Patent ID: 8532888
Filing Date: 2013-09-10
Classification: B60W,E02F,F04B,F16H,F17D,Y10T

Abstract:
1. A control device for a hydrostatic transmission vehicle equipped with a hydrostatic transmission including a variable displacement pump to be driven by an engine and a variable displacement hydraulic motor to be rotated by a pressurized oil from the variable displacement pump, the control device comprising: a vehicle speed setting section configured to set a set vehicle speed based on both a travel command and a gear stage command instructed by an operator, the set vehicle speed being a maximum vehicle speed corresponding to the travel command and the gear stage command; a low rotation matching engine speed setting section storing a correspondence of an upper limit of an engine speed with respect to the set vehicle speed for limiting the upper limit of the engine speed to a predetermined partial engine speed set to be lower than a high idle engine speed when the set vehicle speed is in a preliminarily set low and intermediate speed range, the low rotation matching engine speed setting section being configured to set the upper limit of the engine speed using the set vehicle speed set by the vehicle speed setting section based on the correspondence; a pump and motor displacement control section configured to control respective displacements of the variable displacement pump and the variable displacement hydraulic motor based on the set vehicle speed for allowing a vehicle speed to reach the set vehicle speed set by the vehicle speed setting section even when the engine is rotated at the partial engine speed; a hydraulic sensor configured and arranged to detect a pressure in a hydraulic circuit including the variable displacement pump and the variable displacement hydraulic motor, a torque limit setting section configured to obtain the engine speed and set a torque limit usable for the hydrostatic transmission based on the obtained engine speed, a vehicle speed limit setting section configured to set a vehicle speed limit based on the detected pressure in the hydraulic circuit and the torque limit set by the torque limit setting section, and a vehicle speed selection section configured to select a lower one of the set vehicle speed set by the vehicle speed setting section and the vehicle speed limit set by the vehicle speed limit setting section, the pump and motor displacement control section being configured to execute the control using the vehicle speed selected by the vehicle speed selection section as the set vehicle speed.