JPS60206542A - Method of joining metallic shaft to shaft of rotary body made of ceramics - Google Patents

Abstract

PURPOSE:To contact a metallic sleeve closely to the shaft of a rotary body and join them easily and at low cost by inserting the metallic sleeve externally to the shaft of the rotary body and after softening the metallic sleeve by heating, deforming it by pressing. CONSTITUTION:An impeller 6 made of ceramic having a short shaft part 4 formed in a body is placed on a base stand 13, and a metallic sleeve 5 a little longer than a shaft part 14 having the same coefficient of thermal expansion as the ceramic is inserted externally to the shaft part 4 keeping clearance of 20- 100mu to the shaft part 4. Current is applied to a heating coil 3 enclosing the metallic sleeve 5 from a high frequency power source 2, and the metallic sleeve 5 is softened by heating to about 600 deg.C. Then, a cylindrical lower die 8 enclosing the metallic sleeve 5 is placed on the impeller 6, and axial load is applied to the metallic sleeve 5 from above by an upper die 7. Thus, the metallic sleeve 5 is squeezed between the shaft part 4 and lower die 8, and fitted firmly to the shaft part 4. A cylindrical part 9 is provided in the upper die 7 to avoid striking of the upper die 7 on the shaft part 4.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for joining a metal shaft to a shaft of a rotating body made of ceramics, which is applied to a blade wheel of an exhaust turbocharger for an internal combustion engine.

Simply using ceramic materials for the blades, which are exposed to high-temperature exhaust air, will help reduce the weight and improve the performance of turbochargers. but,
Ceramic materials are hard and brittle, so they lack toughness against the load torque of the rotating shaft and may break. For this purpose, for example, as shown in Japanese Utility Model Application Publication No. 58-48701, a metal shaft is inserted and supported through a ceramic impeller, and a metal ring is shrink-fitted to both the metal shaft and the boss of the impeller. Things are being suggested. However, shrink-fitting the metal ring is extremely time-consuming, making mass production difficult and expensive, and there is also a risk that the metal ring may loosen due to heat from the blade wheel exposed to high-temperature gas.

In addition, by creating a minute gap between the ceramic and the metal,
Other known methods include a metallization method in which silver solder or the like is filled in this gap, and a method in which a ceramic material is press-fitted into a metal fitting hole. However, the metallization method does not provide sufficient bonding strength, and the strength decreases particularly at high temperatures. Furthermore, in the ceramic material press-fitting method, the press-fitted portion may loosen because the thermal expansion coefficients of metal and ceramic are different.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for joining a metal shaft to a shaft of a rotating body made of ceramics, which can be easily put into practical use with simple equipment and mass-produced at low cost.

For this reason, the configuration of the present invention is such that a metal sleeve having a slightly longer length than the shaft (having almost the same coefficient of thermal expansion as the ceramic) is fitted onto the shaft of a rotating body made of ceramics, the metal sleeve is heated and softened, and the metal sleeve is heated and softened. The shaft portion and the metal sleeve are inserted into a cylindrical lower mold, and the upper mold is pressed against the edge of the metal sleeve to deform it, thereby bringing the metal sleeve into close contact with the shaft portion.

In the present invention, a shaft portion is provided on a blade wheel made of ceramics such as silicon nitride or silicon carbide, a metal sleeve having a coefficient of thermal expansion approximately equal to that of the ceramic is fitted onto this shaft portion, and the metal sleeve is fitted into a lower press die. Then, it is heated and softened using a high-frequency heating coil.

The metal sleeve is pressurized and deformed by a press upper die to press the metal sleeve against the shaft of the impeller. Since the metal sleeve is heated and softened, it smoothly bites into the groove of the ceramic shaft portion and is tightly fitted without causing tissue destruction of the bonding surface of the ceramic. The pressurized state by the upper die is maintained until the temperature of the metal sleeve drops to about 200°C. In this way,
A metal shaft is joined to the end surface of a metal sleeve, which serves as a metal shaft joined to a ceramic shaft, by tacking or friction bonding.

The present invention will be described based on an embodiment. As shown in FIG. 1, a short shaft portion 4 is integrally formed with a blade wheel 6 made of ceramics, and the blade wheel 6 is placed on a base 13. Then, a metal sleeve 5 made of a metal having a coefficient of thermal expansion equivalent to that of ceramics, for example, nickel-chromium steel called Kovar, is inserted into the shaft portion 4 with a gap of about 20 to 100 μm, as shown in FIG. As shown in FIG. 2, the heating coil 3 surrounding the metal sleeve 5 is energized from the high frequency power source 2 to a predetermined temperature of approximately 60°C.
The metal sleeve 5 is softened by heating to 0°C.

Next, as shown in FIG. 3, a cylindrical lower mold 8 surrounding the metal sleeve 5 is placed on the impeller 6, and an axial load is applied to the metal sleeve 5 by the upper mold 7. As a result, the metal sleeve 5 is crushed between the shaft portion 4 and the lower die 8, and is firmly fitted to the shaft portion 4. In this case, the metal sleeve 5 is slightly longer than the shaft portion 4,
Further, as shown in FIG. 3, a cylindrical portion 9 is provided on the upper mold 7 so that the shaft portion 4 does not come into contact with it.

Furthermore, in order to obtain a tight fit between the shaft part 4 and the metal sleeve 5, as shown in FIG. Leave some space between them. It is important that the groove 10 of the shaft portion 4 has a shape that prevents the ceramic structure from being destroyed by the sliding force of the metal sleeve 5. Specifically, the depth of the groove 10 is set to 0.3 to 0.5IIllI11. It is preferable that the inclination angle of the side wall is 15 to 30 degrees. The heating and softening of the metal sleeve 5 causes the metal to flow during press molding, preventing destruction of the metal surface and providing sufficient bonding strength.

According to the present invention, the metal sleeve 5 which has been heated and softened as described above is crushed and brought into close contact with the groove 10 of the shaft portion 4, so that the metal sleeve 5 is formed against the shaft portion 4 of the impeller 6. The shaft portion is integrally joined.

According to this method, since only a compressive load is applied to the shaft portion 4 of the impeller 6, a tight fit can be obtained without fear of cracking, and the coefficient of thermal expansion is almost the same as that of ceramics even under temperature changes. Since the nickel-chromium steel having the same properties as above is used, sufficient strength can be obtained for the rotation of the impeller 6 from 1 to 1 lb. Then, by joining a metal shaft to the end face of the metal sleeve 5 by friction welding or the like, the turbine wheel and the blower wheel can be connected to form an exhaust turbo supercharger.

As described above, in the present invention, the metal sleeve 5 made of nickel-chromium steel, which has a coefficient of thermal expansion almost equal to that of ceramics, is closely joined to the shaft portion 4 of the impeller 6 made of ceramics by press working. , the blade wheel 6 and the metal shaft can be efficiently connected using general mechanical equipment,
It is easy to reduce costs through mass production.

[Brief explanation of the drawing]

Figures 1, 2 and 3 are side sectional views showing steps for achieving the method of joining a metal shaft to the shaft of a ceramic rotating body according to the present invention, and Figure 4 is a ceramic rotating body. FIG. 3: Heating coil 4: Shaft 5 Metal sleeve 6: Impeller 7: Upper mold 8: Lower mold Patent applicant Isuzu Motors Co., Ltd. Agent Patent attorney Toshio Yamamoto fil Figure 3

Claims (1)

[Claims] A metal sleeve that is slightly longer than the shaft and has almost the same coefficient of thermal expansion as the ceramic is fitted onto the shaft of a rotating body made of ceramic, and the metal sleeve is heated and softened to form the shaft and the metal sleeve into a cylindrical shape. A metal shaft relative to the shaft of a ceramic rotating body, wherein the metal shaft is inserted into a lower mold of the ceramic rotating body, and is deformed by pressing an upper mold against an edge of the metal sleeve to bring the metal sleeve into close contact with the shaft. joining method.