JPS6060032B2 - fuel injection valve - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in fuel injection valves for diesel engines.

A conventional fuel injection valve for a diesel engine is shown in FIG.

In the figure, 1 is a fuel injection valve main body, 2 is an oil passage within the fuel injection, and 3 is a needle valve, which is slidably inserted into the fuel injection valve main body 1. 4 is a needle valve push rod; 5 is a needle valve spring; the spring force presses the needle valve 3 onto the needle valve seat 102 via the push rod 4;

Reference numeral 6 is a fuel valve opening pressure adjustment screw, which makes the spring force variable.

In operation, fuel oil is compressed by a fuel injection pump (not shown), becomes high pressure, and is sent into an injection pipe (not shown).
It reaches oil leak 101 through oil passage 2 inside the fuel injection valve.

The needle valve 3 is pressed by a spring 5 and does not rise unless the pressure exceeds a certain pressure, that is, a valve opening pressure Po. Therefore, the high pressure waves sent from the fuel injection pump will cause oil leakage 1.
When the pressure reaches the valve opening pressure Po or higher at step 1, the needle valve rises and the fuel is ejected from the nozzle 8 into the fuel chamber (not shown) in the cylinder of the engine, where it is ignited and combusted to produce output. When the fuel injection pump finishes discharging, the pressure in the oil reservoir 101 on the fuel injection valve side decreases, and the needle valve 3 is pressed by the spring 5 to close, thereby ending the injection. During this time, leakage from the sliding portion of the needle valve 3 reaches the spring chamber 7 and is discharged through the discharge port 10. Fuel injection is performed through the above process, and Fig. 2 shows the pressure of the oil leak 101, that is, the injection pressure P, and the lift of the needle valve 3 with the crank angle θ as the horizontal axis. . As shown in the figure, when the injection pressure P increases and reaches the valve opening pressure Po, the needle valve begins to lift, and the needle lifts while the high pressure is maintained, but as the pressure decreases, the closing pressure Pc is reached. Finally,
The valve starts to close, and at the end of the valve closing, the pressure drops to the injection end pressure Pe. During this process, as shown in the upper part of the figure, the plunger lead begins to open the oil drain hole (static discharge end position).
Letting the crank angle of θde be θi, injection ends from this point. The injection period ΔθiA is the total injection period Δ
This corresponds to 30 to 40% of θi. This period is called injection elongation, and if it is long, combustion will deteriorate and thermal efficiency will decrease. Therefore, it is generally desired to complete this end quickly and provide a sharp jet. One of the reasons for this is that the valve opening pressure of the fuel injection valve is generally
Then, when the needle valve diameter in Fig. 1 is D and the needle valve seat diameter is D, the valve closing pressure Pc has the following relationship, Pc≦PO, and generally Ds<DN, about D,2ζ213DN2. Therefore, PO is low, and therefore the valve opening pressure P.

This is because the injection continues lazily at a lower pressure, resulting in poorly atomized fuel spray and, furthermore, being injected into the oxygen-deficient combustion chamber at the end of combustion, which needs to be improved. An object of the present invention is to provide a fuel injection valve that can achieve good cutoff at the end of fuel injection, and is characterized by applying hydraulic pressure to the back side of the needle valve of the fuel injection valve. A pressurizing device to assist the closing action of the needle valve and an automatic auxiliary needle valve are provided, and the opening pressure of the auxiliary needle valve is set slightly lower than the maximum injection pressure. A portion of the high-pressure fuel oil supplied to the valve was used as a hydraulic source for closing the needle valve.

This makes it possible to improve combustion in diesel engines and reduce fuel consumption.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a sectional view showing a fuel injection valve according to a first embodiment of the present invention.

In the figure, 1 is a fuel injection valve main body, 2 is an oil passage within the fuel injection valve, 3 is a needle valve, 4 is a needle valve push rod, 5 is a valve spring, and 6 is a valve opening pressure adjustment screw.

7 is a spring chamber, 8 is a spout, 10 is a discharge port, 101 is an oil sump,
102 is a needle valve seat.

In these, the push rod 4 is the intermediate hardware 110. It has the same structure as the conventional one, except that it is slidably inserted in a relatively narrow gap. Next, 120 is an injection valve holder main body, and the above-mentioned intermediate hardware 110 is sandwiched between this and the injection valve main body 1.

Reference numeral 121 denotes a sub-needle valve of automatic valve type, which is slidably inserted into the holder body 120.

122 is an auxiliary needle valve push rod, and 123 is an auxiliary needle valve spring, which presses the auxiliary needle valve 121 onto the auxiliary needle valve seat 124 via the auxiliary needle valve push rod 122.

125 is a screw for adjusting the opening pressure of the auxiliary needle valve.

Reference numeral 126 denotes an oil reservoir constituting the pressure chamber of the auxiliary needle valve, which is provided to avoid the spring chamber 7 and is connected to the oil passage 2 in the fuel injection valve by an oil passage 127.

128 is an auxiliary needle valve spring chamber, and 129 is an oil discharge hole of the spring chamber 128.

In these configurations, the opening pressure of the needle valve 3 is set to, for example, 400 k9 /
The opening pressure of the auxiliary needle valve 121 is set to a value higher than that and lower than the maximum injection pressure. A hydraulic chamber 103 for closing the needle valve is provided at the end opposite to the valve seat 1021 of the needle valve, and is connected to the downstream side of the valve seat 124 of the auxiliary needle valve through a thin oil passage 111. The oil passage 111 and the hydraulic chamber 1 for closing the needle valve
A pressurizing device is constructed in 03. The operation in the case of the above configuration will be described.

Fuel oil is compressed to a high pressure by a fuel injection pump (not shown) and is sent into an injection pipe (not shown), and reaches an oil sump 101 via an oil path 2 in the fuel injection valve.

High-pressure waves sent from the fuel injection pump flow into oil sump 1.
At 01, constant pressure P. (valve opening pressure)", the needle valve 3 rises, and the oil is ejected from the nozzle 8 into the combustion chamber (not shown) in the cylinder of the engine, where it ignites and burns. On the other hand, the oil sump 126 of the auxiliary needle valve 121 The pressure in the oil sump 126 is also approximately the same as that in the oil sump 101 because it is connected by the oil path 2 and the oil path 127, but the pressure in the oil sump 126 is a constant pressure P.

When the pressure exceeds L, (secondary needle valve opening pressure), the second needle valve 121 rises, and the hydraulic pressure reaches the hydraulic chamber 103 via the oil passage 111. The oil passage 111 is narrow, and the oil pressure in the oil pressure chamber 103 is the oil sump 1.
It rises slightly later than 26. When the fuel injection pump finishes discharging, the pressure in the oil reservoir 126 drops, but the force that tries to close the needle valve 3 is different from the conventional one because the hydraulic pressure in the hydraulic chamber 103 acts in addition to the spring force of the conventional one. Therefore, the needle valve closing pressure is higher than that of the conventional one, and injection can be completed at a high pressure. In addition, in the process of decreasing the pressure, the pressure in the oil reservoir 126 decreases and the auxiliary needle valve 121 closes. After the injection ends, the fuel in the hydraulic chamber 103 gradually leaks from the slit in the sliding part of the push rod 4 and is further discharged to the outside from the discharge port 10, so that the pressure in the hydraulic chamber 103 will be low by the time of the next injection. There is. Therefore, the beginning of injection is the same process as the conventional one. Fuel injection is performed after the above process, and FIG. 4 shows the injection characteristics.The injection characteristics are shown in FIG. Progress is shown.

That is, the start of injection is the same as the conventional one, but the injection pressure is P.

When the maximum injection pressure is reached, the control auxiliary needle valve 121 opens, so the injection pressure is near the maximum injection pressure, as shown by the solid line, and is slightly lower than the conventional one, shown by the broken line. When the secondary needle valve 122 for control is opened, the pressure in the hydraulic chamber 103 rises with a little delay from the injection pressure due to the throttling characteristics of the oil passage 111, increasing the actual closing pressure of the needle valve 3. Therefore, in the conventional system, the valve starts closing at the valve closing pressure PO, completely closes at Pe, and has an injection period of Δ06, and the valve closes with an elongation of θ, A from 0de, but in the case of the present invention, , since the pressure of PO5 is applied to the needle valve 3 in addition to the pressure of PO, the valve starts closing at P″.
''.The valve is completely closed at .theta.68. Therefore, the elongation from .theta.68 is .theta.''1A, and the injection period is greatly shortened. At this time, the valve closing oil pressure once reaches PCLO, as shown in the figure.
After that, the pressure gradually decreases and settles down to a pressure equivalent to the supply oil pressure of the fuel injection system, completing one injection. The present invention as described above has the following effects.

It has the effect of cutting the low-pressure part at the end of injection and providing sharp injection, thus improving combustion in diesel engines, reducing exhaust smoke and improving fuel efficiency.

FIG. 5 is a sectional view showing a fuel injection valve according to a second embodiment of the present invention. The differences from the first embodiment described above are as follows.

(1) The gap between the needle valve push rod 4 and the intermediate hardware 110 is wider than that of the first embodiment, and is similar to the conventional one.

(2) The downstream of the valve seat 124 of the auxiliary needle valve and the upper part of the spring chamber 7 are connected by a thin oil passage 112 and an oil passage 113. (3) A piston 71 is slidably inserted above the spring chamber 7.

The oil passages 112, 113 and the piston 71 constitute a pressurizing device. In the case of the above configuration, the process is the same as that of the first embodiment until the auxiliary needle valve 121 opens.

Thereafter, the oil pressure is applied to the upper surface of the piston 71 via the oil passages 112 and 113.

Therefore, since the spring 5 is compressed, the opening pressure of the needle valve becomes higher than that of the conventional one, and the effect is the same as that of the first embodiment. FIG. 6 is a sectional view showing a fuel injection valve according to a third embodiment of the present invention.

The differences from the second embodiment described above are as follows.

(1) A piston 71 is slidably installed in the spring chamber 7. In the second embodiment, the spring is compressed by the movement of the piston, but in this embodiment, the piston compresses the spring on the upper part of the push rod 4 due to its movement. Press the receiver.

(2) The valve opening pressure adjustment screw is omitted.

If necessary, it can be adjusted by a known method such as using shims. The oil passages 112, 113 and the piston 71 constitute a pressurizing device. The operation is similar to the second embodiment until the piston moves.

When the piston descends, it pushes against the spring receiver at the top of the push rod 4, so injection ends at a pressure substantially higher than that of conventional ones.
A similar effect can be obtained.

[Brief explanation of drawings]

Figure 1 is a sectional view showing a conventional fuel injection valve, and Figure 2 is a cross-sectional view of a conventional fuel injection valve.
3 is a sectional view showing the fuel injection valve of the first embodiment according to the present invention, and FIG. 4 is a diagram showing the relationship between the injection pressure and needle valve lift of the fuel injection valve shown in FIG. 5 is a diagram showing the relationship between valve closing oil pressure, injection pressure, and needle valve lift; FIG. 5 is a sectional view showing the fuel injection valve of the second embodiment of the present invention; FIG.
The figure is a cross-sectional view, not showing a fuel injection valve according to a third embodiment of the present invention. 1...Fuel injection valve main body, 2...Fuel injection valve internal oil passage, 3...Needle valve, 4...Needle valve push rod, 5... ...Needle valve spring, 8...Nozzle, 71...Zeston, 101,126...
・Oil sump, 102, 124... Valve seat, 103...
・Pressure chamber for closing needle valve, 110...Intermediate hardware, 120
... Injection valve holder main body, 121 ... Secondary needle valve, 111, 112, 113, 127 ... Oil passage.

Claims (1)

[Claims] 1. In a fuel injection valve for a diesel engine having an automatic valve type needle valve that opens and closes depending on the hydraulic pressure of fuel oil discharged from a fuel injection pump and injects the fuel oil into the cylinder, the fuel injection valve has a fuel injection valve in the injection valve holder body of the fuel injection valve. an automatic valve type sub-needle valve which is provided in the fuel injection needle valve and whose opening pressure is set to be higher than the opening pressure of the fuel injection needle valve and lower than the maximum injection pressure, and an oil in the fuel injection valve to the fuel injection needle valve. An oil passage to the auxiliary needle valve is provided branching from the auxiliary needle valve, and the hydraulic pressure of the oil discharged from the auxiliary needle valve is applied to the back side of the fuel injection needle valve to activate the fuel injection needle valve. A fuel injection valve characterized by being equipped with a pressurizing device that biases the valve in the valve opening direction.