Rotary overflow cut-off control
The circuit of the Sumitomo excavator: When the rotation starts, most of the hydraulic oil is discharged through the rotation relief valve, as shown in Figure 2-32. High pressure flow is required at the beginning. Mode 3 swing compensation pressure 294MPa During this pressure difference period, almost all the flow from the pump flows to the relief valve.
The circuit of Sumitomo Type 5 excavator: When the rotation is started, the proportional valve on the front side is used to reduce the flow and remove the remaining hydraulic oil, as shown in Figure 2-33. The pilot pressure oil input to the front proportional valve is fed into the reverse control valve section, 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-operational walking;
②There is no accessory running 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.
Slewing speed limit control
The Sumitomo Type 5 excavator uses the proportional valve on the front side to limit the flow rate during single rotation to keep the rotation speed unchanged when the maximum flow rate of the hydraulic pump becomes larger, as shown in Figure 2-34.
The end conditions of the slewing overflow cut-off control are: ① When the slewing operation stops; ② Walking operation; ③ The arm is raised, the arm is input and output, and the bucket is turned on/off.
At present, the pilot pressure of the proportional valve on the front side enters the reverse control part, and the flow rate is only reduced on the proportional valve on the front side. The operating conditions of the slewing limit control: ① other accessories are not operated: ② walking is not operated
Reverse control
The reverse control circuit of the 1.3 type excavator The reverse control circuit of the Sumitomo 3 type excavator can reduce the discharge flow of the hydraulic pump as the reverse control pressure increases, and no energy saving control is taken, as shown in Figure 2-35.
① The discharge oil of the hydraulic pump raises the predetermined pressure of the low-end relief valve of the control valve downstream of the reverse control regulating valve, and the reverse control pressure increases.
② The servo piston of the adjustment part of the hydraulic pump can move in a certain direction. To a certain extent, moving left will reduce the flow rate. However, the discharge pressure of the pump is the reverse control pressure and pressure loss.
Reverse control circuit of 2.5 type excavator
The reverse control circuit of the Sumitomo Type 5 excavator adopts an energy-saving function, which can change the reverse control overflow and reduce the reverse control pressure, as shown in Figure 2-36. The low pressure and low flow under operation are given here, so it has the effect of energy saving
① When the operation is completed in the past 1s, the solenoid valve opens the reverse control, and the decompression spring is released.
②When the discharge pressure of the hydraulic pump drops, the reverse control pressure also drops, so that the valve in the reverse control pressure operates.
③ Pilot pressure is generated by the back hydraulic pump through the reverse control section
④ When other operations start, detect the pilot pressure and recover within about 0.s.
