Читать книгу Hydraulic Fluid Power - Andrea Vacca - Страница 16

A hydraulic system is used to control a bidirectional conveyor. The system uses a 50 kW internal combustion engine (shaft speed of 1800 rpm) to drive a 35 cm³/rev variable displacement axial piston pump. The conveyor is driven by a 20 cm³/rev fixed displacement hydraulic motor (a bidirectional gear motor with a drain, rated speed of 1800 rpm). The control of the direction of rotation of the motor is achieved by means of 4/3 directional control valve, manually operated. The motor does not rotate in rest condition. The maximum system pressure has to be limited to 200 bar, and for this purpose one or more pressure relief valves can be used.

Draw the schematic of the circuit according to the basic rules of the ISO 1219 standard of representation, and comment on the operation of the system in standby conditions.

Given:

The generic description of a hydraulic system, which includes:

 a prime mover (internal combustion engine), with power and shaft speed of n = 1800 rpm;

 a variable displacement hydraulic pump (axial piston type) driven by the abovementioned engine, Vp = 35 cm3/rev;

 a 4/3 directional control valve (details of the position not given), manually operated;

 a hydraulic bidirectional motor, Vm = 20 cm3/rev, connected to the above valve; and

 one or more relief valves (pressure setting p* = 250 bar), which accomplish the safety function (preventing excessive system pressurization).

Find:

The hydraulic schematic according to the ISO standard of representation.