JPH065021B2 - Turbocharged engine - Google Patents

Description

TECHNICAL FIELD The present invention relates to a turbocharger in which a blower provided in an intake passage is driven by a turbine driven by exhaust gas to pressurize and supply intake air. It concerns an engine with a machine.

[Prior Art] Conventionally, this type of turbocharger has been widely used as a means for increasing the output of an engine by improving the charging efficiency.

By the way, this type of turbocharger is difficult to drive at a high speed to an extent that effectively improves the charging efficiency of the engine during low-speed operation of an engine with a small exhaust gas flow rate, and various problems are solved in order to solve this problem. Has been made.

In Japanese Patent Laid-Open No. 172427/1983, the volute passage of the turbine casing is divided into three in the axial direction of the turbine impeller to form a total of three scrolls, and a second group exhaust gas pipe is provided for the scrolls. A turbocharger has been proposed which is selectively switched and connected.

By the way, as shown in FIG. 5 showing changes in the cylinder pressure and the exhaust gas pressure thereafter, when the exhaust port is opened at the timing EO, the pressure P drops from P ₁ to P ₂ all at once, and the exhaust gas becomes exhaust gas. It expands in the passages to and then to the pressure in the turbine, decreasing from pressure P ₂ to P ₃ . In that case, the energy corresponding to the area indicated by the hatched area A in FIG. 5 is released to the exhaust passage as so-called blowdown energy. This blowdown energy is converted into the internal energy of the exhaust gas when the volume of each exhaust passage is large, in other words,
It is consumed in the rise of exhaust gas temperature.

In a normal exhaust manifold, the passage cross-sectional area of each exhaust passage is set to a value that is not large enough to prevent exhaust resistance during high-speed, high-load operation of the engine. When the engine is running at a low speed, the blowdown energy cannot be effectively utilized, and the exhaust gas temperature rises only.

For this reason, even in the turbocharger described in the above publication, blowdown energy is consumed for the rise of the exhaust gas temperature in the exhaust passage of each cylinder leading to each scroll, so that the effective use thereof is not achieved.

[Object of the Invention] An object of the present invention is to provide a turbocharged engine that can effectively utilize blowdown energy to improve the efficiency of the turbocharger particularly during low-speed operation.

Therefore, according to the present invention, in the engine provided with the turbocharger having a plurality of scrolls which are partitioned from each other, the exhaust passage of each cylinder is constituted by the first, second and second exhaust passages. , The first exhaust passage and the second exhaust passage are respectively connected to a predetermined scroll, and an exhaust port communicating with one of the exhaust passages is earlier than an exhaust port communicating with the other exhaust passage. While opening, both exhaust ports are configured to close at substantially the same timing.

EFFECTS OF THE INVENTION According to the present invention, since the exhaust passage of each cylinder is divided into two, the passage area of each exhaust passage can be set small, and one of the exhaust passages can be opened at an early timing. Therefore, the blowdown energy of the exhaust gas can be directly applied to the turbine even when the engine speed is low, and the supercharging efficiency during low speed operation can be improved. Further, in the present invention, a switching valve for switching the introduction passage for introducing the exhaust gas to each scroll is not necessary for each scroll.

Further, in the present invention, the two exhaust passages of each cylinder are closed at substantially the same timing, so that the exhaust time can be sufficiently secured, and the exhaust resistance can be reduced even during high speed and high load operation.

[Examples] Examples of the present invention will be specifically described below.

As schematically shown in the overall configuration diagram in FIG. 1, an engine E including first to fourth cylinders # 1 to # 4 is provided with a blower 6 provided in an intake passage 5 and an exhaust gas flowing down an exhaust passage 10. A turbocharger 9 is connected to a turbine 7 driven by gas by a turbine output shaft 8.

As shown in FIG. 2, the turbine 7 of the turbocharger 9 has first, second and second scroll chambers 7P and 7S partitioned by a partition wall 7a.

With respect to the two scroll chambers 7P and 7S of the turbine 7, in the present invention, the exhaust passages of the cylinders # 1 to # 4 are provided with first, second, and
It is composed of two exhaust passages 10P and 10S. The first exhaust passages 10P, ..., 10P of the respective cylinders are connected in common and then the first scroll chamber 7P of the turbine 7 is connected.
Connect to. In addition, the second exhaust passage 10S of each cylinder, ...,
10S connects them in common and then connects them to the second scroll chamber 7S.

In FIG. 1, numeral 11 is a waste gate valve, and in this embodiment, the first exhaust passage 1 having a large exhaust gas flow rate.
It is installed upstream of the 0P turbine.

Next, the first and second exhaust ports 12P and 1 of the cylinders # 1 to # 4, which are in communication with the first and second exhaust passages 10P and 10S, respectively.
The opening / closing timing of 2S will be described.

As shown in FIG. 3, the first exhaust valve Vp that opens and closes the first exhaust port 12P has a predetermined timing compared to the opening timing Eos of the second exhaust valve Vs that opens and closes the second exhaust port 12S. The opening timing Eop is set as early as possible, and the closing timing Ecp is slightly delayed as compared with that (Ecs) of the second exhaust valve Vs.

According to the setting of the exhaust valve timing, as shown in FIG. 4 showing the pressure changes in the first and second exhaust passages 10P and 10S, respectively, the pulsed pressure wave is generated immediately after the first exhaust valve Vp is opened. Wp is generated in the first exhaust passage 10P, and this pressure wave is not attenuated directly in the first portion of the turbine 7.
Since it is brought into the scroll 7P, the turbine 7 can be efficiently driven.

In other words, the blowdown energy A described with reference to FIG. 5 can be effectively used, the turbine drive efficiency can be improved particularly in the low speed operation range, and the output performance of the engine in the low speed range can be improved. can do.

In the above embodiment, the opening timing of the first exhaust valve is set earlier than the opening timing of the second exhaust valve, and the closing timing is delayed, but the present invention is not limited to this. The point is that one of the exhaust passages may be opened earlier than the other so that blowdown energy can be used. No, but the timing is almost the same,
It suffices to secure a sufficient opening period as a whole and sufficiently reduce the exhaust resistance even at high speed and high load operation.

[Brief description of drawings]

1 is an overall schematic explanatory view of an engine with a turbocharger according to an embodiment of the present invention, FIG. 2 is a sectional explanatory view of a turbocharger, FIG. 3 is a graph showing exhaust valve timing, and FIG.
FIGS. 5 (a) and 5 (b) are graphs showing exhaust valve timings and changes in exhaust pressure in each exhaust passage corresponding to the exhaust valve timings, and FIG. . 7 ... Turbine, 7P, 7S ... 1st, 2nd scroll, 9
... turbocharger, 10P ... 10S ... first and second exhaust passages.

Claims (1)

[Claims] 1. An engine including a turbocharger comprising a turbine having a plurality of scrolls partitioned by partition walls and a blower connected to a turbine output shaft, wherein two exhaust passages are provided in each cylinder of the engine. An exhaust port that is divided into exhaust passages, and these two exhaust passages are independently connected to a predetermined scroll of the turbocharger, and an exhaust port that communicates with one of the two exhaust passages communicates with the other. The engine with a turbocharger is characterized by opening both of the exhaust ports at almost the same timing while opening at an earlier timing than the above.