Electromagnetic valve

1. An electromagnetic valve, comprising:

a valve seat assembly including a high pressure port opened in a controlled pressure region of a high pressure, a low pressure port opened in a drainage region of a low pressure, a fluid passage formed between said high pressure port and said low pressure port and a valve seat formed in said fluid passage;

a plunger assembly including a plunger disposed to be slideable reciprocatively within a column-like hollow plunger chamber and a valve element provided at one end portion of said plunger so as to open and close said fluid passage in cooperation with said valve seat;

a coil housed within a case for driving said plunger upon electrical energization of said coil to thereby displace said plunger assembly to a valve-closed position at which said fluid passage is closed by said valve element while upon electrical deenergization of said coil, said plunger assembly is displaced to a valve-opened position at which said fluid passage is opened by said valve element under the influence of hydraulic pressure prevailing in said controlled pressure region;

a coil cooling fluid sump space provided between an outer peripheral portion of said coil and said case; and

a coil cooling fluid passage provided so as to communicate said coil cooling fluid sump space with said controlled pressure region for allowing a fluid to flow into said coil cooling fluid sump space from said controlled pressure region, said coil cooling fluid passage including a small-diameter communicating passage portion provided so as not to exert influence to the hydraulic pressure prevailing in said controlled pressure region.

2. An electromagnetic valve according to claim 1 ,

wherein said valve seat assembly includes a third port opened in a region of high pressure, a second fluid passage formed between said third port and said high pressure port and a second valve seat formed in said second fluid passage, and

wherein said plunger assembly further includes a second valve element for opening and closing said second fluid passage in cooperation with said second valve seat, said second valve element closes said second fluid passage at said valve-opened position while opening said second fluid passage at said valve-closed position.

3. An electromagnetic valve according to claim 1 ,

wherein said small-diameter communicating passage portion which is communicated with said coil cooling fluid sump space is so formed in said plunger assembly as to extend along a direction in which said plunger assembly is displaced.

4. An electromagnetic valve according to claim 1 ,

wherein said small-diameter communicating passage portion communicating with said coil cooling fluid sump space is formed in said valve seat assembly.

5. An electromagnetic valve according to claim 1 ,

wherein said plunger chamber forms a part of said coil cooling fluid passage communicating said small-diameter communicating passage portion to said coil cooling fluid sump space, and

wherein a relief orifice is formed in a plate which constitutes a wall of said plunger chamber located in opposition to said valve element, said relief orifice being pierced at a position deviated from a center axis of said plunger.

6. An electromagnetic valve according to claim 1 ,

wherein said plunger chamber forms a part of said coil cooling fluid passage communicating said small-diameter communicating passage portion to said coil cooling fluid sump space, and

wherein a plate constituting a wall of said plunger chamber on a side opposite to said valve element tightly closes said plunger chamber on said side.