JPH0338452Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a fuel injection nozzle for a diesel engine.

A conventional fuel injection nozzle is used to inject high-pressure fuel sent from a fuel injection pump through an injection pipe into a combustion chamber of an engine in the form of a mist. When the pressure of the supplied fuel becomes higher than the set pressure of the nozzle spring that presses the needle valve against the injection hole at the tip of the nozzle, the needle valve is pushed up and the injection hole opens, and fuel is injected from there. The higher the fuel pressure at this time, the more atomized the fuel is, the longer the distance it flies, and the shorter the injection period, improving combustion conditions.

The fuel sent to the injection nozzle is already pressurized to more than 100 kg/cm ² by the injection pump.
There is an injection nozzle equipped with a plunger for further pressurizing this at the injection nozzle. this is,
The fuel supplied from the pump is supplied through check valves from the fuel supply passage to the high pressure chamber and from the high pressure chamber to the pressure accumulation chamber that accommodates the needle valve, and the fuel supplied to the high pressure chamber is transferred to the large diameter low pressure piston. The pressure is then increased by a small-diameter high-pressure plunger integrated with this, and the pressure is accumulated in the pressure storage chamber.Then, by reducing the pressure applied to the low-pressure piston, the needle valve that closes the nozzle at the tip of the nozzle is raised, and the The fuel is injected from the nozzle holes. Control of fuel supply, pressurization, and injection is performed by three-way ball poppet type solenoid valves.

In such a fuel injection nozzle equipped with a pressure accumulator, fuel can be pressurized according to the cross-sectional area ratio of the low-pressure piston and the high-pressure plunger based on the Palcas principle. For example, if the cross-sectional area ratio is 10:1, a fuel pressure of 10 times, that is, 1000 Kg/cm ² or more can be obtained. It is thought that if fuel is injected at such a high pressure, atomization of the fuel will be promoted, the flying distance will be increased, and the injection period will be shortened, thereby providing suitable combustion conditions. However, when fuel is injected at such high pressure, the high pressure causes the fuel to be injected all at once, resulting in most of the fuel being injected during the ignition delay period, which can lead to explosive combustion during the next combustion period. There is a problem in which the fuel burns and generates a lot of noise.

The object of this invention is therefore to provide a fuel injection nozzle with a pressure accumulator that has improved initial injection conditions.

This invention is intended to solve the above-mentioned problems, and its contents will be explained using FIG. 1, which corresponds to an embodiment.

This invention allows the fuel supplied from the pump to be passed from the fuel supply passage 3 to the high pressure chamber 14 via the first check valve 14.
5, the fuel in the high pressure chamber 15 is supplied to the pressure accumulation chamber 23 via the second check valve 18, and a needle valve 19 for opening and closing the nozzle hole 24 is provided in the pressure accumulation chamber 23, A nozzle spring 20 and the needle valve 1 are compressed between the valve 19 and the second check valve 18.
9 and the second check valve 18, a distance L is provided between the needle valve 19 and the second check valve 18 to allow the needle valve 19 to rise.
8 and the high pressure chamber 15 is an oil passage 1 for a fuel passage.
A push rod 10 having a pressure of 0a is provided, and an interval l is provided between the push rod 10 and the needle valve 19, which is smaller than the interval L that allows the needle valve 19 to rise, and the distance between the push rod 10 and the high pressure chamber 15 is In between, a valve spring 1 biases the push rod 10 toward the downward direction of the needle valve 19.
7, a high-pressure plunger 7 for pressurizing the high-pressure chamber 15 faces into the high-pressure chamber 15, and a solenoid valve 2 for controlling the flow of pressurized fuel acting on the high-pressure plunger 7. 2 is de-energized and the high-pressure plunger 7 pressurizes the high-pressure chamber 15 to accumulate fuel in the pressure accumulator chamber 23, and the solenoid valve 2 is energized and the high-pressure plunger 7 depressurizes the high-pressure chamber 15. The above needle valve 19
is raised by the distance L while resisting the biasing force of the nozzle spring 20, and then raised to the distance L while resisting the nozzle spring 20 and the valve spring 17.

Therefore, first, the fuel pressure in the high pressure chamber 15 and the pressure accumulation chamber 23 increases by de-energizing the solenoid valve 2, and then,
By energizing the solenoid valve 2, the pressure in the high pressure chamber 15 is reduced.
At this time, the needle valve 19 slowly ascends to the first stage until it hits the lower end of the push rod 10, a small amount of fuel is injected, and the tapered surface 19b at the tip of the needle valve 19 is injected.
When the pressure applied to the needle valve 19 becomes high enough,
The second stage begins to rise rapidly and the remaining fuel is injected.

An embodiment of this invention will be described below with reference to the accompanying drawings. In FIG. 1, an injection nozzle, generally designated 50, is provided with a laterally actuated ball-poppet type solenoid valve 2 in a head cap 1. One ball 2a of this electromagnetic valve 2 controls the flow of fuel between the fuel supply passage 3 and the piston pressurizing passage 5 above the low pressure piston 4, and the other ball 2b controls the flow of fuel between this pressurizing passage 5 and the piston pressurizing passage 5. The flow of fuel to and from the discharge passage 6 is controlled through the spiral groove 2d of the sliding pin 2c. These controls are performed by a solenoid 2e of the electromagnetic valve 2 via an actuating pin 2f. When solenoid 2e is off, operating pin 2f
moves to the left so that the fuel supply passage 3 and the piston pressurizing passage 5 are in communication with each other, and when the solenoid 2e is turned on, the pressure of the fuel supplied to the fuel supply passage 3 causes the sliding pin 2c to move to the right. direction to connect the pressurizing passage 5 and the discharge passage 6.

The large-diameter low-pressure piston 4 is integrally formed with a small-diameter high-pressure plunger 7 protruding from its lower side.
The low pressure piston 4 is slidably held within the cap 1 and the high pressure plunger 7 is slidably held within the plunger body 8. A plunger spring 9 is interposed between the low pressure piston 4 and the plunger body 8 to press the low pressure piston 4 upward and press the plunger body 8 downward. At the bottom of the plunger body 8,
A rod holder 11 that slidably holds a push rod 10 is coupled to the plunger body 8, the rod holder 11, and a nozzle body 12 located below the plunger body 8, which are held to the head cap 1 by a retaining nut 13. .

The fuel supply passage 3 formed in the cap 1 is
First check valve 1 provided in plunger body 8
4 leads to a high-pressure chamber 15 in which a high-pressure plunger 7 slides. A third check valve 16 is provided below the plunger 7 in the high pressure chamber 15 and is urged upward by a valve spring 17 interposed between it and the head of the push rod 10. . Third check valve 16 and push rod 10
each has an oil passage 16 passing through its center.
a, 10a are formed, and push rod 1
0 is slidably held in a hole 18a passing through the center of the second check valve 18 in the upper part of the nozzle body 12. A recess 18b is formed at the top of the second check valve 18, into which the push rod 1 is inserted.
Side holes 10b, which are formed at 0 and communicate with the oil passage 10a, face each other. The upper part of the needle valve 19 at the lower part of the second check valve 18 is also slidably held in the through hole 18a of the second check valve 18, and the spring seat 19a in the middle of the second check valve 18 and the needle valve 19 A nozzle spring 20 is interposed between the nozzle tip 20 and the nozzle spring 20, which presses the second check valve 18 against the rod holder 11 and presses the tapered surface 19b at the tip of the needle valve 19 against the seat surface 21a inside the tip of the nozzle tip 21. It is strong. In this state, the lower end of the push rod 10 and the needle valve 19
A certain distance l is formed between the upper end of the second check valve 18 and the upper surface of the spring seat 19a of the needle valve 19, which corresponds to a pre-lift amount to be described later. A distance L is formed which is larger than l. The space within the nozzle body 12 and nozzle tip 21 from the second check valve 18 to the tip of the needle valve 18 via the guide 22 constitutes a pressure accumulation chamber 23. A nozzle hole 24 is formed at the tip of the nozzle tip 21, and the entire nozzle tip 21 is connected to the nozzle body 12 by a nozzle nut 25.

Next, the operation of this fuel injection nozzle 50 will be explained. First, as shown in FIG. 2, when fuel pressurized to about 200 kg/cm ² is supplied to the head cap 1 from a fuel pump driven by a shaft (not shown) in the fuel supply passage 3, the plunger body Push open the first check valve 14 in 8 to open the high pressure chamber 1.
5. At this time, the ball 2a blocks the flow to the piston pressurizing passage 5. Hyperbaric chamber 1
5, the fuel enters the oil passage 16 of the third check valve 16.
a and flows out from the side hole 10b of the push rod 10 through the oil passage 10a, pushes down the second check valve 18, enters the pressure accumulation chamber 23, and fills up to the tip of the needle valve 19. The second check valve 18 is connected to the high pressure chamber 15
When the fuel pressures in the pressure storage chamber 23 and the pressure storage chamber 23 become equal, it closes.

Next, as shown in FIG. 3, when the solenoid valve 2 is turned off and the ball 2a is pushed by the setting force of the return spring 29 inside the solenoid valve, the fuel supply passage 3 and the piston pressurizing passage 5 are brought into communication. Then, fuel enters from the pressurizing passage 5 and pressurizes the upper surface of the low pressure piston 4. As a result, the high pressure chamber 15 and the pressure accumulation chamber 2
The fuel in 3 is pressurized by the high pressure plunger 7,
The first check valve 14 is closed, and the third check valve 16 first opens and closes when the pressures above and below it are equal.

Next, as shown in FIG. 4, when the solenoid valve 2 is turned on and the ball 2a blocks communication between the fuel supply passage 3 and the piston pressurizing passage 5, the fuel in the pressurizing passage 5 is transferred to the sliding pin 2c. The oil is returned to the oil tank (not shown) from the discharge passage 6 through the spiral groove 2d. As a result, the low pressure piston 4 rises, and
The pressure in the high pressure chamber 15 decreases, and the needle valve 19 is first raised by the prelift amount l shown in FIG. That is, since the upper part of the needle valve 19 is open to the oil passage 10a of the push rod 10, it receives the same pressure as the high pressure chamber 15, and the lower part of the needle valve 19 is open to the oil passage 10a of the push rod 10.
8, this high pressure is applied to the tip tapered surface 19b of the needle valve 19. However, at this initial stage, the tip tapered surface 19b is in close contact with the seat surface 21a of the nozzle tip 21 and its pressure-receiving area is small, and the spring pressure of the nozzle spring 20 is high, so the needle valve 19 rises only slightly. , the needle valve 19 moves by the prelift amount l over time.
By the time the needle valve 19 has moved by this pre-lift amount l, the pressure applied to the needle valve tip tapered surface 19b has also increased due to the increase in the pressure receiving area, and the needle valve 19 is moved by the nozzle spring 20 and the valve spring 17.
The lift amount of the remaining L-l is increased against the pressure of . In this way, the needle valve 19 first injects a small amount of fuel when increasing the prelift amount 1, and rapidly injects a large amount of fuel when increasing the remaining lift amount L-l. FIG. 5 shows the relationship between time and fuel injection amount at this time. Such characteristics vary depending on the pressure receiving area of each part of the needle valve 19, the set pressure of the nozzle spring 20 and the valve spring 17, and the like.

As shown in FIG. 6, the second check valve 18 is provided with an oil passage 18c leading from a recess 18b at its top to a pressure accumulation chamber 23 at its side, with a ball 26 interposed therein that acts as a check valve. It may be a structure.
In this case, when fuel is supplied to the pressure accumulation chamber 23, it is not supplied by pushing open the entire check valve 18, but by pushing open only the small ball 26, so that the nozzle spring 20 is connected to the needle valve. There is an advantage in that it only needs to be considered as a counter force during the pre-lift of No. 19. As a result, the seal inside the pressure accumulating chamber 23 becomes perfect, and stable injection amount characteristics with little fluctuation in injection amount can be obtained each time. In addition, various modifications can be made to this idea.

As described above, the fuel injection nozzle according to this invention can pressurize the fuel supplied from the fuel pump to about 2000 kg/cm ² using the low-pressure piston and high-pressure plunger and inject it, thereby promoting atomization of the fuel. By increasing flight distance and shortening the injection period, it is possible to significantly reduce the smoke level in the partial load range. Further, since the fuel injection timing can be easily adjusted by on/off control of the electromagnetic valve, it is possible to obtain preferable combustion conditions that match the engine characteristics. Furthermore, since fuel injection can be divided into two stages and the initial injection rate can be kept low, favorable injection quantity characteristics for good combustion can be obtained, and the generation of noise can also be kept low.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a fuel injection nozzle showing an embodiment of this invention, Fig. 2 is a diagram illustrating the operation of the fuel injection nozzle according to this invention during fuel supply, and Fig. 3 is a diagram illustrating the operation of the fuel injection nozzle according to this invention. FIG. 4 is a diagram explaining the action of the fuel injection nozzle when pressurizing fuel, FIG. 4 is a diagram explaining the action of the fuel injection nozzle according to this invention when injecting fuel, and FIG. FIG. 6, a graph showing the injection quantity characteristics, is a partial cross-sectional view showing the main parts of another embodiment of this invention. 1... Cap, 2... Solenoid valve, 3... Fuel supply passage, 4... Low pressure piston, 5... Piston pressurizing passage, 6... Fuel discharge passage, 7... High pressure plunger, 10... Push rod, 14...First check valve, 15...High pressure chamber, 16...Third check valve, 1
8...Second check valve, 19...Needle valve, 23...Accumulation chamber, 24...Nozzle hole.

Claims (1)

[Scope of utility model registration request] The fuel supplied from the pump is supplied from the fuel supply passage 3 to the high pressure chamber 15 via the first check valve 14, and the fuel in the high pressure chamber 15 is supplied to the pressure accumulation chamber 23 via the second check valve 18. A needle valve 19 for opening and closing the nozzle hole 24 is provided in the pressure accumulation chamber 23, and a nozzle spring 20 and the needle valve 19 are compressed between the needle valve 19 and the second check valve 18. A gap L is provided between the second check valve 18 and the needle valve 19 to allow the needle valve 19 to rise, and an oil passage 10a for a fuel passage is provided between the second check valve 18 and the high pressure chamber 15. A push rod 10 is provided, a distance 1 is provided between the push rod 10 and the needle valve 19 that is smaller than the distance L that allows the needle valve 19 to rise, and the distance 1 is provided between the push rod 10 and the high pressure chamber 15. A valve spring 17 is provided to urge the push rod 10 toward the downward direction of the needle valve 19,
A high-pressure plunger 7 for pressurizing the high-pressure chamber 15 is provided facing into the high-pressure chamber 15, and a solenoid valve 2 is provided to control the flow of pressurized fuel acting on the high-pressure plunger 7, and the solenoid valve 2 is de-energized. Then, the high pressure chamber 15 is pressurized by the high pressure plunger 7 to accumulate fuel in the pressure accumulating chamber 23, and the electromagnetic valve 2 is energized so that the high pressure chamber 1 is pressurized by the high pressure plunger 7.
5, the needle valve 19 is raised by the distance l while resisting the biasing force of the nozzle spring 20, and then the nozzle spring 20
A fuel injection nozzle characterized in that the fuel injection nozzle is configured to be raised to the distance L while resisting the valve spring 17.