Electromagnetic actuator and hydraulic pressure adjustment mechanism

A hydraulic pressure adjustment mechanism, comprising:

• an electromagnetic actuator including:
• a stator, which has a first surface at one end in an axial direction and a second surface at another end in the axial direction, and is made of a first soft magnetic material having a tubular space formed in the axial direction;
• and
• a movable element, which is disposed in the tubular space, and is configured to move along the axial direction,
• wherein the stator has:
• a coil, which is provided in the stator, and is configured to excite the stator,
• a core portion, which is arranged between the coil and the movable element, and extends from a first surface side of the stator towards a second surface side of the stator, and
• a protrusion portion, which is arranged between the coil and the movable element and which protrudes from the second surface side of the stator towards the first surface side of the stator;
• a spool valve configured to reciprocate in a sleeve by the movable element of the electromagnetic actuator;
• and
• a plurality of ports, which are formed in the sleeve, and is configured to open and close along with a reciprocating motion of the spool valve,
• wherein the movable element includes a movable element core made of a second soft magnetic material and a permanent magnet and at least one of a radially inner side and a radially outer side of the permanent magnet is covered by the movable element core,
• wherein the permanent magnet of the movable element is magnetized so that first magnetic flux, which is generated from the permanent magnet and flows from a second end surface of the permanent magnet through the movable element core to a first end surface of the permanent magnet opposite the second end surface without flowing through the stator, flows in the axial direction in a first direction opposite to a second direction of a second magnetic flux which is generated and flows, when the coil is energized, in the movable element core, through a portion of the movable element core located in a radial direction from the permanent magnet, and,
• wherein, when the coil is energized, the movable element moves from a first position where the second end surface of the permanent magnet that faces the second surface side of the stator does not extend past an end surface of the core portion of the stator that also faces the second surface side of the stator, in the second direction to a second position where the second end surface of the permanent magnet extends past the end surface of the core portion of the stator.