Hydraulic system for construction machinery

Abstract

A hydraulic system for a construction machine is disclosed, which can prevent off-course travel of the machine when a combined operation of a traveling device and a working device such as a boom is performed. The hydraulic system for a construction machine includes first and second hydraulic pumps, left and right traveling operation levers and actuator operation levers for first and second working devices, a left traveling motor connected to a discharge flow path of the first hydraulic pump and an actuator for the first working device, a right traveling motor connected to a discharge flow path of the second hydraulic pump and an actuator for the second working device, a first pressure compensated valve installed on one side of an upper stream and a downstream of the first control valve, a second pressure compensated valve installed on one side of an upper stream and a downstream of the second control valve, a third pressure compensated valve, a fourth pressure compensated valve installed on one side of an upper stream and a downstream of the fourth control valve, a first orifice connected to the first pressure compensated valve of the first control valve, a first load sensing line connected to the fourth pressure compensated valve of the fourth control valve, and a hydraulic tank, a second orifice connected to the second pressure compensated valve of the second control valve, a second load sensing line connected to the third pressure compensated valve of the third control valve, and the hydraulic tank, a confluence valve installed in a confluence flow path of the first and second hydraulic pumps, a traveling communication valve installed in a flow path connecting the downstream of the left traveling first pressure compensated valve to the downstream of the right traveling third pressure compensated valve, and a controller controlling communication of the traveling communication valve when a combined operation for simultaneously operating the traveling device and the working device is performed.

1 . A hydraulic system for a construction machine, comprising:
 first and second hydraulic pumps connected to an engine;   a left traveling operation lever, a right traveling operation lever, and actuator operation levers for first and second working devices outputting an operation signal in proportion to an operation amount by an operator;   a left traveling motor connected to a discharge flow path of the first hydraulic pump to be driven by a first control valve that is shifted by an operation of the left traveling operation lever;   a right traveling motor connected to a flow path that is branched from a discharge flow path of the second hydraulic pump to be driven by a third control valve that is shifted by an operation of the right traveling operation lever;   a hydraulic actuator for the working device connected to the flow path that is branched from the discharge flow path of the first hydraulic pump to be driven by a fourth control valve that is shifted by an operation of the actuator operation lever for the first working device;   a hydraulic actuator for the working device connected to the discharge flow path of the second hydraulic pump to be driven by a second control valve that is shifted by an operation of the actuator operation lever for the second working device;   a first pressure compensated valve which is installed on one side of an upper stream and a downstream of the first control valve and of which an opening amount is controlled according to a difference between a maximum load sensing pressure of an actuator connected to the first hydraulic pump and a discharge flow path pressure;   a second pressure compensated valve which is installed on one side of an upper stream and a downstream of the second control valve and of which an opening amount is controlled according to a difference between a maximum load sensing pressure of an actuator connected to the second hydraulic pump and a discharge flow path pressure;   a third pressure compensated valve which is installed on one side of an upper stream and a downstream of the third control valve and of which an opening amount is controlled according to the difference between the maximum load sensing pressure of the actuator connected to the second hydraulic pump and the discharge flow path pressure;   a fourth pressure compensated valve which is installed on one side of an upper stream and a downstream of the fourth control valve and of which an opening amount is controlled according to the difference between the maximum load sensing pressure of the actuator connected to the first hydraulic pump and the discharge flow path pressure;   a first orifice connected to the first pressure compensated valve of the first control valve, a first load sensing line connected to the fourth pressure compensated valve of the fourth control valve, and a hydraulic tank;   a second orifice connected to the second pressure compensated valve of the second control valve, a second load sensing line connected to the third pressure compensated valve of the third control valve, and the hydraulic tank;   a confluence valve which is installed in a confluence flow path that connects the discharge flow paths of the first and second hydraulic pumps in parallel, of which an opening amount is controlled according to operation amounts of the traveling operation levers or the actuator operation levers for the first and second working devices, which sums discharge flow rates of the first and second hydraulic pumps, and which makes the first load sensing line and the second load sensing line communicate with each other;   a traveling communication valve installed in a flow path connecting the downstream of the left traveling first pressure compensated valve to the downstream of the right traveling third pressure compensated valve to open or close the flow path by an external control signal; and   a controller outputting a control signal for controlling the traveling communication valve to shift the flow path to a communication position when a combined operation for simultaneously operating a traveling device and the working device is performed.   
     
     
         2 . The hydraulic system for a construction machine according to  claim 1 , wherein the traveling communication valve is composed of a solenoid valve that is shifted by an electric signal from the controller. 
     
     
         3 . The hydraulic system for a construction machine according to  claim 1 , wherein the traveling communication valve is connected to a solenoid valve that outputs pilot signal pressure that corresponds to the control signal from the controller so that the traveling communication valve is shifted when the pilot signal pressure is supplied. 
     
     
         4 . The hydraulic system for a construction machine according to  claim 3 , wherein the solenoid valve is composed of a valve having characteristics that the solenoid valve is on/off-shifted according to existence/nonexistence of an input of the electric signal. 
     
     
         5 . The hydraulic system for a construction machine according to  claim 1 , wherein the solenoid valve is composed of a valve having characteristics that the solenoid valve outputs pilot pressure in proportion to an input size of the electric signal. 
     
     
         6 . The hydraulic system for a construction machine according to  claim 1 , wherein the left and right traveling operation levers and the actuator operation levers for the first and second working devices comprise operation amount sensing means for sensing operations of the operation levers and transmitting detection signals to the controller. 
     
     
         7 . The hydraulic system for a construction machine according to  claim 6 , wherein the operation amount sensing means is composed of a pressure sensor. 
     
     
         8 . The hydraulic system for a construction machine according to  claim 1 , wherein the controller senses the operations of the left and right traveling operation levers by detecting the operation amounts through a sensing means for sensing the operation amounts of the left and right traveling operation levers and a sensing means for sensing the operation amounts of the actuator operation levers for the first and second working devices, and in the case where at least one of the operations of the actuator operation levers for the first and second working devices is sensed, the controller does not output the control signal to the traveling communication valve if the difference between the operation amounts of the left and right traveling operation devices exceeds a set value, while the controller outputs the control signal to the traveling communication valve if the difference between the operation amounts of the left and right traveling operation devices is smaller than the set value. 
     
     
         9 . The hydraulic system for a construction machine according to  claim 1 , wherein the left and right traveling operation levers and the actuator operation levers for the first and second working devices comprise electric operation devices that output electric signals to the controller in proportion to the operation amounts. 
     
     
         10 . The hydraulic system for a construction machine according to  claim 1 , wherein the left and right traveling operation levers and the actuator operation levers for the first and second working devices comprise hydraulic operation devices that output pilot signal pressure in proportion to the operation amounts. 
     
     
         11 . A hydraulic system for a construction machine, comprising:
 first and second hydraulic pumps connected to an engine;   a left traveling operation lever, a right traveling operation lever, and an actuator operation lever for a first working device outputting an operation signal in proportion to an operation amount by an operator;   a left traveling motor connected to a discharge flow path of the first hydraulic pump to be driven by a first control valve that is shifted by an operation of the left traveling operation lever;   a right traveling motor connected to a discharge flow path of the second hydraulic pump to be driven by a third control valve that is shifted by an operation of the right traveling operation lever;   a hydraulic actuator for a working device connected to the flow path that is branched from the discharge flow path of the first hydraulic pump to be driven by a fourth control valve that is shifted by an operation of the actuator operation lever for the first working device;   a first pressure compensated valve which is installed on one side of an upper stream and a downstream of the first control valve and of which an opening amount is controlled according to a difference between a maximum load sensing pressure of an actuator connected to the first hydraulic pump and a discharge flow path pressure;   a third pressure compensated valve which is installed on one side of an upper stream and a downstream of the third control valve and of which an opening amount is controlled according to the difference between the maximum load sensing pressure of the actuator connected to the second hydraulic pump and the discharge flow path pressure;   a fourth pressure compensated valve which is installed on one side of an upper stream and a downstream of the fourth control valve and of which an opening amount is controlled according to the difference between the maximum load sensing pressure of the actuator connected to the first hydraulic pump and the discharge flow path pressure;   a first orifice connected to the first pressure compensated valve of the first control valve, a first load sensing line connected to the fourth pressure compensated valve of the fourth control valve, and a hydraulic tank;   a second orifice connected to a second load sensing line connected to the third pressure compensated valve of the third control valve and the hydraulic tank;   a confluence valve which is installed in a confluence flow path that connects the discharge flow paths of the first and second hydraulic pumps in parallel, of which an opening amount is controlled according to an operation amount of the traveling operation lever or the actuator operation lever for the first working device, which sums discharge flow rates of the first and second hydraulic pumps, and which makes the first load sensing line and the second load sensing line communicate with each other;   a traveling communication valve installed in a flow path connecting the downstream of the left traveling first pressure compensated valve to the downstream of the right traveling third pressure compensated valve to open or close the flow path by an external control signal; and   a controller controlling the traveling communication valve to shift the flow path to a communication position when a combined operation for simultaneously operating a traveling device and the working device is performed.   
     
     
         12 . The hydraulic system for a construction machine according to  claim 11 , wherein the traveling communication valve is composed of a solenoid valve that is shifted by an electric signal from the controller. 
     
     
         13 . The hydraulic system for a construction machine according to  claim 11 , wherein the traveling communication valve is connected to a solenoid valve that outputs pilot signal pressure that corresponds to the control signal from the controller so that the traveling communication valve is shifted when the pilot signal pressure is supplied. 
     
     
         14 . The hydraulic system for a construction machine according to  claim 13 , wherein the solenoid valve is composed of a valve having characteristics that the solenoid valve is on/off-shifted according to existence/nonexistence of an input of the electric signal. 
     
     
         15 . The hydraulic system for a construction machine according to  claim 11 , wherein the solenoid valve is composed of a valve having characteristics that the solenoid valve outputs pilot pressure in proportion to an input size of the electric signal. 
     
     
         16 . The hydraulic system for a construction machine according to  claim 11 , wherein the left and right traveling operation levers and the actuator operation lever for the first working device comprise operation amount sensing means for sensing operations of the operation levers and transmitting detection signals to the controller. 
     
     
         17 . The hydraulic system for a construction machine according to  claim 16 , wherein the operation amount sensing means is composed of a pressure sensor. 
     
     
         18 . The hydraulic system for a construction machine according to  claim 11 , wherein the controller senses the operations of the left and right traveling operation levers by detecting the operation amounts through a sensing means for sensing the operation amounts of the left and right traveling operation levers and a sensing means for sensing the operation amount of the actuator operation lever for the first working device, and in the case where the operation of the actuator operation lever for the first working device is sensed, the controller does not output the control signal to the traveling communication valve if the difference between the operation amounts of the left and right traveling operation devices exceeds a set value, while the controller outputs the control signal to the traveling communication valve if the difference between the operation amounts of the left and right traveling operation devices is smaller than the set value. 
     
     
         19 . The hydraulic system for a construction machine according to  claim 11 , wherein the left and right traveling operation levers and the actuator operation lever for the first working device comprise electric operation devices that output electric signals to the controller in proportion to the operation amounts. 
     
     
         20 . The hydraulic system for a construction machine according to  claim 11 , wherein the left and right traveling operation levers and the actuator operation lever for the first working device comprise hydraulic operation devices that output pilot signal pressure in proportion to the operation amounts. 
     
     
         21 . A hydraulic system for a construction machine, comprising:
 first and second hydraulic pumps connected to an engine;   a left traveling operation lever, a right traveling operation lever, and an actuator operation lever for a second working device outputting an operation signal in proportion to an operation amount by an operator;   a left traveling motor connected to a discharge flow path of the first hydraulic pump to be driven by a first control valve that is shifted by an operation of the left traveling operation lever;   a right traveling motor connected to a flow path that is branched from a discharge flow path of the second hydraulic pump to be driven by a third control valve that is shifted by an operation of the right traveling operation lever;   a hydraulic actuator for a working device connected to the discharge flow path of the second hydraulic pump to be driven by a second control valve that is shifted by an operation of the actuator operation lever for the second working device;   a first pressure compensated valve which is installed on one side of an upper stream and a downstream of the first control valve and of which an opening amount is controlled according to a difference between a maximum load sensing pressure of an actuator connected to the first hydraulic pump and a discharge flow path pressure;   a second pressure compensated valve which is installed on one side of an upper stream and a downstream of the second control valve and of which an opening amount is controlled according to a difference between a maximum load sensing pressure of an actuator connected to the second hydraulic pump and a discharge flow path pressure;   a third pressure compensated valve which is installed on one side of an upper stream and a downstream of the third control valve and of which an opening amount is controlled according to the difference between the maximum load sensing pressure of the actuator connected to the second hydraulic pump and the discharge flow path pressure;   a first orifice connected to a first load sensing line connected to the first pressure compensated valve of the first control valve, and a hydraulic tank;   a second orifice connected to the second pressure compensated valve of the second control valve, a second load sensing line connected to the third pressure compensated valve of the third control valve, and the hydraulic tank;   a confluence valve which is installed in a confluence flow path that connects the discharge flow paths of the first and second hydraulic pumps in parallel, of which an opening amount is controlled according to an operation amount of the traveling operation lever or the actuator operation lever for the second working device, which sums discharge flow rates of the first and second hydraulic pumps, and which makes the first load sensing line and the second load sensing line communicate with each other;   a traveling communication valve installed in a flow path connecting the downstream of the left traveling first pressure compensated valve to the downstream of the right traveling third pressure compensated valve to open or close the flow path by an external control signal; and   a controller controlling the traveling communication valve to shift the flow path to a communication position when a combined operation for simultaneously operating a traveling device and the working device is performed.   
     
     
         22 . The hydraulic system for a construction machine according to  claim 21 , wherein the traveling communication valve is composed of a solenoid valve that is shifted by an electric signal from the controller. 
     
     
         23 . The hydraulic system for a construction machine according to  claim 21 , wherein the traveling communication valve is connected to a solenoid valve that outputs pilot signal pressure that corresponds to the control signal from the controller so that the traveling communication valve is shifted when the pilot signal pressure is supplied. 
     
     
         24 . The hydraulic system for a construction machine according to  claim 23 , wherein the solenoid valve is composed of a valve having characteristics that the solenoid valve is on/off-shifted according to existence/nonexistence of an input of the electric signal. 
     
     
         25 . The hydraulic system for a construction machine according to  claim 21 , wherein the solenoid valve is composed of a valve having characteristics that the solenoid valve outputs pilot pressure in proportion to an input size of the electric signal. 
     
     
         26 . The hydraulic system for a construction machine according to  claim 21 , wherein the left and right traveling operation levers and the actuator operation lever for the second working devices comprise operation amount sensing means for sensing operations of the operation levers and transmitting detection signals to the controller. 
     
     
         27 . The hydraulic system for a construction machine according to  claim 26 , wherein the operation amount sensing means is composed of a pressure sensor. 
     
     
         28 . The hydraulic system for a construction machine according to  claim 21 , wherein the controller senses the operations of the left and right traveling operation levers by detecting the operation amounts through a sensing means for sensing the operation amounts of the left and right traveling operation levers and a sensing means for sensing the operation amount of the actuator operation lever for the second working device, and in the case where the operation of the actuator operation lever for the second working device is sensed, the controller does not output the control signal to the traveling communication valve if the difference between the operation amounts of the left and right traveling operation devices exceeds a set value, while the controller outputs the control signal to the traveling communication valve if the difference between the operation amounts of the left and right traveling operation devices is smaller than the set value. 
     
     
         29 . The hydraulic system for a construction machine according to  claim 21 , wherein the left and right traveling operation levers and the actuator operation lever for the second working device comprise electric operation devices that output electric signals to the controller in proportion to the operation amounts. 
     
     
         30 . The hydraulic system for a construction machine according to  claim 21 , wherein the left and right traveling operation levers and the actuator operation lever for the second working device comprise hydraulic operation devices that output pilot signal pressure in proportion to the operation amounts.