Novel Non-Torque Reactive Trailing Arm Air Suspension: Cholan Suspension - A Novel `Non-Torque Reactive' Air Suspension

Present long-haul trucks use higher torque output engines. New trucks also use engine power for more accessories than a few years ago. New brake regulation mandates 30% reduction in stopping distance, that is 30% increase in braking torque. Acceleration requirements need to be maintained while engine has to also expend power for additional units like power take off and to comply with EPA regulations. Insatiable drive to save costs is always on top of fleet owners' To Do list.

To save fuel, truck manufacturers generally concentrate on increasing efficiency of engine, given that not much could be done on transmission losses as units like turbine/clutch, transmission gear box and drive line parts are long established and standardized. A truck suspension is usually not suspected to contribute to lower fuel economy.

Here is a novel suspension that saves fuel, especially applied to
high volume, high-mileage-logging `Class 8 Highway Trucks'.

The Challenge

Most Class 8 tractors used in highway long haul applications invariably use `Torque Reactive Trailing Arm Pneumatic Suspensions'. In those suspensions the trailing arm is clamped to axle rendering the axle to swing along with trailing arm about a pivot at the front end of trailing arm. Disadvantages of those `torque reactive' suspensions are:

When a stationary truck starts to move, engine torque applied on wheels induces opposite torsional reaction on driven axle. This reaction tends to rotate trailing arms clamped to axle about axle axis. The tendency is countered by vertical load of suspended mass acting on front end of trailing arms. In other words the reaction on axle tends to lift loaded chassis of truck. Inversely, during braking, brake torque reaction on axle tends to pull chassis down. While this type of reaction effect in a front engine mounted rear axle driven sedan aids in increasing traction during acceleration, in heavy trucks it is detrimental to truck performance in many ways.

What happens when axle tends to react to drive torque and braking torque?

1)Tendency to lift chassis means severe unwanted stress on frame mounted hanger brackets, trailing arms, axle housing, tires, axle shafts, differential gears, ring gear-pinion gear contact points, bearings in propeller shaft UJs, transmission gears, clutch/turbine, right up to engine and its mounts on frame. Just for the reason that a suspension is reactive, all parts in power transmission path, being series, experience equivalent additional high load. Tires are more stressed at road contact points during acceleration since power available is used both to move truck forward and to overcome the effect of reaction torque. Engine power is not efficiently used during acceleration in a torque reactive suspension. This phenomenon occurs when accelerating from any speed, though not as severe as when accelerating a stationary truck. Even at a cruising speed there is constant reaction on axle and corresponding tendency to lift chassis. This exerts a constant additional strain at tire contact which adds to tire rolling resistance. Similarly braking power is not efficiently utilized since a portion of braking power is unnecessarily used to pull chassis down instead of aiding to slow the vehicle, resulting in loss of traction which is very much required during braking.

2) Pinion shaft angle changes, resulting in severe torsional and inertial vibration emanating from all parts in the line of power transmission. Happens all the time during acceleration, braking, coasting, cruising, jounce and rebound. This change in pinion shaft angle gets aggravated with the implementation of brake regulation FMVSS 121(74 FR 37122) that demands 30% reduction in stopping distance and corresponding 30% increase in brake torque, causing more damage to drive-line parts and more disturbing vibration. Worse in a panic braking situation.

The Viable Solution

Patent: US 8,602,430 B2

Suspension Arrangement in a Tandem Axle

Leading / Trailing Configuration for 52" Bogie Spread

Trailing / Trailing Configuration

This new invention is based off a simple four bar mechanism. Main difference between this invention and prior inventions is, this invention uses a spherical joint between trailing arm and axle while prior similar inventions generally use pivoted joint. Further, this invention uses a vertically resilient portion of trailing arm, forward of axle, to absorb energy while prior inventions use a rigid beam all through. Other novelty is that the vertically resilient portion of trailing arm between axle joint and hanger bracket joint doubles as a link of four bar mechanism. Unlike a pivoted axle joint which generally requires a cylindrical hole in the trailing arm to connect to axle, the spherical joint does not require a hole in the trailing arm thereby preserving its structural integrity.

Trailing Arm Assembly

The Invention Solves/Mitigates Several Technical Problems Existing In `Torque-Reactive Trailing Arm Air Suspensions'

And

Provides Many Tangible Benefits To Truck Performance:

Increase in mileage due to

.....Reduced rolling resistance during acceleration and all operating speeds

.....Effective use of fuel to move vehicle forward than rising frame

.....Reduced friction loss between all parts in the path of power transmission

Substantial reduction in universal joint excited vibration and therefore better driver comfort through out full stroke of jounce and rebound, acceleration, braking, coasting and cruising.

Longer service life of drive line components between engine and axles

Lower truck down time

Enhanced ride, handling and steering response

Smoother acceleration and braking without wheel hops or chassis jerks

Negligible frame squat (frame rise and frame drop) -

.....Better driver comfort

.....Better acceleration response

.....Better braking response, increases braking performance by effective use of braking torque

More suitable for brake performance requirement per FMVSS 121(74 FR 37122) due to non-reactive nature

Adjustable ride height without change in any component of suspension while maintaining required pinion angle

Geometrically configured to have least effect on roll steer and bump steer

Suitable for high torque engine applications

Flexibility to use higher axle ratios

Reduces rolling resistance on driven axle tires in all speed and substantially during acceleration

Longer tire life due to lesser rolling resistance and tire strain

Reduced `torque reaction effect' on engine mounts paving way for their economical design and weight reduction

Active Roll Over Stiffness is provided by

.....resistance to twisting of a torsionally(across length) resilient trailing arm helped by freedom of the trailing arm to articulate about spherical joint.

.....the system of two trailing arms and the stabilizer connecting their rear ends forming a virtual anti-roll bar

Anti-Roll Mechanism

The concept can be extended to driven/non-driven steer axle and non-driven rear axles.The concept as applied to the "Application Specification" has been thoroughly ENGINEERED considering primary forces experienced by the components in the suspension system. Components are designed for manufacturability and are to contemporary worldwide truck industry standards.

The Suspension is Engineered to perform and achieve what is stated above.