Wheeled work vehicle

1. A wheeled work vehicle comprising:

a prime mover;

a hydraulic pump driven by the prime mover;

a traveling hydraulic motor driven by hydraulic fluid supplied from the hydraulic pump;

a wheel driven by rotational power of the traveling hydraulic motor;

a transmission that is interposed between the traveling hydraulic motor and the wheel and transmits the rotational power of the traveling hydraulic motor to the wheel with a change in speed, the transmission having at least two speed stages, the two speed stages being a first speed stage and a second speed stage as a higher speed stage than the first speed stage;

a traveling control valve that controls a direction and a flow rate of the hydraulic fluid to be supplied from the hydraulic pump to the traveling hydraulic motor, the traveling control valve having a first interruption position that interrupts supply of the hydraulic fluid from the hydraulic pump to the traveling hydraulic motor;

a changeover valve that shifts a speed stage of the transmission through supply and discharge of hydraulic fluid to and from the transmission by a position of the changeover valve being selectively switched; and

a controller that controls the traveling control valve and the changeover valve, wherein

the controller is configured to

switch the traveling control valve to the first interruption position,

then switch the position of the changeover valve such that the speed stage of the transmission is shifted from the second speed stage to the first speed stage, and

switch the traveling control valve from the first interruption position to an original position side before the switching

in a case where the controller shifts the speed stage of the transmission from the second speed stage to the first speed stage.

2. The wheeled work vehicle according to claim 1 , wherein

the traveling control valve is a pilot valve driven by supply of an operating pilot pressure, and switched to the first interruption position by interruption of the supply of the operating pilot pressure,

the wheeled work vehicle further includes a selector valve that controls driving of the traveling control valve by the supply of the operating pilot pressure to the traveling control valve, the selector valve having a second interruption position that interrupts the supply of the operating pilot pressure to the traveling control valve, and,

the controller is configured to

switch the selector valve to the second interruption position to indirectly control the traveling control valve such that the traveling control valve is switched to the first interruption position, and

switch the selector valve from the second interruption position to an original position side before the switching to indirectly control the traveling control valve such that the traveling control valve is switched from the first interruption position to the original position side before the switching.

3. The wheeled work vehicle according to claim 2 , wherein

the selector valve is a solenoid proportional valve whose position is controlled according to magnitude of driving power input from the controller, and

the controller is configured to gradually increase the driving power input to the selector valve to switch the selector valve from the second interruption position to the original position side before the switching.

4. The wheeled work vehicle according to claim 1 , wherein

the controller is configured to

measure an elapsed time from a start of control for switching the position of the changeover valve, and

start control for switching the traveling control valve from the first interruption position to the original position side before the switching after a measured elapsed time exceeds a threshold value.

5. The wheeled work vehicle according to claim 4 , further comprising:

an inclination angle sensor that detects an inclination angle of the vehicle with respect to a horizontal plane in a traveling direction, wherein

the controller is configured to lower the threshold value when a detected value of the inclination angle sensor is larger than a set inclination angle determined in advance, compared to a case where a detected value of the inclination angle sensor is equal to or smaller than the set inclination angle.