Fuel pressure regulator

Claim 1

A fuel pressure regulator for use in a fuel injection system for an internal combustion engine, of the type in which a fuel is supplied under pressure from a fuel source through a main fuel conduit and through fuel injectors into the engine and an excess part of the fuel supply is returned from the main fuel conduit through a return pipeline to said fuel source, said fuel pressure regulator comprising: a housing defining therein a fuel passage having an upstream end adapted to be communicated with said main fuel conduit and a downstream end adapted to be communicated with said return pipeline; said fuel passage including a substantially cylindrical first part, a substantially cylindrical second part disposed downstream of said first part in substantially coaxial relationship thereto, said second part having a diameter greater than that of said first part, and an annular shoulder interconnecting said first and second parts and forming a first valve seat; an axially elongated double-headed first valve member including first and second heads formed at the upstream and downstream ends and connected by an intermediate portion of a reduced diameter; said first head defining therein a restriction passage and being snugly and slidably disposed in said first cylindrical part of said fuel passage; said second head having a substantially cylindrical portion which can be slidably and snugly received in said first cylindrical part of said fuel passage and a substantially annular portion which extends radially outwardly from said cylindrical head portion and is disposed in said second cylindrical part of said fuel passage; a compression spring disposed in said second cylindrical part of said fuel passage to bias said first valve member toward the upstream end of said fuel passage so that said annular portion of said second head of said valve member is moved into sealing engagement with said first valve seat; the inner peripheral surface of said first cylindrical part of said fuel passage cooperating with said first valve member to define an annular fuel chamber which is always communicated through said restriction passage with the upstream end of said fuel passage; said first valve member being movable to its open position when the fuel pressure in said fuel chamber exceeds a predetermined pressure level determined by said compression spring, to allow the fuel to flow from said fuel chamber to said second cylindrical part of said fuel passage and into said return pipeline; means defining a bypass fuel passage bypassing said restriction passage and having a downstream end connected to said fuel chamber, said bypass fuel passage including a second valve seat disposed between the upstream and downstream ends thereof; said bypass fuel passage defining means including a diaphragm carrying a second valve member disposed in opposite relationship to said second valve seat; said diaphragm being operative to move said second valve member away from said valve seat when the fuel pressure at said upstream end of said fuel passage exceeds a second predetermined pressure level higher than said first predetermined pressure level, to allow the fuel to flow from the upstream end of said fuel passage through said bypass passage to said fuel chamber and thus to said second cylindrical part of said fuel passage.