion engine 10 is controlled under the second operating condition, the amount of NOx generated may be larger than when the internal combustion engine 10 is controlled under the first operating condition. Therefore, under the second operating condition, the control device 100 sets the throttle opening D to an opening smaller than full opening, as shown in FIG. 4(a). Therefore, the amount of exhaust gas is reduced. By reducing the amount of exhaust gas itself, the amount of NOx emitted to the outside of the internal combustion engine 10 through the exhaust passage 21 can be maintained low.

[0041] <Effects of the embodiment> (1) During execution of specific control, the control device 100 controls the internal combustion engine 10 to avoid the region of the excess air ratio λ where the amount of NOx generated increases. This makes it possible to reduce the amount of NOx emitted into the outside air during the period when the SCR catalyst 24 is not yet warmed up. That is, in this embodiment, the first operating condition in which the throttle opening D is fully opened is used to promote the warming up of the SCR catalyst 24, and it is possible to reduce the amount of NOx emitted into the outside air throughout the entire period during which the SCR catalyst 24 is being warmed up.

[0042] (2) When the specific control is being executed, the control device 100 selects the second operating condition when the target output PQ is relatively large. This causes the control device 100 to perform rich combustion in the internal combustion engine 10. This prevents a situation in which the target output PQ cannot be achieved because too much priority is given to reducing NOx emissions.

[0043] <Example of change> The above embodiment can be modified as follows: The above embodiment and the following modifications can be implemented in combination with each other within the scope of technical compatibility.

[0044] The specific control is not limited to being performed during warm-up of the SCR catalyst 24. The specific control may be performed at any time during operation of the internal combustion engine 10. The specific control may be performed from the beginning to the end of operation of the internal combustion engine 10. As described in the above embodiment, the specific control controls the internal combustion engine 10 while avoiding the region of the excess air ratio λ where the amount of NOx generated increases. Therefore, by performing the specific control, the amount of NOx generated and, in turn, the amount of NOx emitted into the outside air can be reduced, not only during warm-up of the SCR catalyst 24.

[0045] The first set value U1 is not limited to the example in the above embodiment. The first set value U1 may be any value greater than 1.2. The first set value U1 may be any value that is effective in reducing NOx emissions into the outside air. An optimal value may be set as appropriate depending on the circumstances under which specific control is performed.

[0046] The second set value U2 is not limited to the example in the above embodiment. The second set value U2 may be a value equal to or less than 1.0. Like the first set value U1, the second set value U2 may be set to a value that is effective from the viewpoint of suppressing NOx emissions into the outside air.

[0047] The first operating condition is not limited to the example described in step S10 of the above embodiment. The first operating condition may be any condition that defines the fuel injection amount F and the throttle opening D such that the excess air ratio λ in the cylinder 11 is equal to or greater than the first set value U1 while satisfying the target output PQ of the internal combustion engine 10. For example, the throttle opening D may be set to an opening smaller than full opening under the first operating condition. Furthermore, it is not essential that the first operating condition include the ignition timing Y. Furthermore, the first operating condition is not limited to a combination of values ​​for the fuel injection amount F and the throttle opening D, and may define a range of values ​​for the fuel injection amount F and the throttle opening D.

[0048] The second operating condition is not limited to the example described in step S20 of the above embodiment. The second operating condition may define the conditions for the fuel injection amount F and the throttle opening D such that the excess air ratio λ in the cylinder 11 is equal to or less than the second set value U2 while satisfying the target output PQ of the internal combustion engine 10. For example, the throttle opening D may be fully open under the second operating condition. As with the first operating condition, it is not essential that the second operating condition include the ignition timing Y. As with the first operating condition, the second operating condition may define ranges of values ​​for the fuel injection amount F and the throttle opening D.

[0049] The method for determining the criterion value PN is not limited to the example of the above embodiment. If the criterion value PN is determined as a value that can determine whether the target output PQ can be achieved under the first operating condition, the first operating condition can be selected for opportunities where the target output PQ can be achieved. The criterion value PN may be set to a value appropriate for determining whether to select the first operating condition or the second operating condition, depending on the situation in which specific control is performed.

[0050] The method of determining whether to select the first operating condition or the second operating condition is not limited to the example of the above embodiment using the reference value PN. Depending on the magnitude of the target output PQ, the target output PQ may be achieved under either the first or second operating condition. For such cases, the specific control may be modified as follows. After performing the first acquisition process and the second acquisition process, the control device 100 performs the following selection process. If the first specific condition is met and the target output PQ can be achieved under either the first or second operating condition, the control device 100 selects the second operating condition. The control device 100 then controls the internal combustion engine 10 under the second operating condition. The first specific condition requires that the engine speed NE be limited to less than a predetermined specified speed. Lean combustion is performed under the first operating condition, whereas stoichiometric combustion or rich combustion is performed under the second operating condition. Therefore, even if the same target output PQ is realized under the first operating condition and the second operating condition, when the internal combustion engine 10 is controlled under the second operating condition, the engine torque TK becomes larger than when the internal combustion engine 10 is controlled under the first operating condition. Also, the engine rotation speed NE becomes smaller. Therefore, in situations where it is desired to suppress the engine rotation speed NE, it is effective to select the second operating condition as in this modified example.

[0051] An example of the first specific condition is that the vehicle speed V is equal to or less than a predetermined specified vehicle speed. Here, when the vehicle speed V is low, background noise, such as road noise and wind noise, is reduced. When the background noise is low, it is preferable to reduce the operating noise of the internal combustion engine 10 in order to improve the quietness inside the vehicle. Therefore, by setting the above content as the first specific condition, the engine rotation speed NE and therefore the operating noise of the internal combustion engine 10 can be reduced when the vehicle speed V is low. When the above content is adopted as the first specific condition, the specified vehicle speed may be set to a vehicle speed V at which the background noise is deemed to be appropriately reduced. Furthermore, the specified rotation speed may be set to a value at which the operating noise of the internal combustion engine 10 is deemed to be less noticeable to occupants.

[0052] When the target output PQ can be achieved under both the first and second operating conditions, the following configuration can also be adopted. That is, when the second specific condition is met and the target output PQ can be achieved under both the first and second operating conditions, the control device 100 selects the first operating condition in the selection process. The second specific condition is a condition that requires limiting the engine torque TK to less than a predetermined specified torque. As described above, even if the same target output PQ is achieved under the first and second operating conditions, when the internal combustion engine 10 is controlled under the first operating condition, the engine torque TK is smaller than when the internal combustion engine 10 is controlled under the second operating condition. Therefore, in situations where it is desired to suppress the engine torque TK, it is effective to select the first operating condition as in this modified example.

[0053] An example of the second specific condition is that the internal combustion engine 10 is idling. In this case, the specified torque may be set to a value that is effective from the viewpoint of improving fuel economy, for example. The configuration of the internal combustion engine 10 is not limited to the example of the above embodiment. For example, the fuel injection valve 18 may be configured to supply fuel into the cylinder 11 via the intake passage 15. The internal combustion engine 10 only needs to have the fuel injection valve 18 that supplies hydrogen gas into the cylinder 11 and the throttle valve 16 that adjusts the intake air amount G.

[0054] The overall configuration of the vehicle 500 is not limited to the example of the above embodiment. For example, the vehicle 500 may have a motor generator in addition to the internal combustion engine 10 as a drive source of the vehicle 500. [Explanation of symbols]

[0055] 10...Internal combustion engine 11...cylinder 14...Crankshaft 16...Throttle valve 18...Fuel injection valve 100...Control device

Claims

1. The control target is an internal combustion engine having a cylinder, a fuel injection valve that supplies hydrogen gas into the cylinder, and a throttle valve that adjusts the amount of intake air, a first operating condition is a condition of a fuel injection amount of the fuel injection valve and an opening degree of the throttle valve such that an excess air ratio in the cylinder is equal to or greater than a predetermined specified value that is greater than 1.2 while satisfying a target output of the internal combustion engine; When the second operating condition is a condition of the fuel injection amount and the opening degree that satisfies the target output while making the excess air ratio in the cylinder equal to or less than 1, an acquisition process for acquiring the first operating condition and the second operating condition according to the target output; a selection process for selecting either the first operating condition or the second operating condition acquired in the acquisition process according to an operating state of the internal combustion engine; When a first specific condition that requires limiting the rotation speed of the output shaft of the internal combustion engine to less than a predetermined specified rotation speed is satisfied, and when the target output can be achieved under either the first operating condition or the second operating condition, the selection process selects the second operating condition. Control device for internal combustion engines.

2. The control target is an internal combustion engine having a cylinder, a fuel injection valve that supplies hydrogen gas into the cylinder, and a throttle valve that adjusts the amount of intake air, a first operating condition is a condition of a fuel injection amount of the fuel injection valve and an opening degree of the throttle valve such that an excess air ratio in the cylinder is equal to or greater than a predetermined specified value that is greater than 1.2 while satisfying a target output of the internal combustion engine; When the second operating condition is a condition of the fuel injection amount and the opening degree that satisfies the target output while making the excess air ratio in the cylinder equal to or less than 1, an acquisition process for acquiring the first operating condition and the second operating condition according to the target output; a selection process for selecting either the first operating condition or the second operating condition acquired in the acquisition process according to an operating state of the internal combustion engine; When a second specific condition that requires limiting the torque of the internal combustion engine to less than a predetermined specified torque is satisfied, and when the target output can be achieved under either the first operating condition or the second operating condition, the selection process selects the first operating condition. Control device for internal combustion engines.

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