JPH07167013A - Cavitation phenomenon prevention mechanism in fuel injection pump for diesel engine, and plunger erosion prevention method - Google Patents

Abstract

PURPOSE:To prevent the occurrence of a cavitation phenomenon at a fuel flow port by forming a turbulence generating irregular section in the inner wall of the fuel flow port provided in a barrel in the fuel injection pump composed of the barrel and a plunger fitted into this barrel. CONSTITUTION:A fuel injection pump for a diesel engine is made up of a cylindrical barrel 1, and of a columnar plunger 2, and injects fuel oil out of a fuel flow port 4 by way of a recessed section and the fuel flow port 4 when the recessed section line 9 of the plunger 2 and the fuel flow port 4 are intersected with each other as the plunger 2 is moved up and down. Fuel oil injected into the fuel flow port 4 is divided into two, that is, a flow along the radial direction and a flow toward an outlet (Y flow) while being diffused toward a space where pressure is low. In this place, irregularities 11 are provided into the inner wall shape of the fuel flow port 4, turbulence is generated in a part of the Y flow by hitting fuel oil against the irregularities, and splashes go round toward the depth of the fuel flow port 4, so that the occurrence of a cavitation phenomenon within the fuel flow port 4 is thereby avoided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanism for preventing a cavitation phenomenon (cavitation) which occurs in a fuel outflow hole of a barrel in a Bosch type fuel injection pump of a diesel engine, and a fuel outflow hole of a plunger thereby. The present invention relates to a method for preventing erosion of a plunger, which is characterized by preventing erosion (cavitation erosion) due to a cavitation phenomenon of a surface in contact with.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 1, in a Bosch type fuel injection pump for a diesel engine, which comprises a barrel and a plunger fitted to the barrel, as shown in FIG. The phenomenon that erosion marks A are formed and cannot be used often occurs. Such erosion of the plunger is caused by the cavitation phenomenon (cavitation) that occurs in the fuel outflow holes of the barrel, and is called erosion due to the cavitation phenomenon (cavitation erosion).
Methods for preventing erosion (cavitation erosion) due to this hollowing phenomenon have been studied in various fields. For example, (a) a method of forming a semicircular cut at the intersection of the recess cut line of the plunger with the fuel outflow hole to increase the opening speed to reduce the fuel oil injection flow velocity generated at the initial opening, ) The recess cut line of the plunger is made shallow, and the flux of the fuel injection flow generated at the beginning of opening is made small and linear so that it does not diffuse throughout the fuel outflow hole. It is a method to prevent (cavitation) from occurring.

[0003]

These conventional methods are as follows.
The idea is to improve a plunger that cannot be used because it is damaged and cannot be broken. That is,
The former attempts to form a semi-circular notch in the recess cut line of the plunger, but this is to identify the intersection of the semi-circular cut and the fuel outlet hole provided in the recess cut line. In addition, it is difficult and the recess cut line itself is always required to have high precision for fuel injection. Therefore, if a cut is made in this line, the original performance often deteriorates. It is extremely difficult to get an effect.
In the latter case, the injection flow rate of the fuel oil is reduced so that the injection flow rate is often insufficient, resulting in a lack of practicality. As described above, none of the conventional measures against the cavitation phenomenon (cavitation) that occurs in the fuel outflow hole and the erosion (cavitation erosion) due to the cavitation phenomenon of the plunger surface is not satisfactory.

The inventor of the present invention, based on the erosion marks A of many plungers that cannot be used due to erosion due to the cavitation phenomenon (cavitation erosion), causes of the cavitation phenomenon, its timing, the state of the jet flow, the cavity As a result of confirming the erosion situation due to aging phenomenon and conducting intensive research based on those technical findings, an effective cavitation prevention mechanism with a simple structure and cavitation of the plunger surface based on it We have succeeded in developing a plunger erosion prevention method that prevents erosion (cavitation erosion) due to phenomena.

[0005]

According to the present invention, in order to prevent the cavitation phenomenon (cavitation) B occurring in the fuel outflow hole 4, the following means is applied to the barrel 2.

The first invention for which a patent is sought is a fuel injection pump for a diesel engine, which comprises a barrel 1 and a plunger 2 fitted to the barrel 1, and a fuel outflow hole 4 formed in the barrel 1. A cavitation preventing mechanism for a fuel injection pump of a diesel engine, characterized in that a turbulent flow generation uneven portion 11 is formed on an inner wall.

In order to prevent the cavitation phenomenon (cavitation) B occurring in the fuel outflow hole 4,
The turbulent flow generation uneven portion 1 is formed on the inner wall of the fuel outflow hole 4 of the barrel 1.
He came up with the means of forming 1. Although the constituent means of the present invention is simple, the idea is epoch-making. It is not an improvement in the shape of the injection port that causes the hollowing phenomenon, the injection method, or the plunger 2 that causes damage, but the idea is completely changed and the shape of the inner wall of the fuel outflow hole 4 of the barrel 1 is improved. This is an epoch-making idea in that the use of the hollowing phenomenon B is prevented by adding it.
Such a novel and epoch-making idea can only be recalled by the long-standing research results of accurately analyzing and confirming the state of the fuel jet when it is injected.
Therefore, although the structure according to the present invention is simple, the effect of preventing the hollowing phenomenon is extremely efficient and effective. The first aspect of the present invention has this basic structure as a main part and is a basic invention of a cavitation phenomenon (cavitation) prevention mechanism.

The second invention to be patented is the barrel 1 as the turbulent flow generating uneven portion 11 described in the first invention.
A diesel groove characterized in that a concave groove portion 11a or a convex portion 11b is formed in an inner wall in the vicinity of the plunger 2 side of the fuel outflow hole 4 provided in the above in a direction orthogonal to the axial direction of the fuel outflow hole 4. It is a mechanism for preventing cavitation in a fuel injection pump of an engine.

This second invention is an embodiment invention which embodies the turbulent flow generating uneven portion 11 of the first invention which is the basic invention. This invention also intends to prevent the cavitation phenomenon by providing the turbulent flow generation concavo-convex portion 11 for controlling the jet flow in the fuel outflow hole 4, and its principle and basic configuration are common to the first invention. , Are included in the technical scope.

The turbulent flow generation unevenness portion 11 formed on the inner wall portion of the fuel outflow hole 4 according to the present invention has a specific shape and size as to the size of the fuel injection pump, the fuel injection amount, and the injection pressure. It is designed in consideration of the size of the fuel outflow hole, etc., but basically, it does not impair the fuel injection supply, which is the essential function of the fuel injection pump, and the fuel flow out by the jet flow. A concave groove portion 11a or a convex portion 11b having a shape and size capable of causing turbulence in a part of the jet flow so that a region close to a vacuum cannot be formed in the hole 4.
Alternatively, it is necessary to be either the concavo-convex combination portion. That is, the turbulent flow generation uneven portion does not have to be limited in its specific shape as long as it satisfies such basic conditions.

The third invention to be patented is a fuel injection pump for a diesel engine, which comprises a barrel 1 and a plunger 2 fitted to the barrel 1, and a fuel outflow hole 4 provided in the barrel 1. By forming a turbulent flow generation uneven portion 11 on the inner wall, a part of the fuel jet flow generated at the initial opening when the recess cut line 9 of the plunger and the fuel outflow hole 4 begin to intersect is generated. A turbulent flow is caused by hitting the uneven portion 11 to temporarily reduce the flow velocity and the energy thereof, and at the same time, the cavitation phenomenon (cavitation) is prevented from occurring in the fuel outflow hole 4 due to the turbulent splash, thereby making it possible to plan. The erosion control of the plunger of the diesel engine is characterized by preventing erosion (cavitation erosion) due to the cavitation phenomenon of the surface of the jar 2 in contact with the fuel outflow hole 4. It is a method.

The third aspect of the present invention is a method for preventing erosion of a plunger, which prevents erosion (cavitation erosion) due to a cavitation phenomenon on the surface of the plunger 2. Conventionally, the erosion mark of the plunger is recognized as a defect of the plunger, and the plunger is strengthened to improve it so as not to be damaged, or the shape of the recess cut line 9 or the shape of the recess 8 of the plunger is hollow. Various ideas have been made to control the injection state and jet flow of fuel by improving the plunger, which is considered to be the cause of causing the injection of fuel such as the phenomenon of gasification. The present invention is completely different from this idea, and the true cause of the hollowing phenomenon is not due to the shape of the plunger 2 or not only to the jet flow, but to the mutual relation between the jet flow and the shape of the fuel outflow hole 4. It is based on the idea of controlling the jet flow by obtaining the knowledge that it will occur and improving the shape of the inner wall of the fuel outflow hole 4 of the barrel 1. In this way, it seems that there is no causal relationship between the inner wall of the fuel outflow hole 4 of the barrel and the prevention of the erosion of the plunger. As a result of a thorough study of the cause of the hollowing phenomenon and the jet flow,
It was the first time we could think of and develop such knowledge.

[0013]

As a result of research, the inventor has clarified the cause of the cavitation phenomenon (cavitation) in the fuel outflow hole 4 of the barrel in the Bosch fuel injection pump of the diesel engine, and based on the clarified findings, This is to develop a mechanism for preventing cavitation phenomenon (cavitation) and a method for preventing erosion (cavitation erosion) on the surface of the plunger 2 due to the cavitation phenomenon. Hereinafter, the cause of the cavitation phenomenon (cavitation) will be described first, and then the reason why the developed prevention mechanism can prevent the cavitation phenomenon (cavitation) will be described.

Since oil is a liquid, it is possible to transmit the force by itself, but it is not possible to store the force. However, at the same time when the fuel injection of the diesel engine is finished and the fuel outflow hole is opened, it is very powerful. It is also true that high-pressure fuel oil with energy flows out, causing a cavitation phenomenon B in the fuel outflow hole. It is also clear from the fact that erosion (cavitation erosion) occurs on the surface of the plunger due to cavitation, which causes erosion marks A, often causing the plunger to become unusable.

First, observing why energy is accumulated in the high-pressure fuel oil, the energy sources are the internal pressure wave and the gas expansion wave, and it is considered that both are accumulated together. The internal pressure wave means that the steel material is expanded by the internal pressure of the pipe or the like when the fuel oil jetted at high pressure passes through the components such as the pipe from the pump to the nozzle.
At the moment the fuel outflow hole opens, it is the strong pressure and flow velocity that the steel material contracts and gives to the fuel oil.The gas expansion wave is due to the high pressure of the gas contained in the fuel oil, such as petroleum gas, during the jetting. Although it was compressed, it refers to the pressure and flow velocity that are given when it expands at the same time as the opening of the fuel outflow hole to become an oil flow and to flow out. The internal pressure wave and the gas expansion wave are accumulated in the oil while the fuel oil is being injected at a high pressure, and cause a large flow velocity at the same time as the opening of the fuel outlet hole, which causes the fuel oil to be ejected. The jetting of fuel oil has a function of drawing out the air in the fuel outflow hole 4 to the outside, which temporarily creates a region in the inner part of the fuel outflow hole 4 in a state close to a vacuum. The fact that a temporary and rapid region close to a vacuum is formed is called a cavitation phenomenon (cavitation) B. When this cavitation phenomenon (cavitation) B occurs, a state close to a rapid vacuum is generated, The remaining particles move violently in an explosive state, eroding the surrounding walls. The erosion mark A often formed on the surface of the plunger 2 in contact with the fuel outflow hole 4 is caused by the erosion (cavitation erosion) due to the cavitation phenomenon.

Further, the internal pressure wave has a very high flow velocity in the initial outflow, but is not durable and has a short time (approximately 1/10000).
The gas expansion wave has a relatively slow flow velocity, but the durability is superior to the internal pressure wave (almost 5/1000).
(0 seconds) There is a property. These two are intertwined to create a temporary hollowing phenomenon. However, in order to create a temporary vacuum-like state (cavitation phenomenon) in the fuel outflow hole, a very high flow velocity is momentarily required. Therefore, the internal pressure wave is the main force, and It was also found that the time for such a hollowing phenomenon was extremely short, starting immediately after the fuel outflow hole began to open, and ending by the time the plunger rose by 1.5 mm to 2.0 mm.

Further, observing the mechanism and process for producing the hollowing phenomenon, as shown in FIGS. 5 to 7, the fuel outflow hole 4 provided in the barrel 1 has a cylindrical shape and is in contact with the plunger 2. The inner opening 4a is formed in a circular shape. On the other hand, an oblique concave cut line 9 is formed on the side surface of the plunger 2 which is fitted in the barrel 1 in a vertically movable manner and is in contact with the fuel outflow hole 4. It is set up. Therefore, the cylindrical fuel outflow hole 4 and the oblique recess cut line 9 are opened or closed at the intersecting portion as the plunger 2 moves up and down. The opening 10 is arcuate, and the arc-shaped portion is constituted by the cylindrical opening portion 4a, and the chord portion is constituted by the oblique concave cut line 9. Therefore, the initial opening 10a as the plunger 2 rises becomes equal to a point as shown in FIG. 5, and then becomes an opening 10b equal to a line as shown in FIG. 6, and further opened to form an arcuate opening as shown in FIG. It becomes 10c.

At this time, observing the flow of the fuel oil ejected from the opening 10 into the cylindrical fuel outflow hole 4, as shown in FIG. 3, the flow along the length direction of the cylindrical fuel outflow hole 4 ( Hereinafter, the flow is referred to as the X flow) and a flow that diffuses in the fuel outflow hole 4 and strikes the inner wall of the fuel outflow hole 4 toward the outlet (hereinafter referred to as the Y flow). That is,
The jet flow from the arc side of the opening 10 becomes a flow of X flow in the length direction along the inner wall of the fuel outflow hole 4, and the jet flow from the chord side is jetted from the oblique concave cut line 9 at the moment. Since it suddenly becomes a space, it expands toward the lower pressure side of the space and flows out while curving, diffuses in the cylindrical fuel outflow hole 4, collides with the inner wall, and then becomes a Y-flow toward the outlet. A huge amount of energy is accumulated in the flow of the Y flow at this time, and the air in the fuel outflow hole 4, particularly in the plunger side region, is strongly sucked, so that a temporary cavitation phenomenon (vacuum) occurs in that region. It has been found that a (state) region is generated.

The inventor then causes a part of the flow of the X flow or the Y flow, which causes the cavitation phenomenon, to enter the turbulent flow generation uneven portion 11 provided on the inner wall of the fuel outflow hole, A turbulent flow is generated, which reduces the enormous energy of the X flow and especially the Y flow, and the turbulent flow generated at that time causes the splashes and jets of the fuel oil to flow back to the plunger side region in the fuel outflow hole 4. It is intended to prevent the hollowing phenomenon from occurring by ejecting outside so that a state close to a vacuum does not occur. Further, if the cavitation phenomenon in the fuel outflow hole can be prevented in this way, the surface of the plunger is not eroded, and the generation of erosion marks can be prevented.

[0020]

EXAMPLES The present invention will be described in detail below with reference to the drawings and examples. FIG. 2 is a vertical cross-sectional side view of a main part of a fuel injection pump of a diesel engine including a plunger, showing an embodiment in which a hollowing prevention mechanism according to the present invention is formed on the barrel thereof. 2 is an enlarged view of a main part of FIG. 2 and illustrates a hollowing phenomenon prevention mechanism provided in the fuel outflow hole 4 of the barrel and a flow of the fuel oil when the fuel oil is ejected from the opening into the fuel outflow hole 4. FIG.

As shown in FIG. 2, the fuel injection pump of the diesel engine is composed of a cylindrical barrel 1 and a cylindrical plunger 2, and the plunger 2 is inside a barrel hole 3 of the barrel 1. It is fitted so that it can move up and down.

The cylindrical barrel 1 is provided with a cylindrical fuel outlet hole 4 penetrating from the inner opening 4a of the cylindrical hole 3 to the outlet on the outer wall side at an appropriate position on the side wall thereof. As shown in FIG. 1, it is not only a columnar shape, but its head is composed of a circumferential groove called an oil passage groove 5, a vertical groove 6 and a triangular oil ejection groove 7. Recess 8
Are formed. Since the slanted recess cut line 9 forming the triangular oil ejection groove 7 functions as a shutter for adjusting the injection timing and the injection amount, particularly highly accurate processing is required. ing.

That is, when the plunger 2 is fitted in the barrel 1 and moved up and down, the recess cut line 9 of the plunger 2 and the fuel outflow hole 4 of the barrel 1 intersect each other to form the recess 8. The fuel outflow hole 4 is in open communication, and the fuel oil is ejected through the fuel outflow hole 4.
Therefore, the cylindrical fuel outflow hole 4 and the slanted concave cut line 9 are opened or closed at the inner opening 4a intersecting with the vertical movement of the plunger 2, but the combination at that time is used. The opening 10 formed by is formed in an arc shape, and the arc-shaped portion is formed by the inner opening 4a in the cylindrical fuel outlet hole 4, and the chord portion is formed by the oblique recess cut line 9. When showing the opening operation state in detail,
As shown in FIGS. 5, 6 and 7, first, the plunger 2
As shown in FIG. 5, the opening initial stage 10a corresponding to the rise of No. 1 becomes equal to a point, and then becomes an opening 10b equal to a line as shown in FIG. 6, and further opened to become an arcuate opening 10c as shown in FIG. The fuel oil is ejected from the opening 10 into the cylindrical fuel outflow hole 4, and is ejected from the outer outlet of the fuel outflow hole 4.

As the inventor observes the flow of the fuel oil jetted into the fuel outflow hole 4 at this time, as shown in FIG.
It has been found that the flow of the fuel oil ejected causes a region near the vacuum in the plunger side region in the fuel outflow hole 4, which causes the hollowing phenomenon B. Then, it was confirmed that the erosion mark A on the surface of the plunger 2 occurred when the cavitation phenomenon B occurred.

That is, energy is accumulated in the fuel oil jetted at a high pressure by the internal pressure wave and the gas expansion wave, and this becomes a large flow velocity at the same time as the opening 10 of the fuel outflow hole 4 and the fuel oil flows outward from the fuel outflow hole 4. However, the fuel oil injected into the fuel outflow hole 4 diffuses in the flow direction along the length direction of the cylindrical shape (X flow) and diffuses in the low pressure space direction in the cylindrical shape. And the flow is divided into two directions, that is, the flow (Y flow) toward the outlet after hitting the inner wall on the opposite side of the flow. Confirmed. In this case, the X flow lowers the surrounding lateral pressure, and
The Y flow that diffuses and flows in the direction of the low-pressure space gives a flow velocity to the residual air in the fuel outflow hole and the remaining retained fuel oil in the previous process and draws it toward the outside. A region near the plunger inside is temporarily brought into a state close to a vacuum, and a cavitation phenomenon B is caused in this region.

As described above, as a result of the research, the inventor of the present invention causes the cavitating phenomenon B due to the flow direction energy of the fuel oil at the time of jetting, namely the X flow and the Y flow, and the main cause thereof is the fuel Based on the relationship with the shape of the outflow hole 4, it was found that the residual air and the residual fuel oil are in the Y flow that draws outward. Therefore, based on this knowledge, the inventor recalls that if a turbulent flow is generated in a fuel oil flow, particularly a part of the Y flow, it is possible to reduce the flow velocity and the enormous energy of the Y flow, etc. , Paying attention to hitting the inner wall of the fuel outflow hole 4,
By providing unevenness on the inner wall shape of and hitting it,
A turbulent flow is caused in a part of the Y flow, and the turbulent flow and droplets migrate to the inner part of the fuel outflow hole 4 so that a region close to a vacuum cannot be formed, and a cavitation phenomenon occurs due to this. (Cavitation) is prevented, and erosion (cavitation erosion) of the plunger surface caused by the cavitation phenomenon (cavitation) is prevented.

That is, according to the present invention, as a method for controlling the flow of jetted fuel oil so as not to cause a hollowing phenomenon, the barrel 1 is used.
The turbulent flow generation uneven portion 11 as described above is formed on the inner wall of the fuel outflow hole 4 provided in, and the cavitation phenomenon prevention effect is realized by this.

Incidentally, the uneven portion 11 for generating turbulent flow in the embodiment.
As shown in FIG. 4, a groove 11a is formed in an appropriate position on the inner wall of the fuel outflow hole 4 provided in the barrel 1 in the vicinity of the plunger side in a direction orthogonal to the axial direction of the fuel outflow hole 4. Of course, as shown in FIG. 5, the protrusions 11b may be formed at appropriate places on the inner wall.

Further, as in the illustrated embodiment, in the fuel injection pump of the diesel engine which is composed of the barrel 1 and the plunger 2 fitted to the barrel 1, the inner wall of the fuel outflow hole 4 provided in the barrel 1 Since the turbulent flow generation uneven portion 11 is formed in the turbulent flow, a part of the fuel jet flow generated at the beginning of opening when the recess cut line 9 of the plunger and the fuel outflow hole 4 begin to intersect is generated. A turbulent flow can be caused by hitting the projecting concavo-convex portion 11, thereby temporarily reducing the flow velocity and energy, and causing a cavitation phenomenon (cavitation) in the fuel outflow hole 4 due to turbulent flow or splash. To prevent erosion (cavitation erosion) due to the cavitation phenomenon of the surface of the plunger in contact with the fuel outflow hole 4.

[0030]

The first and second inventions of the present application are a turbulent flow in an inner wall of a fuel outflow hole provided in a barrel in a fuel injection pump of a diesel engine including a barrel and a plunger fitted to the barrel. By adopting the extremely simple structure of forming the irregularities for generation, it is possible to effectively prevent the cavitation phenomenon (cavitation) in the fuel injection pump, which has been difficult for diesel engine industry for many years. is there. The invention of the present application was developed for the first time when there was a scientific elucidation based on many years of experience and research by the inventor regarding the cavitation phenomenon (cavitation), and the structure of the corresponding technology is simple and sufficient. It is an excellent technique and a highly practical technique in that the effect of preventing the phenomenon of cavitation is certain.

The greatest inconvenience caused by the cavitation phenomenon (cavitation) in the fuel injection pump is cavitation erosion due to the cavitation phenomenon of the plunger surface which requires high precision. The sudden formation of erosion marks on the surface of the plunger due to such damage significantly reduces or loses the function of the plunger, making it unusable. In the past, due to this, many plungers with a long useful life could not be used, and waste and the troublesomeness of having to replace the plunger each time were the cause of diesel engineer's trouble.
In the conventional industry, improvements have been attempted with the idea of improving a broken plunger into an unbreakable plunger, but such an attempt often deteriorates the original function of the plunger and is not practical. On the other hand, the present invention is
Changing the idea from the past, leaving the plunger as it is,
By improving the barrel, it is intended to prevent the cavitation phenomenon that is the cause of erosion and thereby prevent the erosion of the plunger, and the erosion prevention method is a revolutionary technical idea. is there.

[Brief description of drawings]

FIG. 1 is a side view of a main part of a plunger showing a state in which an erosion mark due to a cavitation phenomenon is formed on a head surface of the plunger and the plunger cannot be used.

FIG. 2 is a vertical cross-sectional side view of essential parts of a fuel injection pump including a barrel having a hollowing phenomenon prevention mechanism and a plunger according to the present invention.

FIG. 3 is an enlarged view of a portion corresponding to a main part of FIG. 2 before improvement, showing a structure inside a fuel outflow hole of a conventional barrel and a flow of fuel oil when the fuel oil is injected from an opening into the fuel outflow hole. It is an explanatory view explaining how a hollow phenomenon occurs.

FIG. 4 is an enlarged view of a main part of FIG. 2, showing a state in which an embodiment of a cavitation phenomenon prevention mechanism is provided in the fuel outflow hole and a flow of the fuel oil when the fuel oil is ejected from the opening into the fuel outflow hole. It is an explanatory view explaining.

FIG. 5 is an enlarged view of a main part of FIG. 2, showing a state in which another embodiment of the hollowing phenomenon prevention mechanism is provided in the fuel outflow hole and a flow of the fuel oil when the fuel oil is ejected from the opening into the fuel outflow hole. It is an explanatory view explaining.

FIG. 6 shows a state of an opening formed by intersecting a fuel outflow hole of the barrel and a recess cut line of the plunger with the vertical movement of the plunger, and is a main part showing an initial state of the opening. FIG.

FIG. 7 is a side view of the main part showing the same opening as in FIG. 5 and showing a state in which fuel oil is jetted out a little further.

FIG. 8 is a side view showing the same opening portion as FIG. 5, showing a state where the opening is further enlarged and the ejection pressure of fuel oil is reduced.

[Explanation of sign]

 DESCRIPTION OF SYMBOLS 1 ... Burrell 2 ... Plunger 3 ... Cylindrical hole 4 ... Fuel outflow hole 8 ... Recessed portion 9 ... Recessed cut line 10 ... Opening 11 ... Turbulent flow generation uneven portion A ... Erosion mark B ... Cavitation phenomenon

Claims (3)

[Claims] 1. A fuel injection pump for a diesel engine comprising a barrel and a plunger fitted to the barrel, wherein a turbulent flow generating uneven portion is formed on an inner wall of a fuel outlet hole provided in the barrel. A mechanism for preventing cavitation in a fuel injection pump of a diesel engine. 2. The cavitation phenomenon preventing concavo-convex portion according to claim 1, wherein the inner wall near the plunger side of the fuel outflow hole provided in the barrel has a direction perpendicular to the axial direction of the fuel outflow hole. A cavitation preventing mechanism in a fuel injection pump of a diesel engine, characterized in that a groove or a protrusion is formed. 3. A fuel injection pump for a diesel engine, comprising a barrel and a plunger fitted to the barrel, wherein a turbulent flow generating uneven portion is formed on an inner wall of a fuel outlet hole provided in the barrel. The turbulent flow is caused by causing a part of the fuel jet flow generated at the initial stage of opening when the recess cut line of the plunger and the fuel outflow hole begin to intersect with the turbulent flow generation irregularity to temporarily cause the flow velocity. Cavitation phenomenon (cavitation) in the fuel outflow hole due to turbulent droplets is prevented, which causes cavitation erosion of the surface of the plunger in contact with the fuel outflow hole. A method for preventing erosion of a plunger of a diesel engine, which is characterized in that