JPH0330697B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is directed to an engine intake system, in particular, to open a plurality of intake ports such as two ports into a combustion chamber of the engine, and to open the same to each intake port. This invention relates to a type of intake device equipped with an intake valve that opens and closes.

(Prior art) Conventionally, in a reciprocating engine, two intake ports with approximately equal opening areas are opened for each combustion chamber to ensure a large opening area, and an intake passage formed in the cylinder head is By connecting each intake port at a large angle along the axial direction of the combustion chamber and allowing intake air to flow straight into the combustion chamber, the engine's filling efficiency is maximized and the engine output is increased. The intake structure is well known.

Such a two-port intake structure is advantageous in that it can achieve high output during high-load operation, but on the other hand, during low-load operation with a small amount of intake air, the intake air flow rate becomes weaker and combustibility decreases. In terms of fuel efficiency,
There is also a disadvantage in terms of emission.

In order to eliminate this drawback, a low-load intake passage and a high-load intake passage with a shutter valve interposed are connected to the above two intake ports, and the shutter valve is closed when the engine is operating at low load. , a device in which air is taken only from the low-load intake passage is known (for example, Japanese Patent Application Laid-Open No. 1989-1999)
(See Publication No. 44419).

However, such measures are not necessarily effective as low-load measures. In other words, the opening area of the two intake ports was originally designed to be maximized in order to achieve high output, so even if only one intake port is used, during extremely low load operation where the amount of intake air is small, the opening area will be reduced. is still too large to effectively improve the intake air flow velocity, making it impossible to effectively form the swirl that is essential for improving combustibility.

It seems that such a problem can be solved by narrowing down the passage area of the low-load intake passage, as disclosed in Japanese Patent Laid-Open No. 56-146015, but in that case, the passage area of the high-load intake passage The original purpose of high output cannot be achieved unless the passage area is made very large, and if the passage area is actually increased, the imbalance with the passage area of the low-load intake passage increases, resulting in low-load A so-called switching shock occurs when switching from a low load to a high load, and when the load is high, intake air concentrates in the high load intake passage with less intake resistance, effectively increasing the output. There is a contradiction in that it is not possible to secure an effective intake passage area to achieve this goal. Furthermore, for the purpose of achieving high output, the port connection part of the intake passage is formed along the axial direction of the combustion chamber, as mentioned above, so by increasing the intake air velocity, the flow velocity within the combustion chamber can be increased. Even if a fast flow is generated, it is not generated as an effective swirl along the circumferential direction of the combustion chamber. Therefore, there is a problem in that this intake air flow is attenuated early in the compression stroke. However, if you restrict the low-load intake passage too much in an attempt to increase the flow velocity as much as possible, the load range that can be covered will be limited accordingly, and if you open the shutter valve in a relatively low load range, the high-load intake passage will also be able to handle the load. It becomes necessary to supply intake air. In that case, since the two intake ports are formed to face each other with respect to the horizontal center line of the combustion chamber, the intake flow taken in from the low-load intake port and the intake flow taken in from the high-load intake port are different. If the swirls collide with each other, the swirl is further weakened, if not eliminated, and it is difficult to ensure good combustibility due to the swirl.

As described above, restricting the low-load intake passage and the intake port connected thereto is not only inconsistent with the objective of achieving high output, but also causes various new problems.

The applicant aimed at increasing the output of the engine.
without substantially changing the intake port system.
In Japanese Patent Application No. 176,776/1987, we have already proposed an engine intake system equipped with an intake structure that can generate a swirl that is effective in improving combustibility within the combustion chamber during low-load operation of the engine. .

The proposed invention relates to an engine intake system in which a plurality of intake ports are opened to combustion chambers of an engine, and each intake port is opened and closed by an intake valve. An on-off valve is provided in the intake passageway, and the on-off valve is closed during low-load operation and opened during high-load operation, and the passage area of the intake passage is controlled to increase or decrease depending on the operating condition of the engine. The basic feature is that an auxiliary intake passage is provided, which branches from the bottom of the intake passage, is connected to any one of the intake ports, and has a passage area smaller than that of the intake passage.

That is, in this invention, during low-load operation of the engine when the on-off valve is closed, intake air flows exclusively through the auxiliary intake passage formed at the bottom side of the intake passage and flows through the engine at a high flow rate through the intake port to which this passage is connected. is supplied to the combustion chamber. In that case, since the auxiliary intake passage is formed at the bottom side of the intake passage, it necessarily forms a shallow angle with respect to the mating surface of the cylinder head and cylinder block, and the intake air flowing into the combustion chamber is It is possible to generate a swirl that rotates in the circumferential direction of the chamber, and during high-load engine operation when the on-off valve is opened, intake air is drawn in efficiently from multiple intake ports, ensuring the original high output. This is possible.

Therefore, according to the present invention, it is possible to improve combustibility during low-load operation, as well as improve fuel efficiency and emission performance, without sacrificing the original purpose of the two-intake port system, which is to increase engine output. However, there is still room for improvement.

One of them is the problem of the switching shock that may occur when switching from a low load to a high load as described above. In other words, while the on-off valve is opened from the low-load region where the auxiliary intake passage is used exclusively, when moving to the high-load region, a large amount of intake air flows into the combustion chamber from each intake port at once, so the charging amount decreases. increases rapidly, causing a kind of torque shock.

(Object of the Invention) The object of the present invention is to expand the low load range that can be covered with the on-off valve closed while maintaining the swirl during low-load operation. The purpose of this is to prevent the above-mentioned switching shock by ensuring a sufficient amount of intake air when the valve is closed so that the intake air amount gap is as small as possible.

(Structure of the Invention) Therefore, the present invention opens a plurality of intake ports in parallel to the combustion chamber, each of which is opened and closed by an intake valve, and which is opened and closed by an on-off valve that closes at low load and opens at high load. Branched downstream of the on-off valve,
An intake passage with each branch end connected to the intake port, an upstream opening opening into the low wall of the intake passage upstream of the on-off valve, and a downstream opening opening above the branch point of the intake passage. An auxiliary intake passage is provided in a low wall on the downstream side of the on-off valve and opens toward one of the intake ports, and the passage wall on the other intake port side of the auxiliary intake passage is connected to the other intake port. The present invention provides an intake device for an engine, which is formed so as to be inclined from the intake port side to the one intake port side where the auxiliary intake passage opens so as to follow the flow of intake air to the one intake port.

With this setting, the intake port opening of the auxiliary intake passage can be provided in the common passage before the intake passage branches, so it is possible to secure a large opening area, especially the width dimension, and as a result, the auxiliary intake passage A large passage cross-sectional area can be secured, and the operating range that can be covered by the auxiliary intake passage can be expanded.

At the same time, as mentioned above, since the auxiliary intake passage is provided on the low wall of the intake passage and is formed so as to be inclined toward the one intake port side where the auxiliary intake passage is opened, the auxiliary intake passage can flow down the auxiliary intake passage to the one side. The intake air flowing into the combustion chamber from the intake port is directed in the circumferential direction of the combustion chamber, thereby creating a strong swirl within the combustion chamber.

(Effects of the Invention) Therefore, according to the present invention, the load range that can be covered with the on-off valve closed can be expanded to the high load side while maintaining swirl performance, and the load range can be expanded from low load to high load. A so-called switching shock at the time of transition can be effectively prevented.

(Example) Hereinafter, an example of the present invention will be described in more detail.

As shown in FIG. 1, the combustion chamber 2 of one cylinder 1 of the engine E has first and second intake ports of approximately the same diameter, which are approximately symmetrical with respect to the center line l in the width direction of the cylinder block of the engine E. 4 and 5 are opened,
Exhaust ports 6 and 7 are located at positions facing the first and second intake ports 4 and 5 across the longitudinal center line m.
is opened.

The intake passage 8 that supplies intake air to the first and second intake ports 4 and 5 gradually branches within the cylinder head (see FIG. 2), and before the first and second intake ports 4 and 5, The branched intake passage 1 is divided into two by a partition wall 9 formed to protrude substantially along the width direction center line l.
0 and 11 are connected to the first and second intake ports 4 and 5, respectively. As shown in the figure, a shutter valve 12 is provided on the upstream side of the intake passage 8. Although this shutter valve 12 is not specifically shown, a well-known opening/closing control mechanism (for example, a link mechanism connected to a throttle valve) closes the intake passage 8 during low load operation of the engine E, and closes the intake passage 8 during high load operation. Its opening/closing is controlled so that it opens according to the load. On the upstream side of the shutter valve 12 in the intake passage 8, the upstream opening 13a of the auxiliary intake passage 13 is arranged at the bottom of the intake passage 8, with the upstream opening 13a of the auxiliary intake passage 13 being biased towards the first intake port 4 with respect to the center line of the intake passage 8. It has an opening in the wall. This auxiliary intake passage 13
has a downstream opening 13b as an intake port opening slightly upstream from the tip 9a of the partition wall 9 that partitions the branched intake passages 10 and 11.
By setting the downstream opening 13b at such a position, a sufficient width dimension can be particularly ensured. The auxiliary intake passage 13 is gently curved so as to cross the width direction center line l, and communicates between the upstream opening 13a and the downstream opening 13b.
That is, the passage wall 13c of the auxiliary intake passage 13 on the second intake port 5 side is curved so as to be inclined from the second intake port 5 side toward the first intake port 4 side.

As specifically shown in FIG. 2, the auxiliary intake passage 13 is formed in a bottom wall 14 forming the bottom of the intake passage 8, and its downstream opening 13b is located at the upstream end 9a of the partition wall 9, That is, branch intake passage 1
It is set slightly upstream from the 0 and 11 branch points. Therefore, the intake air flowing down the auxiliary intake passage 13 may be distributed to both the branch intake passages 10 and 11, but the auxiliary intake passage 13 is formed to be inclined toward the first intake port 4 side. Because
The intake air is given directivity toward the first intake port 4, and almost the entire amount flows from the first intake port 4 to the combustion chamber 2.
This results in an inflow into the interior. The auxiliary intake passage 13 has a branch intake passage 10 that is curved in the axial direction of the cylinder 1 immediately upstream of the first intake port 4.
It crosses the mating surface C of the cylinder block 31 and the cylinder head 30 at a slight angle of inclination, and therefore has directionality in the circumferential direction of the combustion chamber 2.

Slightly downstream of the upstream opening 13a of the auxiliary intake passage 13, a shutter valve 12 for opening and closing the intake passage 8 is provided so as to be inclined diagonally downward toward the downstream. A fuel injection valve 17 is attached to a mounting portion 16a provided in advance on the upper wall 16 of the intake passage 8. In this case, the fuel injection port 18 is connected to the shutter valve 1
It is set so as to be located slightly downstream of the rotation shaft 12b of No. 2 and on the center line of the intake passage 8.

Note that the intake valve 1 that opens and closes the first intake port 4
5. An intake valve (not shown) that opens and closes the second intake port 5 and an exhaust valve 1 that opens and closes the exhaust ports 6 and 7
9 (the other is not shown) are driven to open and close at predetermined timings synchronized with the rotation of the engine E by a well-known overhead cam mechanism 20.

Further, as shown in FIG. 1, the spark plug 21
is set in a portion where the first and second intake ports 4 and 5 and exhaust ports 6 and 7 are not provided, more specifically, in the central portion of the combustion chamber 2.

With the configuration of the auxiliary intake passage 13 described above, the passage area of the auxiliary intake passage 13 can be made sufficiently large, so that the load range that can be handled with the shutter valve 12 closed can be expanded, and the auxiliary intake passage Since the intake air flowing down the combustion chamber 13 has directivity in the circumferential direction of the combustion chamber 2, a good swirl can be maintained within the expanded load range.

Furthermore, since the intake air amount when the shutter valve 12 is closed can be secured so that the load range is expanded to the high load side, even if the shutter valve 12 is opened to a high load operation, the shutter valve 12 The rate of increase in intake air when the valve is opened can be made relatively small, and so-called switching shocks can be reliably prevented.

During high-load operation when the shutter valve 12 is opened, sufficient intake air is supplied from the first and second intake ports 4 and 5, ensuring the high output inherent to the two ports.

[Brief explanation of drawings]

FIG. 1 is an explanatory sectional view of a main part of an engine showing an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view taken in the - line direction of FIG. 2... Combustion chamber, 4, 5... First and second intake ports, 8... Intake passage, 9... Partition wall, 10, 11
...Branch intake passage, 12...Shutter valve,
13...Auxiliary intake passage, (13b...Downstream opening,
13c...second intake port side passage wall), 14...
Bottom wall, 15...Intake valve.

Claims (1)

[Claims] 1 A plurality of intake ports, each opened and closed by an intake valve, are opened in parallel into the combustion chamber, and are opened and closed by an on-off valve that closes at low load and opens at high load, and are branched downstream of the on-off valve, with each branch end an intake passage connected to each of the intake ports, an upstream opening opening at the bottom wall of the intake passage upstream from the on-off valve, and a downstream opening upstream from the branch point of the intake passage; An auxiliary intake passage that opens toward one of the intake ports is provided in the bottom wall downstream of the on-off valve, and the passage wall on the other intake port side of the auxiliary intake passage is auxiliary from the other intake port side. 1. An intake device for an engine, characterized in that an intake passage is formed to be inclined toward one intake port where an intake passage opens so as to follow the flow of intake air to the one intake port.