Control system for hydrogen addition internal combustion engine

Page 1 — bibliographic record

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Drawing sheet — no readable text.

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Patent Application Publication Dec. 21, 2006 Sheet 2 of 5 US 2006/0283423 A1 Fig. 2

START

YES

Calculate the Target Hydrogen Calculate the r yg. Addition Ratio with the Degree of Addition Ratio by Using a M:ap Gasoline Heaviness,

Temperature Cooling by Using a MapWater for Normal Property Gasoline Determine the Amount of Actual S4

Hydrogen Addition

RETURN

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Patent Application Publication Dec. 21, 2006 Sheet 3 of 5 US 2006/0283423 A1 Fig. 3

Two Seconds Have

Elapsed after Startup

Hydrogen Addition Ratio > A lower-limit Value

Set an initial Value for the Decrease the Hydrogen Hydrogen Addition Ratio Addition Ratio S5 Determine the Actual

Amount of Hydrogen Addition

RETURN

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Patent Application Publication Dec. 21, 2006 Sheet 4 of 5 US 2006/0283423 A1

Fig. 4

lapsed after Startup

YES

Control the Idling Speed by increasing/Decreasing the Gasoline niection Amount

Determine the Amount of Gasoline injection Amount increase Af

Calculate the Heaviness Index in Accordance

Amount Af by with

Usingthea increase

Map

Calculate the Hydrogen Addition Ratio Lower-limit Value

CoolinginWater accordance with thebyHeaviness Temperature Index and Using a Map

RETURN

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Patent Application Publication Dec. 21, 2006 Sheet 5 of 5 US 2006/0283423 A1 Fig. 5

START

The Combustion NO

Status Deteriorated

YES

Culculate the Target Hydrogen

Addition Ratio by Using a Map Culculate the Target Hydrogen for a Situation where the Addition Ratio by Using a normal Map Combustion Status is Deteriorated

Determine the Amount of S34

Actual Hydrogen Addition

RETURN

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US 2006/0283423 A1 Dec. 21, 2006

CONTROL SYSTEM FOR HYDROGEN ADDITION ensures that the ratio of hydrogen gas addition increases INTERNAL COMBUSTON ENGINE with an increase in the degree of hydrocarbon fuel heavi CSS.

TECHNICAL FIELD

0010. The second aspect of the present invention ensures 0001. The present invention relates to a control system that the ratio of hydrogen gas addition increases with an for a hydrogen addition internal combustion engine. increase in the degree of hydrocarbon fuel heaviness. There fore, even when the degree of the heaviness is varied, it is

BACKGROUND ART possible to inhibit the combustion state from deteriorating. 0011. According to a third aspect of the present inven 0002. It is known that an internal combustion using tion, there is provided the control system for a hydrogen gasoline as fuel reduces the amount of nitrogen oxide (NO) addition internal combustion engine, which is improved as in an exhaust gas when hydrogen gas is Supplied in addition described above, wherein the fuel property judgment means to gasoline. A technology disclosed, for instance, by Japa judges the property of the hydrocarbon fuel in accordance nese Patent Laid-open No. 2004-116398 determines the with the engine speed prevailing immediately after startup, hydrogen addition ratio So as to reduce the NO, exhaust an ignition timing feedback correction value prevailing amount, and operates an internal combustion engine by immediately after startup, or a hydrocarbon fuel injection injecting gasoline and hydrogen in accordance with the amount feedback correction value prevailing immediately determined ratio.

after startup.

Patent Document 1 0012. The third aspect of the present invention can judge 0003 Japanese Patent Laid-open No. 2004-116398 the property in accordance with the engine speed prevailing immediately after startup because the engine speed

Patent Document 2 decreases immediately after startup when the hydrocarbon 0004 Japanese Patent Laid-open No. Hei 6-200805 fuel is heavy. Further, when the hydrocarbon fuel is heavy, the ignition timing feedback correction value prevailing 0005. However, the aforementioned conventional tech immediately after startup or the hydrocarbon fuel injection nology does not consider the property of gasoline. There amount feedback correction value prevailing immediately fore, if the gasoline property changes, the combustion within after startup increases. Therefore, the third aspect of the a cylinder may deteriorate. The degree of gasoline atomi present invention can judge the property in accordance with Zation within a cylinder decreases particularly when the these correction values.

gasoline is heavy at cold startup. Consequently, cold hesi tation is likely to occur, and driveability deteriorates due, for 0013. According to a fourth aspect of the present inven instance, to improper acceleration or engine stop. Further, tion, a control system for a hydrogen addition internal emission deteriorates if the combustion state deteriorates combustion engine that uses hydrocarbon fuel and hydrogen because of the gasoline property. gas as combustion fuel, the control system comprises addi tion ratio initial value setup means and addition ratio

DISCLOSURE OF THE INVENTION decrease means. The addition ratio initial value setup means sets a predetermined initial value for the ratio of hydrogen 0006 The present invention has been made to solve the gas addition to the hydrocarbon fuel at startup. The addition above problem. It is an object of the present invention to ratio decrease means decreases the ratio of hydrogen gas maintain a good combustion State even when the gasoline addition to the hydrocarbon fuel when a predetermined property changes in a hydrogen addition internal combustion period of time elapses after startup. engine in which gasoline and hydrogen gas are both used as 0014. The fourth aspect of the present invention can set combustion fuel.

a predetermined initial value for the ratio of hydrogen gas 0007 According to one aspect of the present invention, a addition to the hydrocarbon fuel at startup. Therefore, when control system for a hydrogen addition internal combustion the employed initial value is greater than normal, it is engine that uses hydrocarbon fuel and hydrogen gas as possible to inhibit the combustion state from deteriorating at combustion fuel, the control system comprises fuel property startup. As a result, the present invention can offer good judgment means and addition ratio increase means. The fuel emission and driveability.

property judgment means judges the property of hydrocar 00.15 According to a fifth aspect of the present invention, bon fuel. The addition ratio increase means increases the ratio of hydrogen gas addition to the hydrocarbon fuel when the control system for a hydrogen addition internal combus the hydrocarbon fuel is found to be heavy. tion engine, which is improved as described above, further comprises fuel property judgment means for judging the 0008. When the hydrocarbon fuel is found to be heavy, property of hydrocarbon fuel. The addition ratio decrease the first aspect of the present invention increases the ratio of means decreases the ratio of hydrogen gas addition to a hydrogen gas addition to the hydrocarbon fuel. It is therefore lower-limit value that is derived from the property of the possible to inhibit the combustion state from deteriorating hydrocarbon fuel.

due to the use of heavy fuel. As a result, the present 0016. When a predetermined period of time elapses after invention can offer good emission and driveability. startup, the fifth aspect of the present invention decreases the 0009. According to a second aspect of the present inven ratio of hydrogen gas addition to a lower-limit value that is tion, there is provided the control system for a hydrogen derived from the property of the hydrocarbon fuel. It is addition internal combustion engine, which is improved as therefore possible to minimize the amount of hydrogen use, described above, wherein the addition ratio increase means thereby providing increased system efficiency.

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0017 According to a sixth aspect of the present inven 0025 FIG. 4 illustrates the processing steps performed tion, there is provided the control system for a hydrogen by the system according to the second embodiment. addition internal combustion engine, which is improved as 0026 FIG. 5 illustrates the processing steps performed described above, wherein the fuel property judgment means by the system according to the third embodiment. judges the property of the hydrocarbon fuel in accordance with the engine speed prevailing immediately after startup, BEST MODE FOR CARRYING OUT THE an ignition timing feedback correction value prevailing INVENTION immediately after startup, or a hydrocarbon fuel injection amount feedback correction value prevailing immediately 0027 Embodiments of the present invention will now be after startup. described with reference to the accompanying drawings. 0018 When the hydrocarbon fuel is heavy, the engine Like elements in the drawings are designated by like refer speed is decreased immediately after startup. Therefore, the ence numerals and will not be described repeatedly. The sixth aspect of the present invention can judge the property present invention is not limited to the embodiments described below.

in accordance with the engine speed prevailing immediately after startup. Further, when the hydrocarbon fuel is heavy, First Embodiment the ignition timing feedback correction value prevailing immediately after startup or the hydrocarbon fuel injection 0028 FIG. 1 illustrates the configuration of a system that amount feedback correction value prevailing immediately is equipped with a hydrogen addition internal combustion after startup increases. Therefore, the sixth aspect of the engine 10 according to a first embodiment of the present present invention can judge the property in accordance with invention. A cylinder of the internal combustion engine 10 these correction values. contains a piston 12, which reciprocates within the cylinder. 0.019 According to a seventh aspect of the present inven The internal combustion engine 10 also includes a cylinder head 14. A combustion chamber 16 is formed between the tion, a control system for a hydrogen addition internal piston 12 and cylinder head 14. The combustion chamber 16 combustion engine that uses hydrocarbon fuel and hydrogen communicates with an intake port 18 and an exhaust port 20. gas as combustion fuel, the control system comprises means The intake port 18 and exhaust port 20 are respectively for acquiring the amount of engine speed decrease imme provided with an intake valve 22 and an exhaust valve 24. diately after startup, an ignition timing feedback correction value prevailing immediately after startup, or a hydrocarbon 0029. The intake port 18 is provided with a gasoline fuel injection amount feedback correction value prevailing injection valve 26, which injects gasoline (hydrocarbon fuel) immediately after startup. The control system further com into the intake port 18. The intake port 18 is also provided prises addition ratio increase means that increases the ratio with a hydrogen fuel port injection valve 28, which injects of hydrogen gas addition to the hydrocarbon fuel when the hydrogen into the intake port 18. amount of engine speed decrease, the ignition timing feed 0030 The gasoline injection valve 26 communicates with back correction value, or the hydrocarbon fuel injection a gasoline tank 34 via a gasoline Supply pipe 32. The amount feedback correction value is not Smaller than a gasoline Supply pipe 32 is provided with a pump 36, which predetermined value. is positioned between the gasoline injection valve 26 and 0020 When the amount of engine speed decrease imme gasoline tank 34. The pump 36 is capable of generating a diately after startup, the ignition timing feedback correction predetermined pressure to Supply gasoline to the gasoline value prevailing immediately after startup, or the hydrocar injection valve 26. The gasoline injection valve 26 opens bon fuel injection amount feedback correction value pre when it receives a drive signal that is supplied from the Vailing immediately after startup is not Smaller than a outside, and injects a certain amount of gasoline into the predetermined value, it can be judged that the combustion intake port 18. The amount of gasoline injection into the state prevailing in a cylinder is deteriorated. Therefore, the intake port 18 varies with the period of time during which seventh aspect of the present invention can inhibit the the gasoline injection valve 26 is open. combustion state from deteriorating by increasing the ratio 0031. The system according to the present embodiment of hydrogen gas addition to the hydrocarbon fuel. As a includes a hydrogen tank 38, which stores hydrogen in result, the present invention can offer good emission and gaseous state under high pressure. The hydrogen tank 38 driveability. communicates with a hydrogen Supply pipe 40. The hydro 0021. Other and further objects, features and advantages gen Supply pipe 40 communicates with the hydrogen fuel of the invention will appear more fully from the following port injection valve 28. As the hydrogen fuel to be supplied description. to the hydrogen fuel port injection valve 28, the system according to the present embodiment uses the hydrogen gas

BRIEF DESCRIPTION OF DRAWINGS that is filled into the hydrogen tank 38 from the outside. However, the present invention is not limited to the use of 0022 FIG. 1 illustrates the configuration of a system that Such hydrogen fuel. An alternative is to use hydrogen-rich is equipped with a hydrogen addition internal combustion gas that contains highly concentrated hydrogen and is gen engine according to embodiments of the present invention. erated within a vehicle or supplied from the outside. 0023 FIG. 2 illustrates the processing steps performed 0032. The hydrogen supply pipe 40 is provided with a by the system according to the first embodiment. regulator 44. When this configuration is employed, the hydrogen in the hydrogen tank 38 is supplied to the hydro 0024 FIG. 3 illustrates the processing steps performed gen fuel port injection valve 28 while the pressure is by the system according to the second embodiment. decreased by the regulator 44 as predefined. Therefore,

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when the hydrogen fuel port injection valve 28 opens upon is possible to inhibit the combustion status from deteriorat receipt of a drive signal that is Supplied from the outside, the ing due to the use of heavy fuel. hydrogen fuel port injection valve 28 injects hydrogen into 0039 The gasoline property is judged according, for the intake port 18. The amount of hydrogen injection varies instance, to the engine speed prevailing immediately after with the period of time during which the hydrogen fuel port startup. If the gasoline is heavy, the engine speed prevailing injection valve 28 is open. immediately after startup is lower than when the gasoline 0033. Further, the hydrogen supply pipe 40 is provided property is normal. Therefore, a threshold value for heavi with a fuel pressure sensor 48, which is positioned between ness judgment is predetermined, and the gasoline is judged the regulator 44 and hydrogen fuel port injection valve 28. to be heavy when the engine speed prevailing immediately The fuel pressure sensor 48 generates an output in accor after startup is below the threshold value. dance with the pressure of the hydrogen supplied to the 0040. Further, when the engine speed prevailing imme hydrogen fuel port injection valve 28. The system according diately after startup is decreased, feedback corrections are to the present embodiment controls the regulator 44 in made by exercising control so as to advance the ignition accordance with the output generated by the fuel pressure timing or increase the amount of gasoline injection. There sensor 48. Therefore, even when the hydrogen supplied from fore, the gasoline property may be judged in accordance the hydrogen tank 38 varies in pressure, hydrogen can be with the amount of ignition timing correction or gasoline supplied to the hydrogen fuel port injection valve 28 under injection amount correction.

a steady pressure.

0041 When the gasoline is judged to be heavy, the 0034. The system according to the present embodiment amount of hydrogen addition is determined in accordance includes an ECU 50. To enable the ECU 50 to grasp the with the degree of heaviness. In this instance, it is preferred operation status of the internal combustion engine 10, the that the amount of hydrogen addition be determined while ECU 50 is connected not only to the aforementioned fuel considering the cooling water temperature, because the pressure sensor 48, but also to a KCS sensor for knocking combustion status prevailing in a cylinder varies with the detection and various other sensors (not shown) for detect cooling water temperature.

ing, for instance, the throttle opening, engine speed, exhausts temperature, cooling water temperature, lubricat 0042 Next, the processing steps performed by the system ing oil temperature, and catalyst floor temperature, etc. The according to the present embodiment will be described with ECU 50 is also connected to actuators such as the afore reference to a flowchart in FIG. 2. First of all, step S1 is mentioned gasoline injection valve 26, hydrogen fuel port performed to judge the gasoline property in accordance with injection valve 28, and pump 36, etc. When this configura the engine speed prevailing immediately after startup. In this tion is employed, the ECU 50 can arbitrarily select an instance, the gasoline property may be judged in accordance injection valve to inject fuel in accordance with the opera with the amount of ignition timing correction or gasoline tion status of the internal combustion engine 10. injection amount feedback correction as described earlier. 0035. Therefore, when the hydrogen fuel port injection 0043. If the judgment result obtained in step S1 indicates valve 28 injects hydrogen in accordance with the operation that the gasoline is heavy, the flow proceeds to step S2. In status of the internal combustion engine 10, it is possible to step S2, a target hydrogen addition ratio is calculated in maintain a good combustion state in a cylinder (in the accordance with parameters that indicate the degree of combustion chamber 16), thereby reducing the NO, exhaust gasoline heaviness, cooling water temperature, and other amount. operating conditions. For calculation, a map for heavy gasoline is used. The target hydrogen addition ratio is 0.036 Meanwhile, the gasoline property varies and affects calculated with the degree of gasoline heaviness, cooling the combustion status prevailing in a cylinder. The gasoline water temperature, and other parameters applied to the map. injected from the gasoline injection valve 26 is likely to In this instance, the heavier the gasoline, the higher the adhere to the wall surface of the intake port 18 or the inner target hydrogen addition ratio. Further, the lower the cooling wall Surface of a cylinder particularly when the gasoline is water temperature, the higher the target hydrogen addition heavy. Then, unstable combustion may result due to a ratio. The reason is that the combustion status deteriorates decrease in the degree of gasoline atomization, when the with a decrease in the cooling water temperature. gasoline is heavy.

0044) If, on the other hand, the judgment result obtained 0037. Therefore, the system according to the present in step S1 indicates that the gasoline is not heavy but normal, embodiment judges the gasoline property. When the gaso the flow proceeds to step S3. In this instance, a map for line is heavy, the system according to the present embodi normal gasoline is used for calculation. The target hydrogen ment increases the amount of hydrogen injection from the addition ratio is calculated with the cooling water tempera hydrogen fuel port injection valve 28. Consequently, a good ture and other parameters applied to the map. The target combustion state can be maintained even when the gasoline hydrogen addition ratio calculated in steps S2 and S3 is heavy. represents the ratio of hydrogen gas combustion energy to 0038 Emission/driveability deterioration due to the gaso the engine load factor.

line property mainly occurs during a first idling period, 0045. After completion of step S2 or S3, the flow pro which comes immediately after startup. It is therefore pre ceeds to step S4. In step S4, the amount of actual hydrogen ferred that the amount of hydrogen gas be increased during addition from the hydrogen fuel port injection valve 28 is the first idling period. However, even when the amount of determined in accordance with the target hydrogen addition hydrogen gas is increased during an idling period that comes ratio calculated in step S2 or S3. More specifically, the after the first idling period or during a normal operation, it amount of hydrogen addition is determined by determining

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the load factor from the accelerator opening and engine addition ratio is calculated from the cooling water tempera speed, multiplying the load factor by the target hydrogen ture by using a map. A sufficiently great initial value is set addition ratio, and multiplying the obtained result by a so that good combustion results without regard to the predetermined coefficient. The internal combustion engine gasoline property. This ensures that a good combustion state 10 is then operated in accordance with the determined is maintained during the first idling period. Thus, steady hydrogen addition amount. idling can be conducted. As a result, it is possible to properly 0046. As described above, the first embodiment can inhibit emission and driveability from deteriorating due to increase the amount of hydrogen gas addition when the the fuel property during the first idling period. gasoline is judged to be heavy. Therefore, the first embodi 0053) If, on the other hand, the judgment result obtained ment properly inhibits the combustion status from deterio in step S11 indicates that a period of longer than two seconds rating due to the use of heavy fuel, thereby offering good has elapsed after startup, the flow proceeds to step S13. In emission and driveability. this instance, step S12 has already been performed, so as to Second Embodiment maintain idling steady during the first idling operation. Since only the required amount of hydrogen gas is Supplied 0047 A second embodiment of the present invention will accordingly, steps S13 and beyond are performed to now be described. The second embodiment employs the decrease the hydrogen addition ratio. same system configuration as indicated in FIG. 1. The 0054 More specifically, step S13 is performed to judge second embodiment particularly inhibits emission and drive whether the current hydrogen addition ratio is greater than a ability from deteriorating during the first idling period, lower-limit value. As described later with reference to the which comes immediately after startup.

flowchart in FIG. 4, the lower-limit value for the hydrogen 0.048 When the gasoline is heavy, it adheres to the wall addition ratio is determined from a heaviness index, which surface of the intake port 18 or the inner wall surface of a indicates the degree of gasoline heaviness. cylinder. Thus, emission and driveability may deteriorate 0055. If the judgment result obtained in step S13 indi because cold hesitation is likely to occur particularly at cold cates that the current hydrogen addition ratio is greater than startup. As such being the case, the second embodiment the lower-limit value, the flow proceeds to step S14. Step increases the hydrogen addition amount during the first S14 is performed to decrease the hydrogen addition ratio by idling period by setting a great initial value for the hydrogen a predetermined value. If, on the other hand, the judgment addition ratio. After the end of the first idling period, the result obtained in step S13 indicates that the current hydro second embodiment exercises control so as to decrease the hydrogen addition amount to a lower-limit value that varies gen addition ratio is not greater than the lower-limit value, with the gasoline property. the flow proceeds to step S15.

0049. When a great initial value is constantly employed 0056. After completion of step S12 or S14, the flow proceeds to step S15. Step S15 is performed to determine the for the hydrogen addition ratio as described above, it is actual amount of hydrogen addition from the hydrogen fuel possible to inhibit the combustion status prevailing during port injection valve 28 in accordance with a target hydrogen the first idling period from being affected by the gasoline addition ratio, which was determined in step S12 or S14. property. This makes it possible to employ a low idling More specifically, the hydrogen addition amount is deter speed setting, provide increased fuel efficiency during the mined by determining the load factor from the accelerator first idling period, and offer good emission and driveability. opening and engine speed, multiplying the load factor by the Further, since the hydrogen addition amount is decreased to target hydrogen addition ratio, and multiplying the obtained a required level after the end of the first idling period, the result by a predetermined coefficient. The internal combus amount of hydrogen use can be minimized to provide tion engine 10 is then operated in accordance with the increased system efficiency. determined hydrogen addition amount. 0050. Next, the processing steps performed by the system 0057 Next, the process for calculating the lower-limit according to the second embodiment will be described with value for the hydrogen addition ratio, which is used in step reference to flowcharts in FIGS. 3 and 4. The flowchart in S13 as indicated in FIG. 3, will be described with reference FIG. 3 indicates processing steps that are performed to set to FIG. 4. First of all, step S21 is performed to judge a high hydrogen addition ratio for the first idling period and whether two seconds have elapsed after startup, that is, decrease the hydrogen addition ratio to a lower-limit value whether a first idling operation is currently performed. If the after the end of the first idling period. The flowchart in FIG. elapsed time from startup is not longer than two seconds, a 4 indicates processing steps that are performed to calculate first idling operation is currently performed; therefore, the the lower-limit value, to which the hydrogen addition ratio flow proceeds to step S12. If, on the other hand, more than is decreased after the end of the first idling period, in two seconds have elapsed after startup, the process termi accordance with the degree of gasoline heaviness. nates (RETURN).

0051. The processing steps shown in FIG. 3 will now be 0.058 When the flow proceeds to step S22, steps S12 to described. First of all, step S11 is performed to judge S15 have already been performed as indicated in FIG. 3 to whether two seconds have elapsed after startup, that is, add hydrogen gas in accordance with the hydrogen addition whether a first idling operation is currently performed. If the ratio initial value. With hydrogen already added in accor elapsed time from startup is not longer than two seconds, a dance with the hydrogen addition ratio initial value, step S22 first idling operation is currently performed; therefore, the is performed to control the idling speed by increasing/ flow proceeds to step S12. decreasing the gasoline injection amount. 0.052 Step S12 is performed to set an initial value for the 0059. When the idling speed is stabilized at a desired hydrogen addition ratio. The initial value for the hydrogen value, step S23 is performed to determine the prevailing

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amount of gasoline injection amount increase Af. If the 0066. When intra-cylinder combustion becomes unstable gasoline is heavy, the degree of gasoline atomization is low; due to the gasoline property, the aforementioned factor, or therefore, the value Affor the first idling period is greater other factor, the third embodiment provides a good com than normal. bustion state by increasing the hydrogen gas addition amount.

0060. In step S24, the heaviness index is calculated in 0067. The processing steps performed by the system accordance with the increase amount Af, which was deter mined in step S23, by using a map that defines the relation according to the present embodiment will now be described ship between the increase amount Alf and the degree of with reference to a flowchart in FIG. 5. First of all, step S31 gasoline heaviness (heaviness index). In this instance, the is performed to judge the intra-cylinder combustion status in greater the increase amount Af, the higher the degree of accordance with the engine speed prevailing immediately heaviness and thus the greater the heaviness index. after startup. When the intra-cylinder combustion status is deteriorated due to the gasoline property or the aforemen 0061. In step S25, the hydrogen addition ratio lower-limit tioned factor, the engine speed decreases immediately after value is calculated in accordance with the heaviness index startup. Therefore, a threshold engine speed is predefined for and cooling water temperature. The greater the heaviness combustion status judgment. If the engine speed prevailing index, the higher the degree of gasoline heaviness and thus immediately after startup is lower than the threshold engine the hydrogen addition amount needs to be increased to speed, step S31 judges that the intra-cylinder combustion provide stable combustion. Therefore, a great lower-limit status is deteriorated.

value is set. Further, when the cooling water temperature 0068 If the engine speed is decreased due to intra decreases, the hydrogen addition amount needs to be cylinder combustion status deterioration immediately after increased to provide good combustion. Therefore, a great startup, feedback corrections are made by exercising control lower-limit value is set. After completion of step S25, the to advance the ignition timing or increase the gasoline process terminates. injection amount. In step S31, therefore, the intra-cylinder 0062) When the processing steps shown in FIG. 4 are combustion status may be judged in accordance with the performed, the hydrogen addition ratio lower-limit value can amount of ignition timing correction or gasoline injection be determined in accordance with the increase amount Af of amount correction.

gasoline injection amount for the first idling period. The 0069. If the judgment result obtained in step S31 indi hydrogen addition ratio lower-limit value is determined cates that the combustion status is deteriorated, the flow while considering the gasoline property. Therefore, when proceeds to step S32. In step S32, a target hydrogen addition hydrogen is added beyond the lower-limit value after the end ratio is calculated in accordance with parameters that indi of the first idling period by performing the processing steps cate the degree of combustion status deterioration, cooling in FIG. 3, it is possible to inhibit the combustion status from water temperature, and other operating conditions. More becoming unstable due to the gasoline property. As a result, specifically, the target hydrogen addition ratio is calculated good emission and driveability can be offered. with the engine speed decrease amount, ignition timing 0063 As described above, the second embodiment correction amount, or gasoline injection amount correction increases the hydrogen addition amount during the first amount and cooling water and other operating condition idling period by setting a great initial value for the hydrogen indicating parameters applied to a map for use in a situation addition ratio. It is therefore possible to inhibit the combus where the combustion status is deteriorated. In this instance, tion status from deteriorating due to the gasoline property the greater the engine speed decrease amount or the afore during the first idling period. This ensures that a stable idling mentioned correction amount, the higher the target hydrogen operation is performed. Consequently, good emission and addition ratio setting. Further, when the cooling water tem driveability can be offered. Further, since the hydrogen perature decreases, the combustion status deteriorates; there addition amount is decreased to a required level after the end fore, the target hydrogen addition ratio setting increases. of the first idling period, the amount of hydrogen use can be 0070) If, on the other hand, the judgment result obtained minimized to provide increased system efficiency. in step S31 indicates that the combustion status is normal, the flow proceeds to step S33. In this instance, the target

Third Embodiment hydrogen addition ratio is calculated with the cooling water temperature and other operating condition indicating param 0064. A third embodiment of the present invention will eters applied to a normal map.

now be described. When combustion becomes unstable immediately after startup due to the gasoline property or 0071. After completion of step S32 or S33, the flow proceeds to step S34. In step S34, the amount of actual other factor, the third embodiment increases the hydrogen hydrogen addition from the hydrogen fuel port injection addition amount to provide good combustion in a cylinder. valve 28 is determined in accordance with the target hydro The system configuration employed for the third embodi gen addition ratio determined in step S32 or S33. More ment is the same as indicated in FIG. 1. specifically, the hydrogen addition amount is determined by 0065. If combustion instability encountered at startup is determining the load factor from the accelerator opening and not due to the gasoline property, it is conceivable, for engine speed, multiplying the load factor by the target instance, that fuel ignitability may be lowered by gasoline hydrogen addition ratio, and multiplying the obtained result droplets formed on the ignition plug. Combustion instability by a predetermined coefficient. The internal combustion also occurs if, for instance, the gasoline is bubbled at a high engine 10 is then operated in accordance with the deter temperature before it is injected from the gasoline injection mined hydrogen addition amount.

valve 26 so that the amount of gasoline injection from the 0072. As described above, the third embodiment can gasoline injection valve 26 is Smaller than a specified value. increase the hydrogen gas addition amount if a predeter

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mined value is exceeded by the amount of engine speed 5. The control system for said hydrogen addition internal decrease immediately after startup, the amount of ignition combustion engine according to claim 4, further comprising: timing correction, or the amount of gasoline injection amount correction. Thus, the third embodiment can properly fuel property judgment means for judging the property of inhibit the combustion status from deteriorating at startup, hydrocarbon fuel, thereby offering good emission and driveability.

wherein said addition ratio decrease means decreases said 1. A control system for a hydrogen addition internal ratio of hydrogen gas addition to a lower-limit value combustion engine that uses hydrocarbon fuel and hydrogen that is derived from the property of the hydrocarbon gas as combustion fuel, said control system comprising: fuel.

fuel property judgment means for judging the property of 6. The control system for said hydrogen addition internal hydrocarbon fuel; and combustion engine according to claim 5, wherein said fuel addition ratio increase means that, when the hydrocarbon property judgment means judges the property of the hydro fuel is found to be heavy, increases the ratio of hydro carbon fuel in accordance with the engine speed prevailing gen gas addition to the hydrocarbon fuel.

2. The control system for said hydrogen addition internal immediately after startup, an ignition timing feedback cor combustion engine according to claim 1, wherein said rection value prevailing immediately after startup, or a addition ratio increase means ensures that said ratio of hydrocarbon fuel injection amount feedback correction hydrogen gas addition increases with an increase in the value prevailing immediately after startup. degree of hydrocarbon fuel heaviness.

3. The control system for said hydrogen addition internal 7. A control system for a hydrogen addition internal combustion engine according to claim 1, wherein said fuel combustion engine that uses hydrocarbon fuel and hydrogen property judgment means judges the property of the hydro gas as combustion fuel, said control system comprising: carbon fuel in accordance with the engine speed prevailing means for acquiring the amount of engine speed decrease immediately after startup, an ignition timing feedback cor immediately after startup, an ignition timing feedback rection value prevailing immediately after startup, or a hydrocarbon fuel injection amount feedback correction correction value prevailing immediately after startup, value prevailing immediately after startup. or a hydrocarbon fuel injection amount feedback cor 4. A control system for a hydrogen addition internal rection value prevailing immediately after startup; and combustion engine that uses hydrocarbon fuel and hydrogen addition ratio increase means that increases the ratio of gas as combustion fuel, said control system comprising: hydrogen gas addition to the hydrocarbon fuel when addition ratio initial value setup means that sets a prede said amount of engine speed decrease, said ignition termined initial value for the ratio of hydrogen gas timing feedback correction value, or said hydrocarbon addition to the hydrocarbon fuel at startup; and fuel injection amount feedback correction value is not addition ratio decrease means that decreases said ratio of Smaller than a predetermined value. hydrogen gas addition to said hydrocarbon fuel when a predetermined period of time elapses after startup.