KR100440828B1 - A fuel injection pump for internal combustion engines, in particular big, slow marine diesel engines - Google Patents

Abstract

A fuel injection pump for supplying a variable amount of fuel to injection nozzles disposed in an operating cylinder of an engine, wherein the injection nozzle has a needle having a spring incorporated therein in a nozzle hole, , Wherein a plunger (3) having an upper edge portion (4) formed between a side and an end surface and at least one helically extending tilting transition edge (6) is movable in the barrel, The transition edge portion defines a groove (5) on the side of the plunger, the groove communicating with the end face of the plunger through an axial passage, the wall of the barrel having at least one transition hole (11) And the hole is closed by the side of the plunger below the top edge during movement from the bottom position to the top position of the plunger and is then effective The orifice member is at least partly closed by the inclined transition edge portion for conversion of excess fuel at the end of the plunger and the hole is reduced relative to the cross section of the hole to provide an increased static pressure in the transition hole during a portion of the plunger movement A fuel injection pump for an internal combustion engine, particularly a large-sized low speed marine diesel engine, provided in some of the holes. In order to overcome the problem of erosion and pressure oscillations in large pumps, the pump comprises flow restriction means 13, in which at least one switching hole 11 is arranged away from the wall of the barrel, (20) located between the cylindrical walls of the chamber (2).

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a fuel injection pump for an internal combustion engine, particularly a large-sized low-speed ship diesel engine,

In the conventional fuel injection pump, each inclined changing edge portion is aligned with a hole passing through the wall of the barrel, and the plunger is configured such that the hole is blocked by the upper edge portion of the plunger at the beginning of the movement of the plunger, When supplied to the nozzles, the holes are also exposed by the inclined transition edges behind them. Such arrangements will work satisfactorily in small and medium sized engines, but in large low speed diesel engines, the size and size of the pump, which must be taken to damp the pressure changes in the injector at the beginning and end of the effective pump stroke A problem arises. Such problems can be caused by erosion at the sides of the plunger which prevents cavitation in the holes due to high flow rates. However, an increase in the cross-section of the holes can not be achieved soon, since it is necessary to delay pressure relief by exhibiting a constant flow resistance if the holes are not blocked by the inclined transition edges. This delay is necessary to prevent flue gas from entering the injection nozzle and to prevent cavitation at the nozzles. In addition, when a fuel having an internal lubrication characteristic is used, it is preferable to obtain an even larger bearing surface between the plunger and the barrel in order to reduce the risk of fusion in the region of the upper edge portion of the plunger.

A jet pump of the type described above is disclosed in US-A-418156. The means for increasing the static pressure in the transition holes is a spring loaded valve that controls the fuel flow into or out of the feed chamber. The device is complex and requires high power consumption from a pump supplying fuel to the feed chamber. Another device for increasing the static pressure in the transition hole is disclosed in US-A-5 150 160 and German Published Unexamined Patent Application No. 25 32 US-A-4 957 418 discloses a fuel injection pump having a plunger for venting with transition holes in a barrel, wherein means for providing a static pressure increase of the transition holes is disclosed in U.S. Pat. Lt; / RTI > Said means comprising a restrictive orifice disposed in the hole, the closing of which initiates an injection stroke to begin pressure relief at the end of the stroke. These known devices cause lateral pressure on the plunger, which results in increased wear of the plunger in the case of fuel with weak lubrication characteristics.

The present invention relates to a fuel injection pump for an internal combustion engine, particularly a large low speed marine diesel engine, which supplies a variable amount of fuel to an injection nozzle arranged in an operating cylinder of an engine, Wherein the injection pump comprises a barrel and a plunger having an upper edge formed between a side and an end surface and at least one helically extending tapered transition edge, Wherein the tapered transition edge portion forms a groove in the side surface of the plunger and the groove communicates with the end surface of the plunger through the axial passage and the wall of the barrel controls the start and end of the effective pump stroke Said holes being open to a peripheral supply chamber for receiving fuel under moderate pressure, Wherein the timing hole is blocked by the side of the plunger below the top edge during movement from the bottom position to the top position of the plunger and then the pressure relief hole is used to switch over fuel to the end of the effective pump stroke An orifice member is provided in at least some of the holes to reduce the hole with respect to the cross section of the hole to provide an increased static pressure in the holes during a portion of the plunger movement.

1 is an axial cross-sectional view of a fuel injection pump according to the present invention;

2 is a partial cross-sectional view of the barrel wall according to line II-II according to FIG.

3 is a diagram showing the pressure of the fuel injection pump according to the present invention during fuel injection.

Figures 4a, 4b and 4c schematically show the blocking holes in the longitudinal section.

It is an object of the present invention to provide a fuel injection pump of the type defined in the preamble of the claims, which is simple in construction, which can prevent erosion on the upper surface of the plunger and which can use fuel with weak lubrication characteristics. The object of the present invention is achieved by a pump characterized in that the orifice is arranged in the group of timing holes. The invention relates to a fuel injection pump in which the start and end of an effective pump stroke are controlled by a plurality of sets of holes will be. This feature allows the plunger to obtain a relatively large bearing surface and to obtain optimized dimensions of the hole size and shape of the barrel that are not clogged or clogged by the plunger and the orifice members cause any unbalanced pressure on the plunger The configuration according to the present invention has been proven to eliminate the erosion of the plunger and to reduce the wear of the plunger which cooperates with a set of timing holes and a set of pressure relief holes shaped toggle holes. Will be described in more detail with reference to the accompanying drawings.

In the axial view of Figure 1, the fuel injection pump 1 comprises a barrel 2 in which the plunger 3 is movable. The barrel 2 is constructed of a conventional type of pump housing and includes a supply chamber surrounding the middle portion of the barrel to allow excess fuel to be delivered therefrom and to allow fuel to be supplied therefrom during the return stroke of the plunger . The plunger (3) includes a top edge (4) formed between its end face and its side face. The plunger further comprises a groove (5) formed by a tilted diverting edge (6) extending spirally along the side of the plunger in the direction of its end face. The inclined, transitional edge portion 6 is, for example, at an angle of 120 [deg.], And the plunger is normally provided with two transitional edge portions 6 disposed opposite to each other. The barrel 2 is provided with connecting means 7 for a rotating mechanism whereby the plunger can be rotated for adjustment of the delivery flow rate and the connecting means 8 is a roller guide adapted to move the plunger in the axial direction . These rotating mechanisms are not objects of the present invention and are those which are commonly used. The plunger 3 also includes an axial passage 9 for communicating the space 10 above the end face of the plunger with the groove 5.

The injection pump is adapted to deliver a variable volume of fuel to the injection nozzles of the operating cylinders of the diesel engine. The fuel delivery amount is adjusted by the rotation of the plunger 3. When an effective pump stroke is initiated, the plunger blocks the timing holes and transition holes 11 formed in the barrel 2 of the injection pump during the upward movement of the end face 4, and then the effective pump stroke is terminated The sloping transition edge portion 6 is prevented from clogging the pressure relief holes 12 so as to be supplied to the supply chamber around the barrel barrel 2 via the axial passage 9, the groove 5 and the switching hole 12 The fuel is discharged and the pressure in the pump chamber on the end face 4 of the plunger is relieved.

For example, in a fuel injection pump for a large, low speed diesel engine for a marine vessel, a problem arises due to the large size of the pump and the high pressure when the fuel is injected, The above-described jet pump of the present invention using timing holes and pressure relief holes that are separately specially designed is dispensed with. The timing holes are formed to effectively prevent cavitation that interferes with the fuel flow discharged at a large velocity. In addition, the pressure relief holes are configured to obtain adequate damping of the inverted fuel or to prevent cavitation at the injection nozzle until the risk of pressure vibration that may cause gasoline in the cylinder to enter the injection nozzles is relieved. Moreover, the bearing surface between the top of the plunger and the wall of the barrel can be of a suitable size by making the axial spacing between the holes 11, 12 an appropriate dimension.

The timing holes are configured in a larger cross-section than the pressure relief holes (12). Cavitation is most effectively prevented, however, by disposing the orifice member 13 at the timing hole outlet to the supply chamber as shown in Fig. 2 in accordance with the present invention. The flow passage by the orifice member is configured such that the pressure in the timing hole in front of the orifice member exceeds the pressure in the supply chamber just before the switching hole is closed when the edge portion of the end surface 4 of the plunger passes .

The pressure relief holes 12, which are not blocked by the inclined transition edge portion 6, have a diffusor-shaped longitudinal contour and are configured to have the smallest cross-section at the wall of the barrel. It is necessary for the pressure relief holes to have a small cross section at the wall of the barrel as described above to obtain a sharp exposure of the hole and to obtain a precise pressure change in the injector.

3 shows the pressure variation in the fuel injection pump according to the invention, which is derived as a function of the crank angle. The fully derived curve indicates the pressure in the pump chamber 10. The curve shows the pressure of the pump chamber which begins to increase at the moment the plunger 3 is moved up, where the timing hole 11 is blocked by the plunger below its upper edge 4, Fuel is injected into the operating cylinder of the engine. At point 16, the switching holes are not clogged and the pressure in the pump chamber falls in the damping process and acts against the pressure oscillations in the injector to cause the needle to perform an exact closing action on the jetting noises. A dotted line 17 shows the pressure change in the chamber between the side of the plunger and the orifice member, and the chamber is provided with an appropriately sized orifice member 13. A gradual pressure drop can be obtained and the pressure drop effectively prevents cavitation in the side holes adjacent the plunger side.

Figures 4a, 4b and 4c show longitudinal cross-sectional views of the transition holes of the schematic embodiments. 4A shows an embodiment in which the flow restriction means in the form of an orifice member 21 is disposed in the switching hole 20 close to the outlet 22 to the supply chamber. In this embodiment, the largest sized chamber is pressurized by the switching holes and the pressure is relieved, with the result that the maximum possible volume of the chamber between the orifice member and the inlet and the maximum possible pressure retention are achieved. The orifice member may be in the flow direction of the passages under an angle to the axis of the conversion hole or in a plurality of passages. The advantage of the passage at an angle to the axis of the transition hole is that the pressure relieved fluid does not contact the supply chamber wall on the opposite side vertically, thereby reducing the risk of erosion of the supply chamber wall. The chamber between the wall of the barrel and the orifice member may further be non-cylindrical. This shape can be conical, for example, with the transition hole formed in the wall of the barrel being somewhat smaller than the diameter of the feed chamber, into which the orifice member is inserted. In this way a flow control effect acts on the hole and orifice member formed in the wall of the barrel, which can be beneficial in the absence of separate timing and transition holes.

In Fig. 4b, the orifice member 23 is arranged close to the middle of the hole 20, whereby the chamber can be made smaller and the distance between the opposite wall of the supply chamber and the orifice member 23 can be made larger Wherein the fluid flowing from the orifice member can cause erosion.

Figure 4c shows preferred embodiments of the switching holes 20 provided with the orifice members. The orifice member 24 is disposed in the middle of the transition hole such that the transition hole is formed as a diffuser 25 in a direction toward the outlet 22 to the supply chamber. The purpose of the diffuser 25 is to reduce the jetting rate leaving the orifice member. The appropriate dimensions of the orifice member 21, 22 or 24 allow the pressure to rise in front of the orifice member of the transition hole when the transition hole is clogged, thereby eliminating the risk of cavitation and reducing the pressure relief, Degradation can be achieved. If necessary, additional damping can be achieved by proper design of the axial passage of the plunger.

Claims (3)

CLAIMS 1. A fuel injection pump for supplying a variable amount of fuel to injection nozzles disposed in an operating cylinder of an engine, the injection nozzle having a needle with a spring incorporated therein in a nozzle hole, the injection pump including a barrel A plunger having a top edge formed between a side surface and an end surface and at least one helically extending tapered edge is movable in the barrel and the tapered cut edge forms a groove in the side surface of the plunger Said grooves communicating with the end face of the plunger through axial passages and the wall of the barrel having a separate set of holes controlling the start and end of an effective pump stroke, And the holes are constituted by a timing hole and a pressure relief hole, and during the movement from the bottom position of the plunger to the upper position The timing hole is clogged by the side of the plunger below the top edge and the pressure relief hole is not blocked by the inclined cut edge for the switching of excess fuel at the end of the effective pump stroke, Wherein the orifice member is provided in at least some of the holes with a reduced hole with respect to the cross section of the hole to provide an increased static pressure in the orifice member, Wherein the fuel injection pump is disposed at a downstream side of the fuel injection pump. delete delete