JP2002266722A - Fuel injection valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form suitable spray by adding a turning component using a turning element, and to accurately control the amount of spraying by variably controlling the lift amount of a needle valve. SOLUTION: The turning element 3 provided with a fuel passage 22 extending in the tangential direction of the needle valve 1 is arranged on the outer periphery of the needle valve 1, and an outlet opening portion 22a is faced to the outer peripheral surface 1a of the needle valve 1. When the valve is closed, the outlet opening portion 22a is wholly covered by the outer peripheral surface 1a of the needle valve 1 (A). When the needle valve 1 lifts to open a nozzle hole 12, fuel is made to flow through the fuel passage 22 and injected with the turning component from the nozzle hole 12. In the case of full lift, the outlet opening portion 22a is wholly opened like as (C), and on the other hand, when the lift amount is restricted at low lift, the outlet opening portion 22a is partially covered by the outer peripheral surface 1a, and a substantial area of the passage is narrowed, so that a reduction in flow speed is prevented and the turning component is added with sufficiently strength.

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 suitable for, for example, an in-cylinder direct injection type four-cycle spark ignition internal combustion engine. The present invention relates to an improvement of a fuel injection valve which imparts a swirl component to a flowing fuel flow.

[0002]

2. Description of the Related Art As one type of fuel injection valve of an internal combustion engine, a so-called fuel injection valve, which generates a swirling flow in an injection hole to increase a spray angle and promote atomization of injected fuel, is called a so-called fuel injection valve. Swirl injectors are conventionally known.

A typical method for generating this swirling flow is to arrange a swirling element (so-called swirler) on the outer periphery of a needle valve on the upstream side of the injection hole. On the other hand, a plurality of fuel passages directed in an eccentric direction are formed, for example, in a groove shape, and a fuel flows from these fuel passages from a substantially tangential direction of the injection hole to impart a swirl component. I have.

On the other hand, in order to more precisely control the fuel injection amount of the electromagnetic fuel injection valve over a wide range from a small flow rate to a large flow rate, the needle valve lift amount at the time of fuel injection is controlled in a plurality of steps or continuously. A technique for performing variable control has been proposed in, for example, Japanese Patent Application Laid-Open No. 5-321786. The fuel injection valve described in this publication also has a swirl injection valve that includes a swirl element on the outer periphery of the needle valve and imparts a swirl component to the spray.

[0005]

When the technique of variably controlling the lift amount of the needle valve is applied to the swirl injection valve using the swirl element as described above, compared with the high lift control in which the lift amount is large, The swirling flow strength in the injection hole at the time of low lift control with a small lift is significantly reduced, and as a result, a problem arises in that a desired spray angle and atomization of fuel cannot be achieved during low lift control. Hereinafter, this is shown in FIGS.
This will be described in more detail with reference to FIG.

FIG. 2 shows a flow characteristic of a general electromagnetic swirl injection valve when the injection pulse time is changed. In a swirl injection valve that forms a spray by imparting a swirl component to a fuel flow in an injection hole, a cavity is formed in the injection hole by swirling of fuel, and the actual opening area of the injection hole portion is reduced. As a result, the flow rate is reduced at the injection hole portion, and the change in the flow rate due to the change in the lift amount becomes small at a certain lift amount or more. That is, as shown in FIG. 2, the lift amount is set to three of A (small), B (medium), and C (large).
When the lift amount is changed in stages, the lift amount is changed from B (medium) to C
Even if it increases to (large), the amount of change in the flow rate is small. On the other hand, when the lift amount is reduced from B (medium) to A (small), the flow rate change amount is large. This is because when the lift is small, the passage area between the needle valve and the valve seat surface becomes small, and this restricts the flow rate. That is, when the flow rate is to be largely changed by the lift amount, it is necessary to set the passage area between the needle valve and the valve seat surface to be sufficiently smaller than the actual opening area in the injection hole portion. In addition, by setting the low lift amount, the minimum injection pulse width can be shortened.

On the other hand, when the lift amount is reduced, the spray angle decreases as shown in FIG. The lift amounts A, B, and C in the figure correspond to the lift amounts in FIG. As described above, at the time of low lift, the passage area between the needle valve and the valve seat surface becomes small and a throttle is formed, so that the pressure upstream of the position of the throttle becomes higher. Therefore, the pressure difference between the front and rear of the groove-shaped fuel passage in the swirling element arranged on the upstream side is reduced, and the flow velocity of the fuel flowing through the fuel passage is reduced. Becomes smaller. That is, for example, if the lift amount is changed between A and B in the figure, the spray angle will change greatly. For the same reason, when the passage area of the fuel passage of the swirling element is changed under the condition that the lift amount is constant, the spray angle changes as shown in FIG.

As described above, when making the lift amount variable for controlling the injection amount, ensuring a large change amount of the flow rate and forming a good spray are in a trade-off relationship, and both are compatible. It was difficult.

[0009]

According to a first aspect of the present invention, there is provided a swirl element having a fuel passage formed in an eccentric direction with respect to an injection hole, which is disposed on an outer periphery of a needle valve. A fuel injection valve configured to impart a swirl component to the fuel flow in the injection hole; a lift amount control means for changing a lift amount of the needle valve; and a lift amount control means for changing the lift amount of the needle valve. Passage area control means for changing the passage area of the fuel passage of the swirl element, wherein the total passage area of the fuel passage in the swirl element is relative to the passage area between the lifted needle valve and the valve seat surface. It is characterized in that it is always configured to be substantially equal or less.

As shown in FIG. 4, when the lift amount is constant and the passage area of the fuel passage of the swirl element is increased,
As a result of the decrease in the flow velocity of the fuel, the spray angle becomes small. Conversely, if the passage area is reduced, the flow velocity of the fuel becomes high and the spray angle becomes large.

FIG. 5 shows the relationship between the passage area of the fuel passage in the swivel element (total passage area when there are a plurality of fuel passages) and the lift amount (corresponding to the passage area between the needle valve and the valve seat surface). The change of a spray angle is shown. Note that the straight line M in FIG.
Indicates a line in which the total passage area of the fuel passage of the swirl element and the passage area between the needle valve and the valve seat surface are equal to each other. As shown in this figure, as the lift amount increases with respect to the fuel passage area of a certain swirl element, the spray angle also increases, but the passage area between the needle valve and the valve seat surface is swirled. When the fuel passage area becomes substantially equal to the element, the spray angle becomes substantially constant even if the lift amount is further increased. This is because, when the passage area between the needle valve and the valve seat surface becomes large with respect to the fuel passage area of the swirl element, the influence of the above-mentioned passage between the needle valve and the valve seat surface being restricted is almost restricted. It is because it disappears. The smaller the fuel passage area of the swirling element, the larger the spray angle.
Therefore, when the lift amount is reduced by the lift amount control means, the flow area in the fuel passage is sufficiently reduced by reducing the fuel passage area of the swirling element by the passage area control means. It can be maintained at a high level, and a decrease in the spray angle can be avoided. In particular, the total passage area of the fuel passage of the swivel element is kept below the passage area between the needle valve corresponding to the lift amount and the valve seat surface, and near the straight line M in FIG. However, the flow rate and the spray angle can be favorably controlled with a smaller lift amount, which is effective.

In a second aspect of the present invention, the passage area control means is arranged such that the outlet opening of the fuel passage faces the outer peripheral surface of the needle valve, and the lift of the needle valve The outlet opening is partially covered with the outer peripheral surface in accordance with the amount, so that the passage area of the fuel passage is changed.

In this configuration, when the valve is closed, the outlet opening of the fuel passage of the swirl element is substantially closed by the outer peripheral surface of the needle valve. Then, when the needle valve is lifted, the outlet opening is opened to the small diameter portion or the concave portion on the needle valve tip side,
Although the fuel flows, the outlet opening is partially covered according to the lift amount of the needle valve, and a substantial passage area of the fuel passage is obtained according to the lift amount.

A third aspect of the present invention is a further reduced version of the second aspect.
In the invention, the outlet opening is formed such that the width dimension in the direction orthogonal to the central axis of the needle valve gradually increases along the lift direction of the needle valve. As described above, when the lift amount is small, the outlet opening is largely covered by the outer peripheral surface of the needle valve, and when the lift amount is large,
Although the area to be covered is small, as described above, if the width dimension is made larger as the lift increases, the change in the opening area with respect to the change in the lift amount increases.

Further, in the invention according to claim 4, the lift amount control means is configured to be slidable in parallel with the needle valve and to be positioned in contact with the nozzle body. A first spring for urging the stopper toward the nozzle body, a second spring for urging the needle valve in a normally closed direction, and the needle valve so as to face the first stopper via a predetermined gap. And a second stopper that abuts a part of the needle valve to regulate a full lift amount, and is configured to change the lift amount in two stages of height. That is, when the needle valve lifts, it first comes into contact with the first stopper, and if the force in the lift direction of the needle valve is relatively small, the lift amount is regulated by the first stopper to a low lift. If the force in the lift direction of the needle valve exceeds the valve closing force including the spring force of the first and second springs, the needle valve further lifts together with the first stopper. Reach.

A fifth aspect of the present invention embodies the invention of the fourth aspect.
In the invention according to the first aspect, a low lift defined by the first stopper is controlled by controlling a current to the coil for attracting the needle valve;
The high lift defined by the second stopper is switched.

[0017]

According to the present invention, in the fuel injection valve in which the swirl element is used to increase the spray angle and atomize the spray, the needle valve lift amount can be variably controlled for highly accurate control of the injection amount. It is possible to avoid a decrease in the spray angle at the time of a low lift and an increase in atomization, which are problems when applying the method. That is, it is possible to achieve both the formation of an appropriate spray by giving the swirl component and the highly accurate control of the injection amount by the variable control of the needle valve lift amount.

In particular, according to the second aspect of the present invention, the needle passage itself can be used to mechanically variably control the fuel passage area of the swirl element. It is possible to avoid a decrease in flow strength.

Further, according to the third aspect of the invention, the change in the opening area with respect to the change in the lift amount becomes large, so that the passage area can be made sufficiently small at the time of a low lift to give a strong turning component.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows an electromagnetic fuel injection valve for a direct injection type internal combustion engine according to the present invention. As shown in the drawing, the needle valve 1 is slidably disposed in the nozzle body 2, and has a tip portion having an injection hole 12 at the center of the tip of the nozzle body 2.
Is opened and closed. A swivel element 3, which will be described later, is attached to a distal end portion of the nozzle body 2 so as to surround the outer periphery of the needle valve 1. A cup-shaped first stopper 4 is slidably disposed on the base end side of the nozzle body 2. The first stopper 4 is slidably fitted to the nozzle body 2 and is pressed against the flange 2 a of the nozzle body 2 by the first spring 5. Needle valve 1
Is urged in the closing direction by the spring force of the second spring 6, and a large-diameter receiving portion 13 is formed at an intermediate portion, and between the receiving portion 13 and the first stopper 4. Is provided with a first gap Δ1 corresponding to the lift amount at the time of low lift.

The nozzle body 2 includes a nozzle nut 11
The fuel nozzle 14 is fixed to a nozzle holder 9 made of a magnetic material, a fuel inlet 14 is formed at an end of the nozzle holder 9, and a coil 10 is provided inside the nozzle holder 9.
Is arranged. An armature 7 made of a magnetic material is fixed to a base end of the needle valve 1 penetrating the first stopper 4 so as to receive a magnetic force of the coil 10. The end surface of the armature 7 faces a second stopper 8 formed on the nozzle holder 9, and a second gap Δ2 corresponding to the full lift of the needle valve 1 is provided between the two.

Accordingly, when the magnetic force generated by the coil 10 is sufficiently large, the needle valve 1 is lifted together with the first stopper 4 even after contacting the first stopper 4 to reach a full lift. However, when the magnetic force generated by the coil 10 is relatively small, the lift of the needle valve 1 is regulated by the first stopper 4, and the needle valve 1 enters a low lift state determined by the first gap Δ1.

As shown in FIGS. 7 to 9, the swivel element 3 has a cylindrical shape closely fitted to the inner peripheral surface of the nozzle body 2, and the inner peripheral surface is the outer peripheral surface 1a of the needle valve 1. Close together with a very small gap. An axially extending fuel introduction groove 21 is formed in the outer peripheral surface in contact with the inner peripheral surface of the nozzle body 2, and an end surface in contact with the bottom surface of the nozzle body 2 so as to intersect the fuel introduction groove 21. In addition, a fuel passage 22 reaching the inner peripheral surface is formed in a groove shape. The fuel passage 22 is formed in a linear shape and in a direction eccentric to the injection hole 12, that is, along the tangential direction of the needle valve 1. Thereby, the fuel introduction groove 21
The fuel flowing into the injection hole 12 through the fuel passage 22 has a swirl component. The outlet opening 22a of the fuel passage 22 faces the outer peripheral surface 1a of the needle valve 1, and is substantially closed by the outer peripheral surface 1a when the valve is closed. In this embodiment, the fuel passage 22
Has a rectangular cross-sectional shape as shown in FIG. 9, and the outlet opening 22a has the same shape. The fuel passage 22 and the fuel introduction groove 21 are provided in a plurality, for example, at four positions at intervals of 90 degrees.

Further, as shown in FIG.
The seat wire 23 at the tip of the conical portion is seated on the valve seat surface 24 upstream of the injection hole 12, but the seat wire 23 has a smaller diameter than the outer peripheral surface 1a. The boundary with the outer peripheral surface 1a, that is, the outer peripheral surface 1
When the edge 25a is closed, the nozzle body 2
It is located at the height of the bottom surface.

Next, the operation of the above embodiment will be described with reference to FIG.

As shown in FIG. 6A, first, when the valve is closed, the outer peripheral surface 1a of the needle valve 1 covers the entire outlet opening 22a of the fuel passage 22. In this state,
Since the injection hole 12 is closed, no fuel flows.

Then, when the needle valve 1 is lifted and the injection hole 12 is opened, fuel flows through the fuel passage 22 and is injected from the injection hole 12 with a swirl component. For example, as shown in FIG. 6C, the entire outlet opening 22a is opened.

On the other hand, when the lift is limited to a low lift, as shown in FIG.
Edge 25 of the outer peripheral surface 1a of the
The outlet opening 22a is partially covered by the outer peripheral surface 1a. Therefore, the substantial passage area of the fuel passage 22 is reduced, the flow velocity of the fuel flowing therethrough is prevented from decreasing, and the swirl component can be given sufficiently strong. As described above, the fuel passage 2 is set so that the total passage area of the swirling element 3 at the time of the low lift is substantially equal to or smaller than the passage area between the needle valve 1 and the valve seat surface 24.
2, etc. are set.

In the case of the cross-sectional shape of the fuel passage 22 as shown in FIG. 9, the passage area basically changes in proportion to the lift amount as shown by the characteristic a in FIG.

On the other hand, the sectional shape of the fuel passage 22 and the shape of the outlet opening 22a can be trapezoidal as shown in FIG. 10 or FIG. That is, as for the opening shape of the outlet opening 22a, its width dimension gradually increases along the lift direction of the needle valve 1. With such a configuration, the change in the passage area with respect to the change in the lift amount becomes large, as indicated by the characteristic b in FIG. Therefore, the passage area can be sufficiently reduced for a slight decrease in the lift amount.

FIG. 13 illustrates the current control for realizing the two-step control of the lift amount in the fuel injection valve as described above. And the applied current waveform of FIG. As shown in the figure, the current waveform at the time of the low lift gives a rising current waveform that can overcome the valve closing force due to the fuel pressure and the urging force of the first spring 5 to open the valve, and then maintains the low current in a short time. . By such current control, it is possible to prevent the urging force of the second spring 6 from being overcome to reach the full lift. On the other hand, at the time of a full lift (high lift), a larger rising current is applied, and the valve closing force due to the fuel pressure and the first and second springs 5 and 5 are increased.
Overcome the bias of 6 to reach full lift.

[Brief description of the drawings]

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

FIG. 2 is a characteristic diagram showing a relationship between a general lift amount and a flow rate characteristic.

FIG. 3 is a characteristic diagram showing a relationship between a lift amount and a spray angle in a conventional fuel injection valve.

FIG. 4 is a characteristic diagram showing a relationship between a passage area of a swirling element and a spray angle when a lift amount is constant.

FIG. 5 is a characteristic diagram collectively showing the influence of the lift amount and the passage area of the swirling element on the spray angle.

FIG. 6 is an explanatory diagram of a passage area control action by a needle valve in the embodiment of the present invention.

FIG. 7 is an enlarged view of a main part of the turning element and the needle valve.

FIG. 8 is a sectional view taken along the line AA of FIG. 7;

FIG. 9 is a sectional view taken along the line BB of FIG. 7;

FIG. 10 is a sectional view similar to FIG. 9, showing another embodiment.

FIG. 11 is a sectional view similar to FIG. 9, showing still another embodiment.

FIG. 12 is a characteristic diagram showing a relationship between a lift amount and a passage area.

FIG. 13 is a waveform chart showing an applied current for controlling the lift amount in two stages.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Needle valve 3 ... Revolving element 4 ... 1st stopper 5 ... 1st spring 6 ... 2nd spring 8 ... 2nd stopper 22 ... Fuel passage

Claims (5)

[Claims] 1. A fuel injection valve in which a swirl element having a fuel passage extending in a direction eccentric to an injection hole is arranged on an outer periphery of a needle valve so as to impart a swirl component to a fuel flow in the injection hole. , A lift amount control means for changing a lift amount of the needle valve, and a passage area control means for changing a passage area of the fuel passage of the turning element according to a change in the lift amount of the needle valve, A fuel injection valve, wherein a total passage area of the fuel passage in the swirl element is always substantially equal to or less than a passage area between the lifted needle valve and the valve seat surface. 2. The passage area control means, wherein the outlet opening of the fuel passage faces the outer peripheral surface of the needle valve, and the outlet opening is partially formed by the outer peripheral surface in accordance with the lift amount of the needle valve. The fuel injection valve according to claim 1, wherein the fuel injection valve is configured to change a passage area of the fuel passage by being covered. 3. The outlet opening is formed such that a width dimension in a direction orthogonal to a central axis of the needle valve gradually increases along a lift direction of the needle valve. The fuel injection valve according to claim 2. 4. The lift amount control means is configured to be slidable in parallel with the needle valve and to be positioned in contact with the nozzle body, and to direct the first stopper toward the nozzle body. A first spring that urges the needle valve in a closing direction, and a second spring that urges the needle valve in a normally closed direction, and is formed at an intermediate portion of the needle valve so as to face the first stopper via a predetermined gap. 2. The apparatus according to claim 1, further comprising a receiving portion, and a second stopper that abuts on a part of the needle valve to regulate a full lift amount, and is configured to change the lift amount in two steps of height. 4. The fuel injection valve according to any one of claims 1 to 3. 5. A low lift defined by the first stopper and a high lift defined by the second stopper are switched by current control to a coil for attracting the needle valve. The fuel injection valve according to claim 4.