Claims
- 1. In an internal combustion engine wherein a tubularly formed valve guide is formed with a bore for a metal valve shank said valve guide being encircled by a component embracing it in at least an area where it is exposed to exhaust gases, the improvement which comprises the valve guide being a sintered body consisting of partially stabilized zirconium oxide having a porosity less than 3%, and composed of up to 80 wt. % cubic modification, between 20 and 60 wt. % tetragonal modification, and up to 6 wt. % monoclinic modification, the sum of the amount of the various modifications being 100 wt. %, wherein the partially stabilized zirconium oxide has a homogenous structure and is formed by grains in the cubic modifications in which tetragonal precipitations are present.
- 2. The valve guide of claim 1 wherein the zirconium oxide is partially stabilized with one or more oxides selected from the group of magnesium, calcium, and yttrium.
- 3. The valve guide of claim 1 wherein the bore of the valve guide has a centerline average roughness R.sub.a of less than 1 micron.
- 4. The valve guide of claim 3 wherein the bore of the valve guide has a centerline average roughness R.sub.a of 0.03 to 0.1 micron.
- 5. The valve guide of claim 2 wherein the bore of the valve guide has a centerline average roughness R.sub.a of less than 1 micron.
- 6. The valve guide of claim 5 wherein the bore of the valve guide has a centerline average roughness R.sub.a of 0.03 to 0.1 micron.
- 7. The valve guide of claim 1 wherein the bending strength .sigma..sub.B of the partially stabilized zirconium oxide is at least 400 MPa.
- 8. The valve guide of claim 2 wherein the bending strength .sigma..sub.B of the partially stabilized zirconium oxide is at least 400 MPa.
- 9. The valve guide of claim 4 wherein the bending strength .sigma..sub.B of the partially stabilized zirconium oxide is at least 400 MPa.
- 10. The valve guide of claim 5 wherein the bending strength .sigma..sub.B of the partially stabilized zirconium oxide is at least 400 MPa.
- 11. The valve guide of claim 6 wherein the bending strength .sigma..sub.B of the partially stabilized zirconium oxide is at least 400 MPa.
- 12. In a valve guide for a blow-off valve of an exhaust gas turbocharger, the improvement which comprises the valve guide being a sintered body consisting of partially stabilized zirconium oxide having a porosity less than 3%, and composed of up to 80 wt. % cubic modification, between 20 and 60 wt. % tetragonal modification, and up to 6 wt. % monoclinic modification, the sum of the amounts of the various modifications being 100 wt. %, wherein the partially stabilized zirconium oxide has a homogenous structure and is formed by grains in the cubic modification in which tetragonal precipitations are present.
- 13. The valve guide of claim 12, wherein the zirconium oxide is partially stabilized with one or more oxides selected from the group of magnesium, calcium, and yttrium.
- 14. The valve guide of claim 12, wherein the bore of the valve guide has a centerline average roughness R.sub.a of less than 1 micron.
- 15. The valve guide of claim 14, wherein the bore of the valve guide has a centerline average roughness R.sub.a of 0.03 to 0.1 micron.
- 16. The valve guide of claim 13 wherein the bore of the valve guide has a centerline average roughness R.sub.a of less than 1 micron.
- 17. The valve guide of claim 16, wherein the bore of the valve guide has a centerline average roughness R.sub.a of 0.03 to 0.1 micron.
- 18. The valve guide of claim 12, wherein the bending strength .sigma..sub.B of the partially stabilized zirconium oxide is at least 400 MPa.
- 19. The valve guide of claim 13, wherein the bending strength .sigma..sub.B of the partially stabilized zirconium oxide is at least 400 MPa.
- 20. The valve guide of claim 15, wherein the bending strength .sigma..sub.B of the partially stabilized zirconium oxide is at least 400 MPa.
- 21. The valve guide of claim 16, wherein the bending strength .sigma..sub.B of the partially stabilized zirconium oxide is at least 400 MPa.
- 22. The valve guide of claim 17, wherein the bending strength .sigma..sub.B of the partially stabilized zirconium oxide is at least 400 MPa.
Priority Claims (1)
Number |
Date |
Country |
Kind |
3301912 |
Jan 1983 |
DEX |
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CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation-in-part of copending application Ser. No. 803,502, filed Nov. 27, 1985, and now abandoned, the contents of which are incorporated herein by reference, which, in turn, is a continuation of application Ser. No. 571,479, filed Jan. 17, 1984, now abandoned.
US Referenced Citations (4)
Foreign Referenced Citations (2)
Number |
Date |
Country |
78119 |
Jun 1980 |
JPX |
115804 |
Sep 1981 |
JPX |
Non-Patent Literature Citations (1)
Entry |
An Introduction to Zirconia by Dr. R. Stevens, Jun. 1983, pp. 11-17. |
Continuations (1)
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Number |
Date |
Country |
Parent |
571479 |
Jan 1984 |
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Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
803502 |
Nov 1985 |
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