JPH10122083A - Fuel injection valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection valve capable of controlling its injection quantity according to the internal pressure of an associated cylinder with its simple structure. SOLUTION: A fuel injection valve comprises a nozzle body 27 which is movable in the lift direction of a needle valve 15 upon receiving pressure in an associated combustion cylinder, a first regulation member 31 for regulating the nozzle body at the upper portion thereof in the lift direction, and a second regulation member 37 for regulating the nozzle body at the lower portion thereof in the lift direction. The fuel injection valve thus constituted injects fuel of a quantity corresponding to the combustion state according to the internal pressure of the combustion cylinder at its first injection position where a smaller quantity of fuel is injected or second injection position where a larger quantity of fuel is injected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel injection valve for directly injecting high-pressure fuel into a combustion cylinder of an engine, and more particularly to a fuel injection valve for injecting fuel by lifting a needle valve by exciting an electromagnetic coil. .

[0002]

2. Description of the Related Art There is known a so-called direct injection gasoline engine in which high-pressure gasoline fuel is directly injected from an injector into a cylinder (combustion cylinder) of an engine.

In such a direct injection gasoline engine,
During low-load operation, stratified combustion is known in which a rich air-fuel mixture is unevenly distributed in the vicinity of an ignition plug, and the air-fuel mixture is generally diluted while maintaining good ignitability. According to such stratified combustion, misfire and a decrease in thermal efficiency can be prevented. In such stratified combustion, it is desirable to reduce the amount of fuel injected from the fuel injection valve in order to unevenly distribute a rich mixture above the combustion cylinder. This stratified combustion injects fuel during the compression process in the cylinder, and injects the fuel when the internal pressure in the cylinder is high.

On the other hand, it is known that during high-load operation, homogeneous combustion is performed in which the injected fuel is uniformly diffused in the cylinder and ignited. In such homogeneous combustion, a lean mixture is uniformly dispersed in the cylinder, and it is desirable to increase the amount of fuel injected from the fuel injection valve. In the homogeneous combustion, fuel is injected during a suction process in a cylinder of a gasoline engine, and the fuel is injected when the internal pressure in the cylinder of the gasoline engine is low.

[0005] The stratified combustion and the homogeneous combustion as described above,
It is adjusted by the fuel injection timing, but in the case of stratified combustion, it is necessary to reduce the amount of fuel injected under high cylinder pressure, and in the case of homogeneous combustion, it is necessary to increase the amount of fuel injected under low cylinder pressure. is there.

The control of the injection amount is disclosed in Japanese Patent Laid-Open No. 5-248.
Conventionally, as disclosed in Japanese Patent No. 277, the control is performed only by the electronic control unit, and the control is not performed in relation to the internal pressure in the cylinder. Therefore, there is a problem that control becomes complicated and responsiveness is poor.

On the other hand, Japanese Patent Application Laid-Open No. Sho 62-150071
In the publication, a nozzle cylinder having an injection hole has a pressure receiving surface for receiving the internal pressure of the fuel cylinder. When the internal pressure of the fuel cylinder is lower than a predetermined pressure, the nozzle cylinder is moved by the internal pressure of the fuel cylinder, There is disclosed a configuration in which the supply hole is closed to inhibit injection.

[0008]

However, the technique disclosed in this publication controls the injection by the internal pressure in the engine cylinder, but in the case of low pressure, the injection is prohibited. Cannot be adjusted.

Therefore, an object of the present invention is to provide a simple configuration,
An object of the present invention is to provide a fuel injection valve capable of adjusting an injection amount according to an internal pressure in a cylinder.

[0010]

According to one aspect of the present invention, a needle valve is lifted from a nozzle body by exciting an electromagnetic coil provided in a housing to form the needle valve on the nozzle body. In a fuel injection valve for injecting fuel into a combustion cylinder from a selected injection hole, the nozzle body is provided movably in a lift direction of the needle valve by receiving pressure in the combustion cylinder, and is provided in a lift direction of the nozzle body. A first regulating member that regulates the upper side; and a second regulating member that regulates the lower side of the nozzle body in the lift direction. When the internal pressure in the combustion cylinder is higher than a predetermined value, the first regulating member is positioned by the first regulating member. The fuel is injected from the first injection position, and when the internal pressure in the combustion cylinder is equal to or less than a predetermined value, the fuel is injected from the second injection position located by the second regulating member. That.

According to the first aspect of the invention, when the internal pressure in the combustion cylinder is higher than a predetermined value, the nozzle body receives the pressure in the combustion cylinder and moves upward in the lift direction of the needle valve. However, when the nozzle body moves by a predetermined amount, it is regulated by the first regulating member, and the nozzle body is located at the first ejection position.
Since the first injection position is located above the lift direction of the needle valve, the lift amount of the needle valve relative to the injection hole formed in the nozzle body is reduced.
Therefore, at the first injection position, the amount of fuel injected from the injection hole is small. On the other hand, when the internal pressure in the combustion cylinder is lower than the predetermined value, the nozzle body moves downward in the lift direction of the needle valve, but is regulated by the second regulating member to be located at the second injection position. Since the second injection position is located below the lift direction of the needle valve, the lift amount of the needle valve relative to the injection hole formed in the nozzle body increases. Therefore, at the second injection position, the injection amount of the fuel injected from the injection hole is larger than the injection amount at the first injection position.

Therefore, when the internal pressure of the engine combustion cylinder is high, the injection amount of fuel can be reduced, and when the internal pressure is low, the injection amount can be increased. Since such position regulation can be performed only by the first regulation member and the second regulation member, the configuration is simple. Further, since the injection amount is controlled in response to a change in the internal pressure in the combustion cylinder, the responsiveness is excellent.

According to a second aspect of the present invention, in the first aspect of the present invention, the nozzle body has a pressure receiving surface for receiving the pressure of the fuel to be supplied, and a back pressure surface for receiving the in-cylinder pressure in the combustion cylinder. Wherein the housing includes first urging means for urging the nozzle body upward in the lift direction, and second urging means for urging the needle valve downward in the lift direction. The nozzle body is provided so as to be liftable in a range of a gap formed between the nozzle body and the nozzle body, and the resultant force of the urging force of the first urging means and the pressure received on the back pressure surface is equal to the second urging means. The nozzle body moves upward in the lift direction when the resultant pressure is greater than the resultant force of the pressure received by the pressure receiving surface.

According to the second aspect of the present invention, the downward moving force of the nozzle body is a resultant force (first resultant force) of the pressure receiving surface and the urging force of the first urging means, and Is a resultant force of the back pressure surface and the biasing force of the second biasing member (second resultant force). When the first resultant force is larger than the second resultant force, the nozzle body moves upward. Therefore, it is located at the first injection position. Therefore, the area of the pressure receiving surface,
By adjusting the area of the back pressure surface, the urging force of the first urging means or the urging force of the second urging means, it is possible to easily adjust the internal pressure in the combustion cylinder when switching the injection amount.

In this case, it is desirable to use a spring for the first urging means or the second urging means and adjust the urging force of the spring.

[0016]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. A fuel injection valve 1 according to an embodiment of the present invention injects gasoline directly into a combustion chamber (cylinder) of a gasoline engine, and is used for a so-called direct injection gasoline engine.

That is, as shown in FIG. 3, a fuel injection valve 1 according to the present invention is arranged in a cylinder 3 of a gasoline engine, and injects fuel K into a combustion chamber 5. Although the injection timing of the fuel from the fuel injection valve 1 will be described later, it differs between a low-load operation (during low-speed rotation) and a high-load (during high-speed rotation). To be injected. In FIG. 3, reference numeral 9 denotes an ignition plug.

First, the overall configuration of the fuel injection valve 1 will be described with reference to FIG. 1. FIG. 1 schematically shows the fuel injection valve 1 for general description. Are omitted or simplified for simplicity.

The fuel injection valve 1 includes a fuel supply pipe 13 and an electromagnetic coil 17 that lifts the needle valve 15 by excitation in a main body 11 thereof.
The excitation and demagnetization 7 is controlled by a control device (not shown) connected via a connector 19.

A spring seat 21 is fitted in the fuel supply pipe 13.
The upper end of the first spring 25 is held at the lower end of the first spring. The lower end of the first spring contacts the armature 23 and urges the armature 23 downward. The armature 23 is in contact with the lower end of the fuel supply pipe 13 and its upward movement is restricted. This armature 2
An upper end of the needle valve 15 is integrally fixed to a lower portion of the needle 3, and the needle valve 15 is integrally lifted when the armature 23 is lifted upward.

A housing 29 for holding the nozzle body 27 is provided at a lower portion of the main body 11, and a space for moving the above-described armature 23 is formed in the housing 29. The stopper (first regulating member) 31 restricts the movement.

FIG. 2 is an enlarged view of the structure inside the housing 29, which is a feature of the present invention. A holding hole 3 for slidably holding the nozzle body 27 is provided at a lower end portion of the housing 29.
The upper end 27 a of the nozzle body 27 is housed in the holding hole 33 in a liquid-tight state by an O-ring 35. The upper end surface of the nozzle body 27 faces the fuel supply passage 36, and has a pressure receiving surface 27b that receives the pressure of the supplied fuel. The upper end portion 27a of the nozzle body is provided at the peripheral edge thereof so as to be able to contact the lower end surface of the upper stopper 31, and the upward movement of the nozzle body 27 is restricted.

At the lower end of the housing 29, a lower stopper (a second stopper) for regulating the downward movement of the nozzle body 27 is provided.
A restricting member 37 protrudes toward the upper end 27 a of the nozzle body 27. The lower stopper 37 comes into contact with a locking surface 27c formed on the upper end portion 27a of the nozzle body, and a gap having a dimension L is formed between the end surface of the lower stopper 37 and the locking surface 27c. Is formed. This dimension L is a dimension in a state where the upper end portion 27a of the nozzle body 27 is in contact with the lower stopper 37.
Is the range that can be lifted.

In the housing 29, a recess 41 is provided adjacent to the lower stopper 37 for accommodating the second spring 39.
The lower end of the second spring 39 is held in the concave portion 41, and the upper end of the second spring 39 contacts the locking surface 27c of the nozzle body to urge the nozzle body 27 upward. .

In the nozzle body 27, a fuel passage 43 communicating with the fuel passage 36 is formed.
The needle valve 15 extends into the inside 3. An injection hole 45 is formed at the lower end of the nozzle body 27, and the tip of the nozzle body 27 is seated on a valve seat 47 formed around the injection hole 45 so as to close the injection hole 45. .

A back pressure surface 27e is formed on the lower end surface of the nozzle body 27. The back pressure surface 27e is exposed in the cylinder of the engine and receives the pressure in the engine cylinder.

Next, the fuel injection valve 1 according to the present embodiment
The operation of will be described. During fuel injection, the electromagnetic coil 17 is excited and the armature 23 is lifted upward. As a result, the needle valve 15 is lifted upward, and high-pressure fuel in the fuel passage 43 is injected from the injection hole 45 of the nozzle body 27.

When the electromagnetic coil 17 is demagnetized, the nozzle body 27 is moved downward together with the armature 23 according to the urging force of the first spring 25, seated on the valve seat 47, closing the injection hole 45, and injecting fuel. To stop.

Here, the injection timings during the high load operation and the low load operation will be described with reference to FIG. When the engine has four cycles, the intake process, compression process, expansion process,
FIG. 4 shows the relationship between the crank angle and the in-cylinder pressure in that case.

During the suction step, the piston (see FIG. 3) 7
Is in a descending process, the in-cylinder pressure becomes 0, and during the compression process, the piston 7 is in an ascending process, and the in-cylinder pressure gradually increases. Thereafter, when the piston 7 reaches the top dead center and the in-cylinder pressure increases to a maximum, the fuel is ignited to perform an expansion and exhaust process.

During high load operation, in the suction step where the in-cylinder pressure is low, fuel is injected from the fuel injection valve 1 to perform homogeneous combustion, but the in-cylinder pressure during fuel injection is low and almost zero.

On the other hand, during low load operation, fuel is injected from the fuel injection valve 1 to perform stratified combustion during the compression step in which the in-cylinder pressure increases, but the in-cylinder pressure during fuel injection is increased to a high pressure. I have.

In the low load operation, that is, during stratified combustion, fuel is injected from the fuel injection valve 1 as described above. In this case, since the in-cylinder pressure is high, the nozzle body 27 The back pressure surface 27e rises by receiving the in-cylinder pressure, and the pressure receiving surface 27b is located at the first injection position where the pressure receiving surface 27b contacts the upper stopper 31 as shown in FIG.

The relationship between the pressure acting on the nozzle body 27 during the low load operation is as follows: the pressure acting on the pressure receiving surface 27b is Ff, the urging force (spring constant) of the first spring 25 is Fsh, and the pressure acting on the back pressure surface 27c is Assuming that the pressure to be applied is Fc and the urging force FsB of the second spring 39, the following force relationship is obtained.

(Fsh + Ff) <(FsB + Fc) That is, the first resultant force (F) for urging the nozzle body 27 downward.
Since the second resultant force (FsB + Fc) for urging the nozzle body 27 upward is larger than sh + Ff), the nozzle body 27 moves upward and contacts the upper stopper 31.
It is located at the injection position.

In the first injection position, the nozzle body 27
Is lifted upward, the relative movement distance of the needle valve 15 lifted by the excitation of the electromagnetic coil with respect to the injection hole 45 is reduced, and the discharge amount discharged from the injection hole 45 is reduced. Therefore, during the stratified operation, the fuel injection amount can be reduced, so that the atomization at the time of stratified combustion can be reduced.

On the other hand, in the case of high load operation, that is, during homogeneous combustion, the in-cylinder pressure is almost 0, and the nozzle body 27
Receives the pressure Ff acting on the pressure receiving surface 27b and the urging force (spring constant) Fsh of the first spring 25, and descends against the urging force FsB of the second spring 39, so that the locking surface 27c is moved downward by the lower stopper. 37, and is located at the second injection position.

The relationship between the forces acting on the nozzle body 27 in this case is as follows.

(Fsh + Ff)> (FsB + Fc) That is, the first resultant force (F) for urging the nozzle body 27 downward.
sh + Ff) is larger than the second resultant force (FsB + Fc) that urges the nozzle body 27 upward, so that the nozzle body 27 moves downward and comes into contact with the lower stopper 35.
It is located at the injection position. The in-cylinder pressure Fc is 0 in this case.

In the second injection position, the nozzle body 27
Is lower, the relative movement distance of the needle valve 15 lifted by the excitation of the electromagnetic coil with respect to the injection hole 45 increases, and the discharge amount discharged from the injection hole 45 increases. Therefore, the fuel injection amount can be increased during the homogeneous combustion operation.

From the above equation, the second spring 39
, That is, the spring constant can be determined. In this case, it is desirable that the spring constant of the second spring 39 be set so as to satisfy the following relationship.

(FsB + Fc)> (Fsh + Ff)> (F
sB) In the present embodiment, the allowable range (dynamic range) of the injection amount is increased, the combustion injection amount is small during stratified combustion of the engine, and the injected fuel can be increased during homogeneous combustion.
The spray condition of the fuel is good, the combustion is stable, and the exhaust characteristics of the engine are also excellent. Note that the allowable range of the injection amount can be determined by the dimension L of the gap between the end surface of the lower stopper 37 and the locking surface 27c.

In addition, since the injection amount is changed in accordance with the in-cylinder pressure, the responsiveness of the fuel injection valve 1 is good, and since the configuration includes the regulating member and the second spring, the configuration is simple. .

By adjusting the area of the pressure receiving surface 27b, the area of the back pressure surface 27e, the spring constant of the first spring 25 or the spring constant of the second spring 39,
Adjustment with the internal pressure for switching the injection amount can be easily performed.

The present invention is not limited to the above-described embodiment, but can be variously modified without departing from the gist of the present invention. For example, adjustment with the internal pressure for switching the injection amount
The present invention is not limited to setting the spring constant of the spring 39, and may be one of setting the area of the pressure receiving surface 27b, the area of the back pressure surface 27e, and the spring constant of the first spring 25.

[0046]

According to the first aspect of the present invention, the nozzle body is provided so as to be movable in the lift direction of the needle valve by receiving the pressure in the combustion cylinder, and regulates the upper part of the nozzle body in the lift direction. Since it is configured to include the restricting member and the second restricting member that restricts the lower part of the nozzle body in the lift direction, the first fuel injection amount is small according to the internal pressure in the combustion cylinder.
An amount of fuel can be injected according to the combustion state between the injection position and the second injection position having a large injection amount, and the responsiveness is excellent and the configuration is simple.

According to the second aspect of the present invention, the nozzle body has a pressure receiving surface for receiving the pressure in the engine cylinder, a back pressure surface for receiving the in-cylinder pressure in the combustion cylinder, and a nozzle body that is located upward in the lift direction. Since the first urging means for urging the needle valve and the second urging means for urging the needle valve downward in the lift direction are provided, the invention according to claim 1 can be realized with a concretely simple structure. . Further, by adjusting the area of the pressure receiving surface, the area of the back pressure surface, or the urging force of the first urging means or the urging force of the second urging means, it is easy to adjust the internal pressure for switching the injection amount. Can be.

[0048]

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic configuration of a fuel injection valve according to the present invention.

FIG. 2 is a sectional view showing a characteristic portion of the fuel injection valve shown in FIG. 1;

FIG. 3 is a sectional view showing a use state of the fuel injection valve according to the present invention.

FIG. 4 is a graph showing a relationship between fuel injection timing and in-cylinder pressure.

[Explanation of symbols]

 Reference Signs List 1 fuel injection valve 15 needle valve 25 first spring (first biasing means) 27 nozzle body 27b pressure receiving surface 27c locking surface 27e back pressure surface 31 upper stopper (first regulating member) 37 lower stopper (second regulating member) 39 second spring (second biasing means)

Claims (2)

[Claims] 1. A fuel injection valve which lifts a needle valve from a nozzle body by exciting an electromagnetic coil provided in a housing and injects fuel into a combustion cylinder from an injection hole formed in the nozzle body. A first regulating member that is movable in the lift direction of the needle valve upon receiving the pressure in the combustion cylinder, and that regulates the upper part of the nozzle body in the lift direction; A regulating member, wherein when the internal pressure in the combustion cylinder is higher than a predetermined value, fuel is injected from a first injection position located by the first regulating member, and the internal pressure in the combustion cylinder is equal to or less than a predetermined value. In some cases, fuel is injected from a second injection position located by the second regulating member. 2. The nozzle body includes a pressure receiving surface that receives a pressure of fuel to be supplied and a back pressure surface that receives an in-cylinder pressure in a combustion cylinder, and the housing urges the nozzle body upward in a lift direction. A first urging means, and a second urging means for urging the needle valve downward in the lift direction, wherein the nozzle body is located within a gap formed between the second regulating member and the nozzle body. The nozzle body is provided so as to be liftable, and when the resultant force of the urging force of the first urging means and the pressure received on the back pressure surface is larger than the resultant force of the pressure received on the second urging means and the pressure receiving surface. The fuel injection valve according to claim 1, wherein the valve moves upward in the lift direction.