Work vehicle and control method for same

• US 9,677,246 B2
• Filed: 12/09/2014
• Issued: 06/13/2017
• Est. Priority Date: 01/29/2014
• Status: Active Grant

• Current Assignee: Komatsu Ltd.
• Original Assignee: Komatsu Ltd.
• Inventors: Yoshizawa, Masao, Miyamoto, Shunsuke, Kishimoto, Yasuki
• Primary Examiner(s): Black, Thomas G
• Assistant Examiner(s): LOUIE, WAE LENNY
• Application Number:
  US14/763,869
• Publication Number:
  US 20150361636A1
• Time in Patent Office: 917 Days
• Field of Search: 701 50, 701 22, 701 84, 2804461, 180 65245, 414685, 903902
• CPC Class Codes: B60K 6/387 Actuated clutches, i.e. clutches engaged or disengaged by electric, hydraulic or mechanical actuating means
• CPC Class Codes: B60K 6/445 Differential gearing distribution type
• CPC Class Codes: B60K 6/54 Transmission for changing ratio
• CPC Class Codes: B60W 10/08 including control of electric propulsion units, e.g. motors or generators
• CPC Class Codes: B60W 20/00 Control systems specially adapted for hybrid vehicles hybrid vehicle design, B60K6/00; electric vehicles B60L
• CPC Class Codes: B60W 20/10 Controlling the power contribution of each of the prime movers to meet required power demand
• CPC Class Codes: B60W 2300/17 Construction vehicles, e.g. graders, excavators
• CPC Class Codes: B60W 2540/10 Accelerator pedal position
• CPC Class Codes: E02F 3/34 with bucket-arms , i.e. a pair of arms, e.g. manufacturing processes, form, geometry, material of bucket-arms with a single arm E02F3/283 directly pivoted on the frames of tractors or self-propelled machines
• CPC Class Codes: E02F 3/422 Drive systems for bucket-arms, front-end loaders, dumpers or the like
• CPC Class Codes: E02F 9/2075 of the hybrid type for vehicles in general B60W20/00
• CPC Class Codes: E02F 9/2079 Control of mechanical transmission for hydrostatic transmission or hydraulic torque converter E02F9/2253
• CPC Class Codes: E02F 9/2253 Controlling the travelling speed of vehicles, e.g. adjusting travelling speed according to implement loads, control of hydrostatic transmission
• CPC Class Codes: E02F 9/2292 Systems with two or more pumps
• CPC Class Codes: E02F 9/2296 Systems with a variable displacement pump
• CPC Class Codes: Y02T 10/62 Hybrid vehicles
• CPC Class Codes: Y10S 903/902 Prime movers comprising electrical and internal combustion motors

Abstract

A control unit of a work vehicle has a transmission requirement determination unit, a command-torque determination unit, and a tractive force limiting unit. The transmission requirement determination unit determines a required tractive force on the basis of an operating amount of an accelerator operating member. The required tractive force is a target tractive force of a travel device. The command-torque determination unit determines an output torque of the electric motor so that the tractive force of the vehicle reaches the required tractive force. The tractive force limiting unit reduces the required tractive force to a value less than a value corresponding to the operating amount of the accelerator operating member when the vehicle is excavating.

Claims

1. A work vehicle, comprising:

an engine;

a hydraulic pump driven by the engine;

a work implement driven by hydraulic fluid discharged from the hydraulic pump;

a power transmission device having an electric motor;

a travel device that causes the vehicle to travel due to driving power outputted from the power transmission device;

an accelerator operating member; and

a control unit configured to control the power transmission device;

the control unit including

a transmission requirement determination unit for determining, on the basis of an operating amount of the accelerator operating member, a required tractive force that is a target tractive force of the travel device;

a command-torque determination unit for determining an output torque of the electric motor so that the tractive force of the vehicle reaches the required tractive force; and

a tractive force limiting unit for reducing the required tractive force to a value lower than a value corresponding to the operating amount of the accelerator operating member while the vehicle is excavating.

2. The work vehicle according to claim 1, wherein

the tractive force limiting unit corrects the operating amount of the accelerator operating member to a value smaller than the actual operating amount while the vehicle is excavating;

and

the transmission requirement determination unit determines the required tractive force on the basis of the corrected operating amount of the accelerator operating member.

3. The work vehicle according to claim 1, wherein

the tractive force limiting unit reduces the required tractive force to a value less than a value corresponding to the operating amount of the accelerator operating member while the vehicle is excavating and when a discharge pressure of the hydraulic pump is greater than a predetermined threshold.

4. The work vehicle according to claim 1, wherein

the tractive force limiting unit reduces the required tractive force in response to the discharge pressure of the hydraulic pump.

5. The work vehicle according to claim 1, further comprising

a work implement operating member for operating the work implement;

the control unit including

an engine requirement determination unit for determining an engine required horsepower; and

a required throttle determination unit for determining a command throttle value for the engine on the basis of the engine required horsepower; and

the engine requirement determination unit determining the engine required horsepower on the basis of a transmission required horsepower, which is determined on the basis of the required tractive force, and a work implement required horsepower, which is determined on the basis of an operating amount of the work implement operating member.

6. The work vehicle according to claim 1, wherein

the power transmission device further has an input shaft and an output shaft and transmits driving power from the engine to the travel device;

and

the power transmission device is configured to change a rotation speed ratio of the output shaft with respect to the input shaft by changing the rotation speed of the electric motor.

7. The work vehicle according to claim 2, wherein

the tractive force limiting unit reduces the required tractive force to a value less than a value corresponding to the operating amount of the accelerator operating member while the vehicle is excavating and when a discharge pressure of the hydraulic pump is greater than a predetermined threshold.

8. The work vehicle according to claim 7, wherein

the tractive force limiting unit reduces the required tractive force in response to the discharge pressure of the hydraulic pump.

9. The work vehicle according to claim 8, further comprising

a work implement operating member for operating the work implement;

the control unit including

an engine requirement determination unit for determining an engine required horsepower; and

a required throttle determination unit for determining a command throttle value for the engine on the basis of the engine required horsepower; and

the engine requirement determination unit determining the engine required horsepower on the basis of a transmission required horsepower, which is determined on the basis of the required tractive force, and a work implement required horsepower, which is determined on the basis of an operating amount of the work implement operating member.

10. The work vehicle according to claim 9, wherein

the power transmission device further has an input shaft and an output shaft and transmits driving power from the engine to the travel device;

and

the power transmission device is configured to change a rotation speed ratio of the output shaft with respect to the input shaft by changing the rotation speed of the electric motor.

11. A control method for a work vehicle comprising

an engine, a hydraulic pump driven by the engine, a work implement driven by hydraulic fluid discharged from the hydraulic pump, a power transmission device having an electric motor, a travel device for causing a vehicle to travel due to the driving power outputted by the power transmission device, and an accelerator operating member,

the control method comprising:

a step for determining a required tractive force which is a target tractive force of the travel device on the basis of an operating amount of the accelerator operating member;

a step for determining an output torque of the electric motor so that the tractive force of the vehicle reaches the required tractive force; and

a step for reducing the required tractive force to a value lower than a value corresponding to the operating amount of the accelerator operating member while the vehicle is excavating.