JP2003214168A - Intake device in internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the ignition and combustion characteristics, and to prevent the knocking by applying the tumble flow and the swirl flow to the intake into a cylinder 2. <P>SOLUTION: The tumble flow is applied in a first half period L1 of an open period L of an intake valve 13 to the cylinder 2, and the swirl flow is applied to a second half period L2 of the open period L of the intake valve 13. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a four-cycle internal combustion engine and an intake system for the internal combustion engine.

[0002]

2. Description of the Related Art In order to promote combustion in the combustion chamber at the top of a cylinder, it is effective to give a flow to a mixture of air and fuel. As a means for flowing the mixture, the mixture is introduced into the cylinder. It is known to generate a swirl flow that swirls in the cylinder in the circumferential direction and a tumble flow that swirls in the cylinder in the axial direction at the time of intake.

These two types of bulk flow have a major role of giving turbulent energy in the process of forming the air-fuel mixture and the combustion process after that, but microscopically, they have both roles. It also has features. For example, according to the former swirl flow as the flow state, a strong flow state can be obtained in the outer peripheral portion of the combustion chamber, while according to the latter tumble flow, the strong flow state can be obtained in the substantially central portion of the combustion chamber. It has the characteristics of flow that can be obtained.

Further, the flow velocities in the swirl flow and the tumble flow increase in proportion to the load and the rotational speed of the internal combustion engine, that is, the intake air amount.

Japanese Unexamined Patent Publication No. 8-61072, which is a prior art, discloses the former swirl flow system for intake air into a cylinder in a low load / low rotation operating range where the intake air amount is small depending on the operating state of the internal combustion engine. In addition, it is proposed to switch to the latter tumble flow system in the high load / high rotation operating range where the intake air amount is large.

[0006]

However, in an operating range where the intake air amount is small, such as when the load is low or the rotation speed is low, the swirl flow is closer to the center of the combustion chamber where the ignition and combustion of the air-fuel mixture first starts. Also, since a predetermined flow state cannot be obtained in the substantially central portion of the combustion chamber by flowing in the outer circumferential direction, there is a problem that rapid ignition / combustion cannot be achieved.

Further, in an operating region where the intake air amount is large, such as high load or high rotation, the tumble flow having a high flow velocity concentrates in the substantially central portion of the combustion chamber, so that the flow state of the intake air in the combustion chamber. However, the air-fuel ratio of the air-fuel mixture in the outer portion is likely to be extremely non-uniform because it is extremely strong in the substantially central portion of the combustion chamber and sharply weakens in the outer portion. Therefore, there is a problem in that the tumble flow alone may increase knocking probability and the compression ratio cannot be increased.

It is a technical object of the present invention to provide an intake system that solves the above problems by using a swirl flow system and a tumble flow system together in one intake stroke.

[0009]

In order to achieve this technical object, the first aspect of the present invention is that "the intake port with the intake valve to the combustion chamber at the top of the cylinder is connected to the intake air flowing into the cylinder. A tumble port that imparts a tumble flow that swirls in the axial direction and a swirl port that imparts a swirl flow that swirls in the circumferential direction of the cylinder to the intake air that flows into the cylinder are configured, and It is switched so as to inhale from the tumble port in the first half of the period and inhale from the swirl port in the latter half of the opening period of the intake valve. "

According to a second aspect of the present invention, "a ceiling surface of an intake port with an intake valve to the combustion chamber at the top of the cylinder is directed to the intake air flowing into the cylinder along the ceiling surface in the axial direction of the cylinder. While providing a tumble flow that swirls to the bottom, the bottom surface of the intake port is configured to give a swirl flow that swirls in the circumferential direction of the cylinder to the intake air flowing into the cylinder along the bottom surface, ,
Intake air into the cylinder in the intake port is made to follow the ceiling surface in the first half of the opening period of the intake valve and to follow the bottom surface in the latter half of the opening period of the intake valve. The switching valve is installed. It is characterized by

Furthermore, a third aspect of the present invention is characterized in that, in the second aspect, the switching valve is a rotary type switching valve that rotates in synchronization with the crankshaft. There is.

[0012]

In the first aspect of the present invention, the tumble flow is formed in the cylinder by introducing the intake air from the tumble port in the first half of the stroke of the opening period of the intake valve. By introducing intake air from the swirl port in the latter half of the opening period of the intake valve, a swirl flow is formed to surround the tumble flow.

That is, in the cylinder, a tumble flow can be preformed in the central portion thereof, and then a swirl flow can be formed so as to surround the outside of the tumble flow.
Then, in this flow state, by being compressed toward the combustion chamber in the compression stroke due to the upward movement of the piston,
In addition to the crushing of most of the tumble flow, the swirl flow also crushes to a certain degree to become micro-turbulence.

As described above, most of the tumble flow is crushed to become microturbulence, but a certain swirl flow swirls the outer peripheral portion of the combustion chamber in the circumferential direction and the end gas of the combustion chamber is discharged. It forms a role of preventing the knocking induction caused by it. Of course, the swirl flow in the outer peripheral portion of the combustion chamber also serves to prevent knocking, but is eventually crushed to become micro-turbulence and also serves to achieve normal combustion.

Thus, the fluid state based on the tumble flow is ensured in the substantially central portion of the combustion chamber, and the fluid state based on the swirl flow is ensured in the outer portion of the combustion chamber in the substantially central portion. Therefore, it is possible to simultaneously achieve reliable ignition / combustion in a low load and / or low rotation operation range and reliable knock suppression in a high load and / or high rotation operation range, and to reduce exhaust gas pollution. And an effect of reducing fuel consumption can be achieved.

According to the second aspect of the invention, the generation of the tumble flow and the subsequent generation of the swirl flow can be realized by the same intake port without using separate ports. Therefore, a great simplification of the structure can be achieved.

Further, according to the third aspect of the present invention, during the intake stroke, the switching from the tumble flow to the swirl flow can be performed smoothly in a timely manner and reliably in synchronization with the rotation of the crankshaft. , The durability can be improved.

Moreover, according to the rotary type switching valve in the third aspect, the passage can be substantially closed at the time of the switching, so that the tumble flow and the swirl flow can be independently formed, and the flow There is an advantage that the stratification of can be surely achieved.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1, FIG. 2 and FIG. 3 show the first embodiment.

In the figure, reference numeral 1 denotes a cylinder block in a four-cycle internal combustion engine, and a cylinder 2 provided in the cylinder block 1 is provided with a piston 3 which reciprocates in conjunction with a crankshaft (not shown). Built-in.

Reference numeral 4 denotes a cylinder head which is fastened to the upper surface of the cylinder block 1 so as to close the top of the cylinder 2. The cylinder head 4 has a combustion chamber 5 on the lower surface of the cylinder head 4. The spark plug 6 is attached to a substantially central portion of the combustion chamber 5 in plan view, and the exhaust valve 7 is provided.
There are two exhaust ports 8 provided with.

The cylinder head 4 is provided with one intake port 9 and two ports 10 and 11 branching from the intake port 9.
As shown in FIG. 3, the opening into the combustion 5 at 11 is synchronized with the rotation of the crankshaft from a proper timing C before the top dead center (crank angle of 0 degree) in the intake stroke. Each intake valve 13 is provided so as to open a period L until a proper time D after a dead point (180 degrees in crank angle).

Then, one of the ports 10 and 11 is projected in a side view so as to open obliquely downward with respect to the cylinder 2 at a portion near the center of the combustion chamber 5 in plan view. By being curved into a mold, a tumble port that gives a tumble flow that swirls in the axial direction of the cylinder 2 to the intake air from the one port 10 into the cylinder 2 is formed, as shown by the solid arrow A in FIG. On the other hand, the other port 11 of the both ports 10 and 11
By arranging so as to extend tangentially to the cylinder 2 in a plan view, the other port 1
The swirl port is configured to give a swirl flow that swirls in the circumferential direction of the cylinder 2 to the intake air from 1 to the cylinder 2 as shown by the double-dashed line arrow B in FIGS. 1 and 2.

Further, a switching valve 14 is provided at a branch portion from the intake port 9 to both the ports 10 and 11, and the switching valve 14 is controlled by an actuator 15 which synchronizes with the rotation of the crankshaft. The intake port 9 is communicated with the one port (tumble port) 10 in the first half period L1 of the open period L of 13 and the intake port 9 is opened in the latter half period L2 of the open period L of the intake valve 13. The switching operation is performed so as to communicate with the other port (swirl port) 11.

In this structure, the intake of air into the cylinder 2 starts when the intake valve 13 opens and ends when the intake valve 13 closes.

In this case, the intake air into the cylinder 2 is
During the first half period L1 of the open period L of the intake valve 13, one port (tumble port) is operated by the switching valve 14.
By being introduced from 10, a tumble flow is formed in the cylinder 2 as shown by a solid arrow A in FIG.
Next, during the latter half timing L2 of the opening period L of the intake valve 13, the switching valve 14 introduces it from the other port (swirl port) 11, thereby making it possible to perform the operation shown in FIGS.
As indicated by the two-dot chain line arrow B, a swirl flow is formed so as to surround the tumble flow.

As a result, a tumble flow indicated by a solid arrow A is formed in the center of the cylinder 2 in advance, and then a swirl flow indicated by a two-dot chain line arrow B surrounds the outside of the tumble flow. In this flow state, the tumble flow is crushed mainly in the substantially central portion of the combustion chamber 5 by being compressed toward the combustion chamber 5 in the compression stroke due to the upward movement of the piston 3. On the other hand, while becoming a micro turbulence, a certain proportion, that is, a part of the swirl flow flows so as to swirl around the outer peripheral portion of the combustion chamber 5 in the circumferential direction, and thus a substantially central portion of the combustion chamber 5 is formed. The flow state based on the tumble flow can be reliably given to a portion outside the substantially central portion in the combustion chamber 5 based on the swirl flow, and Combustion is initiated by the ignition by the spark of the ignition plug 6 which is provided in a portion of the approximate center of the baking chamber 5.

Further, in the compression ignition type internal combustion engine,
Ignition and combustion are started by fuel injection from a fuel injection valve provided in place of the spark plug 6 instead.

In this case, the swirl flow that swirls the outer peripheral portion of the combustion chamber 5 in the circumferential direction promotes the mixing of the fuel of the end gas and the air in the combustion chamber 5, and the swirl flow of the spark ignition type internal combustion engine. In addition to preventing abnormal combustion by knocking, it also functions to prevent soot generation by normal combustion.

Next, FIGS. 4, 5 and 6 show a second embodiment.

In this figure, reference numeral 21 denotes a cylinder block in a four-cycle internal combustion engine, and a cylinder 22 provided in this cylinder block 21 is provided with a piston 23 which reciprocates in conjunction with a crankshaft (not shown). Built-in.

Reference numeral 24 denotes a cylinder head which is fastened to the upper surface of the cylinder block 21 so as to close the top of the cylinder 22, and the cylinder head 24 has:
A combustion chamber 25 is formed on the lower surface of the combustion chamber 25 so as to be open at the top of the cylinder 22, a spark plug 26 is attached to the combustion chamber 25 at a substantially central portion in plan view, and an exhaust valve 27 is further provided. An exhaust port 28 is provided.

An intake port 29 to the combustion chamber 25 is provided in the cylinder head 24, and an opening of the intake port 29 into the combustion 25 is synchronized with the rotation of the crankshaft. As shown in FIG. 6, a period L'from an appropriate time C'before the top dead center (0 degrees at the crank angle) to an appropriate time D'after the bottom dead center (180 degrees at the crank angle) in the intake stroke. Intake valve 30 designed to open
Are provided respectively.

The intake port 29 is arranged so as to extend tangentially to the cylinder 22 in a plan view, and the bottom surface 29a in the intake port 29 is arranged.
Is applied to the intake air flowing into the cylinder 22 along the bottom surface 29a, as shown by an alternate long and two short dashes line arrow B'in FIGS. 4 and 5, in the circumferential direction of the cylinder 22. On the other hand, the ceiling surface 29b in the intake port 29 is connected to the intake air flowing into the cylinder 22 along the ceiling surface 29b by a solid arrow A'in FIG.
As shown by, the configuration is such that a tumble flow that swirls in the axial direction of the cylinder 22 is applied.

Further, in the intake port 29, there is provided a rotary switching valve 31 which rotates at a half speed in synchronization with the rotation of the crankshaft, the axis of which is the intake port 29.
Is provided such that the outer peripheral surface 31a extends in a direction traversing and the outer peripheral surface 31a is in contact with or close to the bottom surface 29a in the intake port 29. By providing the valve passage 32 in which a half portion is cut out, intake air from the intake port 29 is supplied to the rotary switching valve 3
In the first half period L1 ′ of the opening period L ′ of the intake valve 30 by the rotation of 1, the intake port 2 passes through the valve passage 32 of the switching valve 31 as shown by the solid arrow A ″ in FIG.
9 along the ceiling surface 29b, and the intake valve 3
In the latter half period L2 ′ of the open period L ′ of 0, as shown by the two-dot chain line arrow B ″ in FIG. 6, the bottom surface 29a in the intake port 29 passes through the valve passage 32 of the switching valve 31.
The configuration is such that the switching operation is performed so as to flow along the line.

In addition, between the rotary switching valve 31 and the power transmission wheel 33 corresponding thereto, the phase changing means 34 for advancing or retarding the phase of the switching valve 31 with respect to the phase of the crankshaft. Is provided. In addition,
As the phase changing means 34, for example, Japanese Patent Application Laid-Open No. 4-1
A conventionally known hydraulic valve timing mechanism described in JP-A-09007, JP-A-8-210158 and JP-A-8-218823 is used.

In this structure, the intake of air into the cylinder 22 starts when the intake valve 30 opens and ends when the intake valve 30 closes.

In this case, the intake air into the cylinder 22 is the first half period L of the open period L'of the intake valve 30.
In FIG. 1, the switching valve 31 is introduced so as to flow along the ceiling surface 29b in the intake port 29, so that the tumble flow is introduced into the cylinder 2 as shown by the solid arrow A'in FIG. 4 and FIG. 5 by being introduced so as to flow along the bottom surface 29a in the intake port 29 in the latter half timing L2 ′ of the opening period L ′ of the intake valve 30. A swirl flow is formed so as to surround the tumble flow as indicated by a chain line arrow B '.

As a result, a tumble flow indicated by a solid arrow A'is formed in the center of the cylinder 22 in advance, and then a swirl flow indicated by a chain double-dashed arrow B'is applied outside the tumble flow. Can be formed to surround,
In this flow state, by being compressed toward the combustion chamber 25 in the compression stroke due to the upward movement of the piston 23,
The tumble flow is crushed mainly in the combustion chamber 25 at a substantially central portion to become microturbulence, while a certain proportion of the swirl flow swirls the end gas in the combustion chamber 25.
The flow state based on the tumble flow is surely applied to a substantially central portion of the combustion chamber 25, and the flow state based on the swirl flow is reliably applied to a portion of the combustion chamber 25 outside the substantially central portion. Then, the ignition is started by the spark of the spark plug 26 provided at the substantially central portion of the combustion chamber 25, and the combustion is started.

Further, in the compression ignition type internal combustion engine,
Ignition and combustion are started by fuel injection from a fuel injection valve provided in place of the spark plug 26 instead.

Furthermore, by advancing or retarding the phase of the switching valve 31 with respect to the crankshaft by the phase varying means 34, the period for generating the tumble flow in the open period L of the intake valve 30 is shortened to generate the swirl flow. Change the period to be longer or open period L of intake valve 30
Of these, the period for generating the tumble flow can be arbitrarily changed to be long and the period for generating the swirl flow can be shortened.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional front view showing a first embodiment of the present invention.

FIG. 2 is a sectional plan view taken along the line II-II of FIG.

FIG. 3 is a diagram showing a process in the first embodiment.

FIG. 4 is a vertical cross-sectional front view showing a second embodiment of the present invention.

5 is a plan sectional view taken along line VV of FIG.

FIG. 6 is a diagram showing a stroke in the second embodiment.

[Explanation of symbols]

1,21 cylinder block 2,22 cylinders 3,23 piston 9,29 intake port 13,30 intake valve 10 tumble ports 11 swirl port 14 Switching valve 29a Bottom surface in intake port 29b Ceiling surface inside the intake port 31 Rotary switching valve

Claims (3)

[Claims] 1. A tumble port for imparting a tumble flow swirling in the axial direction of the cylinder to an intake port with an intake valve to the combustion chamber at the top of the cylinder, and an intake air flowing into the cylinder. And a swirl port that imparts a swirl flow that swirls in the circumferential direction of the cylinder to the intake valve, inhaling air from the tumble port in the first half of the opening period of the intake valve and in the latter half of the opening period of the intake valve. An intake system for an internal combustion engine, wherein the intake system is switched to intake air from the swirl port at a certain time. 2. A form in which a tumble flow swirling in the axial direction of the cylinder is applied to the intake air flowing into the cylinder along the ceiling surface in the intake port with an intake valve to the combustion chamber at the top of the cylinder. On the other hand, the bottom surface of the intake port is configured to give a swirl flow that swirls in the circumferential direction of the cylinder to the intake air flowing into the cylinder along the bottom surface. A switching valve is provided so that the intake air to the intake valve follows the ceiling surface in the first half of the opening period of the intake valve and follows the bottom surface in the latter half of the opening period of the intake valve. An intake system for an internal combustion engine, characterized by: 3. The intake system for an internal combustion engine according to claim 2, wherein the switching valve is a rotary switching valve that rotates in synchronization with a crankshaft.