车轮和轮胎基本知识

WheelsDemands of the wheels∙Low weight,∙Large inner diameter for large brake discs,∙High form stability and elasticity,∙Good heat dissipation (frictional heat),∙Simple change of the wheels and tyres with tyre damages.Assembly of a wheelThe wheel consists of the wheel and the wheel disc with central boring and bolt holes. Instead of the wheel disc, a wheel star is present or wheels or a wheel where steel spokes are connected with the hub.The wheel is connected on the flange of the wheel hub which is pivoted pivot able with the steering knuckle adaptor end, with wheel nuts or wheel bolts. Other than that, the brake discs or the brake drums are mounted firm using bolts to the flange of the wheel hub.With open lying bearings, the hub cover takes over the task of protecting the bearing and is a fat storage fort he fat reserves at the same time. RimsThere are rims which are fitted firm with the wheel disc and those which can be removed. Other than that, undivided rims are differed through rims (drop centre rims) and multiple part rims (Trilex), which find their use with Light and Heavy Goods Vehicles.Drop base rimsFor passenger vehicles, generally undivided drop centre rims are used. They are riveted or welded fest with the wheel disc or are casted or forged from alloy metals with the wheel disc as one piece.The cross section of the rim can be symmetrical or unsymmetrical.AT_40_00141.Rim flange2.Rim opening3.Rim diameter4.Drop centre rim5.Rim bed seat6.Hump235416Hump rimsWhen using tubeless belted tyres, drop centre ring rims have to be used of which the rim shoulder, near to the drop centre rim, has a circulating round increment = Hump (H).If the increment is not round and is flattened then one terms this as aFlat-Hump (FH). Both of these should prevent that the tyre bulges when driving with higher speeds in curves that the rim shoulder is not pressed into the drop centre rim through the high lateral forces. With tubeless tyres, the air can escape quickly so that an accident could be the result.Measurements and terms on the rimsThese details are Normed. The rim terms are stamped in each wheel by the manufacturer. They consist principally from 2 dimensions, the rim opening (a) in inches and the rim diameter (D) in inches. Both dimensions are separated with an ”x” in drop centre rims.Coded letters after the rim diameter give information about the type of rim. Press-in depthThis is the dimension from the middle of the rim to the inner contact surface of the wheel disc.Through welding the rim and wheel disc, the press-in depth can be chosen. Therefore, the rim is determined for a certain chassis as the press-in depth relate direct with the kingpin offset.Positive press-in depthThe inner contact surface, based on the middle of the rim, is displaced to the outer side of the rim.Negative press-in depthThe inner contact surface is displaced to the inner side of the rim. Through using the rim with smaller positive or negative press-in depths, the spur widthof the vehicle can be widened.AT_40_0001AT_40_0015Example 6 ½ J x 13 H6 ½ = Rim opening in InchesJ = Code letter for the measurements of the rim flange X = undivided drop centre rim13= Rim diameter in inchesH = one Hump on the outer shoulderTyresDemands of the Tyres∙Absorption of the weight of the vehicle,∙Absorption of small road surface impacts,∙Transformation of driving, brake and lateral forces,∙Low effort when parking,∙Low rolling resistance therefore lower inner friction and heat development,∙Sufficient length of life,∙ A low noise and vibration rolling.AssemblyValve, inner tube and the rim band are components of a tyre. The rim band is only used in mopeds and vehicles where the tube has to be protected against the nipple heads of the spokes. The inner tube has to comply with the size of the tyre.The tyre consist of:∙Carcass (Fabric carcass),∙Belt (principally by radial tyres),∙Intermediate construction with contact surface (Protector),∙Bulges with inlaying steel wire core.AT_40_00081.Contact surface2.Intermediateconstruction3.Side rubber4.Valve5.Bulge6.Belt7.Air tight rubber layer8.Fabric carcass(Carcass)9.Rim flange10.Hump11.Rim shoulder11168109172543CarcassThis is based on gummed cord threads which are generally manufactured from Rayon, Steel, Polyester or Aramid. The threads are layered over each other and this is either in a diagonal leading angle to the driving direction (Diagonal tyre) or right angular to the driving 6direction (Radial tyres).When winding, the threads are wound around two steel rings (Bulge cores) and are then anchored through vulcanisationIntermediate constructionThis consists of multiple fibre layers and rubber padding, absorbs impacts and protects the carcass.BeltThis consists of multiple layers of rubber embedded steel wires, textile threads, nylon or aramid fibres. The belt lies above the carcass and is finished so that the wires or fibres cross. The belt can be folded with high speed tyres which raises the stability. Contact surfaceThis is provided with a profile. The longitudinal profile gives the tyre a lateral holding, the transverse profile transfers the driving force. The lateral shoulders of the contact surface create a transfer to the side wall which protects the carcass.AquaplaningOn a wet road surface, a water wedge can be created between the tyres and the surface of the road which lifts the vehicle and it is then unable to be controlled. To reduce the danger of Aquaplaning, the profile grooves have to have a minimal depth so that they can absorb lots of water.Other than that, they need certain forms so that the water can flow outwards with a high speed and over a short time. The driving speed is has to be adjusted to the state of the profile, the water depth and the road surface.AT_40_0009 1.Folded Aramid belt2.Carcass3.Bulge core2 31Dimensions and terms of the tyresTyre sizeThis is determined through the details of 2 dimensions: Tyre width in mm; Rim diameter in inches.Cross section ratioThe different tyre categories, e.g. balloon tyres, low cross section tyres, being able to recognise how the relationship of the tyre height and tyre width is determined. The tyre term is given in percent.Modern tyres have a greater width than height. If the height of the tyre values e.g. 80% of the width then the height : width = 0,8 : 1. As the percent value is used in the tyre terms, one would say 80er tyre.Speed categoriesThey differ the tyres of a passenger vehicle than that of a commercial vehicle against their registered top speed. Every high speed is Registered with a letter. Tyre load carrying capacityThese differ the tyres against their stress capability. For the terming in the past, the PR number was used. The specification 4 PR (Ply Rating) meant that because of the stability of its carcass, that it could be loaded like a tyre with 4 layers of cotton thread. The PR number is not actual any more and has been replaced by a Load Index LI.This is the code number which shows the highest carrying capacity of the tyre The tyre carrying capacity is according to the vehicle manufacturer in connection with the highest speed, air pressure and downfall.Example for the tyre termsBalancingThe weight of a turning tyre is never the same over the complete circumfer-ence.On the point where the greater mass appears is where the unbalancing takes place, which means that a centrifugal force is created and the greater they are the greater the turning moment is.Static unbalanceIf e.g. through blocking brakes, a point on the contact surface of the tyre is rubbed off, then on the opposite positional large mass of a centrifugal force which, with higher speeds, can lead to the jumping of the tyre on the road surface.The fault can be found when the wheel is oscillated, the heaviest part of the wheel will stop at the bottom.On the opposite side of the heaviest point of the wheel, a balancing weight with the required weight has to be fixed onto the wheel. The wheel is now statically balanced.Dynamic unbalanceIt is rare when the weight mass lies in the same level as the compensation mass on the wheel. The wheel is statically balanced, but at higher turning moments, the centrifugal forces of the turning moment act diagonally to the axle and make the wheel stagger. In this case, it has a dynamic unbalance. The size and position of the compensating weight are calculated on a balancing machine.If the tyre still runs unbalanced then a radial run out is present. If the radial run out exceeds 1 mm on the contact surface then the tyre has to be rotated on the wheel to reduce the run out (Matching).。