Leakage modulation in hydraulic systems containing a three-way spool valve
AssigneeEaton Intelligent Power Limited
InventorMichael Rannow
Life of this patent
Estimating the term…
Abstract
Hydraulic systems and associated methods configured to reduce leakage past a spool valve when the system is in a neutral state. Leakage reduction is achieved by shifting the spool valve within the spool bore. The shifting direction can depend on whether the system has a relatively high load or a relatively low load in the neutral state. The amount of shifting can depend on the pressure differential between the supply line and the work port, and/or the pressure differential between the work port and the tank line.
Claims20
A hydraulic system, the hydraulic system having an operational state and a neutral state and comprising:
- a fluid supply line in fluid communication with a work port, the work port being in fluid communication with a tank line connected to a tank;
- a spool valve having a spool disposed in a spool bore defining an axis, the spool being axially moveable within the bore and being adapted to regulate fluid flow from the supply line to the work port and from the work port to the tank;
- and
- a driver that drives a first axial shifting of the spool when the hydraulic system is in the neutral state and there is a first pressure differential between the supply line and the work port, or that drives a second axial shifting of the spool when the hydraulic system is in the neutral state
- and there is a second pressure differential between the work port and the tank line.
11-20. (canceled)
A three-way spool valve comprising:
- a valve body defining a valve bore that extends along an axis, the valve body also including a supply port, a work port and a tank port all in fluid communication with the valve bore;
- a spool positioned within the bore, the spool including a first land axially separated from a second land by a flow passage, the spool being axially moveable along the axis between first and second positions;
- wherein in the first position the second land blocks fluid communication between the work port and the tank port and the flow passage provides direct fluid communication between the supply port and the work port;
- and
- wherein in the second position the first land blocks fluid communication between the supply port and the work port and the flow passage provides direct fluid communication between the work port and the tank port, the valve being operable in a neutral state where the spool is maintained in a shifted neutral axial position in which:
- a) the first land blocks fluid communication between the supply port and the work port;
- b) the second land blocks fluid communication between the work port and the tank port;
- and c) the spool has first and second deadband distances having different magnitudes, the first deadband distance being equal to a first axial distance the spool is required to travel to open fluid communication between the supply port and the work port, and the second deadband distance being equal to a second axial distance the spool is required to travel to open fluid communication between the work port and the tank port.
Dependencies are inferred from the claim text.