| 摘要 |
A hydraulic system for a construction machine having a pressure compensation valve is disclosed, which improves operability when a combined operation of a swing device and an attachment is performed. The hydraulic system includes a hydraulic pump, attachment and swing operation devices, an attachment actuator and a swing motor connected to the hydraulic pump, a first control valve controlling hydraulic fluid being supplied to the actuator, a second control valve controlling hydraulic fluid being supplied to the swing motor, a check valve installed on a flow path for detecting load pressures of the actuator to take a maximum pressure of the load pressures, a first pressure compensation valve having an opening amount that is controlled by a difference between the maximum load sensing pressure and the pressure of a discharge flow path of the first control valve, a second pressure compensation valve having an opening amount that is controlled by a difference between the maximum load sensing pressure and the pressure of the discharge flow path of the second control valve, a maximum load pressure sensor detecting the pressure of a maximum load sensing pressure line, and a control unit controlling a discharge flow rate of the hydraulic pump, wherein the system is configured so that the swing load pressure is not connected to the first pressure compensation valve on the attachment side when a combined operation of the swing device and the attachment is performed. |
| 主权项 |
1. A hydraulic system for a construction machine, comprising:
a variable displacement hydraulic pump connected to an engine; an attachment operation device and a swing operation device outputting operation signals in proportion to operator's operation amounts; at least one attachment actuator connected to a discharge flow path of the hydraulic pump to be driven by the operation of the attachment operation device; a first control valve installed in the discharge flow path and shifted to control a start, a stop, and a direction change of the actuator in response to the operation of the attachment operation device; a swing motor connected to a flow path branched from the discharge flow path to be driven by the operation of the swing operation device; a second control valve installed in the flow path and shifted to control a start, a stop, and a direction change of the swing motor in response to the operation of the swing operation device; a check valve installed in a flow path for detecting load pressures of the attachment actuator to take a maximum pressure of the detected load pressures; a first pressure compensation valve installed on a downstream side of the discharge flow path to have an opening amount that is controlled by a difference between the maximum load sensing pressure and the pressure on the downstream side of the discharge flow path; a second pressure compensation valve installed on the downstream side of the flow path to have an opening amount that is controlled by a difference between the maximum load sensing pressure and the pressure on the downstream side of the flow path; a pressure sensor detecting a discharge pressure of the hydraulic pump; a maximum load pressure sensor detecting a pressure of a maximum load sensing pressure line; an attachment operation amount detection means for detecting the operation amount of the attachment operation device; a swing operation amount detection means for detecting the operation amount of the swing operation device; and a control unit receiving an input of detection values of the pressure sensor of the hydraulic pump, the maximum load pressure sensor, the attachment operation amount detection means, and the swing operation amount detection means, and outputting a control signal for controlling a discharge flow rate of the hydraulic pump through a flow control valve, wherein one of output ports of the first pressure compensation valve is connected to the attachment actuator through a spool of the first control valve, and the other of the output ports thereof is connected to the maximum load sensing pressure line, and wherein one of output ports of the second pressure compensation valve is connected to the swing motor through a spool of the second control valve, and the other of the output ports thereof is not connected to the maximum load sensing pressure line, but is connected to a swing load pressure sensor for detecting a load pressure of the swing motor. |
