JPS6032936A - Variable-capacity type radial turbine - Google Patents

Abstract

PURPOSE:To allow the wall face in a scroll to be precisely machined, improve the surface roughness and size precision, and correctly control the clearance with a tongue-like member by forming a turbine housing in a split assembly body. CONSTITUTION:A turbine housing 28 and a casing cover 29 are separately produced by casting; then the turbine housing 28 is machined so that the inner wall face 28a of a side wall 28A and the outside face of a scroll side wall 28C are made D in height and the stepped face 29a including the inner periphery of the scroll side wall 28C has the same diameter from the turbine axis; and the casing cover 29 is machined at both faces to a thickness of F, then the face at a right angle to the stepped face 29a is machined to a thickness of C for finishing.

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 a variable displacement radial turbine in which a turbine wheel storage space and a scroll are formed by an assembly consisting of a turbine housing and a housing cover. Regarding type radial turbines.

(Prior Art) Generally, the characteristics of a turbocharged engine are roughly determined by the A/R ratio of the turbocharger, and the larger the A/R ratio, the more suited for high speed the engine is, and the higher the torque in the high rotation range. Here, the A/R ratio is the passage cross-sectional area A of the scroll inlet (exhaust nozzle) divided by the distance R from the axis of the wheel to the center of gravity of the cross-section of the inlet. Therefore, a variable displacement radial turbine has been proposed in which the cross-sectional area A can be varied using a tongue-like member (variable nozzle) according to the operating conditions of the engine, and the torque can be increased from a low-speed operating range to a high-speed operating range. ing.

As a conventional variable displacement radial turbine, the one shown in FIGS. 1 and 2, for example, is known (Japanese Unexamined Patent Publication No. 84123/1983). To roughly explain this thing with reference to Fig. 1.2, 1 is a turbine housing formed by casting or the like, and inside (approximately the center part) of this housing 1 is a space with a generally circular cross section in which a turbine wheel 2 is housed. 3 is formed, and an annular scroll 4 surrounding this space 3 is formed on the radial direction (radial direction) outer side of the space 3. The scroll 4 has a narrow opening at its radially inner end and communicates with the space 3, and an inlet portion 4A of the scroll 4 extends tangentially to the scroll 4 and is connected to an exhaust manifold. On the other hand, an outlet portion 3A of the space 3 that opens at one end in the axial direction of the turbine wheel 2 is connected to an exhaust pipe. Therefore, the exhaust gas flows into the scroll 4 through the inlet portion 4A, rotates the turbine wheel 2, and then flows out through the outlet portion 3A. At this time, an airfoil-shaped tongue member 5 is swingably supported on the turbine housing 1 of the scroll inlet portion 4A, and the flow path of the inlet portion 4A is cut off according to the swinging position of the tongue member 5. The area (corresponding to A above) is changed. Note that this tongue-like member 5 is swung by an actuator 6 via a link 7 depending on the operating conditions of the engine (for example, the engine speed). Further, the turbine wheel 2 is connected to a compressor wheel (not shown) by a wheel shaft 8, and this wheel shaft 8 is rotatably supported by a sensor hanging 9 via a hair ring 10. Note that 11 is a shroud forming a side wall of the housing 1 on the side facing the outlet portion 3A of the space 3, and this shroud 11 is sandwiched between the turbine housing 1 and the center housing 9, which are fastened with bolts 12. equipped. 13 is a ring seal interposed between the shroud 11 and the wheel shaft 8. Further, a predetermined clearance C is formed between both side surfaces 5A, 5B of the tongue-shaped member 5 and the inner wall surfaces IA, 1B of the turbine housing 1 to the scroll inlet portion 4 to prevent the tongue-shaped member 5 from sticking. has been done. This tongue-like member 5 is inserted into the scroll inlet portion 4A of the housing 1, and the link 7 is press-fitted from the outside.

However, in such a conventional variable displacement radial turbine, since the turbine housing 1 was an integrally molded cast product, the scroll 4 etc., especially the inner wall surfaces IA and IB of the inlet portion 4A, were cast surfaces themselves, It was not possible to precisely control the clearance C between the both side surfaces 5A and 5B of the tongue-shaped member 5. As a result, this clearance C has to be increased in order to avoid interference. If this happens, the amount of exhaust gas (indicated by the arrow in Figure 2) flowing into the scroll 4 through the clearance C will increase, causing the turbocharger to become smaller. There are problems in that the flow rate cannot be adjusted (the throttling effect by the tongue member 5 is reduced), and a speed difference occurs in the exhaust gas flowing into the scroll 4, which increases loss due to mixed flow and reduces turbine efficiency.

(Purpose of the Invention) Therefore, the present invention enables precision machining of the inner wall surface of the scroll by making the turbine housing a separate assembly, improves its surface roughness and dimensional accuracy, and improves the clearance between it and the tongue member. The purpose of this invention is to obtain an assembly which solves the above-mentioned problems and facilitates dimensional processing.

(Structure of the Invention) The variable displacement radial turbine according to the present invention has a turbine wheel housed therein, a scroll formed so as to surround the turbine, and an oscillating motion at the inlet of the scroll. The freely provided tongue-shaped member allows the cross-sectional area of the flow path at the inlet portion to be varied. The turbine housing forms a radial outer peripheral wall of the scroll and a supporting side wall of the turbine wheel. The side wall on the side opposite to the side wall on the support side is formed by a housing cover, and the housing cover is formed in a substantially disc shape concentric with the turbine wheel and is fixed to the turbine housing. .

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

3 and 4 show a first embodiment of the invention. In FIGS. 3 and 4, reference numeral 21 denotes a center hanging, and this center hanging 21 rotatably supports the wheel shaft unit via a bearing 22. 24 is an oil passage formed inside the center hanging 21. The wheel shaft unit connects the turbine wheel 5 and a compressor wheel (not shown).
Both wheels δ are interposed in the intake and exhaust passages, respectively. The turbine wheel 5 is mounted within a turbine casing, and the casing has inside thereof a space 26 in which the wheel 5 is housed and a scroll 27 surrounding the space. The casing is formed by an assembly of a turbine housing part and a housing cover 29, and the turbine housing 28 is assembled with the shroud (heat insulator) 30 and the center hanging 2.
1 by a retainer plate 40. This turbine housing 28 has one end side of the scroll 27 (
The side wall 28A forming the side that pivotally supports the wheel shaft blade of the left turbine wheel 25 in FIG. 3A, and the side wall 2
8A, and an outer peripheral wall 28B that forms a side wall on the outer peripheral side of the rising scroll 27 (parallel to the axis of the wheel shaft 23). Note that the outer circumferential wall 28B on the side of the scroll insertion slot 27A is further bent slightly radially inward to form a scroll side wall 28C. On the other hand, the housing cover 29 is fixed to the housing U by bolts 31 so as to face the side wall 28A, and forms a side wall on the other end side of the scroll 27 (the right side in FIG. 3A), and its center is It has a disk-shaped portion 29A located on the axis of the wheel shaft device, and a cylindrical portion 29B protruding toward the shroud 30 from near the center of the disk-shaped portion 29A. A stepped surface 29a is formed at the outer edge of the disc-shaped portion 29A, and this stepped surface 29a is connected to the outer peripheral wall 28B.
and the side wall 28C, and are fixed to each other via a gasket 41. Therefore, the scroll 27 is formed by the side wall 28A of the turbine housing n, the side wall 28G of the outer circumferential wall 2881, the inner wall surface of the disc-shaped portion 29A of the housing cover 29, and the outer circumferential surface of the cylindrical portion 29B of the cover 29, while the shroud 30 and the throat-shaped inner peripheral surface of the cylindrical portion 29B form a space in which the turbine wheel 25 is accommodated. This space and the scroll 27 communicate with each other through a narrow opening formed by one end of the cylindrical portion 29B and the shroud 30. The other end opening of the cylindrical portion 29B is connected to an exhaust pipe, and the inlet portion (nozzle portion) 27A of the scroll 27 is connected to an exhaust manifold. A tongue-shaped member 32 (made of stainless steel, for example) curved into a wing shape is swingably provided in the scroll inlet portion 27A.
2, the cross-sectional area of the flow path of the inlet portion 27A is variable. That is, the tongue-like member 32 has a shaft 33 fixed to its base end (the shaft 33 is integrally formed with the tongue-like member 32), and this shaft 33 is rotatably supported by the bush 34. There is. The bushing 34 is the casing cover 290
The bushing 34 is press-fitted into the insertion hole of the disc-shaped part 29A, and its tip protrudes slightly into the scroll 27.
The protrusion of the shaft 33 supported by! (A substantially rectangular threaded portion is formed.) An arm 36, which is a rectangular plate, is fixed by a nut 35. FIG. 3B shows the arm 36, which has a rectangular hole 36A into which the threaded portion of the shaft 33 is inserted, and a shaft portion 36B connected to an actuator (not shown). Therefore, the tongue-like member 32 can be swung by the actuator via the arm 36 and the shaft 33. In addition, both sides of the tongue-shaped member 32 (
(plane perpendicular to the axis of the wheel shaft device) 32a,
32b is precisely finished by machining together with the inner wall surface 28a of the side wall 28A of the turbine housing section that faces this side surface 32a.

Furthermore, in the present invention, in order to accurately manage the clearance on both side surfaces of the tongue-shaped member 32 and facilitate dimension processing thereof,
The height of the outer peripheral wall 28B and the scroll side wall 28C of the turbine housing 28 is D, the width of the tongue member 32 is B, the length of the bushing 34 excluding the thickness of the flange part is E, and the thickness of the disc-shaped bush 4. The thickness is set to be F, and the thickness from a plane perpendicular to the stepped surface 29a is C. Thus, after manufacturing the turbine housing 28 and the casing cover 29 separately by casting or the like, the turbine housing 28 is made such that the inner wall surface 28a of the side wall 28A and the outer surface of the scroll side wall 28G have a height of D. The step surface 29a including the inner circumferential surface of the scroll side wall 28G is machined so that it has the same diameter from the turbine axis, and the casing cover 29 is machined on both sides so that its thickness becomes F, and then the step surface 29a is machined so that it has the same diameter from the turbine axis. By processing a surface perpendicular to the surface 29a, it is finished to a thickness C. In this embodiment, an example is shown in which a stainless steel sealing material 41 is interposed, but it goes without saying that in such a case, the thickness C should be adjusted in consideration of the thickness of the sealing material 41. do not have.

Thus, the housing inner wall surface 28a and the tongue-like member side surface 32a
The clearance Δa between the casing cover side 929b and the tongue member side surface 32b is determined by Δβ,=D+C−B−E, and the clearance Δ12 between the casing cover side 929b and the tongue member side surface 32b is determined by Δx2=E−F. Therefore, first, the overall Casing cover 29 processed to have a thickness of F and a thickness of C from the stepped portion
Then, a bush 34 having a shaft length E is inserted, and then the shaft part 33 of the tongue-shaped member 32 processed into ItlB is fitted into the bush 34, and the arm 36 is fixed. Next, the assembled casing cover 29 is fitted onto the turbine housing 28 whose inner wall surface 28a has been machined so as to match the circular stepped portion 29a, and fastened with bolts 31.

As a result, it is possible to suppress the exhaust gas from flowing into the scroll 27 through this clearance, and exhaust gases having different flow velocities are not mixed, so that loss due to mixed flow can be prevented. Therefore, the turbine efficiency improves when the flow rate is small, the intercept engine speed (engine speed at which a constant boost pressure is obtained) decreases, and the torque also increases. In other words, if the turbine efficiency is poor, even if the intercept engine speed decreases, the torque will not increase due to the increase in exhaust pressure. Therefore, it is necessary to advance the intercept point (reduce the intercept engine speed) and increase the torque. This reduces the turbine capacity and increases the turbine efficiency. Further, in the present invention, the housing cover 29 is formed of a disk-shaped member concentric with the turbine wheel 25, and the housing cover 29 is configured to close the turbine housing 28 from its side surface (the side surface facing the disk portion 28A). Since the parts are joined together, it is easy to assemble.
Compared to the case where the cover 29 is joined to the annular portion 28B, processing of the joint part is not required (otherwise, loss due to FM friction of exhaust gas within the scroll 27 will increase).
, and the outer peripheral surface of the blade of the turbine wheel device and the cylindrical portion 29
The clearance between B and the inner wall surface can also be precisely set.

FIG. 5 shows a second embodiment of the invention. In this embodiment, the cross-sectional shape of the scroll 37 is approximately fan-shaped except for its inlet portion 37A. That is, the respective scroll forming surfaces 38a and 39a of the disk portion 38A of the turbine housing 3 and the cylindrical portion 39B of the housing cover 39
is formed by an inclined surface. As a result, the flow rate of the exhaust gas inside the scroll 37 increases in proportion to the reciprocal of the radial position, so compared to a scroll with a rectangular cross section (for example, 27), the wetted area of the high flow rate portion becomes smaller and friction Losses are reduced and turbine efficiency is increased. The other configurations and operations are the same as those of the previous embodiment, and will therefore be omitted.

FIG. 6 shows a third embodiment of the present invention. In this embodiment, a capacity changing member (7) approximately disk-shaped and having a predetermined thickness is attached to the side wall surface of the scroll 47.
) are fixed with bolts 51.

As a result, the flow passage cross-sectional area of the scroll 47 can be changed, and the minimum capacity of the turbine can be changed arbitrarily.

In particular, in the case of 31 products of various types and small sizes, the housing 48 and the cover 49 are installed separately (for example, for each different exhaust capacity).
It is extremely effective in terms of cost since the manufacturing process can be omitted.

The other configurations and operations are the same as those of the first embodiment, and will therefore be omitted.

FIGS. 7 and 8 show a fourth embodiment of the present invention. This embodiment uses a perfectly circular capacity changing member 60. In this case, the housing cover 59 is fixed to the housing 58 with the peripheral edge of the disc portion 59A abutting the end surface of the annular portion 58B of the turbine housing 58. That is, the annular portion 58B on the side of the scroll insertion portion 57A is not bent. This shows the cutting allowance when cutting the annular part 58B into a circular shape by increasing the wall thickness on the cover 59 side of the annular part 58B (× in FIG. 8). This shows the receiving surface of the volume N changing member 60. ). As a result, the capacity changing member 60
is extremely easy to manufacture. The other configurations and operations are the same as those of the third embodiment, and will therefore be omitted.

(Effects) As explained above, according to the present invention, the clearance between the inner wall surface of the scroll and the side surface of the tongue member can be precisely controlled, the flow rate of the turbine can be reduced, and the turbine efficiency can also be increased. I can do it. As a result, we were able to significantly improve engine torque at low engine speeds.

In addition to the above-mentioned effects, each of the embodiments described above has the effect of further reducing the flow rate and facilitating manufacturing.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of a conventional variable displacement radial turbine, FIG. 2 is a sectional view taken along arrow nu in FIG. 1, and FIG. 3A is a first embodiment of a variable displacement radial turbine according to the present invention. A schematic sectional view showing an example, FIG. 3B is a front view of the arm, FIG. 4 is a sectional view of the turbine housing, FIGS.
FIG. 7 is a sectional view similar to FIG. 3A showing the second, third and fourth embodiments of the present invention, respectively, and FIG. 8 is a diagram showing the turbine housing of the fourth embodiment. 25-----Turbine wheel, 26----Turbine wheel storage space, 27.3
7.47.57---Scroll, 27A, 37A
, 47A, 57A ----- Scroll inlet section, 28.38.48.58 -- Turbine housing, 28A, 38A, 48A, 58A ----- Disc part of turbine housing (turbine wheel support 28B, 38B, 48B, 58B --- Annular part of the turbine housing (side wall on the scroll radial outer end side), 29.39.49.59 --- Bousing cover, 29A, 39A, 49A, 59A --- Disc part of housing cover (side wall on the side facing the disc part of the turbine housing), 32 --- Single tongue-shaped member. Figure 5 Car, Figure 6

Claims (1)

[Claims] A turbine wheel is housed inside, an annular scroll is formed to surround the turbine wheel, and a tongue-like member is provided at the inlet of the scroll to swing to vary the cross-sectional area of the flow path at the inlet. In the variable displacement radial turbine, the side wall on the radially outer end side of the scroll and the side wall on the support side of the turbine wheel are formed by the turbine housing, and the side wall on the side opposite to the side wall on the support side is formed by the turbine housing. A variable displacement radial turbine characterized in that it is formed by a generally disc-shaped housing cover that is fixed to a housing and concentric with a turbine wheel.