TRANSMISSION CONTROL DEVICE AND METHOD FOR WORKING VEHICLE
First Claim
1. A transmission control device of a work vehicle composed of an engine, a travel device and a power transmission unit, the power transmission unit including a torque converter, a lock-up clutch and a transmission, the power transmission unit being configured to transmit an output of the engine to the travel device via either the torque converter or the lock-up clutch, and subsequently via the transmission, the transmission control device being configured to shift a high-speed gear of the transmission down to a low-speed gear in accordance with reduction in a vehicle speed, the transmission control device comprising:
- a load increase rate computation portion configured to compute an increase rate of a load acting on the work vehicle; and
a transmission control portion configured to shift the high-speed gear down to the low-speed gear with producing a lock-up state in which the lock-up clutch is engaged when the load increase rate is less than a load increase rate threshold in shifting the high-speed gear down to the low-speed gear, and producing a torque converter state in which the lock-up clutch is disengaged when the load increase rate is equal to or greater than the load increase rate threshold in shifting the high-speed gear down to the low-speed gear.
1 Assignment
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Accused Products
Abstract
A transmission control device includes a load increase rate computation portion and a transmission control portion. The load increase rate computation portion is configured to compute an increase rate of a load acting on the work vehicle. The transmission control portion is configured to shift a high-speed gear down to a low-speed gear with producing a lock-up state in which a lock-up clutch is engaged when the load increase rate is less than a load increase rate threshold in shifting the high-speed gear down to the low-speed gear, and producing a torque converter state in which the lock-up clutch is disengaged when the load increase rate is equal to or greater than the load increase rate threshold in shifting the high-speed gear down to the low-speed gear.
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Citations
6 Claims
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1. A transmission control device of a work vehicle composed of an engine, a travel device and a power transmission unit, the power transmission unit including a torque converter, a lock-up clutch and a transmission, the power transmission unit being configured to transmit an output of the engine to the travel device via either the torque converter or the lock-up clutch, and subsequently via the transmission, the transmission control device being configured to shift a high-speed gear of the transmission down to a low-speed gear in accordance with reduction in a vehicle speed, the transmission control device comprising:
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a load increase rate computation portion configured to compute an increase rate of a load acting on the work vehicle; and a transmission control portion configured to shift the high-speed gear down to the low-speed gear with producing a lock-up state in which the lock-up clutch is engaged when the load increase rate is less than a load increase rate threshold in shifting the high-speed gear down to the low-speed gear, and producing a torque converter state in which the lock-up clutch is disengaged when the load increase rate is equal to or greater than the load increase rate threshold in shifting the high-speed gear down to the low-speed gear. - View Dependent Claims (3)
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2. A transmission control device of a work vehicle composed of an engine, a travel device and a power transmission unit, the power transmission unit including a torque converter, a lock-up clutch and a transmission, the power transmission unit being configured to transmit an output of the engine to the travel device via either the torque converter or the lock-up clutch and subsequently via the transmission, the transmission control device being configured to shift a high-speed gear of the transmission down to a low-speed gear in accordance with reduction in a vehicle speed, the transmission control device comprising:
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an acceleration detection portion configured to detect a reduction rate of a speed of the work vehicle; and a transmission control portion configured to shift the high-speed gear down to the low-speed gear with producing a lock-up state in which the lock-up clutch is engaged when the vehicle speed reduction rate is less than a vehicle speed reduction rate threshold in shifting the high-speed gear down to the low-speed gear, and producing a torque converter state in which the lock-up clutch is disengaged when the vehicle speed reduction rate is equal to or greater than the vehicle speed reduction rate threshold in shifting the high-speed gear down to the low-speed gear. - View Dependent Claims (4)
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5. A transmission control method for controlling a transmission of a work vehicle in which an output of an engine is transmitted to a travel device via either a torque converter or a lock-up clutch, and subsequently via a transmission, where a high-speed gear of the transmission is configured to be shifted down to a low-speed gear in accordance with reduction in a vehicle speed, the transmission control method comprising:
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computing an increase rate of a load acting on the work vehicle; and shifting the high-speed gear down to the low-speed gear with producing a lock-up state in which the lock-up clutch is engaged when the increase rate of the load acting on the work vehicle is less than a load increase rate threshold in shifting the high-speed gear down to the low-speed gear, and producing a torque converter state in which the lock-up clutch is disengaged when the increase rate of the load acting on the work vehicle is equal to or greater than the load increase rate threshold in shifting the high-speed gear down to the low-speed gear.
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6. A transmission control method for controlling a transmission of a work vehicle in which an output of an engine is transmitted to a travel device via either a torque converter or a lock-up clutch, and subsequently via a transmission, where a high-speed gear of the transmission is shifted down to a low-speed gear in accordance with reduction in a vehicle speed, the transmission control method comprising:
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computing a reduction rate of speed of the work vehicle; and shifting the high-speed gear down to the low-speed gear with producing a lock-up state in which the lock-up clutch is engaged when the reduction rate of the speed of the work vehicle is less than a vehicle speed reduction rate threshold in shifting the high-speed gear down to the low-speed gear, and producing a toque converter state in which the lock-up clutch is disengaged when the reduction ratio of the speed of the work vehicle is equal to or greater than the vehicle speed reduction ratio threshold in shifting the high-speed gear down to the low-speed gear.
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Specification