JPS6082267A - Joint structure between ceramic shaft and metallic shaft - Google Patents

Abstract

PURPOSE:To prevent deterioration in quality such as cracking or the like by forming the butt contact parts between a ceramic shaft and a metallic shaft to the diameter smaller than the finish diameter of the ceramic shaft thereby preventing thermal cracking of the ceramic shaft and eliminating oscillation in finishing by grinding. CONSTITUTION:The butt contact parts d2 and d4 between a ceramic shaft 27 and a metallic shaft 21 are made to the diameter smaller than the finish diameter d1 of the ceramic and are subjected to brazing 29 by heating. The generation of thermal stress cracking of the ceramics owing to a difference in the coefft. of expansion between both shafts is prevented. The much better result is obtd. if the end of the ceramics 27 is preliminarily chamfered in this stage. Since the ceramics 7 is a hardly machineable material, the margin for finish grinding is made as small as possible but even if the brazing material 29 has a wetting and oozing part 30 in the stage of grinding, said part does not contact with a grindstone and therefore the ceramic is finished without grinding oscillation and a crack, etc. are not induced. The deterioration in quality is thus obviated.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a joint structure between a ceramic shaft and a metal shaft, for example, a metal motor shaft in a stirrer of a chemical device and a ceramic shaft that holds a stirring tool. The present invention relates to a joining structure between a ceramic shaft and a metal shaft, which is applied to joining a metal impeller shaft and a ceramic turbine rotor shaft in a turbocharger, gas turbine, etc.

(Prior Art) Conventionally, as a structure in which a ceramic shaft and a metal shaft are joined, there is a structure shown in FIG. 1, for example. That is,
FIG. 1 is a sectional view showing an impeller and turbine assembly for a turbocharger (turbine supercharging a), in which a threaded portion 1a is formed at one end of a metal shaft 1, and a flange portion 1b is formed at the other end. and a thrust bearing collar 2 on the flange 1b side.
After inserting, fit the metal impeller 3 and the metal shaft 1, and tighten the nuts i and 5 to the male threaded part 1a of the metal shaft 1 through the washer 4 (= J and then the metal impeller 3 and metal shaft 1
The joint end of the metal shaft 1 and the joint end of the ceramic shaft 7 integrally molded with the ceramic turbine rotor 6 are butted against each other and are welded using a brazing filler metal 2. Note that 11 is an impeller side bearing, and 12 is a rotor side bearing.

In such joining of the metal shaft 1 and the ceramic shaft 7, the grindability of the ceramic shaft 7 is not as good as that of the metal shaft 1, so as shown in the EnZ diagram, the diameter of the metal shaft 1 is the diameter of the ceramic shaft 7. The brazing metal 2 is brazed to the metal shaft 2 in a state in which the metal shaft 1 is made slightly larger to the extent that it can be corrected in the subsequent finishing polishing process, and the brazing metal 2 is made to protrude to obtain high joint strength. By grinding a lot, the coaxiality of the ceramic shaft 7 and the metal shaft 1 can be achieved accurately, and after the final polishing, the diameter of the ceramic shaft 7, the metal shaft 1, and the brazing material 2 is made to be the same. Ta.

However, in such a conventional joining structure between the ceramic shaft 7 and the metal shaft 1, the diameter of the metal shaft 1 is made slightly larger than the diameter of the ceramic shaft 7, and the brazing material 2 is used to connect both shafts 1 and 7 at the joining part. After making it so that it protruded from the outer periphery, the parts of the metal shaft 1, brazing material 2 and ceramic shaft 7 were polished to the same diameter, and "Rou 4 = J Manual" 284 published by Kogaku Tosho Co., Ltd. As shown in the figure on page 1, it was common practice to join so that the brazing material protruded near the joint, so when finishing using a grindstone, the grinding wheel separates the metal part containing the brazing material and the ceramic part. There are cases where the metal part and the ceramic part are ground at the same time, and at this time, the grinding resistance generated between the metal part and the ceramic part is greatly different, and this causes vibrations that can cause the ceramic part to crack or crack. There was a problem. In addition, the brazing filler metal 2 protruding from the joint flows to the outer circumference of the ceramic shaft 7, and when this brazing filler metal 2 solidifies and shrinks, a force that strongly pulls the outer circumference of the ceramic shaft 7 in the axial direction acts, causing the vicinity of the joint to There was also a problem in that the ceramic shaft 7 was susceptible to cracks in the radial direction. The occurrence of such cracks is particularly undesirable for turbine rotor/impeller assemblies that rotate at high speeds.

(Purpose of the Invention) This invention has been made by focusing on the conventional problems as described above, and it is possible to obtain sufficient bonding strength and to improve bonding using brazing metal and grinding with a grindstone after brazing bonding. The purpose of the present invention is to provide a joining structure between a ceramic shaft and a metal shaft, which does not cause defects such as cracks or cracks in the ceramic shaft even when processed, and allows a joint with excellent strength and quality to be obtained.

(Structure of the Invention) The present invention provides a joining structure in which a ceramic shaft and a metal shaft are butted and brazed, in which at least the joint end of the ceramic shaft or the metal shaft, or both the ceramic shaft and the metal shaft is connected to the ceramic shaft. The ceramic shaft is characterized in that it is formed to have a smaller diameter than the finished shaft diameter and is provided with a brazing material reservoir, and the brazing material in the brazing material reservoir is kept on the inner diameter side of the finished shaft diameter of the ceramic shaft.

The ceramics constituting the ceramic shaft in this invention include SiC, Si3N4°S i3 N4 A
J1203 r Al2O'3, Z ro,.

Various types of ceramic materials are used, such as cermet materials that are a mixture of ceramics and metals, ceramic composite materials, etc., and are not necessarily limited to single ceramic materials.

Also, as for the metal that makes up the metal shaft, see A.

Elements or alloys of Mg, Fe, Cu, etc., or composite materials to which ceramics and the like are added are also used, and the material is not necessarily limited to single metals.

Of the ceramic shaft and the metal shaft, at least the joining end of the ceramic shaft or the metal shaft, or both the ceramic shaft and the metal shaft, is formed to have a smaller diameter than the finished shaft diameter of the ceramic shaft to form a brazing material pool. However, in this embodiment, for example, as shown in FIG. 3, the joining end of the ceramic shaft 27 is formed to have a smaller diameter d2 than the finished shaft diameter d of the ceramic shaft 27 to accommodate the brazing material 22. Depending on the manner in which the brazing material reservoir 30 is provided, or as shown in FIG.
In some embodiments, the brazing material pool 30 is formed to have a smaller diameter d4 than the diameter d4 of the brazing material 22, and as shown in FIG. Shaft 21 and ceramic shaft 27
Finished shaft diameter d+, d3 (d+=d3 in the example shown)
) There is a mode in which a brazing filler metal reservoir 30 is provided which is formed to have a smaller diameter d2+d4 than the brazing filler metal 22 therein.

In either embodiment, the brazing material 22 in the brazing material reservoir 30 is kept on the inner diameter side of the finished shaft diameter d1 of the ceramic shaft 27.
On the 1 side, the brazing filler metal 22 may protrude to the outer diameter side of the finished shaft diameter d3. In this case, the brazing filler metal 29 should be particularly kept on the inner diameter side of the finished shaft diameter d of the ceramic shaft 27. It is best to consider the heating conditions during brazing, the wettability of ceramics, the amount of brazing filler metal supplied, etc.
For example, the heating temperature should be 30 to 100°C higher than the melting point of the brazing material, and the heating rate should be as slow as possible to obtain a uniform temperature distribution of the brazing material, which will ensure a uniform flow of the brazing material during soldering. do it like this. Furthermore, in order to improve the wettability of the brazing filler metal, the ceramic shaft 27 may be subjected to an appropriate wettability improving treatment, such as an active metal treatment, or, conversely, a brazing filler metal penetration preventive agent may be used to prevent the brazing filler metal 22 during brazing. It is often done to control the flow,
In this way, the brazing material 22 within the brazing material reservoir 3° is kept on the inner diameter side of the finished shaft diameter d of the ceramic shaft 27.

After joining the ceramic shaft 27 and the metal shaft 21 with the brazing material 2.2 in this way, the finished shaft diameter d, d3
Using a grindstone, grind the ceramic shaft 27 and/or
Alternatively, the metal shaft 21 is finished by grinding. At this time, the ground surface of the ceramic shaft 27 having the diameter d1 is not in a speed ratio with the brazing material 22 on the joint end side, and is on the inner diameter side than the ground surface. Because of the tip of the brazing filler metal 22, it is possible to avoid the situation where the grindstone grinds the brazing filler metal 22 part, that is, the metal part and the ceramic part at the same time. This eliminates the need to polish the shaft 27, thereby avoiding vibrations caused by the difference in grinding resistance of the grinding wheel between the metal part and the ceramic part, and preventing defects such as cracks and fractures from occurring in the ceramic shaft 27. It is sufficient to perform finish polishing under grinding conditions that correspond to the metal part and the ceramic part respectively. Furthermore, even if the brazing filler metal 22 flows to the outer diameter side of the finished surface of the metal shaft 21, the metals will not touch each other during finish grinding. Since the grinding surface is concentrated, no vibration is generated in the grindstone, and a good grinding finish is possible.

In the cases shown in FIGS. 3 to 5 above, finish grinding is performed on both the ceramic shaft 27 and the metal shaft 21 after brazing, but in this invention, finish grinding is not necessarily performed on both. However, if the ceramic shaft 27 does not need to be finished polished, the brazing filler metal 22 flowing out from the butt-joint portion remains in the brazing filler metal pool 30 particularly at the ceramic shaft 27, and the ceramic shaft 27 The effect of the present invention can be obtained by preventing the metal from flowing out onto the outer circumferential surface of the metal shaft 21, and it is also possible to finish polishing the metal shaft 21 side to achieve coaxiality between the two shafts 21 and 27. This invention also includes such cases.

(Embodiment 1) FIG. 6 is a diagram showing Embodiment 1 of the present invention, and in FIG. 21 is a thrust bearing collar inserted into the flange 21b side, 23 is a metal impeller fitted to the metal shaft 21, 24 is a washer, 25 is a nut screwed into the male thread 21a of the metal shaft 21, and 26 is a ceramic. manufactured turbine rotor, 2
7 is a ceramic shaft integrally molded with the turbine rotor 26; 22 is a ceramic shaft 27 and a metal shaft 21 formed by a brazing wire 1;
The brazing materials to be joined, 31, an impeller side bearing, and 32, an a-side bearing, are of 4"h construction, almost the same as the impeller and turbine assembly shown in FIG.

In this case, the ceramic shaft 27 and gold Ji
For joining with the ff shaft 21, as shown in FIG. 7, the joining ends of both the ceramic shaft 27 and the metal shaft 21 are connected to a diameter smaller than the finished shaft diameter d5 of the ceramic shaft 27 and the metal shaft 21, respectively. d6 to form a brazing filler metal accumulation part 3
0, and after the ceramic shaft 27 and the metal shaft 21 are joined via the brazing material 22, the brazing material 22 in the brazing material reservoir 30 is placed on the inner diameter side of the finished shaft diameter ds of the ceramic shaft 27. Then, use a grindstone to finish the ceramic shaft 27 to a finished shaft diameter d5, and also remove the metal shaft 21 and, in some cases, the brazing material 2.
2 to the finished shaft diameter d5.

In this grinding and finishing, the brazing filler metal 22 remains on the inner diameter side of the ground finish surface of the ceramic shaft 27, so when finishing the grinding of the ceramic shaft 27, the brazing filler metal 22 is not ground at the same time, and the brazing filler metal 22 is not ground at the same time, but on the side of the ceramic shaft 27. The brazing filler metal 22 that has flowed remains unprocessed. On the other hand, the metal shaft 21
The brazing filler metal 22 flowing to the side does not need to stay on the inner diameter side of the ground surface of the metal shaft 21, and even if it flows to the outer diameter side of the ground surface, the grinding conditions of the grinding wheel for metal are similar. Since there is no large gap between the metal shaft 21 and the ceramic 2x, the brazing material 22 is ground at the same time as the metal shaft 21 is ground.
Grinding can also be carried out extremely well. Moreover, since the brazing material 22 cures and flows on the surfaces of the metal shaft 21 and the ceramic shaft 27, the surface of the brazing material 22 is solidified in a concave state.

In the case of Example 1, the entire ceramic shaft 27 is ground and finished, but only the bearings 31 and 32 are ground and finished, and the parts between the bearings 31 and 32 and between the bearings 32 and 32 are finished by grinding. The portion between it and the turbine rotor 26 may be left unpolished.

(Embodiment 2) FIG. 8 is a diagram showing Embodiment 2 of the present invention, and in this case also is a sectional view showing the impeller and turbine assembly of the turbocharger, and the parts corresponding to FIG. 6 are the same. The signs are i and j. In the case shown in FIG. 8, in order to improve the joint strength, the joint position is not restricted to the fitting between the bearings 31 and 32, that is, the rotor side bearing 32
This figure shows a case in which the butt joint is provided between the turbine rotor 26 and the butt joint 26 to enlarge the area of the butt joint. In this case as well, as shown in FIG. 7, as shown in FIG. Finished shaft diameter d7 of flange portion 21b
The brazing material reservoir 30 is formed to have a smaller diameter d8 than the diameter d8, and the solder in the brazing material reservoir 50 is formed after the ceramic shaft 27 and the metal shaft flange 21a are joined via the brazing material 2. The material 22 is attached to the ceramic shaft 27.
The finished shaft diameter d7 is kept on the inner diameter side, and then a grindstone is used to finish the finished shaft diameter d7.

Even when doing this, when finishing the ceramic shaft 27 by grinding, the brazing filler metal 22 remains on the inner diameter side of the ground surface, so the brazing filler metal 22 is not ground at the same time, and the ceramic shaft 27 Brazing filler metal 2 flowing to the side
2 remains unprocessed, and there is no possibility that abnormal vibrations will occur in the grinding wheel during grinding, causing defects such as cracks and cracks in the ceramic shaft 27. In addition, in this embodiment, since the metal shaft 21 is long, the shaft of the turbine/impeller assembly is made of a metal with excellent toughness, so it is resistant to vibrations etc. during high-speed rotation. This has the advantage of improving performance and making it possible to reduce the shaft diameter.

Note that the joint part is the metal shaft 21 and the ceramic shaft 27.
The four parts are formed by flowing according to the wettability of the brazing filler metal 29, so that the four parts can be used as an IR when the bearing lubricating oil is repelled by centrifugal force.Separate grooves are provided on the ceramic shaft. Processing can be omitted.

(Effects of the Invention) As described above, according to the present invention, in the joining structure in which the ceramic 611 and the metal shaft are butted and brazed, at least the joining end of the ceramic shaft or the metal shaft is connected to the ceramic shaft. The diameter of the ceramic shaft is smaller than that of the finished shaft, and the brazing material pool is provided, and the brazing material in the soldering material pool is kept on the inner diameter side of the finished shaft diameter of the ceramic shaft. The solder metal in the filler metal pool is fixed on the inner diameter side of the ceramic shaft, especially on the ceramic shaft side, compared to the finished shaft diameter of the ceramic shaft. The brazing filler metal solidifies on the outer circumferential surface of the ceramic shaft, and the shrinkage that occurs during solidification no longer causes problems such as cracks and cracks in the ceramic shaft. Even when grinding and finishing the joint part as necessary after joining, the metal part containing the brazing material and the ceramic part are not continuous, so the optimal grinding conditions for the metal part and/or the ceramic part, respectively. This makes it possible to grind and finish the metal part and the ceramic part separately, which eliminates the occurrence of abnormal vibrations in the grinding wheel that would occur in the case of grinding the metal part and the ceramic part at the same time, which was the case in the past. It has an extremely excellent effect in that it does not cause defects such as cracking or cracking.

It is possible to bond the ceramic shaft and the metal shaft extremely well.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view of a turbine rotor/impeller assembly for a turbocharger having a conventional joining structure of a ceramic shaft and a metal shaft, Fig. 2 is an enlarged explanatory view of the joining part in Fig. 1, and Figs. FIG. 5 is an enlarged explanatory view of a joint portion between a ceramic shaft and a metal shaft, showing an embodiment of the present invention;
FIG. 6 is a longitudinal cross-sectional view of a turbo rotor/impeller assembly for a turbocharger employing a joining structure of a ceramic shaft and a metal shaft according to Embodiment 1 of the present invention, and FIG. 7 is an enlarged explanatory view of the joining portion in FIG. 6. , FIG. 8 is a longitudinal cross-sectional view of a turbine rotor/impeller assembly for a turbocharger that employs a joining structure of a ceramic shaft and a metal shaft according to a second embodiment of the present invention, and FIG. 9 is an enlarged view of the joining portion of FIG. 8. It is an explanatory diagram. 21... Metal shaft, 27... Ceramic shaft, 22... Brazing metal, 30... Brazing metal accumulation part. Representative Patent Attorney Ko IM Figure 1 Figure 2 29 11611 7F! J

Claims (1)

[Claims] (1) In a joining structure in which a ceramic shaft and a metal shaft are butted and brazed, at least the joining end of the ceramic shaft or the metal shaft is formed to have a smaller diameter than the finished shaft diameter of the ceramic shaft to prevent a brazing material pool. A joining structure for a ceramic shaft and a metal shaft, characterized in that the brazing material in the brazing material reservoir is kept on the inner diameter side of the finished shaft diameter of the ceramic shaft.