JPH041188B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dual fuel injection valve used in a diesel engine, for example, when two types of fuel, such as light oil and alcohol, are used.

For example, in a diesel engine, alcohol may be used as the main fuel (first fuel) and light oil may be used as the auxiliary fuel (second fuel). That is, since alcohol, which is the first fuel, has poor ignitability, light oil, which has good ignitability, is injected together with the alcohol to ensure that the alcohol, which is the main fuel, is ignited. Therefore, in an engine that uses two types of fuel as described above, a different fuel injection means is required to inject alcohol and light oil into the fuel chamber, respectively.

This invention was made in view of the above points, and is effective as a fuel supply device for a diesel engine that injects alcohol, which is the main fuel, into the engine fuel chamber, followed by light oil with good ignitability. The purpose of the present invention is to provide a dual-type fuel injection valve that can be used in the following situations.

As a means of injecting and supplying different types of fuel, such as diesel oil and alcohol, to an internal combustion engine,
For example, the one shown in Japanese Patent Application No. 57-89355 is being considered. That is, in this dissimilar fuel injection supply means, as shown in FIG.
2, and an auxiliary fuel tank 14 for storing light oil 13 as auxiliary fuel, and the fuel alcohol 11 in the main fuel tank 12 is supplied to an injection pump 16 by an oil feed pump 15.
This injection pump 16 is constructed of, for example, a four-cylinder bottle type, and has four outlet ports,
,, is equipped. The injection order is →
→→. The camshaft 17 of the injection pump 16 is rotationally driven by a diesel engine (not shown), and fuel alcohol is pumped out from the respective delivery ports in accordance with the rotation angle of the engine.

The injection pump 16 is connected to the four outlet ports through the first fuel supply passages 18a to 18d, respectively.
It communicates with the injection valves 19a to 19d provided for each cylinder fuel chamber of the cylinder engine, so that main fuel alcohol is distributed from the injection pump 16 to each of the injection valves 19a to 19d.

Light oil 13 stored in the auxiliary fuel tank 14
is taken out by the oil feed pump 20, and the oil is taken out by the oil feed pipe 21.
It is distributed and supplied to four pressure feeders 22a to 22d via. In this case, each of the pressure feeders 22a to 22d is driven and controlled by throttle mechanisms 23a to 23d provided in the middle of the first fuel supply paths 18a to 18d when fuel alcohol is force fed to each of the passages 18a to 18d. The pressure feeders 22a to 22
d and the portions corresponding to the aperture mechanisms 23a to 23d are constructed as represented by 22 and 23, respectively, in FIG.

That is, the pressure feeder 22 has one end connected to the oil feed pipe 2.
An oil supply communication passage 221 that communicates with the second fuel supply passage 221 is formed through the fuel supply passage 221, and the other end of this communication passage 221, which is the outlet side, communicates with the second fuel supply passage 24. The oil feed passage 221 has valve chambers formed by enlarged diameter portions on both sides divided at the center, and spherical check valve bodies 222 and 2 are respectively formed for each valve chamber.
Stores 23. This check valve body 222, 223
are set in pressure contact with the inlet side of each valve chamber by a spring, and when the inlet pressure increases due to the outlet side pressure and a pressure counteracting the spring force acts, the spring resists the spring force. The valve is opened when the valve is opened.

Further, a cylinder chamber 224 is provided in communication with the oil supply passage 221 between the valve chambers including the check valve bodies 222 and 223, and a piston 225 is set within the cylinder chamber 224. A pressure conduit 23 is connected from the throttle mechanism 23 to the back of the piston 225.
Apply pressure via 1. In this case, the piston 225 is provided with a spring 226 that resists the pressure from the pressure conduit 231 side.
The piston 225 is driven in a state where the back pressure of It will begin to send out light oil.

Further, the throttle mechanism 23 is formed with a communication passage 232 that communicates with the first fuel supply passage 18.
A branch passage 234 is provided by branching from 32 via a small diameter portion 233, and this branch passage 234 is communicated with the pressure impulse line 231. That is, the internal pressure of the first fuel supply passage 18 is lower than that of the branch passage 2.
34 to the pressure conduit 231, and increases the pressure of the piston 225. When alcohol fuel is force-fed from the injection pump to the first fuel supply path 18, the piston 225 of the pressure feeder 22 is driven, and the pressure in the piston 225 is increased. The light oil in the chamber 224 flows into the check valve body 22.
3 to the second fuel supply path 24.

The second fuel passages 24a to 24d from the pressure feeders 22a to 22d configured in this way are distributed and connected to the injection valves 19a to 19d. In this case, the passage 24a is connected to the valve 19c, and the passage 24b is connected to the valve 19.
a, the passage 24c is connected to the valve 19d, and the passage 24d is connected to the valve 19b.

The injection valve 19 to which alcohol fuel and light oil are branched and supplied in this manner is constructed as representatively shown at A in FIG. 3. That is, a needle valve 192 is set in a body 191 so as to be freely movable in the axial direction, and a tapered seat part 193 having a reduced diameter at the tip of the needle valve 192 controls opening and closing of an injection port formed in the body 191. It's getting old.
In this case, a force in the direction of closing the injection port is applied to the needle valve 192 by a spring mechanism (not shown). Also, body 19
1, a first fuel passage 194 communicating with the first fuel supply passage 18 and a second fuel passage 195 communicating with the second fuel supply passage 24 are formed. Furthermore, a conical cavity is formed by a tapered surface in the vicinity of the seat part 193 at the tip of the needle valve 192, and this cavity is formed by a first cavity 1 having a large diameter in the upper part.
96 and a second empty space 197 adjacent to the seat portion 193. And the first blank space 1
96 has a first fuel passage 194 and a second cavity 19
7, the second fuel passages 195 are opened respectively.

That is, when alcohol fuel is sequentially delivered from the delivery ports of the injection pump 16, pressure acts on the pressure feeders 22a to 22d from the throttle mechanisms 23a to 23d in accordance with the delivery pressure, and drives the respective pistons 225. By doing so, from each of the pressure feeders 22a to 22d, the corresponding injection valve 1
9c, 19a, 19d, and 19b are pressurized with a specified amount of light oil, and the space 19 of each valve 19a to 19d is
7 is filled. And this second empty space 197
When alcohol fuel is pumped from the first fuel supply passage 18 in a state filled with light oil and is supplied to the first cavity 196 via the first fuel passage 194, the supply pressure increases. The needle valve 192 is raised, the seat portion 193 is separated from the injection port, and the light oil in the second cavity 197 is filled with the first one.
The alcohol in the empty space 196 is now injected.

In this case, each injection valve 1 is
The injection operation is performed in steps 9a to 19d, and the gas oil is set to be supplied from the pressure feeder during the alcohol supply operation to the other injection valves in the process until the alcohol is pumped from the injection pump 16. In each of the injection valves 19a to 19d, alcohol is pumped into the first cavity 197 while the second cavity 197 is always filled with light oil. Therefore, an injection operation is performed in which light oil is first injected from the injection port, and then alcohol fuel is injected.

FIG. 4 shows the process of the above-mentioned injection operation, with the horizontal axis representing the cam rotation angle that drives the injection pump 16. Indicates when fuel is injected. In this injection time B, a diagonally shaded portion D indicates the time when light oil is injected, and another diagonally shaded portion E indicates the time when the second space 197 is filled with light oil.

Further consideration of the operation of the fuel injection valve 19 in the fuel injection operation described above reveals that the second
When the light oil is fed to the second cavity 197 through the fuel passage 195, the light oil collides with the needle valve 192, splits into two directions, and fills the second cavity 197. However, the fed light oil is divided into two directions, and while it makes a half-circle around the needle valve 192, it flows toward the first space 196 along the tapered surface that forms the space due to the centrifugal force of the light oil itself. try Therefore, in order to fill the second cavity 197 with 100% light oil, it is necessary to feed excess light oil with respect to the volume of the cavity 197.

Figure 5 shows the injection state of diesel oil and alcohol when such an injection valve 19 is used. Figure A shows the injection rate dQ/dt, and Figure B shows the diesel oil ratio R (diesel oil/(diesel oil + alcohol)). ) is shown. In the figure,
A is the change in the injection rate of the entire fuel, a is the change in the injection rate of only the light oil component at this time, and b is the change in the light oil ratio.

That is, at the beginning of injection, only approximately 100% of the light oil filled in the second cavity 197 is injected, but the ratio of diesel oil soon decreases and
Light oil overflowing into 96 is gradually injected along with alcohol. Here, whether or not the injected fuel is compression ignited is determined by the ignitable light oil ratio level, which is determined from the compression ratio of the engine, the airflow conditions around the fuel, etc.
It is necessary that a value higher than R _p be given at the beginning of injection. In addition, in order to generate a sufficiently large spark that can sustain the combustion into alcohol, it is simultaneously required to maintain the ignitable light oil level R _p or higher above the range of t ₀ for a certain period of time. (t _e
≧ _tp ). In this case, the absolute amount of light oil injected during that time is also an important condition. That is, the volume of the second space 197 and the amount of light oil supplied are determined so as to satisfy each of these conditions.

Further, as such an injection valve 19, a structure as shown in B of FIG. 3 (Japanese Patent Application No. 1989-89355)
is being considered. That is, the needle valve 192
A cavity 198 for filling only light oil is formed around the tip of the fuel passage 195, and this cavity 198 is filled with light oil from the second fuel passage 195. And the first
When alcohol is introduced at high pressure from the fuel passage 194, the light oil in the space 198 is forced out from the injection port, so that the light oil and alcohol are continuously injected in that order.

If this is done, the light oil ratio can be effectively improved, but the volume of the space 198 will be small enough to match the required amount of light oil, and there is a risk that stagnation will occur in the flow of light oil in the space 198. , especially the first
It is necessary to take measures to ensure that light oil flows smoothly near the opening of the fuel passage 194 and the opposite side 199.

This invention further improves the above points,
It is an object of the present invention to provide a dual-type fuel injection valve that can reliably set a sufficient light oil ratio and sufficiently improve ignition and combustion characteristics.

That is, the type 2 fuel injection valve according to the present invention is
In the direction of the tip of the needle valve, a cylindrical part whose diameter is sufficiently smaller than that of the cylindrical stem serving as the sliding part is configured so that the diameter is reduced from the stem part through a tapered part, and the outer periphery in the direction of the tapered part is mainly formed. The first point where fuel is introduced
A cylindrical second cavity communicating with the first cavity is formed on the outer periphery of the columnar part, and the second cavity is filled with auxiliary fuel. be.

An embodiment of the present invention will be described below with reference to the drawings. Figure 6 shows its configuration, with body 3
1, a needle valve 32 is provided so as to be freely movable in the axial direction. This needle valve 32 has a cylindrical stem 33, which is a sliding part, with a tapered part 3 in the distal direction.
4, a cylindrical portion 35 having a sufficiently smaller diameter than the stem 33 is formed, and a seat portion 36 with a tapered surface is further formed in the distal end direction of this cylindrical portion 35.
is formed. A needle pin 37 of, for example, a pintle type or a throttle type is provided protruding from the tip of the seat portion 36. The seat portion 36 is brought into contact with the injection port formed in the body 31, and a spring mechanism (not shown) presses the needle valve 32 in the direction of the injection port, so that the seat portion 36 seals the injection port. By moving the needle valve 32 against the spring, the injection port is opened and fuel injection is performed.

Further, a first cavity 38 in the shape of a ring is formed in the body 31 corresponding to the outer circumferential part of the tapered part 34 of the needle valve 32, and the first cavity 38 is provided with a first cavity 38 for supplying the first fuel. The first fuel passage 39 connected to the passage 18 is opened. Further, a second cavity 40 is formed in the outer circumference of the cylindrical portion 35 of the needle valve 32, which is divided into a cylindrical shape and is continuous to the first cavity 38. That is, this second space 40 is the cylindrical part 35
A second fuel passage 41 is formed in a thin cylindrical shape on the outer periphery of the second space 40, and a second fuel passage 41 is opened toward the axis in a portion of the second space 40 in the distal direction close to the seat portion 36. . This second fuel passage 41 is communicated with the second fuel supply passage 24, and is connected to the second fuel supply passage 24.
For example, light oil, which is auxiliary fuel, is supplied to the empty space 40 and filled. In this case, the volume of the second space 40 is set to a value that approximates the volume of light oil required for one fuel injection.

That is, first, when the amount of light oil required for one fuel injection is fed from the second fuel passage 41, this light oil flows from the lower part of the second cavity 40 and hits the columnar part 35, and Cylindrical space 40 divided into directions
As it circulates inside, it fills upwards. At this time, inside the second void 40 and the first void 38, etc.
Although the alcohol remains full since the end of the previous injection, the light oil flowing in from below pushes it up and causes the alcohol to flow back from the first cavity 38 to the first fuel passage 39. At this time, the pressure inside this injection valve increases slightly, but does not reach the valve opening pressure that pushes up the needle valve 32.

In this way, the inside of the second cavity 40 is filled with approximately 100% light oil from the bottom to the top.

During the injection operation, alcohol is supplied at high pressure from the first fuel passage 39, and this alcohol flows into the wide first cavity 38, the flow rate of which decreases, and the pressure is evenly distributed within the cavity 38. It starts to have a dispersive effect. When this pressure reaches the valve opening pressure, the pressure acts on the tapered portion 34 to raise the needle valve 32, separating the seat portion 36 from the injection port and injecting fuel.

In this case, the force acting on the first cavity 38 equally acts on the upper end surface of the second cavity 40, and the fuel gas oil in this cavity 40 flows uniformly in the injection direction. Approximately 100% of the light oil filling the second cavity 40 is first injected out. Alcohol is then injected following this light oil.

In such an injection process, the needle valve 32
Even if the height rises, the cross-sectional shape of the second cavity 40 does not change because the second cavity 40 is formed in a cylindrical shape. In particular, the shape of the boundary between the filled diesel oil and alcohol does not change. Therefore,
At the boundary between light oil and alcohol, no turbulence occurs in the flow, and mixing of light oil and alcohol at this boundary is difficult to occur.

If we look at the injection characteristics of the injection valve constructed in this way, it will be as shown in Figure 7.
The light oil injection rate dQ/dt, as shown by a2, has a characteristic that the front part swells more fully than a shown in FIG. 5. Further, as shown by b2, the light oil ratio R also has a characteristic that the front part swells more than b shown in FIG. 5, and a large spark can be effectively generated in the engine combustion chamber. In other words, with less diesel oil,
It becomes possible to obtain more reliable ignition and combustion sustainment characteristics.

In the above embodiment, the second cavity 40 is formed into a cylindrical shape having a uniform wall thickness in the axial direction by using the cylindrical portion 35 of the needle valve 32. However, as shown in FIG. 8, the diameter of the lower part of the cylindrical part 35 of the needle valve 32, that is, the end in the direction of the seat part 36 is reduced by the tapered part 42, and the direction of the injection port of the second cavity 40 is widened. It may also be formed. In this case, since the boundary between light oil and alcohol is formed into a cylindrical shape with the same wall thickness as in the previous embodiment, the same effects as in the previous embodiment can be obtained.

At the same time, by configuring the lower part to be wide, it is not only possible to set the range of the cylindrical cavity to be small, but also to reduce the flow resistance of light oil in the part near the seat part 36, so that light oil can flow in this vicinity. It can be easily filled.

Further, in the previous embodiment, the second fuel passage 41 is
Although the fuel passage 41a is set in the normal direction toward the axial direction with respect to the cavity 40, the fuel passage 41a may be formed in the tangential direction as shown by the broken line in B in FIG. This is effective in reducing the number of stagnation parts.

Incidentally, the fuel used in such a dual fuel injection valve is not limited to the above-mentioned light oil and alcohol, but also
Eucalyptus oil, orange oil, castor oil, gasoline,
Liquid fuels such as kerosene and heavy oil can be used selectively, and among them, those with good compression ignition properties can be used as auxiliary fuel, and the others can be used in combination as main fuel.

As described above, according to the present invention, when injecting two types of fuel, for example, light oil which is an auxiliary fuel with good compression ignitability, and alcohol which is a main fuel,
It is possible to inject diesel oil and then alcohol in that order so as to effectively set the characteristics of the diesel injection rate and ratio of diesel oil.For example, the effect is remarkable when applied to diesel engines that use alcohol as the main fuel. It's something new.

[Brief explanation of drawings]

Fig. 1 is a diagram explaining the fuel supply system for the injection valve related to the present invention, Fig. 2 is a diagram showing the configuration of the pressure feeder section that performs auxiliary fuel control of the above system, and A and B in Fig. 3 are respectively A cross-sectional configuration diagram showing an example of an injection valve considered so far, FIG. 4 is a diagram explaining the fuel supply injection operation state of the above system, A in FIG.
B is a diagram illustrating the injection characteristics of auxiliary fuel in the injection valve, FIG. 6 is a cross-sectional configuration diagram illustrating a two-type fuel injection valve according to an embodiment of the present invention, and A is a line AA in diagram B. , B is a sectional view taken along the line B-B of FIG. A, FIG. 7 is a diagram explaining the auxiliary fuel injection characteristics of the above-mentioned injection valve, and FIG. It is a sectional view explaining a valve. 31...Body, 32...Needle valve, 33...
...Stem part, 34...Tapered part, 35...Cylindrical part, 36...Seat part, 38...First cavity, 3
9...First fuel passage, 40...Second cavity, 4
1,41a...second fuel passage.

Claims (1)

[Claims] 1. A needle valve having a cylindrical stem portion with a seat portion having a smaller diameter than the stem portion in the distal direction;
a body that holds the needle valve movably in the axial direction; first and second fuel passages formed in the body toward the tip of the needle valve; The first valve is formed between the outer circumference of the valve and the inner surface of the body.
a first cavity in which a fuel passage opens; and a second fuel passageway formed between the outer periphery of the needle valve and the inner surface of the body, continuing from the first cavity toward the distal end of the needle valve. a second cavity in which a passage opens, and a portion of the needle valve corresponding to the second cavity is a cylindrical portion having a smaller diameter than a stem portion of the needle valve; A dual fuel injection valve characterized in that a portion corresponding to the cavity is formed into a cylindrical shape having a diameter larger than the cylindrical portion, and the second cavity is configured in a cylindrical shape. 2. The dual fuel injection valve according to claim 1, wherein the second fuel passage is opened close to the second cavity toward the tip of the needle valve. 3. The dual fuel injection valve according to claim 1, wherein the second fuel passage is formed in a substantially tangential direction with respect to the periphery of the cylindrical second space. 4. The dual fuel injection valve according to claim 1, wherein the volume of the second space increases in a circular ring shape toward the tip of the needle valve.