Description
Valves of the type Rexroth 4WS2EM are electrically operated, 2-stage directional servo valves with porting pattern according to ISO 4401-05-05-0-05. They are mainly used to control position, force, pressure or velocity. These valves are made of an electro-mechanical converter (torque motor) (1), a hydraulic amplifier (principle: nozzle flapper plate) (2) and a control spool (3) in a sleeve (2nd Stage) which is connected with the torque motor via a mechanical feedback.
An electrical input signal at the coils (4) of the torque motor generates a force by means of a permanent magnet which acts on the armature (5), and in connection with a torque tube (6) results in a torque. This causes the flapper plate (7) which is connected to the torque tube (6) via a bolt to move from the central position between the two control nozzles (8), and a pressure differential is created across the front sides of the control spool (3). The pressure differential results in the spool changing its position, which results in the pressure port being connected to one actuator port and, at the same time, the other actuator port being connected to the return flow port.
The control spool is connected to the flapper plate or the torque motor by means of a bending spring (mechanical feedback) (9). The position of the spool is changed until the feedback torque across the bending spring and the electromagnetic torque of the torque motor are balanced and the pressure differential at the nozzle flapper plate system becomes zero.
The stroke of the control spool and consequently the flow of the servo valve are regulated proportionally to the electrical input signal. It must be noted that the flow depends on the valve pressure drop.
Rexroth 4WS2EM Directional valve are made of an electro-mechanical converter (torque motor) (1), a hydraulic amplifier (principle: nozzle flapper plate) (2) and a control spool (3) in a sleeve (2nd Stage) which is connected with the torque motor via a mechanical position feedback.
- Size 10
- Component series 5X
- Maximum operating pressure 315 bar
- Maximum flow 180 l/min
- Area of application in accordance with the Explosion Protection Directive 2014/34/EU: II 1G
- Type of protection: Ex ia IIC T4 Ga according to EN 60079-0 / EN 60079-11
An electrical input signal at the coils (4) of the torque motor generates a force by means of a permanent magnet which acts on the armature (5), and in connection with a torque tube (6) results in a torque. This causes the flapper plate (7) which is connected to the torque tube (6) via a bolt to move from the central position between the two control nozzles (8), and a pressure differential is created across the front sides of the control spool (3).
The pressure differential results in the spool changing its position, which results in the pressure port being connected to one actuator port and, at the same time, the other actuator port being connected to the return flow port.
The control spool is connected to the flapper plate or the torque motor by means of a bending spring (mechanical feedback) (9). The position of the spool is changed until the feedback torque across the bending spring and the electromagnetic torque of the torque motor are balanced and the pressure differential at the nozzle flapper plate system becomes zero.
The stroke of the control spool and consequently the flow of the servo valve are regulated proportionally to the electrical input signal. It must be noted that the flow depends on the valve pressure drop.
Function, section
Valves of type 4WS2EM are electrically operated, 2-stage directional servo valves. They are mainly used to control
position, force, pressure or velocity.
The valves basically comprise of an electro-mechanical converter (torque motor) (1), a hydraulic amplifier (nozzle flapper plate principle) (2) and a control spool (3) in a sleeve (2ndstage) which is connected with the torque motor via a mechanical feedback.
An electrical input signal at the coils (4) of the torque motor generates a force by means of a permanent magnet which acts on the armature (5), and in connection with a torque tube (6) results in a torque. This causes the flapper plate (7) which is connected to the torque tube (6) via a bolt to move from the central position between the two control nozzles (8), and a pressure differential is created across the front sides of the control spool (3).
This pressure differential results in the control spool (3) changing its position, which results in the pressure port being connected to one actuator port and, at the same time, the other actuator port being connected to the return flow port.
The control spool (3) is connected to the flapper plate or the torque motor by means of a bending spring (mechanical feedback) (9). The position of the control spool (3) is changed until the feedback torque across the bending spring and the electro-magnetic torque of the torque motor are balanced and the pressure differential at the nozzle flapper plate system becomes zero.
The stroke of the control spool (3) and consequently the flow of the servo valve are controlled proportionally to the electrical input signal. It must be noted that the flow depends on the valve pressure drop. External control electronics (servo amplifier) serve the actuation of the valve, amplifying an analog input signal (command value) so that with the output signal, the servo valve is actuated in a flow-controlled form.
Version “-104”
This is a directional servo valve in 3-way version which means that depending on the input signal either P to B
or B to T is connected. Channel A is always blocked in the control area.
External control electronics (separate order)
External control electronics (servo amplifier) serve the actuation of the valve, amplifying an analog input signal (command value) so that with the output signal, the servo valve is actuated in a flow-controlled form.
Feature
- 4/3-way version, can also be used as 3-way version
- For intended use in potentially explosive areas of zone 0
- Valve to control position, force, pressure or velocity
- 2-stage servo valve with mechanical feedback, 1st stage as nozzle flapper plate amplifier
- For subplate mounting
- Porting pattern according to ISO 4401-05-05-0-05 with ports X and Y
- Dry control motor, no contamination of the solenoid gaps by the hydraulic fluid
- Wear-free control spool return element
- External control electronics in modular design, additional safety barrier (separate order)
- Valve is adjusted and tested
- Internal/external pilot oil supply and return can be ordered individually
- Spool with flow force compensation
- Control sleeve centrically fixed, thus low susceptibility to temperature and pressure
- Pressure chambers at the control sleeve with gap seal, therefore no wear of the seal ring
- Filter for 1st stage freely accessible from the outside
Specification
General
| Type | 4WS2EM 10…XH | |
| Size | 10 | |
| Component series | 5X | |
| Porting pattern | ISO 4401-05-05-0-05 | |
| Installation position | Any – ensure that during start-up of the system, the valve issupplied with sufficient pressure (? 10 bar)! | |
| Surface protection | Valve body, cover, filter screw | nitro-carburated |
| Cap | anodized | |
| Storage temperature range | ” +5 … +40 °C | |
| Weight | 03.56.00 kg | |
| Ambient temperature range | “-20 … +60 °C | |
Hydraulic
| Type | 4WS2EM 10…XH | |
| Maximum operating pressure | 315 bar | |
| Maximum operating pressure | Anschluss A | 315 bar |
| Port B | 315 bar | |
| Port P | 10 … 210; 10 … 315 bar | |
| Maximum return flow pressure | Port T | Pilot oil return, external |
| Pilot oil return, internal | ||
| Port Y | Pressure peaks < 100, static < 10 bar | |
| Hydraulic fluid | Mineral oil (HL, HLP) according to DIN 51524; | |
| Ignition temperature > 150 °C | ||
| Hydraulic fluid temperature range | “-15 … +60 °C | |
| preferably | ” +40 … +50 °C | |
| Maximum admissible degree of contamination of the hydraulic fluid, cleanliness class according to ISO 4406 (c) 1) | Class 18/16/13 | |
| Viscosity range | 15 … 380 mm²/s | |
| preferably | 30 … 45 mm²/s | |
| Feedback system | mechanical | |
| Hysteresis (dither-optimized) | ? 1.5 % | |
| Range of inversion (dither-optimized) | ? 0.3 % | |
| Response sensitivity (dither-optimized) | ? 0.2 % | |
| Zero adjustment flow over the entire operating pressure range 2) | ? 3 % | |
| Zero shift upon change of | Hydraulic fluid temperature | ? 1 %/20° C |
| Ambient temperature | ? 1 %/20° C | |
| Operating pressure 80 … 120 % of pP 3) | ? 2 %/100 bar | |
| Return flow pressure 0 … 10 % of pP 3) | ? 1 %/bar | |
1)The cleanliness classes specified for the components must be adhered to in hydraulic systems. Effective filtration prts faults and simultaneously increases the life cycle of the components.
2)long-term ? 5%
3)pP = operating pressure in bar
| Rated flow (tolerance ±10 % with valve pressure differential ?p = 70 bar (35 bar/edge)) 1) 2) | l/min | 5 | 10 | 20 | 30 | 45 | 60 | 75 | 90 | ||||||||
| Zero flow (with spool overlap “E”, measured without dither signal) 3) 4) | |||||||||||||||||
| l/min | x = 0.7 | x = 0.9 | x = 1.2 | x = 1.2 | x = 1.2 | x = 1.5 | x = 1.5 | x = 1.7 | |||||||||
| Maximum control spool stroke at mechanical end position (in case of error) related to nominal stroke | 120 … 170 % | 120 … 170 % | 120 … 170 % | ||||||||||||||
| Pressure amplification with 1 % control spool stroke change (from the hydraulic zero point) 4) 5) | % | ? 30 | ? 60 | ? 80 | |||||||||||||
1)Tolerance ±10 % with valve pressure differential ?p = 70 bar
2)qv nom = rated flow in l/min
3)qV,L = zero flow in l/min
4)pP = operating pressure in bar
5)of pp with 1 % spool stroke change (from the hydraulic zero point)
Notice:The specified technical data were measured with HLP32 and ?Oil = 40 ±5 °C.
Electrical
| Type | 4WS2EM 10…XH | ||
| Size | 10 | ||
| Rated current per coil | mA | 30 | |
| Protection class according to EN 60529 | IP65 (If a suitable and a correctly mounted mating connector are used.) | ||
| Type of signal | analog | ||
| Resistance per coil | ? | 85 | |
| Inductivity 1) | Parallel connection | H | 00.25 |
1)With 60 Hz and 100% rated current
Notice:
In case of control using non-Rexroth amplifiers, we recommend a superimposed dither signal.
Information on explosion protection
| Area of application according to directive 2014/34/EU | II 1G | ||
| Valve solenoid type of protection according to EN 60079-0 / EN 60079-11 | Ex ia IIC T4 Ga | ||
| Power supply of the valve only by certified, intrinsically safe electric circuits with the following maximum values | Admissible voltage Umax | V | 09.03 |
| Admissible current Imax | mA | 390 | |
| Admissible power Pmax | mW | 907 | |
Conditions for use in zone 0
- The valve cap is made of die-cast aluminum. For the use as a device of category 1 in zone 0, the valve cap must be protected in a way that ensures thatin case of rare operating failures, no explosive sparks from friction, impact or grinding can occur.
- Notice: The ignition temperature of the hydraulic fluid used must be at least 150 °C.
Required clearance area for bursting protection
- The indicated clearance area for bursting protection (see “Dimensions”) must be kept clear so that in the error case, overpressure can escape from the valve cap through the blanking plug.
Download Datasheet: Directional servo-valves 4WS2EM 10…XH Rexroth
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