JPH03206302A - Radial ceramic turbine rotor - Google Patents

Abstract

PURPOSE:To prevent a degreased crack in a blade part so as to improve connecting strength by forming a shaft hole less tapered than a fitting hole, from a blade part front surface over to a shaft part point end, in the case of a turbine rotor in which a blade part is connected to a shaft part through a cone-shaped fitting hole. CONSTITUTION:In a rotor main unit, a blade part 1 and a shaft part 2, which are respectively formed of ceramic, are connected by the center part 3 of the blade part 1 through ceramic paste. Here a shaft hole 6 is formed from the front surface 4 of the blade part 1 over to the point end 5 of the shaft part 2. Then connection of the rotor main unit is a connection by substantially mutual fitting of cone-shaped irregularities. A taper smaller than the taper of a cone in a connection surface 7 is provided on the shaft hole 6. Thus a degreased crack in the blade part 1 is prevented so that connecting strength is improved, while improper connection between the blade part 1 and the shaft part 2 is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radial type ceramic turbine rotor.

Silicon ceramics such as silicon nitride, silicon carbide, and sialon are more stable at high temperatures than metals and are less susceptible to oxidative corrosion and creep deformation, so active research is being conducted on their use as engine parts.

In particular, radial turbine rotors made from these ceramic materials are lighter than metal rotors, can raise engine operating temperatures, and have excellent thermal efficiency, so they are attracting attention as automotive turbocharger rotors or gas turbine rotors. are collecting.

As a conventional radial type turbine rotor, one disclosed in Japanese Patent Application Laid-Open No. 57-88201 is known, and as shown in FIG. 2, a blade portion 1 having a complicated three-dimensional shape is For example, the shaft part 2 is shaped by injection molding, for example, by mold press, and then molded by rubber press, and the two are joined into, for example, a conical fitting shape.
It was burnt down and made into a one-piece ceramic turbine rotor. However, with this method, (1) degreasing cranks tend to occur in the thick part of the wing after injection molding, and (2) it is necessary to precisely match the shapes of the wing and shaft at the time of joining, resulting in shape mismatch. In this case, bonding defects such as voids are likely to occur on the bonding surface, and the thickness of the paste applied to the bonding interface becomes uneven, which tends to reduce the bonding strength. There were drawbacks such as difficulty in determining and poor workability.

The purpose of the present invention is to eliminate the above-mentioned drawbacks found in conventional products, which occur in the degreasing process during the manufacture of ceramic cylinder rotors, which consist of blades and shafts. This is to prevent degreasing cracks in the thick parts of the wing parts, which are easy to occur.

Another object of the present invention is to facilitate the joining of the wing portion and the shaft portion, to prevent joint defects such as voids in the joint portion, to make the joining layer of the ceramic paste uniform, and to increase the joining strength.

Still another object of the present invention is to improve workability by utilizing the shaft hole provided in the front surface of the wing part as a center hole during final processing after firing.

That is, the gist of the features of the present invention is that a ceramic wing section and a ceramic shaft section are joined by a substantially conical fitting hole provided in the wing section via a ceramic bulk paste. This is a radial type cylinder rotor characterized by having a shaft hole which has a smaller taper than the fitting hole from the front surface of the blade toward the tip of the shaft, and which is opened in the front surface of the blade.

Further details of the present invention will be explained in detail below.

In the radial ceramic turbine rotor of the present invention, as shown in FIG. It has a shaft hole 6 in the direction from 4 to the tip 5 of the shaft portion. The radial type ceramic turbine rotor of the present invention includes:
The joining is substantially by fitting conical projections and recesses, preferably the shaft hole 6 has a smaller taper than the conical taper of the joint surface 7, and the diameter of the shaft hole 6 in the front surface 4 of the wing section is 2 to 5 mm. The taper of the shaft hole relative to the rotor central axis 8 is at most 5 degrees, preferably 2 degrees or less.

The radial ceramic turbine rotor of the present invention will be explained.

First, Y203, Mg○, CeO, SrO, Bed, B
, C, etc. are added and sufficiently kneaded to prepare a homogeneous mixture. Next, a binder such as a resin or wax is heated and kneaded into this mixture to prepare a ceramic raw material for injection molding. As shown in FIG. 1, the diameter after firing is 2 to 5 mm from the front surface 4 of the blade toward the tip 5 of the shaft, and the diameter is at most 5 degrees with respect to the central axis 8 of the rotor, preferably 2 degrees or less. The wing portion 1 is obtained by injection molding using a mold adjusted to have the shaft hole 6.

Alternatively, the wing portion 1 is obtained by forming the shaft hole 6 in the molded body after injection molding using a carbide drill or the like. Next, binders such as resin and wax contained in the molded body obtained by injection molding are removed by heating in an electric furnace to perform degreasing. The heating conditions depend on the type of resin and wax, etc.
It varies depending on the content, but up to a temperature of 500°C.
The rate of temperature increase is 10°C/h or less, preferably 10°C/h or less, to a temperature of 300°C. Separately from this, a shaft portion or a shaped body is formed using the ceramic raw material by a conventional ceramic shaping method such as an injection molding method, a slip casting method, a mold pressing method, a rubber pressing method, or the like. in this case,
Although the wing portion or shaped body and the shaft portion or shaped body do not necessarily need to be made of the same material, it is preferable that they be made of the same material because the difference in thermal expansion is small. After that, the wing part or shape body and the shaft part or shape body were
After calcining at 0 to 12,000°C, the bonding surface 7 is machined to form conical concave and convex fittings. At this time, it is preferable for the shaft tip 5 to fit into the shaft hole 6, so the conical tip may remain, but the diameter of the shaft hole 6, that is, 2 to 5 mm.
It may also be somewhat rounded. And the wing l
After applying a heat-resistant ceramic paste preferably made of the same material as the wing portion 1 and the shaft portion 2 to the joint surface 7 of the wing portion 1 and the shaft portion 2, the two shapes are brought into close contact with each other. The joining of the double-sided bodies is performed only at a part of the taper forming the joint surface 7, and the shaft end 5 fits into the shaft hole 6. At this time, excess paste on the joint surface 7 flows into the shaft hole 6, so that the paste layer on the joint surface 7 becomes uniform and the joint strength increases. The paste that has flowed into the shaft hole 6 does not interfere with subsequent processes. Further, when the shaft hole 6 is used as a center hole, it also satisfactorily fulfills its role.

Cover the closely spaced precepts with an elastic material such as latex rubber,
Rubber press is performed at a pressure of 5 ton/cmz or less. Thereafter, the blade portion 1, the shaft portion 2, or the ceramic tank paste is fired at an optimal firing temperature and atmosphere to obtain a strongly bonded integral ceramic turbine rotor. Further, in order to obtain the final product shape, the shaft hole 6 is used as a center hole, and the blade portion 1 and shaft portion 2 are precisely machined to obtain a radial type ceramic turbine rotor as shown in FIG.

The reason why the diameter of the shaft hole 6 is set to 2 to 5 mm in the present invention is as follows.
If the diameter is less than 2 mm, the shaft hole 6 should be removed when or after the wing part 1 is shaped.
This is because it is difficult to provide holes therein and does not function sufficiently as binder release holes during degreasing. Further, if the diameter of the shaft hole 6 is 5 mm or more, the contact area between the wing portion and the shaft portion will be reduced, and there is a possibility that breakage may occur from the shaft portion tip 5. 2-5
If it is about mm, it will not cause damage when the rotor rotates at high speed.

In the turbine rotor, the maximum stress is applied to the portion of the shaft portion 2 that fits into the blade portion 1, but since this portion has a wall thickness greater than that of the blade portion 1, it can sufficiently withstand the large tensile stress caused by high-speed rotation.

Furthermore, the reason why a maximum taper of 5 degrees is preferred as the taper of the shaft hole 6 is that the purpose of the present invention can be sufficiently achieved with a taper of 5 degrees, and the diameter of the shaft hole at the tip 5 of the shaft portion should not be made too large. It's for a reason.

Hereinafter, the present invention will be explained in more detail with reference to Examples.
The invention is not limited to this example.

Actual 114L Si3N for pressureless sintering with 100 parts by weight of Si:+N4 powder with an average particle size of 1 μm (the same applies hereinafter) and 2 parts of Sr, 3 parts of Mg, and 3 parts of CeOz added as sintering aids.
A mixture was prepared. 15% by weight of polyethylene wax (hereinafter the same) and 2% of stearic acid were added to a portion of this mixture and heated and kneaded to prepare a ceramic raw material for injection molding. Then, a mold was prepared so as to obtain a radial turbine rotor in which the maximum diameter of the blade part 1 was 50 mm, and the blade part front face 4 had a shaft hole 6 with a diameter of 2 mm and a taper of 5 degrees with respect to the center axis of the rotor. The ceramic raw material was injection-molded using the injection molding method, and the wing portion 1 was produced. Next, it was heated to 400°C at 3°C/h in an electric furnace and held for 5 hours to degrease it. After degreasing, each part of the molded body was observed, and no cracks were observed at all.

On the other hand, a raw material prepared by adding 2% polyvinyl alcohol to the mixture and thoroughly kneading the mixture was pressed into a mold, and then wasostatically compressed using a rubber press to obtain a shaped shaft body. Then, a shaft portion 2 whose tip was machined into a conical shape was manufactured using a lathe.

After smoothing the joint surface 7 of the obtained blade part 1 and shaft part 2 by lathe processing, the joint surface was coated with 4 parts of Mg0, 3 parts of SrO, and 2 parts of Ce○2.
After baking a paste of Si:+N4 powder containing 4.5 parts 1
Apply the coating to a thickness of 00 μm, and apply it to the wing part 1 and shaft part 2.
After applying it closely, cover the whole thing with latex rubber and 2 tons.
Rubber pressing was performed at a pressure of /cm2 to obtain a molded body in which the wing portion 1 and the shaft portion 2 were firmly joined and integrated. It was then incinerated at 1720°C for 30 minutes in a nitrogen atmosphere. Thereafter, the shaft hole 6 on the front surface of the blade section 1 was used as a center hole, and the rotor was precisely finished using a lathe to obtain the radial type ceramic turbine rotor shown in FIG. 1.

In order to perform a rotation test on the obtained ceramic turbine rotor, a metal shaft was attached after the unharness of a part of the rotor was set to 0.005 g'cm.

This increased unbalance was removed, and the balance was adjusted so that the overall unbalance was 0.005 g-cm. Thereafter, a test was conducted using a rotating tester while gradually increasing the number of rotations, and no damage occurred even at a number of rotations of 22,000 rpm.

Practical Team 1 A SiC mixture for pressureless sintering was obtained by adding 3 parts of B4C and 2 parts of B4C as sintering aids to 100 parts of SiC powder consisting of a β layer as a seed with an average particle size of 0.5 μm.

5% of EVA resin and 15% of polyethylene wanox were added to a portion of this mixture and heated and kneaded to prepare a ceramic raw material for injection molding. Thereafter, the ceramic raw material is injected into a mold to obtain a radial turbine rotor in which the maximum diameter of the blade 1 after burning is 90 mm, and the blade 1 is obtained. A 5 mm shaft hole 6 was drilled from the front surface 4 to the center using a carbide drill. Next, the temperature of the shaped body was raised to 500'C at a heating rate of 3°C/h, and the temperature was increased to 500'C.
The binder was removed by holding at 00'C for 10 hours. When the wing portion was observed after degreasing, no cracks were observed.

On the other hand, a raw material prepared by adding 2% polyvinyl alcohol to the mixture and thoroughly kneading the mixture was pressed into a die and then wasostatically compressed using a Lahar press to obtain a shaped body. Then, a shaft portion 2 whose tip was machined into a conical shape was manufactured using a lathe.

After smoothing the joint surface 7 of the obtained wing part 1 and shaft part 2 by lathe processing, a paste of SiC powder containing a sintering aid was applied to the joint surface to a thickness of 100 mm after firing. Apply,
After the wing part 1 and the shaft part 2 were brought into close contact, the entire body was covered with latex rubber, and a rubber press was performed at a pressure of 3 ton/cm2 to obtain a precept-shaped body in which the wing part 1 and the shaft part 2 were firmly joined and integrated. . Then, under normal pressure in an argon atmosphere,
It was burned at °C for 30 minutes. The shaft hole 6 in the front of the rear wing part 1
The center hole was precisely finished using a lathe to obtain the radial type ceramic rotor pin rotor shown in Fig. 1.

In order to perform a rotation test on the obtained ceramic turbine rotor, the unbalance of a part of the rotor was set to 0.02 g-cm, and then a metal product shaft was attached. This removes the increased unbalance and reduces the overall unbalance to 0.
The balance was adjusted so that the weight was 0.02 g-cm. Thereafter, a test was carried out using a rotation tester while gradually increasing the number of rotations, and the product did not break even at a number of rotations of 100.00 O rpm.

As described above, in the radial ceramic turbine rotor of the present invention, the blade portion and the shaft portion are fitted with substantially conical irregularities, and the shaft hole is provided from the front surface of the blade portion toward the tip of the shaft portion. We were able to prevent the crank from degreasing the parts, reduce joint failures between the wing parts and the shaft parts, and increase joint strength. Furthermore, the shaft hole on the front surface of the wing can be used as a center hole during machining of the final shape, improving work efficiency. As described above, the ceramic turbine rotor of the present invention can be manufactured much more efficiently than the conventional ceramic turbine rotor, and is extremely useful industrially.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an example of a radial ceramic turbine rotor of the present invention, and FIG. 2 is a sectional view of a conventional radial ceramic turbine rotor. 1... Wing part 2... Shaft part 3... Center part 4... Wing front face 5... Shaft tip 6... Shaft hole 7... Joint surface 8... Rotor central axis

Claims (1)

[Claims] 1. In a ceramic wing section and a ceramic shaft section that are joined through a substantially conical fitting hole provided in the wing section via a ceramic paste, the fitting is performed from the front surface of the wing section toward the tip of the shaft section. The taper is smaller than the matching hole, and
A radial ceramic turbine rotor characterized by having a shaft hole opened in the front surface of a blade part.