JPH0348335B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a variable displacement radial turbine, and particularly to a variable nozzle structure of a variable displacement turbine suitable as an exhaust turbine in a turbocharger.

<Prior art> In a radial turbine used as an exhaust turbine of a turbocharger, it is sometimes desired to ensure a supercharging effect even in a region where the engine rotational speed is low. By narrowing the upstream passage of
It is preferable to increase the inflow velocity of the fluid. However, when the passage is narrowed in this way, the inlet pressure of the turbine, that is, the back pressure against the exhaust gas of the engine increases, which causes a disadvantage that the efficiency of the engine is reduced.

Therefore, as described in Japanese Patent Publication No. 38-7653, a plurality of movable vanes are arranged in an annular manner in the nozzle portion facing the outer circumference of the turbine wheel, and by tilting these movable vanes, a structure is created between these vanes. If the effective nozzle opening area is changed, the supercharging effect can be ensured even in the low speed range of the engine, and the back pressure against the engine exhaust can be reduced in the medium to high speed range of the engine. can be kept. However, according to the above configuration,
Since these vanes are disposed in regions where the fluid velocity is relatively high, fluid resistance losses tend to be relatively large, resulting in a problem in that the efficiency of the turbine is reduced. In addition, since the nozzle is formed between adjacent movable vanes, the nozzle opening area can change significantly due to a slight deviation in the tilting angle of the vane, especially in areas where the nozzle opening area is small. There is a problem with the control accuracy. Particularly when such a turbine is utilized as an exhaust turbine in a turbocharger, it is difficult to reliably adjust these movable vanes due to their exposure to the high temperature exhaust gas stream.

As disclosed in Japanese Unexamined Patent Publication No. 53-136113, there is also a structure in which a flap forming a part of the wall of the scroll passage of the turbine casing can be tilted to vary the cross-sectional area of the scroll passage. It has become publicly known. Although this type of variable nozzle structure has a simple structure and can adjust the velocity of fluid flowing into the turbine wheel with relatively little resistance loss, the variable nozzle structure does not necessarily have a sufficiently wide variable range. In addition, especially when the flap opening degree is large, the flow of fluid toward the turbine wheel is disturbed, and the flow velocity distribution becomes uneven, which causes a problem in that the efficiency of the turbine decreases.

<Problems to be Solved by the Invention> In the variable capacity turbine as described above, the vane forming the variable nozzle is located between the inner surface of the turbine casing and the inner surface of the base plate that closes the bearing side of the turbine wheel. Since the thermal expansion coefficient of the turbine casing side, which has a particularly complex shape, is uneven, it is necessary to precisely control the side clearance of the movable vane in the variable nozzle part, especially in high-temperature environments. can be a problem.

In addition, in order to solve the problems of the conventional type variable capacity turbine mentioned above, it is better to arrange the variable nozzle in an annular shape on the outside of the nozzle part facing the outer periphery of the turbine wheel. This is noticeable and it is difficult to prevent leakage from the movable vane portion.

In view of the problems of the prior art and the knowledge of the inventor, the main object of the present invention is to provide a variable capacity system that can reliably control the rate of fluid inflow into a turbine wheel even in a high temperature environment. The object of the present invention is to provide a variable nozzle structure for a turbine.

<Means for Solving the Problems> According to the present invention, such an object includes a turbine wheel, a turbine casing formed around the outer periphery of the turbine wheel, and an axial passage facing the front surface of the turbine wheel. and,
A variable nozzle structure for a turbine in which a variable nozzle consisting of a fixed vane and a movable vane is annularly disposed on a certain circumference outside the outer circumference of the turbine wheel, the turbine wheel bearing of the turbine casing A base plate that closes the side and a top plate that defines a surface that faces the inner surface of the base plate are interposed between the two plates through fixed vanes provided at equal intervals along the circumferential direction on the outer periphery of the turbine wheel. A variable nozzle structure for a turbine, the variable nozzle structure being connected by a fastener, and configured so that the space between the fixed vanes can be opened and closed by rotating the movable vane along the inner surface between the two plates. This is achieved by providing In particular, the fixed vane is integrally formed on the top plate side, the axial end of the fixed vane on the base plate side is coupled to the base plate with a fastener, and the movable vane is pivotally supported on the base plate side. In order to tiltably receive the movable vane, the space formed by the base plate and the top plate gradually expands from the outer circumference to the inner circumference, and the top plate is provided with the axial passage. It is preferable to provide a cylindrical portion connected to the inner end of the tube in a floating manner and in a generally airtight manner.

<Function> In this way, the inner surface of the base plate and
A variable nozzle is formed by the cooperation of the surface facing the top plate which is separate from the turbine casing, the fixed vane, and the movable vane.
Since the base plate and the top plate are rigidly connected by the fixed vane part, and because the top plate can take a relatively homogeneous disc shape, the base plate and top plate are designed in consideration of thermal deformation. It becomes possible to suitably control the accuracy between each side end of the movable vane.

In addition, by gradually expanding the gap that accommodates the movable vane from the outer periphery to the inner periphery,
When the variable nozzle opening is small, the gap between the movable vanes is minimized to increase turbine efficiency, and when the variable nozzle is fully open, the gap between the movable vanes is maximized to avoid the possibility of movable vane sticking.

<Examples> Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 and 2 show an engine turbocharger to which a variable displacement turbine according to the present invention is applied. This turbocharger has a casing consisting of a compressor casing 1 that forms a scroll of the compressor part, a back plate 2 that closes the back side of the compressor casing, and a structure that pivotally supports the main shaft of the turbocharger and lubricates the bearing. Built-in lubrication part casing 3
and a turbine casing 4 forming a scroll of the turbine section.

A scroll passage 5 and an axial passage 6 are formed inside the compressor casing 1, and a compressor is provided in the center of the scroll passage 5 and adjacent to the inner end side of the axial passage 6. A wheel 7 is provided. The compressor wheel 7 is attached to one end of a main shaft 8 of a turbocharger rotatably supported in the center of the lubricating part casing 3 in a manner described later. On the compressor side, the scroll passage 5 constitutes an intake outlet passage, and the axial passage 6 constitutes an intake inlet.

The compressor casing 1 and the back plate 2 are integrated by screwing bolts 10 onto the outer periphery of the compressor casing 1 via a ring member 9.
is connected.

The main shaft 8 is pivotally supported in the bearing holes 11 and 12 formed inside the lubricating part casing 3 by the radial bearing metal 13 as described above. Further, a thrust bearing metal 14 is interposed between the back plate 2 and the end face of the lubricating part casing 3, and a collar 15, a thrust bearing metal 14, a bushing 16, and a compressor are attached to the stepped part of the main shaft 8. By fitting the wheels 7 in this order and screwing the nut 18 onto the threaded portion 17 cut into the compressor side end of the main shaft 8, the thrust direction of the main shaft 8 is supported and the compressor wheel 7 is mounted. It will be done. Note that the collar 15 functions as a spacer for setting the clamping pressure of the thrust bearing metal 14.

When tightening the nut 18, by grasping the hexagonal section 19 provided at the free end of the threaded portion 17 with another tool, it is possible to prevent the main shaft 8 from rotating together, and also to prevent the main shaft 8 from rotating at the same time. The inconvenience of applying excessive torsional force is avoided.

The turbine casing 4 defines therein a scroll passage 21, an inlet opening 21a thereof opening in the tangential direction, an outlet passage 22 extending in the axial direction, and an opening 22a thereof.

A back plate 23 serving as a base plate is interposed between the turbine casing 4 and the lubricating part casing 3. The connection between the turbine casing 4 and the lubricating part casing 3 is achieved by tightening a nut 26 through a ring member 25 to a stud bolt 24 screwed onto the side of the turbine casing 4. This is done by sandwiching the outer peripheral part of the lubricating part casing 3 and the outward flange 23a of the back plate 23 between the ring member 25 and the ring member 25.

A fixed vane member 27 is disposed at the center of the scroll passage 21 to partition the inside of the scroll passage into an outer circumferential passage 21b and an inflow passage 21c. This fixed vane member 27 includes a cylindrical portion 28a formed at the center, a disk portion 28b forming a top plate formed radially outward from an axially intermediate portion of the cylindrical portion 28a, and a disk portion 28b forming a top plate. It consists of a fixed vane 29 that protrudes along the axial direction from the outer periphery toward the lubricating part casing 3, and has a cylindrical part 28a.
A turbine wheel 30 formed on the other end side of the main shaft 8 is received inside. And the cylindrical part 28a
However, the double metal seal ring 31
The seal ring 31 is connected to the inner end of the outlet passage 22 via the seal contact in a substantially floating and generally airtight manner, and the axial end of the fixed vane 29 is connected to the inner end of the outlet passage 22 by a bolt 32. It is coupled to the back plate 23.

As shown in FIG. 2, four fixed vanes 29 are formed on the outer periphery of the fixed vane member 27 so as to concentrically surround the turbine wheel 30. These fixed vanes 29 each have a partial arc shape, and are provided at equal widths and equal intervals along the circumferential direction. The gap between these fixed vanes 29 is opened and closed by a movable vane 34 fixed to the free end of a pin 33 rotatably attached to the back plate 23. These movable vanes 3
4 has an arc shape with the same curvature as the fixed vane 29, and is located on approximately the same circumference. Further, these movable vanes 34 are pivoted at positions close to the circumferential end edges of the corresponding fixed vanes 29, and are configured to be able to tilt only toward the inside of the circumference. When the vanes are tilted most outwardly, both vanes 29 and 34 form a continuous airfoil shape. Therefore, these fixed vanes 29 and the corresponding movable vanes 34
The four vanes form leading and trailing edge portions, respectively, for fluid flowing through the vanes. The pins 33 that support these movable vanes 34 are each connected to an actuator having an appropriate structure (not shown) via appropriate link mechanisms 35, and these movable vanes 34 are controlled by a separate control signal.
The inclination angle of is adjusted.

Further, a shield plate 36 extending to the back of the turbine wheel 30 is interposed between the back plate 23 on the turbine side and the lubricating part casing 3, and the heat of the exhaust gas flowing through the exhaust turbine part is transferred to the lubricating part casing 3. This prevents the air from being transmitted to the inside of the casing 3. In addition, in order to prevent the exhaust gas from the turbine side from leaking toward the inside of the lubricating part casing 3, the center hole 37 of the lubricating part casing 3 of the main shaft 8 is provided.
An annular groove 38 functioning as a labyrinth groove is recessed in a portion penetrating the groove.

Next, the lubrication system for this turbocharger will be explained.

A lubricating oil introduction hole 40 is bored in the upper end of the lubricating part casing 3 in FIG. The lubricating oil is supplied to the radial bearing metal 13 and the thrust bearing metal 14 through a drilled lubricating oil passage 41. The lubricating oil discharged from each lubricating part is transferred to the lubricating part casing 3.
The lubricating oil is discharged from the lubricating oil outlet 42 defined within the
The oil is collected in an oil sump (not shown).

In particular, in order to prevent the lubricating oil supplied to the thrust bearing metal 14 from adhering to the outer circumferential surface of the bushing 16 and flowing into the compressor side, the outer circumferential surface of the bushing 16 is inserted into the center of the back plate 2 through the seal ring 43. It passes through the hole 44, and a guide plate 45 is interposed between the back plate 2 and the thrust bearing metal 14, with a bushing 16 inserted through the hole provided at the center thereof. Further, the lower end portion of this guide plate 45 is formed into a curved shape.

Therefore, the lubricating oil flowing out from the thrust bearing metal 14 is thrown away from the outer peripheral surface of the bushing 16 by centrifugal force, is caught by the guide plate 45, and is returned to the oil sump.

The turbine section of such a turbocharger reaches a considerably high temperature during operation, and problems arise due to uneven thermal expansion of each section, especially the gaps on both sides of the movable vane 34 and the possibility of sticking. According to the example, the back plate 23 and the disk portion 28b, each side end of which is opposite to each other, of the movable vane 34 are rigidly connected by connecting the inner end of the fixed vane 29 to the back plate 23 with the bolt 32. Moreover, since the fixed vane member 27 is substantially floatingly connected to the turbine housing 4 forming the scroll passage 21 via the seal ring 31, the thermal influence of the turbine housing 4 is somewhat alleviated. Therefore, the accuracy of the side clearance of the movable vane 34 can be appropriately controlled.

Further, as clearly shown in FIG. 3, the width of the gap defined by the back plate 23 and the disk portion 28b for tiltably receiving the movable vane 34 is a at the outer peripheral portion. On the other hand, since it gradually expands so that b (a<b) at the inner circumference,
It is possible to cope with the tendency of the inner peripheral side to deform inward due to thermal deformation, and there is no fear that the movable vane 34 will stick. That is, when the variable nozzle opening degree is small, the gaps between the end faces of the movable vane and the inner surfaces of the back plate 23 and the disk portion 28b are minimized to increase the turbine efficiency, and the accuracy of the clearance is relatively lowered. When the variable nozzle is fully opened, which has little effect on performance, the gaps between both end surfaces of the movable vane and the back surface 23 and the inner surface of the disk portion 28b are maximized, thereby avoiding the movable vane from becoming stuck.

Next, the operation of this embodiment will be explained.

When the engine speed is low and the exhaust gas flow rate is relatively small, the movable vane 34 is tilted outward as shown by the solid line in FIG. The edge and
The gap between the nozzle formed at the lap portion with the rear edge of the movable vane 34 is set to the minimum gmin. Therefore, the exhaust gas is throttled and accelerated to the maximum extent by this nozzle, becomes a swirling flow in the inflow path 21c between the fixed vane member 27 and the turbine wheel 31, and then reaches the turbine wheel 30, so that the exhaust gas is The turbine wheel 31 is accelerated
As a result, the supercharging effect can be ensured even in the low speed range of the engine.

When the rotational speed of the engine increases and the supercharging effect becomes sufficient, the movable vane 34 is tilted inward as shown by the imaginary line, and a space is formed between the fixed vane 29 and the movable vane 34. Increase the size of the nozzle. As a result, the exhaust flow is not accelerated and reaches the turbine wheel 30 with relatively little resistance in the flow path, making it possible to reduce the exhaust back pressure to the engine.

<Effects of the Invention> As described above, according to the present invention, the resistance loss of the fluid flowing into the turbine can be suppressed to a minimum, and the variable area of the variable nozzle can be made extremely large. Since the dimensional accuracy between the inner surface and the disk portion can be easily controlled, the effect is extremely large in improving manufacturability and reliability.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a turbocharger to which a variable displacement turbine according to the present invention is applied. FIG. 2 is a view taken from the - line in FIG. 1 when looking at the turbine casing side. Figure 3 is - of Figure 2.
Figure 3 is a cross-sectional view taken along a line, exaggerating the taper imparted to the cavity receiving the movable vane; 1... Compresssa casing, 2... Back plate,
3... Lubricating part casing, 4... Turbine casing, 5... Scroll passage, 6... Axial passage, 7... Compressor wheel, 8... Main shaft,
9...Ring member, 10...Bolt, 11, 12
... Bearing hole, 13 ... Radial bearing metal, 14
...Thrust bearing metal, 15...Color, 16
. . . Bushing, 17 . . . Threaded portion, 18 .
1c...Inflow passage, 22...Outlet passage, 22a...
Outlet opening, 23... back plate, 23a... flange,
24... Stud bolt, 25... Ring member,
26...Nut, 27...Fixed vane member, 28
a... Cylindrical part, 28b... Disc part, 29... Fixed vane, 30... Turbine wheel, 31... Seal ring, 32... Bolt, 33... Pin, 3
4...Movable vane, 35...Link mechanism, 36...
...shield plate, 37 ... center hole, 38 ... annular groove, 40 ... lubricant oil introduction hole, 41 ... lubricant oil passage, 42 ... lubricant oil discharge hole, 43 ... seal ring, 44 ... center hole , 45...Guide plate.

Claims (1)

[Scope of Claims] 1. A turbine wheel comprising: a turbine wheel; a turbine casing formed around the outer periphery of the turbine wheel; and an axial passage facing the front surface of the turbine wheel; A variable nozzle structure for a turbine in which a variable nozzle consisting of a fixed vane and a movable vane is arranged in an annular manner on a circumference of the turbine, the variable nozzle structure comprising a base plate that closes a bearing side of a turbine wheel of the turbine casing, and an inner surface of the base plate. and a top plate defining a surface facing the turbine wheel, and are coupled by a fastener through fixed vanes provided at equal intervals along the circumferential direction on the outer periphery of the turbine wheel between the two plates, A variable nozzle structure for a turbine, characterized in that the space between the fixed vanes can be opened and closed by rotating the movable vane along an inner surface. 2. The fixed vane is integrally formed on the top plate side, and the axial end of the fixed vane on the base plate side is coupled to the base plate by a fastener, and the movable vane is pivotally supported on the base plate side. A variable nozzle structure for a turbine according to claim 1, characterized in that: 3. Claim 1, characterized in that the gap defined by the base plate and the top plate for tiltably receiving the movable vane gradually widens from the outer circumference to the inner circumference. Variable nozzle structure of the turbine described in. 4. The turbine according to claim 1 or 2, wherein the top plate has a cylindrical portion connected to the inner end of the axial passage in a floating manner and in a generally airtight manner. Variable nozzle structure.