JPH0814053A - Method and device for controlling intake air for engine - Google Patents

Abstract

PURPOSE:To reduce the generation of a toxic component in exhaust gas through combustion of lean air-fuel mixture at high combustion efficiency and to provide low fuel consumption properties by dividing an intake passage into an intake passage for feeding fuel air-fuel mixture having an opening part formed closer to the center of a cylinder and an intake passage for feeding air having an opening part formed closer to the outer periphery of the cylinder. CONSTITUTION:The opening part 2a of a first intake passage 2A through which air-fuel mixture is introduced is formed closer to a center in which the ignition plug 6 of a cylinder 1 is positioned. Thus, the flow of air-fuel mixture in a combustion chamber is surrounded with a flow S2 of outside air introduced through a second intake passage 2B and swirls in such a state to be confined in the vicinity of the center of the combustion chamber. At the compression process of an engine, compression is effected by a rising piston as the more rich state of fuel than that of the flow S2 of outside air is held. Air-fuel mixture is momentarily burnt through ignition by an ignition plug 6 and flame is spread over the whole of the combustion chamber. Thereby, even when air-fuel mixture being more lean than a theoretical air ratio is used, the air-fuel mixture is momentarily burnt and high combustion efficiency is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly relates to an intake control method and an intake control device applicable to a two-valve type small engine having one intake valve and one exhaust valve.

[0002]

2. Description of the Related Art Conventionally, there is known an intake system structure of an engine which burns fuel leaner than a stoichiometric air-fuel ratio with high combustion efficiency to obtain high output and low fuel consumption (for example, JP-A-5-99101). Issue). The intake system structure of this engine is a 5-valve type engine having three intake valves and two exhaust valves, and the intake ports that communicate with the three intake valves are connected to the intake ports vertically Are formed independently of each other so as to form a longitudinal vortex laminar flow, and intake air-fuel mixture from the central intake port near the spark plug and air from both intake ports. . Therefore, in the combustion chamber,
Since the longitudinal vortexes of air on both sides flow while forming a three-layered longitudinal vortex with the longitudinal vortex of the air-fuel mixture sandwiched therebetween, the air-fuel mixture in the center is compressed and ignited while maintaining a high mixing ratio. This allows
Although the entire air-fuel mixture including the air sucked from the intake ports on both sides is lean, the combustion efficiency is high, and the fuel consumption rate is low by using this lean air-fuel mixture.

[0003]

However, the above-described intake system structure of the engine is intended to form a three-layered longitudinal vortex laminar flow in the combustion chamber, and therefore has a relatively large size with three intake valves. However, it is not suitable for a small engine having one intake valve and one exhaust valve, and even if it is applied, the expected effect cannot be expected. Further, in order to form a longitudinal vortex of the air-fuel mixture and air, the intake ports communicating with each intake valve are formed in an inverted triangular shape in cross section and are attached at an angle, which complicates the configuration.

Therefore, the present invention burns a lean air-fuel mixture with high combustion efficiency to reduce harmful components in exhaust gas and reduce fuel consumption even in a small engine having one intake valve and one exhaust valve, for example. It is an object of the present invention to provide an intake control method and an intake control device for an engine, which can obtain the desired characteristics.

[0005]

In order to achieve the above object, an engine intake control method according to a first aspect of the present invention provides an intake passage for introducing intake air into a combustion chamber in a cylinder. A first intake passage having an opening near the center and a second intake passage having an opening closer to the outer periphery of the cylinder than the first intake passage are divided to supply fuel to the first intake passage. The opening degrees of the second intake passage and the first intake passage are set so that the air flow rate ratio between the second intake passage and the first intake passage is larger when the engine load is low than when it is high load. 2 The opening degree of the intake passage is controlled.

An engine intake control device according to a second aspect of the present invention is an intake passage which is divided into a first intake passage and a second intake passage, and which introduces intake air into a combustion chamber in a cylinder.
A single intake valve that opens and closes each opening of the first and second intake passages to the combustion chamber, wherein the opening of the first intake passage is of a cylinder larger than the opening of the second intake passage. A fuel supply unit located near the center, which supplies fuel to the first intake passage, a first throttle valve that throttles the first intake passage, and a second throttle valve that throttles the second intake passage. A valve opening control means for controlling the opening of the second throttle valve so that the air flow rate ratio between the second intake passage and the first intake passage becomes larger when the engine load is low than when it is high load. Is equipped with.

In the intake control device for an engine according to a third aspect, the first throttle valve and the second throttle valve according to the second aspect are connected by a link mechanism.

According to a fourth aspect of the present invention, there is provided an intake control system for an engine, wherein the valve opening control means according to the second aspect controls the valve drive machine for driving the second throttle valve and the valve drive machine based on the load of the engine. And a driving machine control means for controlling.

Further, according to a fifth aspect of the present invention, there is provided an intake control device for an engine, wherein an intake passage for introducing intake air into a combustion chamber in a cylinder while rotating the cylinder in a constant swirling direction around a center of the cylinder, and a top portion of a piston. And a protrusion that pushes out the intake air in the combustion chamber near the top dead center of the piston to generate a squish flow in the direction opposite to the swirling direction.

According to a sixth aspect of the present invention, in addition to the structure of the fifth aspect, the engine intake control device further faces the cylinder head and is pushed out by the front face of the protrusion, which is located on the front side in the turning direction. A suppression portion that suppresses the squish flow is formed.

[0011]

According to the invention of claim 1 or 2, in the intake stroke of the engine, the fuel mixture is supplied to the combustion chamber through the first intake passage and the second intake passage is supplied into the combustion chamber. Through which air is supplied.
Here, the first intake passage has an opening near the center of the cylinder, the second intake passage has an opening near the outside of the first intake passage, and the first intake passage and the second intake passage Since there is a difference in each air flow rate, a spiral swirl flow is generated in the combustion chamber, in which the air-fuel mixture and the air form two layers and swirl in the lateral direction toward the lower side.

The opening of the first intake passage is controlled by the operation of the first throttle valve which is interlocked with the operation of the throttle lever.
The second throttle valve for controlling the opening degree of the intake passage is controlled by the valve opening control means so that the air flow rate ratio between the second intake passage and the first intake passage becomes larger when the engine load is low than when it is high load. Is activated. For example, when the engine has a high load, the air flow rates of both intake passages are substantially the same, and when the engine has a low load, the air flow rate of the second intake passage is controlled to be larger than the air flow rate of the first intake passage. Therefore, when the engine load is low, the flow velocity of the air from the second intake passage becomes larger than the flow velocity of the air-fuel mixture from the first intake passage, and the swirl flow is strengthened.

Since the first intake passage for introducing the air-fuel mixture into the combustion chamber has an opening near the center of the cylinder where the spark plug is located, the air-fuel mixture sucked into the combustion chamber is
Due to the generation of the two-layered swirl flow described above, the engine swirls in a state of being confined near the center of the cylinder, and in the compression stroke of the engine, the fuel is compressed while maintaining a state in which the fuel is richer than the swirl flow of the outside air. Since the air-fuel mixture in this state is ignited, that is, ignited in a state close to the stoichiometric air-fuel ratio, high combustion efficiency can be obtained. In addition, the air-fuel mixture that is leaner than the stoichiometric air-fuel ratio is used as a whole together with the air introduced from the second intake passage, and low fuel consumption can be realized.

In addition, when the engine is under a low load where the combustion efficiency tends to decrease, the swirl flow is strengthened to increase the combustion speed and prevent the combustion efficiency from decreasing as described above. As described above, since the lean mixture as a whole can be burned with high combustion efficiency even when the engine load is low, harmful components in the exhaust gas can be reduced. Further, since the opening degrees of both intake passages are differentially controlled according to the load of the engine to control the air flow ratio of both intake passages, there is an advantage that the air-fuel ratio of the air-fuel mixture can be widely controlled.

Further, since the intake passage for introducing intake air into the combustion chamber in the cylinder is divided to provide the first intake passage and the second intake passage, the intake valves form a pair of first and first intake passages. Two
Only one needs to be provided for the intake passage. Therefore, for example, when applied to a small engine having one intake valve and one exhaust valve, effects such as high combustion efficiency, low fuel consumption, and reduction of harmful components in exhaust gas can be obtained.

According to the third aspect of the invention, the opening of the first throttle valve is controlled by the throttle lever, and the second throttle valve mechanically connected to the first throttle valve by the link mechanism is the second throttle valve. The opening degree is controlled in conjunction with the first intake passage so that the air flow rate ratio between the intake passage and the first intake passage is greater when the engine load is low than when it is high load. Therefore, it can be easily put to practical use in a small engine equipped with a carburetor.

According to the invention of claim 4, the driving machine control means detects the load of the engine on the basis of the air flow rate of the first intake passage sensed by an air flow meter or the like, and based on the detected air flow rate of the motor, The opening degree of the second throttle valve is controlled through such a valve driving machine. Therefore, by setting the opening degree of the second throttle valve to be larger than the opening degree of the first throttle valve in the driving machine control means when the engine load is low, even in a small engine of the electronic fuel control system. It can be put to practical use easily.

According to the fifth aspect of the invention, in the intake stroke of the engine, intake air is introduced into the combustion chamber of the cylinder from the intake passage so as to swirl in a constant swirling direction around the center of the cylinder. Next, when the piston rises near the top dead center in the compression stroke of the engine, the intake air (swirl flow) that swirls in a certain swirling direction hits a protrusion formed on the top of the piston and is pushed out, and the swirling direction is reversed. A squish flow in the direction is generated. As a result, a large number of minute vortices of intake air are generated, which is advantageous for ignition and flame propagation. Immediately thereafter, the ignition plug ignites the flame, and the flame resulting from the ignition instantly spreads throughout the combustion chamber due to the presence of many minute vortexes, and the combustion efficiency is improved.

According to the invention of claim 6, the suppressing portion formed on the cylinder head so as to face the front surface of the protrusion of the piston which is located on the front side in the swirling direction of the intake air, the intake air is pushed out to the front surface of the protrusion, The generation of a squish flow in the same direction as the swirling direction is suppressed, the strength of the squish flow in the opposite direction is maintained high, and the generation of a minute vortex flow is promoted. Therefore, the combustion efficiency is further improved.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic plan view showing a part of an embodiment of the present invention in a cutaway manner, and FIG. 2 is a side view showing a part thereof in a cutaway manner.

In this embodiment, a small engine in which one intake pipe 2 and one exhaust pipe 3 are connected to the cylinder 1 is illustrated. As shown in FIG. 1, the intake passage 2 for introducing intake air into the combustion chamber 1a in the cylinder 1 is divided into a first intake passage 2A and a second intake passage 2B by a partition wall 2C.
The passage areas (cross-sectional areas) of both intake passages 2A and 2B are set to be substantially the same in this embodiment, but may be set to be different.

The openings 2a, 2b of the intake passages 2A, 2B to the combustion chamber 1a are opened and closed by a single intake valve 4, as shown in FIG. The partition wall 2C is a carburetor 7 which will be described later.
To the openings 2a and 2b, the valve stem 4a of the intake valve 4 is set to penetrate the partition wall 2C. The opening 3 a of the exhaust pipe 3 to the combustion chamber 1 a is also opened / closed by the single exhaust valve 5. As shown in FIG. 1, the opening 2a of the first intake passage 2A of the intake pipe 2 is located closer to the center of the cylinder 1 where the spark plug 6 is provided than the opening 2b of the second intake passage 2B. There is.

Air is introduced into the intake pipe 2 via an air cleaner A / C. The carburetor 7 is installed in the first intake passage 2A.
Is provided. In the carburetor 7, fuel is supplied from the fuel injection nozzle 8 shown as an example of fuel supply means to the first intake passage 2A due to the pressure difference of the intake air flow, and is mixed with air at a ratio close to the stoichiometric air-fuel ratio. Only air is supplied to the second intake passage 2B via the air cleaner A / C. The flow rate of the air-fuel mixture supplied from the first intake passage 2A to the combustion chamber 1a is controlled by the opening degree of the first throttle valve 9 provided in the first intake passage 2A, and from the second intake passage 2B to the combustion chamber 1a. The flow rate of the supplied air is controlled by the opening degree of the second throttle valve 10 provided in the second intake passage 2B. The opening of the first throttle valve 9 is controlled in conjunction with the operation of a throttle lever (not shown), for example. On the other hand, the second throttle valve 10
Is controlled to a predetermined opening corresponding to the opening of the first throttle valve 9 by the valve opening control means described later.

The first throttle valve 9 and the second throttle valve 10 are the link mechanism 11 shown in FIG. 3 as an example of the valve opening control means.
Are interconnected by. A cam 13 is fixed to a support shaft 12 that supports the first throttle valve 9 so as to rotate integrally. On the other hand, a pinion 15 is fixed to a support shaft 14 that supports the second throttle valve 10 so as to rotate integrally. The rack 16 meshed with the pinion 14 has a spring 17
By the cam follower pin 1 that is urged in the direction from one end to the cam 13 and protrudes from the other end of the rack 17.
8 is pressed against the cam surface 13 a of the cam 13.

In the above link mechanism, for example, the opening of the throttle lever is proportional to the load of the engine,
The first throttle valve 9 that operates in conjunction with this throttle lever
Is controlled so that the opening degree increases in proportion to the increase in engine load, as indicated by the characteristic curve indicated by A in FIG. The amount of fuel injected from the fuel injection nozzle 8 is
It is automatically determined based on the opening degree of the throttle valve 9. The cam follower pin 18 makes sliding contact with the cam surface 13a of the cam 13 that rotates integrally with the first throttle valve 9, the rack 16 is moved in the direction of the arrow in FIG. 3, and the second gear is passed through the pinion gear 15 meshing with the rack 16. The opening degree of the throttle valve 10 is controlled.

That is, the second throttle valve 10 is operated when the engine is under a load of 1/4 to 3/4 lower than the full load (4/4) as shown by the characteristic curve B in FIG. The opening degree (+ 20%) is controlled to be larger than the throttle valve 9 of No. 1 by a substantially constant amount. In this embodiment, since the passage areas of both the intake passages 2A and 2B are set to be substantially the same, the opening ratio B / A
Is approximately equal to the air flow rate ratio between the second intake passage 2B and the first intake passage 2A. The second throttle valve 10 which is interlocked with the first throttle valve 9
The control of the opening degree B of is set by the cam profile of the cam surface 13a of the cam 13. When the engine load is near zero, the amount of fuel is small and the ignitability is poor. Therefore, the opening degree B of the second throttle valve 10 is set to almost zero to suppress the fuel dilution. Load is 0 to 1/4
In the range of, the valve opening is increased almost linearly.

Next, the operation of the above embodiment will be described. In the intake stroke of the engine, the first intake passage 2 of FIG.
The air-fuel mixture is supplied into the combustion chamber 1a through A, and the air is supplied into the combustion chamber 1a through the second intake passage 2B. In the combustion chamber 1a, the air-fuel mixture and the air flow along the inner peripheral surface of the combustion chamber 1a. As a result, as shown in FIGS. 1 and 2, an air flow S2 exists outside the air-fuel mixture flow S1. A two-layered spiral swirl flow S is generated which is directed downward along the inner wall of the cylinder 1 while swirling in a constant lateral direction.

Since the opening 2a of the first intake passage 2A for introducing the air-fuel mixture is provided near the center of the cylinder 1 where the spark plug 6 is located, the flow S1 of the air-fuel mixture in the combustion chamber 1a is Combustion chamber 1 surrounded by air flow S2
The piston 1 that swirls while being confined near the center of a and rises in the compression stroke of the engine while maintaining a state where the fuel is richer than the outside air flow S2
Compressed by 9. This air-fuel mixture is instantly burned by ignition by the spark plug 6, and its flame spreads throughout the combustion chamber 1a. Therefore, even if the air-fuel mixture leaner than the stoichiometric air-fuel ratio is used, it is possible to instantly burn and obtain high combustion efficiency.

Here, when the engine load is a low load of 3/4 or less, the opening B of the second intake passage 2B is larger and the air flow rate is larger, as shown in FIG. Since the flow velocity of air in the second intake passage 2B is higher than the flow velocity of the air-fuel mixture in the first intake passage 2A, the outside air flow S2 is
It becomes stronger than the flow S1 of the air-fuel mixture inside. As a result, the flow S1 of the air-fuel mixture is confined inside, and a strong swirl flow S is generated in a state where both the flows S1 and S2 are difficult to mix. As a result, the combustion speed increases even when the engine load is low, where combustion efficiency tends to decrease,
High combustion efficiency can be maintained.

Therefore, low fuel consumption can be realized by using the air-fuel mixture leaner than the stoichiometric air-fuel ratio, and high combustion efficiency can always be obtained by strengthening the swirl flow when the engine is under a low load, where the combustion efficiency tends to decrease. Can be maintained. Since it is possible to burn the lean air-fuel mixture with high combustion efficiency at all times, the harmful components in the exhaust gas can be remarkably reduced. Further, since the opening degrees of both intake passages 2A and 2B are differentially changed according to the load of the engine, the air flow rate ratio between the second intake passage 2B and the first intake passage 2A (≈B / A) is changed, It is also possible to widely control the air-fuel ratio of the air-fuel mixture by changing the cam profile of the cam 13 in FIG.

Further, since the intake pipe 2 for introducing intake air into the combustion chamber 1a of the cylinder 1 is divided into two and the first intake passage 2A and the second intake passage 2B are provided, the intake valve 4 is It suffices to provide only one for the first and second intake passages 2A, 2B forming a pair. Therefore, it is applied to a small engine having one intake valve 4 and one exhaust valve 5, for which it is difficult to provide a large number of valves in terms of space, and high combustion efficiency, low fuel consumption, and harmful components in exhaust gas The effect of reduction can be obtained. The present invention can also be applied to an engine having two or more intake valves and two exhaust valves.

FIG. 5 is a schematic plan view showing another embodiment of the present invention. In the above embodiment, the carburetor 7 is applied to the engine of the type that controls the supply of the air-fuel mixture, whereas in this embodiment, the fuel supply is controlled by the electronic fuel control method. When applied to the engine of.

When the opening of the first throttle valve 9 is changed by operating the throttle lever according to the operating condition, the air flow meter 21 detects the amount of intake air to the first intake passage 2A due to the change. Since the air amount in the first intake passage 2A is almost proportional to the fuel supply amount, the central processing unit 20 receiving the intake air amount detection signal responds to the intake air flow rate, that is, the engine load as shown in FIG. , Calculates the optimum amount of supplied fuel, and sends a duty pulse corresponding to the calculated value to the fuel injector 24. The fuel injector 24 controls the injection time of the fuel F supplied from the fuel tank (not shown) based on the duty pulse received from the central processing unit 20, and the fuel injector 2
The amount of fuel ejected from No. 4 is controlled so as to be approximately the stoichiometric air-fuel ratio.

On the other hand, the central processing unit 20 includes the second throttle valve 1
The motor 22 shown as an example of a valve driver that drives 0 is operated to control the opening degree of the second throttle valve 10 in accordance with the engine load as shown in FIG. Therefore,
The central processing unit 20 also functions as drive machine control means for controlling the motor 22 as a valve drive machine.

FIG. 7 is a partially cutaway perspective view of still another embodiment of the present invention. At the top of the piston 19,
Substantially triangular protrusions 29, 29 are formed at two locations opposed to the center of the protrusions. Combustion chamber 1a of cylinder 1
As shown in FIG. 8A, which shows the plane of the piston 19, an intake passage (not shown) is provided in the intake stroke of the engine.
The intake air 25 is introduced as a swirl flow so as to swirl around the center of the cylinder 1 in a constant swirling direction.
When the piston 19 rises to the vicinity of the top dead center in the compression stroke, the swirling intake air 25 is pushed out by the rear surface 29a of the projections 29, 29 which is located on the rear side of the intake air 25 in the swirling direction, and is opposite to the swirling direction. A directional reverse squish flow 31 is generated. As a result, the intake air 25 is converted into a large number of minute vortexes 26 by disturbing the flow in a certain direction near the top dead center, that is, immediately before ignition, and the combustion efficiency is improved by the turbulent combustion.

On the other hand, the cylinder head 1b of the cylinder 1 is gently inclined with respect to the rear surface 29a of the protrusion 29 as shown in FIG. 8B which is a sectional view taken along line BB of FIG. 8A. The inclined surfaces 28 face each other so as not to interfere with the reverse squish flow 31. On the other hand, the front surface 2 of the protrusion 29
For 9b, a suppressing portion 33 is formed on the front surface 29b with a predetermined gap, the suppressing portion 33 protruding downward from the lower surface of the cylinder head 1b. The suppressing portion 33 has the protrusion 29.
The front surface 29b suppresses the generation of the squish flow 35 that swirls in the same direction as the intake air 25, and promotes the generation of the minute vortex flow 26. Therefore, the combustion efficiency is further improved.

Further, the embodiment of FIGS. 7 and 8 may be combined with the intake control mechanism of the first embodiment shown in FIGS. 1 to 4 or the intake control mechanism of the second embodiment shown in FIGS. 5 and 6. For example, it is possible to use a strong swirl flow in which the intake air swirls in a fixed swirling direction around the center of the cylinder 1,
The minute vortex flow 26 can be generated more effectively.

[Brief description of drawings]

FIG. 1 is a schematic plan view showing a cutaway part of an embodiment of the present invention.

FIG. 2 is a side view showing a partially broken view of the above embodiment.

FIG. 3 is a perspective view showing a valve opening control means in the embodiment.

FIG. 4 is a characteristic diagram showing control by the valve opening control means of the above.

FIG. 5 is a plan view showing a main part of another embodiment of the present invention in a cutaway manner.

FIG. 6 is a characteristic diagram showing the relationship between the engine load and the fuel supply amount in the above embodiment.

FIG. 7 is a perspective view showing a part of another embodiment of the present invention in a cutaway manner.

FIG. 8 (a) is a plan view showing the operation of the above embodiment,
(B) is a cross-sectional view taken along line BB of (a),
(C) is sectional drawing cut | disconnected along CC line of (a).

[Explanation of symbols]

1 ... Cylinder, 1a ... Combustion chamber, 1b ... Cylinder head,
2 ... Intake pipe (intake passage), 2A ... First intake passage, 2a ... Opening of first intake passage, 2B ... Second intake passage, 2b ... Opening of second intake passage, 4 ... Intake valve, 8 ... Fuel injection nozzle (fuel supply means), 9 ... First throttle valve, 10 ... Second throttle valve, 11
... Link mechanism (valve opening control means), 20 ... Central processing unit (drive machine control means), 22 motor (valve drive machine), 33 ...
Suppressing part, 29 ... Protrusion.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location F02M 69/00 C (72) Inventor Shinichi Tanba 1-1 Kawasaki-cho, Akashi-shi, Hyogo Kawasaki Heavy Industries Akashi Plant Co., Ltd. (72) Inventor Tetsuaki Shirai 1-1 Kawasaki-cho, Akashi City, Hyogo Prefecture Kawasaki Heavy Industries Ltd. Akashi Factory

Claims (6)

[Claims] 1. An intake passage for introducing intake air into a combustion chamber in a cylinder, the first intake passage having an opening near the center of the cylinder, and the opening closer to the outer periphery of the cylinder than the first intake passage. The second intake passage is divided into a second intake passage, fuel is supplied to the first intake passage, and the opening degrees of the second intake passage and the first intake passage are set to the air flow rates of the second intake passage and the first intake passage. An intake control method for an engine, wherein the opening of the second intake passage is controlled so that the ratio becomes larger when the engine load is low than when the engine load is high. 2. A first intake passage and a second intake passage are divided,
An intake passage that introduces intake air into a combustion chamber in a cylinder, and a single intake valve that opens and closes each opening of the first and second intake passages to the combustion chamber, the opening of the first intake passage The portion is located closer to the center of the cylinder than the opening of the second intake passage, and further includes fuel supply means for supplying fuel to the first intake passage, and a first throttle valve that throttles the first intake passage. A second throttle valve that throttles the second intake passage, and the second throttle valve so that the air flow rate ratio between the second intake passage and the first intake passage is greater when the engine load is low than when it is high load. An intake control device for an engine, comprising: a valve opening control means for controlling the opening of a throttle valve. 3. The intake control device for an engine according to claim 2, wherein the first throttle valve and the second throttle valve are connected by a link mechanism. 4. The valve opening control means according to claim 2, further comprising a valve drive machine that drives the second throttle valve, and a drive machine control means that controls the valve drive machine based on a load of the engine. Intake control device for the engine. 5. An intake passage for introducing intake air into the combustion chamber in the cylinder while swirling in a constant swirling direction around the center of the cylinder, and an intake passage formed in the top of the piston, near the top dead center of the piston. An intake control device for an engine, comprising: a protrusion for pushing out intake air to generate a squish flow in a direction opposite to the turning direction. 6. The engine according to claim 5, wherein the cylinder head is further provided with a suppressing portion that opposes a front surface of the protrusion located on the front side in the turning direction and that suppresses a squish flow extruded by the front surface. Intake control device.