Fuel pumping apparatus

A fuel pumping apparatus for supplying fuel to a supercharged compression ignition engine includes an injection pump having a control member the setting of which is determined by a governor including speed responsive means and a governor spring the force exerted by which is adjustable and opposes the action of the speed responsive means. A stop member is provided to limit the extent of movement of the control rod and the stop is engageable with a cam surface formed on a pivotal lever the setting of which is controlled by an air pressure responsive member subjected to the air pressure existing in the inlet manifold of the engine. In addition the pivot for the lever is mounted on a carrier member which is loaded by a spring. The spring can be deflected under certain operating conditions of the engine, by the force exerted by the governor spring and this provides a measure of torque control.

This invention relates to fuel pumping apparatus for supplying fuel to a 
supercharged compression ignition engine, the apparatus comprising an 
injection pump including a control member movable axially to vary the rate 
of fuel supply to the engine and governor means including an operator 
adjustable member, speed responsive means and a governor spring, for 
determining the setting of the control member. 
The maximum amount of fuel which can be supplied to an engine must be very 
carefully controlled in order that the emission of smoke from the exhaust 
of the engine does not exceed that permitted by the prevailing 
regulations. The maximum amount of fuel which can be supplied to an engine 
alters with the operating conditions of the engine and in the case of a 
supercharged engine the pressure of air in the inlet manifold of the 
engine is a very important factor. When the pressure is low than a reduced 
quantity of fuel can be supplied as compared with the situation when the 
pressure in the inlet manifold is high. It is also desirable to provide 
for torque control and the object of the invention is to provide a fuel 
pumping apparatus of the kind specified in a simple and convenient form. 
According to the invention an apparatus of the kind specified comprises a 
housing, a stop member movably mounted in a wall of the housing said stop 
member being positioned to be engaged by said control member to determine 
the maximum rate of fuel supply by the apparatus, a pivot carrier mounted 
in the housing said pivot carrier being movable in the direction of 
movement of said stop member, a lever pivotally mounted on said pivot 
carrier, one end of said lever defining a cam surface engageable with said 
stop member to determine the position thereof, a fluid pressure operable 
member operatively connected to the other end of said lever, means whereby 
in use, said member can be subjected to the pressure of air in the air 
inlet manifold of the associated engine, first resilient means opposing 
movement of said fluid pressure operable member by said air pressure, and 
second resilient means biasing said pivot carrier, said second resilient 
means, being deflected by force exerted by the governor spring, to modify 
the maximum rate of fuel supply under certain operating conditions of the 
engine.

With reference to FIG. 1 of the drawings the apparatus comprises an 
injection pump 10 having an axially movable control member 11 the setting 
of which determines the amount of fuel which is supplied to the engine at 
each injection stroke that is to say the rate of fuel supply to the 
engine. 
A mechanical governor is provided to determine the setting of the control 
member 11 and this includes a lever 12 which is pivotally connected at one 
end to a portion 13 of the housing of the apparatus and which intermediate 
its ends, is pivotally connected to the control member 11. The lever 12 at 
its end remote from its pivotal connection with the housing is connected 
to one end of a governor spring 14 the other end of which is connected to 
an operator adjustable lever 15. As the lever 15 is moved angularly in the 
clockwise direction, the governor spring 14 will exert an increased force 
on the lever 12 which will pivot in the clockwise direction thereby moving 
the control member 11 to increase the amount of fuel supply to the engine. 
For opposing the force exerted by the governor spring 14 a centrifugal 
weight mechanism generally indicated at 16 is provided. Essentially the 
weight mechanism includes a plurality of weights 17 which are mounted in a 
cage (not shown), the cage being driven at a proportion of the engine 
speed. Conveniently the cage is mounted on the drive shaft of the 
injection pump. The weights 17 are pivotally mounted at 18 and extensions 
of the weights bear against a flange 19 which is pivotally connected to 
the lever 12. As the speed of rotation of the cage increases the weights 
move outwardly and a force is applied to the lever 12 in opposition to the 
force exerted by the governor spring 14. With increasing speed the lever 
12 will be moved angularly in the anti-clockwise direction as seen in FIG. 
1, to reduce the amount of fuel which is supplied to the engine. The 
engine speed is therefore controlled and an increased or decreased 
governed speed of the engine can be obtained by movement of the operator 
adjustable lever 15. 
In order to control the emission of smoke from the exhaust of the engine it 
is necessary to provide a maximum fuel stop which limits the extent of 
movement of the control member 11 under the action of the governor spring 
14. As shown in FIG. 1 a stop member 20 is provided but the setting of the 
stop member is adjustable during operation of the engine as will now be 
described. 
The stop member engages at its end remote from the control member 11, a cam 
surface 21 which is defined on a pivotal lever 22. The lever is pivotally 
mounted in a carrier 23 and this is loaded towards the injection pump 10 
by means of a coiled compression spring 24. The extent of such movement is 
limited by means not shown and the extent by which the spring 24 can be 
compressed is also limited. 
The end of the lever 22 remote from its connection with the carrier 23, is 
connected to a rod 25 which is coupled to a fluid pressure operable member 
26 and this is located within a cylinder 27 having a connection 28 to the 
air inlet manifold of the associated engine. Moreover, a coiled 
compression spring 29 is provided which biases the fluid pressure operable 
member 26 against the action of fluid pressure. 
The associated engine is a supercharged compression ignition engine, the 
supercharging being effected by means of a compressor which is driven by a 
turbine powered by the exhaust gases of the engine. With such an 
arrangement it is well known that the effectiveness of the turbine depends 
upon the speed of and the load on the associated engine. At low speeds and 
low loads the turbine does not provide sufficient power to drive the 
compressor at a speed at which there is any substantial increase in the 
air pressure within the air inlet manifold, over and above atmospheric 
pressure. As the speed of operation of the engine increases however the 
energy in the exhaust gases increases and the turbine operates at a higher 
speed so that a substantial increase of the pressure within the air inlet 
manifold is obtained. The increased air pressure within the air inlet 
manifold results in a higher mass of air in the cylinder at the end of the 
compression stroke. An increased amount of fuel can therefore be supplied 
to the engine. 
The pumping apparatus is enabled to supply an increased maximum amount of 
fuel by virtue of the fact that the increased pressure in the air inlet 
manifold effects movement of the fluid pressure operable member 26 against 
the action of the spring 29. Such movement results in pivotal movement of 
the lever 22 and by virtue of the shaping of the cam surface 21, the stop 
member 20 is able to move an increased amount towards the right as seen in 
FIG. 1. As a result of such movement, the control member 11 is moved by 
the governor spring to provide the increased quantity of fuel. It is 
emphasised that it is only when the control member 11 is in contact with 
the stop member 20 that an increase in the amount of fuel supplied takes 
place. Conveniently the coil compression spring 29 is pre-loaded so that 
it is only when the pressure in the air inlet manifold rises above a 
predetermined value is there any movement of the fluid pressure operable 
member 26. 
The carrier 23 has a position dependent upon the spring 24 and the 
provision of the movable carrier provides what is known in the art as 
"torque control." In practice this means that as the speed of the engine 
increases towards the point at which the normal governor action will come 
into operation to reduce the amount of fuel supply to the engine, there is 
a slight reduction in the amount of fuel supplied to the engine as the 
speed increases. In other words the torque provided by the engine 
decreases as the engine speed increases as opposed to the situation where 
with a fixed maximum fuel stop the torque would remain substantially 
constant until the governor action explained above took place. In the 
position shown in FIG. 1, the spring 24 has moved the carrier 23 towards 
the left thereby reducing the amount of fuel supplied to the engine. If 
for example, the engine speed fell then the force exerted by the 
centrifugal governor on the lever 12 would decrease and the control member 
11 would be moved towards the right, by the predominating force of the 
governor spring 14, thereby effecting compression of the spring 24 hence 
an increased quantity of fuel would be supplied to the engine. 
Turning now to FIGS. 2, 3 and 4 the stop member 20 is shown as slidable 
within a bush 30 secured in the wall of a housing 31. Moreover, the lever 
22 is pivotally connected by means of a pin 32 on the carrier 23 which is 
of forked construction, the portion of the lever 22 defining the cam 
surface 21 being disposed between the forked portions of the carrier 
member. The main body of the carrier member 23 is integral with a rod 33 
about which is located the spring 24. The rod 33 includes a screw threaded 
portion which is in screw thread engagement with a sleeve 34 slidably 
mounted within a bore defined in a body portion 35 which is adjustably 
mounted within the wall of the housing 31. The sleeve 34 at its end remote 
from the main body portion of the carrier 23 engages a washer which acts 
as an abutment for the adjacent end of the coiled compression spring 24. 
The axial position of the sleeve on the rod 33 determines the pre-load of 
the spring 24. The other end of the coiled compression spring bears 
against the base wall of the bore in the body portion 35 and the rod 
member 33 extends with clearance through the base wall and has secured 
thereon a retaining nut 36. The retaining nut 36 determines the extent of 
movement of the carrier member 23 under the action of the spring 24 whilst 
the abutment of the main portion of the carrier member 23 with the body 
portion 35 determines the amount by which the carrier member can move 
against the action of the spring 24. 
The end of the rod 25 is secured against the base wall of a cup-shaped 
member 37 and sandwiched between the outer surface of the cup-shaped 
member and a retaining plate 38 is a diaphragm 39 the outer peripheral 
surface of which is trapped between the housing and a cover plate 40 which 
is secured to the housing. As is seen in FIG. 4, an inlet connection 41 is 
provided in the cover portion for connection to the inlet manifold of the 
associated engine. The diaphragm 39 constitutes the fluid pressure 
operable member which has been referred to earlier in the specification 
but in this case the cylinder 27 is replaced by a chamber which houses the 
cup-shaped member 37 and the diaphragm. The coil compression spring 29 
abuts against the inner surface of the base wall of the cup-shaped member 
37 and at its other end it bears against a stack of washers 42 interposed 
between the spring and the housing. The rod 25 is connected by means of a 
pin 43 to the lever 22 and the pin 43 extends laterally as seen in FIG. 4, 
and is engageable by a tongue 44 extending from an adjustable plate 45 
secured by means of a bolt 46 within the housing. 
As seen in FIG. 3, the housing 31 is provided with a side opening which is 
covered by a plate 47. The plate 47 is retained in position by means of a 
securing bolt 48 and this bolt is utilized to allow air to enter and leave 
the housing during movement of the diaphragm. For this purpose the bolt 48 
is provided with a bore 49 which at one end communicates with the interior 
of the housing 31 and which at its other end is closed by a porous plug 
50. The plug acts as a filter and in order to minimise so far as possible, 
the possibility of an operator removing the bolt 48, the head is provided 
with a cup-shaped cover 51 the side wall of which is deformed at several 
points beneath a ledge defined on the head of the bolt 48. The cover is 
free to rotate but at the same time allows the passage of air through the 
porous plug 50. 
The operation of the practical construction is the same as described with 
reference to FIG. 1. In the practical construction however three points of 
adjustment are provided. Firstly the thickness of the stack of washers 42 
can be adjusted as also can be the setting of the tongue member 44. The 
position of the tongue member 44 determines by means of pin 43, lever 22 
and stop member 20, return the movement of the cup-shaped member and hence 
the maximum fuel available at light load. The thickness of the stack of 
washers effectively adjusts the pre-load of the spring 29 and thereby in 
conjunction with the position of the tongue member 44 determines the 
predetermined pressure in the air inlet manifold at which an increase of 
fuel can take place. 
The setting of the body part 35 within the housing is also adjustable and 
this determines the maximum amount of fuel which can be supplied to the 
engine when the pressure in the air inlet manifold is as high as it can 
attain that is to say when the diaphragm 39 has compressed the spring 29 
the maximum extent. The extent of movement of the pivot carrier can be 
adjusted by adjustment of the nut 36 on the rod 33 and by adjustment of 
the sleeve 34 relative to the rod. 
In the arrangement shown in FIG. 5 the plate 45, the tongue 44 and nut 46 
are omitted. Moreover, the pin 43 is replaced by a pin 43a which is 
shorter than the pin 43 and the tongue is replaced by a wheel 52 which is 
mounted on a threaded bolt 53 secured in the wall of the housing. A lock 
nut 54 is provided. The advantage of this arrangement is that adjustment 
is facilitated. 
In the two examples the tongue and wheel limit the movement of the 
respective pin under the action of the spring 29. It is possible in each 
case to arrange instead that the extent of movement of the pin under the 
action of air pressure is limited. In the case of the arrangement of FIG. 
2 this is achieved by mounting the plate 45 upside down so that the tongue 
44 lies at the lower end of the plate. In the case of the arrangement of 
FIG. 5 the wheel 52 during assembly is positioned beneath the pin 43a.