Explanation of Hydraulic Circuit and Operations (standard model) Other Circuits Auto pressure boost circuit (bucket close)
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When an attachment is operated, this circuit boosts the control valve main relief set pressure from 34.3 MPa to 37.3 MPa according to the engine load ratio and hydraulic load pressure, then ends the pressure boost after 8 sec. As an example, this section explains bucket-close operations. By moving the remote control valve to the bucket-close side, the pilot pressure oil is fed via the cushion valve to the control valve pb7 port and switches the bucket spool to the close side. At the same time, the output signal from the upper pilot pressure sensor that detected the pressurized oil separated from the pilot internal path is input to computer A, which judges that there is upper operation. Furthermore, computer A judges that there is a boost in the main pump P1 and P2 pressure, outputs the ON (24 V) signal to the pressure boost relief solenoid, switches the valve, and the pilot pressure oil is fed to the control valve main relief valve PH port to hold the pressure boost relief set pressure for 8 sec. There is no boost for the option circuit and during travel operation.
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Pressure line Tank line Pilot pressure line Pilot tank line Electric line
1
Cushion valve
11
Upper pilot pressure sensor
2
Bucket (close)
12
Console lever lock switch
3
Bucket (open)
13
Digging force incresed
4
Remote control valve (boom, bucket)
14
Monitor display
5
Lever lock
15
Computer A
6
Boost pressure relief
16
P1 pressure sensor
7
5 stack solenoid valve
17
P2 pressure sensor
8
Control valve
18
Hydraulic pump
9
Bucket
19
Check valve
10
Bucket cylinder
20
Oil cooler
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