A transmission (21) as a power transmission device for a vehicle comprises an input shaft (22), an output shaft (23), a planetary continuously variable transmission mechanism (31), a direct connecting mechanism (27), and an idler gear (29). The direct connecting mechanism (27) comprises a direct connecting clutch (30). The planetary continuously variable transmission mechanism (31) comprises a planetary gear mechanism (32), a pump side clutch (33), a hydraulic pump (36), a hydraulic motor (38), and a motor side clutch (40). The hydraulic pump (36) and the hydraulic motor (38) are connected via a pair of main lines (37A, 37B). An electromagnetic on-off valve (41) capable of switching between a communicating state and a blocking state between the pair of main lines (37A, 37B) is provided between the pair of main lines (37A, 37B).

A transmission (21) as a power transmission device for a vehicle comprises an input shaft (22), an output shaft (23), a planetary continuously variable transmission mechanism (31), a direct connecting mechanism (27), and an idler gear (29). The direct connecting mechanism (27) comprises a direct connecting clutch (30). The planetary continuously variable transmission mechanism (31) comprises a planetary gear mechanism (32), a pump side clutch (33), a hydraulic pump (36), a hydraulic motor (38), and a motor side clutch (40). The hydraulic pump (36) and the hydraulic motor (38) are connected via a pair of main lines (37A, 37B). An electromagnetic on-off valve (41) capable of switching between a communicating state and a blocking state between the pair of main lines (37A, 37B) is provided between the pair of main lines (37A, 37B).

A control mechanism for a hydrostatic transmission includes a piston rod, a neutral biasing spring, a piston, a cylinder case provided with a first fluid chamber and a second fluid chamber, a solenoid valve capable of selectively supplying pressurized fluid to the first fluid chamber and the second fluid chamber, a pivot shaft configured to swingably support the cylinder case, and a first relief valve configured to flow the hydraulic fluid from the first fluid chamber to the second fluid chamber when a hydraulic pressure in the first fluid chamber exceeds a set pressure, and a second relief valve configured to flow the hydraulic fluid from the second fluid chamber to the first fluid chamber when a hydraulic pressure in the second fluid chamber exceeds a set pressure.

A control mechanism for a hydrostatic transmission includes a piston rod, a neutral biasing spring, a piston, a cylinder case provided with a first fluid chamber and a second fluid chamber, a solenoid valve capable of selectively supplying pressurized fluid to the first fluid chamber and the second fluid chamber, a pivot shaft configured to swingably support the cylinder case, and a first relief valve configured to flow the hydraulic fluid from the first fluid chamber to the second fluid chamber when a hydraulic pressure in the first fluid chamber exceeds a set pressure, and a second relief valve configured to flow the hydraulic fluid from the second fluid chamber to the first fluid chamber when a hydraulic pressure in the second fluid chamber exceeds a set pressure.

A neutral valve includes a spool inserted in a housing so as to be movable in a predetermined direction, the spool configured to move to a neutral position set such that a first and second port are connected to each other through a valve passage, a first offset position located at neutral position's first side in the predetermined direction and set such that second port and valve passage are disconnected from each other, and a second offset position located at neutral position's second side in the predetermined direction and set such that first port and valve passage are disconnected from each other. The spool's outer peripheral portion includes a first pressure receiving surface receiving first port's fluid pressure to be pushed toward the first side in the predetermined direction and a second pressure receiving surface receiving second port's fluid pressure to be pushed toward second side in the predetermined direction.

An HST control mechanism includes a rotary member, a servo unit, a telescopic member, and a biasing device. The rotary member for controlling a displacement of a hydrostatic transmission (HST) is pivoted outside of a casing incorporating the HST. The servo unit includes a telescopically movable actuator and a valve controlling the telescopic movement of the actuator. The actuator is interlockingly connected to the rotary member. The servo unit is pivotally supported on the casing via a first pivot. The servo unit rotates centered on the first pivot as the rotary member rotates according to the telescopic movement of the actuator hydraulically controlled by the valve. The telescopic member is pivotally supported on the casing via a second pivot. The telescopic member is provided with the biasing device that biases the telescopic member and the rotary member toward a position corresponding to a neutral state of the HST.

An HST control mechanism includes a rotary member, a servo unit, a telescopic member, and a biasing device. The rotary member for controlling a displacement of a hydrostatic transmission (HST) is pivoted outside of a casing incorporating the HST. The servo unit includes a telescopically movable actuator and a valve controlling the telescopic movement of the actuator. The actuator is interlockingly connected to the rotary member. The servo unit is pivotally supported on the casing via a first pivot. The servo unit rotates centered on the first pivot as the rotary member rotates according to the telescopic movement of the actuator hydraulically controlled by the valve. The telescopic member is pivotally supported on the casing via a second pivot. The telescopic member is provided with the biasing device that biases the telescopic member and the rotary member toward a position corresponding to a neutral state of the HST.

A control apparatus for controlling a linear solenoid by controlling a driving current supplied to the linear solenoid through a feedback control. The feedback control is executed by a feedback control system having parameters that are determined in accordance with an ILQ design method. In a frequency characteristic of a gain of a transfer function representing a ratio of an output to a disturbance in the feedback control system, the gain is lower than 0[dB] throughout all frequency ranges.

A control apparatus for controlling a linear solenoid by controlling a driving current supplied to the linear solenoid through a feedback control. The feedback control is executed by a feedback control system having parameters that are determined in accordance with an ILQ design method. In a frequency characteristic of a gain of a transfer function representing a ratio of an output to a disturbance in the feedback control system, the gain is lower than 0[dB] throughout all frequency ranges.

A transmission (21) as a power transmission device for a vehicle comprises an input shaft (22), an output shaft (23), a planetary continuously variable transmission mechanism (31), a direct connecting mechanism (27), and an idler gear (29). The direct connecting mechanism (27) comprises a direct connecting clutch (30). The planetary continuously variable transmission mechanism (31) comprises a planetary gear mechanism (32), a pump side clutch (33), a hydraulic pump (36), a hydraulic motor (38), and a motor side clutch (40). The hydraulic pump (36) and the hydraulic motor (38) are connected via a pair of main lines (37A, 37B). An electromagnetic on-off valve (41) capable of switching between a communicating state and a blocking state between the pair of main lines (37A, 37B) is provided between the pair of main lines (37A, 37B).