Pump assembly

Abstract

A pump assembly for use in delivering fuel to a common rail of an internal combustion engine, including a pumping plunger ( 28; 128 ) which is co-operable with an intermediate drive member in the form of a tappet ( 34 ). The tappet ( 34 ) is co-operable with an engine-drive cam ( 11 ), in use, so as to impart drive to the plunger ( 28; 128 ). A cam rider member ( 38 ) of generally tubular form has an inner surface which co-operates with the cam ( 11 ) and an outer surface which cooperates with the bucket tappet ( 34 ). A main pump housing ( 10 ) is provided with a radially extending opening ( 18 a ) within which is received, at a first end thereof, a separate pump head ( 20 a ) and, at a second end thereof, the tappet ( 34 ) so that the opening ( 18 a ) serves to guide axial movement of the tappet ( 34 ), in use. The separate pump head ( 20 a ) is provided with a plunger bore ( 26 ) which serves to guide movement of the plunger ( 28; 128 ) and within which is defined a pump chamber ( 30 ) in which fuel is pressurised as the plunger ( 28 ) is driven.

1 . A pump assembly for use in delivering fuel to a common rail of an internal combustion engine, the pump assembly comprising: 
 a pumping plunger ( 28 ;  128 ) which is co-operable with an intermediate drive member ( 34 ), the intermediate drive member ( 34 ) being further co-operable with an engine-drive cam ( 11 ), in use, so as to impart drive to the pumping plunger ( 28 ;  128 ),    a cam rider member ( 38 ) having an inner surface which is co-operable with the cam ( 11 ) and an outer surface which is co-operable with the intermediate drive member ( 34 ),    a main pump housing ( 10 ) provided with a radially extending opening ( 18   a ) within which is received, at a first end thereof, a separate pump head ( 20   a ) and, at a second end thereof, the intermediate drive member ( 34 ) so that the main pump housing ( 10 ) serves to guide movement of the intermediate drive member ( 34 ), in use, the separate pump head ( 20   a ) being provided with a plunger bore ( 26 ) which serves to guide movement of the plunger ( 28 ;  128 ) and within which is defined a pump chamber ( 30 ) in which fuel is pressurised as the pumping plunger ( 28 ) is driven.    
     
     
         2 . The pump assembly as claimed in  claim 1 , wherein the main pump housing ( 10 ) is provided with an axially extending opening ( 17 ) for receiving an engine drive shaft ( 12 ), in use, and wherein an innermost end of the radially extending opening ( 18   a ) opens into the axially extending opening ( 17 ).  
     
     
         3 . The pump assembly as claimed in  claim 1  or  claim 2 , the pump assembly comprising first, second and third pump units ( 20   a ,  20   b ,  20   c ) equi-angularly spaced around the cam ( 11 ), each of the first, second and third pump units ( 20   a ,  20   b ,  20   c ) including a plunger ( 28 ) and an intermediate drive member ( 34 ) which is received within a respective one of a first, second or third radially extending opening ( 18   a ,  18   b ,  18   c ) provided in the main pump housing ( 10 ).  
     
     
         4 . The pump assembly as claimed in  claim 1  or  claim 2 , the pump assembly comprising first and second pump units ( 20   a ,  20   b ) only, each of the first and second pump units including a plunger ( 28 ) and an intermediate drive member ( 34 ) which is received within a respective one of a first or second radially extending opening provided in the main pump housing ( 10 ), the first and second radially extending openings being arranged substantially diametrically opposite one another.  
     
     
         5 . The pump assembly as claimed in any one of  claims 1  to  4 , wherein the intermediate drive member takes the form of a tappet ( 34 ) having opposed tappet sidewalls and a tappet base, wherein the tappet side walls are guided within the radially extending opening ( 18   a ) in the main pump housing ( 10 ) and the tappet base co-operates with a flat ( 38   a ) on the outer surface of the cam rider member ( 38 ).  
     
     
         6 . The pump assembly as claimed in  claim 5 , further comprising means ( 35 ) for allowing fuel to be displaced from, and supplied to, the radially extending opening ( 18   a ) in the main pump housing ( 10 ) as the tappet ( 34 ) reciprocates, in use.  
     
     
         7 . The pump assembly as claimed in  claim 6 , wherein said means for allowing fuel to be displaced from, and supplied to, the radially extending opening ( 18   a ) includes a sidewall opening ( 35 ) provided in the tappet sidewall.  
     
     
         8 . The pump assembly as claimed in any one of  claims 1  to  7 , wherein the main pump housing ( 10 ) includes an insert means which defines a guide path for the intermediate drive member ( 34 ).  
     
     
         9 . The pump assembly as claimed in  claim 8 , wherein the insert means is one of an insert sleeve of generally cylindrical form or a coating applied to an internal surface of the opening ( 18   a ,  18   b ,  18   c ).  
     
     
         10 . The pump assembly as claimed in  claim 9 , wherein the plunger bore and the insert member are substantially co-axially aligned.  
     
     
         11 . The pump assembly as claimed in any one of  claims 1  to  7 , wherein an internal surface of the radially extending opening ( 18   a ,  18   b ,  18   c ) defines the guide path for the intermediate drive member ( 34 ).  
     
     
         12 . The pump assembly as claimed in any one of  claims 1  to  11 , wherein the pump head ( 20   a ) is provided with an extension ( 24 ) which projects into the radially extending opening ( 18   a ,  18   b ,  18   c ) to define an increased plunger sealing length.  
     
     
         13 . The pump assembly as claimed in any one of  claims 1  to  12 , wherein the pump chamber ( 30 ) has. an outlet valve. arrangement including a valve member ( 41 ) which is engageable with a valve seating ( 47 ) to open and close communication between the pump chamber ( 30 ) and the common rail, wherein opening movement of the valve member ( 41 ) is limited by means of a stop plug ( 46 ) which defines, at least in part, at least two flow paths for fuel.  
     
     
         14 . The pump assembly as claimed in  claim 13 , wherein the stop plug ( 46 ) has an outer surface provided with at least two axially extending recesses to define a flow path for high pressure fuel.  
     
     
         15 . The pump assembly as claimed in  claim 14 , wherein the stop plug ( 46 ) has an outer surface provided with four axially extending recesses, equi-angularly spaced around the outer surface of the stop plug, to define four separate flow paths for high pressure fuel.