Patent ID: 6041163
Filing Date: 2000-03-21
Classification: B66F,Y10S

Abstract:
An apparatus for controlling a pump motor of a forklift truck through the use of a driving transistor connected between a battery and the pump motor, comprising:a) current detection means for detecting electric current flowing through the pump motor, the current detection means including,(i) a shunt for sensing the current flowing through the pump motor to generate a first voltage signal, the shunt having a first terminal connected to the pump motor and a second terminal coupled to the battery,(ii) means for amplifying the first voltage signal to a predetermined level to produce a second voltage signal, and(iii) means for converting the second voltage signal to a current detection signal, the amplifying means includes: an operational amplifier with inverted and non-inverted input terminals, each connected to the first and second terminals of the shunt, and an output terminal; gain decision means having a first resistor connected between the inverted input terminal of the amplifier and the first terminal of the shunt, a second resistor connected between the inverted input terminal and the output terminal of the amplifier, a third resistor connected between the non-inverted input terminal of the amplifier and the second terminal of the shunt, and a fourth resistor connected to the inverted input terminal; and bias means for providing a bias voltage signal via the fourth resistor to the operational amplifier; andb) control means responsive to the current detection signal for determining load condition of the pump motor to apply a varying control signal to the driving transistor so that a varying amount of electric current can be fed to the pump motor in proportion to the load exerting on the pump motor.