JPS61101666A - Fuel injection device - Google Patents

Abstract

PURPOSE:To effect preliminary injection stably by a method wherein a dodge plunger is arranged so as to oppose to the plunger pressurizing chamber of a distributing type fuel injection pump while the displacement of the pressurizing chamber is increased when the pressure of the pressurizing chamber has overcome the set pressure of an energizing means of the dodge plunger. CONSTITUTION:A fuel pumping plunger 5 is inserted rotatably and recipro catably into the housing head 4a of the fuel injection pump 2 and the plunger pressurizing chamber 8 is defined between the tip end surface thereof and one end face of the first body element 6a of a body 6. The pressurizing chamber 8 is communicated with the inside of the element 6a through a communicating hole 9 while a spacer 10, a cylinder 11 and the spacer 12 are accommodated between second body element 6b, screwed into the element 6a, and the element 6a sequentially. The dodge plunger 11 is inserted into the cylinder 11 and is energized to the left by the energizing means 18. When the pressure in the pressurizing chamber 8 has overcome the set pressure of the energizing means 18, the dodge plunger 11 is moved to the right and the displacement of the pressurizing chamber 8 may be increased.

Description

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

(Prior art and its problems) In general, pilot injection (preliminary injection) is performed as a means to reduce combustion noise in diesel engines, that is, a part of the total injection amount is injected (pilot injection) prior to main injection. Injection) It is known that it is effective to inject the remaining fuel after the previously injected fuel is ignited to sufficiently increase the temperature inside the cylinder.

Conventionally, the nozzle of a fuel injection valve equipped with such a pilot injection function is a throttle nozzle, that is, a nozzle needle that reduces the injection amount at the beginning of the lift and widens the gap near the end of the lift so that the required amount of fuel is injected. It was a configured nozzle.

However, since the throttle area of the throttle nozzle greatly changes over time due to carbon clogging, the injection rate waveform changes greatly, and therefore there is a problem in that stable preliminary injection cannot be performed.

FIG. 6 is a diagram showing the flow rate characteristics of the throttle nozzle in terms of the relationship between the rotor flow rate value and the lift, in which the solid line shows the new state and the broken line shows the state after time has elapsed. Further, FIG. 7 is a diagram showing the flow rate characteristics of the bottle nozzle in terms of the relationship between the rotor flow rate value and the lift, in which the solid line shows the new state and the broken line shows the state after time, respectively.

The method of measuring the flow rate characteristics shown in Figures 6 and 7 uses a mechanism that can slightly lift the nozzle needle, and measures air by blowing air into the nozzle hole through a rotor flow meter. As shown in Fig. 6, the rotor flow rate value does not change in a continuous straight line with the lift, but the flow rate change stops midway, whereas the Bintle nozzle has the characteristic that the rotor flow rate changes in response to the lift as shown in Fig. 7. The rotor flow rate value changes continuously in a straight line.

(Object of the Invention) The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fuel injection device that can perform stable preliminary injection over a long period of time.

(Means for Solving the Problems) In order to solve the above-mentioned problems, in the present invention, a dodge plunger is disposed opposite to the tip surface of the plunger for fuel pressure feeding via a plunger pressurizing chamber, and the plunger pressurizing chamber is connected to the plunger pressurizing chamber. When the pressure of the dodge plunger overcomes the set pressure of an urging means for urging the dodge plunger toward the plunger pressurizing chamber, the dodge plunger is displaced to increase the volume of the plunger pressurizing chamber. and a fuel injection valve without a throttle section, and a dodge plunger is disposed opposite to the tip surface of the plunger for pumping fuel via a plunger pressurizing chamber so that the pressure in the plunger pressurizing chamber is A fuel injection pump configured to increase the volume of the plunger pressurizing chamber by displacing the dodge plunger when it overcomes a set pressure of a biasing means that biases the dodge plunger toward the plunger pressurizing chamber;
A two-stage open-valve pressure fuel injection system that has a nozzle without a throttle section and creates an initial injection stroke that limits the lift of the nozzle needle to a small value at the beginning of injection, and then creates a main injection stroke that maximizes the lift of the nozzle needle during the subsequent main injection. It consists of a valve.

(Example) Embodiments of the present invention will be described below based on the drawings.

First, one embodiment of the present invention will be described based on FIGS. 1 to 4. FIG. 1 shows the main parts of a fuel injection device according to the present invention. In the figure, 1 is a fuel injection device, which is composed of a fuel injection pump 2 and a fuel injection valve 3. As shown in FIG. The fuel injection pump 2 is of a distribution type, and a plunger 5 for pumping fuel is inserted into a head portion 4a of a housing 4 so as to be able to reciprocate. A cylindrical body 6 is located on the axial extension of the plunger 5 and protrudes from the outer surface of the head portion 4a. As shown in FIG. 2, the body 6 is a short-axis cylindrical first body element 6a having a short-axis cylindrical shape with one end closed and the other end open. The outer peripheral surfaces of one end of the two-body element 6b are screwed together.

An outer circumferential surface on one end side of the first body element 6a is screwed and fixed to an inner circumferential surface of the attachment hole 7 of the head portion 4a.

A plunger pressurizing chamber 8 is defined between one end surface of the first body element 6a and the tip surface of the plunger 5,
The plunger pressurizing chamber 8 communicates with the inside of the first body element 6a through a communication hole 9 in the center of one end wall of the first body element 6a.

One spacer 10 is provided between the inner side surface of one end wall of the first body element 6a and one end of the second body element 6b in order from the first body element 6a side to the second body element body 6b side. ,
The cylinder 11 and the second spacer 12 are held in an overlapping state.

A communication hole 13 is bored in the center of the first spacer 10 to communicate the through hole 9 with the inside of the cylinder 11 . A dodge plunger 14 is slidably fitted into the cylinder 11. The dodge plunger 14 has a stepped small diameter portion 14b at one end of a main body 14a fitted radially into the cylinder 11, and a shaft portion 14c protruding from the other end, and the shaft portion 14c is connected to the second spacer. The second spacer 12 extends inward through the large diameter hole 16 through the central through hole 15 of the second spacer 12, and the movable spring receiving member 1 is attached to the extending end.
7 is installed.

The front end surface of the dodge plunger 14 is connected to the plunger pressurizing chamber 8. It faces the front end surface of the fuel pressure-feeding plunger 5 via communication holes 9 and 13.

The dodge plunger 14 is urged toward the plunger pressurizing chamber 8 side (left side in FIG. 2) by an urging means 18. The biasing means 18 is composed of a coil spring 18a, and the spring 18a is interposed between the movable spring receiving member 17 and the adjusting screw 19, which is a fixed spring receiving member,
The adjusting screw 19 is screwed onto the inner circumferential surface of the second body element 6b on the other end side. The adjusting screw 19 sets the set pressure of the spring 18a, and has a vent hole 20 bored inside its axis.

When the pressure inside the plunger pressurizing chamber 8 is lower than the biasing force of the biasing means 18, the dodge plunger 1
A full lift gap exists between the other end surface of the main body 14a of No. 4 and the second spacer 12. When the pressure within the plunger pressurizing chamber 8 overcomes the biasing force of the biasing means 18, a gap between the tip surface of the dodge plunger 14 and the plunger pressurizing chamber 8 is communicated with the plunger pressurizing chamber 8. A space is formed.

On the other hand, the fuel injection valve 3 has a nozzle 23 fixed to the tip of a nozzle holder 21 with a retaining nut 22, as shown in FIG. The nozzle 23 consists of a nozzle body 24 and a nozzle needle 25 fitted into the nozzle body 24 so as to be able to move up and down, and the nozzle needle 25 is of a bottle type without a throttle part as shown in FIG. As the nozzle needle 25 moves up and down, the opening area of the nozzle hole 26 at the center of the lower end surface of the nozzle body 24 can be varied.

A pressure stage 28 of the nozzle needle 25 is located in an oil reservoir 27 in the nozzle body 24,
The oil reservoir 27 includes a feed hole 29 provided in the nozzle body 24, an oil collection groove 30, and a nozzle holder 21.
The fuel inlet 32 is connected to the fuel inlet 32 on the side of the nozzle holder 21 through a feed hole 31 provided in the nozzle holder 21 .
is connected to the discharge port of the delivery valve 34 of the fuel injection pump 2 via a hose 33, as shown in FIG. A needle journal portion 35 on the upper end surface of the nozzle needle 25 is fitted into a lower end portion of a pressure pin 36. The nozzle needle 25 is inserted in the valve closing direction (
A coil-shaped nozzle spring 39 is interposed as a biasing means for biasing the nozzle in the downward direction in the figure. In FIG. 3, 40 is a cap nut, 41 is a hollow screw, and 42 is an overflow nipple.

(Function) Next, the function of the fuel injection device 1 of the present invention having the above configuration will be explained. The fuel pressure-feeding plunger 5 rotates in synchronization with an internal combustion engine (not shown), and at the same time reciprocates in the left-right direction in the figure by a face cam (not shown).

During the reciprocating movement, when the plunger 5 is in the suction stroke moving leftward in the figure, the suction slit 5a formed in the plunger 5 and the suction hole 4b formed in the head portion 4a of the housing 4 are connected to each other. communicates with each other, and introduces the fuel in the pump chamber 43 of the housing 4 into the plunger pressurizing chamber 8.

Further, when the fuel pressure-feeding plunger 5 is in a discharge stroke in which it moves to the right in the figure, the plunger communicates with the inside of the plunger pressurizing chamber 8 through a hole 5b bored inside the axial center of the plunger 5. The discharge boat 5c of No. 5 communicates with a discharge hole 4c formed in the head portion 4a of the housing 4, and the fuel in the plunger pressurizing chamber 8 is transferred to the delivery valve 34 and the hose 3.
The oil is introduced from the fuel inlet 32 of the fuel injection valve 3 into the oil reservoir 27 via the feed hole 31 → oil collection groove 30 → feed hole 29 via the fuel inlet 3 . When the fuel pressure in the oil reservoir 27 acts on the pressure stage 28 of the nozzle needle 25 and overcomes the biasing force of the spring 39, the nozzle needle 25 rises within the range of the entire lift gap L1 and its seat portion 25a is separated from the seat portion 24a of the nozzle body 24, fuel is injected from the nozzle hole 26, and thereafter, when the pressure in the oil reservoir 27 decreases, the nozzle needle 25 is lowered by the biasing force of the spring 39. When the seat portion 25a comes into close contact with the seat portion 24a of the nozzle body 24, fuel injection is stopped.

During the discharge stroke of the plunger 5, the plunger pressurizing chamber 8
The pressure inside the plunger pressurization chamber 8 increases, and the counter-plunger pressurization chamber 8 against the dodge plunger 14 due to the pressure inside the plunger pressurization chamber 8
When the dodge plunger 14 overcomes the biasing force (valve opening pressure) to the side, the dodge plunger 14 moves toward the side opposite to the plunger pressurizing chamber 8 within the range of the entire lift gap, and the plunger pressurizing chamber 8 moves by the amount of the movement.
The volume of the fuel injection valve 3 increases, thereby reducing the pressure inside the plunger pressurizing chamber 8, and as the pressure decreases, the fuel injection valve 3
The pressure in the oil reservoir 27 decreases, and the nozzle needle 25 descends and closes. That is, until the dodge plunger 14 lifts, the pressure in the oil reservoir 27 causes the nozzle needle 25 to rise and open to perform fuel injection (pilot injection), and as the pressure rises thereafter, the dodge plunger 1
Due to the pressure drop in the oil reservoir 27 caused by the lift in step 4, the nozzle needle 25 moves downward and closes, stopping fuel injection.Then, as the pressure increases further, the nozzle needle 25 rises again and opens, injecting fuel (main injection). This is what we do.

Therefore, the nozzle 23 of the fuel injection valve 3 has a nozzle needle 25 of a bottle type without a throttle part,
Since the nozzle needle 25 moves up and down in the nozzle hole 26 for each injection, it is as if the nozzle hole 26 is constantly being cleaned, and the problem that the nozzle hole 26 becomes clogged with carbon is unlikely to occur. Therefore, stable pilot injection can be obtained over a long period of time.

(Other Embodiments) Next, other embodiments of the present invention will be described based on FIG. In this embodiment, the same parts as those in the above-mentioned embodiment will be described with the same reference numerals in the drawings.

That is, the embodiment shown in FIG. 5 serves as a biasing means for biasing the nozzle needle 25 of the fuel injection valve 3 in the valve closing direction.
In addition to the nozzle spring 39, a second coiled nozzle spring 44 is provided.
The only difference from the embodiment shown in FIGS. 1 to 4 is that a bushing rod 45 is provided. The second nozzle spring 44 is connected to the cap nut 4
The lower end surface of the adjusting screw 46 provided on the inside of the bushing rod 45 is interposed between the spring bearing member 47 on the upper end surface of the bushing rod 45, and the lower end surface of the bushing rod 45 is connected to the needle journal portion of the nozzle needle 25. 35
The upper end surface of the projection 37b protruding from the upper surface of the movable spring receiving member 37a at the upper end of the pressure pin 36a fitted therein faces the upper end surface of the projection 37b with an initial lift gap L2 therebetween. Then, the pressure in the oil reservoir 27 is applied to the first (lower side in the figure) nozzle spring 3.
9, the nozzle needle 25 rises and opens by the initial lift circumferential gap L2, and then the oil sump 27
When the pressure inside overcomes the resultant force of the first nozzle spring 39 and the second nozzle spring 44, the nozzle needle 25 further rises and opens by the entire lift gap L1.

The rest of the structure and operation of the embodiment shown in FIG. 5 are the same as those of the embodiment shown in FIGS. 1 to 4 described above.

However, while the nozzle needle 25 is moving, the lift of the nozzle needle 25 can be held down to the initial lift, so that the area of the nozzle hole is mechanically held down so that it does not expand, and the pressure inside the injection pipe is therefore reduced. This has the unique effect of immediately closing the nozzle needle 25 to ensure a fuel injection pause state.

As the fuel injection valve in the present invention, a two-stage valve opening pressure type fuel injection valve having the structure shown in FIG. 8 can also be implemented. In FIG. 8, the same functional parts as in FIG. 5 are given the same reference numerals.

(Effects of the Invention) As described above, the first aspect of the fuel injection device of the present invention is that a dodge plunger is disposed opposite to the tip end face of a plunger for pumping fuel via a plunger pressurizing chamber, and the pressure in the plunger pressurizing chamber is as high as the pressure of the plunger pressurizing chamber. A fuel injection pump configured to increase the volume of the plunger pressurizing chamber by displacing the dodge plunger when it overcomes a set pressure of a biasing means that biases the dodge plunger toward the plunger pressurizing chamber, and a throttle. A second fuel injection valve is provided with a dodge plunger facing the front end of the plunger for pumping fuel via a plunger pressurizing chamber, and the pressure in the plunger pressurizing chamber causes the dodge plunger to move into the plunger. A fuel injection pump that increases the volume of the plunger pressurizing chamber by displacing the dodge plunger when it overcomes a set pressure of an urging means that urges the pressurizing chamber, and a nozzle without a throttle part. A two-stage valve-opening pressure type fuel injection valve that creates an initial injection stroke in which the lift of the nozzle needle is limited to a small value at the beginning of injection, and a main injection stroke that maximizes the lift of the nozzle needle in the subsequent main injection. It is.

Therefore, stable preliminary injection can be performed over a long period of time.

[Brief explanation of drawings]

1 to 4 show one embodiment of the present invention, FIG. 1 is a configuration diagram of main parts of a fuel injection device of the present invention, FIG. 2 is an enlarged sectional view of a dodge plunger portion, and FIG. 3 is a fuel injection device. 4 is an enlarged sectional view of the nozzle tip, FIG. 5 is a sectional view of a fuel injection valve showing another embodiment of the present invention, FIG. 6 is a flow rate characteristic diagram of a throttle nozzle, FIG. 7 is a flow rate characteristic diagram of a bottle nozzle, and FIG. 8 is a sectional view of a fuel injection valve showing still another embodiment of the present invention. 1...Fuel injection device, 2...Fuel injection pump, 3.
...Fuel injection valve, 5...Fuel pressure feeding plunger, 8.
...Plunger pressurization chamber, 14...Dodge plunger,
18...Biasing means, 18a...Coil spring, 23.
... Nozzle, 26... Nozzle hole, 39... First nozzle spring, 44... Second nozzle spring.

Claims (2)

[Claims] 1. A dodge plunger is disposed opposite to the tip surface of the plunger for fuel pressure feeding through a plunger pressurizing chamber, and the pressure in the plunger pressurizing chamber becomes a set pressure of a biasing means that biases the dodge plunger toward the plunger pressurizing chamber. When you win,
A fuel injection device comprising a fuel injection pump configured to increase the volume of the plunger pressurizing chamber by displacement of the dodge plunger, and a fuel injection valve without a throttle section. 2. A dodge plunger is disposed opposite to the tip surface of the fuel pressure-feeding plunger via a plunger pressurizing chamber, and the pressure in the plunger pressurizing chamber becomes a set pressure of a biasing means that biases the dodge plunger toward the plunger pressurizing chamber. When you win,
The fuel injection pump is configured to increase the volume of the plunger pressurizing chamber by displacement of the dodge plunger, and has a nozzle without a throttle part, and has an initial injection stroke in which the lift of the nozzle needle is limited to a small value at the initial stage of injection. This fuel injection system consists of a two-stage valve opening pressure type fuel injection valve that produces a main injection stroke that maximizes the lift of the nozzle needle during the subsequent main injection.