GB2304384A - Distributor pump for fuel supply to an engine - Google Patents

Abstract

A distributor pump arrangement for charging an accumulator (42) comprises a plurality of pumping plungers (28) housed in bores and actuated by a rotatable swash plate (24). One surface of the swash plate together with a surface of a housing is ported to form a distributor for distributing fuel from the accumulator to the combustion spaces of an associated engine. A three-way valve (50 or 52) controls the flow of fuel from the accumulator to a respective recess in the swash plate surface, the recess registering in turn with ports (74), each leading to a particular combustion space. Delivery to a port is terminated when the valve is switched to a position connecting the recess to a low pressure region.

Description

DISTRIBUTOR PUMP This invention relates to a distributor pump arrangement, and in particular to an arrangement suitable for charging an accumulator and distributing pressurized fuel from the accumulator to the cylinders of an associated engine, in turn.

In such distributor pumps, it is desirable for the drive torque of the pump to be low and relatively smooth. In a known form of pump, a plurality of pumping plungers are reciprocable in bores provided in a rotatable distributor member, the plungers carrying shoe and roller arrangements which are arranged to engage the cam lobes on a cam ring. On rotation of the distributor member, the plungers are moved inwardly at the same time by the cam lobes, and it will be understood that the drive torque of the pump is non-uniform and this can lead to wind up of the pump drive mechanism. Such distributor pumps also tend to be relatively bulky, a relatively long length of the distributor member being required to distribute the pressurized fuel to the cylinders of the associated engine, in use.

It is an object of the invention to provide a compact distributor pump in which the above described disadvantages are reduced.

According to the present invention there is provided a distributor pump arrangement comprising a plunger reciprocable in a bore under the influence of a swash plate arrangement in order to charge an accumulator, and a face distributor arrangement arranged to distribute fuel from the accumulator to the cylinders of an associated engine in turn, in use.

The provision of a swash plate arrangement for driving the plunger reduces the sudden changes in torque which occur in the known arrangement, each pumping stroke of the plunger occurring over approximately half of each revolution of the swash plate.

It will be recognised that the provision of a face distributor arrangement requires less axial space than a conventional distributor arrangement thus permitting the provision of a relatively compact arrangement.

The face distributor arrangement conveniently comprises a first, relatively fixed, element and a second element rotatable with respect to the first element, the second element preferably comprising part of the swash plate arrangement. It will be recognised that such an arrangement further permits the provision of a relatively compact distributor pump arrangement.

The invention will further be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic cross-sectional view of a distributor pump in accordance with an embodiment of the invention; Figure 2 is a diagrammatic view of the face distributor arrangement of the pump of Figure 1; Figure 2a is a view similar to Figure 2 of an alternative arrangement; Figure 3 is a view similar to Figure 1 of a second embodiment; and Figure 4 is a diagrammatic view of the face distributor arrangement of the pump of Figure 3.

The distributor pump illustrated in Figure 1 is intended for use with an eight cylinder engine, the pump comprising a housing 10 having a passage 12 extending therethrough, the passage 12 including an enlarged region 14 at an end thereof. A drive shaft 16 extends within the passage 12, bearings 18, 20 being provided to rotatably support the drive shaft 16 within the housing 10.

The end of the drive shaft 16 extending within the enlarged region 14 is provided with splines 22 which engage a swash plate 24 which is rotatable within the enlarged region 14. The swash plate 24 is arranged to engage slippers 26 carried by the heads of eight equiangularly spaced plungers each of which is reciprocable within a respective bore 30 provided in the housing 10. Each of the bores 30 extends substantially parallel to the passage 12 extending through the housing 10. Each of the plungers comprises a plunger member 28 which is reciprocable within a bucket 29, a spring 32 being provided between each plunger member 28 and bucket 29 in order to bias the plunger members 28 out of the bores 30 to ensure that the plungers remain in contact with the slippers 26 provided on the swash plate 24.Each plunger member 28 is provided with a groove permitting communication between the interior of the bucket 29 in which the spring 32 is housed so as to relieve the pressure therein to the enlarged region 14. The buckets 29 are reciprocable within the bores 30, a very small clearance existing between the buckets 29 and bores 30 so that seals are formed between each of the buckets 29 and the respective bore 30.

Each of the bores 30 is arranged to receive fuel through a respective inlet non-return valve 34, the inlet side of which communicates with the outlet of a transfer pump comprising vanes 36 provided on the drive shaft 16, the transfer pump being arranged to receive fuel from an inlet 38 provided in the housing 10. Each of the bores 30 further communicates with a respective outlet non-return valve 40 arranged to permit the flow of fuel from the bores 30 but to substantially prevent fuel flowing through the non-return valve 40 to return to the bore 30. The outlet side of each of the non-return valves 40 is connected to one another by means of an annular passage (not shown), which communicates with an accumulator 42 through a passage 44.In the embodiment illustrated in Figure 1, the accumulator 42 comprises a single, relatively large recess provided in the housing 10, the accumulator 42 being closed by means of a bolt 46 in screw-threaded engagement with the housing 10.

The housing 10 is provided with a plate 48 which closes the enlarged region 14 of the passage 12. The plate 48 may be secured to the housing 10 by means of bolts (not shown) or any other suitable means.

The plate 48 carries two three-way valves 50, 52 which communicate with the accumulator 42 by means of passages 54, 56 provided in the plate 48, and passages 58, 60 provided in the housing 10. The threeway valves 50, 52 also communicate with respective part annular recesses 62, 64 provided on the surface of the plate 48 facing the housing 10, the connection between the part annular recesses 62, 64 and the three-way valves 50, 52 being by means of passages 66, 68 provided in the plate 48.

The plate 48 is further provided with eight outlet ports 70 for connection to delivery lines for communication with the cylinders of an associated engine. Each of the outlet ports 70 communicates by means of respective delivery passages 72 to respective ports 74 provided on the face of the plate 48 facing the housing 10. As illustrated in Figure 2, the ports 74 are arranged so as to define a circle, the circle being concentric with that defined by the part annular recesses 62, 64. The concentric circles defined by the part annular recesses 62, 64 and the ports 74 are centred upon the axis of rotation of the drive shaft 16 and hence that of the swash plate 24.

The surface of the swash plate 24 which faces the plate 48 is provided with a recess 76 which extends radially of the swash plate 24 and is of sufficient length to permit communication between one of the part annular recesses 62, 64 and one of the ports 74. It will be recognised that on rotation of the drive shaft 16, the swash plate 24 is rotated with respect to the plate 48, and a position will be reached in which the recess 76 no longer aligns with the original one of the ports 74, and further rotation of the drive shaft 16 will result in the recess 76 aligning with another of the ports 74.

In use, fuel is supplied to the inlet 38 from a suitable fuel reservoir, and the drive shaft 16 is arranged to be driven at a speed related to engine speed. Rotation of the drive shaft 16 results in movement of the vanes 36 of the transfer pump which results in fuel from the inlet 38 being pumped at a relatively low pressure to the inlet non-return valves 34, a regulator (not shown) or other control arrangement being provided in order to control the quantity of fuel supplied through the inlet non-return valves 34. Starting from the position illustrated in Figure 1, the plunger 28 in the uppermost one of the bores 30 is in its innermost position, and rotation of the drive shaft 16 away from this position causes fuel to enter the bore 30 through the inlet non-return valve 34, fuel flow from the accumulator 42 to the bore 30 being prevented by the outlet non-return valve 40.Fuel continues to flow into the bore 30 until the rotation of the drive shaft results in the plunger member 28 occupying the position illustrated in the lower part of Figure 1, and it will be recognised that further movement of the drive shaft from this position results in the plunger member 28 being moved inwardly. As illustrated in Figure 1, the plunger member 28 moves independently of the bucket 29 thus even though the bucket 29 does not always move within the bore 30 by the maximum possible amount, the plunger member 28 remains with the slipper carried thereby in engagement with the swash plate 24.

The inward movement of the plunger member 28 results in the bucket 29 being pushed inwardly to pressurize the fuel within the bore 30 the fuel being unable to escape from the bore 30 through the inlet nonreturn valve 34. Once the pressure of fuel within the bore 30 exceeds the pressure of fuel within the accumulator 42 and is further able to overcome the force exerted by the spring on the outlet non-return valve 40, the outlet non-return valve 40 opens permitting fuel from the bore 30 to pass through the passage 44 to the accumulator 42. Such a flow of fuel out of the bore 30 continues until the position is reached in which the plunger member 28 is in its innermost position.In order to avoid excessive fuel pressure within the accumulator 42, a pressure relief valve (not shown) may be provided, although usually a metering arrangement is provided to control the supply of fuel to the bores 30 in order to maintain the fuel pressure within the accumulator at the correct pressure.

Although the distribution function of the distributor pump to be described hereinafter is described separately from the function of charging the accumulator 42 with pressurized fuel, it will be recognised that the two functions occur simultaneously.

Fuei from the accumulator 42 is delivered to both of the three-way valves 50, 52 through the passages 54, 56, 58, 60. In the position illustrated in Figure 1, the three-way valve 50 is arranged to permit communication between the part annular recess 62 and the accumulator 42, thus the part annular recess 62, the recess 76, provided in the swash plate 24, and a first port 74a, passages 72 and outlet ports 70 are receiving fuel at high pressure from the accumulator 42.In order to terminate the delivery of fuel, the three-way valve 50 is switched so as to terminate communication between the accumulator 42 and the part annular recess 62 and instead a volume of relatively low pressure is permitted to communicate with the part annular recess 62 thus reducing the pressure of fuel within the part annular recess 62, resulting in the pressure in the line connected to the cylinder of the associated engine reducing, and hence in the closure of the injection nozzle of that cylinder. Further rotation of the drive shaft 16 and swash plate 24 results in the communication between the recess 76 and the port 74a being broken.Continued rotation of the drive shaft 16 results in communication occuring between the recess 76 and the ports 74b, 74, 74d and 74e, in turn, in each case without either of the three-way valves 50, 52 permitting high pressure fuel to be supplied to the part annular recesses 62, 64.

Further rotation results in communication occuring between the part annular recess 64 and port 74f through the recess 76. Once such communication has been established, the three-way valve 52 is used to control fuel delivery from the accumulator to the injector connected to the port 74f.

The above cycle is then repeated, in each case the recess 76 being rotated by approximately 225 between each fuel delivery. It will be recognised that with such an arrangement, fuel delivery is controlled alternately by the three-way valve 50 and the three-way valve 52.

Throughout the pumping cycle, the swash plate 24 is pushed against the plate 48 by the force exerted by the springs 32 and the fuel pressure in the bores 30. Thus, a seal is formed and maintained between the swash plate 24 and plate 48 limiting leakage therebetween. However, a small amount of leakage may be desirable in order to lubricate the swash plate 24.

Figure 2a illustrates an alternative arrangement to that illustrated in Figure 2. Operation of the arrangement of Figure 2a is similar to that of Figure 2 and will not be described in detail.

The embodiment illustrated in Figure 3 comprises a housing 80 including a passage 82 extending therethrough the passage 82 including an enlarged region 84. A drive shaft 86 extends within the passage 82, the drive shaft 86 being supported by suitable bearings, and carrying a swash plate 88 which is rotatable within the enlarged region 84.

The housing 80 is provided with eight equiangularly spaced bores 90 surrounding the passage 82, the bores 90 each receiving a respective plunger member and bucket arrangement 92 which is reciprocable therein. The plunger and bucket arrangement 92 illustrated in the upper part of Figure 3 is similar to those illustrated in Figure 1, the plunger member of the arrangement 92 illustrated in the lower part of Figure omitting the enlarged head present in the arrangement 92 illustrated in the upper part of Figure 3.

Each of the bores 90 is arranged to receive fuel from a transfer pump including vanes 96 which are provided on the drive shaft 96, fuel from the transfer pump being communicated to the bores 90 through respective inlet non-return valves 98 which are arranged to permit the flow of fuel from the transfer pump to the bore 90, but to substantially prevent fuel flowing from the bore 90 towards the transfer pump. The transfer pump is provided with a regulator 112. Each of the bores 90 further communicates with a respective outlet non-return valve 100 which is arranged to permit fuel to flow out of the bore 90, but to substantially prevent fuel flow through the non-return valve 100 towards the bore 90.

The upper part of Figure 3 illustrates an embodiment in which each of the outlet non-return valves 100 communicates with a respective accumulator 102 provided within the housing 80, the accumulators 102 communicating with each other by means of an annular recess 104 provided in the end of the housing 80. An alternative accumulator arrangement is illustrated in the lower part of Figure 3 in which each of the outlet non-return valves 100 communicates by means of a respective passage 106 to an annular accumulator 108 provided at an end of the housing 80.

In order to regulate the pressure of fuel within the accumulator 102, 108, a fuel metering arrangement 110 may be provided between the inlet and outlet of the transfer pump, the arrangement taking the form of, for example a throttle arrangement. The arrangement 110 permits control of the quantity of fuel entering the bores 90, the spring 94 maintaining contact between the plungers members and the swash plate 88 so that such contact occurs even when only a small quantity of fuel is delivered to the bores 90.

The output pressure of the transfer pump as determined by the regulator 112 is used to control the operation of a safety valve 116 associated with the accumulator 102, 108. The valve 116 is arranged such that if the engine stops, and hence the transfer pressure falls, the valve 116 is arranged to open in order to relieve the accumulator pressure. A solenoid actuator 117 is also provided to permit opening of the valve 116 to enabe the accumulator to be vented.

As in the embodiment illustrated in Figure 1, the housing 80 is closed by means of a plate 120 which carries three-way valves 122, 124 which are arranged to communicate with the high pressure fuel in the accumulator 102, 108 through passages 126, 128. The three-way valve 122 communicates through a passage 130 with an annular recess 132 provided on the surface of the plate 120 facing the swash plate 88. The three-way valve 124 communicates through a passage 134 with a port 136 provided on the surface of the plate 120 facing the swash plate 88 at a location aligned with the axis of rotation of the drive shaft 86.

The plate 120 is further provided with eight equiangularly spaced outlet ports 138. Four of the outlet ports 138 communicate through passages 140 to ports 142 which are located in positions radially outward of the annular recess 132. The other four outlet ports 138 communicate through passages 144 with ports 146 provided on the surface of the plate 140 facing the swash plate 88, the ports 146 being positioned between the port 136 and the annular recess 132.

The surface of the swash plate 88 facing the plate 120 is provided with a pair of radially extending recesses 148, 150, the recess 148 being arranged to provide communication between the annular recess 132 and the ports 142 when the recess 148 is aligned with one of the ports 142.

Similarly the recess 150 is arranged to permit communication between the port 136 and the ports 146 when the recess 150 aligns with the ports 146. The swash plate 88 is further provided with a pair of concentric, part annular shaped recesses 152, 154, the part annular recess 152 being arranged to permit communication between the ports 142 other than the port 142 aligned with the recess 148, and the part annular recess 154 being arranged to permit communication between the ports 146 other than the port 146 communicating with the recess 150 on rotation of the swash plate 88.

The recesses 152, 154 are arranged to receive fuel at transfer pressure through suitable passages (not shown). Thus, fuel at transfer pressure is supplied to the delievery lines for supplying fuel to each of the injectors other than the injector being supplied with high pressure fuel to permit the collapse of any cavities in those lines before the next injection through a particular line. The recesses 152, 154 further aid in lubrication of the swash plate 88, and tends to counter balance the pumping load applied to the swash plate 88.

In use, the accumulator is charged in a manner similar to that described with reference to Figure 1, and further description of the charging process will not be described. Starting from the position illustrated in Figure 3, high pressure fuel is supplied from the accumulator 102, 108 to the three-way valve 122 through the passage 126, the three-way valve 122 permitting the fuel to flow through the passage 130 to the annular chamber 132 and from there to the recess 148 provided in the swash plate 88. As shown in Figure 3, the recess 148 is aligned with one of the ports 142 thus fuel from the accumulator 102, 108 is permitted to flow to the uppermost of the outlet ports 138. As illustrated in Figure 4, the outer three of the ports 142 are in communication with one another through the part annular recess 152 and are thus at the same pressure as one another.Also as shown in Figure 4, each of the ports 146 communicates with the part annular recess 154 and are thus at the same pressure as one another.

When fuel delivery is to be terminated, the three-way valve 122 is switched so as to break the communication between the accumulator 102, 108 and the annular recess 132, and instead the annular recess 132 is connected to a volume of relatively low pressure through the valve 122 thus permitting the pressure of fuel delivered by the distributor pump to be reduced, resulting in the injection nozzle closing and hence in termination of fuel delivery. As the drive shaft 86 rotates, the swash plate 88 also moves eventually resulting in the communication between the recess 148 and the corresponding one of the ports 142 being broken, further rotation of the swash plate 88 resulting in the recess 150 communicating with one of the ports 146.Once such communication has been achieved, the three-way valve 124 is switched so as to permit communication between the accumulator 102, 108 and the port 136 thus permitting fuel from the accumulator 102, 108 to flow through the recess 150 to the port 146 and from there to the respective outlet port 138. At the same time, the part annular recess 152 is in communication with all four of the ports 142 thus all of the ports 142 are at the same pressure as one another, and similarly the part annular recess 154 communicates with the three ports 146 which are not in communication with the recess 150.

As the recesses 148, 150 are both provided on the part of the swash plate 88 of greatest thickness, the pressure within these recesses acts against the force exerted by the plunger arrangements 92 which are coming towards the limit of their inward travel, thus the pressure within the recesses assists in balancing the forces tending to cause friction, wear, galling or welding of the swash plate 88.

It will be recognised that in the embodiments illustrated in each of the accompanying drawings, it is necessary for the housing 10, 80 to be sealed to the plate 48, 120 in order to reduce the leakage of fuel therebetween. Such sealing can be performed in any suitable known manner, but one particularly suitable type of seal is a seal known as a corruseal.

The accompanying drawings illustrate the inlet and outlet non-return valves 34, 40, 98, 100 as ball valves. It will be understood, however, that other types of non-return valve for example poppets could be used.

Although in each of the described embodiments two three-way valves are used, a single such valve could be used provided it is capable of switching sufficiently fast and capable of delivering sufficient fuel in the time available, in use, in the Figure 1 arrangement the two part annular recesses 62, 64 being replaced by an annular recess.

The accompanying drawings are diagrammatic, and it will be understood that the embodiments could be modified in order to minimize drilling lengths and dead volumes to provide a simple, compact configuration.

Claims (2)

1. A distributor pump arrangement for charging an accumulator with fuel and distributing pressurized fuel from the accumulator to the combustion spaces of an associated engine comprising a plunger movable in a bore under the influence of a swash plate arrangement in order to charge the accumulator, and a face distributor arrangement for distributing the pressurized fuel in the accumulator to the combustion space of the associated engine.

2. A pump according to Claim 1, in which the face distributor arrangement comprises a first relatively fixed element and a second element which is part of the swash plate arrangement, and which is rotatable relative to the first element.