JPS6093121A - Suction device of engine - Google Patents

Abstract

PURPOSE:To form a strong swirl in the combustion chamber in a low load running area by delaying the valve-opening time of an intake valve installed to an intake air port being not connected to an auxiliary intake air path, as compared with the valve-opening time of an intake air port connected to an auxiliary intake air path. CONSTITUTION:In a low load running area where a closing valve 18 is closed, all the intake air passing through a main intake air path 11 is led to an auxiliary intake air path 20 from an opening 19, and a swirl is formed in a combustion chamber 4. The intake valve of the 1st intake air port 5 is opened at earlier timing than the opening time of the intake valve of the 2nd intake air port 6. And, when the intake valve of the 1st intake air port 5 is opened, the intake air staying in the main intake air path 11 in the down-stream side from the closing valve 18 and the 1st and the 2nd branch intake air paths 15, 16 is sucked into the combustion chamber 4 together with the intake air from the auxiliary intake air path 20. Thus, immediately after opening the valve, the quantity of intake air from the 1st intake air port 5 is increased, and the swirl in the combustion chamber 4 is also intensified.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an engine intake system, particularly an engine in which a plurality of intake ports are opened in one combustion chamber, and at least one of the intake ports is connected to an engine load. The present invention relates to an engine intake system of a type that is selectively used according to the type of engine.

(Prior Art) It is known to provide a plurality of intake ports in the combustion chamber of an engine and to selectively use these intake ports depending on the engine load. For example, in the engine disclosed in Japanese Unexamined Patent Application Publication No. 2003-111012, a branch intake passage is connected to each of two intake ports formed in the cylinder head, and the branch intake passage is connected to a common main intake passage. ni w, f
I! jf, it has been done.

One of the branch intake passages is provided with an on-off valve, and the main intake passage is provided with a throttle valve, and these throttle valves and on-off valves work together to open the 9 throttle valves beyond a certain opening. The on-off valve is designed to open when the door is turned off. In other words, since one branch intake passage is closed by an on-off valve when the engine is operating at low load, intake air is supplied from the bottom of the other branch intake passage at a relatively high flow rate, and during high load operation, intake air is supplied from both sides. A high filling amount can be ensured by being supplied from a branch intake passage. However, in this public notice, 1
The softened engine intake system is intended to ensure sufficient intake air charge during high-load operation;
The cross-sectional area of each branch intake passage is not very small, and even if only one branch intake passage is used during low-load operation, the intake flow rate is cannot be sufficiently increased.

In addition, the shape of the intake boat allows the intake air flow to be introduced almost along the axial load direction of the combustion chamber in order to ensure a high amount of light* during high-load operation1. Cross section n! Coupled with the fact that it cannot be made very small, this makes it difficult to form a strong swirl inside the combustion chamber during low-load operation.

%Kaisho 5S-233// Publication No. 5S-233// discloses that in an engine intake system having - number of intake boats, an auxiliary intake passage with a small cross section is opened in each intake boat, and the auxiliary intake passage is closed during low load operation. A technique has been disclosed in which a thin high-speed intake air flow is blown into the air. The engine intake system described in this publication uses a high-speed intake air flow blown into the combustion chamber during low-load operation to form intense turbulence near the center of the combustion chamber, especially near the ignition plug, thereby scavenging air around the ignition plug. The aim is to promote stable combustion by increasing the flame propagation speed. However, with this intake system, although the auxiliary intake passage is effective in operating conditions where the engine load is very low, such as idling, in operating areas where the engine load increases even slightly, the auxiliary intake passage alone is insufficient. Since the amount of intake air cannot be secured, it becomes necessary to open a branch intake passage that is continuous to each intake boat. Therefore, if the branched intake path is opened even slightly in this manner, the flow velocity of the intake air flow from the auxiliary intake passage is rapidly reduced, and the turbulent flow within the combustion chamber is weakened. therefore,
This intake system cannot provide a satisfactorily stable combustion condition over the range from the region where the engine load is much higher than the idling state to the medium load region.

(Object of the Invention) The present invention provides an intake system in which a plurality of intake boats are opened in one combustion chamber to ensure a high amount of light tJi4 of intake air during high-load operation, over a relatively wide range of low-load operation. The object of the present invention is to form a swirl that is strong against combustion over a long period of time, thereby achieving a good combustion state.

(Structure of the invention) In order to achieve the above object, the present invention has the following configuration.

That is, the engine intake device according to the invention includes a plurality of intake boats opening into a combustion chamber, a branch intake passage connected to each of the plurality of intake boats, and a branch intake passage connected to the upstream side of the branch intake passage. a main intake passage, an on-off valve provided in the main intake passage and opened during load operation, and an auxiliary intake branched from the main intake passage upstream of the on-off valve and connected to one of the intake boats. a passage; an intake valve provided in each of the plurality of intake boats;
The opening timing of the intake valve provided on the intake boat to which the auxiliary intake passage is not in contact with the auxiliary intake passage 11
When the intake valve of the intake boat is opened, the line is connected.
and an intake valve actuation device that controls the opening and closing of the front S14 intake valve so that it opens and closes more slowly. According to the present invention, during low-load operation when the opening/closing tie is closed, intake air is supplied to the combustion chamber through the auxiliary intake passage. Since the auxiliary intake passage is formed to have a smaller cross-sectional area than the branch intake passage, a relatively high flow velocity can be maintained even during low-load operation with a small intake air amount. Furthermore, since the auxiliary intake passage opens into one of the plurality of intake boats, it is possible to send intake air in a biased direction toward the combustion chamber, creating a strong swirl inside the combustion chamber. . In addition, the intake valve of the intake boat to which the auxiliary intake passage is connected opens by swimming 7 more than the intake valves of other intake boats, so the intake air that accumulates in the intake system downstream of the on-off valve is When the intake boat connected to the intake passage is opened, the intake air is drawn into the combustion chamber, producing the effect of strengthening the swirl of intake air within the combustion chamber.

The aforementioned JP-A-5. The intake device described in Patent No. 23311 has a configuration that generates swirl within the combustion chamber.
Strong turbulence occurs along the peripheral wall of the combustion chamber and is less likely to occur near the center, making it impossible to maintain good combustion in an engine with the spark plug placed near the center. Based on this recognition, a small-diameter auxiliary intake passage is opened in each of the - intake ports, and a narrow heavy-speed (frt)
, is symmetrically blown into the combustion chamber to generate turbulent noise near the center of the combustion chamber. The present invention, combined with such a known intake device, generates a strong swirl within the combustion chamber by blowing a high-speed intake air flow with a relatively medium τ in a direction biased against the fine details of the entire combustion chamber. . In particular, the present invention strengthens the swirl by varying the opening timing of the intake valve depending on the entire intake boat, and is based on a completely different idea from the above-mentioned known intake device.

(Effects of the Invention) In the present invention, as described above, since the auxiliary intake passage for sending intake air to the combustion chamber during low-load operation is installed in one of the plurality of intake boats, the amount of intake air is reduced. Even during low angle '#r operation with a small angle '#r, it is possible to supply a relatively high-speed intake air flow in a direction biased toward the center of the combustion chamber, and a strong swirl can be formed within the combustion chamber. In addition, the intake valves of the intake ports to which the auxiliary intake passage is not connected open at a later timing than the intake valves of the intake ports to which the auxiliary intake passage is connected, so that the intake valves accumulate in the intake system downstream of the on-off valve. The intake air is sucked out into the combustion chamber together with the intake air from the auxiliary intake passage, producing the effect of increasing the swirl within the combustion chamber.

(Employment 1 of the embodiment) Interchanging FIG. 7 and FIG. 2, the engine E has a cylinder block 1 having cylinders 71a and a cylinder head 2 attached to the upper part of the cylinder block 1. issue? A piston 3 is disposed in the cylinder 1a17''l so as to be able to reciprocate in the axial direction, forming a combustion chamber 4 within the cylinder 1a.The cylinder head 2 has first and second intake boats 5.6 and an exhaust port 7. formed, first, second
An intake valve 8 is attached to each intake boat 5.6, and an exhaust valve 9 is attached to the exhaust port 7. Referring to Figure 1,
The seventh and third intake boats 5.6 have approximately the same diameter and are arranged approximately symmetrically with respect to the cylinder center Wt in the width direction of the cylinder block 1, and the exhaust port 7 is located across the longitudinal center line m of the cylinder block 1. It is arranged at a position facing the second intake port 6.

The intake thread extends from the main intake passage 11 extending from the air cleaner 10.
A throttle valve is disposed in the main intake passage ll. As shown in FIG. 1, the main intake passage 11 extends into the cylinder head 2, and is formed in the vicinity of the intake port 5.6 by a partition formed substantially along the cylinder center line t in the middle direction of the cylinder tab. First and second branch passages 15.16 are partitioned by a wall 14 and communicate with the first and second intake boats 5.6, respectively. The exhaust port 7 is connected to the exhaust passage 17 to constitute an exhaust system. This exhaust system may have a normal configuration. In the main intake passage 11, a fuel injection valve 23 is disposed upstream τ111 of the partition wall 14, and fuel at a rate determined based on a signal corresponding to engine operation conditions is supplied to the combustion chamber 4.

An on-off valve 18 is provided within the main intake passage 11 .

The opening/closing valve 18 is closed in a low-load operation region where the opening degree of the throttle valve is relatively small due to movement of the throttle valve 12, and is opened when the throttle valve 12 is opened more than a predetermined number of times. - be accomplished.

An opening 19 is formed at the bottom of the main intake passage 11 slightly upstream of the on-off valve 18.
An auxiliary intake passage 20 is formed extending below 111 w a . The auxiliary intake passage 20 is connected from the lower side of the main intake passage 11 to the lower side of the first branch passage 15 through an opening 21 to the intake port 5.

At the top of the cylinder head 2, an intake valve 8 and an exhaust valve 9 are provided.
A valve drive mechanism 25 for opening and closing is arranged. This valve drive mechanism 25 is connected to an engine crankshaft (not shown).
and a cam 2 formed on the camshaft 26 and corresponding to each of the intake valve 8 and the exhaust valve 9.
7. The cam 27 engages one end of a swinging arm 28 arranged to correspond to each of the intake valve 8 and the exhaust valve 9, and the other end of the swinging arm engages with a tappet 29 provided on the valve shaft of each valve. is engaged in. In the engine of this example, as shown in FIG. 3, the intake valve 8 of the first intake port 5 to which the auxiliary intake port 20 is connected is
The intake valve 8 of the second intake boat 6 opens at a timing earlier than that of the intake valve 8 of the second intake boat 6, and closes almost simultaneously with the intake valve 8 of the second intake boat 6.

As shown in Fig. 2, the intake port 5 opens into the combustion chamber 4 at an angle close to the axial direction of the cylinder A 1a in order to ensure high light ti4 violet during high-load operation. Although not shown, the first intake port 5 also has a similar shape.

On the other hand, since the auxiliary intake passage 20 opens to the first intake port 5 from below the main intake passage 11 and the first branch passage 15, it is oriented at a relatively shallow angle with respect to the combustion chamber 4. Furthermore, since the first intake port 5 is arranged to be biased to one side with respect to the center line t of the cylinder pore 1a, the intake air jetted into the combustion chamber 4 at a shallow angle from the auxiliary intake passage 2021 is directed toward the combustion chamber 4. This generates a strong swirl in the horizontal plane. In order to facilitate the generation of this d-whirl, it is desirable that the shape of the auxiliary intake passage 20 be formed in the vicinity of the opening 21 so that the lug faces in a tangential direction to the peripheral wall of the cylinder bore la.

In a low load region where the on-off valve 18 is closed, the main intake passage 1
1 through the auxiliary intake passage 20 from the opening 18.
is guided through the opening 21 into the first intake port 5 to reach the combustion value. Hakusuke intake passage 20 is a branch passage 15.1
Since the cross-sectional area is smaller than each of No. 6, a relatively cylindrical flow velocity can be maintained even during low-load operation with a small intake lid. Furthermore, since the auxiliary intake passage 20 is oriented in the circumferential direction of the cylinder block 1a at a relatively shallow angle as described above, the intake air flow injected from the auxiliary intake passage 20 into the combustion chamber 4 is Form a strong swirl within 4. In this case, the intake valve 8 of the first intake port 5 opens at an earlier timing than the intake valve 8 of the first intake port 1-16 as described above. When opened, the main intake passage 11 and the first
The intake air accumulated in the co-branch intake passages 15 and 16 is drawn into the W combustion chamber 4 together with the intake air from the auxiliary intake passage 20. Therefore, the amount of intake air from the first intake port 5 immediately after the valve is opened increases, and the swirl within the combustion chamber 4 can be strengthened.

In the above-described embodiment of the invention, the intake boat 5.6
The ignition plug 22 is disposed in a portion where the exhaust port 7 is not formed, that is, in a portion facing the first intake port 5 across the longitudinal centerline mff of the cylinder block 1. This portion corresponds to the swirl trajectory caused by the intake air flow from the first intake port 5, and this arrangement ensures that the air around the spark plug 22 is scavenged and stable ignition and combustion can be obtained.

[Brief explanation of drawings]

Fig. 1 is a schematic plan view of an engine intake system showing one embodiment of the present invention, Fig. 2 is a vertical sectional view of an engine with a main cylinder installed, and Fig. 3 is an engine intake system according to an embodiment of the present invention. 3 is a chart showing the opening timing of the intake valve in the 1... Cylinder block, ]a... Cylinder bore,
2...Cylinder head, 3...Piston, 4...-
ffifi chamber, 5.6... Intake boat, 7... Exhaust port, 11... Main intake passage, 15.16... Branch intake passage, 18... Opening/closing valve, 19... Opening, 20・
...Auxiliary intake passage, 25...Valve drive mechanism.

Claims (1)

[Claims] A plurality of intake ports opening into a combustion chamber, a branch intake passage connected to each of the plurality of intake ports, a main intake passage connected to an upstream side of the branch intake passage, and a main intake passage provided in the main intake passage. an on-off valve that is opened during high-load operation; an auxiliary intake passage that branches from the main intake passage above the on-off valve and is connected to one of the intake ports; and an auxiliary intake passage that is provided in each of the plurality of intake ports. The valve opening timing of the intake valve provided at the intake port to which the auxiliary intake passage is not connected is later than the opening timing of the intake valve provided to the intake port to which the auxiliary intake passage is connected. and an intake valve operating device for controlling the opening and closing of the intake valve.