US 12,291,849 B2
Hydraulic system in work machine
Yuji Fukuda, Sakai (JP)
Assigned to KUBOTA CORPORATION, Osaka (JP)
Filed by Kubota Corporation, Osaka (JP)
Filed on Feb. 9, 2022, as Appl. No. 17/667,539.
Application 17/667,539 is a division of application No. 16/851,102, filed on Apr. 17, 2020, granted, now 11,280,064.
Application 16/851,102 is a division of application No. 16/012,761, filed on Jun. 20, 2018, granted, now 10,662,980, issued on May 26, 2020.
Claims priority of application No. 2017-193603 (JP), filed on Oct. 3, 2017; and application No. 2017-193604 (JP), filed on Oct. 3, 2017.
Prior Publication US 2022/0154428 A1, May 19, 2022
Int. Cl. E02F 9/22 (2006.01); F15B 13/042 (2006.01); F15B 15/18 (2006.01); F15B 20/00 (2006.01); F16H 61/433 (2010.01); F16H 61/478 (2010.01)
CPC E02F 9/2267 (2013.01) [E02F 9/2285 (2013.01); E02F 9/2292 (2013.01); F15B 13/0422 (2013.01); F15B 15/18 (2013.01); F15B 20/007 (2013.01); F15B 2211/205 (2013.01); F15B 2211/355 (2013.01); F15B 2211/50572 (2013.01); F15B 2211/55 (2013.01); F15B 2211/575 (2013.01); F15B 2211/6355 (2013.01); F15B 2211/67 (2013.01); F16H 61/433 (2013.01); F16H 61/478 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A hydraulic system in a work machine, comprising:
a travel motor to be driven by hydraulic oil to rotate a drive shaft of a travel machine of the work machine;
a travel pump to supply the hydraulic oil to the travel motor to drive the travel motor;
a hydraulic pump to supply pilot hydraulic oil;
a pilot oil path connecting the hydraulic pump and the travel pump to supply the pilot hydraulic oil to the travel pump;
a travel operation device provided in the pilot oil path between the hydraulic pump and the travel pump and including an operation member, the travel operation device being configured to generate a pilot pressure and an additional pilot pressure in accordance with an operation amount of the operation member, the pilot pressure being supplied via the pilot oil path;
an additional pilot oil path connecting the travel operation device and the travel pump to supply the additional pilot pressure to the travel pump, the travel pump being configured to control a flow direction of the hydraulic oil supplied to the travel motor based on the pilot pressure and the additional pilot pressure;
a drain oil path divided from the pilot oil path, the drain oil path comprising:
a first coupling oil path connecting the pilot oil path and the additional pilot oil path; and
a second coupling oil path divided from the first coupling oil path;
a pressure selection valve provided in the first coupling oil path to select a selected pressure of the pilot hydraulic oil from the pilot pressure and the additional pilot pressure to apply the selected pressure to the pilot hydraulic oil in the second coupling oil path;
a pressure adjustment valve provided in the second coupling oil path to control the selected pressure to be an adjusted pilot pressure, the pressure adjustment valve being an electromagnetic valve;
a switch operable by a driver; and
a controller configured to receive an operation of the switch and electrically connected to the pressure adjustment valve to allow the pressure adjustment valve to change the selected pressure to the adjusted pilot pressure and to disallow the pressure adjustment valve to change the selected pressure to the adjusted pilot pressure based on the operation of the switch,
wherein the operation member is an operation lever configured to be operated in a first direction and a second direction; and
wherein the travel operation device includes:
a first operation valve connected to the pilot oil path to supply the pilot pressure of the pilot hydraulic oil to the travel pump when the operation lever is operated in the first direction; and
a second operation valve connected to the additional pilot oil path to supply the additional pilot pressure of the pilot hydraulic oil when the operation lever is operated in the second direction.