SYSTEM / Control System Boom Mode Selector Control Purpose: Reduces vibration of the machine at digging and grading work. Operation: 1. The signals from each pressure sensor are sent to MC. 2. When the following conditions exist, MC activates solenoid valve unit (SC). 3. Pressure oil from the pilot pump flows through solenoid valve unit (SC) and acts on the boom overload relief control valve. 4. When the boom overload relief control valve is shifted, relief set pressure of the overload relief valve decreases. 5. Consequently, as holding pressure at the boom cylinder rod side decreases, vibration of the ma- chine is reduced during boom lower operation.
(Refer to the Control Valve group, Boom Overload Control Valve group / COMPONENT OPERA- TION.) Condition: Work Mode: Digging mode Boom Mode Selector Switch: ON Pressure Sensor (Travel Right/Left) No output Pressure Sensor (Boom, Arm, Bucket, Swing and Attachment): Output from either pressure sensor Boom Mode Selector Switch M1J1-03-001 NOTE: Overload Relief Pressure: During normal operation: 35.3 MPa (360 kgf/cm 2 , 5132 psi) @110 L/min During operation: 11.8 MPa (120 kgf/cm 2 , 1715 psi) @110 L/min NOTE:
When output of each pressure sensor (boom raise/lower, arm roll-out/in, bucket roll-out/in, swing, travel right/left, attach- ment (optional) or counterweight (optional)) becomes 0.7 MPa (7.1 kgf/cm 2 , 102 psi) or higher, MC recognizes that the control lever is operated. T2-2-50