JPS5947150B2 - Fuel injection device for internal combustion engines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection nozzle used in an internal combustion engine, and more particularly to a fuel injection nozzle of the type used in combination with a high-pressure fuel pump to directly inject into the combustion chamber of an internal combustion engine.

Conventionally, so-called piston-type injection nozzles and poppet-type injection nozzles have been widely used as fuel injection nozzles for diesel engines and gasoline engines.

Thus, a so-called torch has a main combustion chamber that burns a relatively lean mixture, and a sub-combustion chamber that burns a relatively rich mixture and uses the flame to ignite and burn the lean mixture in the main combustion chamber. The fuel injection nozzle for the auxiliary combustion chamber of the internal combustion engine has a fuel injection amount of at least 0.2 mm3 per injection.
In some cases, a range of maximum LOmm3 is required from 1000 rpm or less, and in this case, it is necessary to stably perform fuel injection with a minimum of 0.2 rnvt3 even in the lowest rotation speed range of 1000 revolutions per minute or less.

On the other hand, even in the maximum rotation speed range of 6000 revolutions per minute or more, it is necessary to inject a maximum of 10 rum3 of fuel in a short time of about o, ooi seconds.

However, to meet the above requirements, conventional piston-type injection nozzles are not applicable because, although it is possible to inject a small amount in a low rotation range, it takes several times the time required to inject the maximum amount in a high rotation range. be.

Furthermore, although the poppet type injection nozzle satisfies the required value regarding the injection time, it has the disadvantage that injection of a small amount of fuel becomes unstable in a low rotation range.

In view of the above-mentioned points, the present invention focuses on the fact that the cause of instability of minute injection in a fuel injection nozzle is the instability of residual pressure after fuel injection, and provides a pressure regulating mechanism to constantly increase this residual pressure to a constant value. The purpose of the present invention is to provide a fuel injection nozzle for an internal combustion engine that is integrally provided with the injection nozzle, thereby fully satisfying both the conditions of small amount injection in the lowest rotation speed range and large amount injection in the highest rotation speed range. It has been done.

The present invention will be described below with reference to embodiments shown in the drawings.

The injection nozzle main body 1 has an injection valve chamber 2 and a pressure regulation chamber 4 of the pressure regulation mechanism 3 adjacent to each other, separated by a partition wall 5, and both chambers 2 and 4 are separated by a communication hole 6 bored in the partition wall 5. It is communicated.

A poppet-shaped injection valve 8 having a large-diameter valve portion 7 with a conical outer circumferential surface at its tip is inserted into the injection valve chamber 2, and the conical outer circumferential surface of the valve portion 7 is connected to the nozzle. It is opposed to a valve seat 9 formed at the tip of the main body 1, and is normally pressed against the valve seat 9 by the action of a compression spring 10 fitted around the injection valve 8 for sealing. are doing.

A pressure regulating piston 11 is fitted into the pressure regulating chamber 4, and a pressure regulating valve 12 integrally formed and protruding from the top of the pressure regulating piston 11 slides closely into the communicating hole 6. It can be inserted freely.

A notch 13 is formed around the pressure regulating valve 12 over a required length from the tip, and when a part of this notch 13 is exposed inside the pressure regulating chamber 4, the pressure regulating chamber 4 and the injection The valve chamber 2 is communicated with the valve chamber 2 through a notch 13.

The pressure regulating piston 11 of the pressure regulating mechanism 3 is pressurized at its back by a pressure regulating spring 14.
The other end is a threaded adjuster 1 screwed into the nozzle body 1.
It is supported by a catch seat 16 of No. 5.

A high pressure passage 17 is formed in the wall forming the pressure regulation chamber 4 at a position close to the opening of the communication hole 6 of the nozzle body 1 into the pressure regulation chamber 4, and a high pressure injection pump 18 is installed in this high pressure passage 17. They are connected via a fuel supply pipe 20 via a discharge valve 19 .

The high-pressure injection pump 18 is driven by an internal combustion engine or the like, increases the pressure of the liquid fuel sent by the low-pressure pump 22 from the fuel tank 21 to an appropriate pressure, measures the appropriate amount, and pumps it through the fuel supply pipe 20.

If necessary, a plurality of fuel supply pipes 20 may be provided to distribute and feed the fuel under pressure.

A fuel return passage 23 is formed in the wall of the pressure regulating chamber 4, and a fuel return pipe 24 communicating with the fuel tank 21 is connected to this return passage 23.
Fuel leaking from around the fuel tank 1 is returned to the fuel tank 21.

Next, the operation of the above embodiment will be explained.

The fuel pumped from the high-pressure injection pump 18 is transferred to the discharge valve 19
The fuel exits through the fuel supply pipe 20 and reaches the pressure regulating mechanism 3.

In the pressure regulating mechanism 3, since the pressure regulating piston 11 is initially pressed by the pressure regulating spring 14, the notch 1 of the pressure regulating valve 12 formed integrally with the pressure regulating piston 11
3 is in a state of being blocked from the communication hole 6.

Therefore, the pressure inside the pressure regulating chamber 4 increases, and the pressure regulating piston 11
rises in the figure against the pressure regulating spring 14.

Along with this, the pressure regulating valve 12 also rises, and as a result, the pressure regulating valve 12
Since a part of the notch 13 formed at the surface is exposed in the pressure regulating chamber 4, fuel in the pressure regulating chamber 4 flows into the injection valve chamber 2 through this notch 13.

Since the injection valve chamber 2 is filled with fuel in advance, the pressure inside the injection valve chamber 2 increases due to the pressure of the fuel flowing in through the notch 13, and this pressure increase causes the valve section 7 of the injection valve 8 to open. Pushed downward in the figure, the valve part 7 finally overcomes the valve closing force of the spring 10 and separates from the valve seat 9, and fuel is injected from the gap formed between the valve seat 9 and the valve seat 7. Ru.

When the fuel is injected as described above, the pressure regulating chamber 4
Since the internal pressure also decreases, the pressure regulating piston 11 is pushed back by the pressing force of the pressure regulating spring 14, and the pressure regulating piston 11 is pushed back by the pressure regulating spring 14.
When the set pressure of the pressure regulating spring 14 determined by the position of the pressure regulating spring 14 and the fuel pressure are balanced, the pressure regulating piston 11 becomes stationary.

During the return of the pressure regulating piston 11, the pressure regulating valve 12
The notch 13 is first hidden by the communication hole 6, and the communication between the pressure regulating chamber 4 and the injection valve chamber 2 is cut off, and the subsequent return operation of the pressure regulating valve 12 reduces the internal volume of the injection valve chamber 2 and closes the valve. The pressure inside the chamber 2 is increased to an appropriate level in preparation for the next fuel injection.

Note that in the process of the second fuel injection, the pressure in the injection valve chamber 2 decreases for a very short time due to the rise of the pressure regulating valve 12.

However, the internal volume of the injection valve chamber 2 is limited to the fuel supply pipe 20,
Since the volume is generally several minutes to several tens of minutes smaller than the total internal volume of the high pressure passage 11 and the pressure regulation chamber 4, a portion of the notch 13 is exposed inside the pressure regulation chamber 4 when the pressure regulation valve 12 rises. Immediately after this, the pressure inside the injection valve 2 increases.

If you look at the pressure inside the injection valve chamber 2 microscopically, it will be 01. in Fig. 3. G
As shown in the second point, a pressure drop is observed for a very short period of time, but
This is localized within the injection valve chamber 2, and when viewed from the entire system from the discharge valve 19 to the valve section 7, the pressure level is as shown in FIG. 3, and normal injection can be maintained.

Here, when comparing the fuel pressure in the high-pressure fuel supply system including the fuel supply piping for micro-injection between the conventional poppet-type injection nozzle not equipped with the pressure regulating mechanism 3 according to the present invention and the injection nozzle according to the present invention, it is found that: Figure 2 shows the pressure waveform of a conventional poppet-type injection nozzle.
The injection shown in Fig. 1 is carried out at point A1, where the pressure PS increases due to fuel pressure from 8 and exceeds the opening pressure PO of the injection valve.
The pressure suddenly drops to PR and becomes B1.

Even if fuel is pumped from the high-pressure injection pump 18 at the next injection timing, the amount is so small that the fuel pressure is spent increasing the PR value to 01, and the fuel is not injected. Intermittent injection continues with a second injection.

Although the above example shows intermittent injection every other time, irregular injection such as intermittent injection every few times or unsteady intermittent injection may also be performed.

FIG. 3 shows the pressure waveform of the injection nozzle according to the present invention. Initially, due to the injection of Dl, the fuel pressure decreases to PR and becomes El, but due to the action of the pressure regulating mechanism 3, it recovers to the pressure PT and becomes Fl. Then, in response to the second fuel pumping, injection is performed at B2, and as a result, the pressure drops to B2, but it immediately recovers to F2 in the same way as above, so normal injection is connected even in a small amount injection. Ru.

In this case, the fuel pressure PT can be set to the optimum condition by rotating the regulator 15 and changing the set pressure of the pressure regulating spring 14.

As explained above, the present invention is equipped with a pressure regulating mechanism that has the function of immediately recovering the pressure drop in the high-pressure fuel supply system after injection by the fuel injection valve and maintaining it at a predetermined pressure. Even if the fuel pressure in the high-pressure piping system drops by a certain amount after injection, it will immediately increase the fuel pressure to the appropriate level, ensure the next fuel injection, and maintain normal injection action even in the case of a small amount of injection. There is an effect that can be achieved.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a fuel injection nozzle according to the present invention, FIG. 2 is a fuel pressure characteristic diagram of a high-pressure fuel supply system using a conventional poppet-type injection nozzle, and FIG. 3 is a fuel pressure characteristic diagram showing an embodiment of a fuel injection nozzle according to the present invention FIG. 2 is a custom diagram of fuel pressure in a high-pressure fuel supply system using an injection nozzle. 2. Injection valve chamber, 3. Control pressure mechanism, 8.
... Injection valve, 11 ... Pressure regulating piston, 1
2...Pressure regulating valve, 20...Fuel supply piping.

Claims (1)

[Scope of Claims] 1(a) An injection valve chamber and a pressure regulating chamber formed through a partition wall in the axial direction of the nozzle body; (b) Normally closed by a compression spring disposed within the injection valve chamber; (c) a communication hole formed in the partition wall so as to communicate the injection valve chamber and the pressure regulation chamber; (d) a pressure regulation chamber disposed within the pressure regulation chamber; a pressure regulating piston urged toward the partition wall by a spring; (e) a pressure regulating valve driven by the pressure regulating piston and slidably moving within the communication hole; (f) a pressure regulating piston urged toward the partition wall; (g) a notch formed in the pressure regulating valve that communicates the communication hole with the pressure regulating chamber when it moves a predetermined amount in a direction away from the partition wall against a pressure spring; (g) the pressure regulating valve in the pressure regulating chamber; A fuel injection device for an internal combustion engine, comprising: a high-pressure passage that guides high-pressure fuel from the injection pump into a space between the piston and the partition wall; (h) a fuel return passage that returns surplus fuel in the pressure regulating chamber to the fuel tank;