JPH0380972B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an intake system for an engine that can substantially uniformize the strength of swirl in each cylinder to prevent torque fluctuations.

Conventionally, engine intake systems have been equipped with a low-load intake port and a high-load intake port for each cylinder, a single intake valve for opening and closing both intake ports, and a high-load intake port for high-load use. A model equipped with an on-off valve that opens when a load is applied has been proposed (Utility Model Publication No. 54-61118).

The intake system of this engine closes the high-load intake port with an on-off valve during low-load conditions, allowing intake air to be drawn into the combustion chamber only from the low-load intake port, increasing the intake flow rate and strengthening the swirl. , which promotes fuel atomization and improves combustion performance and fuel efficiency.At the same time, when the load is high, the on-off valve opens and intake air is drawn from the high-load intake port in addition to the low-load intake port, improving charging efficiency. This has the advantage of improving output performance.

However, as described below, the conventional engine intake system described above does not give any consideration to equalizing the strength of the swirl in each cylinder, resulting in an imbalance in the strength of the swirl in each cylinder. The drawback is that there is a difference in combustibility between cylinders, resulting in torque fluctuations.

That is, the intake system of the conventional engine described above is
The low-load ports of each cylinder that communicate with the tournament-type inlet manifold have the same inflow angle with respect to the combustion chamber. However, when using the above tournament type inlet manifold,
The intake air in the intake passages to the two outer cylinders flows toward the outside of the cylinder row due to its inertia, resulting in a relatively large flow rate, while in the intake passages to the inner two cylinders, the intake air bends inward. The flow rate is relatively low. However, as mentioned above, in the conventional engine intake system, the inflow angle of all low-load intake ports is set uniformly, so the strength of the swirl in the inner cylinder where the intake air flow is insufficient is lower than that in the outer cylinder. The disadvantage is that the strength of the swirl in each cylinder becomes unbalanced, resulting in differences in combustibility and torque fluctuations.

Therefore, an object of the present invention is to uniformize the strength of the swirl in each cylinder by setting different inflow angles of the low-load intake port to the combustion chamber for the cylinders at both ends of the cylinder row and the cylinder at the center of the cylinder row. An object of the present invention is to provide a novel intake system for an engine that can be used in various ways and that can prevent torque fluctuations from occurring.

For this reason, the engine intake system of the present invention is
An engine comprising at least three or more cylinders, each cylinder having a low-load intake port and a high-load intake port, and each intake port communicating with an intake collecting section via an inlet manifold. By forming each of the above-mentioned low-load intake ports so that the width thereof becomes continuously narrow from upstream to downstream, the flow speed is increased with small intake resistance, and the swirl of all cylinders is strengthened. Of the load intake ports, the low-load intake ports of the cylinders at both ends of the cylinder row are inclined toward the outside of the cylinder row to follow the flow of intake air, reducing intake resistance and reducing the swirl of the cylinders at both ends. At the same time, the inflow angle of the low-load intake port of the cylinder in the center of the cylinder row with respect to the combustion chamber is set larger than that of the cylinders at both ends, and the swirl of the cylinder in the center is set to be more oriented in the tangential direction of the combustion chamber. By compensating the strength of the swirl, the strength of the swirl in each cylinder is made uniform.

The present invention will be explained in detail below using an example having four cylinders.

FIG. 1 is a longitudinal sectional view of one cylinder A, FIG. 2 is a horizontal sectional view, and FIGS. 3 and 4 are sectional views of essential parts, respectively.

In Fig. 1, 1 is a cylinder arranged vertically, 2 is a cylinder head, 3 is a combustion chamber, 4 is an intake port formed in the cylinder head 2, 5 is the intake port 4, and the air-fuel mixture is located below. a low-load intake port 6 that supplies air-fuel mixture to the combustion chamber 3 in a horizontal direction; and a high-load intake port 7 that is located above and supplies air-fuel mixture to the combustion chamber 3 in a direction inclined with respect to the horizontal plane.
A partition wall 8 divides both the low-load intake port 6 and the high-load intake port 7 into the combustion chamber 3.
a single intake valve that opens and closes at an opening to the air; 11 is an intake collecting part such as a carburetor or an electronic fuel injection part; 12 is an intake collecting part 11; a low-load intake port 6; and a high-load intake port 7; The inlet manifold 13 is rotatably supported on the inlet manifold 12 by a shaft 14, and is an on-off valve that opens and closes the intake port 7 for high loads, and the on-off valve 13 is closed during low loads. The air-fuel mixture is supplied to the combustion chamber 3 only from the low-load intake port 6, increasing the flow velocity of the air-fuel mixture, strengthening the swirl in the combustion chamber 3, promoting fuel atomization, and improving combustion performance. , while improving fuel efficiency, it opens during high loads and supplies the air-fuel mixture from the high-load intake port 7 to the combustion chamber 3, improving intake efficiency and charging efficiency, and improving output performance. There is.

In addition, 15 is an exhaust port formed in the cylinder head 2, 16 is an exhaust valve, 17 is a camshaft, 1
8 and 18 are rocker arm shafts, 19 and 19 are rocker arms, and 20 and 20 are valve springs.

On the other hand, in FIG. 2, B, C, and D are cylinders having substantially the same structure as the cylinder A described above.

The four cylinders A, B, C, and D are arranged so that the center line of each cylinder 1, 1, 1, 1 is vertically arranged, and each cylinder 1, 1, 1, 1 is arranged in the same horizontal plane so that they are straight. It forms a line of cylinders. The inlet manifold 12 that supplies the air-fuel mixture to each of the cylinders A, B, C, and D is formed in a banana shape to make the intake resistance due to the bending of the intake passage 25 smaller than that of a tournament-type manifold, and to The air-fuel mixture flowing from the base _25F of the cylinder 25 to the branch passages _25A , _25B , _25C , and _25D is deflected outward in the cylinder row direction due to its inertia. Therefore, as shown by the arrows V _A , V _B , V _C , and V _D in FIG. The flow of the air-fuel mixture in the cylinders 25 _A and 25 _D is directed toward the outside of the cylinder row rather than the flow of the air-fuel mixture in the branch passages 25 _B and 25 _C leading to the central cylinders B and C.

As shown in FIG. 2, the low-load intake ports 6, 6, 6, 6 of each of the cylinders A, B, C, and D are connected to the inner (center side) wall surfaces _27A ,
_27B , _27C , and _27D are inclined outward in the direction of the cylinder row, and the above-mentioned low-load intake ports 6, 6,
6, 6 are formed so that their widths become continuously narrower from upstream to downstream, thereby increasing the flow speed of the air-fuel mixture with small intake resistance. Furthermore, the low-load intake ports 6, 6 of the cylinders B and C in the center of the cylinder row
The outward inclination angle of the inner wall surfaces 27 _B and 27 _C is
The angle of inclination is set to be larger than the outward inclination angle of the inner wall surfaces 27 _A and 27 D of the low-load intake ports 6 and 6 of the cylinders A and _D at both ends of the cylinder row, and The inflow angles β, β of the low-load intake ports 6, 6 with respect to the combustion chamber 3 are set larger than the inflow angles α, α of the low-load intake ports 6, 6 of the cylinders A, D at both ends with respect to the combustion chamber 3. There is. Therefore,
In the central cylinders B and C, the air-fuel mixture flows into the combustion chambers 3 and 3 more tangentially than in the cylinders A and D at both ends.

In the engine intake system configured as described above, the engine is currently in a low load state, and each cylinder A,
B, C, D high load intake ports 7, 7, 7, 7
It is assumed that the on-off valves 13, 13, 13, 13 are closed.

At this time, the air flows from the intake collecting part 11 through the base _25F of the inlet manifold 12 to the branch passage 25.
Since the inlet manifold is banana-shaped, the air-fuel mixture flowing to _A , _25B , _25C , and _25D flows into the second
As shown by the arrows V _A , V _B , V _C , and V _D in the figure, all
The air flows only into the low-load intake ports 6, 6, 6, 6 of each cylinder A, B, C, and D in an outward streamline in the direction of the cylinder row with respect to the center of the cylinder row. The low-load intake ports 6, 6, 6, 6 are inclined outward in the cylinder row direction by the inner wall surfaces _27A , _27B , _27C , _27D , and Since it follows the flow line of the air, the intake resistance due to bending of the passage is small, the air-fuel mixture is efficiently sucked into the combustion chamber, and each of the above-mentioned low-load intake ports 6, 6,
Since the widths of 6 and 6 are continuously narrowed, the flow speed of the air-fuel mixture is increased with small intake resistance. In this way, at low load, the low load intake ports 6, 6,
In addition to the fact that the air-fuel mixture is taken in only from the air-fuel mixtures 6 and 6, the direction of the low-load intake ports 6, 6, 6, and 6 is along the streamline of the air-fuel mixture in the inlet manifold 12, and Port 6, 6,
6, 6 are continuously narrowed, the air-fuel mixture is forced to flow horizontally into the combustion chamber 3 at high speed with small intake resistance, and a strong swirl is generated as indicated by the arrows S _A , S _B , It is efficiently generated as shown in S _C and S _D ,
Fuel atomization is promoted and combustion performance and fuel efficiency are improved.

Furthermore, the inflow angles β, β of the low-load intake ports 6, 6 of the cylinders B, C at the center of the cylinder row with respect to the combustion chambers 3, 3 are the same as those of the low-load intake ports 6, 6 of the cylinders A, D at both ends. The inflow angle α, is set larger than α,
Because they are oriented more tangentially, the velocity components of streamlines V _B and V _C in the inner branch passages 25 _B and 25 _C towards the outside in the cylinder row direction are
Even if the velocity components of the streamlines V _A and V _C toward the outside in the cylinder row direction at 5 _A and 25 _C are smaller, the swirl of the central cylinders B and C compensates for the difference in velocity components. The strength of the swirl in each cylinder A, B, C, and D is made uniform, and no torque fluctuation occurs.

Next, assuming that the engine is operating under high load, the on-off valves 13, 13,
13, 13 open, the air-fuel mixture flows through the low-load ports 6, 6, 6, 6 and the high-load intake ports 7,
7, 7, 7 to the combustion chambers 3, 3, 3, 3, the charging efficiency is improved and the output performance is improved.

In the above embodiment, a banana-shaped inlet manifold is used, but a tournament-type inlet manifold may also be used. In this case, the air-fuel mixture is attenuated and flows inward to the cylinder in the center of the cylinder row, but the inflow angle of the low-load intake port of the cylinder in the center of the cylinder row with respect to the combustion chamber is adjusted inward to the cylinder row. This inflow angle is set to be larger than the inflow angle of the low-load intake ports of the cylinders at both ends of the cylinder row, which is inclined toward the outside of the cylinder row, in the tangential direction of the combustion chamber of the central cylinder. The inflow velocity component of the air-fuel mixture may be increased to balance the swirl strength of each cylinder.

Further, in the above embodiment, four cylinders are provided, but it goes without saying that any number of cylinders may be provided as long as there are three or more.

As is clear from the above description, in the engine intake system of the present invention, the inflow angle of the low-load intake port of the cylinder in the center of the cylinder row with respect to the combustion chamber is set to be larger than that of the cylinders at both ends of the cylinder row. ,
Since the swirl strength of the central cylinder is compensated for, the swirl strength of each cylinder can be made uniform.
Torque fluctuations can be eliminated. Further, the low-load intake port of each cylinder is formed so that its width becomes continuously narrower from upstream to downstream,
In addition to increasing the flow rate of the mixture with small intake resistance,
Among the low-load intake ports mentioned above, the low-load intake ports of the cylinders at both ends of the cylinder row are inclined outward in the direction of the cylinder row to create intake resistance along the flow of intake air through the inlet manifold that communicates with the intake collecting section. Since it is small, a strong swirl can be generated efficiently and combustion performance and fuel efficiency can be improved.

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional view of one embodiment of the present invention;
The figure is a cross-sectional view of the above embodiment, and FIGS. 3 and 4 are cross-sectional views of essential parts, respectively. DESCRIPTION OF SYMBOLS 1... Cylinder, 3... Combustion chamber, 5... Partition wall, 6... Intake port for low load, 7... Intake port for high load, 8... Intake valve, 11... Intake gathering part, 12... ...Inlet manifold, 13...
Open/close valve.

Claims (1)

[Claims] 1. At least three or more cylinders are provided, each cylinder is provided with a low-load intake port and a high-load intake port, and the upstream end of each intake port is connected to an intake collecting section at one end. In an engine that is connected to an inlet anifold that communicates with The low-load cylinder ports of the cylinders at both ends of the cylinder row are inclined toward the outside of the cylinder row, and the inflow angle of the low-load intake port of the cylinder at the center of the cylinder row with respect to the combustion chamber is set larger than that of the cylinders at both ends. An engine intake device characterized by: