JP2001059431A - Cylinder injection type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the fuel consumption at the time of stoichiometric combustion. SOLUTION: The cylinder injection type internal combustion engine is provided with a first inlet valve and a second inlet valve which are respectively provided at a pair of inlet ports separately connected to a combustion chamber, a first cam 51 which is provided on an inlet cam shaft 50 to open or close the first inlet valve, and a second cam 52 for opening or closing the second inlet valve. The first cam 51 is provided with a main lift part 51a for opening the first inlet valve during the inlet stroke, and a sub-lift part 51b for opening the same inlet valve during the exhaust stroke. The sub-lift part 51b has a three-dimensional shape with which the amount of cam-lift continuously varies along the direction of the cam shaft. The second cam 52 is provided with only a main lift part 52a for opening the second inlet valve during the inlet stroke.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct injection internal combustion engine in which fuel is directly injected into an engine combustion chamber.

[0002]

2. Description of the Related Art A direct injection type internal combustion engine in which fuel is directly injected from a fuel injection valve into an engine combustion chamber is different from a so-called intake port injection type internal combustion engine.
Stratified combustion (lean combustion) in which the air-fuel ratio is set to an extremely lean side is performed by unevenly distributing the mixture having a high fuel concentration in the vicinity of the ignition plug. In the cylinder injection type internal combustion engine, by performing such lean combustion, pump loss and cooling loss can be reduced as compared with the intake port injection type internal combustion engine, and the fuel efficiency can be greatly improved. Become like

In such an in-cylinder injection type internal combustion engine, if lean combustion is performed even when the fuel injection amount is increased, the air-fuel mixture in the vicinity of the ignition plug is injected because fuel is directly injected into the engine combustion chamber. It is unavoidable that the fuel concentration becomes excessively high, which leads to deterioration of the combustion state and, consequently, reduction of the engine output. For this reason, when the fuel injection amount increases, even in such an in-cylinder injection type internal combustion engine, as in the case of the intake port injection type internal combustion engine, the fuel is substantially uniformly dispersed in the engine combustion chamber, Stoichiometric combustion is performed with the fuel ratio set to the stoichiometric air-fuel ratio (stoichiometric). As a result, the fuel concentration of the air-fuel mixture in the vicinity of the ignition plug is appropriately maintained, and the deterioration of the combustion state as described above is also avoided.

As described above, in the cylinder injection type internal combustion engine,
By switching the combustion mode between lean combustion and stoichiometric combustion based on the engine operation state such as the fuel injection amount, fuel efficiency is improved while ensuring engine output.

[0005]

However, the throttle valve is throttled during stoichiometric combustion compared to lean combustion, so that pump loss increases, and furthermore, the inner peripheral wall of the engine combustion chamber is increased. Since the temperature of the combustion gas that comes into contact with the air becomes high, the cooling loss also increases. Therefore, at the time of such stoichiometric combustion, deterioration of fuel efficiency is inevitable as compared with the case of lean combustion.

As described above, in the conventional in-cylinder injection type internal combustion engine, although the fuel efficiency is improved as compared with the intake port injection type internal combustion engine, the combustion method is set to lean combustion. In the operating region where the combustion system is set to the stoichiometric combustion, the improvement of the fuel efficiency is naturally limited.

The present invention has been made in view of such circumstances, and an object thereof is to provide an in-cylinder injection type internal combustion engine capable of improving fuel efficiency during stoichiometric combustion.

[0008]

The means for achieving the above object and the effects thereof will be described below. According to the first aspect of the present invention, the first intake valve and the second intake valve provided in a pair of intake ports respectively connected to the engine combustion chamber, and the first intake valve provided in the intake camshaft. A first cam for opening and closing the intake valve and a second cam for opening and closing the second intake valve, the in-cylinder injection type internal combustion engine having only the first cam out of the two cams. A lift portion for opening one intake valve during the exhaust stroke is formed.

According to the above configuration, when the first intake valve is opened, the inside of the intake port corresponding to the first intake valve is provided.
During the exhaust stroke, the burned gas in the engine combustion chamber is
The gas flows as R (Exhaust Gas Recirculation) gas. Therefore, during the intake stroke following the exhaust stroke, the EGR gas is introduced into the engine combustion chamber from the intake port corresponding to the first intake valve, so that the EGR gas is introduced.
A layer of gas is formed. On the other hand, during the intake stroke, a layer of fresh air is formed by introducing air (fresh air) from the intake port corresponding to the second intake valve into the engine combustion chamber.

Therefore, even if a large amount of EGR gas is introduced into the engine combustion chamber during stoichiometric combustion, the EGR gas is stratified as described above and is not uniformly dispersed in the engine combustion chamber. Is suppressed, and a stable combustion state is ensured by a combustible mixture formed by air in a fresh air layer containing almost no EGR gas.

[0011] On the other hand, by introducing a large amount of EGR gas into the engine combustion chamber during stoichiometric combustion, the throttle valve is inevitably opened to reduce pump loss, and the EGR gas layer Since the temperature rise is suppressed, the cooling loss is also reduced. As a result, it is possible to improve fuel efficiency during stoichiometric combustion by reducing such pump loss and cooling loss.

According to a second aspect of the present invention, in the direct injection internal combustion engine according to the first aspect, each of the intake ports is connected to the engine combustion chamber substantially in parallel. .

According to such a configuration, the flow directions of the EGR gas and fresh air introduced from each intake port during the intake stroke become substantially parallel, and it is difficult for these EGR gas and fresh air to mix in the engine combustion chamber. Becomes As a result, a layer of EGR gas is formed at a position near the intake port corresponding to the first intake valve, and a layer of fresh air is formed at a position near the intake port corresponding to the second intake valve.
Stratification of EGR gas and fresh air in the engine combustion chamber is promoted. Therefore, according to the above configuration of the invention described in claim 2, the operation and effect of the invention described in claim 1 can be suitably exhibited.

According to a third aspect of the present invention, in the cylinder injection type internal combustion engine according to the second aspect, a fuel injection valve for directly injecting fuel into the engine combustion chamber corresponds to the second intake valve. It is said that fuel is injected toward the intake port side.

According to such a configuration, the fuel is injected from the fuel injection valve toward the fresh air layer formed near the intake port corresponding to the second intake valve. A more stable combustion state is ensured by the air-fuel mixture in the layer.

According to a fourth aspect of the present invention, in the cylinder injection type internal combustion engine according to the first aspect, only the intake port corresponding to the first intake valve among the intake ports is provided with the engine combustion. The swirl port forms a swirl in the room.

According to this configuration, only the intake port corresponding to the first intake valve is a swirl port for forming a swirl in the engine combustion chamber. Therefore, the EGR introduced from the intake port into the engine combustion chamber during the intake stroke. The gas is
The swirl flows while swirling along the inner circumferential wall of the engine combustion chamber (the inner circumferential wall of the engine cylinder), and the fresh air introduced into the engine combustion chamber from the intake port corresponding to the second intake valve is swirl-generated. It gathers near the rotation axis of the flow, in other words, substantially at the center of the engine combustion chamber. Therefore, the layer of fresh air is formed at a position substantially at the center of the engine combustion chamber, and the layer of EGR gas is formed at a position surrounding the layer of fresh air. Stratification is promoted. Therefore, the operation and effect of the invention described in claim 1 can be suitably exhibited.

Further, since the layer of fresh air is surrounded by the layer of EGR gas, heat propagation from the layer of fresh air to the inner peripheral wall of the engine combustion chamber during the combustion stroke is suppressed by the layer of EGR gas. . Moreover, since the EGR gas layer has a large heat capacity and excellent heat insulation properties, such heat propagation can be more suitably suppressed. Therefore, according to the configuration of the invention described in claim 4, the cooling loss can be more effectively reduced, and the fuel efficiency can be further improved.

According to a fifth aspect of the invention, there is provided a cylinder injection type internal combustion engine according to any one of the first to fourth aspects.
The sub-lift portion is set so that its lift characteristic continuously changes along the axial direction of the intake camshaft, and a displacement means for displacing the intake camshaft in the axial direction; And control means for controlling the amount of displacement caused by the engine according to the operating state of the engine.

By introducing a large amount of EGR gas into the engine combustion chamber during stoichiometric combustion as described above, pump loss and cooling loss can be reduced to improve fuel efficiency. For example, at the time of engine high load operation, securing of engine output may be given priority over improvement of fuel efficiency. In such a case, it is necessary to reduce the introduction amount of the EGR gas or stop the introduction.

In this regard, according to the above-described structure of the invention, it is possible to appropriately control the introduction amount of the EGR gas according to the engine operating state such as the engine load.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] A first embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a cross-sectional structure in the vicinity of a combustion chamber 18 of a direct injection internal combustion engine 10, and FIG.
2 shows a cross-sectional structure along line -2. As shown in these figures, the cylinder block 14 of the internal combustion engine 10 includes:
A plurality of cylinders (only one of which is shown in FIG. 1) 15 is formed, and a piston 16 is provided in the cylinder 15 so as to be able to reciprocate. A combustion chamber 18 is defined by the piston 16, the cylinder 15, and the cylinder head 12 of the internal combustion engine 10.

The cylinder head 12 is formed with a first intake port 33 and a second intake port 34 which constitute a part of an intake passage. The intake ports 33 and 34 are connected to the combustion chamber 18 respectively. ing. As shown in FIG. 2, these intake ports 33 and 34 are straight ports extending substantially in parallel, and are connected to the combustion chamber 18 at positions substantially symmetric with respect to a plane S1 passing through the center of the combustion chamber 18 and extending in the radial direction. It is open.

The upstream portions of the intake ports 33 and 34 join together to form a single passage, which is connected to a surge tank (not shown) constituting a part of the intake passage. 18, in other words, the length of each of the independent passages in each of the intake ports 33 and 34 is, as will be described later, changed from the combustion chamber 18 to the first intake port 33 during the exhaust stroke. The burned gas flowing into the second intake port 34 is set so as not to flow into the second intake port 34.

The cylinder head 12 includes the combustion chamber 1
8, a first exhaust port 43 and a second exhaust port 44 which form part of an exhaust passage are formed.
These exhaust ports 43, 44 are connected to the respective intake ports 33, 3
4 are open to the combustion chamber 18 at positions adjacent to the openings 33a and 34a, respectively.

The cylinder head 12 has spark plugs 22 corresponding to the combustion chambers 18 of the respective cylinders 15.
And a fuel injection valve 20. The electrode 22a at the tip of the ignition plug 22 is located substantially at the center between the openings 33a, 34a of the intake ports 33, 34 and the openings 43a, 44a of the exhaust ports 43, 44 in the combustion chamber 18, and It is located closer to the opening 34a of the second intake port 34 than the plane S1.

The tip of the fuel injection valve 20 is located on the plane S1 in the combustion chamber 18, and fuel is directly injected into the combustion chamber 18 from an injection hole (not shown) formed in the tip. You. As shown in FIG. 2, the injection hole is formed so that the fuel spray is directed toward the opening 34 a of the second intake port 34.
The fuel injection direction is set.

The fuel injection timing and fuel injection amount of the fuel injection valve 20 are set as follows. That is,
At the time of these settings, first, the combustion method of the internal combustion engine 10 is selected based on the engine speed and the depression amount (accelerator opening) of an accelerator pedal (not shown). In the internal combustion engine 10 of the present embodiment, lean combustion is selected in the low-load, low-speed range, and stoichiometric combustion is selected in the high-load, high-speed range. When lean combustion is selected as the combustion method, the fuel injection timing is set during the compression stroke, and the fuel injection amount is set based on the engine speed and the accelerator opening. On the other hand, when stoichiometric combustion is selected as the combustion method, the fuel injection timing is set during the intake stroke, and the fuel injection amount is set based on the engine speed and the intake air amount.

Openings 33 of the intake ports 33, 34
The first and second intake valves a and 34a are respectively opened and closed by a first intake valve 31 and a second intake valve 32 provided to be reciprocally movable in the cylinder head 12. Similarly, each exhaust port 43, 44
The openings 43a and 44a of the first exhaust valve 41 and the second exhaust valve 4
2, respectively.

FIG. 3 shows a part of an intake camshaft 50 on which cams 51 and 52 for opening and closing the intake valves 31 and 32 are formed. The intake camshaft 50 is supported by the cylinder head 12 so as to be rotatable and movable in the axial direction (hereinafter, referred to as “cam axis direction”). A first cam 51 for opening and closing the first intake valve 31 and a second cam 52 for opening and closing the second intake valve 32 correspond to each cylinder 15 on the intake camshaft 50. (Only one of the first cam 51 and the second cam 52 is shown in FIG. 3).

As shown in FIG. 4, the first cam 51 includes a main lift portion 51a for opening the first intake valve 31 during an intake stroke, and a sub-lift for opening the intake valve 31 during an exhaust stroke. Part 51b. This sub-lift section 5
1b has a three-dimensional shape in which the cam lift amount L (see FIG. 3) changes continuously along the cam axis direction. On the other hand, the second cam 52 does not have a portion corresponding to such a three-dimensionally shaped sub-lift portion, and during the intake stroke,
Only the main lift portion 52a for opening the intake valve 32 of the second embodiment.

Therefore, as shown in FIG. 5, during the intake stroke, the main lift portions 51a, 52a of the cams 51, 52 are provided.
Opens the respective intake valves 31, 32, and during the exhaust stroke,
In addition to the exhaust valves 41 and 42, the first intake valve 31 is also opened based on the lift by the sub-lift section 51b.

When the first intake valve 31 is opened during the exhaust stroke, a part of the burned gas generated during the expansion (explosion) stroke is also used during the next expansion stroke. 18 to remain.

That is, the burned gas in the combustion chamber 18 flows out of the combustion chamber 18 to the exhaust ports 43 and 44 when the exhaust valves 41 and 42 are opened in the exhaust stroke. Furthermore,
At this time, if the first intake valve 31 is open, the combustion chamber 1
A part of the burned gas in 8 flows out to the first intake port 33 as EGR gas. The EGR gas that has flowed out to the first intake port 33 in this way re-opens the combustion chamber 18 from the first intake port 33 with the opening of the first intake valve 31 in the intake stroke following the exhaust stroke.
It will flow into the inside. As a result, the next combustion is performed while a part of the burned gas (EGR gas) generated in the combustion chamber 18 during the expansion stroke remains in the combustion chamber 18.

By performing the so-called internal EGR, the fuel efficiency is improved by reducing the pump loss and the cooling loss, and the generation of nitrogen oxides due to the decrease in the combustion temperature is suppressed.

As shown in FIG.
Is provided with an actuator 60 for displacing the intake camshaft 50 in the camshaft direction. Based on the operation of the actuator 60, the intake camshaft 5
0 is displaced in the cam axis direction, so that the valve lift amount of the first intake valve 31 during the exhaust stroke is continuous according to the displacement amount, as shown by the solid line, the one-dot chain line, and the two-dot chain line in FIG. Will be changed.

The operation of the actuator 60 is as follows.
The adjustment is performed based on the pressure of the oil supplied from the hydraulic system 90 of the internal combustion engine 10. This supply oil pressure is applied to the actuator 6
The control position of the solenoid valve 70 is adjusted based on the switching position of the solenoid valve 70 provided in a hydraulic path (not shown) between the hydraulic system 90 and the hydraulic system 90.
Engine operating conditions (eg engine speed and engine load)
Is controlled based on the As a result, the valve lift of the first intake valve 31 during the exhaust stroke is controlled based on the engine operating state.

For example, when stoichiometric combustion is selected as the combustion method of the internal combustion engine 10, the valve lift is controlled so as to become relatively smaller as the engine load increases. Therefore, the introduction amount of the EGR gas decreases as the engine load increases. As a result, the fuel efficiency is improved by introducing the EGR gas when the engine load is low, while the engine output is secured when the engine load is high.

Next, the flow of the EGR gas from the exhaust stroke to the intake stroke during stoichiometric combustion will be described with reference to FIGS.
This will be described with reference to FIG. 6 illustrates the flow of the EGR gas during the exhaust stroke, and FIG. 7 illustrates the flow of the EGR gas during the intake stroke. FIG. 6 illustrates the cross-sectional structure of the combustion chamber 18 as in FIG. 2 (see FIGS. 6 and 7). The illustration of the fuel injection valve 20 is omitted). FIG. 8 shows a simplified sectional structure of the combustion chamber 18.

When the piston 16 rises during the exhaust stroke and the volume of the combustion chamber 18 decreases, as shown by an arrow in FIG.
The burned gas in the combustion chamber 18 is supplied to each exhaust port 43, 4
4, and also flows out into the first intake port 33 as EGR gas through the opening 33a. At this time, the EGR gas moves inside the first intake port 33 to the upstream side thereof, but does not reach the portion where the intake ports 33 and 34 join. That is, the EGR gas flowing into the first intake port 33 is
Never go around. Then, during the exhaust stroke, the first
When the intake valve 31 is closed, the EGR gas is temporarily confined in the first intake port 33.

Next, when the piston 16 descends during the intake stroke and the volume of the combustion chamber 18 increases, the EGR gas in the first intake port 33 becomes as shown by the solid arrow in FIG.
Air is introduced into the combustion chamber 18 through the opening 33a, and air (hereinafter, referred to as “hereinafter”) from the second intake port 34 through the opening 34a, as indicated by a dashed line arrow in FIG.
“Fresh air”) is introduced into the combustion chamber 18.

Here, since each intake port 33, 34 is connected substantially in parallel to the combustion chamber 18, EGR gas and new air introduced from each of these intake ports 33, 34 into the combustion chamber 18 during the intake stroke. The air is hardly mixed in the combustion chamber 18. As a result, as shown in FIG. 8, in the combustion chamber 18, a region on the first intake port 33 side (a region having a semicircular cross section hatched by a two-dot chain line in FIG. 8) is A layer of EGR gas is formed by the EGR gas introduced from 33, and a region on the second intake port 34 side (a region having a semicircular cross section surrounded by a two-dot chain line in FIG. 34
A fresh air layer (fresh air layer) is formed by the fresh air introduced from the inside. That is, the inside of the combustion chamber 18 is stratified, and layers having different concentrations of the EGR gas and fresh air are formed.

Further, during the intake stroke, these layers are formed and the fuel injection valve 20 (not shown in FIG. 8)
The fuel is injected toward the fresh air layer. For this reason,
The new gas layer becomes a fuel-rich gas mixture layer.
The fuel concentration in the GR gas layer is lower than in the fresh gas layer.

After that, when the intake stroke is completed, the ignition plug 2 is set at the later stage of the subsequent compression stroke or at the beginning of the expansion stroke.
2, the mixture in the combustion chamber 18 explodes and expands during the expansion stroke. Here, the contribution of the EGR gas layer to the engine combustion is low, and the engine combustion is performed based on the explosion and expansion of a mixture of a fresh air layer substantially containing fresh air (air) and fuel. Become. Therefore, a large amount of EGR is stored in the combustion chamber 18 during stoichiometric combustion.
Even when gas is introduced, engine combustion is performed properly, and a stable combustion state is ensured.

On the other hand, a large amount of E
The introduction of the GR gas inevitably opens the throttle valve (not shown) of the internal combustion engine 10, so that the pump loss is reduced. Further, in the portion where the EGR gas layer exists in the combustion chamber 18, the combustion temperature becomes extremely low, and the temperature rise is suppressed to a small amount. Therefore, the amount of heat transmitted to the inner peripheral wall of the cylinder 15 decreases, and the cooling loss also decreases. It will also decrease.

According to the above-described embodiment, the following effects can be obtained.
(1) By stratifying the inside of the combustion chamber 18 with EGR gas and fresh air during stoichiometric combustion, it is possible to introduce a large amount of EGR gas into the combustion chamber 18 and perform combustion without deteriorating the combustion state. it can. As a result, the pump loss and the cooling loss can be reduced, and the fuel efficiency during stoichiometric combustion can be improved.

(2) Since each intake port 33, 34 is connected to the combustion chamber 18 in a substantially parallel manner, EGR introduced from each intake port 33, 34 during the intake stroke.
The gas and fresh air are hardly mixed in the combustion chamber 18, and the stratification of the EGR gas and fresh air in the combustion chamber 18 can be promoted. Therefore, the effect described in the above (1) can be more suitably achieved.

(3) Further, during the exhaust stroke, the first intake valve 3
By setting the shape of the sub-lift portion 51b for opening the valve 1 so that the cam lift amount changes continuously in the cam axis direction, and displacing the intake camshaft 50 in the cam axis direction by the actuator 60, during the exhaust stroke, Since the valve lift of the first intake valve 31 can be changed, the amount of EGR gas introduced can be appropriately controlled in accordance with the engine operating state.

(4) In particular, in controlling the amount of EGR gas introduced as described above, the amount of EGR gas introduced is reduced as the engine load increases during stoichiometric combustion. The fuel efficiency during combustion can be improved, and the engine output can be appropriately ensured during high engine load.

[Second Embodiment] Next, a second embodiment of the present invention will be described.
This embodiment will be described with reference to FIGS. 9 to 12, focusing on differences from the first embodiment.

FIG. 9 shows a cross-sectional structure of the combustion chamber 18 as in FIG. As shown in the figure, in the present embodiment, the spark plug 22
Is mounted on the cylinder head 12 so as to be located substantially at the center of the cylinder head 12. The fuel injection direction of the injection hole of the fuel injection valve 20 is set so that the fuel spray is directed toward the center of the combustion chamber 18. Furthermore, each intake port 33, 3
4 is different from the first embodiment in that the first intake port 33 is a swirl port connected to the combustion chamber 18 in a curved state in the vicinity of the combustion chamber 18.

Next, the flow of the EGR gas during the stoichiometric combustion from the exhaust stroke to the intake stroke will be described with reference to FIGS. 10 to 12, focusing on differences from the first embodiment.

FIG. 10 illustrates the flow of the EGR gas during the exhaust stroke, and FIG. 11 illustrates the flow of the EGR gas during the intake stroke. The cross-sectional structure of the combustion chamber 18 is shown similarly to FIG. 9 (FIGS. 10 and 10). The fuel injection valve 20 is not shown in FIG. 11). FIG. 12 shows a simplified sectional structure of the combustion chamber 18.

When the piston 16 rises during the exhaust stroke and the volume of the combustion chamber 18 decreases, the burned gas in the combustion chamber 18 is discharged to each exhaust port 4 as shown by an arrow in FIG.
3, and also flows out as EGR gas into the first intake port 33 through the opening 33a.

Next, when the piston 16 descends during the intake stroke and the volume of the combustion chamber 18 increases, the EGR gas in the first intake port 33 is released as shown by the solid arrow in FIG. While being introduced into the combustion chamber 18 through 33a, fresh air is introduced into the combustion chamber 18 from the second intake port 34 through the opening 34a thereof, as indicated by the dashed line arrow in FIG.

Since only the first intake port 33 among the intake ports 33 and 34 is a swirl port, the intake air introduced from the intake port 33 into the combustion chamber 18 is The swirl flows while swirling along the peripheral wall, and the intake air introduced into the combustion chamber 18 from the second intake port 34 is in the vicinity of the rotation axis where the flow velocity of the swirl flow is low, in other words, in the combustion chamber 18. It comes to gather in the center.

As a result, as shown in FIG. 12, the first intake port 3 is located in the region near the inner peripheral wall of the cylinder 15 (in the figure, the region having a circular cross section hatched by a two-dot chain line).
An EGR gas layer is formed by the EGR gas introduced from 3, and a second intake port is provided in a substantially central region of the combustion chamber 18 (a region having a circular cross section surrounded by a two-dot chain line in the drawing). The fresh air introduced from 34 causes a fresh air layer to be formed. That is, the combustion chamber 18
Is stratified, and layers having different concentrations of EGR gas and fresh air are formed.

Further, during the intake stroke, each layer is formed as described above, and the fuel injection valve 20 (FIG. 1) is formed.
2 is not shown), fuel is injected toward the fresh air layer. For this reason, the fresh gas layer becomes a mixed gas layer containing a large amount of fuel, while the fuel concentration in the EGR gas layer is lower than that in the fresh gas layer.

Thereafter, when the intake stroke is completed, the ignition plug 2 is set at the later stage of the subsequent compression stroke or at the beginning of the expansion stroke.
2, the mixture in the combustion chamber 18 explodes and expands during the expansion stroke.

Here, the engine combustion is performed based on the explosion and expansion of the air-fuel mixture existing substantially on the fresh air layer side, and the contribution of the EGR gas layer to the engine combustion is reduced. At the time, a large amount of EG
The point that a stable combustion state is ensured even when R gas is introduced, and that the pump loss and the cooling loss are reduced by the introduction of the EGR gas are the same as in the first embodiment.

Therefore, also in this embodiment, the same operation and effect as the effects (1), (3) and (4) described in the first embodiment can be obtained. (5) Further, in the present embodiment, each of the intake ports 33, 34
Since the first intake port 33 is a swirl port and the second intake port 34 is a straight port, the intake air introduced into the combustion chamber 18 from the first intake port 33 during the intake stroke is The swirl flows swirling along the peripheral wall, and the intake air introduced into the combustion chamber 18 from the second intake port 34 is supplied to the combustion chamber 1.
8 will be gathered at the approximate center. As a result, the combustion chamber 18
The stratification of the EGR gas and fresh air in the inside can be promoted, and the operation and effect described in (1) can be more suitably achieved in the first embodiment.

(6) Further, since the fresh air layer is surrounded by the EGR gas layer, heat propagation from the fresh air layer to the inner peripheral wall of the cylinder 15 is suppressed by the EGR gas layer in the combustion stroke. Moreover, since the EGR gas layer has a large heat capacity and excellent heat insulation properties, such heat propagation can be more suitably suppressed. Therefore,
The cooling loss can be reduced more effectively, and the fuel efficiency can be further improved.

(7) Further, in this embodiment, the fresh air layer is formed near the center of the combustion chamber 18 and the EGR gas layer is formed near the inner peripheral wall of each cylinder 15 so as to surround the fresh air layer. Therefore, each of these layers is
Are located concentrically around the axis when the reciprocating motion occurs. Therefore, during the expansion stroke, the piston 16
Can be suppressed from being applied to the piston 16, and uneven wear between the piston 16 and the inner wall of the cylinder 15 can be minimized.

Each of the embodiments described above can be implemented by changing the configuration as described below. In the above embodiments, in addition to the first intake valve and the second intake valve, a third intake valve and a third cam that opens and closes the third intake valve are further provided. A configuration in which only the first cam is provided with the sub-lift section may be adopted.

In the above embodiments, the sub-lift section 51
By making b a three-dimensional shape in which the maximum cam lift amount changes continuously along the cam axis direction, the amount of EGR gas introduced during the exhaust stroke can be changed. The EGR gas introduction amount may be changed by forming a three-dimensional shape in which the lift timing changes continuously along the cam axis direction.

In the above embodiments, the sub-lift section 51
b is formed over substantially the entire area in the cam axis direction. For example, by forming the sub-lift section 51b from the middle in the cam axis direction, an area where the sub-lift section 51b is not formed in the first cam 51 is formed. It may be formed. According to such a configuration, for example, the introduction of the EGR gas is stopped at the time of full load of the stoichiometric combustion, and the engine output can be improved.

In each of the above embodiments, a hydraulic actuator is used as the actuator for displacing the intake camshaft 50 in the cam axis direction. However, for example, an electromagnetic solenoid actuator or a pneumatic actuator may be employed. Good.

In the second embodiment, a swirl valve may be provided in the second intake port 34 to further promote stratification of the EGR gas.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a sectional structure near a combustion chamber.

FIG. 2 is a sectional view of the combustion chamber according to the first embodiment, taken along line 2-2 of FIG. 1;
Sectional drawing which shows the cross-section along the line.

FIG. 3 is a schematic configuration diagram showing an intake camshaft, an actuator, and the like.

FIG. 4 is an enlarged perspective view showing a first intake cam and a second intake cam.

FIG. 5 is a graph showing a relationship between a valve lift amount of an intake valve and an exhaust valve and a crank angle.

FIG. 6 is a sectional view of a combustion chamber showing a flow of burned gas during an exhaust stroke in the first embodiment.

FIG. 7 is a sectional view of a combustion chamber showing a flow of burned gas during an intake stroke in the first embodiment.

FIG. 8 is a schematic cross-sectional view of the combustion chamber showing an EGR gas layer and a fresh air layer formed in the combustion chamber in the first embodiment.

FIG. 9 is a sectional view showing a sectional structure of a combustion chamber in a second embodiment.

FIG. 10 is a sectional view of a combustion chamber showing a flow of burned gas during an exhaust stroke according to the second embodiment.

FIG. 11 is a sectional view of a combustion chamber showing a flow of burned gas during an intake stroke in a second embodiment.

FIG. 12 is a schematic sectional view of the combustion chamber showing an EGR gas layer and a fresh air layer formed in the combustion chamber in the second embodiment.

[Explanation of symbols]

10 internal combustion engine 12 cylinder head 14 cylinder block 15 cylinder 16 piston 18
Combustion chamber, 20: fuel injection valve, 31: first intake valve, 32
... second intake valve, 33 ... first intake port, 33a ... opening, 34 ... second intake port, 34a ... opening, 41 ... first exhaust valve, 42 ... second exhaust valve, 43 ... first 1 exhaust port, 43a ... opening, 44 ... second exhaust port, 44a
... Opening, 22 ... Spark plug, 22a ... Electrode, 50 ... Intake camshaft, 51 ... First cam, 51a ... Main lift part, 51b ... Sub lift part, 52 ... Second cam, 52
a: Main lift unit, 60: Actuator, 70: Solenoid valve, 80: Control device, 90: Hydraulic system.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02B 31/00 331 F02B 31/00 331A 31/02 31/02 HL F02D 41/02 325 F02D 41/02 325A F02M 25/07 520 F02M 25/07 520A 570 570A 580 580A (72) Inventor Takanobu Ueda 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Masato Kawauchi 1 Toyota Town, Toyota City, Aichi Prefecture Address Toyota Motor Corporation F term (reference) 3G016 AA06 AA15 AA19 BA03 BA06 BA28 BA34 BA37 BA42 BA43 CA13 CA24 CA36 CA48 DA01 DA22 3G023 AA02 AA18 AB03 AC05 AD07 AD09 AG01 AG02 AG03 3G062 BA04 BA09 EA01 A09 A21 3 AA10 AA11 BA09 BB01 BB06 DA01 DA04 DA14 DC09 DF04 DF09 DG05 DG09 EA06 EA07 EA22 FA21 FA24 GA05 GA06 HA11Z HA13X HB01X HB02X HC09X HD07X HE01Z HF08Z 3G301 HA04 HA13 HA17 JA02 KA08 KA09 LB04 MA11 MA18 PA01Z PE01Z PF03Z

Claims (5)

[Claims] 1. A first intake valve and a second intake valve provided in a pair of intake ports respectively connected to an engine combustion chamber, and the first intake valve provided in an intake camshaft. An in-cylinder injection type internal combustion engine including a first cam that opens and closes and a second cam that opens and closes the second intake valve, wherein the first intake valve is provided only in the first cam of the two cams. A direct injection type internal combustion engine characterized by forming a lift portion for opening a valve during an exhaust stroke. 2. The direct injection internal combustion engine according to claim 1, wherein each of the intake ports is connected to the engine combustion chamber substantially in parallel. . 3. The in-cylinder injection type internal combustion engine according to claim 2, wherein the fuel injection valve for directly injecting fuel into the engine combustion chamber comprises:
An in-cylinder internal combustion engine, which injects fuel toward an intake port corresponding to the second intake valve. 4. The in-cylinder injection internal combustion engine according to claim 1, wherein only one of the intake ports corresponding to the first intake valve is a swirl port forming a swirl in the engine combustion chamber. An in-cylinder injection internal combustion engine. 5. The in-cylinder injection internal combustion engine according to claim 1, wherein the sub-lift portion is set such that its lift characteristic continuously changes along the axial direction of the intake camshaft. In-cylinder injection, further comprising: a displacement means for displacing the intake camshaft in the axial direction thereof; and a control means for controlling a displacement amount by the displacement means in accordance with an engine operating state. Type internal combustion engine.