JPH01187320A - Exhaust for engine with turbo supercharger - Google Patents

Abstract

PURPOSE:To restrain the occurrence of knocking by providing bypass passages bypassing a turbine in confrontation with respective cylinders in such a manner that the resistance of a bypass passage against a cylinder at which knocking is liable to occur may be made small. CONSTITUTION:At a two cylinder rotary piston engine, a turbo supercharger 8 is interveniently furnished at part of the way of an exhaust passage 10 from respective cylinders 1F, 1R. This exhaust passage 10 forms the portion of the upper stream side of a turbine 8a into two independent exhaust passages 13f, 13r independent by respective cylinders. Also, two bypass passages 14f, 14r which bypass the turbine 8a and connect the scroll portions of respective independent exhaust passages 13f, 13r with the exhaust passage 10 on the lower side, are provided, and both passages 14f, 14r are opened/closed by means of a common waste gate valve 15. And in this instance, the bypass passage 14r for the cylinder 1R at which knocking is liable to occur, out of bypass passages 14f, 14r, is made larger at its passage diameter, and is made smaller at its passage resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an exhaust system for a turbocharged engine.

(Prior Art) Conventionally, in engines equipped with a turbocharger, the exhaust introduction passage that introduces exhaust gas into the turbine of the turbocharger is divided into a plurality of independent passages, and an on-off valve is installed in some of the passages. At low speeds and low loads, the on-off valve is closed to increase the flow rate of exhaust gas to the turbine and improve turbine efficiency, while at high speeds and high loads, the on-off valve is opened to accommodate the increase in exhaust gas flow rate. For example, the technology
It is publicly known as seen in Japanese Patent No. 0-1230.

Furthermore, in a multi-cylinder engine, it is also conceivable that exhaust passages from each cylinder are formed independently and introduced into the turbine of a turbocharger.

On the other hand, in order to regulate the upper limit of supercharging pressure to a predetermined value, a bypass passage is provided that bypasses the turbine of the turbocharger and communicates the exhaust passages upstream and downstream of the turbine, and the supercharging pressure is maintained at a predetermined value in this bypass passage. A technique is also known in which a wastegate valve is provided that opens when the temperature rises above a certain level.

(Problem to be Solved by the Invention) However, in the turbocharged engine as described above, the installation of the turbocharger increases the pressure in the exhaust passage of each cylinder, that is, the exhaust pressure, and as a result, the pressure in the exhaust passage of each cylinder increases. As the amount of exhaust gas carried into the intake stroke increases, the temperature of the intake air in the cylinder increases, making knocking more likely to occur, and if the exhaust pressure differs in each cylinder, the degree of knocking will also vary. In addition, the cooling performance of the engine differs for each cylinder depending on the cooling water distribution path, etc., and knocking tends to occur in cylinders with high temperatures due to the influence of the combustion chamber wall temperature.

If the knocking performance of each cylinder is different, the boost pressure etc. must be controlled according to the performance of the cylinder where knocking occurs, and the engine output performance etc. may not be fully demonstrated due to the set loss. There is sex.

Therefore, in view of the above circumstances, the present invention has been developed to provide a turbo supercharging system that adjusts the exhaust pressure of the cylinder where knocking occurs in accordance with the engine temperature distribution, etc., and adjusts the knocking performance of each cylinder to reduce set loss. The purpose of the present invention is to provide an exhaust system for an attached engine.

(Means for Solving the Problems) In order to achieve the above object, the exhaust system of the present invention independently forms exhaust passages from each cylinder of the engine to the turbine of the turbocharger, and each exhaust passage upstream of the cylinder is independently formed. A bypass passage is provided, which communicates the exhaust passage with the exhaust passage downstream of the turbine and opens when the boost pressure exceeds a predetermined value. It is a small version of the .

The passage resistance of the bypass passage can be reduced by, for example, increasing the passage diameter or shortening the passage length.

(Function) In the exhaust system of a turbocharged engine as described above,
A bypass passage is provided for each cylinder, which bypasses the turbine from the independent exhaust passage of each cylinder upstream of the turbine and communicates with the exhaust passage downstream of the turbine. By reducing the resistance of the bypass passage to
By matching the knocking performance with other cylinders, various settings can be made at the same level.

(Example) Hereinafter, each embodiment of the present invention will be described along with the drawings.

Embodiment 1 This embodiment is shown in FIG. 1 and is an example of a two-cylinder rotary piston engine.

The engine body 1 includes a front side housing 2, a front rotor housing 3, an intermediate side housing 4, a rear rotor housing 5, and a rear side housing 6 arranged in this order from the front side. 1 cylinder IF and rear 2nd cylinder I
It is composed of R.

The cooling water flows in from the inlet of the front side housing 2, flows axially to the rear through the cooling water passage 7 of the hot zone, flows to the cold zone side in the rear side housing 6, and then flows axially to the front side again. It flows out from the front side housing 2, and has a large cooling effect on the first cylinder IF, and the temperature of each part is lower than that of the first cylinder IF.
The 2nd cylinder IR is higher than the cylinder IF, and the temperature condition is 2nd.
The cylinder IR is in a state where knocking is more likely to occur.

Further, this engine includes a turbo supercharger 8 that supercharges intake air to each cylinder IF and IR, and a turbine 8a of the turbo supercharger 8 is connected to an exhaust passage 10 that discharges exhaust gas from each cylinder IF and IR. It is interposed in the middle. This exhaust passage 10 is
Exhaust boat of 1st and 2nd cylinder IF, IR 11.11
The exhaust passage 10 on the upstream side leading from the turbine 8a to the turbine 8a has first and second independent exhaust passages 13f and 13 which are independent for both cylinders.
r, and the first and second independent exhaust passages 13f
, 13r is constituted by a manifold portion connected to each exhaust port 11.11 and a scroll portion on the outer periphery of the turbine 8a.

Further, first and second bypass passages 14f bypass the turbine 8a and communicate the scroll portions of the first and second independent exhaust passages 13f and 13r on the upstream side with the exhaust passage 10 on the downstream side.

14r is provided, and both bypass passages 14f and 14r are opened and closed by a common waste gate valve 15,
The parts downstream from the waste gate valve 15 are merged and provided in common. The waste gate valve 15 is
It is operated according to the boost pressure by a drive mechanism (not shown),
When the boost pressure rises above a predetermined value, both bypass passages 14
f and 14r are opened.

The second bypass passage 14r is a second independent exhaust passage 1 corresponding to the second cylinder IR where knocking is likely to occur.
3r, and its passage diameter is the first bypass passage 14f.
It is formed larger so that the passage resistance is reduced.

According to this embodiment, the temperature of the cooling water flowing through the engine body 1 increases as it flows from the front side to the rear side, and knocking is likely to occur on the second cylinder IR side.
The wastegate valve 15 is used in areas where engine load and rotational speed increase, boost pressure increases, and knocking occurs.
is opened, a portion of the exhaust gas flows through the first and second bypass passages 14f and 4'' bypassing the turbine 8a, regulating the turbine rotation speed and suppressing the increase in supercharging pressure. Since the passage diameter of the second bypass passage 14'' for the second cylinder IR is large and its passage resistance is small, the exhaust pressure of the second independent exhaust passage 13r upstream of the turbine 8a of the second cylinder IR is equal to the exhaust pressure of the first cylinder IF. This reduces the amount of exhaust gas carried into the intake stroke, improves anti-knocking performance by lowering the intake air temperature, and provides knocking characteristics similar to those of the first cylinder IF.

Embodiment 2 This embodiment is shown in FIG. 2 and shows an example of a three-cylinder rotary piston engine.

The engine body 21 includes first to third cylinders 21A, 21B, and 21C in order from the front side.
Side housings 22, 28 and two intermediate housings 24, 26 at the front and rear ends are disposed on both sides of the rotor housing 23° 25, 27 of 21C. As in the previous example, the cooling water flows through the cooling water passage 30 from the front side to the rear side, makes a U-turn at the rear side housing 28, and flows out from the front side housing 22, and the temperature distribution is from the front side to the rear side, that is, the first The knocking performance increases in order from the cylinder 21A to the third cylinder 21C, and the knocking performance is most likely to occur in the third cylinder 21C from the first cylinder 21A to the third cylinder 21C.

In the exhaust passage 31 for the supercharger 32, the upstream side of the turbine 32a is the exhaust port 2 of each cylinder 21A to 21C.
First to third independent exhaust passages 33a to 33c are formed separately for each of the two, and these independent exhaust passages 3
First to third bypass passages 34a to 34c are formed, respectively, to communicate with the turbines 3a to 33c and bypass the turbine 32a. The bypass passages 34a to 34c are opened and closed by a common waste gate valve 35 according to the boost pressure, and are joined downstream from the waste gate valve 35 to form a common bypass passage.

Further, the bypass passages include a first bypass passage 34a to a second bypass passage 34b and a third bypass passage 34.
The structure is such that the passage length becomes shorter as c increases, and the passage resistance decreases in order.

In this embodiment as well, the knocking occurs in the region where the waste gate valve 35 is opened and the bypass passage 34a is opened.
~ When opening 34c, the first cylinder 21A to the third cylinder 2IC
The passage resistance of the bypass passages 34a to 34c is smaller in order, and the exhaust pressure is increased in order from the first cylinder 21A to the second cylinder 21B.
It becomes lower in the first and third cylinders 21C, improving the knocking resistance, and acts to make the knocking performance under the same condition with respect to the engine temperature. This makes it possible to equalize various settings for each cylinder and reduce set loss.

According to the embodiment described above, the passage resistance of the bypass passage is adjusted in accordance with the knocking performance such as the engine temperature distribution, and the exhaust pressure of the cylinder where knocking is likely to occur is set to be lowered. It is possible to match the level of occurrence of cylinder knocking.

Note that in the above embodiment, the degree of occurrence of knocking is determined only with respect to engine temperature; however,
What is necessary is to find out in which cylinder knocking is likely to occur and set the passage resistance of the bypass passage accordingly.

(Effects of the Invention) According to the present invention as described above, a bypass passage that bypasses the turbine is provided for each cylinder, and the resistance of the bypass passage to the cylinder where knocking is likely to occur is reduced. When this bypass passage is open, knocking can be suppressed by lowering the exhaust pressure of the relevant cylinder, and various settings can be made to match the knocking performance of other cylinders at the same level, effectively reducing overpressure. It is possible to exhibit a feeding effect and reduce set loss.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a supercharged engine according to a first embodiment of the present invention, and FIG. 2 is a schematic diagram of a supercharged engine according to a second embodiment. 1.21...Engine body, IF, IR, 21
A~21C... Cylinder, 8.32... Turbo supercharger, 8a, 32a... Turbine, 10
．． 31...Exhaust passage, 13f, 13r, 33a
~33cm ---Independent exhaust passage, 14f, 14r, 3
4a ~34cm---Bypass passage, 15.35...
...Wastegate valve.

Claims (1)

[Claims] (1) A turbo supercharger is provided, and an exhaust passage from each cylinder of the engine is formed independently for the turbine of the turbo supercharger,
A bypass passage is provided which communicates each of the above-mentioned independent exhaust passages with an exhaust passage downstream of the turbine and opens when the boost pressure exceeds a predetermined value, and among the bypass passages, bypasses the cylinders where knocking is likely to occur. An exhaust system for an engine equipped with a turbocharger, characterized in that a passage has a small passage resistance.