Solenoid actuator

A solenoid actuator attached to a hydraulic equipment comprises a shaft connected to the hydraulic equipment, a plunger fixed to the shaft, a coil which magnetically drives the plunger, and a first bearing and a second bearing supporting the shaft on both sides of the plunger. A plunger front chamber is formed between the first bearing and the plunger, a plunger rear chamber is formed between the plunger and the second bearing, and a second bearing rear chamber is formed on the opposite side of the second bearing to the plunger rear chamber. To secure an oil flow between these chambers, a plunger exterior oil passage, a second bearing oil passage, and a shaft-penetrating oil passage are provided, thereby realizing a preferable balance between oil pressures acting on the second bearing.