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Pump assemblyRelated Patent Categories: Pumps, Three Or More Cylinders Arranged In Parallel, Radial, Or Conical Relationship With Rotary Transmission Axis, Radial CylindersPump assembly description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070041848, Pump assembly. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] The invention relates to a pump assembly suitable for use in a common rail fuel injection system for supplying high pressure fuel to a compression ignition internal combustion engine. In particular, the invention relates to a pump assembly of the type having a cam rider mounted upon an engine driven cam and an intermediate drive member which is coupled to a pumping plunger and which co-operates with the cam rider, in use, so as to impart reciprocating, pumping motion to the plunger. [0002] In a known common rail fuel pump of radial pump design, three pumping plungers are arranged at equi-angularly spaced locations around an engine driven cam. Each plunger is mounted within a plunger bore provided in a main pump housing. As the cam is driven in use, the plungers are caused to reciprocate within their bores in a phased, cyclical manner. As the plungers reciprocate, each causes pressurisation of fuel within a pump chamber defined at one end of the associated plunger bore. The delivery of fuel from the pump chambers to a common high pressure supply line is controlled by means of delivery valves. The high pressure line supplies fuel to a common rail, or other accumulator volume, for delivery to the downstream injectors of the common rail fuel system. [0003] The cam carries a cam rider which extends co-axially with the drive shaft and is provided with a plurality of flats, one for each of the plungers. An intermediate drive member in the form of a tappet co-operates with the flat on the cam rider and couples to the plunger so that, as the tappet is driven upon rotation of the cam, drive is imparted to the plunger. [0004] It is important in pumps of this type that movement of both the plunger and of the tappet is guided as the parts are driven. However, from a manufacturing point of view, this is difficult to achieve in a pump assembly in which the main pump housing defines the guide path for both parts. [0005] It is with a view to addressing this incompatibility that we provide a fuel pump assembly of improved construction. [0006] According to the present invention, there is provided a pump assembly for use in delivering fuel to a common rail of an internal combustion engine, the pump assembly comprising a pumping plunger which is co-operable with an intermediate drive member, the intermediate drive member being co-operable with an engine-drive cam so as to impart drive to the plunger, in use, the pump assembly further comprising a cam rider member having an inner surface which is co-operable with the cam and an outer surface which is co-operable with the intermediate drive member, a main pump housing provided with a radially extending opening within which is received, at a first end thereof, a separate pump head and, at a second end thereof, the intermediate drive member so that the radially extending opening serves to guide movement of the intermediate drive member, the separate pump head being provided with a plunger bore which serves to guide movement of the plunger and within which is defined a pump chamber in which fuel is pressurised as the plunger is driven. [0007] In one preferred embodiment of the invention, the pump assembly comprises first, second and third plungers which are equi-angularly spaced around the engine drive cam, the cam rider member being provided with first, second and third surfaces for co-operation with first, second and third intermediate drive members, respectively, each intermediate drive member being coupled to an associated one of the plungers and wherein each of the intermediate drive members is guided within a respective one of first, second or third radially extending openings provided in the main pump housing, each of the first, second and third plungers being guided within a respective one of first, second or third plunger bores provided within a respective one of first, second or third pump heads mounted upon the main pump housing. [0008] This preferred embodiment of the pump assembly may therefore be considered as having three pump `units` radially spaced around the cam, each pump unit having a pump head and a plunger coupled to an intermediate drive member for mounting within a radially extending opening in the main pump housing. The radially extending opening defines a chamber which is flooded with fuel and within which the intermediate drive member reciprocates, in use. [0009] It will be appreciated that the pump assembly of this preferred embodiment of the invention is not limited to having three pump units, and a greater number of pump units may be provided, if required. [0010] Preferably, the intermediate drive member takes the form of a tappet, typically a bucket-shaped tappet, having facing tappet sidewalls and a tappet base, wherein the tappet side walls are guided within the main pump housing and the tappet base co-operates with a flat on the outer surface of the cam rider member. It is further preferable to provide the pump assembly with means for allowing fuel to be displaced from, and supplied to, the chamber defined by the radially extending opening in the main pump housing. For example, each tappet sidewall may be provided with a sidewall opening in the form of a window to allow fuel to flow into the chamber and around the tappet during the plunger return stroke, and also to allow fuel to be displaced from the chamber during the plunger pumping stroke. [0011] The pump assembly has several benefits over known pump assemblies. As each plunger is guided within a separate pump head (i.e. a housing part separate from the other pump heads), and each tappet is guided within the main pump housing which is separate from the pump heads, the guidance bores are much easier to machine than in an assembly in which the plunger and the tappet are both guided within the main pump housing. This may pose another problem as any misalignment or `tilt` of the pump heads relative to the main pump housing can lead to off-axis side loading of the plungers and/or tappets, resulting in an undesirable degree of wear. With this in mind, it is a preferable feature of the invention that the tappets are guided within the main pump housing, which is that part of the pump assembly carrying and locating both the drive shaft and the cam rider member. [0012] A benefit is also provided over other known pumps in which each tappet is provided with a roller which co-operates with the outer surface of the cam. The benefit is achieved as the requirement for individual rollers for each tappet is avoided by the use of the single cam rider which drives all three plungers and tappets. [0013] In use, as the cam is rotated by the drive shaft, the cam rider is caused to ride over the cam surface. The flat, or flattened region, of the surface of the cam rider member co-operates with the base of the tappet with the result that the tappet is driven axially, radially outward from the cam shaft, whilst a degree of relative sliding movement between the rider flat and the tappet occurs in a lateral direction (as the cam rider is able to slide relative to the axially guided tappet). [0014] Preferably, the main pump housing is provided with an axially extending opening s for receiving the drive shaft. In a three plunger pump, each of first, second and third radially extending openings communicate, at respective inner ends thereof, with the axially extending opening in the main pump housing. The cam rider preferable takes the form of a generally tubular member arranged co-axially with the drive shaft. [0015] In one embodiment, the main pump housing includes an insert means which defines a guide path for the tappet. For example, an insert member may be received within the inner end of each of the first, second and third radially extending openings so that each insert member defines a guide path for a respective one of the tappets. The insert member may be of generally cylindrical form such that it takes the form of a sleeve. Preferably, the plunger bore and the insert member are substantially co-axially aligned. [0016] The insert means may alternatively take the form of a hardened coating e.g. a steel coating. This is particularly advantageous if the main pump housing is to be formed from cast iron, which is convenient and relatively light, as the hardness of the steel insert means (e.g. sleeve member or coating) avoids wear of the main pump housing. [0017] Alternatively, an internal surface of the radially extending opening may define the guide path for the tappet. [0018] In a further preferred embodiment, each pump head is provided with an extension which projects into the respective radially extending opening to define an increased plunger sealing length. This has the benefit of improving pump efficiency as losses due to leakage are reduced. [0019] The pump chamber of each pump unit has an outlet valve arrangement including a valve member which is engageable with a valve seating to open and close communication between the pump chamber and the common rail, whereby opening movement of the valve member is limited by means of a stop plug which defines at least two flow paths for fuel. [0020] Preferably, the stop plug has an outer surface provided with at least two axially extending recesses to define a flow path for high pressure fuel. An outlet valve of this construction is particularly convenient to manufacture. [0021] The advantageous features of the present invention are applicable not only to a pump assembly having three pump units (i.e. three plungers) but also to pump assemblies having just two pump units. In another preferred embodiment, therefore, the pump assembly may include only first and second pump units. [0022] In other words, the pump assembly may comprise a first plunger which is reciprocable within a first plunger bore provided in a first pump head and co-operable with a first intermediate drive member which is reciprocable within a first radially extending opening provided in the main pump housing, the pump assembly further comprising a second plunger which is reciprocable within a second plunger bore provided in a second pump head and co-operable with a second intermediate drive member which is reciprocable within a second radially extending opening provided in the main pump housing, wherein the first and second pump heads are received within a respective one of the first and second radially extending openings, at radially outermost ends thereof, said openings being located substantially diametrically opposite one another within the main pump housing. [0023] The present invention will now be described, by way of example only, with reference to the accompanying drawings in which: [0024] FIG. 1 is a perspective view of the pump assembly of the present invention, Continue reading about Pump assembly... Full patent description for Pump assembly Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Pump assembly patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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