Compression Ring

A compression ring to be used in a spark-ignition engine using hydrogen gas fuel and to be fitted to a piston ring groove of a piston installed in a cylinder, wherein

• a substrate of the compression ring is high-alloy steel or low-alloy steel,
• a coating of the compression ring includes at least one selected from the group consisting of PVD coating, DLC coating, hard chrome plating coating, and nitride coating,
• an outer periphery shape of the compression ring is a barrel shape or an eccentric barrel shape,
• an abrasion value T of the outer periphery of the compression ring is less than or equal to 10, wherein the abrasion value T is determined by an abrasion resistance test performed with a reciprocating friction tester under abrasion resistance test conditions to evaluate an outer peripheral sliding surface of the compression ring,
• TW1 (μm) is an amount of abrasion of the outer peripheral sliding surface in the test with dropping of 1 mL/hour of a bearing oil and 0.5 mL/hour of distilled water,
• TO1 (μm) is an amount of abrasion of the outer peripheral sliding surface in the test with dropping of only 1 mL/hour of the bearing oil and no distilled water, and
• T
• ⁡
• (
• μm
• )
• =
• TW
• ⁢
• 1
• -
• TO
• ⁢
• 1
• ;
• A/T≥100 is satisfied, wherein A(HV0.1) is a surface Vickers hardness of the outer peripheral sliding surface;
• and
• an abrasion index M of the outer periphery of the compression ring is less than or equal to 0.09, wherein
• Ft (N) is defined as a tension of the compression ring, S13 (mm) is defined as a length in an axis direction of the outer peripheral sliding surface of the compression ring, and
• in a case where the piston is disposed so that the outer periphery of the compression ring abuts with a cylinder bore, D (mm) is defined as an inner diameter of the cylinder bore, a11 (mm) is defined as a distance in a radius direction between an upper connection point of the compression ring and an inner wall of the cylinder bore, a12 (mm) is defined as a distance in a radius direction between a lower connection point of the compression ring and the inner wall of the cylinder bore, and
• Fd
• =
• Ft
• /
• D
• ,
• head
• ⁢
• h
• =
• (
• a
• ⁢
• 11
• +
• a
• ⁢
• 12
• )
• /
• 2
• ,
• outer periphery inclination OSt=h/(S13/2), and
• the abrasion index M=T×Fd×Ost, wherein the abrasion resistance test conditions are as follows:
• Stroke:
• 50 mm
• Load:
• 100 N
• Speed:
• 600 cycles/min
• Temperature control of upper test piece:
• room temperature
• Temperature control of lower test piece:
• room temperature
• Bearing oil:
• Shell Tetra Oil 2SP, Shell Lubricants Japan K.K.
• Dropping conditions of bearing oil:
• dropping once every one minute and controlling the total amount of dropping to 1 mL/hour
• Dropping conditions of distilled water:
• dropping once every one minute and controlling the total amount of dropping to 0.5 mL/hour
• Test time:
• 60 minutes
• The test is performed after the trial run is performed under the following conditions.
• Load:
• 20 N
• Speed:
• 100 cycles/min
• Temperature of upper test piece before test:
• room temperature
• Temperature of lower test piece before test:
• room temperature
• Bearing oil:
• Shell Tetra Oil 2SP, Shell Lubricants Japan K.K.
• Dropping conditions of bearing oil:
• dropping once every one minute and controlling the total amount of dropping to 0.08 mL/5 min, and
• Test time:
• 5 minutes.