Piston ring
Horizontal steam engine. The piston is shown at D. The three piston rings prevent steam from
escaping between chambers A and B.Piston ring. The piston ring (PR) is a split band presd against the wall of the cylinder by springs (S) mounted in the inner "junk ring" (JR). The tongue (T) maintains the al as the ring expands
and splits apart.
Spring-loaded piston rings.
A piston ring is a split ring that fits into a groove on the outer diameter
of a piston in a reciprocating engine such as an internal combustion
engine or steam engine.
The three main functions of piston rings in reciprocating engines are :
1.Sealing the combustion chamber so that there is no transfer of gas
from the combustion chamber to the crank.
2.Supporting heat transfer from the piston to the cylinder wall.
3.Regulating engine oil consumption.
The gap in the piston ring compress to a few thousandths of an inch
when inside the cylinder bore.History
The split piston ring was invented by John Ramsbottom who reported
果茶的做法
the benefits to the Institution of Mechanical Engineers in 1854. It soon
replaced the hemp packing hitherto ud in steam engines. The u of
piston rings at once dramatically reduced the frictional resistance, the
leakage of steam, and the mass of the piston, leading to significant
increas in power and efficiency and longer maintenance intervals.
Piston Ring [1]==Automotive== Piston rings have been an area of
犯人在跳舞considerable focus and development for internal combustion engines.
The needs of diel engines and small piston-ported two-stroke engines
have been particularly difficult. Piston rings may account for a
considerable proportion of the total friction in the engine, as much as
24%.[2] This high friction is a result of the design compromis needed
to achieve good aling, long lifetime and low friction. Sealing is
achieved by multiple rings, each with their own function, using a
metal-on-metal sliding contact.
Rings are also sprung to increa this contact force and maintain a
clo al, either by the stiffness of the ring itlf or by a parate
spring behind the al ring. It is important that rings float freely in their
grooves within the piston, so that they can stay in contact with the
cylinder. Rings binding in the piston, usually due to a build-up of
either combustion products or a breakdown of the lubricating oil is a
common cau of failure, especially for diel engines.
Lubrication of piston rings is difficult and has been a driving force to
improvements in the quality of motor oil. The oil must survive high
temperatures and harsh conditions with a high-speed sliding contact.
Lubrication is particularly difficult as the rings have an oscillating
motion rather than continuous rotation, as for a bearing journal. At the
瑕疵是什么意思limits of piston movement, the ring stops and revers direction. This
A pair of piston rings mounted on a 47mm
李宁运动
two-stroke cycle scooter piston.
disrupts the normal oil wedge effect of a hydrodynamic bearing,
leading to pronounced wear and the formation of a 'step' in the cylinder
bore around the height of the upper ring. Noting that some sleeve valve
中选engines suffered far less from such wear, complex designs such as a
rotating cylinder liner have been considered, just to address this
problem.聊天聊什么话题好
Most automotive pistons have three rings: The top two while also
controlling oil are primarily for compression aling (compression
rings); the lower ring is for controlling the supply of oil to the liner which lubricates the piston skirt and the compression rings (oil control rings). At least two piston rings are found on most piston and cylinder combination.Typical compression ring designs will have an esntially rectangular cross c
tion or a keystone (right angled trapezoidal) cross ction. The periphery will then have either a barrel profile (top compression rings) or a taper napier form (cond compression rings or scraper rings). There are some taper faced top rings and on some old engines simple plain faced rings were ud.
Oil control rings typically are of three types:
1.single piece cast iron
2.helical spring backed cast iron or steel
3.multipiece steel
The spring backed oil rings and the cast iron oil rings have esntially the same range of peripheral forms which consist of two scraping lands of various detailed form. The multipiece oil control rings usually consist of two rails or gments (the are thin steel rings) with a spacer expander spring which keeps the two rails apart and provides the radial load.
The piston might be a fairly loo fit in the cylinder. If it were a tight fit, it would expand as it got hot and might stick tight in the cylinder. If a piston sticks (izes) it could cau rious damage to the e
ngine. On the other hand, if there is too much clearance between the piston and cylinder walls, much of the pressure from the burning gasoline vapour will leak past the piston (a condition known as blow-by) and into the crankca, and the push on the piston from combustion will be much less effective in delivering power.Wear due to ring load on the bore
Piston rings are subject to wear as they move up and down the cylinder bore due to their own inherent load and due to the gas load acting on the ring. To minimize this, they are made of wear-resistant materials, such as cast iron and steel, and are coated or treated to enhance the wear resistance. Two-stroke port design is critical to ring life. Newer modern motorcycle manufacturers have many single function but rrated ports to retain the ring. Typically, top ring and oil control rings will be coated with chromium, or Nitrided, possibly plasma sprayed or have a PVD (physical vapour deposition) ceramic coating. For enhanced scuff resistance and further improved wear, most modern diel engines have top rings coated with a modified chromium coating known as CKS or GDC, a patent coating from Goetze which has aluminium oxide or diamond particles respectively included in the chrome surface. The lower oil control ring is designed to leave a lubricating oil film, a few micrometres thick on the bore, as the piston descends.Three piece oil rings, i.e. with two rails and one spacer, are ud for four-stroke gasoline engines.
Fitting new piston rings
When fitting new piston rings or breaking them in within an engine, the end gap is a crucial measurement. In order that a ring may be fitted into the "grooves" of the piston, it is not continuous but is broken at one point on its circumference. The ring gap may be checked by putting the ring into the bore/liner (squared to bore) and measuring with a feeler gauge. End gap should be within recommended limits for size of bore and intended "load" of engine. Metals expand with a ri in temperature, so too small a gap may result in overlapping or bending when ud under hot running conditions (racing, heavy loads, towing) and, even at normal temperatures, a small ring gap may lead to ring gap closure, ring breakage, bore damage and possible izure of the piston. Too large a gap may give unacceptable compression and levels of blow-by gas or oil consumption. When being measured in a ud bore, it may indicate excessive bore wear or ring wear. (Radial wear on ring face reduces thickness of ud/worn ring (face wear in bore) esntially decreasing face circumference of ring and thereby increasing size of ring end gap.)
It is considered good practice to build a new engine with the ring gaps staggered around the circumference of the bore. This means that any escaping gas must negotiate a labyrinth before escaping past the rings. However, while the engine is running, the rings will tend to rotate around the
环境污染的原因
piston and not remain in the position as fitted. Many rings will then stick in one spot at random and remain there for the life of the engine. For this reason, ring position during build cannot be considered to be important although most engine builders would feel uncomfortable asmbling an engine with the gaps aligned.
When fitting new rings to a ud engine, special "ridge dodger" rings are sometimes ud for the top compression ring, to improve compression and oil consumption without reboring the cylinder. The have a small step of iron removed from the top ction to avoid making contact with any wear ridge at the top of the cylinder, which could break a conventional ring. The are not widely recommended, however, as they are usually not required and may give inferior oil consumption. A more acceptable method is to remove the wear ridge with a "ridge reamer" tool before lightly honing the bore to accept new rings. In fact, if the "ridge " is measured it will generally be apparent it is not really a ridge but a relatively local hollow caud by the top ring near the ring reversal point. The upper edge of this hollow will take the form of a "ramp" about 2mm long from the point of maximum wear to the point of zero wear. In this ca, there is not actually any ridge to hit, so light honing may be all that is required.
During engine asmbly, a piston-ring compressor is ud to evenly squeeze the rings long enough t
o slide the piston into the cylinder.
Rings are not a very expensive part, but fitting new ones is usually very costly. This is becau to fit them, the mechanic must esntially take the whole engine apart. Therefore the labour costs are the major factor. Once going that far, one might as well correct many other problems found inside - so fitting new rings is usually done as part of an entire engine rebuild/reconditioning.
Notes
[1]/
[2]VDi-richtlinie 2840 Kohlenstoffschichten, Grundlagen, Schichttypen, Eigenschafte
External links
•Tech Tips for Automotive Mechanics (/ContentData.aspx?Contentid=82)•Federal-Mogul Piston Ring Handbook (/korihandbook/en/index.htm)
•Piston Ring Muum (jp/e/piston/index.html)
•Construction of Piston Rings (/martech/marine-engineering/main-engine/ 6919-piston-rings)
•Types of Ring Gaps for Piston and Seal Rings (/ringgaps.html)
•Glossary of Ring Gaps types (/asts/files/GROVER-ProductSheet.pdf)
Article Sources and Contributors4 Article Sources and Contributors
Piston ring Source: en.wikipedia/w/index.php?oldid=610747674 Contributors: Andy Dingley, AnkhMorpork, Artemis on Mars, Ayax el cronopio, Becoindia, Bert111, Bert52, BoH, Bobblewik, Canzo, Cobalt327, CsDix, D.239.356, DKwik, Daveh4h, Dcirovic, DonSiano, ECWAnna, ERcheck, Eric Shalov, Geologyguy, Globbet, Gongafa, Gprince007, Hans van der broeke, HemperorOfSmokeLandVillez.dum, Hooperbloob, Hrneo, Hu12, IanOfNorwich, Iepeulas, Interiot, J.delanoy, Jaccobezema1, Jason Quinn, Jatkins679, John Chamberlain, Kallemax, Krap101, Light current, Lrostad, Luk, Lumos3, Magioladitis, Master of Puppets, Mohammadmoradi, Nimbus227, Oxymoron83, Pak21, Pennfe08, PhilKnight, Pie7044, Pmlineditor, RJFJR, RedWolf,
Relax4686, Rgoodermote, Rogerzilla, Sceptre, Seoadorn, Silverxxx, Sonett72, South Bay, Stabinmathew, SteveBaker, Three-quarter-ten, Totensiebush, Typ932, Ussschrotti, Veinor, 113
anonymous edits
Image Sources, Licens and Contributors
Image:horizontal steam engine.png Source: en.wikipedia/w/index.php?title=File:Horizontal_steam_engine.png Licen: Public Domain Contributors: John Chamberlain
安保措施
Image:piston ring illustrated.png Source: en.wikipedia/w/index.php?title=File:Piston_ring_illustrated.png Licen: Public Domain Contributors: John Chamberlain
Image:Piston rings.jpg Source: en.wikipedia/w/index.php?title=File:Piston_rings.jpg Licen: Creative Commons Attribution-Sharealike 2.0 Contributors: Andy Dingley,
FlickreviewR, Interiot, MECU, Rouvix
Image:47mm piston rings.jpg Source: en.wikipedia/w/index.php?title=File:47mm_piston_rings.jpg Licen: Public Domain Contributors: Original uploader was Kallemax at
en.wikipedia
Licen
Creative Commons Attribution-Share Alike 3.0
//creativecommons/licens/by-sa/3.0/
