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EP-4015871-B1 - WORK VEHICLE

EP4015871B1EP 4015871 B1EP4015871 B1EP 4015871B1EP-4015871-B1

Inventors

  • YAMAGUCHI, TETSUO
  • IWASE, RYOMA
  • YAMAWAKI, KOMEI

Dates

Publication Date
20260506
Application Date
20211102

Claims (5)

  1. A work vehicle comprising: an engine (1); a speed changing apparatus (18) including a hydrostatic stepless speed changing mechanism (18A) and configured to subject motive power from the engine (1) to speed changing and output the motive power; a travelling apparatus (6, 7) configured to travel on the motive power received from the speed changing apparatus (18); a speed detector (27) configured to detect a speed of the travelling apparatus (6, 7); a pressure detector (25, 26) configured to detect a hydraulic pressure in a closed circuit of the hydrostatic stepless speed changing mechanism (18A); and a controller (80); characterized in that the speed changing apparatus (18) is a hydromechanical speed changing apparatus including a planetary gear mechanism (50A, 50B) on an output side of the hydrostatic stepless speed changing mechanism (18A), wherein the motive power of the hydrostatic stepless speed changing mechanism (18A) and the motive power of the engine (1) are composited by the planetary gear mechanism (50A, 50B), wherein the controller (80) is configured or programmed to: determine, by means of a determination module (81) and based on the speed and the hydraulic pressure, whether the hydrostatic stepless speed changing mechanism (18A) has a swashplate angle suitable for stopping the work vehicle; and change the swashplate angle by means of an angle control module (82) based on a result of the determination by the determination module (81), such that the rotation speed outputted from the hydrostatic stepless speed changing mechanism (18A) and the rotation speed of the engine (1) offset each other.
  2. The work vehicle according to claim 1, wherein the controller (80) is configured or programmed to determine, by means of the determination module (81), whether the swashplate angle is an angle at which a rotation speed of the motive power outputted from the speed changing apparatus (18) is not greater than a predetermined rotation speed.
  3. The work vehicle according to claim 1 or 2, wherein the controller (80) is configured or programmed to change the swashplate angle by means of the angle control module (82) in a case where the speed is not greater than a predetermined value and the hydraulic pressure is higher than or equal to a predetermined value.
  4. The work vehicle according to any one of claims 1 to 3, further comprising: a braking apparatus (97) configured to brake the travelling apparatus (6, 7); wherein the controller (80) is configured or programmed to change the swashplate angle by means of the angle control module (82) when the travelling apparatus (6, 7) is being braked.
  5. The work vehicle according to any one of claims 1 to 4, wherein the closed circuit of the hydrostatic stepless speed changing mechanism (18A) includes: a hydraulic pump (30) drivable by the motive power from the engine (1); a hydraulic motor (31) drivable by hydraulic oil from the hydraulic pump (30); and a hydraulic path (32) through which the hydraulic oil circulates between the hydraulic pump (30) and the hydraulic motor (31), and the pressure detector (25, 26) is disposed on the hydraulic path (32).

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a work vehicle. 2. Description of the Related Art For example, a work vehicle disclosed in JP 2017-58000A includes a speed changing apparatus (referred to as a "hydromechanical stepless transmission" in the document) that includes a hydrostatic stepless speed changing mechanism (referred to as a "first stepless transmission" in the document). A swashplate angle of the hydrostatic stepless speed changing mechanism is controlled when the work vehicle is being decelerated. Incidentally, when the work vehicle is being decelerated, a hydraulic pressure in a closed circuit of the hydrostatic stepless speed changing mechanism tends to increase. When the hydraulic pressure in the closed circuit increases, the temperature of hydraulic oil tends to be higher than an appropriate temperature, and there is a risk that the efficiency of motive power transmission performed by the hydrostatic stepless speed changing mechanism will be affected. Therefore, it is desirable to employ a configuration in which the swashplate angle of the hydrostatic stepless speed changing mechanism is appropriately controlled based on the hydraulic pressure in the closed circuit of the hydrostatic stepless speed changing mechanism. US 2011/048829 discloses a work vehicle which can be prevented from slipping. JP H11 311329A discloses a power recovery control method for a vehicle. SUMMARY OF THE INVENTION Preferred embodiments of the present invention control the swashplate angle of a hydrostatic stepless speed changing mechanism within an appropriate range of load, in a work vehicle. A work vehicle according to a preferred embodiment of the present invention including: an engine;a speed changing apparatus including a hydrostatic stepless speed changing mechanism and configured to subject motive power from the engine to speed changing and output the motive power;a travelling apparatus configured to travel on the motive power received from the speed changing apparatus;a speed detector configured to detect a speed of the travelling apparatus;a pressure detector configured to detect a hydraulic pressure in a closed circuit of the hydrostatic stepless speed changing mechanism,the speed changing apparatus being a hydromechanical speed changing apparatus including a planetary gear mechanism on an output side of the hydrostatic stepless speed changing mechanism, the motive power of the hydrostatic stepless speed changing mechanism and the motive power of the engine being composited by the planetary gear mechanism; anda controller configured or programmed to: determine, by means of a determination module and based on the speed and the hydraulic pressure, whether the hydrostatic stepless speed changing mechanism has a swashplate angle suitable for stopping the work vehicle; andchange the swashplate angle by means of an angle control module, based on a result of the determination by the determination module, such that the rotation speed outputted from the hydrostatic stepless speed changing mechanism and the rotation speed of the engine offset each other. According to the preferred embodiment of the present invention, the hydraulic pressure in the closed circuit is detected by the pressure detector, and the determination module performs determination processing based on the speed and the hydraulic pressure. Accordingly, the swashplate angle control module is capable of performing control for changing the swashplate angle based on appropriate control of the hydraulic pressure. Therefore, the efficiency of motive power transmission performed by the hydrostatic stepless speed changing mechanism is kept favorable even in an operation environment in which the hydraulic pressure tends to increase. Thus, the swashplate angle of the hydrostatic stepless speed changing mechanism is controlled within an appropriate range of load. With a preferred embodiment of the present invention, in the work vehicle, the controller is configured or programmed to determine, by means of the determination module, whether the swashplate angle is an angle at which a rotation speed of the motive power outputted from the speed changing apparatus is not greater than a predetermined rotation speed. According to this configuration, the rotation speed of the motive power outputted from the speed changing apparatus becomes low, and accordingly, a load on the hydrostatic stepless speed changing mechanism is reduced. The planetary gear mechanism is precisely configured, but according to this configuration, an excessive load is unlikely to be applied to the planetary gear mechanism because a load on the hydrostatic stepless speed changing mechanism is reduced. With a preferred embodiment of the present invention, in the work vehicle, the controller is configured or programmed to change the swashplate angle by means of the angle control module in a case where the speed is not greater than a predetermined value