JPH0771257A - Intake air control device for two-valve engine - Google Patents

Abstract

PURPOSE:To improve combustion by providing an angle of an intake passage in the vicinity of an intake control valve near a plane perpendicular to a cylinder axis, thereby providing intake flow throttled by the intake control valve easy to flow along a ceiling, and easily generating tumble in a combustion chamber. CONSTITUTION:A cylinder head 4 connected to a cylinder block 3 through a head bolt 10 is provided with intake and exhaust passages 11, 12. Intake and exhaust valves 15, 16 are arranged in combustion chamber openings 11a, 12a of the intake and exhaust passages 11, 12, which valves are opened and closed by rotation of exhaust cam shafts 5, 6. An ignition plug is arranged on a combustion chamber ceiling 4a eccentrically from a center of the combustion chamber. In such a two-valve engine, an intake control valve 18 for throttling the intake passage from a bottom wall is arranged on the bottom wall in the vicinity of the combustion chamber opening 11a of the intake passage 11, between the intake can shaft 5 and the head bolt 10 in a plane perpendicular to an axis C of the combustion chamber. The intake flow is easy to flow along the ceiling, accordingly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-valve engine having one intake valve and one exhaust valve for each cylinder, and in particular, an intake control valve is provided on the bottom wall of the intake passage near the combustion chamber opening. Intake control structure for a two-valve engine.

[0002]

2. Description of the Related Art In a multi-valve engine such as a four-valve engine or a five-valve engine in which a plurality of intake valves are provided for each cylinder to improve the charging efficiency, the fuel consumption rate of the engine is increased. In order to improve the air-fuel ratio in order to improve the air-fuel ratio, the intake opening area to the combustion chamber is large when the lean-burn operation is performed. Combustion may become unstable due to the low flow rate of intake air to.

In order to deal with this, an intake control valve is provided on the bottom wall of the intake passage of the engine near the opening of the combustion chamber, and when the intake amount is small, the intake passage is controlled from the bottom wall side by the intake control valve. By narrowing down, the flow velocity of the intake flow sent into the combustion chamber is increased and the flow is biased toward the top wall side, and a tumble (longitudinal vortex) is caused in the combustion chamber by the intake flow flowing from the opening of the intake passage, thereby The technique of stabilizing the lean burn is already known. (JP-A-5
(See Japanese Patent Publication No. 179965)

[0004]

By the way, in a two-valve engine in which one intake passage opened and closed by an intake valve and one exhaust passage opened and closed by an exhaust valve are opened for each cylinder, the two-valve engine is connected to the combustion chamber. The intake opening area of the engine did not become large, and the decrease in the intake flow velocity into the combustion chamber did not pose a problem even in the operating region where the intake amount was small.
Heretofore, it has not been considered that the intake control valve causes tumble in the combustion chamber to stabilize the lean combustion.

However, even in a two-valve engine, when trying to further improve the fuel efficiency of the engine by setting the air-fuel ratio higher, in the case of a multi-valve engine, in order to avoid the destabilization of the combustion that occurs. It is of course conceivable to provide an intake control valve to stabilize the combustion in the same manner as the above, and the multi-valve engine (four-valve engine) is also disclosed in the above cited document (JP-A-5-179965). Is specifically disclosed, and it is described that it can be applied to a two-valve engine.

However, when the well-known technique disclosed as the embodiment of the multi-valve engine as described above is directly applied to the two-valve engine, as a result, the desired combustion improving effect cannot be obtained. was there.
Then, as a result of examining the cause, it was found that the following was one of the causes.

That is, regarding the intake passage and the exhaust passage opened to the combustion chamber, the valve stems of the intake valve provided in the intake passage and the exhaust valve provided in the exhaust passage form a predetermined sandwich angle on the axial surface of the cylinder. To make
Although extending obliquely upward in opposite directions, the intake passage form in a multi-valve engine such as a 4-valve engine is directly applied to a 2-valve engine, and an intake control valve is provided near the opening of the combustion chamber. If provided, the intake passage near the intake control valve rises sharply from the plane orthogonal to the cylinder axis, so when the intake flow is throttled by the intake control valve, it becomes difficult for the intake flow to flow along the ceiling wall. Tumble is less likely to occur in the combustion chamber.

The present invention is based on the above findings.
The purpose is to eliminate the inconvenience in improving combustion in a valve engine.Specifically, by making the angle of the intake passage near the intake control valve close to the plane orthogonal to the cylinder axis, The purpose of the present invention is to make it easier for the intake air flow that is throttled by the control valve to flow along the ceiling wall so that tumble is likely to occur in the combustion chamber and to sufficiently obtain the effect of improving combustion.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems and to achieve the object, the present invention is directed to a combustion chamber ceiling formed on a lower surface of a cylinder head, in which a cylinder block and a cylinder head are connected by head bolts. An intake passage and an exhaust passage are respectively drawn from the wall into the cylinder head, and an intake valve that is opened and closed by rotation of an intake cam shaft arranged above the cylinder head is installed in the combustion chamber opening of the intake passage. In a two-valve engine in which exhaust valves are respectively provided at the openings of the combustion chambers of the passages, and the electrodes of the spark plugs are arranged on the top wall of the combustion chambers deviating from the center of the combustion chambers, the intake control structure of the intake valve An intake control valve for narrowing the intake passage from the bottom wall side is provided on the bottom wall near the opening of the combustion chamber, and the intake control valve is orthogonal to the axis of the cylinder. In the surface, it is characterized in that disposed between the head bolts and the intake camshaft.

[0010]

[Operation] With the above configuration, the angle of the intake passage near the intake control valve is close to the plane orthogonal to the axis of the cylinder, so the intake flow throttled by the intake control valve is along the ceiling wall. It becomes easier to flow, and even if the intake control valve is arranged relatively far from the combustion chamber opening outside the head bolt,
The required tumble can be generated in the combustion chamber.

Further, when the intake control valve is simply arranged closer to the combustion chamber opening in order to facilitate the occurrence of tumble, due to the structure of the engine, the head bolt is viewed from the center of the combustion chamber and is located closer than the intake control valve. Although it may be necessary to change the distance further, the rigidity of the head may be reduced, deformation, gas leakage, etc. may occur, but as described above, the intake control valve is relatively far from the combustion chamber opening outside the head bolt. Even if the head bolt is arranged in the above position, the tumble is surely generated, so that it is not necessary to change the position of the head bolt, and the problems such as deterioration in rigidity of the head, deformation, and gas leakage are eliminated.

If the intake control valve is arranged outside the intake cam shaft, the shape of the engine itself in plan view becomes larger than the conventional one, and the intake control valve becomes too far from the combustion chamber opening. Tumble is less likely to occur.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 7 show an embodiment of the present invention. FIG. 1 shows a longitudinal cross section of a main part of one cylinder of a multi-cylinder two-valve engine, and FIG. A cross section taken along line A is shown, FIG. 3 shows the positional relationship between the intake camshaft, the intake control valve, and the head bolt, FIG. 4 shows the lower surface of the combustion chamber top wall, and FIG. A state in which the vicinity of the intake control valve is viewed from the upstream side is shown, FIG. 6 shows the intake control valve in a fully open state, and FIG. 7 shows the intake control valve in a fully closed state.

The two-valve engine 1 has a crankcase 2
The cylinder block 3 and the cylinder head 4 are stacked on top of each other and connected by head bolts 10, and the head cover 7 is mounted on the intake cam shaft 5 and the exhaust cam shaft 6 of the cylinder head 4, which is formed on the cylinder block 3. A piston 8 is slidably inserted in the formed cylinder bore 3a, and the piston 8 is connected by a connecting rod 9 to a crankshaft (not shown).

The cylinder head 4 has a recess formed on the lower surface thereof to form the ceiling wall 4a of the combustion chamber of each cylinder. The recess 4a, the cylinder bore 3a of the cylinder block 3 and the piston 8 form A combustion chamber is defined in each cylinder.

One intake passage 11 and one exhaust passage 12 are drawn out into the cylinder head 4 from the recessed portion on the lower surface of the cylinder head, that is, from the top wall 4a of the combustion chamber, and the intake passage 11 and the exhaust passage 12 are separated from each other. The combustion chamber openings 11a and 12a are respectively arranged at inclined portions of the combustion chamber top wall 4a that face each other across the zenith portion 4b, and the intake valve 15 is provided in the combustion chamber opening 11a of the intake passage 11.
However, exhaust valves 16 are provided at the combustion chamber openings 12 a of the exhaust passage 12.

Regarding the intake valve 15 and the exhaust valve 16, the respective valve stems 15a and 16a form a predetermined angle on the axial surface of the cylinder.
The intake lifters 15b, which extend obliquely upward in opposite directions to each other, are provided at the upper ends of the valve stems 15a and 16a.
And between the exhaust lifter 16b and the cylinder head 4 via valve springs 15c and 16c, respectively.
The exhaust valves 15 and 16 are mounted on the cylinder head 4.

The intake valve 15 and the exhaust valve 16
Are the respective valve springs 15c and 16
The intake camshaft and the exhaust camshaft 6 are always urged in the closing direction by c and are arranged on the lifters 15b and 16b at right angles to the cylinder axis and parallel to each other.
Directly or via a rocker arm to resist the resilience of the valve springs 15c and 16c.
It is moved in the opening direction by pressing 5b and 16b.

The combustion valve opening 1 is formed by the intake valve 15.
The combustion chamber opening 11
An intake control valve 18 is provided on the bottom wall in the vicinity of a, and upstream of the intake control valve 18, a butterfly throttle valve 31 that opens and closes by a throttle operation via a connecting pipe 20 and a joint 21 and an intake negative pressure of the engine automatically. An automatic variable Venturi type carburetor 30 having a piston valve 32 that opens and closes is connected.

The intake control valve 18 is provided in the intake passage 11 of each cylinder.
Is formed as a part of a single rotatable rotary shaft 17 disposed across the intake passage 11, and the lower portion thereof is embedded in the bottom wall of the intake passage 11 of the intake passage 11 of the rotary shaft 17. The upper part that crosses over is shaped so as to be cut along the upper surface of the bottom wall of the intake passage 11, and the remaining notch functions as a valve.

Although not shown, the intake control valve 1
A control pulley is fixedly attached to the outer end of the rotary shaft 17 on which the control valve 8 is formed. This control pulley is connected to the drive pulley fixed to the control motor by a cable, and the throttle valve of the throttle valve is detected by the throttle opening sensor. Based on the opening signal and the engine rotation speed signal from the rotation sensor, through the ECU and the control motor, in the closing direction when the intake air amount is small, such as the low / medium speed / low load operation range, the high speed / high load operation range When the intake air amount is large, the intake control valve is rotated in the opening direction.

The combustion chamber openings 11a and 12a of the intake passage 11 and the exhaust passage 12 are as shown in FIG.
As shown in FIG. 2, the zenith portion 4b of the combustion chamber top wall 4a is arranged so that the line connecting these centers passes through substantially the center of the combustion chamber.
Are disposed so as to face each other with the center of the combustion chamber in between, and on one side of a line connecting the centers of the respective combustion chamber openings 11a and 12a, the combustion chamber being separated from the center of the combustion chamber. A spark plug 50 is arranged on the top wall 4a.

Further, the combustion chamber opening 11 of the intake passage 11
The intake passage 11 extending from a toward the carburetor connection portion 21 toward the upstream side has a configuration in which the combustion chamber opening 11a of the intake passage 11 passes through substantially the center of the combustion chamber and the combustion chamber openings 11a,
It is swung to the side opposite to the side on which the spark plug 50 is arranged with reference to the line connecting the centers of 12a.

In the vicinity of the intake control valve 18 of the intake passage 11, as shown in FIG. 5, the entire intake passage 11 is displaced to the side opposite to the spark plug 50 with respect to the combustion chamber opening 11a. At the same time, the top wall of the intake passage 11 above the intake control valve 18 is projected downward and bulged by the boss portion 4c of the valve guide 14, so that the cross-sectional shape of the intake passage 11 at that portion is a concave portion with a narrow central portion. It has a shape.

As shown in FIG. 4, on the lower surface of the combustion chamber top wall 4a, a vertical wall 4e is formed on the side opposite to the side where the electrode 51 of the spark plug 50 is arranged, and the vertical wall 4e is formed downward. The protruding squish portion 4d is formed, and the masking effect is maintained by the vertical wall 4e of the squish portion 4d and the intake valve 15, and the flow of the intake air flow from the vertical wall 4e of the squish portion 4d toward the spark plug is maintained. Will occur.

By the way, the intake control valve 18 shown in FIG.
As shown in FIG. 1, the combustion chamber opening 1 of the intake passage 11 is
Slightly upstream from 1a, the rotating shaft 17 is arranged between the head bolt 10 and the intake cam shaft 5 in a plane orthogonal to the cylinder axis C.

The head bolt 10 includes an intake control valve 18
In the plane orthogonal to the axis C of the cylinder with respect to such a head bolt 10, the head bolt 10 is provided at substantially the same position as in the case of a general two-valve engine in which is not provided. By adopting a configuration in which the rotary shaft 17 of the intake control valve 18 is arranged between the head bolt 10 and the intake cam shaft 5, the intake passage 11 near the intake control valve 18 is provided in the cylinder. It is almost parallel to the plane orthogonal to the axis C.

Regarding the control of the intake flow by the intake control valve 18 of the two-valve engine having the above-mentioned structure, the intake control valve 18 has a cutout surface when the intake amount is large, such as in a high speed / high load operation range. Is rotated in the opening direction until it becomes substantially flush with the bottom wall of the intake passage, and as shown in FIGS. 6A and 6B, the intake flow burns when the intake passage 11 is fully open. When the intake air is fed into the room and the intake air amount is small, as in the low / medium speed / low load operation range, the intake control valve 18 is rotated in the closing direction so that the cutout surface thereof rises, and
As shown in (A) and (B), the bottom wall side of the intake passage 11 is narrowed to a fully closed state, and the intake air flow passes between the upper edge of the valve 18 and the top wall of the intake passage 11. Are sent to the combustion chamber.

Therefore, even when the intake air amount is small, the speed of the intake air flow fed into the combustion chamber is increased, and
Since the intake air flow is biased toward the top wall side of the intake passage 11,
Direction can be given to the intake air flow and tumble can be generated in the combustion chamber.

Moreover, since the intake passage 11 near the intake control valve 18 is close to parallel to the plane orthogonal to the cylinder axis C, the intake flow throttled by the intake control valve 11 is It becomes easy to flow along the top wall of the intake passage 11, and even if the intake control valve is not located in the immediate vicinity of the combustion chamber opening, the intake flow narrowed and directed by the intake control valve 11 is As indicated by an arrow 3 in FIG. 3, the tumble can be surely caused in the combustion chamber by flowing along the ceiling wall 4a of the combustion chamber.

Further, the intake passage 1 near the intake control valve 18
Since the angle 1 is close to the plane orthogonal to the axis of the cylinder, the angle between the intake and exhaust valve stems can be increased to increase the valve area.

Although one embodiment of the intake control structure for the two-valve engine of the present invention has been described above, the present invention is not limited to this. For example, the embodiment uses an automatic variable venturi type carburetor to fuel the fuel. Is applied to a two-valve engine of a type in which fuel is supplied by the fuel injection valve, but it is also applicable to a two-valve engine of a type in which fuel is supplied by a fuel injection valve. Various modifications as shown in FIGS. 8 to 12 are possible.

That is, what is shown in FIGS. 8A and 8B is the upper edge 1 of the intake control valve 18 in the fully closed state.
8a is cut in a gentle concave shape, and the area of the central narrow cross section of the intake passage 11 when expanded by the intake control valve 18 is expanded.

9 and 10 are those in which a part of the upper edge 18a of the intake control valve 18 in the fully closed state is cut, and the intake control valve 18 is shown in FIG.
The area of the portion of the intake passage 11 which is closer to the spark plug side when the throttle is closed is expanded.

Further, in the structure shown in FIG. 11, a portion of the upper edge 18a of the intake control valve 18 located below the boss 4c in the fully closed state is cut, and the intake passage when throttled by the intake control valve 18 is cut. The area of the central narrow section of 11 is expanded, and a groove 18d for draining the fuel accumulated upstream of the control valve to the downstream is provided on the bottom surface 18c of the intake control valve 18.

Further, in the structure shown in FIG. 12, a groove 18e is provided on the bottom surface of the intake control valve 18 and along the cutout surface 18b so as to have a gap between the intake control valve 18 and the main body. A plate 18f is additionally provided. In such a case, when the valve is closed, the fuel accumulated upstream of the control valve is sucked out from the groove 18e along the plate 18f, and the sucked fuel is absorbed in the combustion chamber. It is atomized by the intake air flowing into the combustion chamber and supplied to the combustion chamber.

[0037]

According to the intake control structure of the two-valve engine of the present invention as described above, even if the intake control valve is arranged in the two-valve engine without changing the position of the head bolt, the intake control valve can be used. Since the narrowed intake air flow easily flows along the ceiling wall, tumble can be reliably generated in the combustion chamber, and lean combustion in the two-valve engine can be effectively improved.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of an intake control structure for a two-valve engine of the present invention.

2 is a cross-sectional view of the embodiment shown in FIG. 1 taken along the line 1A-A in FIG.

FIG. 3 is an explanatory diagram showing a positional relationship between an intake valve, an intake control valve, and a head bolt in the embodiment shown in FIG.

4 is a bottom view of the combustion chamber top wall of the embodiment shown in FIG. 1. FIG.

5 is an explanatory view showing a state of the intake passage near the intake control valve of the embodiment shown in FIG. 1 as viewed from the upstream side.

6A and 6B are explanatory views showing the intake control valve in a fully opened state in the embodiment shown in FIG. 1 as viewed from the upstream side of the intake passage, and FIG. 6B is the center of the intake control valve in that state. FIG.

7 (A) is an explanatory view showing the intake passage when the intake control valve is fully closed in the embodiment shown in FIG. 1, and FIG. 7 (B) shows the intake control valve in that state. FIG.

FIG. 8 is a diagram showing a first modified example of the intake control valve portion of the present invention, in which (A) the intake control valve is fully closed and the intake passage is viewed from the upstream side; The central part longitudinal cross-sectional view of an intake control valve.

FIG. 9 is an explanatory view showing a second modification of the intake control valve portion of the present invention, showing a fully closed intake control valve as viewed from the upstream side of the intake passage.

FIG. 10 is an explanatory view showing a fully closed intake control valve of the third modified example of the intake control valve portion of the present invention when the intake passage is viewed from the upstream side.

FIG. 11 is a diagram showing a fourth modified example of the intake control valve portion of the present invention, in which (A) the intake control valve is fully closed and the intake passage is viewed from the upstream side; The central part longitudinal cross-sectional view of an intake control valve.

FIG. 12A is a vertical cross-sectional view of a central portion of an intake control valve and FIG. 12B is a horizontal cross-sectional view of the intake control valve according to a fifth modification of the intake control valve portion of the present invention.

[Explanation of symbols]

 1 2 Valve engine 3 Cylinder block 4 Cylinder head 4a Combustion chamber top wall 5 Intake camshaft 6 Exhaust camshaft 10 Head bolt 11 Intake passage 11a Intake passage combustion chamber opening 12 Exhaust passage 12a Exhaust passage combustion chamber opening 15 Intake valve 16 Exhaust valve 18 Intake control valve 50 Spark plug 51 Electrode of spark plug

Claims (1)

[Claims] 1. A cylinder block and a cylinder head are connected by head bolts, and an intake passage and an exhaust passage are drawn into the cylinder head from a combustion chamber top wall formed on the lower surface of the cylinder head, respectively, and An intake valve, which is opened and closed by the rotation of an intake cam shaft arranged above the cylinder head, is provided in the combustion chamber opening, and an exhaust valve is provided in the combustion chamber opening in the exhaust passage. In a two-valve engine in which electrodes of spark plugs are arranged on the top wall of the combustion chamber, an intake control valve for narrowing the intake passage from the bottom wall side is provided on a bottom wall of the intake passage near the opening of the combustion chamber. At the same time, the intake control valve is arranged between the head bolt and the intake cam shaft in a plane orthogonal to the axis of the cylinder. Air intake control structure of gin.