JPH0374568A - Fuel injection device for internal combustion engine - Google Patents

Abstract

PURPOSE:To reduce kinetic energy supplied to a movable core in an air blast valve for injecting fuel together with compressed air by setting a needle, the movable core and energizing means for energizing the needle and the movable core in such a way as to satisfy a specific relation. CONSTITUTION:An air blast valve 20 switches a nozzle 23 provided at one end of a needle insertion hole 22 formed in a body 21, by a needle 25 driven by a movable core 32 axially moved by the excitation of a solenoid 34. The compressed air from compressed air source 43 is supplied to the needle insertion bole 22 through a lead-in path 41, an air passage 44, an inflow passage 50, a nozzle chamber 46 faced by the injection port 42 of a fuel injection valve 51, and an outflow passage 47. In this case, when the mass of the needle 25 and the movable core 32 is made M1, M2 and the energizing force of a first and a second compression springs 30, 33 at the valve closed and opened time of the nozzle 23 is made F1, F2, the needle 25, the movable core 32 and the compression springs 30, 33 are set in such a way that the enumerated value by an expression (F1/F2-1).M2/(M1+M2) becomes less than 0.3.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a fuel injection device for an internal combustion engine.

[Conventional technology]

Conventionally, a nozzle opening is formed at one end of the compressed air passage, a fuel supply opening is formed in the middle of the compressed air passage, a valve body for opening and closing the nozzle opening is formed at the tip of the needle, and the rear end of the needle is movable. The needle is engaged with the core, and the needle is biased toward the movable core by a first compression spring to close the nozzle port, and the movable core is biased toward the needle by a second compression spring. A so-called air blast valve is known which opens a nozzle opening by displacing a needle against the biasing force of a first compression spring by electromagnetically driving the needle.

Further, Japanese Patent Application Laid-Open No. 63-248965 discloses an air blast valve in which the rear end of the needle and the movable core are disposed in a sealed chamber filled with fuel.

[Problem to be solved by the invention]

However, in the former air blast valve, when the solenoid is energized to attract the movable core to the stator, the needle is displaced against the spring force of the first compression spring to open the nozzle opening, and then the solenoid is turned off. , the needle and the movable core are compressed into the second compression spring by the spring force of the first compression spring.
The nozzle is displaced in the valve closing direction against the spring force of the compression spring. The displacement of the needle ends at the position where the valve body closes the nozzle port, but bouncing occurs because the movable core has kinetic energy in the direction of closing the nozzle port. That is, the movable core is displaced to a position where the force acting on the movable core in the nozzle opening closing direction is equal to the spring force of the second compression spring, and then the movable core is moved to open the nozzle opening again by the spring force of the second compression spring. The valve is displaced in the direction of the valve. At this time, there is a problem in that when the movable core engages with the rear end of the needle again, the needle is displaced in the valve opening direction, thereby opening the nozzle opening.

On the other hand, in the latter air blast valve, the kinetic energy of the movable core when it re-engages with the rear end of the needle can be attenuated by the damping effect of the fuel, but this effect is not sufficient and the nozzle still The mouth is forced open. Another problem is that the structure for preventing fuel leakage becomes complicated, and furthermore, if steam is generated in the fuel, the behavior of the movable core becomes unstable.

[Means to solve the problem]

In order to solve the above problems, according to the present invention, a nozzle port is formed at one end of the compressed air passage, a fuel supply port is formed in the middle of the compressed air passage, and a valve for opening and closing the nozzle port is provided at the tip of the needle. the rear end of the needle is engaged with one end of the movable core, the needle is biased toward the movable core by the first biasing means to close the nozzle port, and the movable core is engaged with one end of the movable core. The needle is biased toward the needle by the biasing means of the first biasing means, and the movable core is electromagnetically driven to displace the needle against the biasing force of the first biasing means to open the nozzle opening and supply fuel. In a fuel injection device that uses compressed air to inject fuel supplied into a compressed air passage from a nozzle port, the mass of the needle is M11, the mass of the movable core is M2, and the 10th bias when the nozzle port is closed. Assuming that the biasing force of the means is F I % and the biasing force of the 20th biasing means in the nozzle mouth closed state is F2, then M2 will be decreased and Mt +M2 will be increased.

By reducing the kinetic energy given to the movable core when the nozzle opening is closed,
Displacement of the needle caused by bouncing of the movable core after the nozzle port is once closed can be sufficiently reduced.

〔Example〕

Figures 6 and 7 show a two-stroke engine.

6 and 7, 1 is a cylinder block, 2 is a piston, 3 is a cylinder head, 4 is a combustion chamber,
5 is a pair of air supply valves, 6 is an air supply port, 7 is a pair of exhaust valves, 8 is an exhaust port, and 9 is a spark plug. A mask wall 10 is formed on the inner wall surface of the cylinder head 3 to close an opening between the peripheral edge of the air intake valve 5 on the exhaust valve 7 side and the valve seat during the full opening period of the air intake valve 5. Therefore, when the intake valve 5 opens, fresh air flows into the combustion chamber 4 from the side opposite to the exhaust valve 7 as shown by the arrow N. An air blast valve 20 is located on the inner wall surface of the cylinder head 3 located between a pair of air supply valves 5.
is placed.

FIG. 1 shows a partially sectional side view of the air blast valve 20.

Referring to FIG. 1, the body 21 of the air blast valve 20
A straightly extending needle insertion hole 22 is formed inside, and a nozzle port 23 is formed at one end of the needle insertion hole 22, and the other end is formed in the body 21 coaxially with the axis A of the needle insertion hole 22. The spring chamber 24 is connected to the spring chamber 24. A needle 25 having a smaller diameter than the needle insertion hole 22 is inserted into the needle insertion hole 22, and the opening and closing of the nozzle port 23 is controlled by a valve portion 26 formed at the tip of the needle 25. In this embodiment, the nozzle port 23 is arranged within the combustion chamber 4 (see FIG. 7). A drive unit housing 27 is attached to the upper end of the body 21 in which the spring chamber 24 is formed, and the spring chamber 2 is located in the lower end of the drive unit housing 27.
A stator 28 is fixed opposite to 4. A spring retainer 29 is fixed to the needle 25 located near the upper end of the spring chamber 24, and a first compression spring 30 serving as a first biasing means is installed in the spring chamber 24 between the spring retainer 29 and the body 21. is inserted. This first compression spring 30
The spring force urges the needle 25 toward the movable core 32 located above, and the nozzle opening 23 is normally closed by the valve portion 26 of the needle 25. The needle 25 passes through the stator 28 , and the rear end 31 of the needle 25 projects from the stator 28 . A movable core 32 is engaged with this rear end portion 31, and the movable core 32 is biased toward the needle 25 by a second compression spring 33, which is a second biasing means.

This movable core 32 has an axis A within the drive unit housing 27.
The movable core insertion hole 40 is disposed in a movable core insertion hole 40 formed in the direction so as to be slidable in the axis entry direction. The biasing force of the second compression spring 33 in the nozzle opening direction is about half of the biasing force of the first compression spring 30 in the nozzle opening closing direction, and therefore, the difference in the biasing forces of these compression springs 30°33 As a result, the nozzle port 23 is always closed. A solenoid chamber 3 is provided between the stator 28 and the drive housing 27.
9 is formed, and within this solenoid chamber 39 is a stator 2.
A solenoid 34 is arranged around 8. When this solenoid 34 is energized, the movable core 32 slides inside the movable core insertion hole 40 toward the stator 28 , and as a result, the needle 25 resists the spring force of the first compression spring 30 and moves toward the nozzle port 23 . Since the nozzle port 23 is slidably displaced in the direction, the nozzle port 23 is opened.

The needle 25 is made of a hard hardened material to ensure a seal between the nozzle port 23 and the valve body 26 over a long period of use, while the movable core 32 is made of a magnetic material and is therefore relatively soft. It is made of shell annealed material.

FIG. 2 shows an enlarged view of the engagement portion between the needle 25 and the movable core 32. ′! Referring to Figure J2, a cylindrical recess 35 is formed around the axis A on the bottom surface 32a of the movable core 32 facing the needle rear end 31, and a cylindrical seat 36 is fitted into the recess 35. Ru. This seat 36 is made of the same material as the needle 25 and has the same hardness as the needle 25. The outer diameter of the catch seat 36 is slightly larger than the outer diameter of the needle 25, and is 173 mm larger than the outer diameter of the movable core 32.
That's about it. Therefore, the movable core 32 has a sufficiently large area facing the stator 28 and can receive sufficient suction force. A concave engagement surface 37 is formed by a spherical surface smaller than a hemisphere at the engagement portion of the catch seat 36 with the needle 25 . On the other hand, the rear end portion 31 of the needle has a hemispherical convex engagement surface 38.
is formed.

The concave engagement surface 37 is formed by a spherical surface having a slightly larger diameter than the convex engagement surface 38, for example, the radius of the spherical surface forming the concave engagement surface 37 is 1.3 mm, and the spherical surface forming the convex engagement surface 38. The radius of is assumed to be 12+nm. In this way, even if the needle 25 and the movable core 32 are engaged with each other and operated for a long period of time, the catch seat 36 can be prevented from being worn out.

FIG. 3 shows a bottom view of the movable core 32. Referring to FIGS. 2 and 3, an annular recess 61 is formed around the axis A on the bottom surface 32a of the movable core 32. As shown in FIG.

This annular recess 61 is connected to the outer periphery of the cylindrical recess 35 and the movable core 3.
2. Located approximately in the center of the outer periphery. An annular rubber 60 having a rectangular cross section is baked and molded in the annular recess 61 .
The tip of 0 is made to protrude toward the stator 28.

Top surface 2 of stator 28 facing bottom surface 32a of movable core 32
A Teflon coating is applied on Bb to prevent the rubber 60 from sticking to the top surface 28b of the stator 28. The solenoid 34 (FIG. 1) is energized and the movable core 32
The position at which the movable core 32 is stopped is determined by the protruding length of the annular rubber 60, and therefore the stroke of the movable core 32 can be determined by the protruding length of the annular rubber 60.

Referring again to FIG. 1, a plate member 5, which is a lid made of a non-magnetic material, is provided at the upper end of the drive unit housing 27.
5 is fixed. A central portion of the plate member 55 extends along the axis A and forms a compressed air introduction path 41. An annular seal ring 56 is disposed on the outer peripheral surface of the plate member 55 to seal between the drive unit housing 27 and the plate member 55. A cylindrical spring insertion hole 57 is formed on the side opposite to the bottom surface 32a of the movable core 32, and the second compression spring 33 is inserted into this spring insertion hole 57. The other end of the second compression spring 33 is locked to the plate member 55.

A strainer 42 is provided in the middle of the compressed air introduction path 41, and the compressed air introduction path 41 is communicated with a compressed air source 43. The compressed air introduction path 41 communicates with the inside of the solenoid chamber 39 via an air passage 44 formed within the drive unit housing 27 . A communication hole 45 is formed in the flange portion 28a of the stator 28, and this communication hole 45 is connected to the solenoid 39.
and the spring chamber 24 are communicated with each other. Therefore, the compressed air introduction path 41 is communicated with the spring chamber 24 via the air passage 44, the solenoid chamber 39, and the communication hole 45. Therefore, these air passages 44, solenoid chamber 39, communication hole 45, and spring chamber 24 are filled with compressed air.

The needle 25 has a large diameter portion 25a extending in the axis entry direction approximately in the center thereof, and the large diameter portion 25a is slidably fitted into the needle insertion hole 22a below the spring chamber 24. .

A cylindrical nozzle chamber 46 having an axis B parallel to the axis A is formed within the body 21 . The lower end of the nozzle chamber 46 is
Through the compressed air outflow passage 47, the needle large diameter portion 25a
It communicates with the needle insertion hole 22 below. The compressed air outflow passage 47 extends obliquely to the needle insertion hole 22 toward the nozzle opening 23 . The compressed air outlet passage 47 is obliquely connected to the nozzle chamber 46 at an angle slightly greater than 90 degrees with the axis B, for example about 110 degrees. Referring to FIGS. 1 and 4, the connection part of the compressed air outflow passage 47 with the needle insertion hole 22 is a small diameter part 47a, and the axis X of the small diameter part 47a is aligned with the compressed air outflow passage 47.
is deflected upward from the axis Y of This amount of deviation is equal to the difference between the inner diameter of the compressed air outflow passage 47 and the inner diameter of the small diameter portion 47a.

As a result, a stepped portion 48 is formed at the connection portion between the small diameter portion 47a and the compressed air outflow passage 47. This step 48 is the fourth
As shown in the figure, there is no step at the top 48a, and the step increases downward, reaching the maximum step at the bottom 48b.

Referring again to FIG. 1, 49 is a compressed air outflow passage 47.
It is a stopper for sealing one end of the. A side surface of the nozzle chamber 46 is communicated with the spring chamber 24 via a compressed air inflow passage 50. The compressed air inflow passage 50 includes a horizontal passage 50a that extends straight from the side surface of the nozzle chamber 46 in a direction perpendicular to the axis B;
It is provided with an inclined passage 50b that bends upward and is obliquely connected to the spring chamber 24.

A nozzle 52 of a fuel injection valve 51 is arranged within the nozzle chamber 46 . The fuel injection valve 51 is arranged coaxially with the axis B.

The nozzle 52 is also arranged on the axis B, and the nozzle 52 is connected to the axis B.
Fuel with a small spread angle is injected along the Therefore, the fuel injected from the fuel injection valve 51 is transferred to the compressed air outlet passage 4.
7. The injected fuel collides with the inner wall surface with great force, and as a result, the injected fuel is rapidly turned into an emulsion.

FIG. 5 shows a plan view of the body 21 from which the assembly parts above the body 21, the needle 25, etc. have been removed. Fifth
Referring to the figure, the compressed air outflow passage 47 is formed along an axis Y that connects the axis A and the axis B. On the other hand, the compressed air inflow passage 50 is formed along the axis. This axis line passes through the axis line and is a tangent to the outer peripheral side surface of the nozzle chamber 46. As a result, the nozzle chamber 46 of the compressed air inflow passage 50
The opening area can be increased.

Referring to FIG. 1, the needle insertion hole 22, the compressed air outflow passage 47, the nozzle chamber 46, and the compressed air inflow passage 50
is communicated with a compressed air source 43 via the spring chamber 24 and the compressed air introduction path 41. Therefore, the needle insertion hole 22, the compressed air outflow passage 47, the nozzle chamber 46, and the compressed air inflow passage 50 are filled with compressed air.

Fuel is injected into this compressed air from the nozzle 52 along the axis B. The compressed air outflow passage 47 is connected to the nozzle chambers 46 and 90.
Since the injected fuel collides with the inner wall surface of the compressed air outflow passage 47, the fuel is rapidly converted into an emulsion. Most of this injected fuel accumulates in the compressed air outflow passage 47 immediately upstream of the step portion 48. At this time, a small amount of fuel accumulates at the nozzle opening 23 at the tip of the needle insertion hole 22. Next, when the solenoid 34 is energized, the movable core 32 is slidably displaced toward the stator 28,
As a result, the movable core 32 moves the needle 25 to the first compression spring 3
Since it is moved in the direction of the nozzle port 23 against the spring force of 0, the nozzle port 23 is opened. As soon as the needle 25 opens the nozzle port 23, a small amount of fuel accumulated in the nozzle port 23 is forced out from the nozzle port 23 into the combustion chamber 4 (FIG. 7) and ejected. needle 2
5 opens the nozzle port 24, compressed air from the compressed air source 43 passes through the compressed air introduction path 41 to the solenoid chamber 3.
The compressed air flows into the spring chamber 24 and the compressed air inflow passage 5.
After flowing into the needle insertion hole 22 through the compressed air outlet passage 47 and the compressed air outflow passage 47, the air flows toward the nozzle port 23. Since the solenoid 34 is cooled while the compressed air passes through the solenoid chamber 39, the solenoid 34 is prevented from overheating. Furthermore, since the compressed air is heated by the solenoid 34, atomization of the fuel can be improved. The compressed air flowing through the nozzle chamber 46 and the compressed air outflow passage 47 atomizes the fuel adhering to the inner wall surfaces of the nozzle chamber 46 and the compressed air outflow passage 47 and the fuel accumulated in the stepped portion 48, and mixes with the fuel while flowing through the nozzle port. The fuel is carried away toward 23 and ejected from the nozzle port 23. Therefore, fuel spray that is atomized and well mixed with air is ejected from the nozzle port 23. That is, from the beginning of injection when the needle 25 opens the nozzle port 23 and injects fuel and air, atomized fuel that is well mixed with air can be ejected from the nozzle port 23, and a good air-fuel mixture can be produced. can be formed. Further, since the compressed air inflow passage 50 opens in the tangential direction of the nozzle chamber 46, the compressed air flows while swirling along the inner circumferential wall surface of the nozzle chamber 46. Therefore, the fuel adhering to the inner circumferential wall surface of the nozzle chamber 46 can be efficiently carried away.

FIG. 7 shows a case where the air blast valve 20 is applied to a two-stroke engine, and fuel injection from the air blast valve 20 starts a little before the air intake valve 5 closes. When the engine is operated at low load, the flow rate of fresh air N flowing into the combustion chamber 4 is slow, so the injected fuel gathers around the spark plug 9, thus achieving good ignition. On the other hand, during high-load engine operation, strong loop scavenging is performed because the flow rate of fresh air N is high, and the injected fuel is carried along the inner wall surface of the combustion chamber 4 by the fresh air flow N flowing in a loop shape. A homogeneous mixture is formed inside. As a result, the engine can ensure high output.

FIG. 8 shows the metered fuel injection amount from the fuel injection valve 51,
The relationship with the flow rate of air ejected from the nozzle port 23 is shown.

Conventionally, when most of the fuel metered by the fuel injection valve 51 is accumulated in the nozzle port 23, the fuel is forced out of the nozzle port 23 in a liquid state by air pressure, and fuel injection from the nozzle port 23 is started. Initial fuel atomization and mixing with air were not good. Furthermore, since air does not flow out from the nozzle port 23 until after the fuel has been pushed out, as shown in FIG. 8, the air flow rate tends to decrease as the fuel injection amount increases. In this embodiment, most of the fuel flows through the compressed air outflow passage 47.
Since almost no fuel accumulates in the step 48 of the fuel and in the nozzle port 23, the air flow path is not blocked by the fuel, and the air can flow out from the nozzle port 23 together with the fuel. Therefore, as shown in FIG. 8, the air flow rate hardly changes depending on the fuel injection amount, and the maximum air flow rate can be lowered compared to the conventional one, as shown by the dashed line. .

FIG. 9 shows the displacement of the movable core 32 and needle 25 of a conventional air blast valve. Referring to FIG. 9, when the solenoid is turned on at point (a), the movable core 32 begins to displace toward the stator 28 at point (b), so that the needle also resists the spring force of the first compression spring 30. Then, the nozzle port 23 starts to be displaced in the valve opening direction. At time (c), the annular rubber 60 attached to the bottom surface 32a of the movable core 32 is locked to the top surface 28b of the stator 28, and the displacement of the movable core 32 is completed. On the other hand, the needle 25 is further displaced toward the opening direction of the nozzle opening 23, and is displaced to a position where the spring force of the first compression spring 30 and the force acting on the needle 25 in the opening direction of the nozzle opening 23 are balanced, resulting in overshoot. do. At this time, the movable core 32 and the rear end portion 31 of the needle 25 are disengaged. Subsequently, the needle 25 is displaced toward the movable core 32 by the first compression spring 30, and the movable core 32 and the rear end portion 31 of the needle 25 are engaged again. Subsequently, when the solenoid 34 is turned off at time (d), the needle 25 is displaced in the direction of closing the nozzle port 23 by the spring force of the first compression spring 30.
Therefore, the movable core 32 is also displaced toward the plate member 55 against the spring force of the second compression spring 33. (
At time e), the valve body 26 engages with the nozzle port 23 and closes the nozzle port 23, so that the displacement of the needle 25 ends. On the other hand, the movable core 32 is further displaced toward the plate member 55 to a position where the spring force of the second compression spring 33 and the force acting on the movable core 32 toward the plate member 55 are balanced. At this time, the movable core 32 and the rear end portion 31 of the needle 25 are disengaged. Subsequently, the movable core 32 is moved to the needle 25 by the second compression spring 33.
The movable core 32 and the rear end portion 31 of the needle 25 engage with each other again at the (to) point.At this time, the movable core 32 absorbs the kinetic energy in the opening direction of the nozzle opening 23. The needle 25 is displaced in the opening direction of the nozzle opening 23 and the nozzle opening 23 is opened.When the needle 25 is displaced in the opening direction of the nozzle opening 23, the spring of the first compression spring 30 is The force acts on the needle 25 and the movable core 32 to displace the nozzle port 23 in the direction of closing the nozzle port 23, thereby closing the nozzle port 23. In this way, at the point (e), the nozzle port 23 is closed.
Immediately after the valve is once closed, the bouncing of the movable core 32 causes the needle 25 to malfunction, causing the nozzle port 23 to open at the same time. If the nozzle port 23 is once closed and then opened again due to malfunction of the needle 25, the following problems may occur, for example. When the amount of injected fuel increases, such as when the load is high, all the fuel supplied into the air blast valve 20 is not completely injected from the nozzle port 23, and some fuel is deposited near the nozzle port 23. It adheres and remains inside the needle insertion hole 25. In this way, when the nozzle port 23 is once closed and then reopened, the liquid fuel remaining near the nozzle port 23 will be pushed out from the nozzle port 23 in the latter half of the compression stroke, and this fuel will be atomized well. The problem arises that it does not work.

FIG. 10 shows a schematic model diagram for considering the amount of overshoot of the movable core 32. The mass of the needle 25 is M
l, the mass of the movable core 32 is M2, the spring coefficient of the first compression spring 30 is kls, the spring coefficient of the second compression spring 33 is 2, the normal lift amount of the needle 25 is y1, the overshoot amount of the movable core 32, that is, the The amount of displacement from the closed position of the nozzle port 23 toward the plate member 55 shown in FIG. . Here, the main purpose is to understand the tendency of the correlation between the amount of overshoot of the movable core 32 and the specifications of each part, and the frictional resistance of each sliding part and the like are ignored. Applying the law of conservation of energy, we perform the following considerations. The energy stored by the displacement y of the first compression spring 30 is transferred to the needle 25 and the movable core 3.
Considering that everything is given in 2, then holds true. On the other hand, it is possible to consider that the energy given to the movable core 32 is given to the second compression spring 33 due to this. When calculating the overshoot amount X of the movable core 32 by eliminating V from equations (1) and (2), we get:
If the overshoot amount X of the movable core 32 is 2, and the spring loads of the first compression spring 30 and the second compression spring 33 when the nozzle port 23 is closed are respectively F and F2, the following equation holds true.

Fl = Zl '+...(
4〉F2=22 ・k2...
(5) However, Fl > F2 Here, Zl and Z2 are the displacement amounts of the first compression spring 30 and the second compression spring 33 when the nozzle port 23 is closed. From equations (4) and (5), substituting equation 6) into equation (3).If C is set to 1 for simplicity, the following is obtained. From equation (8), in order to reduce the overshoot amount X of the movable core 32, it is necessary to decrease the ratio of Fl and F2, decrease the mass M2 of the movable core 32, and increase the mass Ml of the needle 25. . Mass Ml of needle 25
It cannot be increased because increasing the fuel injector will reduce the responsiveness of the fuel injector. Moreover, the nozzle opening 23 is ΔF (=Fl−F2
), a force greater than a predetermined value is required as ΔF, but by increasing both Fl and F2, Fl/F2 can be reduced without maintaining ΔF above a predetermined required value. Incidentally, the amount of displacement of the needle 25 due to malfunction is approximately proportional to the amount of overshoot X of the movable core 32. Therefore, the amount of displacement of the needle 25 can be estimated from ε.

Table 1 below shows the movable core 32 when M is a constant value and ε is changed by changing Mz, Ft and F2.
The amount of displacement caused by malfunction of the needle 25 due to overshoot is shown. FIG. 11 is a plot of the relationship between ε and the amount of displacement of the needle, and it can be seen that as ε is decreased, the amount of displacement of the needle is also decreased in proportion to ε. 3 shows a conventional example, in which the amount of displacement of the needle 25 is 75 -, and has the above-mentioned problems. 3 shows this embodiment, and the displacement amount of the needle 25 can be reduced to 34-.

FIG. 12 shows the movable core 32 and needle 2 of this embodiment.
The displacement of 5 is shown. Referring to FIG. 12, the amount of overlap 5-1 of the needle 25 at time (c) is
By decreasing the mass M2 and increasing the set load F1 of the first compression spring 30, it is possible to significantly reduce the load. When the valve is closed, the movable core 32
By reducing the kinetic energy of the needle 25, the amount of displacement of the needle 25 at the point in time can be greatly reduced. Further, as the amount of displacement of the needle becomes smaller, the time during which the needle is open becomes very short, and thus almost no fuel is ejected from the nozzle port 23.

Referring again to FIG. 11, the displacement of the needle is 45-
If it is less than 0.3, there is no problem as described above in practical use.

Note that this embodiment does not utilize the damping effect of fuel, so there is no need to seal the fuel and fill the area around the movable core 32 with fuel, so the structure is simple. Steam is generated and the movable core 3
The behavior of 2 does not become unstable.

〔Effect of the invention〕

By reducing the kinetic energy applied to the movable core, the amount of displacement of the needle caused by bouncing of the movable core after the nozzle port is once closed can be reduced to a range that does not interfere with engine operation.

[Brief explanation of drawings]

Figure 1 is a longitudinal cross-sectional view of the air blast valve, Figure 2 is an enlarged view of the engaging portion between the needle and movable core in Figure 1, Figure 3 is a bottom view of the movable core, and Figure 4 is the figure in Figure 1. Fig. 5 is a plan view of the body with the upper part removed, Fig. 6 is a bottom view of the inner wall surface of the cylinder head of the two-stroke engine shown in Fig. 7, The figure is a side sectional view of a two-stroke engine, Figure 8 is a diagram showing the relationship between fuel injection amount and air flow rate, Figure 9 is a diagram showing the displacement of the movable core and needle of a conventional air blast valve, and Figure 1 The figure is a model diagram for examining the displacement of the movable core and needle, and Figure 11 is ε
FIG. 12 is a diagram showing the relationship between the amount of displacement of the needle and the amount of displacement of the needle, and FIG. 12 is a diagram showing the displacement of the movable core and the needle of the air blast valve according to the embodiment of the present invention. 20... Air blast valve, 23... Nozzle port, 25
... Needle, 26 ... Valve part, 30 ... First compression spring, 32 ... Movable core, 33 ... Second compression spring, 52 ... Spout. Fig. 2 Fig. fig. Fig. fig. Fig. fig. Fig. Fig. 11 Fig. 10 Fig. 12 Fig.

Claims (1)

[Scope of Claims] A nozzle port is formed at one end of the compressed air passage, a fuel supply port is formed in the middle of the compressed air passage, and a valve body for opening and closing the nozzle port is formed at the tip of the needle. engaging a rear end of the needle with one end of the movable core;
The needle is urged toward the movable core by a first urging means to close the nozzle port, and the movable core is urged toward the needle by a second urging means, and the movable core is urged toward the needle by a second urging means. By electromagnetically driving the movable core, the needle is displaced against the urging force of the first urging means to open the nozzle port, and the fuel is supplied from the fuel supply port into the compressed air passage. In the fuel injection device, the mass of the needle is M_1, the mass of the movable core is M_2, and the first urging means in the nozzle port closed state. The biasing force of F
_1, and the urging force of the second urging means in the nozzle mouth closed state is F_2, then [(F_1/F_2)-1]・M_2/(M_1+M_
A fuel injection device for an internal combustion engine in which the value calculated by 2) is 0.3 or less.