JP3425982B2 - Engine intake valve arrangement - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake valve arrangement structure for an engine, and more particularly to an intake valve arrangement structure provided with three intake valves, which inhibits a longitudinal vortex (tumble) of the intake air in a combustion chamber. The present invention relates to improvement of a diameter and a position of a valve head of an intake valve that can suppress a flow.

[0002]

2. Description of the Related Art Conventionally, as an engine provided with three intake valves, second and third intake valves are arranged on both sides of a first intake valve, and the second intake valve opening is formed by one intake passage. Further, there is a type in which the openings of the first and third intake valves are led out to the cylinder outer wall by bifurcated intake passages, and a switching valve is provided in the intake passage on the side of the second intake valve. In such an engine, it is general that the first to third intake valves have valve heads of the same diameter and are arranged so that each valve head is located on a concentric circle.

In such an engine, the passage on the side of the second intake valve is closed by the switching valve at the time of the low intake air amount in order to generate tumble at the time of the low intake air amount and stabilize the combustibility. The intake air is caused to flow only in the bifurcated intake passage on the side of the first and third intake valves, whereby the intake flow velocity is increased and the intake flow is given directionality in the cylinder axis direction, thereby generating tumble. . Some tumbles are generated by devising the shape of the intake passage without providing the switching valve.

[0004]

When the engine is viewed in the cam axis direction, the intake valve openings on both left and right sides are located closer to the center of the combustion chamber, while the central intake valve opening is It is located closer to the radial end of the combustion chamber. Therefore, the third
The intake flow from the opening of the intake valve flows vertically from the center of the cylinder toward the side of the exhaust valve, whereas the intake flow from the center first intake valve flows vertically from the center of the cylinder toward the side opposite to the exhaust valve. Tend. As described above, since the inflow position and the angle when the intake air flows into the cylinder are different, there is a problem that the intake air flows from the intake valve openings interfere with each other and, as a result, the generation of tumble is hindered.

The present invention has been made in view of the above problems of the prior art, and provides an intake valve arrangement structure for an engine, which can efficiently generate tumbles at low speeds, improve combustibility, and improve engine characteristics. The purpose is to do.

[0006]

The invention according to claim 1 is the first
In an intake valve arrangement structure of an engine in which second and third intake valves are arranged on both sides of the intake valve, the valve head of the first intake valve and the valve heads of the second and third intake valves are set to have different diameters. When viewed in the cylinder axis direction, the edge of the valve head surface of the first intake valve on the side of the center of the combustion chamber is burned with a line connecting the intersections of the axis of the second and third intake valves and the valve head surface. It is located between the center of the chamber and the axial line of the first intake valve on the opposite side of the spark plug across the straight line from the outer end of the valve seat on the intake side to the lower side of the contact surface of the valve head of the intake valve. The dimension m to the edge is set smaller than the dimension from the outer end of the valve seat on the exhaust side to the lower edge of the contact surface of the valve head of the exhaust valve, and the cam nose formed coaxially with the intake cam shaft causes Driving the first to third intake valves It is a symptom. Further, the invention of claim 2 is characterized in that the valve head of the first intake valve is set to have a smaller diameter than the valve heads of the second and third intake valves.

[0007]

With the intake valve arrangement structure for an engine according to the present invention, the valve heads of the first intake valve and the valve heads of the second and third intake valves are set to have different diameters. The combustion chamber center side edge portion of the valve head surface can be arranged so as to be located on a straight line connecting the intersections of the axis lines of the second and third intake valves and the valve head surface, or to the cylinder center side from the straight line, The valve holding angle formed by the first intake valve and the second and third intake valves becomes smaller, the intake flow from the first intake valve opening shifts to the exhaust valve side, and the intake air from the second and third intake valve openings is correspondingly increased. Is close to the inflow position and angle. As a result, it is possible to suppress the interference between the intake air flows and efficiently generate tumble in the combustion chamber, and it is possible to improve engine performance. Further, the dimension from the outer end of the valve seat on the intake side to the lower edge of the contact surface of the valve head of the intake valve is made smaller than that on the exhaust side, so that the first intake valve opening and the second, third
It is possible to secure a large wall thickness at the boundary with the intake valve opening.

According to the second aspect of the present invention, the valve head of the first intake valve located in the center is made smaller in diameter and moved closer to the center of the combustion chamber, so that the distance between the central intake valve opening and the outer wall of the cylinder is increased. Therefore, it is possible to reduce the adverse effect of the outer wall of the cylinder on the inflow of intake air, so-called masking.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 4 are views for explaining an intake valve arrangement structure of a 5-valve engine according to an embodiment of the present invention, FIG. 1 is a sectional side view of an engine in which the device of the present embodiment is adopted, and FIG. FIG. 4 is a plan view showing the bottom surface of the intake valve, FIG. 3 is a plan view with the head cover removed, and FIG.

In the figure, reference numeral 2 is a cylinder head of an engine equipped with the apparatus of this embodiment, and a head cover 3 is attached to an upper mating surface of the cylinder head 2 by a cover bolt (not shown). In addition, 4 is a seal packing.

On the lower mating surface of the cylinder head 2, a combustion recess 2a which constitutes a combustion chamber with a piston (not shown).
Is recessed. As shown by the broken line in FIG. 2, three intake valve openings 21a to 21c and two exhaust valve openings 22a and 22b are arranged and formed in the combustion recess 2a so as to form a substantially circular shape. Here, the three intake valve openings 21a to 21
c, the diameter of the first intake valve opening 21b is set to be smaller than the diameter of the second and third intake valve openings 21a and 21c on both sides, and the center point of the first intake valve opening 21b is the second point. , Is set to be closer to the combustion chamber center O from the circumference passing through the center points of the third intake valve openings 21a and 21c. The second and third intake valve openings 21a and 21c are set to have the same diameter. Further, 30 is a squish portion formed flat on the mating surface on the cylinder block side, and since the first intake valve opening 21a is brought close to the center O of the combustion chamber,
A squish area is also formed outside the first intake valve opening 21a.

The second intake valve opening 2 located on the upper side of FIG.
Reference numeral 1a is one straight intake passage 2b, and the first intake valve opening 21b located at the center and the third intake valve opening 21c located on the lower side in FIG. 2 are bifurcated intake passages 2c and the exhaust valve opening. Reference numerals 22a and 22b are bifurcated exhaust passages 2d which are led out to the outer wall of the cylinder head. Here, the intake passage 2b
The cylinder head outside opening 2e has a substantially circular shape, while the opening 2f of the intake passage 2c has a substantially rectangular shape. As a result, the opening size can be made smaller than that in the case of a circular opening while ensuring the required opening area. Although not shown, a switching valve, which is closed when the intake air amount is low, is arranged upstream of the intake passage 2b, and a fuel injection valve is arranged in the intake passage 2c. An ignition plug 5 is screwed into the center of the combustion recess 2a, and the electrode of the plug 5 is located at the center O of the combustion chamber.

Further, intake valves 6a to 6c having valve heads 6a 'to 6c' having diameters corresponding to the intake valve openings 21a to 21c are provided at the intake valve openings 21a to 21c, and exhaust valve openings 22a and 22b are provided with the intake valves 6a to 6c. Exhaust valves 7a and 7b each having a size are arranged. As a result of setting the diameters and arrangement positions of the intake valve openings 21a to 21c as described above, the first intake valve 6b is obtained.
Has a smaller diameter than the valve heads 6a ', 6c' of the second and third intake valves 6a, 6c, and the combustion of the valve head 6b 'of the first intake valve 6b when viewed in the cylinder axial direction. The edge 6d on the chamber center O side has the above-mentioned second and third edges.
Axes of intake valves 6a, 6c and valve heads 6a ', 6c'
It is located on the straight line L connecting the intersections B with the surface. The edge 6d may be located closer to the center O of the combustion chamber than the straight line L. The second and third valve heads 6b ',
6c 'has the same diameter.

Here, as a result of bringing the first intake valve opening 21b closer to the center O of the combustion chamber, the thickness of the boundary portion between the first intake valve opening 21b and the second or third intake valve opening 21a, 21c becomes smaller. There may be a shortage. Therefore, as shown in FIG. 4, for the valve seat 23b on the intake side, the outer end 23
b'and valve heads 6a 'to 6c' of the intake valves 6a to 6c
The dimension m to the lower edge of the contact surface is set to be smaller than that on the exhaust side to make the valve seat small, thereby ensuring a sufficient wall thickness.

Each of the intake valves 6a-6c and the exhaust valves 7a, 7c
The reference characters b pass through the valve guide 8 and extend obliquely upward so as to form a predetermined valve holding angle, and project into the cam chamber. Further, a valve spring 10 is interposed between a retainer 9a attached to the upper ends of the valves 6a to 6c, 7a and 7b and a spring seat of the cylinder head 2 so that the valves 6a to 6c are provided. , 7a, 7b are openings 21a-21c,
It is urged in the direction to close 22a, 22b.

Intake and exhaust camshafts 11 and 12 are arranged in parallel above the intake and exhaust retainers 9a, respectively. The intake and exhaust camshafts 11 and 12 are formed with three intake cam noses 11a to 11c and two exhaust cam noses 12a and 12b for each cylinder, and each cam nose is a lifter 9b attached to the retainer 9a. Is in sliding contact with.

The journal portions 11d and 12c of the intake and exhaust camshafts 11 and 12 are pivotally supported by intake bearings 13 and exhaust bearings 14, which are arranged in the center of each of the cylinders, two and two respectively. There is. The intake bearings 13 have the cam nose 11b at the center and the cam noses 11 on both sides.
It is formed between a and 11c, and the cylinder head 2
It is composed of a journal receiving portion 13a formed on the side and a cam cap 13c fixed to the journal receiving portion 13a by a pair of cap bolts 13b. The exhaust bearing 14 is formed between the two cam noses 12a and 12b, and has a journal receiving portion 14a formed on the cylinder head 2 side and a cam cap 14c fixed to the journal receiving portion 14a by a pair of cap bolts 14b. Consists of. Also, 13
Reference numerals d and 14d are positioning pins of the cam caps 13c and 14c, and the insertion hole 1 for the positioning pin on the cylinder outer wall side.
3e and 14e are extended downward to serve also as oil passages as described later.

Intake of the outer wall of the cylinder head 2
The vertical oil passage 1 is provided in the upper portion of the exhaust passages 2c and 2d.
Reference numerals 5 and 16 are formed parallel to the cam shafts 11 and 12.
The vertical oil passage 15 on the intake side is provided in the cylinder head 2
It is connected to an oil supply pump through a vertical oil passage 15b formed in the vertical direction and a transverse oil passage 2f formed in the horizontal direction. Similarly, the vertical oil passage 16 on the exhaust side is connected to the oil supply pump via the vertical oil passage 16b and the transverse oil passage 2f.

The vertical oil passages 15 and 16 are connected to the journal receiving portions 13a and 14a of the intake and exhaust bearings 13 and 14 by the branch oil passages 15a and 16a. In this case, the branch oil passages 15a, 16a
Extends obliquely upward so as to penetrate the lower portions of the pin insertion holes 13e, 14e which are part of the bolt holes of the cap bolts 13b, 14b. That is, the pin insertion hole 13
e and 14e are also used as part of the branch oil passages 15a and 16a. As a result, lubricating oil can be supplied to the bearings 13 and 14.

Next, the function and effect of this embodiment will be described. As described above, in the conventional engine, the intake valve located in the center and the intake valves located on the left and right outer sides have the same valve head diameter and are arranged on the same circumference. Therefore, the inflow position and the inflow angle of the intake air flow into the combustion chamber are different between the center and the outside, so that there is a problem that tumble generation is hindered.

On the other hand, in this embodiment, the first intake valve 6
The diameter of the valve head 6b 'of b is set to the second and third intake valves 6
It is set smaller than the diameter of the valve heads 6a 'and 6c' of a and 6c, and the valve head 6b 'of the first intake valve 6b is further set.
The combustion chamber center side edge portion 6d of the
Since it is arranged on the straight line L connecting the intersections B of the axes of a and 6c and the valve head surface, the first intake valve 6b can be moved closer to the center O of the combustion chamber. Therefore, the valve holding angle between the first intake valve 6b and the second and third intake valves 6a, 6c becomes small, which causes the intake position of the intake air from the first intake valve opening 21b to flow into the combustion chamber,
The inflow angle is close to the inflow position and angle from the second and third intake valve openings 21a and 21c. As a result, mutual interference of the intake air flows can be suppressed to efficiently generate tumbles, and the combustibility can be improved especially when the intake air amount is low. Further, since the first intake valve opening 21b is made smaller and is brought closer to the center O of the combustion chamber, the squish area 30 becomes smaller than the first intake valve opening 21b.
The flammability of the engine can be improved also from the point that this squish area is expanded to the outside of the engine. The present invention can also be applied to an engine in which the first intake valve and the second and third intake valves are parallel.

Further, since the first intake valve opening 21b is set to be small and is brought closer to the center O of the combustion chamber, the distance from the outer edge of the first intake valve opening 21b to the cylinder peripheral wall is increased, and the intake air is introduced by masking. The resistance can be reduced.

Further, since the dimension m of the valve seat 23b on the intake valve side is set to be smaller than that on the exhaust side, it is possible to secure the necessary wall thickness between the intake valve opening and the combustion chamber center O side.
Avoid strength problems.

Since the dimension from the outer end of the valve seat on the intake side to the lower edge of the contact surface of the valve head of the intake valve is smaller than that on the exhaust side, the first intake valve opening and the second and third intake valves are provided. This has the effect of ensuring a large thickness at the boundary with the valve opening.

[Brief description of drawings]

FIG. 1 is a sectional side view of an engine to which an intake valve arrangement structure according to an embodiment of the present invention is applied.

FIG. 2 is a bottom view of the engine of the embodiment.

FIG. 3 is a plan view showing a state where a head cover and a cam cap of the engine of the embodiment are removed.

FIG. 4 is an enlarged cross-sectional view near the intake valve opening of the engine of the above embodiment.

[Explanation of symbols]

6a second intake valve, 6a 'Valve head of the second intake valve 6b First intake valve 6b 'Valve head of first intake valve 6c Third intake valve 6c 'Valve head of third intake valve 6d Edge of the cylinder head side of the valve head surface of the first intake valve B The intersection of the axes of the second and third intake valves and the valve head surface L Straight line connecting B and B above O 2 Combustion chamber center

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Claims (2)

(57) [Claims] 1. An intake valve arrangement structure for an engine in which second and third intake valves are provided on both sides of a first intake valve, wherein a valve head of the first intake valve and a valve of the second and third intake valves are provided. The head and the diameter are set differently, and when viewed in the cylinder axial direction, the edge portion of the valve head surface of the first intake valve on the center side of the combustion chamber is
The second, is positioned between the straight line and the combustion chamber center line connecting an intersection between the axis and the valve head surface of the third intake valve, further
Opposite the spark plug with the axis of the first intake valve across the straight line
The intake side from the outside end of the valve seat on the intake side.
The dimension m up to the lower edge of the contact surface of the valve head of the valve
The valve head of the exhaust valve from the outer end of the valve seat on the air side
Set smaller than the dimension up to the bottom edge of the contact surface
The cam nose formed so as to be coaxial with the cam shaft
An intake valve arrangement structure for an engine, characterized in that the first to third intake valves are driven . 2. The intake valve arrangement structure for an engine according to claim 1, wherein the valve head of the first intake valve has a smaller diameter than the valve heads of the second and third intake valves.