GB2149023A - Fuel injection pumps - Google Patents

Abstract

A fuel injection pump includes an axially movable rotary distributor member 11 having a recess 15 communicating with a bore 12 containing a pump plunger 13 actuable by cam lobes on a cam ring 23 which is angularly adjustable to control the timing of fuel delivery. The recess has leading and trailing edges which are mutually inclined and registers alternately with a fuel inlet port 17 and an outlet 16. Axial movement of the distributor is effected by a governor including weights 35, a lever 31 and a spring 33. If the cam is moved angularly to vary the timing of delivery the fuel quantity will vary and this is corrected by moving the pivot point of the lever 31 in the governor. The pivot point is defined by a pin 32 which engages a cam profile 23A on the cam. <IMAGE>

Description

SPECIFICATION Fuel injection pumps This invention relates to rotary distributor type fuel injection pumps for supplying fuel to a multicylinder internal combustion engine and of the kind comprising a rotary distributor member housed in a body, a plunger mounted in a transverse bore in the distributor member, an angularly adjustable multi-lobed cam mounted in the body and arranged to impart inward movement to the plunger as the distributor member rotates, passage means in the distributor member of delivering fuel displaced from the bore to angularly spaced outlet ports in turn and means for varying the amount of fuel delivered by the pump through said outlets.

A known way of varying the amount of fuel delivered by the pump through the aforesaid outlets, is to arrange for the bore to be completely filled with fuel before inward movement of the plunger takes place and during the inward movement of the plunger to spill some of the fuel from the bore so that only a proportion of the total quantity of fuel displaced from the bore flows through an outlet. This spillage of fuel can be effected by an axially movable spill muff mounted on the distributor member. A disadvantage of this construction is that the provision of a spill muff requires that the distributor member should be extended in length, the spill muff being mounted upon an unsupported portion of the distributor member.An- alternative construction is to mount the distributor member for axial movement in the body and an example of this form of pump is described in British published application 2091 351A.

With such a pump when it is required to vary the timing of fuel delivery, the cam is moved angularly but this also influences the quantity of fuel delivered by the pump and in order to maintain the delivered quantity of fuel constant, axial adjustment of the setting of the distributor member using a fuel control linkage responsive to the angular setting of the cam is required. The illustration of the pump in the aforementioned application is diagrammatic and in practice the design, assembly and the adjustment of the linkage presents considerable difficulty.

The object of the present invention is to provide a pump of the kind disclosed in published application 2091351A in a simple and convenient form.

According to the invention in a pump of the kind specified said distributor member is axially movable and said passage means opens into a recess on the periphery of the distributor member, said recess having a leading and trailing edge in relation to the direction of rotation of the distributor member, said edges being mutually inclined, the pump including a plurality of inlet ports which are alternately arranged with said outlet ports. said recess registering with said ports as the distributor member rotates a source of fuel under pressure connected to said inlet ports, a cupshaped drive member surrounding the portion of the distributor member containing the bore, said drive member being connected to a drive shaft and defining an axially extending radial slot in which is located a cam follower associated with said plunger, means for driving said distributor member from said drive member, a thrust member located within said drive member, axially extending pins in the base wall of said drive member, said pins acting to transmit axial movement to the thrust member and the distributor member from an axially movable sleeve mounted on the drive shaft, thereby to vary the amount of fuel delivered through said outlet ports, a lever having one end engaged with said sleeve and its other and coupled to a governor spring, a pivot for said lever and speed responsive means acting to urge the sleeve against the action of the resilient means, said pivot comprising pin means mounted in the body and engageable with a cam profile on said cam whereby as the cam is moved angularly to vary the timing of fuel delivery, the pivot of the lever will be adjusted to maintain the quantity of fuel delivered substantially constant.

Examples of fuel pump in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a diagrammatic sectional side elevation of one form of the apparatus, Figure 2 is a section on the line A-A of Fig.

1, Figure 3 is a developed view of a portion of the pump seen in Fig. 1, Figures 4 and 5 are perspective views of parts of the pump shown in Figs. 1 and 2, but removed from the pump, and Figures 6, 7 and 8 are views similar to Figs. 1, 4 and 5 respectively showing another form of apparatus.

Referring to Figs. 1-5 of the drawings, the pump comprises a body 10 in which is mounted a rotary cylindrical distributor member 11. The distributor member is axially movable within the body and has formed therein a transverse bore 1 2 in which is mounted a pair of pumping plungers 1 3. The bore containing the plungers communicates with a passage 14 formed in the distributor member and which opens into a recess 1 5 formed in the periphery of the distributor member. The shape of the recess will be described with reference to Fig. 3 in due course. Also formed in the body 10 are a plurality of outlet ports 1 6 only one of which is illustrated.The outlet ports are equiangularly spaced about the axis of rotation of the distributor member and in use are connected to the fuel injection nozzles respectively of the associated engine. Alternately arranged with the outlets 1 6 are inlet ports 17, these lying in the same radial plane as the outlet ports.

The ports 1 7 are connected to a source of fuel 1 8 under pressure.

The recess 1 5 is movable in relation to the ports in the direction of the arrow indicated in Fig. 3 and it has a leading edge 1 9 and a trailing edge 20. The two edges are mutually inclined and the edge 20 in the particular example extends parallel to the axis of rotation of the distributor member.

In order to effect inward movement of the plungers 13 cam followers 21 are provided, each follower comprising a shoe portion and a roller. The shoe portion is in engagement with the outer end of the respective plunger and the roller is arranged to engage with cam lobes 22 formed on the internal surface of an annular cam ring 23 which is mounted within the body and is angularly adjustable therein.

In the particular example the pump is intended to supply fuel to a four cylinder engine and hence four outlet ports 16. four inlet ports 1 7 and four equiangularly spaced cam lobes 22 are provided. The cam followers are driven by a cup-shaped drive member 24 which is mounted at the end of a drive shaft 25 arranged in use to be driven in timed relationship with the associated engine. The skirt of the cup shaped drive member 24 defines a pair of slots in which are located the cam followers respectively. Moreover, mounted on the distributor member are a pair of plates 26 which extend into the slots in the skirt of the drive member so that that distributor member is driven by the drive member but at the same time, is capable of relative axial movement.

In order to effect axial adjustment of the distributor member there is located within the cup-shaped drive member 24, a thrust member 27 which is of annular form and which conveniently has a uniform thickness skirt portion 28 extending therefrom, the skirt portion locating within the skirt portion of the drive member. The thrust member is engaged by a pair of pins 29 which extend through the base wall of the drive member 24 and at their outer ends, the pins 29 engage an axially movable sleeve 30 mounted above the drive shaft 25.The skirt portion 28 associated with the thrust member 27, is provided with a pair of slots complementary to the slots in the skirt portion of the drive member and the side walls of the shoes 21 as shown in Fig. 4, are provided with steps 31 respectively which can engage with the internal surface of the skirt portion 28 to limit the extent of outward movement of the plungers.

The sleeve 30 engages one end of a lever 31 the pivot for which is defined by a pin 32 slidably mounted in the body 10. The other end of the lever 31 is coupled to resilient means in the form of a coiled tension spring 33 the other end of which is connected to a manually adjustable lever 34. The sleeve 30 is movable against the action of the spring 33 by means of a speed responsive mechanism in the form of a plurality of centrifugal weights 35 housed within a cage 36 coupled to and driven by the drive shaft 25.

The end of the pin 32 remote from the lever 31 engages with a cam profile 23A defined on the side wall of the cam 23 and this profile is such that as the cam 23 is moved angularly to vary the timing of delivery of fuel, axial adjustment of the pin 32 will take place so that the pivot point for the lever 31 changes.

The operation of the pump will now be described. The plungers as shown in Fig. 2, have just completed their inward movement and as shown in Fig. 3, the recess 1 5 has just moved out of register with an outlet 1 6 but is in full register with an inlet port 1 7. As the distributor member continues to rotate, the plungers are allowed to move outwardly by the cam lobes and fuel is supplied to the bore 1 2 by way of the recess 1 5 and the passage 14, the fuel flowing through one of the inlet ports 1 7. The maximum outward movement of the plungers is limited by the abutment of the step 31 with the skirt portion 28.As continued rotation of the distributor member takes place, the leading edge 1 9 of the recess moves into register with an outlet 1 6 and the trailing edge 20 of the recess starts to cover the previously uncovered inlet port 1 7. As soon as this takes place the plungers start to move inwardly and fuel is delivered to the outlet 1 6 which is now uncovered to the recess. The flow of fuel continues until the leading edge 1 9 uncovers the next inlet port 1 7 and as soon as this port is uncovered the fuel displaced by the plungers flows to the source 1 8 rather than through an outlet 1 6.

The amount of fuel displaced can be adjusted by altering the axial position of the distributor member and if the distributor member is moved towards the right the quantity of fuel delivered will be reduced and vice versa.

The spring 33 in conjunction with the weights 35 acts as a normal mechanical governor and as the speed increases, the distributor member will be moved towards the right to decrease the amount of fuel delivered.

Angular adjustment of the cam 23 to vary the timing of delivery of fuel will have an influence upon the quantity of fuel delivered to the engine for a given axial setting of the distributor member. For example, if the cam is moved to retard the timing of fuel delivery, the fuel quantity will bye reduced since the plunger will start to move inwardly later during the time an outlet 1 6 is exposed to the recess. This variation in the quantity of fuel delivered is compensated for by movement of the pin 32 by the cam profile 23A on the side wall of the cam 23.

The distributor member is returned towards the left as shown in Fig. 1 by the action of a light spring (not shown) acting upon the right hand end of the distributor member.

The form of pump shown in Figs. 6-8 inclusive, is substantially the same as the pump shown in the earlier figures. The exception however is the fact that the thrust member 27 of Fig. 1 is formed separately from the skirt portion 28. In Fig. 6 the thrust member is indicated at 38 and is again interposed between the pins 29 and the distributor member. The equivalent of the skirt portion 28 is provided but in this case it is formed as a separate part 39 axially fixed within the drive member 24. The skirt portion again has slots to accommodate the plungers but its internal peripheral surface tapers outwardly away from the drive shaft. In like manner, the stop surfaces 40 formed on the cam followers 21 are similarly shaped so that as the distributor member is moved towards the right as shown in the drawings, the plungers will be allowed to move further in the outwards direction.

The practical effect of the above modification is to cause as the quantity of fuel delivered by the pump is reduced, advancement of the timing of fuel delivery. This is achieved owing to the fact that in order to reduce the quantity of fuel delivered by the apparatus, the distributor member is moved towards the right as shown in the drawings. Such movement however by virtue of the inclination of the steps 40 and the internal surface of the skirt portion 39, results in further outward movement of the plungers so that the plungers will start to move inwardly earlier during the cycle of operation.

It is also possible to determine the initial rate of fuel delivery. In the form of pump shown in Fig. 1 the thickness of the skirt portion 28 can be chosen so that the plungers always engage the cam lobes at a particular point on their profile. This point may be where the cam rate is constant or it may be where it is rising to the constant value. In the case of the example shown in Fig. 6, by suitable shaping of the stop surfaces and suitable positioning of the cam lobes, the initial rate of fuel delivery can be made to vary as the quantity of fuel delivered is varied.

In the example of Fig. 6, as with the example of Fig. 1, adjustment of timing by moving the cam ring 23 angularly, will by virtue of the movement of the pivot pin 32, result in substantially no variation in the quantity of fuel delivered by the pump.

Torque control can be obtained in one of two ways the first of which is to shape one or both of the edges 19, 20 of the recess 1 5 and the second of which is to modify the profile of the cam 23A.

Claims (3)

1. A rotary distributor type fuel injection pump for supplying fuel to a multi-cylinder internal combustion engine and of the kind comprising a rotary and axially movable distributor member housed in a body, a plunger mounted in a transverse bore in the distributor member, an angularly adjustable multi-lobed cam mounted in the body and arranged to impart inward movement to the plunger as the distributor member rotates, passage means in the distributor member for delivering fuel displaced from the bore to angularly spaced outlet ports in turn, a recess on the periphery of the distributor member, said passage means opening into said recess, said recess having a leading and trailing edge in relation to the direction of rotation of the distributor member, said edges being mutually inclined, the pump including a plurality of inlet ports which are alternately arranged with said outlet ports, said recess registering with said ports as the distributor member rotates, a source of fuel under pressure connected to said inlet ports, a cup-shaped drive member surrounding the portion of the distributor member containing the bore, said drive member being connected to a drive shaft and defining an axially extending radial slot in which is located a cam follower associated with said plunger, means for driving said distributor member from said drive member, a thrust member located within said drive member, axially extending pins in the base wall of said drive member, said pins acting to transmit axial movement to the thrust member and the distributor member from an axially movable sleeve mounted on the drive shaft, thereby to vary the amount of fuel delivered through said outlet ports, a lever having one end engaged with said sleeve and its other end coupled to a governor spring, a pivot for said lever and speed responsive means acting to urge the sleeve against the action of the resilient means, said pivot comprising pin means mounted in the body and engageable with a cam profile on said cam whereby as the cam is moved angularly to vary the timing of fuel delivery, the pivot of the lever will be adjusted to maintain the quantity of fuel delivered substantially constant.

2. A pump according to Claim 1 including means for varying the extent of outward movement of the plunger as the distributor member is moved axially, the arrangement being such that as the distributor member is moved axially to vary the amount of fuel delivered the timing of fuel delivery will be varied.

3. A rotary distributor type fuel injection pump for supplying fuel to a multi-cylinder internal combustion engine comprising the combination and arrangement of parts substantially as hereinbefore described with reference to the accompanying drawings.