Fuel tank isolation solenoid valve for vehicle

1. A fuel tank isolation solenoid valve for a vehicle, the fuel tank isolation solenoid valve comprising:

an upper case;

a bobbin mounted in the upper case;

a coil wound around the bobbin;

a core mounted in the bobbin, the core having therein a plunger passage that is open at a lower end thereof;

a lower case coupled to the upper case, the lower case including:

a first passage configured to communicate with a fuel tank,

a second passage configured to communicate with a canister, and

a communication passage defined between the first passage and the second passage;

a plunger having a lower open space formed therein and a plurality of first vent holes configured to allow the first passage to communicate with the lower open space, the plunger being disposed in the plunger passage and configured to vertically move;

a main seal mounted on a lower surface of the plunger;

a valve body disposed in the communication passage to be vertically moved and having a plurality of second vent holes, wherein the plurality of second vent holes are vertically formed through the valve body and are configured to allow the first passage to communicate with the second passage;

a sealing plate mounted on the lower case at an outer circumference of the communication passage so as to be in airtight contact with both a lower surface of the main seal and an upper surface of the valve body;

a first spring disposed between a lower surface of the core and a lower end of the plunger; and

a second spring disposed between a lower surface of the valve body and a bottom surface of the communication passage.

2. The fuel tank isolation solenoid valve of claim 1 , further comprising: a diaphragm disposed between and connected to an outer surface of the plunger and an inner surface of the core.

3. The fuel tank isolation solenoid valve of claim 2 , wherein the plunger further has a vent hole formed therein, the vent hole configured to allow an upper space in the diaphragm to communicate with the lower open space in the plunger.

4. The fuel tank isolation solenoid valve of claim 1 , wherein the plunger has a first spring-holding groove formed in an outer circumference of a lower end thereof, the first spring configured to be fitted and held in the first spring-holding groove.

5. The fuel tank isolation solenoid valve of claim 1 , wherein the plunger includes a stopper on an upper surface thereof, and the stopper is configured to contact with an upper end surface of the plunger passage formed in the core while buffering the upper end surface of the plunger.

6. The fuel tank isolation solenoid valve of claim 1 , wherein the valve body includes a sealing wall projecting from an upper surface thereof at an inner circumference inwardly spaced apart from the second vent holes, the sealing wall configured to come into airtight close contact with the main seal.

7. The fuel tank isolation solenoid valve of claim 1 , wherein the valve body includes a vertical guide pin formed at a center of the upper surface thereof, and the vertical guide pin is configured to enter and come out of the lower open space in the plunger.

8. The fuel tank isolation solenoid valve of claim 1 , wherein the valve body has a second spring-holding groove formed in an outer circumference of the lower surface thereof, and the second spring is configured to be fitted and held in the second spring-holding groove.

9. The fuel tank isolation solenoid valve of claim 1 , wherein the sealing plate includes a fitting wall formed on a lower surface thereof, and the lower case has a fitting groove formed in an outer circumference of the communication passage, the fitting wall configured to be fitted and held in the fitting groove.

10. The fuel tank isolation solenoid valve of claim 1 , wherein: when an overpressure, which is a pressure higher than a reference pressure, acts on the valve body through the first passage and the first vent holes in the plunger from the fuel tank,

the valve body is lowered while compressing the second spring,

the overpressure sequentially passes through the first vent holes and the lower open space in the plunger and the second vent holes in the valve body, and acts on the second passage, and

the overpressure is released.

11. The fuel tank isolation solenoid valve of claim 1 , wherein: when an over-negative pressure, which is a pressure lower than a reference pressure, acts on a lower portion of the plunger through the second vent holes in the valve body from the canister,

the plunger is raised while compressing the first spring,

the over-negative pressure passes through the second vent holes in the valve body and acts on the first passage communicating with the fuel tank, and

the over-negative pressure is released.