Spark-ignition direct fuel injection valve

A spark-ignition direct fuel injection valve includes, at least, a seat member provided with a fuel injection hole and a valve seat and a valve body which controls fuel injection from the injection hole by contacting and separating from the valve seat. In the spark-ignition direct fuel injection valve: the injection hole has an injection hole inlet which is open inwardly of the seat member and an injection hole outlet which is open outwardly of the seat member; an opening edge of the injection hole inlet has a first round-chamfered portion formed on an upstream side with respect to a fuel flow toward the injection hole inlet; and an extending length (L) of the injection hole does not exceed three times a hole diameter (D) of the injection hole.

TECHNICAL FIELD

The present invention relates to a spark-ignition direct fuel injection valve which is a fuel injection valve for use in an internal combustion engine, for example, a gasoline engine and which prevents fuel leakage by making a valve body contact a valve seat and injects fuel directly into a cylinder by separating the valve body from the valve seat.

BACKGROUND ART

When a fuel injection valve for injecting fuel directly into a cylinder of an internal combustion engine is used, for example, its fuel spray characteristics affect the output characteristics and fuel economy of and the environmental burden caused by the internal combustion engine. A technique has been known in which the spray characteristics of a fuel injection valve are changed by appropriately changing the shape of a fuel injection hole of the fuel injection valve (see Patent Literature 1).

CITATION LIST

Patent Literature

SUMMARY OF THE INVENTION

Technical Problem

The fuel injection valve disclosed in the above patent literature is a fuel injection valve for use in a diesel engine. In the fuel injection valve disclosed in the above patent literature, fuel is injected at higher speed to make fuel particles finer. In the case of the fuel injection valve disclosed in the above patent literature, however, the distance of fuel injection (fuel spray length) becomes long to possibly cause, at the time of fuel injection into a cylinder, fuel adhesion to a suction valve or the inner wall surface of the cylinder.

Solution to Problem

The spark-ignition direct fuel injection valve according to claim1of the present invention comprises, at least, a seat member provided with a fuel injection hole and a valve seat and a valve body which controls fuel injection from the injection hole by contacting and separating from the valve seat. In the spark-ignition direct fuel injection valve: the injection hole has an injection hole inlet which is open inwardly of the seat member and an injection hole outlet which is open outwardly of the seat member; an opening edge of the injection hole inlet has a first round-chamfered portion formed on an upstream side with respect to a fuel flow toward the injection hole inlet; and an extending length (L) of the injection hole does not exceed three times a hole diameter (D) of the injection hole.

Advantageous Effects of Invention

According to the present invention, at the time of fuel injection into a cylinder, fuel adhesion to a suction valve and the inner wall surface of the cylinder can be suppressed.

DESCRIPTION OF EMBODIMENTS

First Embodiment

A spark-ignition direct fuel injection valve according to a first embodiment of the present invention, will be described below with reference toFIGS. 1 to 9.FIG. 1is a sectional view of an electromagnetic fuel injection valve representing an example of a spark-ignition direct fuel injection valve of the present embodiment. The electromagnetic fuel injection valve100is a normally-closed, electromagnetically driven fuel injection valve used in a gasoline engine of a direct fuel injection type. When a coil108is de-energized, a valve body101is pressed against a seat member102by the bias force of a spring110thereby sealing fuel. This state is called a valve-closed state.

Fuel is supplied into the electromagnetic fuel injection valve100from a fuel supply port112. For a direct fuel injection valve like the electromagnetic fuel injection valve100, the supply fuel pressure ranges from 1 MPa to 40 MPa.

FIG. 2is an enlarged sectional view of a vicinity of fuel injection holes formed through an end portion of the electromagnetic fuel injection valve100. A nozzle body104is, at an end portion thereof, joined with the seat member102, for example, by welding. The seat member102has an inner conical surface through which plural fuel injection holes201, being described in detail later, are formed. A conical surface portion upward of, as seen inFIG. 2, the fuel injection holes201makes up a valve seat surface203. In a valve-closed state, the valve body101is in contact with the valve seat surface203of the seat member102, thereby sealing fuel. A contact portion202(hereinafter referred to as a spherical portion) on the valve body101side to contact the valve seat surface203is spherically formed. Therefore, the conical valve seat surface203and the spherical portion202come into linear contact with each other. The axial center of the valve body101coincides with a central axis204of the electromagnetic fuel injection valve100.

When the coil108shown inFIG. 1is energized, a core107, yoke109, and anchor106making up a magnetic circuit in the electromagnetic fuel injection valve100generate magnetic fluxes, and a magnetic attraction force is generated in the gap between the core107and the anchor106. When the magnetic attraction force exceeds the total of the bias force of the spring110and the fuel pressure, the valve body101is attracted by the anchor106toward the core107while being guided by a guide member103and a valve body guide105and is displaced upward as seen in the diagram. The resultant state is referred to as a valve-open state.

When the electromagnetic fuel injection valve100enters a valve-open state, a gap is formed between the valve seat surface203and the spherical portion202of the valve body101causing fuel injection to be started. When fuel injection is started, the energy provided as the fuel pressure is converted into a kinetic energy. As a result, the fuel reaches the fuel injection holes201to be directly injected into a gasoline engine cylinder, not shown.

Shape of Fuel Injection Holes201

FIG. 3is a sectional view of the seat member102shown inFIG. 2taken along line A-A. For descriptive convenience, the valve body101is omitted inFIG. 3. Description of the present embodiment is based on an example case in which the number of the fuel injection holes201formed through the seat member102is six. In the following description, the six fuel injection holes201will be individually denoted as201ato201f, respectively, as being ordered, as shown inFIG. 3, counterclockwise about an apex301of the valve seat surface203with the fuel injection hole201abeing approximately in the 10 o'clock position. Also, a portion or a point (position) identical between the fuel injection holes201will be represented by a same reference numeral postfixed with a letter (among a to f) identical to the letter postfixed to the reference numeral201to represent the corresponding fuel injection hole.

Each fuel injection hole201has a fuel injection hole inlet304and a fuel injection hole outlet305. The opening edge of each fuel injection hole inlet304is curvedly chamfered. The chamfered portion of each fuel injection hole inlet304will be referred to as a round-chamfered portion1304. Each fuel injection hole outlet305is, as shown inFIG. 2, recessed from the outer surface of the seat member102. Therefore, a portion outside each fuel injection hole outlet305(a portion downward of each fuel injection hole outlet305as seen in the diagram) of the seat member102is cut away so as to prevent interference with the fuel being injected.

The positional relationship between the fuel injection hole inlet304aand the fuel injection hole outlet305aof the fuel injection hole201awill be described below. A plane which contains a line (hereinafter referred to as a nozzle axis or an injection hole axis307connecting a center point302aof the fuel injection hole inlet304aand a center point306aof the fuel injection hole outlet305aand which is parallel to the central axis204of the electromagnetic fuel injection valve100will be referred to as a first plane11a. A plane which contains a line303aconnecting the center point302aof the fuel injection hole inlet304aand the apex301of the valve seat surface203(i.e. the apex of the conical surface) and which also contains the central axis204of the electromagnetic fuel injection valve100will be referred to as a second plane12a. The fuel injection hole inlet304aand the fuel injection hole outlet305aof the fuel injection hole201aare positioned such that the first plane11aand the second plane12aintersect each other. In other words, the central axis204of the electromagnetic fuel injection valve100and the injection hole axis307aare in a twisted positional relationship. InFIG. 3, a reference sign308arepresents an angle (included angle) formed between the first plane11aand the second plane12a.

For the fuel injection holes201b,201d, and201e, the respective positional relationships between the fuel injection hole inlets304b,304d, and304eand the corresponding fuel injection hole outlets305b,305d, and305eare identical with the positional relationship between the fuel injection hole inlet304aand the fuel injection hole outlet305aof the fuel injection hole201a. Therefore, in the fuel injection hole201b, the first plane11band the second plane12bintersect each other; in the fuel injection hole201d, the first plane11dand the second plane12dintersect each other; and in the fuel injection hole201e, the first plane11eand the second plane12eintersect each other. That is, the injection hole axes307b,307d, and307eare each in a twisted positional relationship with the central axis204of the electromagnetic injection valve100.

In the fuel injection holes201cand201f, the positional relationships between the fuel injection hole inlets304cand304fand the fuel injection hole outlets305cand305fare as follows. That is, in the fuel injection hole201c, a first plane11cand a second plane12ccoincide with each other and, in the fuel injection hole201f, a first plane11fand a second plane12fcoincide with each other. Therefore, the included angle between the first plane11cand the second plane12cand the included angle between the first plane11fand the second plane12fare 0 degree. Injection hole axes307cand307fboth intersect the central axis204of the electromagnetic fuel injection valve100. Between the fuel injection holes201a,201b,201d, and201ein each of which the included angle is not 0 degree and the fuel injection holes201cand201fin each of which the included angle is 0 degree, there is no difference in the operational effects being described later.

FIG. 4is a diagram for describing, based on the fuel injection hole201aas an example, the injection hole shape and the fuel flow.FIG. 5 (a)is a sectional view parallel to the central axis204of the electromagnetic fuel injection valve100of the fuel injection hole201a, as a present example, and schematically shows fuel flows in the fuel injection hole201a.FIG. 5 (b)is a sectional view taken along line C-C inFIG. 5 (a)and schematically shows, out of the fuel velocity components at the fuel injection hole outlet305a, those velocity components spreading in radial directions of the fuel injection hole201a.FIG. 6is a diagram for describing the orientation of each of the injection hole axes307ato307fof the electromagnetic fuel injection valve100.FIG. 7is a diagram for describing, regarding each fuel injection hole, the relationship between the injection hole length divided by the injection hole diameter and the in-plane spreading force of fuel being described later.FIGS. 8 and 9are diagrams for describing existing techniques and correspond toFIG. 5for the present embodiment.

Referring toFIG. 4, reference sign413adenotes a virtual plane bisecting the included angle308aformed between the first plane11aand the second plane12a. Also, regarding the fuel injection hole201a, reference signs414aand415adenote two points where a round-chamfered portion1304aof the fuel injection hole inlet304aand the virtual plane413aintersect each other. Between the two points, the point414aon the upstream side with respect to the fuel flow being described later has a larger curvature radius than that of the point415aon the downstream side with respect to the fuel flow.

In this embodiment, the opening inlet edge of each fuel injection hole201is circumferentially round-chamfered such that the upstream point414ais larger in curvature radius than the downstream point415a. The opening inlet edge of each fuel injection hole201, however, need not necessarily be entirely circumferentially round-chamfered. It may be round-chamfered only where breaking away of the fuel flow becomes intolerably large. Hence, round-chamfering the opening inlet edge of each fuel injection hole201on the upstream side only is also allowable. According to the present invention, the opening inlet edge of each fuel injection hole is to be round-chamfered at least on the upstream side.

When, as in the case of the fuel injection hole201a, the included angle308aformed between the first plane11aand the second plane12ais not 0 degree, the fuel flows as described in the following. Though not shown inFIG. 4, the fuel supplied through the fuel supply port112into the electromagnetic fuel injection valve100flows toward the fuel injection hole inlet304athrough the gap formed, in a valve-open state, between the valve seat surface203and the spherical portion202of the valve body101and along the valve seat surface203. This fuel flow is denoted by a reference sign410a.

The fuel flow410atoward the fuel injection hole inlet304ais turned, at the fuel injection hole inlet304a, into a direction toward the fuel injection hole outlet305a, that is, into the direction of the injection hole axis307aconnecting the center point302aof the fuel injection hole inlet304aand the center point306aof the fuel injection hole outlet305a. This fuel flow is denoted by a reference sign411a. Subsequently, the fuel flows inside the fuel injection hole201atoward the fuel injection hole outlet305a, not shown inFIG. 4. This fuel flow is denoted by a reference sign412a.

Regarding the fuel flows410ato412a, the fuel changes its flow direction most sharply at the point414a, so that its inertial force for breaking away from the inner wall surface of the fuel injection hole201ais largest at the point414a. That is, the point414ais where it is easiest for the fuel to break away from the inner wall surface of the fuel injection hole201a. Also, regarding the fuel flows410ato412a, the fuel changes its flow direction at the point415amore gently than at the point414a. Therefore, at the point415a, it is less easy for the fuel to break away from the inner wall surface of the fuel injection hole201athan at the point414a.

As described above, at the round-chamfered portion1304aof the fuel injection hole inlet304a, the curvature radius of the portion, denoted as the point414a, on the upstream side with respect to the fuel flow is larger than the curvature radius of the portion, denoted as the point415a, on the downstream side with respect to the fuel flow. It is, therefore, possible to suppress breaking away of the fuel from the inner wall surface of the fuel injection hole201aaccording to the manner in which the fuel flows into the fuel injection hole201a.

As shown inFIG. 4, besides the included angle308aformed between the first plane11aand the second plane12a, an included angle309ais also formed between the first plane11aand the second plane12a, so that, besides the virtual plane413abisecting the included angle308a, a virtual plane416abisecting the included angle309ais also conceivable. Furthermore, two points417aand418aare conceivable as points where the round-chamfered portion1304aand the virtual plane416aintersect each other. Determining the curvature radii of the round-chamfered portion1304arequires that at least the portions where it is easiest for the fuel to break away from the inner wall surface of the fuel injection hole201aand where it is least easy for the fuel to break away from the inner wall surface of the fuel injection hole201abe determined. Hence, regarding the present embodiment, the included angle309aand the virtual plane416awill not be particularly referred to in the following.

Referring toFIG. 5 (a), assume that: extending length L of the fuel injection hole201aequals the length of the injection hole axis307a; and diameter D of the fuel injection hole201ais a diameter at an inner surface501aparallel to the injection hole axis307aof the fuel injection hole201a. InFIG. 5 (a), reference sign508adenotes the fuel having entered the fuel injection hole201aafter flowing along the valve seat surface203while breaking away of the fuel is suppressed by the round-chamfered portion1304a.

In the electromagnetic fuel injection valve100of the present embodiment, the extending length L and diameter D of the fuel injection hole201aare preferably in a relationship of L/D≦3. With L/D being 3 or less, the fuel508ahaving entered the fuel injection hole201ais injected from the fuel injection hole outlet305awithout being completely rectified in the fuel injection hole201a. This allows, out of the fuel velocity components at the fuel injection hole outlet305a, velocity components509aspreading in radial directions of the fuel injection hole201ato be made large as shown inFIG. 5 (b)(i.e. the in-plane spreading force of the fuel becomes large). Therefore, out of the fuel velocity components at the fuel injection hole outlet305a, the velocity components in the injection hole axis direction can be made small. This reduces the fuel injection speed at the fuel injection hole outlet305a, so that the distance over which the fuel is sprayed (fuel spray length) is reduced.

Results of simulations carried out by the present inventors are shown inFIG. 15.FIG. 15 (a)shows simulation results obtained with L/D=1, where L is the extending length L of the fuel injection hole210aand D is the diameter D of the injection hole inlet304.FIG. 15(b) shows simulation results obtained with L/D=3.

The fuel coming to the injection hole inlet304from a fuel sealing section, not shown, located in an upper right portion as seen in each diagram flows into the fuel injection hole passing the round-chamfered portion1304a. When, at this time, L/D is about 1, the fuel is injected, as denoted as1500a, without being rectified in the fuel injection hole. It is shown that, even when L/D is 3, the fuel flow is not completely rectified in a portion corresponding to an L/D value of 1 and that, as the value of L/D increases, the fuel flow is gradually increasingly rectified as denoted by1500cand1500d. If the fuel flow is completely rectified, the velocity components radially spreading in the fuel injection hole reduce to increase the fuel spray length.

That is, for the fuel entering each fuel injection hole201via the fuel injection hole inlet304thereof to be then injected from the fuel injection hole outlet305thereof into a cylinder, L/D≦3 is considered to represent an upper limit value of L/D not to allow the fuel to be completely rectified in the fuel injection hole.

A case in which, as shown inFIG. 8 (a), an extending length L′ of a fuel injection hole201′ is long relative to a diameter D (diameter at an inner surface801parallel to an injection hole axis307′ of the fuel injection hole201′) of the fuel injection hole201′ (i.e., a case in which L′/D>3) will be described in the following. As described above,FIGS. 8 (a)and8(b) correspond toFIGS. 5 (a)and5(b), respectively.

When the value of L′/D is larger than 3, the fuel flowing along the valve seat surface203and entering the fuel injection hole201′ while breaking away of the fuel is suppressed by a round-chamfered portion1304′ is rectified, as denoted by808, while flowing in the fuel injection hole201′. That is, as shown inFIG. 8 (b)which is a sectional view taken along line C′-C′ inFIG. 8 (a), velocity components809radially spreading at an injection hole outlet305a′ are reduced (the in-plane spreading force of the fuel is reduced). As a result, the velocity components of the fuel in the injection axis direction become larger to increase the fuel injection speed at the injection hole outlet305aand to increase the fuel spray length.

FIG. 7shows a curve701representing an in-plane spreading force of fuel with the horizontal axis representing L/D and the vertical axis representing the in-plane spreading force of fuel. The in-plane spreading force of fuel is dependent on the radially spreading velocity components at each fuel injection outlet305. The radially spreading velocity components of fuel at each injection hole outlet305are generated when the fuel entering each fuel injection hole201is not completely rectified in the fuel injection hole201. When the value of L/D does not exceed 3, the fuel can be injected, without being completely rectified, from each fuel injection hole outlet305. This reduces the fuel spray length.

A case in which, as shown inFIG. 9 (a), no round-chamfered portion1304of the present embodiment is provided at a fuel injection hole inlet304″ will be described. Assume that a diameter D of a fuel injection hole201″ (the diameter of the fuel injection hole201″ at an inner surface901) and an extending length L of the fuel injection hole201″ shown inFIG. 9 (a)are, to be similar to the present embodiment described above, in a relationship of L/D≦3. Also, as described above,FIGS. 9 (a)and9(b) correspond toFIGS. 5 (a)and5(b), respectively.

Even with an L/D value of 3 or less, when the fuel injection hole inlet304″ has no round-chamfered portion1304, the fuel breaks away from the inner wall surface901of the fuel injection hole201″ as shown inFIG. 9 (a). Reference signs910aand910bdenote boundaries between the fuel flow and spaces inside the fuel injection hole201″. The space formed between the fuel flow boundaries910aand910band the inner wall surface901of the fuel injection hole201″ are broken-away areas formed by breaking away of the fuel.

In the examples shown inFIGS. 9 (a)and9(b), the value of L/D is 3 or less, so that fuel908having entered the fuel injection hole201″ is injected from a fuel injection hole outlet305″ without being completely rectified in the fuel injection hole201″. However, the cross-sectional area of the fuel908flowing in the fuel injection hole201″ is smaller than the cross-sectional area of the fuel injection hole201″ by a total cross-sectional area of the broken-away areas formed inside the fuel injection hole201″. This practically reduces the area of the fuel injection hole outlet305″ (the cross-sectional area of the fuel injection hole201″), so that the fuel injection speed increases. That is, the velocity components in the direction of the injection hole axis of the fuel increase resulting in a higher speed of fuel injection from the fuel injection hole outlet305″. As a result, the fuel spray length increases. Thus, merely setting a small L/D value does not reduce the fuel spray length.

InFIG. 9 (b), the arrows representing velocity components are shown deviated from the cross-sectional center of the fuel injection hole. This is because of the difference, caused by breaking away of the fuel as shown inFIG. 9 (a), between the distance from the fuel flow boundary901aon the downstream side to the inner surface901and the distance from the fuel flow boundary901bon the upstream side to the inner surface901.

Orientations of Injection Hole Axes307ato307f

The orientations of injection hole axes307ato307fwill be described with reference toFIG. 6. In the present embodiment, the injection hole axes307ato307fare oriented along the generatrix of either one of two virtual circular cones sharing a vertex and an axis and having different vertex angles. In the following description, of the two virtual circular cones, the one with a smaller vertex angle will be represented by reference sign601and the other one with a larger vertex angle will be represented by reference sign602.

The injection hole axes307a,307c, and307eare oriented along the generatrix of the virtual circular cone601that has a vertex on the central axis204(not shown inFIG. 6) of the electromagnetic fuel injection valve100and a central axis coinciding with the central axis204. The injection hole axes307b,307d, and307fare oriented along the generatrix of the virtual circular cone602that shares the vertex and axis with the virtual circular cone601and has a vertex angle larger than that of the virtual circular cone601. Thus, in the present embodiment, the lines307respectively connecting the center points302of the fuel injection hole inlets304and the center points306of the fuel injection hole outlets305of the respective fuel injection holes201are oriented along the conical surface of either one of the two virtual circular cones601and602.

Operational Effects

The electromagnetic fuel injection valve100of the present embodiment described above renders the following operational effects:

(1) Each fuel injection hole inlet304has a round-chamfered portion1304, and the extending length L of the fuel injection hole201aand the diameter D of the fuel injection hole201aare in a relationship of L/D≦3. This prevents breaking away of the fuel inside each fuel injection hole201, so that the area of each fuel injection hole outlet305(cross-sectional area of each fuel injection hole201) can be prevented from being practically reduced and so that the fuel injection speed can be prevented from increasing. Hence, the fuel spray length can be effectively prevented from increasing and, at the time of fuel injection into a cylinder, fuel adhesion to a suction valve or the inner wall surface of the cylinder can be effectively suppressed.
(2) The round-chamfered portion1304of each fuel injection hole inlet304is formed such that a point denoted as414on the upstream side with respect to the fuel flow has a larger curvature radius than that of a point denoted as415on the downstream side with respect to the fuel flow. This makes it possible to effectively prevent, according to the manner in which the fuel flows into each fuel injection hole201, the fuel from breaking away from the inner wall surface of each fuel injection hole201. Therefore, at the time of fuel injection into a cylinder, fuel adhesion to a suction valve or the inner wall surface of the cylinder can be effectively suppressed.
(3) Two points where a virtual plane413bisecting an included angle308and a round-chamfered portion1304intersect each other are determined and, of the two points, the one on the upstream side with respect to the fuel flow has a curvature radius larger than that of the other point on the downstream side with respect to the fuel flow. In this way, the radius curvature of the round-chamfered portion1304can be appropriately set according to the manner in which the fuel comes in. This makes it possible to securely prevent breaking away of the fuel in each fuel injection hole201. Therefore, at the time of fuel injection into a cylinder, fuel adhesion to a suction valve or the inner wall surface of the cylinder can be securely suppressed.
(4) Each fuel injection hole inlet304is formed on the inner conical surface of the seat member102. This allows the fuel flow toward the fuel injection hole inlet304to be rectified along the conical surface, so that the curvature radii of different portions of the opening edge of the round-chamfered portion1304can be set with ease and so that breaking away of the fuel from the inner wall surface of each fuel injection hole201can be effectively prevented according to the manner in which the fuel flows into the fuel injection hole201. Therefore, at the time of fuel injection into a cylinder, fuel adhesion to a suction valve or the inner wall surface of the cylinder can be effectively suppressed.
(5) The valve seat surface203is formed on the conical inner surface of the seat member102. This, combined with the effects of the fuel injection hole inlets304formed on the inner surface of the seat member102, allows the fuel flow toward the fuel injection hole inlets304to be rectified along the conical surface. Therefore, as described above, breaking away of the fuel from the inner wall surface of each fuel injection hole201can be effectively prevented according to the manner in which the fuel flows into the fuel injection hole201. Hence, at the time of fuel injection into a cylinder, fuel adhesion to a suction valve or the inner wall surface of the cylinder can be effectively suppressed.
(6) The injection hole axes307ato307fare oriented along the generatrix of either one of the two virtual circular cones601and602that share a vertex and an axis and have different vertex angles. This makes it possible to generate diversified fuel spray shapes. Thus, superior layoutability is offered for fuel injection into an internal combustion engine.

Second Embodiment

A spark-ignition direct fuel injection valve according to a second embodiment of the present invention will be described below with reference toFIG. 10. In the following description, the constituent elements identical to those used in the first embodiment will be represented by the corresponding reference signs used in describing the first embodiment, and they will be described centering on differences from the first embodiment. Their aspects not particularly described in the following are the same as in the first embodiment.FIG. 10is a sectional view showing a structure of the electromagnetic fuel injection valve100according to the second embodiment and corresponds toFIG. 5 (a).

In the electromagnetic injection valve100of the second embodiment, a side surface1001of each fuel injection hole is configured such that the cross-sectional area is gradually larger from the fuel injection hole inlet304toward the fuel injection hole outlet305. In the second embodiment, diameter D of each fuel injection hole201represents a diameter1010measured at a boundary between a round-chamfered portion1007of the fuel injection hole inlet304and the fuel injection hole side surface1001(the boundary being where the cross-sectional area of the fuel injection hole201is smallest).

In the electromagnetic fuel injection valve100of the second embodiment, fuel1008flowing into each fuel injection hole201from the valve seat surface203along the round-chamfered portion1007without breaking away is, after radially spreadingly flowing in the fuel injection hole201, injected from the fuel injection hole outlet305. Therefore, it is possible to suppress the velocity components in the injection hole axis direction by increasing the radially spreading velocity components. In this way, the fuel spray length can be further reduced compared with the case of the electromagnetic fuel injection valve100of the first embodiment, so that, at the time of fuel injection into a cylinder, fuel adhesion to a suction valve and the inner wall surface of the cylinder can be effectively suppressed.

In the other respects, the fuel injection valve of the second embodiment is structured identically to the fuel injection valve of the first embodiment. For example, the opening inlet edge of each injection hole201is round-chamfered, and the upstream point414a(seeFIG. 4) has a curvature radius larger than that of the downstream point415a(seeFIG. 4).

Third Embodiment

A spark-ignition direct fuel injection valve according to a third embodiment of the present invention will be described below with reference toFIG. 11. In the following description, the constituent elements identical to those used in the first embodiment will be represented by the corresponding reference signs used in describing the first embodiment, and they will be described centering on differences from the first embodiment. Their aspects not particularly described in the following are the same as in the first embodiment.FIG. 11is a sectional view showing a structure of the electromagnetic fuel injection valve100according to the third embodiment and corresponds toFIG. 5 (a).

In the electromagnetic fuel injection valve100of the third embodiment, each fuel injection hole inlet304has a round-chamfered portion1107and each fuel injection hole outlet305has a round-chamfered portion1101. A downstream end portion of the round-chamfered portion1107and an upstream end portion of the round-chamfered portion1101coincide with each other. In the third embodiment, diameter D of each fuel injection hole201represents diameter1110at a boundary (where the cross-sectional area of the fuel injection hole201is smallest) between the round-chamfered portion1107and the round-chamfered portion1101, the boundary being the downstream end portion of the round-chamfered portion1107and also the upstream end portion of the round-chamfered portion1101.

Unlike for the round-chamfered portion1107of each fuel injection hole inlet304, it is not necessary, for the round-chamfered portion1101of each fuel injection hole outlet305, to set appropriately varied radii of curvature for different portions of the opening edge for the fuel flow. The round-chamfered portion1101may have a uniform radius of curvature.

In the electromagnetic fuel injection valve100of the third embodiment, fuel1108having entered, without breaking away, each fuel injection hole201from the valve seat surface203and along the round-chamfered portion1107is injected from the fuel injection hole outlet305after radially spreadingly flowing over the round-chamfered portion1108. Therefore, it is possible to suppress the velocity components in the injection hole axis direction by increasing the radially spreading velocity components. In this way, the fuel spray length can be further reduced compared with the case of the electromagnetic fuel injection valve100of the first embodiment, so that, at the time of fuel injection into a cylinder, fuel adhesion to a suction valve and the inner wall surface of the cylinder can be effectively suppressed.

Fourth Embodiment

A spark-ignition direct fuel injection valve according to a fourth embodiment of the present invention will be described below with reference toFIG. 12. In the following description, the constituent elements identical to those used in the first embodiment will be represented by the corresponding reference signs used in describing the first embodiment, and they will be described centering on differences from the first embodiment. Their aspects not particularly described in the following are the same as in the first embodiment.FIG. 12is a sectional view showing a structure of the electromagnetic fuel injection valve100according to the forth embodiment and corresponds toFIG. 5 (a).

In the electromagnetic fuel injection valve100of the fourth embodiment, a side surface1201of each fuel injection hole is configured such that the cross-sectional area is gradually smaller from the fuel injection hole inlet304toward the fuel injection hole outlet305. In the fourth embodiment, diameter D of each fuel injection hole201represents a diameter1210measured at a boundary between a round-chamfered portion1207of the fuel injection hole inlet304and the fuel injection hole side surface1201. In the electromagnetic fuel injection valve100of the fourth embodiment, fuel1208flowing into each fuel injection hole201from the valve seat surface203along the round-chamfered portion1207without breaking away is, after radially convergingly flowing along the fuel injection hole side surface1201, injected from the fuel injection hole outlet305.

Therefore, in the fourth embodiment compared with the first to third embodiments, the fuel velocity components spreading in the radial directions of each fuel injection hole201are suppressed to some extent. With the value of L/D not exceeding 3, however, the fuel1208entering each fuel injection hole201is injected from the fuel injection hole outlet305without being completely rectified in the fuel injection hole201. Therefore, of the fuel velocity components at the fuel injection hole outlet305, the velocity components spreading in the radial directions of the fuel injection hole201become larger whereas the velocity components in the injection hole axis direction become smaller. Hence, the speed at which the fuel is injected from the fuel injection hole outlet305decreases causing the fuel spray length to be reduced, so that, at the time of fuel injection into a cylinder, fuel adhesion to a suction valve and the inner wall surface of the cylinder can be effectively suppressed.

Also, in the electromagnetic injection valve100of the fourth embodiment, the overall flow rate in the electromagnetic fuel injection valve100can be suppressed. Therefore, the electromagnetic fuel injection valve100of the fourth embodiment can be easily applied to an internal combustion engine with a small displacement.

Fifth Embodiment

A spark-ignition direct fuel injection valve according to a fifth embodiment of the present invention will be described below with reference toFIG. 13. In the following description, the constituent elements identical to those used in the first embodiment will be represented by the corresponding reference signs used in describing the first embodiment, and they will be described centering on differences from the first embodiment. Their aspects not particularly described in the following are the same as in the first embodiment.FIG. 13is a sectional view showing a structure of the electromagnetic fuel injection valve100according to the fifth embodiment and corresponds toFIG. 5 (a).

In the electromagnetic fuel injection valve100of the fifth embodiment, each fuel injection hole201has an elliptical cross-section. In the fifth embodiment, diameter D of each fuel injection hole201represents a diameter1310of a circle which equals in area a cross-sectional ellipse13at a boundary between a round-chamfered portion1307of the fuel injection hole inlet304and a side surface1301of the fuel injection hole201(the boundary being where the cross-sectional area of the fuel injection hole201is smallest). The ellipse13has a major axis13aand a minor axis13b.

In the electromagnetic fuel injection valve100of the fifth embodiment, the elliptical fuel injection hole inlet304is oriented such that the major axis13ais approximately perpendicular to the fuel flow from the upstream side (upper right side as seen in the diagram) of the valve seat surface203. That is, the fuel injection hole inlet304is widely open to the fuel flowing in from the upstream side of the valve seat surface203. In this way, as compared with when the fuel injection hole inlet304is truly circular, breaking away of the fuel in the fuel injection hole201can be effectively suppressed. Furthermore, fuel1308flowing into the fuel injection hole201through the fuel injection hole inlet304without breaking away from the round-chamfered portion1307is ejected from the fuel injection hole outlet305after radially spreadingly flowing in the fuel injection hole201. It is, therefore, possible to suppress the fuel velocity components in the injection hole axis direction by increasing the radially spreading fuel velocity components. In this way, compared with the case of the electromagnetic fuel injection valve100of the second embodiment in which the side surface of each fuel injection hole is formed such that the cross-sectional area of the fuel injection hole is increasingly larger from the fuel injection hole inlet toward the fuel injection hole outlet, the fuel spray length can be further reduced. Hence, at the time of fuel injection into a cylinder, fuel adhesion to a suction valve and the inner wall surface of the cylinder can be effectively suppressed.

In the present embodiment, even if the diameter of each fuel injection hole201is made uniform as in the electromagnetic fuel injection valve100of the first embodiment, similar operational effects to those described above can be achieved. Also, in the present embodiment, even if a round-chamfered portion is provided at each of the inlet and outlet of each fuel injection hole as in the electromagnetic fuel injection valve100of the third embodiment, similar operational effects to those described above can be achieved. Furthermore, in the present embodiment, even if the side surface of each fuel injection hole is formed such that the cross-sectional area of the fuel injection hole is gradually smaller from the fuel injection hole inlet toward the fuel injection hole outlet as in the electromagnetic fuel injection valve100of the fourth embodiment, similar operational effects to those described above can be achieved.

Sixth Embodiment

A spark-ignition direct fuel injection valve according to a sixth embodiment of the present invention will be described below with reference toFIG. 14. In the following description, the constituent elements identical to those used in the first embodiment will be represented by the corresponding reference signs used in describing the first embodiment, and they will be described centering on differences from the first embodiment. Their aspects not particularly described in the following are the same as in the first embodiment.FIG. 14is a sectional view showing a structure of the electromagnetic fuel injection valve100according to the sixth embodiment and corresponds toFIG. 5 (a).

In the electromagnetic injection valve100of the sixth embodiment, the cross-sectional shape of each fuel injection hole201is approximately triangular. In the sixth embodiment, diameter D of each fuel injection hole201represents a diameter1410of a circle which equals in area a cross-sectional triangle14at a boundary between a round-chamfered portion1407of the fuel injection hole inlet304and a fuel injection hole side surface1401(the boundary being where the cross-sectional area of the fuel injection hole201is smallest). The triangle14is an equilateral triangle having a side14a.

In the electromagnetic fuel injection valve100of the sixth embodiment, the triangular fuel injection hole inlet304of each fuel injection hole is oriented such that the side14ais approximately perpendicular to the fuel flow from the upstream side (upper right side as seen in the diagram) of the valve seat surface203. That is, the fuel injection hole inlet304is widely open to the fuel flowing in from the upstream side of the valve seat surface203. In this way, as compared with when the fuel injection hole inlet304is truly circular, breaking away of the fuel in the fuel injection hole201can be effectively suppressed. Furthermore, fuel1408flowing into the fuel injection hole201through the fuel injection hole inlet304without breaking away from the round-chamfered portion1407is ejected from the fuel injection hole outlet305after radially spreadingly flowing in the fuel injection hole201. It is, therefore, possible to suppress the fuel velocity components in the injection hole axis direction by increasing the radially spreading fuel velocity components. In this way, compared with the case of the electromagnetic fuel injection valve100of the second embodiment in which the side surface of each fuel injection hole is formed such that the cross-sectional area of the fuel injection hole is increasingly larger from the fuel injection hole inlet toward the fuel injection hole outlet, the fuel spray length can be further reduced. Hence, at the time of fuel injection into a cylinder, fuel adhesion to a suction valve and the inner wall surface of the cylinder can be effectively suppressed.

In the present embodiment, even if the diameter of each fuel injection hole201is made uniform as in the electromagnetic fuel injection valve100of the first embodiment, similar operational effects to those described above can be achieved. Also, in the present embodiment, even if a round-chamfered portion is provided at each of the inlet and outlet of each fuel injection hole as in the electromagnetic fuel injection valve100of the third embodiment, similar operational effects to those described above can be achieved. Furthermore, in the present embodiment, even if the side surface of each fuel injection hole is formed such that the cross-sectional area of the fuel injection hole is gradually smaller from the fuel injection hole inlet toward the fuel injection hole outlet as in the electromagnetic fuel injection valve100of the fourth embodiment, similar operational effects to those described above can be achieved.

Modifications

(1) By taking into consideration the distances between the electromagnetic fuel injection valve100and the top, bottom and side surfaces of a cylinder of an internal combustion engine, the curvature radius of the round-chamfered portion1304may be varied along the circumference of the opening edge of the fuel injection hole inlet304so as to make appropriate the fuel spray lengths toward the top, bottom and side surfaces of the internal combustion engine cylinder. In this way, a suitable state of air-fuel mixture can be achieved in the cylinder while suppressing fuel adhesion to a suction valve and the inner wall surface of the cylinder.
(2) Preferably, the curvature radius of the round-chamfered portion1304is set to gradually vary along the circumferential direction of the opening edge of the fuel injection hole inlet304. It is, however, sufficient if the chamfered portion1304has at least a difference in curvature radius between the upstream side and the downstream side with respect to the fuel flow. Even if the curvature radius of the chamfered portion1304sharply or discontinuously changes along the circumferential direction of the opening edge, the operational effects of the present invention are not detracted from. Also, the opening edge of the fuel injection hole inlet304is required to be chamfered at least on the upstream side with respect to the fuel flow. Chamfering on the downstream side is not imperative.
(3) The fuel injection hole inlet304can be provided with the round-chamfered portion1304at the opening edge thereof, for example, by letting a liquid containing dispersed abrasive grains flow therethrough or by blasting the opening edge. Alternatively, the opening edge portion the curvature radius of which is not to be increased may be hardened by heat treatment so as to increase the abrasion resistance of the portion and so as to, thereby, generate a curvature radius difference between the portion and the other portion not subjected to such heat treatment.
(4) In the above description, whether or not the distance between the center point302of the fuel injection hole inlet304of each fuel injection hole201and the central axis204of the electromagnetic fuel injection valve100is different between the fuel injection holes201and whether or not the adjacent fuel injection holes201are equidistantly spaced apart are not mentioned. However, whether or not the distance between the center point302of the fuel injection hole inlet304of each fuel injection hole201and the central axis204of the electromagnetic fuel injection valve100is different between the fuel injection holes201does not detract from the above-described operational effects. Also, whether or not the adjacent fuel injection holes201are equidistantly spaced apart does not detract from the above-described operational effects.
(5) Even though the above description is based on the assumption that the number of the fuel injection holes201formed through the seat member102is six, the present invention does not limit the number of the fuel injection holes201to six. That is, even if the number of the fuel injection holes201formed through the seat member102is not six, operational effects similar to those of the above embodiments can be achieved.
(6) According to the above description, the fuel injection hole axes307ato307fare oriented based on two virtual cones601and602. However, the present invention does not limited the number of the virtual cones to two. For example, the number of the virtual cones may be 3 or more.
(7) The above embodiments and the modifications may be combined.

The present invention is not limited to the above embodiments and can be applied to various types of spark-ignition direct fuel injection valves.

LIST OF REFERENCE SIGNS