JPH048310Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention performs fuel injection in two stages, pilot injection and main injection, by installing a dodge plunger that presses the needle valve via a nozzle spring. The present invention relates to a fuel injection valve.

[Prior Art] An example of a conventional fuel injection valve of this type is the one described in Japanese Patent Application Laid-Open No. 61-255268. As shown in FIG. 7, this fuel injection valve includes a needle valve 2 that is seated and separated from a valve seat 1, a needle valve 2 that is seated and separated from a tapered valve seat hole 3, and a needle valve 2 that is seated and separated from a valve seat 1, and a needle valve 2 that is seated and separated from a valve seat hole 3 having a tapered shape. The needle valve 2 is lifted by the fuel sent from the passage 6 to the fuel storage chamber 7, and a branch passage 8 branched from the passage 6 is provided. by the fuel sent through the dodge plunger 5
By lifting the fuel injection hole 9, fuel is injected from the injection hole 9 in two stages: pilot injection and main injection.

In other words, if the diameter and seat diameter of the needle valve 2 are D ₁ and d ₁ , respectively, and the diameter and seat diameter of the dodge plunger 5 are D ₂ and d ₂ , respectively, then the pressure receiving area of the needle valve 2 when it is open and when it is closed is S _O1 and S _C1 are as follows: S _O1 = πD ₁ ² /4 S _C1 = π (D ₁ ² − d ₁ ² )/4, and the pressure receiving area of the dodge plunger 5 when the valve is open and closed is S _O2 , S _C2 S _O2 = πD ₂ ² /4 S _C2 = π(D ₂ ² −d ₂ ² )/4. These pressure receiving areas have the following relationship.

S _O2 > S _O1 > S _C1 > S _C2 Therefore, when fuel is sent to the fuel storage chamber fuel 7 from the valve closed state shown in FIG. 7A, the needle valve first opens as shown in FIG. 7B. 2 lifts. Immediately after that, the dotsuji plunger 5 lifts. Then,
Since the pressure receiving area of the dodge plunger 5 increases from S _C2 to S _O2 , the dodge plunger 5 lifts against the nozzle spring 4 to the maximum lift position. As a result, the pressing force of the nozzle spring 4 against the needle valve 2 becomes greater than the pressing force of the fuel, so that the needle valve 2 is seated as shown in FIG. 7C.
Pilot injection is performed from the start of lifting of the needle valve 2 until the needle valve 2 is seated. After needle valve 2 is seated,
When the fuel pressure increases further, the needle valve 2 starts to lift again, as shown in FIG. 7D, and main injection is performed.

Note that after the main injection, the needle valve 2 is seated, and then the dot plunger 5 is seated, returning to the original state shown in FIG. 7A.

[Problems to be solved by the invention] As mentioned above, according to the conventional fuel injection valve, fuel injection is supposed to be performed in two stages, but in reality, the problem is that pilot injection is hardly performed. It was hot.

That is, as is clear from FIG. 7A, when the dodge plunger 5 is seated in the valve seat hole 3, the seating portion of the dodge plunger 5 and the sliding portion 5
A ring-shaped closed space S is formed between the upper end of a and the upper end of a. The high-pressure fuel that flows into the sealed space S when the dodge plunger 5 is lifted is contained by the dodge plunger 5 being seated. Due to the fuel sealed in this sealed space S,
The dodge plunger 5 is constantly pressed toward the needle valve 2, and the pressure receiving area of the dodge plunger 5 when seated becomes larger than S _C2 by that much. As a result, when the fuel is pumped, the dodge plunger 5 lifts before or almost simultaneously with the needle valve 2 starting to lift, and there is no longer a delay in the lift of the dodge plunger 5. This has resulted in a situation where pilot injections are almost never performed.

[Purpose of the invention] This invention was made to solve the above problem, and can prevent high-pressure fuel from being trapped in a closed space, thereby ensuring pilot injection. The purpose of the present invention is to provide a fuel injection valve that can

[Structure of the device] In order to achieve the above object, this device is designed to open the valve between the sealed space and the low pressure side of the fuel when the dodge plunger is seated in the valve seat hole. It is characterized by forming a leak passage which is closed when the dodge plunger is lifted a predetermined distance from the valve seat hole.

[Example] Hereinafter, an example of this invention will be described with reference to FIGS. 1 to 6.

1 to 3 show an embodiment of this invention, and reference numeral 11 in the figures indicates the valve body. The valve body 11 includes a nozzle body 12 and a holder body 13. The nozzle body 12 and the holder body 13 are connected to each other by a nut 14 that
Fixed via 5.

Inside the nozzle body 12, a needle valve sliding hole 16, a fuel reservoir chamber 17, a valve seat 18, and an injection hole 19 are formed in order from the upper end to the lower end. A needle valve 20 is provided in the hole 16.
is slidably provided. A valve portion 21 is formed at the lower end of the needle valve 20 and is seated on and separated from the valve seat 18.

On the other hand, inside the holder body 13, a plunger housing hole 23 and a spring housing hole 24 are formed at the upper end side and the lower end side, respectively, sandwiching the partition wall 22 in the center. The plunger storage hole 23 and the spring storage hole 24 are communicated with each other through a communication hole 25 formed in the partition wall 22.

In the plunger storage hole 23, a valve seat plate 27 having a through hole 26 formed in the center with approximately the same diameter as the communication hole 25, a ring-shaped shim 28, and a cylinder member 29 are arranged in order upward from the partition wall 22. They are each inserted and fixed by a bolt 30 screwed into the upper end of the plunger housing hole 23. Inside the cylinder member 29, a cylinder hole 31, a tapered valve seat hole 32, and an inflow hole 33 are formed in order from the lower end side to the upper end side. It is provided so as to be slidable in any direction and in a liquid-tight manner.
A valve seat 34a that is seated and separated from the valve seat hole 32 is provided at the upper end of the dodge plunger 34.
is formed. This valve part 34a is the valve seat hole 32
When seated in the cylinder hole 31, which is located between the seating portion of the dodge plunger 34 relative to the valve seat hole 32 and the upper end of the sliding portion 34b of the dodge plunger 34, similar to the conventional fuel injection valve described above, A sealed space S is defined by the inner peripheral surface of the cylinder hole 31 and the outer peripheral surface of the dodge plunger 34. Further, in the seated state, the lower end surface of the dodge plunger 34 is spaced apart from the valve seat plate 27 by a distance L, and the dodge plunger 34 can be lifted by this distance L.

Note that the lift distance L can be changed as appropriate depending on the thickness of the shim 28.

Further, a nozzle spring 35 is arranged inside the spring storage hole 24. This nozzle spring 35 supports the dodge plunger 34 in the seating direction (upward) via an upper spring seat 37 and a shaft portion 34C formed on the lower end surface of the dodge plunger 34.
while urging the needle valve 20 through the lower spring seat 37 and the shaft portion 20a formed on the upper end surface of the needle valve 20.
is urged in the seating direction (downward).

Further, a plug 38 to which a fuel pipe (not shown) is connected is fixed to the upper end of the nozzle body 13 with a nut 39, and a fuel supply hole 40 is formed in the plug 38. . The fuel supply hole 40 includes a passage 41 formed between the holder body 13, the spacer 15, and the nozzle body 12.
communicates with the fuel storage chamber 17 via the
A gap 42 formed between the lower end surface of the plug 38 and the upper end surfaces of the holder main body 13 and the bolt 30;
It communicates with the inflow hole 33 via an introduction hole 43 formed in the bolt 30 . Therefore, when fuel is pumped, the needle valve 20 and the dodge plunger 34
is lifted against the nozzle spring 35.

Note that the pressure-receiving areas of the needle valve 20 when it is open and closed are S _O1 and S _C1 , respectively, and the dodge plunger 3 is
4, the pressure receiving area when the valve is open and when the valve is closed, respectively.
Of course, when S _O2 and S _C2 are set, S _O2 > S _O1 > S _C1 > S _C2 .

By the way, as described above, if the fuel injection valve is simply configured as described above, high-pressure fuel is confined within the closed space S, and the dodge plunger 34 is pressed downward by this fuel. Therefore, the pressure receiving area of the dot plunger 34 does not change to two stages, and pilot injection is no longer performed.

Therefore, in the fuel injection valve of this invention, a leak passage is formed in the dodge plunger 34, and the fuel in the space S is released to the outside through this leak passage. That is, Figures 1 to 3
In the embodiment shown in the figure, the dodge plunger 3
A flattened portion 44 is formed on the outer peripheral surface of the sliding portion 34b of No. 4, and a leak passage 45 is formed between this flattened portion 44 and the inner peripheral surface of the cylinder member 29. In this leak passage 45, the flat portion 44 is connected to the sliding portion 34b.
Since it extends from the upper end to the lower end, its upper end is open to the closed space S, and its lower end is open from the lower end of the cylinder member 29. Therefore, the fuel sealed in the sealed space S by the dodge plunger 34 being seated in the valve seat hole 32 travels to the lower end of the cylinder member 29 through the leak passage 45, and further passes through the valve seat plate 27. The spring storage hole 24 is reached through the through hole 26 and the communication hole 25. The fuel that has reached this spring storage hole 24 passes through a return passage 46 formed between the holder main body 13 and the plug 38, a pipe fitting 47 provided on the plug 38, and a pipe (not shown) to the low pressure of the fuel. It is adapted to be returned to a side fuel tank (not shown). As is clear from the fact that the spring storage hole 24 is connected to the fuel tank, the pressure inside the spring storage hole 24 is approximately the same as the internal pressure of the fuel tank.
The overflowing fuel will be returned to the fuel tank.

Further, the distance W from the center of the dodge plunger 34 to the flat portion 44 is the distance W from the center of the dodge plunger 34 to the through hole 26 of the valve seat plate 27.
is larger than the radius R of . Therefore,
When the dodge plunger 34 lifts and its lower end surface hits the valve seat plate 27, the lower end of the leak passage 45 is blocked by the valve seat plate 27, thereby blocking the leak passage 45 from the through hole 26. The return passage 46 is thus blocked off.

In this way, in the above fuel injection valve, since the fuel in the sealed space S is returned to the fuel tank via the leak passage 45, the dodge plunger 34 is moved in the lift direction by the fuel in the sealed space S. Never be pressured. Therefore, by lifting the dot plunger 34 after the needle valve 20 has been lifted, the pilot injection can be reliably performed. Moreover, when the dodge plunger 34 is lifted to the maximum, the leak passage 45 is blocked from the return passage 46, so that fuel does not leak out from the leak passage 45 during injection, and therefore, during injection. This can prevent fuel pressure from dropping.

In addition, while the Dotsuji plunger 34 is being lifted,
Fuel will leak out through the leak passage 45, but the time from when the dodge plunger 34 starts lifting until it reaches the maximum lift position is extremely short, and the amount of fuel that leaks out during that time is extremely small. . Therefore, the fuel pressure rarely decreases during fuel injection, and does not affect fuel injection.

Next, another embodiment of this invention will be described. In the following embodiments, only points different from the above embodiments will be explained.

In the fuel injection valve shown in FIG. 4, a leak passage 48 is formed inside the dodge plunger 34. In this case, it goes without saying that one end of the leak passage 48 opens on the outer peripheral surface of the dodge plunger 34 facing the sealed space S, and the other end opens on the lower end surface of the dodge plunger 34 that is spaced apart from the through hole 26 of the valve seat plate 27. It is. Therefore, Dotsuji Plunger 3
4 is seated in the valve seat hole 32, the fuel in the sealed space S is discharged through the leak passage 48 and the through hole 26, the communication hole 25 shown in FIG. It is returned to the fuel tank via the joint 47. On the other hand, when the dotsuji plunger 34 hits the valve seat plate 27, the leak passage 4
The lower end opening of 8 is shielded by the valve seat plate 27,
This blocks the leak passage 45 from the through hole 26 and, in turn, from the return passage 46.

In addition, the fuel injection valve shown in FIGS. 5 and 6 has a leak passage 49 that is connected to a diagonal hole 49a that is open to the closed space S, and a horizontal hole that intersects with this diagonal hole 49a and opens to the outer peripheral surface of the dodge plunger 34. A return passage 50 is made to pass through the wall of the cylinder member 29, and an annular groove 51 forming a part of the return passage 50 is formed on the inner peripheral surface of the cylinder member 29. 3
4 is seated in the valve seat hole 32, the horizontal hole 49b of the leak passage 49 and the annular groove 51 face each other with a length l in the axial direction of the dodge plunger 34. In this case, the opposing length l
is made shorter than the maximum lift distance L of the dodge plunger 34, and the horizontal hole 49b is blocked by the cylinder member 29 before the dodge plunger 34 reaches the maximum lift position, and the horizontal hole 49b (leak passage 49) and the return passage are 50 is cut off.

[Effects of the invention] As explained above, according to the fuel injection valve of this invention, when the dodge plunger is seated in the valve seat hole between the sealed space and the low pressure side of the fuel, it is opened and the sealed space and the fuel are separated. This is because a leak passage is formed that communicates with the low pressure side of the valve seat and is closed when the dodge plunger lifts a predetermined distance from the valve seat hole.
It is possible to prevent high-pressure fuel from being trapped in a closed space, thereby ensuring pilot injection, and when the dodge plunger lifts a predetermined distance, the leak passage is covered, so there is no leakage during injection. Effects such as being able to prevent the fuel pressure from decreasing can be obtained.

[Brief explanation of drawings]

Figures 1 to 3 show an embodiment of this invention, in which Figure 1 is a longitudinal sectional view, Figure 2 is an enlarged sectional view of the main part, and Figure 3 is taken along the line - - of Figure 2. 4 is a sectional view taken in the direction of arrows; FIG. 4 is a view similar to FIG. 2 showing another embodiment of this invention; FIGS. 5 and 6 are views showing still other embodiments of this invention; is a view similar to FIG. 2, FIG. 6 is a sectional view taken along the line - in FIG. 5, and FIGS. 7B is a diagram showing a state in which the needle valve and the dot plunger are both seated, FIG. 7B is a diagram showing a state in which pilot injection has started, FIG. 7C is a diagram showing a state in which pilot injection is completed, and FIG. FIG. 3 is a diagram showing a state in which main injection is being performed. 11... Valve body, 20... Needle valve, 27... Valve seat plate (member on the valve body side), 29... Cylinder member,
31... Cylinder hole, 32... Valve seat hole, 34...
Dotsuji plunger, 34a...valve part, 34b...
Sliding part, 35... Nozzle spring, 45, 4
8, 49... Leak passage, 46, 50... Return passage, S... Closed space.

Claims (1)

[Scope of utility model registration request] The valve body 11 is provided at one end of the valve body 11, and is seated on the valve seat 18 to close the injection hole 19, and is lifted from the valve seat 18 to open the injection hole 19, so that the pumped fuel is transferred to the injection hole. a needle valve 20 for injecting from 19; and a needle valve 20 inside the valve body 11;
A cylinder hole 31 is formed in a line with the needle valve 20 and the end opposite to the needle valve 20 is connected to the fuel pumping side through a valve seat hole 32 having a tapered hole shape. A dodge plunger 34 that is movably provided and has a valve portion 34a formed at one end that seats in the valve seat hole 32, and this dodge plunger 3.
4 and the needle valve 20, the needle valve 2
0 on the valve seat 18 and a nozzle spring 35 that seats the dodge plunger 34 in the valve seat hole 32, and when the dodge plunger 34 is seated in the valve seat hole 32, 32 and the dodge plunger 34
In the fuel injection valve in which a sealed space S is formed inside the cylinder hole 31 between the sliding portion 34b and the sliding portion 34b with respect to the cylinder hole 31, the dodge plunger 34 is provided between the sealed space S and the low pressure side of the fuel. a leak passage 45 that is opened when the valve seat hole 32 is seated to communicate the sealed space S with the low pressure side of the fuel, and is closed when the dodge plunger 34 is lifted a predetermined distance from the valve seat hole 32; 4
8,49.