A work vehicle comprising: an engine; a travel device for causing the vehicle to travel, the travel device being driven by a drive force from the engine, the travel device having a transmission; a hydraulic pump for discharging hydraulic fluid, the hydraulic pump being driven by the drive force from the engine; a work implement driven by hydraulic fluid from the hydraulic pump; a torque converter device for transmitting the drive force from the engine to the travel device, the torque converter device having a torque converter and a lockup clutch; an accelerator operation member operated by an operator; an accelerator operation detector for detecting the operation amount of the accelerator operation member; and a controller for controlling the engine on the basis of an engine torque curve for defining a relationship between the engine speed, the engine output torque, and the operation amount of the accelerator operation member, wherein the controller is configured to: automatically change a speed of the transmission and switch the lockup clutch in accordance with a vehicle speed; control the engine on the basis of a first engine torque curve during torque conversion travel in which the lockup clutch is in a non-connected state; control the engine on the basis of a second engine torque curve during lockup travel in which the lockup clutch is in a connected state; and the engine output torque of the second engine torque curve is less than the engine output torque of the first engine torque curve in a predetermined speed range that includes a switch speed at which a switch is made from the torque conversion travel to the lockup travel when at least the operation amount of the accelerator operation member is a predetermined operation amount that is less than maximum. an engine; a travel device for causing the vehicle to travel, the travel device being driven by a drive force from the engine, the travel device having a transmission; a hydraulic pump for discharging hydraulic fluid, the hydraulic pump being driven by the drive force from the engine; a work implement driven by hydraulic fluid from the hydraulic pump; a torque converter device for transmitting the drive force from the engine to the travel device, the torque converter device having a torque converter and a lockup clutch; an accelerator operation member operated by an operator; an accelerator operation detector for detecting the operation amount of the accelerator operation member; and a controller for controlling the engine on the basis of an engine torque curve for defining a relationship between the engine speed, the engine output torque, and the operation amount of the accelerator operation member, wherein the controller is configured to: automatically change a speed of the transmission and switch the lockup clutch in accordance with a vehicle speed; control the engine on the basis of a first engine torque curve during torque conversion travel in which the lockup clutch is in a non-connected state; control the engine on the basis of a second engine torque curve during lockup travel in which the lockup clutch is in a connected state; and the engine output torque of the second engine torque curve is less than the engine output torque of the first engine torque curve in a predetermined speed range that includes a switch speed at which a switch is made from the torque conversion travel to the lockup travel when at least the operation amount of the accelerator operation member is a predetermined operation amount that is less than maximum. automatically change a speed of the transmission and switch the lockup clutch in accordance with a vehicle speed; control the engine on the basis of a first engine torque curve during torque conversion travel in which the lockup clutch is in a non-connected state; control the engine on the basis of a second engine torque curve during lockup travel in which the lockup clutch is in a connected state; and the engine output torque of the second engine torque curve is less than the engine output torque of the first engine torque curve in a predetermined speed range that includes a switch speed at which a switch is made from the torque conversion travel to the lockup travel when at least the operation amount of the accelerator operation member is a predetermined operation amount that is less than maximum.