JPS63212761A - Fuel injection device - Google Patents

Abstract

PURPOSE:To stably obtain a low injection ratio at a low speed by using a two-step cam as the cam of a fuel injection pump and using an adaptation valve and a damping valve for a feed valve device. CONSTITUTION:When the rotation of an engine is a low speed such as at the time of idling, for example, the residual pressure in an injection pipe 22 is kept high by an adaptation valve 26. Therefore, the stroke of a plunger 7 until the pressure of a nozzle chamber 34 reaches the valve opening pressure or higher may be small, thus the injection is started by the front-step portion of a two-step characteristic cam. At this front-step portion, the pressure rise ratio of a high-pressure chamber 8 is made small, the pressure rise ratio is made further small and smooth by a damping valve 27 with an orifice 27a. Accordingly, the lift of the nozzle needle of a fuel injection valve 28 is controlled, the injection period can be extended with the same injection quantity, thus the smooth combustion with a low injection ratio can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fuel injection device, particularly to a fuel injection device used in a diesel engine such as an automobile.

(Prior art) In a fuel injection pump, for example, Utility Model Application No. 60-1289
As shown in Japanese Patent No. 68, it is known to use a so-called two-stage cam and an Angleich delivery valve. The two-stage cam has a cam characteristic in which the first stage has a low speed region and the second stage has a high speed region, as shown in FIG. 6, for example.
The speed of the plunger changes depending on the area of use, making it possible to adjust the oil delivery rate. In addition, the Angleich delivery valve has an Angleich slit in the suction collar of the delivery valve to maintain a high residual pressure in the injection pipe when the engine is running at low speed. According to this, when the engine speed is low, the stroke of the plunger until injection starts is shortened, and the low speed section of the front stage of the cam is used, resulting in a low injection rate, resulting in gentle combustion and less knocking noise. On the other hand, at high speeds, the residual pressure in the injection pipe decreases, so the stroke of the plunger becomes longer until injection starts, and the high-speed region after the cam is used, resulting in a high injection rate and increasing engine output. It is something that can be done.

(Problems to be Solved by the Invention) However, even if the oil delivery rate is adjusted on the fuel injection pump side in this way, the actual injection rate of fuel injected from the fuel injection valve does not necessarily have the same characteristics. For example, even if the oil delivery rate on the fuel injection pump side is low, if the nozzle opens suddenly, the injection rate will become high. Therefore, it is necessary to improve the nozzle flow rate characteristics of the fuel injection valve, and in the case of a low oil delivery rate, it is desirable to reduce the opening area of the nozzle hole. For this purpose, it is possible to use a pin-type nozzle, but if carbon adheres between the nozzle hole and the pin part of the nozzle needle after long-term use, the fine injection rate control described above cannot be achieved. For example, there was a problem that the injection became unstable, such as the knocking sound not disappearing.

Therefore, an object of the present invention is to provide a fuel injection device that can stably obtain a low injection rate at low speeds.

(Means for Solving the Problems) Accordingly, the present invention provides a fuel injection pump that includes a plunger, a cam that reciprocates the plunger, and a delivery valve device provided on the discharge side of the plunger. The cam is provided with cam characteristics having a low-speed region in the front stage and a high-speed region in the rear stage, and the delivery valve device includes an Angleich valve that increases residual pressure in the injection pipe at low speeds and an orifice. A fuel injection valve comprising a damping valve and a nozzle body having a nozzle needle having a bottle portion and a nozzle hole in which the nozzle needle is seated and into which the pin portion is inserted. , is characterized in that at least one of the pin portion and the injection hole is provided with a tapered portion.

(Function) Therefore, at low speeds, the residual pressure in the injection pipe is kept high by the Angleich valve of the delivery valve device in the fuel injection pump, so the stroke of the plunger until the start of injection can be reduced, and the low speed region of the cam is It is possible to reduce the oil delivery rate of the fuel used and delivered from the fuel injection pump. On the other hand, in fuel injection valves, a nozzle with a pin part is used, so when the oil delivery rate is low, the nozzle lift is small and the nozzle hole area is small, and at least one of the bottle part and the nozzle hole is Since the tapered portion is provided, a predetermined nozzle hole area can be secured even if carbon is deposited after long-term use. Furthermore, since the delivery valve device of the fuel injection pump is provided with a damping valve having an orifice, reflection of fuel pressure can be reduced, pressure fluctuations on the nozzle side can be reduced, and variations in injection periods can be reduced. Therefore, injection at a low injection rate can be stably ensured at low speeds, and the above object can be achieved.

(Example) In FIG. 1, the fuel injection pump 1 is, for example, a distribution type,
It has a housing 3 that constitutes a suction space 2, a drive shaft 4 is inserted into this housing 3, a feed pump 5 is attached to this drive shaft 4, and fuel is supplied to the suction space 2 by driving the feed pump 5. It is supposed to be done.

Further, a cylinder 6 is fixed to one end of the housing 3,
A plunger 7 is slidably inserted into the cylinder 6, and a high pressure chamber 8 is formed surrounded by the cylinder 6 and the plunger 7.

The plunger 7 has a cam disk 9 attached to the drive shaft 4 mentioned above.
It is mated through. A cam is formed on the periphery of the other surface of the cam disk 9, and a roller 10 abuts on this cam, and this roller 10 is rotatably supported by a roller holder 11. Therefore, the plunger 7 reciprocates along the cam profile and rotates together with the drive shaft 4 and the cam disc 9. The roller holder 11 has a timer 1
2, and the advance angle is operated by this timer 12. The cam has a two-stage cam characteristic as shown in FIG.
It has a low speed region I, and becomes a high speed region after a predetermined cam angle θ1. For example, the speed V in the low speed range is 0.2 to 0.25 m/sec, and in the case of six cylinders, the predetermined cam angle θ1 is required to be 11° to 126°.

The plunger 7 described above has a number of suction groups 13 formed at the tip facing the high pressure chamber 8, the number of which corresponds to the number of cylinders of the engine. Further, a suction boat 14 is formed in the cylinder 6 and communicates with the suction group 13 at a predetermined angle. The other end of this suction boat 14 is connected to the suction space 2 via a suction passage 15 formed in the housing 3. Further, a vertical hole 16 is formed in the axial direction of the plunger 7, one end of which opens into the high pressure chamber 8. A distribution boat 17 formed in the plunger 7 is connected to the vertical hole 16, and this distribution boat 17 communicates with a distribution passage 18 formed in the housing 3 and the cylinder 6 at a predetermined angle. Further, a spill boat 19 is formed at the other end of the vertical hole 16 at a portion facing the suction space 2, and a control sleeve 20 is fitted around the spill boat 19, and the position of the control sleeve 20 is adjusted by a governor to inject water. The amount is controlled.

The delivery valve device 21 has one end connected to the distribution passage 18 described above, and the other end connected to a fuel injection valve 23 described later through an injection pipe 22. This delivery valve device 21 includes a holder 24 screwed to the housing 3, and a holder 24 screwed to the housing 3.
4, and an Angleich valve 26 and a damping valve 27 are provided within the holder 24. The Angleich valve 26 has a first
The damping valve 27 is pressed against the valve seat body 25 by the second spring 28, and the damping valve 27 is pressed against the holder 2 by the second spring 29.
It is pressed to 4.

As shown in FIGS. 2 and 3, the Angleich valve 26 includes a main body 26a that is seated at the tip of the valve seat body 25, and a main body 26a that is inserted into the valve seat body 25 to guide the Angleich valve 26. It has a spring part 26b, and a suction back collar 26c that is located between the main body part 26a and the spring part 26b and is inserted into the valve seat body 25, and a notch 26d is formed in the suction collar 26c. ing. As described above, since the notch 26d is formed in the suction collar 26c, at high speeds, the suction amount is the same as that without a notch, but at low speeds, fuel bypasses from the notch 26d, reducing the suction amount. Reduce. As a result, the residual pressure of the fuel in the injection pipe is high at low speeds and low at high speeds. In addition, as another embodiment, a similar Angleich effect can be obtained by forming vertical grooves in the valve seat body 25.

As shown in FIG. 4, the damping valve 27 has an orifice 27a formed at its center.

This damping valve 27 is opened against the second spring 29 during discharge, so that it does not interfere with the pressure feeding of the fuel, and at the same time, due to the action of the orifice, it dampens the pressure fluid generated between the inside of the fuel injection pipe and the nozzle. have. In addition, if this damping valve 27 is not provided, especially when fuel is being pumped at a constant speed, as shown in FIG. The pressure caused by the pressure wave is added to the pumping pressure by the plunger, and the pressure inside the nozzle chamber rises in a stepwise manner, resulting in a shelf in the fuel pressure change. Therefore, in the absence of this damping valve 27, if the pressure in the shelf area where the pressure rises is small is defeated by the opening pressure of the nozzle, the needle valve of the nozzle will open and close unstablely, resulting in no injection. It becomes stable.

For this purpose, a damping valve 27 is provided, and an orifice 27
By attenuating the pressure wave by a, the shelf of pressure change can be eliminated, as shown in FIG. This shortens the period in which the pressure and the valve opening pressure match, making injection stable.

In FIG. 5, a specific example of the nozzle tip of the fuel injection valve described above is shown, and the pin type nozzle has a nozzle needle 30
and the nozzle body 3 on which this nozzle needle 30 is seated.
1, and a pin portion 32 at the tip of the nozzle needle 30.
is formed.

This pin portion 32 is inserted into a nozzle hole 33 formed in the nozzle body 31. Further, the pin portion 32 and the injection hole 33 are each formed in a tapered shape. Therefore, even if carbon becomes clogged between the pin portion 32 and the nozzle hole 33, when the nozzle needle 30 lifts, a corresponding nozzle hole area can be obtained, and the fuel in the nozzle chamber 34 can be injected from the nozzle hole 33. do. The flow rate characteristics of the nozzle are as shown in FIG. 9. At the beginning of the lift, the fuel is throttled between the pin part 32 and the nozzle hole 33, so the flow rate with respect to the nozzle lift is small, but it reaches a predetermined value. .

When lifted above this level, the pin portion 32 separates from the nozzle hole 33 and the flow rate increases rapidly.

In this embodiment, both the pin portion 32 of the nozzle needle 30 and the nozzle hole 33 of the nozzle body 31 are tapered, but it is also possible to have only one tapered shape.
As shown in Japanese Patent No. 9-134373, only a portion of the pin portion 32 may be cut into a tapered shape.

In the above configuration, since the drive shaft 4 of the fuel injection pump 1 is rotated by the engine, the plunger 7 rotates simultaneously with the drive shaft 4 and reciprocates along the cam profile of the cam disk 9.

During the suction stroke in which the plunger 7 retreats, the suction group 13 of the plunger 7 and the suction port 14 of the cylinder 6 communicate with each other, and the high pressure chamber 8 is connected to the suction space 2 via the suction passage 15.
fuel is inhaled. During the discharge stroke in which the plunger 7 moves forward, as the stroke of the plunger 7 increases, the volume of the high pressure chamber 8 decreases and the pressure of the fuel within the high pressure chamber 8 increases, and the distribution port 17 of the plunger 7 18 to open the Angleich valve 26 and damping valve 27 of the delivery valve device 24, and the fuel is sent to the fuel injection valve 23 via the injection pipe 22. And the fuel injection valve 23
In this case, the pressure in the nozzle chamber 34 becomes higher than the valve opening pressure,
The nozzle needle 30 lifts and fuel is injected from the injection hole 33 into the combustion chamber of the engine. Then, as the stroke of the plunger 7 further increases, the spill port 19 finally comes off the control sleeve 20 and opens into the suction space 2, and the fuel in the high pressure chamber 9 flows through the vertical hole 16 and the spill port 19 into the suction space 2. The pressure of the fuel in the high pressure chamber 9 decreases rapidly, and in response to this, the pressure of the fuel in the nozzle chamber 3 decreases rapidly.
The pressure of fuel No. 4 also drops rapidly and the injection ends.

When the engine is rotating at a low speed, such as when idling, the residual pressure in the injection pipe 22 is kept high by the Angleich valve 26. Therefore, the stroke of the plunger 7 until the pressure in the nozzle chamber 34 reaches the valve opening pressure may be small, so that injection is started at the front stage of the cam. In this front stage portion, the rate of pressure increase in the high pressure chamber 8 is reduced, and the damping valve 27 further reduces the rate of pressure increase, making it smooth as shown in FIG. Therefore, in the fuel injection valve 23, the lift of the nozzle needle 30 is limited to the following, and fuel injection is completed within this range. For this reason,
If the injection amount is the same, the injection period can be extended, resulting in gentle combustion at a low injection rate. As a result of experiments, the injection period can be extended by about 1.5 times compared to conventional ones.
This made it possible to eliminate the knocking sound.

When the engine speed increases, the suction amount of the Angleich valve 26 increases, the residual pressure in the injection pipe 22 gradually decreases, and the stroke of the plunger 7 until the start of injection becomes longer. Therefore, at medium speeds and medium loads, both the low speed region in the front stage and the high speed region in the rear stage of the cam are used, and on the other hand, in the fuel injection valve 23, the maximum lift of the nozzle needle 30 exceeds a predetermined value. Thus, it is possible to obtain an ideal injection rate pattern in which preliminary combustion is performed at a low injection rate at the beginning of injection, and then the injection rate is increased to a high injection rate.

Furthermore, as the engine speed increases, the amount of suction back by the Angleich valve 26 becomes larger, the stroke of the plunger 7 until the start of injection becomes larger, and only the latter part of the cam is used. Therefore, the pressure of the fuel at high pressure -8 increases rapidly, and in the fuel injection valve 23, the nozzle needle 23 suddenly lifts, the opening area of the nozzle hole 33 becomes large, and a high injection rate can be achieved. be.

In the above embodiment, a distributed fuel injection pump is used, but the present invention is not limited to this, and for example, a sub-type fuel injection pump may be used.

(Effects of the Invention) As described above, according to the present invention, the cam of the fuel injection pump is a so-called two-stage cam with a low-speed region in the front stage and a high-speed region in the rear stage, and the delivery valve device has a low-speed region. An Angleich valve that increases the residual pressure in the injection pipe and a damping valve having an orifice are used, and the fuel injection valve is provided with a tapered part on at least one of the pin part and the injection hole, so that the cam's low speed is reduced at low speeds. Even if carbon is deposited between the pin part and the nozzle hole after a long period of time when the area is used, the opening area of the nozzle hole of the fuel injector can be kept small, and the damping valve allows pressure changes to change smoothly. This makes it possible to obtain stable injection at a low injection rate and eliminate knocking noise. Also, at medium speeds and medium loads, the front low speed part and the latter high speed part of the cam are used, making it possible to obtain an injection rate pattern in which the injection rate is initially low and then suddenly increases to a high injection rate. Combustion is ideally carried out in the combustion chamber of the engine, resulting in effects such as reducing NOx.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, FIG. 2 is a cross-sectional view showing the Angleich valve used in the above, and FIG.
Figure 4 is a sectional view showing the damping valve used in the above, Figure 5 is a sectional view showing the nozzle tip of the fuel injection valve used in the above, and Figure 6 is the same as the above. A diagram showing the cam characteristics of the cam used, Figure 7 is a diagram showing the relationship between the high pressure chamber and nozzle pressure when a damping valve is not used, and Figure 8 is a diagram showing the relationship between the high pressure chamber and nozzle pressure when a damping valve is used. A diagram showing the relationship with the nozzle pressure, and FIG. 9 is a diagram showing the flow rate characteristics of the nozzle. l...Fuel injection pump, 7...Plunger, 9...
- Cam disk, 21... Delivery valve device, 22... Injection pipe, 23... Fuel injection valve, 26... Angleich valve, 27... Damping valve, 30... Nozzle needle, 31... ... Nozzle body, 32 ... Pin part, 33
...Blow hole. Figure 4 d Figure 5 Figure 7 Figure 8 Cam angle -

Claims (1)

[Claims] In a fuel injection device having a fuel injection pump and a fuel injection valve that injects fuel sent from the fuel injection pump via an injection pipe, the fuel injection pump includes a plunger, a cam that reciprocates the plunger, a delivery valve device provided on the discharge side of the plunger, the cam is provided with a cam characteristic having a low-speed region in the front stage and a high-speed region in the rear stage, and the delivery valve device The fuel injection valve is composed of an Angleich valve that increases the residual pressure in the pipe, and a damping valve that has an orifice. What is claimed is: 1. A fuel injection device comprising: a nozzle body having a hole formed therein; and at least one of the pin portion and the nozzle hole having a tapered portion.