JPS59200055A - Fuel injection device for compression firing engine - Google Patents

Abstract

PURPOSE:To aim at lowering the injection rate of fuel in an initial stage of fuel injection, as well at lowering engine noise and at enhancing the reliability of the fuel injection device in order to restrain the generation of nitrogenoxide, and to reduce the minimum fuel injection amount, by providing a restrictor which restricts fuel stream counterflowing through a spill port. CONSTITUTION:Along with the progress of fuel injection, the pressure of fuel compressed in an accumulating chamber 12 continuously lowers so that an injection terminating control valve 13 is depressed by a spring 14 to open, and therefore, the fuel in the accumulating chamber 12 counter-flows into passages 3a, 4a through passages 4b, 3b. At this time a suction return valve 20 is in its closed condition so that fuel does not overflow from a spill port 18, and therefore, the pressure of the fuel passage 4a is naturally made equal to the pressure in the accumulating chamber 12, resulting in a needle valve 8 tending to close. Since a restrictor 3f is disposed in a part of the passage 3a between the passage 3b and the suction return valve 20, the needle valve 8 initiates to close in a short time by pressure waves of fuel counter-flowing from the passage 3b.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of an accumulator type fuel injection device for a compression ignition engine (hereinafter referred to as a "diesel engine").

Accumulator type fuel injection system shortens the fuel injection period.

Although increasing the injection rate improves the thermal efficiency of the engine, due to its characteristics, the injection rate immediately after the start of injection increases.

It is difficult to control the small amount of fuel injection, making it difficult to apply to small engines, and it also causes the combustion pressure to rise rapidly.

Combustion pressure also increases.

This not only impairs engine reliability, but also increases combustion noise and nitrogen oxides in the exhaust.

If the fuel injection pressure is simply increased for the purpose of further increasing the injection rate, cavitation erosion may occur in the high-pressure fuel passage of the fuel injection device due to the sudden and high pressure amplitude of the fuel, which may destroy the injection device.

As a means of solving this problem, the present inventor previously applied for a patent application filed in 1986-670.
According to No. 5, an injection end control valve is installed in the fuel passage between the fuel passage communicating with the atmospheric pressure side of the needle valve and the pressure accumulation chamber, and when the needle valve is closed, pressure is applied in the direction to close it. We have developed an invention that significantly shortens the valve speed and injection period compared to conventional accumulator fuel injection systems.

In addition to the above-mentioned invention, the present invention provides an arrangement in which, when the needle valve is opened, a throttle that throttles the flow of fuel flowing backward through the spill boat in the high-pressure fuel passage is connected to the fuel tank at the point where the passage from the control valve at the end of injection merges with the high-pressure fuel passage. By installing it on the side, the fuel injection rate at the initial stage of injection is reduced.

This suppresses the pressure rise rate and maximum pressure in the engine's combustion chamber, reducing engine noise.

The purpose is to improve reliability, suppress the generation of nitrogen oxide, and reduce the minimum fuel injection amount.

This will be explained in detail with regard to embodiments of the present invention.

As shown in FIG. 1, there is an injection device according to the present invention.

A nozzle assembly is connected to an injection pump device at the tip of the device.

The example in Figure 1 shows a unit injector type,
A rear end female screw 2 is screwed onto the end screw of the outer frame 1 of the injection pump device A and a nut constituting the outer frame of the nozzle assembly/body B. First, the specific structure of this nozzle assembly B will be explained. A control valve body 3 is inserted into the nut 2 from above. Upper spacer 4. Pressure accumulator 5. Lower spacer 6
and the needle valve body 7 are housed tightly and strongly compressed together.

An injection lower a is integrally formed at the tip of the needle valve body 7, and the opening and closing of this injection port is controlled by the valve seat 7b of the valve body and the valve face 8a of the needle valve 8.

The large diameter portion 8b of the needle valve 8 is fitted into the needle valve body 7 so as to be movable up and down.
At the upper end of this large diameter part, that is, on the atmospheric pressure side, there is a spring holder 9.
The spring 10 is firmly attached between the spring receiver 9 and the upper spacer 40, and the spring force presses the needle valve 8 downward to ensure that the nozzle face 8a and the valve seat 7b are seated.

A fuel passage 7c is provided within the needle valve body 7, and this passage communicates with a space 11 provided on the outer periphery of the needle valve small diameter portion 8c.

A fuel passage 6a is also formed in the lower spacer 6, and the upper end of this passage communicates with the pressure accumulating chamber 12 in the pressure accumulating cylinder 5, and the lower end communicates with the passage 7C in the needle valve body 7. There is.

The upper spacer 4 has passages 4b and 4c that communicate the fuel passage 4a that communicates with the atmospheric pressure side of the needle valve 8 and the pressure accumulation chamber 12.
is formed.

The fuel passage 4a communicates with a fuel passage 6a of the control valve body 6 and fuel passages 3b and 3c branching from this passage 3a, and furthermore, the passage 3a communicates with the fuel passage 1a of the outer frame 1. In the device, a throttle 3f is formed in the fuel passage 6a, as shown in detail in FIG.

The fuel passages 4a and 5a+5'g communicate with the atmospheric pressure side of the needle valve 8.

Reference numeral 16 denotes an end-of-injection control valve, which is provided between the passage 6b and the fuel passage 4b, and its large diameter portion isb fits into the control valve body 6 so as to be movable up and down, as shown in FIG. The valve face 13a of this control valve is pushed down by a compression spring 14 inserted into the outer frame 1, and pressed against the bottom of a recess 4# that opens into a passage 4 formed in the spacer 4. .

When the control valve 16 rises at the end of injection, this valve face 13a seats on the valve seat 3d of the control valve body 3 and blocks the flow of fuel between the passage 6b and the passage 4b.

On the other hand, between the fuel passage 3c and the passage 4c, a reverse flow valve 16 is provided in the control valve body 3 to block the backflow of fuel from the passage 4c to the passage 3c, and to allow fuel to flow in the opposite direction. When installing, the passage 3c is normally closed by a compression spring 15 housed within the upper spacer 4. A fuel return passage 17 returns fuel leaking from the sliding surfaces of the control valve body 3 and the end-of-injection control valve 16 to the fuel tank.

Reference numeral 18 designates a spill boat provided in the barrel 23. In the present invention, a throttle 18a is formed in the spill port 18 as shown in detail in FIG. 18 + and to prevent a sudden drop in pressure within the chicken bar 23 described later...Next, the injection pump device A inside the main body 1 will be explained.
A known suction-back valve 2o that fits loosely within the suction-back valve body 19 and prevents leakage has a function as a check valve by means of a compression spring 21, and a stopper 22 regulates the lift of the valve.

A plunger 24 slidably inserted within the barrel 26
has the same structure as the well-known Bosch type with a positive lead.

In the barrel 26, between the fuel port 25 and the fuel passage 26,
A check valve 28 is provided which is operated by a spring 27 and prevents the fuel from flowing back from the five passages 26 to the inlet 25.

In addition, between the fuel population 25 and the fuel return port 29.

It is necessary to properly prevent leakage between the fuel return port and the atmosphere using an O-ring or the like.

Note that the barrel 26 and the suction-back valve body 19 are attached to the main body 1 with screws 50.

The plunger 24, which has exactly the same structure as the Bosch type, is rotatably connected and driven by a crosshead 34 that is fitted into a hollow part at the upper end of the outer frame 1 so as to be able to move up and down, and has a passage 24a inside. and the notch surface 24b of the positive lead
The oil supply ends when the fuel injection device communicates with the spill port 17, and the amount of oil discharged due to the lifting height of the plunger thereafter passes through the spill port and is discharged from the fuel return port 29.9 Next, the operation of the fuel injection device of the present invention will be explained. do.

In FIG. 1, the amount of fuel to be injected at one time from a metering oil pump (for example, a Cummins PT pump or an electronically controlled metering oil pump) is 25. Chamber 2 in barrel 26 via check valve 28 and passage 26
3a.

As the plunger 24 descends from the top dead center, the check valve 28 is closed by high pressure oil, the pressure inside the chicken bar 25a increases, and the suction return valve 20 is pushed down, causing the fuel passage 1a,
It is fed under pressure to the atmospheric pressure side of the needle valve 8 via 3a and 4a.

At this time, the injection end control valve 13 is pushed down by the spring 14, and as shown in FIG. 2, its valve face 13a is separated from the valve seat 6d of the control valve body 3, and the valve is opened.

The fuel fed under pressure to the first passage 6a passes through the first passage 3b, the end-of-injection control valve 16, and the passage 4b, and is then fed under pressure into the pressure accumulation chamber 12.

As is well known, fuel oil is an elastic fluid, and its volume decreases in proportion to the increase in pressure and is stored in the pressure accumulator chamber 12.

The pressure inside the pressure accumulator 12 is set to the set pressure 1, for example io.

When the pressure reaches O atmospheric pressure, the injection end control valve 16 is pushed up against the downward force of the spring 14, so that the valve seat 3d and the valve face 13a are brought into contact and closed, blocking the connection between the passage 6b and the passage 4b. be done.

From this time on, the check valve 16 opens and the fuel that has passed through the nine passages 3c and 4c is further compressed to a high pressure and stored in the pressure storage chamber 12, and this pressure passes through the fuel passages 6a and 7c to the needle valve 8. It is added to the lower part 8d.

The pressure inside the passage 4a is also high as in the pressure storage chamber 12, and the pressure of the intake is applied to the upper side (atmospheric pressure side) of the large diameter portion 8 of the needle valve. In this state, the force of the spring 10 + fuel pressure Needle valve 8
In order to overcome the force pushing up the valve seat 7b, the pulsiface 8a is strongly pressed against the valve seat 7b, and the fuel is not splashed out from the injection lower a.

As the engine rotates, the plunger 24 is further pushed down, and when the maximum fuel injection amount is reached, the maximum pressure on the high pressure side of the injection system reaches, for example, 2000 atmospheres. Surface 24
b communicates between the passage 24a and the spill port 18.

As a result, the fuel oil on the high pressure side in the chamber 23a passes through the passage 24a, passes through the spill port 18, and then passes through the fuel return port 29.
overflows into.

However, since the spill port 18 is provided with the throttle 18a, the pressure inside the chamber 23a is gradually reduced.

Therefore, the suction-back valve 2o closes slowly.

Due to its suction and return action, passages 1a + 3a and 4
The pressure inside a is gradually lowered, and the atmospheric pressure that pushes down the large diameter portion 8b of the needle valve 8 also gradually disappears.

On the other hand, the high-pressure fuel in the pressure accumulation chamber 12 is pushed up by the reverse valve 16, and the injection path control valve 13 is pushed up because the pressure is, for example, 100.0 atmospheres or more, and the valve face 13a and valve seat 3d continue to close, and the fuel are passages 1a, 3a and 4a.
It does not flow back inward.

When the pressure on the atmospheric pressure side of the needle valve 8 decreases to a value as described above, the force of (area of the large diameter portion 8b of the needle valve - area of the small diameter portion 8c of the needle valve) x pressure is applied against the force of the spring 10. By gently pushing up the needle valve 8, the space between the valve face 8a and the valve seat 7b is opened, and fuel is injected into the engine combustion chamber from the injection lower a through this space. Immediately after the start of fuel injection, the lift of the needle valve 8 is small, so the valve face 8'a and valve seat 7
Since the area between a and a is narrowed, the amount of fuel injected per hour is small.

As time progresses, the chamber 23a and the passage 1a+
The fuel in 5a+ and 4a passes through the throttle 18a and overflows the pressure on the fuel tank side, lowering the pressure on the atmospheric pressure side of the needle valve 8. Accordingly, the lift of the needle valve 8 gradually increases, and the injection Increase the rate (fuel per hour, injection amount).

As the fuel injection progresses, the pressure of the fuel compressed in the pressure storage chamber 12 continues to decrease, and when it finally drops to, for example, 1000 atmospheres, the injection path control valve 16 is pushed down by the spring 14, and as shown in FIG. The valve is opened, and the fuel in the pressure accumulation chamber 12 flows back into the passages 5a and 4a through the passages 4b and 3b.

At this time, as described above, the suction valve 20 is in a closed state, the fuel does not overflow from the spill port 18, and the pressure in the fuel passage 4a is naturally the same as that in the pressure accumulator 12, and the upper part of the large diameter portion 8b of the needle valve This pressure is applied to the atmospheric pressure side and the needle valve 8 attempts to close. In the present invention, a part of the passage 3a between the passage 3b and the suction-back valve 20 is provided with the throttle 3f as described above.

The pressure wave of the fuel flowing backward from the passage 3b is reflected in front of the throttle 93f, rapidly reaches the atmospheric pressure side of the needle valve 8, and the needle valve 8 begins to close in a short time due to the action of this pressure wave.

Incidentally, in a conventional pressure accumulator type fuel injection device that does not have the throttle 18a, when the pressure in the fuel passage 4a disappears, the spring 1
When the pressure in the pressure accumulator x (area of the large diameter portion of the needle valve - area of the small diameter portion of the needle valve) is greater than the pressing force of 0, the needle valve 8 opens, but at the same time, pressure is also applied to the valve face 8a. Because it will be added.

Due to the increase in the pressure receiving area, the needle valve 8 is rapidly pushed up and fully opened.

In addition, in a pressure accumulator type fuel injection device having an injection path control valve 15 without a throttle 3f, after the injection path control valve 160 is opened, in addition to the fuel in the low pressure passages 3a and 4a, 9 If the fuel in the passage 1a is also compressed and then released, the pressure on the atmospheric pressure side of the needle valve 8 will not increase. 8
The rate of pressure increase on the atmospheric pressure side of the valve decreases, and the valve closing speed decreases by the amount of the decrease.

In a fuel injection device other than a unit injector type, such as a Bosch type, one passage 1a is replaced with a long injection pipe, and the valve closing speed is further reduced due to the volume and length of the injection pipe.

To explain the above phenomenon in more detail with reference to FIG. 6, the solid line 0-1 shows the pressure increase during pressure accumulation in the pressure accumulation chamber 12.

In the pressure accumulation chamber type fuel injection device, there is no need to rapidly accelerate the plunger due to its structure, so the flow velocity of the fuel during pressure accumulation is low (9) The resistance of the throttle 3f in the present invention is also low during pressure accumulation.

When point 1 is reached, the flow path between the cutout surface 24b of the plunger 24 and the spill port 18 opens, and the flow path 9 opens.
The high pressure fuel in the chamber 1a and the chamber 25a overflows from the spill port 18.

At this time, in the structure without the throttle 5f and the throttle 18a, the pressure in the passage 4a decreases rapidly, the pressure on the atmospheric pressure side of the needle valve 8 disappears, and the lift of the needle valve 8 rapidly closes due to the above-mentioned reason. The value increases from the valve state 1a to 1x as shown by the one-dot chain line, and the valve opens.

Accompanying this, the injection rate suddenly increases from 0 1C to 1y as shown by the dashed line, and thereafter the pressure in the accumulator continues to decrease following the solid line 1-2.

Accordingly, the injection rate also continues to decrease following the line 1y-2z.

Such a high injection rate at the beginning of injection causes a large amount of fuel to be rapidly burned in the combustion chamber of the engine.

There was a sudden pressure rise, and as mentioned above, high noise was generated.
Moreover, the combustion pressure becomes high, generating high stress in various parts of the engine, the combustion temperature also increases, and a large amount of nitrogen oxide is generated.

In the present invention, the provision of the throttles 3f and 18a provides flow resistance, which allows the pressure on the atmospheric pressure side of the needle valve 8 to be gradually reduced.

Accordingly, the lifting height of the needle valve 8 is also determined by the solid line 1a-2a in Figure 6.
It gradually increases as shown in .

When the lift of the needle valve 8 is low, the area between the valve face 8a and the valve seat 7b is smaller than the area of the injection lower a, which acts as a throttle and naturally lowers the injection rate.

Therefore, the injection rate is low at the beginning of injection and increases as the lift of the needle valve 8 increases, as shown by the solid line 1 cm2c.

This kind of fuel injection with a low injection rate at the beginning of injection.

It is possible to first ignite a small amount of fuel in the combustion chamber of the engine and then burn it according to the injection rate after ignition.
With lower noise due to lower pressure rise rate.

Lower combustion pressure reduces stress in various parts of the engine.

Furthermore, the generation of nitrogen oxides can be suppressed by lowering the combustion temperature.

When the internal pressure of the pressure accumulation chamber 12 decreases to the pressure at point 2 in the latter half of fuel injection, the end-of-injection control valve 13 opens as described above.

In a structure without a throttle 6f, this is caused by fuel flowing backward from the pressure accumulation chamber 12 through the end-of-injection control valve 16.

The fuel in the passages 4a + 3a and 1a is compressed to increase the pressure, and this pressure pushes the atmospheric pressure side of the needle valve 8 and closes it, so the passage 4 of the present invention having the throttle 3f
Compared to the structure that compresses only fuel a and 6a, the valve closing speed is slow, and the needle valve 8 continues to close following the solid line 2a-3x, during which the injection rate follows the dashed line 2z-'5z. The needle valve 8 is closed at point 3x.

Injection ends at point 6z.

On the other hand, in the structure of the present invention having the throttle 3f, the valve closing speed is high as described above, and the valve continues to close rapidly following the solid line 2a-6, and the injection rate during this period is represented by the solid line 2cm3c.

As mentioned above, the present invention increases the valve closing speed.

This shortened the fuel injection period and enabled combustion with high thermal efficiency.

Next, the point that the pressure accumulator type fuel injection device of the present invention facilitates fuel injection amount control at low output will be explained in detail based on FIG. In the conventional structure, when the output is low, the pressure in the pressure accumulating chamber is accumulated low according to the injection amount, as shown by the dotted line 0°-1°.

When the non-pilling port 18 is opened by the cutout surface 24b of the plunger 24, the needle valve 8 is moved along the dashed-dotted line 1a-1 as described above.
The valve suddenly opens following the line x, and the pressure in the pressure accumulator reaches the dotted line 1゛-2.
When it reaches the 9 point 21, the injection end control valve 13 opens, and as a result, the needle valve 8 moves to the dotted line 2'
'Continue to close the valve by following x' Point 3' Close the valve at x.

The injection rate during this period is 1cm1' as shown by the dashed-dotted line due to the above-mentioned reason.
7-2' Follow y-6°2, dashed line 1C-I'
The area force t surrounded by y-2'y-3'z-1c is the fuel injection amount during this period.

On the other hand, in the structure of the present invention having the throttle 3f and the throttle 18a, the lifting height of the needle valve 8 is changed along the line 1a-2'a-3 due to the change in the pressure inside the pressure storage chamber 12 shown by the nine-dot line 1'-2' as described above.
', and the injection rate during this period is indicated by the dotted line 1 c-2' c-
'5' d.

The fuel injection amount during this period is the dotted line 1cm2'c-3'd-1c
The area surrounded by

The reason why 11y is lower than 1y and the dotted line 1cm2'C is lower than the line ic-2cIc is that the pressure inside the pressure accumulator at the beginning of injection is lower than 1.

Comparing the area 1 c-1'y-2'y-3' z-1c and the area 1 cm2'c-3' d-1c, it is clear that the latter method of the present invention reduces the minimum injection amount. will be understood.

Note that the throttle 18a of the spill port 18 is installed in the plunger 240 passage 24 instead of being installed in the spill boat 18.
Even if you reduce the area of a and install it here, the effect will not change at all.

That is, FIG. 5 shows the barrel 23. of FIG. The vicinity of plunger 24 and spill port 18 is shown.

The difference from FIG. 1 is that the plunger 24 is provided with a diaphragm 24c having an end surface 24d.

In addition, although the plunger 24 has a reverse lead in FIG. 5, this has no effect on the operation and effect of the present invention.

Next, to explain the operation of the embodiment shown in FIG. 5, as shown in FIG. After the oil is supplied to the chamber 12, the notch surface 24b of the plunger 24.

Open the flow path with the spill boat 18 (and open the flow path with the spill boat 18)
The high-pressure fuel in the tank a begins to overflow, but as shown in FIG. 5, the gap between the throttle 24c and the spill boat 18 is small and acts as a resistance to the fuel passing through and overflowing.

The operation and effect of the embodiment shown in FIG. 5 will be further explained in detail with reference to FIG. 7. A solid line 0-1 shows the pressure increase in the pressure accumulator 12 when the injection amount is large.

When point 1 is reached, the flow path between the cutout surface 24b and the spill boat 18 is opened, and the needle valve 8 of FIG. 1 begins to open as described above.

However, as shown in FIG. 5, there is a throttle 24c between the notch surface 24b and the spill boat 18.

Since the flow path area is narrow, it becomes a resistance, so the opening speed of the needle valve is slow, following the solid line 1a-1b, and the injection rate is the solid line 1 x
Follow -17.

Further, when the plunger 24 descends, it opens the flow path between the end face 24d and the spill port 18, rapidly increasing the flow path area, and the lifting height of the needle valve 8 increases rapidly, reaching a maximum of .

When the head becomes large and the pressure in the accumulator decreases to point 2,
Due to the above-mentioned reason, the end-of-injection control valve 16 opens, and the lift of the needle valve 8 begins to close rapidly from point 2a.

Close at point 2b.

During this period, the injection rate increases rapidly from point 1y to point 1z, as shown by the solid line, and thereafter continues to decrease toward point 2x as the pressure in the pressure accumulator decreases, and ends at point 9, 2y.

When the fuel injection amount is small7, for example, when the engine is running at idle, the pressure in the accumulator increases as shown by the dotted line 01-1°, and the pressure in the accumulator rises as shown by the dotted line 01-1°, and the pressure in the accumulator rises between the notch surface 24b of the plunger 24 and the spill boat 18 in FIG. The needle valve 8 begins to open.

As shown in FIG. 5, when the injection amount is small, the throttle 24c facing the spill boat 18 is long, and the structure is such that the overflow of fuel into the spill boat 18 is continued to be throttled during the entire period of fuel injection. The opening speed of the needle valve is low9
Open the valve by following the dotted line 1a-2'a.

At this time, the trap injection rate is naturally low and the injection continues following the dotted line 1x-2'x.

Therefore, the rate of decrease in the pressure in the pressure accumulator is also low, as indicated by the dotted line 1'.
-2' and when the pressure decreases to point 2', the injection end control valve 1 opens at point 9 2'b and the needle valve closes at point 9 21y, ending injection as described above.

As described above, in the present invention, when the needle valve is opened in the pressure accumulation type fuel injection device, the throttle that throttles the fuel flow flowing backward in the high-pressure fuel passage is set from the point where the passage from the end-of-injection control valve merges with the high-pressure fuel passage. Since it is installed on the fuel tank side, it not only increases the injection rate during high output with a large amount of fuel injection, improving thermal efficiency and preventing black smoke emissions, but also lowering the initial injection rate of fuel injection. can reduce noise, combustion power and nitrogen oxide emissions.

In addition, the injection rate is lowered at low outputs when the amount of fuel injection is small, which not only enables low-noise operation, but also reduces the minimum amount of fuel injection with the help of the end-of-injection control valve. can be easily adjusted.

Incidentally, in the above explanation, the injection device according to the present invention has been explained as an integral unit in which the injection pump device A and the nozzle assembly B are integrated.
Like a normal fuel injector.

Even if the injection pump device A and the nozzle assembly B are separated and connected by a high-pressure pipe (not shown) corresponding to the two passages 1a, the functions and performance of the present invention are completely the same. It is.

Further, the shape of the aperture 24c in FIG. 5 is not limited to a cylindrical shape, and may be a five-cone shape or any other shape as long as it changes the injection rate according to the load.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of the fuel injection device according to the present invention, FIG. 2 is an enlarged sectional view of the end-of-injection control valve, FIG. Figure spills
Enlarged cross-sectional view of the vicinity of the boat. Fig. 5 is a cross-sectional view of a main part showing another embodiment of the present invention in which a throttle is formed in the plunger, and Figs. It is a graph showing the relationship with angle. A... Injection pump device, B... Nozzle assembly, 1.
...Outer frame, 2...Nut, 3...Control valve body +3a+
3b+60...fuel passage, 3f...throttle, 4...
Spacer. 4a+4b, 4c...Fuel passage, 5...Pressure cylinder, 6
... Spacer, 6a... Fuel passage, 7... Needle valve body, 7a... Injection port, 7c... Fuel passage, 8... Needle valve, 8a... Valve face, 10... ...Spring, 12
...Accumulation chamber, 13...End of injection control valve, 14...
Compression spring, 16... check valve. 17... Fuel return passage, 18... Spill boat. 18a... Throttle, 19... Suction-back valve body, 20... Suction-back valve. 21... Compression spring, 26... Barrel, 24... Plunger, 25... Fuel inlet, 26... Fuel passage,
28... Check valve, 24c... Throttle, 24d... End face, 29... Fuel return port. Patent applicant: Naimita Technology Research Institute Co., Ltd.) Figure 41

Claims (1)

[Claims] (i) A spill port is provided in the barrel in which the plunger is inserted, a suction return valve is provided in the high pressure fuel passage communicating with the barrel, and a needle valve is provided to control the valve opening pressure by the pressure of this passage and the spring force. and has an injection port that is opened and closed by the needle valve, and a pressure accumulation chamber is provided in a part of the high-pressure fuel passage,
and the needle valve is closed by applying fuel pressure to the fuel passage side and the atmospheric pressure side of the needle valve while the pressure is being accumulated in the pressure accumulation chamber,
The valve opens by reducing the pressure on the atmospheric pressure side,
In a fuel injection device for a compression ignition engine that starts fuel injection, the fuel passage between the fuel passage communicating with the atmospheric pressure side of the needle valve and the pressure accumulation chamber is opened at a set pressure after the needle valve is opened. (An end-of-injection control valve is provided, and when the valve is opened, the high-pressure fuel in the pressure accumulation chamber is introduced into the atmospheric pressure side of the needle valve to close the needle valve, and when the needle valve is opened, For a compression ignition engine, characterized in that a throttle for restricting the flow of fuel flowing back through the spill boat in the high-pressure fuel passage is provided on the fuel tank side from the point where the passage from the end-of-injection control valve merges with the high-pressure fuel passage. Fuel injection device.