Design of a Crank-Slider Spool Valve for Switch-Mode Circuits With Experimental Validation

Abstract

A challenge in realizing switch-mode hydraulic circuits is the need for a high-speed valve with fast transition time and high switching frequency. The work presented includes the design and modeling of a suitable valve and experimental demonstration of the prototype in a hydraulic boost converter. The design consists of two spools driven by crank-sliders, designed for 120 Hz maximum switching frequency at a flow rate of 22.7 lpm. The fully open throttling loss is designed for <2% of the rated pressure of 34.5 MPa. The transition time is less than 5% (0.42 ms at 120 Hz) of the total cycle and the duty cycle is adjustable from 0 to 1. Leakage and viscous friction losses in the design are less than 2% of the rated hydraulic energy per cycle. The experimental results agreed well with the model resulting in a 3% variation in transition time. The use of the high-speed valve in a pressure boosts converter demonstrated boost ratio capabilities of 1.08–2.06.

Development of High-Speed On–Off Valves and Their Applications

“…Koktavy et al provided a crank-slider 3/2 spool valve in 2018 [33]. As shown in Figure 10, two spools actuated by the crank-shaft serve as the slider in the crank-slider mechanism.…”

A Review of Switched Inertance Hydraulic Converter Technology1

“…The valve showed very good performance with a maximum switching frequency of 120 Hz and a flow rate of 22.7 L/min. The leakage of the valve is very low (0.065 L/min), when tested at the pressure difference of 194bar and at the rotating speed of the input shaft of the crank-slider of less than 0.32rad/s [64]. This mechanism was able to recuperate the energy with a flywheel and avoided the bang-bang actuation with a solenoid, or the throttling process with a servo valve, thus minimized the energy needed in the pilot stage and greatly simplified the control strategy.…”

“…20: The Crank-slide spool valve developed by Koktavy et al in 2017 [64] In 2017, Koktavy et al designed a new switching valve with two spools combined and driven by a crank-slider mechanism to alternately switch the flow from the supply line to port A or port B shown in Fig. 20 [64]. The valve showed very good performance with a maximum switching frequency of 120 Hz and a flow rate of 22.7 L/min.…”

Characteristic investigation of a magnetostrictive fast switching valve for digital hydraulic converter

“…Kudzma et al 19 designed a 2/3 way two-stage linear fast switching spool valve with multiple grooves actuated by a two-stage servo valve with proportional throttling dissipation. Koktavy et al 20 developed a dual spool switching valve driven by a bulky crank-slider mechanism, which was validated in a pressure boost converter circuit. As far as spool valve is concerned, it is relatively easy to perform position control of spool driven by solenoids 18 and a hydraulic pilot stage.…”

“…These literatures mentioned above indicated that it is inadequate to push forward the development of DHCs only by improving the performance of electromagnetic actuators 18 or hydraulic amplifiers 19 and mechanical equipment, 20 while these drawbacks evoked the advent of similar linear valves driven by intelligent material typically on behalf of piezoelectric stack (PZT) 22 and giant magnetostrictive material (GMM). 23,24 The piezoelectric actuator makes the valve easy to attain higher response frequency within a micron stroke.…”