Work vehicle and method for controlling same

Patent metadata

Field	Value
Publication number	US-9815471-B2
Application number	US-201414892647-A
Country	US
Kind code	B2
Filing date	Dec 16, 2014
Priority date	Dec 17, 2013
Publication date	Nov 14, 2017
Grant date	Nov 14, 2017

Abstract

A work vehicle is equipped with an engine, a hydraulic pump, a work implement, a travel device, an accelerator operating member, a work implement operating member, and a control unit. The hydraulic pump is driven by the engine. The work implement is driven by hydraulic fluid discharged from the hydraulic pump. The travel device is driven by the engine. The accelerator operating member changes the engine rotation speed. The work implement operating member operates the work implement. The control unit causes the speed of the work implement to increase by causing the engine rotation speed to increase when an operation amount of the work implement operating member is increased.

First claim

What is claimed is:

1. A work vehicle comprising:
an engine including a throttle device;
a hydraulic pump driven by the engine;
a work implement operatively arranged to be driven by hydraulic fluid discharged from the hydraulic pump;
a travel device driven by the engine, the travel device including at least one axle and at least one wheel to move the work vehicle;
a power transmission device including an input shaft, a gear mechanism, an output shaft, and a motor, the input shaft being arranged to receive driving power from the engine and input the driving power to the gear mechanism, the gear mechanism having a plurality of gears including a motor gear, the output shaft being arranged to receive the driving power transmitted through the gear mechanism and transmit the driving power to the travel device, the motor having a motor shaft fixed to the motor gear, the power transmission device being configured such that a rotation speed ratio of the output shaft with respect to the input shaft is changed by changing a rotation speed of the motor;
an accelerator operating device including an accelerator operating member and an accelerator operation detector, the accelerator operating member being configured to be operated by an operator to change an engine rotation speed, and the accelerator operation detector being configured and arranged to detect an operation amount of the accelerator operating member;
a work implement operating device including a work implement operating member and a work implement operation detector, the work implement operating member being configured to be operated by the operator to operate the work implement, and the work implement operation detector being configured and arranged to detect an operation amount of the work implement operating member; and
a control unit operatively arranged to receive detection signals from the accelerator operation detector and the work implement operation detector and to transmit a command to the throttle device to control the engine rotation speed, the control unit being programmed to increase a speed of the work implement by increasing the engine rotation speed such that a discharge flow rate of the hydraulic pump increases when the operation amount of the work implement operating member is increased, the control unit being configured to determine a target tractive force value based on the operation amount of the accelerator operating member and to control an output torque of the motor so that a tractive force of the vehicle becomes equal to the target tractive force value regardless of the operation amount of the work implement operating member.

2. A method for controlling a work vehicle equipped with an engine, a hydraulic pump driven by the engine, a work implement driven by hydraulic fluid discharged from the hydraulic pump, a travel device including at least one axle driven by the engine, an accelerator operating member for changing an engine rotation speed, and a work implement operating member for operating the work implement, and a power transmission device arranged and configured to transmit rotation of the engine to the at least one axle, the power transmission device including an input shaft, a gear mechanism, an output shaft, and a motor, the input shaft being arranged to receive driving power from the engine and transmit the driving power to the gear mechanism, the output shaft being arranged to receive the driving power transmitted through the gear mechanism and transmit the driving power to the travel device, the motor being connected to the gear mechanism, the power transmission device being configured such that a rotation speed ratio of the output shaft with respect to the input shaft is changed by changing a rotation speed of the motor, the method comprising:
a step for determining a target tractive force of the travel device for moving the work vehicle;
a step for causing a speed of the work implement to increase by causing the engine rotation speed to increase when an operation amount of the work implement operating member is increased; and
a step for controlling an output torque of the motor such that a tractive force of the travel device becomes equal to the target tractive force value regardless of the operation amount of the work implement operating member.

3. The work vehicle according to claim 1 , wherein
the output shaft is coupled to the at least one axle of the travel device.

4. The work vehicle according to claim 1 , wherein
the control unit causes a discharge capacity of the hydraulic pump to increase in response to an increase of the operation amount of the work implement operating member when the operation amount of the work implement operating member is equal to or less than a predetermined operation amount,
the discharge capacity of the hydraulic pump becomes a maximum capacity when the operation amount of the work implement operating member is the predetermined operation amount, and
the control unit executes the increasing of the engine rotation speed in response to an increase in the operation amount of the work implement operating member when the operation amount of the work implement operating member is greater than the predetermined operation amount.

5. The work vehicle according to claim 1 , wherein
the control unit has a storage unit configured to store required flow rate information which defines a relationship between the operation amount of the work implement operating member and a required flow rate to the hydraulic pump,
the control unit determines the required flow rate corresponding to the operation amount of the work implement operating member by referring to the required flow rate information, and
the control unit determines the engine rotation speed on the basis of the required flow rate and the discharge capacity of the hydraulic pump.

6. The work vehicle according to claim 5 , further comprising
a work implement control valve configured to control a hydraulic pressure supplied to the work implement; and
a capacity control device having a load sensing valve and configured to control the discharge capacity of the hydraulic pump so that a differential pressure between a discharge pressure of the hydraulic pump and an outlet hydraulic pressure of the work implement control valve becomes a predetermined value.

7. The work vehicle according to claim 1 , wherein
the control unit is programmed to reduce the target tractive force value to be lower than a value determined based on the operation amount of the accelerator operating member when the engine rotation speed is increased in response to an increase in the operation amount of the work implement operating member.

8. The work vehicle according to claim 7 , wherein
the control unit reduces the target tractive force so that the tractive force of the vehicle is reduced in comparison to before the operation of the work implement operating member.

9. The work vehicle according to claim 7 , wherein
the power transmission device has a planetary gear mechanism, and
the control unit reduces the target tractive force so that the tractive force of the vehicle is maintained regardless of the operation amount of the work implement operating member.

10. The work vehicle according to claim 7 , wherein
the control unit reduces the target tractive force by multiplying the target tractive force by a predetermined reduction rate.

Assignees

• Komatsu Mfg Co Ltd

Inventors

• Yoshizawa Masao
• Miyamoto Shunsuke
• Yamada Kenichi

Classifications

• F04B49/06

  Control using electricity (regulating by means of floats actuating electric switches F04B49/04) · CPC title

• E02F9/2296

  Systems with a variable displacement pump · CPC title

• E02F9/2253

  Controlling the travelling speed of vehicles, e.g. adjusting travelling speed according to implement loads, control of hydrostatic transmission · CPC title

• B60W30/1888 Primary

  Control of power take off [PTO] · CPC title

• B60W30/1886

  Controlling power supply to auxiliary devices · CPC title