Pilot injection pump

Abstract

The present invention adds a separate pilot pumping chamber and associated pumping plungers and cam followers axially offset from the main pumping chamber and pumping plungers. The axis of the pilot plunger bores is angularly offset from the axis of the main plunger bores so that the pilot plungers are actuated by a different set of cam lobes of the cam profile. This arrangement allows one pumping chamber to be refilled while the other pumping chamber is being discharged. A pilot injection event well in advance of the main injection can take place without refilling problems because each pumping chamber fills once for an injection event that includes a pilot and main injections. Discharge passages from the respective pumping chambers are ported to deliver the pilot and main fuel pulses to the same discharge port.

1 . In a rotary distributor fuel pump having a rotor including a plurality of simultaneously actuated main pumping plungers for delivering high pressure fuel sequentially through a main discharge passage to a plurality of discharge ports each associated with a respective fuel injector, the improvement comprising: 
 a distinct plurality of simultaneously actuated pilot pumping plungers and associated pilot pumping passage fluidly connectable to said discharge ports, and means for timing the actuation of the pilot plungers for advance overlap phasing relative to the actuation of the main plungers whereby fuel discharged by the pilot plungers through the associated pilot passage is delivered to a discharge port in advance of fuel delivered to the same discharge port from the main discharge plungers.    
   
   
       2 . The improved rotary distributor fuel pump of  claim 1 , comprising a cam profile surrounding said main and pilot pumping plungers and a cam follower between each of said main and pilot pumping plungers and said cam profile, 
 wherein said main pumping plungers reciprocate in main plunger bores having a common first axis and said pilot pumping plungers reciprocate in pilot plunger bores having a common second axis, said means for timing including an angular offset between said first and second axes.    
   
   
       3 . The improved rotary distributor fuel pump of  claim 1 , wherein said main pumping plungers reciprocate in substantially co-planar main plunger bores communicating with a main pumping chamber and said pilot pumping plungers reciprocate in substantially co-planar pilot plunger bores in communication with a pilot pumping chamber, said rotor having a rotational axis and said main plunger bores are axially offset along said rotational axis relative to said pilot plunger bores.  
   
   
       4 . In a rotary distributor fuel pump having a plurality of simultaneously actuated main pumping plungers for delivering high pressure fuel sequentially to a plurality of discharge ports each associated with a respective fuel injector, a method of delivering a pilot discharge with the main discharge to each injector, comprising simultaneously actuating a plurality of pilot plungers in advance overlap phasing relative to the actuation of the main plungers and delivering the fuel discharged from the pilot plungers to the same discharge port in advance of the fuel delivered from the main discharge.  
   
   
       5 . A rotary distributor fuel injection pump comprising: 
 (a) a substantially tubular hydraulic head having a front end and a back end, a plurality of substantially coplanar fuel inlet ports spaced cirumferentially around the head, and a plurality of substantially coplanar fuel discharge ports spaced cirumferentially around the head;    (b) a substantially cylindrical rotor closely coaxially situated within the head and supported for rotation therein, said rotor having a front portion extending axially from the front end of the hydraulic head and a back portion journalled in the head, said front portion including means for engaging a rotary drive;    (c) a first plurality of substantially coplanar plunger bores situated in the front end and extending radially to a first common pumping chamber, each of said first plunger bores having a pumping plunger reciprocally situated therein;    (d) a second plurality of substantially coplanar plunger bores situated in the front end and extending radially to a second common pumping chamber, each of said second plunger bores having a pumping plunger reciprocally situated therein;    (e) a first inlet/discharge passage extending through the rotor from the first pumping chamber to the surface of the rotor, for sequential alignment with each of the inlet ports as the rotor is driven;    (f) a second inlet/discharge passage extending through the rotor from the second pumping chamber to the surface of the rotor, for sequential alignment with each of the inlet ports as the rotor is driven;    (g) a stationary cam profile including a plurality of angularly spaced lobes surrounding the first and second pumping plungers, respectively;    (h) cam roller means situated between each pumping plunger and the cam profile;    (i) whereby rotation of the rotor produces (i) simultaneous reciprocal movement of said first pumping plungers between a charging phase wherein fuel is drawn into the first pumping chamber through an inlet port and the first inlet/discharge passage and a first discharge phase wherein the drawn fuel is pressurized and discharged through the first inlet/discharge passage and a discharge port, (ii) simultaneous reciprocal movement of said second pumping plungers between a charging phase wherein fuel is drawn into the second pumping chamber through an inlet port and the second inlet passage and a second inlet/discharge phase wherein the drawn fuel is pressurized and discharged through the second inlet/discharge passage into a discharge port; and    (j) wherein the first and second discharge phases are sequential, said first and second inlet/discharge passages are configured to deliver said first and second fuel discharges to the same discharge port and said first and second fuel discharges partially overlap in time.    
   
   
       6 . The rotary distributor fuel injection pump of  claim 5 , wherein each discharge port comprises a first discharge passage in the head alignable with said first inlet/discharge passage in the rotor, a second discharge passage in the head alignable with said second inlet/discharge passage in the rotor, and a common discharge opening at the surface of the head.  
   
   
       7 . The rotary distributor fuel injection pump of  claim 5 , wherein each inlet port comprises a first inlet passage in the head alignable with said first inlet/discharge passage in the rotor, a second inlet passage in the head alignable with said second inlet/discharge passage in the rotor, and a common inlet opening at the surface of the head.  
   
   
       8 . The rotary distributor fuel injection pump of  claim 5 , wherein the back portion of the rotor includes an internal cavity, a discharge control valve situated in the cavity, a control passage extending from the control valve to a control port at the surface of the rotor for sequential alignment with each of the discharge ports in the head, whereby operation of the control valve diverts fuel into said control cavity and thereby limits the quantity of fuel discharged from the pump through the discharge port.  
   
   
       9 . The rotary distributor fuel injection pump of  claim 8 , wherein each discharge port in the head includes a control passage extending from the discharge opening in the head to the control port.  
   
   
       10 . The rotary distributor fuel injection pump of  claim 5 , wherein the first cam profile and a diameter of said first plungers define a first pumping chamber discharge quantity and rate and the cam profile and a diameter of said second plungers define a second pumping chamber discharge quantity and rate, and the first discharge quantity is smaller than the second discharge quantity and the first discharge rate is slower than the second discharge rate.  
   
   
       11 . The rotary distributor fuel injection pump of  claim 5 , wherein said first plunger bores have a common first axis and said second plunger bores have a common second axis, an angular offset between said first and second axes timing the first and second discharge phases such that the total fuel discharge rate delivered to a discharge port during the overlap of the first and second discharge phases, increases linearly.  
   
   
       12 . The rotary distributor fuel injection pump of  claim 5 , wherein the first and second discharge phases have respective maximum discharge rates, said first plunger bores have a common first axis and said second plunger bores have a common second axis, an angular offset between said first and second axes timing the first and second discharge phases such that the second discharge phase begins while the first discharge rate is declining from maximum.  
   
   
       13 . A rotary distributor fuel pump comprising: 
 a hydraulic head with an outside surface and defining a cylindrical bore, said hydraulic head including a plurality of substantially coplanar fuel inlet ports and a plurality of substantially coplanar fuel discharge ports;    a rotor received in said bore including: 
 a plurality of main pumping plungers that are simultaneously actuated to deliver a main pulse of high pressure fuel sequentially through a main discharge passage sequentially to each of said fuel discharge ports;  
 a plurality of pilot pumping plungers that are simultaneously actuated to deliver a pilot pulse of high pressure fuel through a pilot pumping passage sequentially to each of said fuel discharge ports; and  
   an actuating assembly to actuate said pilot pumping plungers and said main pumping plungers,    wherein said pilot pulse is delivered to each said fuel discharge port in advance of said main pulse and said pilot and main pulses partially overlap in time at each said fuel discharge port.