4.1.13. Noise качения tyres
The general information on noise качения
Noise качения, perceived by a human ear, are the fluctuations proceeding from a source of a sound and by air reaching ear.
Here the noise arising at the expense of certain features, and also effects are interesting at качении tyres (a noise source).
The reason of occurrence of noise in большей parts depends on a combination of tyres and a road covering.
The structure of a surface and material of a road cloth also strongly influence noise качения. Noise level on wet road, for example, much more above, than on the dry.
Profiling of drawing of a protector strongly influences noise level. Tyres with cross-section flutes at an angle 90 more noisy, than tyres with diagonal flutes.
Small blocks of a protector are astable. Because of their strong deformation at качении tyres air is shaken. Air fluctuations are created. Which lead to noise.
Wider tyres шумнее. For water drainage they should have more flutes. At качении because of these flutes air at the expense of what also there are air fluctuations is superseded.
The other effects influencing on шумность.
Tyre fluctuation is a principal cause of noise качения. They arise because of excitation of air columns in protector flutes.
Air pulsation is a compression and air expansion at arrival of the area of contact of the tyre on a road cloth at which it is deformed protector blocks.
Шумность basically it is defined by tyres and a road covering.
The qualities of a road covering influencing on шумность, is a roughness (roughness), structure and a material.
In parametres of influence of the tyre, except other, the width of the tyre and a disk are. Wider tyre because of большей creates the areas of contact to a road covering of more noise as the volume of air and big "weight" is squeezed out больший is raised in fluctuations, than at the smaller size.
Wider the disk also increases the area of contact of the tyre. Thus, influence on шумность same, as well as at the wide tyre. Besides wider disks negatively affect on демпфирующих properties of the tyre.
Noise качения tyres are audible in cars at which the engine is established in a forward part, it is better on back seats as aerodynamic noise and an engine sound in this place of salon disturb less.
Deterioration of a protector in the form of a path of the sawtooth form
Deterioration of a protector in the form of a path of the sawtooth form is a step deterioration of separate blocks of a protector that can lead raised шумности. Deterioration of the sawtooth form occurs because of non-uniform deformation of blocks of a protector on a surface of contact of the tyre to a road covering. Such kind of deterioration is more often shown on неведущих, than on leaders.
New tyres are more inclined to deterioration of a protector of the sawtooth form as high blocks of a protector are more elastic. With reduction of depth of drawing of a protector rigidity of blocks of a protector raises, propensity to such type of deterioration decreases.
A – Blocks of a protector of the new tyre; protector blocks if to look in a direction качения an arrow 1, are identical on height in front and behind.
B – Deterioration of a protector in the form of a path of the sawtooth form; protector blocks if to look in a direction качения an arrow 1, in front above, than behind the marksman 2.
C – profile Blocks, a kind in a direction качения an arrow 1, have strong deterioration in a forward part of "tooth" of the marksman 3.
At strongly expressed deterioration of a protector in the form of a path of the sawtooth form can become appreciable amplified шумность tyres.
|Fig. 4.11. A kind of deterioration of the sawtooth form
Strong deterioration of a protector in the form of a path of the sawtooth form occurs at too big convergence wrong pressure of air in tyres to the big blocks of a protector the tyres established on wheels not driving of an axis extreme passage of bends.
Tyres with not directed drawing of a protector
At detection of deterioration of a protector in the form of a path of the sawtooth form it is necessary to change a direction качения tyres. If the strengthened deterioration of a protector in the form of a path of the sawtooth form and raised шумность is found out, it is necessary to rearrange wheels cross-wise. It will reduce deterioration.
On cars with a forward drive efficiency of this approach will be even more appreciable thanking большему истиранию tyres on a forward axis.
Noise качения directly after shift of wheels will hardly more strongly, however after run of 500-1000 km normal level шумности again will be reached.
Tyres with the directed drawing of a protector
At the raised deterioration of a protector in the form of a path of the sawtooth form on tyres of a back axis – mainly at a forward drive – it is necessary to rearrange back wheels forward. At the strengthened sawtooth deterioration on external edges on one axis both tyres it is necessary to turn on a disk. After that the left wheel should be mounted on the right party, and the right wheel on the left.
Stains of deterioration because of movement with the blocked wheels
|Fig. 4.12. Deterioration stains on a protector because of braking with the blocked wheels
The given kind of deterioration is a consequence of strong braking with the blocked wheels at which on the area of contact of the tyre with a road covering protector rubber (fig. 4.12
At sliding of tyres on a road cloth it is developed warmly friction which reduces resistance истиранию a protector material.
Even the most wearproof rubber mixes of protectors do not exclude stain of deterioration which can be formed at extreme braking.
And even the brake systems equipped ABS, do not exclude short-term blocking and by that small deterioration.
Degree such истирания essentially depends on speed of movement, a road covering and loading on a wheel. Following examples are for descriptive reasons resulted.
At braking of the car with the blocked forward wheels on a dry road covering to a full stop deterioration of rubber on the area of contact equal to a post card, will make:
– About 57 km/h = 23,8 m of a brake way to 2,0 mm;
– About 75 km/h = 41,8 m of a brake way to 3,3 mm;
– About 92 km/h = 71,6 m of a brake way to 4,8 mm.
Tyres with similar damages are unsuitable for the further operation and should be replaced.
The reasons неплавности a course
The reasons неплавности a course the various. Неплавность a course can appear including because of deterioration of tyres. While in service tyres not always wear out in regular intervals on all surface of a protector. Because of it already there is a small disbalance which prevents quiet качению earlier ideally отбалансированного wheels.
Such disbalance is not felt yet on a wheel, however takes place. It strengthens deterioration of the tyre and reduces thereby service life.
That throughout all service life of the tyre to provide optimum safety, an optimum smooth course and uniform deterioration, it is recommended to balance disks with tyres not less than two times during service life of tyres.