JPH10318094A - Fuel injection nozzle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration with age of exhaust gas performance by resetting valve opening pressure after long time operation of a diesel engine to a value equivalent to initial valve opening pressure while satisfying need of maintenance free. SOLUTION: A circular inner circumferential projection 35 having an inner diameter smaller than that of a guide portion 34 is integrally formed between an oil reservoir 32 of a nozzle body of a fuel injection nozzle and the guide portion 34. A circular elastic body 10 is fixed such that a pressure receiving part 14 of a needle 3 is faced to a rear end surface of the inner circumferential projection 35. Measurement of clearance between the pressure receiving part 14 of the needle 3 and the circular elastic body 10 is set to (L) equivalent to an abrasion amount of a seat after long time operation. An inner diameter of the circular elastic body 10 is set to a value DR which is set considering a lowering rate of energization load of a spring 5 after long time operation. Opening valve pressure after long time operation is thus set equally to initial valve opening pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection nozzle for spraying fuel into an internal combustion engine in a mist state, and more particularly, to a needle opening pressure after a long term operation of a diesel engine. The present invention relates to a fuel injection nozzle for a diesel engine that is kept equal.

[0002]

2. Description of the Related Art In recent years, with the tightening of exhaust gas regulations for diesel engines, it is necessary to suppress a decrease in the valve opening pressure of a fuel injection nozzle in order to prevent deterioration of exhaust gas performance over time. This is because when the valve opening pressure is reduced, the needle is lifted earlier, so that the injection amount of the fuel injected into the combustion chamber of the diesel engine is larger than a set value (for example, the optimum injection amount with respect to the intake air amount). The unburned fuel in the atmosphere in the combustion chamber increases.

[0003] As a result, when the diesel engine is operated for a long period of time, that is, when the fuel injection nozzle is used for a certain period of time, a large amount of smoke (black smoke) is generated in the exhaust gas, and the surrounding environment is deteriorated. . In order to solve the above-mentioned problem by suppressing a decrease in the valve opening pressure of the fuel injection nozzle, Japanese Patent Application Laid-Open No.
JP-A-6064 and JP-A-56-39864 propose a technique in which the thickness of an adjusting shim is adjusted to reduce the amount of wear of a spring whose urging load is set to the valve opening pressure. ing.

[0004]

However, in the above-mentioned conventional fuel injection nozzle, the amount of wear of the spring is reduced to reduce the decrease in the valve opening pressure of the fuel injection nozzle. Driving (for example, a diesel engine vehicle is 100,000 km to 20 km
After traveling 10,000 km), it was impossible to keep the valve opening pressure of the fuel injection nozzle equal to the initial state.

[0005] In addition to the wear of the spring, the causes of the decrease in the valve opening pressure of the fuel injection nozzle include wear of the seat portion of the needle and the seat portion of the nozzle body, and settling of the spring itself. It is thought that even if an attempt is made to reduce the valve opening pressure of the fuel injection nozzle by reducing only the wear amount of the fuel injection nozzle, the effect as expected cannot be obtained.

Therefore, conventionally, when the valve opening pressure of the fuel injection nozzle is much lower than the initial valve opening pressure and the exhaust gas performance is deteriorated, the needle, the nozzle body or the spring itself is replaced by a new one and the urging load of the spring is changed. It is necessary to return the initial urging load to the initial urging load, or replace the adjusting shim for adjusting the urging load of the spring with a thicker one to return the urging load of the spring to the initial urging load. For this reason, conventionally, the fuel injection nozzle does not have a durable life until the end of the life of the diesel engine vehicle itself, and there is a problem that the maintenance-free demand cannot be satisfied.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to return the valve opening pressure after operating the internal combustion engine for a long period of time so as to be equal to the initial valve opening pressure while satisfying the maintenance-free demand. It is an object of the present invention to provide a fuel injection nozzle capable of preventing the characteristic deterioration of exhaust gas.

[0008]

According to the first aspect of the present invention, by operating the internal combustion engine for a long period of time, the urging means is worn, the needle and the seat body of the nozzle body are worn, and the urging means is used. Although the biasing load of the biasing means decreases due to settling or the like, valve opening pressure return means for returning the valve opening pressure after operating the internal combustion engine for a long time to the initial valve opening pressure,
The fuel injection nozzle is provided. Therefore,
Even after operating the internal combustion engine for a long time, that is, even after using the fuel injection nozzle for a long time, the timing at which the needle is disengaged from the seat and fuel is injected from the injection hole of the nozzle body does not become early, and the fuel injection is not performed. The volume is returned to the set value. As a result, the valve opening pressure of the fuel injection nozzle can be returned to the initial valve opening pressure without replacing the nozzle body, the needle and the valve opening pressure adjusting means, so that the unburned fuel in the atmosphere in the combustion chamber of the internal combustion engine can be returned. Does not increase, and the performance deterioration of the exhaust gas can be suppressed.

According to the second aspect of the present invention, by operating the internal combustion engine for a long period of time, the urging means is worn, the needle and the seat of the nozzle body are worn, and the urging means is set. The biasing load of the biasing means decreases,
By providing an annular body having an inner diameter smaller than the guide portion between the guide portion of the nozzle body and the oil reservoir, and around the pressure receiving portion and the insertion portion, after long-term operation of the internal combustion engine,
The distance between the sliding portion of the needle and the annular body when the needle is seated on the seat portion of the nozzle body is reduced. As a result, the pressure receiving area of the pressure receiving portion of the internal combustion engine after a long period of operation becomes smaller than the pressure receiving area of the pressure receiving portion of the needle in the initial state of the fuel injection nozzle, and the urging load of the coil spring is reduced. Even if it has decreased, if the pressure of the fuel in the oil sump does not approach the initial valve opening pressure, the needle will not separate from the seat portion, and the fuel injection amount will be returned to the set value.

According to the third aspect of the present invention, the inner diameter of the annular body is set in consideration of the decrease in the biasing load of the spring after the internal combustion engine has been operated for a long time, and the internal combustion engine has been operated for a long time. The valve opening pressure of the fuel injection nozzle is returned to the initial valve opening pressure by setting the clearance between the sliding portion of the needle and the annular body in consideration of the subsequent wear amount of the needle and the seat portion and the wear amount of the spring. be able to. According to the fourth aspect of the invention, even if the pressure receiving portion of the needle collides with the annular body, the impact can be absorbed.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 and FIG. 2 show an embodiment of the present invention. FIG. 1 is a view showing the overall structure of a fuel injection nozzle for a diesel engine. FIG. FIG. 3 is a diagram showing a structure.

The fuel injection nozzle 1 of this embodiment is attached to a cylinder head of a sub-combustion diesel engine,
The tip of the needle 3 is fitted into the injection hole 2 provided at the tip of the nozzle body, and when the needle 3 is lifted off, an annular gap between the injection hole 2 and the tip of the needle 3 is formed. This is a throttle-type nozzle that generates a hollow conical spray from the sub combustion chamber.

The needle 3 is formed in the shape of a stepped round bar, and has a pin portion 11, a seat portion 12, an insertion portion 13, a pressure receiving portion 14, a sliding portion 15, and a projecting portion from the front end to the rear end. 16 and the like are formed in order. The pin portion 11 is provided with the injection hole 2
It is a cylindrical portion that fits inside. The seat 12 is
The small-diameter pin portion 11 and the medium-diameter insertion portion 13 are connected to each other, and are truncated conical portions that are seated on the nozzle body. Insertion part 13
Is a columnar portion that connects the seat portion 12 and the pressure receiving portion 14.

The pressure receiving portion 14 connects the medium-diameter insertion portion 13 and the large-diameter sliding portion 15, and has a truncated cone shape which receives a supply pressure upward from the fuel supplied around the insertion portion 13. Part. The sliding portion 15 is a cylindrical portion having the largest outer diameter in the needle 3 and is slidably displaced in the nozzle body. The protruding portion 16 is a columnar portion provided on the rear end side of the sliding portion 15 and having a smaller outer diameter than the sliding portion 15. A coil spring (corresponding to the urging means of the present invention) 5 is connected to the protruding portion 16 via a pressure pin (spring seat) 4.

When the supply pressure of the diesel oil (hereinafter referred to as fuel) becomes higher than the valve opening pressure, the needle 3 lifts and injects fuel from the injection hole 2 into the sub-combustion chamber. When the fuel supply pressure becomes lower than the valve closing pressure, the needle 3 sits on the nozzle body and terminates the fuel injection.
The valve opening pressure of the needle 3 is determined by changing the urging load (urging force) of the spring 5 toward the seating side of the needle 3 by the thickness of the adjusting shim 6 inserted between the nozzle body and the spring 5. Adjusted. Here, the spring 5
The adjusting shim 6 constitutes the valve opening pressure adjusting means of the present invention.

The nozzle body of this embodiment comprises a nozzle holder 7, a tip packing 8, a nozzle body 9, an annular elastic body 10, and the like. And the annular elastic body 10
The nozzle holder 7, the tip packing 8, the nozzle body 9 and the needle 3, except for the above, have a predetermined shape after being manufactured separately from chromium or carbon steel such as chrome molybdenum steel such as SCM415 or SCR steel. It is formed by performing cutting and polishing.

The nozzle holder 7 is formed in a circular tube shape.
The nozzle body 9 is assembled to the distal end surface via the tip packing 8 by the tightening force of the retaining nut 21, and connects the fuel pump (not shown) and the fuel injection nozzle 1 to the outer periphery of the joint portion 22 on the upper end side in the figure. Injection pipes (not shown) are tightened. A cylindrical spring chamber (hollow portion) 23 for accommodating the pressure pin 4, the spring 5, and the adjusting shim 6 is formed in the axial center portion of the nozzle holder 7. A substantially round hole-shaped fuel hole 24 through which fuel flows is formed on the side wall of the spring chamber 23 of the nozzle holder 7. At the inlet side of the fuel hole 24, a bar filter 25 for filtering impurities contained in the fuel is inserted.

The tip packing 8 has an annular plate shape and is sandwiched between the front end face of the nozzle holder 7 and the rear end face of the nozzle body 9. And tip packing 8
A fuel hole 26 having a substantially round hole shape communicating with the fuel hole 24 is formed. Further, the axial center portion of the tip packing 8 communicates with the spring chamber 23, and the inside thereof projects from the projection 1 of the needle 3.
6 is formed with a shaft hole 27 through which reciprocating displacement is inserted. The tip end of the sliding portion 15 of the needle 3 comes into contact with the tip packing 8 when the needle 3 is lifted to the maximum.

The nozzle body 9 is formed in a substantially cylindrical shape so that the needle 3 can be slidably housed therein. A seat portion (valve seat portion) 31 having an inverted truncated cone shape on which the seat portion 12 of the needle 3 is seated is formed downstream of the injection hole 2 formed on the tip end surface of the nozzle body 9 in the fuel supply direction. Have been. And the seat part 31
On the downstream side in the fuel supply direction, a substantially elliptical oil reservoir 32 is formed in which the insertion portion 13 of the needle 3 is inserted so as to be displaceable inside in the sliding direction, and the fuel is stored. A substantially round fuel hole 33 is formed so as to communicate from the oil reservoir 32 to the rear end face of the nozzle body 9. The fuel holes 33 are connected to the fuel holes 24 through the fuel holes 26.
Is in communication with

Further, the sliding portion 1 of the needle 3 is provided between the oil sump 32 and the rear end face of the axial center portion of the nozzle body 9.
A guide portion 34 having a round hole shape is formed for guiding the sliding member 5 in the vertical direction (reciprocating direction). Further, between the oil reservoir 32 and the guide portion 34, an annular inner peripheral convex portion 35 protruding toward the inner peripheral side by a predetermined dimension is integrally formed. The inner diameter of the inner peripheral convex portion 35 is
And has a diameter substantially the same as the inner diameter of an annular elastic body 10 described later.

The annular elastic body 10 is a component corresponding to the annular body of the present invention. The annular elastic body 10 is fixed on the rear end surface of the inner peripheral convex portion 35 so as to face the pressure receiving portion 14 of the needle 3 in the axial direction, and is elastically deformable. It is integrally formed of a material (for example, rubber), and constitutes the valve opening pressure return means of the present invention together with the inner peripheral convex portion 35 of the nozzle body 9. Inside the annular elastic body 10, the insertion portion 13 and the pressure receiving portion 14 of the needle 3 are movably inserted in the sliding direction.

Next, a method of correcting the valve opening pressure of the fuel injection nozzle 1 of the present embodiment will be briefly described with reference to FIG. Fuel injection nozzle 1 of the present embodiment
In order to return the valve opening pressure after the diesel engine has been operated for a long time to the initial valve opening pressure at the time of new product, the gap size (L) between the pressure receiving portion 14 of the needle 3 and the annular elastic body 10 and the annular shape The inner diameter (DR) of the elastic body 10 and the inner peripheral convex portion 35 is determined as follows based on experimental values and calculated values.

First, a 200,000k diesel engine vehicle
m, when the seat portion 12 of the needle 3 and the seat portion 31 of the nozzle body 9 are seated,
And what value the amount of wear of the spring 5 shows was investigated. As a result of conducting a plurality of experiments, the average value of the sheet wear amount was 0.02 mm in the throttle type nozzle as in the present embodiment. The average value of the amount of wear of the spring 5 was 0.01 mm. As a result, in the present embodiment, as shown in FIG. 2, the gap dimension (L) between the pressure receiving portion 14 of the needle 3 and the annular elastic body 10 is set to 0.03 mm.

Next, the inner diameter (DR) of the annular elastic body 10 and the inner peripheral convex portion 35 is calculated using a calculation formula described later. First, the outer diameter of the sliding portion 15 of the needle 3 is set to φDG.
The outer diameter of the insertion portion 13 of the needle 3 is φDS, and the inner diameter of the elastic annular body 10 is φDR. Also,
The initial urging load of the spring 5 is set to F0, and the urging load of the spring 5 reduced by wear or settling after driving the diesel engine vehicle for 200,000 km is set to Fn. Further, the initial pressure-feeding fuel pressure receiving area of the pressure receiving portion 14 of the needle 3 is A0, and the pressure-feeding fuel pressure receiving area of the pressure receiving portion 14 after the diesel engine vehicle travels 200,000 km is An. Then, the initial valve opening pressure of the fuel injection nozzle 1 is set to P0 (generally 1
50kgf) and 200,000km for diesel engine vehicles
The valve opening pressure of the fuel injection nozzle 1 after traveling is defined as Pn.

Initial valve opening pressure (P0) of fuel injection nozzle 1
Is determined by P0 = (initial load of spring) / (compressed fuel receiving pressure area), and is given by the following equation (1) and equation (2).

## EQU1 ## P0 = F0 / A0

A0 = {π × (DG ² −DS ² )} / 4

P0 = 4F0 / {π × (DG ² −DS ² )}

In addition, a diesel engine vehicle is 200,000 km
After running, that is, after the diesel engine has been operated for a long time, the valve opening pressure (Pn) is reduced by the spring 5 and the urging load (Fn) of the spring 5 due to wear of the seat portions 12 and 31. Generally, the load is reduced by 1% of the initial biasing load (for example, 20 kgf), so that Pn <P0 in the related art.

However, in this embodiment, as described above, the gap between the pressure receiving portion 14 of the needle 3 and the annular elastic body 10 is set to a value corresponding to the set or wear of the spring 5 after the diesel engine vehicle travels 200,000 km. It is set to L (for example, 0.03 mm) that is obtained by integrating the amount and the amount of sheet wear. Accordingly, the pressure-feeding fuel receiving pressure area (An) at that time is obtained from the following equation (4), and the valve opening pressure (Pn) at that time is obtained from the following equation (5).

## EQU4 ## An = {π × (DR ² −DS ² )} / 4 <A0

## EQU5 ## Pn = Fn / An

Then, the diesel engine car is 200,000 k
m after opening the valve opening pressure (Pn).
In order to make it equal to (0) (Pn = P0), the equations (3) to (5) are substituted into the equation (6), and the inner diameter dimension (DR) of the annular elastic body 10 and the inner peripheral convex portion 35 is calculated by the following equation (7). It is calculated from the equation.

## EQU6 ## An = Fn / P0

## EQU7 ## DR ² = {4Fn / (P0 × π)} + DS ²

As described above, in consideration of a decrease in the biasing load (Fn) of the spring 5 after being used for a long time from the time of new product, the inner diameter dimension (DR) of the annular elastic body 10 and the inner peripheral convex portion 35 is considered.
Is set, the valve opening pressure (Pn) after driving the diesel engine vehicle for 200,000 km, that is, after operating the diesel engine for a long time, is changed to the initial valve opening pressure (P
0) (Pn ≒ P0).

[Operation of Embodiment] Next, the operation of the fuel injection nozzle 1 of this embodiment will be briefly described with reference to FIGS.

The fuel pressurized to a high pressure by the fuel pump is supplied to a fuel hole 24 formed in the nozzle holder 7 through an injection pipe. The fuel is supplied to the oil reservoir 32 around the insertion portion 13 of the needle 3 through the fuel hole 26 formed in the tip packing 8 and the fuel hole 33 formed in the nozzle body 9, and the fuel in the oil reservoir 32 is Supply pressure rises quickly.

When the supply pressure of the fuel in the oil sump 32 becomes higher than the valve opening pressure determined by the biasing load of the spring 5, the pressure receiving portion 14 receives the supply pressure of the fuel and is displaced upward in the drawing. By obtaining the force, the seat portion 12 of the needle 3 is lifted off from the seat portion 31 of the nozzle body 9 and the rear end surface of the sliding portion 15 of the needle 3 comes into contact with the front end surface of the tip packing 8 (maximum lift). I do.
At this time, a hollow conical spray is generated in the sub-combustion chamber of the diesel engine from the annular gap between the injection hole 2 and the pin portion 11 of the needle 3.

Thereafter, when the fuel pumping operation from the fuel pump is completed and the fuel in the injection pipe is returned to a low-pressure fuel line (for example, an oil pan or a fuel tank), the supply pressure of the fuel in the oil sump 32 is reduced. descend. And oil sump 3
When the supply pressure of the fuel in the nozzle 2 becomes lower than the valve closing pressure, the needle 3 is lowered and the seat 12 is seated on the seat 31 of the nozzle body 9, so that the injection hole 2 is closed by the pin 11 of the needle 3. Injection to the diesel engine ends.

[Effects of the Embodiment] As described above, the fuel injection nozzle 1 of the present embodiment operates after the diesel engine has been operated for a long period of time, ie, the diesel engine vehicle has a 200,000 k
Even after traveling m, the valve opening pressure of the needle 3 can be kept equal to the initial valve opening pressure. Therefore, the needle 3, the nozzle body 9 or the spring 5 itself is replaced with a new one, and the urging load of the spring 5 is changed. It is not necessary to return to the initial urging load or replace the adjusting shim 6 for adjusting the urging load of the spring 5 with a thicker one. For this reason, the durable life of the fuel injection nozzle 1 can be extended until the end of the life of the diesel engine vehicle itself, and the demand for maintenance-free can be satisfied.

Since the valve opening pressure of the needle 3 is kept equal to the initial valve opening pressure even after the diesel engine has been operated for a long period of time, the needle 3
The timing at which the fuel is sprayed from the injection hole 2 away from the nozzle 1 is not advanced, and the fuel injection amount is returned to the vicinity of a predetermined set value. For this reason, even after the diesel engine has been operated for a long time, the unburned fuel in the atmosphere in the sub-combustion chamber of the diesel engine does not increase, and the performance deterioration of the exhaust gas can be suppressed.

In the fuel injection nozzle 1 of this embodiment, the annular elastic body 10 is provided on the inner peripheral convex portion 35 of the nozzle body 9.
Is fixed, even if the pressure receiving portion 14 of the needle 3 collides with the annular elastic body 10, the impact force can be absorbed. Therefore, the amount of wear of the pressure receiving portion 14 can be reduced, and the pressure-feeding fuel can be reduced. Changes in the pressure receiving area can be suppressed. Thus, the change in the valve opening pressure of the fuel injection nozzle 1 as described above can be reduced.

[Modification] In this embodiment, the present invention is applied to a throttle type nozzle, but the present invention may be applied to a pintle type nozzle or a hole type nozzle. Further, in the present embodiment, the present invention is attached to the cylinder head of the sub-combustion chamber type diesel engine to spray the fuel into the sub-combustion chamber, but the present invention is attached to the cylinder head of the direct injection type diesel engine to transfer the fuel to the combustion chamber. May be sprayed.

In this embodiment, the nozzle body is composed of the nozzle holder 7, the tip packing 8, the nozzle body 9, the elastic ring 1
Although the nozzle body is constituted by the nozzle body 7 and the retaining nut 21 and the like, the nozzle body may be constituted by the nozzle holder 7, the nozzle body 9 and the retaining nut 21 and the like, or the nozzle body may be constituted only by the nozzle body 9. In this case, the annular elastic body 10 may be omitted, and only the inner peripheral convex portion 35 may be formed integrally with the inner periphery of the guide portion 34 of the nozzle body 9.

In this embodiment, the coil-shaped spring 5 is used as the urging means, but a plate-shaped spring may be used as the urging means. Further, an elastic body such as a cushion rubber or an air cushion may be used as the urging means. In the present embodiment, the spring 5 and the adjusting shim 6 are provided as the valve-opening pressure adjusting means, but the other elastic body and the valve-opening pressure adjusting screw and the like as described above are provided as the valve-opening pressure adjusting means. Is also good.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an entire structure of a fuel injection nozzle (Example).

FIG. 2 is a schematic view showing a main structure of the fuel injection nozzle of FIG. 1 (Example).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuel injection nozzle 2 Injection hole 3 Needle 5 Spring (valve opening pressure adjusting means, urging means) 6 Adjusting shim (valve opening pressure adjusting means) 9 Nozzle body 10 Annular elastic body (valve opening pressure returning means, annular body) 11 Pin part 12 Seat part 13 Insertion part 14 Pressure receiving part 15 Sliding part 16 Projection part 31 Seat part 32 Oil reservoir 34 Guide part 35 Inner circumference convex part (valve opening pressure return means)

Claims (4)

[Claims] An injection hole for injecting fuel into an internal combustion engine, a tubular nozzle body having a seat portion upstream of the injection hole in a fuel supply direction, and the seat is slidably housed in the nozzle body. A needle that closes the injection hole by seating on the portion and opens the injection hole by separating from the seat portion; and a biasing unit that biases the needle toward a side seated on the seat portion, Valve opening pressure adjusting means for adjusting the urging load of the urging means to the valve opening pressure of the needle, wherein the fuel injection nozzle is provided after operating the internal combustion engine for a long time. A fuel injection nozzle comprising a valve opening pressure return means for returning a valve opening pressure to an initial valve opening pressure. 2. The fuel injection nozzle according to claim 1, wherein the needle has a cylindrical sliding portion that is slidably displaced in the nozzle body, and a cylindrical shape having an outer diameter smaller than the sliding portion. An insertion portion, and a pressure receiving portion that connects the sliding portion and the insertion portion, wherein the nozzle body is a guide portion that slidably displaces the sliding portion, and the sheet portion is closer to the seat portion than the guide portion. And an oil sump through which the insertion portion is inserted. The urging means is a coiled spring. The valve opening pressure return means is provided between the guide portion and the oil sump. A fuel injection nozzle having an annular body provided around the pressure receiving portion and the insertion portion and having an inner diameter smaller than that of the guide portion. 3. The fuel injection nozzle according to claim 2, wherein the annular body has an inner diameter set in consideration of a decrease in the biasing load of the spring after the internal combustion engine has been operated for a long period of time. A fuel, wherein the clearance between the sliding portion and the annular body is set in consideration of the amount of wear of the needle and the seat portion and the amount of wear of the spring after the internal combustion engine has been operated for a long period of time. Injection nozzle. 4. The fuel injection nozzle according to claim 2, wherein the annular body is a ring-shaped elastic body capable of elastic deformation.