1. The main pump hydraulic control circuit
The two sets of multi-way reversing valves supplied by the two main pumps are provided with a fixed throttle valve F and G at the outlet oil circuit ends, which are used to adjust the flow of the hydraulic pump when it is empty to reduce the flow. small. When the middle position of each reversing valve is not working, due to the throttle effect of the throttle valve, the pressure in front of the valve increases. This increased pressure oil feeds back into the variable pump control regulating cylinder, pushing the regulating cylinder to move and making the inclined axis pump The inclination angle becomes smaller, thereby reducing the output flow of the pump. Only when any reversing valve in the multi-way valve works, the pressure difference between the front and rear of the throttle valve does not increase much, and does not affect or change the tilt angle of the pump, thereby increasing the pump output flow to meet the requirements of the excavator repairing various working conditions. Speed requirements.
2. Boom hydraulic circuit
The action of the boom is jointly supplied with oil by the reversing valves 26 and 46. The control of the hydraulic reversing valve is controlled by the pressure reducing valve type remote control valve 30, and the control oil is supplied by the auxiliary pump (gear pump). When the valve 30 is operated to the left, the operating pressure oil from the auxiliary pump reaches the left end of the valve 30 and the valve 26 and the right end of the valve 46 through the one-way valve 32, so that the valve 26 works in the left position and the valve 46 works in the right position. The hydraulic oil from the front pump reaches point A through the reversing valve 46, and the pressure oil from the rear pump reaches point B through the reversing valve 26, and flows into the rodless cavity of the boom to lift the boom. The oil returns to the tank through valves 26 and 46 respectively. In the same way, when the valve 30 is manipulated to the right, the boom is lowered.
The boom lift set pressure is guaranteed by the overload replenishment valve 17, and the set pressure is 32MPa; the boom lower set pressure is guaranteed by the overload replenishment valve 18, and the set pressure is 30MPa.
Three, stick hydraulic circuit
When the pressure reducing valve type remote control valve 19 works in the right position, the principle is the same as the above principle. The stick hydraulic valve 44 works in the left position and 43 right position. The pressure of the two main pumps merges into the stick hydraulic cylinder 29 at point E. Without rod cavity, the stick hydraulic cylinder extends, and the rod cavity returns oil through the hydraulic valve. In this working condition, the set pressure of the overload supplement valve 24 is 32 MPa. When valve 19 works in the left position, valve 44 works in the right position and 43 works in the left position. The hydraulic inlet of the two main pumps merges into the rod cavity of the stick hydraulic cylinder at point D, the stick retracts, and the rodless cavity returns oil through their respective The hydraulic valve returns directly to the fuel tank. In this working condition, the set pressure of the overload charge valve 25 is 30MPa.
Four, bucket hydraulic circuit
The bucket hydraulic circuit is composed of a pressure reducing valve type remote control valve 15, a reversing valve 12, a bucket hydraulic cylinder 14, and a front pump. The working principle is the same as the above. The pressure reducing valve type remote control valve 15 is operated at different positions on the left and right sides, and the valve 12 works at different positions on the left and right, so that the large or small cavity of the bucket hydraulic cylinder can be filled with pressure oil. The bucket is used for excavation or unloading operations. During excavation, the set pressure of the overload charge valve 13 is 30MPao
Five, rotary hydraulic circuit
The swing hydraulic circuit is composed of a pressure reducing valve type remote control valve 31, a hydraulic valve 45, a swing hydraulic motor 37, a brake valve 38, a brake hydraulic cylinder 39, and a rear pump.
When the pressure reducing valve type remote control valve 31 is on the left or right side, the hydraulic valve 45 works in the right or left position, so that the reversing hydraulic motor rotates left and right.
The overload and vacuum replenishment of the rotary hydraulic motor are solved by the overload valve 36 and the one-way valve on the respective rotary hydraulic motor circuit. The overload pressure is set to 24.5MPa, and two reverse one-way valves are used for vacuum replenishment.
When the hydraulic valve 45 is in the neutral position, the pressure control oil from the auxiliary pump flows to the hydraulic control end of the hydraulic valve to make the hydraulic valve work in the lower position. At this time, the pressure oil from the auxiliary pump enters the brake hydraulic cylinder again. The lower cavity of 39 (with rod cavity) compresses the spring of the upper cavity (without rod cavity) of the brake hydraulic cylinder, and the piston rises, thereby driving the brake mechanism device to hold the hydraulic motor and realize the braking and stopping of the hydraulic motor.
When the hydraulic valve 45 is in the left and right working positions, since the hydraulic valve does not control hydraulic oil, the valve works in the upper position, and the brake cylinder is in a relaxed state without braking.
Six, crawler walking hydraulic circuit
The crawler walking hydraulic circuit consists of hydraulic pumps (front pump, rear pump and auxiliary pump), reversing valves 9, 11, balance valve 1, overload valve 4, solenoid valve 3, hydraulic valve 2, speed regulating valve 41, and walking hydraulic motor 40. Inclined axis tilting piston 6, brake cylinder 5, high and low pressure main safety valves 7, 8, shuttle valve and pressure reducing valve type remote control valve 28 and other components.
When the operating pressure reducing valve type remote control valve 28 is at different positions on the left and right, the reversing valves 9, 11 are also at different working positions on the right and left at the same time. The pressure oil from the rear and front pumps reaches the left and right through the reversing valve. The walking hydraulic motor drives the crawler to move forward or backward.
In the hydraulic circuit, many control valves or valve groups are set up for speed limit, balance, speed regulation, braking and other requirements. The brief working principles and functions are introduced as follows.
In order to realize the speed limit and vacuum replenishment of the traveling hydraulic motor, there is a balance valve 1 (a valve group, including a one-way valve and a hydraulically controlled three-position four-way balance valve); in order to select the circuit pressure, there is a two-position Three-way solenoid valve 3, so that the high-pressure main safety valve 7 and low-pressure main safety valve 8 can be controlled by the shuttle valve; in order to realize the brake hydraulic motor and control the tilt angle of the inclined axis hydraulic motor, a speed adjustment is set in the circuit Valve 41, brake cylinder 5 and inclined axis tilting piston 6.
Many circuits in the hydraulic system of the whole vehicle can realize confluence and compound operation. They are: the merging compound operation of the boom circuit and the stick circuit; the merging compound operation of the swing circuit and the walking circuit; the merging compound operation of the boom circuit and the walking circuit; the merging compound operation of the stick circuit and the walking circuit; the bucket circuit Combined operation with merging circuit.
The merging compound action of the boom circuit and the arm circuit is through the left positions of valves 30 and 19 to achieve the raising and extension of the boom and the stick; the merging compound action of the swing circuit and the walking circuit is through the operation of valve 31, After the valve 45 is in the left and right working positions, the valve 42 is operated to the upper position and the left end of the valve 10 is unloaded, so that the valve 10 can be operated in the right position, so that it is used for both the rotary circuit and the left-hand hydraulic motor. The heavy-loaded rear pump gets the supplemental flow from the front pump through valve 47; the combined combined action of the boom circuit and the walking circuit, the combined combined action of the stick circuit and the walking circuit, and the combined combined action of the bucket circuit and the walking circuit The basic working principle is the same as above.
