project report on eletromagnetic cutch

PROJECT REPORT ON ELECTRO MAGNETIC CLUCH

ABSTACT:

A clutch is a device used to make and brake contact from the transmission. When it engages,

then power is transferred from engine to gear box and when it disengage, power flow is stop,

hence it is called free running of engine. There is an innovation done in automobile industry,

called electro magnetic clutch, which is recently used by Renault Car Company, which uses the

basic principle of electrical energy as well as magnetic forces.

This project revels the manufacturing of electro magnetic clutch. In place of Engine, shaft is

directly attached to variance (variable motor) and clutch disc as well as pressure plate is used, in

between them friction material called “Asbestos” used to grip between the pressure plate and

clutch plate. This project shows, experimental analysis of Electro magnetic clutch, and at last at

which speed clutch engage as well as disengage is measured and when clutch disengage, at that

time speed of flywheel is also measured.

ORGINAL VIEW OF PROJECT:

(Figure 1-layout of project)

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INTRODUCTION:

Definition of clutch:

The clutch is an important part in the transmission system of automobiles. It transmits

power from the engine to gear box at various speeds. No shock is caused during this

transmission of power.

Purpose:

The function of the clutch is to temporarily disconnect the engine from the gear box unit.

When the gear has to be changed from the first to the second ,it should be done after

disconnecting the engine from the gear box. If this is not done ,the gear teeth might

break. The clutch is thus helpful when starting, shifting gears and idling.

Principle of operation:

The clutch works on the principles of friction. When two friction surfaces are brought in

contact with each other and pressed they are united due to the friction between them. If

now one is resolved, the other will also revolve. The friction between the two surfaces

depends upon the area of the surfaces, pressure applied upon them and co-efficient of

friction of the surface materials. The two surfaces can be separated and brought into

contact when required. The driving member is kept rotating. When the driven member is

brought in contact with the driving member, it also starts rotating. When the driven

member is separated from the driving member it does not revolve. This is the principle on

which a clutch operates.

Requirement of a clutch:

1. Torque transmission: - The clutch should be able to transmit maximum torque of

the engine.

2. Gradual engagement:- The clutch should engage gradually to avoid sudden jerks.

3. Heat dissipation: - The clutch should be able to dissipate large amount of heat which

is generated during the clutch operation due to friction.

4. Dynamic balancing:- The clutch should be dynamically balanced. This is

particularly required in the case of high speed engine clutches.

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5. Vibrating damping: - The clutch should have suitable mechanism to damp

vibrations and to eliminate noise produced during the power transmission.

6. Size:- The clutch should be as small as possible in size so that it will occupy

minimum space.

7. Free pedal play: - The clutch should have free pedal play in order to reduce effective

clamping load on the carbon thrust bearing and wear on it.

8. Easy in operation: - The clutch should be easy to operate requiring as little exertion

as possible on the part of the driver.

9. Lightness:- The driven member of the clutch should be made as light as possible so

that it will not continue to rotate for any length of time after the clutch has been

disengaged.

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Main parts of the clutch:-

The main parts of clutch are divided into three groups:

1. Driving members…..

The driving members consist of a flywheel mounted on the engine

crankshaft.

(Figure 2-flywheel couple with clutch)

2. Driven members….

The driven member consists of the disc or plate, called the clutch plate.

(Figure 3-Pressure plate and Clutch plate)

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3. Operating members…..

The operating members consist of a foot pedal, linkage, release or throw

out bearing, release levers and springs.

(Figure 4:-Pedal, Bearing and spring)

(Figure 5:- Layout of whole clutch assembly)

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ASSEMBLY OF CLUTCH:

EXPLODED VIEW OF CLUTCH ASSEMBLY:

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Types of friction material:-

The friction materials of the clutch plate are generally of three types :

1. Mill board type.

2. Moulded type.

3. Woven type.

Mill board type friction materials mainly include asbestos sheets treated with different

type of impregnates.

Moulded type friction materials are made from a matrix of asbestos fiber and starch

or any other suitable binding materials.

Woven type facing materials are made by impregnating a cloth with certain binders or

by wearing threads of brass or copper wires covered with long fiber asbestos and cotton.

The woven type friction materials are further classified into types-laminated

type and solid woven type.

The most common friction materials are as follows :

1. Leather …….. Co-efficient of friction 0.27.

(Figure 6-Lather friction material)

2. Cork. ………Co-efficient of friction 0.32.

(Figure 7-Cork friction material)

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3. Fabric ……….Co-efficient of friction 0.40.

(Figure 8-Fabric friction material)

4. Asbestos ……..Co-efficient of friction 0.20.

(Figure 9-Asbestos friction material)

5. Reybestos and Ferodo ….. Co-efficient of friction 0.20

(Figure 10- Reybestos and Ferodo friction material)

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Properties of good friction lining :-

1. Good wearing properties.

2. High coefficient of friction.

3. High resistance to heat.

4. Good binder in it.

5. Cheap and easy to manufacture.

Types of clutches:-

Different types of clutches are as follows:

1. Friction clutch :

(a) Single plate clutch.

(b) Multiplate clutch:

(1) Wet clutch.

(2) Dry clutch.

(c) Cone clutch.

(1) External clutch.

(2) Internal clutch.

2. Centrifugal clutch.

3. Semi-centrifugal clutch.

4. Diaphragm clutch.

(a) Tapered finger type.

(b) Crown spring type.

5. Positive clutch.

(a) Dog and Spline clutch.

6. Hydraulic clutch.

7. Electro-magnetic clutch.

8. Vacuum clutch.

9. Over running clutch or free-wheel unit.

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SIGLE PLATE CLUTCH:

(Figure 11-Single Plate Clutch)

MULTIPLATE CLUTCH:

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(Figure 12-Multi Plate Clutch)

CONE CLUTCH:-

(Figure 13-Cone Clutch)

CENTRIFUGAL CLUTCH:

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(Figure-14-Centrifugal Clutch)

SEMI-CENTRIFUGAL CLUTCH:

(Figure-15- Semi Centrifugal Clutch)

DIAPHRAGM CLUTCH:

(Figure-16-Diaphragm Clutch)

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DOG AND SPLINE CLUTCH:

(Figure-17-Dog and Spline Clutch)

ELECTROMAGNETIC CLUTCH:

(Figure-18-Electro Magnetic Clutch)

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VACCUME CLUTCH:

(Figure-19-Vaccume Clutch)

HYDRAULIC CLUTCH:

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(Figure-20-Hydralic Clutch)

COMPLETE DELAILS OF THE ELECTROMAGNETIC

CLUTCH:-

Why we used Electromagnetic Clutch?

Function of clutch is to engage or disengage the engine from the transmission system.

Hence it is inserted between the flywheel as well as gear box. It is consists of main

important parts like clutch plate, pressure plate, friction disc, operating lever etc. In

clutch engage as well as disengage are very important, because due to which clutch is

used. But when clutch is applied at that time, some clearance is there in the clutch pedal

called clutch pedal play and due to which, proper disengage of clutch is not achieve and

clutch will slip or dragged.

There is a need to use some system incorporated in clutch system, to prevent above

situation. Hence, if we shift gear and at that time clutch will disengage hence the it is

very simple for driver and force require to engage as well as disengage the clutch is also

neglected, hence a new type of clutch used in automobile vehicles called “Renault Car”

called electromagnetic clutch.

In this clutch system, when gear shift lever is applied at that time, due to MMF clutch

will disengage and when release lever, clutch will engage.

Basic operation of electromagnetic clutch:-

The clutch has four main parts: field, rotor, armature, and hub (output) (Figure-22). When

voltage is applied the stationary magnetic field generates the lines of flux that pass into

the rotor. (The rotor is normally connected to the part that is always moving in the

machine.) The flux (magnetic attraction) pulls the armature in contact with the rotor (the

armature is connected to the component that requires the acceleration), as the armature

and the output start to accelerate. Slipping between the rotor face and the armature face

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http://en.wikipedia.org/wiki/Electric_field

http://en.wikipedia.org/wiki/Hub_gear

http://en.wikipedia.org/wiki/Armature_(electrical_engineering)

http://en.wikipedia.org/wiki/Rotor_(electric)


continues until the input and output speed is the same (100% lockup). The actual time for

this is quite short, between 1/200th of a second and 1 second.

Disengagement is very simple. Once the field starts to degrade, flux falls rapidly and the

armature separates. One or more springs hold the armature away from the rotor at a

predetermined air gap.

Voltage/current - and the magnetic field

(Figure-21) (Figure-22)

If a piece of copper wire was wound, around the nail and then connected to a battery, it

would create an electro magnet. The magnetic field that is generated in the wire, from the

current, is known as the “right hand thumb rule”. (FIGURE-21) The strength of the

magnetic field can be changed by changing both wire size and the amount of wire (turns).

EM clutches are similar; they use a copper wire coil (sometimes aluminum) to create a

magnetic field.

The fields of EM clutch can be made to operate at almost any DC voltage, and the torque

produced by the clutch or brake will be the same, as long as the correct operating voltage

and current is used with the correct clutch. If a 90 V clutch, a 48 V clutch and a 24 V

clutch, all being powered with their respective voltages and current, all would produce

the same amount of torque. However, if a 90 V clutch had 48 V applied to it, this would

get about half of the correct torque output of that clutch. This is because voltage/current

is almost linear to torque in DC electromagnetic clutches.

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http://en.wikipedia.org/wiki/Voltage

http://en.wikipedia.org/wiki/File:V-1_right_hand_thumb_rule.gif


A constant power supply is ideal if accurate or maximum torque is required from a

clutch. If a non regulated power supply is used, the magnetic flux will degrade, as the

resistance of the coil goes up. Basically, the hotter the coil gets the lower the torque will

be, by about an average of 8% for every 20°C. If the temperature is fairly constant, but

there may not be enough service factor in your design for minor temperature fluctuation.

Over-sizing, the clutch would compensate for minor flux. This will allow the use a rectified

power supply which is far less expensive than a constant current supply.

Based on V = I × R, as resistance increases available current falls. An increase in

resistance, often results from rising temperature as the coil heats up, according to: Rf = Ri

× [1 + αCu × (Tf - Ti)] Where Rf = final resistance, Ri = initial resistance, αCu = copper

wire’s temperature coefficient of resistance, 0.0039 °C-1, Tf = final temperature, and Ti =

initial temperature.

Engagement Time:

There are actually two engagement times to consider in an electromagnetic clutch. The

first one is the time it takes for a coil to develop a magnetic field, strong enough to pull in

an armature. Within this, there are two factors to consider. The first one is the amount of

ampere turns in a coil, which will determine the strength of a magnetic field. The second

one is air gap, which is the space between the armature and the rotor. Magnetic lines of

flux diminish quickly in the air. The further away the attractive piece is from the coil, the

longer it will take for that piece to actually develop enough magnetic force to be attracted

and pull in to overcome the air gap. For very high cycle applications, floating armatures

can be used that rest lightly against the rotor. In this case, the air gap is zero; but, more

importantly the response time is very consistent since there is no air gap to overcome. Air

gap is an important consideration especially with a fixed armature design because as the

unit wears over many cycles of engagement the armature and the rotor will create a larger

air gap which will change the engagement time of the clutch. In high cycle applications,

where registration is important, even the difference of 10-15 milliseconds can make a

difference, in registration of a machine. Even in a normal cycle application, this is

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important because a new machine that has accurate timing can eventually see a “drift” in

its accuracy as the machine gets older.

The second factor in figuring out response time of a clutch is actually much more

important than the magnet wire or the air gap. It involves calculating the amount of

inertia that the clutch needs to accelerate. This is referred to as “time to speed”. In reality,

this is what the end-user is most concerned with. Once it is known how much inertia is

present for the clutch to start then the torque can be calculated and the appropriate size of

clutch can be chosen.

Most CAD systems can automatically calculate component inertia, but the key to sizing a

clutch is calculating how much inertial is reflected back to the clutch or brake. To do this,

engineers use the formula: T = (WK2 × ΔN) / (308 × t) Where T = required torque in lb-

ft, WK2 = total inertia in lb-ft2, ΔN = change in the rotational speed in rpm, and t = time

during which the acceleration or deceleration must take place.

There are also online sites that can help confirm how much torque is required to

accelerate a given amount of inertia over a specific time. Remember to make sure that the

torque chosen, for the clutch, should be after the clutch has been burnished.

DETAILS OF PROJECT MADE BY US:-

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project report on eletromagnetic cutch

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