To perform appropriate pump torque control by preventing hunting from being caused by interference between speed sensing control at the low temperature of hydraulic oil and the control of the number of revolutions of a prime mover.
A regulator 31 controls displacement volumes of hydraulic pumps 2 and 3 so that the absorption torque of the hydraulic pumps 2 and 3 cannot exceed set maximum absorption torque. A rotary sensor 33, an oil temperature sensor 34, a proportional solenoid valve 35 and a controller 23 perform the speed sensing control so that the maximum absorption torque of the hydraulic pumps 2 and 3 which is set by the regulator 31 can be decreased depending on deviation between the target number and the actual number of the revolutions of the prime mover 1. A second correction coefficient computing portion 45 and a control gain correction portion 49 of the controller 23 change the control gain of the speed sensing control so that the control gain can be lowered as the temperature of the hydraulic oil is decreased on the basis of the detection value of the oil temperature sensor 34.
ISHIKAWA HIROJI
KARASAWA HIDEO
OKANO YASUO
NAKAMURA KAZUNORI
KOWATARI YOICHI
| JP2002364603A | 2002-12-18 | |||
| JPH11101183A | 1999-04-13 |
| WO2004018877A1 | 2004-03-04 |
Next Patent: GROUND STRENGTH INDICATING METHOD AND APPARATUS FOR USE THEREIN