JP2001280183A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize high heat efficiency by reducing the discharge concentration of nitrogen oxides in a wide engine speed and load range. SOLUTION: A compression ignition-type or spark ignition-type internal combustion engine supplies uniform stoichimetic mixture formed of air and fuel to a cylinder without heating it and makes the stoichiometic mixture having a compression rate at which selfignition is possible and knocking is generated. The fuel amount smaller than the stoichiometic mixture in the cylinder is supplied, either the air amount in the cylinder or the remaining gas amount is changed, and self-ignition of mixture is generated in the cylinder in a wide range of the air-fuel ratio according to the engine speed and the amount of fuel to be supplied, and therefore, the air supply amount and the remaining gas amount are adjusted to self-ignite and burn lean mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention utilizes the self-ignition of a combustible air-fuel mixture by compression, controls the amount of air and the amount of residual gas, and self-ignites the air-fuel mixture. The present invention relates to an internal combustion engine that realizes high thermal efficiency by reducing the emission concentration of nitrogen oxides.

[0002]

2. Description of the Related Art In an internal combustion engine, if an air-fuel mixture in which fuel and air are mixed in advance is burned at an appropriate time regardless of the air-fuel ratio, and the output can be adjusted, the thermal efficiency of the engine is improved. It is well known that this is achieved primarily by a reduction in pump losses and a high specific heat ratio of the lean mixture. It is also known that if the generation of heat by combustion is completed in a short period of time, that is, if the combustion period is shortened, isocapacity is improved and thermal efficiency is improved. On the other hand, it is known that the combustion of a sufficiently diluted mixture in an internal combustion engine significantly reduces the emission of nitrogen oxides. And
It is known that a compression ignition internal combustion engine employing a compression ignition combustion scheme of a lean mixture that focuses on these characteristics can achieve high thermal efficiency and suppress the emission concentration of nitrogen oxides to several ppm or less.

However, in the above-mentioned compression self-ignition type internal combustion engine,
The occurrence of the self-ignition depends on the reactivity of the air-fuel mixture and the history of pressure and temperature rise associated with piston compression, making it difficult to maintain an appropriate ignition timing over a wide range of engine speeds and required loads. . In addition, at high load, the emission of nitrogen oxides increases due to the increased fuel supply,
Since a large amount of heat is generated in a short time, pressure vibration similar to knocking and lower frequency combustion noise are generated.
Further, the emission concentrations of hydrocarbon compounds and carbon monoxide containing unburned fuel are not low, and they tend to increase at low load.

In the compression ignition type internal combustion engine, a variable compression ratio system, self ignition control based on fuel properties, and the like have been proposed for the purpose of maintaining an appropriate ignition timing in a wide range of engine speed and required load. In either case, the ignition timing can be adjusted in theory. However, it is difficult to realize a mechanism that changes the amount of movement of the piston or a mechanism that moves the cylinder head as the variable compression ratio system. Further, a system in which a sub-chamber or a sub-piston is provided in the combustion chamber to continuously change the volume of the combustion chamber has not been put into practical use due to its complicated structure. That is, it is not easy to realize a means for freely changing only the compression ratio.

Means for changing the effective compression ratio by changing the closing timing of the intake valve has been put to practical use.
Unless the lift curve is changed, the opening timing of the intake valve also changes at the same time, so it is necessary to consider the overlap period when both the intake and exhaust valves are open and the interference between the valve and the piston. It is difficult to change. Furthermore, at high loads, it is necessary to reduce the compression ratio to suppress early ignition, but at the same time, the amount of operating gas also decreases, so increasing the output requires an increase in the amount of air by the turbocharger. However, there is a problem that the mechanism and the control become complicated.

Further, the means for changing the self-ignition characteristics by changing the properties of the fuel is not a technology that can be practically used at present because the problem of the social infrastructure for providing the fuel must be solved.

Furthermore, in order to reduce nitrogen oxides at high load, a method of supplying a large amount of air by a supercharger is conceivable, but this may increase combustion noise similar to knocking. In that case, the operation cannot be continued. Also, the efficiency of the entire engine system may decrease due to the increased power required to supercharge a large amount of air.

A method of reducing nitrogen oxides under high load and suppressing combustion noise similar to knocking by circulating a large amount of exhaust gas or remaining in a cylinder has been considered. To self-ignite under high conditions, it is necessary to raise the temperature of the air-fuel mixture, that is, the temperature at the time of combustion cannot be reduced so much, and that the nitrogen oxides and combustion noise cannot be sufficiently reduced. Research (Nakano et al., "Combustion Characteristics and Auto-Ignition Control of Premixed Compression Ignition Engines", Automotive Engineering Society No.9910 Symposium, (1999), p20-25.)

Further, a method of purifying nitrogen oxides with a three-way catalyst or a selective reduction catalyst by bringing the air-fuel ratio of exhaust gas close to the stoichiometric air-fuel ratio at a high load can be considered. If it is not possible to change the stoichiometric air-fuel ratio in a short period of time, it is necessary to use a condition in which the air-fuel ratio is around 18 and the emission concentration of nitrogen oxides is high. It is.

It is conceivable to use an occlusion reduction type catalyst as the catalyst, but this means requires a method of forming rich exhaust gas under a wide range of required load conditions. In order to realize the combustion with a rich air-fuel mixture, a method of supplying a large amount of exhaust gas or burned gas into the cylinder or a method of reducing the amount of air by a throttle can be considered. However, there is no report that any of the methods has shifted to rich combustion in a short period of time without causing misfire in the compression ignition type internal combustion engine, and it is not easy to realize the method.

[0011] For the above reasons, an internal combustion engine that achieves both a reduced emission of nitrogen oxides and high thermal efficiency by applying compressed auto-ignition combustion of a premixed gas to a wide range of operating conditions has not yet been put to practical use.

On the other hand, a technique for mixing the burned gas generated in the previous cycle with newly supplied air to generate self-ignition combustion is disclosed in, for example, JP-A-11-236833. According to the invention, a four-stroke cycle type engine is provided with means for changing the opening / closing timing of intake and exhaust valves, whereby the temperature of the air-fuel mixture and the effect of dilution are adjusted to achieve desired combustion.

However, in a four-stroke cycle internal combustion engine, when the opening / closing timing of the overhead valve is largely changed, it is necessary to avoid contact between the valve and the upper surface of the piston when the piston is near top dead center. However, in order to avoid this in an internal combustion engine having a high compression ratio, a mechanism for changing the valve lift in a complicated manner is required. It has also been considered to prevent the burned gas from being released to the outside of the cylinder by closing the exhaust valve early before the top dead center, but using a three-dimensional cam, the hydraulic control valve, or the like has been considered. Unless the opening timing of the exhaust valve is prevented from being greatly advanced, a reduction in thermal efficiency due to a shortening of the expansion stroke will be caused, and a complicated mechanism will still be required for realization.

Further, in the four-stroke cycle type internal combustion engine, when the burned gas generated in the previous cycle is left in the cylinder by adjusting the opening / closing timing of the valve,
Most of the burned gas requires a process of once being discharged into the intake passage or the exhaust passage and then re-inhaled. In this process, the temperature of the burned gas decreases. Therefore, the effect of promoting the ignition of the burned gas is also reduced, that is, it becomes difficult to adjust the self-ignition combustion in a wide operating range.

According to the present invention, the air-fuel ratio of the air-fuel mixture in the cylinder is made closer to the stoichiometric ratio with an increase in the required load. In this case, a relatively high load generates a large amount of nitrogen oxides. It is necessary to use an air-fuel ratio of around 18, which causes a problem of emission of a large amount of nitrogen oxides. Further, in the present invention, an internal combustion engine in which the stoichiometric air-fuel ratio of the air-fuel mixture in the cylinder is used irrespective of the required load is shown. In this case, however, the specific heat ratio is reduced by a large amount of the burned gas. The inevitable decrease in thermal efficiency is explained by basic knowledge of thermodynamics. As described above, it is not easy to realize an internal combustion engine that realizes compression ignition combustion under a wide range of operating conditions based on the method disclosed in the present invention.

On the other hand, with respect to a two-stroke cycle type diesel engine, there is an invention disclosed in, for example, JP-A-11-153043. The invention provides a means for dispersing and supplying fuel to a cylinder at an early stage of a compression stroke, and for supplying air to a cylinder without using a mechanical supercharger at least up to half of the maximum fuel amount to be supplied. The present invention combines a conventional diesel engine with high-dispersion spraying and a method for reducing smoke and nitrogen oxides under high-load conditions from a method that does not require active control of the ratio. The present invention is directed to a subject that is substantially different from the present invention.

Further, in a two-stroke cycle type internal combustion engine, a method for inducing self-ignition combustion by positively using burned gas of the previous cycle, that is, residual gas remaining in the cylinder even after completion of the scavenging stroke, ATAC
(S. Ohnishi et al., "Active Thermo-Atomosphere Co
mbustion (ATAC)-A New Combsution Process for Int
ernal Combustion Engines ", SAE Paper 790501, (197
9).) And AR combustion (Y. Ishibashi et al., "A Low Pressur
e Pneumatic Direct Injection Two-Stroke Engineby A
ctivated Radical Combustion Concept ", SAE paper 98
0757, (1998).) Already exists.

However, these prior arts improve the irregular combustion at low load in a two-stroke cycle type internal combustion engine used near the stoichiometric ratio, and emit harmful substances and increase fuel consumption due to incomplete combustion. It is intended to solve a problem that is clearly different from the problem to be solved by the present invention.

Further, in the prior art relating to the two-stroke cycle type internal combustion engine using self-ignition combustion, the compression ratio is generally set to 8 or less in order to avoid abnormal combustion such as knocking during operation by spark ignition combustion under high load. However, since the air-fuel ratio is close to the stoichiometric ratio, high thermal efficiency cannot be expected.

[0020]

As described above, in order to increase the thermal efficiency of an internal combustion engine, it is important to burn a lean mixture at a high compression ratio in a short time. FIG. 1 shows the relationship between the air-fuel ratio and the thermal efficiency by numerical simulation. Referring to FIG. 1, it can be understood that a lean air-fuel ratio improves the thermal efficiency. However, it can be understood that even if extreme leaning is realized, most of the calorific value from the fuel is consumed by heat loss, so that there is no effect on improving the thermal efficiency.

FIG. 2 shows the relationship between the compression ratio, the combustion period, and the thermal efficiency by numerical simulation. Referring to FIG. 2, it can be understood that a high compression ratio and a short combustion period improve thermal efficiency. In an actual internal combustion engine, an extremely high compression ratio increases frictional loss, so it is generally said that increasing the compression ratio above about 14 does not substantially improve engine efficiency. The combustion period is shorter than that of the conventional spark ignition type internal combustion engine because an extremely short combustion period may cause damage to the engine due to an increase in the rate of increase of the pressure in the cylinder or the maximum value. Corner 1
Around 0 degrees is appropriate. Unless this combustion is started at an appropriate time near the top dead center, high thermal efficiency cannot be realized. Further, the emission amount of nitrogen oxides can be reduced by burning a lean mixture. A conventional combustion method for compressively igniting a lean premixed gas has been researched and developed for the purpose of realizing these combustion characteristics.

However, a self-ignition system based on a feasible configuration that achieves both high thermal efficiency and low nitrogen oxide emission concentration under a wide range of operating conditions using a combustion method of compressively igniting a premixed gas or a combustion method similar thereto. No internal combustion engine has been proposed.

[0023]

The problem to be solved by the present invention is to generate compressed auto-ignition combustion of an air-fuel mixture at a desired time within a wide range of engine speed and required load by means that can be easily realized. It is an object of the present invention to provide a compression self-ignition internal combustion engine.

It is another object of the present invention to provide a compression ignition type internal combustion engine which generates compression ignition combustion at an appropriate time and reduces the emission concentration of nitrogen oxides and realizes high thermal efficiency.

The present inventors have observed that auto-ignition combustion is strongly affected by the reactivity and temperature of the mixture. The reactivity of the air-fuel mixture changes depending on the fuel property, the air-fuel ratio, and the concentration of a diluent gas such as burned gas. The temperature of the air-fuel mixture affects the self-ignition of the air-fuel mixture as a temperature history due to a temperature before the start of compression or a temperature change during the compression stroke. For the compression ignition type internal combustion engine, the fuel to be used is limited, and when the supply fuel amount and the engine speed required for the required output are determined, the controllable elements are the air-fuel ratio, the concentration of the dilution gas, and the air-fuel mixture. Temperature history. It is not impossible to control these three elements individually (for example, adjusting the amount of new air by intake throttle, introducing burned gas by exhaust gas recirculation (EGR), and controlling the temperature by heating or cooling the intake air). , It is a complex approach that is as difficult to implement as that shown in previous inventions and research presentations. Therefore, there is a need for a method of controlling the air-fuel ratio, the concentration of the diluent gas, and the temperature history of the air-fuel mixture by a simple method to realize ignition of the compression self-ignition internal combustion engine in a wide range.

The present inventors have focused on the fact that the above three factors can be simultaneously controlled by changing the amount of new supply air in the cylinder during the compression stroke and the amount of remaining burned gas in the previous cycle. Further, in the two-stroke cycle internal combustion engine, it is easy to use the residual gas,
We noticed that the temperature was sufficiently higher than the residual gas and external EGR of a 4-stroke cycle internal combustion engine. In addition, since the number of explosions in a two-stroke cycle internal combustion engine is twice as large as that in a four-stroke cycle internal combustion engine, the amount of fuel consumed in one combustion is half that of a four-stroke cycle internal combustion engine. We focused on the output being the same even if it did.

Based on these facts, the present inventors have a compression ratio at which abnormal combustion occurs and a normal operation cannot be continued in the conventional concept, and a residual amount of residual combustion gas (residual gas amount) in the previous cycle. And the amount of newly supplied air (supply amount)
Invented a two-stroke cycle internal combustion engine that properly adjusts the engine pressure. This makes it possible to obtain sufficient conditions in the cylinder for auto-ignition combustion in a wide range of operating conditions.

[0028]

According to the first aspect of the present invention,
If a uniform theoretical air-fuel mixture formed by air and fuel is supplied to a cylinder without heating, the theoretical air-fuel mixture is capable of self-ignition or a compression-ignition or spark-ignition internal combustion engine having a compression ratio equivalent to knocking. An engine that supplies a smaller amount of fuel than the formation of a stoichiometric mixture to be supplied to the cylinder, and changes at least one of an amount of air supplied to the cylinder and a residual gas amount to change an engine speed and a supplied fuel. A two-stroke cycle type internal combustion engine characterized in that a self-ignition of an air-fuel mixture is generated within a cylinder in a wide air-fuel ratio range corresponding to an amount of fuel.

Here, the internal combustion engine of the present invention is characterized in that it has a relatively high compression ratio as compared with the ignitability of fuel. That is, a high compression ratio here means that a uniform theoretical air-fuel mixture is supplied to a cylinder without special external heating, and at the start of compression, the inside of the cylinder is brought to atmospheric pressure only by the theoretical air-fuel mixture. If the compression ratio is high enough to cause auto-ignition only by compression of the piston, or if not all of the stoichiometric air-fuel mixture is forcibly ignited to generate flame propagation, It means that the compression ratio is so high that king occurs. Here, the uniform theoretical air-fuel mixture means a degree of uniformity formed when new supply air and fuel are mixed by a fuel supply device on an air supply passage such as a port injection spark ignition gasoline engine. It does not mean only theoretical perfect uniformity.

Further, the internal combustion engine of the present invention is characterized in that the amount of fuel supplied per cylinder in one cycle during operation thereof is relatively small as compared with the cylinder volume. That is, the relatively small amount of fuel here means that the amount of fuel is smaller than the amount of fuel mixed into a uniform theoretical mixture filled with the cylinder at atmospheric pressure.

According to a second aspect of the present invention, if a uniform theoretical air-fuel mixture formed by air and fuel is supplied to a cylinder without being heated at a scavenging rate of 60% or more, the theoretical air-fuel mixture can self-ignite. The internal combustion engine according to claim 1, wherein the internal combustion engine has a compression ratio corresponding to occurrence of knocking.

The invention according to claim 3 is the internal combustion engine according to claim 1, wherein the mixture in the cylinder is made lean to reduce nitrogen oxides and increase thermal efficiency.

According to a fourth aspect of the present invention, by controlling the self-ignition to occur in the vicinity of or later than the top dead center, it is possible to suppress the nitrogen oxides discharged from the engine and increase the thermal efficiency. The internal combustion engine according to claim 1, wherein

The invention according to claim 5 is characterized in that when the amount of fuel in the cylinder is small, the oxygen concentration in the cylinder is reduced, and when the amount of fuel is large, control is performed to increase the oxygen concentration. The internal combustion engine according to claim 1.

According to a sixth aspect of the present invention, in order to advance the ignition timing, the air supply amount is decreased or the residual gas amount in the cylinder is increased, and to delay the ignition timing, the air supply amount is increased or the residual air amount in the cylinder is increased. The internal combustion engine according to claim 1, wherein control is performed to reduce the gas amount.

According to a seventh aspect of the present invention, there is provided at least one of an air supply amount control means for changing an air amount in a cylinder and a residual gas amount control means for changing a residual gas amount in the cylinder. The ignition timing is controlled by controlling at least one of the amount of air supplied to the cylinder and the amount of residual gas in the cylinder by at least one of the amount control means and the residual gas amount control means. Item 2. The internal combustion engine according to item 1.

[0037]

The internal combustion engine according to the present invention has a compression ratio in which normal combustion cannot be continued due to abnormal combustion in the conventional concept, and appropriately adjusts the residual gas amount and the supply amount. This is a stroke cycle type internal combustion engine that can realize self-ignition combustion at a wide range of engine speeds and appropriately adjust the ignition timing.

The self-ignition combustion realized in the two-stroke cycle type internal combustion engine forms a combustible mixture diluted with the residual gas and air, and increases a high temperature residual gas under a low required load condition. By increasing the air under conditions where the required load is high, combustion can be completed in a short period of time under a wide range of operating conditions.

The two-stroke cycle type internal combustion engine has a combustion cycle of a four-stroke cycle type internal combustion engine.
Therefore, at the same required load, the amount of fuel used in one combustion is about one-half in the two-stroke cycle type internal combustion engine as compared with the four-stroke cycle type internal combustion engine.
Accordingly, it is possible to realize the operation in the same load range as that of the four-stroke cycle type internal combustion engine having the same displacement by the self-ignition combustion of the lean air-fuel mixture.

With the above effects, in the two-stroke cycle type internal combustion engine of the present invention, it is possible to burn a lean mixture at an appropriate time in a short period under a wide range of operating conditions. It is possible to achieve both a reduction in oxide emission concentration and high thermal efficiency.

[0041]

3 and 4 show an embodiment in which the present invention is realized as an overhead valve type two-stroke cycle type internal combustion engine equipped with a supercharger and a fuel injection valve for directly supplying fuel into a cylinder. Is shown. Referring to FIGS. 3 and 4, 1 is an engine body, 2 is a cylinder block, 3 is a cylinder head, 4 is a piston, 5 is a combustion chamber, and 6 is an electronically controlled fuel injection valve for directly injecting fuel into a cylinder. Attachment position, 8 is a scavenging valve, 9 is a scavenging port, 10 is an exhaust valve, 11
Indicates exhaust ports, respectively. The scavenging port 9 is connected to a surge tank 13 via a corresponding air supply branch 12, and the surge tank 13 is connected to an air cleaner 17 via an air supply duct 14, an air supercharger 15 and an air supply duct 16. .
The supercharger 15 is driven by an electric motor 18. On the other hand, the exhaust port 11 is connected to an exhaust duct 20 via an exhaust manifold 19.

The electronic control unit 50 comprises a digital computer, a ROM (read only memory) 52, a RAM (random access memory) 53, and a CPU (microprocessor) 5 connected to each other by a bidirectional bus 51.
4, an input port 55 and an output port 56 are provided. The output voltage of the required load sensor 61 that generates an output voltage proportional to the amount of depression of the accelerator pedal is output from the corresponding A / D converter 5.
7 to the input port 55.

Further, the input port 55 is connected to a crank angle sensor 62 which generates an output pulse every time the crankshaft rotates, for example, by 10 °. The output form of the crank angle sensor may be any as long as it can calculate or express the number of revolutions of the engine and the TDC and ignition timing of each cylinder. On the other hand, the output port 56 is connected via a corresponding drive circuit 58 to an electric motor 18 for driving the air charge supercharger 15 and an electronically controlled fuel injection valve installed at the mounting position 6 of the electronically controlled fuel injection valve. You.

FIG. 5 shows an example of the basic effect of the embodiment of the present invention, in which the load is about 40% and the load is about 85%.
% When operating the two-stroke cycle type internal combustion engine according to the embodiment of the present invention realized by the configuration shown in FIGS. 3 and 4 with the supplied fuel amount corresponding to Changes in the emission concentration of oxide (NOx), net torque, and ignition timing are shown with the air-fuel ratio (A / F) on the horizontal axis. As shown in FIG. 5, under the condition of a load of about 40%, the air-fuel mixture is changed to a lean condition by increasing the air-fuel ratio from about an air-fuel ratio of about 15. By making the air-fuel mixture lean, that is, increasing the amount of air in the cylinder and reducing the amount of residual gas, the ignition timing before the top dead center near the air-fuel ratio of about 15 is delayed toward the top dead center. At the same time, the emission of nitrogen oxides is greatly reduced and the thermal efficiency is increased.

Further, the range of the air-fuel ratio at which the emission of nitrogen oxides is greatly reduced and high thermal efficiency is realized is about 2
It turns out that it is wide from 0 to 32. On the other hand, even under the condition of about 85% load, the same effects and tendencies as those of the above-described about 40% load condition are obtained, and the range of the air-fuel ratio in which the nitrogen oxide emission is greatly reduced and high thermal efficiency is realized at the same time is as follows. About 35-4
It turns out that it is 9 and wide. The mechanism for greatly reducing the emission of nitrogen oxides and achieving high thermal efficiency in such a wide range of air-fuel ratio can be explained as follows.

When the amount of air in the cylinder increases and the amount of residual gas decreases at the same time, the average temperature of the air-fuel mixture in the cylinder decreases due to the decrease in the amount of high-temperature residual gas, so that the temperature at which self-ignition is unlikely to occur. However, on the other hand, the condition that the oxidation reaction of the fuel molecules easily proceeds can be obtained by increasing the oxygen amount in the cylinder by increasing the amount of air.

Further, when the amount of air in the cylinder increases, the specific heat ratio of the air-fuel mixture increases, and the degree of temperature rise due to compression increases. Therefore, the decrease in temperature due to the decrease in the amount of residual gas is canceled out. The effect of direction can be expected.

By the above two effects, self-ignition combustion is generated at an appropriate time in a wide range of air-fuel ratio. The condition that the above-mentioned emission of nitrogen oxides is greatly reduced and high thermal efficiency is realized at the same time when the ignition timing is near or later than the top dead center is achieved, and the heat generation rate becomes 10%. If this time is defined as the ignition timing, this range can be expressed as 5 ° before top dead center. Here, the heat generation ratio is calculated with respect to a total heat release amount generated by heat generation corresponding to a heat flame, and does not consider heat generation of a cold flame which is often observed in paraffinic hydrocarbons.

FIG. 6 shows a change in the heat release rate with respect to the crank angle as a representative result under the conditions shown in FIG. During a period in which clear heat generation is observed, that is, a combustion period, for example, combustion is performed even in an extremely lean air-fuel mixture such as an air-fuel ratio of 32 at an air-fuel ratio of 32 at a load of approximately 40% and an air-fuel ratio of 49 at a load of approximately 85%. The period is completed in a short period of about 10 °, and it can be seen that the self-ignition combustion realized by the embodiment of the present invention realizes efficient combustion with high isovolume.

FIG. 7 shows a two-stroke cycle type internal combustion engine according to the embodiment of the present invention realized by the configurations shown in FIGS. 3 and 4 by adjusting the air supply ratio from low load to high load. FIG. 6 shows a change in heat release rate with respect to a crank angle under a condition in which appropriate combustion is realized in the vicinity of a dead center. It shows that it is possible to realize an efficient self-ignition combustion.

FIG. 8 shows an example of an air-fuel ratio, an air-fuel ratio, and an exhausted NOx concentration with respect to a load in the two-stroke cycle type internal combustion engine according to the embodiment of the present invention realized by the configuration shown in FIGS. Is shown. Under the conditions shown in FIG.
As the load increases, the air-fuel ratio increases, and as a result, the air-fuel ratio of the air-fuel mixture changes to lean. As a result of appropriate combustion obtained by this operation, the emission concentration of NOx is always maintained at 10 ppm or less regardless of the required load.

In the example of the embodiment shown in FIGS. 7 and 8, only the amount of fuel supplied and the air supply ratio are changed in response to a change in load. That is, the basic control factors for adjusting the output in the two-stroke cycle type internal combustion engine realized in the embodiment of the present invention shown in FIGS. 3 and 4 are the supplied fuel amount and the air supply ratio. FIG. 9 shows an example of the relationship between the supplied fuel amount and the air supply ratio. In order to smoothly operate the engine based on the relationship between the supplied fuel amount and the air supply ratio shown in this embodiment and FIG. 9, the digital computer 50 shown in FIG. It is necessary to control the amount of fuel injected from the fuel injection valve and the amount of air supplied by the supercharger.

Therefore, in this embodiment, the engine speed N
The relationship between the rotational speed A of the electric motor driving the supercharger and the fuel injection amount B with respect to the required load L and the fuel injection amount B is determined in advance by an experiment, and the relationship is shown in the form of a map shown in FIGS. Is stored in the ROM 52. Thus, an appropriate amount of fuel and an appropriate amount of air are supplied into the cylinder according to the engine speed and the required load.

[0054]

[Other Embodiments] FIG. 11 shows another embodiment. In this embodiment, the same components as those in the embodiment shown in FIG. 4 are denoted by the same reference numerals.

As shown in FIG. 11, in this embodiment, a fuel injection valve is provided in the scavenging port. The fuel injector is driven by a corresponding drive circuit 58 connected to the output port 56 of the electronic control unit 50 shown in FIG.

[0056]

[Other Embodiments] FIG. 12 shows another embodiment. In this embodiment, the same components as those in the embodiment shown in FIG. 3 are denoted by the same reference numerals.

In the embodiment shown in FIG. 12, the compressor 2
4 and a turbocharger having an exhaust turbine 25.
The air supply duct 14 is connected to the air cleaner 17 via the compressor 24 and the air supply duct 16. The exhaust duct 20 is connected to an exhaust duct 26 via an exhaust turbine 25.
An air flow meter 21 for detecting an intake air amount is disposed in the air supply duct 21, and an output voltage of the air flow meter 21 is input to an input port 55 via a corresponding A / D converter 57. A throttle valve 22 for adjusting the amount of air supply is provided in the air supply duct 14, and the throttle valve 22 is driven by an electric motor 23. The electric motor 23
Are connected to the output port 56 via the corresponding drive circuit 58.

Also in the embodiment shown in FIG. 12, it is necessary to change the amount of fuel supplied and the air supply ratio in response to a change in load. However, in the embodiment shown in FIG. 12, since the scavenging is performed by the turbocharger having the compressor 24 and the exhaust turbine 25, the rotation speed of the supercharger cannot be directly adjusted. Therefore, the digital computer 50 shown in FIG. 12 needs to control the injection amount from the fuel injection valve and the opening of the throttle valve with respect to the engine speed and the required load.

In the present embodiment, the relationship between the fuel injection amount B and the required intake air amount C with respect to the machine speed N and the required load L is obtained in advance through experiments. Further, the throttle valve opening D with respect to the required intake air amount C and the actual intake air amount C ′ detected from the air flow meter 21 is obtained in advance. These are shown in FIG.
(A), (B), and (C) are stored in the ROM 52 in the form of maps. Thus, an appropriate amount of fuel and an appropriate amount of air are supplied into the cylinder according to the engine speed and the required load.

In the case of a turbocharger, a condition may occur in which a required intake air amount cannot be obtained for a required load. In this case, the realizable output and the rotational speed can be calculated by applying the actual intake air amount and the rotational speed detected from the air flow meter 21 to the map of FIG. 13B. Is applied to the map of FIG. 13 (A), the amount of suppliable fuel can be calculated backward. At this time, the throttle valve opening is maintained at a fully opened state or a state close thereto.

The present invention can be variously modified and modified without departing from the spirit thereof. For example,
It is possible to realize by a crankcase scavenging method, and to apply and implement different scavenging means such as chenille scavenging and uniflow scavenging. Further, by providing an exhaust flow control device capable of reducing the flow rate of exhaust gas in the vicinity of the exhaust hole or on the exhaust passage, it is possible to realize a configuration in which the residual gas amount is positively controlled.

[Brief description of the drawings]

FIG. 1 is a diagram showing an air-fuel ratio and an indicated thermal efficiency reproduced by a numerical simulation.

FIG. 2 is a diagram showing a combustion period and a compression ratio and an indicated thermal efficiency reproduced by a numerical simulation.

FIG. 3 is an overall view of a two-stroke cycle type internal combustion engine showing a typical embodiment of the present invention.

FIG. 4 is a side sectional view of an engine body and an inner view of a cylinder head as viewed from a combustion chamber side.

FIG. 5 is a graph showing the relationship between the emission concentration of nitrogen oxides, thermal efficiency, ignition timing, and air-fuel ratio.

FIG. 6 is a diagram showing that combustion that can be completed in a short period of time at an optimum ignition timing by adjusting the supply air amount is obtained.

FIG. 7 is a diagram showing that combustion that can be completed in a short period of time at an optimal ignition timing under a wide load condition is obtained.

FIG. 8 is a diagram showing that the nitrogen oxide emission concentration can be reduced under a wide range of load conditions by adjusting the air supply ratio.

FIG. 9 is a diagram showing a relationship between an amount of supplied fuel and an amount of air for realizing appropriate self-ignition combustion.

FIG. 10 shows a map of the rotation speed of the electric motor driving the supercharger and the fuel injection amount with respect to the required load and the engine rotation speed.

FIG. 11 is a side sectional view of an engine main body and an inner view of a cylinder head viewed from a combustion chamber side, showing another embodiment of the present invention.

FIG. 12 is an overall view of a two-stroke cycle type internal combustion engine showing another embodiment of the present invention.

FIG. 13 shows a map of a fuel injection amount and a throttle valve opening degree with respect to a required load and an engine speed.

[Explanation of symbols]

4 ... Piston 5 ... Combustion chamber 6 ... Mounting position of an electronically controlled fuel injection valve that injects fuel directly into the cylinder 15 ... Charge supercharger

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 23/00 F02D 23/00 E 41/02 351 41/02 351 43/00 301 43/00 301R 301N F02M 25/07 510 F02M 25/07 510B 550 550R F-term (reference) 3G023 AA02 AA05 AB01 AB05 AC02 AC04 AD03 AF02 AF03 AG02 AG03 3G062 AA02 AA10 BA02 BA04 GA06 GA15 GA17 GA18 3G084 AA00 AA02 A09 BA08 BA09 DA08 BA09 DA08 AA03 AA06 AA09 AB02 BA02 BA06 DB02 DB03 DC09 DE03S FA17 FA24 3G301 HA03 HA04 HA09 HA11 HA15 JA02 JA25 LA00 LB02 LB04 MA01 NC02

Claims (7)

[Claims] 1. If a uniform stoichiometric mixture formed by air and fuel is supplied to a cylinder without heating,
A compression ignition type or spark ignition type internal combustion engine having a compression ratio capable of self-ignition of the stoichiometric air-fuel mixture or knocking, supplying a fuel amount smaller than the formation of the stoichiometric air-fuel mixture supplied into the cylinder. A configuration in which at least one of the amount of air supplied to the cylinder and the amount of residual gas is changed to generate self-ignition of the air-fuel mixture in the cylinder in a wide air-fuel ratio range in accordance with the engine speed and the amount of fuel supplied. An internal combustion engine of a two-stroke cycle type, characterized in that: 2. If a uniform stoichiometric air-fuel mixture formed by air and fuel is supplied to a cylinder without being heated at a scavenging rate of 60% or more, the stoichiometric air-fuel mixture is capable of self-ignition or compression equivalent to knocking. The internal combustion engine of claim 1, having a ratio. 3. The internal combustion engine according to claim 1, wherein a lean air-fuel mixture in the cylinder reduces nitrogen oxides and increases thermal efficiency. 4. The control system according to claim 1, wherein the self-ignition is controlled to occur at or near a top dead center, thereby suppressing nitrogen oxides discharged from the engine and increasing thermal efficiency. An internal combustion engine according to claim 1. 5. The method according to claim 1, wherein the control is performed such that the oxygen concentration in the cylinder is reduced when the fuel amount in the cylinder is small, and the oxygen concentration is increased when the fuel amount is large. Internal combustion engine. 6. To advance the ignition timing, reduce the supply amount or increase the residual gas amount in the cylinder. To delay the ignition timing, increase the supply amount or decrease the residual gas amount in the cylinder. 2. The internal combustion engine according to claim 1, wherein the internal combustion engine is controlled. 7. At least one of an air supply amount control means for changing an air amount in a cylinder and a residual gas amount control means for changing a residual gas amount in the cylinder is provided. 2. The internal combustion engine according to claim 1, wherein at least one of the gas amount control means controls at least one of the amount of air supplied to the cylinder and the amount of residual gas in the cylinder to control the timing of the occurrence of self-ignition. organ.