Rotary overflow cut-off control
Sumitomo excavator circuit: When the swing is started, most of the hydraulic oil is discharged through the swing relief valve. High pressure flow is required at the beginning. Mode 3 swing compensation pressure is 294MPa. During this pressure difference period, almost all the pump discharge flow flows to the overflow valve.
The circuit of the Sumitomo 5 excavator: When the slewing starts, the proportional valve on the front side is used to reduce the flow and remove the remaining hydraulic oil. The pilot pressure oil input to the front proportional valve is sent to the reverse control valve part, and only the flow of the front proportional valve decreases. When the pressure discharged by the hydraulic pump is significant, the flow rate gradually increases
The operating conditions controlled by the rotary relief valve are:
①Non-operated walking;
②There is no accessory operation except the bottom;
③Instant rotation operation.
The control after the rotary overflow cut-off control operation, when the pressure discharged by the hydraulic pump is significant, the flow rate gradually increases.
Rotation speed limit control
The Sumitomo 5 excavator uses a proportional valve on the front side to limit the flow during a single rotation, so as to keep the rotation speed constant when the maximum flow of the hydraulic pump becomes larger.
The end conditions of the slewing overflow cut-off control are: ①when the slewing operation stops; ②walking operation; ③the arm is raised, the arm is input and output, and the bucket is opened/closed.
At present, the pilot pressure of the front proportional valve enters the reverse control part, and the flow only reduces the operating conditions of the rotation limit control on the front proportional valve: ①Other accessories are not operating: ②Walking is not operating
Reverse control
The reverse control circuit of the 1.3 type excavator The reverse control circuit of the Sumitomo 3 type excavator can make the discharge flow of the hydraulic pump decrease with the increase of the reverse control pressure, and no energy-saving control is adopted.
① The discharge oil of the hydraulic pump increases the predetermined pressure of the low-end relief valve of the control valve downstream of the reverse control regulating valve, and reversely controls the pressure increase.
②The servo piston of the regulating part of the hydraulic pump can move in a certain direction, and to a certain extent it will reduce the flow rate by moving it to the left. However, the discharge pressure of the pump is the reverse control pressure and pressure loss.
Reverse control loop of 2.5 type excavator
The reverse control loop of the Sumitomo 5 excavator adopts an energy-saving function, which can change the reverse control overflow and reduce the reverse control pressure. Here is the low pressure and low flow rate under operation, so it has the effect of energy saving
① When the operation is completed and the solenoid valve opens for reverse control in the past 1s, the pressure reducing spring is released.
②When the discharge pressure of the hydraulic pump drops, the reverse control pressure also drops, so that the valve that controls the pressure in the reverse direction operates.
③The back side hydraulic pump generates pilot pressure when passing through the reverse control part
④ When other operations start, detect the pilot pressure and recover within about 0.s.
