WORK VEHICLE AND METHOD OF CONTROLLING WORK VEHICLE

• US 20160083930A1
• Filed: 11/25/2014
• Published: 03/24/2016
• Est. Priority Date: 12/16/2013
• Status: Active Grant

• Current Assignee: Komatsu Ltd.
• Original Assignee: Komatsu Ltd.
• Inventors: MONDEN, Hiroshi, MIYAZAKI, Shogo, MIYAMOTO, Shunsuke, NOHARA, Tatsuro
• Granted Patent: US 9,752,304 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B60K 17/08 of mechanical type
• CPC Class Codes: B60K 2025/026 by a hydraulic transmission
• CPC Class Codes: B60K 25/02 directly from an engine shaft
• CPC Class Codes: B60K 6/365 with the gears having orbital motion
• 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: B60W 10/10 including control of change-speed gearings
• 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 30/19 Improvement of gear change, e.g. by synchronisation or smoothing gear shift
• CPC Class Codes: B60Y 2200/415 Wheel loaders
• CPC Class Codes: E02F 3/283 with a single arm pivoted directly on the chassis linkage mechanism for it E02F3/3405
• CPC Class Codes: E02F 9/2079 Control of mechanical transmission for hydrostatic transmission or hydraulic torque converter E02F9/2253
• CPC Class Codes: F16H 2037/104 Power split variators with one end of the CVT connected or connectable to two or more differentials
• CPC Class Codes: F16H 2061/163 Holding the gear for delaying gear shifts under unfavorable conditions, e.g. during cornering
• CPC Class Codes: F16H 2200/2007 with two sets of orbital gears
• CPC Class Codes: F16H 2200/2035 with two engaging means
• CPC Class Codes: F16H 3/728 with means to change ratio in the mechanical gearing
• CPC Class Codes: F16H 61/16 Inhibiting or initiating shift during unfavourable conditions, e.g. preventing forward reverse shift at high vehicle speed, preventing engine over speed unintentional control input F16H61/18
• CPC Class Codes: Y02T 10/62 Hybrid vehicles

Abstract

A power transmission includes first and second clutches for switching a transmission path for a driving force therein. A clutch controlling unit provided for a work vehicle is configured to switch the transmission path from one to the other of first and second modes when a speed ratio parameter reaches a mode switching threshold. The clutch controlling unit is configured to keep setting the transmission path in the other mode even when the speed ratio parameter again reaches the mode switching threshold until a switching prohibition period having a predetermined initial value expires as long as a period of time elapsed after mode switching is included in the switching prohibition period. A trigger detecting unit provided for the work vehicle is configured to make the switching prohibition period expire when detecting a predetermined operation in the switching prohibition period.

Claims

1. A work vehicle, comprising:

an engine;

a hydraulic pump configured to be driven by the engine;

a work implement configured to be driven by a hydraulic oil discharged from the hydraulic pump;

a travelling apparatus configured to be driven by the engine;

a power transmission configured to transmit a driving force from the engine to the travelling apparatus;

a controller configured to control the power transmission; and

an operating device configured to be operated by an operator,

the power transmission including

an input shaft,

an output shaft,

a gear mechanism having a planetary gear mechanism, the gear mechanism being configured to transmit a rotation of the input shaft to the output shaft,

a motor connected to a rotary element of the planetary gear mechanism,

a first clutch for switching a transmission path for the driving force in the power transmission into a first mode, and

a second clutch for switching the transmission path for the driving force in the power transmission into a second mode,

when the transmission path is set in the first mode, the first clutch being configured to be engaged and the second clutch being configured to be disengaged,

when the transmission path is set in the second mode, the second clutch being configured to be engaged and the first clutch being configured to be disengaged,

in the power transmission, a speed ratio of the output shaft to the input shaft varying when a rotational speed of the motor varies,

when a speed ratio parameter corresponding to the speed ratio is a predetermined mode switching threshold, a rotational speed ratio of the motor to the input shaft in the first mode and a rotational speed ratio of the motor to the input shaft in the second mode becoming equal, and

the controller including

a clutch controlling unit configured to switch the transmission path from one to the other of the first and second modes when the speed ratio parameter reaches the mode switching threshold,

a trigger operation detecting unit configured to detect whether or not a predetermined operation is performed by the operator, and

a timer configured to measure a period of time elapsed from a first point of time at which the transmission path is switched into the other mode,

the clutch controlling unit being configured to keep setting the transmission path in the other mode even when the speed ratio parameter again reaches the mode switching threshold until a switching prohibition period expires as long as the elapsed period of time is within the switching prohibition period, the switching prohibition period having a predetermined initial value, and

the trigger operation detecting unit being configured to make the switching prohibition period expire when detecting the predetermined operation in the switching prohibition period.

2. The work vehicle according to claim 1, wherein

one of a first range and a second range is defined as an admissible range whereas the other of the first range and the second range is defined as an inadmissible range, the first range being a range in which the speed ratio parameter is greater than or equal to the mode switching threshold, the second range being a range in which the speed ratio parameter is less than or equal to the mode switching threshold,

the controller is configured to perform a control of making the speed ratio parameter equal to the mode switching threshold when the speed ratio parameter belongs to the inadmissible range at a second point of time that the switching prohibition period expires, and

the clutch controlling unit is configured to switch the transmission path into the one mode when the speed ratio parameter is made equal to the mode switching threshold.

7. The work vehicle according to claim 1, wherein

the operating device includes a brake operating member, and

the predetermined operation is an operation of changing an operating amount of the brake operating member by a predetermined amount of change or greater.

8. The work vehicle according to claim 1, wherein

the operating device includes an accelerator operating member, and

the predetermined operation is an operation of changing an operating amount of the accelerator operating member by a predetermined amount of change or greater.

9. The work vehicle according to claim 1, wherein

the operating device includes a forward/rearward movement switch operating member, and

the predetermined operation is an operation of moving the forward/rearward movement switch operating member to a position different from a position thereof located at the first point of time.

10. The work vehicle according to claim 1, wherein

the operating device includes a gearshift operating member, and

the predetermined operation is an operation of operating the gearshift operating member so as to shift into a gear stage different from a gear stage set at the first point of time.

11. The work vehicle according to claim 10, wherein

the gearshift operating member is a shift range lever, and

the predetermined operation is an operation of moving the shift range lever to a position different from a position thereof located at the first point of time.

12. The work vehicle according to claim 10, wherein

the gearshift operating member is a kick down button, and

the predetermined operation is an operation of pressing down the kick down button.

3. A work vehicle, comprising:

an engine;

a hydraulic pump configured to be driven by the engine;

a work implement configured to be driven by a hydraulic oil discharged from the hydraulic pump;

a travelling apparatus configured to be driven by the engine;

a power transmission configured to transmit a driving force from the engine to the travelling apparatus; and

a controller configured to control the power transmission,

the power transmission including

an input shaft,

an output shaft,

a gear mechanism having a planetary gear mechanism, the gear mechanism being configured to transmit a rotation of the input shaft to the output shaft,

a motor connected to a rotary element of the planetary gear mechanism,

a first clutch for switching a transmission path for the driving force in the power transmission into a first mode, and

a second clutch for switching the transmission path for the driving force in the power transmission into a second mode,

when the transmission path is set in the first mode, the first clutch being configured to be engaged and the second clutch being configured to be disengaged,

when the transmission path is set in the second mode, the second clutch being configured to be engaged and the first clutch being configured to be disengaged,

in the power transmission, a speed ratio of the output shaft to the input shaft varying when a rotational speed of the motor varies,

when a speed ratio parameter corresponding to the speed ratio is a predetermined mode switching threshold, a rotational speed ratio of the motor to the input shaft in the first mode and a rotational speed ratio of the motor to the input shaft in the second mode becoming equal, and

the controller including

a clutch controlling unit configured to switch the transmission path from one to the other of the first and second modes when the speed ratio parameter reaches the mode switching threshold,

a timer configured to measure a period of time elapsed from a first point of time at which the transmission path is switched into the other mode, and

a speed ratio variation detecting unit configured to detect whether or not the speed ratio parameter deviates from a third range including the mode switching threshold,

the clutch controlling unit being configured to keep setting the transmission path in the other mode even when the speed ratio parameter again reaches the mode switching threshold until a switching prohibition period expires as long as the elapsed period of time is included in the switching prohibition period, the switching prohibition period having a predetermined initial value, and

the speed ratio variation detecting unit being configured to make the switching prohibition period expire when detecting deviation of the speed ratio parameter from the third range including the mode switching threshold.

4. The work vehicle according to claim 3, wherein

the controller is configured to perform a control of making the speed ratio parameter equal to the mode switching threshold after the switching prohibition period expires due to deviation of the speed ratio parameter from the third range, and

the clutch controlling unit is configured to switch the transmission path into the one mode when the speed ratio parameter is made equal to the mode switching threshold.

5. The work vehicle according to claim 3, wherein

one of a first range and a second range is defined as an admissible range whereas the other of the first range and the second range is defined as an inadmissible range, the first range being a range in which the speed ratio parameter is greater than or equal to the mode switching threshold, the second range being a range in which the speed ratio parameter is less than or equal to the mode switching threshold,

where the first range is defined as the admissible range, the speed ratio variation detecting unit is configured to set a range of greater than or equal to a value that is less than the mode switching threshold by a predetermined value as the third range, and

where the second range is defined as the admissible range, the speed ratio variation detecting unit is configured to set a range of less than or equal to a value that is greater than the mode switching threshold by a predetermined value as the third range.

6. The work vehicle according to claim 3, wherein

one of a first range and a second range is defined as an admissible range whereas the other of the first range and the second range is defined as an inadmissible range, the first range being a range in which the speed ratio parameter is greater than or equal to the mode switching threshold, the second range being a range in which the speed ratio parameter is less than or equal to the mode switching threshold,

the controller is configured to perform a control of making the speed ratio parameter equal to the mode switching threshold when the speed ratio parameter belongs to the inadmissible range at a second point of time that the switching prohibition period expires, and

the clutch controlling unit is configured to switch the transmission path into the one mode when the speed ratio parameter is made equal to the mode switching threshold.

13. A method of controlling a work vehicle equipped with a power transmission,

the power transmission including

an input shaft,

an output shaft,

a gear mechanism having a planetary gear mechanism, the gear mechanism being configured to transmit a rotation of the input shaft to the output shaft,

a motor connected to a rotary element of the planetary gear mechanism,

a first clutch for switching a transmission path for a driving force in the power transmission into a first mode, and

a second clutch for switching the transmission path for the driving force in the power transmission into a second mode,

when the transmission path is set in the first mode, the first clutch being configured to be engaged and the second clutch being configured to be disengaged,

when the transmission path is set in the second mode, the second clutch being configured to be engaged and the first clutch being configured to be disengaged,

in the power transmission, a speed ratio of the output shaft to the input shaft varying when a rotational speed of the motor varies,

when a speed ratio parameter corresponding to the speed ratio is a predetermined mode switching threshold, a rotational speed ratio of the motor to the input shaft in the first mode and a rotational speed ratio of the motor to the input shaft in the second mode becoming equal, and

the control method comprising:

switching the transmission path from one to the other of the first and second modes when the speed ratio parameter reaches the mode switching threshold,

detecting whether or not a predetermined operation is performed by an operator,

measuring a period of time elapsed from a first point of time at which the transmission path is switched into the other mode,

setting the transmission path in the other mode even when the speed ratio parameter again reaches the mode switching threshold until a switching prohibition period expires as long as the elapsed period of time is within the switching prohibition period, the switching prohibition period having a predetermined initial value, and

making the switching prohibition period expire when the predetermined operation is detected in the switching prohibition period.

14. A method of controlling a work vehicle equipped with a power transmission,

the power transmission including

an input shaft,

an output shaft,

a gear mechanism having a planetary gear mechanism, the gear mechanism being configured to transmit a rotation of the input shaft to the output shaft,

a motor connected to a rotary element of the planetary gear mechanism,

a first clutch for switching a transmission path for a driving force in the power transmission into a first mode, and

a second clutch for switching the transmission path for the driving force in the power transmission into a second mode,

when the transmission path is set in the first mode, the first clutch being configured to be engaged and the second clutch being configured to be disengaged,

when the transmission path is set in the second mode, the second clutch being configured to be engaged and the first clutch being configured to be disengaged,

in the power transmission, a speed ratio of the output shaft to the input shaft varying when a rotational speed of the motor varies,

when a speed ratio parameter corresponding to the speed ratio is a predetermined mode switching threshold, a rotational speed ratio of the motor to the input shaft in the first mode and a rotational speed ratio of the motor to the input shaft in the second mode becoming equal, and

the control method comprising:

switching the transmission path from one to the other of the first and second modes when the speed ratio parameter reaches the mode switching threshold,

measuring a period of time elapsed from a first point of time at which the transmission path is switched into the other mode,

detecting whether or not the speed ratio parameter deviates from a predetermined third range including the mode switching threshold,

setting the transmission path in the other mode even when the speed ratio parameter again reaches the mode switching threshold until a switching prohibition period expires as long as the elapsed period of time is within the switching prohibition period, the switching prohibition period having a predetermined initial value, and

making the switching prohibition period expire when deviation of the speed ratio parameter from the third range including the mode switching threshold is detected.