Patent ID: 8380408

Claim:
A speed change control system for industrial vehicle, comprising: a speed ratio detecting unit that detects a speed ratio of speeds of an input shaft and of an output shaft of a torque converter; a torque converter speed ratio-based speed changer that shifts up or shifts down a speed stage of a transmission in response to the detected speed ratio; a determination unit that determines an upshift condition is established when the detected speed ratio is equal to or greater than an upshift determination threshold, and determines a downshift condition is established when the detected speed ratio is equal to or smaller than a downshift determination threshold which is smaller than the upshift determination threshold; a vehicle speed detection unit that detects a vehicle speed; a speed change control unit that, when the determination unit determines that the upshift condition is established, permits an upshift by the torque converter speed ratio-based speed changer if the vehicle speed detected by the vehicle speed detection unit is equal to or higher than a predetermined value, and prohibits the upshift by the torque converter speed ratio-based speed changer if the vehicle speed detected by the vehicle speed detection unit is lower than the predetermined value; a clutch cutting mechanism that releases a clutch for traveling when a brake pedal is depressed to a predetermined extent or more, and connects the clutch for traveling when the brake pedal is no longer depressed to the predetermined extent or more; and a clutch cutting detection unit that detects an operation state of the clutch cutting mechanism, wherein: the speed change control unit permits the upshift when a connection of the clutch is detected by the clutch cutting detection unit, and prohibits the upshift when a release of the clutch is detected by the clutch cutting detection unit.