JPH0676771B2 - Stratified combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an engine and an intermediate stratified charge combustion type engine.

(Prior Art) Conventionally, in an engine, try to realize low fuel consumption and low NOx by the synergistic effect of reducing pumping loss by eliminating the throttle valve and adopting a direct injection method that directly injects fuel into the combustion chamber. Attempts are being made to

However, when the throttle valve is abolished in this way, a large amount of air is always introduced into the combustion chamber regardless of the load condition of the engine. If the excess air ratio is large and the injected fuel is mixed with all the air in the cylinder, the air-fuel ratio of the air-fuel mixture becomes over lean, which causes problems such as ignition failure. Therefore, in the low load operation region, the injected fuel is mixed with a part of the air introduced into the combustion chamber to locally form a mixture layer having a concentration close to the stoichiometric air-fuel ratio in the combustion chamber, and the mixture is formed. The so-called stratified combustion in which the air layer portion is ignited and burned becomes an indispensable condition.

From such a background, as disclosed in Japanese Patent Laid-Open No. 58-85319, an injector is provided in the intake passage, and fuel is injected from the injector toward the combustion chamber immediately before the intake valve is closed to inject the fuel into the combustion chamber. Form a rich mixture layer on top,
An engine that has attempted to realize stratified combustion has been proposed.

However, in this method, two layers having different air-fuel mixture concentrations are formed by injecting fuel into a part of an air layer having substantially uniform flow characteristics in the entire combustion chamber, and the fuel injection is performed by the intake valve. Since it is performed immediately before closing, even if the rich mixture layer is formed in a good state in the upper part of the combustion chamber at the beginning of the compression stroke,
Near the end of the compression stroke, the rich mixture layer is attenuated or destroyed due to the turbulence of the air in the combustion chamber due to the upward movement of the piston. It is assumed that it will not happen.

Therefore, although it has been theoretically explained that low fuel consumption and low NOx can be realized by eliminating the throttle valve and adopting the direct injection method as described above, if a specific successful example is found. The current situation is that there are none.

(Object of the invention) The present invention is intended to solve the problems pointed out in the above-mentioned prior art, and to introduce a plurality of air layers in the combustion chamber by introducing the air into the combustion chamber without throttling. In the above stratified combustion engine, the purpose is to realize a high level of stratified combustion by more reliably stratifying the air layer in the combustion chamber.

(Means for Achieving the Purpose) As a means for achieving the above object, the stratified combustion engine of the present invention has a main intake passage for supplying air so as to generate a swirl flow in the outer peripheral portion of the combustion chamber, A sub-intake passage for supplying air to the center of the combustion chamber so as to generate an air flow having a flow direction different from that of the swirl flow,
Further, at least in the low load operation region of the engine, intake air is introduced from both the main intake passage and the auxiliary intake passage, and the first air layer is formed by the air introduced into the outer peripheral portion of the combustion chamber through the main intake passage. To form a second air layer by the air introduced through the auxiliary intake passage in the center of the combustion chamber, and to introduce intake air through the auxiliary intake passage after the middle stage of the intake stroke. Intake control means that can be executed at a certain time, and fuel supply means that supplies fuel toward the second air layer are provided.

(Operation) According to the present invention, by the above means, (1) since the first air layer and the second air layer formed in the combustion chamber in the intake stroke have different flow characteristics, the stratified state can be maintained. (2) The second air layer that contributes to combustion is formed from the middle stage of the intake stroke to the latter half of the intake stroke. In the second air layer in which the period from formation to the compression top dead center is short, the attenuation or destruction of the second air layer during the compression stroke is small, and thus the stratified state is relatively well maintained. Since the fuel is supplied toward the interior, stratified combustion in the combustion chamber is effectively achieved.

(Embodiment) A preferred embodiment of the present invention will be described below with reference to FIGS. 1 to 6.

(I: Structure) FIGS. 1 and 2 show a multi-cylinder stratified combustion engine for an automobile according to an embodiment of the present invention. In each drawing, reference numeral 1 is a cylinder block, 2 is a cylinder head, and 3 is a cylinder head. Is a combustion chamber, and 4 is a piston.

The cylinder head 2 is opened and closed by an intake valve 6 2
One intake passage, that is, a main intake passage 11 and an auxiliary intake passage 12, which will be described later, and an exhaust passage 15 that is opened and closed by the exhaust valve 7 are formed.

The main intake passage 11 is of a helical port type intended to generate a swirl flow, and a portion of the main intake passage 11 near the main intake port 13 opening to the combustion chamber 3 is formed in a substantially spiral shape. Therefore, the air introduced into the combustion chamber 3 from the main intake passage 11 through the main intake port 13 is the same as in FIGS.
In the figure, a swirl flow is formed along the outer peripheral portion of the combustion chamber 3 as indicated by an arrow A ₁ . Incidentally, the passage area of the main intake passage 11 is set to a size such that the main intake passage 11 alone can cover the required air amount during high-load operation of the engine.

The sub intake passage 12 has a passage area smaller than that of the main intake passage 11, and the sub intake port opening to the combustion chamber 3 thereof.
Reference numeral 14 denotes a position in the main intake passage 11 near the main intake port 13 and through the main intake port 13 to the combustion chamber 3
The opening is formed so that the central part of the can be seen. Therefore, the air introduced into the combustion chamber 3 from the auxiliary intake passage 12 through the auxiliary intake port 14 is the air flow substantially along the axial direction of the piston 4 as indicated by an arrow A ₂ in FIGS. 1 and 2. To appear.

On the other hand, the outer ends of the main intake passage 11 and the sub intake passage 12 are connected to the intake manifold 5, respectively. The intake manifold 5 has a merging passage portion 30 extending in the cylinder row direction.
A main intake branch passage 31 connected to the main intake passage 11 of the cylinder head 2 and a sub intake branch passage 32 connected to the sub intake passage 12 respectively branched from the confluent passage portion 30 for each cylinder.
And have. A rotary valve 41, which will be described later, is provided in the sub intake air passage 32, and the sub intake air passage 32 is opened and closed by the rotary valve 41.

As shown in FIGS. 1 and 3, the rotary valve 41 has a passage 42 capable of overlapping and communicating with the auxiliary intake branch passage 32, and a belt that is wound around a pulley 48 attached to one end of a valve shaft 46 thereof. It can be rotated in synchronization with the crankshaft (not shown) of the engine via (not shown). Also,
The valve shaft 46 is provided with a phase control device 47 which receives a control signal from the control device 27 and adjusts the rotational phases of the rotary valve 41 and the crankshaft, in other words, the opening timing of the rotary valve 41. There is.

On the other hand, on the outer side of the rotary valve 41, a cylindrical spacer 43 is fitted so as to be relatively rotatable. This spacer 43
Is an opening 44 that overlaps with the passage 42 of the rotary valve 41 and allows the passage 42 and the auxiliary intake distribution passage 32 to communicate with each other.
It has a closing portion 45 which overlaps with 42 and closes the passage 42, and the opening timing of the passage 42 of the rotary valve 41 by adjusting the rotation position thereof by the actuator 49, in other words, The opening time of the rotary valve 41 can be increased or decreased.

The control device 27 controls the operation of the phase control device 47 and an actuator 49, which will be described later, based on the engine speed, the load, the atmospheric temperature, the water temperature, the intake pressure, and each control element, and the fuel injection amount and The injection timing is also controlled.

The phase control device 47 and the actuator 49 are connected to the control device.
The relative opening characteristic of the auxiliary intake passage 12 with respect to the main intake passage 11 is set by performing appropriate control based on the control signal from 27, and in particular, in this embodiment, the characteristic is specified as described below. ing.

That is, the main intake passage 11 is opened for a period indicated by an arc L ₁ in FIG. 4 in accordance with the operation of the intake valve 6, and intake is introduced throughout this period. On the other hand, the auxiliary intake passage 12
Is opened for a predetermined period only during the period indicated by the solid line arc L ₂ in FIG. 4, that is, in the middle of the intake stroke of the engine. Further, in this case, if the engine load increases, the required intake air amount increases accordingly, and if the opening time of the auxiliary intake passage 12 is set to the same value, the intake air amount introduced from the auxiliary intake passage 12 at high load, that is, Therefore, the amount of air that directly contributes to the mixture formation is insufficient. Therefore, in this embodiment, in order to compensate for the shortage of the intake air amount due to the increase of the engine load, the operating characteristic of the actuator 49 is set to the spacer 43 to increase the engine load as shown in FIG. with set to such properties may be rotated in a direction to extend the opening time of the rotary valve 41, the opening time of the auxiliary air intake passage 12 with an increase in engine load, the solid line arc L ₂ in Figure 4 range To the range shown by the broken line arc L ₂ ′ in FIG.

The reason for setting the opening timing of the auxiliary intake passage 12 to the middle timing of the intake stroke as described above is as follows.

That is, in terms of realizing stratified combustion, it is effective to maintain the air layer by the air introduced from the auxiliary intake passage 12 as close to the compression top dead center of the piston as will be described later, but in this embodiment, As shown in FIG. 1, the main intake branch passage 31 and the auxiliary intake branch passage of the intake manifold 5
32 are communicated with each other through the merging passage portion 30, and the air of the same pressure is introduced into the main intake passage 11 and the sub intake passage 12, respectively. Therefore, as described above, when the opening timing of the sub intake passage 12 is set to the latter half of the intake stroke from the viewpoint of maintaining the air layer, when the intake air is introduced from the sub intake passage 12, the main intake passage is already in the combustion chamber 3. Since a large amount of air is introduced from 11 and its internal pressure is high, the introduction of air from the sub-intake passage 12 may be hindered, which may adversely affect the realization of stratified charge combustion. As described above, it is set in the middle stage of the intake stroke.

As shown by the chain lines in FIG. 1 and FIG. 2, the main intake branch passage 31 and the sub intake branch passage 32 of the intake manifold 5 are partitioned by a partition wall 57 to make them independent passages. When the supercharger 56 is used to supply the pressurized air to the side of the branch passage 32, the pressure of the air introduced from the side of the auxiliary intake passage 12 is lower than the pressure introduced from the side of the main intake passage 11. Since it is also high, it is possible to set the opening timing of the auxiliary intake passage 12 in the latter half of the intake stroke of the engine as shown by the solid line arc L ₃ in FIG. Also, in this case,
As the engine load increases, it is necessary to accelerate the opening timing of the auxiliary intake passage 12 to compensate for the shortage of the intake amount when the engine load increases. It is conceivable to change the rotational phase between the rotary valve 41 and the rotary valve 41.

In FIGS. 1 and 2, reference numeral 8 is an injector, which is inclined so that fuel can be injected toward the center of the combustion chamber 3. Further, reference numeral 9 is a spark plug, and this spark plug 9 is the injector 8 described above.
On the other hand, it is arranged so as to be located on the downstream side of the swirl flow (arrow A ₁ ).

(II: Operation and Its Action) Next, the operation of this engine and its action will be briefly described.

When the engine is operated, the negative pressure of the intake air that accompanies the downward movement of the piston 4 causes the main intake passage 11 and the auxiliary intake passage 2 to enter the combustion chamber 3.
Air is introduced from both. In that case, the air introduced from the main intake passage 11 becomes a swirl flow that swirls down along the outer peripheral portion of the combustion chamber 3 as shown by an arrow A ₁ in FIGS. 1 and 2, respectively. First air layer 51 (boundary line 1) having a strong swirl
Outer part). On the other hand, the air introduced from the auxiliary intake passage 12 becomes an air flow that flows down in the central portion of the combustion chamber 3 in the piston axial direction as shown by an arrow A ₂ , but has a strong swirl on the outer peripheral portion of the combustion chamber 3. First with flow
Since there is an air layer 51 of the first air layer 51, the stagnation in the central portion of the first air layer 51 results
To form an air layer 52. That is, in the combustion chamber 3, there are two air layers 51 and 52 having different flow characteristics.

The fuel is injected from the injector 8 into the second air layer 52 of the two air layers 51, 52 in the combustion chamber 3 in the vicinity of the compression top dead center of the piston. An air-fuel mixture layer is locally formed in the air-fuel mixture, and ignition / combustion occurs in this air-fuel mixture layer to realize stratified combustion. Incidentally, this stratified charge combustion is performed throughout the entire operating range of the engine, but its effect is most noticeable especially in the low load operating range where ignition failure is likely to occur due to the over lean phenomenon of the air-fuel mixture, and the combustion improvement of the engine or It contributes to the improvement of exhaust emission.

By the way, in order to perform the stratified charge combustion more favorably and surely, the first air layer 51 and the second air layer 52 in the combustion chamber 3 near the compression top dead center that most affects the combustion. Is required to be maintained while maintaining a good stratified state. In this embodiment, as a first means, the first air having a strong swirl on the outer peripheral portion of the combustion chamber 3 is used as described above. A layer 51, and an air layer having a flow characteristic different from that of the first air layer 51 inside the first air layer 51, specifically, having a flow in the piston axial direction and finally stagnant. The existing second air layer 52 is formed, and the separation state resulting from the difference in the flow characteristics between the two layers is utilized to maintain the stratified state of the air layer. In addition to this, as a second means, the rotary valve 41 controls the opening and closing of the auxiliary intake passage 12 to supply the second air layer 52 that directly contributes to the formation of the air-fuel mixture in the middle to the latter half of the intake stroke. By this, the time from the formation of the second air layer 52 to the compression top dead center of the piston is shortened as much as possible, and the stratified state of the second air layer 52 is the As much as possible, it is prevented from being damped or destroyed by the disturbing action.

By the mutual function of these two means, the stratified state of the first air layer 51 and the second air layer 52 in the combustion chamber 3 is maintained in a better state up to near the compression top dead center,
As a result, a higher level of stratified combustion can be reliably realized even under the required conditions such as when the engine is under low load operation.

In the above embodiment, the rotary valve 41 is provided in the sub intake passage 32 of the intake manifold 5 communicating with the sub intake passage 12 as a means for adjusting the volume of the second air layer 52 according to the engine load. , The rotational phase difference between the rotary valve 41 and the crankshaft or the rotary valve 41
Although the phase difference between the spacer 43 and the rotary valve 41 fitted on the outer side of is adjusted respectively, this is not limited to the present invention.For example, the auxiliary intake passage 12 is always an open passage. , The strength of the swirl caused by the air introduced from the main intake passage 11 side is adjusted, and the first air layer 51 and the second air layer 51
It is also possible to adjust the volume of the second air layer 52 by utilizing the difference in kinetic energy from the air layer 5 of FIG.

Further, in the above embodiment, the air layer 52 of FIG. 2 is constituted by an air flow having a flow in the piston axial direction, but the present invention is not limited to this, and in the sense of separation of the air layer. If the flow characteristics of the two layers in contact with each other are different, the purpose can be achieved. For example, the air introduced from the sub intake passage 12 is swirled by the air introduced from the main intake passage 11. A swirl flow having a swirl in the opposite direction may be used.

(Effects of the Invention) In the stratified combustion engine of the present invention, the main intake passage for supplying air so as to generate a swirl flow in the outer peripheral portion of the combustion chamber, and the swirl flow in the central portion of the combustion chamber in the flow direction. And an auxiliary air intake passage for supplying air so as to generate different air flows, and further, at least in a low load operation region of the engine, intake air is introduced from both the main air intake passage and the auxiliary air intake passage so that the combustion chamber It is possible to form a first air layer by the air introduced through the main intake passage in the outer peripheral portion and a second air layer by the air introduced through the auxiliary intake passage in the central portion of the combustion chamber. In addition, the intake control means is adapted to allow the introduction of the intake air through the auxiliary intake passage at a time after the middle stage of the intake stroke, and the fuel is supplied toward the second air layer. A fuel supply means is provided.

Therefore, according to the stratified combustion engine of the present invention, (1) since the flow characteristics of the first air layer and the second air layer formed in the combustion chamber in the intake stroke are different, It is easy to maintain. (2) The second air layer that contributes to combustion is formed in the middle of the intake stroke to the latter half of the intake stroke. In the second air layer in which the stratified state is maintained relatively well, because the period from the formation of the layer to the compression top dead center is short and the attenuation or destruction of the second air layer during the compression stroke is small. Since the fuel is supplied toward, the effect that the stratified combustion in the combustion chamber is effectively achieved is obtained.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a main part of a stratified charge combustion engine according to an embodiment of the present invention, FIG. 2 is a lateral sectional view taken along the line II-II of FIG. 1, and FIG. 3 is an enlarged view of the rotary valve shown in FIG. FIG. 4 is an operation characteristic diagram of the main intake passage and the auxiliary intake passage, and FIG. 5 is an operation characteristic diagram of the rotary valve shown in FIG. 1 ... Cylinder block 2 ... Cylinder head 3 ... Combustion chamber 4 ... Piston 5 ... Intake manifold 6 ... Intake valve 7 ... Exhaust valve 8 ... Injector 9 ... Spark plug 11 ... Main intake passage 12 ...... Sub intake passage 13 ...... Main intake port 14 ...... Sub intake port 15 ...... Exhaust passage 41 ...... Rotary valve 43 ...... Spacer 51 ...... First air layer 52 ...... Second air layer

Claims (1)

[Claims] 1. A main intake passage for supplying air so as to generate a swirl flow in an outer peripheral portion of a combustion chamber, and an air flow having a flow direction different from that of the swirl flow in a central portion of the combustion chamber. An auxiliary air intake passage for supplying air, and at least in a low load operation region of the engine, intake air is introduced from both the main intake air passage and the auxiliary intake air passage to the outer peripheral portion of the combustion chamber through the main intake air passage. And a second air layer formed by the air introduced through the sub-intake passage in the central portion of the combustion chamber, and a second air layer formed by the air introduced through the sub-intake passage. Stratification comprising intake control means capable of performing all the intake introduction after the middle stage of the intake stroke, and fuel supply means adapted to supply the fuel toward the second air layer. Burn engine.