Comfort Hydraulics: Pitching Vibration Damping

The driving speeds of mobile machines in agriculture have steadily risen in recent years. This affects tractors with front loader as well as yard and wheel loaders and telescopic loaders. These mostly unsuspended vehicles tend to oscillate due to the mass distribution and the spring effect of the tires in both speed and direction changes as well as when driving over bumps.

The kinematic of the lift mast, the tires and the weight of the cargo have a very big influence on these “pitching vibrations“. The lift mast, which acts as a lever arm, passes the impulse to the machine. Via the frame of the machine, this force is directed into the tires and results in deformation of the tire as single spring element in the chain. When driving over bumps, the movement impulse runs in reverse direction from the floor to the tire via the frame to the lift mast to the lifted mass. 

The resulting pitching vibrations, on the one hand, stress the machine parts and also lead to an impairment of the driving comfort and the driving safety. 

The driver must reduce the driving speed in order to safely operate the machine: a declining handling rate is the result. The goal is to reduce pitching vibrations and to dampen vibrations from the system “machine“as quickly as possible. The overall objective is to reduce initiated accelerations, so that disturbing pitching movements do not arise at all.

Through connection of hydraulic accumulators on the pressure-loaded cylinder side and activation of the opposite side to the tank, there is a decoupling of the lift mast to the machine. Thanks to this decoupling, accelerations of the lever arm will not be transmitted to the machine and vice versa. The decoupling is effected by the gas filling of the hydraulic accumulator, the damping via fluid friction and gas friction in the hydro-pneumatic system. Depending on the cylinder size, lever arm ratio and driving speed, there are very different flow rates, which oscillate back and forth between accumulator and cylinder.  The control blocks can be fitted with valves for flow rates from 70 up to 300 l/min.

The customized control blocks out of aluminum or steel are almost always adapted to the structural conditions of the machine. By using screw-in or flange valves, the degrees of freedom in the design of the block are kept as high as possible. The integration of accumulators or other functions such as pipe rupture protection are always possible.  

If necessary, the pitching vibration damping of ARGO-HYTOS can also easily be implemented afterwards in the current series of the OEMs.  Depending on the design, a connection of the control block with the control pressure supply of the machine and a separate tank line may be required, in the simplest case only an electrical signal is required. Due to the experience in the hydro-pneumatic suspension and damping systems, ARGO-HYTOS precisely designs the pitching vibration damping that matches your machine. Already in the design phase, possible solutions are discussed with you, also with regard to the relevant rules and regulations.

Info
Depending on the application, requirements and request, various functional elements can be combined almost arbitrarily.

• Directional control valves for switching on and off 70 - 300 l/min
• Pressures up to 350 bar
• Block material of galvanized aluminum or steel
• With or without accumulator protection and accumulator discharge
• Accumulator without pre-charge
• With constant or load-dependent pre-charge of the accumulator
• With / without pipe rupture protection in the block
• Piloting or bypassing of the pipe rupture protection in the activated state
• Accumulator integrated in the control block
• Control block for pipeline installation
• Control block for flange mounting directly at the lifting cylinder