JPH06323209A - Alcohol reforming engine provided with auxiliary chamber - Google Patents

Abstract

PURPOSE:To provide an alcohol reforming engine for reforming the alcohol fuel injected into an auxiliary chamber by utilizing the thermal energy of an exhaust gas and for improving fuel consumption. CONSTITUTION:A control valve 7 provided on a connection hole 3 communicating between a primary chamber 1 and a secondary chamber 2 is released in the vicinity of the compression top dead center and is closed before an exhaust valve 28 is released, in an alcohol reformed engine. The alcohol fuel injected from a fuel injection nozzle 8 into the auxiliary chamber 2 is injected at the time of exhaust stroke at the time of high temperature, while it is injected at the timing when the control valve 7 is released before the compression top dead center at the time of low temperature. The closing timing of the control valve 7 is expedited corresponding to a partial load signal by the controller 6. At the time of starting at low temperature, an EGR gas is controlled to be left in a cylinder 27 by throttling the opening of the exhaust valve 28, or the EGR gas is controlled to flow from an exhaust port 29 into the cylinder 27 by releasing the exhaust valve 28 for a short period of time at the time of suction stroke.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alcohol reforming engine provided with a sub chamber for reforming alcohol fuel such as methanol with the heat of combustion gas.

[0002]

2. Description of the Related Art In recent years, environmental pollution caused by exhaust gas exhausted from an engine has become a problem, and an alcohol engine has recently attracted attention. In the alcohol engine, the content of carbon dioxide gas and carbide in the exhaust gas is very small compared to fuels such as gasoline and light oil. However, an alcohol engine that uses alcohol fuel has a problem of poor ignition performance. That is,
Alcohol has a higher latent heat for vaporization than gasoline, and for example, gasoline requires 0.7% of the latent heat of vaporization of fuel, whereas alcohol requires 5% of the latent heat of vaporization of fuel, Alcohol fuel has the property of being difficult to vaporize. Moreover, the alcohol fuel injected from the fuel injection nozzle into the compressed air in the combustion chamber lowers the temperature of the compressed air and the wall surface of the combustion chamber due to vaporization, which worsens ignition.

Conventionally, alcohol reforming engines have been disclosed in JP-A-3-145558 and JP-A-3-145559.
There are some disclosed in Japanese Patent No. For example, JP-A-3-
The alcohol reforming engine disclosed in Japanese Patent No. 145559 crosses each of the above passages, an intake passage through which an air-fuel mixture of alcohol fuel and intake air flows, an exhaust passage through which exhaust gas from a combustion chamber flows, an air passage through which intake air flows. Honeycomb reactor disc that exchanges heat with a fluid and reforms the fuel, a fuel injection nozzle that is disposed in the intake passage upstream of the disc and that injects alcohol fuel, and the disc is rotated. It consists of a driving motor.

[0004]

By the way, in an alcohol engine that uses alcohol such as methanol as a fuel, it is necessary to improve fuel efficiency by reforming methanol.
It is well known in the art. The reason is that methanol decomposes thermally, and by applying heat energy to methanol, it decomposes into hydrogen gas and carbon monoxide. That is, when a heat quantity of 20 Kcal per mol of methanol is applied, methanol is thermally decomposed into hydrogen and carbon monoxide [CH ₃ OH + 20 Kcal → 2H ₂ + CO].
Therefore, methanol has hydrogen gas and carbon monoxide as fuel, and the methanol fuel is reformed.

Further, in a heat shield engine, when the combustion chamber has a heat shield structure, the temperature of the exhaust gas exhausted from the combustion chamber is 1500 when the engine is operating at high speed and high load.
It has risen to ℃. Therefore, it is preferable to use the exhaust gas discharged from the heat shield engine to thermally decompose and reform the alcohol fuel. However, when the engine is operating at low speed and low load, the wall surface of the combustion chamber is not in a high temperature state, the fuel takes heat of vaporization from the wall surface, and the vaporization cannot be promoted. When the fuel is alcohol, Since the latent heat for vaporization is high, the phenomenon appears significantly. Therefore, there are problems of improving combustion and reforming alcohol fuel when the temperature of exhaust gas or the wall temperature is low at the time of engine start, partial load, and the like.

[0006] Therefore, an object of the present invention is to solve the above-described problems, and the thermal energy of exhaust gas is absorbed in alcohol fuel to reform the alcohol fuel from hydrogen gas and carbon monoxide. In order to achieve, by providing a control valve in the communication hole that communicates the sub chamber and the main chamber, by controlling the injection timing of the fuel injection nozzle for injecting alcohol fuel into the sub chamber, the opening and closing timing of the control valve and exhaust valve, The heat energy of the exhaust gas is effectively used to heat and vaporize the alcohol fuel for thermal decomposition, improve combustion at partial load, improve ignition combustion at low temperature start,
It is an object of the present invention to provide an alcohol reforming engine including a sub chamber for increasing the heat generation amount by reforming alcohol fuel, improving thermal efficiency, and improving fuel efficiency.

[0007]

In order to achieve the above object, the present invention is configured as follows. That is, the present invention relates to a sub-chamber provided in a cavity formed in a cylinder head, a fuel injection nozzle for injecting alcohol fuel into the sub-chamber, an exhaust valve arranged in an exhaust port formed in the cylinder head, and a cylinder side. A formed main chamber, a communication hole that communicates the sub chamber with the main chamber, a control valve that opens the communication hole near the compression top dead center and closes before opening the exhaust valve, and detects an engine load The present invention relates to an alcohol reforming engine having a sub-chamber, which has a load sensor and a controller that performs control for advancing the closing timing of the control valve in response to a partial load signal from the load sensor.

Further, in the alcohol reforming engine having the sub chamber, a temperature sensor for detecting an engine temperature is provided, and the controller expands the control valve in response to a temperature higher than a predetermined temperature of the temperature sensor. It is closed after the bottom dead center of the stroke, then the fuel injection timing from the fuel injection nozzle is injected during the exhaust stroke, and the control valve is expanded before the bottom dead center of the expansion stroke in response to a temperature lower than a predetermined temperature of the temperature sensor. Then, the fuel injection timing from the fuel injection nozzle is controlled to be injected before the top dead center of the compression stroke.

Further, in the alcohol reforming engine having the sub chamber, the controller responds to a temperature lower than a predetermined temperature of the temperature sensor by narrowing the degree of opening of the exhaust valve to supply EGR gas into the cylinder. The control is made to remain.

Further, in the alcohol reforming engine having the sub chamber, the controller opens the exhaust valve for a short period during an intake stroke in response to a temperature of the temperature sensor which is equal to or lower than a predetermined temperature, and the exhaust gas is exhausted. The control is performed so that the EGR gas flows into the cylinder through the port.

[0011]

The alcohol reforming engine having the sub chamber according to the present invention is constructed as described above and operates as follows. That is, an alcohol reforming engine including this sub-chamber is provided with a sub-chamber in a cavity formed in a cylinder head, and an exhaust valve is arranged in an exhaust port formed in the cylinder head to supply alcohol fuel to the sub-chamber. Fuel is injected from a fuel injection nozzle, the main chamber formed on the cylinder side and the sub chamber are communicated with each other by a communication hole, a control valve is arranged in the communication hole, and the control valve is opened near the compression top dead center and The exhaust valve is set to be closed before opening, and in particular, because the controller performs control for advancing the closing timing of the control valve in response to the partial load of the detection signal from the load sensor, The high-temperature exhaust gas remains, and when the alcohol fuel is injected from the fuel injection nozzle into the sub-chamber in an atmosphere in which the exhaust gas remains, the alcohol fuel has heat energy which the exhaust gas has. And the heat energy stored in the wall of the sub chamber, it is heated and vaporized to be sufficiently pyrolyzed and reformed, so that the calorific value of the fuel can be increased and the exhaust gas energy can be effectively recovered to improve the thermal efficiency. And fuel efficiency can be improved.

Further, at the opening / closing timing of the control valve, the control valve closes the communication hole from the middle of the period during which the control valve takes intake air into the main chamber, that is, the intake stroke and the compression period, to near the compression top dead center. By controlling the communication hole to open at the end of compression, the gas fuel can be burned at a high compression ratio regardless of the octane number, and the thermal efficiency can be improved.

Further, the alcohol reforming engine is provided with a temperature sensor for detecting an engine temperature, and the controller closes the control valve after the expansion stroke bottom dead center in response to a temperature above a predetermined temperature of the temperature sensor. Then, if control is performed to inject the fuel injection timing from the fuel injection nozzle during the exhaust stroke, reforming of the alcohol fuel can be effectively achieved, and the calorific value of the fuel can be increased.

Further, in response to a temperature below a predetermined temperature of the temperature sensor by the controller, the control valve is closed before the bottom dead center of the expansion stroke, and then the fuel injection timing from the fuel injection nozzle is increased on the compression stroke. By performing the injection control before the dead center, by injecting the fuel into the high temperature air flowing into the sub chamber, the ignitability of the fuel is increased,
Combustion is facilitated, and fuel injection is performed in conformity with the opening timing of the control valve, so that exhaust gas can appropriately remain in the sub chamber at low temperature and partial load, and from the main chamber. The alcohol fuel receives the heat energy of the high temperature gas blown into the sub chamber, and the alcohol fuel can be efficiently burned. Further, in response to a temperature below a predetermined temperature of the temperature sensor, the degree of opening of the exhaust valve is reduced to allow EGR gas to remain in the cylinder, or the exhaust valve is opened for a short period during the intake stroke to open the exhaust port. By flowing the EGR gas into the cylinder through the exhaust gas, the exhaust gas can be appropriately left in the sub chamber.

Alcohol fuel has a calorific value of 9000 kc
al / kg, for example, the temperature of the exhaust gas is 500 ° C
It receives thermal energy of ~ 600 ° C and is thermally decomposed into a mixed gas of CO and H ₂ . Due to the thermal decomposition of methanol, the calorific value of the mixed gas is increased to 12000 kcal / kg and reformed. Moreover, since the mixed gas of CO, H ₂ and vaporized fuel obtained by reforming the alcohol fuel has a high combustion speed and a low combustion temperature, smoke, N 2
It is possible to suppress the generation of O _{x and the} like.

Further, when the control valve opens the communication hole, highly compressed intake air flows from the main chamber through the communication hole into the sub chamber to reform and generate alcohol fuel. gas fuel and the vaporized fuel and intake air are mixed to ignite a combustion, generation of the NO _X is suppressed at high burn in large fuel-rich equivalence ratio.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an alcohol reforming engine having a sub chamber according to the present invention will be described below with reference to the drawings.
1 is a sectional view showing an embodiment of an alcohol reforming engine having a sub chamber according to the present invention, FIG. 2 is an explanatory view showing timings of a control valve and a fuel injection nozzle of the alcohol reforming engine of FIG. 1, FIG. 1 is an explanatory view showing the relationship between the control valve incorporated in the alcohol reforming engine of FIG. 1 and the sub chamber wall, and FIG. 4 is an embodiment of the control valve incorporated in the alcohol reforming engine of FIG. FIG. 5 is a process flow chart showing an embodiment of the operation of the alcohol reforming engine provided with this sub chamber.

The alcohol reforming engine equipped with this sub-chamber is a sub-chamber engine that uses alcohol such as methanol as fuel, and is a mixture of monocarbon dioxide CO and hydrogen gas H _{2 obtained} by thermally decomposing alcohol fuel. By reforming into gas and vaporized fuel to increase the amount of heat generation, the combustion at the time of partial load of the engine is improved, and the ignition / combustion at the time of low temperature start is improved to improve the thermal efficiency.

This alcohol reforming engine comprises a cylinder block 26, a cylinder head 4 fixed to the cylinder block 26, a cavity 22 formed in the cylinder head 4, and a sub chamber 2 arranged in the cavity 22 of the cylinder head 4. Cylinder liner 18 that is formed in the cylinder liner 18 that composes the cylinder 27 and that fits in the hole 24 of the cylinder block 26
7, reciprocating piston 3, and headliner 10
It has a main chamber 1 formed by The sub chamber wall 9 and the headliner 10 are arranged in a structure in which a heat insulating air layer 20 is formed between the cavity 22 of the cylinder head 4 and the cavity 22 with a heat insulating gasket 21 interposed therebetween. The piston 3 is composed of a piston head 15 made of ceramics, and a piston skirt 16 having a heat shield air layer 23 formed on the piston head 15 and fixed by a metal flow of a coupling ring 29 or the like. Therefore, the main chamber 1 includes the headliner 10 and the piston head 15.
And the high degree of heat shielding is configured, and the sub chamber 2
The heat shield air layer 20 and the sub-chamber wall 9 constitute a high-level heat shield structure.

In the head liner 10, the head lower surface portion 12 and the liner upper portion 11 are integrally formed of ceramics such as silicon nitride having heat resistance and high temperature and high strength. The communication hole 5 that connects the main chamber 1 and the sub chamber 2 is provided with the headliner 10.
A plurality of head lower surface portions 12 are formed in an inclined state from the sub chamber 2 to the main chamber 1 toward the cylinder peripheral direction. A central communication hole 31 is formed in the center of the sub chamber 2, and a valve seat 17 is formed around the central communication hole 31. The control valve 7 is arranged in the central communication hole 31, and the valve face 32 of the control valve 7 is seated on the valve seat 17.

In this alcohol reforming engine, in particular, the sub chamber wall 9 forming the sub chamber 2 disposed in the cavity 22 formed in the cylinder head 4 and the exhaust gas disposed in the exhaust port 29 formed in the cylinder head 4. Valve 28, the sub chamber 2
Fuel injection nozzle 8 having multiple injection holes 14 for injecting alcohol fuel, head liner 10 including head lower surface portion 12 and liner upper portion 11 forming main chamber 1 formed on the cylinder side, sub chamber 2 and main chamber 1 has a communication hole 5 and a central communication hole 31 communicating with each other, and a control valve 7 for opening and closing the communication hole 5 and the central communication hole 31. In addition, in this alcohol reforming engine, a plurality of exhaust ports 35 in which the exhaust valves 28 are arranged are formed in the head lower surface portion 12. Although not shown, the intake port is formed in the cylinder head 4 or the lower part of the cylinder. Since the lower surface 12 of the head having the communication hole 5 and the central communication hole 31 is exposed to high temperature, the head liner 10 forming the lower surface 12 of the head is made of ceramics such as silicon nitride having high heat resistance and high temperature and high strength. It is preferable.

Further, the alcohol reforming engine equipped with this sub chamber has a load sensor 25 for detecting the engine load L.
And a temperature sensor 34 for detecting the engine temperature T such as the combustion chamber wall temperature, and the control valve 7 and the exhaust valve 2 in response to detection signals from the load sensor 25 and the temperature sensor 34.
The controller 6 controls the valve timing and valve lift of the fuel injection nozzle 8 and the injection timing of the fuel injection nozzle 8. The control valve 7 and the exhaust valve 28 are configured to be opened and closed by the electromagnetic valve drive devices 13 and 30 so that the valve timing and the valve lift are controlled by the electromagnetic force.

In this alcohol reforming engine, the communication holes 5 and the central communication hole 31 are controlled by the controller 6 to open near the compression top dead center and close before the exhaust valve 28 opens. Further, the controller 6 responds to the partial load signal from the load sensor 25, and
The control for accelerating the closing time is performed, for example, the control for accelerating the closing timing indicated by the reference symbol LC in FIG. 2 to the closing timing indicated by the reference symbol SC. In addition, the controller 6
In response to the detected temperature T which is equal to or higher than the predetermined temperature T ₁ of the temperature sensor 34, the control valve 7 is closed after the bottom dead center of the expansion stroke, and then, as indicated by the symbol FH in FIG. The fuel injection timing from the injection hole 14 is controlled so that the fuel is injected during the exhaust stroke. The controller 6 also closes the control valve 7 before the bottom dead center of the expansion stroke in response to the detected temperature T which is equal to or lower than the predetermined temperature T ₁ of the temperature sensor, and then, as indicated by the symbol FL in FIG. The fuel injection timing from the multiple injection holes 14 of the fuel injection nozzle 8 is controlled to be injected before the top dead center of the compression stroke.

In addition, in this alcohol reforming engine, the controller 6 responds to the temperature T of the temperature sensor 34 which is equal to or lower than the predetermined temperature T ₁ , that is, the open degree of the exhaust valve 28 in response to a low temperature condition such as a low temperature start. Squeeze and put E in cylinder 27
It can be configured to perform control for leaving the GR gas. Alternatively, the controller 6 uses the temperature sensor 34.
In response to a temperature T equal to or lower than the predetermined temperature T ₁ , that is, a low temperature state such as a low temperature start, the exhaust valve 28 is opened for a short period during the intake stroke and the EGR is introduced into the cylinder 27 through the exhaust port 29.
It is possible to control the flow of gas. By controlling the exhaust valve 28 by the controller 6 as described above, sufficient EGR gas can be made to exist in the cylinder 27, and when the compression stroke is entered in that state, the compression end temperature can be raised, By opening the control valve 7 in the vicinity of the compression top dead center, high temperature gas flows from the main chamber 1 to the sub chamber 2, and the alcohol fuel injected into the sub chamber 2 is sufficiently heated and vaporized to be thermally decomposed and reformed. can do.

Regarding this alcohol reforming engine,
The sub chamber wall 9 is heated by the thermal energy of the exhaust gas to store heat, and the alcohol fuel is stored in the sub chamber wall 9.
It receives heat from the wall surface and heats vaporizes and thermally decomposes the alcohol fuel to reform it. The fuel injection nozzle 8 for injecting alcohol fuel into the sub chamber 2 has multiple injection holes 14 and is installed so as to inject an appropriate amount of alcohol fuel into the sub chamber 2 from the multiple injection holes 14. The alcohol fuel injected from the multiple injection holes 14 of the fuel injection nozzle 8 into the sub chamber 2 is heated by absorbing thermal energy from the sub chamber wall 9.
It vaporizes and thermally decomposes into hydrogen and carbon monoxide [C
H ₃ OH + 20 Kcal → 2H ₂ + CO], the alcohol fuel is reformed, and the fuel efficiency is improved.

In this alcohol reforming engine, as shown in FIGS. 1 and 3, the connecting hole formed in the sub-chamber wall 9 has a head lower surface portion of the head liner 10 which connects the main chamber 1 and the sub-chamber 2 with each other. It is composed of a communication hole 5 formed in 12 and a central communication hole 31. The control valve 7 that opens and closes the communication hole 5 and the central communication hole 31 that form the communication hole includes the sub chamber wall 9 and the sub chamber 2.
Is arranged in the cylinder head 4 so as to penetrate through the center thereof.
The control valve 7 includes, in particular, as shown in FIGS. 3 and 4, a protrusion 33 that fits into the central communication hole 31 and closes the valve seat 1.
A valve face 32 having a conical surface for seating on the valve 7 and closing the communication hole 5 is provided. Further, a plurality of communication holes 5 are formed so as to be inclined from the valve seat 17 toward the wall surface of the cylinder, and the central communication hole 31 has a large passage sectional area in the center of the cylinder.

Further, the control valve 7 is driven by an electromagnetic force by the electromagnetic valve driving device 13, and can control the opening / closing operation by a command of the controller 6 in response to an engine operating state such as an engine load and an engine temperature. . The communication valve 5 is first opened by the solenoid valve drive device 13, and then
The valve may be lifted in two steps in which the central communication hole 31 is opened. The electromagnetic valve driving device 13 that opens and closes the control valve 7 can be configured to open the communication hole 5 with a small electromagnetic force and open the central communication hole 31 with a large electromagnetic force, for example. For example, when a small current flows through the electromagnetic coil in response to a command from the controller 6 in response to a detection signal from the load sensor 25 that detects the engine load, a small electromagnetic force is applied and the control valve 7 is lifted slightly. When the control valve 7 rises slightly, the conical surface valve face 32 separates from the valve seat 17, the communication hole 5 opens, and the opening degree becomes minute. Next, when a large current flows through the electromagnetic coil in response to a command from the controller 6, a large electromagnetic force is applied and the control valve 7
Is greatly lifted. If the control valve 7 rises significantly,
The projecting portion 33 comes out of the central communication hole 31 and the central communication hole 31 is opened.

Next, one embodiment of the operation of the alcohol reforming engine will be described with reference to the process flow charts of FIGS. 2 and 5. Drive the engine and load sensor 2
The engine load L is detected by 5 and the engine temperature T such as the combustion chamber wall temperature is detected by the temperature sensor 34 (step 40). The controller 6 compares whether the engine temperature T detected by the temperature sensor 34 is higher than a predetermined temperature T ₁ or whether the engine load L detected by the load sensor 25 is higher than a predetermined temperature L _1. It is judged (step 41).

In step 41, the temperature sensor 34
When the engine temperature T detected by the load sensor 25 is higher than the predetermined temperature T ₁ , or when the engine load L detected by the load sensor 25 is higher than the predetermined temperature L ₁ , the engine load L is a high load, Since the wall surface temperature of the chamber wall body 9 is high, the alcohol fuel injected into the sub chamber 2 is in a state in which it can sufficiently give the thermal energy for reforming from the wall surface of the sub chamber 2. Therefore, in response to a command from the controller 6, the multi-injection hole 14 of the fuel injection nozzle 8 causes the sub chamber 2
A predetermined amount of alcohol fuel corresponding to the engine load L is injected therein during the exhaust stroke (step 42). The alcohol fuel injected into the sub chamber 2 absorbs heat from the wall surface of the sub chamber wall body 9, is heated and vaporized, and is thermally decomposed into a reformed fuel. The control valve 7 is compressed by the command of the controller 6 before the top dead center 0 to 20.
The communication hole 5 is opened by lifting at a temperature of 50 ° C., and compressed air is introduced from the main chamber 1 to the sub chamber 2. The intake air introduced into the sub chamber 2 is promoted to be mixed with the reformed fuel and is ignited and burned.

Then, the gas pressure in the sub chamber 2 rises due to the combustion of the reformed fuel. When the engine load L is high, the temperature of the wall surface is sufficient to reform the alcohol fuel, and the alcohol fuel injected into the sub chamber 2 absorbs heat from the wall surface. The effect of lowering the temperature can be exerted. Next, in the expansion stroke, the gas in the sub-chamber 2 such as flame and unburned air-fuel mixture is ejected to the peripheral side of the cylinder 27 through the communication hole 5, and the control valve 7 reaches the maximum lift amount and communicates with the center. The hole 31 is opened, and the piston 3 is moved downward. Gases such as flames and unburned air-fuel mixture in the sub-chamber 2 are blown out into the main chamber 1 at a stroke, promoting the mixing with the fresh air existing in the main chamber 1 and burning. Work faster by reducing speed and completing combustion in a short period of time. Next, the exhaust valve 28 is connected to the exhaust port 3
5 is opened to shift to the exhaust stroke, and the control valve 7 is closed after the exhaust stroke bottom dead center BDC according to a command from the controller 6 (step 43). The combustion gas, that is, the exhaust gas is the main chamber 1.
Is exhausted through the exhaust port 35. Further, when the intake port or the scavenging port is opened, the intake stroke or the scavenging stroke is started, intake air is introduced into the cylinder 27, and the cycle is repeated to drive the engine.

In step 41, if the engine temperature T detected by the temperature sensor 34 is not higher than the predetermined temperature T ₁ , or the engine load L detected by the load sensor 25 is not higher than the predetermined temperature L ₁ . In this case, since the engine load L is low and the wall temperature of the sub chamber wall 9 is low, the alcohol fuel injected into the sub chamber 2 has sufficient thermal energy to be reformed from the wall of the sub chamber 2. Is not in a state that can be given to. Therefore, at the command of the controller 6, the multiple injection holes 14 of the fuel injection nozzle 8 are
Then, a predetermined amount of alcohol fuel corresponding to the engine load L is injected into the sub chamber 2 at 20 ° before the compression top dead center (step 44). Further, in response to a command from the controller 6, the control valve 7 is lifted at 0 to 20 ° before the compression top dead center TDC to open the communication hole 5, and compressed air is introduced from the main chamber 1 to the sub chamber 2 (step 45). . Next, the control valve 7 is closed at 20 ° before the expansion stroke bottom dead center BDC. Therefore, the alcohol fuel injected into the sub chamber 2 absorbs the high temperature gas blown from the main chamber 1 into the sub chamber 2 and the heat from the wall surface of the sub chamber wall body 9, and is heated and vaporized,
The intake air introduced into the sub chamber 2 is pyrolyzed into a reformed fuel and mixed with the reformed fuel to be ignited and burned.

In step 41, the temperature sensor 34
When the engine temperature T detected by the engine is not higher than the predetermined temperature T ₁ , or when the engine load L detected by the load sensor 25 is not higher than the predetermined temperature L ₁ , the controller 6 opens the exhaust valve 28. The control is performed so that the EGR gas remains in the cylinder 27 at a reduced rate, or the exhaust valve 28 is opened for a short period during the intake stroke to allow the EGR gas to flow into the cylinder 27 through the exhaust port 35 (step 46). By controlling the opening degree or opening / closing timing of the exhaust valve 28 in this way,
Exhaust gas can be appropriately left in the cylinder 27 at low temperature and at partial load, the gas blown into the sub chamber 2 can be heated to a high temperature, and alcohol fuel can be reformed efficiently. .

[0033]

The alcohol reforming engine having the sub chamber according to the present invention is constructed as described above and has the following effects. That is, an alcohol reforming engine including this sub-chamber is provided with a sub-chamber in a cavity formed in a cylinder head, and an exhaust valve is arranged in an exhaust port formed in the cylinder head to supply alcohol fuel to the sub-chamber. Fuel is injected from a fuel injection nozzle, the main chamber formed on the cylinder side and the sub chamber are communicated with each other by a communication hole, a control valve is arranged in the communication hole, and the control valve is opened near the compression top dead center and The exhaust valve is set to be closed before opening, and in particular, control is performed to accelerate the closing time of the control valve in response to the detection signal from the load sensor being a partial load by the controller. The high temperature exhaust gas can remain, and the alcohol fuel injected from the fuel injection nozzle is effectively modified by the high temperature gas and the thermal energy accumulated in the sub chamber wall. It is. The alcohol fuel is heated by the thermal energy of the fuel gas, and is also thermally decomposed by being heated by the thermal energy of the wall surface of the sub-chamber wall body in which the heat is stored, and is thermally decomposed into CO and H ₂ for reforming and ignition. The heat generation amount can be increased while improving the property, and the exhaust gas energy can be effectively recovered.

Further, since the intake air is introduced into the main chamber in a state where the communication hole and the central communication hole are closed and the main chamber and the sub chamber are cut off, a high compression ratio for highly compressing the intake air can be realized. . Then, alcohol fuel is injected in a state where air does not exist in the sub chamber, and the fuel is reformed by exhaust gas energy in a state where the fuel is sealed in the sub chamber, so that an appropriate fuel flow rate can be supplied and the reformed fuel is self-contained. Never ignite. Further, even if the intake air has a high compression pressure in the main chamber, the sub-chamber is closed by the control valve to shut off from the main chamber, and the activated reformed fuel in the sub-chamber self-ignites. Knocking does not occur.

Further, when the control valve is actuated and the communication hole is opened, the air that is highly compressed and has a high temperature flows from the main chamber into the sub chamber at once, and the reformed fuel and the intake air are separated from each other. Mixing is accelerated at once and ignited, and high-speed combustion is performed in the sub-chamber in a fuel-rich state with a large equivalence ratio, so that the generation of NO _X is suppressed. Then, the pressure in the sub-chamber increases at once due to the combustion, and the combustion is promoted, and at the same time, the flame ejects from the sub-chamber to the main chamber at once through the communication hole and the central communication hole, and the flame is It mixes with fresh air in the main chamber, promotes premixed combustion and shortens the combustion speed to complete ideal secondary combustion. Accordingly, the alcohol reforming engine, NO _X, can significantly reduce the generation of HC and the like, can provide a high efficiency of the engine.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of an alcohol reforming engine provided with a sub chamber according to the present invention.

FIG. 2 is an explanatory diagram showing timings of a control valve and a fuel injection nozzle of the alcohol reforming engine of FIG.

FIG. 3 is an explanatory diagram showing a relationship between a control valve incorporated in the alcohol reforming engine of FIG. 1 and a sub chamber wall body.

FIG. 4 is an explanatory diagram showing an embodiment of a control valve incorporated in the alcohol reforming engine of FIG.

5 is a process flow chart for explaining an embodiment of the operation of the alcohol reforming engine of FIG. 1. FIG.

[Explanation of symbols]

 1 Main Chamber 2 Sub Chamber 3 Piston 4 Cylinder Head 5 Communication Hole 6 Controller 7 Control Valve 8 Fuel Injection Nozzle 9 Sub Chamber Wall Body 10 Headliner 13, 30 Solenoid Valve Drive Device 22 Cavity 25 Load Sensor 27 Cylinder 28 Exhaust Valve 31 Central Communication hole 34 Temperature sensor 35 Exhaust port

Claims (4)

[Claims] 1. A sub-chamber provided in a cavity formed in a cylinder head, a fuel injection nozzle for injecting alcohol fuel into the sub-chamber, an exhaust valve arranged in an exhaust port formed in the cylinder head, and a cylinder side. The main room,
A communication hole that connects the sub chamber and the main chamber, a control valve that opens the communication hole near the compression top dead center and closes before opening the exhaust valve, a load sensor that detects an engine load, and the load. An alcohol reforming engine having a sub-chamber, comprising a controller for accelerating the closing timing of the control valve in response to a partial load signal from a sensor. 2. A temperature sensor for detecting an engine temperature, wherein the controller closes the control valve after an expansion stroke bottom dead center in response to a temperature of the temperature sensor equal to or higher than a predetermined temperature, and then the fuel injection. The fuel injection timing from the nozzle is injected during the exhaust stroke, and the control valve is closed before the bottom dead center of the expansion stroke in response to the temperature below the predetermined temperature of the temperature sensor, and then the fuel from the fuel injection nozzle is closed. The alcohol reforming engine having a sub chamber according to claim 1, wherein the injection timing is controlled to be injected before the top dead center of the compression stroke. 3. The controller, in response to a temperature of the temperature sensor equal to or lower than a predetermined temperature, controls the degree of opening of the exhaust valve so that the EGR gas remains in the cylinder. An alcohol reforming engine including the sub chamber according to 2. 4. The controller is responsive to a temperature lower than a predetermined temperature of the temperature sensor to open the exhaust valve for a short period during an intake stroke so that EGR gas flows into the cylinder through the exhaust port. The alcohol reforming engine having the sub chamber according to claim 2, which is performed.