Hydraulic Pump Displacement Controlled by Solenoids

The Digital Displacement pump, referred to as the E-dyn 96, combines radial pistons with high-speed solenoid valves to produce an efficient variable-displacement hydraulic pump. The pump’s output is controlled activating cylinders required to meet the load demand on each revolution of the shaft. Pumping elements are 12 cylinders arranged in three groups of four. This method of control is said to result in fast response, precise control, and high efficiency by exactly matching the pump output to demand. The pump is in pre-production for industrial applications, with several units already in the field with customers.

Fig. 1
The Artemis axial-piston, Digital Displacement pump uses solenoid valves to control displacement.

When tested side-by-side at 1,800 rpm with a conventional axial-piston swashplate pump, the E-dyn 96 showed higher efficiency under all conditions, particularly at partial load. At 30% displacement, the swashplate pump exhibited an efficiency of 70%, whereas the E-dyn 96 was at 90%. In the pressurized standby (full pressure compensation) mode, the E-dyn 96 displayed one-tenth the losses of the swashplate pump. Over a typical varying duty cycle, losses in the E-dyn 96 pump could be about one-fourth those produced by the swashplate axial-piston pump. Depending on the duty cycle, this could result in more than $5,000 per year in electricity power consumption, plus additional savings associated with reduced cooling requirements.

Electronic Control

Fig. 2
The Digital Displacement pump uses three banks of four cylinders and can produce four separate output flows. Click on image for larger view.

E-dyn 96 includes an electronic controller that integrates process control and provides closed-loop control for pressure, flow, power, or other combined parameters. The basic pump can be configured to supply up to four independent fluid outlets at different pressures, and with independent control functions. In many cases, the controller can replace PLC functionality for system protection and auxiliary functions.  The controller also includes diagnostics for quick fault finding, plus reporting of machine health to the central machine controller or operator.

E-dyn 96 works with a standard induction motor; it does not require an expensive and complicated servo motor drive to boost efficiency and controllability. In many applications, such as hydraulic power units for injection molding machines and presses, the E-dyn 96 can be a drop-in replacement for existing variable-displacement pumps.

The Digital Displacement pump is currently undergoing development at Artemis Intelligent Power Ltd., Loanhead, Scotland. For more information, call +44 131-440-6260, or contact the firm via e-mail

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