JPS6113091B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an intake system for a multi-cylinder engine, and more particularly to an intake system that performs efficient inertial supercharging.

To increase the volumetric efficiency of the engine's intake air,
It is effective to provide a supercharging device such as an exhaust turbo supercharger or to perform inertial supercharging using the inertia of the air in the intake passage.

However, if a supercharging device is installed as in the former case,
The structure of the intake device becomes complicated and its weight increases significantly, and furthermore, maintenance of the intake device requires a large amount of cost and labor. In addition, when performing inertial supercharging as in the latter case, the structure is relatively simple and inexpensive, and although it has the advantage of requiring almost no maintenance cost, However, the drawback was that the volumetric efficiency of intake air could not be increased.

That is, in the conventional inertial supercharging device for a typical multi-cylinder engine, as shown in FIG.
2f is divided into two groups A and B that do not include cylinders whose intake strokes overlap, and the intake manifolds 3a,
3b was installed. An air vessel 4 is connected to the atmosphere through each of the intake manifolds 3a and 3b and the secondary chamber of the Eculina or the Eculina.
By communicating these through intake passages 5a and 5b, respectively, inertial supercharging is performed using air column vibrations within these intake passages 5a and 5b.

Here, the resonance frequency F of the air in the intake passages 5a and 5b is as follows, where S is the speed of sound, A is the cross-sectional area of the intake passage, L is the length, and V is the volume of the air vessel 4. It is well known that it is given by the formula.

Further, when the excitation frequency for the intake air matches the resonance frequency, the vibration of the intake air is effectively utilized, and the volumetric efficiency of the intake air is increased. Therefore, in the past, specific numerical values for each of the elements were determined in order to match the resonance frequency to the excitation frequency in the high-speed rotation region where maximum output is required.
As shown by the dashed line in the figure, the volumetric efficiency was high in the high-speed rotation region.

However, even though automobile engines, for example, are frequently operated in the mid- to low-speed rotation range, the volumetric efficiency of the intake air cannot be increased very much in this range, so the fuel consumption rate does not necessarily improve, and the The torque is low and drivability is not necessarily improved.

Conversely, if the resonant frequency in the intake passages 5a and 5b is matched to the medium-low speed rotation range, the volumetric efficiency of the intake air in the high-speed operation range becomes low, resulting in a decrease in maximum output. Because there is
Conventional systems had the disadvantage that ideal inertial supercharging could not always be performed.

The present invention has been made in view of the above, and includes:
By improving the intake manifold, the volumetric efficiency of intake air in the high-speed rotation range can be increased without sacrificing the volumetric efficiency of the intake air in the low-speed rotation range, thereby improving engine drivability and fuel consumption. With the goal.

The present invention will be described below with reference to an embodiment shown in FIG.

In the figure, cylinders 11a, 11b, . Intake manifolds 12a and 12b are provided for each cylinder group A and B.

Further, both the intake manifolds 12a, 12b
are communicated with the air vessel 15 via collective passages 13a, 13b and a common intake passage 14, respectively. Note that this air vessel 15 is communicated with the atmosphere via an air cleaner (not shown), but a volume portion on the secondary side of the air cleaner, a turbo intercooler, or the like may be used as the air vessel.

Here, both the intake manifolds 12a, 1
The lengths of the collective passages 13a and 13b of the passages 2b are substantially the same. In addition, each collective passage 13a, 13
b and the common intake passage 14 through a passage made of a pipe or the like curved with an appropriate curvature without any sudden direction change, and also connect both the collective passages 13a, 13b with a sudden direction change. By communicating with one cylinder group without the other, the intake manifold of the other cylinder group acts as an auxiliary air vessel.

By forming the length of the common intake passage 14 to be shorter than the length of each collective passage 13a, 13b, both intake manifolds 12a, 12b
The length L1 of the passage from to the air vessel 15 is
It is made shorter than the length L2 of the passage connecting both intake manifolds 12a and 12b. 16 is an exhaust manifold.

In the above configuration, if it is assumed that the intake stroke of the cylinder belonging to the first group A has started, when air begins to flow into the cylinder due to the start of the intake stroke, the intake stroke of the cylinder that has started the intake stroke Port pressure decreases. Then, the influence of this pressure drop is transmitted from the collecting passage 13a of the intake manifold 12a to the other collecting passage 13b and the intake passage 14 at the speed of sound.

As the intake stroke started as described above progresses, the flow velocity at the intake port portion is gradually accelerated. Therefore, the pressure at the intake port decreases by the above acceleration and flow resistance. Then, as the intake stroke further progresses, the influence of the start of the inflow reciprocates at the speed of sound in the passage connecting the two intake manifolds 12a and 12b and the passage from the intake manifold 12a to the air vessel 15, and at the same time Pressure decreases by the amount of flow resistance.

Furthermore, when reaching the final stage of the suction stroke, the inflow speed at the suction port decreases, so the pressure increases.

This increase in pressure can be said to be the result of being pushed by the inertia of the air column, and at the end of the suction stroke, the air is pushed in by the increased pressure as described above.

In other words, the negative pressure wave generated in the intake port at the start of the intake stroke reaches the end of the passage at the speed of sound, becomes a positive pressure wave, and returns to the intake valve just before the valve closes, causing air to be pushed in. So-called inertial supercharging is performed.

Here, the resonance frequency F of the air in the passage is as described above, where S is the speed of sound, A is the cross-sectional area of the passage, L is the length, and V is the volume of the enlarged part (air vessel). It goes without saying that the effect of inertial supercharging (volume efficiency of intake air) is highest when the resonance frequency of the air in the passage matches the vibration frequency related to the engine rotation speed. do not have.

Therefore, as described above, if the length L2 of the passage that communicates the two intake manifolds 12a and 12b is made larger than the length L1 of the passage from each manifold to the air vessel 15, the cross-sectional area of each passage becomes Identical and each intake manifold 12
If the internal volumes of a and 12b are the same as the internal volume of the air vessel 15, the resonance frequency F2 when one intake manifold is regarded as an auxiliary air vessel is the resonance frequency of the air vessel 15.
It will be smaller than F1.

For this reason, if the lengths L1 and L2 of the passages are appropriately selected, the volumetric efficiency of the intake air can be improved in both the medium-low speed rotation region and the high-speed rotation region of the engine, as shown by the solid line in Fig. 3. can be made larger.

Therefore, inertia supercharging is not only carried out in the high-speed rotation range as in the past, but also in the high-speed rotation range where maximum output is required and the medium-low speed rotation range where operation is frequent. Inertial supercharging takes place. For this reason, there is no risk of insufficient low-speed torque as in the conventional case, and the torque curve becomes flat, improving engine drivability. Furthermore, as a result of inertial supercharging being performed in the medium and low speed rotation range where the engine is frequently operated, the fuel consumption rate of the engine is significantly improved.

In the embodiment, two types of resonance frequencies are obtained by dividing the engine cylinders into two groups and using the secondary side volume of the air cleaner as an air vessel. Of course, by dividing the cylinders into groups of three or more and increasing the number of resonance frequencies, it is possible to increase the inertial supercharging rate (volume efficiency) almost uniformly over all operating regions. It is.

Further, in the embodiment, a part of the passage from each intake manifold to the air vessel is shared, and
Although the two intake manifolds are communicated through the remaining portion, each of these passages may be made independent.

As explained above, according to the present invention, the cylinders of a multi-cylinder engine are divided into a plurality of groups, the overlapping of intake strokes within the same group is eliminated, and a collection of intake manifolds is provided corresponding to each cylinder group. By making the passages communicate smoothly with each other and by making the length of each collecting passage different from the length of the passage from the communicating part of these collecting passages to the air vessel, a smooth passage from each intake manifold to the air vessel can be created. Each intake manifold can be used as an auxiliary air vessel by varying the length and the length of the smooth passage that communicates each intake manifold with each other, so it can be used at multiple locations in the engine's rotation range. The peak volumetric efficiency of intake air can be made to appear. Therefore, it is possible to provide sufficient inertia supercharging not only in the high-speed rotation range as in the past, but also in the medium-low speed rotation range where operation is frequently performed, thereby improving the torque characteristics of the engine and reducing the fuel consumption rate. can be improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view of a conventional example, FIG. 2 is a schematic plan view of an embodiment of the present invention, and FIG. 3 is a characteristic diagram of the volumetric efficiency of intake air. 10...Multi-cylinder engine, 11a, 11b,...
...11f...Cylinder, 12a, 12b...Intake manifold, 13a, 13b...Collection passage, 1
4...Intake passage, 15...Air vent cell.

Claims (1)

[Claims] 1 The cylinders are divided into multiple groups so that cylinders with overlapping intake strokes are not included in the same group, while the intake manifolds provided corresponding to each cylinder group and the air vessels connected to the atmosphere are assembled respectively. In a multi-cylinder engine that communicates with each other through passages, the intake manifolds are communicated with each other through passages without sudden direction changes, and the length of the passage from each intake manifold to the air vessel and the length of the passage between the intake manifolds are determined. An intake system for a multi-cylinder engine, characterized in that the lengths of passages that communicate with each other are made different.