北京华德比例方向阀4WRA型电磁比例换向阀4WRA6W6-10B/24Z4/M4WRA6M6-10B/24Z4/V4WRA10EB10-10B/24Z4/V4WRA10W10-10B/24NZ4/V4WRA6MA6-10B/24NJZ4/M)