KR101122187B1 - Fuel injection device for diesel engine and manufacturing method thereof and valve device - Google Patents

Abstract

An object of the present invention is to prevent wear and spalling in the seat portion of a fuel injection device for a diesel engine. By moving the needle valve 2 inside the nozzle main body 1 to which fuel is supplied, the opening and closing of the seat surfaces 6 and 11 which the nozzle main body and the needle valve contact, and from the nozzle hole 8 opened to the nozzle main body A fuel injection device for a diesel engine that controls the injection of fuel, comprising a alloy steel obtained by nitriding alloy nozzles and portions of the nozzle body and the seat valves 6 and 11 of the needle valve, the first layer of the compound layer and the diffusion layer. Remove it. Since the high toughness second layer becomes a sheet surface, wear resistance and fatigue resistance can be improved, and in particular, spalling can be prevented from occurring in the sheet portion of the nozzle body.

Description

FUEL INJECTION DEVICE FOR DIESEL ENGINE AND MANUFACTURING METHOD THEREOF AND VALVE DEVICE}

INDUSTRIAL APPLICABILITY The present invention relates to a diesel engine for moving a needle valve inside a nozzle body to which fuel is supplied to open and close a seat surface in contact with the nozzle body and the needle valve, and to control fuel injection from a nozzle hole opened in the nozzle body. The present invention relates to a fuel injection device or a valve device, and more particularly, to a technology for improving durability of a seat part.

In general, the fuel injection device for a diesel engine has a nozzle body (nozzle body) to which fuel is supplied therein, and a needle valve made to be slidable inside the body. At the time of fuel injection, the needle valve is moved by the pressure of the fuel supplied to the nozzle body, and the seat surface where the nozzle body and the needle valve are in contact with each other inside the nozzle body is opened, and the fuel is opened from the nozzle hole opened in the nozzle body. Spray it. When not injecting fuel, the needle valve pressed by a load such as a spring abuts against the nozzle body, closes the seat surface, and stops fuel injection from the nozzle.

In this way, the seat portion of the fuel injection nozzle for the diesel engine receives high impact force repeatedly at the closing valve, causing wear and spalling. Spalling is a phenomenon in which a crack occurs at the boundary between the surface hardened layer and the base material and the surface hardened layer is peeled off. In particular, with the recent increase in the spray pressure, a decrease in the service life due to premature wear of the seat portion or the occurrence of spalling has become a problem. Wear occurs on both the needle valve and the nozzle body, but the nozzle body tends to wear significantly. In addition, spalling occurs in the nozzle body. For stable long time operation of the diesel engine, improvement of wear resistance and spalling resistance of the seat portion is important.

In a conventional fuel injection nozzle for a diesel engine, a coarse material such as SKH51 is used as a needle valve, a carburized material such as SNCM420 is used as a nozzle body, or a nitride material such as SKD61 is used. SKH51 tempered material of needle material is high speed steel called 'Mo High' and has good toughness and wear resistance. The microstructure is a relatively large angular process carbide (MC, M ₆ C) and fine precipitated carbides (Cr ₂₃ C ₆ , Mo ₂ C) produced by tempering at the high temperature tempered martensite matrix. . The SNCM420 carburized material of the nozzle body material is a fine carbide deposited on the low temperature tempering martensite matrix, and is softened when used above the tempering temperature because it is affected by the tempering temperature. In the SKD61 nitride, fine complex carbide (M ₆ C) is dispersed in a high temperature tempered martensite matrix, and hard nitride is dispersed in a diffusion layer.

MEANS TO SOLVE THE PROBLEM The present inventors obtained the following knowledge as a result of the careful study about wear and spalling which generate | occur | produce in the seat part of the conventional fuel injection apparatus for diesel engines.

In other words, as a factor affecting the wear resistance of the sheet portion, relatively large co-crystals (MC, M ₆ C) precipitated in SKH 51 can be considered. This carbide precipitated in the seat portion of the needle valve is angled and harder than the known one, so that it floats on the surface without abrasion, and it is conceivable to shave the seat portion toward the nozzle body. In particular, if the quenching temperature is too high or the holding time is too long, it is angular and coarse, so attention is required.

Next, regarding the spalling of the sheet part, the shear stress caused by contact becomes a problem. The above-described carbides are considered to be caused by the scratching force at the time of seat seating to increase the shear stress in the vicinity of the surface, so that spalling occurs easily. do.

Nitriding layers, such as SKD61 nitride, are generally considered to be divided into two, a compound layer on the outermost surface and a diffusion layer therein. Since the compound layer of outermost surface is fragile and weak in impact force, it is generally removed by grinding | polishing.

However, in the seat part of the fuel injection device for diesel engines, even when a compound layer was removed, the seating surface might be fatigue-broken (spalled) by cyclic impact force.

The present invention has been made to solve such a problem, and an object thereof is to prevent wear and spalling from occurring in a seat portion of a fuel injection device for a diesel engine that repeatedly receives high impact force at the time of closing valve.

SUMMARY OF THE INVENTION [

The inventors of the present invention analyzed a damaged product in order to investigate the cause of the seating surface fatigue failure by the cyclic impact force even when the compound layer was removed in the seat portion of the fuel injection device for a diesel engine. As a result, it has been found that new phenomena occur at certain sites in the diffusion layer.

In the case where the surface is nitrided to increase the rigidity of the alloy steel, the compound layer on the outermost surface and the diffusion layer region (first layer) having a relatively high nitrogen content directly below it are prone to break due to precipitation of hard nitride in the particle system and particles. It is well damaged by repeated high impact forces. However, according to the knowledge of the inventors of the present invention, the diffusion layer region immediately below the compound layer is composed of a diffusion layer region (first layer) having a relatively high nitrogen content, and a diffusion layer region (second layer) having a low toughness and low nitrogen content, By removing the first layer, it is considered that the diffusion layer region (second layer) having low toughness and low nitrogen content can be used as the sheet surface, and durability can be improved against fatigue accompanying impact at the nozzle closing valve.

The present invention has been made on the basis of the above findings and knowledge by the inventors of the present invention, and the part of the nozzle body and the needle valve is formed of a nitrided alloy steel, and the first layer of the compound layer and the diffusion layer is formed from the surface thereof. By removing, it provides the fuel injection value for diesel engines which made the 2nd layer tough and low nitrogen content into a sheet surface.

The present invention also provides a method for showing the second layer of the diffusion layer of nitrided steel on the surface. That is, the method of observing the structure of steel is conventionally provided, and provides the method of the etching discovered only by the trial and error experiment of this inventor, and by such a method, the 1st layer of a diffusion layer and By separating the second layer so that the second layer can be observed, determining the amount of polishing necessary for exposing the second layer to the surface, and performing polishing by this amount of polishing, thereby removing the compound layer and the diffusion layer from the surface of the sheet surface made of nitrided alloy steel. It is to provide a method of removing only the first layer to expose the second layer to the surface.

That is, the fuel injection value for the diesel engine of Claim 1 of this invention,

A fuel injection device for a diesel engine that opens and closes a seat portion in which a nozzle body and a needle valve contact by moving a needle valve inside a nozzle body supplied with fuel, and controls fuel injection from a nozzle hole opened in the nozzle body.

The part which becomes the said seat part of the said nozzle main body and the said needle valve consists of alloy steel which was nitrided, and the 1st layer of a compound layer and a diffusion layer is removed from the surface of the part used as the said seat part of the said nozzle main body at least. It is done.

The fuel injection device for a diesel engine according to claim 2 is a fuel injection device for a diesel engine according to claim 1,

The first layer of the compound layer and the diffusion layer is removed from the surface of the portion serving as the seat portion of the needle valve.

The fuel injection device for a diesel engine according to claim 3 is a fuel injection device for a diesel engine according to claim 1 or 2,

The part which becomes the said sheet part of the said nozzle main body is a 2nd layer of the diffusion layer by which surface roughness becomes smooth at least less than Ra 0.4 by grinding | polishing. It is characterized by the above-mentioned.

The manufacturing method of the fuel injection device for diesel engines of Claim 4 is

Method of manufacturing a fuel injection device for a diesel engine which moves the needle valve inside the nozzle body supplied with fuel to open and close the seat portion where the nozzle body and the needle valve contact, and controls fuel injection from the nozzle hole opened in the nozzle body. As

The nozzle body and the needle valve is formed of alloy steel,

Next, the entire surface of the nozzle body and the needle valve are nitrided,

Next, the surface of the nozzle body and the portion of the needle valve which becomes the seat portion is polished to remove the first layer of the compound layer and the diffusion layer,

Next, the nozzle body and the needle valve are assembled.

The manufacturing method of the fuel injection device for diesel engines of Claim 5 is a manufacturing method of the fuel injection device for diesel engines of Claim 4,

Mirror-polished the cross section of the same nitriding alloy steel with the same material as the nozzle body and the needle valve, and etching the cross section with 10% or more of nitric acid alcohol and observing with a microscope to observe the first layer and the first layer of the diffusion layer. And checking the boundary between the two layers and polishing the surfaces of the nozzle body and the portion of the needle valve to determine the polishing amount necessary to remove the first layer of the compound layer and the diffusion layer. It is done.

The valve device according to claim 6,

A valve device which is installed in a fuel injection device for a diesel engine and moves a valve body inside a main body supplied with fuel from an inlet, opens and closes a seat portion in contact with the main body and the valve body, and discharges fuel from the outlet of the main body.

The part which becomes the said seat part of the said main body and the said valve body consists of alloy steel which was nitrided, and the 1st layer of a compound layer and a diffusion layer is removed from the surface.

The valve device of Claim 7 is a valve device of Claim 6,

A main body having an inlet through which the fuel flows in and an outlet through which the fuel flows out, the inlet having a tapered body sheet portion;

A valve body which is movably housed in the main body and has a valve body seat portion which abuts the inlet in contact with the main body seat portion;

It is formed in the inside of the main body and has a pressing means for closing the inlet by the valve body seat portion abuts the body seat portion by a predetermined pressing force,

When the force acting on the valve body by the fuel pressure at the inlet becomes greater than or equal to the pressing force as compared to the force acting on the valve body by the fuel pressure at the outlet, the valve body seat portion and the body seat portion are separated from the fuel. From the entrance to the exit,

When the force acting on the valve body by the fuel pressure at the inlet is smaller than the sum of the force acting on the valve body by the fuel pressure at the outlet and the pressing force, the valve body seat portion and the main body seat portion contact each other. Is configured to block the flow path of the fuel,

A valve device formed in a fuel injection device for a diesel engine,

The body seat portion and the valve body seat portion are made of alloyed steel that is nitrided, and the first layer of the compound layer and the diffusion layer is removed from the surface thereof.

In the fuel injection device or valve device for a diesel engine of the present invention, the nitrided alloy steel applied to the nozzle body (or the main body) and the needle valve (or the valve body) is formed of the outermost compound layer and the diffusion layer underneath. It has a 1st layer and the 2nd layer with toughness which is further lower layer. However, the boundary between the first layer and the second layer of the diffusion layer cannot be confirmed by etching with about 3% (about 3 to 5%) of nitrate alcohol, which has conventionally been used to observe the structure of steel. In the method for measuring the depth of nitride layer of steel specified in JIS G 0562, a method for measuring the metal structure of the nitride layer depth by etching with about 3% alcohol nitrate is specified. Only the type is defined and there is no awareness of the existence of the second layer. Of course, it is impossible to separate the boundary between the first layer and the second layer of the diffusion layer by this measuring method.

However, according to the method of the present invention, the cross section of the nitrided alloy steel is etched in an ultrasonic cleaner for several ten seconds using at least 10%, such as about 15% alcohol nitrate, and then the cross section is observed with a scanning electron microscope. Thus, the boundary between the first layer and the second layer of the diffusion layer can be separated.

Therefore, when analyzing the conventional damaged goods, fatigue failure of the sheet | seat part generate | occur | produced in the specific site | part of a diffusion layer, and it confirmed that this corresponded to the boundary of the 1st layer of the surface side of a diffusion layer, and the inside 2nd layer. Therefore, the seat part of the fuel injection device or valve device for a diesel engine of the present invention measures the depth of the first layer by the method described above, determines the polishing amount based on the measurement result, and the seat part of the nitrided alloy steel. The portion corresponding to this can be removed by polishing by the determined polishing amount, and only the second layer having more toughness can be exposed to the surface and used.

As described above, according to the fuel injection device or valve device for a diesel engine of the present invention, the material of the nozzle body (or body) and the needle valve (or valve body) is made of nitrided alloy steel, and from the surface of the compound layer and the diffusion layer, Since the 1st layer is removed, the 2nd layer with high toughness becomes a sheet | seat part, and durability can be improved with respect to the fatigue accompanying the impact at the time of nozzle closing valve (valve body movement). That is, the wear resistance and the fatigue resistance are improved, and by reducing the frictional force, the shear stress in the vicinity of the surface at the time of seating can be reduced, and the occurrence of spalling in the sheet portion of the nozzle body (or the main body) can be prevented.

By reducing wear and damage of the seat portion of the fuel injection device or valve device for a diesel engine, it is possible to prevent aging change in injection characteristics, fuel leakage due to seat failure, and the like. Fuel leakage due to aging change in injection characteristics and poor seating deteriorates engine performance (especially exhaust gas components), but according to the present invention, it is possible to improve the performance of the engine by improving the durability of the seat portion of the fuel injection nozzle or valve device. It can be maintained for a long time. Therefore, the replacement cycle of the fuel injection device or the device assembly can be increased, thereby reducing the cost of replacement.

Embodiment of this invention is described with reference to FIGS.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing of the fuel injection apparatus for the diesel engine of embodiment of this invention.

2 is a cross-sectional view showing a machining process of the nozzle body of the fuel injection device for a diesel engine of the embodiment; FIG. 3 is a cross-sectional view showing a machining process of the needle valve of the fuel injection device for a diesel engine according to the embodiment; It is a figure of the electron microscope photograph which showed the form of the nitride layer of nitrided alloy steel (SKD61) which is a fuel injection device material for diesel engines of embodiment.

Fig. 5 is a schematic diagram showing an outline of a reciprocating wear test applied to each material of the above embodiment and a comparative example, Fig. 6 is a view showing the trick of a seizure test in the reciprocating wear test, and Fig. 7 is the reciprocating motion. The figure which shows the method of the sliding movement speed variation test in abrasion test.

FIG. 8 is a view comparing frictional force of each material of the embodiment and the comparative example obtained in the reciprocating wear test, FIG. 9 is a view showing an external photograph of the test piece of the comparative example after the reciprocating wear test, FIG. The figure which shows the external appearance photograph of the test piece of the said embodiment after a reciprocation wear test, FIG. 11 is the figure which shows the external appearance photograph of the test piece of the said embodiment after the said reciprocation wear test, FIG. It is a figure which shows the external photograph of the test piece of the said embodiment afterwards.

FIG. 13 is a cross-sectional view of a valve device applied as a check valve, a relief valve, or the like to a fuel injection device for a diesel engine according to another embodiment of the present invention.

1. Structure of fuel injection device for diesel engine of embodiment (Fig. 1)

As shown in FIG. 1, the fuel injection device for diesel engines of this example has the nozzle main body 1 (nozzle body) to which fuel is supplied, and the needle valve 2 made movable in the inside.

The nozzle main body 1 is a substantially cylindrical block body with a thin tip, and the guide hole 3 of the needle valve 2 is formed in the center of the base end part. The front of the guide hole 3 is a fuel accumulator 4 having an enlarged diameter, so that fuel is supplied into the fuel accumulator 4 from the outside through the fuel supply hole 5. A tapered sheet portion 6 is formed at the tip of the fuel storage portion 4. In front of the seat portion 6, a hole 7 having a small diameter connected to the fuel storage portion 4 is formed, and a nozzle hole formed in the wall portion of the hole 7 is connected to the outside to communicate with the outside. (8) is formed.

The needle valve 2 includes a round rod-shaped base portion 10 (needle diameter φ D) held slidably in the guide hole 3 of the nozzle body 1 and the inner diameter of the fuel storage portion 4. Round rod-shaped tip portion 12 having a smaller diameter and integrally formed with the base portion 10 and having a tapered sheet portion 11 formed at its tip contacting the sheet portion 6 of the nozzle body 1. Diameter φd <φD).

The needle valve 2 is pressurized by the load W by a pressure means such as a spring in a direction in which the seat portion 11 is in contact with the seat portion 6 of the nozzle body 1, and is not subjected to an external force. In the state, the seat portion 11 of the needle valve 2 is in contact with the seat portion 6 of the nozzle body 1 to close between the seat portions 6 and 11, so that the fuel accumulation portion 4 and the nozzle are closed. The gap between the holes 8 is blocked. At the time of fuel injection, fuel of predetermined pressure is supplied from the fuel supply hole 5 into the fuel accumulation part 4, and the needle valve 2 is guided to the guide hole 3 upwards by the force of an internal pressure increase, and upwards. It moves, and between the seat parts 6 and 11 is opened, and fuel is injected from the nozzle hole 8 to the outside.

2. Manufacturing process (FIGS. 2-4)

In the fuel injection nozzle for the diesel engine of this example, a material obtained by nitriding the surface of the steel of SKD61 or similar to the nozzle body 1 and the needle valve 2 under predetermined conditions is used. Since the nozzle body 1 is required to have high strength, impact resistance and abrasion resistance at the same time, it is impossible to replace it with a metal material other than steel and has alloys of Al, Cr, Mo, V, Ti, etc., which make stable nitrides. Steel is preferred. After forming the nozzle main body 1 and the needle valve 2 with SKD61, it is nitrided, and the compound layer and the diffusion layer of the nozzle body 1 and the needle valve 2 in the seat portions 6 and 11 are formed. One layer is removed by polishing, and the tough second layer is used as the sheet portions 6 and 11.

That is, in FIGS. 2 and 3 showing the nitriding polishing process, the C and D portions are the sheet portions 6 and 11, and the first layer is removed after nitriding. In polishing of the said sheet part, surface roughness of the finishing surface which consists of a 2nd layer is made small, and it finishes more smoothly. For example, it is preferable to make surface roughness smooth below Ra 0.4 by grinding | polishing using sandpaper about # 800. By finishing the surface in this way, the frictional coefficient can be lowered by reducing the influence on friction of carbides and the like precipitated from the material.

In addition, in FIG.2 and FIG.3 which showed the nitriding-polishing process, although B, E, and F part are grind | polishing because they are functionally necessary, there is no problem even if a 1st layer remains. Part A acts as a stopper when the injection valve is opened, which causes a large impact. Since the nitride layer is peeled off by this impact, the nitride layer of the A part is completely removed from both the first layer and the second layer. The G part is nitrided into a conical shape as shown in Fig. 3A for processing reasons, but finally, the conical part is cut and removed as shown in Fig. 3B. In the A and G sections, the processing differs depending on the processing equipment and the processing method.

In the above polishing step in which the first layer of the compound layer and the diffusion layer in each of the sheet portions 6 and 11 is removed by polishing, and the second layer having the toughness is left as the sheet portion, the first layer and the second layer of the diffusion layer It is necessary to clearly recognize the boundary and to determine the amount of polishing (thickness to be polished). That is, the nitriding situation of the surface varies according to the type of steel employed and the nitriding conditions, and the size of the boundary between the first layer and the second layer of the diffusion layer is determined by experiment and observation in advance by experiment and observation. It is because it is necessary to grind only that much in a process and to expose a 2nd layer reliably on the surface of the sheet part 6,11.

The boundary between the first layer and the second layer in the diffusion layer cannot be confirmed by etching with 5% alcohol nitrate as defined in JIS and the like. According to the knowledge obtained by the trial and error experiments of the present inventors, a certain kind of steel which has been nitrided on the surface under a predetermined condition is cut perpendicularly to the surface to show a cross section, which is about 10% or more, preferably about 15% When the nitrate is etched in an ultrasonic cleaner for several ten seconds, the boundary between the first layer and the second layer can be confirmed by observing the cross section with a scanning electron microscope.

4 is an electron micrograph showing the form of the surface nitride layer in the alloy steel SKD61 employed as a material of the fuel injection device for a diesel engine of this example. In this figure, the white bars (micron bars) at the bottom of the photographs each represent 200 µm. The compound layer is about 10 µm on the surface, and the black layer on the surface corresponds to this in the drawing. By observing the surface nitride layer in this cross section, the polishing amount (dimensions) necessary for removing the compound layer and the first layer and showing the second layer is determined.

In addition, the purpose of nitriding the surface of steel in this example is to improve rigidity, and in other special steels, the required degree of hardness cannot be obtained in view of the purpose of this example. Moreover, considering wear resistance, adhesion occurs easily at the contact of steel and steel, and wear is fast. However, contact between nitride and steel or nitrided steel has the advantage that adhesion is difficult to occur, the coefficient of friction is low, and the wear is slow. . Moreover, since it is a nitride layer even if it is a 2nd layer, compared with the other steel which is not nitrided, there exists sufficient hardness. In addition, when the friction coefficient is decreased, the shear force due to the friction of the surface is reduced, there is an advantage that the spalling resistance is improved.

In the SKD61 employed in this example, the precipitated carbide appeared on the surface, but compared with SKH51, which is a conventionally adopted material, SKD61 is a smaller rounded carbide and has less damage such as abrasion than its counterpart. It is large and angled, and wear and tear is greater than the mating material. In this example, not only the nozzle body 1 but also the needle valve 2 is nitrided to lower the friction coefficient, so that spalling and wear resistance are improved, and as described above, the surface roughness is made smaller and smoother. The influence on the friction of precipitated carbides and the like is reduced.

3. Reciprocating wear test (Figs. 5 to 12)

(1) Test method (Figs. 5 to 7)

In order to confirm the effect of the fuel injection device for the diesel engine of the present example manufactured as described above, test specimens of the same material as that provided in the nozzle body 1 and the needle valve 2 in this example are prepared, and for comparison. Provide the specimen with the reciprocating wear test and compare the results.

As shown in Fig. 5, the reciprocating wear test causes a pin test piece whose tip shape is a spherical surface having a radius of 50 mm to contact the upper surface of a plate-shaped test piece of a predetermined size (14 × 10 × 115 mm) with a predetermined load. The lubricating oil is dropped in the sliding movement region of the upper surface of the plate-shaped test piece at 9 ml / h, and the pin test piece is reciprocated in a stroke of 100 mm along the longitudinal direction of the plate-shaped test piece.

Fig. 6 shows the method of the quenching test that continues the test while increasing the load with the passage of the test time until a scuff occurs by the method of the reciprocating wear test. The test conditions are as follows.

Test load: Step up to 5kgf / 5min and load up to 100kgf.

Test temperature: plate specimen heating temperature 150 ℃ constant, lubricant container room temperature

Average sliding movement speed: 1.5 m / s

Stroke: 100mm

Lubricant loading: 9ml / h

Lubricant: MARINE T204 from NIPPON OIL CORPORATION

The material and surface treatment of the specimens provided for the test are as follows.

Plate test pieces: Two kinds of # 800 polishing finish in addition to the SKD61 polishing after nitriding and the SKD61 polishing after nitriding.

Pin specimens: SKD61 and SKD61 two kinds of nitriding and polishing.

FIG. 7 shows in more detail the sliding movement speed variation mode and the step-up mode of the load in the sliding movement operation with respect to the plate test piece of the pin test piece in the quenching test shown in FIG. 6.

That is, after the start of the start, the sliding movement speed is set at 0.02 m / s, and the load is kept at 5 kgf for several cycles (a). Next, it speeds up at 1.5 m / s and hold | maintains for 5 minutes (b). Next, the temperature is dropped to 0.02 m / s and held for several cycles (c). Next, after stepping up a load to 10 kgf, several cycles are hold | maintained (d). Thereafter, the load is similarly stepped up to 100 kgf (e).

(2) Test result (Figs. 8-12)

Fig. 8 shows the results of the quenching test carried out using two types of SKD61 and SKD61 post-nitrification polishing as the pin test pieces, and the addition of # 800 polishing finish in addition to the SKD61 post-nitrification polishing as the plate test piece. This result indicates that, when the nitrided and polished pin is used, the frictional force is consistently low up to the load of 100 kgf compared with the case where it is not nitrided.

9-11 shows the external photograph of the pin test piece and plate test piece after a sliding movement speed fluctuation test.

The combination of no pin test piece SKD61 nitriding treatment and polishing after plate test piece SKD61 nitriding wears to the extent that the spherical surface of the pin test piece completely disappears, as shown in FIG. 9.

In contrast, the combination of pin test piece SKD61 nitriding after polishing and plate test piece SKD61 post-nitriding polishing is such that a small wear trace is observed at the center of the spherical surface of the pin test piece. This shows that quenching disappeared by nitriding the pin test piece after nitriding.

In addition, in the combination of the pin test piece SKD61 no nitriding treatment and the surface roughness test produced by # 800 polishing finish in addition to the plate test piece SKD61 post-nitrification polishing, as shown in FIG. In comparison, it can be seen that quenching is reduced and the condition is improved.

In addition, in the combination of the pin test piece SKD61 nitridation polishing and the plate test piece SKD61 nitridation polishing, the surface roughness was tested by # 800 polishing finish, as shown in FIG. Good results have been obtained.

Although not shown, according to the measurement results of the shape of the pin test piece after the test, the wear amount of the combination of the test after the surface roughness by the # 800 polishing finish in addition to the polishing after the pin test piece SKD61 nitriding treatment and the polishing after the plate test piece SKD61 nitriding was performed. This was the least.

The result of having measured the size (diameter) of the wear trace of the pin test piece after a sliding movement speed variation test is demonstrated.

Combination of the pin test piece SKD61 no nitriding treatment with the plate test piece SKD61 nitriding after polishing resulted in damage at a load of 30 kgf, so that the wear trace was 7.81 mm, which was almost the size of the outer diameter of the pin test piece (equivalent to Fig. 9). .

Next, in the combination of the pin test piece SKD61 no nitriding treatment and the plate test piece SKD61 nitriding, after the # 800 polishing finish, the wear trace widths in the sliding movement trace direction were 1.51 mm and 1.58 mm, which were almost the same in the two tests. (Equivalent to FIG. 11).

Next, the combination of pin test piece SKD61 nitriding after polishing and plate test piece SKD61 nitriding after polishing showed a wear width in the sliding movement trace direction of 1.54 mm, which was a better result than no pin test piece SKD61 nitriding ( Equivalent to FIG. 10).

In addition, in the combination of the pin test piece SKD61 nitriding after polishing and the plate test piece SKD61 nitriding after polishing, the surface roughness was tested by the # 800 polishing finish, the wear trace widths in the sliding movement trace direction were 1.44 mm and 1.43 mm. Almost the same result was obtained in two tests, which was a good result compared to no pin test piece SKD61 nitriding (equivalent to FIG. 12).

From the above results, it has been found that by nitriding and polishing both the pin test piece and the plate test piece, the frictional force can be reduced and the wear resistance can be improved. It has also been found that the wear resistance is further improved by reducing the surface roughness of the test piece.

From these results, in the fuel injection device for the diesel engine, at least each seat portion of the nozzle body and the needle valve is nitrided, and the nitrided seat portions of the nozzle body and the needle valve are polished together to show a second layer of the diffusion layer, or Good results can be obtained if at least the sheet portion of the nozzle body is polished to show the second layer of the diffusion layer.

In addition, unlike polishing to remove the compound layer or the first layer of the diffusion layer in order to prevent spalling from the nitrided surface, further polishing of the sheet portion showing the second layer by polishing causes friction against carbides and the like deposited on the surface. The effect on the surface is reduced, the surface roughness is reduced, and the friction coefficient is lowered, whereby a better result can be obtained.

4. Effect of Embodiment

The wear state of the seat portion after comparing the fuel injection device for the diesel engine of the present example and the conventional product with the diesel engine was used.

The fuel injection value for the diesel engine of this example is obtained by grinding after nitriding SKD61 the seat portion of the nozzle body and the needle valve to remove the first layer of the compound layer and the diffusion layer.

In a conventional product, the nozzle body is SKD61 and the needle valve is SKH51 (the nozzle body is nitrided).

When used under the same conditions, the wear of the conventional product was 3 to 4 µm, whereas the wear was reduced to 2 µm in this example.

In the embodiment described above, after nitriding the entire surfaces of the nozzle body 1 and the needle valve 2 made of alloy steel, the two seat portions 6 and 11 of the nozzle body 1 and the needle valve 2 are subjected to nitriding treatment. By removing the first layer of the compound layer and the diffusion layer from the surface, the same effects as described above were obtained. However, only the seat parts 6 and 11 of the nozzle body 1 and the needle valve 2 are made of alloy steel obtained by nitriding treatment, and the other parts of the nozzle body 1 and the needle valve 2 are made of other metal. You may comprise cheaply as a material. In addition, each of the seat portions 6 and 11 of the nozzle body 1 and the needle valve 2 is formed of an alloy steel obtained by nitriding treatment, and from the surface of the seat portion 6 of the nozzle body 1, a compound layer and a diffusion layer are formed. Even when the first layer is removed and only the compound layer is removed from the surface of the seat portion 11 of the needle valve 2, wear and tear may be caused in the seat portion 6 of the nozzle body 1 which is particularly prone to durability problems. The effect is that spalling is less likely to occur.

5. Other Embodiments (FIG. 13)

Although the embodiment described above relates to the nozzle part in which fuel injection is performed in the fuel injection device for diesel engines, the valve device of this example is formed in the fuel system of the fuel injection device for diesel engines, and checks the pump which feeds fuel. It can be used for valves (suction valves, discharge valves, isostatic valves), relief valves (safety valves) that operate so that the pressure does not exceed a certain value.

The structure of this valve apparatus is demonstrated.

The main body 21 of the valve device has an inlet 23 through which the fuel flows in and an outlet 24 through which the fuel flows out, and the inlet 23 and the outlet 24 are connected to an internal space 25 to communicate with each other. The inlet 23 is formed with a tapered body sheet portion 26. In the space 25 inside the main body 21, the valve body 22 is housed in a movable manner. At one end of the valve body 22 toward the inlet 23, a tapered valve body seat 27 is formed in contact with the body seat 26 to close the inlet 23. In the space 25 of the main body 21, the valve body 22 is introduced at a predetermined pressing force between the outlet 24 and the receiving portion 28 formed at the other end of the valve body 22. A spring 29 as a pressurizing means for pressurizing toward 23 is formed, and as described later, when the fuel pressure toward the inlet 23 is small, the valve body seat portion 27 is formed by the spring 29. Is in contact with the main body sheet portion 26 so that the inlet 23 is closed. In addition, in this example, the valve body seat portion 27 is tapered, but other shapes, for example, may be planar.

The relationship between the pressing force of the spring 29 and the pressure of the fuel is set as follows.

That is, the force exerted by the fuel pressure at the inlet 23 to the valve body 22 is different from the force applied by the spring 29 to the valve body 22 as compared with the force exerted by the fuel pressure at the outlet 24 to the valve body 22. When the valve body 22 becomes large, the valve body 22 is pushed back toward the outlet 24 (the lower side of the drawing) in spite of the pressing force of the spring 29, and the valve body seat 27 and the main body seat 26 are separated and a gap is formed. The fuel moves from the inlet 23 to the outlet 24 through the gap.

When the force exerted by the fuel pressure at the inlet 23 to the valve body 22 is less than the sum of the force exerted by the fuel body at the outlet 24 to the valve body 22 and the pressing force of the spring 29, The valve body 22 moves toward the inlet 23 (upper side of the drawing), and the valve body seat portion 27 and the main body seat portion 26 come into contact with each other to block the flow path of the fuel. At this time, since the valve body 22 collides with the main body 21, each seat portion is worn in the conventional structure. However, in the present example, the following solutions to wear are devised.

That is, the main body seat part 26 and the valve body seat part 27 are made of alloyed steel that is nitrided, and the first layer of the compound layer and the diffusion layer is removed from the surface thereof. The materials, manufacturing methods, microstructure, properties, modifications, and the like of these sheet portions are the same as those of the above-described fuel injection device for diesel engines, and therefore the description thereof is cited.

In the prior art, since the carburizing material of SCM420 and SUJ2 were applied to the valve body, the wear of the seat was caused in each seat part. However, the wear in the seat part can be reduced by the configuration as in this example. Product life can be extended.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing of the fuel injection apparatus for the diesel engine of embodiment of this invention.

2 is a cross-sectional view showing a machining step of the nozzle body 1 of the fuel injection device for a diesel engine of the above embodiment.

3 is a cross-sectional view showing a machining process of a needle valve of a fuel injection device for a diesel engine according to the embodiment.

4 is an electron micrograph showing the form of a nitride layer of nitrided alloy steel (SKD61) that is a material of the fuel injection device for a diesel engine of the embodiment.

5 is a schematic diagram showing an outline of a reciprocating wear test applied to each material of the above embodiment and comparative example.

Fig. 6 is a diagram showing the trick of the test for burning in the reciprocating wear test.

FIG. 7 is a view showing the points of the sliding movement speed variation test in the reciprocating wear test.

Fig. 8 is a diagram comparing the frictional force of the respective materials of the above-described embodiment and the comparative example obtained in the reciprocating wear test.

9 is a view showing appearance photographs of a test piece of a comparative example after the reciprocating wear test.

Fig. 10 is a diagram showing an appearance photograph of a test piece of the embodiment after the reciprocating wear test.

Fig. 11 is a diagram showing appearance pictures of the test piece of the embodiment after the reciprocating wear test.

It is a figure which shows the external photograph of the test piece of said embodiment after the said reciprocating abrasion test.

FIG. 13 is a cross-sectional view of a valve device applied as a check valve, a relief valve, or the like to a fuel injection device for a diesel engine according to another embodiment of the present invention.

Reference numerals of respective constituent parts of the above-described embodiments are shown below.

Explanation of symbols on the main parts of the drawings

1: Nozzle body (nozzle body) of fuel injection device for diesel engine

2: Needle valve of fuel injection device for diesel engine

3: guide hole

4: fuel storage

5: fuel supply hole

6: Seat part of nozzle body

8: nozzle hole

10: base of needle valve

11: Seat of needle valve

12: distal end of the needle valve

21: main body of the valve device

22: valve body of the valve device

23: entrance

24: exit

26: main body seat

27: valve body seat

29: spring as pressing means

Claims (7)

By moving the needle valve 2 inside the nozzle main body 1 to which fuel is supplied, the seat part 6 and 11 which the nozzle main body 1 and the needle valve 2 contact are opened and closed, and the nozzle main body 1 A fuel injection device for a diesel engine that controls fuel injection from the nozzle hole 8 opened in the The part of the nozzle body 1 and the needle valve 2, which becomes the seat portions 6 and 11, is made of alloyed steel that is nitrided, and a compound layer that is fragile and susceptible to impact strength at its outermost surface from the surface thereof and its Diffusion layer of lower layer and nitrided alloy steel diffusion layer, which has relatively high nitrogen content on the surface side of the site where fatigue breakdown occurs, hard nitride easily precipitates in grain boundaries and particles, and is easily damaged by repeated impact force. Of the diffusion layer having a relatively low nitrogen content and low toughness inside the site where fatigue fracture occurs in the diffusion layer of the nitrided alloy steel, which is the lower layer of the first layer and is removed from the surface layer of the first layer. A fuel injection device for a diesel engine, characterized in that the inner second layer. By moving the needle valve 2 inside the nozzle main body 1 to which fuel is supplied, the seat part 6 and 11 which the nozzle main body 1 and the needle valve 2 contact are opened and closed, and the nozzle main body 1 A fuel injection device for a diesel engine that controls fuel injection from the nozzle hole 8 opened in the The part which becomes the said seat part 6, 11 of the said nozzle main body 1 and the needle valve 2 consists of alloy steel which was nitrided, and becomes the said seat part 6 of the nozzle main body 1 The fragile and weakly weak compound layer on the outermost surface from the surface of the part, and the lower layer, which is relatively rich in nitrogen on the surface side of the site where fatigue fracture occurs in the diffusion layer of nitrided alloy steel, and hard nitride precipitates in grain boundaries and particles. The first layer on the surface side of the diffusion layer, which is liable to be damaged and is easily damaged by repetition of the impact force, is removed, and the relatively nitrogen in the inside of the site where fatigue fracture occurs in the diffusion layer of the alloyed steel which is a lower layer of the first layer. A fuel injection device for a diesel engine, comprising a second layer inside the diffusion layer having a low content and toughness. The method according to claim 1 or 2, A fuel injection device for a diesel engine, characterized in that the portion of the nozzle body (1) serving as the sheet portion (6) is the second layer of the diffusion layer whose surface roughness is smoothed at least less than Ra 0.4 by polishing. By moving the needle valve 2 inside the nozzle main body 1 to which fuel is supplied, the seat part 6 and 11 which the nozzle main body 1 and the needle valve 2 contact are opened and closed, and the nozzle main body 1 A method of manufacturing a fuel injection device for a diesel engine that controls the fuel injection from the nozzle hole 8 opened in the The nozzle body 1 and the needle valve 2 are formed of alloy steel, Next, the entire surface of the nozzle body 1 and the needle valve 2 is nitrided, Next, the surface of the nozzle body 1 and the portion of the needle valve 2, which is the seat portion 6 and 11, is polished, so that the compound layer on the outermost surface and the weak weak impact force and its lower layer are nitrided alloy steel. In the diffusion layer of, there is a relatively high nitrogen content on the surface side of the site where fatigue breakdown occurs, and hard nitride is easily precipitated in grain boundaries and particles, and the first layer on the surface side of the diffusion layer that is easily damaged by repeated impact force is removed. In the diffusion layer of the nitrided alloy steel, which is the lower layer of the first layer, the second layer inside the diffusion layer having a relatively low nitrogen content and a toughness in the portion where fatigue fracture occurs is left, Next, the method of manufacturing a fuel injection device for a diesel engine, characterized in that the nozzle body (1) and the needle valve (2) are assembled. The method of claim 4, wherein Mirror-polished a cross section of the same alloy nitrided with the same material as the nozzle body 1 and the needle valve 2, etching the cross section with 10% or more of nitric acid alcohol, and then observing it under a microscope to obtain a diffusion layer. Check the boundary between the first layer and the second layer of, and polish the surface of the portion of the nozzle body 1 and the needle valve 2 to be the seat portion 6, 11 to the compound layer and the diffusion layer. And determining the amount of polishing necessary to remove the first layer of the fuel injection device of the diesel engine. The seat portion which is installed in the fuel injection device for the diesel engine and is in contact with the main body 21 and the valve body 22 by moving the valve body 22 inside the main body 21 supplied with fuel from the inlet 23 ( A valve device for opening and closing the 26 and 27 to discharge fuel from the outlet 24 of the main body 21, The part which becomes the said seat part 26, 27 of the said main body 21 and the valve body 22 consists of a nitrided alloy steel, and the compound layer and its lower layer which are fragile and weak to impact force which are the outermost surface from the surface. In the diffusion layer of nitrided alloy steel, relatively high nitrogen content is located on the surface side of the site where fatigue fracture occurs, and hard nitride easily precipitates in grain boundaries and particles, and is easily damaged by repeated impact force. One layer is removed, and the lower layer of the first layer is made of a second layer in the diffusion layer having a relatively low nitrogen content and a toughness in the portion where fatigue fracture occurs in the diffusion layer of the nitrided alloy steel. Valve device characterized in that. A main body 21 having a fuel inlet 23 through which the fuel flows in and an outlet 24 through which the fuel flows out; A valve body 22 movably housed in the main body 21 and having a valve body seat portion 27 that abuts the inlet 23 in contact with the main body seat portion 26; It is formed in the main body 21 and closes the inlet 23 by bringing the valve body 22 into contact with the main body seat 26 by a predetermined pressing force. With the pressing means 29, When the force acting on the valve body 22 by the fuel pressure of the inlet 23 becomes larger than the pressing force compared to the force acting on the valve body 22 by the fuel pressure of the outlet 24, The valve body seat portion 27 and the body seat portion 26 are separated, and fuel moves from the inlet 23 to the outlet 24, When the force acting on the valve body 22 by the fuel pressure of the inlet 23 is smaller than the sum of the force acting on the valve body 22 by the fuel pressure of the outlet 24 and the pressing force. The valve body seat part 27 and the main body seat part 26 are in contact with each other, and the fuel flow path is blocked. A valve device formed in a fuel injection device for a diesel engine, The main body seat portion 26 and the valve body seat portion 27 are formed of a nitrided alloy steel, and are separated from the surface of the compound layer on the outermost surface and weak to impact force, and a lower layer and a diffusion layer of the nitrided alloy steel. The first layer on the surface side of the diffusion layer having a relatively high nitrogen content on the surface side of the site where fatigue breakage occurs, the hard nitride easily precipitates in grain boundaries and particles, and which is easily damaged by repetition of impact force is removed. A valve device comprising a second layer inside a diffusion layer having a relatively low nitrogen content and a relatively low nitrogen content inside a site where fatigue failure occurs in a diffusion layer of a nitrided alloy steel in one layer.

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