GB2079364A - Distribution fuel injection pump for use with a diesel engine - Google Patents

Abstract

When the pressure of supercharged air from a turbocharger increases, a cam (57) moves in a predetermined direction and controls a metering valve (24) fitted slidably on a fuel distribution plunger (11) through a maximum injection control lever (55) so as to initially close a cutoff port (23) provided in the plunger (11), thereby increasing the amount of fuel injected into the cylinders of a diesel engine. When the pressure of the supercharged air increases beyond a predetermined value due to, for example, an operating fault, the cam (57) moves further in the same direction to open the cutoff port (23), thereby decreasing the distribution of fuel to the cylinders and protecting the engine. <IMAGE>

Description

SPECIFICATION Distribution fuel injection pump for use with a diesel engine The present invention relates to a distribution fuel injection pump for use with a diesel engine having an exhaust gas turbocharger, and more particularly to a system for the control of the maximum amount of fuel injected to the engine and thus the super charged pressure (hereinafter referred to as the boost pressure) in the engine.

Generally, a distribution fuel injection pump con trols the amount of fuel injected to a diesel engine by causing a metering valve to open or close a cutoff port provided in a fuel distribution plunger driven rotationally and reciprocally synchronously with the running of the engine. The opening or closing of the cutoff port is effected by control of the position of the metering valve using a tension lever. In the distribu tion fuel injection into a diesel engine having an exhaust turbocharger, a maximum fuel injection control lever which controls the maximum fuel injection position of the tension lever is controlled by the cam of a boost pressure adjustment device operative in response to the boost pressure from the exhaust gas turbocharger.

The configuration of the cam is designed such that the amount of fuel injected increases in proportion to the increase in the boost pressure, taking the form of a truncated cone, for example. When the max imum boost pressure is regulated to protect the exhaust gas turbocharger, fuel injection does not increase beyond a predetermined or maximum amount of fuel corresponding to the maximum boost pressure.

Although the exhaust gas turbocharger may run excessively owing to some trouble with the max imum boost pressure limiter, however, the cam configuration is such that it maintains the predeter mined injection amount corresponding to the max imum boost pressure. Thus, the amount of fuel injected can increase thus increasing the pressure within the engine cylinders, thereby possibly damaging the engine.

It is therefore an object of the present invention to provide a distribution fuel injection pump which serves to decrease the amount of fuel injected when the boost pressure comes into a dangerous region exceeding the predetermined maximum value.

The present invention provides a distribution fuel injection pump for use with a diesel engine with a turbocharger which includes a cam which moves in a predetermined direction when the pressure of the supercharged air from the turbocharger increases and which controls a metering valve fitted slidably on a fuel distribution plunger through a maximum injection control lever so as to close a cutoff port provided in the plunger thereby increasing the amount of fuel injected into the cylinders of a diesel engine. When the pressure of the supercharged air increases beyond a predetermined value, the cam further moves in the same direction, but the cam serves to open the cutoff port, thereby decreasing the distribution of fuel to the cylinders.

In the accompanying drawings: Figure lisa diagramaticfragmentary crosssectional view of a preferred embodiment of the distribution fuel injection pump according to the present invention; Figure2 is a diagramatic illustration of a combination of the pump according to the present invention and a diesel engine having a turbocharger; and Figures 3A, 3B and 3C are diagramtic illustrations of different operational conditions of the essential portions of the pump.

Referring to the drawings and particularly Figure 1, there is shown a preferred embodiment of a fuel injection pump, for use with a diesel engine to be shown later, according to the present invention, generally designated by the reference numeral 10. A plunger 11 is slidably and rotably inserted in a plunger barrel 12 fixed in the housing 13. The plunger 11 includes fuel inlet grooves 14 of the same number as the cylinders of the engine provided equidistantly around the outer periphery of the plunger 11. The plunger 11 and plunger barrel 12 cooperate to form a hydraulic chamber 15 whose volume is changed according to the extent to which the plunger 11 is inserted into the barrel 12.This chamber receives fuel through fuel intake passage 16, 17 provided in the housing 13 and barrel 12 respectively from a fuel reservoir 18 in the housing when one of the fuel inlet grooves 14 is brought into communication with the intake passage 17. The hydraulic chamber 15 also communicates with a fuel discharge passage 19 which extends axially through the plunger 11 and which has a fuel outlet port 20 that can communicate with any one of the fuel outlet passages 21 distributed around the barrel 12 in the housing 13 leading to the corresponding engine cylinders, not shown, through the corresponding delivery valves, also not shown.The fuel discharge passage 19 also communicates with a cutoff port 23 provided in that part of the plunger 11 not inserted in the barrel 12 and which is opens in to the reservoir 18 when a metering valve 24 is moved to the left in the figure along the plunger 11 so as to uncover the cutoff port 23.

The plunger 11 is secured at its left-hand end to a disc cam 25 which is connected in an axially slidable manner to a coupling 26. This coupling is in turn connected to a drive gear 27 which is also connected to a drive shaft 28. The disc cam 25 has the same number of cam faces 29 as the cylinders of the engine and is resiliently urged against rollers, not shown, each pivotably supported by a roller casing 30 which is also rotatable about the coupling 26.

Thus, when the drive shaft 28 rotates, the cam faces 29 pass over the rollers so that the plunger 11 reciprocates axially by a predetermined cam lift while rotating. A pump 31 feeds fuel from an inlet 32 through a passage 33 into the reservoir 18.

A governor 34 includes a shaft 35 secured to the housing 13 which supports a gear 37 pivoted thereon which in turn meshes with, and is driven by, the drive gear 27. A flyweight holder 38 is secured to the gear 37 and accommodates a plurality of flyweights 39 triangular in section disposed around a sleeve 40 slidably fitted on the shaft 35 such that a flange 41 of the sleeve 40 is loosely engaged with recesses 42 in the flyweights whereby as the rotational speed of the drive shaft 28, the drive gear 27, and therefore the governor gear 37 increase, the flyweights 39 are centrifugally moved outward so as to move away from the sleeve 40 about their corners 43, thereby moving the sleeve 40 to the right in Figure 1. The end of the governor sleeve 40 contacts a starting lever 44 supported on a pivot 45 on which a tension lever 46 is also pivotably supported.A spring 47 is provided under tension between the levers 44 and 46. The starting lever 44 is connected to the metering valve 24 by a ball-recess connection 48 such that the movement of the governor sleeve 40 controls the position of the metering valve 24 relative to the cutoff port 23. The tension lever 46 is connected to the accelerator pedal, not shown, through an idler spring 49, a main spring 50 and a hook 51 attached to a control lever, not shown, to the accelerator pedal, also not shown, such that when the accelerator pedal is depressed, the tension lever 46 is turned counterclockwise about the pivot 45 in Figure 1,thereby closing the cutoff port 23.

A position adjustment device 52 adjusts the initial position of the metering valve 24 relative to the cutoff port 23. The adjustment device 52 includes an adjustment screw 53 contacting the upper end of the tension lever 46 which is also urged at its lower end to the left by a spring 54.

When the plunger 11 moves to the left in Figure 1 while rotating, thereby effecting a fuel intake stroke, the fuel within the reservoir 18 is drawn into the hydraulic chamber 15 through the passages 16, 17 and one of the fuel inlet-grooves 14 aligned with the passage 17. When the plunger 11 is switched to its compression stroke, the fuel drawn into the hydraulic chamber 15 is forced through one of the fuel outlet passages 21 aligned with the outlet 20 and injected through a delivery valve, not shown, into the corresponding cylinder of the engine. When the cutoff port 23 is then displaced from the metering valve 24 and opened to the reservoir 18, the fuel within the hydraulic chamber 15 is spilt from the cutoff port 23, thereby stopping fuel injection. Thus, adjustment of the position of the metering valve 24 stops the fuel injection, i.e. controls the amount of fuel injected.Similarly, if the metering valve 24 is moved to the right in Figure 1, the amount of fuel injected increases.

The extreme left-hand position of the tension lever 46, corresponding to the maximum amount of fuel injected, is controlled by an L-shaped maximum injection control lever 55 of a boost pressure adjustment device 56. The lever 55 is pivoted at 56 and engages at one end with the tension lever 46 so as to control the position of maximum fuel injection and engages at the other end with a cam 57 through an opening 58 provided in the side wall of a cylindrical cam casing 59. The cam 57 is formed on the outer surface of a plunger 60 which is slidable in the cylindrical casing 59 whose lower end is closed in an air-tight manner. The upper end of the plunger 60 is connected to a diaphragm 61 which partitions the housing of the boost pressure adjustment device 56.

The boost pressure from an exhaust gas turbochargerto be illustrated in Figure 2 is admitted into a pressure chamber 62 through an T-shaped inlet passage 63 which is secured to the upper wall of the pressure chamber 62. The cam casing 59 is firmly supported by the base 64 of the housing of the boost pressure adjustment device 56. A return spring 65 is provided between the diaphragm 61 and the base 64 so as to return the diaphragm 61 to its initiai position.The plunger 60, including the cam 57, is provided with a T-shaped passage, shown by broken lines 66, to facilitate the movement of the plunger 60 by removing the air present below the plunger 60 in the casing 59 which may otherwise obstruct the movement of the plunger through the passage 66 to a chamber 67 formed below the diaphragm 61, thence through a passage 68 in the base 64, a filter 69 in a passage 70 communicating with the passage 68 and out to the atmosphere. Fuel is prevented from entering the chamber 67 and the chamber 74 formed between the lower end of the plunger 60 and the base of the cam casing 59. The fuel within the reservoir 18 is fed back through a filter 71 provided within an outlet device 72 and an outlet port 73 to a fuel tank, not shown.

When the boost pressure increases, the cam 57 is lowered by the diaphragm 61, whereas when the boost pressure decreases, the cam 57 is raised by the resiliency of the return spring 65. As will be seen from Figure 1,the cam 57 takes the form of a hyperboloid of revolution having a gradually curved concave side surface which includes a first tapered portion A serving to increase the amount of fuel injected according to the increase in the boost pressure within the chamber 62, and a second tapered portion B serving to decrease the amount of fuel gradually as the boost pressure increases beyond a predetermined value. The predetermined value of the boost pressure is selected to be the maximum boost pressure permissible in a boost pressure control device provided in the exhaust gas turbocharger shown in Figure 2.A typical boost pressure control device is for example an exhaust bypass type, as shown in Figure 2, wherein a bypass valve 74 is provided midway in the exhaust passageway 75 between the exhaust manifold 76 of a diesel engine 77 and a turbine 78 of the turbocharger 79.

Thus when the boost pressure, that is the discharge pressure from a compressor 80, exceeds a predertermined value, the bypass valve 74 is opened by an actuator 81 so that the adjustment of the amount of exhaust gas fed to the turbine 78 maintains the boost pressure below the predetermined value, the maximum boost pressure, to prevent the pressure within the cylinders, not shown, of the engine 77 from increasing so far as to damage the engine. The boost pressure from the compressor 80 is fed to the inlet 63 of the boost adjustment device 56 through a passageway 82 and also to the cylinders of the engine through the intake manifold 83. The pump drive shaft 28 is driven through a pulley 84 and a belt 85 attached to the engine shaft 86. The pump 10 is supported by frames 87 on the engine 77 and feeds fuel through pipes 88 to the cylinders of the engine.

In operation, the amount of fuel injected into the engine is controlled by the tapered portion A of the cam 57 of the boost pressure adjustment device 56 in the range in which a maximum boost pressure control means such as the exhaust gas bypass valve 74 operates. Figure 3A shows the condition in which the supercharged pressure from the compressor 80 is not supplied to the chamber 62. In this situation, when the maximum injection amount control lever 55, moving together with the accelerator, is moved tufts completely open position, the tension lever 46 abuts the cam 57 through the control lever 55 so that the position of the metering valve 24 is determined carresponding to the completely open position.

Figure 3B shows the condition in which the supercharged pressure in its normal range is supplied to the pressure chamber 62, in which case the cam 57 is forced downward and the control lever 55 is rotated clockwise in Figure 1 so that the position of the metering valve 24 corresponding to the completely open position of the control lever 55 is moved more to the right than in Figure 3A, thereby increasing the amount of fuel injected.

Conventionally, if a turbocharger is to be selected under the assumption that an exhuast gas bypass is provided as small a turbocharger as possible tends to be selected, in order to set the turbocharger to a relatively high speed at its maximum output so as to be used at a relatively high efficiency. The exhaust gas valve such as that shown by 74 in Figure 2 is controlled to be opened and closed by the boost pressure admitted to an actuator such as that shown by 81 turning about a pivot such as that shown by 89 in Figure 2 so that when the boost pressure inlet pipe such as 82 and the actuator are broken, it is closed.

Thus there is a possibility that the bypass valve such as that shown by 74 can break so that the whole of the exhuast gas flows into the turbocharger 79, thereby running the turbocharger excessively and damaging its bearings. Further, if the maximum injection amount continues to be maintained corresponding to the maximum predetermined boost pressure while the turbocharger is running excessively so as to increase the pressure in the cylinders, the engine itself would be damaged.

However, when the boost pressure increases excessively, the cam 57 is used in the range of the tapered portion B thereof, thereby decreasing the amount of fuel injected. Figure 3C shows the condition where a boost pressure higher than the predetermined value is supplied to the ppressure chamber 62 because the boost pressure control device 79 has some defect or has broken down. In this situation, the cam 57 contacts the maximum injection amount control lever 55 in its injection decreasing part and the metering valve 24 moves to the left in the Figure, thereby decreasing the amount of fuel injected.

Accordingly, when the boost pressure control device 79 is broken, the exhuast gas energy fed to the turbine 78 is decreased by a decrease in the amount of fuel injected so that excessive running of the turbocharger, excessive increase in the boost pressure and therefore an increase in the pressure (combustion pressure) in the cylinders of the engine are avoided.

Claims (4)

1. Adistributionfuel injection pump for use with a diesel engine with a turbocharger, comprising: a) a fuel distributing plunger, driven rotationally and reciprocally synchronously with the operation of the engine, for distributing fuel to the cylinders of the engine sequentially, the plunger having a cutoff port open to the outside thereof; b) a metering valve, slidably fitted on the plunger and which can open and close the cutoff port so that when the cutoff port is opened to the outside, the distribution of fuel to the cylinders decreases; c) a tension lever pivotted at a point along its length, the lever being connected at one end to the metering valve; d) means connected to the other end of the tension lever for imparting a bias to the tensionlever so as to cause the metering valve to close the cutoff port; ; e) a cam responsive to the pressure of supercharged airfromtheturbochargerto be movable in a predetermined direction; f) an injection control lever pivotted at a point along its length, the lever being normally urged against the cam by the other end of the tension lever; and g) the cam having such a configuration that when the pressure of the supercharged air exceeds a predetermined value, the amount of fuel injected into the engine decreases.

2. The pump of claim 1, wherein the cam has an arcuate recess provided thereon along the direction in which the cam is movable.

3. The pump of claim 1 or 2, wherein the cam takes the form of a hyperboloid of revolution.

4. A distribution fuel injection pump substantially as described with reference to, and as illustrated in, the accompanying drawings.