Pumps – Three or more cylinders arranged in parallel – radial – or... – Radial cylinders
Reexamination Certificate
2000-02-09
2001-10-16
Freay, Charles G. (Department: 3746)
Pumps
Three or more cylinders arranged in parallel, radial, or...
Radial cylinders
C417S470000, C092S072000
Reexamination Certificate
active
06302659
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a multi-chamber positive displacement pump, and in the preferred embodiment of the invention provides a positive displacement pump suitable for delivering high pressure fuel to the fuel injection system of an internal combustion engine. It is to be understood, however, that the invention is not limited to this application and may be utilised in a wide range of multi-chamber positive displacement pumps.
2. State of the Art
Common rail fuel injection systems for internal combustion engines require the provision of a high pressure pump for supplying fuel at high pressure to the common rail or to an accumulator associated therewith. Such pumps must typically operate at pressures up to 1600 bar, and may in the future need to operate at pressures in excess of 2000 bar, and must accordingly be of the positive displacement type. In order to utilise common rail fuel injection technology in mass produced automobile engines the required fuel pump must be effective at delivering the required fuel volume and pressure, but must in addition be highly reliable, compact, and economical to manufacture. The requirements for compact and economical design are particularly difficult to meet in a pump which is required to deliver fuel reliably over many years at the pressures required by common rail fuel injection systems.
Whilst it is generally recognised that reducing the number of individual components in a particular assembly leads to an increase in reliability and a reduction in manufacturing costs, this general desideratum is often at variance with requirements for a compact design and is particularly difficult to achieve in a relatively complex mechanism such as a multi-chamber positive displacement pump.
SUMMARY OF THE INVENTION
It is the object of the present invention to provide a multi-chamber positive displacement pump in which the number of individual components is reduced as compared with prior art pumps without significant sacrifice in terms of reliability or compactness of design.
According to one aspect of the present invention there is provided a multi-chamber positive displacement pump comprising: a unitary housing in which is formed a plurality of cylinders; a pumping plunger slidably mounted in each cylinder to define a pumping chamber; means for reciprocating the pumping plungers in order cyclically to vary the volume of the pumping chambers to effect delivery of a pumped fluid from the pumping chambers; and a delivery passage connected to each of the pumping chambers to receive pumped fluid therefrom, the delivery passage comprising at least one gallery formed in the unitary housing and open to an end face of the housing and passageways which extend through the unitary housing from the gallery to the pumping chambers, the gallery being closed by an end plate which is secured to the unitary housing.
The use of a unitary housing which defines both the pumping chambers and the delivery passageway in association with an end plate which closes the galleries which form part of the delivery passages reduces to a minimum the number of components necessary for the body of the pump and minimises the number of high pressure seals required within the pump. The reduction in the number of components required and the resultant reduction in the number of seals which must be effected significantly reduces the production costs of the pump and improves the reliability thereof. In the preferred embodiment of the invention these improvements are achieved without any sacrifice in the overall size of the pump, as compared with comparable pumps having a larger number of individual components.
In the preferred embodiment of the invention the passageways in the unitary housing which form part of the delivery passage are formed by drillings which are machined from the galleries. The galleries can be formed in an end face of the housing by any convenient means, for example when the housing is forged or cast or as a subsequent machining operation, and can be formed to facilitate drilling of the passageways as required. In the preferred embodiment of the invention, in which the pump has three pumping chambers, it is preferred to provide three galleries each close to an associated pumping chamber. A delivery valve is located in a bore which connects each gallery to its associated pumping chamber and passageways associated with two of the galleries connect those galleries to the third gallery. Preferably, an outlet passage extends though the unitary housing from the third gallery to the exterior of the pump.
Preferably, the feed passages which are required to feed fluid which is to be pumped to the pumping chambers are also formed by way of galleries in an end face of the unitary housing and passageways formed in the unitary housing. The end face in which the feed galleries are formed can conveniently be the same end face as that in which the delivery galleries are formed whereby the end plate can be used to close both the delivery galleries and the feed galleries. In the case of a pump in which hydraulic pressure is used to effect movement of the pumping plungers in the feed direction, the working fluid passages which are used to supply working fluid to the pumping plunger return pistons are also formed by way of galleries in an end face of the unitary housing and passageways formed within the unitary housing. Again, the end face in which the working fluid galleries are formed is preferably the same end face as that in which the delivery galleries are formed, and the end plate is used to close the working fluid galleries.
In a particularly preferred embodiment of the invention delivery galleries, feed galleries and working fluid galleries are all formed in the same end face of the unitary housing and a common end place is used to close all the galleries.
In a particularly preferred embodiment of the invention the unitary housing defines a central chamber which houses the cam or crank mechanism used for driving the pumping plungers. In this case, an aperture is provided in the unitary housing extending from the exterior thereof to the central chamber at a point diametrically opposite each of the cylinders. The aperture may be used to gain machining access for the purposes and machining the cylinders and any bores required to house tappet gear or return pistons associated with the pumping plungers. After manufacture, the apertures are preferably closed by a plug. Under these circumstances, the feed passageways and/or the working fluid passageways can extend via the aperture. In the preferred embodiment, the working fluid passageways extend via the apertures and the closure plugs used to close the apertures after manufacture incorporate a peripheral groove to provide communication through the aperture between different parts of the working fluid passageways.
It will be appreciated that the effective closing of the delivery galleries is of critical importance. Given the very high pressures present in the delivery galleries it is difficult to provide conventional elastomeric seals which will be effective to give the required sealing. Accordingly, in the preferred embodiment of the invention the delivery galleries are sealed at the end plate by means of deformable hard material seals which, during assembly of the pump, are squeezed between the end plate and the unitary housing. By way of example, the hard material may be soft iron. In order to exert the clamping force necessary to deform the soft iron into sealing engagement with the unitary housing the screws used to secure the end plate to the unitary housing are preferably positioned adjacent each delivery gallery. Preferably, each delivery gallery has associated therewith at least two screws to produce the required clamping force.
The pressures present in the feed galleries and working fluid galleries are very substantially lower than those associated with the delivery galleries and accordingly the feed galleries and working fluid galleries can be sealed at the end plate by means
Collingborn Peter Alban George
Cooke Michael Peter
Parker Stephen Michael
Thornthwaite Ian Roy
Freay Charles G.
Gallagher Thomas A
Gordon David P.
Jacobson David S.
Solak Timothy P.
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