Closed-center hydraulics system overview
Closed-center hydraulic pump
 
Main hydraulic pump

Main hydraulic pump

The main hydraulic functions on the S680 and S690 Combines utilize a closed-center hydraulic system. The system is equipped with a pressure-flow compensated (PFC) pump that varies the pressure and flow required to meet the immediate needs of the main hydraulic functions on the combines.
The pump only produces enough oil pressure to meet the system's demands as they occur. As a result, the pump is always in a low-pressure standby mode. The benefits of having low-pressure standby are:
  • Runs cooler than conventional open-center hydraulic systems
  • Less horsepower required
  • Easier engine starting
The variable-pressure hydraulic pump is an axial piston pump and features:
  • Piston-style design for quick response
  • 3100-psi high-capacity output
  • Solid robust design
  • Bigger front-end attachment lift capacity
  • Low noise (due to pressure flow on demand)
 
The closed-center system is ideally suited for S680 and S690 Combines that typically operate larger/wider headers because it:
  • Provides pressure-based header float to better maintain the constant ground pressure required by wider, heavier heads
  • Features higher-flow valve blocks for the fast hydraulic response needed with larger heads
  • Provides improved precision control (for the operator)
Header height (raise/lower) valve block with pressure control
 
Header height valve block

Header height valve block

The closed-center hydraulic system utilizes a separate header height (feederhouse raise/lower) control valve that features integrated pressure control.
The header height valve eliminates the need for an accumulator in the header raise and lower hydraulic circuit and results in:
  • Faster header-lift response time
  • More efficient control of raising and lowering the header
The header height raise/lower control valve is located on the left-hand side of the front axle frame and provides:
  • Close location to the feederhouse lift cylinders for faster raise/lower response
  • Easy-to-replace cartridge valve design (no need to replace the whole valve)
  • A 26 percent higher-flow capacity compared to the open-center design for easier lifting of heavier or wider heads
 
The header-height-valve block controls flow rates for:
  • Feederhouse raising and lowering
  • Header height sensing
  • Header float
Reel lift and lateral tilt valve block
 
Reel lift and lateral tilt valve block

Reel lift and lateral tilt valve block

Reel-lift-valve-block location

Reel-lift-valve-block location

The closed-center hydraulic system also features a separate reel lift and lateral tilt valve with proportional control. This valve provides:
  • Feederhouse lateral tilt adjustment – The speed can be increased or decreased if the system is too fast or slow during manual commands
  • Feederhouse lateral tilt sensitivity adjustment – This allows increase in sensitivity when in automatic mode if more response is needed. Decrease sensitivity if the system is not stable (jerky up and down)
  • Close location to the header and lateral tilt (left-hand side of feederhouse) - This enables for quicker operational response
  • Easy-to-replace cartridge valve design - There is no need to replace the entire valve
This valve controls flow rates for:
  • Reel raise and lower
  • Reel extend and retract
  • Feederhouse lateral tilt position
Primary control valve
 
Primary-control-valve block

Primary-control-valve block

Primary valve solenoids and wire harness

Primary valve solenoids and wire harness

The primary-control-valve block for the closed-center hydraulic system is located on the left-hand side of the separator body. The primary-control-valve block features a split electrical and valve design in that the valve block is placed on the rear side of a bulkhead panel and the electrical portion (solenoids, harnessing, etc.) is placed on the front side of the same panel.
 
The split design allows for easier serviceability while providing centrally located diagnostic ports. The primary-control-valve block controls flow for:
  • Unloading auger swing
  • Variable threshing speed
  • Folding grain tank extension/covers (if equipped)
The primary valve also features easy-to-replace cartridge valve technology (no need to replace the entire valve).
 
Last Updated : 04-May-2011