JPH0353454B2 - - Google Patents

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. The present invention relates to an improvement of a multi-cylinder engine intake system designed to improve the performance.

(Prior Art) Conventionally, in the intake system of an engine, a negative pressure wave (pressure wave of negative pressure) generated with the start of intake is reflected at the opening 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 ( The positive pressure wave returns to the intake port as a positive pressure wave, and the positive pressure wave reaches the intake port just before the intake valve closes, pushing the intake air into the combustion chamber. This is the so-called intake inertia. Some devices are designed to increase the filling efficiency of intake air depending on the effect. 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 matches the opening and closing period of the intake valve, and the intake inertia effect is enhanced. 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. 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, even though pressure waves are generated in each cylinder, in the high rotation range, the intake air in each cylinder is simply By shortening the effective length of the passage, etc., the intake inertia effect is only increased by pressure propagation between each cylinder and the upstream opening end of the corresponding intake passage, and this improves the intake air filling efficiency. There's room. 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, and 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 the high rotation range, respectively. In particular, in the high rotation range where high output is required, pressure waves generated in other cylinders are effectively used between each cylinder to further increase intake air filling efficiency in the high rotation range and improve output. The purpose is to

Furthermore, an 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 provides an intake air intake system for an external cylinder engine in which an intake expansion chamber and each cylinder are connected by independent intake passages for each cylinder, which are independent from each other. equipment is assumed. Based on this premise, a communication section that branches off from the middle of each independent intake passage and communicates each independent intake passage with each other, and communication between each independent intake passage through this communication section is established depending on the operating state of the engine. and control means for controlling. The intake expansion chamber and the communication chamber are formed by partitioning the tank with a partition wall so that one side of the partition wall in the tank is the intake expansion chamber and the other side is the communication section, and the communication section are arranged in parallel with the intake expansion chamber, and the volume of the communication portion is set smaller than the volume of the intake expansion chamber. Further, each of the independent intake passages is connected to a side surface of the intake expansion chamber opposite to the engine body, curves along the intake expansion chamber and the communication portion, and then is directed toward the side opposite to the intake expansion chamber of the communication portion. The upstream portion of each of the curved independent intake passages is connected to the tank so as to be adjacent to the intake expansion chamber and the communication section, using a part of the wall forming the intake expansion chamber and the communication section as a passage forming wall. It is assumed that the area is divided into sections.

(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. The negative pressure wave that occurs is reversed and reflected into a positive pressure wave in the intake expansion chamber, so
The passage length for obtaining the intake inertia effect is relatively long from the intake expansion chamber to each cylinder, thereby increasing the intake inertia effect in the low rotation speed 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 waves are inverted and reflected into positive pressure waves, the effective length of the intake passage for obtaining the intake inertia effect becomes shorter. Moreover, the pressure waves from other cylinders are effectively propagated without being attenuated much by the communication portion having a smaller volume than the air expansion chamber.
The synergistic effect of these pressure waves greatly increases the filling efficiency in the high rotation range.

In that case, in order to make the passage length of each independent intake passage the same, the intake expansion chamber, which is arranged parallel to the longitudinal direction of the engine, has a smaller volume than the intake expansion chamber, and the tank is partitioned by a partition wall. Therefore, the upstream portion of each independent intake passage is integrally arranged in parallel with the intake expansion chamber, and the upstream portion of each independent intake passage is formed adjacent to the intake expansion chamber and a portion of the wall constituting the communication portion as a passage forming wall. The intake expansion chamber, the communication section, and the upstream portion of each independent intake passage are integrally formed adjacent to each other in one tank, so the passage length from each cylinder to the branch point of the communication section in the middle of each independent intake passage It becomes possible to form a small and compact intake system while effectively ensuring the same effect as described above.

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

1 to 5 show a first embodiment in which the present invention is applied to a 4-cylinder 4-cycle engine.
The figure shows its schematic structure, and FIGS. 2 to 5 show its specific structure. In the illustrated engine, first to fourth cylinders 4a to 4d are formed in series in the longitudinal direction of an engine main body 1 consisting of a cylinder block 2, a cylinder head 3, and the like. A combustion chamber 6 is formed above the piston 5 in each of the cylinders 4a to 4d, an intake port 7 and an exhaust port 8 are opened in the combustion chamber 6, and an intake valve 9 and an exhaust port are connected to these ports 7 and 8, respectively. A valve 10 is provided. Further, the combustion chamber 6 is equipped with a spark plug 11.

Each intake port 7 of each of the cylinders 4a to 4d has
Independent intake passages 12 to 15 for each cylinder that are independent from each other
The downstream ends of these independent intake passages 12~
The upstream end of 15 is connected to an intake expansion chamber 16 extending parallel to the longitudinal direction of the engine (crankshaft 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 intake pipe 17
A throttle valve 18 is provided to control the amount of intake air. In addition, each of the independent intake passages 12 to
A fuel injection valve 20 connected to the fuel passage 19 is disposed near the downstream end of the fuel injection valve 15 .

In the middle of each of the independent intake passages 12 to 15, there is an intake expansion chamber 16 (that is, in the longitudinal direction of the engine).
These independent intake passages 12 to 15 extend parallel to
A communication portion 22 that communicates these independent intake passages 12 to 15 with each other is connected via a branch hole 21 that branches from the intake passage. 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, respectively. Each of the on-off valves 23 is integrally fixed to a valve shaft 24 extending in the longitudinal direction of the communication portion 19 so as to be interlocked with each other, and although not shown, the actuator is controlled by a control circuit that receives an output from an engine rotation speed detecting means or the like. The communication section 22 controls the communication between the independent intake passages 12 to 15 depending on the engine operating condition, and is closed in the low rotation range where the engine rotation speed is less than a set value, and the communication between the independent intake passages 12 to 15 is controlled by the communication section 22. A control means 25 is configured to control the engine to be opened in a high rotation range exceeding a 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 open or closed state at low loads. It may be maintained.

The intake system structure of the communication portion 22 and the intake expansion chamber 16 is formed so that both extend parallel to the longitudinal direction of the engine, as shown in detail in FIGS. 2 to 5. By dividing the tank 26 interposed in the intake system into upper and lower parts with a partition wall 27, a relatively large capacity intake expansion chamber 16 and a relatively small capacity communication section 22 are partitioned into the tank 26. There is. In other words, the communication part 2
2 is formed by a part of the constituent wall (partition wall 27) constituting the intake expansion chamber 16, and is arranged in parallel with the intake expansion chamber 16. Furthermore, the communication portion 2
Branch hole 2 of each independent intake passage 12 to 15 at the lower end of 2
1 is opened, and each independent intake passage 12a to 15 on the upstream side of the location where this branch hole 21 is formed.
a is curved, and its upstream end is opened to the side of the intake expansion chamber 16 on the side opposite to the engine body 1.

In addition, the upstream curved portions 12a to 15a of each of the independent intake passages 12 to 15 that curve along the intake expansion chamber 16 and the communication portion 22 and then point toward the side opposite to the intake expansion chamber of the communication portion 22 are connected to the tank. A portion 26a is integrally formed along the circumferential surface of the tank 26 and constitutes the intake expansion chamber 16 of the tank 26 and the independent intake passages 12a to 15a outside thereof. Portions 26b constituting the outer independent intake passages 12a to 15a are integrally molded, and these 26
a, 26b are connected via a partition wall 27, and downstream portions 12b to 15b of each independent intake passage 12 to 15 are connected to these, thereby forming a compact intake system. .

Next, to describe the operation of the above embodiment, each on-off valve 23 is closed by the control means 25 and the communication portion 2 is closed.
In a state where the communication between the independent intake passages 12 to 15 is cut off, the negative pressure wave generated during the intake stroke is propagated to the intake expansion chamber 16 and reflected there. In other words, the negative pressure wave is transmitted through the relatively long passage. As a result of the propagation of the reflected waves, the oscillation period of such pressure waves matches the intake valve opening/closing period in the low rotation range, increasing the inertia effect of intake air in the low rotation range, and reducing intake air filling. Efficiency is increased. 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 provided 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, the pressure waves propagated from other cylinders are also relatively small. Through the small-volume communication portion 25, it acts effectively without any damping, and the filling efficiency in the high rotation range is greatly increased. Therefore, at least when the load is high, the opening/closing valve 23 is opened at a lower rotational speed than a predetermined rotational speed corresponding to an intermediate rotational speed between the respective rotational speeds at which the intake inertia effect between the low rotational speed range and the high rotational speed range is obtained. By closing the on-off valve 23 and opening the on-off valve 23 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 appropriate sizes of the intake expansion chamber 16 and the communication portion 22 to effectively exert the above-mentioned effects are as follows: The intake expansion chamber 16 has a capacity of 0.5 times or more the exhaust volume, and the communication portion 22 has a capacity of 0.5 times or more the exhaust volume. It is desirable to keep the capacity 1.5 times or less. Furthermore, the communication portion 22 has a smaller capacity than the intake expansion chamber 16;
In addition, the cross-sectional area of the communication portion 22 is equal to that of each independent intake passage 12 to
It is desirable to make the cross-sectional area larger than No. 15.

In this case, the communication portion 22 is arranged in parallel with the intake expansion chamber 16 by dividing the tank 26 into upper and lower parts by the partition wall 27, and is connected to a part of the wall (partition wall 27) that constitutes the intake expansion chamber 16. Since the air intake system is formed in this way, it is possible to form an intake system that exhibits the above-mentioned functions and effects in a compact and small size, and its mountability on a vehicle can be improved. Further, curved portions 12a to 15a of each independent intake passage 12 to 15 on the upstream side of the branch hole 21 are formed along the circumferential surface of the tank 26, and the intake expansion chamber 16 of the tank 26
and a portion 26a constituting the independent intake passages 12a to 15a outside thereof, and a communication portion 22 of the tank 26.
By integrally molding and the portion 26b constituting the independent intake passages 12a to 15a on the outside thereof and connecting them via the partition wall 27, the above-mentioned intake system can be made more compact, and the moldability is improved. It is also possible to improve the ease of assembly.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but also includes various other modifications. For example, FIG. 6 shows a second embodiment of the present invention, in which a portion of the outer wall of a tank 28 forming the intake expansion chamber 16 is used in common to form the communication portion 22. That is, in this example, the tank 28 forming the intake expansion chamber 16 and the tank 2 forming the communication section 22
9 are arranged vertically in parallel, sharing a part of their outer walls so that the communication portion 22 is formed by a part of the wall constituting the intake expansion chamber 16. Furthermore, the upstream curved portions 12a to 15a of the independent intake passages 12 to 15 are formed along the circumferential surfaces of the tanks 28 and 29, and the upper and lower portions, which are integrally molded as dividing surfaces at the upper and lower middle positions of the tank 29, are joined. This is what constitutes the 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 electrical expansion chamber 16 and the communication section 22 are separated, for example, as shown by imaginary lines in FIG. The communication path 30 provided in the partition wall 27 communicates with the
The present invention can also be applied to a device in which intake air filling efficiency is further increased by causing intake air pressure vibration between the intake air expansion chamber 16 and the communication portion 22, which communicate through the intake air expansion chamber 16 and the communication portion 22.

Furthermore, the present invention is not limited to a four-cylinder engine as in the above embodiments, but can be applied to other multi-cylinder engines, such as a five-cylinder engine.
It can also be applied to cylinder engines and six-cylinder engines. In a 4-cylinder engine, the intake stroke of each cylinder is 180°, but in a 6-cylinder engine, for example, it is 120°. Therefore, when applying to a 6-cylinder engine, the communicating portion 22 should be formed short. For example, 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 substantially 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 are communicated with each other,
Since the communication through the communication part is controlled according to the engine operating condition, the inertia effect of the intake air can be enhanced in both the low rotation range and the high rotation range, and especially in the high rotation range, the communication between the cylinders is made possible through the communication part. Propagating pressure waves can further increase intake air filling efficiency and significantly improve output at high rotation speeds. Moreover, the tank is divided by a partition wall, and the intake expansion chamber and the communication section having a smaller volume are arranged side by side, and the upstream portion of each independent intake passage is integrated along the intake expansion chamber and the communication section. The intake expansion chamber, the communication section, and the upstream portion of each independent intake passage are integrally formed next to each other in one tank, creating a small and compact intake system that achieves the above effects. This makes it possible to improve on-vehicle compatibility.

[Brief explanation of drawings]

The drawings illustrate embodiments of the invention and show FIGS.
The drawings show the first embodiment; FIG. 1 is a schematic sectional view thereof, FIG. 2 is a sectional view showing a specific structure, FIG. 3 is a partially broken perspective view of the same, and FIGS. 4 and 5 are respectively FIG. 3 is a sectional view taken along the - line and the - line in FIG. 2; FIG. 6 is a diagram corresponding to FIG. 2 showing the second embodiment. 1...Engine body, 4a to 4d...Cylinder, 1
2 to 15...Independent intake passage, 12a to 15a...
Upstream curved portion, 16... Intake expansion chamber, 22...
Communication portion, 23... Opening/closing valve, 25... Control means, 2
6... Tank, 27... Partition wall, 28, 29...
tank.

Claims (1)

[Scope of Claims] 1. In an intake system for an external cylinder engine in which an intake expansion chamber and each cylinder are connected to each other by independent intake passages for each cylinder that are independent from each other, each independent intake passage is branched from the middle of each of the independent intake passages to form an independent intake passage. A communication section that communicates the passages with each other, 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 intake expansion chamber and the communication chamber are connected to a tank. By partitioning the tank with a partition wall, one side of the partition wall of the tank is formed as an intake expansion chamber and the other side is formed as a communication section, and the communication section is arranged in parallel with the intake expansion chamber,
Further, the volume of the communication portion is set smaller than the volume of the intake expansion chamber, and each of the independent intake passages is connected to a side surface of the intake expansion chamber opposite to the engine body, and the intake expansion chamber and the communication The upstream portion of each of the curved independent intake passages is a part of the constituent wall that constitutes the intake expansion chamber and the communication section. An intake system for a multi-cylinder engine, characterized in that a passage forming wall is formed in the tank so as to be adjacent to an intake expansion chamber and a communication section.