Patent ID: 7712565
Filing Date: 2010-05-11
Classification: B60K,F16H

Abstract:
1. An HST travel system for a working machine, said HST travel system comprising: a hydraulic pump; one first hydraulic motor connected to said hydraulic pump in a closed circuit and driven by a hydraulic fluid delivered from said hydraulic pump; one second hydraulic motor connected to said hydraulic pump in a closed circuit in parallel with said first hydraulic motor and driven by the hydraulic fluid delivered from said hydraulic pump; a first travel unit connected to said first hydraulic motor through a first reduction gearing; a second travel unit connected to said second hydraulic motor through a second reduction gearing; and control means for selectively switching over a drive mode between low-speed four-wheel drive in which said first and second travel units are both driven and high-speed two-wheel drive in which said first hydraulic motor is controlled to zero displacement and only said second travel unit is driven, wherein when the drive mode is switched over from the low-speed four-wheel drive to the high-speed two-wheel drive, said control means controls a displacement of said second hydraulic motor to absorb an excessive flow rate of the hydraulic fluid, which is generated upon said first hydraulic motor being brought to the zero displacement from an effective displacement, at the same timing as when said first hydraulic motor is controlled to the zero displacement from the effective displacement, and when the drive mode is switched over from the high-speed two-wheel drive to the low-speed four-wheel drive, said control means controls the displacement of said second hydraulic motor to supply the hydraulic fluid at a flow rate, which is required by said first hydraulic motor upon said first hydraulic motor being brought to an effective displacement from the zero displacement, at the same timing as when said first hydraulic motor is controlled to the effective displacement from the zero displacement.