JPS6093120A - Suction device of engine - Google Patents

Abstract

PURPOSE:To form a strong swirl in the combustion chamber over a relatively wide range of low load operating area by locating a main intake air path so that its center axis deviates toward the side of an intake air port connected to an auxiliary intake air path. CONSTITUTION:In a low load 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 enters the combustion chamber 4, forming a strong swirl. In a load area where the closing valve 18 begins to open, the intake air stream of the main air path 11 begins to flow into the branch intake air paths 15, 16, and the flow rate of intake air passing through the auxiliary intake air path 20 is reduced. For the main intake air path 11, its center axis 11a arranged to deviate toward the side of the first intake air port 5. The intake air stream reaching the 1st intake air port 5 from the 1st branch intake air path 15 becomes larger than the intake air stream reaching the 2nd intake air port 6 from the 2nd branch intake air path 16. The intake air stream reaching the 1st intake air port 5 from the 1st branch intake air path joins the intake air stream reaching the 1st intake air port 5 passing through the auxiliary intake air path 20.

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 the intake ports depending on the total engine load. For example, in the engine disclosed in Japanese Unexamined Patent Application Publication No. 1983-79, a branch intake passage is connected to each of two intake ports formed in the cylinder head, and this branch intake passage is connected to a common main intake connected to the passage.

One of the branch intake passages is provided with an on-off valve, and the main intake passage is provided with a throttle valve.The throttle valve and the on-off valve work together to prevent the throttle valve from opening beyond a certain degree. The on-off valve is opened when the In other words, one branch intake passage is closed by an on-off valve when the engine is operating at low load, so intake air is supplied at a relatively high flow rate only from the other branch intake passage, and during high load operation, intake air is supplied from both branches. High filling f supplied from the intake passage
l can be secured. However, the engine intake system described in this publication is designed to ensure a sufficient amount of intake air during high-load operation.
The cross-sectional area of each branch intake passage is not formed very small, and even if only one branch intake passage is used during low-load operation, when the negative j is very small, such as during idling operation, It is not possible to increase the intake flow rate sufficiently.

In addition, the shape of the intake port is designed to introduce the intake air almost along the axis of the combustion chamber in order to ensure the amount of air filling during high-load operation. Coupled with the fact that the cross-section of the barrel cannot be made very small, this makes it difficult to form a strong swirl inside the combustion chamber during low-load operation.

Japanese Unexamined Patent Publication No. 3, 23377 discloses that in an engine intake system having - intake ports, an auxiliary intake passage with a small cross-sectional area is opened in each intake port i, and this auxiliary intake passage is opened during low-load operation. A technique has been disclosed for blowing a narrow high-speed intake air flow through the passage. Rr to this bulletin
The engine intake system mounted on No. 2 has a high-speed intake air flow that is forced into the combustion chamber during low-load operation.
In particular, a strong turbulent flow is formed near the ignition plug to promote scavenging air around the ignition plug, and to reduce the flame propagation speed ft'fjJ.
The aim is to ensure stable combustion. However, in this intake system, the auxiliary intake passage is effective in operating conditions where the engine load is very small, such as idling operation, but in operating areas where the engine load increases even slightly, the auxiliary intake passage alone is insufficient. Since a sufficient amount of intake air cannot be secured, it becomes necessary to open branch intake passages that are continuous with each intake port. When the branch intake passage is opened even slightly, the flow velocity of the intake air from the auxiliary intake passage decreases rapidly, and the turbulence within the combustion chamber is weakened. Therefore, this intake system cannot provide a satisfactorily stable combustion condition over a range from a region where the engine load is slightly higher than the idling state to a medium load region.

(Purpose of the Invention) The present invention provides an intake system in which a plurality of intake ports are opened in one combustion chamber to ensure a high filling amount of intake air during high-load operation, which has a relatively wide low-load continuous range. It is an object of the present invention to form a swirl that is strong against combustion traps over a range, thereby obtaining a good combustion state.

(Structure of the Invention) In order to achieve the above object, the unexploded tq has the following structure. That is, the engine intake device according to the present invention includes a plurality of intake ports opening into a combustion chamber, a branch intake passage connected to each of the plurality of intake ports, and a main intake passage connected to the upstream side of the branch intake passage. an intake passage, an on-off valve provided in the main intake passage and opened during high-load operation, and an auxiliary intake branched from the main intake passage on the upstream side of the on-off valve and connected to one of the intake dates. The main intake passage is characterized in that the main intake passage is arranged such that its central axis is biased toward the intake port to which the auxiliary intake passage is connected.

According to the present invention, during low-load operation when the on-off valve is closed, intake air is supplied to the combustion chamber through the entire 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 rate 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 multiple intake ports, it is possible to send intake air in a direction biased to the center of the combustion chamber, creating a strong swirl inside the combustion chamber. A″j
I can do that. In addition, by placing the center axis of the main intake passage off to the side of the intake port to which the auxiliary intake passage is connected, the flow of intake air from the main intake passage is assisted in the load range where the on-off valve begins to open. In this load range, the intake air flow from the auxiliary intake passage is maintained to some extent, so the intake port to which the auxiliary intake passage is connected tends to be concentrated. l-
The intake air flow passing through will be greater than the intake air flow from other intake ports, and a certain degree of swirl will be formed in the combustion chamber.

The aforementioned Tokkai Sho A-! r-,2! ,! / The intake system described in the / issue has a configuration that generates swirl in the combustion guide, and strong turbulence occurs along the peripheral wall of the combustion chamber and is less likely to occur near the center, so the ignition plug is placed near the center. Good combustion cannot be maintained with an engine placed in Based on this recognition, small-diameter auxiliary intake passages are opened in each of the intake ports, and by blowing thin high-speed #L symmetrically into the combustion chamber from these auxiliary intake passages, intense air flow is generated near the center of the combustion chamber. The idea is to create turbulence. Unlike such known intake devices, the present invention forms a swirl that is strong against combustion guide by blowing a relatively small high-speed intake air flow in a direction biased to the axis of the combustion chamber. It is. In particular, in the present invention, by arranging the central axis a of the main intake passage so as to be offset as described above, swirl can be generated in the combustion chamber even in a load range where the on-off valve begins to open.

(Effects of the Invention) In the present invention, as described above, the auxiliary intake passage that sends intake air to the combustion chamber during low-load operation is connected to one of the plurality of intake ports. Even during low-load operation, it is possible to supply a relatively high-speed intake air flow in a direction biased toward the center of the combustion chamber, making it possible to form a strong swirl within the combustion chamber. In addition, because the center axis of the main intake passage is biased toward the intake port to which the auxiliary intake passage is connected, a certain amount of swirl is generated within the combustion chamber even in the load range where the on-off valve begins to open. This makes it possible to maintain stable combustion conditions over a relatively wide range of low angle loads.

(Description of Embodiments) Referring to FIGS. 1 and 2, an engine E has a cylinder block 1 having a cylinder pore 1a and a cylinder head 2 attached to the upper part of the cylinder block 1. A piston 3 is arranged to be able to reciprocate in the axial direction, and forms a combustion chamber 4 within the cylinder pore 1a. First and second intake boats 5.6 and an exhaust port 7 are formed in the cylinder head 2, an intake valve 8 is formed in each of the first and second intake boats 5.6, and an exhaust valve 9 is formed in the exhaust port 7. Installed. Referring to diagram M1, the first and second intake ports 5.6 have almost the same diameter, and the cylinder block 1
are arranged substantially symmetrically with respect to the cylinder center 11Mt in the width direction, and the exhaust port 7 is arranged at a position facing the second intake port 6 across the longitudinal center line m of the cylinder block 1.

The intake system runs from the air cleaner 10 to the main intake passage 11.
A throttle valve 12 is disposed within the main intake passage 11. As shown in FIG. 7, the main intake passage 11 extends into the cylinder head 2 and is located near the intake port 5.6.
They are partitioned by a partition wall 14 formed substantially along the cylinder center line t in the width direction of the cylinder block, and constitute first and gg2 branch passages 15 and '16 that communicate with the seventh and co-intake ports 5.6, respectively. are doing. The exhaust port 7 is
It is connected to the exhaust passage 17 and forms an exhaust system ')44. This exhaust system can be of normal construction. A fuel injection valve 23 is arranged in the main intake passage 11 on the upstream side of the partition wall 14, and a predetermined amount of fuel is supplied to the combustion chamber 4 based on a signal corresponding to engine operating conditions.

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

This opening/closing valve 18 is, for example, linked to the throttle valve 12 so that it is closed in a low-load operation region where the opening degree of the throttle valve is relatively small, and is opened when the throttle valve 12 is opened more than a predetermined number of times. configured.

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 so as to be located below 1. The auxiliary intake passage 20 passes from the lower side of the main intake passage 11 to the lower side of the first branch passage 15 and is connected to the first intake port 5 through an opening 21 .

At the top of the cylinder head 2, an intake valve 8 and an exhaust valve 9 are provided.
A valve wJ mechanism 25 for opening and closing is disposed.

This valve drive mechanism 25 is driven by an engine crankshaft (not shown)! ll-driven camshaft 26 and the camshaft 26
The cams 27 formed on the cams 27 correspond to the intake valves 8 and the exhaust valves 9, respectively. The cam 27 has a swing arm 2 arranged to correspond to each of the intake valve 8 and the exhaust valve 9.
8, and the other end of the swing arm engages with a tappet 29 provided on the valve stem of each valve.

As shown in FIGS. 1 and 3, the main intake passage 11 is
The center axis 11δ is arranged so as to be biased toward the first intake port 5 with respect to the cylinder bore center line t in the middle direction of the cylinder block. That is, the overlap between the main intake passage 11 and the branch intake passages 15 and 16 is larger than that with the branch intake passage 15, as shown in FIG.

As shown in FIG. 2, the intake boat 5 opens into the combustion chamber 4 at an angle close to the direction of line e of the cylinder pore 1a, in order to ensure high filling during high-load operation. Although not shown, the second intake boat 6 also has a similar shape. On the other hand, since the auxiliary intake passage 20 opens from the lower side 1 of the main intake passage 11 and the first branch passage 15 to the seventh intake port 5, the combustion chamber 4
It will be directed at a relatively shallow angle.

Furthermore, the intake port 5 is connected to the cylinder J? 71a
Since the auxiliary intake passage 20 is arranged biased to one side with respect to the center line t, the intake air jetted into the combustion chamber 4 at the force/reduction angle of the auxiliary intake passage 20 is caused by strong swirling within the water/F plane within the combustion chamber 4. Generates a flow or swirl. In order to facilitate the generation of this swirl, it is desirable that the shape of the auxiliary intake passage 20 is formed so as to be oriented substantially tangentially to the peripheral wall of the cylinder pore 1a near the opening 21.

In a low load region where the on-off valve 18 is closed, the main intake passage 1
All of the intake air passing through the first intake port 1 is led from the opening 18 to the auxiliary intake passage 20, and is sent from the opening 21 to the first intake port 5 into the combustion chamber. The auxiliary 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-mounted operation with a small intake air amount. Furthermore, since the auxiliary intake passage 20 is oriented at a relatively shallow angle in the circumferential direction of the cylinder pore 1a, as described above,
It is ejected from the auxiliary intake passage 20 into the combustion chamber 4.

The intake air flow forms a strong swirl within the combustion chamber 4. In the load range where the on-off valve 18 begins to open, the intake air in the main intake passage 11 +1i11. begins to flow into the branch intake passages 15 and 16, and the flow rate of intake air passing through the auxiliary intake passage 20ft decreases.

However, the main intake passage 11 has its central axis 1 as described above.
1a is arranged biased toward the first intake port 5,
The angle in the axial direction between the main intake passage 11 and the first branch intake passage 15 is larger than the angle between the main intake passage 11 and the first branch intake passage 15. The intake air flow reaching the intake port 5 flows through the co-branch intake passage 1.
6 and reaches the second intake port 6. The intake flow that reaches the first intake port 5 from the first branch intake passage 15 merges with the intake flow that passes through the auxiliary intake passage 20 and reaches the first intake port 5 to form an intake swirl in the combustion chamber 4.

In this example, the cylinder head 2 has an intake port 5.
．． The spark plug 22 is disposed in a portion where the exhaust port 6 and the exhaust port 7 are not formed, and in a portion facing the seventh intake boat 5 across the longitudinal center 931m of the cylinder block 1. This part corresponds to the trace of the swirl caused by the intake air flow from the first intake port 5, and this arrangement allows the spark plug 22 to rotate! The air is thoroughly scavenged and stable ignition and combustion can be achieved.

[Brief explanation of drawings]

FIG. 7 is a schematic plan view of an engine intake system according to an embodiment of the present invention, FIG. 3 is a vertical sectional view of an engine according to the present invention, and FIG. It is a diagram showing the axial overlap of one main intake port and a branch intake passage in the device. 1... Cylinder block, 1a... Cylinder pore,
2... Cylinder head, 3... Piston, 4...
Combustion chamber, 5.6... Intake port, 7... Exhaust port, 11... Main intake passage, 15.16... Branch intake passage, 18... Opening/closing valve, 19... Opening, 20... Auxiliary intake passage. Figure 3 1, 1 134-

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; and an auxiliary intake passage that branches from the main intake passage and connects to one of the intake ports upstream of the on-off valve, and the main intake passage is located at the center of the intake passage. An intake device for an engine, characterized in that a shaft is arranged so as to be biased toward an intake port to which the auxiliary intake passage is connected.