JPS6278402A - Ceramic turbo rotor - Google Patents

Abstract

PURPOSE:To improve durability and reliability by so setting the outer diameter of a connecting shaft projectively formed on a ceramic rotor as to satisfy a specific condition and coupling the shaft to a metal rotary shaft only through the recessed bearing shaft part in said metal shaft corresponding to the rotor. CONSTITUTION:A connecting shaft 12 is monolithically formed with the shaft center part of a ceramic rotor 11 and the connecting shaft 12 is coupled to the recess 15 of a metal rotary shaft 13. In this case, the connecting shaft 12 and the metal rotary shaft 13 are kept in a non-contact state at a corresponding part having a circular groove 16 for fitting a seal ring for the recess 15 and coupled to each other at the corresponding part of a shaft part 14 for the bearing of the recess 15. And the outer diameter 'l1' of the connecting shaft 12 for the maximum outer diameter 'L1' of the ceramic rotor 11 is made to satisfy the relations of l1(mm)>=0.07XL1(mm)+4.2, where 40mm<=L1<=150mm and further to cover 80-90% of the outer diameter 'l2' of the bearing shaft part 14, thereby preventing the fracture and similar damage of connected part due to an eccentric stress arising from rotation at high speed and high temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a ceramic turbo rotor constituting an exhaust turbocharger installed in an internal combustion engine or the like equipped with a ceramic rotating body.

[Conventional technology]

In addition to increasing output and reducing fuel consumption, internal combustion engines used for a variety of applications also require improvements in the mechanical strength and mechanical strength of rotating bodies that are exposed to high temperatures, in order to further improve thermal efficiency and rotational response. Heat resistance, 1IliJ I'i': The turbo rotor is made of a ceramic material with excellent wear resistance and low specific gravity, especially sintered bodies such as silicon nitride sialon and silicon carbide, which provides high strength to the rotating shaft where high loads are applied. It has been researched and proposed to use metal materials with excellent workability and to combine them to create a ceramic turbo rotor.

In the ceramic turbo rotor of the above type, the coefficient of thermal expansion of Kovar, Invar, Amber, iron-nickel alloy, etc. is 1.3 Xl0-'/'C to 5.510-
' / 'C and a relatively small metal member are used as a joining metal member having a recess for receiving a connecting shaft that is integrally protruded from the shaft core of the ceramic rotating body, and the connecting shaft is brazed or tightly fitted. After joining by bonding, a metal rotating shaft made of mechanical structural carbon steel or the like is joined to the metal member by means such as pressure welding or welding.

However, the strength of the joining metal member is low at high temperatures, and the opening end of the recessed part of the joining metal member that has received and joined the connecting shaft expands during high-temperature and high-speed rotation, and the ceramic rotating member Wit I
There was a big fear that IQ would be affected. In order to eliminate the above-mentioned drawbacks, as shown in FIG. 2, it has been proposed to use a heat-resistant alloy with high strength at high temperatures, such as Inconel or Hastelloy, as the joining metal member 3.

However, the thermal expansion coefficient of Inconel, Hastelloy, etc. is 11.3 x 10-'/''c to 16.0xlO-
6/°C, silicon nitride is 3.2xlO-
67"c, sialon is 3.Oxlo-6/℃, silicon carbide is about 4.2 Since the difference in thermal expansion between the connecting shaft 2 and the joining metal member 3 is large, the stress generated due to the difference in thermal contraction between the connecting shaft 2 and the joining metal member 3 during brazing or tight fitting is caused by the joining metal member 3 having high toughness. The stress was concentrated on the connecting shaft 2, which is a more brittle material, and was unable to withstand the stress, causing the connecting shaft 2 to break.

Furthermore, in order to eliminate the above-mentioned drawbacks, as shown in FIG. 3, the length of the connecting shaft 2 made of ceramic or porcelain is at least three times its maximum outer diameter. Similarly, it has been proposed that the tight fitting area between the recess 5 bored in the metal rotating shaft 4 and the ceramic connecting shaft 2 be provided at a location where it is likely to be affected by the heat of the exhaust gas flowing inside the bearing housing. ing.

[Problem that the invention seeks to solve]

However, the above proposal focuses only on the required heat resistance characteristics of the joint between the ceramic member and the metal member, and the cost increase associated with the complex and long-axis grinding of the ceramic connecting shaft and the entire mating area of the connecting shaft. Because it is difficult to achieve a uniform tight fit over a wide temperature range from room temperature to high temperatures, the extremely large eccentric stress generated by rapidly changing high-speed rotation is concentrated on the uneven tight fit portion of the connecting shaft. As a result, it was inevitable that the connecting shaft 2 would break in the low-speed rotation range, and the ceramic turbo rotor was not fully satisfactory.

Means for Solving Problems c] The present invention has been made as a result of intensive research in view of the above-mentioned current situation, and has been developed to provide a maximum outer diameter of a ceramic rotating shaft, a ceramic rotating outer diameter, and a ceramic connecting shaft based on various physical properties of a metallic rotating shaft. After finding a correlation between the outer diameter and the outer diameter of the metal bearing shaft, and satisfying this correlation, the length of the connecting shaft is less than three times the maximum outer diameter of the connecting shaft, and a seal ring is attached. The connecting shaft is not in contact with the recess of the metal rotating shaft having a groove, and has a length sufficient to fit in the recess of the oil-cooled bearing shaft. .

〔Example〕

Hereinafter, the present invention will be specifically explained in detail with reference to Examples.

In FIG. 1, reference numeral 11 denotes a ceramic rotating body, and a connecting shaft 12 is integrally molded on the shaft core of the rotating body 11. Further, the connecting shaft 12 of the rotating body 11 is fitted into the recess 15 of the metal rotating shaft 13. In this case, the connecting shaft 12 and the metal rotating shaft 13 are not in contact with each other in the corresponding part having the annular groove 16 for mounting the seal ring in the recess 15, but in the contact part of the bearing shaft part 14 in the recess 15. Then, they are joined by means such as shrink fitting or brazing.

In this example, the JISa point bending strength of the test piece cut out from the ceramic rotating body 11 was 69.0 kg/mm on average.
Although the silicon nitride rotating body exhibits a coefficient of thermal expansion of 2 and has a higher coefficient of thermal expansion than Kovar, Invar, etc., the tightening caused by thermal contraction of the metal member does not affect the atmosphere even if the metal member that fits into the ceramic member is made thinner to relieve stress. Temperature is 500°C ~ 800°
C has physical properties that can withstand high-temperature, high-speed rotation at circumferential speeds of up to 600 m/sec, and has a coefficient of thermal expansion of 5°0 x 10-6/°C to 1 in the temperature range from room temperature to 600°C.
4.0xlO-6/''c, which is lower than conventional Inconel and Hastelloy in the temperature range from room temperature to 650℃.
, Incoloy, which has a 2z yield strength of 90 kg/mm" or more, which is higher than the conventional Inconel and Hastelloy, was processed to the dimensions shown in Table 1, and the connecting shaft 1 was manufactured under the same conditions.
2 were joined by brazing at the corresponding part of the bearing shaft part 14 of the concave part 15 of the metal rotating shaft 13, and four ceramic turbo rotors were manufactured.

In addition, as a comparative example, the metal rotating shaft 13 is made of SCM435, and the second, first and third cases are made of Inconel.
The conventional example was manufactured as shown in FIG. 4 and FIG. However, in both the comparative example and the conventional example, the connecting shaft and the metal rotating shaft were joined by brazing.

/'/' In addition, in the conventional example shown in Fig. 2, after the connecting shaft 2 is brazed and joined to the Inconel joining metal member 3, carbon steel SCM435 for mechanical structure is joined to the joining metal member 3 by electron beam welding. It was joined at part S.

The unbalance of the ceramic soctor horotor manufactured as described above was corrected to less than 0.02 g-Cm using a balance tester, and a 1-year test was conducted on a high-temperature, high-speed rotating surface at a supply gas temperature of 950°C. Obtained the results in the table. The relationship between the maximum outer diameter of the ceramic rotating body and the outer diameter of the connecting shaft of the ceramic rotating body based on the results in Table 2 and the results of the high-temperature, high-speed rotation durability test are shown in Table 5.
As shown in the figure.

〔evaluation〕

As is clear from Tables 1 and 2, when the ratio of the outer diameter of the connecting shaft of the ceramic rotating body to the outer diameter of the bearing shaft of the metal rotating shaft is less than 80χ (sample numbers 1, 9.17, 2
5.33 cannot withstand the eccentric stress caused by high-speed rotation even if the unbalance amount is 0.02g -c+n,
When the connecting shaft breaks at a circumferential speed of 500 m/s and the above ratio exceeds 90χ (sample numbers 5, 13, 2L29.
In 37), the wall thickness of the bearing shaft that receives and joins the connecting shaft becomes thin, and as a result of repeated deformation due to the eccentric stress, it breaks from the innermost corner of the recess, and both have durability problems. .

In addition, when the ratio of the length of the connecting shaft to the maximum connecting diameter of the ceramic rotating body is 3 times or more (sample numbers 7.15, 3
1.39) broke from the connecting shaft at a circumferential speed of 600 m/s or less, and this is thought to be because the eccentric stress was concentrated on the uneven hoof fitting portion.

On the other hand, a comparative example (sample number 8.16, 24, 32.40
), the receiver breaks due to repeated deformation due to the eccentric stress from the innermost corner of the recess where the connecting shaft is received and joined at a circumferential speed of around 500 m/s, and the conventional example ( In sample number 4], 42.43), in the case of sample number 41, the fracture occurred from the connecting shaft at a circumferential speed of 400 m/s, and the connecting shaft was made more than three times the maximum diameter of the connecting shaft, and the required heat resistance of the joint was In the case of sample 'a:' with lower characteristics, +1 No. 42, the fracture occurred at a circumferential speed of 500 m/s from the recessed opening of the metal rotary shaft that receives the connecting shaft, and in the case of sample number 43, the failure occurred at a circumferential speed of 500 m/s. At circumferential speed, the ceramic rotating body broke at the side end in the tight fit area of the connecting shaft. On the other hand, in the case of the present invention (sample numbers 2, 3゜4, 10.11.1
2.18.19, 20, 26, 27, 28, 34, 35
．． 36) Both of them withstood high-temperature, high-speed rotation durability tests at circumferential speeds of 600 m/s, and moreover, were more broken than ceramic rotating bodies. Nothing more was allowed.

Furthermore, from Fig. 5, which shows the relationship between the maximum outer diameter of the ceramic rotating body and the outer diameter of the connecting shaft of the ceramic rotating body (outer diameter of the connection + mm) ≧0.07X (maximum outer diameter of the ceramic rotating body: mm)+4.2 (However, 40 mm ≦ (maximum outer diameter of ceramic rotating body) 5150 mm) The area of ``fractured by the ceramic rotating body'' and the area of ``fractured by the ceramic connecting shaft'' are the boundaries. It can be seen from the results of the high-temperature, high-speed rotation durability test shown in Table 2 that the area of "destruction than ceramic rotating bodies" is more desirable.

〔Effect of the invention〕

As described above, according to the present invention, a main body that satisfies the maximum outer diameter of the ceramic rotating body based on the physical properties of the metal rotating shaft and the correlation between the outer diameter of the ceramic connecting shaft and the outer diameter of the metal bearing shaft is provided. The length of the connecting shaft is three times the maximum diameter of the connecting shaft, and the connecting shaft is not in contact with the recessed part of the metal rotating shaft that has a groove for mounting the seal ring. By fitting in the concave part of the shaft, the required heat resistance properties of the joint between the ceramic member and the metal member are reduced, and the large eccentric stress caused by high-temperature and high-speed rotation is avoided. A ceramic rotor rotor with excellent durability and reliability, which does not cause breakage of the recessed portion or destroy the connecting shaft of the ceramic rotating body, can be obtained.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway cross-sectional view showing a ceramic turbo rotor according to an embodiment of the present invention, FIGS. 2, 3, and 4 are partially cutaway cross-sectional views showing a conventional example of a ceramic turbo rotor, and FIG.
The figure is a diagram showing the relationship between the maximum outer diameter of the ceramic rotor and the outer diameter of the ceramic rotor connecting shaft. 11: Ceramic rotating body 12: Connecting shaft 13: Metal rotating shaft 14: Bearing shaft 15: Four parts 16: Groove 17: Root arc starting point: Maximum outer diameter L2 of ceramic/7-piece grouping body: Connection shaft length 11: Connection shaft outer diameter 7! 2: Bearing shaft outer diameter

Claims (1)

[Claims] 1. In a ceramic turbo rotor formed by joining a ceramic rotating body and a metal rotating shaft, the outer diameter of the connecting shaft integrally protruding from the shaft core of the ceramic rotating body is (outer diameter of connecting shaft: mm)
)≧0.07×(Maximum outer diameter of ceramic rotating body: mm
)+4.2 [However, 40mm≦(maximum outer diameter of ceramic rotating body)≦150mm] and is 80 to 90% of the outer diameter of the bearing shaft supported by the bearing housing of the metal rotating shaft. In addition, the metal rotating shaft has an annular groove for mounting a seal ring on the outer circumferential surface of the concave portion adjacent to the rotating body, and the groove is provided with the groove. A ceramic turbo rotor characterized in that the connecting shaft is not in contact with the recess of the rotating shaft, and the connecting shaft is fitted only in the recess of the bearing shaft. 2. Claim 1, wherein the length from the starting point of the root arc of the connecting shaft integrally protruding from the shaft core of the ceramic rotating body is less than three times the maximum outer diameter of the connecting shaft. Ceramic turbo rotor as described in section. 3. The metal rotating shaft has a thermal expansion coefficient of 5.0×10^-^6/℃ to 14.0℃ in the temperature range from room temperature to 600℃.
The ceramic turbo rotor according to claim 1, which is made of a heat-resistant alloy of 0x10^-^6/°C. 4. The Young's modulus of the metal rotating shaft is 15,000 to 20,0.
The ceramic turbo rotor according to claim 1, which is made of a heat-resistant alloy of 00 kg/mm^2. 5. The metal rotating shaft has a 0.2% proof stress of room temperature to 650℃.
2. The ceramic turbo rotor according to claim 1, which is made of a heat-resistant alloy having a resistance of 90 Kg/mm^2 or more in the temperature range of .