FRENOS Y EMBRAGUES - IBERO · identified by their mode of actuation: mechanical, electrical,...

FRENOS Y EMBRAGUESClutches rely on mechanical or electromagnetic action for torque transmission. However, they are usually

FRENOS Y EMBRAGUES http://profesor.sis.uia.mx/~cosornio/dismaquinas/...

1 of 19 10/28/08 11:22 AM

identified by their mode of actuation:

mechanical,

electrical,

pneumatic, or

hydraulic.

Although the four operating modes are considered highly competitive, each mode actually is restricted to afairly well-defined area of application. Within each area, one method provides definite advantages in terms ofcost, response time, and torque transmission.

http://www.machinedesign.com/bde/mechanical/index.html

FRENOS:

Brakes absorb energy and convert it to heat. Thus, prime concerns in a brake are:

Generating a force capable of retarding a rotating shaft.1.Dissipating or absorbing the heat generated in the process.2.

Mechanical brakes all act by generating frictional forces as two surfaces rub against each other. The stoppingpower or capacity of a brake depends largely on the surface area of frictional surfaces as well as on theactuation force applied. The friction and wear encountered by the working surfaces are severe. Thus, thedurability of a brake or service life between maintenance depends heavily on the type of material used to linethe shoe or pad.

Brake linings

Most brakes use some type of friction lining. Asbestos, once the accepted friction material, has been replacedin most cases by nonasbestos materials.

Contents of the new material, largely proprietary, are also fibers molded or woven into pads or discs. Copperis sometimes added to improve heat dissipation. Cotton-based linings are sometimes used for light-dutyservice.


2 of 19 10/28/08 11:22 AM

Electric Brakes

For heavy-duty service, sintered-metal linings perform better than fiber-based linings. Cermet linings areused for extremely rigorous service.

Linings are attached to the brake shoe either by riveting or bonding. Riveted attachment is simpler, but usablelining depth depends upon the depth of rivet-head countersink. Also, rivet heads may score the drum if thelinings are not replaced soon enough.

Electric brakes operate according to the same principles as electric clutches. The most commonly usedelectric brakes are electrically actuated but rely on mechanical friction for stopping action. Such brakes arealmost the only electrical types suitable when the load must be brought to a full stop. The other electricaltypes -- magnetic-particle, hysteresis, and eddy-current brakes -- are primarily used to provide drag orretarding action where a rapid or precise full stop is not needed.

Ejemplo para selección de Embraguesy frenos

Trig-O-Matic tm LiteModel 700Overload Release Clutches

Trig-O-Matic LiteModel 700Mechanical

This automatic reset, roller detent style overload clutch,combines Centric's 30 plus years experience manufacturingthe Trig-O-Matic with a simpler design. This combinationyields a reliable, low cost alternative to many of the torqueoverload clutches on the market today.

APPLICATIONS

PackagingCartoners, Fillers, Case Packers, Cappers, Labelers,Sealers, Can FormingPaper ConvertingRewinders, Log Saws, Folders, Slitters, AccumulatorsFood ProcessingOvens, Centrifuges, Mixers, Pumps, ExtrudersMaterial HandlingBelt, Drag, Chain, Bucket & Screw Conveyors, PalletizersOther IndustriesChemical, Printing, Portable Lifting/Lowering Systems

MODEL 700 FEATURES


3 of 19 10/28/08 11:22 AM

MOUNTINGCONFIGURATIONS

For mounting flexibility the Model 700 is available in twoshaft mounted bushing models.Bore Bushing Model - for easy mounting and stocking.Taper Bore Bushing Model - for more secure mounting.

OPTIONS

Proximity Sensor PlateFinished Bore & Keyways

Spacer Bar

Simple Cost-Effective DesignLarge Bore CapacityThrough Shaft or End Shaft MountingBidirectional OperationSingle Position IndexingAutomatic ResetAccurate & Repeatable Torque Settings of +/-10%Maximum Torque Limit StopLimit Switch Actuating PlateOperating speeds up to 1000 rpm

CAPACITIES

Size Max. Straight Borein./mm

Max. Taper Borein./mm

Torque Rangein.-lb.Nm

720 1.438/36,5 1.125/28,6 200-70022,6-79,1

730 2.125/54,0 1.750/44,5 600-200067,8-226,0

740 2.750/70,0 2.250/57,2 2000-5000226,0-565,0

Request Catalog 764-ADV. AutoCAD & DXF Drawings Available.

Centric Main Page | Centrifugal Clutch Couplings

Ameriguard | Pneumatic Series H - Model 2000

...Quality Clutches From Yesterday to Tomorrow

Home


4 of 19 10/28/08 11:22 AM

En la figura se puede apreciar el arreglo de conexión de un embrague que a la vez es cople

GEOMETRIA DE LOS EMBREGUES


5 of 19 10/28/08 11:22 AM

Fn = 2ppmáxri(ro – ri ) (a)

Fuerza para operar el embrague

T = mFnrprom ( b) donde rprom = ½ (ro + ri )

Capacidad de transmisión de Par por sup. De contacto.Para desgaste uniforme

Para presión uniforme:

Fn = pp( r2o - r2i ) ( c )

T = 2m (r3o – r3i )/3 ( r2o - r2i ) ( d )

GEOMETRIA DE LOS FRENOS DE TAMBOR DE ZAPATA INERNA


6 of 19 10/28/08 11:22 AM


7 of 19 10/28/08 11:22 AM

ECUACIONES:


8 of 19 10/28/08 11:22 AM

Variables de Diseño:

Fuerza normal Fn

Coeficiente de fricciónGeometría.


9 of 19 10/28/08 11:22 AM


10 of 19 10/28/08 11:22 AM


11 of 19 10/28/08 11:22 AM


12 of 19 10/28/08 11:22 AM


13 of 19 10/28/08 11:22 AM

FRENOS DE DISCO


14 of 19 10/28/08 11:22 AM


15 of 19 10/28/08 11:22 AM

Variables de Diseño:

Fuerza normal FnCoeficiente de Fricción mGeometría do, di, q1 y q2.


16 of 19 10/28/08 11:22 AM

Se recomienda la lectura del artículo:

Electronic Braking Control Developments.

Today´s hydraulic braking systems are expected to be replaced by fully electrical systems, despite variousdevelopment challenges.

Automotive Engineering International. February 1999.

Para obtener las ecuaciones correspondientes se hace sumatoria de momentos alrededor del punto de pivoteode la palanca.

EJERCICIO DE FRENOS Y EMBRAGUES.Explique paso a paso cómo funciona el mecanismo accionador del sistema de embrague.


17 of 19 10/28/08 11:22 AM

1.- Un motor de un automóvil puede desarrollar un máximo par de freno de 2500 lb-pulg. ¿ Cuáles de losembragues de disco siguientes que produce un fabricante pueden ser seleccionados para este coche ?.Dimensiones de las caras en pulgadas:

a.- Do = 8 7/8, Di = 6 1/8, Pa = 34 psib.- Do = 10 , Di = 6 1/8, Pa = 30 psic.- Do = 11 1/16, Di = 6 1/8, Pa = 26.2 psi.En cada caso f= 0.3. 2.- La figura representa los arreglos posibles para un freno de zapatas interiores de un auto.Cara b = 4.5 , r = 8, h = 5, c= 2.5, w = u = 6.5, q = 100°, f = 20°, Para una presión máxima de120 psi, determine la fuerza Q y el par de freno paraSentido de giro manecillas en A y BSentido de giro contramanecillas en A y en BConsidere un coeficiente de fricción de 0.25 Explique el concepto de la autoenergización en ambos incisao A y B.


18 of 19 10/28/08 11:22 AM


19 of 19 10/28/08 11:22 AM

FRENOS Y EMBRAGUES - IBERO · identified by their mode of actuation: mechanical, electrical,...

Documents

Transcript of FRENOS Y EMBRAGUES - IBERO · identified by their mode of actuation: mechanical, electrical,...