JP4370586B2 - Dual operation mode engine system - Google Patents

Description

  The present invention includes a diesel operation mode that operates only with oil fuel such as light oil and DME (DiMethyl Ether), and pilot injection that operates by burning the gas fuel of the main fuel by a self-ignited flame of the pilot-injected oil fuel. In a dual operation mode engine that can be switched to the fuel ignition type gas operation mode, in the diesel operation mode, a cooling fluid such as air or water is injected from the gas fuel injection valve to cool the gas fuel injection valve, and in the diesel operation mode It is an object to prevent the gas fuel injection valve from being overheated by the combustion gas in the combustion chamber and causing the gas fuel injection valve to be damaged such as seizure or sticking.

Currently, 95% of cargo transportation in Japan is carried by trucks and ships powered by diesel engines. Judging from the type of energy used for this, Japan's freight transportation is totally dependent on light oil made from crude oil. In recent years, consumption of crude oil, including light oil, has increased rapidly in India and China due to rapid economic development, and the import volume of crude oil in these countries has increased rapidly. Therefore, in the near future, it is difficult for Japan to import the required amount of crude oil, and there is a concern that freight transportation will be hindered due to the shortage of diesel oil as fuel for diesel engines. In order to avoid the stagnation of freight transportation due to the shortage of light oil, in recent years, the necessity of partial deoiling of truck fuel has been recognized. In recent years, there has been a strong demand for reducing air pollution by reducing particulates and black smoke from truck diesel engines. Due to the need for deoiling fuel and improving air pollution in the freight transportation field, the use of trucks powered by natural gas engines is being promoted, although this is a limited truck use condition. The number of trucks that are used is increasing year by year.

By the way, when a natural gas engine is used in a truck that carries cargo, a huge number of natural gas is required to ensure that natural gas is sufficiently supplied in all regions of Japan as in the current gas oil station. It is necessary to arrange the supply stand in a short time. It is considered impossible to realize this at an early stage because a huge amount of capital investment is required to install a natural gas supply station equivalent in quantity to a light oil supply station nationwide.

Therefore, a diesel oil mode in which a light oil tank and a natural gas tank are installed in a truck and two types of fuel, light oil and natural gas, are installed, and only a light oil is burned, and a flame that self-ignites a small amount of light oil that is pilot-injected. Thus, research and development of a truck using a dual operation mode engine capable of two types of operation modes, ie, a pilot injection fuel ignition type gas operation mode operated by burning gas fuel as a main fuel, is underway.

In trucks powered by this dual operation mode engine, gas oil is always replenished as needed at light oil supply stations already installed throughout the country, and natural gas is only located in a limited area. Supply natural gas when you stop by the supply stand. When the natural gas tank is filled with natural gas, the vehicle travels in a pilot injection fuel ignition type gas operation mode using natural gas as the main fuel. When the natural gas in the natural gas tank runs out, the truck is driven in the diesel operation mode in which only the light oil is operated. As described above, the truck of the dual operation mode engine can be operated while selecting two kinds of fuel, light oil and natural gas. Therefore, the truck driver of the dual operation mode engine can run the truck by arbitrarily selecting light oil and natural gas in consideration of the possibility of replenishment of light oil and natural gas and the price difference. As described above, the dual operation mode engine truck that can select and use two kinds of fuels, natural gas and light oil, as the main fuel can reduce the dependency of light oil in the freight transportation field. It is considered to be extremely effective as a means of avoiding the shortage of diesel oil in Japan, which is feared by the increase in diesel oil consumption caused by China's economic development.

Among these dual operation mode engines, a direct injection type dual operation mode engine having an oil fuel injection valve for directly injecting light oil into the combustion chamber and a gas fuel injection valve for injecting natural gas directly into the combustion chamber is R & D has been ongoing for a long time because of its high thermal efficiency. Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4 and Patent Document 5 are known as materials related to the technology of the direct injection type dual operation mode engine.

The techniques of Patent Document 1 and Patent Document 2 include an oil fuel injection valve that directly injects fuel oil with good compression ignitability such as light oil and DME into the combustion chamber, and gas fuel with poor compression ignitability such as natural gas into the combustion chamber. A gas fuel injection valve that directly injects into the combustion chamber and a spark plug for igniting the gas fuel are provided in the combustion chamber, and the self-injection of only the oil fuel injected from the oil fuel injection valve by stopping the gas injection from the gas fuel injection valve Two types of operation can be switched between a diesel operation mode in which combustion is performed by ignition and a spark ignition gas operation mode in which gas fuel, which is the main fuel injected from the gas fuel injection valve, is combusted with a spark plug. It can be done. In this engine, a liquid fuel such as light oil and a gas fuel such as natural gas are arbitrarily selected as main fuels so that the engine can be operated.

The technique of Patent Document 3 includes an oil fuel injection valve that directly injects fuel oil with good compression ignitability such as light oil into the combustion chamber in the vicinity of the cylinder away from the center of the cylinder and has poor compression ignitability of natural gas or the like. A gas fuel injection valve that directly injects good gas fuel into the combustion chamber is provided in the vicinity of the cylinder away from the center of the cylinder, and a gas fuel injection valve by a flame that self-ignites a small amount of oil fuel pilot-injected from the oil fuel injection valve This is a side-injection pilot-injected fuel-ignited gas engine that operates the engine by burning gas fuel that is the main fuel injected from the engine. This pilot injection fuel ignition type gas engine is characterized in that it emits less particulates, black smoke and carbon dioxide (CO2) than a diesel engine.

In the technique of Patent Document 4, a gas injection valve that directly injects gas into a combustion chamber is provided, and a gas fuel supply device and a high-pressure fluid (air) supply device are connected in parallel to the gas injection valve. The natural gas and high-pressure air are supplied by switching between the natural gas and the high-pressure air according to the crank angle, and during the operation of one cycle of the exhaust stroke-intake stroke-compression stroke-explosion stroke of the cylinder. Is injected multiple times, and the natural gas injected into the combustion chamber is self-ignited to burn the natural gas and operate the engine. Therefore, it is a gas engine that uses only natural gas as fuel. Therefore, it is a gas engine that uses only natural gas as fuel.
In the technique of Patent Document 5, a gas injection valve for directly injecting gas into a combustion chamber is provided, and a gas capable of compression ignition is intermittently injected a plurality of times from the gas injection valve during the compression stroke. Even when the pressure is not high, gas fuel and air are mixed well. Then, the natural gas injected into the combustion chamber is self-ignited to burn the natural gas and operate the engine. Therefore, it is a gas engine that uses only natural gas as fuel.
Published utility model application Published utility model application Published utility model application Sho 62-45339 Patent Publication 2002-38955 Patent Publication 2002-138869

Diesel operation mode and pilot injection in which only two types of fuel are installed on the truck: light oil, DME and other self-ignitable oil fuel, and natural gas and other self-ignitable gas fuel. Power source is a dual operation mode engine capable of two types of operation modes of pilot injection fuel ignition type gas operation mode that operates by burning gas fuel as main fuel by self-ignited flame of small amount of oil fuel The truck can be operated in either the diesel operation mode selected by the driver or the pilot injection fuel ignition gas operation mode.

In the direct injection type dual operation mode engine having an oil fuel injection valve that directly injects oil fuel into the combustion chamber and a gas fuel injection valve that directly injects gas fuel into the combustion chamber, pilot injection fuel ignition In the case of the gas-type gas operation mode, the gas fuel is injected from the gas fuel injection valve into the combustion chamber, the oil fuel is pilot-injected from the oil fuel injection valve into the combustion chamber, and the oil fuel and the gas fuel are burned and operated. . As a result, the oil fuel injection valve and the gas fuel injection valve that are exposed to high-temperature combustion gas in the combustion chamber during engine operation are cooled by the respective fuel injected by the respective valves, The valve portions of the oil fuel injection valve and the gas fuel injection valve are heated by the high-temperature combustion gas in the combustion chamber, and the temperature does not rise excessively. For this reason, the valve portions of the oil fuel injection valve and the gas fuel injection valve do not overheat and cause seizure or damage.

However, in the diesel operation mode, the dual operation mode engine is operated by combustion of only the oil fuel, so that the oil fuel is injected from the oil fuel injection valve, but the gas fuel is not injected from the gas fuel injection valve. For this reason, during the diesel operation mode, the valve portion of the oil fuel injection valve is cooled by the injection of the oil fuel, so that the temperature does not rise excessively even if heated by the high-temperature combustion gas in the combustion chamber. However, since the gas fuel is not injected from the gas fuel injection valve, the valve portion of the gas fuel injection valve is not cooled by the injection of the gas fuel. Therefore, in the diesel operation mode, the valve portion of the gas fuel injection valve is heated by the high-temperature combustion gas in the combustion chamber, and the temperature rises excessively, causing seizure and damage due to overheating.

By the way, Patent Document which is a direct injection type dual operation mode engine separately provided with an oil fuel injection valve for directly injecting oil fuel into the combustion chamber and a gas fuel injection valve for directly injecting gas fuel into the combustion chamber In the technique of No. 1 and Patent Document 2, since the gas fuel is not injected from the gas fuel injection valve in the diesel operation mode that is operated only by the oil fuel, the gas fuel injection valve is not cooled by the injection of the gas fuel. For this reason, the valve portion of the gas fuel injection valve exposed in the combustion chamber is heated by the high-temperature combustion gas in the combustion chamber, causing a problem that the valve portion of the gas fuel injection valve is seized or damaged. Therefore, it is impossible to continuously perform the diesel operation mode in the dual operation mode engine of the techniques of Patent Document 1 and Patent Document 2.

The technique of Patent Document 3 includes an oil fuel injection valve that directly injects fuel oil having good compression ignition properties such as light oil into the combustion chamber in the vicinity of the cylinder far from the center of the cylinder, and in the vicinity of the cylinder far from the center of the cylinder The gas fuel injection valve is equipped with a gas fuel injection valve that directly injects gas fuel with poor compression ignitability such as natural gas into the combustion chamber, and the gas fuel injection valve by a flame that self-ignited a small amount of oil fuel pilot-injected from the oil fuel injection valve A side injection type pilot injection fuel ignition type gas engine that ignites and burns gas fuel, which is the main fuel injected from the engine. A small amount of oil fuel is pilot-injected from the oil fuel injection valve provided in the vicinity of the cylinder wall toward the downstream direction of the swirl in the forward direction of the swirl, and the swirl from the gas oil fuel injection valve provided in the vicinity of the cylinder wall is injected. The main fuel gas fuel is injected in the direction of the swirl and the forward flow in the downstream direction. The engine is operated by burning a gas fuel as a main fuel by a flame in which a small amount of pilot-injected oil fuel is self-ignited.

Thus, in the technique of Patent Document 3, the oil fuel injection valve and the gas oil fuel injection valve are both disposed in the vicinity of the cylinder wall away from the center of the cylinder, and the oil fuel injection direction of the oil fuel injection valve. The gas fuel injection direction of the gas oil fuel injection valve is such that the gas fuel is injected in the direction of the swirl and the forward flow toward the swirl downstream direction. Therefore, the spray of oil fuel injected from the oil fuel injection valve into the combustion chamber and the lump of gas fuel injected from the gas oil fuel injection valve into the combustion chamber become swirls of the air in the cylinder that revolves around the cylinder center. It gets on and turns in the combustion chamber. In this way, the oil fuel spray mass and the gas oil fuel mass injected into the combustion chamber swirl around the cylinder center in the combustion chamber side by side in the swirl flow swirling in the cylinder. Only. For this reason, the gas fuel lump may not come into contact with the oil fuel spray lump when the injection amount of the gas fuel is small for light load operation of the engine. In that case, even if the piston approaches the top dead center and the oil fuel spray self-ignites to form an oil fuel spray flame, the oil fuel spray flame can quickly ignite the gas oil fuel mixture. In some cases, the gas fuel cannot be combusted. At that time, the torque of the engine is instantaneously reduced, which causes a problem that the operation in the smooth pilot injection fuel ignition type gas operation mode becomes impossible. As described above, in the pilot injection fuel ignition type gas engine disclosed in Patent Document 3, there is a possibility that a problem that causes severe torque fluctuation during operation may occur depending on the operating condition of the engine.

Further, in the technique of this Patent Document 3, a pilot injection fuel ignition type gas engine in which oil fuel is always pilot-injected from an oil fuel injection valve and gas fuel as main fuel is injected from the gas fuel injection valve during operation of the engine. It is only driven by. This is a technique in which diesel operation in which only fuel oil is injected from an oil fuel injection valve without injection of gas fuel from the gas fuel injection valve is not performed. Therefore, a truck equipped with the engine of the technology of Patent Document 3 runs in a pilot-injected fuel ignition type gas operation in which a gas fuel as a main fuel is burned and operated by a flame in which a small amount of pilot-injected light oil is self-ignited. This is a technology that cannot be run in diesel operation where only diesel oil is burned. That is, in a truck equipped with the engine of the technology of Patent Document 3, the driver cannot run the truck by selecting two types of operation modes, diesel operation or pilot injection fuel ignition gas operation.

In the technique of Patent Document 4, gas fuel and high-pressure air are always injected into the combustion chamber from the gas injection valve during the one-cycle operation of each cylinder of the engine to promote mixing of the gas fuel and air. It is. It is a simple compression ignition type gas fuel engine that is operated by injecting gas fuel and high pressure air into a combustion chamber in combination and burning the gas fuel by self-ignition. Separately equipped with an oil fuel injection valve that injects oil fuel directly into the combustion chamber and a gas fuel injection valve that injects gas fuel directly into the combustion chamber, the diesel operation mode in which only oil fuel is burned and pilot injection Operation as a direct injection dual operation mode engine capable of two types of operation, pilot injection fuel ignition type gas operation mode, which is operated by burning a gas fuel which is the main fuel by a self-ignited flame of a small amount of oil fuel Can not. Therefore, there are two types of fuel, oil fuel and gas fuel, which are the characteristics of the dual operation mode engine. The engine operator considers the availability of oil fuel and gas fuel and the price difference, and oil fuel is the main fuel. The engine cannot be operated with any gas fuel selected arbitrarily. Further, the technique of Patent Document 4 does not include a means for igniting the injected gas fuel because the gas fuel injected from the gas injection valve in the combustion chamber is self-ignited and burned. Since gas fuel has a low cetane number, self-ignitability is poor, and it is difficult to reliably burn gas fuel at an optimal crank angle under all engine operating conditions. Therefore, in order to put the engine of Patent Document 4 into practical use in various seasons and regions with different temperatures, a means for igniting gas fuel such as an electric spark spark plug and an oil fuel pilot injection is newly provided. It is necessary to add.

In the technique of Patent Document 5, the gas that can be compressed and ignited from the gas injection valve to the combustion chamber is simply divided into a plurality of times during one cycle without considering the swirl direction of the intake air swirl in the combustion chamber. It is designed to be injected. In general, in order to mix the air in the combustion chamber and the injected gas fuel and disperse the gas fuel in the combustion chamber over a wide range, it is necessary to effectively use the swirl energy of the swirl of the air in the combustion chamber. However, the technique of Patent Document 5 does not describe anything about the swirl of the air in the combustion chamber and the direction of gas injection of the gas injection valve. For example, even if gas injection is intermittently performed several times in a direction opposite to the flow of the swirl in the combustion chamber from the gas injection valve, the kinetic energy of the swirl in the combustion chamber and the kinetic energy of the injection of the gas fuel cancel each other. Gas fuel cannot be dispersed widely in the room. Therefore, in the technique of Patent Document 5, since gas fuel and air cannot be sufficiently mixed, incomplete combustion occurs, and a lot of harmful exhaust gases such as carbon monoxide (CO) and hydrocarbons (HC) are discharged. There may be a problem that a necessary engine output cannot be obtained.

The present invention has been devised in view of the above problems. The structure includes an oil fuel injection valve that injects oil fuel with good compression ignitability such as light oil into the combustion chamber, and a gas fuel injection valve that injects gas fuel with poor compression ignitability such as natural gas. The diesel operation mode, in which the gas fuel injection from the engine is stopped and burned by the self-ignition of only the oil fuel injected from the oil fuel injection valve, and the small amount of oil fuel pilot injected from the oil fuel injection valve is self-ignited In a dual operation mode engine capable of switching between a pilot injection fuel ignition type gas operation mode which is operated by burning a gas fuel which is a main fuel injected from a gas fuel injection valve by a flame, the gas fuel injection valve is a gas fuel And a cooling fluid such as pressurized air or water can be arbitrarily switched and ejected. In the diesel operation mode, a cooling fluid is injected from the gas fuel injection valve to cool the gas fuel injection valve, and the valve portion of the gas fuel injection valve is heated by the high-temperature combustion gas in the combustion chamber, and the temperature rises excessively. Prevents defects that cause seizure or damage to parts. The oil fuel injection valve is arranged near the cylinder center line, and the oil fuel is injected radially from the multi-hole nozzle of the oil fuel injection valve toward the inner wall surface of the cylinder. One or a plurality are arranged at positions away from the line so that the gas fuel or the cooling fluid is injected from the gas fuel injection valve in the downstream direction of the swirl. As a result, the gas fuel or cooling fluid flows into the swirl while mixing with the air swirling in the combustion chamber, and the gas fuel / air mixture and cooling fluid are dispersed in the combustion chamber around the entire inner wall surface of the cylinder. And swirl in the combustion chamber. As the piston approaches top dead center in the compression stroke, the air-fuel mixture and cooling fluid in the combustion chamber are compressed. The gas fuel mixture or cooling fluid that is dispersed and swirled together with the swirl around the inner wall of the cylinder moves along the outer peripheral wall of the cavity on the top surface of the piston when the piston approaches the top dead center. It turns. In the pilot injection fuel ignition type gas operation mode, the multi-hole nozzle at the tip of the oil fuel injection valve is swung along the outer peripheral wall of the cavity to the center of the gas fuel mixture that is distributed in the donut state in the cavity. A small amount of oil fuel is pilot-injected from the oil fuel injection valve near the cylinder center line into the piston cavity toward the side wall of the piston cavity. Since the amount of oil fuel pilot injected from the oil fuel injection valve is small, the kinetic energy of the oil fuel spray during pilot injection is small. Therefore, the oil fuel spray at the time of pilot injection has a short reach distance and does not reach the vicinity of the cylinder wall surface but is dispersed in the center of the piston cavity. As a result, in the cavity that is the main part of the combustion chamber, the distribution form of the gas fuel mixture in which the gas fuel and air mixture swirls in the cavity so as to surround the pilot-injected oil fuel spray in the center, and Become. An oil fuel spray flame self-ignited in the center of the cavity near the end of the compression stroke ignites the gas fuel and air mixture dispersed to surround the oil fuel spray and burns the gas fuel mixture As a result, it is possible to realize combustion close to complete combustion with good CO and HC emissions with good fuel efficiency. On the other hand, when the engine is in the diesel operation mode, oil fuel such as light oil or DME is directly injected into the combustion chamber, and the gas fuel is not injected into the combustion chamber from the gas fuel injection valve. Instead, a cooling fluid such as air or water is injected from the gas fuel injection valve to cool the valve portion at the tip of the gas fuel injection valve exposed in the combustion chamber. Thereby, the malfunction which raises the temperature of the valve part of a gas fuel injection valve excessively at the time of a diesel operation mode, and causes a damage is prevented. In particular, when water is injected as a cooling fluid from the gas fuel injection valve, an effect of cooling the gas fuel injection valve and reducing emission of nitrogen oxides (NOx) due to a decrease in combustion gas temperature can be obtained.

In order to achieve the above object, the present invention adopts the following configuration.
That is, in the dual operation mode engine system according to the first aspect of the present invention, a combustion chamber is formed by a cylinder head, a cylinder, and a piston, and the cylinder head is made of the above-described combustion fuel oil such as light oil or DME with good compression ignition. An oil fuel injection valve that directly injects into the chamber and a gas fuel injection valve that directly injects gas fuel with poor compression ignitability such as natural gas into the combustion chamber, and the injection of the gas fuel from the gas fuel injection valve Injected from the gas fuel injection valve by a diesel operation mode in which only the oil fuel injected from the oil fuel injection valve is burned and operated, and a small amount of fuel fuel pilot-injected from the oil fuel injection valve There are two types of operation modes, pilot injection fuel ignition type gas operation mode that operates by igniting and burning the main fuel gas fuel. Capable of switching between gas fuel with poor compression ignitability such as natural gas supplied from a gas fuel supply device and cooling fluid such as air or water supplied from a high-pressure cooling fluid supply device A switching device for supplying the gas fuel injection valve to inject the oil fuel into the combustion chamber from the oil fuel injection valve in the diesel operation mode, and the cooling fluid from the switching device to the gas fuel injection valve. And injecting the cooling fluid into the combustion chamber from the gas fuel injection valve, and pilot-injecting a small amount of oil fuel from the oil fuel injection valve into the combustion chamber in the pilot injection fuel ignition gas operation mode. Gas fuel is supplied from the switching device to the gas fuel injection valve, and gas fuel as main fuel is injected from the gas fuel injection valve into the combustion chamber. Characterized in that way the.

According to the first aspect of the present invention, the cylinder head has an oil fuel injection valve that directly injects into the combustion chamber an oil fuel having a high cetane number such as light oil or DME and a good compression ignitability, and a cetane number such as natural gas. A gas fuel injection valve that directly injects gas fuel with low compression ignitability into the combustion chamber is provided, and gas injection from the gas fuel injection valve is stopped and injected from the oil fuel injection valve into the combustion chamber. Diesel operation mode in which only oil fuel is burned, and main fuel injected directly from the gas fuel injection valve into the combustion chamber by a flame that self-ignited a small amount of oil fuel pilot-injected from the oil fuel injection valve into the combustion chamber To a dual operation mode engine that can be arbitrarily switched to two operation modes, a pilot injection fuel ignition type gas operation mode that operates by igniting and burning gas fuel It is intended to. In this dual operation mode engine, oil fuel with good compression ignitability such as light oil and DME is supplied from the oil fuel supply device to the oil fuel injection valve, and the oil fuel injection valve supplies oil into the combustion chamber by a signal from the electronic control device. Fuel is injected directly. At the same time, the gas fuel supply device supplies a gas fuel with poor compression ignitability such as natural gas to the switching device and a cooling fluid such as air or water from the high-pressure cooling fluid supply device to the switching device. Either gas fuel or cooling fluid such as air or water is selected by a signal from the control device and supplied from the switching device to the gas fuel injection valve, and gas fuel and cooling fluid supplied from the switching device to the gas fuel injection valve Any one of these is configured to be injected from the gas fuel injection valve into the combustion chamber by a signal from the electronic control unit.

In the diesel operation mode, oil fuel supply devices such as light oil and DME with good compression ignitability are supplied to the oil fuel injection valve and injected directly into the combustion chamber from the oil fuel injection valve. Thus, the cooling fluid is selected by the switching device and supplied to the gas fuel injection valve, and the cooling fluid is directly injected into the combustion chamber from the gas fuel injection valve. In this diesel operation mode, the dual operation mode engine is operated only with oil fuel such as light oil or DME. On the other hand, in the pilot injection fuel ignition type gas operation mode, the switching device selects gas fuel such as natural gas and supplies it to the gas fuel injection valve according to a signal from the electronic control unit, and the gas fuel injection valve supplies the main fuel to the combustion chamber. Along with direct injection of gas fuel, the oil fuel injection valve is configured to directly pilot-inject a small amount of good fuel oil with good compression ignitability such as light oil or DME supplied from the oil fuel supply device into the combustion chamber. In this pilot injection fuel ignition type gas operation mode, the dual operation mode engine is operated to burn two types of fuel, oil fuel such as light oil and DME, and gas fuel such as natural gas.

In this pilot injection fuel ignition type gas operation mode, the gas fuel supplied from the gas fuel supply device is directly injected into the combustion chamber as the main fuel from the gas fuel injection valve via the switching device, and from the oil fuel injection valve to the light oil or DME. A small amount of oil fuel with good compression ignitability such as the above is directly pilot-injected into the combustion chamber. This pilot-injected oil fuel first self-ignites, and the flame of this self-ignited oil fuel ignites the gas fuel that is the main fuel injected into the combustion chamber from the gas fuel injection valve to burn the gas fuel. The dual operation mode engine is operated in the pilot injection fuel ignition type gas operation mode.

In the diesel operation mode of the dual operation mode engine, oil fuel such as light oil or DME is only directly injected into the combustion chamber, and the gas fuel is not injected into the combustion chamber from the gas fuel injection valve. Therefore, the valve portions such as the needle valve and the nozzle nozzle at the tip of the gas fuel injection valve disposed in the cylinder head with a structure exposed in the combustion chamber are exposed to the oil fuel combustion flame and heated in the diesel operation mode. For this reason, there is a high risk that the temperature of the valve portion will rise excessively and cause problems such as welding and sticking. According to the first aspect of the present invention, a gas fuel is produced by injecting a cooling fluid such as air or water supplied from a cooling fluid supply device into a combustion chamber from a gas fuel injection valve in a diesel operation mode of a dual operation mode engine. That is, the valve portion of the injection valve is cooled to prevent the temperature of the valve portion from rising excessively.

As described above, the invention according to claim 1 is that the gas fuel injection valve can be cooled by injecting the cooling fluid from the gas fuel injection valve in the diesel operation mode. As a result, even when the gas fuel injection valve is exposed to high-temperature combustion gas in the combustion chamber during the diesel operation mode of the dual operation mode engine, the gas fuel injection valve does not suffer from problems such as welding and sticking. It is that.

The invention according to claim 2 relates to the dual operation mode engine system according to claim 1, wherein the oil fuel injection valve is disposed in the vicinity of a cylinder center line of the cylinder of the cylinder head, and the oil fuel injection valve Oil fuel is injected radially from the multi-hole nozzle at the tip toward the inner wall surface of the cylinder, and one or more gas fuel injection valves are arranged at positions away from the cylinder center line of the cylinder head. The direction in which the gas fuel or the cooling fluid is injected from the single injection nozzle or the multi injection nozzle at the tip of the gas fuel injection valve is the center line of the gas fuel injection valve and the surface of the cylinder head that forms the combustion chamber. Is directed to a downstream direction of a swirl of air swirling in the combustion chamber from a plane including the intersection of the cylinder and the cylinder center line.

In the invention of claim 2, the oil fuel injection valve is disposed in the vicinity of the cylinder center line of the cylinder head. Then, the oil fuel is injected radially from the multi-hole nozzle at the tip of the oil fuel injection valve toward the inner wall surface of the cylinder at substantially equal intervals. Also, when a single gas fuel injection valve is arranged in the cylinder head, the gas fuel injection valve is arranged in the cylinder head at a position away from the cylinder center line, and the single injection nozzle or the multi injection nozzle of the gas fuel injection valve Is disposed so as to be exposed in the combustion chamber. The direction in which the gas fuel or the cooling fluid is injected from the single injection nozzle or the multi injection nozzle of the gas fuel injection valve is the intersection of the center line of the gas fuel injection valve and the surface of the cylinder head forming the combustion chamber and the above The downstream direction of the swirl flow swirling in the combustion chamber from the plane including the cylinder center line.

Further, when two gas fuel injection valves are arranged on the cylinder head, the two gas fuel injection valves are arranged on the cylinder head at a position that is separated from the cylinder center line and substantially opposed to the cylinder center line, A single injection hole or a multiple injection nozzle of each gas fuel injection valve is disposed so as to be exposed in the combustion chamber. The direction in which the two gas fuel injection valves inject the gas fuel or the cooling fluid from the single injection nozzle or the multi injection nozzle is the same as that of the single injection nozzle or the multi injection nozzle of each gas fuel injection valve. The direction of the swirl swirling in the combustion chamber from the respective planes including the position and the cylinder center line is the downstream direction of the swirl flow.

In addition, when three or more gas fuel injection valves are arranged on the cylinder head, all the gas fuel injection valves are arranged on the cylinder head at substantially equal intervals inside the cylinder while being separated from the cylinder center line. A single injection nozzle or a multi injection nozzle of each gas fuel injection valve is disposed so as to be exposed in the combustion chamber. The direction in which the gas fuel or the cooling fluid is injected from the single nozzle nozzle or the multi nozzle nozzle of each of the three or more gas fuel injection valves is the same as that of the single nozzle or the multi nozzle nozzle of each gas fuel injection valve. The direction of the swirl swirling in the combustion chamber from the respective planes including the position and the cylinder center line is the downstream direction of the swirl flow. The gas fuel or the cooling fluid injected in the downstream direction of the swirl of the air swirling in the combustion chamber from the single-hole nozzle or the multi-hole nozzle of the gas fuel injection valve in the pilot injection fuel ignition type gas operation mode swirls in the combustion chamber While being mixed with air, it is caused to flow into the swirl, and the gas fuel / air mixture or cooling fluid is dispersed over the entire circumference of the inner wall surface of the cylinder and swirls in the combustion chamber together with the swirl. As the piston approaches the top dead center in the compression stroke, the air-fuel mixture or cooling fluid in the combustion chamber is compressed. The gas fuel mixture or cooling fluid, which is dispersed around the entire inner wall of the cylinder and swirls together with the swirl, moves to the cylinder head at the center of the top surface of the piston when the piston approaches top dead center. It turns along the outer peripheral wall of the cavity which occupies the main part of the opposing concave combustion chamber.

In the pilot injection fuel ignition type gas operation mode, the oil fuel injection valve arranged near the cylinder center line of the cylinder head when the piston approaches the top dead center and the top clearance, which is the gap between the piston and the cylinder head, becomes small Pilot-injects a small amount of oil fuel into the cavity from the multi-hole nozzle at the tip toward the side wall of the cavity of the piston. The oil fuel injection valve injects oil fuel from each nozzle hole nozzle toward the side wall surface of the piston cavity at an angle in the range of 10 degrees to 20 degrees with respect to the surface constituting the combustion chamber of the cylinder head. In the pilot injection fuel ignition type gas operation mode, since a small amount of oil fuel is pilot injected from the oil fuel injection valve, the kinetic energy of the oil fuel spray during pilot injection is small. Therefore, the spray of oil fuel at the time of pilot injection does not reach the side wall surface of the cavity and is dispersed in the center of the cavity. As a result, in the cavity that occupies the main part of the combustion chamber, the gas fuel mixture is distributed in such a manner that the mixture of the gas fuel and the air swirls so as to surround the spray of the fuel oil injected by the pilot in the center.

As described above, the fuel spray sprayed with the pilot fuel is present in the center of the cavity that occupies the main part of the combustion chamber, and the fuel mixture in which the gas fuel mixture close to the theoretical mixing ratio swirls so as to surround the fuel spray. The oil fuel spray in the center of the cylinder first self-ignites near the end of the compression stroke. Next, the self-ignited oil fuel spray flame ignites the gas fuel / air mixture dispersed so as to surround the oil fuel spray, and the gas fuel mixture burns. Since the gas fuel mixture is dispersed so as to surround the oil fuel spray, the gas fuel mixture is mixed from the inner peripheral surface of the gas fuel mixture in which the flame of the oil fuel spray is dispersed in a donut shape in the cavity. I will ignite my mind. As a result, the gas fuel mixture can be burned smoothly, so that the gas fuel can be burned in a short period of time, resulting in good fuel economy, and the gas fuel mixture can reduce CO and HC emissions. Less combustion is possible. In the diesel operation mode, when water is used as the cooling fluid in the downstream direction of the swirl of the air swirling in the combustion chamber from the single nozzle nozzle or the multi-nozzle nozzle of the gas fuel injection valve, the water spray swirls in the combustion chamber. The air is swirled while being mixed with the air to be dispersed, and dispersed over the entire circumference of the inner wall surface of the cylinder. When the piston approaches the top dead center and the oil fuel injection valve injects the oil fuel into the cavity in which the water spray is dispersed, the endothermic action when the water spray is vaporized by the combustion heat of the oil fuel causes Combustion gas temperature falls and generation | occurrence | production of NOx at the time of diesel operation mode is suppressed.

A third aspect of the present invention relates to the dual operation mode engine system according to any one of the first to second aspects. In the diesel operation mode, the gas fuel injection valve inserts the engine into the combustion chamber per cycle of the engine. In the pilot injection fuel ignition type gas operation mode, the cooling fluid is injected into a plurality of times and the gas fuel is injected into the combustion chamber from the gas fuel injection valve in a plurality of times per cycle of the engine. It is characterized by doing so.

According to the third aspect of the present invention, in the pilot injection fuel ignition type gas operation mode, when the required amount of gas fuel is injected into the combustion chamber per cycle of the engine with one cylinder, the gas fuel injection valve is operated once. Rather than injecting the gas fuel into the combustion chamber by opening the valve, the gas fuel is injected in a plurality of times by opening the valve a plurality of times. In general, when a liquid is injected into a gas, a substance with a high density is injected into a substance with a low density, and the substance with a large density enters into a substance with a low density and is small. Density materials and high density materials mix well. However, in the form of injecting gas into the gas as in the case of injecting gas fuel from the gas fuel injection valve to the air in the combustion chamber, since the density difference between the two is small, the penetrating force of the injected gas fuel is weak In addition, the gas fuel in the combustion chamber is difficult to enter the air, the air and the gas fuel are difficult to mix in the combustion chamber, and a uniform mixture of the gas fuel and air is difficult to form.

However, the gas fuel is intermittently discharged in the one-cycle operation of the cylinder in the downstream direction of the swirl of the air swirling in the combustion chamber from the single injection nozzle or the multi injection nozzle of the gas fuel injection valve arranged away from the cylinder center line. By injecting multiple times, the gas fuel injected into the combustion chamber flows into the swirl while mixing with the air swirling in the combustion chamber as a plurality of lump, It is dispersed while forming a gas fuel / air mixture around the entire circumference. As the piston approaches the top dead center in the compression stroke, the air-fuel mixture in the combustion chamber is compressed. The gas fuel mixture that swirls together with the swirl dispersed all around the inner wall of the cylinder has a concave shape facing the cylinder head at the center of the top surface of the piston when the piston approaches top dead center. It turns along the outer peripheral wall of the cavity which occupies the main part of a combustion chamber.

On the other hand, when the piston approaches the top dead center and the top clearance, which is the gap with the cylinder head of the piston, becomes small, the piston from the multi-hole nozzle at the tip of the oil fuel injection valve arranged near the cylinder center line of the cylinder head A small amount of oil fuel is pilot-injected toward the side wall of the cavity. The oil fuel sprayed by the pilot fuel is small, so the kinetic energy of the oil fuel spray is low. Therefore, the oil fuel spray does not reach the vicinity of the cylinder wall surface but is dispersed in the central portion of the piston cavity. As a result, in the cavity that occupies the main part of the combustion chamber, the gas fuel mixture is distributed in such a manner that the mixture of the gas fuel and the air swirls so as to surround the pilot-injected oil fuel spray in the center. Near the end of the compression stroke, the oil fuel spray flame formed by self-ignition of the oil fuel spray in the center of the cylinder ignites the gas fuel and air mixture dispersed so as to surround the oil fuel spray. The fuel mixture burns. Since the gas fuel mixture is dispersed so as to surround the oil fuel spray, the gas fuel mixture is mixed from the inner peripheral surface of the gas fuel mixture in which the flame of the oil fuel spray is dispersed in a donut shape in the cavity. I will ignite my mind. As a result, the gas fuel mixture injected intermittently several times in one cycle of the cylinder is a mixture close to the theoretical mixture ratio in which the rich portion of the gas fuel is small, so that CO It is possible to realize combustion close to complete combustion with little emission of HC.

A fourth aspect of the invention relates to the dual operation mode engine system according to any one of the first to third aspects. In a four-cycle engine, the gas fuel injection valve enters the combustion chamber during the diesel operation mode. The injection of the cooling fluid to be injected is within the period from the start of the intake stroke to the end of the compression stroke of the cylinder, and the gas fuel injected from the gas fuel injection valve into the combustion chamber in the pilot injection fuel ignition gas operation mode Is injected within the period from the start of the intake stroke of the cylinder to the end of the compression stroke.

In the invention according to claim 4, in the four-cycle engine of the dual operation mode engine system, in the period of time from the start of the intake stroke to the end of the compression stroke from the gas fuel injection valve to the combustion chamber in the pilot injection fuel ignition type gas operation mode Gas fuel is injected into the tank. By injecting the gas fuel during this period, the gas fuel injected directly into the combustion chamber can be prevented from being discharged into the exhaust manifold in an unburned state. Further, by injecting the gas fuel by selecting the injection timing suitable for the injection amount within the period from the start of the intake stroke to the end of the compression stroke, the gas fuel is uniformly mixed in a wide range in the combustion chamber. Can be formed. Therefore, it becomes possible to operate the gas fuel mixture close to a predetermined uniform mixture ratio in all engine operating states, and the gas fuel mixture can be burned close to complete combustion even a little, It is effective in improving fuel efficiency and reducing harmful emissions in the pilot-injected fuel ignition gas operation mode.

In the diesel operation mode, the cooling fluid is injected from the gas fuel injection valve into the combustion chamber within the period from the start of the intake stroke to the end of the compression stroke. Since the pressure in the combustion chamber is lower in the period from the start of the intake stroke to the end of the compression stroke than in the period of the combustion stroke, injection at a low pressure is possible. Therefore, the amount of work required to inject the cooling fluid may be small, and the deterioration of the fuel consumption of the engine can be suppressed, and the valve portion of the gas fuel injection valve can be cooled by the injection of the cooling fluid. When water is injected as a cooling fluid from the gas fuel injection valve within the period from the start of the intake stroke to the end of the compression stroke, the water injected in the combustion stroke evaporates to lower the temperature of the combustion gas, thereby reducing NOx. There is an effect that can be reduced. If air is injected as a cooling fluid from the gas fuel injection valve into the combustion chamber during the period from the start of the intake stroke to the end of the compression stroke, the rotational energy of the swirl increases because the air is injected in the downstream direction of the swirl in the combustion chamber. Mixing of oil fuel such as light oil injected from the fuel injection valve with the air in the combustion chamber is promoted, and there is an effect of improving fuel consumption in the diesel operation mode and reducing CO, HC and particulate emissions.

A fifth aspect of the invention relates to the dual operation mode engine system according to any one of the first to fourth aspects, wherein the cooling fluid injected from the gas fuel injection valve into the combustion chamber during the diesel operation mode. The amount is adjusted according to the operating state of the engine operation.

In the fifth aspect of the invention, the oil fuel injected in proportion to the engine output increases in the diesel operation mode of the dual operation mode engine, so the gas temperature in the combustion chamber also increases. As a result, the temperature of the valve portion of the gas fuel injection valve also increases in proportion to the engine output. Therefore, the temperature of the valve portion of the gas fuel injection valve is suppressed to a specific level or less by adjusting the injection amount of the cooling fluid according to the magnitude of the engine operation load. Thereby, in the light load operation in the diesel operation mode, it is possible to reduce the injection amount of the cooling fluid and reduce the driving energy required for the injection of the cooling fluid. It becomes possible to suppress the deterioration of.

An oil fuel injection valve that directly injects fuel oil with good compression ignitability such as light oil and DME into a combustion chamber and a gas fuel injection valve that directly injects gas fuel combustion chamber with poor compression ignitability such as natural gas into the combustion chamber In the direct-injection dual operation mode engine provided for the engine, during the operation of the pilot injection fuel ignition type gas operation mode, the gas fuel is injected from the gas fuel injection valve and the oil fuel is injected from the oil fuel injection valve. Therefore, the gas fuel injection valve and the oil fuel injection valve are cooled by the fuel injected from each. On the other hand, as shown in the patent document, during operation in the diesel operation mode of the conventional dual operation mode engine, the oil fuel is injected from the oil fuel injection valve, but the gas fuel is not injected from the gas fuel injection valve. Therefore, the gas fuel injection valve is not cooled by the fuel. Therefore, when the dual operation mode engine is operated continuously in the diesel operation mode, the valve portion of the gas fuel injection valve continues to be heated by the combustion gas of the oil fuel in the combustion chamber and overheats, causing seizure and damage. Troubles will occur. According to the first aspect of the present invention, gas fuel having poor compression ignitability such as natural gas is supplied from the gas fuel supply device to the switching device, and cooling fluid such as air or water is supplied from the high pressure cooling fluid supply device to the switching device. In the diesel operation mode, the cooling fluid is selected by the switching device and supplied to the gas fuel injection valve, and the cooling fluid is directly injected into the combustion chamber from the gas fuel injection valve. Is that it can be cooled. Since the gas fuel injection valve is cooled by the injection of the cooling fluid by injecting the cooling fluid from the gas fuel injection valve in the diesel operation mode, the temperature of the valve portion exposed in the combustion chamber of the gas fuel injection valve is excessive. It was made to prevent it from rising. Injecting cooling fluid from the gas fuel injection valve in the direct injection type dual operation mode engine in the diesel operation mode prevents the gas fuel injection valve from excessively rising in temperature and causing damage. There is.

According to a second aspect of the present invention, the oil fuel injection valve is disposed in the vicinity of the cylinder center line of the cylinder head, and the oil fuel is radially radiated from the multi-hole nozzle at the tip of the oil fuel injection valve toward the inner wall surface of the cylinder. Inject. Further, the gas fuel injection valve is disposed at a position away from the cylinder center line, and the surface including the intersection of the center line of the gas fuel injection valve and the contact surface of the cylinder head forming the combustion chamber and the cylinder center line. The gas fuel injection valve injects the gas fuel or the cooling fluid toward the downstream direction of the swirl in the combustion chamber. In the pilot injection fuel ignition type gas operation mode, the gas fuel is injected from the gas fuel injection valve toward the downstream direction of the swirl flow, so it rides on the swirl flow in the combustion chamber and turns around the cylinder center line in the combustion chamber Exercise.

As the piston approaches the top dead center in the compression stroke, the gas fuel is compressed by the piston while turning around the cylinder center line and being converted into an air-fuel mixture. When the piston approaches the top dead center, the gas fuel mixture that is dispersed over the entire circumference of the inner wall surface of the cylinder and swirls together with the swirl has a concave shape facing the cylinder head at the center of the top surface of the piston. It turns along the outer peripheral wall of the cavity which occupies the main part of a combustion chamber. The oil fuel injection valve arranged near the cylinder center line of the cylinder head at a certain timing when the piston approaches the top dead center is moved from the multi-hole nozzle exposed in the combustion chamber at the tip portion to the contact surface of the cylinder head. Oil fuel is pilot-injected toward the side wall surface of the cavity of the piston in a direction that forms an angle in the range of 10 degrees to 20 degrees. Since the amount of oil fuel to be pilot-injected is small, the kinetic energy of the oil fuel spray at the time of pilot injection is small. Therefore, the spray of the oil fuel at the time of pilot injection does not reach the vicinity of the cylinder wall surface but is dispersed in the central portion of the piston cavity. Thus, in the invention according to claim 2, the oil fuel injection valve is disposed in the vicinity of the cylinder center line of the cylinder head, and the gas fuel injection valve disposed at a position away from the cylinder center line is directed in the downstream direction of the swirl. In the cavity that occupies the main part of the combustion chamber before the piston reaches the top dead center, the gas fuel and the air are surrounded by the pilot-injected oil fuel spray in the center. It becomes the distribution form of the gas fuel mixture in which the mixture turns. Gas fuel that the oil fuel spray self-ignites before the top dead center of the piston forms a flame, and this oil fuel spray flame spreads around the side wall surface of the cavity and surrounds the oil fuel spray to swirl Since ignition is performed from the entire inner peripheral surface of the air-fuel mixture, it is possible to quickly burn all the gaseous fuel in the combustion chamber.

According to a third aspect of the present invention, when the required amount of gas fuel is injected into the combustion chamber per cycle in each cylinder in the pilot injection fuel ignition type gas operation mode, the gas fuel injection valve is opened once. Rather than injecting into the combustion chamber, the gas fuel injection valve is opened and closed multiple times so that the injection is intermittently divided into multiple times. When the gas fuel is injected from the gas fuel injection valve into the air in the combustion chamber, the gas is injected into the gas. In this case, since the difference in density between the air and the gas fuel is small, it is difficult for the injected gas fuel to enter the air in the combustion chamber, and the air and gas fuel are mixed in a short time in the combustion chamber. It is difficult to form. However, when gas fuel is injected intermittently in multiple times by causing the gas fuel injection valve to open multiple times, the gas fuel injected from the gas fuel injection valve into the swirl in the combustion chamber Will be dispersed as many lumps. The mass of the gas fuel is widely dispersed in the combustion chamber while being swirled, and mixing of the air and the gas fuel in the combustion chamber is promoted.

At a point near the end of the compression stroke when the piston is near top dead center, the gas fuel mixture passes through a cavity that occupies the central portion of the concave combustion chamber facing the cylinder head at the center of the top surface of the piston. It becomes the distribution form which turns. The spray of the oil fuel injected from the oil fuel injection valve disposed in the vicinity of the cylinder center line in the gas fuel mixture swirling in the cavity forms an oil fuel spray mixture in the center of the cavity. The oil fuel spray self-ignites before the top dead center of the piston to form a flame, and the gas fuel mixture surrounding the oil fuel spray is ignited to efficiently burn the gas fuel mixture. As a result, since it is possible to ignite all the gas fuel mixture in the combustion chamber and burn it completely for a short period of time, it is possible to realize combustion in a good pilot injection fuel ignition type gas operation mode with low fuel consumption and low CO and HC. be able to.

In the invention according to claim 4, in the four-cycle engine of the dual operation mode engine system, in the diesel operation mode, the cooling fluid is injected from the gas fuel injection valve within the period from the start of the intake stroke to the end of the compression stroke. . When water is used as the cooling fluid and water is injected within a period from the start of the intake stroke to the end of the compression stroke, the spray of water dispersed in the combustion chamber is evaporated by the combustion heat of the explosion stroke. The NOx can be reduced by lowering the temperature of the combustion gas by the endothermic action of the water spray at that time, and the increase of the pressure in the cylinder during the explosion stroke due to the volume expansion due to the vaporization of the water spray causes the working fluid in the cylinder to The expansion work is increased, the engine output is increased, and the fuel consumption can be reduced. Further, the swirling speed of the swirl is increased by the injection of water into the combustion chamber, and the mixing of the oil fuel spray and air in the combustion chamber is promoted, and the uniformity of the mixture of the oil fuel spray and air is increased and the oil is increased. Fuel combustion is improved, and in addition to reducing CO, HC and particulate emissions, the effect of reducing fuel consumption can be obtained. In addition, when air is injected into the combustion chamber from the gas fuel injection valve in the intake stroke or the compression stroke, the rotational energy of the swirl increases in order to inject air from the gas fuel injection valve in the downstream direction of the swirl in the combustion chamber, Mixing of oil fuel such as light oil injected from the oil fuel injection valve and air in the combustion chamber is promoted, and the effect of improving diesel combustion is also obtained. In this way, by injecting the cooling fluid at an appropriate timing within the period from the start of the intake stroke to the end of the compression stroke, it is possible to improve combustion and reduce harmful exhaust gas.

In the pilot injection fuel ignition type gas operation mode, the gas fuel is injected from the gas fuel injection valve into the combustion chamber within a period from the start of the intake stroke to the end of the compression stroke. By injecting during this period, the gas fuel directly injected into the combustion chamber can be prevented from being discharged into the exhaust manifold in an unburned state. By injecting the gas fuel by selecting an appropriate injection timing within the period from the start of the intake stroke to the end of the compression stroke, the gas fuel can form a uniform air-fuel mixture in a wide area within the combustion chamber. it can. Therefore, it becomes possible to operate the gas fuel mixture close to a predetermined uniform mixture ratio in all engine operating states, and the gas fuel mixture can be burned in a state close to complete combustion, so that the pilot This has the effect of improving the combustion in the injected fuel ignition gas operation mode and enabling operation with reduced harmful exhaust gas.

In the fifth aspect of the present invention, when the dual operation mode engine is in the diesel operation mode, an amount of light fuel such as light oil or DME proportional to the engine output is injected from the oil fuel injection valve. The temperature of the valve portion exposed to the combustion chamber at the tip of the gas fuel injection valve increases in proportion to the engine output, and increases in proportion to the injection amount of the oil fuel. In order to prevent malfunction of the gas fuel injection valve due to excessive temperature rise of the valve part of the gas fuel injection valve, when the amount of oil fuel injection in the diesel operation mode is large, injection from the gas fuel injection valve into the combustion chamber The amount of the cooling fluid to be increased is increased so that the temperature of the valve portion exposed to the combustion chamber at the tip of the gas fuel injection valve is cooled to a certain temperature or lower. By adjusting the amount of cooling fluid injected from the gas fuel injection valve into the combustion chamber according to the load condition of engine operation in the diesel operation mode, waste of the injection energy of the cooling fluid is prevented and the reduction in engine fuel consumption is minimized, The cooling fluid tank can be made compact by saving the injection amount of the cooling fluid.

The first embodiment of the present invention directly injects fuel oil of a main fuel having good compression ignitability such as light oil or DME from an oil fuel injection valve into a combustion chamber and cools air, water, or the like from the gas fuel injection valve. Diesel operation mode, in which fluid is injected directly into the combustion chamber and burning only oil fuel, and gas fuel of the main fuel with poor compression ignition such as natural gas is directly injected into the combustion chamber from the gas fuel injection valve A pilot-injected fuel ignition system in which a small amount of oil fuel is directly pilot-injected from the oil-fuel injection valve, and the main fuel gas fuel injected from the gas-fuel injection valve is ignited and burned by a combustion flame of the oil fuel. This is a multi-cylinder dual operation mode engine that operates in four cycles that can be switched to two types of operation modes, a gas operation mode. The first embodiment will be described in detail with reference to FIGS. FIG. 1 shows a specific example of supplying oil fuel having good compression ignitability such as light oil or DME to the oil fuel injection valve of each cylinder, and the oil fuel injection valve of each cylinder directly injects the oil fuel into the combustion chamber of each cylinder. The gas fuel injection valve of each cylinder is selected by selecting either a gas fuel with poor compression ignitability such as natural gas or a cooling fluid such as air or water and supplying it to the gas fuel injection valve of each cylinder. It is the schematic diagram which showed the specific structure which injects the gas fuel or cooling fluid selected directly into the combustion chamber of each cylinder.

In the engine main body 10 of the dual operation mode engine of the first embodiment, a combustion chamber 6 is constituted by the cylinder head 1, the cylinder 2 and the piston 3, and a concave cavity 7 facing the cylinder head at the center of the top surface of the piston. The fuel injection valve 4 is disposed in the cylinder head 1 near the cylinder center line A, the gas fuel injection valve 5 is disposed in the cylinder head 1 at a position away from the cylinder center line A, and the combustion chamber 6, oil fuel is injected from the oil fuel injection valve 4, and either gas fuel or cooling fluid is injected from the gas fuel injection valve 5.

First, the method by which the oil fuel injection valve 4 injects oil fuel will be described. Oil fuel such as light oil or DME is led from the liquid fuel tank 21 of the liquid fuel supply device 20 to the supply pump 22 through the supply passage 24 and pressurized by the supply pump 22. The oil fuel pressurized by the supply pump 22 is guided to the common rail 23 through the supply passage 25. The oil fuel guided to the common rail 23 is guided from the common rail 23 to the oil fuel injection valve 4 through the supply passage 26. The oil fuel injection valve 4 which is an electromagnetic valve is opened and closed by a control signal from an electronic control unit (ECU: Electronic-Control Unit) 60, and the oil fuel injection valve 4 is spread over a predetermined crank angle at a predetermined crank angle. Is configured to inject a predetermined amount of oil fuel into the combustion chamber 6.

Next, the method by which the gas fuel injection valve 5 injects gas fuel will be described. The gas fuel is guided from the high-pressure gas fuel cylinder 31 of the gas fuel supply device 30 to the regulator 32 through the supply passage 33, and the pressure is reduced to a predetermined pressure by the regulator 32. The gas fuel decompressed to a predetermined pressure by the regulator 32 is guided to the switching device 50 through the supply passage 34. The switching device 50 is an electromagnetically driven three-way valve that can select either gas fuel or cooling fluid according to a control signal from the electronic control device 60 and send it to the gas fuel injection valve 5. When the switching device 50 receives the control signal from the electronic control device 60 that instructs the gas fuel injection valve 5 to send the gas fuel, the switching device 50 prevents the supply passage 44 and the supply passage 11 from communicating with each other. The supply passage 34 and the supply passage 11 are switched so as to communicate with each other, and the gas fuel supplied from the regulator 32 is switched to guide the gas fuel injection valve 5. Thereby, the gas fuel is sent from the regulator 32 to the gas fuel injection valve 5 via the switching device 50. Then, the gas fuel injection valve 5 is opened over a predetermined crank angle at a predetermined timing of the crank angle by the control signal sent from the electronic control unit 60 to the gas fuel injection valve 5, and a predetermined amount of gas fuel is supplied to the combustion chamber 6. It has a structure that injects into the inside.

Next, a method for the gas fuel injection valve 5 to inject the cooling fluid will be described. The cooling fluid is led from the cooling fluid tank 42 of the high-pressure cooling fluid supply device 40 to the pressurization device 41 through the supply passage 43 and is pressurized to a predetermined pressure by the pressurization device 41. The cooling fluid pressurized to a predetermined pressure by the pressurizing device 41 is then guided to the switching device 50 through the supply passage 44. The switching device 50 is an electromagnetically driven three-way valve that can select either gas fuel or cooling fluid according to a control signal from the electronic control device 60 and send it to the gas fuel injection valve 5. When the switching device 50 receives the control signal from the electronic control device 60 instructing the gas fuel injection valve 5 to send the cooling fluid, the switching device 50 prevents the supply passage 34 and the supply passage 11 from communicating with each other and supplies them. The passage 44 and the supply passage 11 are switched so as to communicate with each other, and the cooling fluid supplied from the pressurizing device 41 is switched to be guided to the gas fuel injection valve 5. Thereby, the cooling fluid is sent from the pressurizing device 41 to the gas fuel injection valve 5 through the switching device 50. The gas fuel injection valve 5 is opened over a predetermined crank angle at a predetermined timing of the crank angle by a control signal sent from the electronic control unit 60 to the gas fuel injection valve 5, and a predetermined amount of cooling fluid is supplied to the combustion chamber 6. It has a structure that injects into the inside.

The dual operation mode engine of the first embodiment includes a diesel operation mode in which only an oil fuel such as light oil or DME is operated, and a pilot injection fuel ignition type that is operated with an oil fuel such as light oil or DME and a gas fuel such as natural gas. It is possible to switch to two types of operation modes, the gas operation mode. In the diesel operation mode, the oil fuel injection valve 4 injects the oil fuel into the combustion chamber 6 as the main fuel, and the gas fuel injection valve 5 injects the cooling fluid into the combustion chamber 6 to burn only the oil fuel. drive. In the pilot injection fuel ignition gas operation mode, the oil fuel injection valve 4 pilot-injects a small amount of oil fuel into the combustion chamber 6, and the gas fuel injection valve 5 is the main fuel gas in the combustion chamber 6. It is operated by injecting fuel and burning oil fuel and gas fuel. Thus, in the pilot injection fuel ignition type gas operation mode, the dual operation mode engine is operated by burning two types of fuel, oil fuel and gas fuel.

Next, in two types of operation modes, that is, a diesel operation mode and a pilot injection fuel ignition type gas operation mode, an oil fuel injection valve 4 that injects oil fuel performed by the electronic control device 60 and a gas fuel that injects gas fuel or cooling fluid. Control with the injection valve 5 is demonstrated based on FIG. 2 which is a control flowchart of the electronic control apparatus 60. FIG. First, an engine driver operates an operation mode selection switch (not shown) to select an operation mode, and an operation mode signal is input to an engine control device (not shown). At the same time, a pressure signal indicating the state of gas fuel filling in the high-pressure gas fuel cylinder 31 is input to an engine control device (not shown). In the engine control device (not shown), for example, when a pressure signal indicating that the high pressure gas fuel cylinder 31 has been reduced to a level at which gas fuel is to be replenished is input to the engine control device, the engine driver temporarily Even if the pilot injection fuel ignition type gas operation mode is selected, an operation mode for instructing a diesel operation mode that does not require gas fuel from an engine control device (not shown) to an electronic control device 60 by a program incorporated in the engine control device (not shown). Make sure the signal is sent. As described above, an engine control device (not shown) incorporates a program that can determine an appropriate operation mode signal while checking the residual gas fuel in the high-pressure gas fuel cylinder 31. An operation mode signal determined by an engine control device (not shown) is sent from the engine control device (not shown) to the electronic control device 60. In the electronic control unit 60, an operation mode signal is input from an engine control unit (not shown) in step S0. An operation mode signal is sent from step S0 to step S1, and the operation mode signal is detected in step S1. Next, regarding the operation mode signal detected in step S1, a determination is made in step S2 as to whether the operation mode signal is a diesel operation mode or a pilot injection fuel ignition gas operation mode.

If it is determined in step S2 that the operation mode signal is the pilot injection fuel ignition type gas operation mode, the process proceeds to step S3 and step S5. In step S3, the switching device 50 sends the gas fuel from the regulator 32 to the gas fuel injection valve 5, and the gas fuel of the main fuel is injected from the gas fuel injection valve 5 into the combustion chamber 6 in step S6. In step S5, a small amount of oil fuel is pilot injected from the oil fuel injection valve 4 into the combustion chamber 6. Thus, in the dual operation mode engine of the first embodiment, the pilot injection fuel ignition type gas operation mode is operated in which the self-ignition flame of the pilot-injected oil fuel burns the gas fuel as the main fuel.

On the other hand, when it is determined in step S2 that the operation mode signal is the diesel operation mode, the process proceeds to step S4 and step S7. In step S4, the switching device 50 sends a cooling fluid such as air or water from the pressurizing device 41 to the gas fuel injection valve 5, and in step S8, the cooling fluid is injected from the gas fuel injection valve 5 into the combustion chamber 6. The In step 7, the main fuel oil fuel is injected into the combustion chamber 6 from the oil fuel injection valve 4. In this way, in the dual operation mode engine of the first embodiment, the operation in the diesel operation mode in which only the oil fuel of the main fuel is burned is performed.

Next, in the pilot injection fuel ignition type gas operation mode of the dual operation mode engine of the first embodiment, the pilot injection and the gas fuel injection valve 5 in which the oil fuel injection valve 4 in one cylinder 2 injects a small amount of oil fuel. The injection of the gas fuel of the main fuel injected by will be described based on FIG. 3, FIG. 4, FIG. 5 and FIG. FIG. 3 is a perspective transparent view of the combustion chamber 6 formed by the cylinder head 1, the cylinder 2, and the piston 3, and the oil fuel injection valve 4 and the gas fuel injection valve 5 disposed in the cylinder head 1. In the dual operation mode engine of the first embodiment, an intake valve (not shown) is opened during the intake stroke in which the piston 3 descends, and the intake air flows through the intake port 12 as an intake air flow 75. 12 is sucked into the combustion chamber 6 through an intake valve (not shown). The intake valve (not shown) is attached to the cylinder head where the intake port 12 opens into the combustion chamber 6, and is a component that controls intake air and makes the combustion chamber 6 airtight. The air sucked into the combustion chamber 6 forms a swirl 70 in the direction shown in FIG. 3 centering on the cylinder center line A in the combustion chamber 6.
Note that an exhaust valve (not shown) attached to the cylinder head 1 in a portion where the exhaust port 13 opens to the combustion chamber 6 opens in the exhaust stroke, and the exhaust gas after the oil fuel or gas fuel burns in the combustion chamber 6. The gas flows through the exhaust port 13 as an exhaust gas flow 76 and is discharged to an exhaust manifold (not shown).

The oil fuel injection valve 4 disposed in the vicinity of the cylinder center line A injects a predetermined amount of oil fuel into the combustion chamber 6 at a predetermined time by a control signal from the electronic control device 60. The oil fuel forms an angle in the range of 10 to 20 degrees with respect to the cylinder head flank 9 and is applied to the inner wall surface of the cylinder 2 (when the piston 3 is close to top dead center, the cavity side wall 8 of the piston 3). Injected from each nozzle hole nozzle of the multi-hole nozzle provided in the valve portion exposed to the combustion chamber 6 of the oil fuel injection valve 4. On the other hand, the gas fuel injection valve 5 disposed in the cylinder head 1 at a position away from the cylinder center line A is a single injection nozzle provided at the tip of the gas fuel injection valve 5 by a control signal from the electronic control device 60 or Gas fuel is injected into the combustion chamber 6 from the multi-hole nozzle at an optimal time (crank angle) within a period from the start of the intake stroke to the end of the compression stroke. This gas fuel is obtained from an intersection of the gas fuel injection valve center line C and the cylinder head contact surface 9 from a single injection nozzle or a multi injection nozzle provided in a valve portion exposed to the combustion chamber 6 of the gas fuel injection valve 5. A velocity vector component that flows backward in the direction of the swirl 70 with respect to the direction of the swirl 70 with respect to the direction of the swirl 70 from the AB surface (the surface indicated by the oblique lines in FIG. 3) including B and the cylinder centerline A (In a direction not having).

When gas fuel is injected once in one cycle at an appropriate timing in the period from the start of the intake stroke to the end of the compression stroke in the downstream direction with respect to the direction of the swirl 70 of the combustion chamber 6 from the gas fuel injection valve 5, The fuel mixture is mixed in the direction of the swirl 70 while mixing with air swirling in the combustion chamber 6, and swirls in the cylinder 2 along with the swirl 70 along the inner wall surface of the cylinder 2. As the piston 3 approaches top dead center in the compression stroke, the gas fuel mixture in which the air in the combustion chamber 6 and the gas fuel are mixed is compressed. Since the cavity 7 occupies the main part of the combustion chamber 6 when the piston 3 approaches the top dead center, the gas fuel is dispersed on the inner periphery of the inner wall surface of the cylinder 2 and swirls integrally with the direction of the swirl 70 until then. The air-fuel mixture swirls along the outer peripheral wall of the cavity 7 disposed at the center of the top surface of the piston. A small amount of oil is injected into the combustion chamber 6 from the oil fuel injection valve 4 in the vicinity of the cylinder center line A at the center of the gas fuel mixture that swirls along the outer peripheral wall of the cavity 7 and is distributed like a donut shape in the cavity. The oil fuel is pilot-injected toward the cavity side wall 8. In the pilot injection fuel ignition type gas operation mode, since the amount of oil fuel pilot-injected from the oil fuel injection valve 4 is small, the kinetic energy of the oil fuel spray during pilot injection is small. Therefore, the oil fuel spray at the time of pilot injection does not reach the vicinity of the cavity side wall 8 but is dispersed in the central portion of the cavity 7 of the piston 3. FIG. 4 shows the gas fuel mixture 72 formed by the gas fuel injection from the gas fuel injection valve 5 and the oil fuel injection from the oil fuel injection valve 4 when the piston 3 approaches the top dead center. The state in which the oil fuel spray 71 is distributed in the cavity 7 is shown in X view (see FIG. 1). In the cavity 7 occupying the main part of the combustion chamber 6 when the piston 3 approaches the top dead center, the gas fuel mixture 72 is swirled so as to surround the pilot-injected oil fuel spray 71 at the center. .

When the compression stroke proceeds and the piston 3 approaches the top dead center and the temperature and pressure in the combustion chamber 6 rise, the pilot fuel oil spray 71 self-ignites. As shown in FIG. 4, since the gas fuel mixture 72 surrounds the oil fuel spray 71 and is distributed in a donut shape, the gas fuel mixture 72 contacts the gas fuel mixture 72 over a wide range of the inner peripheral surface of the gas fuel mixture 72. As a result, the flame of the oil fuel spray 71 can be ignited from the inner peripheral surface of the gas fuel mixture 72. As a result, the gas fuel mixture 72 dispersed in a donut shape is ignited all at once from the inner peripheral surface, and the gas fuel mixture 72 of the main fuel can be smoothly burned in the combustion chamber 6 in a short time. it can. Therefore, the dual operation mode engine of the first embodiment has good cycle efficiency and can be operated in the pilot injection fuel ignition type gas operation mode with little HC or CO harmful exhaust gas.

In general, in a specific operation state in the pilot injection fuel ignition type gas operation mode, the gas fuel is supplied from the gas fuel injection valve 5 into the combustion chamber 6 in which the air sucked into the cylinder 2 is swung in the direction of the swirl 70. Even if the fuel is injected in the downstream direction of the swirl 70, since the gaseous fuel is injected into the gaseous air having a close density, the injected gaseous fuel is difficult to enter the air. It is extremely difficult to mix all the gas fuels with air so as to obtain a theoretical mixing ratio. Therefore, in the dual operation mode engine of the first embodiment, when a required amount of gas fuel is injected into the combustion chamber 6 of each cylinder 2 in a specific operation state in the pilot injection fuel ignition type gas operation mode, In the period from the start of the intake stroke to the end of the compression stroke, the injection timing of the injection suitable for the operating state at that time is selected by the control signal sent from the electronic control device 60 and the gas fuel is injected. By causing the valve 5 to open a plurality of times per cycle, the amount of gas fuel required per cycle is intermittently injected in a plurality of times. As a result, the gas fuel is caused to flow in the combustion chamber 6 in the downstream direction of the swirl 70 while mixing with air along the inner wall surface of the cylinder 2 as a plurality of air-fuel mixture lumps, and the gas fuel mixture lump is uniform. Try to grow into a mixture.

Then, as the piston 3 approaches the top dead center in the compression stroke, the gas fuel is compressed while air and the gas fuel form an air-fuel mixture in the combustion chamber 6. Since the cavity 7 occupies the main part of the combustion chamber 6 when the piston 3 approaches the top dead center, a plurality of gas fuels that are dispersed on the inner periphery of the inner wall surface of the cylinder 2 and swivel together with the swirl 70 until then. The mass of the air-fuel mixture turns around the cavity side wall 8 when the piston 3 approaches the top dead center. A small amount of oil fuel is piloted from the oil fuel injection valve 4 near the cylinder center line A toward the cavity side wall 8 at the center of the cavity 7 where the mass of the gas fuel mixture distributed along the cavity side wall 8 turns. Spray. In the pilot injection fuel ignition type gas operation mode, since the amount of oil fuel pilot injected from the oil fuel injection valve is small, the kinetic energy of the oil fuel spray 71 during pilot injection is small. Therefore, the oil fuel spray 71 at the time of pilot injection does not reach the vicinity of the cavity side wall 8 but is dispersed in the central portion of the cavity 7 of the piston 3. FIG. 5 shows the gas formed by intermittently injecting the gas fuel into the combustion chamber 6 from the gas fuel injection valve 5 into the combustion chamber 6 in several cycles when the piston 3 approaches the top dead center. A state in which the mass of the fuel mixture 73 and the oil fuel spray 71 formed by the pilot injection of the oil fuel from the oil fuel injection valve 4 are distributed in the cavity 7 is shown in X view (see FIG. 1). It is. As shown in FIG. 5, in the cavity 7 occupying the main part of the combustion chamber 6, the distribution in which the gas fuel mixture 73 swirls when intermittently injected so as to surround the pilot-injected oil fuel spray 71 in the center is swirled. It becomes a form.

When the compression stroke proceeds and the piston 3 approaches the top dead center and the temperature and pressure in the combustion chamber 6 rise, the pilot fuel oil spray 71 self-ignites. Since the mass of the gas fuel mixture 73 is distributed so as to surround the oil fuel spray 71, the flame of the oil fuel spray 71 is generated from the center of the cavity 8 with respect to all the mass of the gas fuel mixture 73. 73 masses can be ignited. As a result, all the masses of the gas fuel mixture 73 distributed so as to surround the periphery of the oil fuel spray 71 can be ignited simultaneously from the center direction of the cavity 7, and the main fuel gas in the combustion chamber 6 in a short time. The fuel mixture 73 can be burned smoothly. Therefore, the dual operation mode engine of the first embodiment can be operated in the pilot injection fuel ignition type gas operation mode with high cycle efficiency and low HC and CO harmful exhaust gases.

In the operation of the pilot injection fuel ignition type gas operation mode in the dual operation mode engine of the first embodiment, the gas fuel injection valve 5 is controlled by the electronic control unit 60 according to the engine load and the engine speed state, and the gas fuel To optimize the injection. For example, during the period from the start of the intake stroke to the end of the compression stroke, the gas fuel is injected at a timing suitable for the injection amount of the gas fuel, and the gas fuel injection valves 5 to 1 are used at a low load when the injection amount of the gas fuel is small. The gas fuel is injected once in a cycle, and the gas fuel is injected intermittently in a plurality of cycles from the gas fuel injection valve 5 at medium and high loads when the amount of gas fuel injection is large. As a result, the gas fuel mixture is dispersed over a wide range in the combustion chamber 6 while the engine is operating, and the formation of a rich mixture is suppressed, thereby preventing the deterioration of combustion of the gas fuel. In addition, the injection of gas fuel is completed from the gas fuel injection valve into the combustion chamber 6 within the period from the start of the intake stroke to the end of the compression stroke, so that it is directly injected into the combustion chamber 6. Gas fuel can be prevented from being discharged from the cylinder 2 into the atmosphere in an unburned state. In this way, in the operation of the pilot injection fuel ignition gas operation mode in the dual operation mode engine of the first embodiment, the gas fuel of the main fuel is smoothly set to a predetermined uniform mixing ratio in all operation states. Therefore, it is possible to perform an operation with good cycle efficiency and low HC and CO harmful emissions.

Next, regarding the diesel operation mode of the dual operation mode engine of the first embodiment, the injection of the main fuel oil fuel injected from the oil fuel injection valve 4 and the injection of the cooling fluid injected from the gas fuel injection valve 5 will be described. To do. In the diesel operation mode, the cooling fluid is supplied from the gas fuel injection valve 5 into the combustion chamber 6 at an optimal time within the period from the start of the intake stroke to the end of the compression stroke by the control signal sent from the electronic control unit 60. In the cavity 7 occupying most of the combustion chamber 6, the main fuel oil is injected from the oil fuel injection valve 4 at the timing when the piston 3 approaches the top dead center by the control signal sent from the electronic control unit 60. The dual operation mode engine of the first embodiment operates in the diesel operation mode. Compared to the pilot injection of the oil fuel of the oil fuel injection valve 4 in the pilot injection fuel ignition type gas operation mode, the oil fuel injection of the oil fuel injection valve 4 in the diesel operation mode injects the oil fuel as the main fuel. Therefore, the injection amount of the oil fuel is large, and the injection forms such as the injection pressure, the injection period, and the number of injections are different. The injection of the cooling fluid in the diesel operation mode is performed by the electronic control unit 60 at an optimal injection amount at an optimal number of injections per cycle at an optimal injection timing within a period from the start of the intake stroke to the end of the compression stroke. Control.

In the diesel operation mode, an amount of oil fuel such as light oil or DME proportional to the engine output is injected, the combustion gas temperature in the combustion chamber 6 increases in proportion to the engine output, and the temperature of the nozzle portion of the gas fuel injection valve Increases in proportion to the amount of oil fuel injected. In order to prevent the malfunction of the gas fuel injection valve due to excessive temperature rise, the amount of cooling fluid injected from the gas fuel injection valve into the combustion chamber 6 when the injection amount of oil fuel is large in the diesel operation mode. The temperature of the valve portion of the gas fuel injection valve is cooled to a temperature below a certain level. By adjusting the amount of cooling fluid injected from the gas fuel injection valve into the combustion chamber 6 according to the engine operating load condition in the diesel operation mode, waste of the injection energy of the cooling fluid is prevented, and a decrease in engine fuel consumption is minimized. Therefore, the cooling fluid tank can be made compact by saving the injection amount of the cooling fluid. In addition, since the cooling fluid is injected at the optimal injection timing within the period from the start of the intake stroke to the end of the compression stroke where the pressure in the cylinder 2 is lower than the explosion stroke, the injection pressure of the cooling fluid is increased. Since there is no need to increase the pressure, the pressurizing energy of the pressurizing device 41 may be small. Therefore, there is an effect that significant fuel consumption deterioration due to the driving of the pressurizing device 41 can be avoided. By optimally controlling the cooling fluid injected from the gas fuel injection valve 5 in this way, the driving loss due to the injection of the cooling fluid from the gas fuel injection valve 5 is suppressed in the diesel operation mode, and the cooling fluid tank is made compact. In addition, the gas fuel injection valve 5 cools the gas fuel injection valve 5 exposed in the combustion chamber 6, and the gas fuel injection valve 5 is excessively heated by direct heating by the combustion gas of oil combustion or radiant heat of the combustion gas. And the gas fuel injection valve 5 can be prevented from being damaged by overheating.

Further, the cooling fluid is downstream of the swirl 70 in the combustion chamber 6 from the single injection nozzle or the multi injection nozzle of the gas fuel injection valve 5 arranged away from the cylinder center line A from the gas fuel injection valve 5 as in the case of the gas fuel. Will be injected. The cooling fluid is injected at an optimal time within the period from the start of the intake stroke to the end of the compression stroke, so that the cooling fluid can be stored in the combustion chamber 6 regardless of whether the cooling fluid is air or water. The swirling energy of the swirl 70 of swirling intake air swirling can be increased. The increase in the swirling energy of the swirl 70 causes the spray of oil fuel injected from the oil fuel injection valve 4 into the combustion chamber 6 to be widely distributed in the combustion chamber 6 and also mixes the spray of oil fuel with air. It has the effect of promoting the oil fuel spray mixture to a uniform theoretical mixing ratio. Thereby, the combustion of the oil fuel in the diesel operation mode becomes good, and the reduction of harmful emissions of black smoke, particulates, CO and HC can be obtained.

By the way, water is used as a cooling fluid, and water is injected intermittently at multiple times per cycle at the optimal injection timing within the period from the start of the intake stroke to the end of the compression stroke from the gas fuel injection valve 5. In this case, since the spray of water sprayed at one time has little kinetic energy, the spray of water has a small force penetrating into the combustion chamber 6 and floats in the combustion chamber 6. For this reason, the spray of water reaches the wall surface of the cylinder 2 and the surface of the piston 3 and adheres to the surface as water droplets, which mixes into the lubricating oil during engine operation and reduces the lubricating ability of the lubricating oil. Can be prevented. The spray of water thus intermittently injected does not adhere to the surface of the piston 3 or the inner wall surface of the cylinder 2, and moves away from the gas fuel injection valve 5 while mixing with the intake air in the combustion chamber 6. In the direction, it is carried on the flow of the swirl 70 and dispersed in the combustion chamber 6. When the piston 3 approaches the top dead center, the gas fuel mixture 73 shown in FIG. 5 when the gas fuel is injected a plurality of times per cycle from the gas fuel injection valve 5 in the pilot injection fuel ignition type gas operation mode. Similarly, the sprayed mass of water sprayed intermittently is dispersed in the cavity 8 over the entire circumference of the cavity side wall 8. Before the piston 3 reaches top dead center, oil fuel is injected from the oil fuel injection valve 4 into the cavity 7 filled with water spray, and the diesel operation mode is operated. By burning the oil fuel spray in the cavity 7 filled with water spray, the combustion gas temperature of the oil fuel decreases due to the endothermic effect of the combustion heat of the oil fuel, and the generation of NOx due to the combustion of the oil fuel is suppressed. Is done. Further, due to the volume expansion when the spray of water is vaporized, an increase in the pressure in the cylinder during the explosion stroke increases the work of expansion of the working fluid in the cylinder, thereby increasing the engine output and reducing the fuel consumption. Thus, in the diesel operation mode, when water is injected from the gas fuel injection valve 5 into the combustion chamber 6 as a cooling fluid, NOx emission due to a decrease in the combustion gas temperature of the oil fuel is reduced and fuel consumption is reduced. The effect that can be obtained.

In the first embodiment of the present invention described above, as the liquid fuel supply device 20 in which the oil fuel injection valve 4 injects the oil fuel, it is led from the liquid fuel tank 21 to the supply pump 22 through the supply passage 24 and pressurized by the supply pump 22. The oil fuel pressurized by the supply pump 22 is guided to the common rail 23 by the supply passage 25, and the oil fuel guided to the common rail 23 is guided from the common rail 23 to the oil fuel injection valve 4 by the supply passage 26, and is electronically controlled. A common rail system known in Japanese Patent Publication No. 2002-13453 or the like that injects oil fuel into the combustion chamber 6 from the oil fuel injection valve 4 that is an electromagnetic valve whose opening and closing is controlled by a control signal from the device 60 is used. did. In the first embodiment of the present invention, as a method of injecting oil fuel, an electromagnetic valve whose valve opening and closing is controlled by a control signal from an oil fuel pressurizing pump and an electronic control device other than the common rail system is used. A known unit injector may be used in Japanese Patent Publication No. 2005-291104, which is an injection device in which a certain oil fuel injection valve is integrated. In addition, by using a piezo-type injector capable of opening and closing at high speed with a piezoelectric element for the gas fuel injection valve 5, a plurality of intermittent injections of gas fuel or cooling fluid can be easily performed in one cycle. can do.

In the first embodiment of the present invention, the gas fuel injection valve 5 is provided with one gas fuel injection valve 5 in the cylinder head 1 at a position away from the cylinder center line A, but at a position away from the cylinder center line A. A plurality of gas fuel injection valves may be disposed in the cylinder head 1. When two gas fuel injection valves are provided, each of the two gas fuel injection valves is preferably attached to the cylinder head 1 at a position facing each other while being separated from the cylinder center line A. As in the case of the single gas fuel injection valve 5, the direction in which each gas fuel injection valve injects the gas fuel or the cooling fluid depends on the single injection nozzle or the multi injection nozzle of each gas fuel injection valve. It is desirable to inject into the combustion chamber 6 in the downstream direction of the swirl 70 at the position. FIG. 6 shows the gas fuel injection valve 55 and the gas fuel injection valve 56 from the two nozzle nozzles provided at the tips of the two gas fuel injection valves 55 and the gas fuel injection valve 56 arranged away from the cylinder center line. In the downstream direction of the swirl 70 at each position, a plurality of intermittent gas fuel injections are performed in one cycle in an optimal period within the period from the start of the intake stroke to the end of the compression stroke, and the compression stroke proceeds. When the piston 3 approaches the top dead center, the inside of the cavity 7 radiates from the two nozzle holes provided at the tip of the oil fuel injection valve 4 disposed near the cylinder center line A toward the cavity side wall 8 of the piston 3. Is a pilot-injected fuel ignition type gas operation mode in X view (see FIG. 1) showing a state in which a gas-fuel mixture 74 and an oil-fuel spray 71 are distributed when a small amount of oil fuel is pilot-injected. It is a diagram. The gas fuel mixture 74 in the pilot injection fuel ignition type gas operation mode of the dual operation mode engine having the two gas fuel injection valves of the gas fuel injection valve 55 and the gas fuel injection valve 56 is one gas fuel injection. The main fuel gas fuel is distributed over a wide range in the cylinder 2 in a shorter time than the case of the pilot injection fuel ignition type gas operation mode of the dual operation mode engine having the valve 5, and the mixture of all the injected gas fuels It is possible to reduce the portion of the rich gas fuel mixture as much as possible by bringing the gas close to the theoretical mixture ratio. Combustion of the gas fuel mixture 74 in a state close to all the theoretical mixture ratios becomes complete combustion, which has an effect of improving fuel efficiency by improving cycle efficiency and reducing emission of harmful substances of CO and HC accompanying incomplete combustion. In the diesel operation mode of the dual operation mode engine having two gas fuel injection valves of the gas fuel injection valve 55 and the gas fuel injection valve 56, the spray of water can be dispersed in a wide range in the cavity 7, Sufficient NOx emissions can be reduced in the diesel operation mode.

Further, in the dual operation mode engine of the first embodiment of the present invention, the cylinder group individual control for stopping the operation of some cylinders in a specific operation state by applying the cylinder group individual control engine disclosed in Japanese Patent Publication No. 2005-54771. May be performed. The engine exhaust gas system disclosed in Japanese Patent Publication No. 2005-69238 may be used in combination to reduce fuel consumption and purify exhaust gas. Alternatively, the oil fuel injection valve 4 may be opened in a plurality of cycles in one cycle by a signal from the electronic control unit 60, and the oil fuel may be intermittently injected from the oil fuel injection valve 4 into the combustion chamber 6. good. When air is used as the cooling fluid, the cooling fluid tank 42 is omitted, and the supply passage 44 is connected to the intake pipe downstream of the air cleaner of the dual operation mode engine to supply the cooling air to the pressurizing device 41. May be.

In the dual operation mode engine of the first embodiment, the oil fuel injection valve injects oil fuel into the combustion chamber, and the gas fuel injection valve supplies gas fuel or cooling fluid into the combustion chamber. It is the schematic diagram which showed the specific structure to inject. It is a flowchart of the control regarding the injection of the oil fuel from the oil fuel injection valve of this 1st Embodiment, and the injection of the gas fuel and cooling fluid from a gas fuel injection valve. FIG. 2 is a transparent perspective view of a combustion chamber constituted by a cylinder head, a cylinder and a piston of the first embodiment, and an oil fuel injection valve 4 and a gas fuel injection valve 5 disposed in the cylinder head. FIG. 3 shows a state (X view) of pilot injection of oil fuel and injection of gas fuel once in one cycle in the pilot injection fuel ignition type gas operation mode of the first embodiment. FIG. 2 shows a state (X view) of pilot injection of oil fuel and gas fuel injection intermittently divided into several times in one cycle in the pilot injection fuel ignition gas operation mode of the first embodiment. Two gas fuel injection valves are provided in each cylinder of the first embodiment, and in the pilot injection fuel ignition type gas operation mode, the pilot injection of oil fuel and the state of intermittent injection of gas fuel several times in one cycle (X view) is shown.

Explanation of symbols

(1) Cylinder head (2) Cylinder (3) Piston (4) Oil fuel injection valve (5), (55), (56) Gas fuel injection valve (6) Combustion chamber (7) Cavity (8) Cavity sidewall ( 9) Cylinder head contact surface (10) Engine body (11) Supply passage (12) Intake port (13) Exhaust port (20) Liquid fuel supply device (21) Liquid fuel tank (22) Supply pump (23) Common rail ( 24), (25), (26) supply passage (30) gas fuel supply device (31) high pressure gas fuel cylinder (32) regulator (33), (34) supply passage (40) high pressure cooling fluid supply device (41) Pressurizer (42) Cooling fluid tank (43), (44) Supply passage (50) Switching device (60) Electronic controller (70) Swirl (71) Oil fuel spray (72), (73), (74) gas Mixture (75) Intake Air Flow (76) Exhaust Gas Flow (A) Cylinder Center Line (B) Intersection of Center Line of Gas Fuel Injection Valve and Cylinder Head Surface Forming Combustion Chamber (C) Gas Fuel Injection Valve center line (AB surface) A surface including the cylinder center line A and the intersection A (surface shown by hatching in FIG. 3)
(S0), (S1), (S2), (S3), (S4) Steps (S5), (S6), (S7), (S8) Steps

Claims (5)

A combustion chamber is formed by a cylinder head, a cylinder and a piston, and an oil fuel injection valve for directly injecting fuel oil with good compression ignitability such as light oil or DME into the cylinder chamber and compression ignitability of natural gas or the like. A gas fuel injection valve that directly injects bad gas fuel into the combustion chamber, stops the injection of the gas fuel from the gas fuel injection valve, and burns only the oil fuel injected from the oil fuel injection valve A pilot-injected fuel that is operated by igniting and burning a gas fuel that is a main fuel injected from the gas-fuel injection valve by a combustion flame of a small amount of oil-fuel that is pilot-injected from the oil-fuel injection valve In a dual operation mode engine that can be switched to two types of operation modes, i.e., an ignition gas operation mode, a ceiling supplied from a gas fuel supply device A switching device for arbitrarily switching a gas fuel having poor compression ignitability such as gas and a cooling fluid such as air or water supplied from a high-pressure cooling fluid supply device to supply the gas fuel injection valve; In the operation mode, oil fuel is injected into the combustion chamber from the oil fuel injection valve, and the cooling fluid is supplied from the switching device to the gas fuel injection valve, and the cooling fluid is supplied from the gas fuel injection valve into the combustion chamber. In the pilot injection fuel ignition type gas operation mode, a small amount of oil fuel is pilot injected from the oil fuel injection valve into the combustion chamber and gas fuel is supplied from the switching device to the gas fuel injection valve. A dual operation mode engine system characterized in that gas fuel as main fuel is injected into the combustion chamber from a fuel injection valve. The oil fuel injection valve is disposed in the vicinity of the cylinder center line of the cylinder of the cylinder head, and the oil fuel is radially radiated from the multi-hole nozzle at the tip of the oil fuel injection valve toward the inner wall surface of the cylinder. One or more gas fuel injection valves are arranged at positions away from the cylinder center line of the cylinder head, and gas is supplied from a single injection nozzle or a multi injection nozzle at the tip of the gas fuel injection valve. The swirl of the air swirling in the combustion chamber from the plane including the intersection of the center line of the gas fuel injection valve and the surface of the cylinder head forming the combustion chamber and the cylinder center line is the direction in which the fuel or cooling fluid is injected. The dual operation mode engine system according to claim 1, wherein the engine is directed in a downstream direction. In the diesel operation mode, the cooling fluid is injected into the combustion chamber from the gas fuel injection valve in a plurality of times per cycle of the engine, and in the pilot injection fuel ignition type gas operation mode, the gas fuel injection valve 3. The dual operation mode engine system according to claim 1, wherein gas fuel is injected into the combustion chamber in a plurality of times per cycle of the engine. In the four-cycle engine, the cooling fluid injected from the gas fuel injection valve into the combustion chamber in the diesel operation mode is within a period from the start of the intake stroke to the end of the compression stroke of the cylinder, and the pilot injected fuel 2. The gas fuel injection from the gas fuel injection valve into the combustion chamber in the ignition gas operation mode is within a period from the start of the intake stroke to the end of the compression stroke of the cylinder. 3. The dual operation mode engine system according to 3. 5. The dual operation mode engine system according to claim 1, wherein an amount of cooling fluid injected from the gas fuel injection valve into the combustion chamber during the diesel operation mode is adjusted according to an operation state of the engine. .

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