JP2000314354A - Cylinder fuel injection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure good fuel spray, and realize stable lean combustion by arranging a fuel turning member on the upstream side of a valve seat part of a valve member for opening/closing a fuel passage, and arranging two clearances which are different from each other in the axial direction between the outer wall of the valve member and an inner wall of the fuel turning member, in the fuel turning member. SOLUTION: When an ON-signal is applied on a solenoid coil, a plunger is attracted to a core side, a valve element 6 is moved upward through a rod 25, and is separated from a seat surface of a valve seat of a nozzle member 7, and an injection hole 8 is opened. Fuel is passed from the axial direction groove of a fuel turning member 22 to a diameter direction groove 24, turned and supplied to the seat part, and injected via the injection hole 8. At this time, strong turning effort is obtained by increasing an eccentric quantity in the diametrical direction groove 24 of the fuel turning member 22. Stable turning flow is obtained from the diameter direction groove 24 by arranging a fluid seat part 26 for suppressing fuel which flows a hole 22a in the fuel turning member 22, and thereby fuel turning into film state is promoted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel (gasoline)
Relates to an internal combustion engine that directly injects fuel into a combustion chamber and burns it.
In particular, the present invention relates to an in-cylinder fuel injection device that can generate spray characteristics that can stably burn a lean air-fuel mixture.

[0002]

2. Description of the Related Art An in-cylinder fuel injection device for directly injecting fuel into a combustion chamber has been widely used, compared to an in-pipe fuel injection device for injecting fuel into an intake pipe of an engine.

Japanese Patent Application Laid-Open No. 6-146886 discloses a combustion chamber formed between the upper surface of a piston inserted into a cylinder and the lower surface of a cylinder head, and one side of a reference plane including a center axis of the cylinder. An intake opening end opening to the combustion chamber;
An intake port extending upward from the intake opening end, and formed on the cylinder head so as to be located on the other side of the reference plane;
An exhaust port communicating with the combustion chamber via an on-off valve; and an electromagnetic fuel injection arranged on an intake port side of the combustion chamber such that an injection port faces the combustion chamber. A valve, wherein the intake air introduced into the combustion chamber by the intake port is directed along the central axis from one side of the reference surface toward the upper surface of the piston from the lower surface of the cylinder head toward the upper surface of the piston. On the other side, a vertical vortex is formed from the upper surface of the piston toward the lower surface of the cylinder head. In order to promote the formation of the vertical vortex, the intake port of the intake port is moved to one half in the axial direction. An in-cylinder injection internal combustion engine characterized by being eccentric is disclosed.

[0004] With the above configuration, the electromagnetic fuel injection valve can be mounted in an optimal state for in-cylinder injection, and a strong tumble (longitudinal vortex) flow is formed in the combustion chamber to stabilize even lean combustion. That the engine can be operated.

On the other hand, FIG. 7 shows a main configuration diagram of a direct injection gasoline engine studied by the present inventors. Although details will be described later, the electromagnetic fuel injection valve attached to the direct injection gasoline engine has a 30 °
The injection hole is directed at a cavity (dent) provided on the piston upper surface. The intake air flow introduced from the intake valve portion is formed as a swirling flow flowing around the cavity to prevent the fuel spray injected from the electromagnetic fuel injection valve from adhering to the inner wall surface of the cylinder, and to form Leads to
The engine is configured to operate stably even in lean combustion. This type of direct injection gasoline engine selectively uses homogeneous combustion and stratified combustion depending on the load. According to the authors' experimental analysis results, in homogeneous combustion, it is necessary to diffuse the spray throughout the combustion chamber to homogenize the air-fuel mixture. In the combustion, it was found that it was necessary to make the spray angle narrow and compact because it was necessary to prevent the mixture from being excessively dispersed and to guide the combustible mixture around the spark plug.

In order to generate such a spray, the authors use a swirl-type electromagnetic fuel injection valve. As a related injection valve, there is an intermittent spiral injection valve described in JP-A-60-95186. In the injection valve, a needle valve is inserted into a valve hole provided in a valve body, and an injection hole is connected to a valve seat portion of the valve hole where the valve tip of the needle valve contacts, and the needle valve is a valve seat portion of the valve hole. A swirl injection valve that imparts a swirling motion to fuel when lifted and separated from the valve to open the fuel, wherein the opening area between the valve hole and the needle valve in the vicinity of the tangential passage is determined according to the lift amount of the needle valve. The characteristics such as the angle of fuel spray, penetration force (reach distance), and atomization are controlled in accordance with the lift amount of the needle valve.

[0007]

As described above, a widely dispersed spray is required for homogeneous combustion, and a compact spray is required for stratified combustion. To generate such a spray, a swirling force is applied to the fuel. A swirl type electromagnetic fuel injection valve to be provided is used.

[0008] The swirl type spray becomes a hollow conical shape having a cavity inside at atmospheric pressure, the liquid film at the outlet of the injection hole breaks up rapidly, and the momentum of the droplet is lost, so that the spray reaches. Is suppressed. On the other hand, under pressure, the reaching distance of the spray is suppressed by the increase in the atmosphere density, and the spray is reduced by the pressure difference between the inside and the outside, so that the spray becomes a compact solid structure in form.

The in-cylinder injection gasoline engine according to the present invention requires a wide-angle spray during homogeneous combustion and a compact spray during stratified combustion, and realizes stable combustion by utilizing such a change in the form of spray. ing. For this reason, it is necessary to generate a stable spray under atmospheric pressure. That is, variations in the spray shape under atmospheric pressure, that is, variations in solids and cycles, not only have a large adverse effect on combustion, but also significantly cause engine shutdown (misfire). Optimization of the structure became necessary. The main cause of the variation in the spray shape is due to the unstable operation of the valve member which operates with a gap of several microns at the inner diameter of the fuel swirling member constituting the swirl passage. That is, it is necessary to reduce the variation in the flow rate of the unswirled fuel passing through the gap.

In the former cited example, the design is devised in relation to the adaptation between the strong vertical vortex generated in the combustion chamber and the position of the injection port of the injection valve, and the relation between the timing of fuel injection and the ignitability. No special consideration has been given to
On the other hand, in the latter cited example, breakthrough consideration is given to maintaining macro characteristics such as spray angle and spray reaching distance optimally according to the operating conditions of the engine, but the characteristics of spray are treated from a micro perspective. Therefore, it cannot be said that much attention has been paid to the stabilization of lean combustion of the engine.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a swirl type electromagnetic fuel injection valve for use in a direct injection gasoline engine, in which a variation in the shape of spray is reduced to realize stable lean combustion.

[0012]

For this purpose, the in-cylinder fuel injection device according to the present invention has a fuel passage through which fuel flows, and a valve member for opening and closing the fuel passage. A fuel swiveling member that swirls the fuel upstream of the valve seat,
Further, a fuel injection hole is provided downstream of the valve seat to allow passage of fuel, and a fuel injection hole is provided between the outer wall of the valve member and the inner wall of the fuel swirl member, which perform an axial operation inside the fuel swirl member. Are formed as two different gaps in the axial direction.

[0013] The in-cylinder fuel injection device according to the present invention is provided with a fuel passage through which fuel flows, a valve member for opening and closing the fuel passage, and a fuel passage upstream of a valve seat portion of the valve member. A fuel swirl member that gives a swirl to the fuel valve, and a fuel injection hole that allows fuel to pass therethrough at a downstream side of the valve seat portion, and an outer wall of the valve member that performs an axial operation inside the fuel swirl member; The gap between the fuel swirling member and the inner wall is configured such that the gap is large at the upper part in the axial direction and the length is sufficiently long, and the gap is sufficiently small and the length is short at the lower part in the axial direction. (Line contact).

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a longitudinal sectional view of an electromagnetic fuel injection valve 1 for an in-cylinder fuel injection device showing one embodiment of the present invention, FIG. 2 is a longitudinal sectional view of a main part of an enlarged valve portion, and FIG. And FIG. 4 and FIG. 5 are diagrams showing injection characteristics confirmed by experiments. The structure and operation will be described with reference to each drawing.

The electromagnetic fuel injection valve 1 performs fuel injection by opening and closing a sheet portion in accordance with a duty ON-OFF signal calculated by a control unit. The magnetic circuit includes a core 2 having a bottomed cylindrical yoke 3, a plug 2 a for closing the open end of the yoke 3, and a columnar portion 2 b extending to the center of the yoke 3, and a gap in the core 2. And a plunger 4 facing the other. In the center of the columnar portion 2b, a plunger 4 and a rod 5, and a valve body 6 constituting a valve member (a ball-shaped member in this embodiment, other members as long as they serve as a valve, other members, etc. A spring 10 as an elastic member to be pressed is inserted into and held by a movable portion 4A formed of a nozzle member 7 on a sheet surface 9 on an upstream side of an injection hole portion 8 which allows fuel to pass therethrough. Holes are provided. The upper end of the spring 10 is in contact with the lower end of a spring adjuster 11 inserted into the center of the core 2 to adjust the set load. Columnar portion 2b of core 2
In order to prevent fuel from flowing out to the coil 14 side, a seal ring 12 that is mechanically fixed is provided between the gap portion facing the movable portion 4B side of the yoke 3 and the movable portion 4B.
A coil 14 for exciting the magnetic circuit is wound around the bobbin 13,
The outer periphery is molded with a plastic material. The terminals 17 of the coil assembly 15 composed of these are inserted into holes 16 provided in the flange of the core 2. This terminal 17
Are connected to terminals of a control unit (not shown). A plunger receiving portion 18 for receiving the movable portion 4A is opened at a bottom portion of the yoke 3, and a lower portion thereof is formed with a diameter larger than that of the plunger receiving portion 18 to receive the stopper 19 and the nozzle member 7. Nozzle receiving part 20
Extends through to the end of the yoke.

The movable part 4A is a plunger 4 made of a magnetic material.
And a rod 5 having one end joined to the plunger 4 and a valve element 6 joined to the other end of the rod 5. A hollow portion 5A is provided on the plunger 4 side of the rod 5 to allow fuel to pass therethrough. . The cavity 5A is provided with a fuel outlet 5B. The movable portion 4A is guided in its axial direction by the outer periphery of the plunger 4 abutting against the seal ring 12, and the valve body 6 joined to the other end is provided on the inner wall of the hollow portion of the nozzle member 7. Each of the guide members 21 is guided by being in contact with an inner wall of a cylindrical fuel swirling member 22 inserted into the fuel swirling member 21. The nozzle member 7 is provided with a sheet surface 9 for sheeting the valve element 6 following a cylindrical fuel swirl member 22 for guiding the valve element 6, and is formed at the center of the sheet surface 9. Are provided with injection holes 8 that allow the passage of fuel. The stroke of the movable portion 4A (the amount of upward movement of the shaft) is determined by the size of the gap between the receiving surface 5C of the neck of the rod 5 and the stopper 19. A filter 27 is provided to prevent dust and foreign matter in the fuel and pipes from entering the sheet.

Here, the flow flowing in the fuel swirling member 22 according to the present invention will be described with reference to FIGS. First, the flow will be described with reference to FIG. 3 showing a longitudinal sectional view of a valve portion before the injection valve is improved. The fuel swirling member 22 is provided with an axial groove 23 and a radial groove 24 connected to the axial groove 23. In the present embodiment, the axial groove 23 is formed by a D-cut surface, but may be another shape such as an annular passage. A hole 22a is provided in the center of the fuel swirling member 22, and the valve body 6 joined to the rod 5 is disposed in the hole 22a so as to be movable in the axial direction through a gap h. ing. The pressurized fuel is introduced from above the rod 5, passes through the axial groove 23, and then flows from the radial groove 24 to the downstream injection hole 8. At this time, the fuel is introduced eccentrically from the axial center in the radial groove 24. The so-called swirling is applied to the fuel to promote the atomization at the time of injection. A solid arrow attached to the figure indicates this swirling flow.
On the other hand, the fuel flowing through the gap h between the inner wall surface of the hole 22a and the outer wall surface of the valve body 6 does not pass through the radial groove 24, so that the fuel is not swirled and reaches the downstream injection hole 8. The dotted arrows in the figure indicate this flow, and this flow has an adverse effect on the injection characteristics. This is the so-called leakage amount considered in the present invention. The leakage amount ΔQ is given by the following equation.

[0018]

(Equation 1)

As shown in the above equation, the amount of leakage is proportional to the cube of the gap h. If the gap h is made sufficiently small, the amount of leakage is greatly reduced. However, realizing this in the dimensional control of parts requires high-precision machining on the order of submicrons, which leads to a significant increase in cost. Also, this gap h
Has a function as a guide portion of the valve body 6 which is a valve body, so that it is susceptible to dimensional variations, and its operation is slowed down due to an increase in solid frictional force on the valve body, or it is significantly locked to control the flow rate. Considerable design considerations such as the inability to perform Therefore, the gap h is usually designed to be in the range of several microns to several tens of microns. Under such design conditions, the valve element 6 is
Within a, the degree of freedom of movement increases and the amount of leakage also increases. In addition, the variation in the flow rate due to the ON-OFF operation also increases.

The above equation is for the case where the center of the valve body and the center of the hole 22a are concentric. When the eccentricity is maximum, the leakage amount becomes 2.5 times, so that it is necessary to further consider the variation in the flow rate. .

FIG. 2 is an enlarged sectional view of a main part of the valve according to the present invention. The design change is the fuel swivel member 2
In the second hole 22a, a fluid seal portion 26 having an axial length l and having a different clearance h2 is provided separately from the guide portion. The fluid seal portion 26 is constituted by a gap h2 between the outer wall portion of the rod 5 and the hole 22a, and its axial length l is sufficiently larger than the guide length le (at least 10 times or more). Designed. The gap h2 is designed to be sufficiently large (at least twice or more) as large as the gap h of the guide portion, and care is taken so as not to hinder the axial movement of the valve element.

FIGS. 4 and 5 show the injection characteristics of the valve structure according to the present invention. FIG. 4 shows the relationship between the valve body stroke and the injection flow rate. The solid line indicates the case where the fluid seal length is short (le), and the dotted line indicates the case where the fluid seal length is short (l).
Each case is shown. As is apparent from the figure, when the seal length is long, the flow rate sensitivity to the valve body stroke is reduced, and the flow rate variation is suppressed, so that the control accuracy can be improved. FIG. 5 shows the relationship between the length of the fluid seal and the spray angle. The increase in the seal length reduces the amount of leakage, stabilizes the swirling flow passing through the radial groove 24, and allows the spray to be sprayed. The angle is stabilized.

Returning to FIG. 1, the operation of the injection valve 1 will be described.

The injection valve 1 operates the movable portion 4A to open and close the valve sheet surface 9 in response to an electrical ON-OFF signal applied to the electromagnetic coil 14, thereby controlling fuel injection. When an electric signal is applied to the coil 14, a magnetic circuit is formed by the core 2, the yoke 3, and the plunger 4, and the plunger 4 is attracted to the core 2. When the plunger 4 moves, the valve body 6 integrated with the plunger 4 also moves away from the seat surface 9 of the valve seat of the nozzle member 7 to open the injection hole 8. The fuel is pressurized and adjusted through a fuel pump (not shown) and a regulator for adjusting the fuel pressure, flows into the injection valve 1 from the filter 27, and is supplied to the coil assembly 1.
5, lower passage, outer peripheral portion of plunger 4, stopper 19
The fuel is swirled and supplied to the sheet portion through the gap between the rod 5 and the axial groove 23 of the fuel swirling member 22 through the radial groove 24, and is injected through the injection hole 8.

In this embodiment, the amount of eccentricity Ls (distance between the groove center and the axis) of the radial groove 24 of the fuel swirling member 22 is increased to increase the turning force. When the swirling force is increased, the pressure energy of the fuel is effectively replaced by the swirling speed energy at the injection holes 8 and the fuel is formed into a film. Thereafter, it is injected in a hollow conical shape. In particular, in this embodiment, since the fluid seal portion 26 for suppressing the fuel flowing through the hole 22a in the fuel swirling member 22 is provided, a stable swirling flow is obtained from the radial groove 24, so that the fuel is formed into a film. move on. At this time, the liquid film is rapidly divided and atomized, and the momentum of the droplet is lost, so that the reaching distance is suppressed and the droplet is uniformly dispersed in the circumferential direction.

FIG. 6 shows a second embodiment of the present invention. In this embodiment, the tip of the valve body 28 has a conical shape, and other configurations are the same as those of the first embodiment. In this embodiment, the same operation and effect as those of the first embodiment are obtained. Further, in this embodiment, the flow path downstream of the valve seat portion is gradually narrowed, so that the flow is stabilized and the spray from the injection holes 8 is more uniform in the circumferential direction.

Next, the configuration and combustion operation of the in-cylinder direct-injection gasoline engine 60 used by the authors for the study will be described with reference to FIG. The figure shows an enlarged view of a main part around the engine. Reference numeral 61 denotes an intake air amount control device having a built-in throttle valve, and 62 denotes an intake air amount control device.
It is an intake manifold to which is attached. A cylinder head 63 has an intake valve 64 on the intake manifold 62 side, a spark plug 65 in the center, and an exhaust valve 66 on the side opposite to the intake valve 64.
Is provided. The electromagnetic fuel injection valve 1 for the in-cylinder fuel injection device according to the present invention is attached to the cylinder head 63 near the joint with the intake manifold 62 at an angle of 30 ° to 45 °. The injection direction is arranged so as to be directed to a cavity 69A provided in a piston 69 in the combustion chamber 67. 68 is a cylinder. In the drawing, white arrows indicate the flow of intake air, and hatched arrows indicate the flow of exhaust gas.

The gasoline engine controls the combustion state according to the load as follows. At partial load, stratified charge combustion is performed by late-stage in-cylinder injection (compression stroke injection), and at high load, homogeneous combustion is performed by the in-cylinder injection (intake stroke injection). In the stratified combustion, a layer of a rich air-fuel mixture is formed in the vicinity of the ignition plug 65 to realize stable combustion of a lean air-fuel mixture. In the homogeneous combustion, the mixture is homogenized in the entire combustion chamber, thereby realizing the premixed lean combustion. These aim at realizing both low fuel consumption and high output at the same time, and the spray injected from the electromagnetic fuel injection valve 1 for the in-cylinder fuel injection device has the optimum injection timing during the intake and compression strokes. Is generated according to The injection signal is issued by a control unit (not shown) based on the operation information of the engine.
The figure shows the state of fuel injection during the intake stroke. The atomized fuel is uniformly dispersed in the combustion chamber 67, and the small-diameter droplets having a low velocity are promptly mixed with the air in the combustion chamber 67. You. Thereafter, the air-fuel mixture is compressed in the compression stroke and ignited by the spark plug 65, thereby realizing stable lean combustion in which the amount of emission of unburned gas is suppressed.

[0029]

As described above, according to the present invention,
The axial movement of the valve body in the fuel swirling member can be stably maintained, and the leakage flow between the inner wall of the fuel swirling member and the valve body can be kept constant. As a result, variations in the injection flow rate and the spray angle are reduced, and sprays that are symmetrical in the circumferential direction and that are uniformly dispersed are generated. When such spray is supplied to the combustion chamber of a direct injection gasoline engine, mixing with air is promptly promoted, and lean mixed combustion is realized, so that the emission of unburned gas components is reduced and fuel efficiency is improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an electromagnetic fuel injection valve for an in-cylinder fuel injection device according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of the vicinity of the tip end portion of the fuel injection valve of the present invention.

FIG. 3 is a cross-sectional view around a valve section before the improvement.

FIG. 4 is a diagram showing a relationship between a valve body stroke and an injection flow rate.

FIG. 5 is a view showing a relationship between a length of a fluid seal provided on a fuel swirling member and a spray angle.

FIG. 6 is a sectional view showing the vicinity of a leading end of an electromagnetic fuel injection valve according to a second embodiment of the present invention.

FIG. 7 is an enlarged view of a main part of a direct injection gasoline engine incorporating the electromagnetic fuel injection valve of the present invention.

[Description of Signs] 1 ... Electromagnetic fuel injection valve, 6 ... Valve, 8 ... Fuel injection hole, 2
2 ... fuel swivel member, 23 ... axial passage, 24 ... radial passage, 26 ... fluid seal part.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Makoto Yamamon 502, Kandachi-cho, Tsuchiura-shi, Ibaraki Pref. Machinery Research Laboratories, Hitachi, Ltd. (72) Inventor Shozo Uehara 2520 Ojitakaba, Hitachinaka-shi, Ibaraki Pref. Hitachi, Ltd.Automotive Equipment Business (72) Katsuya Onuki 2520 Ojitakaba, Hitachinaka-shi, Ibaraki Hitachi, Ltd. 3G066 AA02 AA04 AB02 AD12 BA17 BA26 CC06U CC14 CC20 CC21 CC43 CC48 CD10 CE22 DA01

Claims (3)

[Claims] 1. An electromagnetic fuel injection valve for directly injecting fuel into a combustion chamber of an internal combustion engine, comprising: a valve member formed therein with a fuel passage through which fuel flows, for opening and closing the fuel passage;
A fuel swirling member that gives fuel swirl upstream of a valve seat of the valve member; and a fuel injection hole that allows passage of fuel downstream of the valve seat, wherein an axial direction is provided inside the fuel swirling member. The in-cylinder fuel injection device, wherein a gap between an outer wall of the valve member and an inner wall of the fuel swirling member that performs an operation is configured as two different gaps in an axial direction. 2. An electromagnetic fuel injection valve for directly injecting fuel into a combustion chamber of an internal combustion engine, wherein a valve member for forming a fuel passage through which fuel flows and opening and closing the fuel passage is provided.
A fuel swirling member that gives fuel swirl upstream of a valve seat of the valve member; and a fuel injection hole that allows passage of fuel downstream of the valve seat, wherein an axial direction is provided inside the fuel swirling member. A gap is provided between the outer wall of the valve member and the inner wall of the fuel swirling member that perform the operation, the gap at the upper part in the axial direction is large, the length is configured to be sufficiently long, and the lower part in the axial direction is formed. An in-cylinder fuel injection device, wherein a gap is sufficiently small and a length thereof is short (line contact). 3. An electromagnetic fuel injection valve for directly injecting fuel into a combustion chamber of an internal combustion engine, wherein a valve member for forming a fuel passage through which fuel flows and opening and closing the fuel passage is provided.
A fuel swirling member that gives fuel swirl upstream of a valve seat of the valve member; and a fuel injection hole that allows passage of fuel downstream of the valve seat, wherein an axial direction is provided inside the fuel swirling member. A gap between an outer wall of the valve member and an inner wall of the fuel swirling member, which operates, is configured as a fluid seal portion at an upper portion in an axial direction for maintaining a constant amount of fuel passing through the gap, and an axial direction. The in-cylinder fuel injection device, characterized in that the gap is formed at a lower part of the cylinder as a guide portion for stably performing the axial operation of the valve member.