JPH0726539B2 - Multi-cylinder engine intake system - Google Patents

Description

The present invention relates to an intake system for a multi-cylinder engine.

[Conventional technology]

Recently, various vehicle engines have been developed and proposed from the viewpoint of increasing the engine output so as to supercharge intake air by utilizing the so-called dynamic effect of intake air.
The inertial effect of intake air is known as one of the dynamic effects of the intake air. As an intake device utilizing this intake inertia, conventionally, an intake passage is provided between each of a plurality of cylinders and a surge tank. There are some which set the size and shape of the passage according to the engine speed.
In that device, the surge tank becomes large and the intake passage becomes long, which is not preferable in view of the space in the engine room.

Further, as another intake device utilizing the intake inertia, conventionally, for example, as shown in Japanese Utility Model Laid-Open No. 56-105626, a common intake passage downstream of the surge tank is branched to a common intake passage to each cylinder. There is a device in which the size and shape of the intake passage and the branch intake passage are appropriately set. In this device, the surge tank can be small in size because there is only one connection portion of the intake passage to the surge tank. Due to its structure, the branch intake passage is bent, which has the advantage of reducing the distance between the surge tank and the cylinder.

On the other hand, in a vehicle engine, a high pressure wave generated when the intake port is closed is known in addition to the above-described intake inertia as a dynamic effect of intake air. In the intake device described in the above publication, due to the structure of the intake passage, it is possible to cause the high pressure wave generated when the intake port of one cylinder is closed to act on the other cylinders in the intake stroke. It is considered that a larger supercharging effect can be obtained by using two different dynamic effects.

However, in this case, if supercharging is attempted at the same time by two different dynamic effects, the high pressure wave due to the intake inertia and the high pressure wave when the intake port is closed interfere with each other, and the supercharging effect is rather reduced. Will be lost. Therefore, in order to perform supercharging by the two dynamic effects, it is necessary to separately provide an intake system that uses the intake inertia and an intake system that uses the high-pressure wave when the intake port is closed. The problem arises that

By the way, considering the supercharging of the engine, generally, the supercharging utilizing the dynamic effect of intake air is performed in a high engine speed range, that is, in a driving range where a high output is required and the intake inertia is large, In the above case as well, since it was attempted to perform supercharging by both the intake inertia and the high pressure wave when the intake port was closed in the high engine speed range, the high pressure waves interfered with each other as described above, and the supercharging effect That is, the problem of not being able to obtain was generated. If the focus on supercharging is changed so that supercharging due to intake inertia and supercharging due to high pressure waves when the intake port is closed are performed in different regions, high pressure due to intake inertia and high pressure when the intake port is closed It is expected that the pressure waves do not interfere with each other, and in this way, the supercharging effect can be obtained over a wide rotation range.

[Object of the Invention]

In view of such a point, the present invention is to provide a multi-cylinder engine intake device that can obtain a supercharging effect over a wide rotation range.

[Structure of Invention]

Therefore, the present invention provides a common intake passage and a branch intake passage in a multi-cylinder engine having a common intake passage downstream of the surge tank and a branch intake passage branching from one location of the common intake passage to each cylinder. While the added length is set to a length that allows the supercharging effect due to the intake inertia in operating regions other than the high speed region, the length of the branch intake passage between the cylinders is set by the high pressure wave when the intake port is closed in the high speed region. The length is set so that the supercharging effect can be obtained, whereby the supercharging effect by different dynamic effects is obtained in different rotation regions.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an intake system for a multi-cylinder engine according to an embodiment of the present invention. In the figure, reference numeral 1 is an engine, and the engine 1 has four cylinders 2a to 2d, which are first to fourth cylinders.
Branch intake passages 3a to 3d are connected to the intake ports 12 to 2d, respectively, and the upstream ends of the branch intake passages 3a to 3d are connected to the surge tank 4.
It is connected to the downstream common intake passage 5. A throttle valve 7 and an air meter 8 are arranged in the upstream intake passage 6 of the surge tank 4, and an upstream end of the upstream intake passage 6 reaches an air cleaner 9. Branch exhaust passages 10a to 10d are connected to the exhaust ports 13 of the cylinders 2a to 2d, and the downstream ends of the branch exhaust passages 10a to 10d are connected to the common exhaust passage 11.

The length l1 of the intake passage formed by the common intake passage 5 and the branch intake passages 3a to 3d is set to a length at which the supercharging effect due to the inertial effect of intake air can be obtained in the low rotation speed range below the set rotation speed. Also, the length l2 of the branch intake passages 3a to 3d communicating between the intake ports 12 of the cylinders 2a to 2d in which the ignition sequence is continuous (however, in the figure, the branch intake passages between the first and third cylinders 2a and 2c are shown. 3a, 3c
Is set to such a length that the high pressure wave generated by opening and closing the intake port in the high speed range above the set speed acts on the next cylinder in the latter half of the intake stroke. There is. Here, the engine 1 is set to be ignited in the order of first, third, fourth and second.

Next, the operation will be described.

At low engine speeds below the set engine speed, the length l1 of the common intake passage 5 and the branch intake passages 3a to 3d is set to a length at which the inertial effect of intake air can be obtained.
Due to the inertial effect of the intake air, the intake air is efficiently pushed into 2a to 2d, and the filling effect is improved. Thus, so-called inertial supercharging is performed and the engine output is increased.

Also, when the engine reaches a high speed range above the set speed, this time the length l2 of the branch intake passages 3a to 3d between the cylinders 2a to 2d is changed to a high pressure wave when the intake port 12 is closed to the next cylinders 2a to 2d. Since the length is set so that it can work, one cylinder, for example, the first cylinder
When a high pressure wave is generated when the intake port 12 is closed in the cylinder 2a, this high pressure wave is propagated to the cylinder in the next ignition sequence in the latter part of the intake stroke, in this case, the intake port 12 of the third cylinder 3c,
Due to the action of this high pressure wave, the intake air is pushed into the third cylinder 2c to improve the charging efficiency, and thus supercharging is performed and the engine output is increased.

In the device of the present embodiment as described above, the supercharging effect due to the inertial effect of intake air is obtained in the low speed region, and the supercharging effect due to the high pressure wave when the intake port is closed is obtained in the high speed region. As a result, the supercharging effect can be obtained over a wide rotation range, and the drivability of the engine can be greatly improved.

Further, in the present device, compared with the device described in the above-mentioned conventional publication, only the length of the intake passage is appropriately set, so that the structure is simple and compact as in the device described in the conventional publication. In particular, in such a structure, it is possible to change the length of the common intake passage with a relatively simple structure, and in this case, it is possible to efficiently perform inertial supercharging over a wider range of the engine low speed region. it can. In addition, each branch intake passage 3a-3d
Is branched from one location in the common intake passage 5, so there is no volume part in the middle of the path between the cylinders in the ignition sequence, so that the high pressure wave generated when the intake port is closed in the high engine speed range is It is propagated without being attenuated, and a sufficient effect can be expected.

By the way, if the inertial supercharging and the supercharging by the high pressure wave when the intake port is closed are performed in one intake system as described above, the high pressure wave due to the inertial effect and the high pressure wave when the intake port is closed may interfere with each other. Is concerned. In this device, however, the length of the common intake passage is used, and the branch intake passage between the cylinders is set to a length at which the supercharging effect due to the high pressure wave when the intake port is closed is obtained in the high rotation speed region. Since the length of the intake passage is set to a value that provides the effect of inertia supercharging in the low speed range, the high pressure wave due to the intake inertia and the high pressure wave when the intake port is closed interfere with each other in the speed range. In most cases, the above-mentioned supercharging effect can be guaranteed.

Further, FIG. 2 shows an experimental result of the supercharging effect in the present device and a device adapted to perform only inertial supercharging (hereinafter referred to as a conventional device). In the figure, a and b show changes in the engine output with respect to the engine speed in this device and the conventional device.
According to FIG. 2, in the conventional device, as shown by the characteristic curve b, when the engine speed increases, the effect of inertia supercharging appears and the engine output gradually increases, and the common intake passage and the branch intake passage are increased. The engine speed becomes maximum at the engine speed determined by the length, and when the engine speed further increases, the effect of inertial supercharging is weakened and the engine output decreases. On the other hand, in this device, as shown by the characteristic curve a, when the engine speed increases, the effect of inertia supercharging also appears, and the engine output gradually increases to increase the supply intake passage 5 and the branch intake passage 3a. It becomes the maximum at the number of rotations determined by the length l1 of 3d, and the engine output decreases when the engine speed further increases, but when the engine speed exceeds the set number of revolutions, the high pressure when the intake port 12 is closed this time The supercharging effect due to the wave appears, the engine output increases again, and becomes the maximum at the engine speed determined by the length l2 of the branch intake passages 3a to 3d between the cylinders 2a to 2d in which the ignition sequence is continuous. The supercharging effect diminishes and the engine output decreases. Therefore, it can be seen that this device can secure a good engine output over a wider rotation range than the conventional device.

FIG. 3 shows another embodiment of the present invention, which is an example applied to a multi-cylinder engine having two intake systems of low load and high load. That is, the surge tank 15 is divided into two chambers 16 and 17 for low load and high load, and a first throttle valve 19 interlocking with an accelerator pedal is installed in the upstream intake passage 18 of the low load chamber 16 so as to be high. A second throttle valve 21 that is connected to a first throttle valve 19 by a lost motion machine or the like in the upstream intake passage 20 of the load chamber 17 and starts to open when the load exceeds a set load.
Is provided. Also, the low load chamber 16 of the surge tank 15
And a low-load intake passage 23 between the cylinders 22a to 22d, and a high-load intake passage 24 between the high-load chamber 17 of the surge tank 15 and the cylinders 22a to 22d. The high-load intake passage 24 includes a common intake passage 25 on the downstream side of the surge tank 15 and branch intake passages 26a to 26d that branch from the passage 25 and extend to the cylinders 22a to 22d. The passage 25 and the branch intake passages 26a to 26d are set to have the same length as that of the first embodiment. In the figure, 27 is a catalyst for purifying exhaust gas.

In this embodiment, since the structure of the present invention is applied to the high load intake passage 24 having a relatively large passage area, a large supercharging effect due to the dynamic effect of intake air can be obtained.

Although the four-cylinder engine has been described in the above embodiment, the present invention can of course be applied to a multi-cylinder engine other than the four-cylinder engine.

〔The invention's effect〕

As described above, according to the present invention, in the multi-cylinder engine including the intake passage in the chest downstream of the surge tank and the branch intake passage branching from one portion of the common intake passage to each cylinder, the common intake passage The length of the branch intake passage between the cylinders is set when the intake port is closed in the high speed range, while the sum of the length of the branch intake passage is set to a length that can obtain the supercharging effect due to the intake inertia in operating regions other than the high speed region. Since it is set to a length that can obtain the supercharging effect due to the high pressure wave of, it is possible to obtain the supercharging effect by the dynamic effect of intake air over a wide rotation range,
This has the effect of significantly improving the drivability of the engine.

Further, since each branch intake passage is branched from one location of the common intake passage, the high pressure wave generated in the above high speed region is propagated to the cylinder to be ignited next without being attenuated on the way, and a sufficient excess pressure is generated. There is an effect that you can expect a salary effect.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an intake system for a multi-cylinder engine according to an embodiment of the present invention, FIG. 2 is a diagram showing engine output with respect to engine speed for explaining a supercharging effect of the system, and FIG. FIG. 6 is a schematic configuration diagram showing another embodiment of the present invention. 2a to 2d …… Cylinder, 3a to 3d …… Branch intake passage, 4 …… Surge tank, 5 …… Common intake passage, 12 …… Intake port, 15
...... Surge tank, 22a to 22d …… Cylinder, 25 …… Common intake passage, 26a to 26d …… Branch intake passage.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naoyuki Koyama 3-3 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Co., Ltd. (56) References JP-A-56-162223 (JP, A) JP-A-59- 218333 (JP, A)

Claims (1)

[Claims] 1. A multi-cylinder engine having a common intake passage downstream of a surge tank and a branch intake passage branching from one portion of the common intake passage to each cylinder. The length of the intake passage formed by the common intake passage and the branch intake passage,
While setting the length so that the supercharging effect due to the intake inertia can be obtained in the rotation range excluding the high speed range, the length of the branch intake passage that connects between the intake ports of the cylinders in the ignition sequence is An intake device for a timing cylinder engine, characterized in that a high pressure wave generated by opening and closing is set to a length such that a supercharging effect is obtained by exerting it on the next cylinder in the latter half of the intake stroke.