Bosch Rexroth R900927479

Proportional flow control valves of the 2FRE ... type comprise a 2-way function. They are capable of controlling a flow indicated by the electrical command value in a pressure- and largely temperature-compensated manner. The set-up basically consists of a housing (1), proportional solenoid with inductive position transducer (2), metering orifice (3), pressure compensator (4), stroke limitation (5) as well as check valve (6). The flow setting is determined by the indication (0 to 100%) at the command value potentiometer. Via the amplifier as well as the proportional solenoid, the indicated command value has an effect on the adjustment of the metering orifice (3). The position of the metering orifice (3) is recorded by the inductive position transducer. Any existing variations from the command value are corrected by the position control. The pressure compensator (4) keeps the pressure drop at the metering orifice (3) at a constant value at all times. Thus, the flow is pressure-compensated. If the flow controller is only used within a range which is considerably smaller than the maximum intended rated flow of the valve, the response time of the pressure compensator (4) may be shortened by limiting the pressure compensator stroke. This allows for the reduction of unwanted start-up jumps. If the grub screw at the stroke limitation (5) is at the left stop (screwed out), there is no pressure compensator stroke limitation. The low temperature drift is the result of the favorable design of the metering orifice. With command value 0%, the metering orifice is closed. In the event of a power failure or cable break at the inductive position transducer, the metering orifice closes. From the command value 0%, a smooth start-up is possible. Via two ramps in the electric amplifier, the metering orifice can be opened and closed with delay. Via the check valve (6), a free return flow from B to A is possible. With an additional rectifier sandwich plate of the Z4S... type under the proportional flow control valve, the supply and return flow from the actuator can be regulated.