JPH04237826A - Internal combustion engine with supercharger - Google Patents

Abstract

PURPOSE:To obtain a by-pass route structure which can extract supercharger by-pass air from the lower stream side of an inter-cooler provided in an intake surge tank without generating the difference in the amount of intake through each cylinder. CONSTITUTION:A by-pass route 5 is provided almost in parallel with the line of the opening of an intake connection pipe 7 to each cylinder 4 to a surge tank 1, while a plurality of ports 22 opened in the surge tank are arranged in the direction of the stream in the bypass route 5. The opening area of the port 22 is smaller as it is nearer to the lower stream side of the by-pass route 5.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a supercharged internal combustion engine, and more particularly to a supercharger equipped with an intercooler for cooling supercharged air inside a surge tank provided on the downstream side of the supercharger in the engine intake system. The present invention relates to a supercharger bypass passage structure for an internal combustion engine.

0002

[Prior Art] In internal combustion engines with a supercharger, an intercooler is installed in the intake pipe downstream of the supercharger in order to cool the supercharged air and improve the intake air filling efficiency. When a positive displacement supercharger such as a Roots blower is used, the intercooler may become a source of noise. In other words, since the discharge air of a positive displacement turbocharger has relatively large pulsations,
The vibrations of the heat transfer fins of the intercooler caused by this pulsation propagate to the outside from the intercooler casing, which has a thin-walled sheet metal structure, and become a source of noise.

[0003] In order to prevent this, for example, Japanese Patent Laid-Open No. 1983-
Japanese Patent No. 247122 discloses a structure in which an intercooler is housed in a surge tank downstream of a supercharger. Normally, surge tanks are made of aluminum castings and have relatively thick outer walls, so even if the intercooler heat transfer fins vibrate inside the surge tank, the vibrations and noise can be blocked or blocked by the surge tank outer wall. Intake noise is reduced because it is attenuated and does not propagate to the outside. In addition to the problem of noise, housing the intercooler in the surge tank has the advantage of improving responsiveness by reducing the volume of the intake system and simplifying the intake piping.

On the other hand, in a positive displacement turbocharger, a bypass passage is usually provided to recirculate a portion of the discharge air from the turbocharger to the turbocharger inlet side, and the amount of bypass air passing through this bypass passage is adjusted to reduce the overload. supply control. Tokukai Showa 6
Publication No. 1-19935 discloses a configuration in which the bypass passage inlet is connected to an intake pipe on the downstream side of the intercooler, and the air after being cooled by the intercooler is recirculated to the supercharger inlet side. . By recirculating the air after cooling, even when the bypass recirculation amount increases during light load high speed engine operation, the supercharger discharge temperature will not rise excessively due to heat accumulation due to the turbocharger compression work. can be prevented.

[0005]

However, when a bypass passage is connected to the downstream side of the intercooler in an intake system in which an intercooler is disposed within a surge tank, the following problems occur. The surge tank is installed to prevent intake pressure pulsations and intake interference between cylinders, so it is placed close to the engine and connected to each cylinder through a separate intake pipe. There is.

[0006] Therefore, when attempting to connect a bypass passage to the intake system downstream of the intercooler, the bypass passage will inevitably be connected to the surge tank.

FIG. 3 is a diagram showing an example of the above configuration. The surge tank 1 is connected to each cylinder 4 through a short intake connecting pipe 7, and an intercooler 2 is disposed inside the surge tank 1. Also, 5
is a bypass passage, which connects the bypass port 5a that opens downstream of the intercooler 2 of the surge tank 1 and the supercharger 3.
The upstream side is connected. 6 is a bypass control valve that controls the amount of bypass air flowing back to the upstream side of the supercharger 3 through the bypass passage 5.

As shown in the figure, the shape of the surge tank 1 and the arrangement of the intake connecting pipes 5 are designed to minimize the resistance of the pipes leading to each cylinder so that the air supplied from the surge tank 1 to each cylinder 4 is distributed as evenly as possible. This is done so that no difference occurs. However, with the above configuration, there is no problem when the amount of air recirculating through the bypass passage 5 is small due to high load operation, etc., but when the engine is operated at low load and high speed, etc., the intake air amount of each cylinder may vary. There is a problem that arises.

[0009] In low-load, high-speed rotational operation, the rotational speed of the supercharger is high and the amount of intake air in each cylinder is kept low, so a large amount of air is recirculated through the bypass passage 5. For this reason, a pressure distribution occurs in the surge tank 1 in which the pressure decreases toward the bypass port 5a, and a difference occurs in the inlet pressure of each connecting pipe 7, making it impossible to distribute fresh air evenly to each cylinder. .

Particularly in the case of a two-stroke engine, the pressure inside the surge tank 1 is always maintained higher than the pressure on the exhaust pipe 7 side, and the amount of air taken into each cylinder is determined by the pressure difference between the surge tank 1 side and the exhaust pipe 11 side. Ru. Therefore, during low-load operation, this differential pressure is kept low and the amount of intake air in each cylinder is reduced. However, when the pressure difference between the surge tank 1 and the exhaust pipe 11 is small, the pressure distribution described above causes each cylinder to If a difference occurs in the intake port pressure, the amount of intake air in each cylinder will vary greatly. This causes torque fluctuations and deterioration of exhaust gas properties, and in extreme cases, misfires may occur.

In order to prevent this, it is necessary to move the position of the bypass port 5a to the upstream side of the surge tank 1 to equalize the pressure inside the surge tank, but as mentioned above, it is necessary to connect the bypass passage downstream of the intercooler. In this case, the bypass port 5a must be placed near the illustrated position. For this reason, in a configuration in which the intercooler is disposed within the surge tank 7, it is difficult to connect a bypass passage downstream of the intercooler. The present invention aims to solve the above-mentioned problems by providing a bypass passage structure that can take out bypass return air from inside a surge tank without causing the above-mentioned pressure distribution.

0012

[Means for Solving the Problems] According to the present invention, a supercharger is provided in an engine intake pipe, a surge tank is provided in the intake pipe on the downstream side of the supercharger, and an intercooler is provided in the surge tank. , a supercharged internal combustion engine comprising a plurality of connecting pipes that supply intake air from the surge tank to each cylinder, and a bypass passage that communicates a downstream part of the intercooler inside the surge tank to an upstream side of the supercharger, The bypass passage includes a flow path that is substantially parallel to a row of openings formed by the connection ports of the plurality of connection pipes with the surge tank, and the bypass passage is provided with a flow path that is substantially parallel to an opening row formed by each connection port of the plurality of connection pipes with the surge tank, and that allows the flow of water into the surge tank through a plurality of ports arranged along the flow path. There is provided an internal combustion engine with a supercharger, characterized in that the opening area of each of the plurality of ports decreases toward the downstream side in the flow direction within the bypass passage.

[0013]

[Operation] When there is an air flow flowing back to the supercharger inlet side through the bypass passage, the pressure inside the bypass passage decreases as it moves downstream in the flow direction within the passage. Therefore, the difference between the pressure in the surge tank and the pressure in the bypass passage increases as the position moves downstream of the bypass passage. The bypass passage of the present invention includes a plurality of openings arranged along the flow direction and opening into the surge tank, and the opening area of the openings into the surge tank decreases as the bypass passage becomes downstream. Therefore, the throttle resistance to the airflow flowing from the surge tank into the bypass passage through the opening also increases toward the downstream side.

[0014] Therefore, as the differential pressure increases toward the downstream side of the bypass passage, the throttling resistance of the openings also increases. It becomes approximately uniform along the inner flow direction. Therefore, even when the amount of air flowing back through the bypass passage increases, no pressure distribution occurs in the surge tank in the flow direction within the bypass passage.

[0015]

Embodiment FIG. 1 shows the configuration of one embodiment of the present invention. In the figure, 1 is a surge tank installed in the intake pipe 8, 2 is an intercooler located inside the surge tank, and 3 is the intake pipe 8.
This supercharger is provided upstream of the surge tank 1, and in this embodiment, it is a roots-type positive displacement supercharger driven from the engine 10 by a belt (not shown) or the like. Further, 9 is a throttle valve provided on the upstream side of the supercharger in the intake pipe 8, and 5 is a bypass passage connecting the downstream side of the intercooler 2 of the surge tank 1 and the intake pipe between the throttle valve 9 and the supercharger 3. , 6 is a bypass control valve that controls the amount of bypass air that passes through the bypass passage 5 and returns to the upstream side of the supercharger.

In this embodiment, the engine 10 has six cylinders, two
This is a cycle engine, and the intake ports of each cylinder 4 are connected to the downstream side of the intercooler 2 of the surge tank 1 through independent intake connection pipes 7, respectively. In addition, the bypass passage 5
includes a tube member 21 inserted into the surge tank 1. The pipe member 21 extends within the surge tank 1 so as to be substantially parallel to the arrangement of the connection ports of the respective connection pipes 7.

FIG. 2 is an enlarged view showing a cross section of the tubular member 21 including its axis. The tube wall of the tubular member 21 has four hole rows 22a to 22, each consisting of through holes arranged parallel to the axis.
22d is provided, and hole rows 22a, 22c, and 22b are provided.
and 22d (not shown) are arranged at symmetrical positions with respect to the axis of the tubular member 21, respectively, and the hole rows 22a, 22c and 2
2b and 22c are arranged at positions rotated by 90 degrees around the axis. The through holes constituting the hole rows 22a and 22c and the through holes constituting the hole rows 22b and 22c are open at positions separated by a half pitch from each other along the axial direction. The holes are arranged such that the hole diameter gradually decreases from the tip 21a of the surge tank 21 toward the surge tank outer wall penetrating portion 21b. The diameter, pitch, and number of each through hole and the diameter of the tubular member 21 are determined by the bypass passage 5 for each engine.
Under conditions where the amount of bypass air that returns to the inlet side of the supercharger 3 through the through-holes in each hole row is maximized,
It is determined in advance through experiments so that the amount of air flowing into the tube 1 is approximately uniform.

During operation of the engine 10, intake air passes through the throttle valve 9, is pressurized by the supercharger 3, and is supplied to the surge tank 1. This air passes through the heat transfer fins of the intercooler 2 and is cooled, and at the same time flows into the downstream side of the surge tank 1 in a rectified state by passing through the fin rows. Therefore, in this state, the flow is uniform in each cross section perpendicular to the intake flow in the surge tank 1, and the pressure distribution is also uniform. When there is a flow flowing back through the bypass passage 5, air flows into the through holes of the tubular member 21 from this state, but as described above, the flow rate of air flowing into the tubular member 21 from each through hole is approximately Since it is uniform, the pressure distribution of the intake air flow after passing through the tubular member 21 in the direction along the tubular member 21 is also substantially uniform.

[0019] Therefore, the amount of intake air in each cylinder 4 is also substantially uniform, so that variations in the amount of intake air do not occur. In addition, in this embodiment, the bypass passage has a type in which the tubular member 21 is inserted into the surge tank 1, but the tubular member 21 is inserted into the surge tank 1.
For example, a row of through holes similar to those described above may be arranged on the outer wall of the surge tank 1 so as to be parallel to the arrangement of the surge tank connections of the intake connection pipes of each cylinder. It is also possible to have a structure that communicates with a bypass passage.

[0020]

[Effects of the Invention] By having the above-described structure, the present invention can bypass the supercharger downstream of the intercooler without causing variations in the intake air amount of each cylinder in a supercharged internal combustion engine in which the intercooler is disposed in the surge tank. It has the effect of allowing passages to be connected.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of the bypass passage inlet of the embodiment.

FIG. 3 is a diagram showing an example of conventional technology.

[Explanation of symbols]

1...Surge tank 2...Intercooler 3...Supercharger 5...Bypassport 10...Engine 21...Pipe member 22...hole row

Claims (1)

[Claims] 1. A supercharger in an engine intake pipe, a surge tank disposed in the intake pipe downstream of the supercharger, an intercooler disposed in the surge tank, and intake air supplied from the surge tank to each cylinder. In a supercharged internal combustion engine, the turbocharged internal combustion engine includes a plurality of connection pipes for supplying the surge tank, and a bypass passage that communicates a downstream portion of the intercooler inside the surge tank with an upstream side of the supercharger, wherein the bypass passage is connected to the plurality of connection pipes. It has a flow path that is substantially parallel to the row of openings formed by each connection port with the surge tank, and communicates with the inside of the surge tank through a plurality of ports arranged along the flow path. A supercharged internal combustion engine characterized in that the opening area of each port decreases toward the downstream side in the flow direction within the bypass passage.