Plunger pump power control device and control method thereof

Abstract

A plunger pump power control device and a control method thereof. The device comprises a valve body, a valve core, a valve sleeve, a stop plug, a spring pre-loaded mechanism, a feedback mechanism and a slide valve. The slide valve is provided within one end of the valve core. The stop plug is provided at one end of the valve body, and the spring pre-loaded mechanism is provided at the other end of. The valve sleeve, the valve core, and the slide valve are provided between the stop plug and the spring pre-loaded mechanism, and the feedback mechanism is hinged on the valve body. The device enables the hydraulic plunger pump to control the output power, the pump power output is simulated by two broken lines, and the error is less. It is flexible to load variable by the valve core through the pressure of the C-cavity.

What is claimed is: 
     
         1 . A plunger pump power control device, comprising a control valve body ( 1 ), a valve core ( 2 ), a valve sleeve ( 3 ), a stop screwed plug ( 4 ), a spring pre-loaded mechanism ( 5 ) and a feedback mechanism ( 6 ); an oil inlet P, an oil outlet Ps and two oil drain ports T being provided on the control valve body ( 1 ); the oil outlet Ps being externally connected to a variable piston chamber of a pump body; the valve core ( 2 ) being provided within the valve sleeve ( 3 ), and an E-cavity being formed between the valve sleeve ( 3 ) and the valve core ( 2 ) and being in constant communication with the oil inlet P; the stop screwed plug ( 4 ) being provided at one end of the control valve body ( 1 ), and the spring pre-loaded mechanism ( 5 ) being provided at the other end of the control valve body ( 1 ); the valve core ( 2 ) and the valve sleeve ( 3 ) being provided between the stop screwed plug ( 4 ) and the spring pre-loaded mechanism ( 5 ), and the valve sleeve ( 3 ) and the valve core ( 2 ) forming a 3-position two-way structure valve; the feedback mechanism ( 6 ) being hinged on the control valve body ( 1 ), with one end of the feedback mechanism ( 6 ) being connected with the valve sleeve ( 3 ) to drive the valve sleeve ( 3 ) to move in an axial direction and the other end being connected to a variable piston; wherein: a slide valve ( 7 ) is provided at the central part of one end of the valve core ( 2 ), a C-cavity is disposed between the slide valve ( 7 ) and the valve core ( 2 ), and the slide valve ( 7 ) is closely attached to the stop screwed plug ( 4 ) under the action of the pressure of the C-cavity; a ball end of the slide valve ( 7 ) contacts with the stop screwed plug ( 4 ); and oil between the stop screwed plug ( 4 ) and the valve sleeve ( 3 ) is drained via one of the oil drain ports T, and oil between the valve sleeve ( 3 ) and the spring pre-loaded mechanism ( 5 ) is drained via the other of the oil drain ports T. 
     
     
         2 . The plunger pump power control device of  claim 1 , wherein the perpendicularity between the plane of the stop screwed plug ( 4 ) that is near the valve core ( 2 ) and an axis of the slide valve ( 7 ) is within 0.05 mm. 
     
     
         3 . The plunger pump power control device of  claim 2 , wherein the spring pre-loaded mechanism ( 5 ) comprises a first spring seat ( 51 ), a large spring ( 52 ), a small spring ( 53 ), a second spring seat ( 54 ), a screw insert ( 55 ) and a nut ( 56 ); the screw insert ( 55 ) is formed with a groove having a cross section in the form of the inverted character “ ” thereon, the screw insert ( 55 ) is screwed into the control valve body ( 1 ) and is fixed at one end of the control valve body ( 1 ) via the nut ( 56 ); the first spring seat ( 51 ) and the second spring seat ( 54 ) are disposed in the groove opposite to each other, the small spring ( 53 ) and the large spring ( 54 ) are disposed between the first spring seat ( 51 ) and the second spring seat ( 54 ), and the small spring ( 53 ) is disposed inside the large spring ( 52 ). 
     
     
         4 . The plunger pump power control device of  claim 3 , wherein the spring pre-loaded mechanism ( 5 ) further has an adjusting screw ( 57 ), and one end of the adjusting screw ( 57 ) is screwed into the screw insert ( 55 ) and contacts with the second spring seat ( 54 ). 
     
     
         5 . A control method for a plunger pump power control device, comprising the following steps of:
 (1) presetting the value of a spring pre-loaded mechanism ( 5 );   (2) introducing oil at a pump outlet pressure from an oil inlet P into a C-cavity between a valve core ( 2 ) and a slide valve ( 7 ) through an E-cavity, wherein the oil at the pump outlet pressure drives the slide valve ( 7 ) and the valve core ( 2 ) to move in opposite directions, the slide valve ( 7 ) stops at a stop screwed plug ( 4 ), and the valve core ( 2 ) moves towards and compresses the spring pre-loaded mechanism ( 5 ); or the pressure at the oil inlet P is decreased so that the spring pre-loaded mechanism ( 5 ) drives the valve core ( 2 ) to overcome the pressure of the C-cavity to move in a reverse direction; and   (3) performing binarization processing to accomplish the process of increasing or decreasing the pressure of the pump.   
     
     
         6 . The control method for a plunger pump power control device of  claim 5 , wherein the step (3) is specifically as follows: when the pump outlet pressure introduced into the C-cavity increases to exceed the preset value of the spring pre-loaded mechanism ( 5 ), the valve core ( 2 ) moves in a direction in which the spring pre-loaded mechanism ( 5 ) is compressed; when the valve core ( 2 ) moves to such an extent that the oil inlet P and the E-cavity are connected with the oil outlet Ps and the oil outlet Ps is disconnected from the oil drain port T, the pressure oil enters into a variable piston chamber through the oil outlet Ps to drive the variable piston to move towards the plunger pump at a small swing angle; meanwhile, the feedback mechanism ( 6 ) drives the valve sleeve ( 3 ) to move towards the closing direction, and when the valve sleeve ( 3 ) moves to such an extent that the oil inlet P is disconnected from the oil outlet Ps and the oil outlet Ps is connected with the oil drain port T, the pressure oil of the variable piston is drained so that the variable piston is stopped from moving in the small swing angle direction and moves towards the plunger pump at a large swing angle; and meanwhile, the feedback mechanism ( 6 ) drives the valve sleeve ( 3 ) to move in a direction opposite to the moving direction of the variable piston until the oil inlet P is again connected with the oil outlet Ps; the aforesaid two processes are performed alternately so that the variable piston experiences a tiny pulsation motion; and then the process of increasing the pressure of the pump is completed; and
 when the pump outlet pressure introduced into the C-cavity decreases to be below the preset value of the spring pre-loaded mechanism ( 5 ), the oil inlet P and the E-cavity are disconnected from the oil outlet Ps and the oil outlet Ps is connected with the oil drain port T, the variable piston moves towards the plunger pump at a large swing angle; meanwhile, the feedback mechanism ( 6 ) drives the valve sleeve ( 3 ) to move in the direction opposite to the moving direction of the variable piston, and when the valve sleeve ( 3 ) moves to such an extent that the oil inlet P is connected with the oil outlet Ps and the oil outlet Ps is disconnected from the oil drain port T, the pressure oil stops the variable piston from moving and reversely drives the variable piston to move towards the plunger pump at a small swing angle; the aforesaid two processes are performed alternately so that the variable piston experiences a tiny pulsation motion; and then, the process of decreasing the pressure of the pump is completed.