Patent ID: 6039077
Filing Date: 2000-03-21
Classification: F15B,Y10T

Abstract:
Electrohydraulic control valve arrangement for controlling the pressure media supply to and discharge from a hydraulic motor, including:a main control valve constructed as a 3-position-valve, which main control valve includes a piston which is displaceable in alternative directions between end positions in a bore of a housing, which end positions correspond to the maximal values of derestricted cross-section of flow-through paths of the main control valve in alternative functional positions I and II, which steadily increase essentially with increasing displacement of the piston out of a functionally neutral center position 0, and is correspondingly reduced with a nearing of the piston to its center position, andan electrohydraulic servo control valve which is guided by an electronic setpoint value, and which controls said main control valve piston displacement by the alternating application and relieving of pressure in two control chambers of the main control valve, whereina) as the electrohydraulic servo control arrangement an electrohydraulic follow-up servo control valve (14; 14') is provided, which operates with electromechanically controllable position setpoint input and mechanical actual position data feedback in order to pilot the main control valve in a manner guided by the setpoint value, and is constructed as a 4/3 way valve which has a P-supply connection (76), which is in communication with the pressure outlet of a pressure supply unit, as well as a T-return connection (77), which is connected with an unpressurized reservoir of the pressure supply unit, and which further has an A-control connection (78), which is in communication with one of said control chambers (13) of the main control valve (11), and further has as a B-control connection (79), which is in communication with the other of said control chambers (13) of the main control valve (11), wherein in one of the central positions of the main control valve (11) associated central positions of the piston element (66; 66') of the follow-up servo control valve (14; 14') the supply and the user connections are closed off against each other, and in the alternative functional positions I and II in which the follow-up servo control valve (14; 14') is positioned as a function of the given setpoint value, on the one hand the A-control connection (78) is in communication with the P-supply connection (76) and the B-control connection (79) is in communication with the T-return flow connection (77), and on the other hand the A-control connection (78) of the follow-up servo control valve (14; 14') is in communication with its return flow connection (77) and the B-control connection (79) is in communication with the P-supply connection (76) of the follow-up servo control valve (14; 14');b) the servo control valve (14; 14') comprises a sleeve-shaped housing element (99; 99') which is disposed to be moveable in a pressure tight manner in a connection block (114, 114') rigidly connected to the housing of the main control valve (11, 11'), and a piston element (66; 66') which is disposed so as to be moveable in a pressure tight manner in the sleeve-shaped housing element (99; 99'), of which one of these serves as the setpoint value input element, which by means of a controllable electro-motor (131) is driveable in alternative directions for carrying out incremental displacements with respect to the other, which serves as actual position feedback element, which is force-form locking movably connected with the piston (16, 16') of the main control valve (11, 11') and thereby is controllable for carrying out servo-control movements synonymous with the displacement of the setpoint value input element, andc) the servo control valve (14; 14') is provided with a valve spring arrangement (118, 119; 151), which in a non-controlled state of the setpoint input motor (131) adjusts the setpoint input element upon the setpoint input position associated with the operationally neutral central position of the main control valve (11; 11').