Hydraulic circuit for construction equipment

摘要

A hydraulic circuit for construction equipment is provided, which supplements hydraulic fluid of a hydraulic pump for a cooling fan and hydraulic fluid of a main hydraulic pump and uses the supplemented hydraulic fluid as a hydraulic source of a RCV in order to supply signal pressure to a control valve that controls the driving of a hydraulic actuator. The hydraulic circuit includes first to third hydraulic pumps, a first control valve installed in a flow path of the first flow path, a second control valve installed in a flow path of the second hydraulic flow path, a hydraulic motor connected to the third hydraulic pump, a cooling fan connected to the hydraulic motor, a first shuttle valve having an input portion connected to the first hydraulic pump and the third hydraulic pump, a second shuttle valve having an input portion connected to the second hydraulic pump and the third hydraulic pump, and a pilot pressure generation device installed in a pilot flow path connected to the output portions of the first and second shuttle valves and shifted to supply the hydraulic fluid having a relatively high pressure among the hydraulic fluids of the first to third hydraulic pumps to the first and second control valves as pilot signal pressure.

主权项

1. A hydraulic circuit for construction equipment comprising:
first and second variable displacement hydraulic pumps and a third fixed displacement hydraulic pump connected to an engine; a first control valve installed in a flow path of the first hydraulic pump and shifted to control hydraulic fluid supplied to respective hydraulic actuators that drive working devices and a traveling device; a second control valve installed in a flow path of the second hydraulic pump and shifted to control hydraulic fluid supplied to respective hydraulic actuators that drive a swing device, a working device, and the traveling device; a hydraulic motor connected to the third hydraulic pump; a cooling fan connected to the hydraulic motor to discharge cooling wind to an oil cooler installed in a return flow path of the first and second hydraulic pumps so as to cool the hydraulic fluid returning to a hydraulic tank; a temperature sensor detecting a temperature of the hydraulic fluid in the hydraulic tank; an electric relief valve installed in a discharge flow path of the third hydraulic pump to control a set pressure of the hydraulic fluid supplied to the hydraulic motor so as to variably control a rotating speed of the cooling fan; a controller controlling hydraulic pressure that drives the hydraulic motor by varying the set pressure of the electric relief valve in accordance with a detection signal from the temperature sensor; a first shuttle valve installed upstream of the first control valve, the first shuttle valve including one input portion connected to the flow path of the first variable displacement hydraulic pump and the other input portion connected to the discharge flow path of the third fixed hydraulic pump, and outputting high-pressure hydraulic fluid of the hydraulic fluids of the first hydraulic pump and the third hydraulic pump; a second shuttle valve installed upstream of the second control valve, the second shuttle valve including one input portion connected to the flow path of the second variable displacement hydraulic pump and the other input portion connected to the discharge flow path of the third fixed hydraulic pump, and outputting high-pressure hydraulic fluid of the hydraulic fluids of the second variable displacement hydraulic pump and the third fixed hydraulic pump; a pilot pressure generation device installed in a pilot flow path connected to the output portions of the first and second shuttle valves and shifted to supply the hydraulic fluid having a relatively high pressure among the hydraulic fluids of the first to third hydraulic pumps to the first and second control valves as pilot signal pressure; and a pressure reducing valve installed in the pilot flow path, and shifted to supply the hydraulic fluid having a relatively high pressure among the hydraulic fluids of the first to third hydraulic pumps to the pilot pressure generation device as the pilot signal pressure by a set pressure of a valve spring, and shifted to drain the hydraulic fluid to the hydraulic tank when a load that exceeds the set pressure of the valve spring occurs in the pilot pressure generation device.