JPH0625601Y2 - Ceramic rotor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a ceramic turbo rotor having a rotating body made of ceramics in particular.

(Prior Art) Many internal combustion engines used for various purposes including automobile engines are equipped with a turbocharger to improve output and reduce fuel consumption by utilizing energy of exhaust gas. It has become possible to be.

In such a turbocharger (hereinafter, simply referred to as a turbo), it is effective to introduce exhaust gas having a temperature as high as possible in order to improve thermal efficiency.

For this reason, it has been proposed in many cases to construct a rotor for a turbo from a ceramic material having a higher heat resistance strength than a metal material, especially a sintered body of silicon nitride, sialon, silicon carbide or the like.

In such a turbo, a blade that is directly exposed to high-temperature exhaust gas and a rotating shaft that holds the blade or that transmits the rotational force generated by an integrally molded ceramic rotating body to a rotated body such as a compressor. It is conceivable that the rotating body and the rotating shaft are integrally formed of a ceramic material in consideration of the connectivity with the rotating body, the supporting shaft, etc., but there is a problem with this formability, and during firing It is extremely difficult to put into practical use the ceramic turbo rotor in which the rotating body and the rotating shaft are integrally formed, because they are extremely difficult to be deformed, and the polishing and grinding processes are extremely difficult.

Therefore, studies are being carried out on the practical application of a turbo rotor in which a metallic rotating shaft is connected to a ceramic rotating body.

(Problems to be solved by the invention) However, while the ceramic rotating body is made of silicon nitride or the like having excellent thermal shock resistance, the metal rotating shaft is made of ceramic such as Kovar or Invar. A ceramic rotating body is joined by a brazing method, shrink fitting, or the like through a metal having a low coefficient of thermal expansion relatively close to that of the above. With Kovar, Invar, etc., the mechanical strength, particularly the radial crushing strength and hardness of the joining member having the recessed portion fitted into the protruding portion of the ceramic rotating body, are significantly reduced.

As a result, the strength of the Kovar, Invar, etc. is also reduced, so that the brazing strength and shrinkage fitting strength with the ceramic rotating body are also reduced. Moreover, since the turbo rotor is used under high speed rotation, steady rotation at high speed In this state, the housing and the bearing are not in contact with each other, but since they come into direct contact with the housing and the bearing at the time of starting and stopping the rotation, there is a problem that wear resistance is low in Kovar having a low hardness.

That is, if even a slight amount of uneven wear occurs in the joining member that rotates at a high speed, the balance of the turbo rotor will be lost, and the eccentric rotation will occur immediately. There was a risk of causing problems.

Molybdenum and tungsten are superior to Kovar in terms of thermal expansion and hardness, but they are also suitable because they are extremely brittle, difficult to machine, extremely expensive, and easily oxidized. is not.

(Means for Solving Problems) The present invention has been made in view of the above, and a ceramic rotating body and an ordinary metal shaft are made of Kovar as a base material, and titanium nitride (TiN) or Aluminum oxide (Al
₂ O ₃ ) At least one kind of fine powder is added and dispersed in the base material to form a composite, which is joined through a joining member made of a Kovar alloy with improved hardness and radial crushing strength. By providing the rotor, the above problems are eliminated.

(Embodiment) An embodiment of the present invention will be described in detail below with reference to the operation thereof with reference to the accompanying drawings.

FIG. 1 is a vertical cross-sectional view showing an embodiment of a turbo rotor according to the present invention. In the figure, reference numeral 1 is a ceramic rotor used in a portion where a high-speed high-temperature gas body acts. 1 has a plurality of blades 11 radially.
Are integrally provided, and a columnar protrusion 12 is formed at the center of the shaft on one end side, and a base 121 thereof is rounded.

In addition, 2 is a joining member made of Kovar alloy,
At one end thereof, there is a recess 21 that can be fitted onto the protrusion 12, and an opening peripheral edge 211 of the recess 21 is rounded so as to fit with the base 121 of the protrusion 12.

The rotating body 1 and the joining member 2 are joined and joined by means such as brazing and shrink fitting.

Further, a rotary shaft 3 made of carbon steel for machine structure is connected to the other end of the joining member 2 by an electron beam welding method, a butt welding method, or the like.

As such a joining member 2, Kovar, which is conventionally known as a metal having a low coefficient of thermal expansion close to that of ceramics,
Invar or the like was used, but since these metals have problems in wear resistance and strength as described above, in the present invention, Kovar is used as the base material and titanium nitride (TiN) or aluminum oxide (Al ₂ A Kovar-based alloy is used in which a fine powder of O ₃ ) is added to a molten base material to disperse at least one kind of titanium nitride particles or aluminum oxide particles to form a composite.

The joining member 2 and the rotary shaft 3 may be integrated and the whole may be made of a Kovar alloy, but since such an alloy is expensive, the rotary shaft 3 is made of carbon steel for machine structure as described above. It is desirable to do.

Further, as the ceramic material forming the ceramic rotating body 1, non-oxide ceramics such as silicon nitride, sialon, and silicon carbide having high heat resistance, thermal shock resistance, and mechanical strength are suitable.

Next, various physical properties of various Kovar alloys used for the joining member 2 and the ceramic material used for the ceramic rotating body 1 are shown in Table 1 in comparison with Kovar and Invar.

In Table 1, the physical property hardness indicates Vickers hardness, and the radial crushing strength is 15 mm in outer diameter and 10 in inner diameter.
It is calculated by dividing the load when a circular sample of 10 mm in height and 10 mm in height is applied with a compressive load from the diametrical direction by the cross-sectional area, and the bending strength is in accordance with the JIS standard three-point bending test. It was measured.

Since titanium nitride and aluminum oxide added to Kovar improve mechanical properties by dispersing them in Kovar, the volume ratio of titanium nitride particles and aluminum oxide particles dispersed and present in Kovar is important. Therefore, the added amount is expressed in volume%.

That is, when at least one kind of the titanium nitride particles and the aluminum oxide particles is dispersed in Kovar and the volume ratio thereof is increased, the hardness tends to increase at room temperature and 500 ° C., and the radial crushing strength is titanium nitride. When the amount of particles is 0.6, 1.0, 1.3, 1.6% by volume, the Kovar matrix is 120 kg / mm ² at room temperature,
171, 199, 220, 230kg / mm ² , 50 respectively
Against 0 the ℃, Kovar base material is 102 kg / mm ^2, respectively gradually increased to 157,180,201,209kg / mm ^2, at ambient temperature when said addition amount is 2.3 or more volume% 226 kg / mm ² , at 500 ° C, it tends to decrease to 196 kg / mm ² .

This tendency also applies to aluminum oxide particles, and when the internal addition amounts are 0.3, 0.6, and 0.8% by volume,
At room temperature, 141, 152, 160 kg / mm ² , 50 respectively
At 0 ° C, the values gradually increase to 122, 133 and 143 kg / mm ² , respectively, and when the internal addition amount becomes 1.4 vol% or more,
At room temperature a 147 kg / mm ^2, at 500 ℃ 124kg / mm ^2.

Next, the measurement results of the bonding strength of the test piece obtained by joining the Kovar-based alloy and silicon nitride by brazing listed in Table 1 above were compared with the test piece obtained by similarly joining Kovar and Invar with silicon nitride. The results are shown in Table 2.

The test piece is made of silicon nitride and has an outer diameter of 10 m.
A cylindrical body of m and a length of 4.7 mm is brazed and joined with a cylindrical body made of each metal.
mm ² mm at room temperature and 500 ° C, push out the bonded ceramic cylinder from the metal cylinder, measure the pressing load required for release, and divide the obtained value by the bonding area to obtain the bonding strength. And

As is clear from Table 2, Kovar of the comparative example is
As specified in the physical properties of the table, the hardness at 500 ℃ is 82 kg.
/ mm ² , the radial crushing strength at room temperature is 120 kg / mm ² , and the bonding strength of the member made of Kovar and silicon nitride is
It has only 9.8 kg / mm ^{2 at} room temperature and 4.1 kg / mm ² at 500 ° C, while the hardness at 500 ° C according to the present invention is 171.
It can be seen that the joint strength with the Kovar-based alloy, which is as high as kg / mm ² or more and the radial crushing strength is 160 kg / mm ² or more at room temperature, maintains a large joint strength especially at high temperature.

Not only is it mechanically stronger than Kovar, Invar, etc., but its hardness is also greater, which improves the wear resistance of the bearing components, and makes contact with the housing and bearings when the turbo rotor starts and stops. However, the joining member itself is less likely to wear unevenly, and the balance of the turbo rotor is not disturbed.

In addition, the measurement results in Table 2 show only those relating to the test piece formed by brazing silicon nitride and various metals.
Almost the same strength tendency was observed also in the case of brazing or shrink-fitting the other listed alloys with silicon carbide and sialon.

(Effects of the Invention) As described above, according to the present invention, a blade exposed to high-temperature gas and a ceramic rotating body integrally provided with the blade are formed of non-oxide ceramics such as silicon nitride, This is made of Kovar as a base material, and at least one kind of fine powder of titanium nitride and aluminum oxide is added to the base material and dispersed to join the metal rotating shaft through a joining member made of a Kovar alloy Since the turbo rotor is configured as described above, the joining strength does not decrease even in a high temperature range, and the wear resistance of the Kovar-based alloy is improved, so that the joining member may be unevenly worn to cause imbalance. Without, can bring a reliable long-life turbine, turbocharger.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a turbo rotor according to the present invention. DESCRIPTION OF SYMBOLS 1 ... Ceramic rotating body 11 ... Blade 12 ... Projection part 121 ... Base part 2 ... Joining member 21 ... Recessed part 221 ... Opening edge part

 ─────────────────────────────────────────────────── ───Continuation of the front page Judgment panel Judge Yoshio Kimura Judge Judge Watanabe Taijiro Judge Hiromitsu Fukai (56) References JP58-217814 (JP, A) JP55-100948 (JP, A) JP-A-50-30730 (JP, A) JP-B 56-44946 (JP, B2) JP-B 57-5867 (JP, B2) Metal Handbook, 42-3-20, 3rd edition, Maruzen, Pages 441-452 Metal Material Dictionary, Sho 38-5-25, Nikkan Kogyo Shimbun, page 182

Claims (1)

[Scope of utility model registration request] 1. A ceramic rotary body equipped with a blade, wherein a projecting portion integrally formed in the center is made of Kovar as a base material, and titanium nitride (TiN) and aluminum oxide (Al ₂ O ₃ ) are used as the base material. Of at least one kind of fine powder is added and dispersed in the base material and is fitted into a concave portion provided at one end of a joining member made of a Kovar-based alloy, and the other end side of the joining member is made of a metallic rotation member. A ceramic turbo rotor characterized by being formed by joining shafts.