JPS61252830A - Intake device of multicylinder engine - Google Patents

Abstract

PURPOSE:To improve intake efficiency, according to the method wherein an independent intake air passage is coupled form a surge tank to a set of the intake air ports of each cylinder to perform inertia supercharging, and an intake air passage, through which other set of the intake air ports are coupled to each of cylinders which are positioned in the ignition order in succession, is provided to perform dynamic supercharging. CONSTITUTION:When air is intaked from a surge tank 4 to the intake air port of each cylinder, independent intake air passages 3a and 3d are formed to a set of the intake air ports of a first and a fourth cylinder, and each passage length 11 is set to a value being so optimum enough to allow inertia supercharging. A second cylinder 2b and a third cylinder 2c, positioned in the ignition order in succession, are intercoupled through intake air passages 3b and c. A total length 12 of the two passages is set to length by which a pressure wave produced when the one cylinder is closed during high speed operation is propagated when the intake air port of the other cylinder is opened. The dynamic supercharging and said inertia supercharging cause improvement of intake efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an intake system for a multi-cylinder engine.

[Conventional technology]

Recently, various vehicle engines have been developed and proposed in which intake air is supercharged by utilizing the so-called dynamic effect of intake air, with a view to increasing engine output.

Intake inertia effect is known as one of the dynamic effects of this intake air, and as an intake system that utilizes this intake inertia, conventionally, intake passages are provided between each of a plurality of cylinders and a surge tank, and the intake air There are some models in which the dimensions and shape of the passage are set according to the engine speed.
In this device, the surge tank becomes large and the intake passage becomes long, which is not desirable when considering the space in the engine room.

In addition, as another intake device that utilizes intake inertia, conventionally, for example, as shown in Japanese Utility Model Application No. 56-105626, a branch intake passage is branched from a common intake passage downstream of a surge tank to each cylinder. There is a device in which the dimensions and shapes of the intake passage and the branch intake passage are set appropriately.In this device, there is only one connection part of the intake passage to the surge tank, so the surge tank can be small, and Due to its structure, the branch intake passage is curved, which has the advantage of shortening the distance between the surge tank and the cylinder.

On the other hand, in a vehicle engine, in addition to the above-mentioned intake inertia, high pressure waves generated when the intake port is closed are known as dynamic effects of intake air. In the intake system described in the above-mentioned conventional 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 other cylinders in the intake stroke. It is believed that a greater supercharging effect can be obtained by utilizing two different dynamic effects.

However, in this case, if two different dynamic effects are tried to perform supercharging at the same time, the high pressure waves due to intake inertia and the high pressure waves when the intake port is closed will interfere with each other, which will actually reduce the supercharging effect. This will result in Therefore, in order to perform supercharging using two dynamic effects, it is necessary to separately provide an intake system that utilizes intake inertia and an intake system that utilizes high pressure waves when the intake port is closed, resulting in a complex and large structure. A problem arises.

By the way, when considering engine supercharging, supercharging that utilizes the dynamic effect of intake air is generally carried out in the high rotation range of the engine, that is, in the operating range where high output is required and intake inertia is large. In the above case as well, since we tried to perform supercharging using both the intake inertia and the high pressure waves when the intake port is closed in the high engine speed range, the high pressure waves interfere with each other as described above, resulting in the supercharging effect. This resulted in the problem of not being able to obtain the desired results. If we change the focus on supercharging and perform supercharging due to intake inertia and supercharging due to high pressure waves when the intake port is closed in different areas, we can reduce the high pressure due to intake inertia and the high pressure wave when the intake port is closed. There is no interference with pressure waves, and it is expected that by doing so, a supercharging effect can be obtained over a wide rotation range.

[Purpose of the invention]

In view of this point, the present invention aims to provide an intake system for a multi-cylinder engine that can obtain a supercharging effect over a wide rotation range.

[Structure of the invention]

Therefore, in a multi-cylinder engine in which branch intake passages for each cylinder are branched from a common intake passage downstream of a surge tank, the present invention aims to reduce the total length of the common intake passage and the branch intake passage in operating ranges other than high-speed ranges. The length of the branch intake passage between the cylinders is set to a length that provides a supercharging effect due to intake inertia, while the length of the branch intake passage between cylinders is set to a length that provides a supercharging effect due to high pressure waves when the intake port is closed at high speeds. This allows the supercharging effect to be obtained through different dynamic effects in different rotation ranges.

〔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 denotes an engine, and the engine 1 has four air cylinders m2a to 2d, first to fourth, and each branch intake passage 3 is connected to an intake port 12 of each of the multi-cylinders 2a to 2d.
a to 3d are connected, and the upstream ends of the branched intake passages 3a to 3d are connected to a common intake passage 5 downstream of the surge tank 4. A throttle valve 7 and an air meter 8 are disposed in an upstream intake passage 6 of the surge tank 4, and an upstream end of the upstream intake passage 6 reaches an air cleaner 9.

Further, branch exhaust passages 108 to 10d are connected to the exhaust ports 13 of the respective cylinders 2a to 2d, and the branch exhaust passages 108 to 10d are connected to the exhaust ports 13 of the cylinders 2a to 2d.
The downstream ends of 3 to 10d are connected to the common exhaust passage 1).

The length 1) of the intake passage formed by the common intake passage 5 and the branched intake passages 3a to 3d is set to a length that allows a supercharging effect due to the inertia effect of intake air to be obtained in a low rotation range below the set rotation speed. and the cylinders 2a to 2 whose ignition order is consecutive
Branch intake passages 3a to 3 that communicate between the intake ports 12 of d.
d length 12 (However, in the figure, the first and third cylinders 2a,
(Only the length of the branch intake passages 3a and 3c between 2c and 2c is shown.) In the high rotation range above the set rotation speed, the high pressure waves generated by the opening and closing of the intake port act on the next cylinder in the latter half of the intake stroke. The length is set as follows. Here, engine 1 is the first engine. Third. 4th. They are set to fire in the second order.

Next, the effect will be explained.

When the engine rotates at a low speed below the set rotation speed, the length zl of the common intake passage 5 and the branch intake passages 3a to 3d is set to a length that provides the inertia effect of intake air.
The inertial effect of this intake air forces the intake air into each cylinder 2a to 2d efficiently, improving the filling effect, thereby performing so-called inertial supercharging, and increasing the engine output.

Furthermore, when the engine reaches a high rotational speed range higher than the set rotational speed, the high pressure wave when the intake port 12 is closed passes through the length 12 of the branch intake passages 3a to 3d between the cylinders 2a to 2d.
Since the length is set to such a length that it can act on 2d, when a high pressure wave is generated in one cylinder, for example, the first cylinder 2a, when the intake port 12 is closed, this high pressure wave will cause the next ignition in the latter half of the intake stroke. The intake air is propagated to the intake port 12 of the cylinder in sequence, in this case the third cylinder 2C, and the action of this high pressure wave forces the intake air into the third cylinder 2C, improving charging efficiency, and thus supercharging is performed. Engine output will increase.

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

In addition, in this device, compared to the device described in the above-mentioned conventional publication, the length of the intake passage is only set appropriately, so that the structure is simple and compact like the device described in the conventional publication. In particular, with this type of structure, it is possible to vary the length of the common intake passage with a relatively simple structure, and in this case, inertial supercharging can be performed efficiently over a wider range of low engine speeds. can.

By the way, as mentioned above, if one intake system performs inertia supercharging and supercharging by high pressure waves when the intake port is closed, the high pressure waves due to the inertial effect and the high pressure waves when the intake port is closed will interfere. There are concerns.

However, in this device, the length of the common intake passage is used, and the length of the branch intake passage between the cylinders is set so that the supercharging effect due to the high pressure wave when the intake port is closed in the high rotation range is achieved. The length of the intake passage is set to a length that allows inertia supercharging to be achieved in the low rotation range, so high pressure waves due to intake inertia and high pressure waves when the intake port is closed will not interfere in any rotation range. There is little to do, and the above-mentioned supercharging effect can be guaranteed.

Further, FIG. 2 shows the experimental results of the supercharging effect in the present device and a device that performs only inertial supercharging (hereinafter referred to as the conventional device). In the figure, a and b indicate changes in engine output with respect to engine speed in the present device and the conventional device. According to Fig. 2, in the conventional device, as the engine speed increases, the effect of inertial supercharging appears and the engine output gradually increases, as shown in the characteristic curve. The maximum rotational speed is determined by the length of the engine, and as the engine speed increases further, the effect of inertial supercharging weakens and the engine output decreases. On the other hand, in this device, as shown by the characteristic curve a, as the engine speed increases, the effect of inertial supercharging appears in this case as well, and the engine output gradually increases. The maximum engine speed is determined by the length 1) of 3d, and as the engine speed increases further, the engine output decreases, but when the engine speed exceeds the set speed, the high engine speed when the intake port 12 is closed becomes the maximum. A supercharging effect due to the pressure wave appears, and the engine output increases again.
The engine speed reaches its maximum at the engine speed determined by the length 12 of a to 3d, and thereafter the supercharging effect due to the high pressure wave fades and the engine output decreases. Therefore, it can be seen that the present device can ensure good engine output over a wider rotation range than the conventional device.

Further, FIG. 3 shows another embodiment of the present invention, which is an example applicable to a multi-cylinder engine having two intake systems for low load and high load. That is, the surge tank 15 is divided into two chambers 16 and 17, one for low load and one for high load, and a first throttle valve 19 that is linked to the accelerator pedal is located in the intake passage 18 on the upstream side of the low load chamber 16. A second throttle valve 21 is disposed in the upstream intake passage 20 of the load chamber 17 and is connected to the first throttle valve 19 by a lost motion mechanism or the like, and starts to open when the load exceeds a set load.

In addition, the low load chamber 16 of the surge tank 15 and each cylinder 22a
-22d, and a high-load intake passage 24 is provided between the high-load chamber 17 of the surge tank 15 and each cylinder 22a-22d. The load intake passage 24 branches from the common intake passage 25 downstream of the surge tank 15 and connects each cylinder 22a to 2.
The common intake passage 25 and the branch intake passages 268 to 26 are composed of branch intake passages 26a to 26d extending to
d is set to the same length as in 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 can be obtained due to the dynamic effect of intake air.

Although a four-cylinder engine has been described in the above embodiment, the present invention is of course applicable to multi-cylinder engines other than four-cylinder engines.

〔Effect of the invention〕

As described above, according to the present invention, in a multi-cylinder engine in which the branch intake passages of each cylinder are branched from the common intake passage downstream of the surge tank, the length of the common intake passage and the branch intake passage is determined in the high-speed range. The length of the branched intake passage between the cylinders is set to a length that provides a supercharging effect due to intake inertia in other operating ranges, while the length of the branch intake passage between cylinders is set to a length that provides a supercharging effect due to high pressure waves when the intake port is closed at high speeds. I set it to
It is possible to obtain a supercharging effect due to the dynamic effect of intake air over a wide rotation range, which has the effect of significantly improving engine drivability.

[Brief explanation of the drawing]

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 versus engine speed for explaining the supercharging effect of the above system, and FIG. FIG. 2 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~
22d...Cylinder, 25...Common intake passage, 26a~
26d... Branch intake passage.

Claims (1)

[Claims] (1) In a multi-cylinder engine in which branch intake passages for each cylinder are branched from a common intake passage downstream of the surge tank,
The length of the intake passage formed by the common intake passage and the branched intake passage between the surge tank and the intake port,
The length of the branch intake passage that communicates between the intake ports of cylinders with consecutive ignition orders is set to a length that allows the supercharging effect due to intake inertia to be obtained in the rotation range except the high speed range. An intake system for a multi-cylinder engine, characterized in that the length is set so that a supercharging effect can be obtained by applying high pressure waves generated by opening and closing to the next cylinder in the latter half of the intake stroke.