JP4412201B2 - Control device for internal combustion engine using hydrogen - Google Patents

Description

  The present invention relates to a control device for a hydrogen-utilizing internal combustion engine that can be operated using non-hydrogen fuel and hydrogen as fuel.

A hydrogen-based internal combustion engine that performs a hydrogen-added lean burn operation is known (see, for example, Patent Document 1). In this hydrogen-utilized internal combustion engine, the engine warm-up operation is executed until the temperature of the internal combustion engine rises, and then the operation shifts to the hydrogen addition lean burn operation.
However, for example, when the hydrogen supply capacity is low, such as when the amount of hydrogen stored in the hydrogen tank is small, the ratio of hydrogen to non-hydrogen fuel is limited. When the engine temperature is low, if the hydrogen addition ratio is low, sufficient combustion stability cannot be obtained in the combustion chamber. In this case, in order to obtain sufficient combustion stability in the combustion chamber, it is necessary to extend the execution time of the engine warm-up operation.

JP 2004-116398 A

  However, if the execution time of the engine warm-up operation is lengthened, the transition to the hydrogen addition lean burn operation is delayed. For this reason, the whole fuel consumption will worsen. As described above, the conventional hydrogen-utilized internal combustion engine still leaves room for improvement.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a control device for a hydrogen-based internal combustion engine that can improve fuel efficiency while ensuring sufficient combustion stability. To do.

In order to achieve the above object, a first invention is a control device for a hydrogen-based internal combustion engine that can be operated using non-hydrogen fuel and hydrogen as fuel,
Non-hydrogen fuel supply means for supplying non-hydrogen fuel to the internal combustion engine;
Hydrogen supply means for supplying hydrogen to the internal combustion engine;
Hydrogen supply capacity calculation means for calculating the hydrogen supply capacity of the hydrogen supply means;
A switching condition control means for controlling a switching condition from the internal combustion engine warm-up operation by the combustion of non-hydrogen fuel to the hydrogen addition lean burn operation based on the detected hydrogen supply capacity;
The switching condition control means is characterized in that when the hydrogen supply capacity is higher than when the hydrogen supply capacity is low, the threshold value of the engine temperature, which is a switching condition, is set low.

The second invention is a control device for a hydrogen-utilizing internal combustion engine that can be operated using non-hydrogen fuel and hydrogen as fuel,
Non-hydrogen fuel supply means for supplying non-hydrogen fuel to the internal combustion engine;
Hydrogen supply means for supplying hydrogen to the internal combustion engine;
A purification catalyst for purifying exhaust gas discharged from the internal combustion engine;
Hydrogen supply capacity calculation means for calculating the hydrogen supply capacity of the hydrogen supply means;
Catalyst warm-up operation control means for controlling conditions for warm-up operation of the purification catalyst based on the hydrogen supply capacity,
The catalyst warm-up operation control means is characterized in that when the hydrogen supply capacity is higher than when the hydrogen supply capacity is low, the hydrogen addition rate is increased and the retard amount of the ignition timing is increased. To do.

  In a third aspect based on the second aspect, the catalyst warm-up operation control means is configured so that the ratio of the fuel to the intake air amount is smaller than the ratio required for stoichiometric combustion. In which hydrogen is supplied by the non-hydrogen fuel or the hydrogen supply means, and in the expansion stroke or exhaust stroke after the non-hydrogen fuel is burned in the combustion chamber, the hydrogen supply means directly supplies hydrogen into the combustion chamber It is characterized by being.

  In a fourth aspect based on the second aspect, the catalyst warm-up operation control means causes the hydrogen supply means to supply hydrogen to the intake passage when the intake valve and the exhaust valve are both opened or immediately before. It is characterized by being.

  In a fifth aspect based on the second aspect, the catalyst warm-up operation control means is configured such that, in one of the plurality of cylinders, the ratio of the fuel to the intake air amount is higher than the ratio required for stoichiometric combustion. The non-hydrogen fuel supply means supplies the non-hydrogen fuel or the hydrogen supply means with hydrogen so that the ratio of the fuel to the intake air amount is larger than the ratio required for stoichiometric combustion in the other cylinders. Thus, hydrogen is supplied by the hydrogen supply means.

  According to a sixth aspect of the present invention based on the second aspect, the catalyst warm-up operation control means is configured so that the ratio of the fuel to the intake air amount is smaller than the ratio required for stoichiometric combustion. The cycle in which hydrogen is supplied by the non-hydrogen fuel or the hydrogen supply means and the cycle in which hydrogen is supplied by the hydrogen supply means so that the ratio of the fuel to the intake air amount is larger than the ratio required for stoichiometric combustion. It is characterized by being mixed in the cylinders.

  According to the first aspect of the invention, when the hydrogen supply capability is high, it is possible to quickly switch from the internal combustion engine warm-up operation to the hydrogen addition lean burn operation, so that the fuel consumption can be improved. Moreover, even when switching to the hydrogen addition lean burn operation is performed at an early stage, sufficient combustion stability can be obtained by controlling the hydrogen supply amount.

  According to the second invention, when the hydrogen supply capacity is high, the time for the catalyst warm-up operation can be shortened by increasing the retard amount of the ignition timing. Even when the retard amount of the ignition timing is increased, sufficient combustion stability can be obtained by increasing the hydrogen addition ratio.

  According to the third invention, the temperature of the catalyst can be raised by supplying unburned oxygen and hydrogen to the catalyst and reacting them in the catalyst. Therefore, the catalyst warm-up time can be shortened, and the fuel efficiency can be improved.

  According to the fourth invention, the temperature of the catalyst can be raised by supplying oxygen and hydrogen to the catalyst and reacting them in the catalyst. Therefore, the catalyst warm-up time can be shortened, and the fuel efficiency can be improved.

  According to the fifth aspect of the present invention, unburned oxygen is supplied from one cylinder to the catalyst, and unburned hydrogen is supplied from the other cylinders to the catalyst. Can be raised. Therefore, the catalyst warm-up time can be shortened, and the fuel efficiency can be improved.

  According to the sixth aspect of the present invention, unburned oxygen is supplied to the catalyst in the first cycle, and unburned hydrogen is supplied to the catalyst in the second cycle. Can be raised. Therefore, the catalyst warm-up time can be shortened, and the fuel efficiency can be improved.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. As shown in FIG. 1, the system of the present embodiment includes an internal combustion engine 10. Although the internal combustion engine 10 described in the first embodiment has a plurality of cylinders, only one of them is shown in FIG.

  The internal combustion engine 10 includes a fuel injection valve 36 that injects gasoline as non-hydrogen fuel into the combustion chamber 11, and a hydrogen injection valve 44 that injects hydrogen into the combustion chamber 11. The fuel injection valve 36 communicates with the fuel tank 30 through the fuel passage 32. A pump 34 is provided in the middle of the fuel passage 32. The hydrogen injection valve 44 communicates with the hydrogen tank 40 via the hydrogen passage 42. The hydrogen tank 40 stores compressed hydrogen. A pressure sensor 41 for detecting the hydrogen pressure in the hydrogen tank 40 is provided in the vicinity of the connecting portion between the hydrogen tank 40 and the hydrogen passage 42.

  The internal combustion engine 10 includes a spark plug 18 for igniting the air-fuel mixture in the combustion chamber 11. In addition, the system of the first embodiment includes a cooling water temperature sensor 19 that outputs an electrical signal according to the temperature of the cooling water of the internal combustion engine 10.

  An intake passage 12 communicates with the combustion chamber 11 via an intake valve 16. A throttle valve 13 is provided in the middle of the intake passage 12. A throttle opening sensor 14 for detecting the throttle opening TA is provided in the vicinity of the throttle valve 13. An air flow meter 15 is provided upstream of the throttle valve 13 in the intake passage 12. The air flow meter 15 is configured to detect an intake air amount Ga flowing into the internal combustion engine 10.

  An exhaust passage 24 communicates with the combustion chamber 11 via an exhaust valve 20. The exhaust passage 24 is provided with a NOx catalyst (hereinafter simply referred to as “catalyst”) 26 as a purification catalyst. The catalyst 26 is provided with a catalyst temperature sensor 27 that detects the temperature of the catalyst 26. An air-fuel ratio sensor 25 that detects the exhaust air-fuel ratio is provided upstream of the catalyst 26. A NOx sensor 28 that detects the NOx concentration in the exhaust gas is provided downstream of the catalyst 26.

  The intake valve 16 and the exhaust valve 20 are driven by variable valve timing mechanisms 21 and 22, respectively. The variable valve timing mechanisms 21 and 22 are configured to be able to change the valve timing of the intake valve 16 and the exhaust valve 20.

The system shown in FIG. 1 includes an ECU (Electronic Control Unit) 50. The throttle valve 13, throttle opening sensor 14, air flow meter 15, spark plug 18, cooling water temperature sensor 19, variable valve timing mechanism 21, 22, air-fuel ratio sensor 25, NOx catalyst temperature sensor 27, NOx sensor 28, pump 34 described above. The fuel injection valve 36, the hydrogen injection valve 44, and the like are connected to the ECU 50 and controlled by the ECU 50, respectively. The ECU 50 performs overall control of the internal combustion engine 10 such as fuel injection control and ignition timing control.
Further, the ECU 50 can estimate the engine temperature based on the coolant temperature detected by the coolant temperature sensor 19.
Further, the ECU 50 can calculate the hydrogen storage amount in the hydrogen tank 40 based on the hydrogen pressure detected by the pressure sensor 41.

[Features of Embodiment 1]
Next, the operation of the system in the first embodiment will be described.
In the above system, hydrogen can be injected into the combustion chamber 11 from the hydrogen injection valve 44, and gasoline can be injected into the combustion chamber 11 from the combustion injection valve 36. Therefore, according to the above system, hydrogen addition lean burn operation can be executed in addition to the stoichiometric operation with gasoline.
After the internal combustion engine 10 is started, the temperature of the internal combustion engine 10 (hereinafter referred to as “engine temperature”) is low.
Even when the hydrogen addition lean burn operation is performed at a low engine temperature, sufficient combustion stability can be obtained by increasing the ratio of hydrogen addition to the non-hydrogen fuel. Accordingly, when the amount of hydrogen stored in the hydrogen tank 40 is large, the ratio of hydrogen addition to the non-hydrogen fuel can be increased, so that switching from engine warm-up operation to hydrogen addition lean burn operation should be performed at an early stage. Can do.
However, when the amount of hydrogen stored in the hydrogen tank 40 is small, the hydrogen addition ratio is limited to be low for the purpose of extending the travel distance of the vehicle as much as possible. In this case, as described above, if the switching to the hydrogen addition lean burn operation is performed at an early stage, sufficient combustion stability cannot be obtained, so that a sufficient fuel efficiency improvement effect cannot be obtained. Therefore, a sufficient fuel efficiency improvement effect can be obtained by executing the engine warm-up operation by the stoichiometric combustion of gasoline until the engine temperature rises and then switching to the hydrogen addition lean burn operation.

Therefore, in the first embodiment, when the hydrogen storage amount in the hydrogen tank 40 is large (that is, when the hydrogen supply capacity is high), the engine warm-up operation is shifted to the hydrogen addition lean burn operation at an early stage. In this case, sufficient combustion stability can be ensured by increasing the hydrogen addition ratio.
On the other hand, when the amount of hydrogen stored in the hydrogen tank 40 is small (that is, when the hydrogen supply capacity is low), after the engine temperature has sufficiently increased, the engine warm-up operation is switched to the hydrogen addition lean burn operation. In this case, even if the hydrogenation rate is low, sufficient combustion stability is obtained because the engine temperature is high.

[Specific Processing in Embodiment 1]
FIG. 2 is a flowchart of a routine executed by ECU 50 in the first embodiment. According to the routine shown in FIG. 2, after the internal combustion engine 10 is started, the ECU 50 first calculates the amount of hydrogen stored in the hydrogen tank 40 (step 100).

  Next, it is determined whether or not the calculated hydrogen storage amount is larger than a predetermined value (step 102). If it is determined in step 102 that the hydrogen storage amount is larger than the predetermined value, it is determined that the hydrogen supply capacity is high. On the other hand, when it is determined that the hydrogen storage amount is equal to or less than the predetermined value, it is determined that the hydrogen supply capacity is low. As described below, in this routine, the switching condition from the engine warm-up operation to the hydrogen addition lean burn operation is controlled in accordance with the hydrogen supply capability.

(When hydrogen supply capacity is high)
If it is determined in step 102 that the hydrogen storage amount is larger than the predetermined value, it is determined whether or not the cooling water temperature is 30 ° C. or higher (step 104). If it is determined in step 104 that the cooling water temperature is 30 ° C. or higher, it is determined that sufficient combustion stability can be obtained by increasing the hydrogen addition ratio even when the hydrogen addition lean burn operation is started. The In this case, the ECU 50 permits switching from the engine warm-up operation to the hydrogen addition lean burn operation (step 106).
On the other hand, if it is determined in step 104 that the cooling water temperature is lower than 30 ° C., it is determined that sufficient combustion stability cannot be obtained even if the hydrogen addition ratio is increased. In this case, the ECU 50 prohibits switching from the engine warm-up operation to the hydrogen addition lean burn operation (step 110), and continuously executes the engine warm-up operation by the stoichiometric combustion of gasoline (step 112).

(When hydrogen supply capacity is low)
When it is determined in step 102 that the hydrogen storage amount is not more than a predetermined value, it is determined whether or not the cooling water temperature is 60 ° C. or more (step 108). If it is determined in step 108 that the cooling water temperature is 60 ° C. or higher, it is determined that sufficient combustion stability can be obtained at a low hydrogen addition ratio even when the hydrogen addition lean burn operation is started. In this case, the ECU 50 permits switching from the engine warm-up operation to the hydrogen addition lean burn operation (step 106).
On the other hand, if it is determined in step 108 that the coolant temperature is lower than 60 ° C., the ECU 50 prohibits switching from the engine warm-up operation to the hydrogen addition lean burn operation (step 110), and the engine warm-up due to the stoichiometric combustion of gasoline. The machine operation is continuously executed (step 112).

As described above, according to the routine shown in FIG. 2, the switching condition from the engine warm-up operation to the hydrogen addition lean burn operation is controlled according to the hydrogen supply capacity represented by the hydrogen storage amount. Specifically, the cooling water temperature permitting switching to the hydrogen addition lean burn operation was set to 30 ° C. or higher when the hydrogen supply capability was high, and was set to 60 ° C. when the hydrogen supply capability was low. Therefore, when the hydrogen supply capacity is high, the switching to the hydrogen addition lean burn operation can be performed at an early stage, and the fuel efficiency can be improved. Even when switching to the hydrogen addition lean burn operation is executed at an early stage, sufficient combustion stability can be obtained by increasing the hydrogen addition ratio.
Further, when the hydrogen supply capability is low, the engine temperature is further increased by delaying the switching to the hydrogen addition lean burn operation, so that sufficient combustion stability can be obtained even if the hydrogen addition ratio is low.

  In the first embodiment, the system for directly injecting gasoline and hydrogen into the combustion chamber 11 has been described. However, a system for injecting gasoline and hydrogen into the intake port of the intake passage 12 may be used. Further, a system capable of port injection and in-cylinder injection of gasoline may be used. Also in this case, the same effect as in the first embodiment can be obtained.

  In the first embodiment, the system for supplying hydrogen from the hydrogen tank 40 has been described. However, a system for generating hydrogen by performing a reforming reaction or a dehydrogenation reaction of fuel on a vehicle may be used. In this case, the ECU 50 can calculate the hydrogen supply capacity based on the hydrogen generation amount.

In the first embodiment, the system for switching to the hydrogen addition lean burn operation based on the cooling water temperature has been described. However, a system for switching based on the temperature of engine oil or transmission oil may be used. .
Moreover, the threshold value (30 degreeC, 60 degreeC) of the cooling water temperature demonstrated in this Embodiment 1 is an example, and is not limited to this temperature.

  In the first embodiment, the ECU 50 executes the process of step 100, so that the “hydrogen supply capacity calculating means” in the first invention executes the processes of steps 102, 104, and 108. The “switching condition control means” in the first and second inventions is realized.

Embodiment 2. FIG.
The system of the second embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 3 to be described later using the system shown in FIG.

[Features of Embodiment 2]
In the first embodiment, the engine warm-up control based on the hydrogen supply capacity has been described. In the second embodiment, the catalyst warm-up control based on the hydrogen supply capability will be described.
When the temperature of the catalyst 26 decreases when the internal combustion engine 10 is started or during vehicle operation, it is necessary to warm up the catalyst 26 in order to activate the catalyst 26. The catalyst 26 can be warmed up by increasing the temperature of the exhaust gas discharged from the internal combustion engine 10.
As an example of control for increasing the temperature of the exhaust gas, control for delaying the ignition timing of the spark plug 18 can be considered. According to this control, it is possible to reduce the energy used for piston motion among the thermal energy obtained by combustion, so that the temperature of the exhaust gas can be raised. However, as the retard amount of the ignition timing is increased, the temperature of the exhaust gas can be further increased, but the combustion stability is lowered.

By the way, the combustion stability can be improved by increasing the ratio of hydrogen added to gasoline, which is a non-hydrogen fuel. Therefore, when the amount of hydrogen stored in the hydrogen tank 40 is large, the proportion of hydrogen added to the non-hydrogen fuel can be increased, so that the ignition timing can be greatly retarded. Thereby, since the temperature of exhaust gas can be raised more, since catalyst warm-up can be terminated at an early stage, fuel efficiency can be improved.
On the other hand, when the amount of hydrogen stored in the hydrogen tank 40 is small, the hydrogen addition ratio is limited to be low for the purpose of extending the travel distance of the vehicle as much as possible. In this case, as described above, if the ignition timing is significantly retarded, sufficient combustion stability cannot be obtained.

Therefore, in the second embodiment, when the hydrogen storage amount in the hydrogen tank 40 is large, the temperature of the exhaust gas is further increased by significantly retarding the ignition timing. In this case, sufficient combustion stability can be ensured by increasing the hydrogen addition ratio. As a result, the catalyst warm-up can be terminated early and the operation can be switched to the normal hydrogenation lean burn operation, so that the fuel efficiency can be improved.
On the other hand, when the hydrogen storage amount in the hydrogen tank 40 is small, the retard amount of the ignition timing can be reduced. In this case, sufficient combustion stability can be obtained even if the hydrogenation rate is low.

[Specific Processing in Second Embodiment]
FIG. 3 is a flowchart of a routine executed by the ECU 50 in the second embodiment. According to the routine shown in FIG. 3, the ECU 50 first determines whether or not the temperature of the catalyst 26 (hereinafter referred to as “catalyst bed temperature”) is smaller than a predetermined value (step 120). If it is determined in step 120 that the catalyst bed temperature is equal to or higher than the predetermined value, the catalyst warm-up is unnecessary, and thus the process is terminated. On the other hand, when it is determined that the catalyst bed temperature is lower than the predetermined value, it is determined whether or not the hydrogen storage amount in the hydrogen tank 40 is larger than the predetermined value (step 122).
If it is determined in step 122 that the hydrogen storage amount is greater than the predetermined value, it is determined that the hydrogen supply capacity is high. On the other hand, when it is determined that the hydrogen storage amount is equal to or less than the predetermined value, it is determined that the hydrogen supply capacity is low. As will be described below, in this routine, the conditions for the catalyst warm-up operation, specifically, the hydrogen addition ratio, the ignition timing retardation amount, and the warm-up time are controlled according to the hydrogen supply capacity.

When the hydrogen supply capacity is high, a high hydrogen addition ratio is calculated (step 124), a large ignition timing retardation amount is calculated (step 126), and a short warm-up control time is calculated (step 128).
On the other hand, when the hydrogen supply capacity is high, a low hydrogen addition ratio is calculated (step 134), a small ignition timing retard amount is calculated (step 136), and a long warm-up control time is calculated (step 138). .

  Thereafter, the catalyst warm-up operation is executed with the calculated hydrogen addition ratio, ignition timing retardation amount, and warm-up control time (step 130). Thereafter, the catalyst warm-up operation is executed until it is determined in step 132 that the warm-up control time has elapsed.

  When this routine is started after the next time, the catalyst warm-up operation is executed until the catalyst bed temperature becomes equal to or higher than a predetermined value.

As described above, according to the routine shown in FIG. 3, the conditions for the catalyst warm-up operation are controlled according to the hydrogen supply capacity. Specifically, when the hydrogen supply capability is high, the hydrogen addition rate is increased and the ignition timing is significantly retarded compared to when the hydrogen supply capability is low. Thereby, when hydrogen supply capability is high, the temperature of exhaust gas can be raised more. That is, since more heat energy can contribute to catalyst warm-up, catalyst warm-up can be terminated early. Therefore, since it can switch to high fuel consumption driving | operation like hydrogen addition lean burn driving | operation early, a fuel consumption can be improved.
Further, when the hydrogen supply capability is low, sufficient combustion stability can be ensured by reducing the retard amount of the ignition timing.

  In the second embodiment, the ECU 50 executes the processing of steps 122, 124, 126, 128 or steps 122, 134, 136, 138, whereby the “catalyst warm-up control” in the third invention is performed. By executing the processing of steps 124 and 126, the “catalyst warm-up control means” in the fourth invention is realized.

Embodiment 3 FIG.
The system of the third embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 4 to be described later using the system shown in FIG.

[Features of Embodiment 3]
In the second embodiment, the hydrogen storage amount in the hydrogen tank 40 is divided into two cases depending on whether or not the hydrogen storage amount is larger than a predetermined value. In each of the two cases, the hydrogen addition amount, the ignition timing retardation amount, and the warm-up control are performed. The time was set.
In the third embodiment, the hydrogen addition amount corresponding to the hydrogen storage amount is calculated with reference to the map, and the ignition timing retardation amount and the execution time corresponding to the calculated hydrogen addition amount are calculated. Thereby, since catalyst warm-up control can be performed with high accuracy, fuel efficiency can be further improved as compared with the second embodiment.

[Specific Processing in Embodiment 3]
FIG. 4 is a flowchart of a routine executed by the ECU 50 in the third embodiment. According to the routine shown in FIG. 4, as in the second embodiment, the ECU 50 first determines whether or not the catalyst bed temperature is lower than a predetermined value (step 120). If it is determined in step 120 that the catalyst bed temperature is lower than the predetermined value, the amount of hydrogen stored in the hydrogen tank 40 is calculated (step 140).

  Next, the hydrogen addition ratio at the time of catalyst warm-up is calculated with reference to the map shown in FIG. 5 (step 142). FIG. 5 is a diagram showing an example of a map stored in the ECU 50 for calculating the hydrogen addition ratio. In the map, the hydrogen addition ratio is determined in accordance with the hydrogen storage amount, and is further determined in relation to the catalyst bed temperature. More specifically, in the map shown in FIG. 5, the hydrogen addition rate is set higher as the hydrogen storage amount is larger.

  Subsequently, with reference to the map shown in FIG. 6, the ignition timing retardation amount at the time of catalyst warm-up is calculated (step 144). FIG. 6 is a diagram showing an example of a map stored in the ECU 50 for calculating the ignition timing retardation amount. In this map, the ignition timing retardation amount is determined in relation to the hydrogen addition ratio. More specifically, the map shown in FIG. 6 is set so that the ignition timing retardation amount increases as the hydrogen addition ratio increases.

  Thereafter, referring to the map shown in FIG. 7, the catalyst warm-up control execution time is calculated (step 146). FIG. 7 is a diagram illustrating an example of a map stored in the ECU 50 in order to calculate the execution time of the catalyst warm-up control. In this map, the execution time of the catalyst warm-up control is determined in relation to the hydrogen addition rate. More specifically, the map shown in FIG. 7 is set such that the higher the hydrogen addition rate, the shorter the execution time.

  Thereafter, the catalyst warm-up operation is executed with the calculated hydrogen addition ratio, ignition timing retardation amount, and warm-up control time (step 130). Thereafter, the catalyst warm-up operation is executed until it is determined in step 132 that the warm-up control time has elapsed.

  When this routine is started after the next time, the catalyst warm-up operation is executed until the catalyst bed temperature becomes equal to or higher than a predetermined value.

  As described above, according to the routine shown in FIG. 4, the hydrogen addition ratio corresponding to the hydrogen storage amount is calculated with reference to the map, and the ignition timing retard amount and control corresponding to the calculated hydrogen addition ratio are calculated. The execution time was calculated. Therefore, compared with the second embodiment, the catalyst warm-up control can be executed with higher accuracy, and the fuel consumption can be further improved.

  In the third embodiment, the ECU 50 executes the processes of steps 140, 142, 144, and 146, whereby the “catalyst warm-up control” in the third invention executes the processes of steps 142 and 144. Thus, the “catalyst warm-up control means” according to the fourth aspect of the present invention is realized.

Embodiment 4 FIG.
The system of the fourth embodiment can be realized by causing the ECU 50 to execute a routine shown in FIG. 8 to be described later using the system shown in FIG.

[Features of Embodiment 4]
In the second and third embodiments, the control for increasing the exhaust gas temperature by retarding the ignition timing and, as a result, increasing the catalyst bed temperature has been described.
As another control for increasing the catalyst bed temperature, a control for causing an exothermic reaction between oxygen and hydrogen in the catalyst 26 can be considered. However, this control is preferably performed when the hydrogen supply capacity is high because the amount of hydrogen consumption is large. This control will be specifically described. First, lean combustion is performed by controlling the throttle opening TA and the fuel injection amount. Thereby, during the exhaust stroke, oxygen that has not been burned in the combustion chamber 11 (hereinafter referred to as “unburned oxygen”) is supplied to the catalyst 26 via the exhaust passage 24. Further, during this exhaust stroke, an amount of hydrogen that reacts with unburned oxygen is directly injected into the combustion chamber 11 from the hydrogen injection valve 44. The in-cylinder injected hydrogen is not burned in the combustion chamber 11 and is supplied to the catalyst 26. As the unburned oxygen and hydrogen react in the catalyst 26, the catalyst bed temperature rises.

[Specific Processing in Embodiment 4]
FIG. 8 is a flowchart of a routine executed by the ECU 50 in the fourth embodiment. According to the routine shown in FIG. 8, the ECU 50 first determines whether or not the catalyst bed temperature is larger than t1 and smaller than t2 (step 150). t1 is the lowest catalyst bed temperature at which hydrogen and oxygen can react, and t2 is the lowest catalyst bed temperature at which the purification capacity of the catalyst 26 falls within an allowable range. If it is in this temperature range, it is judged that the catalyst bed temperature raising control by the reaction of unburned oxygen and hydrogen should be executed.
When it is determined in step 150 that the catalyst bed temperature is larger than t1 and smaller than t2, it is determined whether or not the hydrogen storage amount is larger than a predetermined value (step 152). When it is determined that the hydrogen storage amount is equal to or less than the predetermined value, that is, when it is determined that the hydrogen supply capacity is low, this control is stopped in order to suppress further consumption of hydrogen.

When it is determined that the hydrogen storage amount is larger than the predetermined value, that is, when it is determined that the hydrogen supply capacity is high, the throttle opening degree TA and the fuel amount are calculated so as to achieve lean combustion (step 154). ). Specifically, the required load and the target air-fuel ratio are determined from the accelerator opening and the engine speed, the intake air amount and the fuel amount are determined from the required load and the target air-fuel ratio, and the throttle opening is determined from the intake air amount. . The fuel may be either gasoline or hydrogen. Further, the ECU can detect the accelerator opening based on a detection signal from an accelerator opening sensor (not shown), and can calculate the engine speed based on a detection signal from a crank angle sensor (not shown).
Thereafter, the amount of unburned oxygen per cylinder is calculated (step 156), and the amount of hydrogen supplied to react with the calculated amount of unburned oxygen is calculated (step 158). Further, the valve opening time of the hydrogen injector 44 corresponding to the calculated hydrogen supply amount is calculated (step 160).

Then, during the exhaust stroke after the lean combustion, the hydrogen injection valve 44 is controlled to open for the calculated valve opening time, whereby hydrogen is directly injected into the combustion chamber 11 (step 162).
From the next time, when this routine is started, the temperature control of the catalyst bed temperature by the reaction of unburned oxygen and hydrogen is executed until the catalyst bed temperature becomes t2 or more.

  As described above, according to the routine shown in FIG. 8, when the hydrogen supply capability is high, unburned oxygen and hydrogen are supplied to the catalyst 26, and they are exothermicly reacted on the catalyst 26. The bed temperature was raised. The catalyst bed temperature can be raised in a shorter time than the control for raising the temperature of the exhaust gas described in the second and third embodiments. Therefore, the catalyst warm-up can be terminated early, and the fuel consumption can be improved because it can be switched to a high fuel efficiency operation such as a hydrogen addition lean burn operation at an early stage.

Of the plurality of cylinders of the internal combustion engine 10, unburned oxygen is supplied to the catalyst 26 by performing lean combustion with gasoline or hydrogen in some cylinders, and rich combustion with hydrogen is performed in other cylinders. Thus, unburned hydrogen may be supplied to the catalyst 26. Also in this case, since oxygen and hydrogen can be reacted on the catalyst 26, the same effect as in the fourth embodiment can be obtained.
Further, in one cylinder, a first cycle in which unburned oxygen is supplied to the catalyst 26 by performing lean combustion with gasoline or hydrogen, and a second cycle in which unburned hydrogen is supplied to the catalyst 26 by performing rich combustion with hydrogen. Cycles may be mixed (switched every one to several cycles). Also in this case, since oxygen and hydrogen can be reacted on the catalyst 26, the same effect as in the fourth embodiment can be obtained.

Embodiment 5 FIG.
In the fifth embodiment, in the system shown in FIG. 1, a hydrogen port injection valve that injects hydrogen into the intake port of the intake passage 12 is provided instead of the hydrogen injection valve 44 that directly injects hydrogen into the combustion chamber 11. Use system (not shown). By using this system and causing ECU 50 to execute a routine shown in FIG. 9 described later, the system of the fifth embodiment can be realized.
Also in the fifth embodiment, as in the fourth embodiment, when the hydrogen supply capacity is high, control is performed to raise the catalyst bed temperature by causing the unburned oxygen and hydrogen to undergo an exothermic reaction in the catalyst 26. .
It is assumed that the control of the fifth embodiment is performed immediately after the engine is started, in which both the negative pressure in the intake passage 12 and the pressure in the exhaust passage 24 are small. In this case, gas can flow from the intake passage 12 to the exhaust passage 24 during the valve overlap period.

[Specific Processing in Embodiment 5]
FIG. 9 is a flowchart of a routine executed by the ECU 50 in the fifth embodiment. According to the routine shown in FIG. 9, the same control as in the fourth embodiment is performed until the hydrogen supply amount is calculated in step 158.

Thereafter, the opening time of the hydrogen port injector corresponding to the calculated hydrogen supply amount is calculated (step 164).
Next, by changing the valve opening / closing timing by the variable valve mechanisms 21, 22, the time during which both the intake valve 16 and the exhaust valve 20 are open (valve overlap period) is expanded (step 166).

Then, during or just before the valve overlap period after lean combustion, the hydrogen port injection valve is controlled to open for the calculated valve opening time, thereby injecting hydrogen into the intake port. The hydrogen injected into the intake port is supplied to the catalyst 26 via the exhaust passage 24 without burning in the combustion chamber 11. In the catalyst 26, the catalyst bed temperature rises due to an exothermic reaction between hydrogen and unburned oxygen.
From the next time, when this routine is started, the temperature control of the catalyst bed temperature by the reaction of unburned oxygen and hydrogen is executed until the catalyst bed temperature becomes t2 or more.

  As described above, according to the routine shown in FIG. 9, as in the fourth embodiment, when the hydrogen supply capability is high, unburned oxygen and hydrogen are supplied to the catalyst 26, and they are supplied to the catalyst 26. The catalyst bed temperature was raised by exothermic reaction at. Therefore, the same effect as in the fourth embodiment can be obtained.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a flowchart of the routine which ECU50 performs in Embodiment 1 of this invention. It is a flowchart of the routine which ECU50 performs in Embodiment 2 of this invention. It is a flowchart of the routine which ECU50 performs in Embodiment 3 of this invention. It is a figure which shows an example of the map which ECU50 has memorize | stored in order to calculate a hydrogen addition ratio. FIG. 6 is a diagram showing an example of a map stored in the ECU 50 for calculating the ignition timing retardation amount. It is a figure which shows an example of the map which ECU50 has memorize | stored in order to calculate the execution time of catalyst warm-up control. It is a flowchart of the routine which ECU50 performs in Embodiment 4 of this invention. It is a flowchart of the routine which ECU50 performs in Embodiment 5 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 11 Combustion chamber 12 Intake passage 13 Throttle valve 14 Throttle opening sensor 16 Intake valve 18 Spark plug 19 Cooling water temperature sensor 20 Exhaust valve 21, 22 Variable valve mechanism 24 Exhaust passage 26 NOx catalyst 27 Catalyst temperature sensor 30 Fuel tank 36 Combustion Injection Valve 40 Hydrogen Tank 41 Pressure Sensor 44 Hydrogen Injection Valve 50 ECU

Claims (1)

A control device for a hydrogen-based internal combustion engine that can be operated using non-hydrogen fuel and hydrogen as fuel,
Non-hydrogen fuel supply means for supplying non-hydrogen fuel to the internal combustion engine;
Hydrogen supply means for supplying hydrogen to the internal combustion engine;
Hydrogen supply capacity calculation means for calculating the hydrogen supply capacity of the hydrogen supply means;
When the engine temperature is lower than a predetermined threshold value, the internal combustion engine warm-up operation is performed by combustion of non-hydrogen fuel, and when the engine temperature becomes equal to or higher than the threshold value, the internal combustion engine warm-up operation is changed to the hydrogen addition lean burn operation. And means for switching operation,
The hydrogen when the higher the hydrogen supply capability as compared with when the supply capability is low, the control unit of the hydrogen utilization internal combustion engine, characterized in that it comprises means for setting low said threshold.

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