Office for Technology Commercialization

High Efficiency Variable Displacement Pump Motor

Technology #20130212

Questions about this technology? Ask a Technology Manager

Download Printable PDF

Image Gallery
Variable Displacement Pump
Perry Y. Li, PhD
Professor, Department of Mechanical Engineering, Deputy Director, Center for Compact and Efficient Fluid Power
External Link (
Thomas Chase, PhD
Professor, Department of Mechanical Engineering
External Link (
Managed By
Kevin Nickels
Technology Licensing Officer 612-625-7289
Patent Protection

US Patent Pending US20170159641

Axial Positon of Rotary Valve

A new discrete piston pump/motor yields an unprecedented combination of simplicity, efficiency and versatility. This new pump/motor, which can be used as a pump, motor, or combination of a pump and motor, varies displacement by changing the axial position of a single novel rotary valve. It improves efficiency by discrete piston displacement that applies high pressure to pistons for only a portion of their stroke and saves energy by using hydro-mechanical valves instead of the more typical electric valves or complex variable cam systems. Instead of varying the stroke length, individual pistons can be enabled and disabled by using two- or three-way valves.

MN-IP Try and Buy
  • Trial period is up to 18 months
  • Trial fee is $10,000 for 12 months
  • Trial fee is wavied for MN companies or if sponsoring $50,000+ research with the University
  • No US patent expenses during trial period
  • $50,000 conversion fee (TRY to BUY)
  • Royalty rate of 3% (2% for MN company)
  • Royalty free for first $1M in sales

** View the Term Sheet **
** Contact Kevin Nickels for specific details. **

Discrete Piston Displacement

In general, variable displacement pump/motors are highly efficient. However, their efficiency decreases substantially at displacements below 50% due to friction and leakage losses that remain constant despite a reduction in displacement. Discrete piston displacement control minimizes these losses, but at a cost of increased energy/electricity. This new design improves the overall efficiency of a variable displacement pump/motor, especially at low displacements, by changing the way the displacement is varied.


  • Can be used as a pump, motor, or combination pump/motor
  • Simple, fast and repeatable on/off control
  • Only one control input needed
  • Bidirectional and capable of freewheeling
  • Robust—no electronic control required
  • Reduces power consumption and enables energy recovery; continuous spinning valve needs no acceleration
  • Potentially more compact and cost-effective
  • Applications may include hydraulic pumps and hydraulic motors

Phase of Development Proof of concept