JP2003314402A - Fuel injection valve provided with fuel heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection valve provided with a fuel heater for an internal combustion engine for better heating the fuel starting from fuel being injected first in a first fuel injection at cold starting of an engine, thus improving startability of the engine, increasing effectiveness of discharge control of unburned harmful components, and better reducing a degree of valve opening lift reduction due to heating of the fuel. <P>SOLUTION: The fuel injection valve comprising a cylindrical fuel injection passage opened as a nozzle hole at a tip, and a needle valve provided inside the fuel injection passage further includes a fuel heater having a heating wire windingly extending around a circumference of the needle valve in the fuel injection passage. A winding density of the heating wire along the fuel injection passage may be higher at a part near the nozzle hole than that of a part far from the nozzle hole. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection valve for an internal combustion engine, and more particularly to a fuel injection valve having a fuel heating heater.

[0002]

2. Description of the Related Art A fuel injection valve for an internal combustion engine generally has a fuel injection passage opened as an injection port having a narrowed tip and a needle valve body for selectively opening and closing the injection port, and the inside of the fuel injection passage is closed. It has a basic structure for injecting the fuel fed under pressure through the injection port when the needle valve body opens the injection port.

Further, in this type of fuel injection valve, the fuel injected at the cold start of the engine is better atomized to improve the startability of the engine and at the same time suppress the generation of harmful unburned components as much as possible. It is known to incorporate a heater for heating fuel flowing in the fuel injection passage. Such a heater, as shown in Japanese Utility Model Laid-Open No. 59-107973, has a fuel injection passage formed as a relatively narrow passage extending parallel to the side of the needle valve. ,
It is provided as a sheath-shaped heater (sheath heater) surrounding a part of the fuel injection passage, or is inserted so as to extend along the fuel injection passage as shown in Japanese Utility Model Laid-Open No. 3-83370. It is provided as a heating wire.

Further, in the fuel injection valve having a structure in which the fuel injection passage is formed as a cylindrical space having a relatively large diameter narrowed to the injection port at the tip, and the needle valve for opening and closing the injection port extends into the fuel injection passage. Japanese Patent Application Laid-Open No. 2000-508041 discloses that a ceramic heater extending in a cylindrical shape around the needle valve element is provided in the fuel injection passage.

[0005]

The heating of the injected fuel at the time of cold start of the engine is effective in improving the startability of the engine. However, the generation of harmful unburned components is suppressed. In order to exert the effect better, it is effective that the first fuel injection is performed so that the fuel is better heated starting from the first injected fuel. For that purpose, the heater for heating the fuel not only has its rising as quickly as possible and has a high heat generation density, but also can heat the fuel existing in the portion in contact with the injection port. Is desired.

On the other hand, in this type of fuel injection valve, the needle valve is biased by a spring toward the closed position where the tip of the needle valve closes the injection port, and when the injection port is opened, the needle valve is provided at the root portion. The armature is attracted by an electromagnet, and the valve opening lift is determined by the armature contacting the core of the electromagnet. Therefore, when the needle valve is heated by the fuel heater to cause thermal expansion, the valve lift is reduced accordingly. Therefore, it is desired that the fuel heater has a structure capable of suppressing thermal expansion of the needle valve due to heating of the fuel by the heater as much as possible.

SUMMARY OF THE INVENTION The present invention addresses the above-mentioned demands for a fuel heating heater for a fuel injection valve of an internal combustion engine, and provides a fuel injection valve having a fuel heating heater that can meet these demands. I am trying.

[0008]

In order to solve the above-mentioned problems, the present invention provides a fuel injection passage that opens as an injection port having a narrow end of a cylindrical space, and a fuel injection passage that extends into the fuel injection passage. A fuel injection valve having a needle valve body for selectively opening and closing the injection port, and configured to inject fuel, which is pumped in the fuel injection passage, through the injection port when the needle valve body opens the injection port. The fuel injection valve is characterized in that it has a fuel heating heater composed of an electric heating wire that swirls around and extends around the needle valve element in the fuel injection passage.

The density of swirling of the heating wire along the fuel injection passage may be made higher in a portion near the injection port than in a portion separated from the injection port.

[0010]

As described above, the fuel injection passage that opens as an injection port having a narrow end in the cylindrical space and the needle valve body that extends into the fuel injection passage and selectively opens and closes the injection port are provided. A fuel injection valve configured to inject fuel, which has been pressure-fed in the fuel injection passage, through the injection port when the needle valve body opens the injection port. If configured as a heating wire that swirls around the body, the heating wire can be made longer than the length of the fuel injection passage, and a large amount of heat is generated compared to the storage space. A heater having a surface area can be formed. Further, in this case, since the fuel flows across the heating wire that swirls and extends, heat transfer from the heating wire to the fuel is performed at a high heat transfer coefficient. Furthermore, in the case of such a swirl-shaped heating wire, by concentrating the ends of the winding around the injection port, it is possible to strongly heat the fuel in contact with the injection port and the surrounding fuel. ,
Even from the time of the first fuel injection, a strong heating effect can be given to the fuel injected first.

Furthermore, by appropriately changing the pitch of the swirl, the density distribution of the heating surface can be set with a large degree of freedom, whereby the density distribution of the heating surface is separated from the nozzle near the nozzle. The heating can be accelerated as the fuel flows in the fuel injection passage from its inlet to the nozzle. By doing so, even if the heating degree of the fuel injected from the injection port is increased, the heating applied to the needle valve accompanying the heating of the fuel can be suppressed within a limited length range close to the injection port, When the entire needle valve is heated, even if the coefficient of thermal expansion is not so high,
Since the length is large, the thermal expansion margin of the whole is large, and it is possible to avoid an undesirable situation in which the valve lift is greatly reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 attached herewith is a schematic view showing an essential part of one embodiment of a fuel injection valve having a fuel heater according to the present invention.

In the figure, reference numeral 1 denotes a housing of a fuel injection valve, which gives the fuel injection valve a nozzle-like form. In the illustrated schematic diagram, the housing 1 is shown as an integral stepped tubular body, but in the implementation, such a housing is an arbitrary combination of several members in consideration of manufacturing and mounting convenience. It can be made into the structure of. The housing is provided with a cylinder-shaped fuel injection passage 2 inside thereof, particularly at its tip portion, and the tip thereof is narrowed to form an injection port 3. In the illustrated embodiment, the fuel injection passage 2 is formed in a cylindrical shape, and the injection port 3 is opened in alignment with the center of the cylindrical fuel injection passage.

A needle valve 4 extending along the central axis of the fuel injection passage 2 is provided in the fuel injection passage 2. The needle valve 4 is provided with a guide hole 6 at its base portion by a holder 5
It is guided and supported so as to slide along, and the injection port 3 is opened and closed by the tip formed in a conical shape. The holder 5 is further provided with a fuel hole 7 for passing fuel and a terminal hole 8 for passing an energizing terminal to a heater described later. Reference numeral 9 is a snap ring for attaching the holder 5. An armature 10 is attached to the rear end of the needle valve 4. The armature is constructed to pass fuel therethrough, as shown diagrammatically as hole 11 in the figure.

Reference numeral 12 denotes an electromagnetic coil, which constitutes an electromagnet which selectively attracts the armature 10 together with a core 13 which is excited by energization thereof. A compression coil spring 15 is provided at the center of the core 13 along a hollow space 14 having a cylindrical shape, and the root of the compression coil spring 15 is supported by a spring holder 16 at the tip thereof.
0, the needle valve 4 is urged by its tip to a closed position in which the injection port 3 is closed.

The fuel pressure-fed by a fuel injection pump (not shown) is introduced into the housing 1 through the gap 14 from the upper part of the drawing, and goes toward the injection port 3 through the fuel injection passage 2. When the electromagnetic coil 12 is not energized, the injection port 3 is closed by the needle valve 4,
When the electromagnetic coil 12 is energized, the needle valve moves the compression coil spring 15 until the armature 10 contacts the core 13.
The ejection port 3 is opened by pulling it upward in the figure against the spring force of. The opening lift of the needle valve in this case corresponds to the clearance L between the armature 10 and the core 13 when the valve is closed.

In the fuel injection passage 2, there is provided a fuel heating heater including a heating wire 17 that turns around the needle valve 4 and turns. The upper end of the heating wire 17 in the figure is
It is connected to a terminal 18 arranged through the terminal hole 8, and its lower end abuts around the injection port 3 of the housing 1 and is grounded via the housing.

As described above, the heating element is a linear heating wire, and the needle valve extends along the central portion of the cylindrical fuel injection passage so that the annular tubular space left between the needle valve extends. By swirling the heating wire around the needle valve, it is possible to form a larger heat generation surface and increase the heat transfer rate as compared with a cylindrical ceramic heater, etc. From that time, a strong heating effect can be given to the fuel injected first. Furthermore, the density of the arrangement of the heating wires 17 that swirl around the needle valve 4 may be higher in the portion near the nozzle 3 than in the portion further away, as shown in the illustrated embodiment. . In the illustrated embodiment, there are two different densities in the portion adjacent to the injection port 3 and the portion separated therefrom, but the change in the density of the heating wire is not limited to this embodiment, and any other suitable density is possible. May be changed.

During operation of the fuel injection valve, that is, the fuel injection passage 2
While the fuel is flowing toward the nozzle 3 inside, the heating wire 17
When electricity is applied to the fuel, the fuel flowing along the fuel injection passage 2 is heated starting from the 0 position where the starting end of the heating wire is located, and its temperature gradually rises toward the injection port 3. Considering a state where a constant current is being applied to the heating wire while the fuel is flowing at a constant flow rate, the fuel is proportional to the density of the heating wire per unit amount in sequence along the flow direction. A certain amount of heat is received, and the temperature rises by a proportional temperature difference. In this case, if such a state continues for a certain period of time or more, even if fuel continues to flow,
The temperature distribution of the fuel along the fuel injection passage 2 becomes steady, and the temperature of each part of the portion of the needle valve 4 extending into the fuel injection passage 2 corresponds to the temperature distribution of the fuel along the fuel injection passage 2. .

Therefore, the degree to which the needle valve 4 is heated and expanded by the operation of the fuel heating heater according to the present invention, and the opening lift of the needle valve is reduced, the fuel heating heater is described in the above Japanese Patent Publication No. 2000-508041. This is compared with the case where the heater is a heater that generates heat at a uniform heat generation density along the fuel injection passage 2 like the cylindrical ceramic heater in the above. When the cylindrical ceramic heater is correspondingly replaced with a heating wire, it corresponds to the heating wire being arranged so as to swirl at a uniform pitch in the fuel injection passage.

FIG. 2 is a graph in which the horizontal axis represents the distance S for each station from the heating start position of the needle valve, and the vertical axis represents the temperature T for each station. When the heat generation density of the heater along the fuel injection passage 2 is uniform, the temperature of each station of the needle valve increases uniformly as it goes away from the heating start position, as indicated by the straight line A, and the distance thereof increases. Reaches a certain maximum temperature Tf corresponding to the amount of energization at the tip where is St. Therefore, in this case, the elongation due to the heating of the needle valve is the accumulation of the elongation at each local portion, and if the minute length of each local portion is ΔS and its temperature is T, the elongation of the entire needle valve,
That is, the reduction amount of the valve opening lift is calculated by (T-To) ΔS = S = 0
To S = St, the value is proportional to the area of the area (triangle 0-e-St) formed by the straight line A with respect to the horizontal axis.

On the other hand, as in the embodiment of the present invention shown in FIG. 1, when the pitch of the heating wire 17 is roughened in the first half of the fuel injection passage 2 and narrowed in the latter half. Even when the temperature of the fuel injected from the injection port is the same and the temperature of the tip of the needle valve is the same temperature Tf, the temperature of each local part reaching that temperature is that which connects the straight lines B ₁ and B ₂ , and the needle valve The total elongation is the area formed by the straight line B ₁ -B ₂ with respect to the horizontal axis, that is, the triangle 0-m-Sm and the quadrangle Sm-
The value is proportional to the sum of m-e-St. This is smaller than the above-mentioned triangle 0-e-St by an amount corresponding to the area of the triangle 0-e-m, and the amount by which the opening lift of the needle valve is reduced due to the fuel heating is reduced by this amount. It means less.

Further, as described above, the disposition density of the heating wire 17 may be set arbitrarily, so that, for example, the heating wire 17 is continuously increased gradually from the starting end to the end adjacent to the injection port, and the local temperature of the needle valve is increased. By changing as shown by the curve C in FIG. 2, even if the final heating temperature of the fuel ejected from the injection port is made higher than Tf, the reduction of the valve lift due to the fuel heating can be further suppressed. Is possible.

Although the present invention has been described above in detail with reference to one embodiment, it will be apparent to those skilled in the art that various modifications can be made to the embodiment within the scope of the present invention.

[Brief description of drawings]

FIG. 1 is a schematic view showing an essential part of one embodiment of a fuel injection valve provided with a fuel heater according to the present invention.

FIG. 2 is a graph showing a mode in which thermal expansion of a needle valve occurs due to a change in heat generation density of a heater along a fuel injection passage, in comparison with the present invention and a known example.

[Explanation of symbols]

1 ... Housing 2 ... Fuel injection passage 3 ... nozzle 4 ... Needle valve 5 ... Holder 6 ... Guide hole 7 ... Fuel hole 8 ... Terminal hole 9 ... Snap ring 10 ... Armature 11 ... Fuel passage hole 12 ... Electromagnetic coil 13 ... Core 14 ... Cylindrical void 15 ... Compression coil spring 16 ... Spring holder 17 ... Electric heating wire 18 ... Terminal

Claims (2)

[Claims] 1. A fuel injection passage that opens as an injection port having a narrowed end in a cylindrical space, and a needle valve body that extends into the fuel injection passage and selectively opens and closes the injection port,
A fuel injection valve configured to inject fuel pumped in the fuel injection passage through the injection port when the needle valve body opens the injection port, and in the fuel injection passage, around the needle valve body. A fuel injection valve having a fuel heating heater composed of a heating wire that swirls and extends in a vertical direction. 2. The density of swirl of the heating wire along the fuel injection passage is set to be higher in a portion near the injection port than in a portion separated from the injection port.
The fuel injection valve described in 1.