Valve train component for an internal combustion engine, and method of making same

Abstract

In order to provide a wear-resistant member which is excellent in wear resistance and pitting resistance, a valve train component is subjected to oxidation treatment to adjust its surface hardness to a preliminary value in a range between 550 and 800, followed by shot peening of at least a contact surface, to adjust the surface hardness to a value in a range between 800 and 1000. In a valve spring retainer, the contact surface is a seating surface against which a valve spring abuts. In a valve lifter, the contact surface is a sliding surface against which a cam lobe abuts. The components subject to the oxidation treatment are each made of a titanium alloy having an alloy composition including from 0.5 to 1.5 wt. % of Fe, from 0.2 to 0.5 wt. % of O and the balance of Ti and unavoidable impurities.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary longitudinal cross-sectional view of an internal combustion engine incorporating a valve spring retainer according to a selected illustrative embodiment of the present invention.

FIG. 2( a) is an enlarged longitudinal cross-sectional view of a valve spring retainer.

FIG. 2( b) is an enlarged longitudinal cross-sectional view of a valve lifter.

FIG. 3 is a cross-sectional view showing the composition of the surface of the base material of a titanium alloy subjected to oxidation treatment.

FIG. 4 is a schematic side view showing how to give shot peening treatment to a valve spring retainer.

FIG. 5 is a graph showing wear-resistance and pitting resistance as a function of the thickness of an α-case layer before shot peening treatment.

FIG. 6 is a graph showing the surface hardness of the base material and thickness of the α-case layer as a function of a coverage in shot peening treatment.

Claims

1. A wear-resistant valve train component member formed from a material comprising titanium, said valve train component member being a product of a process including steps of: case-hardening at least one surface of said member, designated as an abutting surface configured for abutting contact with another member, by oxidation treatment to adjust a surface hardness Hmv (load: 0.1 kg) of said surface to an oxidized value in a range between 550 and 800 Hmv;followed by shot peening said abutting surface to adjust the surface hardness Hmv (load: 0.1 kg) of said surface to a final value in a range between 800 and 1000 Hmv.

2. A wear-resistant valve train component according to claim 1, wherein the shot peening is performed using media having a particle size in a range from about 0.03 mm to about 0.1 mm.

3. A wear-resistant valve train component according to claim 1, wherein an α-case layer, having a thickness in a range from about 5 μm to about 20 μm, is formed by the oxidation treatment.

4. A wear-resistant valve train component according to claim 1, wherein the shot peening is carried out with a coverage of from 100 to 500%.

5. A wear-resistant valve train component member according to claim 1, wherein the member is made of a titanium alloy having, as an alloy composition, from 0.5 to 1.5 wt. % of Fe, from 0.2 to 0.5 wt. % of O and the balance of Ti and unavoidable impurities.

6. A wear-resistant valve train component member according to claim 1, wherein the member is a valve spring retainer having an abutting surface on which a valve spring abuts.

7. A wear-resistant valve train component member according to claim 1, wherein the member is a valve lifter having an abutting surface on which a cam lobe slides.

8. A wear-resistant valve train component member formed from a material comprising titanium, said valve train component member being a product of a process including steps of: case-hardening at least one surface of said member, designated as an abutting surface configured for abutting contact with another member, by oxidation treatment to adjust a surface hardness Hmv (load: 0.1 kg) of said surface to an oxidized value in a range between 550 and 800 Hmv;followed by shot peening said abutting surface to adjust the surface hardness Hmv (load: 0.1 kg) of said surface to a final value in a range between 800 and 1000 Hmv;wherein the shot peening is performed using media having a particle size in a range from about 0.03 mm to about 0.1 mm;and wherein an α-case layer, having a thickness in a range from about 5 μm to about 20 μm, is formed by the oxidation treatment.

9. A wear-resistant valve train component according to claim 8, wherein the shot peening is carried out with a coverage of from 100 to 500%.

10. A wear-resistant valve train component member according to claim 9, wherein the member is made of a titanium alloy having, as an alloy composition, from 0.5 to 1.5 wt. % of Fe, from 0.2 to 0.5 wt. % of O and the balance of Ti and unavoidable impurities.

11. A wear-resistant valve train component member according to claim 8, wherein the member is either a valve spring retainer or a valve lifter.

12. A method of case-hardening a valve train component member formed from a material comprising titanium, said method including the steps of: case-hardening at least one surface of said member, designated as an abutting surface configured for abutting contact with another member, by oxidation treatment to adjust a surface hardness Hmv (load: 0.1 kg) of said surface to an oxidized value in a range between 550 and 800 Hmv; an subsequently, shot peening said abutting surface to adjust the surface hardness Hmv (load: 0.1 kg) of said surface to a final value in a range between 800 and 1000 Hmv.

13. A method of case-hardening a valve train component member according to claim 12, wherein the shot peening is performed using media having a particle size in a range from about 0.03 mm to about 0.1 mm.

14. A method of case-hardening a valve train component member according to claim 12, wherein an α-case layer, having a thickness in a range from about 5 μm to about 20 μm, is formed by the oxidation treatment.

15. A method of case-hardening a valve train component member according to claim 12, wherein the shot peening is carried out with a coverage of from 100 to 500%.

16. A method of case-hardening a valve train component member according to claim 12, wherein the member is made of a titanium alloy having, as an alloy composition, from 0.5 to 1.5 wt. % of Fe, from 0.2 to 0.5 wt. % of O and the balance of Ti and unavoidable impurities.

17. A method of case-hardening a valve train component member according to claim 12, wherein the member is a valve spring retainer having an abutting surface on which a valve spring abuts.

18. A method of case-hardening a valve train component member according to claim 12, wherein the member is a valve lifter having an abutting surface on which a cam lobe slides.