JPH0692722B2 - Ceramic rotor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a ceramic turbo rotor constituting an exhaust turbocharger to be mounted on an internal combustion engine or the like equipped with a ceramic rotating body.

[Conventional technology]

For internal combustion engines used for various purposes, in addition to improving output and reducing fuel consumption, in order to further improve thermal efficiency and improve rotational response, the rotating body exposed to high temperatures must have mechanical strength and heat resistance. , A metal with excellent wear resistance and a small specific gravity, the turbo rotor is made of a sintered body such as silicon nitride, sialon, or silicon carbide, and the rotating shaft on which high load acts has high strength and excellent workability. It has been researched and proposed to use these as materials and combine them into ceramic turbo rotors.

In the type of ceramic turbo rotor as described above,
Kovar, Invar, Amber, iron-nickel alloy, etc. with a relatively small coefficient of thermal expansion of 1.3 × 10 ^-6 / ° C to 5.5 × 10 ^-6 / ° C are integrated into the ceramic rotor shaft core. A metal-made rotating shaft made of carbon steel or the like for machine structural use after being joined by brazing or interference fitting to the connecting shaft Were joined by means such as pressure welding and welding.

However, the strength of the joining metal member is low at high temperatures, and the recess of the joining metal member that receives and joins the connecting shaft has the opening of the recess that expands during high-temperature and high-speed rotation. There was a great risk that the joint with the joining metal member would be separated.

Therefore, in order to solve the above-mentioned drawbacks, it has been proposed to use a heat-resistant alloy such as Inconel or Hastelloy having a high strength at high temperatures for the joining metal member.

[Problems to be solved by the invention]

However, the coefficient of thermal expansion of Inconel, Hastelloy, etc.
From 11.3 × 10 ^-6 / ° C to 16.0 × 10 ^-6 / ° C, silicon nitride is 3.2 × 10 ^-6 / ° C, sialon is 3.0 × 10 ^-6 / ° C, and silicon carbide is 4.2 × 10 ^-6 / ° C. Since the difference in thermal expansion between the metal member and the ceramic member related to the joining is large at about ℃, the stress generated by the difference in thermal contraction between the ceramic member and the metal member at the time of tight fitting is higher than that of the metal member having high toughness. , The brittle material was concentrated on the ceramic member, and the ceramic member was broken without being able to withstand the stress.

[Means for solving problems]

As a result of earnest research in view of the above-mentioned present situation, the present invention has a coefficient of thermal expansion of 5.0 × 10 ⁻⁶ / ° C. to 14.0 × 10 in the temperature range of room temperature to 600 ° C.
It has been found that the adoption of Incoloy, which has a coefficient of thermal expansion lower than that of heat-resistant alloys such as Inconel and Hastelloy at ^-6 / ℃, is good, and the thickness of the metal member for joining made of Incoloy and the outer diameter of the connecting shaft made of ceramic are good. As a result of examining various combinations of
The stress generated by the thermal contraction of the joining metal member concentrates on the ceramic connecting shaft, which is a brittle material, destroys the ceramic member, and the opening end of the concave portion of the joining metal member expands and deforms during high-temperature high-speed rotation, and The optimum combination range of the thickness of the metal member for joining made of Incoloy and the outer diameter of the connecting shaft made of ceramic was found, which does not damage the rotating body.

〔Example〕

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

In the drawing, reference numeral 1 denotes a ceramic rotating body, and a connecting shaft 2 is integrally formed on the shaft core of the rotating body 1.

Further, the connecting shaft 2 of the rotating body 1 is fitted into a concave portion 4 of a joining metal member 3 having an annular groove 5 for mounting a seal ring. In this case, the connecting shaft 2 and the joining metal member 3 are joined by shrink fitting, brazing or the like. The metal rotary shaft 6 is joined to and joined to the joining metal member 3 fitted with the connecting shaft 2 at the joining portion S by means such as pressure welding.

Next, a joining metal member 3 having a maximum outer diameter of the ceramic rotating body 1 of 56 mm and an annular groove 5 for mounting a seal ring 3
In an embodiment of the ceramic turbo rotor outer diameter l ₁ is according to the invention which are 17mm of, the percentage of outer diameter l ₂ of the coupling shaft 2 to the outer diameter l ₁ of the bonding metal member 3 as shown in Table 1 The recess 4 of the joining metal member 3 and the outer diameter l ₂ of the connecting shaft 2 were processed. Incoloy and Kovar are used for the joining metal member 3, and the connecting shaft 2 is used under the same conditions.
Are brazed together, and then the metal rotating shafts 6 are joined to the joining metal member 3 after brazing under the same conditions at the joints S by an electron beam welding method.
Ceramic turbo rotors were produced one by one.

In addition, the thing which used Kovar for the metal member 3 for joining was made into the comparative example.

The ceramic turbo rotor manufactured as described above was corrected for unbalance to less than 0.02 g · cm using a balance tester, and subjected to a high temperature and high speed rotation endurance test at a supply gas temperature of 950 ° C.
The results in the table were obtained.

[Evaluation] As is apparent from Table 1, when the outer diameter l ₂ of the connecting shaft 2 of the ceramic rotary body 1 is less than 70% of the outer diameter l ₁ of the joining metal member 3 (Sample No. 1), Excessive stress due to heat shrinkage of the joining metal member 3 was concentrated on the connecting shaft 2, and the connecting shaft 2 was fractured from the root of the connecting shaft 2 at a low speed of 180,000 rpm or less. Further, comparative examples outside diameter l ₂ is the Kovar case (sample No. 8) and bonding metal members 3 more than 80% of the outer diameter l ₁ of joining metal members 3 of the coupling shaft 2 (Sample No. 9) In all cases, due to insufficient strength of the joining metal member 3, the opening end of the recess 4 was enlarged during high-temperature high-speed rotation, and the ceramic rotor 1 was broken at a low-speed rotation of 180,000 rpm or less.

In contrast, withstand even every minute either Sample No. 2-7 200,000 rotate faster than the rotation durability test according to the present invention, especially the outer diameter l ₁ of the outer diameter l ₂ is joining metal members 3 of the coupling shaft 2 Of 74
% And 76%, sample numbers 4 and 5 were not observed in the high speed rotation endurance test of 240,000 rpm.

〔The invention's effect〕

As described above, according to the present invention, even at any high speed rotation, neither excessive stress is concentrated on the ceramic connecting shaft portion joined to the metal rotating shaft nor deformation of the joining metal member is induced. A ceramic turbo rotor excellent in durability and reliability can be obtained.

[Brief description of drawings]

FIG. 1 is a fragmentary sectional view showing a ceramic turbo rotor according to an embodiment of the present invention. 1: Ceramic rotating body 2: Connecting shaft 3: Joining metal member 4: Recess 5: Groove 6: Metal rotating shaft S: Joining part l ₁ : Outer diameter of joining metal member l ₂ : Outer diameter of connecting shaft

Claims (1)

[Claims] 1. A connecting shaft integrally formed on a shaft portion of a ceramic rotating body is fitted to a joining metal member having an annular groove for mounting a seal ring on the outer periphery, and the joining member is joined. In a ceramic turbo rotor in which a metal member is joined to a metal rotating shaft, an outer diameter l _{2 of the} connecting shaft has a coefficient of thermal expansion of 5.0 × 10 ⁻⁶ / ° C. to 14.0 × 10 ⁻⁶ from room temperature to 600 ° C. A ceramic turbo rotor characterized by being 70 to 80% of the outer diameter l ₁ of the joining metal member made of a heat-resistant alloy having a 0.2% proof stress of 80 kg / mm ² or more from / ° C or from room temperature to 700 ° C.