Recall that solenoid force is a directly proportional to electric current. The electric current flowing through the coil can be calculated by Ohm’s Law: V = I • R, otherwise written as I = V R • Example: D08 12V DC coil resistance is 9.0 at 21°C • With nominal voltage, the current is then I=12V/9.0=1.33 Amps What if the machine’s electrical load is high and the system voltage is only 9V? • Now the current is I=9V/9.0=1.00 Amps
支腿油缸
Use P.O. Check (not counterbalance) for cylinder!
• Flow 12 lpm, Pressure 180 bar, Leakage not specified but typical 6 drops/minute should be sufficient.
插装阀产品培训
HIC 培训，2008年3月
预期培训目标：
• 理解每一种插装阀产品的功能和基本用法。 • 理解每一种插装阀的典型应用。 • 明白如何去阐述样本的含义，明白如何去避免插装阀使用过程中 的一般性问题。 • 有信心和能力去满足客户的需求，绘制一个回路，以及选择正确 的元件。
议程
• Introduction • Paver Valve Example P.O. Check Valves Solenoid Valves Pressure Reducing Valves Relief Valves • Tomato Harvester - Flow Controls - Counterbalance Valves • Skid Steer Loader - Poppet Type Logic Elements • Sod Harvester - Proportional Valves - Spool Type Logic Elements • Manifold Design
应用 – 沥青摊铺机
Screed Lift/Lower
Hopper Lift
Auger Lift
Parking Brake
沥青摊铺机阀组
Auger Cylinder: • Lift • Lower • Flow 16 lpm max. Parking Brake: • On/Off • Pressure 24 bar max. • Flow negligible Hopper Cylinder: • Lift • Lower • Flow 16 lpm max.
• The pilot ratio is the ratio of the pilot piston area to the check valve seat area. • This is typically between 2.5:1 and 4:1. • These ratios will be satisfactory for 95% of all applications. • Pilot-operated check valves are generally sized based on flow and acceptable pressure drop.
FIXED CORE “Non magnetic element”
Plunger fixed on spool
电磁阀(5)
In a 3 position solenoid valve we have a double solenoid with 2 coils.
Manual Override
FIXED CORE (Armature)
液控单向阀 – 压力强化
• Care must be taken when applying a pilot-operated check valve on the rod end of a cylinder with a large bore:rod ratio. In extreme cases the rod pressure is intensified enough that it may be difficult to pilot open the check valve. • Use equations in Sauer-Danfoss Cartridge Valves Technical Information catalog to determine operating pressures and required pilot pressure. • If intensification creates application concerns, use a counterbalance valve.
PLUNGER FIXED CORE
电磁阀(4)
PULL MODE
When the solenoid is in PULL MODE the fixed core is in the back part of the tube; by energising the coil, the magnetic field pulls the spool forward to the fixed section.
液控单向阀 – 回路提示
Locate pilot-operated check valves at or near the actuator to provide maximum load holding in the event of hydraulic line failure. Use pilot-operated check valves for load-holding, not motion (speed) control.(note 1) Do not use pilot-operated check valves with closed-center directional control valves.(note 2)
液控单向阀 – 热膨胀
• Care must be taken when applying a pilot-operated check valve on to a cylinder where duty cycles may be low and temperatures may be high. (note 1) • In these cases, thermal expansion can cause a significant pressure increase for oil trapped between the cylinder and the pilot-operated check. (note 2) • Solutions: • Add a small thermal relief valve or use a counterbalance valve
支腿油缸
Schematic:
• Pilot-operated check valve for load holding. Note that load acts in one direction only (to lower hopper) • 4 way 3 position valve for lift & lower • Orifice to limit flow to 16 lpm
液控单向阀 vs. 平衡阀
液控单向阀 Load Holding Valve Functions: • Prevent load from dropping in case of hose or tube failure. • Prevent load from drifting caused by directional control valve spool leakage • Provide smooth, modulated motion when the load is in a lowering or run-away mode. • Provide smooth, modulated motion when the directional control valve is suddenly closed. 平衡阀
Spool-Type Solenoid Valves
• 2-way 2-position
• 3-way 2-position
• 4-way 2-position • 4-way 3-position
电磁阀 (1)
What is a SOLENOID VALVE ?
Spool
Housing
Cartridge
YES
YES
YES
YES
NO
YES
NO
YES
液控单向阀 – 它们如何工作
Free flow to lift load Check valve holds load Input pressure on piston pilots check open for lowering
液控单向阀 – 先导比和选型
Screed Cylinder: • Lift (single acting) • Float with ~27 bar in rod end of cylinder. • Flow 24 lpm max.
Pump: • 180 bar press. comp. • Enough flow to run everything at once.