JPH04311672A - Fuel injection valve - Google Patents

Abstract

PURPOSE:To provide a fuel injection valve allowing a specially uniform spray pattern to be obtained at the pre-lifting time. CONSTITUTION:A vertically movable needle valve 6 is provided in the valve hole 3a of a nozzle body 3. In this needle valve 6, its valve opening pressure is controlled across two stages by two springs. A guide member 25 for preventing the core oscillation of the needle valve 6 is also provided in the valve hole 3a of the nozzle body 3. This guide member 25 is provided with an outer peripheral part 25a pressed to the inner periphery of the valve hole 3a, and an inner peripheral part 25b brought into sliding contact with the outer periphery of the needle valve 6. The outer peripheral part 25a is formed of soft material and the inner peripheral part 25b is formed of hard material.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection valve, and more particularly to a two-stage valve opening pressure type fuel injection valve in which the opening pressure of a needle valve is controlled by the spring force of two springs.

0002

2. Description of the Related Art In general, fuel injection valves are known in which the opening pressure of a needle valve housed in a nozzle body is controlled by the spring forces of a first spring and a second spring (for example, Publication No. 56-129568). This type of conventional fuel injection valve is used in diesel engines to suppress instability in fuel injection operation such as car knock,
It prevents ignition delays and the generation of nitrogen oxides, and is also effective in reducing noise when the car is running at low speeds.

In this type of device, fuel is supplied into the nozzle body, and when this supply pressure overcomes the spring force of the first spring, the needle valve prelifts to perform initial injection, and then fuel is supplied into the nozzle body. is supplied,
When this supply pressure overcomes the sum of the respective spring forces of the first and second springs, the needle valve is further opened to achieve full lift and main injection is performed.

By the way, conventionally, while the opening pressure of a needle valve is controlled by the spring force of two springs, a plurality of nozzles are bored in the valve seat surface formed in the nozzle body.
Fuel injection valves in which this nozzle opening is opened and closed by a valve portion of a needle valve are known (for example, Japanese Patent Laid-Open No. 1-925
Publication No. 69).

[0005]

[Problems to be Solved by the Invention] However, in a fuel injection valve in which the nozzle opening on the valve seat surface formed in the nozzle body is opened and closed by the valve part of the needle valve, when center runout occurs in the valve part of the needle valve, , there is a problem that variations occur in the fuel spray pattern from each nozzle.

In particular, in a fuel injection valve in which the opening pressure of the needle valve is controlled by two springs, the pre-lift amount is usually set to about 0.03 to 0.10 mm, so at the pre-lift stage, the Even slight center runout causes large variations in the spray pattern from each nozzle.

[0007] Since the prelift stage corresponds to the ignition timing, a uniform spray pattern is required, and if there are variations in the fuel spray pattern at this stage, combustion within the combustion chamber (not shown) of the engine will be uneven. There is a problem that smoke and HC tend to deteriorate.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a fuel injection valve which solves the problems of the above-mentioned conventional techniques and which allows a particularly uniform spray pattern to be obtained at the time of pre-lift.

[0009]

Means for Solving the Problems In order to achieve the above objects, the present invention provides a nozzle holder having a fuel passage for introducing high-pressure fuel from a fuel injection pump, and a fuel passage connected to an end of the nozzle holder. a nozzle body having a valve seat face with a plurality of nozzle holes perforated in communication with the nozzle body, a needle valve having a valve portion housed in the valve hole of the nozzle body and opening and closing each of the nozzle ports on the valve seat face, and a valve opening pressure of the needle valve. A valve opening pressure control spring consisting of two springs that controls the valve opening pressure in two stages, an outer circumferential part that is press-fitted into the valve hole of the nozzle body and comes into pressure contact with the inner circumference of the valve hole, and an inner circumferential part that comes into sliding contact with the outer circumference of the needle valve. and a guide member whose outer circumferential portion is made of a soft material and whose inner circumferential portion is made of a hard material.

0010

[Operation] According to the present invention, when the needle valve is lifted upward, the outer periphery of the needle valve is always in sliding contact with the inner periphery of the guide member, so that the valve shaft of the needle valve may run out at the time of pre-lift. This does not occur, and a uniform fuel spray pattern is obtained from each nozzle. Therefore, in the combustion chamber of a diesel engine, a good combustion state without deterioration of smoke and HC can be obtained. Further, according to the present invention, since the inner peripheral part of the guide member that slides in contact with the needle valve is formed of a hard material, the guide member has excellent wear resistance, and the outer peripheral part that comes in pressure contact with the valve hole. Since the guide member is made of a soft material, the guide member can be easily press-fitted into the valve hole.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

In FIG. 1, reference numeral 1 indicates a fuel injection valve. The fuel injection valve 1 includes a nozzle holder 2, and a nozzle body 3 and a spacer 4 are connected to the lower end of the nozzle holder 2 via a retaining nut 5. Nozzle body 3, spacer 4 and nozzle holder 2
A hole is perforated in each of the upper and lower parts.
A needle valve 6, a lift piece 7, and a push rod 8 are housed in this through hole from below.

The lower end of the push rod 8 is a spherical convex portion, and this convex portion is engaged with a spherical concave portion of the lift piece 7. These push rod 8 and lift piece 7 are urged toward the needle valve 6 via a first spring 12. Further, a second spring 13 is attached around the shaft portion of the push rod 8, and this second spring 13 is supported by spring seats 15 and 16, and the lower spring seat 16 is supported by the spacer 4. ing. These first
The spring 12 and the second spring 13 constitute a valve opening pressure control spring.

A connecting pipe 17 is connected to the upper end of the nozzle holder 2, and a passage 18 communicating with a fuel injection pump (not shown) is bored through the connecting pipe 17. Passages 19 and 20 communicate with this fuel passage 18, and the high-pressure fuel introduced through the passage 18 is
The fuel flows into the fuel reservoirs 22 and 23 through the passage 19 of the nozzle holder 2 and the passage 20 of the nozzle body 3.

As shown in FIG. 2, the needle valve 6 is housed in the valve hole 3a of the nozzle body 3 so as to be vertically movable, and the valve portion 6a of the needle valve 6 is bored in the valve seat surface 3b of the nozzle body 3. The spout 10 can be freely closed. A guide member 25 is press-fitted between the needle valve 6 and the valve hole 3a.
It has a cyclic double structure with 5b. Further, the inner circumferential portion 25b is made of a hard material such as steel, and the outer circumferential portion 25a is made of a soft material such as aluminum that is softer than steel.

Then, as shown in FIG. 3, the outer peripheral portion 25a
The outer circumference of the valve hole 3a is pressed against the inner circumferential wall of the valve hole 3a, and the annular inner circumferential portion 2
The inner periphery of 5b is in sliding contact with the outer periphery of the shaft portion 6a of the needle valve 6. The outer circumferential portion 25a is integrally fixed on the outer circumference of the inner circumferential portion 25b at intervals in the circumferential direction, and the outer circumferential portion 25a
The above-mentioned fuel reservoirs 22, 2 are provided between the outer peripheral portion 25a and the outer peripheral portion 25a.
A communication path 27 is formed that communicates between the three. In addition, in order to efficiently prevent the core run-out of the needle valve 6, the guide member 25 is provided as close to the valve portion 6a of the needle valve 6 as possible.
It is desirable to form it near.

Next, the operation of this embodiment will be explained.

High-pressure fuel pumped from a fuel injection pump (not shown) is temporarily stored in fuel reservoirs 22 and 23, and the pressure of the fuel stored here acts on the pressure receiving portion 6c of the needle valve 6. When the spring force of the first spring 12 is resisted, the needle valve 6, lift piece 7, and push rod 8 are lifted upward. Then, the valve portion 6a of the needle valve 6 is pre-lifted, the injection port 10 of the nozzle body 3 is opened, and a predetermined amount of fuel is initially injected at a predetermined pressure. This pre-lift ends when the lift piece 7 contacts the spring seat 16. That is, the lift piece 7 and the spring seat 16
A gap corresponding to the prelift lift amount L1 is previously formed between the two. This gap is 0.03 to 0.10
It is set to mm.

Fuel is continuously fed under pressure into the fuel reservoirs 22 and 23, and the pressure of the fuel increases, and this pressure increases to the needle valve 6.
When the pressure acts on the pressure receiving part 6c and the valve part 6a and resists the sum of the spring forces of the first spring 12 and the second spring 13, the needle valve 6, lift piece 7, push rod 8 and spring seat 16 are Lift upwards. Then, the valve portion 6a of the needle valve 6 is further lifted, the nozzle 10 is fully opened, and fuel is main injected at a predetermined pressure. This full lift ends when the shoulder 6d of the needle valve 6 contacts the spacer 4. That is, a gap corresponding to the full lift amount L2 is formed in advance between the shoulder portion 6d of the needle valve 6 and the spacer 4. This gap is 0.2~0
．． It is set to 35mm.

In this embodiment, first, the valve opening pressure is controlled in two stages, so when used in a diesel engine, instability in fuel injection operation such as kernel knock is suppressed, and ignition delay and nitrogen Various effects can be obtained, such as preventing the generation of oxides and reducing noise when the car is running at low speeds.

By the way, at the time of the pre-lift, center runout σ tends to occur in the valve portion 6a of the needle valve 6. Valve part 6
When center runout σ occurs in a, the gaps δ1 and δ2 between the valve part 6a and the nozzle 10 will vary, causing irregularities in the fuel spray patterns P1 and P2, resulting in irregular combustion conditions in the combustion chamber of the engine. It becomes uniform and smoke etc. occur.

[0022] The prelift lift amount L1 is 0.03~
Since it is about 0.1 mm, even if a slight center runout σ occurs, the dispersion of the gaps δ1 and δ2 becomes large, and therefore the irregularity of the fuel spray patterns P1 and P2 becomes significantly large.

According to this embodiment, when the valve portion 6a of the needle valve 6 lifts upward, the inner periphery of the inner periphery 25b of the guide member 25 touches the valve shaft 6 of the needle valve 6.
Since the valve stem 6b of the needle valve 6 is always in sliding contact with the outer circumference of the needle valve 6, no center runout σ occurs, and uniform fuel spray patterns P1 and P2 are obtained from each nozzle 10, resulting in extremely uniform smoke. It is possible to obtain a combustion state without the occurrence of.

Furthermore, according to the present embodiment, the inner circumferential portion 25b of the guide member 25 that comes into sliding contact with the needle valve 6 is made of a hard material such as steel, so that the guide member 25 has wear resistance. Since the outer peripheral portion 25a that comes into pressure contact with the valve hole 3a is made of a material softer than steel, such as aluminum, it is extremely easy to press the guide member 25 into the valve hole 3a. Furthermore, since the guide member 25 is a separate body, it can be prepared in advance as a processed product, so when assembling the fuel injection valve, it is only necessary to press fit it into the valve hole 3a. Various effects such as extremely easy assembly and processing can be obtained.

FIGS. 4 and 5 show other embodiments.

A large diameter portion 51 is integrally formed in the needle valve 50, and this large diameter portion 51 has a flat cut surface 5.
1a is formed. Further, on the outer periphery of the large diameter portion 51,
A guide ring 53 formed of a hard material such as steel is fitted, and in the annular space between the outer periphery of the guide ring 53 and the inner periphery of the nozzle body 55, there is a material such as copper or lead that is easily deformed plastically. A soft metal 56 is interposed. The soft metal 56 and the guide ring 53 constitute a guide member. In addition, the inner circumference of the guide ring 53 and the large diameter portion 5
A communication path 57 is formed between the first cut surface 51a and the first cut surface 51a. Further, the upper and lower ends of the soft metal 56 are respectively closed by a stop ring 58 and a flat seat 55a of the nozzle body 55.

According to this embodiment, a hard guide ring 53 is fitted into the large diameter portion 51 of the needle valve 50, and a soft metal 56 such as copper or lead is interposed on the outside thereof. Therefore, in the assembly stage, if there is eccentricity in the needle valve 50 when seated, the soft metal 56 will be plastically deformed in the radial direction by being pushed by the needle valve 50 and the guide ring 53 according to the amount of eccentricity. Guide ring 53
moves in the radial direction, and this guide ring 53 is fixed with the same amount of eccentricity as the amount of eccentricity of the needle valve 50. In addition,
In this case, since the soft metal 56 is also plastically deformed in the circumferential direction, the soft metal 56 uniformly wraps around the outer periphery of the guide ring 53 and the nozzle body 55.
is uniformly interposed within the annular space between the inner periphery of the

According to this, the guide ring 53 is fixed according to the amount of eccentricity of the needle valve 50 during assembly, so that various effects such as easier centering during processing can be obtained.

[0029]

As is clear from the above description, according to the present invention, there is provided a nozzle holder having a fuel passage for introducing high-pressure fuel from a fuel injection pump, and a nozzle holder connected to the end of the nozzle holder and connected to the fuel passage. A nozzle body having a valve seat face in which a plurality of communicating nozzles are perforated, a needle valve having a valve part housed in the valve hole of the nozzle body and opening and closing each of the nozzles on the valve seat face, and a valve opening pressure of the needle valve. A valve opening pressure control spring consisting of two springs that controls in two stages, an outer circumferential part that is press-fitted into the valve hole of the nozzle body and comes into pressure contact with the inner circumference of the valve hole, and an inner circumferential part that comes into sliding contact with the outer circumference of the needle valve. and a guide member whose outer circumferential part is made of a soft material and whose inner circumferential part is made of a hard material, so that the valve shaft of the needle valve described above will not run out during the pre-lift. Therefore, a uniform fuel spray pattern can be obtained from each nozzle, and therefore, an extremely uniform combustion state with little smoke can be obtained in the combustion chamber of the diesel engine.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of a fuel injection valve according to the present invention.

FIG. 2 is a sectional view showing a nozzle body and a needle valve.

FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2;

FIG. 4 is a sectional view showing another embodiment.

FIG. 5 is a sectional view taken along line VV in FIG. 4;

[Explanation of symbols]

2 Nozzle holder 3 Nozzle body 3a Valve hole 3b Valve seat surface 4 Spacer 6 Needle valve 6a Valve part 6b Valve stem 7 Lift piece 8 Push rod 10 Spout 12 First spring 13 Second spring 17 Connecting pipe 18, 19, 20 Fuel passage 22, 23 Fuel reservoir 25 Guide member 25a, 56 outer periphery 25b, 53 Inner circumference 27, 57 Communication path

Claims (1)

[Claims] 1. A nozzle holder having a fuel passage for introducing high-pressure fuel from a fuel injection pump, and a valve seat surface connected to an end of the nozzle holder and having a plurality of nozzles perforated therein communicating with the fuel passage. A nozzle body, a needle valve that is housed in a valve hole of the nozzle body and has a valve part that opens and closes each nozzle on the valve seat surface, and two springs that control the opening pressure of the needle valve in two stages. a valve opening pressure control spring; an outer circumferential portion press-fitted into the valve hole of the nozzle body and in pressure contact with the inner circumference of the valve hole; and an inner circumferential portion slidingly in contact with the outer circumference of the needle valve, the outer circumferential portion being soft. 1. A fuel injection valve comprising: a guide member formed of a hard material; and the inner peripheral portion is formed of a hard material.