Most Daewoo excavators are equipped with K3V112DT-11GR hydraulic pumps produced by Kawasaki Corporation of Japan; DH400LC-3 excavators are equipped with K3V180DTH1 hydraulic pumps.
K3V system hydraulic pump is a drive shaft tandem swash plate type axial variable plunger pump, which is composed of two main pumps, a gear pump and corresponding hydraulic pump regulator. The main pump input shaft is connected to the engine through a flexible coupling, and the two variable pumps rely on their respective regulators to adjust the displacement. The gear pump is installed on the main pump at the rear, which supplies oil to the hydraulic pump regulator, and also to the remote control pilot valve.
1. Structure and function
The main pump is composed of cylinder assembly, swash plate assembly and valve plate assembly. Cylinder block assembly is composed of drive shaft, cylinder block, plunger, shoe pressure plate, ball head and ball seat. The swash plate assembly is composed of a friction swash plate, a swash plate support shaft, and a servo piston. The displacement and pressure of the swash plate are changed by the regulator to change the inclination angle. The flow distribution plate assembly is composed of a valve body, an oil distribution plate and a oil distribution plate pin, etc., and is provided with an oil suction port and an oil discharge port.
The drive shaft of the hydraulic pump rotates at the same speed as the engine, and the cylinder and plunger rotate together to absorb and discharge oil.
When the inclination angle of the swash plate is 0°, the piston has no stroke and does not perform oil discharge; when the inclination angle of the swash plate is increased (ie, a increases), the stroke of the piston increases and the amount of suction/discharge increases. Sliding friction is used between the cylinder and the oil distribution plate (the oil distribution plate is fixed and the cylinder rotates), and the reciprocating movement of the plunger continuously performs oil suction and oil discharge, as shown in Figure 16-60.
2. Hydraulic pump regulator [KR3H (G)-HNOP]
The role of hydraulic pump regulator mainly includes;
(1) The power control follows the oil discharge pressure p of the main pump itself and the oil discharge pressure p of the main pump connected in series with it. Ascending, the hydraulic pump regulator can automatically reduce the swash plate tilt angle of the hydraulic pump (that is, reduce the displacement), and control the input torque below a certain value (when the speed is constant, the input power is controlled to a certain value).
(2) An electromagnetic proportional pressure reducing valve is attached to the power shift control regulator. Changing the command current value of the valve can change the power setting value. Only the secondary pressure pr (power shift pressure) of the electromagnetic proportional pressure reducing valve is transmitted to the power adjustment mechanism of each hydraulic pump controller through the internal passage, and the respective power setting values will change simultaneously. Therefore, the output power of the hydraulic pump can be arbitrarily changed to achieve the optimal operating state according to the operating conditions.
(3) Reverse flow control by hydraulic control pressure The hydraulic control pressure (the size of this pressure depends on the stroke of the spool valve) generated by the spool stroke of the hydraulic control valve automatically controls the displacement of the hydraulic pump. In the neutral position, the flow rate of the central parallel path of the main control valve is the largest, and when the spool stroke is maximum, the flow rate of the central parallel path of the main control valve is the smallest. Introduce the hydraulic control pressure into the hydraulic pump regulator. When the hydraulic control pressure is high (the spool is neutral and the flow rate is maximum), the tilt angle of the hydraulic pump swash plate becomes smaller and the displacement decreases; when the hydraulic pressure is low (the spool stroke increases When large), the inclination angle of the main pump swash plate becomes larger, and the displacement increases. This is the principle of reverse flow control. The structure and working principle of the hydraulic pump regulator are shown in Figure 16-61.
