Sealing in fuel injection pumps
OwnerLloyd E. Johnsoninventor
Life of this patent
Estimating the term…
Abstract
The walls of the plunger (piston) of the fuel metering pump are relatively thin so that, when pressurized, they expand to provide more effective sealing. A plug is then used in the bore of the plunger to reduce its volume. In one embodiment the wall thickness in the portion of the plunger between the valving openings is further reduced to increase the wall expansion, and thus sealing, adjacent the valving openings. In some embodiments, ends of the members about the plunger are provided with skirts to decrease their tendency to expand, thus improving the sealing.
Claims20
In a fuel injection pump for an internal combustion engine, which pump comprises a pump body defining a fuel supply space within which is a relatively low fluid pressure, a fixed cylinder member in said body and having a cylinder chamber, a plunger in that cylinder chamber, precision fitted with a close working clearance to the cylinder member and having a portion external to said cylinder member, a sleeve member in said space, separate from said cylinder member and having a cylindrical chamber within which said portion of said plunger is positioned, said sleeve member being similarly fitted on said portion of the plunger, said plunger being formed about an axis and having a concentric axial bore therein, said plunger reciprocating axially with respect to said members, said plunger having porting means arranged to be closed by reciprocation of the plunger relative to the members, the improvement comprising:
- said bore in said plunger having a diameter not less than one-half nor more than seven-tenths of the outer diameter of said plunger, whereby pressurization in the bore expands the plunger to reduce the clearance between it and the members.
In a fuel injection pump for an internal combustion engine, which pump includes a fixed cylinder member having a cylinder chamber open at one end of the member, the fluid pressure existing at said one end of the member being relatively low as compared to the pressure in said chamber during pumping, a plunger precision fitted with close working clearance within that cylinder chamber and extending out of said open end, said member being subjected to high pressure within said cylinder chamber adjacent said end during operation of said pump, the improvement comprising:
- said cylinder member having a skirt concentric with and symmetrical about said plunger, said skirt having an internal opening through which said plunger extends and of a diameter which is only sufficiently greater than the diameter of the cylinder chamber of the cylinder member than that necessary to provide clearance between the plunger and the skirt and to prevent any pressure build-up of fuel which may flow between the plunger and the cylinder member during the operation of the pump whereby the fluid pressure existing between the plunger and the skirt substantially corresponds to said relatively low pressure and said skirt performs most effectively to provide restraint against enlargement of the cylinder member at said one end of the cylinder member.
In a fuel injection pump for an internal combustion engine, which pump includes a pump body defining a fuel supply space within which is a relatively low fluid pressure, a plunger, an annular member about said plunger, said annular member having an internal wall defining an axial internal opening within which the plunger is precision fitted with a close working clearance, said internal wall having an end, said member being subjected to high pressure within said opening adjacent said end during the operation of said pump, the improvement comprising:
- said member having a skirt integral therewith, extending beyond said end, being symmetrical about the plunger and coaxial with said opening, said skirt having a distal end in said space and an internal wall at a radial distance from said axis which is only sufficiently greater than is the radial distance of the wall defining said opening than that necessary to provide clearance between the plunger and the skirt and to prevent any pressure build-up of fuel which may flow between the plunger and the cylinder member during operation of the pump whereby the fluid pressure existing between the plunger and the skirt substantially corresponds to said relatively low pressure and said skirt performs most effectively to provide restraint against enlargement of the cylinder member at said one end of the cylinder member.
In a fuel injection pump for an internal combustion engine, which pump includes a plunger, an annular member about said plunger, said annular member having an internal wall defining an axial internal opening within which the plunger is precision fitted with a close working clearance, said internal wall having an end, said member being subjected to high pressure within said opening adjacent said end during the operation of said pump, the improvement comprising:
- said plunger having an axially concentric bore longer than the part of said plunger lying within the internal opening of the member, said bore being within the member and having a diameter not less than one-half nor more than seven-tenths of the outer diameter of the plunger, whereby said high pressure in the bore expands the plunger to reduce the clearance between it and the member.
Dependencies are inferred from the claim text.