Patent ID: 7387186

Claim:
A power steering apparatus comprising: a hydraulic power cylinder including first and second pressure chambers and a piston separating the first and second pressure chambers to provide a steering force to a steering mechanism connected with a steering wheel; a reversible pump including first and second outlets to supply a hydraulic pressure selectively to the first pressure chamber or the second pressure chamber; a first fluid passage connecting the first outlet of the reversible pump with the first pressure chamber of the power cylinder; a second fluid passage connecting the second outlet of the reversible pump with the second pressure chamber of the power cylinder; a motor arranged to drive the reversible pump in a forward rotational direction or a reverse rotational direction; a steering assist force sensor arranged to sense a steering assist force to be provided to the steering wheel; a motor control circuit configured to deliver a motor drive signal to the motor to cause the motor to produce the hydraulic pressure in accordance with the steering assist force; a connection passage connecting the first and second fluid passages together; a closing valve which is disposed in the connection passage and which includes, a valve element arranged to open and close the connection passage, an armature arranged to move the valve element to open and close the connection passage, a coil to drive the armature, and a magnetic member of a magnetic material arranged to attract the armature when the coil is energized; and a valve control circuit configured to send a first current to the coil to close the connection passage by moving the armature, to send a second current lower than the first current to the coil after the connection passage is closed, and to deenergize the coil to open the connection passage.