JPH05164020A - Fuel injection valve - Google Patents

Abstract

PURPOSE:To control the eccentricity of the head section of a needle valve to a valve body and make the state of atomization from a fuel injection hole excellent without lowering the valve closing speed of the needle valve when completing injection. CONSTITUTION:A fuel injection valve is provided with a guide mechanism which controls the eccentricity of the head 8' of a needle valve. This guide mechanism has the guide section 28 and a playingly fitting section 29 on the side of a valve body and a section 34 to be guided on the side of the needle valve, and the playingly fitting section 29 is playingly fitted to the section 34 to be guided when the lifting amount of the needle valve is not more than a specified value L3, and the guide section 28 guides the sliding of the section 34 to be guided only when the lifting amount of the needle valve exceeds the specified value L3.

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 for a natural engine.

[0002]

2. Description of the Related Art A fuel injection valve for a direct injection type diesel engine is known, for example, as shown in FIG. 8 (see JP-A-1-203652).

Shown in the figure is a valve body 101 forming an outer shell.
And a fuel injection hole 10 formed on the tip side of the valve body 101.
2, a needle valve 103 movably accommodated in the valve body 101 to open and close the fuel injection hole 102, and a fuel injection hole 10
A first coil spring 104 and a second coil spring 105 for urging the needle valve 103 in the direction of closing 2.
Is a two-stage valve-opening pressure fuel injection valve 100 that is generally configured from a needle valve 10 in which fuel is introduced from an injection pump (not shown).
When the fuel pressure is applied to No. 3, first, the needle valve 103 pre-lifts by a predetermined amount L ₁ to perform the initial injection from the fuel injection hole 102, and then the fuel pressure increases to the first coil spring 104. When the resultant force with the second coil spring 105 is exceeded, the needle valve 103 is further lifted by the distance L ₂ to perform main injection from the fuel injection hole 102. The fuel injection hole 102 is opened and closed by the valve unit 1 formed at the tip of the needle valve.
06 is seated on / separated from the seat portion 107 on the valve body side.

In the two-stage valve-opening pressure fuel injection valve based on such a configuration, the needle lift amount in the initial stage of injection is regulated to a relatively small predetermined amount L ₁ , so that from the start of fuel injection to self-ignition. During the ignition delay period, that is, the fuel injection amount is suppressed to a low level, and as a result, rapid premixed combustion is suppressed, and the production of nitrogen oxides (NOx) can be reduced. Since the reaching distance (i.e., the penetration of the spray) is suppressed to be small, the fuel is prevented from adhering to the cavity wall or the cylinder wall (not shown), and the generation of unburned hydrocarbons (HC) can be reduced. ..

On the other hand, for the purpose of restricting the eccentricity of the needle valve with respect to the valve body, for example, the one shown in FIG. 9 has been conventionally proposed (Japanese Patent Laid-Open No. 59-777).
No. 0, etc.).

In the figure, the fuel injection hole 11 is provided on the tip side.
1, the needle valve 113 is movably accommodated in the valve body 112, and the valve portion 114 formed at the tip of the needle valve is seated / separated from the seat portion 115 on the valve body side so that the fuel injection hole 1
11 is a fuel injection valve 110 that opens and closes, and a guided portion 116 formed as shown in the drawing at the tip end side of the needle valve 113 is slidably guided by a guide portion 117 on the valve body side.
The needle valve tip is restricted from being eccentric with respect to the valve body 112.

That is, the valve portion 114 which is the tip of the needle valve.
Is eccentric with respect to the seat portion 115 on the valve body side, the gap between the fuel injection hole inlet 118 and the valve portion 114 differs for each fuel injection hole. Therefore, the fuel injection timing, the fuel injection amount, and the spray injection The morphology etc. becomes non-uniform for each fuel injection hole,
For example, there is a problem that smoke, which is the main component of the particulate matter (PM), is generated from the fuel injection hole that excessively injects the fuel, but according to this conventional example, such a problem can be solved. ..

[0008]

The fuel injection valve 11 described above is used.
0 restricts the guide portion 117 on the valve body side from slidingly guiding the guided portion 116 on the needle valve side to prevent the needle valve tip portion from being eccentric, but this type of fuel injection used in a diesel engine Since the valve is exposed to a harsh environment such as being directly exposed to combustion accompanied by an explosion, it deforms by receiving external forces such as heat and explosive force. That is, the guide portion 117 and the guided portion 116.
Not only is not secured, but also the guide portion 117 and the guided portion 116 cause a misalignment, so that the sliding resistance between the guide portion 117 and the guided portion 116 increases, and therefore the conventional guide portion 117 Is the guided portion 11 on the needle valve side
Since 6 is always guided by sliding, the needle valve 113 cannot be promptly seated on the seat portion 115, and a decrease in the closing speed of the needle valve at the end of injection is a particular problem.

Further, since it is difficult to secure the coaxiality between the valve portion 114 and the seat portion 115, when the valve is closed, the needle valve tip portion is displaced in its seated position, that is, the seat portion of the valve portion 114. There is a problem in that the seating at 115 is not reliably performed and the injection fuel is cut off at the end of fuel injection.

These problems are caused by fuel dripping from the fuel injection hole 111, carbon deposition around the fuel injection hole 111, cracking of spray due to carbon flower formation, liquid columnarization, and axial direction of spray. It causes a deviation of fuel consumption and causes a problem such that the unburned ratio increases and fuel consumption deteriorates, and harmful exhaust components increase.

In particular, in the two-stage valve opening pressure fuel injection valve 100, the needle valve lift amount at the initial stage of injection is regulated to a relatively small predetermined amount L _1. Therefore, the fuel injection hole inlet 108 at this time is set.
The gap between the valve section 106 and the valve section 106 is very small.
At this time, if there is a slight eccentricity of the tip of the needle valve, the smoke will be significantly worsened, so it is necessary to particularly control the eccentricity of the tip of the needle valve in the initial stage of injection. If the conventional means for restricting eccentricity is applied as it is, the first coil spring 104, which is relatively weaker than the second coil spring 105, biases the needle valve in the valve closing direction at the end of injection. Since the valve portion 106 is seated on the seat portion 107 even further, the seating of the valve portion 106 on the seat portion 107 is particularly deteriorated.

The present invention has been made by paying attention to such a conventional problem, and is provided with a guide mechanism which is a means for restricting the eccentricity of the needle valve with respect to the valve body, and the guide mechanism is also provided. The object of the present invention is to provide a fuel injection valve that solves the above problems by not restricting the movement of the needle valve when the needle valve lift amount falls below a predetermined value.

The present invention has been made by paying attention to such a conventional problem, and is provided with a guide mechanism which is a means for restricting the eccentricity of the needle valve with respect to the valve body, and the guide mechanism is also provided. The object of the present invention is to provide a fuel injection valve that solves the above problems by not restricting the movement of the needle valve when the needle valve lift amount falls below a predetermined value.

[0014]

In order to solve the above problems, a fuel injection valve according to a first aspect of the present invention has a valve body, a needle valve, and a guide mechanism, and the valve body has a tip end thereof. A side portion having a fuel injection hole and a seat portion having a substantially conical shape, and accommodating the needle valve so as to be movable in its axial direction, and the needle valve has a valve portion at its tip. And the valve portion is for seating on / separating from the seat portion to open / close the fuel injection hole, and the guide mechanism is
A guide portion and a loose fitting portion formed on the valve body side, and a guided portion formed on the needle valve side, the loose fitting portion being the guided portion when the needle valve lift amount is equal to or less than a predetermined value. That the guide portion guides the guided portion and regulates the eccentricity of the needle valve tip portion only when the needle valve lift amount exceeds a predetermined value. Characterize.

In the second aspect of the invention, the guide mechanism includes a guided portion formed in a maximum diameter portion on the tip side of the needle valve, a guide portion disposed on the valve body side, and the valve body. A loose fitting portion that is disposed on the side and is located between the guide portion and the seat portion, and the loose fitting portion allows the guided portion to play when the needle valve lift amount is equal to or less than a predetermined value. The guide portion slides and guides the guided portion only when the needle valve lift amount exceeds a predetermined value, and the loose fitting portion and the guide portion serve as guide members. It is characterized in that it is configured separately from the valve body.

In the third aspect of the invention, the guide mechanism includes a guided portion formed in a maximum diameter portion on the tip side of the needle valve, a guide portion disposed on the valve body side, and the valve body. A loose fitting portion that is disposed on the side and is located between the guide portion and the seat portion, and the loose fitting portion allows the guided portion to play when the needle valve lift amount is equal to or less than a predetermined value. The guide portion is configured by a rolling element fitting groove formed in the valve body and a plurality of rolling elements arranged in the rolling element fitting groove, and the plurality of rolling elements are It is characterized in that the guided portion is rolled and guided only when the needle valve lift amount exceeds a predetermined value.

In the fourth invention, the fuel injection valve has first closing means and second closing means that act on the needle valve, and the first closing means is the above-mentioned. The second closing means always acts in the direction of blocking the fuel injection hole, and the second closing means first acts in the direction of blocking the fuel injection hole when the needle valve lift amount exceeds a predetermined lift amount. The predetermined lift amount is set to be larger than the predetermined value.

[0018]

According to the above construction, when the needle valve lifts in the valve opening direction and the valve portion on the needle valve side is separated from the seat portion on the valve body side, fuel is injected from the fuel injection hole.

In the first aspect of the invention, when the needle valve lift amount exceeds a predetermined value, the guided portion on the needle valve side is guided by the guide portion on the valve body side, so that the needle valve tip portion is relative to the valve body. As a result, it is possible to control the fuel injection timing from the fuel injection hole, the fuel injection amount, and the spraying form of the spray to be uniform for each fuel injection hole.

At the end of fuel injection, if the needle valve moves in the valve closing direction and its lift amount falls below a predetermined value, the guided portion on the needle valve side is released from the constraint of the guide portion on the valve body side. Since the needle valve loosely fits in the loose fitting portion, the needle valve can be quickly seated on the seat portion on the valve body side without causing a decrease in valve closing speed. Further, at this time, since the tip of the needle valve is relatively free, the needle valve can obtain a self-aligning action by being pressed against the substantially conical seat portion, that is, the valve portion is While bouncing against the seat, it converges itself to an appropriate seating position. The bouncing is not a movement in the axial direction of the needle valve but a movement in a direction substantially perpendicular to the axial line of the needle valve, which contributes to the improvement of the valve closing speed. Therefore, the shortage of the injected fuel at the end of the fuel injection is improved, and the dripping of the fuel can be prevented.

Further, in the second aspect, when the needle valve lift amount exceeds a predetermined value, the guided portion on the needle valve side is slidably guided by the guide portion on the valve body side, and the needle valve tip portion is moved to the valve body. Eccentricity is regulated. As a result, it becomes possible to uniformly control the fuel injection timing, the fuel injection amount, and the spraying form of the spray from the fuel injection holes for each fuel injection hole. Also,
At the end of fuel injection, if the needle valve moves in the valve closing direction and its lift amount falls below a predetermined value, the guided part on the needle valve side is released from the constraint of the guide part on the valve body side and becomes a loose fitting part. Since the needle valve is loosely fitted, the needle valve can be quickly seated on the seat portion on the valve body side without lowering the valve closing speed. Further, at this time, since the needle valve tip is relatively free,
The needle valve can obtain a self-centering action by being pressed against the substantially conical seat portion, that is, the valve portion bouncing with respect to the seat portion and itself converges to an appropriate sitting position. Therefore, the shortage of the injected fuel at the end of the fuel injection is improved, and the dripping of the fuel can be prevented. Further, since the loose fitting portion and the guide portion are formed as guide members separately from the valve main body, it is possible to secure the accuracy of the above-mentioned predetermined value, facilitate the accuracy, and facilitate the work.

Further, according to the third aspect of the invention, since the positioning of the rolling element fitting groove can be relatively easily and highly accurately obtained as the distance from the base end of the valve body, the prescribed value can be defined relatively easily. Therefore, the manufacturability is easy. At the same time, since the guiding action of the guided portion formed on the needle valve side is performed by rolling guide by point or line contact, it is possible to effectively prevent a decrease in valve closing speed due to friction reduction, and at the end of injection. The fuel shortage can be further improved.

Further, according to the fourth aspect of the invention, since the eccentricity of the needle valve tip can be regulated at a predetermined lift amount which is required to regulate the eccentricity of the needle valve tip, the form of spray from the fuel injection hole at the initial stage of injection can be changed. It is possible to perform uniform control for each fuel injection hole. Further, in such a fuel injection valve, the biasing force of the needle valve in the valve closing direction at the end of fuel injection is relatively small, but when the needle valve lift amount falls below a predetermined value, the needle valve will Since the restraint by the guide mechanism is released, the seat can be quickly seated on the valve body side without lowering the valve closing speed, and fuel shortage can be improved.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. 1 is a partial cross-sectional view showing the tip side of the fuel injection valve according to the present embodiment, FIG. 2 is a partially enlarged cross-sectional view of FIG. 1, and FIG. 3 is a part showing the overall configuration of the fuel injection valve according to the present embodiment. FIG.

Referring to FIG. 3, 1 is a fuel injection valve,
Reference numeral 2 is a valve body that forms the outer shell of the fuel injection valve. The valve body 2 is composed of a nozzle holder 3, a nozzle tip 4 and a retaining nut 5, and the nozzle holder 3 and the nozzle tip 4 are connected by a retaining nut 5 via a spacer 6. A fuel passage 7 connected to an injection pump (not shown) is formed in the valve body 2, and the fuel passage 7 communicates with a fuel injection hole 33 described later.

A needle valve 8 is movably housed in the nozzle tip 4 so as to open and close the fuel passage 7 in the axial direction.
On the base end side, a push rod portion 9 having a relatively small diameter, and a slide portion 10 having a diameter larger than the push rod portion 9,
It is composed of a pressure receiving portion 11 which is a tapered surface and a base diameter portion 12 having a diameter smaller than that of the sliding portion 10. A sliding shoulder 45 is formed by the difference in diameter between the push rod portion 9 and the sliding portion 10, and has a surface perpendicular to the axial direction of the needle valve 8.

On the base end side of the nozzle tip 4, a sliding portion 13 for slidingly guiding the sliding portion 10 and the pressure receiving portion 11 are provided.
A fuel reservoir 14 formed so as to surround the base and a guide portion 15 in which the base diameter portion 12 is loosely fitted are formed.

A spring chamber 18 is formed in the nozzle holder 3 in which a first coil spring 16 which is a first closing means and a second coil spring 17 which is a second closing means are housed. .. First coil spring 1
One end 20 of 6 abuts on the end 19 of the push rod portion 9 via the first retainer 21, and the other end 22 of the spring chamber 1
It is in contact with the wall surface of No. 8 through the shim 23. Also, the second
One end 26 of the coil spring 17 abuts on the proximal end 24 of the nozzle tip 4 via the second retainer 25 arranged in the spacer 6, and the other end 27 of the spring chamber 18 via the shim 23. It is in contact with the wall.

Fuel is introduced from the injection pump (not shown) into the two-stage valve opening pressure fuel injection valve based on the above-mentioned structure and the pressure receiving portion 11 is supplied.
When the fuel pressure is applied to the needle valve 8, first, the needle valve 8 has a predetermined lift amount (hereinafter, referred to as a predetermined lift amount determined between the sliding shoulder 45 and the second retainer 25).
The pre-lift amount) L _{1 is} lifted to perform the initial injection from the fuel injection hole 33, and then, when the fuel pressure rises and exceeds the resultant force between the first coil spring 16 and the second spring 17, the needle valve 8 moves to the first position. Further, the needle valve 8 is further lifted by ΔL determined between the two retainer 25 and the nozzle holder 3, that is, the needle valve 8 is lifted to the full lift amount L ₂ (L ₂ = L ₁ + ΔL), and the main injection from the fuel injection hole 33 is performed.

Referring to FIG. 1, inside the valve body 2, that is, the inside of the tip of the nozzle tip 4, there is a guide portion 28 in which the base diameter portion 12 is loosely fitted, and a tapered shape from this guide portion 28 toward the tip. And a terminal end 30 of which is curved in a direction substantially perpendicular to the axis of the valve body, a seat portion 31 of a substantially conical shape adjacent to the terminal end 30, and a bag-shaped end portion of the seat portion 31. The sack portion 32 and the seat portion 3 are formed.
1 has a plurality of fuel injection holes 33 formed therein.

The tip side of the needle valve 8 has a tip side maximum diameter portion 34 '.
The valve portion 35 and the guided portion 34 are guided by the guided portion 34 slidably guided by the guide portion 28 and the valve portion 35 which can be seated on the seat portion 31. The cylindrical portion 36 having a smaller diameter than the portion 34 is continuous with the first tapered portion 37, and the base diameter portion 12 and the guided portion 34 are continuous with the second tapered portion 38.

That is, the guide mechanism according to the present embodiment is
It is composed of a guide portion 28 and a loose fitting portion 29 on the valve body side, and a guided portion 34 on the needle valve side.

The valve portion 35 is composed of a first valve taper portion 39 on the front end side and a second valve taper portion 40 on the base end side having different angles. Make the seat line 41,
When the valve portion 35 is seated on the seat portion 31, the fuel injection hole 33 is closed.

The first taper portion 37, the guided portion 34, and the second portion
It is a fuel groove 42 that is cut out so as to straddle the taper portion 38, and when the guided portion 34 is slidably guided by the guide portion 28, the base diameter portion 12 and the guide portion 28 are separated from each other. The fuel supplied to the gap 43 is guided to the fuel injection hole 33. Although the fuel groove 42 has a notch so as to straddle the first tapered portion 37, the guided portion 34, and the second tapered portion 38, the present invention is not limited to this, and the guided portion 34 guides the fuel groove 42. When the fuel supplied to the gap 43 can be guided to the fuel injection hole 33 while being slidably guided by the portion 28, for example, by forming a fuel hole in the needle valve 8. Good.

Next, referring to FIG. 2, the second taper portion 38
The loose fitting portion 29 has a gentle inclination angle θ ₁ and a gentle inclination angle θ ₂ , and these inclination angles θ ₁ and θ ₂ are set by the guided portion 34 when the needle valve 8 lifts in the valve opening direction. The guide portion 28 is determined so as to be smoothly guided.

With the valve portion 35 on the needle valve side seated on the seat portion 31 on the valve body side, the guided portion 34 and the second portion
The boundary line A formed by the tapered portion 38 and the guide portion 28
The distance from the boundary line B formed by the loose fitting portion 29 and the loose fitting portion 29 has a predetermined value L ₃ , that is, the needle valve 8 is lifted by the predetermined value L ₃ with respect to when seated and the guide portion 28 is not moved. The positional relationship between the needle valve 8 and the valve body 2 is defined so as to be guided to. Note that the determination of the predetermined value L _3, must be considered as the pre-lift amount L ₁ is the eccentricity of the needle valve tip 8 'is fully restricted, that is, at the time of reaching the pre-lift amount L _1, The amount of fitting (L ₁ -L ₃ ) of the guided portion 34 to the guide portion 28 is defined to be large enough to regulate the eccentricity of the valve portion 35.

Next, the operation will be described based on such a configuration.

Referring also to FIG. 4, when fuel is introduced from an injection pump (not shown) and fuel pressure is applied to the pressure receiving portion 11, the needle valve 8 starts to lift in the valve opening direction at time t ₀ . The fuel is guided to the fuel injection hole 33 through the gap 43 and the fuel groove 42, at which time fuel injection from the fuel injection hole 33 starts. Within a very short time from time t ₀ to time t ₁ , first, the needle valve 8 reaches the pre-lift amount L _1, and the initial injection is performed from here to time t ₂ . Since this pre-lift amount L ₁ is suppressed to a relatively small value, rapid premixed combustion is suppressed, and the production of nitrogen oxides (NOx) is reduced. At the same time, the arrival distance of the spray, that is, the penetration of the spray is suppressed to be small, so that the fuel is prevented from adhering to the cavity wall or the cylinder wall of the piston (not shown), and the generation of unburned hydrocarbons (HC) can be reduced.

In the present embodiment, the needle valve-side guided portion 34, which is loosely fitted at time t ₀ , has the eccentricity of the needle valve tip portion 8 ′ by time t ₁ when the pre-lift amount L ₁ is reached. Since it is fitted into the guide portion 28 on the valve main body side enough to regulate the fuel injection amount, the fuel injection timing, the fuel injection amount, and the spray form of the spray in the initial injection, that is, the pre-lift amount L ₁ are accurately controlled for each fuel injection hole. It becomes possible to do.

That is, the needle valve lift amount in the initial injection is regulated to a relatively small pre-lift amount L ₁ , and the gap between the fuel injection hole inlet 44 and the first valve taper portion 39 at this time is suppressed to a very small value. Since the eccentricity of the needle valve 8 is already regulated, it is possible to solve the problem that the smoke is more significantly deteriorated due to the slight eccentricity of the needle valve tip portion 8 ′.

It should be noted that from time t ₀ when the eccentricity of the needle valve tip portion 8 ′ is not regulated to just before time t _1, it is a very short time and the fuel injection amount at this time is also small, so that the smoke is deteriorated. Little impact.

Further, since the second taper portion 38 and the loose fitting portion 29 have a gentle inclination angle θ _{1 and a} gentle inclination angle θ ₂ ,
When lifted in the valve opening direction, the guided portion 34 moves to the guide portion 2.
8 will be guided smoothly.

When the fuel pressure further rises, the needle valve 8
Reaches the full lift amount L ₂ and performs the main injection with a peak at time t ₃ .

Then, when the pressure feeding of the fuel from the injection pump is completed and the fuel pressure is reduced, the needle valve 8 moves in the valve closing direction, the valve portion 35 is seated on the seat portion 31, and the fuel injection is terminated. In this process, the needle valve lift amount is the predetermined value L
Below ₃ , the guided portion 34 will move to the guide portion 2 on the valve body side.
Since the needle valve tip portion 8 ′ at this time is released from the guiding action of 8, the valve portion 35 having a substantially conical shape is pressed against the seat portion 31 having a substantially conical shape. A self-centering action can be obtained, that is, the valve portion 35 can converge itself to an appropriate seating position while bouncing with respect to the seat portion 31. The bouncing is not a movement in the axial direction of the needle valve but a movement in a direction substantially perpendicular to the axial line of the needle valve, which contributes to the improvement of the valve closing speed. (Hereinafter, bouncing is used with the same meaning.) As a result, as shown in FIG. 5, the injection rate at the beginning of the initial injection (a in the figure) and the injection rate in the main injection (b in the figure) increase. As the amount of fuel injection is increased, the sharpness at the end of injection is improved, and fuel dripping can be prevented. In other words, it is possible to improve the sharpness of the fuel at the end of injection and to obtain the ejection form of the spray in an excellent state at the initial stage of injection.

Next, a second embodiment will be described with reference to FIG.

In this embodiment, the guide portion 28 and the loose fitting portion 29 on the valve main body side in the first embodiment are formed separately from the valve main body 2, that is, the nozzle tip 4, and have the above predetermined value L ₃ . The purpose is to ensure accuracy, ease of accuracy and ease of work.

First, the structure will be described. Reference numeral 51 is a valve main body having a fuel injection hole 52 on the tip side, that is, a nozzle tip, and a needle valve 53 for opening and closing the fuel injection hole 52 is moved in the axial direction in the nozzle tip 51. It is stored as much as possible.

Inside the nozzle tip 51, a seat portion 54 having a substantially conical shape, a bag-like sack portion 55 located on the tip side of the seat portion 54, and a plurality of fuel injection holes 52 opening in the seat portion 54 are provided. Are formed. On the base end side of the seat portion 54 is a shoulder portion 56 which serves as a base for defining a predetermined value L ₃ described later.
The needle valve loose fitting hole 57 is bored while forming the above, and the shoulder portion 56 has a surface perpendicular to the axis of the nozzle tip 51. The needle valve loosely fitting hole 57 is for loosely fitting a guided portion 64, which will be described later, in the entire lift range of the needle valve 53.

A hollow cylindrical guide member 58 is housed in the needle valve loose fitting hole 57.
The tip end side end portion 59 is in contact with the shoulder portion 56. The inner periphery of the guide member 58 has a base end 60 that is largely inclined.
And a guide portion 61 for slidingly guiding a guided portion 64 described later.
And a free fitting portion 62 that is inclined from the guide portion 61 in a taper-like direction.
8 is fixed to the nozzle tip 51 by caulking the base end side end portion 60.

The tip side of the needle valve 53 has a maximum diameter portion 6 on the tip side.
4'and is substantially configured by a guided portion 64 slidably guided by the guide portion 61 and a valve portion 65 which can be seated on the seat portion 54. The valve portion 65 and the guided portion 64 are Cylindrical portion 66 having a smaller diameter than the guided portion 64
With the first tapered surface 67, and the base diameter portion 63 and the guided portion 64 are continuous with each other via the second tapered portion 68.

That is, the guide mechanism according to the present embodiment is
It is composed of a guide member 58 forming a guide portion 61 and a loose fitting portion 62 on the valve body side, and a guided portion 64 on the needle valve side.

First taper portion 67, guided portion 64, second
A plurality of notches are formed so as to straddle the taper portion 68, and the fuel groove 69 is formed, and the base diameter portion 63 and the needle valve loose fitting hole 5 are formed.
The fuel introduced into the gap 70 with respect to 7 is supplied to the fuel injection hole 52.

The valve portion 65 is composed of a first valve taper portion 71 on the front end side and a second valve taper portion 72 on the base end side which have different angles. Seat line 73 at the border
When the valve portion 65 is seated on the seat portion 54, the fuel injection hole 52 is closed.

Further, when the valve portion 65 on the needle valve side is seated on the seat portion 54 on the valve body side, the guided portion 64
The distance between the boundary line A formed by the second taper portion 68 and the boundary line B formed by the guide portion 61 and the loose fitting portion 62 has a predetermined value L ₃ , that is, when seated. Based on the above, the positional relationship between the needle valve 53 and the valve body, that is, the nozzle tip 51 is defined so that the needle valve 53 is slid and guided by the guide portion 61 only after being lifted by the predetermined value L ₃ .

Further, the second taper portion 68 and the loose fitting portion 62.
Is a gentle inclination angle θ ₁ as in the first embodiment, and the inclination angle θ _1
2 and the inclination angles θ ₁ and θ ₂ are
Is considered and determined so that the guided portion 64 is smoothly guided with respect to the guide portion 61 when the valve is lifted in the valve opening direction.

Although not shown in the drawings, the fuel injection valve according to the present embodiment is applied to a two-stage valve opening pressure fuel injection valve that suppresses the fuel injection amount at the initial stage of injection, as in the above embodiments. When fuel is introduced from the pump and fuel pressure is applied to the needle valve 53, the needle valve 53 first causes the pre-lift amount L
_When the valve is lifted by 1 to perform the initial injection from the fuel injection hole 52, and then the fuel pressure rises and exceeds the resultant force of the first coil spring and the second coil spring, the needle valve 53 further causes the full lift amount L ₂ Lift up to the fuel injection hole 5
The main injection from 2 is performed.

The predetermined value L ₃ is determined in the same manner as in the first embodiment so that the eccentricity of the needle valve tip portion 53 ′ is sufficiently restricted at the pre-lift amount L ₁ .

Next, the operation will be described based on such a configuration.

Similar to the first embodiment, when the fuel pressure is applied to the needle valve 53, the needle valve 53 starts to lift in the valve opening direction, and when the lift amount exceeds a predetermined value L ₃ , it loosely fits. The guided portion 64 in the state is the guide portion 61 of the guide member 58.
, That is, the guiding action by the guide mechanism is obtained.
This guiding action regulates the eccentricity of the needle valve tip portion 53 ′ before reaching the pre-lift amount L _1. At the time of initial injection, the fuel injection timing, the fuel injection amount, and the spraying form of the spray are different from each other. Precisely controlled for each hole.

When the fuel pressure applied to the needle valve 53 decreases and the needle valve lift amount falls below a predetermined value L ₃ , the guided portion 64 on the needle valve side is released from the guiding action of the guide portion 61 on the valve body side. The valve portion 65 having a substantially conical shape is pressed against the seat portion 54 having a substantially conical shape to obtain a self-centering action. That is, the valve portion 65 itself converges to an appropriate seating position while bouncing with respect to the seat portion 54.

In the present embodiment, the distance H from the valve body, that is, the base end portion (not shown) of the nozzle tip 51 to the shoulder portion 56 is relatively large, for example, from the cutting amount of the milling cutter which is a cutting tool. It is possible to easily and highly accurately manage, and the positioning of the boundary line B in the guide member 58 as a separate body can be relatively easily and accurately managed as the distance from the tip end portion 59 of the guide member 58. Is possible. Therefore, the predetermined value L formed between the boundary line A and the boundary line B when the valve portion 65 is seated on the seat portion 54 by bringing the shoulder portion 56 and the tip end portion 59 into contact with each other. It becomes possible to obtain ₃ with high precision while facilitating workability.

In this embodiment, the guide member 58 is fixed to the nozzle tip 51 by caulking, but other fixing means such as bonding, welding, press fitting, plastic deformation processing and the like can be considered.

Next, a third embodiment will be described with reference to FIG.

First, the structure will be described. Reference numeral 81 is a valve main body having a fuel injection hole 82 on the tip side, that is, a nozzle tip. Inside the nozzle tip 81, a needle valve 83 for opening and closing the fuel injection hole 83 is arranged in the axial direction. It is stored so that it can be moved.

Inside the nozzle tip 81, a seat portion 84 having a substantially conical shape on the tip side thereof, a bag-like sack portion 85 located further on the tip of the seat portion 84, and a plurality of fuels opened in the seat portion 84 are provided. An injection hole 82 is formed, and a needle valve loose insertion hole 87 is formed on the base end side of the seat portion 84 while forming a shoulder portion 86 substantially perpendicular to the axis of the nozzle tip 81. The needle valve loose insertion hole 87 always fits a guided portion 92, which will be described later, in the entire lift range of the needle valve 83, and is provided between the seat portion 84 and a rolling element fitting groove 89 described later. The loose fitting portion 87a in the example is formed.

The needle valve loose insertion hole 87 has a base end portion (not shown).
At a predetermined distance H from the rolling element fitting groove 89 of a substantially V shape
Are engraved in an annular shape. In this rolling element fitting groove 89, a plurality of rolling elements, that is, balls 90 are arranged so as not to be unevenly distributed, and the needle valve tip portion 83 ′ is eccentric with respect to the valve body, that is, the nozzle tip 81. Considered not to. Here, the guide unit 1 according to the present embodiment
20 is composed of a rolling element fitting groove 89 and a ball 90.

The tip side of the needle valve 83 is a base diameter portion 91, a guided portion 92 which is a maximum diameter portion 92 'on the tip side and which is guided to roll by the ball 90, and a valve portion which can be seated on the seat portion 84. The valve portion 93 and the guided portion 92 have a diameter smaller than that of the guided portion 92.
4 and the first tapered portion 95, and the base diameter portion 91 and the guided portion 92 are continuous through the second tapered portion 96.

That is, the guide mechanism according to the present embodiment is
The guide portion 120 on the valve body side and the loose fitting portion 87a and the guided portion 92 on the needle valve side are configured.

The second taper portion 96 has a gentle inclination angle θ ₁ and is designed so that the guided portion 92 is smoothly guided with respect to the ball 90 when the needle valve 83 lifts in the valve opening direction. ing.

The valve portion 93 is composed of a first valve taper portion 97 on the front end side and a second valve taper portion 98 on the base end side having different angles, and is defined by the boundary between the first valve taper portion 97 and the second valve taper portion 98. Make a seat line 99,
The valve portion 93 is seated on the seat portion 84 so that the fuel injection hole 82
Is blocked.

Although not shown in the drawings, the fuel injection valve according to this embodiment is applied to a two-stage valve opening pressure fuel injection valve for suppressing the fuel injection amount at the initial stage of injection, as in the above embodiment, When fuel is introduced from the injection pump and fuel pressure is applied to the needle valve 83, the needle valve 83 first causes the pre-lift amount L
_When the fuel is lifted by ₁ to perform the initial injection from the fuel injection hole 82, and then the fuel pressure rises and exceeds the resultant force of the first coil spring and the second coil spring, the needle valve 83 further causes the full lift amount L ₂ Lift up to the fuel injection hole 8
The main injection from 2 is performed.

Further, in the state where the valve portion 93 on the needle valve side is seated on the seat portion 84 on the valve body side, the guided portion 92 is
The distance between the boundary line A formed by the second taper portion 96 and the center line B of the substantially V-shaped rolling element fitting groove 89 has a predetermined value L ₃ , that is, when seated. The positional relationship between the needle valve 83 and the nozzle tip 83 is regulated so that the needle valve 83 is guided to the ball 90 only after being lifted by a predetermined value L ₃ .

Next, the operation will be described based on such a configuration.

When fuel pressure is applied to the needle valve 83,
The needle valve 83 starts to lift in the valve opening direction, and when the lift amount exceeds a predetermined value L ₃ , the guided portion 9 that has been in the loose fitting state.
2 obtains the guiding action by the ball 90. This guiding action is intended to regulate that eccentric needle valve tip 83 'to reach the pre-lift amount L _1, fuel injection timing at the time of initial injection, fuel injection quantity and spray the fuel injection holes to jet form of Each can be controlled accurately.

The fuel pressure decreases and the needle valve lift amount reaches the predetermined value L.
Below ₃ , the guided portion 92 moves the ball 90 on the valve body side.
Is released from the guiding action by the valve portion 93, and the valve portion 93 can obtain a self-centering action by being pressed against the seat portion 84 having a substantially conical shape, that is, the valve portion 93 bouncing with respect to the seat portion 84. However, he can converge to an appropriate position himself.

In the present embodiment, the positioning of the rolling element fitting groove 89 can be easily and accurately controlled as the distance H from the valve body, that is, the base end (not shown) of the nozzle tip 81. That is, it is possible to obtain the predetermined value L ₃ between the boundary line A and the center line B of the rolling element fitting groove 89 with high precision while facilitating the workability.

Further, although the guide mechanism in each of the above-mentioned embodiments is the sliding guide by the surface contact, in the present embodiment, since the rolling guide is by the point contact, the friction can be largely reduced and the valve closing can be performed. The decrease in speed can be prevented more effectively. That is, the sharpness of fuel at the end of injection is further improved.

Further, in each of the above-described embodiments, the notched groove is formed in the guided portion so that the fuel is guided to the fuel injection hole, but in the present embodiment, the fuel is not supplied. Since it can pass between the balls 90, it is not necessary to form a notch groove, and there is an advantage that the number of manufacturing steps is further reduced.

Although the ball 90 is used as the rolling element in the present embodiment, the rolling element is not limited to this, and it may be rolled and guided by a cylindrical roller, for example.

In each of the embodiments described above, the two-stage valve-opening pressure fuel injection valve to which the guide mechanism is most effectively applied has been described, but the present invention is not limited to this, and only one closing means is provided. It is also possible to apply to a fuel injection valve that does not have it.

[0081]

As described above, according to the first aspect of the invention, the needle valve tip portion is eccentric because the needle valve tip portion is provided with the guide mechanism for restricting the eccentricity with respect to the valve body. Since the fuel is held without being held, it is possible to control the fuel injection timing, the fuel injection amount, and the spraying form of the spray from the fuel injection holes to be uniform for each fuel injection hole.

At the end of fuel injection, if the needle valve moves in the valve closing direction and its lift amount falls below a predetermined value, the needle valve is released from the constraint of the guide mechanism, so that the valve closing speed decreases. The seat can be quickly seated on the valve body side without inviting. On the other hand, at this time, since the tip of the needle valve is relatively free, the needle valve can obtain a self-centering action by being pressed against the substantially conical seat portion, and ensure a proper seating position. Sit down. As a result, the shortage of the injected fuel at the end of the fuel injection is improved, and the fuel dripping can be prevented.

Further, in the second invention, since the loose fitting portion and the guide portion are formed as guide members separately from the valve body, it is possible to obtain a predetermined value with high accuracy while facilitating workability. Yes, that is, the needle valve tip is held more accurately without eccentricity, so the fuel injection timing from the fuel injection hole, the fuel injection amount, and the spraying form of the spray are controlled to be uniform for each fuel injection hole. can do.

Further, in the third aspect of the invention, since the positioning of the rolling element fitting groove can be obtained relatively easily and with high accuracy as the distance from the base end of the valve body, the prescribed amount of regulation can be relatively defined. It can be done easily and manufacturability is easy. At the same time, since the needle valve guide action is performed by point or line contact, it is possible to effectively prevent the valve closing speed from decreasing due to friction reduction, improve the fuel cutoff at the end of injection, and prevent fuel dripping. it can.

Further, in the fourth aspect of the present invention, at the initial stage of injection in which the needle valve lift amount is suppressed to a relatively small predetermined lift amount, the spray form from the fuel injection holes is controlled to be uniform for each fuel injection hole. It is possible to eliminate the significant deterioration of smoke caused by the slight eccentricity of the needle valve. Further, the urging force in the valve closing direction with respect to the needle valve at the end of fuel injection becomes relatively small, but at this time, the needle valve is released from the constraint by the guide mechanism, which causes a decrease in the valve closing speed. Instead, the seat can be quickly seated on the valve main body side, fuel shortage can be improved, and fuel dripping can be prevented.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing a front end side of a fuel injection valve according to a first embodiment.

2 is a partially enlarged sectional view of FIG.

FIG. 3 is a partial cross-sectional view showing the overall configuration of the fuel injection valve according to the first embodiment.

FIG. 4 is a diagram showing a needle valve lift amount with respect to time.

FIG. 5 is a diagram showing an injection rate with respect to time.

FIG. 6 is a partial cross-sectional view showing a front end side of a fuel injection valve according to a second embodiment.

FIG. 7 is a partial cross-sectional view showing a front end side of a fuel injection valve according to a third embodiment.

FIG. 8 is a sectional view of a conventional two-stage valve opening pressure fuel injection valve.

FIG. 9 is a sectional view of a fuel injection valve having a conventional guide mechanism.

[Explanation of symbols]

1 Fuel Injection Valve 2 Valve Body 8 Needle Valve 8'Needle Valve Tip 16 First Coil Spring (First Closing Means) 17 Second Coil Spring (Second Closing Means) 28 Guide Part (Guide Mechanism) 29 Free Fitting Part (guide mechanism) 31 Seat part 33 Fuel injection hole 34 Guided part (guide mechanism) 35 'Maximum diameter part 35 Valve part 51 Nozzle tip (valve body) 52 Fuel injection hole 53 Needle valve 53' Needle valve tip part 54 Seat Part 58 Guide member 61 Guide part (guide mechanism) 62 Free fitting part (guide mechanism) 64 Guided part (guide mechanism) 64 'Maximum diameter part 65 Valve part 81 Nozzle tip (valve body) 82 Fuel injection hole 83 Needle valve 83 'needle valve tip 84 seat portion 87a loosely fitting portion 89 rolling member fitting groove 90 ball (rolling elements) 92 guided portion 92' maximum diameter 93 valve unit L ₁ a predetermined lift amount L ₃ Value

Claims (4)

[Claims] 1. A valve main body, a needle valve, and a guide mechanism, wherein the valve main body has a fuel injection hole and a substantially cone-shaped seat portion at its tip end side. A valve is housed movably in the axial direction of the needle valve, and the needle valve has a valve portion at the tip thereof, and the valve portion is seated on and away from the seat portion to open and close the fuel injection hole. The guide mechanism includes a guide portion and a loose fitting portion formed on the valve body side, and a guided portion formed on the needle valve side, and the loose fitting portion is a needle valve lift amount. When the needle valve lift amount exceeds a predetermined value, the guide portion guides the guided portion only when the needle valve lift amount exceeds a predetermined value. A fuel injection valve characterized in that it regulates eccentricity. 2. The guide mechanism includes a guided portion formed at a maximum diameter portion on the tip side of the needle valve,
A guide portion disposed on the valve body side and a loose fitting portion disposed on the valve body side and located between the guide portion and the seat portion, wherein the loose fitting portion is a needle. When the valve lift amount is less than or equal to a predetermined value, the guided portion is loosely fitted, and the guide portion slides and guides the guided portion only when the needle valve lift amount exceeds a predetermined value. The fuel injection valve according to claim 1, wherein the loose fitting portion and the guide portion are configured as guide members separately from the valve body. 3. The guide mechanism includes a guided portion formed in a maximum diameter portion on the distal end side of the needle valve,
A guide portion disposed on the valve body side and a loose fitting portion disposed on the valve body side and located between the guide portion and the seat portion, wherein the loose fitting portion is a needle. When the valve lift amount is less than or equal to a predetermined value, the guided portion is loosely fitted, and the guide portion is disposed in the rolling element fitting groove formed in the valve body and the rolling element fitting groove. 2. A plurality of rolling elements according to claim 1, wherein the plurality of rolling elements roll and guide the guided portion only when the needle valve lift amount exceeds a predetermined value. The fuel injection valve described. 4. The fuel injection valve has a first closing means and a second closing means that act on the needle valve, and the first closing means shuts off the fuel injection hole. Always act in the direction, and the second closing means acts only when the needle valve lift amount becomes equal to or more than a predetermined lift amount in the direction of blocking the fuel injection hole. The fuel injection valve according to claim 1, 2 or 3, wherein the amount is set to be larger than the predetermined value.