Shafts coming out of the transmission units and other mechanisms of the car can cause leakage and contamination of oil - this problem is solved by installing oil seals. Read all about the drive seals, their classification, design and applicability, as well as the correct choice and replacement of seals in the article.
What is a drive oil seal?
Drive oil seal (cuff) - a sealing element of various units and systems of vehicles; a ring composite part that ensures the sealing of shafts, bearings and other rotating parts at the points of their exit from the body of the unit.
In any car, tractor and other equipment there are units and mechanisms, from the body of which rotating shafts come out - gearboxes, gearboxes, fan drives and others. Usually there is oil or other lubricant inside these units, and the hole for the shaft can cause loss and contamination of the lubricant. The problem of sealing the exit of rotating shafts outside the housings of the units is solved with the help of special sealing elements - seals (cuffs) of the drive.
The drive oil seal performs several functions:
● Prevention of oil leakage and loss of other lubricant from the body of the unit or mechanism;
● Protection of the mechanism from water, dust and large contaminants;
● Protection of the lubricant from contamination by exhaust and other gases.
Violation of integrity or loss of the oil seal leads to a significant leakage of oil and its contamination, which in the very near future can cause the breakdown of the entire unit. To prevent this, an outdated resource or a faulty drive seal must be replaced in a timely manner. For the correct selection and replacement of sealing elements, it is necessary to understand their existing types, design and applicability.
Typical drive seal design
Types, design and features of drive seals
All oil seals are made in the form of a ring with a U-shaped profile, in which three surfaces stand out:
● Internal or working - consists of working edges, this surface of the oil seal rests on the shaft;
● External - smooth or grooved, this surface of the oil seal is in contact with the body of the unit;
● End - usually flat, this surface is parallel to the body of the unit.
The cuff is installed in the seat in the body of the unit (oil seal box) and rests on the shaft, due to the design, its tight clamping to the body and shaft is ensured, which achieves sealing.
Oil seals are divided into several types according to the presence / absence of various elements and features of work.
First of all, oil seals are divided into two types by design:
● Frameless;
● With reinforcing frame.
Non-reinforced seal design with spring
Construction and basic dimensions of the reinforced oil seal with spring
Oil seals of the first type are made in the form of an elastic ring of synthetic rubber, on the inner surface of which the working edges are formed. As a standard, two working edges are provided in the oil seals - front and rear, but their number can reach four. Inside the ring is a coiled coil spring rolled into a ring, which provides a tight clamping of the oil seal to the shaft.
Seals of the second type are more complicated - inside the ring there is a steel reinforcing frame of one form or another. Most often, the frame has a straight (a plate rolled into a ring) or L-shaped profile, but there are oil seals with frames of a more complex profile. Otherwise, reinforced parts are similar to unreinforced ones.
Oil seals with reinforcing frame are divided into three structural types:
● With closed frame;
● With partially exposed frame;
● With bare frame.
In the design of the first type, the frame is completely located inside the rubber ring of the oil seal, or the ring completely covers only the outer surface of the frame. In the second case, the ring covers the end and part of the outer surface of the frame, and in the third case, the frame is almost completely open. Seals with a partially and completely bare reinforcing frame are more firmly installed in their seat, since they rest on the metal body of the unit with a metal ring. Although such seals provide the worst seal, which makes it necessary to use sealants or additional parts.
The elastic ring of all types of oil seals can be made of various types of synthetic rubber - acrylate, fluoro rubber, butadiene-nitrile, silicone (organosilicon) and others. These materials have unequal resistance to high and low temperatures and lubricants, but they have approximately the same coefficients of friction on steel and mechanical strength.
Drive seals can have various additional elements:
● The anther is a small protrusion in the front of the ring that prevents large contaminants (stones, threads, chips, etc.) from entering the oil seal. The anther can be pressed against the shaft due to its own elasticity or with the help of an additional coiled spring;
● Grooving of the outer surface - grooving of a simple or complex shape, which improves the fit of the oil seal and prevents oil leakage at high speeds and when the temperature rises;
● Hydrodynamic knurling and notches on the inner (working) surface. Dashed notches applied at some angle to the axis of the oil seal, preventing oil leakage at high shaft speeds. Notches can be performed over the entire inner surface, or in the form of several rings on the working surface and working edges.
The oil seals are divided into two groups in the direction of rotation of the shaft:
● For shafts with a constant direction of rotation;
● For shafts with reversible rotation.
Seals for various purposes differ in the type of knurling or notches on the working surface. In oil seals for shafts with a constant direction of rotation, the knurling is made in the form of hatching directed to one side, so such parts are with "right" and "left" knurlings (notches). In reversible omentums, the notch is zigzag or more complex in shape.
Cassette gland design
Finally, drive seals are of two types in terms of protection:
● Normal (standard);
● Cassette.
Conventional oil seals have the design described above. Cassette seals are made in the form of two rings inserted one into the other (the outer ring rests on the body of the unit and rests on the shaft, the inner ring rests on the outer and partially rests on the shaft) - this design withstands significant mechanical loads and provides better protection against the penetration of contaminants. Cassette seals are used on units operating in conditions of increased dustiness and pollution.
In conclusion, we note that in cars, tractors and other equipment, different drive seals are used for their intended purpose: semi-axles of wheels, gearbox shafts and gearboxes, fan drive shafts and others. But the bulk of the parts are located in the transmission, for which they got their name.
How to choose and replace the drive oil seal
Drive seals experience significant loads, which over time lead to wear, damage or complete destruction of the seal. When an oil leak appears, the oil seal must be replaced, otherwise oil consumption will increase and the risk of its contamination will increase, which in general increases the intensity of wear of the parts of the unit. Also, the oil seals must be changed upon resource development - the replacement period is usually indicated by the manufacturer of the unit.
Only those types and models of oil seals that were previously installed and recommended by the manufacturer of the mechanism (determined by the part number in the original catalog) should be used for replacement. In some cases, it is permissible to resort to replacements, but this should be done with caution and taking into account the peculiarities of cuffs for various purposes. For example, the seals of the semi-axles of the drive axles must have a reversible notch (knurling), otherwise soon after their installation there will be an oil leak in certain driving modes or a constant leak due to improper operation of the seal. On the other hand, it does not make sense to put a reversible cuff on the fan, since the sealed shaft always rotates in one direction.
Replacement of drive seals must be carried out in accordance with the instructions for repair and maintenance of the vehicle. This work may require a significant disassembly of the repaired unit, so it is better to trust it to specialists. When replacing the seal yourself, it is necessary to strictly adhere to the recommendations given in the instructions, otherwise there is a high risk of damaging the part or installing it incorrectly. Notching an old cuff can be done with a regular screwdriver or other pointed object, but this must be done carefully so as not to damage the surfaces of the case and shaft. The installation of a new seal is better to perform with the help of a special mandrel that ensures uniform drowning of the oil seal into the oil seal box. Before installation, the cuff is lubricated with lubricant. In cases where a seal with a bare or partially exposed reinforcing frame is used, it is necessary to treat the place of contact of the frame with the body of the unit with a sealant. After performing the work, it is necessary to add oil to the crankcase of the unit.
With the correct selection and replacement of the drive seal, the unit will reliably perform its functions, its work will not be disturbed by leakage and contamination of oil in any operating conditions.
Post time: May-06-2023