JPH0355761Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to an exhaust turbine supercharger equipped with a ceramic turbine wheel, and particularly relates to a mounting shaft integrally projecting from the turbine wheel and a metal shaft into which the mounting shaft is fitted. This relates to technology that improves durability regardless of thermal expansion differences and eccentric center of gravity of ceramic turbine wheels.

Prior Art A type of exhaust turbine supercharger that compresses the intake air of an engine has a ceramic turbine wheel that is rotated by receiving the engine's exhaust flow, and a ceramic turbine wheel that is rotatable around an axis and has one end. There is a type of blower equipped with a metal shaft fixed to the metal shaft and a blower wheel provided at the other end of the metal shaft. In such an exhaust turbine type supercharger, a mounting shaft is integrally provided in the center of the ceramic turbine wheel, and the mounting shaft is fitted into a mounting hole formed at the shaft end of the metal shaft. A wheel is fixed to a metal shaft. Also, Mikiakiaki
As described in Japanese Utility Model Application Publication No. 57-97103 and Japanese Utility Model Application No. 58-67902, the end face of a metal shaft into which a mounting shaft protruding integrally from a turbine wheel made of ceramic or heat-resistant material is fitted, and its turbine. Some have close contact with the wheels.

However, it is inevitable that a ceramic turbine wheel will have an eccentric center of gravity (residual unbalance) due to its unbalance. A bending moment acts on the shaft. As a result, a large concentrated stress is generated at the part where the mounting shaft fits into the mounting hole.
Ceramic turbine wheels with relatively low strength may not be able to withstand long periods of time, and exhaust turbine superchargers may not always have sufficient durability.

That is, for example, as shown in the conventional example shown in FIG. 1, a metal shaft 2 supported rotatably about its axis by a flat bearing 1 has a mounting hole 3 opened at its shaft end. On the other hand, a mounting shaft 5 coaxial with the rotational axis of the ceramic turbine wheel 4 is integrally protruded and is press-fitted until the tip of the mounting shaft 5 comes into contact with the bottom surface of the mounting hole 3. The distal end fitting part 6 of the mounting shaft 5 is fitted with the small diameter part of the mounting hole 3, and the proximal end fitting part 7 of the mounting shaft 5 is fitted with the large diameter part of the mounting hole 3. The turbine wheel 4 is fixed to the metal shaft 2 by tightly fitting at least one of the joint portion 6 and the base end fitting portion 7 . However, during high-speed rotation, a bending moment is generated in the direction of bending the mounting shaft 5 due to the eccentric center of gravity of the turbine wheel 4, and when the proximal end fitting portion 7 is an interference fit, the proximal end fitting portion 7 Part A that comes into contact with the mounting hole opening edge of
However, if the proximal end fitting part 7 is a loose fit, concentrated stress will occur in the stepped part B formed at the boundary between the distal end fitting part 6 and other parts, and the mounting shaft 5 will be There were cases in which the relatively low strength ceramic mounting shaft 5 could not withstand the concentrated stress. Note that 8 indicates the inner wall surface of the housing.

In addition, if the end face of a metal shaft into which a mounting shaft protruding integrally from a ceramic turbine wheel is fitted is in close contact with the turbine wheel, thermal expansion between the metal shaft and the mounting shaft may occur. Due to the difference, stress was applied to the turbine wheel, which could impair its durability.

Purpose of the invention The present invention was made against the background of the above circumstances, and its purpose is to provide an exhaust turbine type supercharger equipped with a ceramic turbine, which has sufficient durability. Our goal is to provide the following.

Structure of the Invention In order to achieve the above object, the gist of the present invention is to provide a mounting shaft integrally protruding from the center of the ceramic turbine wheel, which is concentric with the rotation axis of the ceramic turbine wheel; While forming a predetermined gap with the shaft end of the metal shaft, the turbine wheel is fitted into a mounting hole formed concentrically with the rotation axis of the shaft end of the metal shaft, and the outer periphery of the metal shaft side end of the turbine wheel. The metal shaft is provided with a press-contact elastic member that is press-contacted with the metal shaft under preload.

Function A gap is provided between the end face of the metal shaft into which the mounting shaft protrudes integrally from the ceramic turbine wheel is fitted, and the turbine wheel, so that the metal shaft does not thermally expand due to high-temperature exhaust gas, etc. However, the stress caused by the difference in thermal expansion will not be applied to the metal shaft from the end face of the metal shaft as it is absorbed by the gap. In addition, in the present invention, even if a bending moment occurs in the direction of bending the mounting shaft due to the eccentric center of gravity of the turbine wheel during high-speed rotation, the bending moment is absorbed by the pressure-contact elastic member provided on the metal shaft. Therefore, the bending moment in the direction of bending the mounting shaft is reduced.

Effects of the invention As a result, stress applied from the metal shaft to the turbine wheel due to the difference in thermal expansion between the metal shaft and the ceramic mounting shaft is eliminated, and the bending moment in the direction of bending the mounting shaft is reduced. . Therefore, since concentrated stress on the mounting shaft is reduced, even a ceramic turbine wheel with relatively low strength can withstand a sufficiently long period of time, and an exhaust turbine type supercharger equipped with a ceramic turbine wheel can The durability of the material is greatly improved.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail based on aspects showing it.

FIG. 2 is a connection diagram of an exhaust turbine supercharger 10 to which the present invention is applied, and the exhaust turbine supercharger 10 is driven to rotate according to exhaust oil discharged from the engine 12 via an exhaust pipe 14. and compresses the air supplied to the engine 12 via the intake pipe 16. Note that 18 bypasses the exhaust flow in the high speed range of the engine 12 to prevent the supercharger 10 from overrunning, while suppressing the bypass in the low speed range of the engine 12 to increase the speed of the supercharger 10 to high speeds. Wastegate valve for maintenance.

The turbocharger 10 has a metal shaft 20 rotatably provided around its axis by a plain bearing 1 (not shown).
A ceramic turbine wheel 22 and a blower wheel 24 for compressing intake air are respectively fixed to both ends of the metal shaft 20, which are rotated by receiving the exhaust flow from the engine 12. That is, as the turbine wheel 22 receives the exhaust flow from the engine 12 and is driven to rotate, the blower wheel 24 is also driven to rotate, and as the blower wheel 24 rotates, the intake air supplied into the intake pipe 16 is compressed. It is.

The turbine wheel 22 is made of ceramic, which has excellent heat resistance because it receives high-temperature exhaust flow.
Ceramic has relatively low mechanical strength and has a different coefficient of thermal expansion from the metal shaft 20, so the turbine wheel 2 is installed according to the following mounting structure.
2 is fixed to a metal shaft 20.

That is, as shown in FIG. 3, a stepped mounting hole 26 is formed at the shaft end of the metal shaft 20 and is concentric with the rotation axis thereof, and the main body 23 of the turbine wheel 22 is inserted into the mounting hole 26. A mounting shaft 2 integrally formed in the center concentrically with the rotation axis
8 is attached by press fitting. Mounting shaft 2
8 has a fitting part 30 formed at its tip that tightly fits with the small diameter part of the mounting hole 26, and is fitted until the fitting part 30 contacts the bottom surface of the mounting hole 26. be. The degree of tight fit between the fitting portion 30 and the small diameter portion of the mounting hole 26 is determined by the degree of tight fit between the ceramic mounting shaft 2
The value is set such that a sufficient pullout load can be obtained even if there is a difference in thermal expansion between the metal shaft 20 and the metal shaft 20. A predetermined gap is formed in the mounting shaft 28 other than the fitting portion 30 with respect to the inner wall surface of the mounting hole 26, and when the turbine wheel 22 is fixed to the metal shaft 20, the turbine A predetermined gap C is formed between the main body 23 of the wheel 22 and the shaft end of the metal shaft 20. And metal shaft 2
A spring member 32 is attached to the spring member 32 as a pressing member that presses against the outer peripheral portion of the main body 23 on the metal shaft 20 side. The spring member 32 is a spring portion 3 in the shape of a disc spring.
4 and a cylindrical portion 36 annularly protruding from the periphery of the central hole, and the cylindrical portion 36 is fixed by being press-fitted into the large diameter portion of the mounting hole 26. Since the turbine wheel 22 is attached to the metal shaft 20 after the spring member 32 is attached to the metal shaft 20, the spring portion 34 of the spring member 32 is compressively elastically deformed in the axial direction, and the spring portion 3
The peripheral edge portion of the main body 23 is pressed against the outer peripheral portion of the main body 23 with a predetermined applied load.

According to the exhaust turbine supercharger 10 configured as described above, when the turbine wheel 22 is rotationally driven in response to a high-temperature exhaust flow, first the turbine wheel 22 is rotated due to the difference in thermal expansion between the ceramic and the metal.
Although the gap C between the main body 23 and the metal shaft 20 is narrowed, this change in the gap C is absorbed by further elastic deformation of the spring portion 34. At this time, the spring part 3
The contact position of No. 4 with respect to the turbine wheel 22 moves toward the outer circumferential side. Therefore, the difference in thermal expansion between the metal shaft 20 and the ceramic mounting shaft 28 prevents the metal shaft 20 from coming into contact with the turbine wheel 22 and applying stress to it, thereby preventing loss of durability. Further, as the metal shaft 20 and the turbine wheel 22 fixed thereto rotate at high speed, the ceramic turbine wheel 2
A bending moment M in the direction of bending the mounting shaft 28 is generated based on the eccentric center of gravity remaining in the mounting shaft 28 . That is,
In FIG. 3, for example, if the position of the eccentric center of gravity with respect to the rotation center CL of the turbine wheel 22 is E, a bending moment is generated in the direction M in FIG. 3 due to centrifugal force. However, in this embodiment, the outer peripheral portion of the main body 23 of the turbine wheel 22 is
Since the mounting shaft 28 is supported with a predetermined load by the second spring portion 34, the magnitude of the bending moment actually acting on the mounting shaft 28 is suppressed. The material and shape of the spring member 32 are selected so that sufficient elastic force can be obtained even at high temperatures during use. Therefore, the concentrated stress generated at the stepped portion of the mounting shaft 28 is reduced, and in this respect as well, the durability of the ceramic turbine wheel 22, in other words, the exhaust turbine supercharger 10, is greatly improved. It will be done.

Further, according to this embodiment, the turbine wheel 2
2 is fitted onto the metal shaft 20 at a fitting portion 30 formed at the tip of the mounting shaft 28, and the portion of the mounting shaft 28 other than the fitting portion 30 is provided with a predetermined clearance with respect to the metal shaft 20. , there is an advantage that the stress acting on the mounting shaft 28 is dispersed.

Here, the spring member 32 is attached to the metal shaft 20
Although it is configured separately from the above, it may be an integral structure. For example, a disk-shaped flange portion protruding in the radial direction may be integrally formed at the shaft end of the metal shaft 20, and the outer peripheral edge of the flange portion may be brought into pressure contact with the outer peripheral portion of the main body 23 of the turbine wheel 22. It is. In this case, the applied load is caused by the elastic deformation of the flange itself.

Further, in the above-described embodiment, a predetermined gap is formed in the portion of the mounting shaft 28 other than the fitting portion 30 with respect to the metal shaft 20, but the base of the mounting shaft 28 is also structured to be fitted into the metal shaft 20. Even in such cases, the effects of the present invention can still be obtained.

The above-mentioned embodiment is merely an embodiment of the present invention, and various changes may be made to the present invention without departing from the spirit thereof.

[Brief explanation of the drawing]

FIG. 1 is a drawing showing a structure for attaching a turbine wheel to a metal shaft in a conventional exhaust turbine supercharger. FIG. 2 is a diagram showing an example of the use of an exhaust turbine type supercharger, which is an example of the present invention. FIG. 3 is a diagram showing the mounting structure of the turbine wheel to the metal shaft in the embodiment of FIG. 2. 20...Metal shaft, 22...Turbine wheel, 24...Blower wheel, 26...Mounting hole, 28...Mounting shaft, 32...Spring member (pressing member).

Claims (1)

[Claims for Utility Model Registration] A ceramic turbine wheel that is rotationally driven by receiving the exhaust flow of an engine, a metal shaft that is rotatably provided around an axis and to which the turbine wheel is fixed at one end; In an exhaust turbine supercharger that is equipped with a blower wheel provided at the other end of the shaft and compresses intake air of the engine, a mounting shaft that is concentric with the rotation axis of the turbine wheel is integrally protruded in the center of the turbine wheel. The mounting shaft is fitted into a mounting hole formed at the shaft end of the metal shaft concentrically with the rotational axis while forming a predetermined gap with the shaft end of the metal shaft. An exhaust turbine supercharger equipped with a ceramic turbine wheel, characterized in that the metal shaft is provided with a press-contact elastic member that presses against the outer periphery of the metal shaft side end in a preloaded state.