JP2020139439A - Cylinder head of internal combustion engine - Google Patents

Abstract

To realize a form of a suction port capable of reinforcing a tumble flow without reducing an intake amount.SOLUTION: A pair of suction ports 6 is offset so that a center line 23 thereof approaches a center line 20 of a partition wall 12 in a plan view. Consequently, suctioned air ejected from both suction ports 6 can be easily merged, and resistance due to the suction port 6 can be reduced to prevent a decrease in a suction amount. The portion of an outer surface 19 of the suction port 6 near an outlet is a curved part (or inclined surface) 19b that approaches the center line 20 of the partition wall 12. The suctioned air tends to be guided by the curved part 19b and converge to the farthest portion 3a of a cylinder bore 3. Moreover, since the suction port 6 is narrowed, the flow velocity of suctioned air is also large. Therefore, a strong tumble flow can be generated.SELECTED DRAWING: Figure 4

Description

The present invention relates to a cylinder head of an internal combustion engine, and is intended for an improved technique of an intake port for the purpose of strengthening a tumble flow.

In an internal combustion engine, it is beneficial to generate a tumble flow in the cylinder bore as a means of increasing the mixture of fuel and air to improve combustibility. Therefore, many means for generating a strong tumble flow have been conventionally proposed.

As an example, in Patent Document 1, in a linearly extending intake port, a pair of intake ports are formed in a non-parallel posture so that the center line spreads toward the downstream side, and on the downstream side of both intake ports. It is disclosed that the end portion is formed to be widened in a plan view.

Then, Patent Document 1 explains that the tumble flow can be strengthened because the flow velocity of the intake port toward the upper part of the cylinder bore can be increased.

Japanese Unexamined Patent Publication No. 2016-169668

By the way, in order to strengthen the tumble flow, it is beneficial to increase the flow velocity of the intake air as described in Patent Document 1. In this case, not only the intake air toward the upper part of the cylinder bore but also the cylinder bore. It is understood that it is advantageous to increase the flow velocity of the inflowing intake air itself. Then, if the cross section of the outlet portion of the intake port is narrowed, the flow velocity of the intake air in the cylinder bore can be increased, but if the cross section is too narrow, the inflow amount of the intake air may decrease. Therefore, it is necessary to devise to increase the flow velocity as much as possible while ensuring the inflow performance of the intake air.

On the other hand, the flow of intake air descends along the inner surface of the cylinder bore and then changes direction by the top surface of the piston to become a tumble flow, but if the intake air flowing out from the pair of intake ports is brought together to form an integrated flow. , It is understood that a strong tumble flow can be generated.

However, in Patent Document 1, since the pair of intake ports are arranged so that the distance between the center lines widens toward the downstream side, the intake air tends to diffuse inside the cylinder bore, which does not necessarily strengthen the tumble flow. It is speculated that it may not be connected. In addition, if the downstream part of the intake port is widened, it is understood that the intake speed will decrease, so it is thought that this may be contrary to the strengthening of the tumble flow.

Since the cylinder bore is circular, it can be said that the intake ports discharged from the pair of intake ports toward the inner peripheral surface of the cylinder bore are guided toward each other by the guiding action of the inner surface of the cylinder bore. In an internal combustion engine having a small displacement, such as an internal combustion engine for an engine or a small automobile, in the configuration of Patent Document 1, the intake air ejected from the intake port immediately reaches the inner surface of the cylinder bore, so that the cylinder bore is circular. It is presumed that the diffusion effect by colliding with the inner surface of the cylinder bore is larger than the convergence effect by, and it is difficult to strengthen the tumble flow.

The present invention has been made based on such findings, and aims to realize a form of an intake port capable of generating a strong tumble flow without causing a decrease in the intake amount.

The present invention relates to a cylinder head of an internal combustion engine.
"A pair of intake ports corresponding to each cylinder bore are formed so as to extend substantially parallel to the direction orthogonal to the crank axis in a plan view seen from the cylinder bore axis direction, and the outlets of the intake ports are respectively intake valves. Opened and closed by "
It has a basic structure.

And in the above basic configuration
"In the plan view, the pair of intake ports are offset so that their center lines are located between the axes of the pair of intake valves, and the portions downstream of both intake ports are Its sides are tilted or curved so that it becomes constricted in plan view. "
It has the feature.

In this case, as a means for forming the intake port in a narrowed position, only the outer surface of the inner and outer surfaces of the intake port may be inclined or curved, only the inner surface may be inclined or curved, or the inner and outer surfaces may be inclined or curved. Both sides may be tilted or curved. When the inner surface is inclined or curved, it is preferable to incline the center lines of the pair of intake ports so as to form a V shape because the intake air ejected from the pair of intake ports can easily merge.

In the present invention, since the center line of the intake port is offset inward with respect to the axis of the intake valve, it is possible to suppress the resistance of the intake valve (particularly the resistance of the stem) and secure the required intake amount. it can. In addition, since the distance between the pair of intake ports is smaller than the distance between the pair of intake valves, the intake air discharged from the pair of intake ports is high without being disturbed by the resistance of the stem of the intake valve. Since the straightness can be maintained, it is easy to integrate (merge) with each other in the cylinder bore.

Moreover, since the parts of the outer surface of the pair of intake ports near the outlet are inclined or curved so as to approach each other in a plan view, the cross-sectional area of the exhaust port is narrowed toward the outlet, so that the cylinder bore can be used. The flow velocity of the inflowing intake air can be increased, and the intake air discharged from both intake ports is directed toward the farthest part of the inner surface of the cylinder bore axis (the flow is rectified).

In this way, the intake air discharged from the pair of intake ports is directed toward the farthest part of the inner surface of the cylinder bore while narrowing the distance between them, and the flow velocity is also large. Therefore, the pair of intake ports The intake air emitted from the can be integrated (merged) to create a strong downward flow through the inner surface of the cylinder bore. As a result, even an internal combustion engine having a small displacement can generate a strong tumble flow. As a result, the mixing property of the fuel and the intake air can be improved, which can contribute to the improvement of the thermal efficiency and the prevention of deterioration of the exhaust gas component.

FIG. 5 is a vertical sectional front view of the internal combustion engine according to the embodiment in a closed state, and is a sectional view taken along line I-I of FIG. It is a figure which shows the positional relationship between an intake port, an intake valve, and a cylinder bore, and is the schematic view of II-II of FIG. It is a longitudinal front view in the intake stroke. It is a top view for demonstrating the flow of intake.

Next, an embodiment of the present invention will be described with reference to the drawings.

(1). Basic Structure Next, an embodiment in which the present invention is applied to an internal combustion engine for a vehicle will be described with reference to the drawings. In the following, the front-back and left-right terms are used to specify the direction, but the front-back direction is the crank axis direction, and the left-right direction is the direction orthogonal to the crank axis and the cylinder bore axis. In FIGS. 2 and 4, the cross-sectional display is omitted.

The internal combustion engine has a cylinder block 1 and a cylinder head 2 fixed to the upper surface thereof as an engine main body. A plurality of cylinder bores 3 are formed side by side in the front-rear direction in the cylinder block 1, and a piston 4 is slidably fitted in each cylinder bore 3.

A chevron (trapezoidal tapered cross section) combustion chamber (recess) 5 opened toward the cylinder bore 3 is formed in the cylinder head 2, and the combustion chamber 5 is divided into left and right when viewed from the crank axis direction. In this state, a pair of front and rear intake ports 6 and an exhaust port 7 are open.

That is, in the combustion chamber 5, the outlets (downstream ends) 6a of the pair of front and rear intake ports 6 are open, and the inlets 7a of the pair of front and rear exhaust ports 7 are open, and the cylinder head 2 is provided with intake air. A pair of front and rear intake valves 8 for opening and closing the outlet 6a of the port 6 and a pair of front and rear exhaust valves 9 for opening and closing the inlet of the exhaust port 7 are attached via valve guides (bush) 10 and 11, respectively. The valves 8 and 9 have stems 8a and 9a and umbrella portions 8b and 9b, respectively, and the stems 8a and 9a are slidably fitted to the valve guides 10 and 11.

The pair of intake ports 6 are independent of each other over the entire length thereof, and the inlet (upstream end) 6b is open to the intake side surface 2a of the cylinder head 2. Therefore, the partition wall 12 that separates the pair of intake ports 6 extends over the entire length of both intake ports 6. However, the pair of intake ports 6 may be branched from one gathering inlet portion.

A recess 14 for accommodating the tip of the fuel injection injector 13 is formed on the upper surface of the inlet portion of each intake port 6. Although not shown, an intake manifold is fixed to the intake side surface 2a of the cylinder head 2, and the fuel injection injector 13 is attached to the intake manifold (it can also be attached to the cylinder head 2). ..

The pair of front and rear exhaust ports 7 have a structure in which the exhaust ports 7 are gathered together and the gathering portion (not shown) is opened on the exhaust side surface of the cylinder head 2, and a structure in which each exhaust port 7 is communicated with one built-in collective passage. Both can be adopted. In the former structure, exhaust ports corresponding to the number of cylinder bores 3 are opened on the exhaust side surface of the cylinder head 2, and in the latter structure, one exhaust port is opened on the exhaust side surface of the cylinder head 2.

The cylinder head 2 has a plug arrangement hole 15 penetrating through the central portion of each combustion chamber 5, and the spark plug 16 is mounted in the plug arrangement hole 15.

(2). Details of the intake port The intake port 6 basically has a circular or horizontally elongated oval (or horizontally elongated oval) cross-sectional shape, and as shown in FIG. 1, the intake port 6 is directed from the inlet 6b to the outlet 6a. The height is gradually decreasing. That is, the intake port 6 is narrowed in the longitudinal front view.

On the other hand, as shown in FIG. 2, both intake ports 6 have an inner side surface 18 in contact with the partition wall 12 in a plan view from the direction of the cylinder bore axis, while being a straight portion except for the outlet 6a. The outer surface 19 on the opposite side of the partition wall 12 has a straight portion 19a parallel to the inner side surface 18 in a range of about 1/3 to 3/4 excluding the portion near the outlet 6a, and is 1/1 on the side of the outlet 6a. The portion of about 3 to 1 to 1/4 is a curved portion 19b that approaches the center line 20 of the partition wall 12 (the distance between the partition walls is narrowed) toward the downstream side.

Therefore, in a plan view, the intake port 6 is composed of a straight portion 21 starting from the inlet 6b and occupying a range of more than half, and a tip constricted portion 22 located on the outlet side. It is also possible to use a linear inclined portion instead of the curved portion 19b. The center line 20 of the partition wall 12 passes through the axial center of the cylinder bore 3 in a plan view. Therefore, the center line 20 of the partition wall 12 can also be called a horizontally long center line that divides the cylinder bore 3 into two parts in the front-rear direction.

Further, both intake ports 6 have a partition wall 12 having a size E slightly larger than that of the intake valve 8 so that the center line 23 is located in the area sandwiched between the axes 24 of the two intake valves 8. It is closer to the side of the center line 20 (offset). Therefore, the outlet 6a of the intake port 6 is also offset so as to be closer to the center line 20 of the partition wall 12 than the axial center 24 of the intake valve 8, and the flat area of the outlet 6a of the intake port 6 is the intake air. It is smaller than the flat area of the umbrella portion 8b of the valve 8 (or the opening area of the valve seat 25).

Generally, in an internal combustion engine, the center line 23 of the intake port 6 is set to pass through the axis 24 of the intake port 6, but in the present embodiment, the pair of intake ports 6 are offset so as to be close to each other. .. Therefore, in the intake stroke in which the intake valve 8 is opened, the intake air tends to go toward the farthest portion 3a of the cylinder bore 3.

Moreover, since the portion of the outer surface 19 of both intake ports 6 near the outlet is a curved portion 19b near the center line 23 of the partition wall 12, the intake air is as shown by the arrow 26 in FIG. 4 due to the guiding action. , The directionality is given so as to converge on the farthest portion 3a of the cylinder bore 3. Further, since the intake port 6 is narrowed in the longitudinal front view and the plan view, the flow velocity of the intake air flowing into the cylinder bore 3 is large.

As described above, in the present embodiment, the center line 23 of the intake port 6 is offset inward, the outlet side portion of the outer surface 19 of the intake port 6 is a curved portion 19b, and the intake is taken. As shown in FIG. 3, the intake air flows downward along the inner surface of the cylinder bore 3 and then changes direction at the top surface of the piston 4 to tumble due to the synergistic action with the increase in the flow velocity inside the cylinder bore 3. In the flow 27 being generated, the tumble flow 27 can be made stronger.

Further, since the center line 23 of the intake port 6 is deviated inward from the axis 24 of the intake valve 8 (because the distance between the front and rear intake ports 6 is smaller than the distance between the front and rear intake valves 8), the intake valve 8 Can be suppressed from becoming a resistance to intake air, and the required intake air amount can be secured.

In the conventional type in which the center line 23 of the intake port 6 passes through the axis of the intake valve 8, as shown by the dotted arrow 28 in FIG. 4, the intake air tends to collide with the inner surface of the cylinder bore 3 and disperse in the front-rear direction. Therefore, it is difficult to form a strong flow of intake air inside the cylinder bore 3, and therefore it is difficult to strengthen the tumble flow. In Patent Document 1, since the pair of intake ports 6 are oriented in the directions away from each other in a plan view, it is presumed that the intake air tends to be dispersed in particular.

On the other hand, in the present embodiment, as described above, a strong intake flow is formed inside the cylinder bore 3 by the synergistic effect of the offset mode of the intake port 6 and the mode of the outer surface 19, and the tumble flow is generated. It can be said that it can be strengthened. In particular, when the inner diameter of the cylinder bore 3 is small like an internal combustion engine for a light vehicle or an internal combustion engine for a small vehicle, the intake air discharged from the intake port 6 immediately reaches the inner surface of the cylinder bore 3 and is therefore strong against the flow of intake air. It can be said that it is possible to give direction and to ensure the strengthening of the tumble flow.

Although the embodiments of the present invention have been described above, the present invention can be variously embodied. For example, in the embodiment, the intake port 6 is formed to be narrowed in the longitudinal front view, but it can also be formed in a straight shape in the longitudinal front view. Further, the present invention can be applied to an internal combustion engine of a direct injection type (in-cylinder injection type) instead of the port injection method.

Although it has already been described that only the inner surface 18 or the inner / outer surfaces 18, 19 may be inclined or curved as a means for forming the intake port 6 in a constricted manner, when the inner and outer side surfaces 19, 19 are inclined or curved. It is also possible to make the degree of inclination or curvature different on the inner and outer surfaces, such as loosening the inclination of the inner side surface 18 or reducing the degree of curvature.

The present invention can be embodied in a cylinder head of an internal combustion engine. Therefore, it can be used industrially.

1 Cylinder block 2 Cylinder head 3 Cylinder bore 4 Piston 5 Combustion chamber 6 Intake port 6a Intake port outlet (downstream end)
6b Intake port inlet (upstream end)
7 Exhaust port 8 Intake valve 12 Partition wall 18 Inner surface of intake port 19 Outer surface of intake port 19a Straight part 19b Curved part 20 Center line of partition wall 23 Center line of intake port 24 Axis center of intake port

Claims (1)

A pair of intake ports corresponding to each cylinder bore are formed so as to extend substantially parallel to the direction orthogonal to the crank axis in a plan view seen from the cylinder bore axis direction, and the outlets of the intake ports are respectively formed by an intake valve. It has a structure that opens and closes
In the plan view, the pair of intake ports are offset so that their center lines are located between the axes of the pair of intake valves.
In addition, the side surface of both intake ports on the downstream side is inclined or curved so as to be constricted in a plan view.
Cylinder head of internal combustion engine.

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