GB2310914A - Distributor arrangement - Google Patents

Description

DISTRIBUTOR ARRANGEMENT This invention relates to a distributor arrangement for use in a fuel system of a diesel internal combustion engine. The distributor arrangement is particulariy suitable for use in accumulator type fuel systems, but could alternatively be used in a different type of fuel system.

An accumulator type fuel system includes an accumulator which is arranged to be charged with fuel by a suitable high pressure fuel pump in order to maintain the pressure within the accumulator within a predetermined range, in use. The accumulator is connected to a threeway valve which is also connected to a spill or drain arrangement and a distributor arrangement. The three-way valve is controlled so as to permit communication either between the accumulator and the distributor arrangement or between the distributor arrangement and the spill or drain arrangement.

The distributor arrangement commonly includes a sleeve having a bore within which a rotary distributor member is located. The sleeve has a supply port connected to the three-way valve, and a plurality of delivery ports connected to respective fuel pressure actuable injectors of an associated engine. The distributor member includes a plurality of axially aligned inlet passages which are arranged to register, in turn, with the supply port upon rotation of the distributor member, and an outlet passage which is arranged to register with the delivery ports, in turn, upon rotation of the distributor member. The inlet and outlet passages communicate with one another, and are arranged such that when one of the inlet passages registers with the supply port, the outlet passage registers with one of the delivery ports. The angular position of the distributor member therefore controls which of the injectors is permitted to receive fuel from the accumulator at a particular point in time.

In use, high pressure fuel flows through the distributor member in one direction during delivery, and in the other direction when reducing the pressure of fuel at the injector to terminate injection. Such fuel flow results in heating of the distributor member, and as the clearance between the distributor member and sleeve is very small in order to minimise leakage, thermal expansion resulting from such heating may result in seizure of the distributor arrangement.

According to the present invention there is provided a distributor arrangement comprising a distributor member having an axis, the distributor member being slidable within a sleeve in a direction parallel to the axis, the sleeve having a supply port and a plurality of delivery ports provided therein, the delivery ports being spaced from one another along a line parallel to the axis, the distributor member having a passage provided therein which is registrable with each of the delivery ports, the passage being in constant communication with the supply port, the distributor member being provided with a surface against which high pressure fuel acts, in use, to bias the distributor into sealing engagement with the part of the sleeve in which the delivery ports are provided.

The invention will further be described, by way of example, with reference to the accompanying drawings, in which like reference numerals denote like parts, and in which: Figure 1 is a diagrammatic cross-sectional view of a fuel system incorporating a distributor arrangement in accordance with an embodiment of the invention; Figure 2 is a cross-sectional view along the line X-X of Figure 1; Figure 3 is a view similar to Figure 1 of a second embodiment; and Figure 4 is a cross-sectional view along the line Y-Y of Figure 3.

The distributor arrangement illustrated in Figures 1 and 2 comprises a body 10 having a blind bore of rectangular cross-section provided therein, an end plate 14 being secured to the body 10, for example by bolts or other suitable means, to close the bore 12. A supply passage 16 is provided in the body 10, the supply passage 16 communicating with the bore 12. A three-way valve 18 of conventional form is secured to the body 10, an outlet of the three-way valve 18 communicating with the supply passage 16. The three-way valve 18 further communicates with an accumulator 20 which is arranged to be charged with fuel by a suitable high pressure fuel pump (not shown) and to a conventional spill or drain arrangement 22. The three-way valve arrangement 18 is controlled such that in one position thereof communication is permitted between the accumulator 20 and the supply passage 16, and in another position of the three-way valve 18 communication between the accumulator 20 and supply passage 16 is broken and instead communication is permitted between the supply passage 16 and the spill or drain arrangement 22.

The body 10 is further provided with four outlet passages 24 which are spaced apart from one another in the direction of the axis of the bore 12.

In the arrangement of Figures 1 and 2, the outlet passages 24 are provided in a surface of the bore 12 opposite the surface with which the supply passage 16 communicates. The outlet passages 24 each communicate with respective ports 26 which, in use, are connected to respective fuel pressure actuable injectors 26 of an associated engine.

A distributor member 28 of rectangular cross-section is slidable within the bore 12. As illustrated in Figure 2, the distributor member 28 is of cross-sectional area significantly smaller than the cross-sectional area of the bore 12, thus there is sufficient clearance between the distributor member 28 and the body 10 to permit significant thermal expansion of the distributor member 28 without resulting in seizure of the distributor arrangement. A coiled compression spring 30 is located in the blind end of the bore 12 and engages against an end of the distributor member 28 biasing the distributor member 28 away from the blind end of the bore 12. A passage 32 extends through the distributor member 28, the passage 32 being located so as to be registerable, upon sliding movement of the distributor member 28 with respect to the sleeve 10, with the delivery passages 24 provided in the body 10.

A linear actuator arrangement 34 is provided to slide the distributor member 28 within the bore 12 between the various positions of the distributor member in which the passage 32 registers with one of the delivery passages 24. In the arrangement illustrated in Figure 1, the linear actuator arrangement 34 comprises an actuator rod 36 which is a sealing fit within a bore provided in the cover plate 14, the actuator rod engaging the distributor member 28 such that movement of the actuator rod 36 is transmitted to the distributor member 28 to move the distributor member against the action of the spring 30. Movement of the actuator rod 36 in the embodiment illustrated in Figure 1 is achieved using a linear solenoid 38 together with a sensor 40 for detecting the position of the actuator rod. Alternatively, a stepping rotary cam mechanism could be moved to control movement of the actuator rod 36 and hence the distributor member 28.

In use, starting from the position illustrated in Figure 1, in order to commence injection, the three-way valve 18 is switched so as to permit communication between the accumulator 20 and the supply passage 16.

Such switching of the three-way valve 18 results in high pressure fuel flowing through the supply passage 16 to the bore 12, the high pressure fuel being permitted to flow through the passage 32 to the delivery passage 24 aligned with the passage 32 and from there to the injector 26 associated with that delivery passage 24. The application of high pressure fuel to the injector 26 subsequently results in the injector 26 opening, and hence in fuel being supplied to the cylinder of the associated engine.

In order to terminate injection, the three-way valve 18 is switched so as to break communication between the accumulator 20 and the supply passage 16, and instead to permit communication between the supply passage 16 and the spill or drain arrangement 22. Such communication between the supply passage 16 and the spill or drain arrangement 22 results in high pressure fuel from the distributor arrangement and the passages connecting the distributor arrangement to the open injector 26 being able to flow to the drain or spill arrangement 22, and thus in the pressure therein reducing. Such a reduction in pressure at the injector 26 subsequently results in the injector 26 closing, and hence in injection being terminated. Once the injection has terminated, the linear actuator arrangement 34 is controlled so as to move the actuator rod 36 and hence the distributor member 28 so as to bring the passage 32 into register with another one of the delivery passages 24. Once such movement has been completed, the three-way valve 18 may be controlled so as to permit communication between the accumulator 20 and supply passage 16, breaking communication between the supply passage 16 and the spill or drain arrangement 22, thus repeating the injection cycle.

It will be recognised that when the accumulator 20 communicates with the supply passage 16, high pressure fuel within the bore 12 acts against the exposed surfaces of the distributor member 28, and since one of the surfaces of the distributor member 28 is in engagement with the surface of the bore 12 within which the delivery passages 24 are provided, that surface of the distributor member 28 is not exposed to the high pressure fuel, thus there exists a pressure imbalance resulting in the distributor member 28 being pushed into engagement with the surface of the bore 12 in which the delivery passages 24 are provided, thus sealing the distributor member 28 to the body 10. Such sealing of the distributor member 28 substantially prevents fuel from flowing to the delivery passages 24 other than the delivery passage 24 with which the passage 32 is aligned. The sealing of the distributor member 28 against the body 10 is sufficiently good to allow the delivery passages 24 to be located relatively close to one another and hence in the total travel of the distributor member 28 necessary to allow the passage 32 to register with each of the delivery passages 24, in use, being relatively small. The volume of the bore 12 can therefore be minimised, resulting in wastage of high pressure fuel being reduced.

The arrangement illustrated in Figures 3 and 4 is similar to that illustrated in Figures 1 and 2, and only the differences between the two arrangements will be described in detail.

The main difference between the arrangement of Figures 3 and 4 and that of Figures 1 and 2 is that the bore 12 and distributor member 28 are of circular cross-section rather than rectangular as illustrated in Figures 1 and 2. The distributor member 28 is of similar diameter to the bore 12, although the clearance between the two is still sufficient to permit thermal expansion of the distributor member without resulting in seizure of the distributor arrangement. The distributor member 28 includes a flow channel 42 which communicates continuously with the passage 32, the flow channel 42 defining an area against which high pressure fuel from the accumulator 20 can act, in use, thus biasing the distributor member 28 into engagement with the part of the body 10 in which the delivery passages 24 are provided, and thereby providing a good seal between the distributor member 28 and that part of the body 10.

A further difference between the arrangement of Figures 3 and 4 and that of Figures 1 and 2 is that rather than providing a separate actuator rod 36, the distributor member 28 extends out of the body 10, extending through the end plate 14, thus the actuator 36 and sensor 40 act directly on the distributor member 28 rather than upon an actuator rod as in the arrangement of Figures 1 and 2. As the distributor member 28 is of similar diameter to the bore 12, the distributor member 28 and body 10 form a relatively good seal. Thus the end plate 14 does not need to sealingly engage the distributor member 28. The good seal between the distributor member 28 and body 10 is enhanced by the length of the sealing area therebetween. The enhanced sealing effect enables a greater clearance to be tolerated between the distributor member 28 and body 10.

The arrangement illustrated in Figures 3 and 4 are advantageous in that the pressure imbalance acting on the distributor member 28 due to the presence of the actuator rod 36 no longer exists, and the dead volume which is present in the arrangement of Figures 1 and 2 is significantly reduced. Although not illustrated in Figure 3, the part of the bore 12 containing the spring 30 is connected to a suitable low pressure volume so that movement of the distributor member 28 is not hindered by the presence of fuel within this chamber being required to be pressurized in order to permit such movement.

Claims (4)

1. A distributor arrangement comprising a distributor member having an axis, the distributor member being slidable within a sleeve in a direction parallel to the axis, the sleeve having a supply port and a plurality of delivery ports provided therein, the delivery ports being spaced from one another along a line parallel to the axis, the distributor member having a passage provided therein which is registrable with each of the delivery ports, the passage being in constant communication with the supply port, the distributor member being provided with a surface against which high pressure fuel acts, in use, to bias the distributor into sealing engagement with the part of the sleeve in which the delivery ports are provided.

2. An arrangement as claimed in Claim 1, wherein the distributor member is of rectangular crosssectional shape, the distributor member being slidable within a bore of rectangular cross-sectional shape, the bore being of greater cross-sectional area than the distributor member.

3. An arrangement as claimed in Ctaim 1, wherein the distributor member is of circular cross-sectional shape and is provided with a recess in constant communication with the supply port which defines the said surface against which high pressure fuel acts.

4. A distributor arrangement substantially as hereinbefore described with reference to Figures 1 and 2 or Figures 3 and 4 of the accompanying drawings.