JPS6263125A - Suction device for engine - Google Patents

Abstract

PURPOSE:To make an independent suction passage smoothly connectable to an interconnecting part without altering a passage area of the suction passage, by forming a section of a connecting part of the independent suction passage, to be installed at every cylinder, with the interconnecting part interconnecting the said passage with each other into a flat form. CONSTITUTION:In case of a suction device being in a state of having a suction port 4 of each cylinder 2 interconnected to a suction expansion chamber 9 to be extended in a cylinder train direction via an independent suction passage 8, each interconnecting passage 14 interconnecting each independent suction passage 8 mutually is connected to the point midway in each independent suction passage 8 via each branch passage 13 extending in parallel with the suction expansion chamber 9 and to be branched off from each of these suction passages 8. At each branch passage 13, there is provided with each on-off valve 15, being opened at a high speed range where an engine speed is more than the specified value, side by side. And, a section of a connecting part of each suction passage 8 with the interconnecting part 14 of each independent suction passage 8 is formed into a flat form setting length L1 in a cylinder train direction down to a long diameter (L1=L2) corresponding to a passage diameter L2 of the branch passage 13. With this constitution, dynamic effect of suction air is improved whereby an output improvement is made so as to be promoted.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an intake system for an engine that is designed to improve output through the dynamic effect of intake air.

(Prior art) Conventionally, in an engine intake system, a negative pressure wave generated with the start of intake is reflected at the open end of the intake passage to the atmosphere or the intake expansion chamber on the upstream side of the intake passage, and becomes a positive pressure wave. Taking advantage of the fact that the pressure wave is returned toward the intake port, the pressure wave reaches the intake port just before the intake valve closes and pushes the intake air into the combustion chamber, which is the so-called inertia effect of the intake air, which increases the filling efficiency of the intake air. There is something I did.

For example, as described in Japanese Unexamined Patent Publication No. 56-115819, the length of the intake passage is changed depending on the engine speed, for example, the intake passage for each cylinder is branched into two at the upstream part. A long passage and a short passage are formed by opening the upstream end of the four passages to the intake expansion chamber, etc., and an on-off valve is provided in the short passage, and this on-off valve is opened in the high rotation range. An intake device is known in which the effective length of the intake passage is shortened (see FIG. 6 of the above-mentioned publication) and the inertia effect of intake air is increased in both the low rotation range and the high rotation range.

However, in such a conventional device, an individual intake inertial effect can only be obtained for each intake passage connected to each cylinder of the engine.

By the way, in an engine, air is sequentially taken into each cylinder according to a predetermined order. Therefore, if we consider the pulsation in the intake passage connected to each cylinder,
There is a time lag. From this, if we make effective use of the pressure waves generated in other cylinders,
Focusing on the fact that the above-mentioned intake inertia effect can be expected to be obtained over a wider range, by changing the effective length of the intake passage for each cylinder, we aim to increase the intake inertia effect in the low rotation range and high rotation range respectively. At the same time, especially in the high rotation range where high output is required, the pressure waves generated in other cylinders are effectively used between each cylinder to further increase the intake air filling efficiency in the high rotation range and output. With the aim of improving A communication section is provided that communicates the independent intake passages with each other via a branch passage branched from the middle, and the communication between the independent intake passages through this communication section is achieved by using an on-off valve interposed in the branch passage during engine operation. An application has been filed for an engine intake system which is controlled by opening and closing depending on the state (see Japanese Patent Application No. 59-275487).

However, in such an intake system, the on-off valve acts as resistance in the branch passage in which the on-off valve is interposed, so the passage diameter of the branch passage is made larger than the passage diameter of the intake passage, and the influence of the on-off valve is removed and both The actual passage areas of the roads are made to be equal. Therefore, the passage diameter changes at the connection part of the independent intake passage with the communication part, and the connection between the independent intake passage and the communication part is no longer smooth, so the pressure waves do not propagate smoothly and are attenuated, reducing the dynamic effect of intake. There was a risk that it could not be obtained efficiently.

It is also possible to match the passage diameter of the independent intake passage to the passage diameter of the branch passage at the connection part with the communication part.
If this is done, the passage diameter of the connection part of the independent intake passage with the communication part will be different from the passage diameter of the independent intake passage of other parts determined in advance by design, and the area of one passage will change. There is a risk that the pressure waves will be attenuated in that part, and the dynamic effect of intake will not be achieved efficiently.

(Objective of the Invention) The present invention is capable of smoothly connecting an independent intake passage with a communication portion without changing the passage area of the independent intake passage, and efficiently obtaining dynamic effects of intake air. The purpose of this invention is to provide an intake system for an engine that is capable of achieving high performance.

(Structure of the Invention) In order to achieve the above object, the present invention is characterized in that the connection portion of each independent intake passage with the communication portion is formed into a flat shape whose major axis is the length in the cylinder row direction. shall be.

As a result, a passage diameter is obtained in which the length in the direction of the cylinder row is the major axis and the connection between the independent intake passage and the communication portion is smooth, while a flat shape is obtained in which the length in the direction perpendicular to the cylinder row direction is the minor axis. The passage area of the independent intake passage at the connection portion is almost the same as the passage area of the independent intake passage at other parts.

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

In FIG. 1 showing an embodiment in which the present invention is applied to a four-cylinder engine, l is the engine body.

The first to fourth cylinders 2 are arranged in series in the longitudinal direction. Each cylinder 2 has a piston (not shown).
A combustion chamber 3 is formed above, and an intake port 4 and an exhaust port 5 are opened in this combustion chamber 3.
, , 5 are each provided with an intake valve 6 and an exhaust valve 7.

Each intake boat 4 of each cylinder 2 is connected to the downstream end of an independent intake passage 8 for each cylinder 2. On the other hand, the upstream end of the independent intake passage 8 extends outward from the engine body 1 and communicates with an intake expansion chamber 9 that is curved upward from the engine body 1 and extends parallel to the cylinder row direction (crankshaft direction).

Note that the passage lengths of each independent intake passage 8 are set to be approximately the same length.

Outside air is introduced into the intake expansion chamber 9 through an intake air introduction passage 10, and a throttle valve 11 for controlling the amount of intake air is disposed in this intake air introduction passage 10. Further, a fuel injection valve 12 is disposed near the downstream end of each of the independent intake passages 8 .

In the middle of each of the independent intake passages 8, there is a communication section that extends parallel to the intake expansion chamber 9 in the cylinder row direction and communicates the independent intake passages 8 with each other via a branch passage 13 that branches from each independent intake passage 8. 14 are connected. Note that the passage lengths from the branching point of each independent intake passage 8 from the communication portion 14 to each cylinder 2 are set to be approximately the same length.

Each branch passage 13 is provided with an on-off valve 15 that opens and closes the branch passage 13, and each on-off valve 15 is configured to:
It is fixed to a valve shaft 6 extending in the direction of the cylinder row, and is integrally controlled to open and close via an actuator by a control circuit (not shown) that receives the output of an engine rotation speed detection means, etc. The communication between the independent intake passages 8 is controlled according to the engine operating state, so that it is closed in a low rotation range where the engine speed is less than a set value, and is controlled to be opened in a high rotation range where the engine speed is higher than the set value. It constitutes a control means to Note that the opening/closing operation of the on-off valve 15 according to the engine speed may be performed at least during high loads where output is required, and the on-off valve 15 may be in the open or closed state at low loads. It may be maintained.

The upstream portion 8a of each independent intake passage 8 is an intake expansion chamber 9.
The upstream portion 17a of the intake manifold 17 is curved along the shape of the intake manifold 17, and is integrally molded with the intake expansion chamber 9. Upstream portion 17 of this intake manifold 17
a shares the upstream portion 8a of each independent intake passage 8 and a part of the constituent wall that constitutes the intake expansion chamber 9, and connects the communication portion 14.
It forms the upper part 14a of. On the other hand, the downstream portion 8b of each independent intake passage 8 is also integrally molded to constitute the downstream portion 17b of the intake manifold 17, and a portion of its constituent wall is shared to form the lower portion 14b of the communication portion 14. ing. Therefore, the upstream and downstream portions 17 of the intake manifold 17
By combining a and 17b, each independent intake passage 8 that communicates the intake expansion chamber 9 and the intake port 4 of each cylinder 2, and each independent intake passage 8 that branches from each independent intake passage 8 and communicates with each other. A communicating portion 14 is formed to make the intake system more compact.

Further, as shown in FIG. 4, the cross section of the connecting portion of each independent intake passage 8 with the communication portion 14 has a length Ll in the cylinder row direction.
is the major axis (Ll =
L2), and the connection with the communication portion 14 is smoothly performed without changing the passage area of the independent intake passage 8. As shown in FIG. 5, the curved portion of each independent intake passage 8, for example, the middle of the downstream portion 8b, is formed into a flat shape with a major diameter equal to the length Ll in the cylinder row direction, and the inner peripheral side of the independent intake passage 8 This is done so that there is no difference in passage length between the outer circumferential side and the outer circumferential side.

With the above configuration, when each on-off valve 15 is closed and the communication between the independent intake passages 8 through the communication portion 14 is cut off, the pressure wave of negative pressure generated during the intake stroke is transmitted to the intake expansion chamber 9. In other words, by propagating the negative pressure wave and its reflected wave through a relatively long passage, the oscillation period of such pressure wave matches the intake valve opening and closing period in the low rotation range. As a result, the inertia effect of the intake air in the low rotation range is increased.

Intake air filling efficiency is increased. In this case, since the area of one passage does not change at the connection portion with the communication portion 14, the pressure wave of the negative pressure and its reflected wave are not attenuated.

On the other hand, when the on-off valves 15 are opened and the communication sections 14 communicate with each other, the negative pressure waves generated during the intake stroke are transmitted to the communication sections of the independent intake passages 8. Since the connection with 14 is made smoothly without any change in the passage diameter, the passage length is such that the negative pressure wave reflected at the communication part 14 and its reflected wave propagate without attenuation. By shortening the time, the inertial effect of the intake air is enhanced in the high rotation range, and in this operating range, pressure waves propagated from other cylinders also act effectively through the communication part 14, so that the high rotation speed is increased. The filling efficiency in the area is greatly increased.

Therefore, when the load is high, by closing the on-off valve 15 in the low rotation range and opening the on-off valve 15 in the high rotation range,
Intake air filling efficiency is increased across the entire rotation range, resulting in improved output.

(Effects of the Invention) As described above, the present invention has a flat cross-section at the connecting portion of the independent intake passage with the communication portion, so that the independent intake passage can be connected to the communication passage without changing the passage area of the independent intake passage. The pressure waves are propagated without being attenuated even at the connecting part, and the dynamic effect of intake air can be efficiently obtained.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is an overall configuration diagram of an intake system for a four-cylinder engine, FIG. 2 is a sectional view of the upstream part of the intake manifold taken along the line ■-■ in FIG. The figure is a schematic diagram of the downstream part of the intake manifold taken along line ■-■ in Figure 1, Figure 4 is a sectional view taken along line IV-IV in Figure 1, and Figure 5 is a cross-sectional view taken along line v-v in Figure 1. It is a schematic sectional view. 1...Engine body, 2...Cylinder, 4
...Intake port, 8...Independent intake passage, 9...Intake expansion chamber, 13...Branch passage, 14...Communication section , 15... Open/close valve.

Claims (1)

[Claims] (1) In an engine intake system in which the intake expansion chamber and each cylinder are connected by independent intake passages for each cylinder, each independent intake passage is connected to the intake passage through a branch passage branching from the middle of each independent intake passage. A communication section that communicates with each other, and a control means that controls communication between the independent intake passages through the communication section using an on-off valve provided in the branch passage according to the operating state of the engine, and each of the above-mentioned An intake system for an engine, wherein a cross section of a connecting portion of an independent intake passage with a communicating portion is formed in a flat shape with a major diameter corresponding to a length in a cylinder row direction.