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Piston rings maintain close contact with the cylinder walls through their own spring tension, carrying out such functions as sealing in combustion gases, carrying heat away from the pistons by thermal conduction, and controlling the thickness of the lubricating oil film on the cylinder wall.
They must perform these functions under the severe conditions that occur in combustion chambers, while also playing the important roles of preventing seizure and minimizing wear on cylinder liners. |
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| A piston ring must have both spring-like tension and the properties to become a true circle when closed. In the combustion chamber of engine, NPR’s piston rings serve to seal combustion gas, control lubricating oil, dissipate heat, and prevent wear and seizure under the severe conditions of operation. Now that engines are required to be more compact, lighter, and more sophisticated in performance, the choice of piston ring materials has been widened to include steel in addition to the traditional cast iron. Moreover, in order to enhance their wear resistance and durability, they also undergo various surface treatments including nitriding and PVD treatment. |
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1st ring:
Steel + Cr
2nd ring:
Cast iron
Oil ring:
Nifflex-S (3 piece type) |
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1st ring:
Steel + Cr
2nd ring:
Steel + Nitriding
Oil ring:
Nifflex-H (3 piece type) |
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1st ring:
Steel + PVD
2nd ring:
Cast iron
Oil ring:
2 piece type with high traceability + PVD |
In these environmentally aware times, progress is being made in the introduction of low-emission cars for NOX and HC reductions and in the control of fuel consumption for CO2 reduction. To achieve these purposes, the following techniques have been developed and incorporated in the design of piston rings.
- Piston ring combination for low-friction
- Thinner width compression-and oil control rings
- Advanced surface treatments, and high-durability, low-cost materials
- Optimum design through tuning techniques |
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For passenger car diesel engines |
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For middle/large vehicle diesel engines (3 ring pack) |
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For large vehicle diesel engines (4 ring pack) |
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This is a ring set to meet high speed use and high durability. Steel material is adopted on 1st ring and 2 piece oil ring. Nitriding or PVD treatment is made on 1st ring and oil ring. |
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This is a set of all steel piston rings to meet the high output and emission regulation.
For the 1st (2nd) rings, keystone shape for prevention of sticking are approved, and PVD treatment is made so as to enhance wear resistance and scuffing resistance.
Narrow width and weight reduction enabled with production by steel. |
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For two-stroke motorcycle engines/For four-stroke motorcycle engines
Steel ring pack for high speed engines: Both of Compression/Oil rings are made of steel. Oil ring is NX95F type applicable for ultra thinning design. |
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A chromium plated cast iron 1st ring of proven stability is included along with a chromium plated cast iron two piece oil ring or a steel 3 piece oil ring(Nifflex-S). |
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For development of rotary engines utilized in 1960’s, we participated in seal parts related development from the beginning. We contributed to utilization.
Consist of keystone type Side seals, Cut-off seals with shape of piston ring & Oil sealing rings with true round shape. |
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NPR’s Marine Piston Rings developed along with Japan’s shipbuilding industry.
It’s high performance of UBALLOY®, TARKALLOY® etc. have been world standard.
Various surface modification, which guarantee further upgrade function is also applicable. |
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| Located within the cylinder block, the inside of the cylinder liner constitutes the combustion chamber of the engine. There are a variety of liners, including wet liners whose external circumference is directly exposed to cooling water, dry liners which are fitted into machined cylinder blocks, and aluminum cast-in liners whose inner periphery is machined after being cast into aluminum blocks. |
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As with piston rings, the development of cylinder liners is now being pursued through liner-piston ring combination techniques in order to meet the CO2, NOX, PM, and other emission control standards as well as the requirement for higher fuel efficiency (reduction in weight). |
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NPR products are authorized as genuine parts by clearing the severe quality standard in the domestic and foreign many automakers.
The excellent quality acquires high reliability as NPR brand in the worldwide countries. |
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