Control device for hydrogen engine

Abstract

The invention relates to a control device for a hydrogen engine. A processing circuit for controlling a hydrogen engine is configured so as to perform: injecting, as a fuel injection amount for main injection, a fuel injection amount necessary for generating an engine torque corresponding to a required torque until adjustment of an air amount for switching between ideal proportional combustion and lean combustion is completed; and calculating the fuel injection amount of the post-injection so that the total injection amount of the main injection and the post-injection becomes a value obtained by dividing the actual air amount of the combustion chamber by the theoretical air-fuel ratio.

Description

Technical Field

[0001] This disclosure relates to a control device for a hydrogen engine. Background Technology

[0002] Japanese Patent Application Publication No. 2024-58908 describes a method for changing the air-fuel ratio of the mixture burned in the combustion chamber in a hydrogen engine that generates power by burning hydrogen, depending on the operating conditions.

[0003] In hydrogen engines like those described above, it is sometimes necessary to temporarily and drastically change the air-fuel ratio in order to suppress NOx (nitrogen oxides) emissions. However, when the air-fuel ratio changes drastically, a torque surge is generated, thus deteriorating driving performance. Summary of the Invention

[0004] One type of hydrogen engine control device is a control device applied to a hydrogen engine that uses hydrogen as fuel, which includes a processing circuit. The processing circuit is configured to perform: calculating the required engine torque value, i.e., the required torque; switching between lean combustion and ideal combustion, wherein lean combustion is combustion in which the air-fuel ratio of the mixture burned in the combustion chamber is on the lean side of the stoichiometric air-fuel ratio, and ideal combustion is combustion in which the air-fuel ratio of the mixture is equal to the stoichiometric air-fuel ratio; when the switching between ideal combustion and lean combustion is required, adjusting the air volume of the mixture from the amount required for combustion before the switch to the amount required for combustion after the switch; from the time the switching between ideal combustion and lean combustion is required until the air volume adjustment is completed, performing fuel injection in a manner divided into main injection during the period from the intake stroke to the compression stroke and post-injection during the period from the expansion stroke to the exhaust stroke; calculating the amount of fuel injection required to generate engine torque corresponding to the required torque as the fuel injection amount of the main injection; and calculating the fuel injection amount of the post-injection in such a manner that the total injection amount of the main injection and the post-injection is greater than or equal to the value obtained by dividing the actual air volume of the combustion chamber by the stoichiometric air-fuel ratio.

[0005] The aforementioned control device for the hydrogen engine effectively suppresses both the torque surge and the increase in NOx emissions during the switching between ideal combustion and lean combustion. Attached Figure Description

[0006] Figure 1 This is a schematic diagram illustrating the structure of one embodiment of the control device for a hydrogen engine.

[0007] Figure 2 yes Figure 1 The flowchart shows the combustion switching routine executed by the control device.

[0008] Figure 3 It is not done Figure 2 The time diagram for the combustion switching routine when switching from lean combustion to ideal combustion is shown in part (a), which represents the shift in combustion requirements, part (b) which represents the shift in target air volume and actual air volume, part (c) which represents the shift in fuel injection volume, part (d) which represents the shift in excess air ratio of mixture and exhaust, part (e) which represents the shift in engine torque, and part (f) which represents the shift in ignition timing.

[0009] Figure 4 Is Figure 1 The control device includes a time graph showing the transition from ideal combustion to lean combustion. Part (a) represents the progression of combustion requirements, part (b) represents the progression of target air volume and actual air volume, part (c) represents the progression of fuel injection volume, part (d) represents the progression of excess air ratio in the mixture and exhaust, part (e) represents the progression of engine torque, and part (f) represents the progression of ignition timing.

[0010] Figure 5 Is Figure 1 The control device performs time diagrams for switching from lean combustion to ideal combustion ratio. Part (a) is a time diagram showing the progress of combustion requirements, part (b) is a time diagram showing the progress of target air volume and actual air volume, part (c) is a time diagram showing the progress of fuel injection volume, part (d) is a time diagram showing the progress of excess air ratio in the mixture and exhaust, part (e) is a time diagram showing the progress of engine torque, and part (f) is a time diagram showing the progress of ignition timing. Detailed Implementation

[0011] The following is for reference Figures 1-5 An embodiment of the control device for a hydrogen engine will be described in detail.

[0012] <Structure of Hydrogen Engine 10 and its Control System>

[0013] First, refer to Figure 1 The structure of this embodiment is explained. Figure 1 The hydrogen engine 10 shown is mounted on the vehicle.

[0014] The hydrogen engine 10 includes a combustion chamber 11 for burning a mixture, an intake passage 12 for introducing air into the combustion chamber 11, and an exhaust passage 13 for discharging exhaust from the combustion chamber 11. An air filter 14, an air flow meter 15, and a throttle valve 16 are provided in the intake passage 12. The air filter 14 is a filter for filtering dust and other contaminants from the air. The air flow meter 15 is a detector for detecting the airflow rate within the intake passage 12. The throttle valve 16 is a valve that adjusts the airflow rate by changing the flow path area of ​​the air within the intake passage 12. An injector 17 for injecting hydrogen into the air introduced into the combustion chamber 11 through the intake passage 12 is provided in the combustion chamber 11. Additionally, an ignition device 18 for igniting the mixture by spark discharge is provided in the combustion chamber 11. An air-fuel ratio sensor 19 for detecting the air-fuel ratio of the mixture after combustion in the combustion chamber 11 is provided in the exhaust passage 13. In addition, a three-way catalytic converter 20 carrying a three-way catalytic converter is provided on the downstream side of the air-fuel ratio sensor 19 in the exhaust passage 13.

[0015] The hydrogen engine 10, configured as described above, is controlled by an electronic control unit 21. The electronic control unit 21 includes a processing circuit 22 and a storage device 23. The storage device 23 stores in advance programs and data used in the control of the hydrogen engine 10. In this embodiment, the electronic control unit 21 corresponds to the control device of the hydrogen engine 10.

[0016] The detection signals from the air flow meter 15 and the air-fuel ratio sensor 19 are input to the electronic control unit 21. Additionally, detection signals from the crankshaft angle sensor 24 and the accelerator pedal sensor 26 are also input to the electronic control unit 21. The crankshaft angle sensor 24 detects the rotation angle of the crankshaft 25, which serves as the output shaft of the hydrogen engine 10. The accelerator pedal sensor 26 detects the amount of pressure applied to the accelerator pedal 27. Based on the detection results from these sensors, the electronic control unit 21 determines the operating parameters of the hydrogen engine 10. These operating parameters include the opening of the throttle 16, the amount and timing of hydrogen injection from the injector 17, and the ignition timing of the air-fuel mixture from the ignition device 18. Furthermore, the electronic control unit 21 operates the throttle 16, the injector 17, and the ignition device 18 according to the determined operating parameters, thereby controlling the hydrogen engine 10. The control of the hydrogen engine 10 by the electronic control unit 21 is performed by various processes executed by the processing circuit 22. The processing circuit 22 performs these various processes by executing programs read from the storage device 23.

[0017] Furthermore, based on the detection results of the crankshaft angle sensor 24, the processing circuit 22 calculates the rotational speed of the crankshaft 25, i.e., the engine speed NE. In addition, based on the detection results of the air flow meter 15, the opening of the throttle valve 16, the engine speed NE, etc., the processing circuit 22 calculates the amount of air filling the combustion chamber 11, i.e., the amount of air in the air-fuel mixture that is burned in the combustion chamber 11.

[0018] <Relationship between air-fuel ratio and NOx emissions in hydrogen engine 10>

[0019] In the case of a hydrogen engine 10 installed in a vehicle, it is required to limit the amount of NOx (nitrogen oxides) emitted into the external environment to an acceptable level. At higher combustion temperatures, the amount of NOx generated by the combustion of the air-fuel mixture in the combustion chamber 11 increases compared to lower combustion temperatures. When combustion is performed with an air-fuel ratio that is somewhat leaner than the lean side, the combustion temperature decreases and the amount of NOx generated decreases. Furthermore, when combustion is performed with a lean air-fuel ratio, fuel consumption of the hydrogen engine 10 can be suppressed by reducing heat loss, etc. Therefore, in order to suppress both fuel consumption and NOx emissions, it is preferable to keep the air-fuel ratio of the air-fuel mixture burned in the combustion chamber 11 of the hydrogen engine 10 lean within a range that does not worsen combustion.

[0020] However, lean combustion is sometimes not possible throughout the entire operating range of the hydrogen engine 10. The reason is as follows: There is a limit to the amount of air that can be supplied to the combustion chamber 11. Therefore, during high-load operation burning large amounts of fuel, the amount of air required for lean combustion may sometimes be insufficient to supply the combustion chamber 11.

[0021] In contrast, a three-way catalytic converter 20 carrying a three-way catalytic converter is installed in the exhaust passage 13 of the hydrogen engine 10. The three-way catalytic converter 20 has the ability to purify NOx in the exhaust gas. When combustion occurs at the stoichiometric air-fuel ratio or an air-fuel ratio richer than the stoichiometric air-fuel ratio, the three-way catalytic converter 20 exhibits a high NOx purification capacity. Therefore, when combustion occurs at the stoichiometric air-fuel ratio or an air-fuel ratio richer than the stoichiometric air-fuel ratio, NOx is purified by the three-way catalytic converter 20, and NOx emissions into the external environment can be suppressed. In the following description, combustion at the stoichiometric air-fuel ratio is described as ideally proportioned combustion, and combustion at an air-fuel ratio leaner than the stoichiometric air-fuel ratio is described as lean combustion. In order to suppress NOx emissions, the processing circuit 22 controls the air-fuel ratio of the mixture burned in the combustion chamber 11 of the hydrogen engine 10, so that ideally proportioned combustion occurs in the high-load operating region, and lean combustion occurs in other operating regions.

[0022] <Air-fuel ratio control of hydrogen engine 10>

[0023] Next, the air-fuel ratio control of the hydrogen engine 10 performed by the processing circuit 22 will be explained.

[0024] During air-fuel ratio control, the processing circuit 22 first calculates the required torque TE* based on the detection results of the accelerator pedal sensor 26. The required torque TE* represents the engine torque required to meet the driving force of the vehicle demanded by the driver by pressing the accelerator pedal 27.

[0025] Next, processing circuit 22 sets a target air-fuel ratio (i.e., target air-fuel ratio) for the air-fuel mixture burned in combustion chamber 11 based on the required torque TE* and engine speed NE. For example, processing circuit 22 sets the stoichiometric air-fuel ratio as the target air-fuel ratio in high-load / high-speed operating regions, and sets an air-fuel ratio leaner than the stoichiometric air-fuel ratio as the target air-fuel ratio in other operating regions. In the following description, the operating region where the stoichiometric air-fuel ratio is set as the target air-fuel ratio is referred to as the ideal combustion region, and the operating region where the air-fuel ratio leaner than the stoichiometric air-fuel ratio is set as the target air-fuel ratio is referred to as the lean combustion region.

[0026] Next, the processing circuit 22 calculates the amount of air required to generate engine torque corresponding to the required torque TE* under the condition of setting the air-fuel ratio to the target air-fuel ratio, as the value of the target air volume M*. Then, the processing circuit 22 operates the opening of the throttle valve 16 so that the actual amount of air filling the combustion chamber 11, i.e., the actual air volume M, becomes equal to the target air volume M*. In addition, the processing circuit 22 calculates the fuel injection amount to obtain the air-fuel ratio corresponding to the target air-fuel ratio relative to the actual air volume M. Then, the processing circuit 22 operates the injector 17 to inject the calculated fuel injection amount. Moreover, the processing circuit 22 sets the ignition timing based on the required torque TE* and the engine speed NE. Then, the processing circuit 22 operates the ignition device 18 to perform ignition at the set ignition timing.

[0027] Combustion Switching Routine

[0028] As the operating point of the hydrogen engine 10 varies across the ideal combustion region and the lean combustion region, the combustion of the hydrogen engine 10 switches between ideal combustion and lean combustion. At the boundary between the ideal combustion region and the lean combustion region, the target air-fuel ratio changes discontinuously. Therefore, when switching between ideal combustion and lean combustion, the amount of air supplied to the combustion chamber 11 needs to change significantly. The processing circuit 22 performs processing to perform this combustion switching while suppressing both torque surges and NOx emissions.

[0029] The following is for reference Figures 2-5 This section details the processing performed by the processing circuit 22 during the switching between ideal combustion and lean combustion. Figure 2A flowchart is shown of the combustion switching routine executed by the processing circuit 22 for the purpose of combustion switching. The processing circuit 22 initiates the processing of this routine when either a switch from ideal combustion to lean combustion or a switch from lean combustion to ideal combustion is requested.

[0030] When this routine begins, processing circuit 22 first switches the target air quantity M* from a value corresponding to combustion before the switch to a value corresponding to combustion after the switch in step S100. Next, processing circuit 22 calculates the total injection quantity Q based on the actual air quantity M in step S110. When fuel equivalent to the total injection quantity Q is injected, processing circuit 22 calculates the amount by which the air-fuel ratio of the mixture becomes the stoichiometric air-fuel ratio, and uses this as the value of the total injection quantity Q. In this embodiment, processing circuit 22 divides the actual air quantity M by the stoichiometric air-fuel ratio and calculates the value obtained from this division as the value of the total injection quantity Q.

[0031] Next, the processing circuit 22 calculates the main injection quantity Qm based on the required torque TE* and the actual air volume M. Specifically, the processing circuit 22 calculates the amount of fuel injection required to generate the engine torque corresponding to the required torque TE* relative to the actual air volume M as the value of the main injection quantity Qm. Then, in the next step S130, the processing circuit 22 subtracts the main injection quantity Qm from the total injection quantity Q and calculates the subtracted value as the value of the post-injection quantity Qp. Then, in step S140, the processing circuit 22 instructs the injector 17 to perform a main injection amount equivalent to the main injection quantity Qm and a post-injection amount equivalent to the post-injection quantity Qp. The main injection is the fuel injection performed during the period from the intake stroke to the compression stroke. The post-injection is the fuel injection performed during the period from the expansion stroke to the exhaust stroke. The fuel injected in the main injection burns in the combustion chamber 11, generating engine torque. In contrast, the post-injection is performed from the final stage of combustion in the combustion chamber 11 until the end. Therefore, the post-injection becomes a fuel injection that contributes almost nothing to the generation of engine torque.

[0032] Subsequently, in step S150, the processing circuit 22 determines whether the adjustment of the air quantity from the amount required for combustion before the switch to the amount required for combustion after the switch is complete. In this embodiment, the processing circuit 22 determines that the air quantity adjustment is complete based on the actual air quantity M converging to the target air quantity M*. If the processing circuit 22 determines that the air quantity adjustment is complete (S150: Yes), it ends the processing of this routine in the current combustion switch. Conversely, if the processing circuit 22 determines that the air quantity adjustment is not complete (S150: No), it executes the processing of steps S110 to S150 again after a predetermined control cycle.

[0033] <The Role of the Implementation Method>

[0034] During operation of the hydrogen engine 10, the processing circuit 22 of the electronic control unit 21 calculates the required value of the engine torque generated by the hydrogen engine 10, namely the required torque TE*. Furthermore, based on the required torque TE*, the processing circuit 22 switches the combustion of the air-fuel mixture in the combustion chamber 11 between lean combustion and ideally proportioned combustion. Lean combustion involves setting the air-fuel ratio of the air-fuel mixture burned in the combustion chamber 11 to a leaner side than the stoichiometric air-fuel ratio. Ideally proportioned combustion involves setting the air-fuel ratio of the air-fuel mixture burned in the combustion chamber 11 to the stoichiometric air-fuel ratio. In ideally proportioned combustion, combustion occurs at a stoichiometric air-fuel ratio that the three-way catalytic converter 20 can effectively purify NOx generated during combustion, thereby suppressing NOx emissions. In lean combustion, combustion occurs at a lean air-fuel ratio where the combustion temperature is lower and NOx generation is suppressed, thereby suppressing NOx emissions.

[0035] In ideal combustion and lean combustion, the air-fuel ratio of the mixture burned in combustion chamber 11 is very different, and the amount of air required for the two combustions is also very different. When switching between ideal combustion and lean combustion is required, the processing circuit 22 performs a process to adjust the amount of air in the mixture from the amount required for combustion before the switch to the amount required for combustion after the switch.

[0036] Furthermore, in this embodiment, the processing circuit 22 is implemented for processing during combustion switching. Figure 2 The combustion switching routine is described below. First, we will explain the case of switching between lean combustion and ideal combustion without implementing this routine.

[0037] Figure 3 The control mode of the hydrogen engine 10 is shown when switching from ideal combustion to lean combustion is performed without implementing the combustion switching routine. Figure 3 Part (a) indicates the shift in combustion requirements. Figure 3 Part (b) represents the shifts in the target air volume M* and the actual air volume M. Figure 3 Part (c) represents the shift in fuel injection quantity. Additionally, Figure 3 The portion (d) represents the shift in the excess air ratio of the mixture. Figure 3 The part (e) represents the shift in engine torque. Figure 3 The part (f) indicates the shift in ignition timing. Combustion requirement indicates whether the combustion of the hydrogen engine 10 required by the processing circuit 22 is ideal combustion or lean combustion. Excess air ratio indicates the ratio of the air-fuel ratio to the stoichiometric air-fuel ratio. Furthermore, in... Figure 3 And then Figure 4 , Figure 5 During the period shown in the figure, it is required that the torque TE* and engine speed NE remain constant.

[0038] exist Figure 3 In this case, at time t1, a switch from ideal air-fuel ratio combustion to lean combustion is required. Accordingly, processing circuit 22 changes the value of the target air quantity M* from the value for ideal air-fuel ratio combustion to the value for lean combustion. Then, processing circuit 22 begins adjusting the air quantity from time t1. There is a significant difference between the target air-fuel ratio in ideal air-fuel ratio combustion and lean combustion, requiring a substantial adjustment of the air quantity. Figure 3 In this case, the air volume adjustment is completed at the subsequent time t2.

[0039] Here, we consider controlling the fuel injection quantity during the air quantity adjustment period from time t1 to time t2 in a manner that generates engine torque corresponding to the required torque TE*. Figure 3 In sections (c) to (e), the shifts in fuel injection quantity, excess air ratio, and engine torque under this condition are represented by solid lines. Figure 3 In this case, the torque TE* is required to be constant, so the engine torque remains constant. On the other hand, when the air-fuel ratio is changed from the stoichiometric air-fuel ratio to the lean side, the combustion efficiency increases. Therefore, the amount of fuel injection required to generate the engine torque corresponding to the required torque TE* decreases as the actual air volume M increases. Furthermore, the air-fuel ratio of the mixture burned in the combustion chamber 11 changes towards the lean side as the actual air volume M increases. Therefore, as the actual air volume M increases, the excess air ratio of the mixture also increases.

[0040] As described above, when combustion occurs near the stoichiometric air-fuel ratio, the three-way catalytic converter 20 effectively purifies NOx from the exhaust gas. On the other hand, when the air-fuel ratio of the mixture burned in the combustion chamber 11 is changed from the stoichiometric air-fuel ratio towards the lean side, the amount of NOx generated through combustion gradually decreases. Furthermore, when the air-fuel ratio becomes leaner than a certain degree, the amount of NOx emitted is reduced to an acceptable range. Figure 3 The excess air ratio value "LM" shown in section (d) represents the excess air ratio at which the air-fuel ratio is leaned to a level where NOx emissions are within an acceptable range. Therefore, when the excess air ratio of the mixture burned in combustion chamber 11 is in either the range of "1" or above "LM", NOx emissions into the external environment can be suppressed. Figure 3 In section (d), conversely, the range of values ​​for the excess air rate that cannot adequately suppress NOx emissions is indicated by shading. For example... Figure 3 As shown by the solid line in region (d), when the fuel injection quantity is controlled in a manner that generates engine torque corresponding to the required torque TE*, the value of the excess air ratio varies through the range indicated by the shaded area. Therefore, in this case, an amount of NOx exceeding the permissible level may be emitted into the ambient air during combustion switching.

[0041] The increase in NOx emissions during such combustion switching can be suppressed by controlling the fuel injection quantity in a manner that maintains the air-fuel ratio of the mixture burning in combustion chamber 11 at the stoichiometric air-fuel ratio until the air volume adjustment is complete. Figure 3 Part (c) and Figure 3 In section (d), the shifts in fuel injection quantity and excess air ratio under this condition are represented by double-dotted lines. For example... Figure 3 As shown by the double-dotted line in section (d), in this case, during the air quantity adjustment period from time t1 to time t2, combustion occurs with an air excess ratio of "1", i.e., combustion at the stoichiometric air-fuel ratio. Therefore, under such conditions, the increase in NOx emissions during combustion switching can be suppressed. However, in this case, as... Figure 3 As shown by the double-dotted line in section (c), the fuel injection quantity needs to increase as the actual air volume M increases. Furthermore, as... Figure 3 As shown by the double-dotted line in section (e), engine torque increases along with fuel injection quantity. Therefore, in this case, excessive engine torque exceeding the required torque TE* is generated during combustion switching. If ignition timing is delayed, combustion efficiency decreases, and engine torque decreases. Therefore, consider methods such as... Figure 3 As shown by the double-dotted line in section (f), the ignition timing is delayed to offset the excess engine torque. However, in the latter half of the air volume adjustment period, the excess engine torque increases, requiring a significant delay in ignition timing to offset it. As a result, combustion becomes unstable, potentially causing torque surges in the hydrogen engine 10 due to misfires, thus degrading driving performance.

[0042] The increased NOx emissions and deteriorated driving performance during the aforementioned combustion transition can also occur when switching from lean combustion to ideal combustion. In contrast, processing circuit 22... Figure 2 In the combustion switching routine, the main injection and post-injection processes are performed from the time the combustion switching is requested until the air volume adjustment is completed (S140). Additionally, in the combustion switching routine, the processing circuit 22 calculates the amount of fuel injection required to generate the engine torque corresponding to the required torque TE* as the value of the main injection quantity Qm (S120). Furthermore, in the combustion switching routine, the processing circuit 22 calculates the value of the post-injection quantity Qp by dividing the total injection quantity Q of the main injection and post-injection by the actual air volume M in the combustion chamber 11 and the stoichiometric air-fuel ratio (S110, S130).

[0043] Figure 4The control mode of the hydrogen engine 10 is shown when a combustion switching routine is implemented to switch from ideal combustion to lean combustion. Figure 4 Part (a) indicates the shift in combustion requirements. Figure 4 Part (b) represents the shifts in the target air volume M* and the actual air volume M. Figure 4 Part (c) represents the shift in total injection quantity Q and main injection quantity Qm. Additionally, Figure 4 The part (d) represents the shift of the excess air ratios λm and λe in the mixture and exhaust gas. Figure 4 The part (e) represents the shift in engine torque. Figure 4 The part (f) represents the shift in ignition timing. The excess air ratio λm of the air-fuel mixture represents the excess air ratio of the mixture relative to the fuel that contributes to generating engine torque. Specifically, the excess air ratio λm of the air-fuel mixture is the value obtained by dividing the actual air volume M by the main injection quantity Qm (=M / Qm) and further dividing by the stoichiometric air-fuel ratio. On the other hand, the excess air ratio λe of the exhaust gas represents the excess air ratio relative to the total amount of fuel injected into the combustion chamber 11. Specifically, the excess air ratio λe of the exhaust gas is the value obtained by dividing the actual air volume M by the total injection quantity Q (=M / Q) and further dividing by the stoichiometric air-fuel ratio.

[0044] exist Figure 4 In this case, a switch from ideal combustion to lean combustion is required at time t1. Furthermore, during the period from time t1 to time t2, the amount of air used for combustion switching is adjusted.

[0045] In this embodiment, during the adjustment of air volume, the processing circuit 22 performs fuel injection in a manner that separates the main injection and the post-injection. Figure 4 In (c), the difference between the total injection quantity Q (shown by the solid line) and the main injection quantity Qm (shown by the dashed line) corresponds to the subsequent injection quantity Qp. Furthermore, fuel injection before and after the start of air volume adjustment is all performed within the main injection. Therefore, the total injection quantity Q before time t1 and after time t2 is consistent with the main injection quantity Qm, and the subsequent injection quantity Qp is "0".

[0046] exist Figure 2 In the combustion switching routine, the processing circuit 22 calculates the amount of fuel required to generate engine torque corresponding to the required torque TE* relative to the actual air volume M as the value of the main injection quantity Qm. In contrast, post-injection contributes almost nothing to the generation of engine torque. Therefore, in the case of this embodiment, as... Figure 4 As shown in section (e), excessive engine torque exceeding the required torque TE* will not be generated during the air volume adjustment period. Therefore, the generation of excessive engine torque can be suppressed even without ignition timing retardation.

[0047] On the other hand, the fuel injected in the post-injection phase does not contribute to engine torque generation, but it burns before flowing into the three-way catalytic converter 20. Then, the processing circuit 22 calculates the post-injection quantity Qp in such a way that the ratio of the total injection quantity Q to the actual air quantity M equals the stoichiometric air-fuel ratio. Therefore, the excess air ratio λe of the exhaust becomes "1", and the characteristics of the exhaust flowing into the three-way catalytic converter 20 are substantially the same as when combustion occurs at the stoichiometric air-fuel ratio. Therefore, in this case, the three-way catalytic converter 20 also exhibits the same high NOx purification capacity during air quantity adjustment as in ideally proportioned combustion.

[0048] Figure 5 The control mode of the hydrogen engine 10 is shown when a combustion switching routine is implemented to switch from lean combustion to ideal combustion. Figure 5 Part (a) indicates the shift in combustion requirements. Figure 5 Part (b) represents the shifts in the target air volume M* and the actual air volume M. Figure 5 Part (c) represents the shift in total injection quantity Q and main injection quantity Qm. Additionally, Figure 5 The part (d) represents the shift of the excess air ratios λm and λe in the mixture and exhaust gas. Figure 5 The part (e) represents the shift in engine torque. Figure 5 The part (f) indicates the shift in ignition timing.

[0049] exist Figure 5 In this case, at time t3, a switch from lean combustion to ideal combustion is required. Furthermore, during the period from time t3 to time t4, the amount of air used for the combustion switch is adjusted. In this case, it is also related to... Figure 4 Similarly, during the air volume adjustment period, the amount of fuel injection required to generate the engine torque corresponding to the required torque TE* is implemented as the main injection. Then, the amount of fuel injection required to make the air-fuel ratio of the exhaust flowing into the three-way catalytic converter 20 reach the stoichiometric air-fuel ratio is implemented as the post-injection. Therefore, when switching from lean combustion to ideal combustion, the increase in NOx emissions and the generation of excessive engine torque can also be suppressed.

[0050] <Effects of the Implementation Method>

[0051] As explained above, the control device of the hydrogen engine 10 in this embodiment has the effect of suppressing both the generation of torque shock during the switching between ideal combustion and lean combustion and the increase in NOx emissions.

[0052] <Other Implementation Methods>

[0053] The above-described embodiments can be implemented by modification as follows. The above-described embodiments and the following modifications can be combined with each other within the scope of technical inconsistency.

[0054] ·exist Figure 2 In step S110, the total injection quantity Q can also be calculated by dividing the actual air volume M in the combustion chamber 11 by the stoichiometric air-fuel ratio. In this case, the air-fuel ratio of the exhaust gas flowing into the three-way catalytic converter 20 during the air volume adjustment period becomes an air-fuel ratio that is richer than the stoichiometric air-fuel ratio. If the exhaust air-fuel ratio is equal to or richer than the stoichiometric air-fuel ratio, the three-way catalytic converter 20 can effectively purify NOx. Therefore, in such a case, it is also possible to suppress both the torque shock generated during the switching between ideal combustion and lean combustion and the increase in NOx emissions.

[0055] In the above embodiment, after calculating the total injection quantity Q and the main injection quantity Qm, the post-injection quantity Qp is calculated by subtracting the main injection quantity Qm from the total injection quantity Q. The post-injection quantity Qp can also be calculated using steps other than those described above, as long as the total injection quantity Q can be calculated as a value obtained by dividing the actual air volume M of the combustion chamber 11 by the stoichiometric air-fuel ratio or higher. For example, the following steps can also be performed in the same manner as in the above embodiment. That is, the main injection quantity Qm is calculated in the same order as in the above embodiment, and the value "Mm" obtained by multiplying the main injection quantity Qm by the stoichiometric air-fuel ratio is calculated. Next, Mm is subtracted from the actual air volume M, and the resulting value is used as the value of the excess air volume Me. Then, the excess air volume Me is divided by the stoichiometric air-fuel ratio, and the resulting value is used as the value of the post-injection quantity Qp.

[0056] • The combustion switching routine can also be applied only during the switch from lean combustion to ideal combustion, or during the switch from ideal combustion to lean combustion.

Claims

1. A control device for a hydrogen engine, applicable to a hydrogen engine using hydrogen as fuel, wherein, Equipped with processing circuitry, The processing circuit is configured to execute: The required value for calculating engine torque is the required torque. The combustion process switches between lean combustion and ideal combustion. Lean combustion is combustion in which the air-fuel ratio of the mixture burned in the combustion chamber is on the lean side of the stoichiometric air-fuel ratio. Ideal combustion is combustion in which the air-fuel ratio of the mixture is equal to the stoichiometric air-fuel ratio. When switching between the ideal combustion ratio and the lean combustion is required, the air volume of the mixture is adjusted from the amount required for combustion before the switch to the amount required for combustion after the switch. During the period from the switching between the desired ideal combustion ratio and the lean combustion until the adjustment of the air volume is completed, fuel injection is performed in a manner that divides the period into main injection from the intake stroke to the compression stroke and post-injection from the expansion stroke to the exhaust stroke. The amount of fuel injection required to generate engine torque corresponding to the required torque is calculated as the amount of fuel injection for the main injection. and The fuel injection amount of the post-injection is calculated in such a way that the total injection amount of the main injection and the post-injection is greater than or equal to the value obtained by dividing the actual air volume of the combustion chamber by the theoretical air-fuel ratio.

Images