JPH046678B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a semiconductor structural member and a metal joining member that are applied to joining a ceramic turbine wheel and a metal shaft in an exhaust turbocharger for an internal combustion engine. This relates to a method of joining with.

[Prior Art] The use of ceramic materials for turbine wheels exposed to high-temperature exhaust gas helps reduce the weight and improve the performance of turbochargers. However, since the ceramic material is hard and brittle, it lacks toughness against the load torque of the rotating shaft, and there is a risk of breakage.

For this reason, for example, as disclosed in Japanese Patent Application Laid-open No. 57-93606, a depression is provided on the outer peripheral surface of the boss portion of a turbine wheel made of ceramics, while a cylindrical portion formed at the end of the metal shaft is inserted into the boss portion. It has been proposed that the cylindrical part is fitted onto the outside of the cylindrical part, and the flesh part of the cylindrical part is welded to the recess of the boss part by energy-concentrated welding using an electron beam or laser from the outer circumferential side of the cylindrical part. Although this conventional technology is easy to process, the metal shaft is only locally welded to the recess of the boss, and there is a risk of cracking due to loosening or thermal stress due to the difference in thermal expansion coefficient between metal and ceramics. Not only that, but also during processing, if there is a misalignment between the recess in the boss portion that cannot be seen from the outside and the direction in which the beam is emitted, there is a risk that complete welding may not be achieved.

[Problems to be Solved by the Invention] Therefore, it is possible to avoid loosening or breakage of the fitting portion between the metal structural member and the ceramic structural member due to a difference in coefficient of thermal expansion, and furthermore, it is possible to prevent the fitting portion between the metal structural member and the ceramic structural member from loosening or breaking. A structure is required that allows both to be brought into close contact uniformly over the entire circumferential surface. Therefore, in the case of turbine wheels, ceramics and metals with respective characteristics are used for the turbine wheel, which requires heat resistance, and the rotating shaft, which requires wear resistance and toughness. If the two are joined using a metal joining member having substantially the same coefficient of thermal expansion, loosening or destruction of the fitted portion due to heat can be avoided.

However, when joining a metal structural member to a ceramic structural member, the metal joining member with excellent electrical conductivity is heated by a high-frequency heating coil, and the metal joining member whose hardness has decreased (softened) at high temperatures is deformed under pressure. It is necessary to bring the ceramic structural member and the metal structural member into close contact. According to such a joining method, since the metal joining member that is closely attached has been softened to a Vickers hardness of 150 or less, it flows along the ceramic structural member due to the pressing force, and the ceramic structural member and the metal joining member are almost the same body. It is closely attached in a state close to . However, although metal bonding members can be partially heated efficiently using high-frequency heating coils, when pressed by a press die, the contact between the metal bonding members, the die, and its receiving member becomes strong, and the amount of heat dissipated is reduced. The temperature of the metal bonding member decreases. When the temperature of the metal bonding member decreases, its hardness increases, and the fluidity of the metal bonding member due to pressing force deteriorates, resulting in a decrease in compression bonding properties.

The purpose of the present invention is to prevent the heated metal bonding member from losing heat due to the pressing die and causing a temperature drop, and to maintain the hardness sufficiently while keeping the hardness below a predetermined level. It is an object of the present invention to provide a method for joining a ceramic structural member and a metal joining member, which allows pressure bonding to the ceramic structural member over a long period of time.

[Means for Solving the Problems] In order to achieve the above object, the structure of the present invention covers both end faces of a metal bonding member having a coefficient of thermal expansion equivalent to that of ceramics with a heat insulating material, and the metal bonding member is made of ceramics. The metal bonding member is fitted into a structural member, the metal bonding member is heated, and both end faces are pressed to bring the metal bonding member into close contact with the structural member.

[Function] Heat dissipation from the metal bonding member 2 is improved by providing a heat insulating material formed by applying a coating such as potassium titanate with low thermal conductivity to the surface other than the pressure bonding surface of the metal bonding member 2 to be heat-pressed. can be suppressed. Therefore, the hardness of the metal bonding member is maintained below a predetermined level, and the metal bonding member can be pressed in the axial direction with a die for a sufficient amount of time to bring it into close contact with the ceramic structural member 1a and the metal structural member 3a.

[Examples of the Invention] The present invention will be described based on Examples. FIG. 1 is a side cross-sectional view showing a joining method in which the cylindrical portion 3a of the metal structural member 3 is fitted onto the shaft portion 1a of the ceramic structural member 1, and the metal joining member 2 is used to heat and press the cylindrical portion 3a. A hole 7 is provided in the end wall 8 of the metal structural member 3.
A cylindrical portion 3a having an inner diameter larger than that of the hole 7 is provided. The shaft portion 1a of the ceramic structural member 1 is fitted into the hole 7, and
An end wall 8 of the metal structural member 3 is superimposed on a support surface 9 that supports the shaft portion 1a of the ceramic structural member 1.

According to the present invention, the annular metal bonding member 2 is fitted into the gap between the cylindrical portion 3a and the shaft portion 1a, and thermocompression bonded by the method described below. This metal bonding member 2 has a coefficient of thermal expansion equivalent to that of ceramics.
For example, Kovar (nickel-cobalt alloy) is used. The inner circumferential surface of this metal bonding member 2 is thermocompression bonded to the shaft portion 1a, and the outer circumferential surface to the cylindrical portion 3a. A heat insulating material 4 is provided on both the upper and lower end surfaces. In practice, the heat insulating material 4 is formed by coating both end faces of the metal bonding member 2 with a coating made of potassium titanate or the like having a low thermal conductivity. Other materials with low thermal conductivity include cordierite and zirconia. Its thermal conductivity is that of potassium titanate.
0.000125 cal/cm・sec・℃, cordierite
0.002cal/cm・sec・℃, zirconia is 0.009cal/
cm・sec・℃, and 0.12cal/cm・sec・℃ of iron
This is extremely small compared to 0.039 cal/cm・sec・℃ for stainless steel.

A high frequency heating coil 5 is arranged around the outer periphery of the shaft portion 1a to heat the metal bonding member 2, and then the high frequency heating coil 5 is removed and a cylindrical die 6 is placed.
When pressed against the upper side of the metal bonding member 2, the heated and softened metal bonding member 2 is brought into close contact with the outer peripheral surface of the shaft portion 1a and the inner peripheral surface of the cylindrical portion 3a.

According to the high frequency heating coil 5, the metal joining member 2
and the cylindrical part 3a in contact with this is directly heated,
The shaft portion 1a made of ceramics is a metal joining member 2.
It is heated by heat conduction from. Therefore, there is little heat loss, and the metal bonding member 2 that requires heating can be heated efficiently. Since the heat insulating material 4 is provided on both the upper and lower end surfaces of the metal bonding member 2, heat release from these both end surfaces to the die 6 and the end wall 8 of the metal structural member 3 is suppressed, and the temperature drop in the metal bonding member 2 is suppressed. be able to. For example, if a current with a frequency of about 200 kHz is passed through the high-frequency heating coil 5, the metal bonding member 2 will be heated to nearly 800° C. in a few seconds.

The metal bonding member 2 softens when the temperature exceeds 600℃, and the temperature exceeds 700℃.
At temperatures above ℃, the hardness becomes below Hv60. Therefore, when the metal bonding member 2 is pressed with the die 6 in a thermally softened state, the metal bonding member 2 is crushed and brought into close contact with the outer circumferential surface of the shaft 1a and the inner circumferential surface of the cylindrical portion 3a.

In the case where the conventional metal bonding member 2 is not provided with the heat insulating material 4 on both end faces, as shown by the line 40 in FIG.
After heating, the temperature of the metal joining member 2 reaches approximately 800°C in a = 5 seconds, but the temperature of the metal joining member 2 reaches approximately 700°C by the time the high frequency heating coil 5 is removed and the die 6 is pressed against the metal joining member 2 (time b = 5 seconds). metal bonding member 2
The time for pressing the shaft portion 1a and the cylindrical portion 3a in a thermally softened state was only c = 2 seconds, and the temperature soon reached 600°C or less, making it difficult to sufficiently fluidize the metal bonding member 2. .

However, as in the present invention, by providing the heat insulating material 4 on both end faces of the metal bonding member 2, it is possible to suppress heat release from the metal bonding member 2 to the die 6 and the end wall 8. As shown by line 41, the metal bonding member 2 can be kept at 600°C or higher for several times longer than the conventional method (c ₁ = 6 seconds), thereby fluidizing the metal bonding member 2, The shaft portion 1a and the cylindrical portion 3a can be brought into close contact with each other completely.

FIG. 1 is a principle diagram illustrating the method of joining a ceramic structural member and a metal joining member of the present invention. For example, in the case of a turbine wheel, a shaft portion 1a is attached to the end of the turbine wheel made of ceramics. While integrally formed, a hollow shaft is used as the metal shaft, a cylindrical portion 3a is formed at the end of the shaft, and the shaft portion 1a and the cylindrical portion 3a are bonded by thermocompression using the metal bonding member 2, which can withstand high temperatures. The rotational force of the ceramic turbine wheel can be transmitted to the blower via the metal shaft.

[Effects of the Invention] According to the present invention, as described above, the surface of the metal bonding member 2 interposed between the ceramic structural member 1 and the metal structural member 3 that is remote from the thermocompression bonding surface, specifically the thermocompression bonding surface, Although it has a simple configuration with a pressing surface made of heat insulating material such as ceramics perpendicular to the surface, it can greatly suppress heat dissipation from the metal bonding members, and it can maintain the temperature required for thermocompression bonding using dies for a long time. The thermocompression bonding effect can be greatly improved.

In addition, the metal bonding member 2 is heated and softened and pressed to be uniformly adhered to the inner circumferential surface of the cylindrical portion 3a and the outer circumferential surface of the shaft portion 1a, and the bonding area is wide, so high bonding strength is obtained and heat resistant. It is stable and there is no risk of the joint becoming loose or breaking.

[Brief explanation of drawings]

FIG. 1 is a front cross-sectional view illustrating a method of joining a ceramic structural member and a metal bonding member that is applied to a general ceramic structural member according to the present invention, and FIG. 2 is a front sectional view of a ceramic structural member and a metal bonding member according to the present invention. FIG. 2 is a diagram comparing and comparing the effects of a method of joining a ceramic structural member and a metal joining member using a metal joining member without a heat insulating material. 1: Ceramic structural member, 2: Metal bonding member, 3: Metal structural member, 4: Heat insulating material.

Claims (1)

[Claims] 1. Covering both end faces of a metal joining member having a coefficient of thermal expansion equivalent to that of ceramics with a heat insulating material, fitting the metal joining member to a ceramic structural member, heating the metal joining member, and pressing both end faces. A method for joining a ceramic structural member and a metal joining member, the method comprising bringing the metal joining member into close contact with the structural member.