Fuel pump with vapor lock inhibiting check valve

Details Fuel pump with vapor lock inhibiting check valve Fuel pump with vapor lock inhibiting check valve

2001-01-23

2002-08-27

Freay, Charles G. (Department: 3746)

Pumps

Expansible chamber type

Having pumping chamber pressure responsive distributor

C417S415000, C417S298000, C137S199000, C137S533110

Reexamination Certificate

active

06439863

ABSTRACT:

The present invention is directed to a pump for supplying liquid to a source and is particularly directed to, but not limited to, a fuel pump for supplying fuel for use in an internal combustion engine. The fuel pump is applicable for use with a fuel injection system used in motorcycle engines and the present invention will be described with reference to this application. It is to be appreciated that the pump is also applicable for use in other applications, particularly where priming of the pump is a concern.
Fuel injection systems for internal combustion engines typically require a fuel pump to supply fuel to the fuel and/or delivery injectors of the injection system. When the fuel supply to the fuel pump is interrupted and the remaining fuel in the pump is pumped out, it is necessary to re-prime the fuel pump. Typically, it can take a number of seconds to re-prime a fuel pump because of the presence of air and/or fuel vapour upstream of and within the fuel pump. Generally, this gas must be removed before the fuel pump can operate properly.
A similar problem also exists when the fuel to be delivered by the fuel pump is at a high temperature in a fuel tank, from which fuel is supplied to the fuel pump. At such significantly high temperatures, vapour typically forms and may constitute a significant amount of the fuel volume presented to the fuel pump. This problem is commonly known as “hot fuel handling” and for the fuel pump to operate properly this fuel vapour or gas must also be removed, from the vicinity of the fuel pump.
One way of removing such gas or vapour present upstream from or within the fuel pump is by pumping the gas downstream of the fuel pump, the gas, for example, being subsequently returned to the fuel tank by a fuel regulator. In this scenario it is however difficult for the fuel pump to pump a compressible gas or vapour as it may tend to simply compress and expand within the pump without being displaced therefrom. This results in a significant period of time being taken to displace the gas from the pump before fuel can be supplied to the fuel injection system. Further, in such pumps it may be difficult to achieve a sufficient compression ratio to pump air against a significant back-pressure downstream of the pump. Such a back-pressure may, for example, be presented by a downstream pressure regulator. In particular regard to the Applicant's dual fluid fuel injection system such as that disclosed in U.S. Pat. No. 4,934,329, the contents of which are incorporated herein by reference, this problem may be more prevalent in that it may present an absolute downstream pressure in the range of 750 kPa, whereas a conventional manifold injection system may present a pressure of only 380 kPa, or thereabouts.
One possible solution is the use of a pump having a higher compression ratio which will more effectively facilitate the pumping of gas or vapour downstream of the fuel pump. However, in regard to simple, low cost fuel systems and/or engine applications, this in itself poses a problem from the point of view of achieving a desired low-cost manufacture of the fuel pump. An additional problem is that the power requirements of commercial pumps having the required high compression ratio are generally too high for simple low cost engine applications such as motorcycle or scooter applications.
It is therefore an object of the present invention to provide a pump, and in particular a fuel pump which can be re-primed after an interruption in, or the exhaustion of, the supply of fuel thereto within a shorter period of time than for known fuel pumps, particularly where comparatively high pressures are to be developed.
It is a further object of the present invention to provide a pump and in particular a fuel pump, which has good hot fuel handling capabilities.
With this in mind, there is provided a pump, for pumping fluid including:
a pump body having a pumping chamber therein;
an inlet control means adapted to be in fluid communication with a fluid supply means for supplying fluid to the pump;
and an outlet control means adapted to control the delivery of fluid from the pump;
wherein
when a fluid at least substantially consisting of gas or vapour is supplied to the pumping chamber through the inlet control means, the fluid is pumped upstream from the inlet control means,
and when a fluid at least substantially consisting of liquid is supplied to the pumping chamber through the inlet control means, the fluid is at least substantially pumped through the outlet control means.
Preferably, the pump is a fuel pump arranged to receive fuel from a fuel supply means and to pump fuel through the outlet control means. Further the pump has good “hot fuel handling” capability in that it has the capacity to reject vapour continuously during steady state operation.
The pump according to the present invention is designed to not pump gas, typically in the form of air or vapour, downstream of the pump when such gas is presented to the inlet control means as a significant component of the fluid to be pumped. Any such fluid comprising a significant gas component which enters the pump is instead made to pass back through the inlet control means towards the fluid or fuel supply means. As will be alluded to hereinafter, the gas component within the fluid which enters the pumping chamber is gradually reduced until the gas no longer forms a significant component of the fluid. This point is achieved when the effective compression ratio within the pumping chamber is sufficient to overcome the back-pressure downstream of the outlet control means. At this point in time, the fluid within the pumping chamber will be pumped through the outlet control means. The fluid will be substantially liquid, but under certain conditions may still comprise a small component of gas therein, typically 5% by volume or less.
The pump according to the present invention is therefore effectively self priming and separates any gas from the fluid such that at least substantially only liquid is pumped through the outlet control means. This results in faster re-priming times for the pump, and when applied to fuel pumps for internal combustion engines, allows a high enough effective compression ratio, due to liquid rather than air being in the pumping chamber, which allows pumping against a high back-pressure downstream of the pump.
The inlet control means may include an inlet control member for controlling the flow of fuel and/or gas to and from the pumping chamber. The inlet control member may be accommodated within an inlet bore having an inlet port at one end thereof, and an end stop face at an opposing end thereof. The inlet control member may be freely moveable within the inlet bore between the inlet port and the end stop face of the bore. At least one inlet discharge passage may extend between the end stop face of the inlet bore and the pumping chamber to allow the flow of fluid to and from the inlet bore and the pumping chamber. The discharge passage(s) may be offset relative to the central position of the inlet control member such that fluid flow though the passage(s) may still occur when the inlet control member abuts the end stop face.
The inlet control member may be spherical in shape and the inlet port may be provided with a valve seat upon which the inlet control member can abut to close off the inlet port preventing fluid flow through the inlet bore. It is however to be appreciated that alternative shapes of the inlet control member are also envisaged. For example, the inlet control member may alternatively be disc shaped.
A predetermined clearance may be provided between the internal walls of the inlet bore and the inlet control member. Further, a predetermined axial travel or “stroke” for the inlet control member within the inlet bore may also be provided. The clearance and the stroke may be a function of the diameter of the inlet control member, this function allowing the inlet control means to operate according to the present invention. According to one preferred embodiment, the diametrical clearance is equal

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