GB2324335A

GB2324335A - An in line fuel pump control rack damper

Info

Publication number: GB2324335A
Application number: GB9702415A
Authority: GB
Inventors: John Peter Tonks
Original assignee: ACTIONFORM Ltd
Current assignee: ACTIONFORM Ltd
Priority date: 1997-02-06
Filing date: 1997-02-06
Publication date: 1998-10-21
Also published as: GB9702415D0

Abstract

An in line fuel pump 22 for a diesel engine has a rack 30 controlling fuel valves 28, which are rotary. Movement of the rack 30 toward the throttle open position is damped by a hydraulic shock absorber 44. The control rack is able to return to its closed position unhindered. This prevents the valves 28 opening too suddenly thus allowing engine speed to pick up in order to fully utilise the fuel being delivered and thereby reducing emissions, engine wear and carbon deposits and improving fuel efficiency.

Description

Diesel Engines The present invention relates to diesel engines and in particular to arrangements for controlling their undesirable emissions.

Concern has been growing over recent years about the exhaust emissions of internal combustion engines, including diesel engines, in view of the harmful effect of these emissions on the environment, human health and so on.

Legislation to control vehicle emissions has become increasingly strict and is likely to become even more so in the future. The present inventor has sought to address the problems of diesel engine emission, particularly from diesel engines which use an in-line fuel pump, and the present invention seeks to address these problems.

The invention provides a control device adapted for use in controlling a fuel pump for a diesel engine, comprising damping means operable to provide mechanical damping of the movement of a fuel pump component or components, which movement changes the fuel pump from the throttle-closed condition to the throttle-open condition.

Preferably the pump is an in-line fuel pump.

Preferably the damping means is operable to restrict the rate at which the fuel pump valves can open, to a rate at which substantially all of the additional fuel so supplied can be utilised by the engine. The damping means is preferably operable to damp movement of the fuel pump rack when moving to the throttle-open position. The damping means is preferably arranged so that operation of the fuel pump from the throttle-open condition to the throttle-closed condition is unhindered. The damping means may comprise a resilient member operable to resist movement of the damped component. The resilient member may comprise a surface against which the damped component or components will bear when moving to the throttle-open position. The damped component or components may be free to move away from the said surface when moving away from the throttle-open position.

The resilient member is preferably a shock absorber means, such as a progressive damping shock absorber. The shock absorber means is preferably adjustable and preferably hydraulic.

The device preferably comprises attachment means operable to mount the damping means on the fuel pump. The attachment means may comprise a housing in which damping means is located. The housing is preferably mountable in relation to a part of the rack to allow the rack part to enter the housing as the rack moves to the throttle-open position. The housing is preferably mountable to receive the free end of the rack within the housing.

The housing may comprise an elongate bore into which the free end of the rack may enter through the mouth of the bore, the damping means being mounted in the bore by the presence of the rack end.

The invention also provides a diesel engine comprising a fuel pump and a control device as aforesaid associated with the fuel pump and arranged to damp movement, as aforesaid.

The invention also provides a fuel pump comprising a control device as aforesaid associated with the fuel pump and arranged to damp movement, as aforesaid.

The invention further provides a method of controlling a fuel pump for a diesel engine in which movement of a component of the fuel pump changes the fuel pump from the throttle-closed condition to the throttle-open condition, wherein the said movement of the component or components is damped.

Preferably the pump is an in-line fuel pump.

Preferably the damping restricts the rate at which the fuel pump valves can open, to a rate at which substantially all of the additional fuel so supplied can be utilised by the engine. The damping preferably damps the fuel pump rack when moving to the throttle-open position. The damping is preferably arranged so that operation of the fuel pump from the throttle-open condition to the throttle-closed condition is unhindered. The damping may be provided by a resilient member operable to resist movement of the damped component. The resilient member may comprise a surface against which the damped component will bear when moving to the throttle-open position. The damped component is preferably free to move away from the said surface when moving away from the throttle-open position.

Preferably the damping is provided by a shock absorber means, such as a progressive damping shock absorber. The shock absorber means is preferably adjustable and may be hydraulic.

An embodiment of the present invention will now be described in more detail, by way of example only and with reference to the accompanying drawings, in which: Fig. 1 is a schematic general outline view of a diesel engine having an inline fuel pump; and Figs. 2a and 2b are a partial vertical section and partial plan view of a fuel pump for the engine of Fig. 1, on an enlarged scale.

Turning to Fig. 1, there is shown schematically the outline of a diesel engine 10 having an engine block 12 in which the cylinders (not shown) are located. An inlet manifold 14 provides air to the cylinders. An outlet manifold (not shown) allows exhaust gas to leave. An exhaust turbine 18A in the exhaust manifold is coupled with an induction turbine 18B in the inlet manifold 14 to act together as a turbo charger in conventional manner.

An in-line fuel pump 22, shown schematically in Fig. 1, provides fuel to the cylinders. This is shown in more detail in Figs. 2a and 2b. The pump 22 has a housing 24 in which a chamber 26 contains fuel under pressure from the action of the fuel lift pump. Valves 28, which are rotary in nature, are provided to control egress of fuel from the chamber 26. Each cylinder of the engine has an associated valve 28 and the valves 28 are arranged in-line with the chamber 26. (It is for this reason that this type of pump is known as an in-line fuel pump). The condition of the valves 28 is controlled by a rack 30. Axial movement of the rack 30, in the directions indicated by the double-headed arrow 32, will cause the valves 28 to rotate by interaction between the rack teeth 34 and corresponding pinion teeth 45 on the valves 28.

As is conventional, movement of the rack 30 to the left (as shown in Figs.

2a and 2b) closes the valves and corresponds to the throttle-closed condition of the pump. The throttle-open condition occurs when the rack 30 has travelled to the right in Figs. 2a and 2b, causing the valves 28 to open fully.

Figs. 2a and 2b show the free end of the rack 30. The rack position is controlled at its other end by a throttle shaft which moves the rack 30 under control of a governor, typically a centrifugal or hydraulic governor. In a conventional in-line fuel pump, when the throttle is opened, the rack 30 will be quickly moved to the throttle-open condition, opening the valves 28 and almost immediately providing maximum fuel delivery to the cylinders of the engine.

In accordance with the invention, the fuel pump of Figs. 2a and 2b is provided with additional components, as will now be described. A housing 36A is mounted on the pump housing 24 by means of a threaded engagement 38.

The housing 36A is generally elongate and may be a circular cylinder in which an elongate bore is provided.

The housing 36A contains a resilient member in the form of a shock absorber, such as a progressive damping shock absorber. Preferably the shock absorber is adjustable, and may be hydraulic. Appropriate shock absorbers are commercially available. In one experimental arrangement, an OEM.35 shock absorber manufactured by Enidine Inc., Orchard Park, New York, U.S.A. has been fitted to a Lucas CAV in-line fuel pump which was in use with a Leyland National diesel engine.

The shock absorber 44 has an externally threaded main body which is mounted in the open end of the housing 36A by a threaded engagement 45, and locked in position by a lock nut 40.

It will be apparent from Figs. 2a and 2b that the housing 36A is positioned covering the aperture 42 through which the free end 30A of the rack 30 projects. Furthermore, the housing 36A is substantially axially aligned with the rack 30. In consequence, as the rack 30 moves between its throttle-open and throttle-closed positions, the free end 30A will move into or withdraw from the interior of the housing 36A. As the free end 30A moves into the housing 36A, toward the throttle-open position, the free end 30A of the rack 30 will bear on an end face 46 of the shock absorber 44. However, it can be seen that the free end 30A is free to move away from the end face 46 when moving away from the throttle-open position.

The end face 46 forms the moving component of the shock absorber 44.

Movement of the end face 46 away from the housing 24 is damped by the action of the shock absorber.

The illustrated shock absorber is adjustable by a control 47 at its end remote from the end face 46. In the illustrated arrangement, the setting of the control 47 is protected by a cap 36B which fits over the control 47 and threads onto the main body of the shock absorber 44, to be held in place by a second lock nut 40.

In use, the arrangement just described will perform in the following manner. First, assume that the throttle is closed. The rack 30 will be in the throttle-closed position, toward the left as shown in Figs. 2a and 2b. The valves 28 will be closed. If the throttle is now opened, the conventional arrangements controlling the fuel pump 22 would seek to move the rack 30 fully and almost immediately to its throttle-open position toward the right of Figs. 2a and 2b, thus opening the valves 28 and putting the fuel pump 22 in the throttle-open condition. However, this movement of the rack 30 is damped as soon as the free end 30A makes contact with the end face 46. Further movement of the free end 30A toward the throttle-open condition is damped because this movement requires the shock absorber 44 to be compressed between the free end 30A and the mounting at 45. As a result of this damping, the pump 22 is prevented from moving immediately to its throttleopen condition, but will approach that condition more gradually over a period of time determined by the characteristics of the shock absorber 44.

The arrangement damps movement in the sense that it resists, but does not prevent, movement being caused by another motive force. The arrangement does not change the manner in which the movement is being driven, but provides resistance to that drive.

The total movement of the rack in a typical in-line fuel pump is about 7mm and it has been found in one experimental arrangement that by damping the final distance of about 2mm of this movement, the benefits of the invention can be achieved. However, these dimensions will vary, possibly quite widely, between different pumps and applications. In some, such as marine diesels, dimensions could be very much larger.

The consequences of this on the emission characteristics of the engine are significant. In a conventional arrangement in which the rack moves immediately to the throttle-open condition, maximum fuel delivery to the cylinders would begin immediately. However, the engine speed at this time would still be low. In consequence, this additional fuel cannot be used by the engine. Much of it passes through the engine and appears in the exhaust gases as a dark cloud of fumes. The contents of this dark cloud are unburnt diesel fuel which is a pollutant and is highly visible. Additionally, the fuel is wasted, thus reducing the fuel efficiency of the engine. Some of the unburnt fuel may also be deposited within the engine, increasing engine wear and carbon deposition and reducing engine life.

When properly adjusted, an arrangement according to the invention prevents excess fuel being delivered (which would remain unburnt) but allows adequate fuel for normal engine operation. Initially, the valves can only partly open, because the rack abuts the shock absorber. As engine speed builds up, fuel demands of the engine will increase, but the arrangement will allow progressively more fuel to be delivered, as the damping allows the rack to move further to the throttle-open position. By correctly setting the damping, the fuel delivery can increase at the same rate as the fuel demand. No excess fuel is delivered, and therefore emissions and engine damage caused by unburnt fuel are avoided.

Damping is set by adjusting the position and resistance of the shock absorber. The position determines the point of travel at which the rack 30 will meet the shock absorber 44 and begin to be damped. The resistance determines the strength of the damping applied to the rack, and hence the amount by which the normal movement will be slowed.

Furthermore, it is important to note that the arrangement described has no adverse effect on the power output of the engine. This is because the engine is provided with as much fuel as it can use, but no more. Full engine power is therefore available and there is no adverse safety implication, as there can sometimes be when an engine speed is governed. Furthermore, the damping has no effect on shut down. The rack is not attached to the damping arrangement and is free at any time to move immediately to the throttle-closed position. Thus, emergency shut down of an engine is not inhibited in any way.

Test results show how significant the reduction in emissions can be. A SUN Advanced Smoke Analyser (operating in accordance with standard procedure ASA 200) was used to test diesel smoke output from an engine. This test measures light transmission through the smoke, and thus smoke density.

The result is given as a value of a parameter "K". An engine was first tested without modification in accordance with the invention and achieved a reading of K=2.08. after fitting a device as described above, and immediately re-testing, a result of K=0.85 was achieved. The engine was then run continuously under load and then re-tested. The result was then K=0.55. The difference in the smoke density is clearly visible to the eye. Indeed, to the eye, smoke is virtually wholly eliminated.

Many variations and modifications to the apparatus described above can be arranged without departing from the invention. In particular, many different arrangements for damping can be devised and would designed in each case to fit appropriately on particular designs of fuel pump. While it has been suggested that it is the movement of the rack which should be damped, other arrangements could damp other movement within the fuel pump, to similar effect.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

1. A control device adapted for use in controlling a fuel pump for a diesel engine, comprising damping means operable to provide mechanical damping of the movement of a fuel pump component or components, which movement changes the fuel pump from the throttle-closed condition to the throttle-open condition.

2. A device according to claim 1, wherein the pump is an in-line fuel pump.

3. A device according to claim 1 or 2, wherein the damping means is operable to restrict the rate at which the fuel pump valves can open, to a rate at which substantially all of the additional fuel so supplied can be utilised by the engine.

4. A device according to claim 1, 2 or 3, wherein the damping means is operable to damp movement of the fuel pump rack when moving to the throttle-open position.

5. A device according to any preceding claim, wherein the damping means is arranged so that operation of the fuel pump from the throttle-open condition to the throttle-closed condition is unhindered.

6. A device according to any preceding claim, wherein the damping means comprise a resilient member operable to resist movement of the damped component.

7. A device according to claim 6, wherein the resilient member has a surface against which the damped component or components will bear when moving to the throttle-open position.

8. A device according to claim 7, wherein the damped component or components is or are free to move away from the said surface when moving away from the throttle-open position.

9. A device according to claim 7 or 8, wherein the resilient member is a shock absorber means.

10. A device according to claim 9, wherein the shock absorber is a progressive damping shock absorber.

11. A device according to claim 9 or 10, wherein the shock absorber means is adjustable.

12. A device according to claim 9, 10 or 11, wherein the shock absorber means is hydraulic.

13. A device according to any preceding claim, comprising attachment means operable to mount the damping means on the fuel pump.

14. A device according to claim 13, wherein the attachment means comprise a housing in which damping means is located.

15. A device according to claim 14, wherein the housing is mountable in relation to a part of the rack to allow the rack part to enter the housing as the rack moves to the throttle-open position.

16. A device according to claim 15, wherein the housing is mountable to receive the free end of the rack within the housing.

17. A device according to claim 14, 15 or 16, wherein the housing comprises an elongate bore into which the free end of the rack may enter through the mouth of the bore, the damping means being mounted in the bore by the presence of the rack end.

18. A diesel engine comprising a fuel pump and a control device according to any preceding claim associated with the fuel pump and arranged to damp movement, as aforesaid.

19. A fuel pump comprising a control device according to any preceding claim associated with the fuel pump and arranged to damp movement, as aforesaid.

20. A method of controlling a fuel pump for a diesel engine in which movement of a component of the fuel pump changes the fuel pump from the throttle-closed condition to the throttle-open condition, wherein the said movement of the component or components is damped.

21. A method according to claim 20, wherein the pump is an in-line fuel pump.

22. A method according to claim 20 or 21, wherein the damping restricts the rate at which the fuel pump valves can open, to a rate at which substantially all of the additional fuel so supplied can be utilised by the engine.

23. A method according to claim 20, 21 or 22, wherein the damping damps the fuel pump rack when moving to the throttle-open position.

24. A method according to any of claims 20 to 23, wherein the damping is arranged so that operation of the fuel pump from the throttle-open condition to the throttle-closed condition is unhindered.

25. A method according to any of claims 20 to 24, wherein the damping is provided by a resilient member operable to resist movement of the damped component.

26. A method according to claim 25, wherein the resilient member comprises a surface against which the damped component will bear when moving to the throttle-open position.

27. A method according to claim 26, wherein the damped component is free to move away from the said surface when moving away from the throttle-open position.

28. A method according to any of claims 20 to 27, wherein the damping is provided by a shock absorber means.

29. A method according to claim 28, wherein the shock absorber means is a progressive damping shock absorber.

30. A method according to claim 28 or 29, wherein the shock absorber means is adjustable.

31. A method according to claim 28, 29 or 30, wherein the shock absorber means is hydraulic.

32. A control device substantially as described above, with reference to the accompanying drawings.

33. A method of controlling a fuel pump, substantially as described above, with reference to the accompanying drawings.

34. Any novel subject matter or combination including novel subject matter disclosed, whether or not within the scope of or relating to the same invention as any of the preceding claims.