By a News Reporter-Staff News Editor at Journal of Engineering -- From Alexandria, Virginia, VerticalNews journalists report that a patent by the inventor Horii, Hiroshi (Osaka, JP), filed on December 11, 2012, was published online on June 28, 2016.
The patent's assignee for patent number 9377034 is KUBOTA CORPORATION (Osaka, JP).
News editors obtained the following quote from the background information supplied by the inventors: "As a working machine provided with a load sensing system, there has been a back hoe described in Patent Literature 1.
"In this back hoe, there are equipped a plurality of hydraulic actuators and a main pump composed of a variable displacement hydraulic pump for supplying pressure oil to these hydraulic actuators.
"The load sensing system is provided with: direction switching valves which are provided in correspondence with the respective hydraulic actuators to control a supply direction of the pressure oil discharged from the main pump and supply the pressure oil to the hydraulic actuators; and pressure compensation valves provided in correspondence with the respective direction switching valves functioning so as to keep a front and rear differential pressure of each of the direction switching valves.
"Further, the load sensing system is provided with a flow rate control part for controlling the main pump, in addition to the variable displacement main pump, direction switching valves and pressure compensation valves, and further includes a PPS transmission line for transmitting a discharge pressure of the main pump as a PPS signal pressure to the flow rate control part and a PLS transmission line for transmitting a maximum load pressure among load pressures of the hydraulic actuators as a PLS signal pressure to the flow rate control part.
"The flow rate control part controls the discharge pressure of the main pump so as to maintain the differential pressure obtained by subtracting the PLS signal pressure from the PPS signal pressure to be a constant pressure.
"In the case where the plurality of hydraulic actuators are operated, the load sensing system diverts the discharge flow rate of the main pump so as to supply the pressure oil to each of operated hydraulic cylinders by a quantity corresponding to an operated amount regardless of difference in value of loads acting on the operated hydraulic actuators.
"The pressure compensation valve is provided with a load pressure flow passage for introducing a load pressure of a hydraulic actuator corresponding to the pressure compensation valve and outputting the load pressure to the PLS transmission line."
As a supplement to the background information on this patent, VerticalNews correspondents also obtained the inventor's summary information for this patent: "Technical Problem
"In a back hoe, in a case of continuously performing rapid operations during a working such as a drilling, an operating oil flow rate is suddenly changed and a machine body may likely act violently due to an operation change of a control target of a hydraulic actuator. For the purpose of such a case, conventionally, a certain amount of a diaphragm is adopted in a load pressure flow passage of a pressure compensation valve. By providing the diaphragm in the load pressure flow passage for introducing a load pressure of the hydraulic actuator, a detection sensitivity of the PLS signal pressure is dulled and control responsibility of the main pump is made slow, whereby stability of the machine body can be increased.
"However, on the other hand, when the control target of the hydraulic actuator is activated, although it is desired to be quickly activated, the signal responsibility is reduced due to an effect of the diaphragm and the responsibility at the time of activation becomes slow.
"Therefore, in consideration of the above problem, the present invention has an object to provide a working machine capable of exerting quick responsibility at the time of activating the hydraulic actuator and increasing the stability of the machine body during the actuation after the hydraulic actuator is activated.
"Solution to Problem
"Technical means made by the present invention for solving the problem have specific features as following.
"In a first aspect of the present invention, a working machine includes:
"a plurality of hydraulic actuators;
"a variable displacement hydraulic pump for supplying pressure oil to these hydraulic actuators; and
"a load sensing system for controlling a discharge pressure of the hydraulic pump so as to render a differential pressure obtained by subtracting a maximum load pressure among the hydraulic actuators from a discharge pressure of the hydraulic pump to be a constant pressure,
"wherein the working machine is provided with: a first load pressure flow passage which introduces load pressures of the hydraulic actuators to be outputted to a PLS transmission line which transmits the maximum load pressure among the hydraulic actuators at the time of activating the hydraulic actuators; and
"a second load pressure flow passage which is a flow path for introducing the load pressures of the hydraulic actuators to be outputted to the PLS transmission line during operation after activations of the hydraulic actuators, and wherein a flow rate of the pressure oil therein is reduced than that in the first load pressure flow passage.
"In a second aspect of the present invention, the working machine includes:
"direction switching valves provided in correspondence with the respective hydraulic actuators, the direction switching valves controlling supply directions of the pressure oil discharged from the hydraulic pump to supply the pressure oil to the hydraulic actuators; and
"pressure compensation valves functioning so as to maintain differential pressures before and behind the direction switching valves to be constant, the pressure compensation valves provided in correspondence with the respective direction switching valves,
"wherein the pressure compensation valve is provided with the first load pressure flow passage and the second load pressure flow passage, whereby the first load pressure flow passage functions from a beginning of a stroke to a middle of the stroke of the pressure compensation valve and the second load pressure flow passage functions at a time of a full stroke of the pressure compensation valve.
"In a third aspect of the present invention, a diaphragm is provided in the second load pressure flow passage without providing a diaphragm in the first load pressure flow passage, whereby a flow rate of the pressure oil of the second load pressure flow passage is reduced lower than that of the first load pressure flow passage.
"In a fourth aspect of the present invention, diaphragms are provided in both of the first load pressure flow passage and the second load pressure flow passage and a flow path opening area of the diaphragm of the second load pressure flow passage is made smaller compared to a flow path opening area of the diaphragm of the first load pressure flow passage, whereby a flow rate of the pressure oil of the second load pressure flow passage is reduced lower than that of the first load pressure flow passage.
"In a fifth aspect of the present invention, the pressure compensation valve is provided with a load pressure-introduction port introducing the load pressures of the hydraulic actuators and a load pressure outlet port outputting the load pressures of the hydraulic actuators introduced from this load pressure introduction port to the PLS transmission line,
"wherein the load pressure introduction port and the load pressure outlet port are communicated through the first load pressure flow passage from a beginning of a stroke to a middle of the stroke of the pressure compensation valve, and the communication is switched at the middle of the stroke and thereafter, the load pressure introduction port and the load pressure outlet port are communicated through the second load pressure flow passage.
"Advantageous Effects of Invention
"According to the invention, the following effects are exerted.
"According to the first aspect of the present invention, at the time of activating the hydraulic actuator, since the load pressure of the hydraulic actuator is transmitted to the PLS transmission line via the first load pressure flow passage having a pressure oil flow rate larger than that of the second load pressure flow passage, the control responsibility of the hydraulic pump is high and the control pressure instantly follows to thereby exert quick responsibility.
"Moreover, during the actuation after activating the hydraulic actuator, since the load pressure of the hydraulic actuator is transmitted to the PLS transmission line via the second load pressure flow passage having a flow rate restricted lower than that of the first load pressure flow passage, the transmission responsibility of the PLS signal pressure becomes slow by the second load pressure flow passage and the stability of the machine body of the working machine can be increased by suppressing a following performance of the control pressure to the hydraulic pump.
"According to the second aspect of the present invention, by incorporating the first load pressure flow passage and second load pressure flow passage into the pressure compensation valve, the structure can be simplified.
"According to the third aspect of the present invention, the load pressure of the hydraulic actuator is transmitted by a flow path having no diaphragm at the time of activating the hydraulic actuator and the load pressure of the hydraulic actuator is transmitted by the flow path having a diaphragm during an actuation after activating the hydraulic actuator, whereby it is possible to easily carry out the working machine capable of exerting quick responsibility at the time of activating the hydraulic actuator and increasing the stability of the machine body during the actuation after activating the hydraulic actuator.
"According to the fourth aspect of the present invention, the load pressure of the hydraulic actuator is transmitted by the flow path having the large diaphragm at the time of activating the hydraulic actuator and the load pressure of the hydraulic actuator is transmitted by the flow path having the small diaphragm during an actuation after activating the hydraulic actuator, whereby it is possible to easily carry out the working machine capable of exerting quick responsibility at the time of activating the hydraulic actuator and increasing the stability of the machine body during the actuation after activating the hydraulic actuator.
"According to the fifth aspect of the present invention, the pressure compensation valve is provided with the load pressure introduction port and the load pressure outlet port and these ports are communicated through the first load pressure flow passage from the beginning of the stroke to the middle of the stroke of the pressure compensation valve, and the communication is switched at the middle of the stroke and thereafter these ports are communicated through the second load pressure flow passage, whereby it is possible to easily realize the working machine capable of exerting quick responsibility at the time of activating the hydraulic actuator and increasing the stability of the machine body during the actuation after activating the hydraulic actuator
BRIEF DESCRIPTION OF DRAWINGS
"FIG. 1 is a hydraulic circuit diagram of an essential part;
"FIG. 2 is a hydraulic circuit diagram showing an entire configuration;
"FIG. 3 is a hydraulic circuit diagram showing a left half of the hydraulic circuit of FIG. 2;
"FIG. 4 is a hydraulic circuit diagram showing a right half of the hydraulic circuit of FIG. 2;
"FIG. 5 is a side view of a back hoe; and
"FIG. 6 is a hydraulic circuit diagram according to another embodiment."
For additional information on this patent, see: Horii, Hiroshi. Work Machine. U.S. Patent Number 9377034, filed December 11, 2012, and published online on June 28, 2016. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=9377034.PN.&OS=PN/9377034RS=PN/9377034
Keywords for this news article include: KUBOTA CORPORATION.
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