Proportional Solenoid Valves

Transcription

1 Solenoid Valves Directional Control Pressure Control Flow Control Sizes 1/2 thru thru 250 GPM 5100 PSI WRE Typical Directional Control Models WRKE Principles of Operation solenoid action can be applied to directional control, pressure control, and flow control valves. The principle is to control the movement of the valve spool against a return or centering spring by regulating current flow through a DC solenoid coil. Current is varied by varying the applied voltage to the coil through the appropriate amplifier card. Bosch Rexroth amplifier cards are specifically designed to operate a particular series of valves, and can, therefore, be set up with a minimum of field adjustments. This is particularly important when an amplifier has to be replaced in the field and down-time must be kept to a minimum. Two types of solenoids are used with Bosch Rexroth proportional valves. The first is called a stroke-controlled solenoid because the length of stroke is controlled by feedback from the actuator to cause the valve spool to move to a precise position for the desired valving action. Metering notches on the spool lands are carefully designed to produce a flow orifice directly proportional to the distance the spool is shifted. The second type is called a force-controlled solenoid because there is no feedback from the load. The spool compresses a spring and stops when the applied force is equal to the spring resistance. This type of solenoid is commonly used in pressure control applications, and is also used on the Bosch Rexroth 4WRA series of directional control valves. A proportional solenoid valve operating in an open loop configuration receives no feedback to let it know that the actuator has reached its commanded position or that the commanded pressure or flow has been reached. It is possible, through the use of additional control components such as pressure transducers, encoders, and magneto restrictive feedback devices to use these valves in closed loop applications. Certain applications which once required the use of servo valves can now be accomplished with proportional solenoid valves at greatly reduced cost and increased reliability. 160

2 Solenoid Valves Selection Criteria for Solenoid Valves Selection of proportional solenoid valves is a more demanding process than selection of standard directional valves. The goal is to provide true control of the load rather than simply commanding it to start or stop. It is necessary to have a complete understanding of the machine cycle and the characteristics of the load in order to properly apply a proportional solenoid valve. Following are several important criteria to be considered when designing control circuits: The natural frequency of the system. The range of flows required. The influence of changes in mass, velocity, pressure, and viscosity. Any time delays required. If pressure compensators are required. Pressure intensification when using single rod cylinders or oversize rod cylinders and meter-out pressure compensators. Whether closed loop control must be used or open loop control is adequate. Will valve response time affect system-operation? If so, do servo valves need to be considered? Size selection is not made on the lowest possible pressure drop through a valve as is commonly done when selecting other directional control valves. The most important function of a proportional solenoid directional valve is to be able to meter the flow accurately; and to accomplish this there must be a moderate pressure drop through the valve. A valve model must be selected and a spool variation be chosen so there will be at least a 145 PSI pressure drop through the valve when the spool is fully shifted. An accurate selection can only be made with the aid of the flow graphs in the Bosch Rexroth bulletin for that model. Model numbers listed in this manual are not complete. Additional numerals and letters must be added to specify spool choice and other options. Contact your local Womack office for assistance in selecting the correct valve for your application. Rexroth Amplifier Cards The amplifier cards offered by Bosch Rexroth for operation of solenoid proportional valves perform many functions in addition to simply amplifying the input signal to a level required to drive the proportional solenoid. Some of these functions may include: A voltage stabilization circuit to provide constant voltage for consistent performance. Internal potentiometers that can be adjusted to limit the maximum output command signal. Some amplifier cards contain up to 4 of these potentiometers which allow individual settings of multiple velocities. Internal relays that facilitate selection of pre-set velocities. Some cards contain up to 4 of these relays and also provide LED s to indicate the relay which is activated. A ramp generator to control acceleration and deceleration rates which provide shockfree operation. Potentiometers which allow ramp control for each individual input command. A function generator which eliminates valve deadband, allowing instantaneous reversal with smooth crossover characteristics. Pulse width modulated (PWM) output which reduces system hysteresis and allows amplifiers to be used at high ambient temperatures. 10-volt differential amplifier input which enables interface with programmable controllers, microprocessors, or computers. The following spool types are available. Please consult Rexroth Catalog for more details Spool Types E = EA = V = W = Q = WA = 161

3 Direct Operated, Model 4 WRA(E)B Size PSI 7.9 GPM 4/2 & 4/3 Hysteresis <3.5% Repeatability <1% Sensitivity <1% Frequency response 24 Hz Mounts on standard D03 subplate Two piece solenoid design with removal coils Integrated electronics available (4 WRAEB) Spool types: E, EA, W, WA 4 WRA(E)B directional control valves Model 4 WRA B 6 and 4 WRAE B 6 are direct operated spool valves. They control the direction and quantity of flow to an actuator, for smooth acceleration to a desired velocity. The valve is normally operated by integrated electronics or the appropriate amplifier card. The 4 WRA B 6 can be operated as a switching valve if proportional control is not required. Covered manual overrides are standard to simplify troubleshooting. For more information, refer to Bosch Rexroth Data Sheet RA Direct Operated, Model 4 WRA Size 6 & PSI 25.0 GPM Hysteresis <6% Repeatability <3% Frequency response 4-6 Hz Mounts on standard D03 and D05 subplates Spool types: E, EA, V, W, WA 4 WRA directional control valve Model 4 WRA is a direct operated spool valves. It controls the direction and quantity of flow to an actuator, for smooth acceleration to a desired velocity. The valve is normally operated by the appropriate amplifier card. Covered manual overrides are standard to simplify troubleshooting. For more information, refer to Bosch Rexroth Data Sheet RA

4 Direct Operated, Model 4 WRE with Feedback Size 6 & PSI 70.0 GPM 4/2 & 4/3 Hysteresis <1% Repeatability <1% Sensitivity 0.5% Frequency response 4-6 Hz Mounts on standard D03 and D05 subplates Electrical spool position feedback Spool types: E, EA, V, W, WA 4 WRE directional control valve Model 4 WRE is a direct operated spool valves. It controls the direction and quantity of flow to an actuator, for smooth acceleration to a desired velocity. The valve is normally operated by the appropriate amplifier card. The LVDT feedback device is mechanically linked to the spool. Spool position is fed back to the amplifier card for stroke position verification. For more information, refer to Bosch Rexroth Data Sheet RA Pilot Operated, Model 4 WRZ Size 10 to PSI GPM Hysteresis 6% Repeatability 3% Mounts on standard D05, D07, D08, D10 subplates Spool types: E, EA, W, WA 4-Way directional control valve Model 4 WRZ is a pilot operated, twostaged, spool valve. It controls the direction and quantity of flow to an actuator, for smooth acceleration to a desired velocity. The valve is normally operated by the appropriate amplifier card. For more information, refer to Bosch Rexroth Data Sheet RA WRZ 163

5 Pilot Operated, Model 4 WRK with Feedback Model 4 WRKE Feedback with Integrated Electronics Size 10 to PSI GPM Hysteresis 1% Repeatability 0.5% Mounts on standard D05, D07, D08, D10 subplates Integral electronics (4 WRKE) High Response Time Spool types: E, Q, W 4-Way 4 WRKE 10 Control valves Model 4 WRK and 4 WRKE are pilot operated 2-stage proportional directional valves. They control the direction and quantity of flow to an actuator, for smooth acceleration to a desired velocity. The main stage is under closed loop control so that even at high flow, the spool position is maintained independently of the high flow forces that occur. The valve is normally operated by the appropriate amplifier card, or by the integrated electronics. For more information, refer to Bosch Rexroth Data Sheet RA Pilot Operated, Model 4 WRTE with Feedback and Integrated Electronics Size 10 to PSI GPM Hysteresis 1% Response sensitivity 0.5% Mounts on standard D05, D07, D08, D10 subplates Integral electronics (4 WRKE) Suitable for controlling position, velocity, pressure and force Spool types: E, V, Q, W Model 4 WRTE is a pilot operated 2-stage proportional directional valve. It controls the direction and quantity of flow to an actuator, for smooth acceleration to a desired velocity. The main stage is under closed loop control so that even at high flow, the spool position is maintained independently of the high flow forces that occur. The valve is normally operated by the integrated electronics. For more information, refer to Bosch Rexroth Data Sheet RA WRTE 10

6 Servo Pilot Operated, Model 4 WRD Model 4 WRDE with Integrated Electronics Size 10 to PSI GPM Hysteresis 1% Repeatability 0.5% Electrical feedback on main spool Mounts on standard D05, D07, D08, D10 subplates Integral electronics (4 WRDE) Excellent metering capabilities due to V notched spool Models for pressure, flow, speed and position control Spool types: E, V, Q, W Servo pilot operated proportional directional control valves, Models 4 WRD and 4 WRDE are electronically operated 3-stage proportional directional valves. They control the start, stop, direction and quantity of flow to an actuator, for smooth acceleration to a desired velocity. The main stage is under closed loop control so that even at high flow, the spool position is maintained independently of the high flow forces that occur. The valve is normally operated by the integrated electronics, or the appropriate amplifier card. For more information, refer to Bosch Rexroth Data Sheet RA Model 4 WS2EM Size PSI 5.28 GPM Hysteresis 1.5% Sensitivity 0.2% Frequency response >150 Hz Industrial ruby-on feedback spring for a long wear free service life Mounts on standard D03 Subplate Can be used with linear or rotary feedback devices 4-Way 4 WRDE 10 Electro-Hydraulic Directional Servo Valves 4 WS2EM Valve Model 4 WS2EM 6 is an electrically operated 2-stage servo valve. The valve is usually used for closed loop control of position, force, and velocity. Servo valves offer very high response times, for use when a proportional valve response time is inadequate. Control is achieved by the appropriate amplifier card. For more information, refer to Bosch Rexroth Data Sheet RA

7 Model DBE Pilot Operated Size PSI 8 GPM Size PSI 56 GPM Size PSI 106 GPM Hysteresis ±1.5% of max. setting Repeatability <±2% of max. setting Linearity ±3.5% of max. setting P Pressure Relief Valves Model DBET Direct Operated Size PSI 0.5 GPM Hysteresis ±1.5% of max. setting Repeatability <±2% of max. setting Linearity ±3.5% of max. setting T P Model DBETR Direct Operated with Spool Position Feedback Size PSI 2.5 GPM Hysteresis ±1.0% of max. setting Repeatability <±0.5% of max. setting Linearity ±1.5% of max. setting P T T relief valves DBE, DBET and DBETR are used to remotely control system pressure. For more information, refer to Bosch Rexroth Data Sheet RA and RA for the DBE; RA for the DBET; and RA for the DBETR. 166

8 Model 2 FRE with Feedback Size PSI 6.6 GPM Size PSI 42.5 GPM Hysteresis <±1% Repeatability <1% Frequency response 5 Hz 2-Way Flow Control Valves A B 2 FRE 6 with associated electronic amplifier (ordered separately) flow control valves Model 2 FRE are 2-way valves that control the volume of an oil flow by an electrical signal. They are both pressure and temperature compensated. The valve is normally operated by the appropriate amplifier card. For more information, refer to Bosch Rexroth Data Sheet RA and RA Electronic Amplifier Cards for Valves Each amplifier is identified as to the type of valve it was designed to control. For our Customer, this eliminates the need for field nulling, biasing and tuning of a universal card to match requirements of the valve. As an added convenience, all Customer adjustments, such as velocity set points, etc., are readily accessible through the face plate. Moreover, test jacks are provided to indicate input levels and output levels of the card. VALVE MODEL 4WRAB6 4WRA6 4WRA10 4WRE6 4WRE10 4WRZ 4WRD 2FRE6 2FRE10 & 16 DBET6 DBETR6 DBE6 DBE10 & 25 4WS2EM6 AMPLIFIER CARDS AVAILABLE MDSD (MOBILE DUAL SOLENOID DRIVER) VT-3013, VT-3017, DVT-1X / DSN211, MDSD VT-3014, VT-3018, DVT-1X / DSN211, MDSD VT-5005, VT-5024, VT-5007, VT-5001, DVT-1X/DSF211 VT-5006, VT-5025, VT-5008, VT-5002, DVT-1X / DSF2111 VT-3000, VT-3006, VT-3024, DVT-1X / DSN212, MDSD VT-1610, DVT-1X / PSF213 VT-5010, DVT-1X / SSF213 VT-5004, DVT-1X / SSF214 VT-2000, DVT-1X / DSN212, MDSD VT-5003, DVT-1X / SSF214 VT-2013, DVT-1X / DSN211, MDSD VT-2013, DVT-1X / DSN211, MDSD VT