GB2350650A - Actuator arrangement for rotating a cam ring of a rotary fuel pump - Google Patents

Abstract

A rotary fuel pump for an internal combustion engine has an actuator arrangement comprising a cam 44 and a cam follower 42 which uses leverage to impart angular movement to a rotatable annular scroll plate (10, Fig 1), or cam ring, to limit the outward movement of a reciprocating plunger in a bore to control the amount of fuel delivered to the engine. The linearly movable cam 44 imparts angular movement on a pivoted cam follower 42 which acts on a pivoted lever 32 to move a scroll plate carriage 30 which rotates the scroll plate. Such an actuator arrangement enables a common fuel pump housing type to be used for both clockwise and anticlockwise rotating pumps.

Description

2350650 ROTARY FUEL PUMP This invention relates to a rotary fuel pump for

supplying fuel to an internal combustion engine.

Conventionally, a rotary fuel pump has a rotary cylinder head including a bore and one or more plungers reciprocable within the bore. An annular cam arrangement surrounds the rotary head and is adapted to impart inward movement to the plungers as the head rotates. The pump also includes a distributor, rotatable within the rotary head, having passages formed therein through which fuel is conveyed to and from the bore. The passages in the distributor communicate with either a fuel inlet passage or a fuel outlet passage formed in an outer housing, depending on the angular position of the distributor in relation to the housing. Thus, fuel is either supplied to the bore of the rotary head or discharged therefrom into the engine, depending on the angular position of the distributor.

When the distributor is positioned such that the fuel inlet passage is communicating with the bore, fuel is supplied to the bore under relatively low pressure, thus a pressure is exerted on the plungers within the bore causing outward movement thereof. When the distributor is rotated such that there is communication between the fuel outlet passage in the housing and the flow passages within the distributor, subsequent inward movement of the plungers causes fuel within the bore to be displaced therefrom, through the fuel outlet passage and into the engine.

In order to control the maximum amount of fuel which can be fed to the engine, the outward movement of the plungers within the bore is limited by means of angularly adjustable annular places, commonly referred to as llscroll plates", the or each scroll plate being associated with an end face of each plunger. Rollers located at the end of each plunger abut against the or each scroll plate to limit outward movement of the plungers. The inner surfaces of the scroll platesagainst which the rollers abut are formed with a plurality of arcuate sections, increasing in radius from one end to the other. Thus, the extent to which outward plunger movement is limited, and hence the maximum amount of fuel which can be introduced into the bore, depends on the angular setting of the scroll plates.

Rotary fuel pumps can be either clockwise rotation fuel pumps, for rotation in a clockwise sense, or anticlockwise rotation fuel pumps, for rotation in an anticlockwise sense, depending on the characteristics of the particular engine in which they are to be used. In an anticlockwise rotation fuel pump it is necessary to rotate the scroll plates in an opposite sense to the scroll plates in a clockwise rotation fuel pump to ensure plunger movement, and hence fuelling, is limited or controlled in the correct way in the pumping cycle.

Movement of the scroll plates is conventionally effected by linear movement of an associated scroll plate carriage which engages with the scroll plates. It is well known that the scroll plate carriage in a clockwise rotation fuel pump must be driven in an opposite linear direction to the scroll plate carriage in an anticlockwise rotation fuel pump, depending on the angular sense in which the scroll plates are to be moved to cause the same change in fuelling. The scroll plate carriage is usually driven by an actuator arrangement having a cam follower driven by a cam, the cam follower acting on the scroll plate carriage to effect linear movement thereof. Conventionally, the cam and cam follower are housed within a housing on one side of the rotary fuel pump. The actuator arrangement is mounted on different sides of the housing in clockwise and anticlockwise rotation fuel pumps as the linear direction in which the scroll plate carriage is moved is different in each case for a given change in fuelling. Different housings would therefore be required in order to produce the different types of rotary pump, one housing type being required for a clockwise rotation pump and one for an anticlockwise rotation pump, to accommodate the actuator arrangement on the appropriate side of the pump. The provision of two different housing types would be expensive, and so is undesirable.

It is an object of the invention to overcome this problem and provide a rotary fuel pump which can be arranged within a common housing type irrespective of whether it is to be operated as a clockwise or an anticlockwise rotation pump.

According to the present invention, there is provided a rotary fuel pump for an internal combustion engine, comprising; a housing; a plunger member reciprocable within a bore; an angularly adjustable annular plate provided within the housing, arranged to limit outward movement of the plunger member within the bore, the limit of outward movement being dependent on the angular position of the annular plate; and an actuator arrangement provided within the housing, for imparting angular movement to the annular plate, the actuator arrangement including a cam member and a cam follower member, the cam follower member being arranged to act upon leverage means to effect angular movement of the annular plate.

The rotary fuel pump may include two or more plunger members, each plunger member being cooperable with the annular plate to limit outward movement of the respective plunger member.

The actuator arrangement conveniently includes carriage means for the annular plates, the leverage means acting on the carriage means to effect linear movement thereof, the carriage means cooperating with the annular plate such that linear movement of the carriage means is translated to angular movement of the annular plate in a required direction.

In a conventional clockwise rotation rotary fuel pump, the actuator arrangement includes a cam member driving a cam follower member acting directly on the carriage means. By using an actuator arrangement including additional leverage means, driven by the cam follower and acting on the carriage means instead of the conventional actuator arrangement, the direction of movement of the annular plate can be reversed compared to the direction of movement in a clockwise rotation pump. Thus, the invention provides the advantage that a housing intended for use in, for example, a clockwise rotation rotary pump can also be used to house the actuator arrangement in a rotary fuel pump for anticlockwise rotation. It is not therefore necessary to manufacture two separate housing types for each type of rotary fuel pump.

The housing may be intended for use in a clockwise rotation rotary fuel pump as described hereinbefore, in which the annular plates are driven in one sense for a given change in fuelling, or in an anticlockwise rotation fuel pump, in which the annular plates are driven in the opposite sense for the given change in fuelling. The leverage means may be a single lever, or may be composed of several levers which act upon one another.

The leverage means may have an end-face cooperating with an end-face of the cam follower member, the end-faces being angled such that the cam follower member and the leverage means are free to slide against one another.

According to another aspect of the invention, there is provided an actuator arrangement for imparting angular movement to an annular plate in a rotary fuel pump, the actuator arrangement including a cam member and a cam follower member, the cam follower member acting on leverage means to effect angular movement of the annular plate.

The invention will further be described, by way of example, with reference to the accompanying drawings, in which; Figure 1 is a plan view of a conventional scroll plate which may form part of the present invention; Figure 2 is a side view of a part of a rotary fuel pump in accordance with an embodiment of the present invention; and Figure 3 is a sectional view, along line A-A, of the part of the rotary fuel pump shown in Figure 2.

Referring to Figure 1, there is shown a plan view of a conventional scroll plate 10 for use in a rotary fuel pump having one or more plunger members reciprocable within a bore formed in a rotary cylinder head. A single scroll plate 10 is shown in Figure 1, although in practice the fuel pump may have two such scroll plates. Each plunger member cooperates with a roller 14, located at its outermost end, the rollers 14 cooperating with the scroll plate 10 to 1 im it outward movement of the associated plunger member within the bore.

With reference to Figure 1, the inner surface of the scroll plate 10 is divided into a plurality of equi-angular arcuate sections 12 equal to the number of cylinders in the engine, each arcuate section 12 being equally shaped and increasing in radius from one end to the other. The scroll plate 10 is angularly adjustable by means of a toothed part 16 which is in engagement with a notch 18 formed in the scroll plate 10. The toothed part 16 is carried on a nut 20 traversable along a screw 22 extending tangentially relative to the scroll plate 10. The screw 22 is movable, axially, in the required direction to adjust the fuelling level of the pump by means of a scroll plate carriage which is moved in a linear direction under the action of an actuator arrangement (not shown), conveniently against a spring biasing force.

The arcuate sections 12 formed on the inner surface of the scroll plate 10 limit outward movement of the plunger members by an amount dependent on the angular position of the scroll plate 10, the position of the scroll plate 10 determining the portion of the arcuate sections 12 against which rollers, located at the end of the plunger members, abut at the instant at which the plunger bore of the pump moves out of communication with the fuel inlet passage. As movement of the scroll plate 10 is effected by linear movement of the scroll plate carriage, a greater linear displacement of the scroll plate carriage provides greater angular movement of the scroll plate 10.

In a clockwise rotation rotary fuel pump the scroll plates are moved in a clockwise sense in response to linear movement of the scroll plate carriage in a given direction to reduce the quantity of fuel supplied by the pump. in an anticlockwise rotation fuel pump, it is necessary to move the scroll plates in an anticlockwise direction (i.e. in an opposite direction to the direction of movement in a clockwise rotation fuel pump) and it is therefore necessary to effect linear movement of the scroll plate carriage in an opposite direction to that required in a clockwise rotation pump. Where conventional actuator arrangements are used, the actuator arrangement for the scroll plates must therefore be housed on different sides of the pump housing in rotary fuel pumps of the different types so that the scroll plate carriage, and hence the scroll plates, are moved in the appropriate direction.

Referring to Figure 2, there is shown a side view of a part of an anticlockwise rotation rotary fuel pump in accordance with an embodiment of the present invention, having an actuator arrangement designed to permit the use of a pump housing suitable for use with a clockwise rotation rotary pump.

The fuel pump includes a scroll plate carriage 30 for imparting angular movement to the scroll plates (not shown) in response to linear movement of the scroll plate carriage 30. The scroll plate carriage 30 is moved in a linear direction by means of a lever 32, the end 34 of which engages with an abutment surface 36 of the scroll plate carriage 30. The scroll plate carriage 30 communicates with a screw 40 which carries a nut 38, the nut 38 having a part for engagement with the scroll plate to effect angular movement thereof in response to linear movement of the scroll plate carriage 30, as described previously. The actuator arrangement for the scroll plate also includes a cam 44, linearly moveable in a direction, x, acting on a cam follower 42, linear movement of the cam 44 resulting in angular movement of the cam follower 42. The cam follower 42 acts on the lever 32 which in turn acts on the scroll plate carriage 30.

The surface of the cam 44 includes a recess 46. Starting from a position in which the end surface 48 is located within the recess 46, linear movement of the cam 44 in direction x results in the cam follower 42 moving out of the recess 46 into the position shown in Figure 2. Movement of the cam 44 in direction x therefore gives rise to movement of the cam follower 42 in an anticlockwise direction. The movement of the cam follower 42 causes movement of the lever 32 in a clockwise direction. Thus, referring to Figure 2, the scroll plate carriage 30 is moved linearly in a downward direction i.e. in an opposite direction to direction y. Movement of the cam 44 in the opposite direction would result in the carriage 30 moving in an upward direction in the orientation illustrated in Figure 2.

The actuator arrangement described hereinbefore can be mounted within a housing of the type intended for use with a clockwise rotation rotary pump to move the scroll plates in the sense required for an anticlockwise rotation rotary pump. Clearly, by appropriate selection of the actuator arrangement, using either the conventional arrangement or the arrangement described hereinbefore, a common housing can be used for both clockwise and anticlockwise rotation rotary pumps. The scroll plate carriage and the actuator arrangement can therefore be mounted on the same side of the fuel pump housing in either a clockwise rotation fuel pump or an anticlockwise rotation fuel pump to effect angular movement of the scroll plates in the appropriate direction.

In clockwise rotation fuel pumps the contacting faces of the cam follower 42 and the scroll plate carriage 30 are angled and are free to slide against each other. any suitable technique being employed to control movement of the cam follower 42 in the z direction. Thus, with reference to Figure 3, the cooperation between the cam follower 42 and the carriage 30 ensures that linear movement of the cam follower 42 in the direction z results in linear movement in direction y of the scroll plate carriage 30. In the present invention, where the lever 32 is provided to enable the actuator to be used with an anticlockwise rotation rotary pump, the face 50 of the cam follower 42 makes contact with a face 52 of the lever 32J. the faces 50, 52 being angled such that the cam follower 42 and the lever 32 are free to slide against each other. Thus, linear movement of the cam follower 42 in direction z is converted to angular movement of the lever 32 and. hence, linear movement of the scroll plate carriage 30, as described previously.

Although, in the description hereinbefore, it is suggested that a pump housing intended for use in a clockwise rotation rotary pump can also be used in an anticlockwise rotation rotary pump by using an appropriate actuator arrangement, it will be appreciated that the invention also extends to a fuel pump of the clockwise type which uses a pump housing of the anticlockwise type.

It will be appreciated that the way in which the scroll plate carriage imparts angular movement to the scroll plates may be achieved by means other than the nut and screw arrangement shown in Figures 2 and 3.

Claims (9)

1. A rotary fuel pump for an internal combustion engine, comprising; at least one plunger member reciprocable within a bore; a rotatable annular plate, arranged to limit outward movement of a plunger member within the bore, the limit of outward movement being dependent on the degree of rotation of the annular plate; and an actuator arrangement for imparting angular movement to the annular plate, the actuator arrangement including a cam member and a cam follower member, the cam follower member acting on leverage means to effect angular rotation of the annular plate.

2. The fuel pump as claimed in Claim 1, including two plunger members reciprocable within the bore, each plunger member having an associated annular plate to limit outward movement of the respective plunger member within the bore.

3. The fuel pump as claimed in Claim 2, wherein the actuator arrangement includes carriage means for the annular plates, the leverage means acting directly on the carriage means to effect linear movement thereof, the carriage means communicating with the annular plates such that linear movement of the carriage means is translated to rotational movement of the annular plates in a required direction.

Q.

4. The fuel pump as claimed in any of Claims 1 to 3, wherein the fuel pump is a clockwise rotation pump, in which the annular plates are driven in a clockwise sense.

5. The fuel pump as claimed in any of Claims 1 to 3, wherein the fuel pump is an anticlockwise rotation fuel pump, in which the annular plates are driven in an anticlockwise sense.

6. The fuel pump as claimed in any of Claims 1 to 5, wherein the leverage means take the form of a single lever which may be removable from the actuator arrangement, removal of the lever enabling the direction of rotation of the annular plates to be reversed.

7. The fuel pump as claimed in any of Claims 1 to 6, wherein the leverage means has an end-face communicating with an end-face of the earn follower member, the end-faces being angled such that the cam follower member and the leverage means are free to slide against one another.

8. An actuator arrangement for imparting angular movement to an annular plate in a rotary fuel pump as claimed in any of Claims 1 to 7, the actuator arrangement including a cam member and a earn follower member, the cam follower member acting on leverage means to effect angular rotation of the annular plate.

9. A rotary fuel pump as herein described with reference to the accompanying Figures.