JPH08200168A - Fuel gasifying device, fuel feeding device, and fuel gasifying method - Google Patents

Abstract

PURPOSE: To further increase the vaporizing speed of fuel liquid drips by a method wherein fuel liquid drips are suppressed from floating from heating surface heated to temperature higher than a Leidenfrost point. CONSTITUTION: A groove 7 on the surface layer 6a of which a heater 6 is formed is arranged in an intake manifold between an fuel injector and a combustion chamber in such a manner to cross a fuel flow passage at right angles. The surface 6a is formed in such a manner that conduction layers 11 and 12 are formed with a heater layer 8 nipped therebetween through the medium of insulation layers 9 and 10, and the exposure surfaces 11a and 12a of two conduction layers 11 and 12 are exposed to the inner surface of the groove 7 in a V-shape in cross section. In the groove 7, an electrical field extending from the exposure surface 11a of a plus potential to an exposure surface 12a of a minus potential is generated based on a power source 14. When liquid drips of fuel injected to a fuel injector and lowering are arrested by the groove 7, the liquid drips are pressed against a floating force generated by own steam pressure and held on the inner wall surface of the groove 7 heated to temperature higher than a Leindenfrost point through an EHD effect by an electrical field in the groove 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel vaporization device, a fuel supply device and a fuel vaporization method for vaporizing droplets of fuel injected from a fuel injector while being sent to a combustion chamber.

[0002]

2. Description of the Related Art In order to improve fuel efficiency of an engine and clean exhaust gas, it is preferable that almost complete combustion be realized in a combustion chamber. For that purpose, it is desirable that the fuel sent to the combustion chamber be sufficiently atomized (atomized).

For example, Japanese Laid-Open Patent Publication No. 5-26130 discloses a fuel injector with a heater that can preheat fuel before injection in order to efficiently atomize fuel such as gasoline injected from the fuel injector. It is disclosed.

Further, in Japanese Unexamined Patent Publication No. Sho 49-120023, the heating surface provided at the bottom of the fuel vaporizer is heated by the residual heat of the exhaust gas, and the fuel which has not been completely atomized in the vaporizer is heated. There is disclosed a fuel vaporization device that realizes complete vaporization (including atomization) of fuel by vaporizing the fuel. In this fuel vaporizer, the amount of exhaust gas flowing to the heating surface side is controlled by a baffle that opens and closes via a diaphragm based on the pressure difference between the intake pressure and exhaust pressure of the engine. The temperature of the heating surface is controlled according to the change of the intake pressure of the fuel sucked into. The heating surface is set to a temperature at which the fuel is in a nucleate boiling state. Nucleate boiling produces many bubbles in the droplet,
Since vaporization proceeds not only from the surface of the droplet but also from inside the droplet, the evaporation rate is maximized and the fuel can be vaporized most efficiently. Further, Japanese Patent Application Laid-Open No. 49-120023 discloses, in addition to this structure, a device provided with an electric heater on the heating surface.

[0005]

FIG. 19 is a graph showing the relationship between heater temperature and fuel evaporation time. As shown in the figure, while the fuel temperature is relatively low, vaporization progresses from the droplet surface, and bubbles start to form in the droplet as the temperature rises. Therefore, the evaporation rate becomes maximum. When the heater temperature is higher than the nucleate boiling, a Leidenfrost phenomenon occurs in which the droplet F floats from the heating surface 41 by its own vapor pressure as shown in FIG. 20, resulting in a so-called film boiling state. When the heating surface 41 is heated above the temperature (Landenfrost point) TL at which the Leidenfrost phenomenon occurs, the droplet F and the heating surface 4 are heated.
The contact surface with 1 is lost, heat transfer from the heating surface 41 to the droplet F is significantly impaired, and the evaporation rate is significantly reduced (FIG. 19).

Further, the heating surface 41 has a Leidenfrost point T.
Under the condition of being heated above L, the liquid droplet F floating from the heating surface 41 is sent to the combustion chamber without being completely vaporized by the intake air flow generated in the flow path as shown in FIG. The problem arises. Therefore, the set temperature of the heating surface 41 needs to be lower than the Leidenfrost point TL so that the droplet F is in the nucleate boiling state. This is
It is also mentioned in JP-A-49-120023,
Due to the Leidenfrost phenomenon, it is said that when the heater temperature is raised too high, it has a reverse effect. In other words, the occurrence of the Leidenfrost phenomenon has been a major cause of being unable to raise the evaporation rate further (more than in the nucleate boiling state). As shown in FIG. 19, if the temperature of the heating surface 41 is further increased from the Leidenfrost point TL, the evaporation rate becomes higher than that in the nucleate boiling state, but at such a high temperature, the mixture The filling rate of will be significantly reduced.

The present invention has been made in order to solve the above problems, and its purpose is to suppress the lifting of fuel droplets from a heating surface heated above the Leidenfrost point to thereby prevent the formation of fuel droplets. An object of the present invention is to provide a fuel vaporization device, a fuel supply device, and a fuel vaporization method capable of further increasing the evaporation rate.

[0008]

In order to solve the above problems, in the invention described in claim 1, a heating surface is arranged on the fuel flow path for sending fuel droplets to the combustion chamber, and the heating surface is used. In the fuel vaporization method of vaporizing the droplets, an electric field is generated around the heating surface, and a force in the heating surface direction is applied to the droplets.

According to the second aspect of the present invention, a heating surface having a constant area is provided, and the droplets of fuel attached to the heating surface are heated.
A fuel vaporizer for vaporizing and improving a combustion state of fuel in a cylinder of an engine, comprising electric field generating means for exerting a force in the heating surface direction on the droplet on the heating surface.

According to a third aspect of the present invention, there is provided a fuel vaporization device in which a heating surface having a constant area is arranged on a fuel flow path for sending fuel droplets to the combustion chamber, and the liquid of the fuel adhered to the heating surface. At least one pair of electrodes capable of generating an electric field therebetween was provided with a pair of electrodes that the droplets can straddle and contact.

In the invention of claim 4, the pair of electrodes are formed on the heating surface. In the invention according to claim 5, the pair of electrodes is a first electrode formed on the heating surface.
Electrode and a second electrode spaced apart from the heating surface.

In the invention according to claim 6, a recess is formed in the heating surface, and the pair of electrodes are formed in an exposed state on the inner surface of the recess. In the invention according to claim 7, at least one of the pair of electrodes is formed to project from the heating surface.

According to an eighth aspect of the invention, the pair of electrodes are formed on the heating surface so as to extend in a direction transverse to a fuel flow path for sending the droplets to the combustion chamber in parallel at a predetermined interval. It was In the invention according to claim 9, in the surface layer of the fuel vaporizer that forms the heating surface, conductive layers are formed in multiple layers with an insulating layer interposed, and in the pair of electrodes, the conductive layer is on the heating surface. Formed exposed.

According to a tenth aspect of the present invention, the surface layer of the fuel vaporizer forming the heating surface is a heater layer as a heat source for heating the heating surface, and the pair of electrodes on the heating surface. And a plurality of conductive layers for exposing the film are formed in multiple layers with an insulating layer interposed therebetween.

According to the invention of claim 11, claim 10 is provided.
In the fuel vaporizer, the heater layer is formed so as to be sandwiched between the conductive layers so as to contact the conductive layers so that the heater layers have a resistance value capable of generating heat at a predetermined temperature based on a voltage applied between the conductive layers. Was set.

In a twelfth aspect of the invention, a fuel injector for injecting the fuel is provided in the vaporization chamber,
The heating surface of the fuel vaporization device according to any one of claims 2 to 11 is arranged at the bottom of the vaporization chamber.

According to a thirteenth aspect of the present invention, a discharge port of a passage that connects the vaporization chamber and the intake manifold is provided at a position above the heating surface by a predetermined distance, and the fuel from the vaporization chamber is provided on the passage. A valve for controlling the supply amount of

According to a fourteenth aspect of the present invention, the heating surface of the fuel vaporizer according to the fifth aspect is arranged at the bottom of the vaporization chamber where the fuel injector is provided, and the fuel injector is directed to the fuel injector. A large number of electrode rods serving as the second electrodes were suspended from the above, and the lower ends of the electrode rods were arranged so as to be separated from the first electrodes exposed on the heating surface by a predetermined distance.

[0019]

Therefore, according to the first aspect of the invention, the electric field generated around the heating surface disposed on the fuel flow path causes
A force in the direction of the heating surface acts on the fuel droplets. Therefore, even if the heating surface is heated to a temperature equal to or higher than the Leidenfrost point, the droplet is pressed against the heating surface and heated in contact with the heating surface.

According to the second aspect of the invention, the electric field generated by the electric field generating means exerts a force on the droplet of the fuel in the direction of the heating surface. Therefore, even if the heating surface is heated to a temperature equal to or higher than the Leidenfrost point, the droplet contacts the heating surface against the lifting force due to its own vapor pressure and is heated in the contact state. Further, even if the droplets are separated from the heating surface, if they receive a force acting in the direction of the heating surface, they become a crushed shape and the heat receiving area increases to promote vaporization.

According to the third aspect of the present invention, the droplets of the fuel adhering to the heating surface having a certain area are in contact with each other in such a state as to straddle at least a pair of electrodes provided in a pair or more. By the force received from the electric field generated between the electrodes, the heating surface is held in an attached state.

According to the fourth aspect of the invention, since the pair of electrodes is formed on the heating surface, the fuel droplets adhering to the heating surface are affected by the force received from the electric field generated between the electrodes. It is brought into contact with the heating surface.

According to the fifth aspect of the present invention, the droplets of the fuel adhering to the heating surface include the first electrode formed on the heating surface and the second electrode arranged apart from the heating surface. The electrodes are in contact with each other across the electrodes and are brought into contact with the heating surface heated to a temperature equal to or higher than the Leidenfrost point by the force received from the electric field generated between the electrodes.

According to the sixth aspect of the present invention, when the fuel droplets adhering to the heating surface come into contact with the recess formed on the heating surface, they are guided into the recess by the capillary phenomenon, and the inner wall surface of the recess. The pair of electrodes that are exposed and contact each other. In addition, the surface layer of the heating surface is formed of a multilayer conductive layer,
By forming the concave portion in the surface layer, it becomes possible to expose the pair of electrodes on the inner wall surface by a relatively simple manufacturing method.

According to the seventh aspect of the present invention, the liquid droplets adhering to the heating surface at portions other than the pair of electrodes float up from the heating surface heated above the Leidenfrost point due to the vapor pressure, and the intake flow On the way of being carried along the heating surface by, for example, it collides with the electrode protruding from the heating surface and makes contact with the other electrode, and the force due to the electric field between the electrodes causes the heating on the heating surface. To be in contact with.

According to the eighth aspect of the present invention, the liquid droplets adhering to the heating surface at a portion other than the pair of electrodes form a portion with the heating surface heated to a temperature equal to or higher than the Leidenfrost point by its vapor pressure. There is little contact, it moves like rolling on the heating surface due to the intake air flow, etc., it contacts across a pair of electrodes extending across the fuel flow path midway, and due to the force based on the electric field generated between the electrodes It is brought into contact with the heating surface.

According to the ninth aspect of the present invention, even if there are a plurality of pairs of electrodes exposed on the heating surface, the plurality of pairs of electrodes are connected through the conductive layer, so that the power source and each conductive layer are connected. A predetermined potential can be applied to a plurality of pairs of electrodes only by connecting and.

According to the tenth aspect of the present invention, since the heater layer as a heat source is formed on the surface layer forming the heating surface, the heat of the heater layer that generates heat in the layer just below the heating surface is generated. Is immediately transferred to the heating surface.

According to the eleventh aspect of the present invention, the heater layer sandwiched in contact with the conductive layer in a state capable of conducting electricity is
Heat is generated to a predetermined temperature by the current flowing through itself based on the applied voltage between the conductive layers. Therefore, it is not necessary to form an insulating layer between the conductive layer and the heater layer, and the manufacturing of the fuel vaporizer becomes relatively easy.

According to the twelfth aspect of the invention, fuel is injected from the fuel injector into the vaporization chamber. Among the injected fuel, the liquid droplets attached to the heating surface arranged at the bottom of the vaporization chamber are held on the heating surface heated to the temperature above the Leidenfrost point and quickly vaporized.

According to the thirteenth aspect of the present invention, only the atomized fuel injected from the fuel injector or the fuel vaporized on the heating surface is provided at a predetermined distance above the heating surface. The fuel is supplied from the outlet to the intake manifold through the passage, and the amount of fuel supplied is controlled by opening and closing the valve.

According to the fourteenth aspect of the invention, the fuel injected from the fuel injector is injected to a large number of electrode rods, and almost all of the fuel adheres to the electrode rods. The fuel droplets that have descended along the electrode rod come into contact with both electrodes so as to straddle the first electrode exposed on the heating surface at the lower end, and are based on the electric field generated between the electrodes. By force, even if the heating surface is heated to a temperature above the Leidenfrost point, it is held on the heating surface and quickly vaporized. Then, only the vaporized fuel is supplied to the combustion chamber.

[0033]

【Example】

(First Embodiment) A fuel supply system according to a first embodiment of the present invention will be described below with reference to FIGS.

As shown in FIG. 2, the combustion chamber 2 of the engine 1
An intake manifold 4 is connected to the intake manifold 4 via an intake valve 3. Inside the intake manifold 4, a fuel injector 5 is provided upstream of the intake valve 3 by a predetermined distance in a state in which a nozzle 5a of the fuel injector 5 projects into the intake manifold 4. The heater 6 for fuel vaporization is arranged in the intake manifold 4 at a position corresponding to the injection direction of the fuel injector 5. The heater 6 has a surface layer portion 6a formed in multiple layers.
Is formed on the base material 6b. The base material 6b is for ensuring necessary strength, and the surface layer portion 6a is formed to have a thickness of 1 mm or less.

As shown in FIGS. 1 and 4, the surface layer portion 6a is a heater layer 8 made of PTC ceramic, and stainless steel and copper formed on the upper and lower sides of the heater layer 8 via insulating layers 9 and 10, respectively. Layer 1 made of conductive material such as
It is composed of 1 and 12. On the surface (upper surface) S of the heater 6, a large number of grooves 7 having a V-shaped cross section are formed so as to extend parallel to each other as shown in FIG. 3, and the depth of the grooves 7 reaches the conductive layer 12. Therefore, the cross sections of the conductive layers 11 and 12 are exposed on the inner surface of the groove 7 to form exposed surfaces 11a and 12a as a pair of electrodes. As shown in FIG. 3, the groove 7 is not cut to the end, and the layers 8, 11, and 12 forming the surface layer portion 6a are not divided by the groove 7 and are connected to each other at the end portion. The heater 6 is arranged so that the groove 7 is orthogonal to the axis of the intake manifold 4.

The exposed surfaces 11a, 12a are in a state in which the liquid droplets F trapped in the groove 7 are spaced apart so that they can contact the exposed surfaces 11a, 12a. That is, the width and depth of the groove 7 and the interval between the exposed surfaces 11a and 12a are determined by the particle size distribution of the liquid droplets F ejected from the fuel injector 5 and adhering onto the heater 6, so that complete combustion can be realized. Therefore, it is possible to capture the droplets F having a critical particle size or more, which are allowed to be sent to the combustion chamber 2, in the groove 7, and the droplets F are exposed to the exposed surfaces 11a, 1a.
It is set so that it can be contacted across 2a. In this embodiment, the groove width is set so that the droplet F can be captured in the groove 7 by the capillary phenomenon. Further, the gap between the grooves 7 is set such that the liquid droplets F adhered to the surface S of the heater 6 other than the grooves 7 are less in contact with the surface S due to the vapor pressure thereof and are rolling on the surface S by the intake air flow. The distance is set so as to be caught in the groove 7, that is, to be caught in the groove 7 before being completely lifted and blown. The average particle size of the fuel injected from the fuel injector 5 of this embodiment is about 300 μm.

In this embodiment, each of the layers 8 to 12 is manufactured by a method such as thick film formation or thin film formation on the substrate 6b,
The groove 7 is formed by carving the surface of the heater 6 on which the layers 8 to 12 are formed to a predetermined depth using, for example, a laser.

As shown in FIGS. 1 and 3, the heater layer 8 is connected to a power source 13 such as a battery so that a predetermined voltage is applied in the longitudinal direction of the groove 7. A power supply 14 is applied to the conductive layers 11 and 12 so that a predetermined voltage is applied between the conductive layers 11 and 12 so that the exposed surface 11a has a positive potential and the exposed surface 12a has a negative potential.
Connected with. In this embodiment, both exposed surfaces 11a, 12
About 300V is applied between a. Since the heater layer 8 and the conductive layers 11 and 12 are connected to each other, the number of connection points with each power source 13 and 14 is one.

The Curie temperature of the PTC ceramic which is the material of the heater layer 8 is set to about 300.degree.
The upper layers 9 and 11 of the heater layer 8 are extremely thin (several tens to several hundreds μ).
m), the surface temperature of the heater 6 reaches about 300 ° C. when the heater layer 8 generates heat. Therefore, in the normal intake pressure range (1 atm or less) when the engine is driven,
The surface temperature of the heater 6 is the Leidenfrost point TL (1 atm
Temperature is about 150 ° C) or higher.

In general, when a droplet is brought into contact with the pair of electrodes so as to straddle the electrodes while an electric field is generated between the pair of electrodes, a force corresponding to the ionization degree and the magnitude of the electric field is applied to the droplet. The electro-hydrodynamics (EHD) effect that acts from one electrode toward the other is known. For example, gasoline, light oil, which is usually used as fuel,
A force acts on the liquid such as methanol in the direction of the electric field due to its polarity.

In this embodiment, the exposed surface 1 when the engine is driven
About 300 V is applied between 1a and 12a, and an electric field is generated from the exposed surface 11a having a positive potential to the exposed surface 12a having a negative potential as indicated by an arrow in FIG. The droplet F directly attached to the groove 7 or the droplet F carried to the groove 7 so as to roll on the surface S of the heater 6 is EH.
Due to the suction force based on the D effect, it is pressed against and held by the inner wall surface of the groove 7 while being in contact with both exposed surfaces 11a, 12a against the floating force due to the Leidenfrost phenomenon. There is.

Next, the operation of the fuel vaporizer will be described. When the ignition key is turned on and the engine 1 is run, about 300 V is applied between the exposed surfaces 11a and 12a to generate an electric field in the direction shown by the arrow in FIG. 5A, and the heater layer 8 is energized. . The heater layer 8 will eventually be about 3
When the temperature reaches 00 ° C, the surface S of the heater 6 is heated to about 30
Heat to 0 ° C.

Of the fuel injected from the fuel injector 5, the droplets F that have not been sufficiently atomized fall onto the surface S of the heater 6 and adhere to them. The droplet F directly attached to the groove 7 or the droplet F attached to the groove 7 and trapped in the groove 7 by the capillary phenomenon is, as shown in FIG. 5B, exposed to the exposed surfaces 11a and 12a. It is pressed across the inner wall surface of the groove 7 against the force of rising due to its own vapor pressure due to the attraction force in the direction of the electric field due to the EHD effect based on the electric field generated during the contact. Held to be attached.

Further, the liquid droplet F adhered to the surface S except the groove 7
As shown in FIG. 5B, the surface S is caused by its own vapor pressure.
The contact with the surface is reduced, and the surface moves due to the intake air flow so as to roll and is captured by the groove 7. At this time, the path to the groove 7 is not so long, and the droplet F is captured by the groove 7 before being separated from the surface S. Therefore, most of the droplets F that have dropped onto the surface S (except those that have vaporized before reaching the groove 7) are sequentially captured by the groove 7 and lifted by their own vapor pressure by the suction force of the EHD effect. It is held so as to be pressed against its inner wall surface against the force.

The droplet F has a groove 7 heated to about 300.degree.
Heat is efficiently transferred from the inner wall surface through a wide contact surface with the inner wall surface of the. Therefore, despite the fact that the surface S is heated to about 300 ° C., which greatly exceeds the Leidenfrost point TL, the liquid droplet F is apparently in a state of nucleate boiling on the surface S, and the large evaporation rate makes it quick Be vaporized. Then, only the fuel atomized or vaporized to have a particle size smaller than the critical particle size suitable for realizing complete combustion is supplied to the combustion chamber 2.

As described in detail above, according to the fuel vaporization apparatus of this embodiment, the heater 6 is exceeded beyond the Leidenfrost point TL.
Even if the surface S is heated, the attraction force by the EHD effect based on the electric field generated on the exposed surfaces 11a and 12b causes the droplet F to be a groove that is a part of the surface S against the lifting force due to its vapor pressure. It can be held so as to be pressed against the inner wall surface of 7. Therefore, heat can be transferred from the surface S to the droplet F in a state of being in contact with the surface S of the heater 6 that has been heated beyond the Leidenfrost point TL, and at the temperature for nucleate boiling described in the prior art. The evaporation rate of the fuel droplets can be significantly improved as compared with the heater that heats the heating surface. Therefore, it is possible to supply to the combustion chamber 2 a mixture having a fuel concentration that corresponds well to the amount of fuel injected from the fuel injector 5. Further, since the fuel in the air-fuel mixture supplied to the combustion chamber 2 is all atomized or vaporized, it becomes possible to operate the engine 1 with a lean air-fuel mixture having an appropriate concentration, and to realize almost complete combustion. You can Therefore, the unburned fuel is eliminated and the exhaust gas can be purified, and the fuel consumption can be improved.

Further, since the material of the heater layer 8 is PCT ceramic, temperature control is not required, and a circuit for temperature control is not required, and the temperature rise is immediately effective. Further, since the opening width of the groove 7 is formed to be a groove width that allows the droplet F to be taken in by the capillary phenomenon, the droplet F can be taken in smoothly to the depth of the groove 7 to expose the exposed surfaces 11a, 12a.
It is possible to make contact so as to straddle. Further, the liquid droplets F that are attached to the corners of the groove 7 in a state that a part of the groove 7 is covered with the groove 7 can be taken into the groove 7 by the capillary phenomenon.

Further, the two conductive layers 11, 1 are formed on the substrate 6b.
2 is formed, and the groove 7 is formed in the surface layer portion 6a.
Since a cross section of each conductive layer 11 and 12 is exposed by carving to form a pair of electrodes (exposed surfaces 11a and 12a), a surface S on which a pair of electrodes are arranged with an interval that the droplet F straddles is provided. The heater 6 can be manufactured by a relatively simple manufacturing method. Further, since the groove 7 is formed without being cut to the end of the surface S so as not to divide each layer 8, 11, 12 in the plane direction, the wiring from the power supply 13, 14 can be connected at one or two places for each layer. I can finish it. Further, since the heater layer 8 which is a heat source is formed on the surface layer portion 6a, the surface S can be heated immediately with good effect, and the heat of the heater layer 8 is used for heating the surface S without waste.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS. 6 and 7. The fuel supply system of this embodiment is greatly different from the fuel supply system of the first embodiment in that it has a vaporization chamber.

As shown in FIG. 6, the fuel injector 5 connected to the fuel tank 21 has its injection nozzle 5a.
Is disposed in a state of being projected into the vaporization chamber 22. The fuel injector 5 is set so that the ejected droplet F has a larger particle diameter than that of the first embodiment. A heater 23 is arranged at the bottom of the vaporization chamber 22. The heater 23 has a two-layer structure and is composed of an upper conductive layer 24 made of a conductive material as a first electrode and a lower heater layer 8 made of PCT ceramic. That is, the surface S of the heater 23 is composed of the conductive layer 24.

In the vaporization chamber 22, a large number of electrode rods 2 as second electrodes are provided in the fuel injection region of the fuel injector 5.
5 is suspended, and almost all of the fuel F injected from the fuel injector 5 adheres to the electrode rod 25. The electrode rod 25 hangs down in a state of being slightly separated from the surface S of the heater 23, and the liquid droplet F that has propagated to the electrode rod 25 and descended through the gap is the electrode rod 25 and the conductive layer 24 as shown in FIG. It is set so as to be capable of contacting the surface S formed by.

As shown in FIG. 6, the conductive layer 24 and the electrode rod 25 are connected to the power source 14 of 300 V, and the conductive layer 24 is applied to the ground potential and the electrode rod 25 is applied to the positive potential. The heater layer 8 is connected to a power source 13 and its Curie temperature is set to about 300 ° C.

The vaporization chamber 22 is communicated with the intake manifold 4 via a passage 26, and an electromagnetic valve 27 for controlling the supply amount of vaporized fuel sent from the vaporization chamber 22 to the intake manifold 4 is provided on the passage 26. There is. The operation of the electromagnetic valve 27 is controlled by an ECU (not shown). A passage 26 is provided in the vaporization chamber 22.
The exhaust port connected to the above is provided at a position above the surface of the heater 23 at a predetermined distance, and only the fuel vaporized in the vaporization chamber 22 is supplied to the intake manifold 4 via the passage 26. .

Now, when the ignition key is turned on and the engine 1 is driven, the direction from the electrode rod 25 to the surface S is changed between the electrode rod 25 and the surface S of the heater 23 as shown by the arrow in FIG. An electric field is generated and the heater layer 8
Is energized and the temperature of the heater 23 rises to about 300 ° C. Fuel F injected from the fuel injector 5
Almost adheres to a large number of electrode rods 25, further descends along the electrode rods 25, and as shown in FIG.
And the surface S are in contact with each other.

Here, the droplet F is pressed against the surface S against the lifting force due to its vapor pressure by the suction force by the EHD effect based on the electric field generated between the electrode rod 25 and the surface S. Held in a state. Therefore, about 30
Heat is transferred from the surface S of the heater 23 heated to 0 ° C. to the droplet F through the widely secured contact surface, and the droplet F is heated on the surface S heated above the Leidenfrost point TL. Appears to be like a nucleate boiling,
Evaporate quickly. Then, only the fuel completely vaporized in the vaporization chamber 22 is supplied to the intake manifold 4 through the passage 26 by the opening / closing control of the electromagnetic valve 27.
Since the exhaust port connected to the passage 26 is provided above the surface S of the heater 23, it is possible to prevent the fuel droplets from being accidentally supplied to the intake manifold 4.

Therefore, all the fuel injected from the fuel injector 5 is vaporized in the vaporization chamber 22 and only the vaporized fuel can be supplied to the combustion chamber 2 via the intake manifold 4, so that the complete combustion by the lean mixture is completed. It is possible to realize the above, realize the purification of the exhaust gas, and improve the fuel efficiency. Further, the evaporation rate of the fuel can be further increased as compared with the conventional configuration, and the vaporized fuel in the vaporization chamber 22 is always kept at a desired concentration so as to correspond to the control of the injection amount from the fuel injector 5. The density adjustment is realized at the timing according to the request. Further, according to the present embodiment, all of the injected fuel is vaporized, so that there is no problem even if the injection particle size of the fuel injector 5 is large.

The present invention is not limited to the above embodiments, but may be configured as follows, for example, without departing from the spirit of the invention. (1) As shown in FIG. 8, a plurality of spots 28 may be formed on the entire surface instead of the groove 7, and the exposed surfaces 11a and 12a may be formed on the inner surface of the spot 28. In this case, the diameter of the spot 28 may be set so that the droplet F causes a capillary phenomenon. With this configuration, the same effect as in the first embodiment can be obtained.

(2) As shown in FIG. 9, the conductive layers 11, 1
2 may be exposed flush with the surface S of the heater 6 to form exposed surfaces 11a and 12a as a pair of electrodes. In the case of this configuration, the exposed surface 12a may be formed to extend in a strip shape on the surface S as shown in FIG. 10, or the exposed surface 12a may be formed to be scattered on the surface S as shown in FIG. Good. With this configuration, the same effect as that of the first embodiment can be obtained.
When the heater 6 of FIG. 10 is arranged such that the longitudinal direction of the exposed surface 12a is orthogonal to the axis of the intake manifold 4, the surface S of the heater 6 is exposed except for the exposed surfaces 11a and 12a.
The droplet F that adheres to the surface of the heater 6 and moves in a rolling manner with less contact with the surface S of the heater 6 can be reliably captured on the exposed surfaces 11a and 12a during the movement. Therefore, by reducing the number of exposed surfaces 12a formed on the surface S and the occupied area thereof, the manufacturing of the heater 6 can be made relatively simple.

(3) As shown in FIG. 12, the conductive layer 12 may be protruded from the surface S of the heater 6 and the protruding portion 12b may be formed as an electrode. The protrusions 12b may be formed in a convexly extending state as shown in FIG. 13, or the protrusions 12b may be formed by being scattered on the surface S as shown in FIG. According to this configuration, the liquid droplet F that does not directly adhere to the exposed surfaces 11a and 12a but temporarily rises from the surface S of the heater 6 and moves along the surface S due to the Leidenfrost phenomenon.
Are collided with the protruding portion 12b and captured, and both exposed surfaces 11
It can be held on the surface S by making contact with a and 12a. Therefore, even if the number of the protrusions 12b is small, the droplets F are not missed.
By relatively reducing the number of 2b or the occupied area thereof, the manufacture of the heater 6 can be made relatively simple. Of course, the droplets F moving to roll on the surface S due to their own vapor pressure are also reliably captured by the protrusion 12b.

(4) The smaller the particle size of the droplet F, the slower the descending speed, and the particle size of the droplet F adhering to the surface S tends to become smaller toward the downstream side. The diameters and intervals of the spots 28 (FIG. 8), the exposed surface 12a (FIG. 11), and the protruding portions 12b (FIG. 14) are determined by the droplets F to which they adhere
It may be changed individually depending on the location depending on the particle size distribution of. In addition, the width and interval of the groove 7 (FIG. 4), the exposed surface 12a (FIG. 10), and the protruding portion 12b (FIG. 13) formed in a strip shape on the surface S are changed depending on the location according to the particle size distribution of the droplet F. May be. Furthermore, the protrusion length of the protrusion 12b in FIGS. 13 and 14 may be changed depending on the location. For example, the diameter, the width, and the interval may be set to be smaller as the distance from the fuel injector 5 increases to the downstream side.

(5) A groove 7 (FIG. 4) formed in a belt shape on the surface S, an exposed surface 12a (FIG. 10), and a protruding portion 12b (FIG. 1).
3) may be formed so as to extend in a curved line. For example, it may be spiral or zigzag.

(6) Spots 28 formed on the surface S (FIG. 8), exposed portions 12a (FIG. 11), and protruding portions 12
b (FIG. 14) may be arranged in a staggered pattern. It can be arranged more densely on the surface S.

(8) The conductive layers 11 and 12 and the heater layer 8 may be connected to a common power source. For example, as shown in FIG. 15, the conductive layers 11 and 12 and the heater layer 8 may be connected in series. Further, the conductive layers 11 and 12 and the heater layer 8 may be connected in parallel to a common power source.

(9) As shown in FIG. 16, the heater layer 8 is sandwiched between the conductive layers 11 and 12 in a state in which they can contact each other so that they can be energized, and the heater layer is generated by a current flowing based on an applied voltage between the conductive layers 11 and 12. 8 may be configured to generate heat. In this case, from the applied voltage required between the conductive layers 11 and 12, the thickness of the heater layer 8 is measured in consideration of the specific resistance (Ω / cm) of the heater material so that the resistance of the heater layer 8 becomes an appropriate value. Just design. According to this configuration, the insulating layers 9 and 1
Since it is not necessary to form 0, the manufacturing of the heater 6 becomes easier.

(10) The heat source is not limited to the form of the heater layer 8. As shown in FIG. 17, the surface layer 6 a may be formed on the upper surface of the protective member 30 of the heating element 29, and the surface layer 6 a may be heated by the heating element 29 via the protective member 30. The heating element 29 may be PCT ceramic or other heater material.

(11) The heating element may not be provided. As shown in FIG. 18, the surface layer 6a having the conductive layers 11 and 12 may be formed on the heating plate 31 heated by the residual heat of the exhaust gas EG. The heating plate 31 may be provided in either the vaporization chamber 22 or the intake manifold 4. For example, the surface layer 6a is formed on the heating plate of the fuel vaporizer disclosed in JP-A-49-120023.
May be formed, and the temperature of the heating surface may be set to the Leidenfrost point or higher to improve the evaporation rate of the fuel.

(12) In the fuel injected from the fuel injector 5, droplets are not sufficiently dispersed in the vicinity of the center and there is a portion where the diameter becomes large. However, in order to promote the vaporization of the fuel F in the vicinity of the center, the fuel is injected near the center. It may have a high temperature distribution, or may generate a large electric field near the center against the lifting force.

(13) The electrode rod 25 may be heated in the second embodiment. It is possible to promote vaporization of the droplet F in the process in which the droplet F travels down the electrode rod 25. (14) A net-shaped electrode may be used instead of the electrode rod 25 in the second embodiment. Droplet F attached because the electrode is net-shaped
The surface area of is increased and vaporization is promoted.

(15) The heater material is not limited to PCT ceramic. Ni-Cr (-Fe) alloy, platinum, Si
It can be changed to another material having an appropriate specific resistance such as C. When a heater material having no PCT characteristic is used, a temperature control circuit may be provided to keep the heater 6 at the set temperature.

(16) The width of the groove 7 and the diameter of the spot 28 may be set so that the capillary phenomenon does not occur. (17) Almost all of the droplets F exceeding the critical particle diameter are exposed surface 1
The grooves 7 (FIG. 4), the spots 28 (FIG. 8), and the exposed portions 12a (FIG. 10, so as to be directly attached across the 1a and 12a).
11) and the protrusion 12b (FIGS. 13 and 14) to the heater 6
It may be densely formed on the entire surface.

(18) Since the direction of the force acting on the fuel due to the EHD effect is determined by the direction of the electric field and the polarity of the fuel, the voltage application direction between the conductive layers 11 and 12 (direction of the electric field).
Can be appropriately changed according to the polarity of the fuel so that the fuel is pressed against the heater.

(19) The heaters 6 and 23 may be used below the Leidenfrost point TL. Due to the EHD effect, the droplet F is pressed against the surface S and the contact area thereof is increased, so that heat is well transferred and easily vaporized. In particular, heaters 6 and 2
3 is effective for fuel having poor wettability with the surface S.

The invention, which is grasped from the above-mentioned embodiment and is not described in the scope of claims, will be described below together with the effect thereof. (A) In Claim 5, the recess is formed to have a smaller size on the downstream side of the flow path of the droplet. The droplets ejected from the fuel injector have a faster descending speed as they have a larger particle diameter, and adhere to the upstream side.
The liquid droplet can be contacted so as to surely straddle the pair of electrodes by the concave portion corresponding to the particle diameter.

(B) In the eleventh aspect, the Curie point of the PCT ceramic is set so that the heating surface can be heated above the Leidenfrost point. According to this configuration,
Due to the heat generated by the PCT ceramic, the heating surface can be heated above the Leidenfrost point.

[0075]

As described in detail above, the first to fifth aspects of the invention are described.
According to the invention described in (1), even if the heating surface is heated above the Leidenfrost point, the droplet of the fuel is brought into contact with the heating surface by the force in the direction of the heating surface received from the electric field. It has an excellent effect that it can be further improved.

According to the sixth aspect of the invention, the droplet of the fuel is taken into the concave portion by the capillary phenomenon, so that the pair of electrodes exposed on the inner surface of the concave portion can be surely straddled and contacted. It has an excellent effect.

According to the seventh aspect of the present invention, even if the fuel droplets adhere to the heating surface at a portion other than the pair of electrodes, they are lifted by the vapor pressure and move along the heating surface. Since the droplets are captured again by the electrodes protruding from the heating surface, it is possible to reduce the number or occupied area of the pair of electrodes on the heating surface.

According to the eighth aspect of the invention, the droplets of the fuel that move so as to roll on the heating surface due to less contact with the heating surface due to the vapor pressure are paired extending in the direction crossing the fuel flow path. Since the electrodes are surely contacted and captured by the electrodes, it is possible to reduce the number of the pair of electrodes or the occupied area on the heating surface.

According to the ninth aspect of the invention, since the plurality of pairs of electrodes exposed on the heating surface are connected to each other through the conductive layer, the wiring from the power source can be connected to the conductive layer. It has an excellent effect that it requires few parts.

According to the tenth aspect of the invention, since the heater layer is formed on the surface layer immediately below the heating surface together with the conductive layer, the heating surface can be efficiently heated. According to the invention described in claim 11, since the heater layers sandwiched between the conductive layers are heated by being energized by the applied voltage between the conductive layers, it is not necessary to form an insulating layer between the layers, and the fuel vaporization is performed. The manufacture of the device can be relatively simple.

According to the twelfth aspect of the present invention, also in the fuel supply device having the vaporizing chamber, the heating surface arranged at the bottom of the vaporizing chamber is heated to the Leidenfrost point or higher so that the fuel vaporizing rate is increased. It has an excellent effect that it can improve.

According to the thirteenth aspect of the present invention, only the fuel injected from the fuel injector and atomized and the fuel vaporized on the heating surface can be supplied to the intake manifold by the valve opening / closing control. . According to the invention described in claim 14, almost all of the fuel injected from the fuel injector is attached to a large number of electrode rods, and the droplets of the fuel that have descended along the electrode rods E
By holding on the heating surface by the HD effect and quickly vaporizing it, it is possible to supply only the vaporized fuel to the combustion chamber.

[Brief description of drawings]

FIG. 1 is a partial side sectional view of a fuel vaporization heater according to a first embodiment.

FIG. 2 is a schematic side sectional view of a fuel vaporizer.

FIG. 3 is a perspective view of a fuel vaporization heater.

FIG. 4 is a partial perspective view of a fuel vaporization heater.

FIG. 5 is an operation diagram of a fuel vaporization heater.

FIG. 6 is a schematic side sectional view of a fuel vaporizer of a second embodiment.

FIG. 7 is an operation diagram of a fuel vaporization heater.

FIG. 8 is a partial perspective view of another example of a fuel vaporization heater.

FIG. 9 is a partial side sectional view of a fuel vaporization heater according to another example.

FIG. 10 is a partial perspective view of another example of a fuel vaporization heater.

FIG. 11 is a partial perspective view of another example of a fuel vaporization heater.

FIG. 12 is a partial side sectional view of a fuel vaporization heater according to another example.

FIG. 13 is a partial perspective view of another example of a fuel vaporization heater.

FIG. 14 is a partial perspective view of another example of a fuel vaporization heater.

FIG. 15 is a partial front sectional view of a fuel vaporization heater according to another example.

FIG. 16 is a partial front sectional view of a fuel vaporization heater according to another example.

FIG. 17 is a partial side sectional view of a fuel vaporization heater according to another example.

FIG. 18 is a partial side sectional view of a fuel vaporization heater according to another example.

FIG. 19 is a graph showing a fuel evaporation rate with respect to a heating temperature in the related art.

FIG. 20 is an operation diagram of a fuel vaporization heater according to a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Combustion chamber, 4 ... Intake manifold which comprises a fuel flow path, 5 ... Fuel injector,
6 ... Heater as fuel vaporizer, 6a ... Surface layer, 7 ...
Grooves as recesses, 8 ... Heater layers as heat sources, 9, 1
0 ... Insulating layer, 11, 12 ... Conductive layer forming electric field generating means, 11a ... Exposed surface forming a pair of electrodes, 12a ... Exposed surface forming a pair of electrodes, 12b ... Projection part, 14 ... Electric field generating means , A vaporization chamber, 23 ... A heater as a fuel vaporization heater, 24 ... Conductive layer, 25 ... Electrode rod, 26 ... Passage, 27 ... Electromagnetic valve as a valve, 2
8 ... Recess as spot, 29 ... Heating element, 31 ... Heating plate constituting exhaust gas guide means, F ... Fuel droplets, S ...
Surface as a heating surface.

Claims (14)

[Claims] 1. A fuel vaporization method in which a heating surface is disposed on a fuel flow path for sending fuel droplets to a combustion chamber, and the droplets are vaporized on the heating surface, wherein an electric field is generated around the heating surface. And a fuel vaporization method in which a force in the direction of the heating surface is applied to the droplet. 2. A fuel vaporization device comprising a heating surface having a constant area, for heating and vaporizing fuel droplets adhering to the heating surface to improve the combustion state of fuel in a cylinder of an engine. A fuel vaporizer equipped with an electric field generating means for exerting a force in the direction of the heating surface on the droplet on the surface. 3. A fuel vaporization device in which a heating surface having a constant area is arranged on a fuel flow path for feeding fuel droplets to a combustion chamber, wherein the fuel droplets attached to the heating surface straddle and contact each other. A fuel vaporizer comprising at least one pair of electrodes capable of generating an electric field therebetween. 4. The fuel vaporizer according to claim 3, wherein the pair of electrodes are formed on the heating surface. 5. The fuel vaporizer according to claim 3, wherein the pair of electrodes includes a first electrode formed on the heating surface and a second electrode spaced apart from the heating surface. . 6. The fuel vaporizer according to claim 4, wherein a concave portion is formed on the heating surface, and the pair of electrodes are formed in an exposed state on an inner surface of the concave portion. 7. The fuel vaporizer according to claim 4, wherein at least one of the pair of electrodes is formed so as to project from the heating surface. 8. The method according to claim 4, wherein the pair of electrodes are formed on the heating surface so as to extend in a direction transverse to a fuel flow path for sending the droplets to the combustion chamber in parallel at a predetermined interval. 6. The fuel vaporizer according to claim 6. 9. The surface layer of the fuel vaporizer that forms the heating surface is formed of a plurality of conductive layers with an insulating layer interposed therebetween.
The fuel vaporizer according to claim 3 or 4, wherein the pair of electrodes are formed by exposing the conductive layer on the heating surface. 10. The surface layer of the fuel vaporizer forming the heating surface is a heater layer as a heat source for heating the heating surface, and 2 for exposing the pair of electrodes on the heating surface. The fuel vaporizer according to claim 9, wherein the two conductive layers are formed in multiple layers with insulating layers interposed therebetween. 11. The fuel vaporizer of claim 10, wherein:
The heater layer is formed so as to be sandwiched between the conductive layers so as to contact the conductive layers so that the heater layers can be energized, and the heater layers are set to a resistance value capable of generating heat at a predetermined temperature based on a voltage applied between the conductive layers. . 12. A fuel injector for injecting the fuel is provided in a vaporization chamber, and the fuel injector is provided at a bottom portion of the vaporization chamber.
A fuel supply device in which the heating surface of the fuel vaporizer according to claim 11 is arranged. 13. A valve for controlling a supply amount of fuel from the vaporization chamber on the passage by providing a discharge port of a passage communicating the vaporization chamber and the intake manifold at a position above a predetermined distance from the heating surface. The fuel supply device according to claim 12, further comprising: 14. The heating surface of the fuel vaporizer according to claim 5 is arranged at the bottom of the vaporization chamber in which the fuel injector is provided, and a plurality of the second fuel injection devices are provided at the fuel injection destination of the fuel injector. A fuel supply device in which an electrode rod serving as the electrode is suspended and the lower end of the electrode rod is arranged at a predetermined distance from the first electrode exposed on the heating surface.