Pumps – Combined
Reexamination Certificate
2000-03-08
2001-07-17
Paik, Sang (Department: 3742)
Pumps
Combined
C137S493300
Reexamination Certificate
active
06261069
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to pumps and, more particularly, to an apparatus for equalizing pressure between a lubrication fluid and a combustion fluid to be pressurized by a supply pump.
BACKGROUND OF THE INVENTION
Direct gasoline injection has some distinct advantages over prior art systems with respect to emissions and fuel economy of the engine, mainly because of an increase in the efficiency of the engine.
Currently, efforts are underway to develop a reliable and inexpensive pump capable of generating a relatively high pressure (such as 120 bar and higher) required for supplying a common rail system used in direct gasoline injection. One such pump is shown in U.S. patent application Ser. No. 09/031,859, filed Feb. 27, 1998 and entitled “Supply Pump for Gasoline Common Rail” (International Application No. PCT/US99/03830 published under International Publication No. WO 99/43949), which is assigned to the present assignee hereof and the entire contents of which is hereby incorporated herein by reference. This supply pump, as is typical of pumps in general, includes a rotating shaft having bearings that are lubricated by either a lubrication fluid (oil) or a combustion fluid (fuel) disposed on the low pressure side of the pump. The fuel may be pre-pressurized to 3 or 4 bar by a separate feed pump, e.g., remotely located in a fuel tank. Seals, such as lip seals, which extend radially about the rotating shaft, are employed to prevent escape and/or mixing of either fluid.
While the supply pump described in the International Publication is suitable for its intended purposes, a problem can occur with the supply pump in that because of the differences in pressure between the oil pressure and fuel pressure within the pump, the lip seals may be canted one way or the other into contact with the rotating shaft resulting in premature wear thereof.
Another problem can also arise because of the difference in pressure between the oil and the fuel. In particular, passage by either the oil or the fuel through the seal occurs, due to the canting of the seal and/or other factors, resulting in improper mixing of these fluids. In one direction, mixing of the fuel into the oil may result in a reduction in lubricity of the oil. It will be appreciated that reduced lubricity of the oil can, for example, result in premature wear of the pump and possibly other systems of the engine. Also, potential hazardous waste problems concerning disposal of the oil/fuel mixture may arise. In the opposite direction, the mixing of the oil with the fuel may result in a reduction in engine performance.
SUMMARY OF THE INVENTION
It is, accordingly, an object of the present invention to provide an apparatus which equalizes pressure within a pump between a lubrication fluid and a combustion fluid disposed at a low pressure side of the pump.
It is another object to provide such an apparatus which can adjust the pressure of the lubrication fluid to slightly above that of the combustion fluid.
It is a further object of the invention to provide a pump for supplying a common rail gasoline fuel injection system for a multi-cylinder internal combustion engine.
According to one aspect of the present invention, an apparatus is provided for equalizing pressure between a first region of lubrication fluid for lubricating a pump and a second region of combustion fluid at a low pressure where the pump has a rotatable shaft. The apparatus comprises a wall defining a bore disposed within the pump where the first end of the bore is configured to receive lubrication fluid from the first region and a second end of the bore is configured to receive combustion fluid from the second region. An equalizing element is also provided which is disposed within the bore for separating the lubrication fluid and the combustion fluid. The shuttle is at least partially moveable in response to pressure differences between the first region and the second region generated by changes in volume caused for example by thermal expansion.
In a particular aspect of the invention the equalizing element may comprise either a shuttle or a diaphragm. Means may be provided for biasing the shuttle so as to increase the pressure of the lubrication fluid in the first region relative to the combustion fluid in the second region. The rotating shaft may include a recess which communicates with the bore and the bias means may comprise a coil spring. The coil spring may have an enlarged diameter portion at one end thereof, which may be disposed within the recess of the rotating shaft.
In another aspect at least one seal is disposed on the shuttle which may comprise a pair of lip seals disposed at opposing ends of the shuttle. Optionally, the shuttle may include a pair of recesses laterally spaced along a longitudinal axis of the shuttle and the at least one seal may comprise two O-rings, each of which are disposed within a respective recess of the shuttle. The axial length of the bore and the spacing of the recesses of the shuttle may also be dimensioned such that during movement of the shuttle each respective O-ring engages only that portion of the bore in contact with a respective lubrication fluid or combustion fluid. The shuttle may also be generally cylindrical in shape.
In a further aspect, the pump may comprise a pump housing and the rotatable shaft may be disposed within a pump cavity of the pump housing. A first bearing and a second bearing may be interposed between the rotatable shaft and the pump housing. The first bearing may be in contact with the lubrication fluid and the second bearing may be in contact with the combustion fluid. The first and second bearings may comprise needle bearings or, optionally, the first bearing may comprise a ball bearing and the second bearing may comprise a wet bushing.
In a still further aspect, the rotatable shaft has an external profile and the pump may supply the combustion fluid at a relatively high pressure to a common rail and the pump may further comprise the following. At least one shoe means in sliding engagement with the external profile of the rotatable shaft. Retention means for urging the shoe means against the external profile of the rotatable shaft during rotation thereof. At least one pumping plunger disposed in a plunger bore and being in operative engagement with the shoe means. Each of the plungers having radially outer and inner ends relative to the axis and an internal charging passage which opens toward the cavity at the inner end of the plunger and opens towards the outer end of the plunger bore at the outer end of the plunger. The shoe means sliding on the external profile which is configured for providing reciprocal movement of the plungers. A discharge passage from the outer end of the plunger bore into the housing, and a discharge check valve in the discharge passage for permitting flow only away from the plunger bore. The discharge passage communicating with the common rail such that reciprocation of each plunger includes movement toward an inner limit position for inducing low pressure in the outer end of the plunger bore, thereby drawing combustion fluid in a charging phase of operation from the pump cavity through charging passage into the outer end of the plunger bore, and movement toward an outer limit position for developing a high pressure in the outer end of the plunger bore thereby discharging combustion fluid through the discharge check valve into the common rail in a discharging phase of operation.
In a still further aspect the charging passage includes a charging check valve which is normally closed at the inner end, but which opens to permit flow from the inner to the outer end of the plunger during the charging phase of operation. The lubrication fluid may comprise a lubricating oil and the combustion fluid may comprise gasoline.
In another aspect of the invention an apparatus is provided for equalizing pressure disposed between a lubrication fluid for lubricating a pump and a combustion fluid disposed at a low pressure side of the pump. The apparatus comprises a wa
Alix Yale & Ristas, LLP
Fastovsky Leonid
Paik Sang
Stanadyne Automotive Corp.
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