Method for manufacturing magnetostrictive torque sensor shaft
AssigneeProterial, Ltd.
InventorTeruyuki Nakamura
Life of this patent
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Abstract
Provided is a method for manufacturing a magnetostrictive torque sensor shaft mounting a sensor portion of a magnetostrictive torque sensor. The method includes conducting heat treatment on a shaft material including chrome steel or chrome-molybdenum steel by carburizing, quenching and tempering, and conducting shot peening on the shaft material after the heat treatment at least on a position where the sensor portion is to be mounted. The shot peening is conducted by firing shot with a particle size of not less than 0.6 mm and a Rockwell hardness of not less than 60 at a jet pressure of not less than 0.4 MPa for a jet exposure time of not less than 2 minutes.
Claims20
A method for manufacturing a magnetostrictive torque sensor shaft mounting a sensor portion of a magnetostrictive torque sensor, the method consisting of:
- conducting heat treatment on a shaft material comprising chrome steel or chrome-molybdenum steel by carburizing for one time, quenching, and tempering for plural times such that the surface of the shaft material includes both austenite and martensite;
- and
- conducting shot peening on the shaft material after the heat treatment at least on a continuous surface where the sensor portion is to be mounted,
- wherein the shot peening is conducted by firing shot with a particle size of not less than 0.6 mm and not more than 0.8 mm and a Rockwell hardness of not less than 60 at a jet pressure of not less than 0.4 MPa and not more than 0.6 MPa for a jet exposure time of not less than 2 minutes only once such that further martensitic transformation occurs on the shaft material, such that peak values of martensite in the shaft material having a Miller index of 200 and martensite having a Miller index of 211, respectively, are not less than 1.15 times peak values of martensite in the shaft material with a Miller index of 200 and martensite having a Miller index of 211, respectively, before conducting shot peening, such that sensitivity of the resulting magnetostrictive torque sensor is not less than 4 mV/Nm,
- wherein hysteresis error of the magnetostrictive torque sensor is not more than 3% FS in a range of not less than −40° C. and not more than 150° C., and
- wherein the hardness of the shaft material after the heat treatment step is an HRC of not less than 59 and not more than 62, and
- wherein the shaft surface after the shot peening step has a surface roughness Ra of not more than 0.2 μm.
A method for manufacturing a magnetostrictive torque sensor shaft mounting a sensor portion of a magnetostrictive torque sensor, the method consisting of:
- conducting heat treatment on a shaft material comprising chrome steel or chrome-molybdenum steel by carburizing for one time, quenching, and tempering for plural times such that the surface of the shaft material includes both austenite and martensite;
- and
- conducting shot peening on the shaft material after the heat treatment at least on a continuous surface where the sensor portion is to be mounted,
- wherein the shot peening is conducted by firing shot with a particle size of not less than 0.6 mm and not more than 0.8 mm and a Rockwell hardness of not less than 60 at a jet pressure of not less than 0.4 MPa and not more than 0.6 MPa for a jet exposure time of not less than 2 minutes only once such that further martensitic transformation occurs on the shaft material,
- wherein the shot peening is conducted until a peak value of martensite in the shaft material with a Miller index of (200) is greater than a peak value of austenite in the shaft material with a Miller index of (200),
- wherein before the shot peening is conducted, the peak value of martensite in the shaft material with a Miller index of (200) is smaller than the peak value of austenite in the shaft material with a Miller index of (200),
- wherein peak values of martensite in the shaft material with a Miller index of (200) after conducting shot peening and martensite in the shaft material with a Miller index of (211) after conducting shot peening are not less than 1.15 times peak values of martensite in the shaft material with a Miller index of (200) and martensite in the shaft material with a Miller index of (211) before conducting shot peening, such that sensitivity of the resulting magnetostrictive torque sensor is not less than 4 mV/Nm,
- wherein hysteresis error of the magnetostrictive torque sensor is not more than 3% FS in a range of not less than −40° C. and not more than 150° C.,
- wherein the hardness of the shaft material after the heat treatment step is an HRC of not less than 59 and not more than 62, and
- wherein the shaft surface after the shot peening step has a surface roughness Ra of not more than 0.2 μm.
Dependencies are inferred from the claim text.