JP2003120301A - Cylinder direct injection internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cylinder direct injection internal combustion engine of good fuel consumption using a low cost conventional three-way catalytic converter without NOx trap function. SOLUTION: A cylinder is filled with burned gas to get deficient in oxygen by internal EGR effect while keeping an exhaust valve 7 open until a last stage of a suction stroke. Air and fuel of quantities corresponding to an operating condition are injected and supplied into the cylinder via a two fluid injector 3 in a compression stroke, and combustible gas mixture layer Ga of theoretical air fuel ratio is formed in burned gas Gb in the cylinder and is ignited and burns. Since oxygen is not contained in exhaust gas after combustion, exhaust gas is effectively purified by the conventional three-way catalytic converter. Since a rich spike control is not necessary and pumping loss is reduced, fuel consumption is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder direct injection internal combustion engine.

[0002]

2. Description of the Related Art One example of a direct injection type internal combustion engine in a cylinder is disclosed in Japanese Patent Laid-Open No. 10-288039. In the latter half of the compression stroke, fuel is directly injected into the cylinder to perform stratified combustion in which flammable air-fuel mixture is unevenly distributed near the spark plug, and partial load operation and lean combustion operation are realized without controlling the air amount by the throttle valve. Is what you are trying to do. However, according to such a combustion method, since a large amount of oxygen that has not been used for combustion is present in the exhaust gas, it is possible to apply a three-way catalyst that assumes combustion gas near the stoichiometric air-fuel ratio. The problem arises that you can't.

To solve the above problem, a three-way catalyst having a NOx trap function is used to NOx during lean combustion operation.
It has been proposed that the catalyst be adsorbed on a catalyst and the purification process is performed by a temporary spike control of air-fuel ratio called rich spike. However, the exhaust purification device using the NOx trap catalyst is expensive, and the rich spike control that increases the fuel amount even temporarily causes deterioration of fuel efficiency.

The present invention has been made in view of these problems, and it is possible to continuously operate at a lean air-fuel ratio without using a NOx trap catalyst, and further to eliminate pumping loss. It is an object of the present invention to provide a direct injection type internal combustion engine having a direct injection type.

[0005]

A first aspect of the present invention comprises an injection valve for directly injecting fuel and air into a cylinder, and an anoxic state forming means for making the inside of the cylinder anoxic during an intake stroke. A combustible air-fuel mixture is formed by the fuel and air injected and supplied by the injection valve in the compression stroke in the cylinder, and stratified combustion is performed.

According to a second aspect of the invention, the injection valve is a two-fluid injection valve that simultaneously supplies pressurized fuel and air from a common nozzle section.

According to a third aspect of the present invention, the oxygen-free state forming means of the first aspect is constituted by an exhaust gas recirculation device for recirculating exhaust gas from an exhaust passage to an intake passage, and the recirculated exhaust gas is introduced into a cylinder during an intake stroke. Introduced to form anoxic state.

According to a fourth aspect of the present invention, the anoxic state forming means of the first aspect is constituted by a variable valve operating device capable of controlling the operation of the intake valve and the exhaust valve, and the intake valve is opened during the intake stroke. The exhaust gas from the exhaust passage is introduced into the cylinder by suppressing the above and continuing to open the exhaust valve to form an anoxic state.

According to a fifth aspect of the present invention, the anoxic condition forming means of the first aspect is constituted by a variable valve operating device capable of controlling the operation of the exhaust valve, and the exhaust valve is closed at the beginning of the exhaust stroke. As a result, the burnt gas is left in the cylinder to form an anoxic state.

According to a sixth aspect of the present invention, the anoxic state forming means of the first aspect of the invention is constituted by a variable valve operating device capable of controlling the operation of the intake valve, and restrains the opening of the intake valve during the intake stroke. As a result, the introduction of fresh air is restricted to form an anoxic state in the cylinder.

In a seventh aspect of the invention, the anoxic state forming means of the first aspect of the invention comprises an oxygen trap filter for adsorbing oxygen in intake air, and fresh air from which oxygen has been removed by the oxygen trap filter is introduced. As a result, an anoxic state is formed in the cylinder.

An eighth aspect of the present invention performs the stratified combustion only during a partial load operation, and does not form an anoxic state during a high load operation by using a combustible mixture formed by fresh air from the intake passage and injected fuel. Allow homogeneous combustion operation.

[0013]

In the following inventions, the cylinder is made oxygen-free in the intake stroke, and a combustible mixture is formed by the air and fuel directly injected into the cylinder by the injection valve to form a stratified mixture. To burn. As a result, even during partial load operation, the operation can be performed near the stoichiometric air-fuel ratio to sufficiently suppress the residual oxygen amount in the exhaust gas. Therefore, a three-way catalyst without a NOx trap function (hereinafter referred to as "conventional three-way catalyst") .) Can be applied to purify exhaust gas at low cost, and rich spike control is unnecessary, which is also advantageous in terms of fuel consumption.

The injection valve may be one that injects air and fuel separately, but as shown in the second invention, a two-fluid injection valve that simultaneously injects and supplies air and fuel from a common nozzle portion. By applying, it is possible to promote atomization of fuel and mixing with air to form a better combustible mixture.

The anoxic state forming means is, for example, the third to
It can be configured as shown as the seventh invention.
According to the third aspect of the invention, since the anoxic state is formed by the exhaust gas recirculation, the present invention can be implemented without significantly changing the configuration of the internal combustion engine having the existing exhaust gas recirculation device. According to the fourth to sixth aspects of the invention, since the anoxic state is formed in the cylinder by controlling the opening / closing of the intake valve or the exhaust valve via the variable valve operating device, an internal combustion engine provided with the variable valve operating device. In the above, the present invention can be implemented without providing an additional device such as an exhaust gas recirculation passage. Further, particularly in the third and fourth aspects of the invention, throttle loss or pumping loss due to the throttle does not occur, and fuel efficiency can be further improved. In addition, in the fifth invention, the operation of the intake valve may be further stopped.

According to the seventh aspect of the invention, since oxygen is removed from the fresh air, the oxygen-free state can be formed with a simple structure without applying exhaust gas recirculation or a variable valve operating device.

During a high load operation that requires a sufficient amount of oxygen in the fresh air, it is not necessary to perform an operation in which the inside of the cylinder is anoxic. Therefore, as shown as the eighth invention, the anoxic condition is maintained. The operation for forming and performing stratified combustion may be performed only during partial load.

The above inventions can be applied to any internal combustion engine of either spark ignition type or compression ignition type. The sixth invention is suitable for the spark ignition system because it is difficult to obtain a high compression ratio when the intake action is suppressed, but in a high compression ratio engine, the present invention reduces the actual compression ratio at partial load to improve efficiency. It is also possible to achieve

Here, in the present specification, "anoxic state"
The term does not necessarily mean that oxygen is completely eliminated, but it is the state where oxygen is removed as technically possible, or oxygen is removed to the extent that the desired exhaust purification action can be obtained with a three-way catalyst. It also means the state in which it is being operated.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a first embodiment in which an internal combustion engine according to the present invention is applied to a spark ignition type gasoline engine. In the figure, 1 is a piston, 2 is a combustion chamber, 3 is a two-fluid injection valve for simultaneously injecting fuel and air, 4 is an intake passage, 5 is an intake valve, 6 is an exhaust passage, 7 is an exhaust valve, 8 is an A spark plug, 9 is a variable valve operating device that controls the opening / closing operation of the intake valve 6 or the exhaust valve 7, and 10 is air-fuel injection by the two-fluid injection valve 3, ignition by the spark plug 8, and variable operation according to the operating state. It is a controller that controls the opening / closing operation of the intake valve 5 or the exhaust valve 7 by the valve device 9. Reference numerals 11 and 12 are a rotation speed sensor and a load sensor for outputting an engine rotation speed signal and a load signal to the controller 10 as operation state signals. The load detected by the load sensor 12 is an accelerator pedal operation amount, a throttle valve opening degree, a fuel supply amount, or the like.

The two-fluid injection valve 3 is supplied with air and fuel pressurized to a high pressure capable of counteracting the in-cylinder pressure from an air and fuel supply system (not shown), and supplies them to the combustion chamber 2 at a predetermined ratio. To jet. In this embodiment, the air and the fuel from the two-fluid injection valve 3 form a combustible mixture having a stoichiometric air-fuel ratio.

The controller 10 is configured as a microcomputer including a CPU and its peripheral devices, and in accordance with the detected operating state, homogeneous combustion control for supplying air and fuel during the intake stroke or within a period from the compression stroke to the expansion stroke. The stratified charge combustion control for injecting air and fuel is switched to. To this end, the controller 10 determines a combustion pattern determination unit 10a that determines whether to perform operation in homogeneous combustion or stratified combustion according to operating conditions, and a control parameter during homogeneous combustion operation. A homogeneous combustion control unit 10b and a stratified combustion control unit 10c that determines control parameters during stratified combustion operation are provided.

Combustion pattern determination unit 1 of controller 10
At 0a, the operating region is determined from the engine speed and the load by referring to the map in which the homogeneous combustion region and the stratified combustion region are allocated as shown in FIG. In this case, as shown in the figure, the stratified charge combustion operation is performed in the operation range of medium speed to medium load or less, and the homogeneous combustion operation is performed in the operation range in which the load or the rotation speed is higher than that.

In the homogeneous combustion region, the homogeneous combustion control section 10b
However, in the stratified combustion region, the stratified combustion control unit 10c calculates the fuel injection amount and the injection timing according to the operating state, and controls the injection valve 8 based on the result. The calculation method of the fuel injection amount and the injection timing at this time is arbitrary,
For example, with respect to the injection amount, a basic fuel injection amount is determined by a map search based on the intake air amount and the engine speed, and the control amount is obtained by correcting the basic fuel injection amount as necessary such as the cooling water temperature and the starting correspondence. The air and fuel during the stratified charge combustion operation are basically supplied only from the two-fluid injection valve 3,
During the homogeneous combustion operation, the fuel may be supplied from another fuel supply device, for example, a low pressure fuel injection valve that injects fuel to the intake port.

Further, the homogeneous combustion control section 10b and the stratified combustion control section 10c control the operation of the intake valve 5 or the exhaust valve 7 via the variable valve operating device 9 in their respective operating regions. FIG. 3 is a valve timing chart showing an example of a valve operation control pattern by the variable valve operating device 9. In the figure, (a) shows the valve operating state during homogeneous combustion operation, and (b) shows the valve operating state during stratified combustion operation. As shown in the figure, during the homogeneous combustion operation, the exhaust valve is controlled to open / close at the normal timing of opening in the exhaust stroke region and the intake valve in the intake stroke region. On the other hand, during the stratified charge combustion operation, the exhaust valve is controlled to remain open from the beginning of the exhaust stroke to the end of the intake stroke. At this time, the intake valve is opened or closed at the same timing as in the homogeneous combustion operation, or is kept closed.

Next, the operation in each combustion region will be described. In the homogeneous combustion region, the fresh air from the intake passage 4 is sucked into the cylinder during the intake stroke, and the fuel and air injected from the injection valve 3 during this period cause a homogeneous air-fuel mixture having an air-fuel ratio near the stoichiometry in the cylinder. Is formed. Near the end of the subsequent compression stroke, the mixture is ignited by the spark plug 8 and combustion is started. The exhaust valve 7 opens near the end of the combustion stroke, and the combustion gas in the cylinder is discharged to the outside through the exhaust passage 6 by the end of the exhaust stroke. Since the combustion is in the stoichiometric air-fuel ratio range, the exhaust gas at this time can be easily purified by the conventional three-way catalyst. The load variation in this operating range is dealt with by controlling the air amount with a throttle valve as needed. In the high load operating range, the pumping loss is not so large even if the throttle valve is used.

On the other hand, in the stratified charge combustion region, the exhaust valve 7 continues to open even during the intake stroke as shown in FIG. 4 (a), so the internal EGR action fills the cylinder with the combustion gas in the previous cycle. , Become anoxic. Then, the exhaust valve 7 is closed in the vicinity of the end timing of the intake stroke, and during the subsequent compression stroke, the injection valve 3 injects and supplies the combustion chamber 2 with an amount of air and fuel at a predetermined timing,
As a result, a stoichiometric combustible mixture layer Ga is formed in the vicinity of the spark plug 8 of the combustion chamber 2 filled with the burned gas Gb as shown in FIG. This combustible air-fuel mixture is ignited by the ignition plug 8 near the compression top dead center and enters the expansion stroke. At the end of the expansion stroke, as shown in Fig. 4 (c),
The exhaust valve 7 opens and the combustion gas in the cylinder is pushed out to the exhaust passage 6. However, since the exhaust valve 7 continues to open in the next intake stroke as well, part of the combustion gas from the exhaust passage 6 enters the cylinder. It is sucked back ((a) in FIG. 4), and the above-described anoxic state is again established. By continuing the operation by repeating this cycle, the exhaust passage 6 is always kept in an oxygen-free state in which oxygen does not exist. Therefore, the rich spike control is not necessary even though it is the lean combustion operation, and the inexpensive conventional type three It is possible to purify exhaust gas with the original catalyst. In addition, since it is possible to cope with load fluctuations without using a throttle valve in a region where the load and the rotational speed are relatively low, throttling loss does not occur, and a large effect of improving fuel efficiency can be obtained.

FIG. 5 shows the NOx reduction effect according to the present invention. When a conventional three-way catalyst is applied to a conventional direct injection type internal combustion engine and lean combustion is performed in the medium to low load range, a large amount of oxygen in the exhaust gas in this load range causes the catalyst to stop functioning, resulting in a large amount. NOx will be emitted. On the other hand, according to the present invention, since the amount of oxygen in the exhaust gas can be suppressed over a wide load range and the conversion efficiency of the catalyst can be maintained high, the NOx emission amount can be reduced regardless of the operating state.

Next, another embodiment concerning the opening / closing timing of the intake valve 5 or the exhaust valve 7 for making the inside of the cylinder free of oxygen from the intake stroke to the compression stroke will be described. Figure 3
In (c), the exhaust valve is closed at an early stage of the exhaust stroke. In this way, pumping loss for compressing the residual gas in the cylinder occurs in the exhaust stroke,
Until the subsequent suction stroke, the inside of the cylinder can be kept in anoxic state due to burned gas. In this case, the intake valve may be opened / closed at a normal timing as shown in FIG. (A), or may be kept closed. (D) of the figure shows an embodiment in which the exhaust valve is opened and closed at normal timing while the intake valve is held closed. In this case, since the intake action is hindered in the intake stroke following the exhaust stroke, the inside of the cylinder is in an anoxic state in which the remaining burned gas is partially filled.

As shown in the seventh aspect of the invention, an oxygen trap filter (not shown) for adsorbing oxygen in intake air is provided in the intake passage 4 or upstream thereof, and oxygen is removed by the oxygen trap filter. An anoxic state can also be formed by introducing fresh air. In this case, it is desirable to provide a passage bypassing the oxygen trap filter and a switching valve in the intake passage to enable switching between the anoxic state and the normal state. With such a configuration, the intended purpose can be achieved without using the variable valve operating device.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view schematically showing an embodiment of a direct injection type internal combustion engine according to the present invention.

FIG. 2 is an explanatory diagram regarding a homogeneous combustion region and a stratified combustion region.

FIG. 3 is an operation explanatory view during stratified charge combustion operation according to the embodiment.

FIG. 4 is a timing chart showing an operation pattern of intake and exhaust valves during stratified charge combustion operation.

FIG. 5 is an explanatory diagram showing the effect of the present invention in comparison with a conventional example.

[Explanation of symbols]

1 piston 2 combustion chamber 32 fluid injection valve 4 Intake passage 5 intake valve 6 exhaust passage 7 exhaust valve 8 spark plugs 9 Variable valve device 10 controller 11 Speed sensor 12 Load sensor

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 41/04 330 F02D 41/04 330C F02M 25/07 570 F02M 25/07 570A 67/02 67/02 F Term (reference) 3G023 AA02 AA05 AA18 AB01 AC01 AC04 AF00 AG01 3G062 AA07 AA10 BA04 BA05 BA09 CA07 DA01 GA04 GA06 3G066 AA02 AA05 AB02 AD12 BA17 BA25 CC46 3G092 GAAHA FA03 FA17 FA03 FA17 FA02 FA17 DA02 DA17 DA02 DA01 DA01 DA02 DA17 DA02 DA17 DA02 DA17 DA02 HD07X 3G301 HA01 HA02 HA13 HA16 JA02 JA25 KA06 KA09 LA00 LA01 LA07 MA01 MA11 NC02 ND03 NE14 PA01Z PA11Z PB03A PB03Z PD15A PD15Z PE01Z PE03Z

Claims (8)

[Claims] 1. An injection valve for directly injecting fuel and air into a cylinder, and an anoxic state forming means for making the inside of the cylinder anoxic during an intake stroke, and compressing into the anoxic cylinder. An in-cylinder direct injection internal combustion engine characterized in that a combustible air-fuel mixture is formed by the fuel and air injected and supplied by the injection valve in a stroke to perform stratified combustion. 2. The in-cylinder direct injection internal combustion engine according to claim 1, wherein the injection valve is a two-fluid injection valve that simultaneously supplies pressurized fuel and air from a common nozzle section. 3. The anoxic condition forming means comprises an exhaust gas recirculation device for recirculating exhaust gas from the exhaust passage to the intake passage,
The in-cylinder direct injection internal combustion engine according to claim 1, wherein the recirculated exhaust gas is introduced into the cylinder during an intake stroke to form an anoxic state. 4. The anoxic condition forming means comprises a variable valve operating device capable of controlling the operation of an intake valve and an exhaust valve, and suppresses the opening of the intake valve during the intake stroke and opens the exhaust valve. The in-cylinder direct injection internal combustion engine according to claim 1, wherein the exhaust gas from the exhaust passage is introduced into the cylinder by continuing the operation to form an anoxic state. 5. The anoxic condition forming means is composed of a variable valve device capable of controlling the operation of an exhaust valve, and the burned gas remains in the cylinder by closing the exhaust valve at the beginning of the exhaust stroke. The in-cylinder direct injection internal combustion engine according to claim 1, wherein the in-cylinder state is formed by allowing the oxygen-free state. 6. The anoxic condition forming means comprises a variable valve operating device capable of controlling the operation of an intake valve, and restricts the introduction of fresh air by suppressing the opening of the intake valve during the intake stroke. The in-cylinder direct injection internal combustion engine according to claim 1, wherein an oxygen-free state is formed in the cylinder. 7. The anoxic state forming means is composed of an oxygen trap filter that adsorbs oxygen in intake air, and introduces fresh air from which oxygen has been removed by the oxygen trap filter to create an anoxic state in the cylinder. The in-cylinder direct injection internal combustion engine according to claim 1, which is formed. 8. The stratified combustion is performed only during partial load operation, and during high load operation without forming an anoxic state,
The in-cylinder direct injection internal combustion engine according to claim 1, wherein a homogeneous combustion operation is performed by a combustible mixture formed by fresh air from the intake passage and injected fuel.