Gearshift controller for industrial vehicle

A gearshift controller for an industrial vehicle, comprising:

• a rotational speed detection unit that detects respective rotational speeds of an input axis and of an output axis of a torque converter;
• a solenoid control unit that drives a solenoid for gearshift of a transmission;
• a gearshift control unit having an input unit that inputs signals detected by the rotational speed detection unit and a calculation unit that calculates a speed ratio of rotational speeds of the input axis and of the output axis based on the signals input by the input unit, the gearshift control unit shifting up a speed stage when the calculated ratio of speeds is equal to or more than a first predetermined value and shifting down the speed stage when the calculated ratio of speeds is equal to or less than a second predetermined value, which is smaller than the first predetermined value;
• and
• an operation member with which a downshift to the first speed is instructed by operation thereof by an operator, wherein
• the gearshift control unit further includes
• a memory unit in which there is set a predetermined time period longer than a standard time period required for the vehicle to thrust into earth and sand after the downshift of the speed stage to the first stage upon excavation;
• and
• an output unit that outputs a control signal to the solenoid control unit so as to control the speed stage to be maintained at the first speed for the predetermined time period regardless of the calculated ratio of speeds when the downshift of the speed stage to the first speed is instructed with the operation member, wherein
• the gearshift control unit allows switching to the first speed by operation of the operation member while the vehicle is traveling at a second speed and prohibits the switching to the first speed by operation of the operation member while the vehicle is traveling at a third or higher speed.