JP2002038981A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ideal internal combustion engine for improving exhaust performance, heat efficiency or engine output by changing a composition of fuel supplied to the engine by changing the fuel modifying condition. SOLUTION: Load of the internal combustion engine is judged according to a map determined by torque estimated from the revolutions of the internal combustion engine and the accelerator pedal opening. When load is low, compression ignition combustion is performed by modified fuel containing much dimethyl ether. When load is middle, spark ignition combustion is performed by modified fuel containing much H2 and CO and methanol fuel. When load is high, spark ignition combustion is performed by methanol fuel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine having a fuel reformer and operating an engine using reformed fuel.

[0002]

2. Description of the Related Art As a conventional internal combustion engine, there is one described in, for example, "Fuel Association, Vol. 65, No. 12, 1986". As shown in FIG. 11, a reformer 03 is mounted on an exhaust pipe 02 of an internal combustion engine 01, and reformed fuel is generated by the reformer 03 using exhaust heat. The reformed fuel is supplied from the methanol fuel injection valve 04 to the intake pipe 05 of the internal combustion engine 01 and is burned in the combustion chamber. The methanol fuel injection valve 04 is provided in the intake pipe 05 of the fuel engine 01, and is configured to supply methanol fuel to the internal combustion engine 01 according to the operating state of the engine. When the exhaust gas of the engine becomes higher than a predetermined temperature, the bypass valve 06 is opened to reduce the amount of exhaust gas flowing into the reformer 03, thereby preventing the reformer 03 from being damaged by heat. . Here, the generated reformed fuel is a reformed fuel (MRG: metanoref) mainly composed of hydrogen and carbon monoxide obtained by reforming methanol fuel.
ormed gas), the lean burn limit is high,
Stable engine operation is possible even in a lean region. Thus, the internal combustion engine 01 provided with the reformer 03 simultaneously achieves high efficiency and reduction of the nitrogen oxide concentration (NO _x ) in the exhaust gas. Further, the internal combustion engine 0 having the reformer 03
1 is shown in FIG. 12, in the region where the engine load is low,
Exhaust performance and thermal efficiency are improved by running only reformed fuel,
In an area where the engine load is high, high output is obtained by operation with methanol fuel only.In the middle operation area, reformed fuel is used to improve the exhaust performance while securing the required output. It is configured to operate using methanol fuel in combination.

[0003]

However, in such a conventional internal combustion engine, FIG. 13 (source: "Research on Combustion Technology of Methanol Reformed Fuel Engine", KUBOTA TECHNICA) in a region where the engine load is low.
L REPORT No. 33, 1997, as the excess air ratio increases and the combustion becomes leaner,
Although emissions O _x is reduced, increased emissions of carbon monoxide (CO), it was impossible improving the thermal efficiency with the exhaust performance deteriorates. Further, in a conventional general internal combustion engine that performs compression ignition combustion, there is a problem that the output cannot be improved in an area where the load of the engine is high as compared with an internal combustion engine that performs spark ignition combustion. The present invention has been made in view of such conventional problems,
It is an object of the present invention to provide an internal combustion engine that is ideal for improving exhaust performance, thermal efficiency, or engine output by changing fuel composition supplied to the engine by changing fuel reforming conditions.

[0004]

According to a first aspect of the present invention, there is provided an internal combustion engine which operates by burning liquid fuel or gas fuel supplied from a fuel supply device. When the load is low, compression ignition fuel is supplied to the internal combustion engine to be burned by compression ignition, and when the operation state of the internal combustion engine is medium load or higher, spark ignition fuel is supplied to the internal combustion engine. It is configured to burn by spark ignition. According to a second aspect of the present invention, in the first aspect of the invention, the fuel supply device has a fuel reformer for reforming a fuel composition, and the liquid fuel is a hydrocarbon-based fuel. The gas fuel is a reformed fuel obtained by reforming the liquid fuel with a fuel reformer. The internal combustion engine according to claim 3 is
In the invention according to claim 2, when the hydrocarbon-based fuel is an alcohol-based fuel and the combustion is combustion by compression ignition, a high cetane number fuel obtained by reforming the alcohol-based fuel as the compression ignition fuel is used. When the fuel is supplied to an internal combustion engine and the combustion is performed by spark ignition, at least one of a fuel obtained by reforming an alcohol-based fuel with hydrogen as a main component as a spark ignition fuel or an alcohol fuel is supplied. I have.

According to a fourth aspect of the present invention, when the hydrocarbon-based fuel is light oil fuel and the combustion is compression ignition combustion, light oil is used as the compression ignition fuel. When the fuel is supplied to the internal combustion engine and the combustion is combustion by spark ignition, at least one of a fuel obtained by reforming light oil fuel with hydrogen as a main component or a fuel obtained by reforming the fuel into a high octane number fuel as a fuel for spark ignition. Is supplied. The internal combustion engine according to claim 5 is
In the invention according to any one of claims 2 to 4, when the fuel reformer does not satisfy a preset reforming condition, the fuel before reforming is supplied to the internal combustion engine. According to a sixth aspect of the present invention, in the internal combustion engine according to any one of the second to fifth aspects, the composition of the reformed fuel is controlled by controlling a reforming temperature in the fuel reformer. ing. An internal combustion engine according to a seventh aspect is the second aspect.
The invention according to any one of the above-mentioned items, wherein the engine includes a flow control valve for adjusting an intake air amount in an intake pipe of the engine,
The opening degree of the flow control valve is controlled in accordance with the switching of the combustion mode.

[0006]

According to the internal combustion engine according to the first aspect of the present invention, the fuel and the combustion having the composition suitable for the load of the internal combustion engine can be used.
Exhaust performance, thermal efficiency and output can be improved. According to the second aspect of the present invention, the composition of the fuel can be changed by the fuel reformer provided in the fuel supply device, and the fuel having a composition suitable for the load of the internal combustion engine can be supplied to the internal combustion engine. According to the third aspect of the invention, in the case of alcohol fuel, the thermal efficiency can be improved while reducing the emission of nitrogen oxides and carbon monoxide at the time of combustion by compression ignition, and the exhaust performance can be improved at the time of combustion by spark ignition. Alternatively, engine output can be secured. According to the fourth aspect of the invention, in the case of light oil fuel, operation with high thermal efficiency can be performed during combustion by compression ignition, and exhaust performance or engine output can be improved during combustion by spark ignition. According to the fifth aspect of the invention, when the fuel reformer does not satisfy the preset reforming condition, the internal combustion engine can be stably operated by supplying the fuel before reforming to the internal combustion engine. According to the sixth aspect of the invention, by changing the reforming temperature, fuels having different compositions can be generated. According to the seventh aspect of the present invention, it is possible to eliminate a torque step when switching the combustion mode between combustion by compression ignition and combustion by spark ignition.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic concept of the present invention is shown in FIG. 1 by taking methanol fuel as an example of an alcohol fuel among hydrocarbon fuels and light oil fuel as an example of a hydrocarbon fuel. As shown in FIG. 1A, when the fuel is methanol and the operating state of the engine is a low load, the fuel contains a large amount of dimethyl ether, for example, a cetane number of 40.
Combustion by compression ignition (hereinafter referred to as compression ignition combustion) is performed with a high or higher cetane number reformed fuel, and in the case of a medium load, spark ignition is performed by a reformed fuel containing a large amount of H ₂ and CO and methanol fuel. Combustion (hereinafter, spark ignition combustion) is performed. In the case of a high load, spark ignition combustion is performed using methanol fuel having a high octane number of, for example, about 100 or more. Further, as shown in FIG. 1B, when the fuel is light oil and the operation state of the engine is a low load, for example, a light oil fuel having a high cetane number of about 40 or more is used. Compression ignition combustion is performed. In the case of a medium load, spark ignition combustion is performed with a reformed fuel containing a large amount of H ₂ and CO reformed from light oil and a high octane number fuel. Spark ignition combustion is performed by using high quality octane number fuel having an octane number of about 100 or more.

Hereinafter, embodiments of the present invention based on the above basic concept will be described in detail. <First Embodiment> FIG. 2 is a configuration diagram of an internal combustion engine according to a first embodiment of the present invention. In this embodiment, methanol fuel is used as the hydrocarbon fuel. The reformer 3 is mounted on the exhaust pipe 2 of the internal combustion engine 1 and reforms the fuel using the exhaust heat. The bypass valve 4 controls the exhaust pipe 2 that bypasses the reformer 3 so that the amount of exhaust gas flowing into the reformer 3 is adjusted.
Is configured. The methanol fuel pumped from the fuel tank 5 by the fuel pump 6 is reformed by the reformer 3, and the reformed fuel is switched by switching the switching valve 7 in accordance with the reforming temperature, thereby storing the reservoirs a and the reservoirs. b, and the switching valve 8 is switched in accordance with the operating conditions, so that the reformed fuel in the reservoirs a and b is supplied from the reformed fuel injection valve 10 into the cylinder of the internal combustion engine 1 via the regulator 9. It is configured to supply.

In this embodiment, the fuel supply system is provided separately from the fuel supply system, and methanol fuel pumped from the fuel tank 5 by the fuel pump 6 is supplied to the regulator 11.
Via a methanol fuel injection valve 13 provided in an intake pipe 12 of the internal combustion engine 1 in accordance with an operating condition.
Is configured to be supplied. Controller 14
Are the start information from the ignition switch 15, the rotation speed information from the internal combustion engine rotation detector 16, the temperature information from the internal combustion engine water temperature sensor 17, the temperature information from the temperature sensor 18 in the reformer, the accelerator pedal opening sensor 19 , The pressure information of the reservoirs a and b by the pressure sensors 20 and 21 and the fuel pump 6, the spark plug 22, the reformed fuel injection valve 10, and the methanol fuel injection valve 1.
3. Output control signals to the bypass valve 4, the electronically controlled throttle 23 attached to the intake pipe 12, and the switching valves 7, 8. Thereby, the controller 14
The engine is configured to supply fuel having a different fuel composition according to the operation state of the internal combustion engine 1 and to switch between compression ignition combustion and spark ignition combustion to operate the internal combustion engine.

Next, the compression ignition combustion using the reformed fuel obtained by reforming the methanol fuel will be described. FIG. 3 shows the relationship between the reforming temperature and the reformed fuel composition when the fuel is methanol fuel. When the reforming temperature is high, the composition of the reformed fuel is mainly composed of H ₂ and CO, but when the reforming temperature is low and within a certain range, the reformed fuel containing a large amount of dimethyl ether It consists of. Since dimethyl ether has a high cetane number, reformed fuel containing a large amount of dimethyl ether also has an improved cetane number. In the present embodiment, when the operating state of the engine is low load, reformed fuel containing a large amount of dimethyl ether (hereinafter referred to as reformed fuel A) is supplied to the engine to perform compression ignition combustion, and the operating state of the engine is medium. In the case of load,
A reformed fuel containing a large amount of H ₂ and CO (hereinafter referred to as “reformed fuel B”) and methanol fuel are supplied to the engine to perform spark ignition combustion, and when the operating state of the engine is high, the methanol fuel is supplied. The engine is configured to be supplied to the engine to perform spark ignition combustion.

Here, when the operating state of the engine is low load as described above, the compression ignition combustion is performed by the reformed fuel A. However, since the compression ignition combustion is the self-ignition combustion,
The ignition point is higher than that of spark ignition combustion, and there is no phenomenon that the flame cannot be completely propagated and carbon monoxide remains unburned as in the flame propagation combustion of spark ignition combustion, so that the amount of carbon monoxide emission can be significantly reduced. Therefore, by performing compression ignition combustion, the amount of carbon monoxide emission can be reduced, and at the same time, the lean burn range of reformed fuel, which has been limited by the increase in carbon monoxide emission, can be expanded. And the thermal efficiency of the engine can be improved. Further, compression ignition combustion can be performed by using a fuel having a high cetane number, which is an index indicating ignitability.

When the operating state of the engine is a medium load, spark ignition combustion is carried out with a reformed fuel B containing a large amount of H ₂ and CO and a methanol fuel to reduce NO _x emissions and reduce exhaust gas. The performance can be improved, and when the operating state of the engine is high load, high output required by the engine can be secured by performing spark ignition combustion with methanol fuel. Since methanol fuel is a high octane fuel, even if the engine is configured with a high compression ratio by compression ignition combustion using reformed fuel, stable spark ignition combustion is possible without knocking.

Next, in this embodiment, a control method of the controller 14 for performing fuel generation by the reformer 3 and switching between compression ignition combustion and spark ignition combustion will be described with reference to a flowchart shown in FIG. In the flowchart shown in FIG. 4, in step 10 (referred to as S10 in the figure, the same applies hereinafter), an initialization process is performed in preparation for starting the engine with methanol fuel. That is, in conjunction with the turning on of the ignition switch 15, the reforming fuel injection valve 10 is closed, the fuel pump 6 is turned on, the water temperature of the internal combustion engine 1 is measured from the water temperature sensor 17 of the internal combustion engine, and methanol fuel is measured in accordance with the temperature. The injection period and the injection timing at the time of starting the injection valve 13 are set, and the ignition timing of the ignition plug 22 is set. Further, in order to quickly raise the temperature of the reformer 3 after the start, the bypass valve 4
Is fully closed. In this state, the starter is turned on, methanol fuel is injected, and the ignition plug 22 is ignited to start. In step 20, the engine is operated by continuously supplying methanol fuel. Here, if the reformed fuel in the reservoirs a and b is not in a state where it can be supplied to the engine, spark ignition combustion is performed with methanol fuel regardless of the load on the engine. In step 21, the pressures in the reservoirs a and b are measured and stored as Pa1 and Pb1, respectively, in preparation for the following step of performing pressure control in the reservoirs. In step 22, it is determined that the internal combustion engine is stopped (ignition switch OFF). If the internal combustion engine is not stopped, the process proceeds to step 40. In the case of stopping the internal combustion engine, in step 23, stop processing such as closing the methanol fuel injection valve 13 and the reformed fuel injection valve 10 and turning off the fuel pump 6 is performed.
The control ends.

Step 40, Step 60, Step 8
0 and step 90 generate reformed fuel and store the reservoirs a and b so that the reformed fuel can be stably supplied to the internal combustion engine 1.
For storing reformed fuel therein. That is,
If the pressures Pa and Pb in the reservoirs are equal to or lower than the upper limit values in step 40, the opening degree of the bypass valve 4 is controlled in step 60 so that the reforming temperature Tr falls within the range from the set value 1 to the set value 2. Then, the reformed fuel A is generated and supplied to the storage a, and similarly, the reformed fuel B is generated so as to be in the range of the set value 3 to the set value 4, and is supplied to the storage b. , B
The generation of the reformed fuel is controlled so that the pressures inside are both below the upper limit and above the lower limit. In step 90, if the pressure of the reformed fuel is equal to or higher than the lower limit value, the fuel can be supplied to the engine. Supply. In step 80, if the pressure in the storage is equal to or higher than the upper limit, the process proceeds to step 100 without generating reformed fuel. The generation control of the reformed fuel in step 60 will be described later.

In step 100, it is determined whether the load of the internal combustion engine 1 is low load, medium load or high load. If the load is low, compression ignition combustion is performed with the reformed fuel A in step 110, In this case, the routine proceeds to step 120, where spark ignition combustion is performed using the reformed fuel B and the methanol fuel. If the load is high, the routine proceeds to step 130, where spark ignition combustion is performed with methanol fuel. Here, in step 100, the load is determined based on a map determined based on the rotational speed of the internal combustion engine 1 and the torque estimated from the accelerator pedal opening. In step 110, since there is a case where the mode is switched from spark ignition combustion to compression ignition combustion, the electronically controlled throttle opening is controlled so that a torque step of the internal combustion engine 1 does not occur. That is, at the same load, the throttle opening is large during compression ignition combustion, and the throttle opening is narrowed during spark ignition combustion. The throttle opening is modified to eliminate a large torque step when switching the combustion mode of ignition combustion.
Here, the throttle opening is read based on a map determined by the operating state of the internal combustion engine 1 and the combustion mode, and the throttle opening is switched when the combustion mode is switched to eliminate the torque step.

In step 110 following the above control, in order to supply the reformed fuel A to the engine, the switching valve 8 is switched, the methanol fuel injection valve 13 is closed, and at the same time the reformed fuel injection valve 10 is opened. High quality fuel A to internal combustion engine 1
The engine is operated by compression ignition combustion. Here, the reformed fuel injection valve 10 supplies the reformed fuel in an injection period according to the operation state of the internal combustion engine 1. As described above, the reformed fuel A having a high cetane number (cetane number 40 or more) can be supplied at a low load to perform compression ignition combustion. Step 12
0, also in step 130, for the same reason as in step 110, the throttle opening is controlled so that a torque step of the internal combustion engine 1 does not occur when switching the combustion mode.
In step 120, the switching valve 8 is switched to supply the reformed fuel B and the methanol fuel to the engine,
The reformed fuel injection valve 10 and the methanol fuel injection valve 13 are simultaneously opened, the reformed fuel B and the methanol fuel are supplied into the internal combustion engine 1 and the engine is operated by spark ignition combustion. here,
The reformed fuel injection valve 10 and the methanol fuel injection valve 13 supply the injection amount according to the operation state of the internal combustion engine 1 and the reformed fuel during the injection period, and the ignition plug 22 operates according to the operation state of the internal combustion engine 1. Ignition at the ignition timing. As described above, the reformed fuel B and the methanol fuel can be supplied at the time of medium load, and spark ignition combustion can be performed.

In step 130, in order to supply methanol fuel to the engine, the reformed fuel injection valve 10 is closed and the methanol fuel injection valve 13 is opened at the same time to supply methanol fuel into the internal combustion engine 1 and spark ignition. The engine is operated by combustion. Here, the methanol fuel injection valve 13 supplies the reforming fuel during the injection period and the injection amount according to the operation state of the internal combustion engine 1, and the ignition plug 22 ignites at the ignition timing according to the operation state of the internal combustion engine 1. I do. As described above, at high load, methanol fuel having a high octane number (about 120 octane number) can be supplied to perform spark ignition combustion.

Here, the reformed fuels A,
An example of the generation control method of B will be described based on the control sub-flowchart of FIG. When the storage amounts of the reformed fuels A and B are not enough and the pressures of the storages a and b are less than the upper limit,
The reformed fuel is supplied in order from the lower reservoir pressure. Here, once reforming is started in either of the reservoirs, the pressure in the reservoir rises by a certain pressure relative to the pressure measured before the reforming is started, or until the pressure reaches the upper limit. Continue quality. If either one is satisfied,
The supply of the reformed fuel is repeated from the lower reservoir pressure of the reservoir again so that the reformed fuel is always stored in the reservoirs a and b. More specifically, if the storage amounts of the reformed fuels A and B are not sufficient at step 40 and the pressures of the storages a and b are less than the upper limit, the storage at the lower storage pressure is determined at step 62. To proceed to supply reformed fuel. Here, for example, when the pressure of the reservoir a is lower, the process proceeds to step 63, where the opening degree of the bypass valve 4 is adjusted, and in step 64, the reforming temperature Tr is set to the set values 1a and 2 shown in FIG.
If it is possible to control the distance to a, the process proceeds to step 65,
The reformed fuel A is generated. If the reforming temperature cannot be controlled within the set value even if the valve opening is adjusted, the process proceeds to step 66, and proceeds to step 67 without generating reformed fuel.

In step 67, before starting reforming, FIG.
The pressure Pa1 measured in step 21 is a constant pressure ΔP
Until the pressure in the reservoir reaches the upper limit value, the control is repeatedly performed in the main flowchart shown in FIG. 4. If either one of the conditions is satisfied, the process returns to step 62, and the reservoir pressure is again reduced. Control to supply reformed fuel to the other reservoir. Here step 68
Then, the pressure Pa1 stored in step 21 is updated and stored.

On the other hand, if the pressure in the storage b is lower, the same control is performed in steps 73 to 78,
The reformed fuel is always stored in the storages a and b. The method of controlling the generation of the reformed fuel is not limited to the present embodiment. That is, if the control can be performed between the set values 3a and 4a shown in FIG. 3 in step 74, the process proceeds to step 75, and the reformed fuel B is generated.

As described above, the combustion type is controlled by the controller 14.
Supply of high-cetane number reformed fuel A at low load
Supply, reformed fuel B and methanol fuel at medium load
At high loads, high octane methanol fuel is supplied.
Supply control. As explained so far,
When the operating condition of the Seki is low load, high cetane number dimethyl
Compression ignition combustion with a reformate containing a lot of ether
Exhaust performance and thermal efficiency can be greatly improved.
If the operation state of the Seki is medium load, H _Two , CO-rich
Performs spark ignition combustion with reformed fuel and methanol fuel
NO_x Improve exhaust performance by reducing emissions
When the engine is under heavy load,
Spark ignition combustion using methanol fuel with butane number
As a result, a high output required by the engine can be obtained.

<Embodiment 2> FIG. 6 is a block diagram of an internal combustion engine according to Embodiment 2 of the present invention. In the present embodiment, light oil fuel is used as the hydrocarbon fuel supplied to the internal combustion engine. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. The difference between the configuration of the present embodiment and the first embodiment is that
The fuel in the fuel tank 5 is light oil, and the reformed fuel generated from the light oil is supplied to the storage c and the storage d by switching the switching valve 7 according to the reforming temperature, and according to the operating conditions. Thus, the reforming fuel is supplied from the reforming fuel injection valves 26 and 27 via the regulators 24 and 25 so that the internal combustion engine 1 can perform spark ignition combustion. Further, in the present embodiment, as a separate fuel supply system, light oil fuel is supplied from the light oil fuel injection valve 29 into the cylinder of the internal combustion engine 1 via the regulator 28, so that compression ignition combustion can be performed. I have. Other configurations are the same as those of the first embodiment.

The controller 14 replaces the methanol injection valve 13 and the reformed fuel injection valve 10 in the first embodiment.
Control signals are output to the reformed fuel injection valves 26 and 27 and the light oil fuel injection valve 29. The configuration of the controller 14 other than outputting control signals to the switching valve 7 and the reforming fuel injection valves 26 and 27 is basically the same as that of the first embodiment.
The system is configured to supply fuel having a different fuel composition in accordance with the operating state of the internal combustion engine 1 and to switch between compression ignition combustion and spark ignition combustion to operate the internal combustion engine 1.

Next, the spark ignition combustion using the reformed fuel obtained by reforming the diesel fuel will be described. The light oil fuel represented by C ₁₂ H ₂₆ has the weakest C—C bond among straight chain bonds, as shown by the relationship between the antiknock property and the molecular structure of the paraffinic hydrocarbon in FIG. By dissolving the C—C bond, a fuel represented by C ₆ H ₁₄ having a small number of carbon atoms (hereinafter referred to as C ₆ ) can be obtained, and the anti-knock property can be increased and the octane value can be improved. Actually, by controlling the reforming temperature in a specific temperature range from the set value 1b to 2b so as to have a relationship between the reforming temperature and the reformed fuel composition in the case of the light oil fuel shown in FIG. can be the generated number of C ₆ a high-octane fuel (approximately octane 100). Further, by controlling the reforming temperature within a specific temperature range of the set values 3b to 4b, a reformed fuel containing a large amount of H ₂ and CO can be generated. Therefore, in the present embodiment, when the operating state of the engine is low load, light oil fuel (cetane number 40 or more) is supplied to the engine to perform compression ignition combustion,
In the case of a medium load, a reformed fuel containing a large amount of H ₂ and CO (hereinafter referred to as “reformed fuel C”) obtained by reforming light oil and a high octane number fuel containing a large amount of C ₆ are supplied to the engine to perform spark ignition combustion. When the operating state of the engine is high load, the operating state of the engine is changed so that high octane fuel containing a large amount of C ₆ (hereinafter referred to as reformed fuel D) is supplied to the engine to perform spark ignition combustion. The composition and the combustion mode of the fuel to be supplied are switched accordingly.

Next, in this embodiment, a control method by the controller 14 when switching between fuel generation, compression ignition combustion, and spark ignition fuel by the reformer 3 will be described with reference to a flowchart shown in FIG. In the flowchart shown in FIG. 9, in step 210, an initialization process is performed in preparation for starting the engine using light oil fuel. That is, in conjunction with the turning on of the ignition switch 15, the reforming fuel injection valves 26, 2
7 is closed, the fuel pump 6 is turned on, the water temperature of the internal combustion engine 1 is measured from the internal combustion engine water temperature sensor 17, and the injection period and the injection timing at the time of starting the light oil fuel injection valve 29 are determined according to the temperature of the internal combustion engine 1. Set. Further, in order to quickly raise the temperature of the reformer 3 after the start, the bypass valve 4 is fully closed. In this state, the starter is turned on, and light oil fuel is injected to start the engine.

In step 220, light oil fuel is continuously supplied and the engine is operated. Here, if the reformed fuel in the storages c and d is not in a state where it can be supplied to the engine, compression ignition combustion is performed with light oil fuel regardless of the load on the engine. In step 221, the pressures in the reservoirs c and d are measured in preparation for the following step of controlling the pressure in the reservoir, and P
c1 and Pd1 are stored. In step 222, it is determined that the internal combustion engine is stopped (ignition switch OFF). If the internal combustion engine is not stopped, the process proceeds to step 240. When the internal combustion engine is stopped, in step 223, stop processing such as closing the light oil fuel injection valve 29 and the reforming fuel injection valves 26 and 27 and turning off the fuel pump 6 is performed, and the control is terminated.

Steps 240, 260, 280, and 290 are steps for generating the reformed fuel and storing the reformed fuel in the storage so that the reformed fuel can be stably supplied to the internal combustion engine 1. This is basically the same as Steps 40 to 90 in FIG. 4 of Embodiment 1 except that the reforming temperature, the composition of the reformed fuel to be generated, and the set pressure value in the reservoir are different. Here, the generation control of the reformed fuels C and D in step 60 will be described with reference to FIG. Steps 262 to 2 in FIG.
77 is basically the same as step 62 to step 77 in FIG. 5 of the first embodiment except that the reforming temperature, the composition of the reformed fuel to be generated, and the set pressure value in the storage device are different. Note that the reformed fuel generation control method of the present invention is not limited to the present embodiment. Returning to FIG.
In step 300, it is determined whether the load of the internal combustion engine 1 is low load, medium load, or high load. If the load is low, the process proceeds to step 310 to perform compression ignition combustion with light oil fuel. Proceeding to step 320, the spark ignition combustion is performed with the reformed fuel C and the reformed fuel D. If the load is high, the process proceeds to step 330, and the spark ignition combustion is performed with the reformed fuel D. The method of determining the load in step 300 is the same as step 100 in FIG. 4 of the first embodiment.

In steps 310, 320, and 330, the throttle opening is controlled so that a torque step of the internal combustion engine does not occur when the combustion mode is switched, for the same reason as step 110 in FIG. 4 of the first embodiment. . In step 310 following the above control, in order to supply light oil fuel to the engine, the reformed fuel injection valves 26 and 27 are closed and the light oil fuel injection valve 29 is simultaneously opened to supply light oil fuel into the internal combustion engine 1. The engine is operated by compression ignition combustion. Here, the light oil fuel injection valve 29 supplies light oil fuel with an injection amount and an injection period according to the operation state of the internal combustion engine 1. As described above, it is possible to supply high-cetane number light oil fuel at low load and perform compression ignition combustion.

In step 320, the reformed fuel injection valve 2 is supplied to supply the reformed fuel C and the reformed fuel D to the engine.
At the same time as opening the valves 6 and 27, the light oil fuel injection valve 29 is closed, the reformed fuel C and the reformed fuel D are supplied to the internal combustion engine 1, and the engine is operated by spark ignition combustion. Here, the controller 14
Indicates that the reforming fuel injection valves 26 and 27 supply the reforming fuel C and the reforming fuel D during the injection period according to the operating state of the internal combustion engine 1 and the ignition timing according to the operating state of the internal combustion engine 1. Is controlled to ignite the spark plug 22. As described above, the reformed fuel C and the reformed fuel D can be supplied at the time of medium load, and spark ignition combustion can be performed. In step 330, the light oil fuel injection valve 29 is supplied to supply the reformed fuel D to the engine.
At the same time as the reformed fuel injection valve 26 is closed, the reformed fuel injection valve 27 is opened, the reformed fuel D is supplied into the internal combustion engine, and the engine is operated by spark ignition combustion. Here, the controller 14 controls the reforming fuel injection valve 27 to supply the reforming fuel during the injection period and the injection amount according to the operating state of the internal combustion engine 1 and to ignite at the ignition timing according to the operating state of the internal combustion engine 1. Control is performed so that the plug 22 is ignited. As described above, high octane methanol fuel can be supplied at high load, and spark ignition combustion can be performed.

As described above, the controller 14
Supply light oil fuel to the engine when the operating condition of the
Compression ignition combustion is performed.
Quality fuel D to the engine to perform spark ignition combustion,
When the operation state is high load, the reformed fuel D is supplied to the engine.
To perform spark ignition combustion. Therefore, this implementation
In the configuration, when the operation state of the engine is low load,
Combustion-ignition combustion with cetane number light oil fuel produces exhaust
Performance and thermal efficiency, and the engine
In case, H_Two , CO-rich reformed fuel and C₆ Many
To perform spark ignition combustion with high octane fuel
Than NO_x Improve exhaust performance by reducing emissions
When the engine is in a high load condition, C ₆ Many
Including high-octane fuels
High output required by Seki can be obtained.

The embodiment has been described above by taking methanol fuel and light oil fuel as examples of hydrocarbon fuel. However, the present invention is not limited to methanol fuel and light oil fuel, and other hydrocarbon fuels may be used. Also, by controlling the composition of the reformed fuel according to the fuel reforming conditions and switching the combustion mode according to the operating state of the engine, it is possible to improve the exhaust performance and the thermal efficiency or the engine output. In the description of the embodiment of the invention, an example in which a reformed fuel obtained by reforming a liquid fuel by a fuel reformer as a gas fuel has been described. For example, the gas fuel may be supplied from a fuel storage device that stores gas fuel generated outside the fuel supply device.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of an embodiment of the present invention.

FIG. 2 is a configuration diagram of the first embodiment.

FIG. 3 is a diagram showing a relationship between a reforming composition and a reforming temperature of methanol fuel.

FIG. 4 is a control main flowchart of the first embodiment.

FIG. 5 is a control sub-flowchart diagram of the first embodiment.

FIG. 6 is a configuration diagram of a second embodiment.

FIG. 7 is a graph showing the relationship between the antiknock property and the molecular structure of paraffinic hydrocarbons.

FIG. 8 is a diagram showing a reforming temperature and a composition of reformed fuel (light oil fuel).

FIG. 9 is a control main flowchart of the second embodiment.

FIG. 10 is a control sub-flowchart diagram of Embodiment 2.

FIG. 11 is a configuration diagram of a conventional internal combustion engine.

FIG. 12 is a diagram illustrating an operation region of a conventional reformed fuel and methanol fuel.

FIG. 13 is a diagram showing the exhaust performance and efficiency of a conventional reforming engine.

[Explanation of symbols]

 a, b, c, d Storage device 1 Internal combustion engine 2 Exhaust pipe 3 Reformer 4 Bypass valve 5 Fuel tank 6 Fuel pump 7 Switching valve 8 Switching valve 9 Regulator 10 Reformed fuel injection valve 11 Regulator 12 Intake pipe 13 Methanol fuel Injection valve 14 Controller 15 Ignition switch 16 Internal combustion engine rotation detector 17 Internal combustion engine water temperature sensor 18 Reformer temperature sensor 19 Accelerator pedal opening sensor 20 Pressure sensor 21 Pressure sensor 22 Spark plug 23 Electronically controlled throttle 24 Regulator 25 Regulator 26 Modification Quality fuel injection valve 27 reformed fuel injection valve 28 regulator 29 light oil fuel injection valve

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) F02D 11/10 F02D 11/10 F 19/10 19/10 41/02 325 41/02 325K 375 375 41 / 04 310 41/04 310D 325 325C 360 360E 43/00 301 43/00 301G 301A 301K F02M 21/02 F02M 21/02 K N 27/02 27/02 P (72) Inventor Kazuhiko Ishiwatari Kanagawa-ku, Yokohama, Kanagawa Prefecture No. 2 Takaracho Nissan Motor Co., Ltd. F-term (reference) 3G023 AA02 AA03 AB06 AC02 AC04 AC06 AC07 AC08 AC09 AG05 3G065 CA00 CA12 CA13 DA04 EA08 EA09 GA09 GA10 GA46 JA04 JA09 JA11 KA02 3G084 AA05 BA10 CA11 DA04 EC01 EC03 FA00 FA10 FA20 FA33 3G092 AA06 AA08 AB03 AB05 AB15 BA01 BA08 DC01 DE10Y DE15Y EA09 EC01 FA15 FA24 GA03 G A05 GA06 HB00Z HB03Z HE01Z HE08Z HF08Z 3G301 HA04 HA23 HA24 JA02 JA21 KA06 KA08 KA09 LA00 LA01 LB00 ND02 PB00Z PB08Z PE01Z PF03Z

Claims (7)

[Claims] An internal combustion engine that operates by burning liquid fuel or gas fuel supplied from a fuel supply device, wherein when the operating state of the internal combustion engine is low load, compression ignition fuel is supplied to the internal combustion engine. The internal combustion engine is supplied and burned by compression ignition, and when the operating state of the internal combustion engine is at or above a medium load, fuel for spark ignition is supplied to the internal combustion engine and burned by spark ignition. 2. The fuel supply device according to claim 1, further comprising a fuel reformer for reforming a composition of the fuel, wherein the liquid fuel is a hydrocarbon-based fuel, and the gas fuel is the liquid fuel. 2. The internal combustion engine according to claim 1, wherein the internal combustion engine is a reformed fuel reformed by a reformer. 3. When the hydrocarbon fuel is an alcohol fuel and the combustion is compression ignition combustion, a high cetane number fuel obtained by reforming an alcohol fuel as a compression ignition fuel is supplied to the internal combustion engine. When the combustion is combustion by spark ignition, at least one of a fuel obtained by reforming an alcohol-based fuel with hydrogen as a main component or an alcohol fuel is supplied as a spark ignition fuel. 2. The internal combustion engine according to 2. 4. When the hydrocarbon fuel is light oil fuel and the combustion is compression ignition combustion, light oil fuel is supplied to the internal combustion engine as compression ignition fuel, and the combustion is spark ignition combustion. Is a fuel obtained by reforming light oil fuel with hydrogen as a main component as a spark ignition fuel,
3. The internal combustion engine according to claim 2, wherein at least one of fuels reformed into high octane fuel is supplied. 5. The fuel cell system according to claim 2, wherein when the fuel reformer does not satisfy a predetermined reforming condition, the fuel before reforming is supplied to the internal combustion engine. Internal combustion engine. 6. The internal combustion engine according to claim 2, wherein a composition of the reformed fuel is controlled by controlling a reforming temperature in the fuel reformer. 7. The engine according to claim 2, further comprising a flow control valve for adjusting an intake air amount in an intake pipe of the engine, wherein an opening of the flow control valve is controlled in accordance with switching of a combustion mode. The internal combustion engine according to any one of the above.