GB2230823A - Fuel injection pumping apparatus - Google Patents

Abstract

A fuel injection pumping apparatus of the rotary distributor type has a transverse bore 16 in which is mounted a pair of pumping plungers 17, 18. Extending into the bore is a pair of spill passages 30, 27, the passage 30 being covered by the inner end of the plunger 18 during the initial inward movement of the plunger and the passage 27 communicating with a groove 26 on the plunger 18 which is brought into communication with the pumping chamber defined between the plungers after a predetermined inward movement of the plungers. The groove 26 has an inclined control edge 28 and the angular setting of the plunger 18 in the bore is adjustable to determine the amount of fuel supplied to an associated engine. <IMAGE>

Description

FUEL INJECTION PUMPING APPARATUS This invention relates to rotary distributor type fuel injection pumping apparatus for supplying fuel to a compression ignition engine, the apparatus comprising a rotary distributor member mounted in a body and arranged in use to be driven in timed relationship with an associated engine, a transverse bore formed in the distributor member and a pair of pumping plungers slidable therein, an annular cam surrounding the distributor member, the cam having pairs of equiangularly spaced inwardly directed cam lobes which impart inward movement to the plungers as the distributor member rotates, means for feeding fuel to the pumping chamber defined between the plungers while the plungers are allowed to move outwardly and means for conveying fuel displaced from the pumping chamber to a plurality of outlet ports in turn, the outlet ports in use being connected to the fuel injection nozzles respectively of the associated engine.

With such apparatus cam followers including rollers are located at the outer ends of the plungers and the rollers engage the cam lobes. The termination of delivery of fuel occurs when the rollers move over the crests of the cam lobes and the rate of termination of fuel delivery is determined by the size of the rollers and the curvature cf the crests of the cam lobes. The rapidity of the termination of fuel delivery depends upon the radius of curvature of the cam lobes and the radii of the rollers and in order to increase the rate of termination of delivery the aforesaid radii must be decreased. However, reducing the radii increases the stress in the material forming the cam lobes and the rollers. Furthermore, if it is required to increase the delivery pressure, the stress in the material forming the cam lobes and the rollers will be increased.

The object of the present invention is to provide an apparatus of the aforesaid kind in a simple and convenient form.

According to the invention in an apparatus of the kind specified one of said plungers is angularly adjustable within the bore and said one plunger defines a first control edge which covers a spill path from said pumping chamber during the initial inward movement of the plungers thereby to cause fuel to be delivered through an outlet and a second control edge on the one plunger which opens a spill path from the pumping chamber after a predetermined inward movement of the plungers, the extent of said predetermined inward movement depending upon the angular setting of said one plunger within the bore.

Examples of fuel pumping apparatus in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a sectional side elevation showing part of the apparatus, Figure 2 is a cross section on the line AA of Figure 1, Figure 3 is a section on the line BB of Figure 2, Figure 4 is a view similar to Figure 1 showing a modification, and Figure 5 is a view similar to Figure- 2 taken on the line AA of Figure 4.

Referring to Figures 1 - 3 inclusive of the drawings the apparatus comprises a body 10 in which is located a rotary cylindrical distributor member 11. The distributor member has an enlarged head 12 adjacent one end thereof and this end of the distributor member is coupled to a cup-shaped member 13 the skirt of which surrounds the distributor member, the cup-shaped member 13 being formed integrally with a drive shaft 14 which in use, is driven in timed relationship with the associated engine.

Formed in the distributor member is a pair of diametrically disposed bores 15, 16 which are disposed as clearly seen in Figure 2, at right angles to each other.

Located in the bores 15, 16 are pumping plungers 17 three of which as seen in Figure 2, are of conventional construction. A fourth plunger 18 is located in the bore 16 and this particular plunger is of special construction as will be described.

At the outer ends of the plungers are located cam followers each of which comprises a shoe which is in engagement with the outer end of the plunger and a roller which is located within a groove formed in the shoe. As clearly shown in Figure 2, the cam followers 19 are located in slots 20 formed in the skirt portion of the cup-shaped member 13.

The rollers engage the internal peripheral surface of an annular cam ring 21 on the internal peripheral surface of which are formed at least two pairs of cam lobes which are equiangularly spaced relative to each other. In this manner as the distributor member 11 rotates, the cam followers are moved inwardly at the same time by the cam lobes and inward movement is imparted to the plungers.

The space between the plungers constitutes a pumping chamber to which is connected one end of a longitudinal passage 21A formed in the distributor member and which at one point communicates with a radially disposed delivery passage 22. The delivery passage is positioned to register in turn with a plurality of outlet ports 23 which in use are connected to the injection nozzles of the associated engine.

Also communicating with the passage 21A is an inlet passage 24 which is positioned to register in turn with a plurality of inlet ports 25 formed in the body 10 and connected to a source of fuel under pressure such as a vane type pump the rotary part of which is coupled to the distributor member. The registration of the delivery passage 22 with an outlet port 23 takes place during the whole time the plungers are moved inwardly by the cam lobes and the registration of the inlet passage 24 with an inlet port 25 takes place during the time when the plungers are allowed to move outwardly.

The plunger 18 as clearly seen in Figure 2, is of increased length as compared with the plungers 17 and it has formed on its inner end portion a flat 26A whereby constant communication is assured between the pumping chamber and the passage 21A. Also formed on the plunger 18 is a groove 26 which is in constant communication with a spill passage 27 formed in the distributor member. The lower edge 28 of the groove as shown in Figure 1, is inclined. The spill passage 27 communicates with a space within the interior of the apparatus by way of a pressure relief valve 29 which is spring biased to the closed position. Moreover, a further spill passage 30 is provided and this communicates with the bore 16 at a position where as will be explained, it is covered by the inner end face 31 of the plunger 18 early during the inward movement of the plunger.

In Figures 1 and 2, the plungers are being moved inwardly and delivery of fuel is taking place through an outlet 23. As the plungers continue to move inwardly the lower edge 28 of the groove 26 will be exposed beyond the entrance to the bore 15 and when this occurs fuel from the pumping chamber defined between the plungers can escape by way of the groove 26, the passage 27 and the relief valve 29. Fuel is therefore spilled from the pumping chamber and the supply of fuel through the outlet 23 to the associated injection nozzle ceases. A rapid termination of the delivery of fuel to the associated engine is therefore obtained.As the distributor member continues to rotate the plungers will complete their inward movement, fuel being displaced by way of the valve 29 but at some point, inward movement of the plungers ceases and the delivery passage moves out of register with an outlet 23 and the inlet passage 24 moves into register with an inlet port 25. Fuel is therefore delivered to the pumping chamber and the plungers are moved outwardly their maximum extent as determined by the cam lobes.

Further rotational movement of the distributor member moves the inlet passage 24 out of register with the inlet port and the delivery passage 22 moves into register with the next outlet 23 and the plungers start to move inwardly again under the action of the cam lobes.

During the initial inward movement the passage 30 is open to the pumping chamber and therefore the initial inward movement of the plungers merely causes fuel to be displaced from the pumping chamber to the interior of the apparatus by way of the relief valve. However, at some point the inner end of the plunger 18 covers the port 30 so that spillage of fuel no longer takes place and fuel starts to flow through the outlet 23 until such time as the lower edge 28 of the groove is exposed beyond the end of the bore 15. If the plunger 18 is moved angularly, the position at which the lower edge 28 of the groove is uncovered to the bore 15 can be varied and hence the quantity of fuel which is displaced through the outlets 23 can be varied.

Turning now to Figure 3, it will be seen that the plunger 18 is provided with an aperture in which is located a peg 32 which has a rounded end located in a fork 33 mounted at the end of an axially movable rod 34.

The rod 34 is guided for movement within a drilling formed in the member 13 and it extends through the flange 35 of a collar which is axially slidable upon the drive shaft 14. A pin 36 extends through the rod 34 and the pin is maintained in engagement with the flange by means of a light coiled compression spring 37. The flange 35 is positioned by a governor mechanism responsive to the speed of the associated engine and also to a demand signal provided by the engine operator.

With the arrangement described therefore the start of delivery of fuel to the associated engine takes place at the same time during the inward movement of the plungers and termination of fuel delivery is achieved by spillage of fuel so that the rollers forming part of the cam followers together with the cam ring are not subject to the high stress even if the delivery pressure of the fuel is increased. Moreover, any eccentricity in the location of the cam ring relative to the axis of rotation of the distributor member has a minimal effect upon the timing of fuel delivery and also the quantity of fuel which is eventually supplied to the associated engine.

Turning now to Figures 4 and 5, it will be seen that the passage 30 has been eliminated and the passage 27 now forms the sole spill path for fuel from the pumping chamber. However, the shape of the port defined by the passage 27 at its entrance to the bore is of a special form as more clearly seen in Figure 5 at 38. It will be seen that the port has a lower edge disposed in a plane generally at right angles to the axis of the bore 16 and an upper edge which is inclined. The plunger 18A opposite to the flat 26A, has a first groove 39 which is in constant communication with the pumping chamber, the first groove having an upper edge disposed in a plane normal to the axis of the bore 16. The plunger also has a second groove 40 which is inclined and is connected to the pumping chamber by means of a drilling 41 extending through the plunger.

In operation, the initial inward movement of the plunger by the cam will allow fuel to be displaced from the pumping chamber through the passage 27 but as soon as the upper edge of the groove 39 passes the lower edge of the port 38, the fuel in the pumping chamber will be pressurised and fuel delivery will take place to the associated engine. Such delivery continues until the lower edge of the groove 40 is exposed beyond the upper edge of the port 38 and when this takes place the remaining quantity of fuel displaced from the pumping chamber during inward movement of the plunger will flow by way of the passage 27 to the interior of the housing.

Again by adjusting the angular setting of the plunger, the amount of fuel delivered to the associated engine can be varied.

An alternative arrangement for adjusting the angular position of the plungers 18, 18A is suited to electronic control of the apparatus. In this case the rod 34 is held against movement relative to the cupshaped member 13 and the distributor member is allowed to move axially in one direction under the action of a spring, and in the opposite direction by increasing fluid pressure applied to the end of the distributor member.

The fluid pressure applied to the distributor member, can be controlled by means of an electro-magnetic valve and as the pressure is increased, the distributor member is moved against the action of the spring so that angular movement of the plunger 18, 18A within the bore 16 will take place.

Claims (9)

1. A fuel pumping apparatus of the kind specified in which one of said plungers is angularly adjustable within the bore and said one plunger defines a first control edge which covers a spill path from said pumping chamber during the initial inward movement of the plungers thereby to cause fuel to be delivered through an outlet and a second control edge on the one plunger which opens a spill path from the pumping chamber after a predetermined inward movement of the plungers, the extent of said predetermined inward movement depending upon the angular setting of said one plunger within the bore.

2. An apparatus according to Claim 1 including a first spill passage opening into said bore said first control edge being formed by the inner end of said one plunger which covers the entrance to said first spill passage during the initial inward movement of the plunger, and a second spill passage opening into said bore, said second spill passage communicating with a groove formed on the one plunger, the groove defining said second control edge, the groove being covered by the wall of the bore during said predetermined inward movement of the plunger.

3. An apparatus according to Claim 2 including a further transverse bore intersecting said first mentioned bore and a further pair of plungers therein, said second control edge being uncovered to said further transverse bore after said predetermined inward movement.

4. An apparatus according to Claim 1 including a spill passage opening into said bore, a first groove defining said first control edge and a second groove defining said second control edge formed on the plunger, the grooves communicating with the pumping chamber the first groove being uncovered to the spill passage during said initial movement and the second groove being uncovered to said spill passage after said predetermined inward movement.

5. An apparatus according to any of the preceding Claims in which said second control edge is inclined.

6. An apparatus according to any one of the preceding Claims including a pressure relief valve through which fuel spilled from the pumping chamber flows to a drain.

7. An apparatus according to any one of the preceding Claims including means for adjusting the angular setting of the one plunger.

8. A rotary distributor type fuel injection pumping apparatus comprising the combination and arrangement of ports substantially as hereinbefore described with reference to Figures 1, 2 and 3 of the accompanying drawings.

9. A rotary distributor type fuel injection pumping apparatus comprising the combination and arrangement of ports substantially as hereinbefore described with reference to Figures 4 and 5 of the accompanying drawings.