JP2006132490A - Hydrogen addition internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent generation of smolder in an ignition plug due to water generated by combustion of hydrogen gas, in a hydrogen addition internal combustion engine using hydrogen gas together with gasoline as fuel for combustion. <P>SOLUTION: This hydrogen addition internal combustion engine 10 using hydrogen gas together with hydrocarbon fuel as fuel for combustion is provided with a cold start determination means determining whether or not a current operating state is cold start time (outside air temperature sensor 72, cooling water temperature sensor 74), and with an addition rate change means reducing an addition rate of hydrogen gas to hydrocarbon fuel compared to normal warm start time when the current operating state is cold start time. By reducing the addition rate of hydrogen gas at cold start, generation of smolder in the ignition plug due to water generated by combustion of hydrogen can be prevented and a combustion state in a cylinder after start can be kept favorable. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a hydrogenated internal combustion engine.

In an internal combustion engine that uses gasoline as fuel, it is known that further reduction of nitrogen oxides (NO _x ) in exhaust gas is possible by supplying hydrogen gas in addition to gasoline. For example, Japanese Patent Application Laid-Open No. 2004-116398 discloses an internal combustion engine that includes a hydrogen injector and a gasoline injector and injects hydrogen and gasoline into a cylinder at a predetermined ratio.

JP 2004-116398 A

  However, in the internal combustion engine as described above, water is generated by the combustion of hydrogen, but at the time of starting at a very low temperature, the temperature in the cylinder (combustion chamber) is low, so the spark plug is generated by the water generated by the combustion of hydrogen. May be covered. In this case, since the temperature of the spark plug is also lowered, the smoldering occurs in the spark plug due to moisture. Thereby, the function of a spark plug will be impaired and the problem that the combustion state in a cylinder deteriorates will generate | occur | produce.

  In particular, in an internal combustion engine that directly injects hydrogen into a cylinder, since hydrogen is injected in the vicinity of the spark plug, the possibility of smoldering of the spark plug becomes higher. In addition, when lean burn is performed by adding hydrogen to gasoline, it may be assumed that sufficient dilution cannot be achieved due to combustion deterioration due to plug smoldering.

  The present invention has been made to solve the above-described problems. In a hydrogenated internal combustion engine that uses hydrogen gas together with gasoline as a fuel for combustion, the spark plug is made of water generated by combustion of hydrogen gas. The purpose is to suppress the occurrence of smoldering.

In order to achieve the above object, a first invention is a hydrogenated internal combustion engine that uses hydrogen gas together with hydrocarbon fuel as a combustion fuel, and determines whether or not the current operating state is a cold start time. A cold start determination means, and when the current operating state is a cold start, an addition ratio changing means for reducing the addition ratio of hydrogen gas to the hydrocarbon fuel compared to the warm start,
It is provided with.

  In a second aspect based on the first aspect, the cold start determining means includes an outside air temperature acquiring means for acquiring the outside air temperature, and determines that the cold start time is in the case where the outside air temperature is a predetermined value or less. It is characterized by that.

  According to a third aspect, in the second aspect, the cold start determination unit includes a cooling water temperature acquisition unit that acquires a cooling water temperature, and the outside air temperature is a predetermined value or less and the cooling water temperature is a predetermined value or less. It is characterized in that it is during cold start.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, when the current operating state is a cold start time, a throttle opening degree changing means for making the throttle opening smaller than that at the warm start time is provided. It is further provided with the feature.

  According to the first aspect of the present invention, when the current operating state is a cold start, it is generated by combustion of hydrogen in order to reduce the proportion of hydrogen gas added to the hydrocarbon fuel as compared to a normal warm start. It is possible to prevent the remaining moisture from adhering to the spark plug. Therefore, the occurrence of smoldering in the spark plug can be suppressed, and the combustion state in the cylinder after the start can be kept good.

  According to the second invention, it is possible to determine whether or not the current operation state is a cold start based on the outside air temperature acquired by the outside air temperature acquisition means.

  According to the third aspect of the invention, when the outside air temperature is equal to or lower than the predetermined value and the cooling water temperature is equal to or lower than the predetermined value, it is determined that the engine is cold-started. It becomes possible to judge.

  According to the fourth aspect of the invention, when the current operating state is a cold start, the air-fuel ratio is excessively changed to the lean side in order to make the throttle opening smaller than that at the warm start. Can be suppressed. Therefore, the combustion state can be kept good and the occurrence of misfire can be reliably suppressed.

  An embodiment 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. The present invention is not limited to the following embodiments.

  FIG. 1 is a diagram for explaining the configuration of a system including a hydrogenated internal combustion engine 10 according to Embodiment 1 of the present invention. An intake passage 12 and an exhaust passage 14 communicate with the internal combustion engine 10. The intake passage 12 includes an air filter 16 at an upstream end. The air filter 16 is assembled with an intake air temperature sensor for detecting the intake air temperature THA (that is, the outside air temperature).

  An air flow meter 18 is disposed downstream of the air filter 16. A surge tank 20 is provided downstream of the air flow meter 18. A throttle valve 22 is provided downstream of the surge tank 20. In the vicinity of the throttle valve 22, a throttle sensor that detects the throttle opening degree TA and an idle switch that is turned on when the throttle valve is fully closed are disposed.

  A piston 24 that reciprocates inside the cylinder of the internal combustion engine 10 is provided. The internal combustion engine 10 includes a cylinder head 26. A combustion chamber 28 is formed between the piston 24 and the cylinder head 26. An intake port 30 and an exhaust port 32 communicate with the combustion chamber 28, and the intake port 30 is connected to the intake passage 12, and the exhaust port 32 is connected to the exhaust passage 14. An intake valve 34 and an exhaust valve 36 are disposed in the intake port 30 and the exhaust port 32, respectively.

  A gasoline injection valve 38 for injecting gasoline (hydrocarbon fuel) into the port is disposed in the intake passage 12. A hydrogen fuel port injection valve 40 for injecting hydrogen into the port is disposed in the intake passage 12. The gasoline injection valve and the hydrogen fuel injection valve may be provided so as to inject fuel directly into the cylinder of the internal combustion engine 10.

  A gasoline tank 44 communicates with the gasoline injection valve 38 via a gasoline supply pipe 42. The gasoline supply pipe 42 includes a pump 46 and a gasoline flow meter 48 between the gasoline injection valve 38 and the gasoline tank 44. The pump 46 can supply gasoline at a predetermined pressure to the gasoline injection valve 38. For this reason, the gasoline injection valve 38 is able to inject an amount of gasoline into the intake passage 12 according to the opening time by opening the valve in response to a drive signal supplied from the outside.

  The system of this embodiment includes a hydrogen tank 50 for storing hydrogen in a gaseous state at a high pressure. A hydrogen supply pipe 52 communicates with the hydrogen tank 50. The hydrogen supply pipe 52 communicates with the hydrogen fuel port injection valve 40. In the system of the present embodiment, hydrogen gas charged into the hydrogen tank 50 from the outside is used as the hydrogen fuel supplied to the hydrogen fuel port injection valve 40. However, the hydrogen fuel is supplied to the hydrogen fuel port injection valve 40. The hydrogen fuel to be used is not limited to this, and a hydrogen-rich gas containing high-concentration hydrogen generated on the vehicle or supplied from the outside may be used.

  A regulator 56 is disposed in the hydrogen supply pipe 52. According to such a configuration, the hydrogen in the hydrogen tank 50 is supplied to the hydrogen fuel port injection valve 40 at a predetermined pressure reduced by the regulator 56. For this reason, the hydrogen fuel port injection valve 40 is able to inject an amount of hydrogen into the intake passage 12 according to the opening time by opening the valve in response to a drive signal supplied from the outside.

  In the hydrogen supply pipe 52, a temperature sensor 53 and a fuel pressure sensor 54 are disposed between the regulator 56 and the hydrogen fuel port injection valve 40. The temperature sensor 53 is a sensor that emits an output corresponding to the temperature of hydrogen supplied to the hydrogen fuel port injection valve 40. The fuel pressure sensor 54 is a sensor that emits an output corresponding to the pressure of hydrogen supplied to the hydrogen fuel port injection valve 40. In the system of the present embodiment, the regulator 56 is controlled based on the outputs generated by the temperature sensor 53 and the fuel pressure sensor 54. For this reason, even if the temperature and pressure of hydrogen supplied from the hydrogen tank 50 vary, hydrogen can be supplied to the hydrogen fuel port injection valve 40 at a stable pressure.

An O ₂ sensor 58 and a NOx sensor 60 are incorporated in the exhaust passage 14. The O ₂ sensor 58 is a sensor that generates an output corresponding to the exhaust air-fuel ratio based on the presence or absence of oxygen in the exhaust gas. The NOx sensor 60 is a sensor that emits an output corresponding to the NOx concentration in the exhaust gas. A catalyst 62 for purifying exhaust gas is disposed downstream of the sensors 58 and 60. The catalyst 62 incorporates a catalyst bed temperature sensor 64 for detecting the catalyst bed temperature.

The system of this embodiment includes an ECU 70. In addition to the temperature sensor 53, the fuel pressure sensor 54, the O ₂ sensor 58, the NOx sensor 60, and the catalyst bed temperature sensor 64, the ECU 70 includes an outside air temperature sensor 72 that detects the outside air temperature, and a cooling water temperature sensor 74 that detects the cooling water temperature. Is connected. The ECU 70 also includes a KCS sensor that detects the occurrence of knocking and various sensors (such as a throttle opening, an engine speed, an exhaust temperature, and a lubricating oil temperature) for detecting the operating state of the internal combustion engine 10. (Not shown) is connected. The ECU 70 is connected to actuators such as the gasoline injection valve 38, the hydrogen fuel port injection valve 40, and the pump 46 described above. According to such a configuration, the ECU 70 can arbitrarily select an injection valve that performs fuel injection according to the operating state of the internal combustion engine 10.

  FIG. 2 is a schematic diagram for explaining the operation mode of the system of the present embodiment, and shows each operation mode set according to the engine speed and the load. The system of the present embodiment includes a gasoline combustion region in which the internal combustion engine 10 is operated using only gasoline, and a hydrogen addition lean burn region in which the internal combustion engine 10 is operated by lean burn combustion using both gasoline and hydrogen. Has different modes.

As shown in FIG. 2, the operation is performed in the hydrogen addition lean burn region in the idling to normal rotation region. In addition, the operation is performed in the gasoline combustion region in a higher load and higher rotation region than in the hydrogen addition lean burn region. In the operation in the hydrogen-added lean burn region, hydrogen is added to gasoline and lean burn combustion is performed, so that the combustion state in the cylinder (in the combustion chamber 16) can be improved, and fuel efficiency and efficiency can be improved. it can. Further, emission of NO _x can be suppressed by lean burn combustion, so that emission can be improved.

  In the system of this embodiment configured as described above, the operation is performed in the hydrogenation combustion mode even when the engine is started, but the engine is started when the outside air temperature is extremely low (for example, about −25 ° C. to −30 ° C.). In such a case, moisture generated by the combustion of hydrogen at the first explosion may adhere to the spark plug in a liquid state, which may cause smoldering of the spark plug.

  For this reason, in the system of the present embodiment, when starting the engine when it is cold, particularly when starting the engine at a very low temperature, the hydrogen addition ratio to gasoline is reduced to be lower than usual, thereby suppressing hydrogen combustion. I am doing so. Specifically, it is determined whether or not it is a cold start based on the outputs of the outside air temperature sensor 72 and the coolant temperature sensor 74, and in the case of a cold start, the hydrogen addition ratio is reduced. Thereby, the amount of moisture generated by the combustion of hydrogen can be minimized, and the occurrence of smoldering in the spark plug can be suppressed. Therefore, it is possible to prevent the function of the spark plug from being deteriorated due to the smoldering of the spark plug, and it is possible to reliably prevent the subsequent combustion from deteriorating.

  Here, the hydrogen addition ratio is a ratio of the heat generation amount of hydrogen to the heat generation amount of gasoline, and in the normal hydrogen addition lean burn region, the hydrogen addition ratio is set to a value of about 20%. On the other hand, at the start of cryogenic temperature, it is preferable to reduce the hydrogen addition ratio to about 5%.

  After the start-up, if the explosion process is performed several times in the cylinder, the temperature in the cylinder immediately becomes 100 ° C. or higher. In this state, the water generated by the combustion of hydrogen becomes water vapor and is discharged into the exhaust passage 14 together with the exhaust gas. Therefore, since the smoldering does not occur in the spark plug after the explosion stroke is performed several times, the hydrogen addition ratio can be returned to the normal hydrogen addition lean burn area.

  When the hydrogen addition ratio is decreased, the air-fuel ratio becomes leaner than normal, so it is desirable to reduce the intake air amount by reducing the throttle opening. Thereby, it can suppress that an air fuel ratio shifts to the rich side and an air fuel ratio becomes excessively lean. Therefore, it is possible to prevent misfiring or the like from occurring due to the lean air-fuel ratio. It is preferable to return the throttle opening to the normal value when the in-cylinder temperature sufficiently rises and returns to the hydrogen addition ratio in the normal hydrogen addition lean burn region.

  Next, a processing procedure in the system of the present embodiment will be described based on the flowchart of FIG. First, in step S1, it is determined whether or not the current operating state is when the engine is started. If the engine is starting, the process proceeds to step S2, and if not, the process proceeds to step S5.

  In the next step S2, the outside air temperature Tout is acquired from the output of the outside air temperature sensor 72, and the cooling water outlet temperature Twout is acquired from the output of the cooling water temperature sensor 74. In the next step S3, the outside air temperature Tout is compared with a predetermined threshold value T0, and it is determined whether or not Tout <T0. Here, the value of the threshold value T0 is set to a value of, for example, about −25 ° C. to −30 ° C.

  If Tout <T0 in step S3, the process proceeds to step S4. In this case, since the outside air temperature is extremely low, when the temperature in the cylinder is low, smoldering may occur in the spark plug due to moisture generated by hydrogen combustion. Therefore, in step S4, the coolant outlet temperature Twout is compared with a predetermined threshold value T1, and it is determined whether or not Twout> T1. Here, the threshold value T1 is a threshold value for determining whether or not moisture adheres to the spark plug in a liquid state when hydrogen burns in the cylinder. The value of T1 is, for example, 20 A value of about 30 ° C. to 30 ° C.

  If Tout> T0 in step S3, the process proceeds to step S5. In this case, since it can be determined that the in-cylinder temperature is relatively high, operation in the normal hydrogen addition lean burn region is performed in the following steps. That is, the engine speed and the throttle opening are acquired in step S5, and in the next step S6, the hydrogen addition ratio RH2, the gasoline injection amount (injection period), the engine speed and the throttle opening acquired in step S5, Various parameters such as the hydrogen injection amount (injection period) and the throttle opening TR are obtained from the map. In step S7, the lean burn operation in the hydrogenation combustion mode is performed based on the parameters obtained in step S6. After step S7, the process ends (RETURN).

  If Twout> T1 in step S4, the outside air temperature is extremely low, but the cooling water outlet temperature Twout is equal to or higher than a predetermined value. It can be judged that the state has not decreased so much. Therefore, in this case, the process proceeds to step S5, and the operation in the normal hydrogenation combustion mode is performed in the subsequent steps.

  On the other hand, if Twout ≦ T1 in step S4, the process proceeds to step S8. In this case, since the outside air temperature is extremely low and the cooling water temperature is equal to or lower than a predetermined value, when hydrogen is added to gasoline at a normal hydrogen addition rate and combustion is performed, the water is ignited by moisture generated by the hydrogen combustion. Smoldering may occur on the plug. For this reason, hydrogen reduction control is started in step S8.

  After step S8, the process proceeds to step S9. In step S9, a hydrogen addition ratio RH2 'that is reduced compared to the normal time is calculated. Here, the calculation of RH2 ′ = RH2 × A (A <1) is performed to obtain a hydrogenation rate RH2 ′ smaller than the normal hydrogenation rate RH2. As described above, in the operation in the normal hydrogenation combustion mode, the hydrogenation rate RH2 is about 20%, but here the hydrogenation rate RH2 'is reduced to about 5%.

  Further, since the throttle opening needs to be reduced when the hydrogen addition ratio is reduced, in step S9, the throttle opening TR 'that is reduced from the normal time is calculated. Here, TR ′ = TR × B (B <1) is calculated to obtain a throttle opening TR ′ smaller than the normal throttle opening TR.

  In the next step S10, the operation in the hydrogenation combustion mode is performed based on the hydrogenation rate RH2 'and the throttle opening TR' obtained in step S9. As a result, in a state where the outside air temperature is extremely low and the in-cylinder temperature is very low, the operation is performed with a lower hydrogen addition ratio than usual, so that the water generated by hydrogen combustion is liquid. In this state, it can be prevented from adhering to the spark plug. Therefore, the occurrence of smoldering in the spark plug can be suppressed, and the function of the spark plug can be prevented from being impaired. Thereby, it can suppress reliably that a combustion state deteriorates due to the smoldering of a spark plug.

  In the next step S11, the coolant outlet temperature Twout is acquired again, and in the next step S12, it is determined again whether or not Twout> T1. If Twout> T1 in step S12, the cooling water outlet temperature Twout is higher than the threshold value T1, so that the water generated by the combustion of hydrogen becomes water vapor and is discharged together with the exhaust gas. Therefore, in this case, the process proceeds to step S5, and the operation in the normal hydrogenation combustion mode is performed in the subsequent steps.

  On the other hand, if Twout ≦ T1 in step S12, the cooling water outlet temperature Twout is equal to or lower than the predetermined threshold value T1, so that the process waits in step S12 until the cooling water outlet temperature Twout exceeds the threshold value T1.

  In the flowchart of FIG. 3, the hydrogen reduction control is performed based on both the outside air temperature Tout and the cooling water outlet temperature Twout. However, the hydrogen reduction control may be performed based only on one temperature. Further, hydrogen reduction control may be performed based on the lubricating oil temperature.

  As described above, according to the present embodiment, since the ratio of hydrogen to gasoline is made smaller than usual at the start at cryogenic temperature, moisture generated by hydrogen combustion adheres to the spark plug. Can be suppressed. Therefore, the occurrence of smoldering in the spark plug can be suppressed, and the combustion state in the cylinder after the start can be kept good.

It is a mimetic diagram showing the composition of the system provided with the hydrogenation internal-combustion engine concerning one embodiment of the present invention. It is a schematic diagram for demonstrating the operation mode of one Embodiment of this invention. It is a flowchart which shows the procedure of the process in the system of one Embodiment of this invention.

Explanation of symbols

10 Hydrogenated internal combustion engine 70 ECU
72 Outside air temperature sensor 74 Cooling water temperature sensor

Claims (4)

A hydrogenated internal combustion engine that uses hydrogen gas as a combustion fuel together with a hydrocarbon fuel,
Cold start determination means for determining whether or not the current operation state is a cold start time;
When the current operating state is a cold start, an addition ratio changing means for reducing the addition ratio of hydrogen gas to the hydrocarbon fuel compared to the warm start,
A hydrogenated internal combustion engine comprising:   The hydrogen addition according to claim 1, wherein the cold start determination means includes an outside air temperature acquisition means for acquiring an outside air temperature, and determines that it is a cold start time when the outside air temperature is a predetermined value or less. Internal combustion engine.   The cold start determination means includes a cooling water temperature acquisition means for acquiring a cooling water temperature, and determines that it is a cold start time when the outside air temperature is a predetermined value or less and the cooling water temperature is a predetermined value or less. 3. The hydrogenated internal combustion engine according to claim 2, wherein   The throttle opening changing means for making the throttle opening smaller than that at the time of warm starting when the current operating state is during cold starting is further provided. Hydrogenated internal combustion engine.

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