JP2017155662A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise a temperature of an exhaust purification catalyst while suppressing the deterioration of fuel economy, in a control device of an internal combustion engine having a hydrogen fuel injection valve and a gasoline injection valve.SOLUTION: This control device of an internal combustion engine having an exhaust purification catalyst, a hydrogen injection valve and a gasoline injection valve comprises operation control means for selectively performing hydrogen drive or gasoline drive, and when the hydrogen drive is performed by the operation control means, and a temperature of the catalyst is lower than an activation temperature, and also when the gasoline drive is not performed until now after engine start of the internal combustion engine, normal hydrogen drive for controlling an air-fuel ratio of an air-fuel mixture to a prescribed lean air-fuel ratio which is higher than a theoretical air-fuel ratio is performed.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a control device for an internal combustion engine.

  2. Description of the Related Art A bi-fuel internal combustion engine that uses hydrogen as a primary fuel and gasoline as a secondary fuel and burns these fuels is known. Patent Document 1 discloses a technique for changing the fuel burned in the combustion chamber of the internal combustion engine in accordance with the engine load in such a bi-fuel internal combustion engine. In this technique, when the engine load is low, the air-fuel ratio of the mixture of hydrogen and intake air of the internal combustion engine is set to a lean air-fuel ratio higher than the stoichiometric air-fuel ratio, and the air-fuel mixture is burned in the combustion chamber. On the other hand, when the engine load is higher than the medium load, an air-fuel mixture of hydrogen, gasoline, and intake air of the internal combustion engine is burned in the combustion chamber.

  Patent Document 2 discloses a technique for raising the temperature of an exhaust purification catalyst at the time of starting the engine in a hydrogen internal combustion engine using hydrogen as a fuel. In this technique, the air-fuel ratio of the mixture of hydrogen and intake air of the internal combustion engine is set to a rich air-fuel ratio lower than the stoichiometric air-fuel ratio, and the mixture is burned in the combustion chamber. As a result, the exhaust temperature rises and the exhaust purification catalyst rises in temperature.

Special table 2013-528260 gazette JP 2007-056700 A JP 2006-242076 A

  According to the prior art, in an internal combustion engine using hydrogen and gasoline as fuel, when the engine load is low, the air-fuel ratio of the mixture of hydrogen and intake air of the internal combustion engine is set to a lean air-fuel ratio higher than the stoichiometric air-fuel ratio. The air-fuel mixture is combusted in the combustion chamber at the fuel ratio so that the amount of NOx discharged from the internal combustion engine becomes substantially zero. When the engine load is high in the internal combustion engine, gasoline is burned together with hydrogen in the combustion chamber. At this time, it is necessary to purify the combustion products generated by the combustion of the gasoline with an exhaust purification catalyst. Further, in order to reduce emissions at the time of engine start of the internal combustion engine, the air-fuel ratio of the mixture of fuel and intake air of the internal combustion engine is set to a rich air-fuel ratio lower than the theoretical air-fuel ratio, and the air-fuel mixture is burned in the combustion chamber, The temperature of the exhaust purification catalyst is raised, but in this case, the fuel efficiency is generally deteriorated. In an internal combustion engine using hydrogen and gasoline as fuels, there is still room for improvement in the method for controlling the temperature increase of the exhaust purification catalyst and the suppression of deterioration of fuel consumption.

  An object of the present invention is to increase the temperature of an exhaust purification catalyst while suppressing deterioration of fuel consumption in a control device for an internal combustion engine provided with a hydrogen fuel injection valve and a gasoline injection valve.

In order to solve the above problems, an internal combustion engine control apparatus according to the present invention includes an exhaust purification catalyst provided in an exhaust passage of an internal combustion engine, a first injection valve capable of injecting hydrogen fuel, and a first engine capable of injecting gasoline. A control device for the internal combustion engine having two injection valves, wherein the hydrogen fuel injected by the first injection valve and the intake air sucked by the internal combustion engine according to the operating state of the internal combustion engine An operation control means for selectively executing a first operation for burning an air-fuel mixture or a second operation for burning an air-fuel mixture of the gasoline injected by the second injection valve and the intake air taken in by the internal combustion engine; A normal hydrogen operation means for performing a normal hydrogen operation in which the air-fuel ratio of the mixture of the hydrogen fuel and the intake air is controlled to a predetermined lean air-fuel ratio higher than the stoichiometric air-fuel ratio in the first operation; For driving And a catalyst temperature increase hydrogen operation means for performing a catalyst temperature increase hydrogen operation in which the air fuel ratio of the mixture of the hydrogen fuel and the intake air is controlled to a rich air fuel ratio rather than the predetermined lean air fuel ratio, In the case where the first operation is executed by the operation control means and the temperature of the exhaust purification catalyst is lower than the activation temperature of the exhaust purification catalyst, from the start of the internal combustion engine to the present When the second operation is performed by the operation control means, the catalyst temperature increase hydrogen operation is performed by the catalyst temperature increase hydrogen operation means, and the operation control means is from the start of the internal combustion engine to the present. When the second operation is not performed by the above, the normal hydrogen operation is performed by the normal hydrogen operation means.

  ADVANTAGE OF THE INVENTION According to this invention, in the control apparatus of the internal combustion engine provided with the hydrogen fuel injection valve and the gasoline injection valve, it is possible to raise the temperature of the exhaust purification catalyst while suppressing the deterioration of fuel consumption.

It is a figure which shows schematic structure of the internal combustion engine which concerns on the Example of this invention, and its intake / exhaust system. It is a figure which shows the operation control map of the internal combustion engine which concerns on the Example of this invention. It is a figure which shows the correlation of the exhaust temperature with respect to the excess air ratio in the hydrogen operation which concerns on the Example of this invention, NOx discharge | emission amount, and thermal efficiency. It is a figure which shows the correlation of the exhaust temperature with respect to the excess air ratio in hydrogen operation, NOx discharge | emission amount, and thermal efficiency for demonstrating the comparison with normal hydrogen operation and catalyst temperature rising hydrogen operation. It is a flowchart which shows the catalyst temperature rising control flow which concerns on the Example of this invention.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the present embodiment are not intended to limit the technical scope of the invention to those unless otherwise specified.

(Outline configuration)
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine and its intake / exhaust system according to the present embodiment. An internal combustion engine 1 shown in FIG. 1 is a spark ignition type internal combustion engine having four cylinders 2.

  The internal combustion engine 1 includes a hydrogen fuel injection valve 3 that injects hydrogen fuel into each intake port. Each cylinder 2 is provided with a gasoline injection valve 4 that directly injects gasoline into the cylinder 2. Each cylinder 2 is provided with a spark plug 5 for igniting the air-fuel mixture in the cylinder. In this embodiment, the hydrogen fuel injection valve 3 corresponds to the first injection valve in the present invention, and the gasoline injection valve 4 corresponds to the second injection valve in the present invention.

  The internal combustion engine 1 is connected to the intake passage 6. A compressor 9 a of a turbocharger 9 is installed in the intake passage 6. The internal combustion engine 1 is connected to the exhaust passage 7. A turbine 9 b of a turbocharger 9 is installed in the exhaust passage 7.

  An air flow meter 24 is provided upstream of the compressor 9 a in the intake passage 6. The air flow meter 24 outputs an electrical signal corresponding to the amount (mass) of intake air (air) flowing through the intake passage 6. A throttle valve 10 is provided in the intake passage 6 on the downstream side of the compressor 9a. The throttle valve 10 adjusts the intake air amount of the internal combustion engine 1 by changing the passage cross-sectional area in the intake passage 6. An exhaust purification catalyst 70 is provided in the exhaust passage 7 on the downstream side of the turbine 9b. A temperature sensor 71 is provided downstream of the exhaust purification catalyst 70 in the exhaust passage 7.

  The internal combustion engine 1 is also provided with an electronic control unit (ECU) 20. The ECU 20 is a unit that controls the operating state and the like of the internal combustion engine 1. Various sensors such as the air flow meter 24, the crank position sensor 21, the accelerator position sensor 22, the water temperature sensor 23, and the temperature sensor 71 are electrically connected to the ECU 20. The crank position sensor 21 is a sensor that outputs an electrical signal correlated with the rotational position of the engine output shaft (crankshaft) of the internal combustion engine 1. The accelerator position sensor 22 is a sensor that outputs an electrical signal correlated with an operation amount (accelerator opening) of an accelerator pedal (not shown). The water temperature sensor 23 outputs an electrical signal corresponding to the temperature of the cooling water that cools the internal combustion engine 1 (hereinafter sometimes simply referred to as “cooling water temperature”). The temperature sensor 71 outputs an electrical signal corresponding to the exhaust temperature. Then, the output signals of these sensors are input to the ECU 20. The ECU 20 derives the engine speed of the internal combustion engine 1 based on the output signal of the crank position sensor 21. Further, the ECU 20 derives the engine load of the internal combustion engine 1 based on the output signal of the accelerator position sensor 22. Further, the ECU 20 detects the cooling water temperature with the water temperature sensor 23 and estimates the temperature of the exhaust purification catalyst 70 (hereinafter sometimes simply referred to as “catalyst temperature”) based on the output value of the temperature sensor 71.

  Various devices such as the hydrogen fuel injection valve 3, the gasoline injection valve 4, and the throttle valve 10 are electrically connected to the ECU 20. The various devices are controlled by the ECU 20.

  The internal combustion engine 1 configured as described above includes hydrogen fuel that is injected into the intake port by the hydrogen fuel injection valve 3 and intake air that the internal combustion engine 1 sucks (hereinafter may be simply referred to as “intake air”). The operation of burning the air-fuel mixture in the combustion chamber of the internal combustion engine 1 (hereinafter also referred to as “hydrogen operation”) is performed. In the hydrogen operation according to this embodiment, the air-fuel ratio of the mixture of hydrogen fuel and intake air is controlled so that the amount of NOx discharged from the internal combustion engine 1 becomes substantially zero, as will be described later. In this embodiment, the hydrogen operation corresponds to the first operation in the present invention.

  Further, the internal combustion engine 1 is an operation in which a mixture of gasoline and intake air injected into the cylinder 2 by the gasoline injection valve 4 is combusted in the combustion chamber of the internal combustion engine 1 (hereinafter also referred to as “gasoline operation”). Yes.) In the present embodiment, the gasoline operation corresponds to the second operation in the present invention.

(Operation control)
In the control device for the internal combustion engine 1 according to the present embodiment, the ECU 20 selectively executes the hydrogen operation or the gasoline operation according to the operation state of the internal combustion engine 1. More specifically, the ECU 20 determines whether to perform a hydrogen operation or a gasoline operation based on the engine speed and engine load of the internal combustion engine 1 and controls the operation of the internal combustion engine 1. In the present embodiment, the ECU 20 functions as an operation control unit according to the present invention by controlling the operation of the internal combustion engine 1.

An operation control map of the internal combustion engine 1 in this embodiment is shown in FIG. As shown in FIG. 2, in the internal combustion engine 1, when the operating state belongs to the low load region, the hydrogen operation is performed. The control apparatus for the internal combustion engine 1 according to the present embodiment uses hydrogen fuel and intake air that are injected into the intake port by the hydrogen fuel injection valve 3 in “normal hydrogen operation” to be described later, which is one of the hydrogen operations. The air / fuel ratio of the air / fuel mixture is controlled to a predetermined lean air / fuel ratio higher than the stoichiometric air / fuel ratio. Further, the control device controls the air-fuel ratio to be richer than the predetermined lean air-fuel ratio in “catalyst-temperature-raising hydrogen operation” described later, which is one of the hydrogen operations. In the “normal hydrogen operation” and the “catalyst temperature rising hydrogen operation”, the amount of NOx discharged from the internal combustion engine 1 is substantially zero. That is, the operation region where the hydrogen operation shown in FIG. 2 is performed is set as a region where the amount of NOx discharged from the internal combustion engine 1 is substantially zero. Further, as shown in FIG. 2, when the operation state of the internal combustion engine 1 belongs to the high load region, the gasoline operation is performed.

  Here, FIG. 3 shows the correlation between the exhaust temperature, the NOx emission amount, and the thermal efficiency with respect to the excess air ratio when the internal combustion engine 1 is operating with hydrogen. As shown in FIG. 3, the exhaust temperature decreases as the excess air ratio increases. Further, when the excess air ratio is smaller than a predetermined value, the NOx emission amount decreases as the excess air ratio increases, and when the excess air ratio is equal to or greater than the predetermined value, the NOx emission amount becomes substantially zero. In addition, the thermal efficiency increases as the excess air ratio increases, and when the increase rate of the thermal efficiency per unit increase of the excess air ratio is defined as the change rate, the change rate corresponds to the increase of the excess air ratio. Become smaller. In the normal hydrogen operation performed by the internal combustion engine 1 (hereinafter sometimes simply referred to as “normal hydrogen operation”), as shown in FIG. 3, the internal combustion engine is operated with an excess air ratio at which the thermal efficiency becomes as high as possible. The engine 1 is operated. The air-fuel ratio corresponding to the excess air ratio at this time is the predetermined lean air-fuel ratio in normal hydrogen operation. At this time, the NOx emission amount is substantially zero. In this embodiment, the ECU 20 performs the normal hydrogen operation in which the air-fuel ratio of the mixture of the hydrogen fuel and the intake air is controlled to the predetermined lean air-fuel ratio, so that the normal hydrogen according to the present invention is obtained. It functions as a driving means.

(Catalyst temperature rise control)
As described above, in the control device for the internal combustion engine 1 according to the present embodiment, the ECU 20 selectively executes the hydrogen operation or the gasoline operation according to the operation state of the internal combustion engine 1. When the internal combustion engine 1 is operating with hydrogen, the amount of NOx discharged from the internal combustion engine 1 is substantially zero. Further, in the hydrogen operation in this embodiment, HC and CO are not discharged from the internal combustion engine 1. Therefore, it is not necessary to purify the exhaust by the exhaust purification catalyst 70 during the hydrogen operation. On the other hand, when the internal combustion engine 1 is in gasoline operation, HC, CO, and NOx are discharged from the internal combustion engine 1 as in the conventional gasoline engine. . In some cases, the temperature of the exhaust purification catalyst 70 is lower than the activation temperature of the exhaust purification catalyst 70 when the internal combustion engine 1 is started or during normal hydrogen operation. Therefore, when the temperature of the exhaust purification catalyst 70 is lower than the activation temperature of the exhaust purification catalyst 70, the temperature of the exhaust purification catalyst 70 is raised in order to purify HC, CO, and NOx discharged by the gasoline operation. It is necessary to perform control (hereinafter also referred to as “catalyst temperature rise control”).

  In the prior art, the air-fuel ratio of the mixture of fuel and intake air of the internal combustion engine is set to a rich air-fuel ratio lower than the stoichiometric air-fuel ratio in order to reduce emissions at the time of engine start of the internal combustion engine. The temperature of the exhaust gas purification catalyst is raised, and in this case, the fuel efficiency is generally deteriorated.

  Further, in the normal hydrogen operation according to the present embodiment, the exhaust temperature is lowered as described above. As can be seen from the fact that the NOx emission amount during normal hydrogen operation becomes substantially zero, the exhaust temperature during normal hydrogen operation is lower than the exhaust temperature during gasoline operation. Therefore, during normal hydrogen operation according to the present embodiment, the temperature of the exhaust purification catalyst 70 may be lower than the activation temperature of the exhaust purification catalyst 70.

Here, also in the internal combustion engine 1 according to the present embodiment, when the hydrogen operation is performed in preparation for the discharge of HC, CO, and NOx by the gasoline operation, for example, an air-fuel mixture of hydrogen fuel and intake air It is possible to raise the temperature of the exhaust purification catalyst 70 by burning the air-fuel mixture in the combustion chamber with a rich air-fuel ratio lower than the stoichiometric air-fuel ratio. However, during the hydrogen operation in which it is not necessary to purify the exhaust gas by the exhaust purification catalyst 70, it is important to raise the temperature of the exhaust purification catalyst 70 in preparation for the discharge of HC, CO, and NOx by the gasoline operation. Deterioration of fuel consumption is brought about. Therefore, the inventor of the present invention performs the catalyst temperature increase control during the hydrogen operation based on the operation history from the start of the engine of the internal combustion engine 1 to the present time, so that the fuel consumption of the internal combustion engine 1 resulting from the catalyst temperature increase control is achieved. It has been found that the deterioration of can be suppressed.

  In the control device for the internal combustion engine 1 according to this embodiment, the engine start of the internal combustion engine 1 is performed by hydrogen operation. When the internal combustion engine 1 is performing a hydrogen operation, the ECU 20 determines whether or not the gasoline operation has been performed from the start of the engine to the present, and it is determined that the gasoline operation has already been performed. Therefore, it is assumed that the gasoline operation is performed again in the period from now on, and when the temperature of the exhaust purification catalyst 70 is lower than the activation temperature of the exhaust purification catalyst 70, the temperature of the exhaust purification catalyst 70 is raised. .

  Specifically, when the gasoline operation is not performed from the start of the internal combustion engine 1 to the present time, the temperature of the exhaust purification catalyst 70 is not raised during the hydrogen operation regardless of the catalyst temperature. On the other hand, when the gasoline operation is performed from the start of the engine of the internal combustion engine 1 to the present, a predetermined condition (for example, when the catalyst temperature is lower than the predetermined temperature) during the subsequent hydrogen operation ), The temperature of the exhaust purification catalyst 70 is raised. This is because, when the gasoline operation is performed from the start of the engine of the internal combustion engine 1 to the present time, even if the current operation of the internal combustion engine 1 is the hydrogen operation, the gasoline operation is again performed in the previous period from the present time. It is assumed that the operation is performed, and prepares for the discharge of HC, CO, and NOx by the gasoline operation during the hydrogen operation.

  Even when the temperature of the exhaust purification catalyst 70 is not raised based on the operation history from the start of the engine of the internal combustion engine 1 to the present time, as described above, HC, CO, and NOx are in the internal combustion engine 1 during the hydrogen operation. There is no problem even if the exhaust purification catalyst 70 is not activated.

  In the present embodiment, as described above, when the gasoline operation is performed from the start of the internal combustion engine 1 to the present time, when the predetermined condition is satisfied during the hydrogen operation, the exhaust purification catalyst 70 is obtained. A hydrogen operation for raising the temperature of the catalyst (hereinafter sometimes referred to as “catalyst temperature-raising hydrogen operation”) is performed. Here, the predetermined condition is when the temperature of the exhaust purification catalyst 70 is lower than the activation temperature of the exhaust purification catalyst 70. Whether or not the temperature of the exhaust purification catalyst 70 is lower than the activation temperature of the exhaust purification catalyst 70 depends on whether or not the above-mentioned catalyst temperature estimated based on the output value of the temperature sensor 71 is lower than a predetermined temperature. It can be determined by whether or not there is. Alternatively, the determination can be made based on whether or not the temperature of the cooling water for cooling the internal combustion engine 1 (hereinafter sometimes simply referred to as “cooling water temperature”) is lower than the predetermined water temperature. That is, the temperature of the exhaust purification catalyst 70 is raised to such an extent that the gasoline operation has been performed from the start of the engine of the internal combustion engine 1 to the present and the exhaust purification catalyst 70 can exhibit a predetermined exhaust purification capability. When it is estimated that there is no catalyst, the catalyst temperature increase hydrogen operation is performed. The ECU 20 detects the cooling water temperature with the water temperature sensor 23.

  In the catalyst temperature rising hydrogen operation, the air-fuel ratio of the mixture of hydrogen fuel and intake air is made richer than the predetermined lean air-fuel ratio during normal hydrogen operation, and the air-fuel mixture is combusted. Further, in the catalyst temperature rising hydrogen operation, the ignition timing is retarded. As a result, the exhaust temperature rises and the exhaust purification catalyst 70 can be raised in temperature. In the present embodiment, the ECU 20 performs the catalyst temperature-raising hydrogen operation in which the air-fuel ratio of the air-fuel mixture is controlled to a rich air-fuel ratio rather than the predetermined lean air-fuel ratio. Functions as a hydrogen operation means.

Here, a comparison between the normal hydrogen operation and the catalyst temperature rising hydrogen operation is performed. FIG. 4 is a diagram showing the correlation between the exhaust temperature, the NOx emission amount, and the thermal efficiency with respect to the excess air ratio, for explaining the comparison between the normal hydrogen operation and the catalyst temperature rising hydrogen operation. As shown in FIG. 4, the excess air ratio is smaller in the catalyst temperature rising hydrogen operation than in the normal hydrogen operation. And the exhaust temperature at the time of catalyst temperature rising hydrogen operation becomes higher than the exhaust temperature at the time of normal hydrogen operation. This is due to the influence of the reduction in the excess air ratio and the retarded ignition timing. As a result, the temperature of the exhaust purification catalyst 70 can be raised. In addition, the thermal efficiency during the catalyst temperature rising hydrogen operation is lower than the thermal efficiency during the normal hydrogen operation. This means that the fuel consumption deteriorates due to the catalyst temperature rising hydrogen operation. During the catalyst temperature increase hydrogen operation, the NOx emission amount is substantially zero as in the normal hydrogen operation. Thus, in the catalyst temperature rising hydrogen operation, the operation of the internal combustion engine 1 is performed at an excess air ratio at which the amount of NOx discharged from the internal combustion engine 1 becomes substantially zero and the exhaust temperature becomes as high as possible.

  As described above, in the control apparatus for the internal combustion engine 1 according to the present embodiment, when the operation request for the internal combustion engine 1 is in the hydrogen operation region, the gasoline operation is performed from the start of the engine of the internal combustion engine 1 to the present. When it is determined that the temperature is not low, the catalyst temperature-raising hydrogen operation, in which the thermal efficiency is lower than that in the normal hydrogen operation, is not performed, and the normal hydrogen operation is performed regardless of the catalyst temperature. When it is determined that the gasoline operation has been performed from the time when the internal combustion engine 1 is started to the present, it is assumed that the gasoline operation is performed again from the present to the previous period, and the temperature of the catalyst is increased under a predetermined condition. Hydrogen operation is performed. By performing the catalyst temperature increase control in this manner, the exhaust purification catalyst 70 can be increased in temperature while suppressing deterioration in fuel consumption.

(Catalyst temperature rise control flow)
A catalyst temperature increase control flow in the control apparatus for the internal combustion engine 1 according to the present embodiment will be described with reference to FIG. FIG. 5 is a flowchart showing a catalyst temperature increase control flow in the control apparatus for the internal combustion engine 1 according to this embodiment. In the present embodiment, this flow is repeatedly executed by the ECU 20 at a predetermined calculation cycle during a period from when the internal combustion engine 1 is started to when the engine is stopped. As described above, the engine start of the internal combustion engine 1 is performed by hydrogen operation. Further, when the internal combustion engine 1 is started, an operation history determination flag Nflgm and a catalyst temperature increase hydrogen operation determination flag Nflgm described later are initialized to zero.

  In this flow, first, in S101, the ECU 20 derives an operation request for the internal combustion engine 1 based on the output signal of the accelerator position sensor 22, and it is determined whether or not the operation request is in the hydrogen operation region. The operation control map as shown in FIG. 2 described above is stored in advance in the ROM of the ECU 20. As described above, the hydrogen operation region is set as a region where the amount of NOx discharged from the internal combustion engine 1 is substantially zero. In S101, it is determined whether or not the operation request is in the hydrogen operation region using this map or a function based on the map. If an affirmative determination is made in S101, the ECU 20 proceeds to the process of S102, and if a negative determination is made in S101, the ECU 20 proceeds to the process of S108.

  If an affirmative determination is made in S101, it is then determined in S102 whether or not a catalyst temperature increase hydrogen operation determination flag Nflgmh is zero. The catalyst temperature increase hydrogen operation determination flag Nflgm is set to 1 when it is determined that the operation history determination flag Nflgm is 1, as will be described later. In this flow, when the hydrogen operation is required and the catalyst temperature increase hydrogen operation determination flag Nflgm is 1 and a predetermined condition described later is satisfied, the catalyst temperature increase hydrogen operation is executed. If an affirmative determination is made in S102, the ECU 20 proceeds to the process of S103, and if a negative determination is made in S102, the ECU 20 proceeds to the process of S105.

If an affirmative determination is made in S102, it is then determined in S103 whether or not the driving history determination flag Nflgm is 1. The operation history determination flag Nflgm is set to 1 when it is determined that the operation request of the internal combustion engine 1 is in the gasoline operation region, as will be described later. Here, when the operation history determination flag Nflgm is 0, that is, when it is determined that the gasoline operation has not been performed from the start of the internal combustion engine 1 to the present, the ECU 20 performs the exhaust purification catalyst during the hydrogen operation. Control to raise the temperature of 70 is not executed. If an affirmative determination is made in S103, the ECU 20 proceeds to the process of S104, and if a negative determination is made in S103, the ECU 20 proceeds to the process of S107.

  If an affirmative determination is made in S103, then in S104, the catalyst temperature increase hydrogen operation determination flag Nflgh is set to 1. Here, the process of S104 is performed when the hydrogen operation is requested after the first gasoline operation performed after the engine start of the internal combustion engine 1, in other words, when the hydrogen operation is requested. In addition, the gasoline operation has already been performed after the engine is started. When the catalyst temperature increase hydrogen operation determination flag Nflgmh is set to 1 in S104, the value of the flag is maintained until the internal combustion engine 1 is stopped. When the catalyst temperature increase hydrogen operation determination flag Nflgmh is once set to 1, the catalyst temperature increase hydrogen operation is executed when a predetermined condition described later is satisfied.

  Next, in S105, it is determined whether or not the catalyst temperature Tb is lower than a determination threshold value Tbth. The determination threshold value Tbth is stored in advance in the ROM of the ECU 20 as a catalyst temperature at which the exhaust purification catalyst 70 can exhibit a predetermined exhaust purification capability. In S105, as described above, it may be determined whether or not the cooling water temperature is lower than the predetermined water temperature. If an affirmative determination is made in S105, the ECU 20 proceeds to the process of S106, and if a negative determination is made in S105, the ECU 20 proceeds to the process of S107.

  If an affirmative determination is made in S105, then a catalyst temperature increase hydrogen operation is executed in S106. On the other hand, if a negative determination is made in S105 or a negative determination is made in S103, then a normal hydrogen operation is performed in S107. In S106, the ECU 20 controls the air-fuel ratio of the mixture of hydrogen fuel and intake air to an air-fuel ratio corresponding to the excess air ratio as shown in FIG. That is, the air-fuel ratio is richer than a predetermined lean air-fuel ratio during normal hydrogen operation, the amount of NOx discharged from the internal combustion engine 1 becomes substantially zero, and the exhaust temperature becomes as high as possible. Control to fuel ratio. At this time, the ignition timing is retarded. In S107, the ECU 20 controls the air-fuel ratio of the mixture of hydrogen fuel and intake air to an air-fuel ratio corresponding to the excess air ratio as shown in FIG. That is, the air-fuel ratio is controlled to an air-fuel ratio at which the predetermined lean air-fuel ratio is reached and the NOx amount discharged from the internal combustion engine 1 becomes substantially zero and the thermal efficiency becomes as high as possible. Then, after the process of S106 or after the process of S107, the execution of this flow is terminated.

  When a negative determination is made in S101, that is, when it is determined that the operation request of the internal combustion engine 1 is in the gasoline operation region, the operation history determination flag Nflgm is set to 1 in S108. In S109, it is determined whether or not the catalyst temperature Tb is smaller than the determination threshold value Tbth. The process of S109 is substantially the same as the process of S105 described above. If an affirmative determination is made in S109, the ECU 20 proceeds to the process of S110, and if a negative determination is made in S109, the ECU 20 proceeds to the process of S111.

  If an affirmative determination is made in S109, then a catalyst temperature rising gasoline operation is executed in S110. Here, the catalyst temperature rising gasoline operation is a gasoline operation for raising the temperature of the exhaust purification catalyst 70, and the air-fuel ratio is set to a richer air-fuel ratio than during normal gasoline operation, and the ignition timing is set. Is retarded. On the other hand, if a negative determination is made in S109, then a normal gasoline operation is executed in S111. Here, the normal gasoline operation refers to a normal gasoline operation performed by the internal combustion engine 1. Then, after the process of S110 or the process of S111, the execution of this flow is terminated.

According to the present embodiment, the catalyst temperature raising control is executed based on the above-described flow, whereby the temperature of the exhaust purification catalyst 70 can be raised while suppressing deterioration of fuel consumption.

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 3 ... Hydrogen fuel injection valve 4 ... Gasoline injection valve 5 ... Spark plug 6 ... Intake passage 7 ... Exhaust passage 10 ... throttle valve 20 ... ECU
23..Water temperature sensor 24..Air flow meter 70..Exhaust gas purification catalyst 71..Temperature sensor

Claims (1)

A control device for an internal combustion engine, comprising: an exhaust purification catalyst provided in an exhaust passage of the internal combustion engine; a first injection valve capable of injecting hydrogen fuel; and a second injection valve capable of injecting gasoline,
Depending on the operating state of the internal combustion engine, the first operation for burning the mixture of the hydrogen fuel injected by the first injection valve and the intake air sucked by the internal combustion engine, or the second injection valve Operation control means for selectively executing a second operation for burning an air-fuel mixture of the gasoline and the intake air taken in by the internal combustion engine;
Normal hydrogen operation means for performing normal hydrogen operation in which the air-fuel ratio of the mixture of the hydrogen fuel and the intake air is controlled to a predetermined lean air-fuel ratio higher than the stoichiometric air-fuel ratio in the first operation;
In the first operation, a catalyst temperature increase hydrogen operation means for performing a catalyst temperature increase hydrogen operation in which an air fuel ratio of the mixture of the hydrogen fuel and the intake air is controlled to be a rich air fuel ratio rather than the predetermined lean air fuel ratio; With
In the case where the first operation is executed by the operation control means and the temperature of the exhaust purification catalyst is lower than the activation temperature of the exhaust purification catalyst, from the start of the internal combustion engine to the present When the second operation is performed by the operation control means, the catalyst temperature increase hydrogen operation is performed by the catalyst temperature increase hydrogen operation means, and the operation control means is from the start of the internal combustion engine to the present. When the second operation is not performed, the control device for an internal combustion engine in which the normal hydrogen operation is performed by the normal hydrogen operation means.

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