Friction design method and surface roughness control method for sliding member and production method for sliding mechanism
Provided is a friction design method capable of estimating sliding friction generated between mutual sliding surfaces of two sliding members lubricated with lubricant with high precision. The friction design method sets a friction coefficient μ in a sliding surface model corresponding to mutual sliding surfaces of two sliding members ( 2 and 3 ) lubricated with lubricant (step S 1 ), and, based on a correlation between the friction coefficient μ and an oil film parameter (Λ(Rk) or Λ(Rk+Rpk)) calculated using a core portion level difference (Rk) or a sum of the core portion level difference (Rk) and reduced peak height (Rpk) as a parameter representing surface roughness in the sliding surface model (step S 2 ), sets a target value for surface roughness of the sliding surfaces required to be controlled as a product (steps S 3 to S 6 ).
1. A process of making a sliding member comprising
acquiring a correlation between a friction coefficient and an oil film parameter using a mechanical sliding surface model comprising two sliding members having mutual sliding surfaces lubricated with lubricant;
calculating a composite roughness using a core portion level difference or a sum of the core portion level difference and reduced peak height;
calculating the oil film parameter by dividing an estimated or measured oil film thickness of lubricant between the mutual sliding surfaces of the two sliding members by the composite roughness;
setting a target value for surface roughness of the mutual sliding surfaces of one or more of the two sliding members required to be controlled from the composite roughness; and
processing one or more of the two sliding members to have a surface roughness satisfying the target value.
2. The process of claim 1 further comprising:
calculating a target oil film parameter value corresponding to the target value from the correlation between the friction coefficient and the oil film parameter; and
setting a target value for a core portion level difference of surface roughness of the sliding surface required to be controlled or a target value for a sum of a core portion level difference and reduced peak height of surface roughness of the sliding surface required to be controlled.
3. The process
of claim 2 , further comprising:
setting a target value for a core portion level difference of surface roughness of the sliding surface required to be controlled or a target value for a sum of a core portion level difference and reduced peak height of surface roughness of the sliding surface as an acceptance criterion of a surface of the sliding member.
4. The process of claim 3 , further comprising:
processing the sliding surface based on whether or not a value Svr representing a ratio of a valley portion within surface unevenness of the sliding surface satisfies a formula below:
Svr≤a predetermined value.
5. A production method for a producing sliding mechanism having sliding members with a lubricate disposed between sliding surfaces of the sliding members, comprising:
producing the sliding mechanism, using the process of claim 3 .
6. The process of claim 2 , wherein
the core portion level difference and the reduced peak height are two-dimensional roughness parameters (Rk and Rpk).
7. The process of claim 6 , further comprising:
setting a target value for a core portion level difference of surface roughness of the sliding surface required to be controlled or a target value for a sum of a core portion level difference and reduced peak height of surface roughness of the sliding surface as an acceptance criterion of a surface of the sliding member.
8. The process of claim 7 , further comprising:
processing the sliding surface based on whether or not a value Svr representing a ratio of a valley portion within surface unevenness of the sliding surface satisfies a formula below:
Svr≤a predetermined value.
9. The process of claim 1 , wherein
the core portion level difference and the reduced peak height are two-dimensional roughness parameters (Rk and Rpk).
10. The process of claim 1 , wherein
the core portion level difference and the reduced peak height are three-dimensional roughness parameters (Sk and Spk).
11. The process of claim 1 , further comprising:
setting a target value for a core portion level difference of surface roughness of the sliding surface required to be controlled or a target value for a sum of a core portion level difference and reduced peak height of surface roughness of the sliding surface as an acceptance criterion of a surface of the sliding member.
12. The process of claim 11 , further comprising:
processing the sliding surface based on whether or not a value Svr representing a ratio of a valley portion within surface unevenness of the sliding surface satisfies a formula below:
Svr≤a predetermined value.
13. The process of claim 12 , wherein
the ratio Svr of a valley portion within surface unevenness is calculated from 100-Mr2 or 100-Rmr, wherein
Mr2 and Rmr are two-dimensional roughness parameters,
Mr2 is a material ratio of a core portion of the sliding surface required to be controlled,
Rmr is a relative material ratio of the sliding surface required to be controlled, and
the formula defines a range in which a deviation amount Δμ from a reference is equal to or less than a certain value.
14. The process of claim 12 , wherein
the ratio Svr of a valley portion within surface unevenness is calculated from 100-Smr2 or 100-Smr,
Smr2 and Smr are three-dimensional roughness parameters,
Smr2 is an areal material ratio of a core portion of the sliding surface required to be controlled,
Smr is a relative areal material ratio of the sliding surface required to be controlled, and
the formula defines a range in which a deviation amount Δμ from a reference is equal to or less than a certain value.
15. A production method for producing a sliding mechanism having sliding members with a lubricant disposed between sliding surfaces of the sliding members, comprising:
producing the sliding mechanism using the process of claim 11 to make the sliding members.
16. The production method for the sliding mechanism of claim 15 , wherein the sliding members are one of:
constituent elements of a rolling bearing,
constituent elements of a sliding bearing, or
constituent elements of a ball screw.
17. The production method for the sliding mechanism of claim 16 , wherein
the sliding members comprise a roller head portion and a large flange portion of a tapered roller bearing; and the production method further comprises:
controlling the surface roughness between mutual facing surfaces of the roller head portion and the large flange portion to be Rk, or Rk+Rpk or less.
18. The production method for the sliding mechanism of claim 17 , further comprising:
processing surface roughness of a sliding surface of the roller head portion using Rk+Rpk as a parameter; and
processing surface roughness of a sliding surface of the large flange portion using Rk as a parameter.
19. The process of claim 11 , further comprising:
measuring friction under a rolling-sliding condition using the mechanical sliding surface model, the model comprising:
a ball, and
a groove; and
based on a result of the measurement, controlling a groove area ratio of the groove to a predetermined value or less in such a way as to satisfy a control condition for a desired surface roughness.
20. The process of claim 19 , wherein
the groove comprises parallel grooves.