Greetings!!
What is Suspension?
A suspension is a mechanical (electro-mechanical in present
days) device that was designed to, as the name says to suspend the wheels to
ground. The soul purpose of designing it was to make the vehicle stay on ground
(since it is a ground vehicle :P ), which was a serious problem in earlier days
of motor sports.
The second major use of the Suspension is to provide comfort
while riding/driving. This is called Ride Quality, which is an important factor
in Pricing in Automotive Industry
Todays’ topic:
Air Suspension-
Unfortunately, This suspension is not available in 2
whellers (not yet) because of too many reasons.
This are very famous in heavy vehicles.
<Further topic will only be about 4 wheelers and above>
Traditionally, there are 2 types that are still used
i)
Steel Coil Spring System.
ii)
Leap Spring System.
But, Air Suspension consists of primary component called Air
Springs made up of Rubberized Membrane, which stores the pressurized air.
Air Suspension System consists of
I)
Air Supply Unit- Supplies Air from compressor to
all springs via Reservoir.
II)
Reservoir- it stores additional air pressure for
control/emergency purpose.
III)
Height Sensors- Present on all corners to sense
and modulate air flow to springs.
IV)
Air springs- Pressurized air is supplied to
maintain the height of the vehicle.
Types of Air Springs
a)
Convoluted Air Springs- gives better packaging, distance between axle
and frame is reduced.
b)
Rolling Lobe- Gives better tuning/control.
deflated/ de-presureized(For highways/ unloaded vehicle)
Pressurized(for off road/ loaded)
Types of Air Suspensions:
Open system and Closed system
Open System:
Air is given to ASU(Air Supply Unit), ASU sends air to
Reservoir, and reservoir forwards the air to Air Springs.
Here air flows in only one
direction ASU to Air Springs.
Older System, Noisier, Slower (like
in city buses).
Closed System:
Air is given to ASU(Air Supply Unit), ASU sends air to
Reservoir, and air moves back and forth between Reservoir and Air Springs.
Air flows
in one direction from ASU to Reservoir,
but air flows in both directions between Reservoir and Air Springs.
Modern
system, Faster response time, more efficient, generally quitter.
1)
Adjustable Ride Height
i)
Ingress(Getting into the vehicle) and Egress(getting
out of the vehicle)
ii)
Off-road use:
a)
Higher Ground Clearance.
b)
Higher Approach angle.
c)
Higher Departure angle
d)
Higher Break-Over Angle
iii)
Aerodynamics: Effectively lowers the height of
the vehicle when crusing in highways providing less drag and higher fuel
economy.
iv)
Load leveling: As I mentioned earlier, this
system is very popular in heavy vehicles and pick-ups’. When the vehicle is
loaded in steel springs the height of the vehicle lowers due to the weight. But,
in air suspension the height sensors measure the fall in height and increase
the air pressure in the air spring rubber membrane to meet the targeted height.
(Plz note: air will be same but air pressure in increased)
2)
Improved Ride Quality: due to setting of ride
height, there is no additional drags or so and ride frequency is constant. Hence
even if the vehicle is loaded the vehicle dynamics behaves the same and it
feels the same even if it is loaded.
3)
Minimal heat generation compared to spring types
4)
Lower hystorsis
5)
Less shocks
Cons of Air Suspension :
1)
Expensive
2)
Temperature causes higher air pressure- so
vehicle rise without the control of ASU(presently rectified to some extent by
use of sophisticated height sensors, etc).
