167086 4/3-way proportional valve A B P T Y1 Y2 Y1 Y2 4 1 T 14 Design 13 A 2 P 5 3 B 12 11 10 9 8 7 6 The 4/3-way proportional valve is mounted on a function plate with four quick coupling connectors. The four electrical connections are equipped with safety jackplugs. The component is fitted to the grid system of the slotted assembly board by means of the two blue levers (mounting variant “A”). The valve consists of: Piston (1), housing (2), spring (3), earthing contact (4), electrical connections of solenoid (5), emergency manual override (6), sliding bearing (7), compensating bore (8), solenoid coil (9), plunge (10), spring disc (11), control notch (12), stem (13), pressure tube (14) © Festo Didactic GmbH & Co. KG, 04/2003 Subject to change 1/4 167086 4/3-way proportional valve Function 2/4 The proportional valve is suitable for both the directional control of flow rates and their magnitude and is directly actuated by means of DC solenoid coils. Characteristic of this valve is the continuous adjustability of the piston. The valve is shown in the mid-position in the sectional view. All ports are mutually closed. The valve assumes the mid-position via the two compression springs, if neither of the two solenoids are energised (spring force). If voltage is applied to the solenoid coil (energised) Y2 (9), the plunger (10) pushes the piston (1) against the spring opposite. This connects port P to port A and port B simultaneously to port T. If the solenoid coil Y1 is energised, the piston is pushed in the opposite direction. Port P is then connected to port B and port A simultaneously to port T. The difference between a proportional valve and a switching valve is in the type of adjustability of the piston. Whereas the switching valve only has two statuses, i.e. energised and de-energised, whereby the piston is either completely extended or not at all, the proportional valve can approach any number of intermediate positions. This infinite adjustability is assumed by the proportional solenoid. A force is created if the solenoid is energised, which acts on the plunger. The magnitude of the force is dependent on the magnitude of current flowing through the solenoid coil. The plunger with the stem pushes the valve piston against the opposite compression spring until an equilibrium of forces is established between the force of the plunger and the compression spring. The displacement length of the valve piston is proportional to the magnetic flux applied. From the mid-position, the piston initially needs to traverse an overlap. During this, the ports still remain closed. The control notch (12) of the piston then starts to open against the ridge of the housing. Two groups of control notches always open at any time (P->A and B->T or P->B and A->T). The cross-sectional area of the gap opens up increasingly. The degree at which the area and as such the flow change depends on the shape and number of control notches. A V-shaped notch results in a progressive flow pattern, whereas a rectangular notch produces a linear flow pattern. An emergency manual override (6) also facilitates actuation without electrical energy. Subject to change © Festo Didactic GmbH & Co. KG, 04/2003 167086 4/3-way proportional valve 4 ∆p = l/min 6 MPa 3 4 MPa Flow rate q 2.5 2 2 MPa 1.5 1 1 MPa 0.5 0 1000 mA 500 0 Current I Magnet B 500 mA 1000 Current I Magnet A Flow rate signal characteristic curve 6 MPa Pressure pA, pB 4 2 0 240 mA 120 0 Current I Magnet B 120 mA 240 Current I Magnet A Pressure signal characteristic curve © Festo Didactic GmbH & Co. KG, 04/2003 Subject to change 3/4 167086 4/3-way proportional valve Note The valve ports are identified by letters. A, B Working ports P Supply port T Return-line port (tank connection) The electrical connections are protected against overvoltage. The switching status is indicated by an LED. The emergency manual override must not be actuated by means of a sharp-edged objects (e.g. screwdriver) so that its smooth operation and leak-proofness are maintained. A stiff manual override may result in malfunction of the solenoid valve. Technical data 4/4 Hydraulic Medium Mineral oil, recommended viscosity 22 cSt (mm²/s) Operating pressure p 60 bar (6 Mpa) Max. permissible pressure pmax 120 bar (12 Mpa) Valve construction Directly actuated spool valve Port pattern, hydraulic ISO/DIN 4401 Size 02 Nominal flow rate qN 1.2 l/min when pN = 0.5 MPa/control edge Leakage loss qL <0.01 l/min at 6 Mpa Maximum degree of contamination Class 19/17/14 to ISO ( Class 8 to NAS ) Oil temperature, maximum 75 °C Actuation Proportional solenoid, pressure-tight, pushing Voltage 24 V DC Nominal current 800 mA Resolution <1 mA Switching time – signal jump 0 – 100 % 40 ms Repetition accuracy <1 % Connections, electrical Via 4 mm safety connector plug Connections, hydraulic Via 4 coupling sockets Subject to change © Festo Didactic GmbH & Co. KG, 04/2003