JPS61157716A - Air intake device of multicylinder engine - Google Patents

Abstract

PURPOSE:To improve air intake inertia effect over full rotating area by communicating independent air intake passages connecting an air intake expansion chamber and respective cylinders mutual in a communicating unit provided in parallel with the expansion chamber and by controlling the communication according to engine running condition. CONSTITUTION:Respective air intake ports of cylinders 4a-4d are communicated by lower stream ends of independent air intake passages 12-15, and upper stream ends of the passages are connected to an air intake expansion chamber 16 extending in parallel with the engine longitudinal direction. And on the way of respective passages 12-15, a communicating unit 12 extending in parallel with the chamber 16 and communicating to respective passages 12-15 mutually through branch holes 21 branched from respective passages 12-15 is connected. Each branch hole 21 is provided with an opening and closing valve 23 respectively and each valve 23 is controlled to open and close by a control means 25 through a valve shaft 24. This time, each opening and closing valve 23 is controlled to close in a low rotating area in which engine rotating number is less than a set value and to open in a high rotating area.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides a multi-cylinder engine in which each cylinder and an intake expansion chamber are connected to each other through an independent intake passage. This invention relates to an improvement of the intake III of a multi-cylinder engine in order to improve the performance.

(Prior Art) Conventionally, in an engine intake system, a negative pressure wave (pressure wave of negative pressure) 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 a positive pressure wave ( Taking advantage of the fact that the positive pressure wave becomes a positive pressure wave and is returned toward the intake boat, the positive pressure wave reaches the intake port just before the intake valve closes and forces the intake air into the combustion chamber. Some devices are designed to increase the filling efficiency of intake air using the so-called inertia effect of intake air. When using such technology, if the shape of the intake passage is constant, the oscillation period of the pressure wave generated in the intake passage and the WUm period of the intake valve will match, resulting in an intake inertia effect. is limited to a specific rotation range.

For this reason, as seen in Japanese Patent Application Laid-Open 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 divided into two at the upstream part. They are branched to form a long passage and a short passage, and the upstream ends of these passages are opened to an 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 to increase the intake air. An intake device has been proposed in which the effective length of the passage is shortened (see FIG. 6 of the above-mentioned publication), thereby increasing the inertial effect of intake air in both the low rotation range and the high rotation range.

(Problems to be Solved by the Invention) By the way, according to the above-mentioned conventional intake system, in the case of a multi-cylinder engine, although pressure waves are generated in each cylinder,
In the high rotation range, the effective length of the intake passage for each cylinder is simply shortened to increase the intake inertia effect through pressure propagation between each cylinder and the upstream opening end of the corresponding intake passage. , there is room for improvement in intake air filling efficiency.

That is, if pressure waves generated in other cylinders are also effectively utilized, it is expected that the filling efficiency can be further improved.

Therefore, the present invention has been made with attention to this point,
By changing the effective length of the intake passage for each cylinder, the inertia effect of the intake air is increased in the low rotation range and high rotation range, respectively, and in the high rotation range where high output is required, the inertia effect between each cylinder is increased. By effectively interacting with the pressure waves generated in other cylinders, the intake air filling efficiency in the high rotation range is improved! ! The purpose is to improve the output by fn.

A further object of the present invention is to make the shape and structure of this intake system as compact and small as possible in order to obtain an intake system that performs the above-mentioned functions, thereby improving vehicle mountability.

<Means for Solving the Problems> In order to achieve the above object, the solving means of the present invention is a multi-cylinder engine in which the intake expansion chamber and each cylinder are connected by independent intake passages for each cylinder. Targeting the intake device,
On the other hand, there is a communication section that branches off from the middle of each independent intake passage and communicates each independent intake passage with each other, and the communication between each independent intake passage through this communication section is controlled according to the operating state of the engine. A control means is provided. Further, the communication portion is formed by a part of a wall constituting the intake expansion chamber, and is arranged in parallel with the intake expansion chamber.

(Function) With the above configuration, in the present invention, in a low engine speed range where the engine speed is less than a set value, if the communication between the independent intake passages is cut off by the control means by the communication section, the air will be transmitted from each cylinder. Since the negative pressure wave that occurs is reversed and reflected as a positive pressure wave in the intake expansion chamber, the passage length to obtain the intake inertia effect is relatively long from the intake expansion chamber to each cylinder. This increases the intake inertia effect in the low rotation range.

On the other hand, in a high rotation range where the engine speed is higher than the set value, if the control means communicates the independent intake passages with each other through the communication part, the negative energy propagated from each cylinder at the communication part in the middle of each independent intake passage. Since the pressure wave is inverted and reflected as a positive pressure wave, the effective length of the intake passage for obtaining the intake inertia effect becomes shorter. Moreover, pressure waves from other cylinders are propagated through the communication portion, and the synergistic effect of these pressure waves greatly increases the filling efficiency in the high rotation range.

In this case, the communication portion may be formed by a part of the wall constituting the intake expansion chamber, which is arranged parallel to the longitudinal direction of the engine so that the passage lengths of the independent intake passages are the same. Since they are arranged in parallel in the intake expansion chamber, the passage length from each cylinder to the communication branch point in the middle of each independent intake passage is the same, effectively ensuring the above-mentioned effect, and forming a small and compact intake system. becomes possible.

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

Figures 1 to 5 show a first embodiment in which the present invention is applied to a 4-cylinder, 4-stroke engine, with Figure 1 showing its schematic structure and Figures 2 to 5 showing its specific structure. There is. In the illustrated engine, first to fourth cylinders 48 to 4d are formed in series in the longitudinal direction of an engine body 1 that includes a cylinder block 2, a cylinder head 3, and the like.

A combustion chamber 6 is formed above the piston 5 in each of these 8-air m4a to 4d, an intake boat 7 and an exhaust boat 8 are opened in the combustion chamber 6, and an intake valve 9 and an exhaust boat 8 are connected to these boats 7.8, respectively. A valve 10 is provided. Further, the combustion chamber 6 is equipped with a spark plug 11.

The downstream ends of independent intake passages 12 to 15 for each cylinder, which are independent from each other, communicate with each intake boat 7 of each of the cylinders 4a to 4d, and the upstream ends of these independent intake passages 12 to 15 communicate with each other in the engine longitudinal direction (crank direction). It is connected to an intake expansion chamber 16 extending parallel to the shaft direction). Further, due to this, the passage lengths of the independent intake passages 12 to 15 are set to be approximately the same length. The intake air introduction pipe 1 is provided in the intake expansion chamber 16.
Outside air is introduced through the air intake pipe 7, and a throttle valve 18 for controlling the amount of intake air is provided in the intake air introduction pipe 17. Further, a fuel injection valve 20 connected to the fuel passage 19 is disposed near the downstream end of each of the independent intake passages 12 to 15.

In the middle of each of the independent intake passages 12 to 15, there is a branch hole 21 that extends parallel to the intake expansion chamber 16 (in the longitudinal direction of the engine) and branches from these independent intake passages 12 to 15.
A communication portion 22 that communicates these independent intake passages 12 to 15 with each other is connected thereto. Further, as a result, the lengths of the passages from the communication section branching point of each of the independent intake passages 12 to 15 to each of the cylinders 4a to 4d are set to be approximately the same length.

Each branch hole 21 is provided with an on-off valve 23 that opens and closes the branch hole 18, and each on-off valve 23 is integrally and interlockably fixed to a pulp shaft 24 extending in the longitudinal direction of the communication portion 19. Although not shown, opening and closing are controlled via an actuator by a control circuit that receives an output from an engine rotational speed detection means, etc., and the communication between the independent intake passages 12 to 15 through the communication portion 22 is brought into engine operating state. Accordingly, the control means 25 is configured to close in a low rotation range where the engine rotation speed is less than a set value and to open in a high rotation range where the engine rotation speed is equal to or higher than the set value. Note that the opening/closing operation of the on-off valve 23 according to the engine speed may be performed at least during high loads where output is required, and the on-off valve 23 may be in the same state or in the closed state at low loads. It may be maintained.

The intake system structure of the communication portion 22 and the intake expansion chamber 16 are both formed so as to extend in parallel to the longitudinal direction of the engine, as shown in detail in FIGS. 2 to 5. , the tank 26 installed in the intake system is connected to the partition wall 2
By dividing the tank 26 into upper and lower sections at 7, the intake expansion chamber 16 having a relatively large capacity and the communication portion 22 having a relatively small capacity are defined within the tank 26. In other words, the communication portion 22
is a part of the constituent wall configuring the intake expansion chamber 16 (partition wall 2
7) and arranged in parallel with the intake expansion chamber 16. Furthermore, the branch holes 21 of each of the independent intake passages 12 to 15 are opened at the lower end of the communication portion 22, and each independent intake passage 1 is located upstream of the location where the branch hole 21 is formed.
2a to 15a are curved, and their upstream ends are connected to the intake expansion chamber 1.
It is opened on the side of 6.

In addition, the upstream curved portions 12a to 15a of each of the independent intake passages 12 to 15 are formed along the curve of the tank 26, and the intake expansion chamber 16 of the tank 26 and the independent intake passage 12a outside thereof are ~ Part 2 constituting 15a
6a is integrally molded, and the communication portion 2 of the tank 26
2 and a portion 26b constituting the independent intake passages 12a to 15a outside thereof are integrally molded, and these 26a, 26b
are connected to each other via a partition wall 27, and downstream portions 12b to 15 of each independent intake passage 12 to 15 are connected to these through a partition wall 27.
b is connected to form a compact intake system.

Next, to describe the operation of the above embodiment, the control means 2
5, when the on-off valves 23 are closed and the communication between the independent intake passages 12 to 15 through the communication portion 22 is cut off, the negative pressure waves generated during the intake and intake strokes are propagated to the intake expansion chamber 16 and are In other words, the negative pressure wave and its reflected wave propagate through a relatively long passage, so that the oscillation period of such pressure waves matches the intake valve opening/closing period in the low rotation range. The inertia effect of the intake air at the pump is reduced, increasing the intake air filling efficiency. On the other hand, when the on-off valves 23 are opened by the control means 25 and the independent intake passages 12 to 15 are in communication with each other through the communication section 25, negative pressure waves generated during the intake stroke are reflected at the communication section 22. By shortening the length of the passage used for the propagation of negative pressure waves and reflected waves from the lever, the intake inertia effect is enhanced in the high rotation range, and in this operating range, pressure waves propagated from other cylinders are also transmitted through the communication section. 25, and the charging efficiency in the high rotation range is greatly increased. Therefore, at least when the load is high, the opening/closing valve 23 is turned on at a lower rotation speed after reaching a predetermined rotation speed corresponding to the intermediate rotation speed between the respective rotation speeds at which the intake inertia effect between the low rotation range and the high rotation range can be obtained. By closing the on-off valve 23 and opening it at higher rotation speeds, the intake air filling efficiency can be increased over the entire rotation range, and the output can be improved.

In particular, the intake air filling efficiency in the high rotation range can be further improved by the pressure propagation effect between the cylinders, compared to the conventional case where the intake passage was simply shortened to increase the inertia effect. .

The intake expansion chamber 16 and the communication section 22 have a capacity that is 0.5 times or more the exhaust volume, and the communication section 22 has a capacity that is 0.5 times or more the exhaust volume. It is desirable that the capacity be 1.5 times or less than the displacement. Further, it is desirable that the communication portion 22 has a smaller capacity than the intake expansion chamber 16, and that the cross-sectional area of the communication portion 22 is larger than the cross-sectional area of each of the independent intake passages 12-15.

In this case, the communication section 22 is arranged in parallel with the intake expansion chamber 16 by dividing the tank 26 into upper and lower parts by a partition wall 27, and is connected to a portion of the wall (partition wall 27) constituting the intake expansion chamber 16. As a result, the intake system that exhibits the above-mentioned functions and effects can be formed compactly and compactly, and its mountability on a vehicle can be improved. especially,
As in the above embodiment, the curved portions 12a to 15a on the upstream side of the branch holes 21 of the independent intake passages 1 and 2 to 15 are connected to the tank 2.
A portion 26a formed along the circumferential surface of the tank 6 and constituting the intake expansion chamber 16 of the tank 26 and the independent intake passages 128 to 15a outside thereof, and the communication portion 22 of the tank 26 and the independent intake passage outside thereof. Part 2 composing 128-15a
Partition W by integrally molding 6b and 6b respectively! If they are connected via 27, the intake system can be made more compact, and the moldability and assemblability can also be improved.

It should be noted that the present invention is not limited to the above embodiments,
It also includes various other modifications. for example,
FIG. 6 shows a second embodiment of the present invention, in which a part of the outer wall of a tank 28 constituting the intake expansion chamber 16 is used in common to provide a communication section 22.
It is composed of

That is, in this example, the tank 28 that constitutes the intake expansion chamber 16 and the tank 29 that constitutes the communication section 22 are connected to the communication section 2.
2 are formed by a part of the wall constituting the intake expansion chamber 16, so that they are arranged vertically in parallel, sharing a part of their outer walls. Furthermore, the upstream curved portion 12a of the independent intake passages 12 to 15
15a are formed along the circumferential surfaces of the tanks 28 and 29, and the upper and lower portions of the tank 29, which are integrally molded with the upper and lower intermediate positions serving as dividing planes, are joined to form an intake system. In this example as well, the same effects as in the first example can be achieved.

Furthermore, the present invention is not limited to the case where the intake expansion chamber 16 and the communication section 22 are completely partitioned off as in the above embodiments, but the intake expansion chamber 16 and the communication section 22 are separated, for example, as shown by imaginary lines in FIG. The intake air filling efficiency is improved by communicating through a communication passage 30 provided in the partition wall 27 and causing intake pressure vibration between the intake expansion chamber 16 and the communication part 22, which communicate through the communication passage 30 in the low rotation range. It is also applicable to those designed to further increase the

Furthermore, the present invention is not limited to the four-cylinder engine as in the above embodiments, but can also be applied to other multi-cylinder engines, such as five-cylinder engines and six-cylinder engines. Furthermore, the deviation in the intake stroke of each cylinder is 1800° in a 4-cylinder engine, but 120° in a 6-cylinder engine, for example, so when applying to a 6-cylinder engine, the communication portion 22 should be formed short. In a high rotation range, the pressure waves propagated to a specific cylinder from other cylinders through the communication section 22 and the reflected waves from the communication section 22 can be made to almost match.

(Effects of the Invention) As explained above, according to the present invention, a communication portion is provided midway through which the mutually independent intake passages between the intake expansion chamber and each cylinder communicate with each other, and the communication portion Since the communication is controlled according to the engine operating status,
The inertia effect of the intake air can be enhanced in both the low and high rotation ranges, and especially in the high rotation range, the pressure waves propagating between the cylinders through the communication section further increase the intake air filling efficiency, increasing the output at rotation. can be significantly improved. Furthermore, since the communication portion is arranged in parallel with the intake expansion chamber, the intake system that exhibits the above effects can be formed small and compact, and the ease of mounting on a vehicle can be improved.

[Brief explanation of drawings]

The drawings illustrate embodiments of the invention, and FIGS.
An example is shown, FIG. 1 is a schematic sectional view thereof, FIG. 2 is a sectional view showing a specific structure, and FIG. 3 is a partially broken perspective view of the same.
Figures 4 and 5 are respectively tt421i! ! I's rv
-rvs and v-vm. FIG. 6 is a diagram corresponding to FIG. 2 showing the second embodiment. 1...Engine body, 4a-4d...Cylinder, 12-
15...Independent intake passage, 16...Intake expansion chamber, 22
...Communication part, 23...Opening/opening valve, 25...Control means, 26...Tank, 27...Partition wall, 28.29.
··tank. -221212 t

Claims (1)

[Claims] (1) In an intake system for a multi-cylinder engine in which the intake expansion chamber and each cylinder are connected by independent intake passages for each cylinder that are independent of each other, each independent intake passage is branched from the middle and the independent intake passages are connected to each other. A communication section that passes through the passage, and a control means that controls communication between the independent intake passages through this communication section according to the operating state of the engine, and the communication section is a part of the constituent wall that constitutes the intake expansion chamber. An intake system for a multi-cylinder engine, characterized in that the intake system is formed by a multi-cylinder engine and is arranged in parallel with an intake expansion chamber.