JPH0694855B2 - Engine intake system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to an intake device for an engine, and in particular to two branch intake passages that are branched downstream of a common intake passage.
The present invention relates to an intake device of a type in which one intake port is opened in a combustion chamber of an engine and an intake valve for opening and closing the intake port is arranged for each intake port.

(Prior Art) Conventionally, in a cash register engine, two intake ports having substantially equal opening areas are opened in each combustion chamber to secure a large opening area, and the intake air formed in the cylinder head is formed. By connecting the passages to each intake port at a large angle along the axial direction of the combustion chamber and allowing the intake air to flow straight into the combustion chamber, the charging efficiency of the engine was maximized and the engine output was increased. The intake structure of an engine is well known.

Such a two-port type intake structure is advantageous in that it achieves high output during high load operation, but on the other hand, during low load operation with a small intake amount, the intake flow velocity weakens and combustibility deteriorates, There is a disadvantage that it is disadvantageous both in terms of fuel consumption and emission.

In order to eliminate such a drawback, a low-load intake passage and a high-load intake passage provided with a shutter valve are connected to the two intake ports, respectively, and the shutter valve is closed during low-load operation of the engine so that the high-load intake passage is closed. It is known that intake is performed only from the load intake passage (see, for example, Japanese Patent Laid-Open No. 56-44419).

However, such measures are not always effective as low load measures. That is, since the opening areas of the two intake ports were originally maximized to increase the output, the opening area is reduced during extremely low load operation with a small intake volume even if only one intake port is used. Is still too large to effectively increase the intake flow velocity, and it is not possible to effectively form the swirl that is essential for improving combustibility.

It seems that such a problem can be solved by narrowing the passage area of the low load intake passage, but for the purpose of achieving high output, the port connection portion of the intake passage is in the axial direction of the combustion chamber as described above. Since they are formed in the same direction, even if a high velocity flow is generated in the combustion chamber by increasing the intake velocity, it will not be generated as an effective swirl along the circumferential direction of the combustion chamber. Therefore, there is a problem that the flow of the intake air is damped early in the compression stroke. On the other hand, if you try to increase the flow velocity as much as possible and throttle the low-load intake passage too much, the load range you can bet on is limited accordingly, and you can open the shutter valve in a relatively low load range and also from the high-load intake passage. The need to supply inspiration arises. In that case, since the two intake ports are formed opposite to each other with respect to the horizontal center line of the combustion chamber, the intake flow drawn from the low load intake port and the intake flow drawn from the high load intake port Collided with each other, the swirls were weakened even more, even if they were not eliminated,
There is a drawback that it is difficult to secure good flammability by swirl.

On the other hand, when the engine is operating under a high load, a large amount of intake air is supplied from the two intake ports, so it is possible to ensure the filling amount, but with that alone, the output performance and fuel efficiency of the engine are sufficiently improved. Can not do it. That is, it is necessary to provide an exhaust port and a spark plug in addition to two intake ports in the combustion chamber. If the exhaust port is provided close to one of the intake ports, intake air from the intake port at the time of intake / exhaust overlap will occur. However, there is a problem that the air blows through to the exhaust port side as it is. Therefore, the intake ports may be installed at positions substantially equidistant from both intake ports, but in that case, it becomes difficult to dispose the ignition plug at a position advantageous for improving ignitability. In other words, it is practically difficult to dispose the exhaust port and the spark plug consistently with respect to the two intake ports.

(Object of the Invention) The present invention has been made in view of the problems in the arrangement structure of the exhaust port and the ignition plug in the intake system of the engine having the two intake ports and the two intake ports, and By considering distribution, it is an object of the present invention to provide an intake device for an engine, which can prevent blow-off of fuel from an exhaust port as much as possible and can improve ignition performance of a spark plug.

Therefore, according to the present invention, straight first and second intake ports that are respectively connected to the first and second branched intake passages that are branched downstream of the common intake passage are provided so as to be opened in the combustion chamber. , A spark plug and an exhaust port are provided in the combustion chamber at positions facing the first and second intake ports, respectively, and the intake port and the exhaust port are defined by an extension line of the valve shaft of the intake valve and a valve shaft of the exhaust valve. The extension line is formed to incline in directions opposite to each other with respect to the cylinder axis so as to intersect below the combustion chamber when projected onto a plane including the cylinder axis, and one fuel injection is provided in the common intake passage. A valve is provided, and the fuel injection valve distributes fuel to both the first and second branch intake passages, and has a second fuel distribution amount to the first branch intake passage in the entire load range from low load to high load. More than the amount of fuel distributed to the branch intake passage There is provided an intake device disposed comprising engine position that.

(Effect of the Invention) According to the present invention, in the entire load range from low load to high load, more fuel is distributed to the first intake port facing the spark plug, so that there is rich fuel around the spark plug. While the air-fuel mixture exists and the ignitability by the spark plug is improved, the fuel distribution amount to the second intake port facing the exhaust port is reduced, so that the blow-through of fuel at the time of intake / exhaust overlap can be reduced accordingly. it can.

(Example) Hereinafter, the Example of this invention is described more concretely.

As shown in FIG. 1, in the combustion chamber 2 of one cylinder 1 of the engine E, the cylinder block of the engine E (3 in FIG.
(See), the first and second intake ports 4 and 5 having substantially the same diameter are opened substantially symmetrically with respect to the center line 1 in the width direction, and the positions are opposed to the second intake port 5 across the center line m in the longitudinal direction. Has
The exhaust port 6 is opened.

Intake passage 7 for supplying intake air to the first and second intake ports 4 and 5
Is gradually branched in the cylinder head (see 8 in FIG. 2), and is formed so as to project substantially along the width direction center line 1 in front of the first and second intake ports 4 and 5. It is branched into two branches by the partition wall 9 and the branch intake passages 10 and 11 are connected to the first and second intake ports 4 and 5, respectively. As shown in the figure, the center line 1'of the intake passage 7 is slightly eccentric to the first intake port 4 side with respect to the center line 1 in the width direction, so that the first intake port 4 can be made smaller than the second intake port 5. The shutter valve 12 is provided upstream of the shutter valve 12. The shutter valve 12 is not specifically shown, but the intake passage 7 is closed during low load operation of the engine E by a well-known opening / closing control mechanism (for example, a link mechanism connected to a slot valve).
During high load operation, the opening / closing is controlled so as to open according to the load. Then, the shutter valve 12 of the intake passage 7
On the upstream side, with respect to the center line 1'of the intake passage 7, the upstream opening 13a of the auxiliary intake passage 13 is opened to the bottom wall of the intake passage 7 by being biased toward the second intake port 5 side. The auxiliary intake passage 13 has a downstream side opening 13b which is opened close to the first intake port 4, and is gently curved so as to cross the center line 1 ', and the upstream side opening 13a and the downstream side opening 13b. Communicate with. As shown more specifically in FIG. 2, this auxiliary intake passage 13 is formed in a bottom wall 14 forming the bottom of the intake passage 7, and its downstream side opening 13b has an upstream end portion of the partition wall 9, that is, Intake valve 1 downstream from the branch point of the branch intake passages 10 and 11
It is set at a position as close as possible to the first intake port 4 opened and closed by 5. Therefore, the auxiliary intake passage
The total amount of intake air flowing down through 13 flows into the combustion chamber 2 through the first intake port 4. The auxiliary intake passage 13 has a first
The branch intake passage 10 curved with a large curvature in the axial direction of the cylinder 1 immediately upstream of the intake port 4 intersects the mating surface A between the cylinder block 3 and the cylinder head 8 with a slight inclination angle. And therefore the combustion chamber 2
Has a directivity oriented in the circumferential direction.

A shutter valve 12 that opens and closes the intake passage 7 is disposed obliquely downward toward the downstream side slightly downstream of the upstream opening 13a of the auxiliary intake passage 13, and intake air slightly downstream of the shutter valve 12 is provided. A fuel injection valve 17 is attached to an attachment portion 16a provided in advance on the upper wall 16 of the passage 7.
In this case, the fuel injection port 18 is set so as to be located slightly downstream of the rotary shaft 12a of the shutter valve 12 and on the center line 1'of the intake passage 7 (see FIG. 1). As is well known, the fuel injected by the fuel injection valve 17 does not spread to a certain distance, goes straight, and thereafter spreads in a cone shape. Therefore, as described above, if the fuel injection port 18 is set on the center line l'of the intake passage 7, the center line l'is eccentric to the first intake port 4 side in advance, so that it spreads in a cone shape. Fuel intake 1st and 2nd intake ports 4,5
The distribution ratio for the first intake port 4 side increases.

Therefore, during the low load operation of the engine E in which the intake air is exclusively taken from the first intake port 4, more fuel is mixed with the intake air, and the combustibility of the air-fuel mixture is improved.

Further, during high-load operation of the engine E in which intake is performed from the first and second intake ports 4 and 5, a relatively small amount of fuel is supplied from the second intake port 5 facing the exhaust port 6. Therefore, the amount of blow-through of the fuel during the intake-exhaust overlap can be reduced as much as possible.

It should be noted that the shutter valve 12 is disposed between the upper side opening 13a of the auxiliary intake passage 13 and the fuel injection port 18 and is inclined obliquely downward so as to be virtual from the fully closed position (a) shown by the solid line in FIG. By setting to open around the hour hand to the fully open position (b) indicated by the line, the intake passage volume downstream of the shutter valve 12 when the shutter valve 12 is closed can be minimized. The fuel injection valve 17 is installed at the first, second intake port 4,
At the upstream side of the partition wall 9 of 5, the fuel is supplied to both branch intake passages 10,
Since it is necessary to disperse it in a cone shape over 11 and therefore it cannot be unnecessarily set downstream, it is necessary to install it on the upstream side If the shutter valve 12 is arranged as described above, the fuel injection valve Since the shutter valve 12 can be installed closest to 17 and in the smallest occupied space, it is possible to minimize the intake passage volume downstream of the shutter valve 12, which is the dead volume when the shutter valve 12 is closed.

An intake valve 15 that opens and closes the first intake port 4, an intake valve (not shown) that opens and closes the second intake port 5, and an intake valve 19 that modifies the exhaust port 6 are provided by a well-known overhead cam mechanism 20. The opening and closing are driven at predetermined timings synchronized with the rotation of E.

Further, as shown in FIG. 1, the spark plug 21 has a portion where the first and second intake ports 4 and 5 and the exhaust port 6 are not provided, more specifically, a first intake port 13 in which the auxiliary intake passage 13 is opened. 1 The intake port 4 is arranged at a position opposite to the longitudinal centerline m of the combustion chamber 2 so as to face it.

In other words, the auxiliary intake passage 13 is the spark plug installed.
Connect to the first intake port 4, which is the intake port on the side closer to 21.

As described above, if the relationship between the auxiliary intake passage 13 and the spark plug 21 is selected, the spark plug 21 will be located on the swirl trajectory of the swirl formed by the auxiliary intake passage 13. Scavenging is improved, spark plug 21
The mixture can be ignited with good ignitability. Furthermore, the intake air flowing down through the auxiliary intake passage 13 is
Since the spark plug 21 is first directed through the first intake port 4, the swirl that is stronger than that by the exhaust valve 6 is not generated.

That is, generally, the exhaust valve slightly protrudes into the combustion chamber even when the exhaust port is closed, and the opening 13b of the auxiliary intake passage 13 is provided in the intake port 5 on the side far from the spark plug 21. Then, the swirl is attenuated by the exhaust valve.

Further, during the high load operation of the engine E, the rich air-fuel mixture supplied from the first intake port 4 first directs toward the ignition plug 21, so that the rich air-fuel mixture gathers around the ignition plug 21 and the ignition plug 21 Ignitability is improved.

Next, FIGS. 3 (1) to 3 (9) show cross sections (1) to FIG. 4 in FIG.
As shown in the change in the cross-sectional shape of the intake passage 7 in the cylinder head 8 corresponding to (9), the intake passage 7 having the first circular cross section is shown.
Changes from an elliptical shape to a paddle shape as it goes downstream, and is finally branched into branch intake passages 10 and 11 having two circular cross sections.

The auxiliary intake passage 13 having a flat rectangular cross-section located below the intake valve 7 and having a passage cross-sectional area sufficiently smaller than the passage cross-sectional area of the intake passage 7 is the first intake passage 7 From the position eccentric to the second intake port 5 side (right side in the figure) of the branch intake passage 10 gradually connected to the first intake port 4 side (left side in the figure) and connected to the first intake port 4.
Eventually, it intersects with the bottom surface and finally opens immediately upstream of the first intake port 4.

As shown in FIG. 4, the bottom wall forming the bottom surface of the intake passage 7
By forming the auxiliary intake passage 13 in the inside 14, the auxiliary intake passage 13 is formed at a relatively small inclination angle with respect to the mating surface A of the cylinder block 3 and the cylinder head 8,
Further, when viewed as a plane shape, the second intake port 5 side is crossed to the first intake port 4 side and is smoothly curved, so that particularly when the shutter valve 12 is fully closed, the low load of the engine E is reduced. During operation, the intake air that flows down exclusively through the auxiliary intake passage 13 is throttled to accelerate the flow velocity, and while directing in the circumferential direction of the combustion chamber 2, the first intake port 4
To flow into the combustion chamber 2 and generate a swirl in the combustion chamber 2 in the circumferential direction.

Since this swirl is formed in the circumferential direction, it is not easily attenuated and ignites and burns favorably by the ignition of the spark plug 21 at the end of the compression stroke.

In the above embodiment, the intake passage 7 is branched downstream of the shutter valve 12, and the auxiliary intake passage 13 is formed by crossing from the second intake port 5 side to the first intake port 4 side. It is not limited to.

That is, as shown in FIG. 5, the auxiliary intake passage 23 may be formed straight along the extension of the branch intake passage 10 connected to the first intake port 4.

[Brief description of drawings]

FIG. 1 is an explanatory cross-sectional view of an essential part of an engine showing an embodiment of the present invention, FIG. 2 is a vertical cross-sectional view taken along line II-II of FIG. 1, and FIGS. 3 (1) to (9) are intake passages. Each sectional explanatory view showing changes in sectional shape, FIG. 4 is a longitudinal sectional explanatory view showing each sectional position of FIGS. 3 (1) to (9), and FIG. 5 is another embodiment of the present invention. FIG. 2 is a cross-sectional explanatory view of an essential part of the engine similar to FIG. 1. 2 …… Combustion chamber 4,5 …… First and second intake ports 7 …… Intake passage 10,11 …… Branch intake passage 12 …… Shutter valve 13 …… Auxiliary intake passage 14 …… Bottom wall 15 …… Intake Valve 21 ... Spark plug.

Claims (1)

[Claims] 1. A first and a second branch branched downstream of a common intake passage.
Straight first and second connecting to the branch intake passages
An intake port is provided so as to open in the combustion chamber, and a spark plug and an exhaust port are provided at positions facing the first and second intake ports, respectively, in the combustion chamber, and each of the intake port and the exhaust port is a valve shaft of an intake valve. The extension line of the exhaust valve and the extension line of the valve shaft of the exhaust valve are formed to be inclined in directions opposite to each other with respect to the cylinder axis so as to intersect below the combustion chamber when projected onto a plane including the cylinder axis. One fuel injection valve is provided in the common intake passage, and the fuel injection valve includes the first and second fuel injection valves.
The fuel is distributed to both the branch intake passages, and the fuel is distributed to the first branch intake passage at a position where the fuel distribution amount is larger than the fuel distribution amount to the second branch intake passage in the entire load range from low load to high load. This is the engine intake system.