JPS59231135A - Variable displacement type radial flow turbine - Google Patents

Abstract

PURPOSE:To raise the efficiency of a turbine at the time when the air flow rate is small, by forming projections at the inlet of a scroll in the manner that they project toward the inside of the scroll, and providing a tongue-like member such that it can be brought into engagement with said projections. CONSTITUTION:Exhaust gas is introduced from an exhaust manifold into a scroll 13 via an inlet portion 13A of the scroll 13, and after driving a turbine wheel 12, it is discharged into an exhaust pipe. Here, the velocity of exhaust-gas flow is proportional to the inverse number of the radial position (distance). At the time of high-speed operation of the engine, a tongue-like member 25 is located at its lower-limit position to increase the sectional area of the fluid passage at the inlet portion 13A of the scroll 13. At the time of low-speed operation of the engine, on the other hand, the tongue-like member 25 is located at its upper-limit position where its outer surfaces 27A, 27B are held in tight contact with projections 21A, 21B. Resultantly, the sectional area of the fluid passage at the inlet portion 13A of the scroll 13 is decreased, so that the velocity of exhaust-gas flow is increased.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a variable displacement radial turbine used in a turbocharger, and particularly to an improvement in the shape of a scroll inlet portion in which a tongue-like member for variable displacement is disposed.

(Prior art) In general, the characteristics of a turbocharged engine are the A/R ratio of the turbocharger (the cross-sectional area A of the scroll inlet (exhaust nozzle) divided by the distance R between the center of the turbine wheel and the center of gravity of the cross-section) ), which is roughly determined by
The higher the A/R ratio, the more suitable the output characteristics are for high speeds, and the higher the torque in the high rotation range. Sokote, [a
A variable displacement radial turbine has been proposed in which the cross-sectional area A of the scroll inlet is made variable by a tongue-shaped member according to the operating conditions, and the torque is increased from a low-speed operating range to a high-speed operating range.

As a conventional variable displacement radial turbine, for example, the one shown in Fig. 1.2 is known (Japanese Unexamined Patent Application Publication No. 54
-84123).

This will be briefly explained based on FIG. 1.2. In the same figure, a scroll 2 having a generally fan-shaped cross section is formed in an annular shape around the wheel 1 and has a built-in turbine wheel 1.
Scroll inlet portion 2A of turbine housing 3 having
A tongue-shaped member 4 is disposed in the inlet portion 4 to make the cross-sectional area of the two inlet portions variable depending on the operating conditions of the engine (for example, the engine speed). This tongue-like member 4 is supported by an actuator 5 outside the housing 3 via a link 6 at the entrance portion 2A of the housing 3 so as to be swingable in the direction of arrow X in the figure. In addition, arrow W in the figure indicates the exhaust flow, and at this time, the speed of the exhaust gas is increased in proportion to the reciprocal of its radial position.
The upstream side of this inlet portion 2A is connected to the exhaust manifold of the engine via a passage having a substantially fan-shaped cross section, and the downstream side of the exhaust outlet portion 3A of the housing 3 is connected to a muffler or the like. Here, as shown in detail in FIG.
The surface facing the wheel l has a substantially rectangular shape (rectangle) that is perpendicular to the rotation axis 1A of the wheel l.

That is, since the tongue-like member 4 is disposed at the two scroll entrances, the inner surface of the nozzing 3 protrudes inward and is formed into a substantially rectangular shape. The tongue-like member 4 is swung to a position indicated by Y in the figure in a low rotation range and to a position indicated by Z in a high rotation range, for example, to vary the capacity of the turbine.

However, in such a conventional variable displacement radial turbine, since the two scroll inlets of the turbine housing 3 are formed in a substantially rectangular shape, the tongue-like member 4 is positioned at the Y position, especially when the exhaust gas flow rate is small. ), the fluid friction loss between the rear surface of the tongue member 4 and the parallel inner wall surface of the inlet portion 2A is large at the end of the scroll 2, and the flow path cross-sectional shape at the end of the scroll 2 (before and after the tongue member 4) is large. As a result, a secondary flow is generated in a direction perpendicular to the main flow in the scroll 2, and the inflow angle of the exhaust gas into the wheel 1 is disturbed, resulting in a decrease in turbine efficiency.

(Object of the Invention) Therefore, the present invention provides a scroll inlet portion that is formed to be smoothly continuous with its upstream and downstream portions, and a plate-shaped protrusion that can be engaged with a tongue member at the inlet portion. This aims to prevent sudden changes in the cross-sectional shape of the flow path at the end of the scroll, reduce friction loss at the end, and improve turbine efficiency.

(Structure of the Invention) A variable displacement radial turbine according to the present invention includes a turbine housing in which a scroll having a generally fan-shaped cross section is formed;
a rotatable turbine wheel housed in the turbine housing; a tongue-like member swingably supported at a scroll inlet of the turbine housing so as to vary a flow passage cross-sectional area of the scroll inlet; ,have.

The scroll inlet has a substantially fan-shaped cross section, and the upstream and downstream parts of the scroll inlet are smoothly continuous. Further, the scroll entrance portion is provided with a protrusion portion that protrudes inwardly, and the tongue-like member can engage with this protrusion portion.

(Example) Embodiments of the present invention will be described below based on the drawings.

3 and 4A and 4B show an embodiment of a variable displacement radial turbine according to the present invention. first,
Explain the configuration. In FIG. 3, 11 is a turbine housing, and a turbine wheel 12 is housed in a space formed in the center of the turbine housing 11.

The turbine housing 11 also includes this wheel 12.
An annular scroll 13 is formed to surround the scroll 13, and the scroll 13 has a substantially fan-shaped cross section over its entire circumference, and its radially inner end communicates with the space through a narrow through hole. On the other hand, 14 is a center housing that rotatably supports the turbine wheel 12, specifically supports a wheel shaft 16 (the turbine wheel 12 is connected to an impeller by the wheel shaft 16) via a bearing 15, and this housing An oil passage 17 for lubricating the bearing 15 or cooling the shaft 16 is formed within the oil passage 14 .

Note that 18 is a ring seal interposed between the shaft 16 and the housing 14, and 19 is an annular shroud that closes the space together with the center housing 14 from one end side (left side in FIG. 3). . Further, the opening on the other end side of the space in which the turbine wheel 12 is installed is connected to an exhaust pipe (not shown). It is formed so that its cross section is approximately fan-shaped, and the upstream side portion and downstream side portion of this inlet portion 13A are smoothly continuous without significant change in the cross-sectional shape. In the scroll entrance portion 13A, at a predetermined height position of the inclined inner wall surfaces 20A and 20B, which are formed in an upwardly expanding shape in FIG. Opposed protruding portions 21A and 21B are formed, respectively, and inner surfaces 22A and 22B of these protruding portions 21A and 21B, which are opposed to each other, are inclined so that the distance between them widens downward in the figure. Further, as shown in detail in FIGS. 4A and 4B, this scroll entrance portion 13A has a plate-like tongue member 25 with a substantially trapezoidal cross section (FIG. 3).
is supported so as to be able to freely swing around a shaft 26, and this tongue-like member 25 swings around the scroll inlet portion 13.
The cross-sectional area of the flow path A is variable. That is, the tongue-shaped member 5 is moved between the lower limit position shown by the solid line in FIG. 3 and FIG. 4A and the upper limit position shown by the broken line in FIG. 3 and FIG. At the upper limit position, the scroll inlet section 13A engages with the protrusions 21A and 21B, and its upper surface forms one smooth curved surface. The cross-sectional area of the passing portion is made smaller than that of the lower limit position. That is, at the upper limit position, both outer surfaces 27 of the tongue member 25
A and 27B are the inner surfaces 22A of the protrusion parts 21A and 21B.
, 22B, the tongue-like member 25 is in close contact with the protruding portion 2]A,
21B. The tongue-like member has a wing-like shape as a whole, and is slightly curved along its longitudinal direction as shown in FIG. Further, although not shown, the upstream side of the scroll inlet portion 13A is connected to an exhaust manifold of the engine.

Next, the effect will be explained.

Exhaust gas flows from the exhaust manifold into the scroll 13 through the scroll manifold 13A and into the turbine wheel 12.
is rotated and flows out into the exhaust pipe. In this case, the flow velocity of the exhaust gas is proportional to the reciprocal of the radial position (distance) within the scroll 13. Further, the tongue member 5 is at the lower limit position shown in FIG.
While ensuring a large flow rate by increasing the cross-sectional area of the 3A flow path,
In the low rotation range, the exhaust gas is oscillated to the upper limit position shown in FIG. 4A, reducing the cross-sectional area of the flow path, regulating the flow rate to a small level, and increasing the exhaust flow rate. At this low flow rate, the exhaust gas flowing into the scroll 13 and passing behind the tongue member δ at the terminal end of the scroll 13 passes through a substantially fan-shaped cross section with a small radius position, compared to a conventional rectangular cross section. As a result, the friction loss is significantly reduced. In addition, since the scroll 13 has a sector-shaped cross section all around, the exhaust flow within the scroll 13 does not change suddenly, and the secondary flow (even if it occurs, it is very small) flows against the main flow. There will be no adverse effects. On the other hand, even when the flow rate is large, the tongue-shaped member contacts the wall surface of the fan-shaped scroll 13 without any gaps at its lower limit position, so that the exhaust flow within the scroll 13 is not disturbed.

(Effects) As explained above, according to the present invention, in a variable displacement radial turbine, the turbine efficiency can be significantly increased at low flow rates, and when the engine is installed, supercharging can be achieved without increasing the exhaust pressure. It is possible to increase pressure and greatly improve engine torque.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing a conventional variable displacement radial turbine, Fig. 2 is a sectional view taken along the n-n0 arrow in Fig. 1, and Fig. 3 is an embodiment of a variable displacement radial turbine according to the present invention. Fig. 4 A, B
FIG. 2 is a schematic perspective view showing the operation of the tongue member of the turbine. 11--Turbine housing, 12-----Turbine wheel, 13--Scroll, 13 A-----Scroll inlet section, 21A, 21
B----one protruding member, δ----tongue-like member. Patent Applicant Nissan Motor Co., Ltd. Representative Patent Attorney Yugagun Part 1 Figure 1 194- Figure 2 Figure 3 11 Figure 4 (A) Figure 4 (B-5)

Claims (1)

[Claims] A scroll having a generally fan-shaped cross section is supported in a swingable manner at the scroll inlet of a turbine housing, and the scroll has a substantially fan-shaped cross section so as to surround a space in which a rotatable turbine wheel is housed. A variable tongue-like member is provided, the scroll inlet portion is formed into a substantially fan-shaped cross section and smoothly continuous with the upstream and downstream portions thereof, and the scroll inlet portion is provided with a protruding portion protruding inwardly. . A variable displacement radial turbine, characterized in that the tongue member is engageable with the protruding portion.