Cap sensitive head valve for vehicle fuel system

Reference Number: N 01-05

Inventors: Benjey, Robert P.

USPTO Link: 5417240

Invention Summary

The present invention resides in a novel head valve whose pressure head relief bias is adjustable in response to changing pressure conditions in the filler pipe which indicate the start and finish of a refueling operation. During refueling the bias of the head valve maintains a high pressure head in the tank to ensure proper operation of the filler nozzle shutoff mechanism and to prevent overfilling the fuel tank. When refueling is finished, the closing force or relief bias of the head valve is significantly reduced to maintain a second, lower pressure head in the fuel tank during normal vehicle operation. This is achieved with pressure-responsive control means in the valve body which respond to pressure changes in the filler pipe to reduce the relief bias of the head valve for normal vehicle operation.

The head valve can accordingly be given a refueling relief bias, for example by a spring, which maintains a high pressure head in the fuel tank. When pressure changes in the filler pipe inlet indicate a refueling operation, the refueling bias of the head valve is in effect. However, when pressure changes at the filler pipe inlet indicate the end of the refueling operation, for example when the filler pipe inlet is closed by a cap, the control means are enabled to reduce the relief bias of the head valve and therefore the tank pressure head for normal vehicle operation.

In one embodiment of the invention a head valve is mounted in a hollow valve body in series between a fuel tank vapor inlet and an outlet to the vapor canister, spring-biased to a closed position with a closing force or bias which maintains a first, high pressure head desirable for refueling. A diaphragm control element is located in the valve body adjacent the head valve and in series between the fuel tank vapor inlet and a signal pressure line from the upper end of the filler pipe. The diaphragm control element is movable between a first position in a direction opposed to the closing bias of the head valve, and a second position in a direction away from the closing bias of the head valve. An actuating element on the diaphragm control element is at least selectively connected to the head valve to reduce the closing bias of the head valve in the second position, thereby reducing the tank pressure head maintained by the head valve.

In a particular embodiment the actuating element is a finger which pushes against the closing bias of the head valve in response to filler pipe pressure conditions when the cap is on, and which is pulled out of engagement with the head valve in response to filler pipe pressure conditions when the cap is off. The diaphragm control element is pressure balanced when the cap is on, allowing a spring bias to operate the actuating element and reduce the closing force of the head valve.

With the present invention the relief bias or closing force of the head valve is automatically adjusted to maintain a lower pressure head during vehicle operation, and a higher pressure head during refueling operations, all in response to pressure changes in the filler pipe. In a cap-operated filler pipe the head valve is effectively responsive to the position of the filler pipe cap to automatically adjust the pressure head maintained by the head valve.