Abstract: An upper member of a steel piston has a chemical composition which consists of, in mass %, C: 0.15 to 0.30%, Si: 0.02 to 1.00%, Mn: 0.20 to 0.80%, P: 0.020% or less, S: 0.028% or less, Cr: 0.80 to 1.50%, Mo: 0.08 to 0.40%, V: 0.10 to 0.40%, Al: 0.005 to 0.060%, N: 0.0150% or less, O: 0.0030% or less, and the balance: Fe and impurities, and satisfies Formula (1) and Formula (2), in which, at a cross section parallel to the axial direction of the upper member, the number of Mn sulfides is 100.0 per mm2 or less, the number of coarse Mn sulfides having an equivalent circular diameter of 3.0 ?m or more is within a range of 1.0 to 10.0 per mm2, and the number of oxides is 15.0 per mm2 or less. 0.42?Mo+3V?1.50??(1) V/Mo?0.

Abstract: An upper member of a steel piston has a chemical composition which consists of, in mass %, C: 0.15 to 0.30%, Si: 0.02 to 1.00%, Mn: 0.20 to 0.80%, P: 0.020% or less, S: 0.028% or less, Cr: 0.80 to 1.50%, Mo: 0.08 to 0.40%, V: 0.10 to 0.40%, Al: 0.005 to 0.060%, N: 0.0150% or less, O: 0.0030% or less, and the balance: Fe and impurities, and satisfies Formula (1) and Formula (2), in which, at a cross section parallel to the axial direction of the upper member, the number of Mn sulfides is 100.0 per mm2 or less, the number of coarse Mn sulfides having an equivalent circular diameter of 3.0 ?m or more is within a range of 1.0 to 10.0 per mm2, and the number of oxides is 15.0 per mm2 or less. 0.42?Mo+3V?1.50??(1) V/Mo?0.

Abstract: Provided is a piston temperature state monitoring system for an internal combustion engine and a piston temperature monitoring method for an internal combustion engine which are capable of properly managing a history of a piston temperature. When the number of times of a piston temperature suppression control is counted, if a ratio of a temperature difference which is the difference between a maximum limit temperature and a piston temperature to a margin width which is the difference between the maximum limit temperature and a control start temperature is equal to or less than a count threshold ratio set in advance or calculated, a count output system outputs a count signal.

Abstract: Provided is a piston temperature state monitoring system for an internal combustion engine and a piston temperature monitoring method for an internal combustion engine which are capable of properly managing a history of a piston temperature. When the number of times of a piston temperature suppression control is counted, if a ratio of a temperature difference which is the difference between a maximum limit temperature and a piston temperature to a margin width which is the difference between the maximum limit temperature and a control start temperature is equal to or less than a count threshold ratio set in advance or calculated, a count output system outputs a count signal.

Abstract: There is provided a roof structure of a vehicular body. The roof structure includes right and left side roof rails disposed on opposing sides of the vehicular body. The roof structure further includes a plurality of roof reinforcements installed in a spaced-apart relationship between the side roof rails and extending along a lateral direction across the vehicular body and a roof panel attached to the roof reinforcements, wherein at least one roof reinforcement of the plurality of roof reinforcements is a first roof reinforcement having a maximum width portion wider than a closest relative spacing between the first roof reinforcement and an adjacent roof reinforcement of the plurality of roof reinforcements on a first side of the first roof reinforcement.

Abstract: There is provided a roof structure of a vehicular body. The roof structure includes right and left side roof rails disposed on opposing sides of the vehicular body. The roof structure further includes a plurality of roof reinforcements installed in a spaced-apart relationship between the side roof rails and extending along a lateral direction across the vehicular body and a roof panel attached to the roof reinforcements, wherein at least one roof reinforcement of the plurality of roof reinforcements is a first roof reinforcement having a maximum width portion wider than a closest relative spacing between the first roof reinforcement and an adjacent roof reinforcement of the plurality of roof reinforcements on a first side of the first roof reinforcement.