GB2310916A - Distributor arrangement - Google Patents

Description

DISTRIBUTOR ARRANGEMENT This invention relates to a distributor arrangement for use in supplying fuel to the cylinders of an engine in turn, in use. The distributor arrangement is particularly suitable for use in an accumulator type fuel system.

An accumulator type fuel system comprises an accumulator which is arranged to be charged with fuel by a suitable high pressure fuel pump.

The outlet of the accumulator is connected to a three-way valve which is arranged, in one condition, to permit fuel to be supplied from the accumulator through the valve to a distributor arrangement. In an alternative condition of the three-way valve, communication between the accumulator and the distributor arrangement is broken and instead the distributor arrangement communicates through the three-way valve with a spill or drain arrangement.

In a known arrangement, the distributor arrangement comprises a sleeve having a supply port and a plurality of delivery ports. A distributor member is rotatable within a bore provided in the sleeve, the distributor member being provided with a plurality of inlet passages which are arranged to register, in turn, upon rotation of the distributor member with the supply port of the sleeve. The distributor member further includes a delivery passage which communicates with the supply passages and is positioned so as to register with the delivery ports of the sleeve,-in*.turn, upon rotation of the distributor member. The supply port is arranged to communicate with the threeway valve and the delivery ports are connected to respective fluid pressure actuable injectors of n. associated engine.

In use, the distributor member is arranged to rotate at a speed associated with engine speed, the motion of the distributor member being arranged such that when injection is required by a particular injector, the distributor member is positioned such that the three-way valve communicates with that injector through the distributor arrangement.

Injection is then initiated by switching the valve to supply high pressure fuel from the accumulator to that injector. Such a supply of high pressure fuel opens the injector thus fuel is supplied through that injector. To terminate injection, the supply of fuel from the accumulator is terminated by switching the valve, fuel being permitted to flow from the injector through the valve to the drain or spill arrangement. Such a flow of fuel reduces the fuel pressure at the injector resulting in the injector closing. Continued rotation of the distributor member results in the communication between the injector and the three-way valve being broken, further movement resulting in another of the injectors communicating with the three-way valve, hence permitting subsequent injection through that injector.

In order to minimize leakage, the clearance between the distributor member and sleeve is extremely small. The supply of pressurized, and hence hot, fuel through the distributor arrangement results in thermal expansion of the distributor member and sleeve, and differences in their expansion characteristics may result in seizure of the distributor arrangement. The return flow of fuel through the distributor arrangement in order to terminate injection accentuates this disadvantage, the return fuel being very hot as the pressure energy is graded to heat energy.

Further, as the distributor member rotates continuously within the sleeve, the inlet and delivery passages only register with the supply and delivery ports for a relatively short period of time, thus the timing of fuel injection and quantity of fuel which can be delivered are restricted.

It is an object of the invention to provide a distributor arrangement in which the disadvantages described hereinbefore are reduced.

According to the present invention there is provided a distributor arrangement comprising a body defining a chamber, a supply passage communicating with the chamber, a plurality of delivery ports provided in a surface defining part of the chamber, a rotatable distributor member sealingly engageable with the surface, a flow channel provided in the distributor member and registrable with the delivery ports, in turn, upon rotation of the distributor member to permit fuel flow between the chamber and the delivery ports, in turn, and drive means for intermittently driving the distributor member.

The drive means conveniently takes the form of a Geneva drive 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 part of a fuel system incorporating a distributor arrangement in accordance with an embodiment of the invention; and Figure 2 is a diagrammatic cross-sectional view of the drive arrangement of the distributor arrangement of Figure 1.

The distributor arrangement illustrated in the accompanying drawings comprises a multi-part body 10 first and second parts 12, 14 of which together define a chamber 16. The first part 12 of the body is provided with a supply passage 18 which permits communication between the chamber 16 and a three-way valve 20 which is mounted upon the body 10. The three-way valve 20 is connected to an accumulator 22 or other source of high pressure fuel, and also to a spill or drain arrangement 24 of conventional form. The three-way valve 20 is arranged so as to, in one position thereof, permit communication between the accumulator 22 and the supply passage 18, and in another position thereof to break the communication between the accumulator 22 and supply passage 18 and instead permit communication between the supply passage 18 and the spill or drain arrangement 24.

The second part 14 of the body 10 includes a plurality of delivery ports 26 which communicate through respective passages 28 to ports 30 for connection to respective fuel pressure actuable injectors 32.

The first part 12 of the body 10 is provided with a bore which extends from the chamber 16 so as to be coaxial therewith, a cylindrical bearing sleeve 34, or alternatively, ball or roller bearings, being provided within the bore. A drive shaft 36 is received within the sleeve 34, an end of the drive shaft 36 of enlarged diameter extending into the chamber 16, an annular bearing pad 38 being trapped between the enlarged end of the drive shaft 36 and the first part 12 of the body 10.

The enlarged end of the drive shaft 36 is keyed, for example by a drive dog or Oldham coupling arrangement, to a distributor member 40 which is rotatable within the chamber 16. A coiled compression spring 42 is housed in cylindrical bores provided in the end of the drive shaft 36 and in the distributor member 40, the coiled spring 42 being arranged to bias the distributor member 40 into engagement with the second part 14 of the body 10. A passage 44 is provided in the distributor member 40, the passage 44 being located so as to register, upon rotation of the distributor member, with the delivery ports 26 provided in the second part 14 of the body 10, in turn.

The drive shaft 36, and hence the distributor member 40, is arranged to be driven by a Geneva mechanism type drive arrangement. The drive arrangement comprises an arm 46 which is rotatable about an axis parallel to but spaced from the axis of the drive shaft 36 at a speed associated with engine speed by gears 48, 50, gear 48 being driven by a drive shaft 52 which is an extension of the drive shaft used to drive a pump which, in use, is used to charge the accumulator 22. An end of the arm 46 carries a roller 54 which is rotatable about an axis which extends perpendicularly to the longitudinal axis of the arm 46. The roller 54 is receivable within slots 56 provided in a drive wheel 58 a stub shaft 60 of which is connected to the drive shaft 36.

With the drive arrangement in the position illustrated in Figure 2, it will be recognised that rotation of the arm 46 in a clockwise direction will result in the roller 54 being received within the slot 56 of the drive wheel 58, continued motion of the arm 46 resulting in the drive wheel 58 being driven in an anticlockwise direction, the roller 54 moving further into the slot 56 until the slot 56 extends substantially vertically.

Continued movement of the arm 46 continues to drive the drive wheel 58 in an anticlockwise direction, the roller 54 gradually moving out of the slot 56. When the drive wheel 58 has been rotated in an anticlockwise direction by an angle of 90 , the roller 54 will move out of the slot 56, and thus movement of the drive wheel 58 is terminated. In the illustrated embodiment, further movement of the drive wheel 58 does not occur until the arm 46 has completed a further angular movement of 270 whereupon the roller 54 enters the next slot 56 to result in a further movement of the drive wheel 58 by 90".

For a four cylinder engine, the gearing arrangement of the drive arrangement is such that for every complete rotation of the pump drive shaft 52 the distributor member 40 rotates by one revolution, the distributor member 40 moving by 90" whilst the pump drive shaft 52 moves by 22.5 , the distributor member 40 then remaining stationary whilst the pump drive shaft 52 rotates by a further 67.5 . The distributor member 40 then rotates by a further 90" whilst the pump drive shaft 52 rotates by 22.5 and so on.

The drive arrangement, the location of the passage 44 in the distributor member 40, and the position of the delivery ports 26 in the second part 14 of the body 10 are arranged such that when the drive wheel 58 is stationary, the passage 44 registers with one of the delivery ports 26, movement of the drive wheel 58 resulting in the passage 44 registering with an adjacent one of the delivery ports 26, such registration being maintained whilst the drive wheel 58, and hence the distributor member 40, is stationary.

In use, with the distributor member 40 in the position illustrated in Figure 1, and with the drive arrangement in the position illustrated in Figure 2, injection has terminated, the supply passage 18 being in communication with the spill or drain arrangement 24 through the threeway valve 20. Movement of the drive shaft 52, and hence movement of the arm 46 results in the distributor member 40 being rotated by 90C and registering with the next delivery port 26 (out of the plane of the drawing). When such registration is achieved, movement of the distributor member 40 terminates. Once this position has been achieved, the three-way valve 20 is switched so as to permit communication between the accumulator 22 and the supply passage 18.

The supply of high pressure fuel from the accumulator 22 to the supply passage 18 results in the application of high pressure fuel to the chamber 16, such fuel being permitted to flow through the passage 44 to the delivery port 26 with which the passage 44 is aligned, and hence in fuel being delivered to the injector 32 associated with that delivery port 26.

The application of high pressure fuel to the injector 32 results in the injector 32 opening, and hence in the injection of fuel through that injector 32 to the associated cylinder of the engine.

The high pressure fuel within the chamber 16 also acts against the exposed surfaces of the distributor member 40 thus assisting the spring 42 in urging the distributor member 40 into sealing engagement with the second part 14 of the body 10. Since the distributor member 40 obscures the delivery ports 26 other than the delivery ports 26 aligned with the passage 44, fuel is substantially prevented from flowing to those delivery ports 26.

In order to terminate injection, the three-way valve 20 is switched so as to break the communication between the supply passage 18 and the accumulator 22, and instead to permit communication between the supply passage 18 and the spill or train arrangement 24. Such communication results in fuel flowing to the spill or drain arrangement 24 thus reducing the pressure of fuel within the chamber 16 and the pressure of fuel applied to the injector 32 associated with the delivery port 26 aligned with the passage 44. Such a reduction in pressure applied to the injector 32 results in the injector closing. After injection has been terminated, the roller 54 of the arm 46 enters the next slot 56 provided in the drive wheel 58 thus commencing movement of the distributor member 40 to align the passage 44 with the next delivery port 26 for the next injection.

It will be recognised that as the distributor member 40 is rotatable within a chamber 16, a relatively large clearance being provided between the distributor member 40 and the parts of the chamber defined by the first part 12 of the body 10, thermal expansion of the distributor member 40 with respect to the body 10 is unlikely to result in seizure of the distributor arrangement. Further, as flat surfaces are easier to manufacture than matched rotors and bores as required in the conventional rotary distributor arrangement, the manufacturing process can be simplified.

Although the above described distributor arrangement is particularly suitable for use in an accumulator type fuel system as described hereinbefore, it will be recognised that the distributor arrangement could be used with other types of fuel system.

Claims (3)

1. A distributor arrangement comprising a body defining a chamber, a supply passage communicating with the chamber, a plurality of delivery ports provided in a surface defining part of the chamber, a rotatable distributor member sealingly engageable with the surface, a flow channel provided in the distributor member and registrable with the delivery ports, in turn, upon rotation of the distributor member to permit fuel flow between the chamber and the delivery ports, in turn, and drive means for intermittently driving the distributor member.

2. A distributor arrangement as claimed in Claim 1, wherein the drive means comprises a Geneva drive arrangement.

3. A distributor arrangement substantially as hereinbefore described with reference to the accompanying drawings.