Cone Clutches
A cone clutch serves the same purpose as a disk or plate clutch. However, instead of mating two spinning disks, the cone clutch uses two conical surfaces to transmit friction and torque. The cone clutch transfers a higher torque than plate or disk clutches of the same size due to the wedging action and increased surface area. Cone clutches are generally now only used in low peripheral speed applications although they were once common in automobiles and other combustion engine transmissions. They are usually now confined to very specialist transmissions in racing, rallying, or in extreme off-road vehicles, although they are common in power boats.
The clutch drives between internal and external cones instead of plates. The clutch is engaged when the inner cone (external) is forced into the outer (internal) cone. The cone clutch utilizes the wedging action of the parts to increase the normal force on the lining. Thus an increase in the tangential friction and the torque results. The clutch has improved thermal properties over a plate clutch .
The cone clutch is and axially actuated clutch which is able to transmit a relatively high torque for its size compared to a single disk plate clutch of the same dimensions. This results from the wedging action and increase friction area. Cone clutches are not used widely now and are generally used for low peripheral speed applications.
The cone angle α is always above 8o and is normally between 12o and 15o. if the angle is less than this value than the clutch is liable to jam in engagement.
Nomenclature
Fa = Axial Applied Force (N)
Fn = Axial Normal Force (N)
P = Clutch Power kW
M = Clutch Torque (Nm)
μ = Coefficient of Friction.
& r = Radius of clutch ring thickness dr (m)
r i, r o = Inner, Outer radius of clutch. (m)
n = Rotational Speed (RPM)
p = Pressure for friction surface(N/m2)
p max = Maximum pressure for friction surface(N/m2)
Theory
There are two operating conditions applicable to clutch plates
• Uniform wear. Applicable for practical clutch assemblies after period of operation
• Uniform pressure. Applicable for new clutch plate friction linings.
T = F.μ .(ro + ri ) /( 2.sin α)
From the above formulae for Force and torque it is clear that
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