GB2132705A

GB2132705A - Fuel injection pumps

Info

Publication number: GB2132705A
Application number: GB08330456A
Authority: GB
Inventors: William Robert Burborough
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1982-12-21
Filing date: 1983-11-15
Publication date: 1984-07-11
Also published as: FR2538033A1; ES528193A0; IT1169148B; GB8330456D0; IT8323955A0; US4512727A; JPS59119057A; GB2132705B; DE3344749A1; ES8501058A1; FR2538033B1

Description

1

SPECIFICATION

Fuel injection pumps This invention relatesto fuel injection pumps of the rotary distributortype for supplying fuel to compress ion ignition enginesthe pumps comprising a body part, a rotary distributor member in the body part, the distributor member being arranged in useto be driven in timed relationship with an associated engine, a radial bore in the distributor member and a plunger slidable therein, a cam follower atthe outer end of the plunger, an annularcam ring mounted in the body, said cam ring having a cam lobe on its internal peripheral surface whereby as the distributor member 80 rotates inward movementwill be imparted to the plunger, a delivery passage in the distributor member and an outlet port in the body, said delivery passage being positioned to registerwith said outlet port to receivefuei displaced from the bore bythe inward 85 movement of the plunger, an inlet passage in the distributor member, said inlet passage communicat ing with said bore, an inlet port in the body, said inlet passage communicating with said inlet portto allow fuel flowto said bore during the time the plunger is 90 permitted to move outwardly bythe cam lobe, a lobe pressure pump forsupplying fuel to said inlet port, throttle means for controlling the quantity of fuel supplied to said bore and a stop plate mounted in the body, said stop plate defining a stop surface engage- 95 able bythe cam followerto control the maximum allowed outward movement of the plunger.

With the above type of pump the stop plate serves as the maximumfuel stop and therefore actsto determine the maximum amount of fuel which can be 100 supplied by the pump to the associated engine irrespective of the setting of said throttle means. In orderto start certain types of engine it is necessary to supply an amount of fuel in excess of the normal maximum amount. The radial dimension of the stop surface of the stop plate varies throughout its length and thereforethe angular setting of the stop surface abouttheaxis of rotation of the distributor member determinesthe outward movement of the plunger which takes place before closure of the inlet port. The stop plate is angularly adjustable to allow adjustment of the maximum fuel quantitywhen the pump is manufactured and it is possibleto arrange for such movementto take place when it is required to startthe associated engine. Howeverthe mechanism which is required to achieve such adjustment is complex and must be of a robust nature in orderto withstand the stresses imposed upon it during the use of the pump.

The object of the present invention is to provide a pump of the kind specified in a simple and convenient form.

According to the invention in a pump of the kind specified said stop surface has a radial dimension which varies throughoutthe length of the surface, the pump further comprising an additional inlet port formed in the body, said additional inlet port being positioned to registerwith said inlet passage or a further such passage at least afterthe communication of the first mentioned inlet portwith the inlet passage has been broken and valve means for controlling fuel 130 GB 2 132 705 A 1 flowthrough said additional inlet port.

An example of a fuel injection pump in accordance with the invention will now be described with referenceto the accompnaying drawings in which:Figure 1 is a sectional side elevation of the pump, Figure 2 is a cross section through part of the pump seen in Figure 1, and Figure 3 is a diagram showing the shape of parts of the apparatus of Figure 1 and also thetiming diagram.

Referring to the drawingsthe pump comprises a body 10 in which isformed a bore carrying a rotary cylindrical distributor member 11. The distributor member is coupled to an input shaft 13which extends from the body part and which is adapted to be driven in timed relationship with an engine with which the pump is associated. Formed within an enlarged portion 12 of the distributor member is a transverse bore 14 in which is mounted a pair of reciprocable plungers 15 which are arranged to be moved inwardly as the distributor member rotates, through the intermediary of cam followers respectively, by cam lobes formed on the internal peripheral surface of an annularcam ring 18which is mounted for angular adjustment within the body. The profile of a single cam lobe of the cam ring is seen at29 in Figure 3. Each cam follower includes a shoe 16 and a roller 17 and the followers are located in slots respectively formed in a part 19 driven bythe inputshaft.

Also formed in the distributor member 11 is a longitudinally extending passage 21 which at one end is in communication with the bore 14 and at its other end is in communication with a radially disposed delivery passage 22. The delivery passage 22 is arranged to register in turn with a plurality of equiangularly spaced outlet ports 23 which in use, are connected by pipelines respectivelyto injection nozzles mounted on the associated engine. The aforesaid registration of the passage 22with one of the outlet portstakes place during thewholetimethe plungers 15 are being moved inwardlysothat liquid fuel contained in the bore 14will be displaced to a combustion space of the engine.

At another pointthe longitudinal passage 21 is in communication with a plurality of equi-angularly spaced and radially disposed inlet passages 24. The passages 24 are arranged to register in turn with an inlet port 25 which isformed in the body. In practice in orderto facilitate filling of the bore 14, two inlet ports 25 are provided these being angularly spaced by an amount equal to the angularspacing of the inlet passengers 24which in the case of a pump for supplying fuel to a four cylinder engine is 90.

The inlet ports 25 communicate byway of a passage 25A, with a throttle device 26 the setting of which is controlled by a speed responsive governor. The device 26 communicates with the outlet 27 of a low pressure supply pump 27A having an inlet 28, the supply pump being located in the body 10 of the pump. The arrangement is such that when the inlet passages 24 register with the inlet ports,fuel will flow from the outlet of the low pressure pump to the transverse bore 14to effect outward movement of the plungers. The aforesaid registration takes place only during the time when the delivery passage 22 is out of registerwith an outlet port 23 and du ring the time 2 GB 2 132 705 A 2 when the rollers 17 are clear of the cam lobes. By adjusting the setting of the device 26, the rate atwhich fuel canflowtothe bore 14can be controlled and hence also the amount of fuel delivered to the engine.

In orderto control the maximum amountof fuel which can be supplied bythe pump to the associated engine, a pairof stop plates 29 are positioned on the opposite sides of the cam ring 18. The stop plates 29 are interconnected by a bridge member 30 on which is mounted an actuating peg 31 connected to an adjustment device not shown. The stop plates 29 define, as will be seen in Figure 3, stop surfaces which are referenced 48, having a radial dimension which in fact increases in the direction of rotation of the distributor member, the direction of rotation being indicated bythe arrow 49. The stop plates are angularly adjustable relativeto the body and will be adjusted when the pump is manufactured so that a particular pump will be unable to supply more than a predetermined amount of fuel irrespective of the setting of the throttle device 26.

In Figure 3 abovethe diagram of the cam lobe 29 and the stop surface 48 is a representation of the periods during which the delivery passage is open to an outlet port 23 and the inlet passages 24 are open to the inlet ports 25. The delivery passage 22 is open to an inlet port 23 during the period which is references A and the inlet ports and passages are in communication with each other during the period referenced B. Sincethe position of the inlet ports 25 isfixed in the bodythe angular setting of the stop plates 29 determinesthe maximum amount of fuel which can be supplied to the associated engine.

Turning now particularly to Figure 2, an additional inlet port 50 is provided in the body and this opens onto the periphery of the distributor member at a position to communicate with an inlet passage 24 at least afterthe communication of the inlet passages 24 and the inlet ports 25 has ceased. In the example illustrated, the additional port 50 communicates with an inlet passage 24 before the communication of the inlet ports 25 and the passages 24 is broken. The port 50 communicates with the passage 25A by way of a valve generally indicated at 51 and which comprises a spool 52 which is biased by a coiled compression spring to a position in which fuel flow can take place to the additional port 50. The spool is biased to the closed position by means of fuel under pressure derived from the outlet of the low pressure pump. Figure 3 shows the period during which the additional port 50 is in communication with an inlet passage 24, this period being referenced C. It will be noted f rom Figure 3, that the stop surface defines a step 53 which coincides with the period during which the additional inlet port is open to an inlet passage 24 and as a resultwhen the spool is inthe open position, the plungers can move outwardly an additional amount, this additional amount corresponding to the extra amount of fuel required for starting purposes.

Itwill be appreciated thatthe additional flow of fuel takes place by way of the throttle device 26. However, thiswhen attempting to startthe engine wi!; be at its maximum setting due to the action of the governor. When the associated engine starts,the outlet pressure of the low pressure pump will increase and the spool will move againstthe action of its spring to the closed position sothatthe supply of additional fuel ceases. It is preferred howeverto control the spool by an additional valve and to arrange thatthe spoof can be moved to the closed position at a pressure which is below the minimum pressure which may be developed bythe low pressure pump during operation of the engine. The additional valve will be of the latched varietyto ensure thatthe spool cannot moveto the

Claims

open position exceptwhen the engine is at rest. It may be desirableto arrange thatthe additional valve is also responsibleto engine temperature. CLAIMS

1. Afuel injection pump of the rotary distributor type comprising a body part, a rotary distributor member in the body part, the distributor member being arranged in use to be driven in timed relationship with an associated engine, a radial bore in the distributor memberand a plumger slidable therein, a cam follower atthe outer end of the plunger, an annular cam ring mounted in the body, said cam rihg having a cam lobe on its internal peripheral surface whereby asthe distributor member rotates inward movementwill be imparted to the plunger, a delivery passage in the distributor member and an outlet port in the body, said delivery passage being positioned to registerwith said outlet portto receivefuel displaced from the bore bythe inward movement of the plunger, an inlet passage in the distributor member, said inlet passage communicating with said bore, an inlet port in the body, said inlet passage communicating with said inlet portto allowfuel flowto said bore during the timethe plunger is permitted to move outwardly by the cam lobe, a low pressure pump for supplying fuel to said inlet port, throttle meansfor controlling the quantity of fuel supplied to said bore, a stop plate mounted in the body, said stop plate defining a stop surface engageable bythe cam followerto control the maximum allowed outward movement of the plunger, said stop surface having a radial dimension which varies throughoutthe length of the surface, the pump further comprising an additional inlet portformed in the body, said additional inlet port being positioned to registerwith said inlet passage or a further such passage at least afterthe communication of the first mentioned inlet portwith the inlet passage has been broken and valve means for controlling fuel flow through said additional inlet port.

2. A pump according to Claim 1 in which the radial dimension of said stop surface increases in the direction of rotation of the distributor member.

3. A pump according to Claim 2 in which said valve means is responsive to the outlet pressure of said low pressure pump.

4. Afuel injection pump for supplying fuel to a compression ignition engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to the accompanying drawings.

Printed for Her Majesty's Stationery Office by-TheTweeddale Press Ltd., Berwick-upon-Tweed, 1984. Published atthe Patent Office, 25 Southampton Buildings, London WC2A lAY, from which copies mayheobtained.