굴삭기 IMV용 비례 유량제어밸브 정특성 해석

Static Analysis of Dedicated Proportional Flow Control Valve for IMV

Abstract

Recently, as environmental regulations for earth-moving equipment have been tightening, advanced systems such as electronic control, have been introduced for energy savings. An IMV (Independent Metering Valve) consisting of four 2-way valves, is an electro-hydraulic control systems that provides more flexible controllability, and potential for energy savings in excavators, when compared to the conventional 4-way spool valve system. To fully maximize use of an IMV, the bi-directional flow control valve that can regulate a large amount of flow in both directions, should be adopted. The hydraulic circuit of an IMV applied to an excavator from an overseas construction equipment company, reveals the flow control valve with the compound of proportional solenoid valve for first stage, and 2-way spool valve for the second stage. Moreover, the two spools are interconnected by a feedback spring, presumed to compensate for flow force acting on the second stage spool. This paper addresses the static analysis of flow control valve in an IMV to investigate the improvement of robustness, against flow force by the feedback spring. From the steady-state analysis of flow control valve model, it can be concluded that the feedback spring facilitates maintaining linearity of spool displacement for control input, and relatively constant flow for load disturbance.

Fig. 1 Unidirectional flow control valve

Fig. 2 HSRE(high side regeneration extension)

Fig. 3 2 stage proportional flow control valve

Fig. 4 PSV(Proportional Solenoid Valve)

Fig. 5 PSV control pressure characteristics

Fig. 6 Proportional flow control valve

Fig. 7 FCV χ_v characteristics with Q₄ = k_vf = 0

Fig. 8 FCV χ_v characteristics with k_vf = 0

Fig. 9 FCV χ_v, F_q characteristics at d_lorf = 3mm

Fig. 10 FCV characteristics at d_lorf = 3, 4, 5mm

Fig. 11 Load flow characteristics at constant F_m

Table 1 Assumed PSV specificaitons

Table 2 Assumed flow control valve specifications

Table 3 FCV data with k_vf = 0 at F_m = 1N

Table 4 FCV data with feedback spring at F_m = 1N