US 9,810,246 B2
Hydraulic drive system
Teruo Akiyama, Kokubunji (JP); Noboru Iida, Chigasaki (JP); Kenji Oshima, Tokyo (JP); and Koji Saito, Fujisawa (JP)
Assigned to KOMATSU LTD., Tokyo (JP)
Appl. No. 14/129,414
Filed by Teruo Akiyama, Kokubunji (JP); Noboru Iida, Chigasaki (JP); Kenji Oshima, Tokyo (JP); and Koji Saito, Fujisawa (JP)
PCT Filed Aug. 13, 2012, PCT No. PCT/JP2012/070602
§ 371(c)(1), (2), (4) Date Dec. 26, 2013,
PCT Pub. No. WO2013/027619, PCT Pub. Date Feb. 28, 2013.
Claims priority of application No. 2011-182939 (JP), filed on Aug. 24, 2011.
Prior Publication US 2014/0123639 A1, May 8, 2014
Int. Cl. F15B 15/02 (2006.01); E02F 9/22 (2006.01); F15B 21/08 (2006.01)
CPC F15B 15/02 (2013.01) [E02F 9/2235 (2013.01); E02F 9/2289 (2013.01); E02F 9/2292 (2013.01); E02F 9/2296 (2013.01); F15B 21/087 (2013.01); F15B 2211/20546 (2013.01); F15B 2211/20561 (2013.01); F15B 2211/20576 (2013.01); F15B 2211/27 (2013.01); F15B 2211/613 (2013.01); F15B 2211/633 (2013.01); F15B 2211/6336 (2013.01); F15B 2211/6346 (2013.01); F15B 2211/7053 (2013.01); F15B 2211/785 (2013.01)] 13 Claims
OG exemplary drawing
 
1. A hydraulic driving system comprising:
a hydraulic cylinder including a cylinder tube and a cylinder rod, the cylinder tube having a first end part and a second end part, the cylinder rod having a proximal end part inserted inside the cylinder tube such that the proximal end part can move reciprocally between the first end part and the second end part, the proximal end part of the cylinder rod partitioning an inside of the cylinder tube into a first chamber disposed between the first end part and the proximal end part and a second chamber disposed between the proximal end part and the second end part, the cylinder rod being configured to move in an expansion direction such that the first chamber expands when hydraulic fluid is supplied to the first chamber and exhausted from the second chamber, the cylinder rod being configured to move in a contraction direction such that the first chamber contracts when hydraulic fluid is supplied to the second chamber and exhausted from the first chamber;
a main pump switchable between
a state of supplying hydraulic fluid to the first chamber and sucking in hydraulic fluid from the second chamber, and
a state of supplying hydraulic fluid to the second chamber and sucking in hydraulic fluid from the first chamber;
a hydraulic-fluid path connecting the first chamber and the main pump, the hydraulic-fluid path also connecting the second chamber and the main pump, the hydraulic-fluid path forming a closed circuit between the main pump and the hydraulic cylinder;
a charge pump configured to replenish hydraulic fluid in the hydraulic-fluid path, the charge pump having a maximum discharge flow rate that is smaller than a maximum suction flow rate of the main pump;
a stroke position detector configured to detect a stroke position of the proximal end part of the cylinder rod inside the cylinder tube; and
a pump controller arranged to receive a signal indicating the stroke position from the stroke position detector, the pump controller being programmed to execute a flow rate reduction control when a distance from the stroke position detected by the stroke position detector to a stroke end where the proximal end part of the cylinder rod contacts the first end part or the second end part of the cylinder tube is equal to or smaller than a distance from a reduction start position to the stroke end,
the flow rate reduction control being configured to reduce a suction flow rate of the main pump as the stroke position approaches a reference position so that the suction flow rate is equal to or less than the maximum discharge flow rate of the charge pump when the stroke position is in a range spanning between the reference position and the stroke end, the reduction start position and the reference position being different from each other and different from the stroke end, the reference position being disposed between the reduction start position and the stroke end.