GB1577952A

GB1577952A - Fuel injection pumping apparatus

Info

Publication number: GB1577952A
Application number: GB1805776A
Authority: GB
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1976-05-04
Filing date: 1976-05-04
Publication date: 1980-10-29
Also published as: FR2350471B1; AR216069A1; BR7702840A; AU515095B2; JPS534204A; ES458459A1; IT1085455B; DE2719990A1; FR2350471A1; AU2472977A

Description

(54) FUEL INJECTION PUMPING APPARATUS (71) We, LUCAS INDUSTRIES LI MITED a British Company of Great King Street, Birmingham B 19 2XF do hereby declare the invention for which we pray that a Patent, may be granted to us, and the method by which it is to be performed, to be particularly described in and by the follow ing -statement::- This invention relates to fuel injection pumping apparatus for supplying fuel to an internal combustion engine and of the kind comprising a housing, a rotary distributor member journalled in the housing and which in use is driven in synchronism with the associated engine, a pair of bores formed in the distributor member, a pair of, plungers in said bores respectively, a cam, ring defining a pair of cam lobes for impart ing inward movement to the plungers as the distributor member rotates, a delivery pas sage comm,unicating with said bores, a plurality of outlets in the housing and with which the delivery passage registers in turn as the distributor member rotates and dur ing the time when the plungers are moving inwardly, said cam lobes being shaped so that at the end of the inward movement of the plungers limited outward movement of the plungers is allowed to permit a predeter mined volume of fuel to be returned through the respective outlet.

The provision of the limited outward movement or retraction of the plungers at the end of the delivery of fuel is well known.

It allows the valves in the injection nozzles of the engine and which are connected to the outlets respectively, to close quickly and it also reduces the pressure in the pipe lines interconnecting the outlets with, the nozles by a predetermined amount.

The difficulty with. providing the limited outward movement is, that it does occupy a portion of.the arcuate distance between the ,crests of adjacent cam lobes which could be more usefully employed for example. to allow filling of the bores with fresh fuel. In apparatus for supplying fuel to high speed multi-cylinder engines filling of the bores from a ldw pressure pump takes time and the longer the arcuate distance between the crests of the cam lobes which can be devoted to filling of the bores, the better.

The object of the invention is to provide a pumping apparatus òf the kind specified in a form in which the portion of the arcuate .distance between adjacent cam lobes and which is devoted to plunger retraction is minimised.

According to the invention an apparatus of the kind specified comprises a further pair of plungers and a further pair of cam lobes, said further pair of plungers being housed in bores respectively communicating with said delivery passage and the further pair of plungers and the further cam lobes being positioned so that they co-operate with each other at the same time as the first mentioned plungers and cam lobes are co-operateing with each other to effect delivery of fuel, said further pair of dam lobes being so shaped that no movement is imparted to the further plungers during the period of inward movement of the first mentioned plungers, said further cam lobes being shaped to permit limited outward movement of the further pair of plungers when the limited outward movement of the first mentioned'pair of plungers takes place.

According to a further feature of the invention said cam lobes and further cam lobes are alternately positioned about the cam ring.

One example of a fuel pumping apparatus in accordance with the invention will now be described with reference to the accompanying drawings in which Figure 1 is a known form of pumping apparatus, Figure 2 is a diagrammatic sectional view showing a modification to the apparatus of Figure 1 and for providing fuel to a four cylinder engine, Figure 3 is a view similar to Figure 2 showing the modification for providing fuel to a six cylinder engine and Figure 4 is a developed view of the cam profile shown in Figure 2.

Referring to Figure 1 of the drawings the known form of apparatus comprises a two part housing 9, 10, the housing part 9 being provided with an open end in which is located the part 1() of the housing.

Formed within the part 10 of the housing is a bore in which is mounted a rotary distributor member 11 and this is coupled to an input shaft 12 which is located in the part 9 of the housing. The shaft 12 is adapted to be driven in time relationship with an engine with which the apparatus is associated.

Formed within the distributor member is a transversely extending bore 14 in which is mounted a pair of reciprocable plungers 15 and which are arranged to be moved inwardly as the distributor member rotates, through the intermediary of a pair of rollers 16 respectively, by cam lobes not shown but formed on an annular cam ring 17 mounted for angular movement within the part 9 of the housing.

Also formed in the distributor member 11 is a longitudinally extending passage 18 which at one end is in communication with the transverse bore and at its other end is in communication with a radially disposed delivery passage 19. The delivery passage 19 is arranged to register in turn with a plurality of equi-angularly spaced outlet ports constituted as shown in the drawing, by passages 20. The outlet ports in use, are connected by pipe lines respectively to injection nozzles mounted on the associated engine. The aforesaid registration of the passage 19 with an outlet port takes place during the whole time the plungers 15 are being moved inwardly so that liquid fuel contained in the transverse bore 14 will be displaced to a combustion space of the engine.

At another point the longitudinal passage 18 is in communication with a plurality of equi-angularly spaced and radially disposed inlet passages 22 which are arranged to register in turn with an inlet port 23 formed in the part 1() of the housing, The inlet port 23 is in communication with a control port 25 by wny of a passage 24 and the control port is in communication with the outlet 26 of a feed pump 27.

The effective size of the control port 25 can be varied bv varying the angular setting of a valve member 28 which has a groove formed therein and the arrangement is such that when an inlet passage 22 registers with the inlet port 23 fuel will flow from the outlet of the feed pump to the transverse bore 14 to move the plungers 15 outwardly.

The aforesaid registration takes place only during the time when the delivery passage 19 is out of register with a passage 20 and during the time when the rollers 16 are clear of the cam lobes. By adjusting the setting of the valve member 28, the rate at which fuel can flow to the bore 14 can be controlled and hence also the amount of fuel to the engine.

The feed pump 27 is provided with an inlet which is in communication with an inlet port 30 formed in a hollow part 37 which is secured to the part 10 of the housing. The inlet communicates with the inlet port 30 by way of a passage 29 also formed in the part 37. The part 37 has mounted therein a tubular filter element 32 and a relief valve which includes a spring loaded element 33.

One end of the element 33 is exposed to the pressure of fuel delivered by the feed pump and it controls the size of a spill port 34. The arrangement is such that the feed pump always pumps more fuel than is delivered to the engine with the result that the output pressure of the feed pump is controlled in a manner which is dependent upon the speed of the engine and which increases with the speed thereof.

As previously mentioned the cam ring 17 is angularly adjustable so that the timing of delivery of fuel to the engine can be varied.

This adjustment is achieved by a spring loaded piston 35 mounted in a cylinder 36.

The piston is connected to the cam ring by means of a pin or peg 37 which is in screw thread engagement with the cam ring. Fuel is supplied to one end of the cylinder 36 to move the piston ip opposition to its spring, from the outlet of the feed pump and since the pressure of fuel is dependent upon the speed of rotation of the engine, the angular setting of the cam ring and hence the timing of injection of fuel to the engine is also dependent upon the speed of the engine.

The piston 35 defines with the wall of the cylinder 36 a leakage path so that fuel can leak from the cylinder and a check valve 38 is incorporated in the supply passage and this closes to prevent fuel passing from the cylinder to the supply passage due to the reaction of the rollers 16 with the cam lobes.

As will be observed the cylinder 36 is formed in a body 8 which is secured to the housing part 9 by means of a pair of bolts 7, 6.

The angular setting of the valve member 28 is conveniently controlled by a mechanic- al governor which includes weights 39 accommodated in a cage driven by the shaft 12. The weights act upon an axially movable flanged collar 40 mounted about the drive shaft 12, and the axial movement of the collar is resisted by a governor spring 41 which is mounted between one end of a pivotal lever 42 and an operator adjustable member 43. The other end of the lever 42 engages the collar 40.Furthermore, said one end of the lever 42 is connected by a tie rod 44 to the valve meniber 28 and the arrangement is such that as the speed of rotation of the engine increases the collar 40 will be moved axially by the weights against the action of the governor spring and during this movement the member 28 will be moved angularly to reduce the quantity of fuel delivered to the engine.

In such pumps it is usual to provide for limited retraction of the plungers at the end of the delivery of fuel to permit rapid closure of the valve in the fuel injection nozzle which has just been supplied with fuel. The retraction of the plungers also lowers the pressure in the pipe line connecting the outlet to the nozzle by a predetermined amount, it being appreciated that the outlets 20 will in practice be provided with non-return delivery valves. These valves act to trap the fuel in the pipe lines at the lower predetermined pressure.

Figure 4 shows at 45 the cam lobe profile.

The rollers 16 are effectively moving in the direction of the arrow 46 and as the roller engages the cam lobe inward movement of the respective plunger will occur until the crest ot the cam lobe is reached. As will be seen from Figure 4 the cam lobe then is shaped to permit a limited return movement of the roller this resulting in limited outward movement of the respective plunger and it is during this period that the relief of the fuel pressure takes place as described. It will be appreciated that Figure 4 is appropriate to the modification and therefore the period during which the roller is held against further outward movement is short. In the known form of apparatus this period would be longer and the extend of outward movement would also be greater.

Turning now to Figure 2 the cam ring is shown at 17a. Moreover. there are two pairs of plungers and for convenience these are referenced 15a and 15b. The two sets of plungers are located within transversely extending bores disposed at 900 and the outer ends of the plungers are contacted by shoes supporting the rollers 16 which engage with the cam lobes. The cam ring is provided with two pairs of cam lobes one pair being referenced 45 and the other pair being referenced 47. The cam lobes 45 are diametrically disposed and their shape is as seen in Figure 4. These cam lobes are the lobes which effect delivery of fuel as explained above.The other lobes 47 have a profile as indicated in Figure 4 and it will be noted that the lobes occupy a greater arcuate distance than the lobes 45 and what is particularly important is the fact that the crests of the lobes 47 are flat so that during the delivery of fuel which is effected by the lobes 45, no movement of the plungers the rollers 16 of which are engaging the lobes 47 takes place. However, the lobes 47 are shaped to permit limited outward movement of the plungers in the same manner as the lobes 45. Therefore at the end of the delivery of fuel all four plungers can move outwardly a limited amount so that only half the outward movement of the plungers is required as compared with the prior art pump and furthermore, the period during which retraction takes place considered in terms of arcuate distance, is shorter.If we consider the arrangement shown in Figure 2 then it will be seen that the plungers 15a have just been moved inwardly to deliver fuel. The plungers 15b however have been held against movement during the delivery of fuel but as the distributor member rotates in the clockwise direction as seen in Figure 2, all four plungers will move outwardly to cause the rapid reduction of fuel pressure to achieve rapid closure of the valve of the associated fuel injection nozzle. As the distributor member continues to rotate and as best seen in Figure 4, the rollers 16 move off the plateau provided for the purpose of retraction, however at this time the delivery passage is still in communication with an outlet. Because of the delivery valves however no further flow of fuel from the pipe lines takes place.When the delivery passage 19 moves out of register with the outlet port 20 and an inlet passage 22 moves into register with the inlet port 23, flow of fuel can take place and the plungers 15b will be moved outwardly by the fuel which is flowing from the outlet of the feed pump. It should be noted however that during this time the plungers lSa are being moved inwardly and there will be a small transfer of fuel between the respective bores. The cam profile 47 is such that the inward movement of the plungers 15a is completed before the inlet passage 22 moves out of register with the inlet port 23. During the continued rotation of the distributor member it is the plungers 15b which deliver fuel with the plungers 15a acting only during the retraction period.Thus it will be seen that two pairs of plungers deliver fuel in turn to an outlet but as mentioned. all the plungers operate during the retraction period. As a result the retraction period occupies less of the arcuate spacing between the cam lobes to permit more time for the filling of the bores containing the plungers from the outlet of the feed pump.

The arrangement shown in Figure 3 is for supplying fuel to a six cylinder engine. In this case it will be seen that there are six cam lobes on the cam ring 17b. These lobes are equi-angularly spaced about the cam ring and have the profile of the lobes 45 and 47 of Figure 4. Moreover, it will be noted that they are again alternately spaced so that a lobe 45 will be diametrically opposite a lobe 47. Two pair of plungers are again provided and are disposed in transversely extending bores. In this case however the bores are not disposed at right angles to each other but are spaced at angles of 120/60 . With this spacing therefore two angularly adjacent plungers will effect pumping of the fuel, the other two plungers being operative only for the purpose of retraction.As the distributor member rotates the aforesaid other pair of plungers will effect delivery of fuel and the one pair of plungers will be operative only during the retraction period.

WHAT WE CLAIM IS: 1. A fuel injection pumping apparatus for supplying fuel to an internal combustion engine and comprising a housing, a rotary distributor member journalled in the housing and which in use is driven in synchronism with the associated engine, a pair of bores formed in the distributor member, a pair of plungers in said bores respectively, a cam ring defining a pair of cam lobes for imparting inward movement to the plungers as the distributor member rotates, a delivery passage communicating with said bores, a plurality of outlets in the housing and with which the delivery passage registers in turn as the distributor member rotates and during the time when the plungers are moving inwardly, said cam lobes being shaped so that at the end of the inward movement of the plungers limited outward movement of the plungers is allowed to permit a predetermined volume of fuel to be returned through the respective outlet, a further pair of plungers and a further pair of cam lobes, said further pair of plungers being housed in bores respectively communicating with said delivery passage and the further pair of plungers and the further cam lobes being positioned so that they co-operate with each other at the same time as the first mentioned plungers and cam lobes are cooperating with each other to effect delivery of fuel. said further pair of cam lobes being so shaped that no movement is imparted to the further plungers during the period of inward movement of the first mentioned plungers, said further cam lobes being shaped to permit limited outward movement of the further pair of plungers when the limited outward movement of the first mentioned pair of plungers takes place.

2. An apparatus according to claim 1 including inlet port means in the distributor member and housing and through which fuel is supplied to said bores. said further cam lobes being shaped so that inward movement of the further pair of plungers to the position occupied during delivery of fuel through the outlet. takes place whilst said inlet port means is capable of supplying fuel to tbe bores.

3. An apparatus according to claim 2 in which said inlet port means comprises an inlet port in the housing and a plurality of inlet passages in the distributor member.

4. An apparatus according to anyone of the preceding claims in which said first mentioned plungers and said further plungers effect delivery of fuel alternately to an outlet.

5. An apparatus according to anyone of the preceding claims in which said cam lobes and said further cam lobes are alternately positioned about said cam ring.

6. A liquid fuel pumping apparatus for supplying fuel to an internal combustion engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to Figures 1, 2 and 4 of the accompanying drawings.

7. A liquid fuel pumping apparatus for supplying fuel to an interal combustion engine comprising-the combination and arrangement of parts substantially as hereinbefore described with reference to Figures 1, 3 and 4 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. of Figure 4. Moreover, it will be noted that they are again alternately spaced so that a lobe 45 will be diametrically opposite a lobe 47. Two pair of plungers are again provided and are disposed in transversely extending bores. In this case however the bores are not disposed at right angles to each other but are spaced at angles of 120/60 . With this spacing therefore two angularly adjacent plungers will effect pumping of the fuel, the other two plungers being operative only for the purpose of retraction. As the distributor member rotates the aforesaid other pair of plungers will effect delivery of fuel and the one pair of plungers will be operative only during the retraction period. WHAT WE CLAIM IS:

1. A fuel injection pumping apparatus for supplying fuel to an internal combustion engine and comprising a housing, a rotary distributor member journalled in the housing and which in use is driven in synchronism with the associated engine, a pair of bores formed in the distributor member, a pair of plungers in said bores respectively, a cam ring defining a pair of cam lobes for imparting inward movement to the plungers as the distributor member rotates, a delivery passage communicating with said bores, a plurality of outlets in the housing and with which the delivery passage registers in turn as the distributor member rotates and during the time when the plungers are moving inwardly, said cam lobes being shaped so that at the end of the inward movement of the plungers limited outward movement of the plungers is allowed to permit a predetermined volume of fuel to be returned through the respective outlet, a further pair of plungers and a further pair of cam lobes, said further pair of plungers being housed in bores respectively communicating with said delivery passage and the further pair of plungers and the further cam lobes being positioned so that they co-operate with each other at the same time as the first mentioned plungers and cam lobes are cooperating with each other to effect delivery of fuel. said further pair of cam lobes being so shaped that no movement is imparted to the further plungers during the period of inward movement of the first mentioned plungers, said further cam lobes being shaped to permit limited outward movement of the further pair of plungers when the limited outward movement of the first mentioned pair of plungers takes place.