Two-stage fuel tank isolation valve with integrated pressure relief
A fuel tank isolation valve is provided. The valve includes a valve member disposed within a valve chamber defined by a housing. The valve member is mounted on an alignment pin of a moveable plunger of a solenoid assembly. The valve member includes a first stage valve surface and an opposite second stage valve surface. In a closed disposition, the first stage valve surface is seated on a surface of the moveable plunger, and the second stage valve surface is seated on an inner surface of the housing. In a first stage open disposition, the first stage valve surface of the valve member is unseated from the moveable plunger while the second stage valve surface remains seated. In a second stage open disposition, the second stage valve surface is unseated from the inner surface while the first stage valve surface becomes seated on the surface of the moveable plunger.
1 . A fuel tank isolation valve for an evaporative emissions control system, the fuel tank isolation valve comprising:
a housing having an outer wall defining an internal valve chamber therein, and a transfer passage formed in a portion of the outer wall;
a canister port connected to the housing;
a tank port connected to the housing, the tank port being in selective fluid communication with the canister port via the valve chamber and transfer passage;
a solenoid assembly connected to the housing, the solenoid assembly including a stationary core, a moveable plunger having a first end and a second end longitudinally opposed to the first end, the first end being adjacent the stationary core, a coil that encircles the stationary core and the moveable plunger, the coil actuating the moveable plunger, a primary spring disposed between the stationary core and the moveable plunger, and an alignment pin extending from the second end of the moveable plunger;
a valve member disposed in the valve chamber, the valve member being mounted on the alignment pin, the valve member including a first stage valve surface and an opposite second stage valve surface, the first stage valve surface being seated on an end surface of the moveable plunger at the second end in a closed disposition, the second stage valve surface being seated on an inner surface of the wall of the housing in a closed disposition, the inner surface surrounding the transfer passage; and
a secondary spring engaged with the valve member opposite the moveable plunger.
2 . The fuel tank isolation valve of claim 1 , further comprising a pedestal extending from a surface of the canister port, wherein the secondary spring is seated on the pedestal such that the secondary spring is disposed between the valve member and the pedestal.
3 . The fuel tank isolation valve of claim 1 , further comprising a retainer mounted on the alignment pin, wherein the secondary spring is retained by the retainer such that the secondary spring is disposed between the valve member and the retainer.
4 . The fuel tank isolation valve of claim 1 , wherein the valve member includes a generally tubular main body having a first portion connected to a second portion by a shoulder, the first portion terminating in an annular rim defining the first stage valve surface, and the second portion terminating in an opposite annular rim defining the second stage valve surface.
5 . The fuel tank isolation valve of claim 4 , wherein an inner shoulder surface of the main body defines an internal spring seat, and the secondary spring is seated on the internal spring seat.
6 . The fuel tank isolation valve of claim 4 , wherein the first portion of the main body has a smaller diameter than the second portion of the main body.
7 . The fuel tank isolation valve of claim 4 , wherein the valve member includes a tubular guide portion connected to an inner surface of the main body adjacent the shoulder, the alignment pin extending through the guide portion.
8 . The fuel tank isolation valve of claim 4 , wherein the valve member includes one or more fins extending from the shoulder and beyond the annular rim of the first portion of the main body.
9 . The fuel tank isolation valve of claim 8 , wherein the one or more fins overlap a portion of the moveable plunger.
10 . The fuel tank isolation valve of claim 8 , wherein the valve member includes a plurality of fins circumferentially disposed and spaced around the first portion of the main body.
11 . The fuel tank isolation valve of claim 4 , including a first sealing ring on the annular rim defining the first stage valve surface, and a second sealing ring on the opposite annular rim defining the second stage valve surface.
12 . The fuel tank isolation valve of claim 1 , further including a pressure relief chamber, and a pressure relief valve disposed in the pressure relief chamber.
13 . The fuel tank isolation valve of claim 12 , further including a first relief passage connecting the valve chamber and the pressure relief chamber, and a relief valve seat surrounding the first relief passage, wherein the pressure relief valve includes a poppet seated on the relief valve seat in a closed disposition.
14 . The fuel tank isolation valve of claim 13 , further including a second relief passage connecting the pressure relief chamber and the canister port, wherein the tank port and the valve chamber are in fluid communication with the canister port via the first relief passage, the pressure relief chamber, and the second relief passage in an open disposition of the pressure relief valve.
15 . The fuel tank isolation valve of claim 1 , wherein the valve member is operable between the closed disposition, a first stage open disposition, and a second stage open disposition, wherein activation of the coil draws the moveable plunger toward the stationary core and unseats the first stage valve surface of the valve member from the moveable plunger while the second stage valve surface remains seated, and maintained activation of the coil draws the moveable plunger closer to the stationary core and unseats the second stage valve surface while the first stage valve surface becomes seated on the moveable plunger.
16 . The fuel tank isolation valve of claim 1 , wherein in a first stage open disposition of the valve, the valve comprises a fuel vapor flow path from the tank port into the valve chamber, past the first stage valve surface of the valve member, through the valve member and transfer passage, and into the canister port.
17 . The fuel tank isolation valve of claim 1 , wherein in a second stage open disposition of the valve, the valve comprises a fuel vapor flow path from the tank port into the valve chamber, past the second stage valve surface of the valve member, and through the transfer passage into the canister port.
18 . A method of operating a fuel tank isolation valve, the method comprising the steps of:
providing the fuel tank isolation valve of claim 1 ;
applying a control voltage to the coil of the solenoid assembly, wherein the valve member moves from a closed disposition to a first stage open disposition such that the moveable plunger is drawn toward the stationary core and unseats the first stage valve surface of the valve member from the moveable plunger while the second stage valve surface remains seated; and
maintaining application of the control voltage to the coil of the solenoid assembly, wherein the valve member moves from the first stage open disposition to a second stage open disposition such that the moveable plunger is drawn closer to the stationary core and unseats the second stage valve surface while the first stage valve surface becomes seated on the moveable plunger.
19 . An evaporative emission control system for a vehicle, the system comprising:
a fuel tank;
an evaporative emissions canister; and
the fuel tank isolation valve of claim 1 , wherein the fuel tank isolation valve is connected between the fuel tank and the evaporative emissions canister.