II. GENERAL FEATURES OF BEARINGS
Classification according to intended purpose:
Ball bearings
Single-row or double-row bearings, used for radial loads. In case it is
impossible to achieve total alignment of the housing and the shaft, we
may use an adjustable bearing which has one surface, on which the balls
roll, in the shape of a spherical rim. Thereby a slight offset of the shaft
for a small angle is possible. When axial loads are present, we use thrust
bearings which are mounted in pairs.
For the analysis of single-row ball bearings which represent the majority
of this type of bearings an algorithm has been developed which more
precisely takes into account the geometry of the raceways and the size
of bearing fits. With it we are able to simulate the unevenness of the
mounting surfaces and elasticity of the construction. The algorithm ap-
plies to all types of ball bearings and represents the basis for the analysis
of single-row and double-row roller bearings. With these a somewhat
simplified analysis of the load capacity Is possible, as there are some
particularities, concerning especially the determining of the max. load of
the roller, or the load distribution over its surface.
Roller bearings
Used for higher radial loads.
Tapered roller bearings
Used in pairs, for considerable radial and axial loads.
The feature of their geometry is that the runways of grooves and needles
are tapered. Here, the axes of both cones meet at the same point on the
shaft axis which means that the bearings are able to translate loads in
both directions.
1. THE ROLE OF BEARINGS
A bearing enables guidance of rotating parts and, at the same time, trans-
lates the outer loads of rotating parts of the machine onto the stationary
part of the machine and vice versa.
2. TYPES OF BEARINGS FOR FIRST MOUNTING
There are two standard types of bearings in use:
• rolling bearings, where friction is caused by movement of elements
in contact,
• rolling elements in a bearing (ball, needle or roller) have double mo-
tion: they rotate around the axis of a bearing and around their own
axis which gives rise to rolling friction.
Bearing types:
• ball bearings,
• needle bearings,
• needle deep-drawn bearings,
• plain berings,
• thrust bearings,
• roller bearings.
II. SPLOŠNO O LEŽAJIH
Razvrščanje po namembnosti
Kroglični ležaji
Enoredni ali dvoredni, uporabljamo jih za radialne obremenitve. V kolikor
ne moremo doseči poravnanost gredi z ohišjem, lahko uporabimo pri-
lagodljivi ležaj, ki ima eno od površin, po katerih se kotalijo kroglice, v
obliki krogelnega oboda. S tem omogočamo vrtenje gredi za majhen kot.
Kadar pa nastopijo aksialne obremenitve, uporabljamo ramenske ležaje,
ki jih montiramo v parih.
Za analizo enorednih krogličnih ležajev, ki predstavljajo večino tovrstnih
ležajev, je bil razvit algoritem, ki natančneje upošteva geometrijo tekalnih
površin in velikosti ležajnih ujemov. Pri tem je možno simulirati neravnost
vgradnih površin in elastičnost konstrukcij. Algoritem je razširjen na vse
tipe krogličnih ležajev in predstavlja osnovo za analizo enorednih in dvo-
rednih valjčnih ležajev. Pri teh je možna nekoliko poenostavljena analiza
nosilnosti, ker se pri njih pojavijo nekatere posebnosti, zlasti pri določitvi
dopustne obremenitve valjčka oziroma porazdelitve po njegovi širini.
Valjčni ležaji
Uporabljamo jih za večje radialne obremenitve.
Stožčasti ležaji
Uporabljamo jih v parih, za znatne radialne in aksialne obremenitve.
Pri geometrijski obliki je značilno, da imajo tekalne površine žlebov in
iglic stožčaste oblike. Pri tem se obe osi stožcev stikata v isti točki na osi
gredi, kar pomeni, da s tem ležaji prenašajo obremenitve v obeh smereh.
1. VLOGA LEŽAJA
Ležaj omogoča vodenje vrtečih se delov pri istočasnem prenašanju zu-
nanje obremenitve vrtečega na mirujoči del stroja in obratno.
2. VRSTE LEŽAJEV V UPORABI ZA PRVO VGRADNJO
V uporabi sta dve vrsti standardnih ležajev, in sicer:
• kotalni, pri katerih gibanje dotikajočih elementov povzroča trenje,
• kotalni elementi v ležaju (kroglica, iglica ali valjček) imajo dvojno gi-
banje: vrtijo se okoli osi ležaja in okoli svoje osi, pri čemer nastane
kotalno trenje.
Vrste ležajev:
• kroglični ležaji,
• igličasti ležaji,
• igličasti dolgovlečeni ležaji,
• drsni ležaji,
• aksialni ležaji,
• valjčni ležaji.
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