Design of Continuously Variable Transmission Mechanism for Economy Cars in India

Abstract

Over the past decades, there has been a great effort towards the development of the Continuously Variable Transmission (CVT) as it offers a continuum of the gear ratios between the two limits. It also helps in meeting the goal of reduced exhaust transmission, enhances the fuel economy and improves the dynamic performance of the vehicle by matching the engine performance to the road conditions and the traffic problems. The purpose of this paper is to improve and popularize the use of CVT in Indian cars in and below 1000 cc vehicle. The basic idea of this is to benefit the Indian citizens especially the elderly and the differently abled people with a comfortable and easy drive on the present day where traffic is the major problem. The basic concept, mathematical calculations, design procedure of the same has been discussed in detail.

Appendices

Appendices

1.1 1. Description of Equations

• Equation 1—calculation to find available power after transmission

• Equation 2—calculation to find the thrust force

• Equation 3—calculation to find the drag force

• Equation 4—calculation to find maximum speed of the car

• Equation 5—calculation to find the highest ratio

• Equation 6—calculation to find out factor of safety

• Equation 7—calculation for the tangential force acting on the tires

• Equation 8—calculation of belt length

• Equation 9—calculation of belt speed

• Equation 10—calculation to find the smallest wrap angle

1.2 2. Indices and Abbreviations

µ :

Coefficient of friction

a :

pulley center to center distance (mm)

ar:

vehicles projected frontal area (m²)

bl:

belt length (mm)

cd:

coefficient of drag force {depends on the aerodynamic design of the vehicle

ce:

clutch efficiency

cf :

correction factor [0.91–0.99]

cpf:

clamping force (N)

d ₁ :

smaller diameter (mm)

d ₂ :

larger diameter (mm)

df:

drag force

dr:

differential ratio

ef:

transmission efficiency (including rolling resistance)

fos:

factor of safety

fs:

force due to slope

ft:

tangential force on the tires

hr:

high ratio

l :

maximum load (kg)

lr:

low ratio

m :

mass (kg)

mt:

maximum engine torque (Nm)

n ₁ :

rotational speed of driver pulley (rpm)

n ₂ :

rotational speed of the driven pulley (rpm)

pe:

Engine power (hp)

pi:

percentage inclination

pt:

available power after transmission (hp)

r :

air density (1.2 kg/m³)

rp:

rpm at maximum power

si:

slope inclination

sl:

shaft load (N)

syh:

symmetric high ratio

syl:

symmetric low ratio

t ₁ :

belt load tension 1

t ₁₂ :

ratio of the belt forces

t ₂ :

belt load tension 2

tf:

thrust force (N)

v :

speed of the car (m/s)

vm:

maximum speed of the vehicle (m/s)

wd:

wheel diameter (inch);

α :

smallest wrap angle (in °)

β :

pulley groove angle (in °)