الجمعة، 17 مايو 2013

Front Axle Suspension


Front Axle Suspension of tractor
BRIEF HISTORY:-
The old valve block consists of a ride control valve and a levelling control valve mounted together  as one unit.


Valve is positioned on the right hand side of the rear axle (heavy bracket)
  PROBLEMS WITH THIS DESIGN:-
The valve block and lift cylinder are mounted too far apart therefore have to be connected by two long hoses / tubes.
Reduced performance (sponginess of hoses under load)  
Long run (front to back of tractor)
In this new design and new tractors
use a new semi-active control suspension control system
As with the current (passive) suspension, the new system relies on accumulator pressure to control damping
The primary difference to the passive system is the controller
(RC module) varies the damping via the lockout valves according to vehicle and/or axle movement adjusting to compensate for various tractor system inputs
Always active at key on, regardless of state at key off
Lockout possible <12km/h (above this speed the suspension unlocks)
Momentary switch for lockout, cluster lamp displays status
Self levelling at all times

New Semi Active
Suspension System
CONSISTS OF TWO VALVES MOUNTED SEPARATELY:-
LEVELLING CONTROL VALVE:-
Controls height level of front axle
Mounted on the top of the pump
Single height control line for top up and exhaust
RIDE CONTROL VALVE:-
Controls damping / absorbs shock loads
Positioned on the top of the cylinder
One hose to the accumulator only
Semi-Active Suspension Processor
Inputs:
Lockout switch
Axle position (potentiometer) Levelling and Max suspension travel (anti-bang)
Front body vertical accelerometer
Vehicle forward speed
Low side pressure switch
Vehicle braking
Changes in throttle position
Gear changes
Speed changes
Rear hitch position changes
Outputs:
Load levelling raise solenoid (on/off)
Load levelling lower solenoid (on/off)
Upper damping solenoid (pwm)
Lower damping solenoid (pwm)
Cluster & switch lockout lamps

Components:
A1. Accumulator line
A2. Accumulator
A3. Height control solenoids
A4. Processor
A5. Cab switch
A6. Lockout / damping solenoids
A7. Tie rod
A8. Suspension ram
A9. Fill line
B 1. Lock out valves
B2. Axle support
B3. Fulcrum Point
B4. Axle
B5. Potentiometer
B6. Axle Pivot Point
B7. Pivot Arm (Panhard Rod)
B8. Hydraulic Cylinder



1.Lock out valves
2.Potentiometer
3. Levelling Valve Block
4. Microprocessor
5. In Cab Switch
6. Accelerometer

Suspension Status
Suspension can be off between 0-12 kph.

1. Operator command using switch on the right hand console

  For speeds between 1 and 12 km/h

  This function needed for precise control of front   mounted 

implements.

  No damping - lock out valves are shut

  If height deviates from ‘home’ position raise or lower valves will 

modify the position.

2. When the speed is less than 1 km/h for more than

  1.5 seconds

  For safety


On

Suspension can be on at any speed above 1 km/h

The default is ‘suspension on’ at engine start-up.

Suspension is always on at speeds in excess of 12 km/h.
If commanded off by the driver, when the speed reduces below 12 km/h, the suspension automatically switches off again.

A.Levelling Valve 
1.Raise solenoid valve
2.Lower solenoid valve
B. Ride control valve 
3. Supply line
4. Damping solenoid valve (damping chassis up movements)
5. Damping solenoid valve (damping chassis down movements)
6. Accumulator
7. Pressure switch
8. Ram cylinder
9. Ram rod
10. System safety valve
Operation
Lockout & Levelling – During lockout, OFF mode all the solenoids are de-energised (shut). If the suspension deviates from the mid (calibrated) value, detected by the potentiometer, either of the levelling solenoids 1 or 2 will be commanded to reset the suspension position.
Raise – solenoid 1 is energised and allows oil to pass to the pump via the load sense line and to the ram via the lowering check and solenoid valves. In the raise phase both solenoids 4 & 5 also energised to allow flow to the cylinder side and the accumulator.
Lower – solenoid 2 is energised and allows oil to pass out of the cylinder side the ram to 1. replenish the shortage of oil in the rod side of the shortening ram and 2. to pass through the drop restrictor and lower half of the raise solenoid to tank. In the same process the accumulator oil also flows to tank.
Manual lowering – is much same as the manual lowering screw is only a second input on the solenoid valve.
Suspension & Damping – In the suspension ON mode solenoids 4 &5 are open and all the suspension movements are expected to be absorbed by the accumulator and damping is achieved by restricting oil into the accumulator with solenoid 5 and from 9 to 8 with solenoid 4 all controlled be the controller with its various inputs.
Additional control – In the event of trying to absorb an oversized bump the 210 bar relief valve 10 will open and exhaust an amount of oil, this will immediately be refilled as required as the potentiometer detect a levelling deviation. If the axle drops away from the frame and there is a shortage of oil in the ram head (the accumulator is empty of oil) a depression will be sensed by the ram pressure switch (less than 22 bar) and the processor will command the raise solenoid to operate.