US 12,320,099 B2
Hydraulic system of working machine and method for controlling hydraulic system of working machine
Hiroya Mori, Osaka (JP); and Hiroshi Horii, Osaka (JP)
Assigned to KUBOTA CORPORATION, Osaka (JP)
Filed by KUBOTA CORPORATION, Osaka (JP)
Filed on Jun. 10, 2024, as Appl. No. 18/738,284.
Application 18/738,284 is a continuation of application No. PCT/JP2022/045019, filed on Dec. 7, 2022.
Claims priority of application No. 2021-214936 (JP), filed on Dec. 28, 2021.
Prior Publication US 2024/0328120 A1, Oct. 3, 2024
Int. Cl. E02F 9/22 (2006.01)
CPC E02F 9/2228 (2013.01) [E02F 9/2285 (2013.01); F15B 2211/755 (2013.01)] 9 Claims
OG exemplary drawing
 
1. A hydraulic system of a working machine, comprising:
a working device that includes a movable member and a hydraulic cylinder that swings the movable member;
an electromagnetic proportional valve to change a flow rate of a hydraulic fluid supplied to the hydraulic cylinder; and
a controller to control the flow rate of the hydraulic fluid supplied to the hydraulic cylinder to a predetermined flow rate or less by controlling an electric current supplied to the electromagnetic proportional valve, wherein
the controller includes:
a first calculator to calculate a first electric current value, which is an electric current value of an electric current supplied to the electromagnetic proportional valve in order to control the electromagnetic proportional valve to decelerate an angular velocity of the movable member as an operation length of the hydraulic cylinder approaches a stroke end of the hydraulic cylinder,
a second calculator to calculate a second electric current value, which is an electric current value of an electric current supplied to the electromagnetic proportional valve in order to control the electromagnetic proportional valve to decrease a supply flow rate of the hydraulic fluid to the hydraulic cylinder as the operation length of the hydraulic cylinder approaches the stroke end of the hydraulic cylinder, and
an electric current restrictor to correct the electric current supplied to the electromagnetic proportional valve by the second electric current value in a case where a determination distance, which is an operation length from a current operation position of the hydraulic cylinder to the stroke end, is longer than a first threshold value and is equal to or less than a second threshold value longer than the first threshold value and to correct the electric current supplied to the electromagnetic proportional valve by a selected one of the first electric current value and the second electric current value in a case where the determination distance is equal to or less than the first threshold value.
 
6. The hydraulic system according to claim 1, wherein
the electric current restrictor corrects the electric current supplied to the electromagnetic proportional valve by the first electric current value in a case where the determination distance is equal to or less than the first threshold value.