JPH0281951A - Fuel injection device - Google Patents

Abstract

PURPOSE:To decrease a speed of opening a needle valve and to improve an injection cut of the valve, when it is closed, by providing a fuel introducing chamber, pressing the needle valve in a seating direction by a pressure of fuel from a fuel pressurizing chamber, in a fuel injection device and switching a condition between both the fuel pressurizing and introducing chambers to connection and disconnection conditions. CONSTITUTION:Fuel in a fuel pressurizing chamber 33 is pressurized by a plunger 36 in a fuel injection device 1 and injected from an injection hole 444 via a fuel reservoir chamber 445 by opening a needle valve 446. A spring housing chamber 42a, containing a nozzle spring 46 pressing the needle valve, serves as a fuel introducing chamber and communicates with a fuel pressurizing chamber 33 by a communication path 6 through an electromagnetic opening and closing selector valve 5. The electromagnetic opening and closing selector valve 5 is energized closing after a start of pressurization and deenergized opening before a stop of pressurization, of fuel by the pump plunger 36. Accordingly, when the needle valve is opened, its opening speed is decreased by a damper effect of the fuel introducing chamber to prevent a sudden increase of temperature in ignition, and when the valve is closed, its closing speed is increased by the pressure to improve an injection cut.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a fuel injection device used in a diesel engine or the like.

[Prior Art 1] Generally, a fuel injection device used for a diesel engine or the like includes a fuel pressurizing section and a fuel injection section, as described in Japanese Patent Application Laid-Open No. 60-27775. The fuel pressurizing section is for pressurizing fuel to a high pressure, and includes a fuel pressurizing chamber to which fuel is supplied, and a pump plunge chamber for pressurizing the fuel in the fuel pressurizing chamber. On the other hand, the fuel injection section is for injecting the fuel pressurized by the fuel pressurization section into the combustion chamber of the engine, and has an injection hole that communicates with the fuel pressurization chamber via a valve seat, and a fuel injection hole that is seated on the valve seat. In addition, it includes a needle valve that blocks the injection hole and the fuel pressurizing chamber, and a nozzle spring that biases the needle valve in the seating movement direction.

In the above configuration, when the fuel in the fuel pressurizing chamber is pressurized by the pump plunger, the pressurized fuel causes the needle valve to be lifted against the urging force of the spring. As a result, the fuel pressurizing chamber and the injection hole communicate with each other, and fuel is injected from the injection hole into the combustion chamber of the engine. On the other hand, when the pump plunger finishes pressurizing the fuel, the needle valve is seated on the valve seat by the urging force of the nozzle spring. This ends fuel injection.

[Problem to be Solved by the Invention 1] In the conventional fuel injection device described above, the force to press the needle valve in the seating movement direction is obtained only by the nozzle spring, so the fuel pressure exceeds the valve opening pressure of the needle valve. When the valve is opened, the needle valve suddenly lifts and reaches the fully open state. For this reason, the fuel injection rate reaches its peak at a relatively early stage, as shown by the dashed line in FIG. When the initial fuel injection rate is high, a large amount of fuel is injected during the ignition delay period, and a large amount of fuel is rapidly burned out at the same time as ignition. As a result, the temperature inside the combustion chamber rises rapidly, causing problems such as an increase in the concentration of NOx in the exhaust gas and the generation of loud noise.

In addition, because the needle valve is not seated until the force exerted on the needle valve by the fuel becomes smaller than the biasing force of the nozzle spring, the period of low injection rate continues for a long time, leading to worsening of injection failure. There was a risk that this could lead to the occurrence of

This invention was made to solve the above-mentioned problems, and it is possible to suppress the lift speed of the needle valve to a low speed when the valve is opened, and to seat the needle valve without waiting for the fuel pressure to drop when the valve is closed. It is an object of the present invention to provide a fuel injection device capable of reducing NOx concentration and noise, and suppressing the generation of smoke.

[Means for Solving the Problems 1] In order to achieve the above-mentioned object, the present invention provides four fuel injection sections that are connected to a fuel pressurizing chamber, and a needle valve is connected to the needle valve by fuel introduced from the fuel pressurizing chamber. A fuel introduction chamber that presses in the direction of seating movement is provided, and an on-off switching valve is provided between the fuel introduction chamber and the fuel pressurizing chamber to switch between a communication state and a cutoff state.

[Operation] After the pump plunger starts pressurizing the fuel, close the on-off switching valve. Thereby, the fuel introduced into the fuel introduction chamber from the fuel pressurization chamber is confined within the fuel introduction chamber. After that, the pump plunger is further pressurized and moved, and the pressing force of the pressurized fuel against the needle valve in the direction of the 7F movement is greater than the pressing force of the sealed fuel and the nozzle spring against the needle valve in the seating movement direction. Then, the needle valve starts to move. At this time, the lift speed of the needle valve is suppressed to a low speed due to the damper effect of the fuel confined within the fuel introduction chamber.

Also, the on/off switching valve is opened before the pump plunger finishes pressurizing the fuel. Then, the high pressure fuel in the fuel pressurization chamber flows into the fuel introduction chamber. This inflowing high-pressure fuel presses the needle valve in the seating movement direction, canceling out the pressing force of the fuel in the lifting direction of the needle valve. Therefore, the needle valve can be seated by the nozzle spring without waiting for the fuel pressure to drop, and the fuel injection can be improved.

[Embodiments] Hereinafter, embodiments of the present invention will be described with reference to the attached FIGS. 1 to 6.

1 and 2 show an embodiment of the present invention, and reference numeral 1 in the figures indicates the main body of the apparatus. This device main body 1 includes a main body portion 2. As shown in FIG. The main body portion 2 includes a vertical portion 2a extending in the vertical direction in FIG. 1, and a side portion 2b projecting laterally from an intermediate portion of the vertical portion 2a.

The vertical part 2a is provided with a fuel pressurizing part 3, and
A fuel injection section 4 is provided at the bottom thereof. On the other hand, an electromagnetic on-off switching valve (on-off switching valve) 5 is provided on the side portion 2b.

First, to explain the fuel pressurizing part 3, the vertical part 2a has a large diameter cylinder hole 31, a small diameter cylinder hole 32 aligned with the large diameter cylinder hole 31 and a thin line, sequentially from the upper end surface downward. and a fuel pressurizing chamber 33 are arranged in series.

A follower member 34 is slidably provided in the large diameter cylinder hole 31 . This follower member 34 is urged upward by a plunger spring 35 provided between its upper portion and the vertical portion 2a, and is pressed into contact with a cam portion of a camshaft (not shown).

Then, it reciprocates following the rotation of the camshaft.

In addition, a pump plunger 36 is provided in the small diameter cylinder hole 32.
is slidably provided. This pump plunger 3
6 is attached at its upper end to the lower end of the following member 34 so as to be immovable in the vertical direction.
It is designed to move up and down together with 4. Further, an annular groove 36g is formed on the outer peripheral surface of the pump plunger 36.

This annular groove 36a is communicated with the fuel pressurizing chamber 33 through a communication hole 36b formed inside the pump plunger 36. Further, a fuel supply boat 37 connected to a fuel pump (not shown) is opened at the lower part of the small diameter cylinder hole 32.

In the above configuration, when the pump plunger 36 moves downward,
When the pump plunger 36 covers the opening of the fuel supply boat 37, substantial pressurization of the fuel begins. When the pump plunger 36 moves further down and its annular groove 36a faces the opening of the fuel supply boat 37, the fuel pressurization chamber 3
3 flows back to the fuel supply boat 37 via the communication hole 36b and the annular groove 36g, thereby completing the pressurization of the fuel. In other words, the maximum injection amount in this fuel injection device is regulated by the stroke of the pump plunger 36 from when the fuel supply boat 37 is shielded until the annular groove 36a faces the fuel supply boat 37.

Then, as will be described later, within this maximum injection amount range, by opening and closing the electromagnetic switching valve 5 to control the fuel injection start timing and injection end timing, the actual fuel injection amount in each operating state of the engine can be determined. has been decided. On the other hand, when the pump plunger 36 moves upward, fuel is drawn into the fuel pressurizing chamber 33 from the fuel supply boat 37.

Next, the fuel injection part 4 will be explained. A cylindrical nozzle holder 41 is screwed into the lower end of the vertical part 2a. Inside this nozzle holder 41, a spring holder 42 and a spacer 4 are arranged in order from the vertical part 2a side downward.
3 and an injection nozzle 44 are inserted. These spring holder 42, spacer 43, and injection/zzle 44 are fixed together with nozzle holder 41 to vertical portion 2a by tightening nozzle holder 41.

The injection nozzle 44 is for injecting pressurized fuel in the fuel pressurizing chamber 33 and includes a nozzle body 441 held and fixed by the nozzle holder 41. In this nozzle body 441, a valve housing hole 442, a valve seat 443, and an injection hole 444 that open to the lower end surface (tip surface) of the nozzle body 441 are formed in order from the upper end surface downward.

A fuel reservoir chamber 445 is formed in the center of the valve housing hole 442 . This fuel reservoir chamber 445 includes a nozzle body 441, a spacer 43, a spring holder 42, and a vertical portion 2.
The fuel pressurizing chamber 33 is
is communicated with. In addition, the valve storage hole 442 has
A needle valve 446 is slidably provided. This needle valve 44
6 is a large diameter portion 4 slidably provided in the valve storage hole 442.
46a, and a valve portion 446c seated on the valve seat 443 at the lower end.
When high-pressure fuel is fed to the fuel reservoir chamber 445, the large-diameter portion 44
The diameter difference area of the stepped portion between the small diameter portion 6a and the small diameter portion 446b serves as a pressure receiving surface, and is lifted upward from the valve seat 443 by the pressure of the fuel.

Note that when the needle valve 446 is lifted, the fuel reservoir i) chamber 44
The fuel pumped into the injection hole 44 passes through a passage 447 formed between the outer peripheral surface of the small diameter portion 446b and the inner peripheral surface of the valve housing hole 442 and between the valve seat 443 and the valve portion 446°.
4, from where it is injected into the combustion chamber of the engine (none of which is shown).

The spring holder 42 is formed with a spring storage chamber (fuel introduction chamber) 42a extending upward from its lower end surface. This spring storage chamber 42a has a lower end opening that connects to the valve storage hole 442 through a hole 43a formed in the spacer 43.
It communicates with the upper end of the. In addition, the spring storage chamber 4
A nozzle spring 46 is provided within 2a. This nozzle spring 46 serves to seat the needle valve 446 on the valve seat 443, and thus urges the needle valve 446 downward via the spring receiver 47 and a protrusion 446d formed on the upper end surface of the needle valve 446. It looks like this.

Further, the spring storage chamber 42a is connected to the fuel pressurizing chamber 3 through a communication path 6 formed across the spring holder 42 and the main body portion 2.
3. This communication path 6 consists of an upstream part 6a on the side of the fuel pressurizing chamber 33 and a downstream part 6b on the side of the spring storage chamber 42a. It is configured to be opened and closed by a switching valve 5.

The electromagnetic on-off switching valve 5 is a normally open on-off valve, and is configured as follows. That is, in the side portion 2b, a small diameter hole portion 21, a medium diameter hole portion 22, and a large diameter hole portion 23 are formed in order from the upper end surface to the lower end surface with their axes aligned with each other.

An annular four part 21a is formed on the inner peripheral surface of the small diameter hole part 21, and a four part 21b is formed at a position spaced upward from the annular four part 21a. Annular four part 21a
is communicated with the fuel pressurizing chamber 33 via the upstream portion 6a. On the other hand, the four parts 21.11 are communicated with the spring storage chamber 42a via the downstream part 6b.

Further, a valve body 51 is slidably provided in the small diameter hole portion 21 . The upper end of this valve body 51 protrudes upward from the upper end surface of the side part 2 [1, and the armature 5
2 is fixed by a nut 53. A stator 54 is provided on the upper end surface of the side portion 2b surrounding the armature 52. A solenoid 55 is provided on a surface of the stator 54 facing the armature 52. When this solenoid 55 is energized, the armature 55 is magnetically attracted, thereby causing the valve body 51 to move upward. The upper movement range of the valve body 51 is restricted by hitting an upper stopper 56 provided at the upper end opening of the small diameter hole 21a.

Further, the nut 53 and the stator 54 are opened by a nut 5.
3 and an armature 55, a valve spring 57 is provided that urges the valve body 51 downward. Therefore, when the current supply to the valve/id 55 is stopped, the valve body 51 moves downward. The downward movement range of the valve body 51 is restricted by hitting a lower stopper 59 fixed to the large diameter hole 23 via a shim 58.

Further, an annular groove 51a is formed on the outer peripheral surface of the valve body 51. This annular groove 51a is such that the valve body 51 is connected to the lower stopper 5.
When the valve element 51 abuts against the upper stopper 56, its upper end faces the recess 21b, and its lower end faces the four annular part 21a. It is arranged so as to be spaced apart from above. Therefore, when the valve body 51 is moved upward until it hits the upper stopper 56 by energizing the slide/id 55, the upstream portion 6a and the downstream portion 6b are cut off. On the other hand, when the energization to the solenoid 55 is stopped and the valve body 51 is moved down until it hits the lower stopper 59, the upstream section 6a and the downstream section 6b are brought into communication.

The solenoid 55 is energized by the pump plunger 36.
The solenoid 55 is controlled to stop energizing the solenoid 55 before the annular groove 36a of the pump plunger 36 faces the fuel supply boat 37.

Control of the start time and stop time of energization is performed by a control unit (not shown) such as a microcomputer based on operating conditions such as engine rotational speed and load.

In addition, the reference numeral 24 in the figure is a drain passage, and this drain passage allows communication between the archer 7 chamber 54a formed between the stator 54 and the side portion 2b and the inside of the medium diameter hole 22. , connected to a fuel tank (not shown).

Next, the operation of the fuel injection device having the above configuration will be explained based on FIG. 2. In the case shown in FIG. 2, a valve spring 57 for biasing the valve body 51 downward is provided between the lower end of the valve body 51 and the bottom surface of the medium diameter hole 22. , there is no difference in operation from the one shown in FIG.

The pump plunger 36 moves downward as the camshaft rotates,
When the fuel supply boat 37 is shielded, the pump plunger 3
6 begins to substantially pressurize the fuel. At the beginning of fuel pressurization, as shown in FIG.
The storage chamber 42a is communicated with the storage chamber 42a. Therefore, the fuel in the fuel pressurizing chamber 33 is pressure-fed to the fuel reservoir chamber 445, and is also force-fed to the fuel storage chamber 42a. fuel? ! i1? The fuel pressure-fed to the storage chamber 445 is transferred to the needle valve 4
Try to push 46 upwards. On the other hand, spring storage chamber 4
The fuel pumped into the needle valve 4 and the nozzle spring 46
Push down on 46. This downward force is greater than the upward force. Therefore, needle valve 446 remains seated.

When the control unit determines that it is time to inject the fuel and energizes the valve/id 55 based on that determination, the electromagnetic switch #5 becomes closed, as shown in FIG. 2(B). , the electromagnetic switching valve 5 is located between the upstream portion 6a and the downstream portion 6b of the communication path 6.
Therefore, the fuel pressurizing chamber 33 and the bone storage chamber 42a are disconnected from each other. As a result, the spring storage chamber 4
The fuel within 2a is sealed therein. The resultant force of the downward force of the fuel when it is sealed and the urging force of the nozzle spring 46 becomes the valve opening pressure of the needle valve 446.

Thereafter, as the pump plunger 36 moves further downward, the pressure of the fuel pumped into the fuel reservoir chamber 446 increases, and when the pushing force exceeds the valve opening pressure, the needle valve 446
is lifted from the valve seat 443, and fuel is injected from the injection hole 444.

Here, when the needle valve 446 is lifted, the bone storage chamber 42
The IJ7 speed is suppressed to a low speed due to the resistance of the fuel confined in the a (so-called damper effect). Therefore, the needle valve 446 does not lift to the fully open state all at once, but gradually lifts, and the communication area between the needle valve 446 and the valve seat 443 gradually expands. Therefore, as shown by the solid line in FIG. 3, according to this fuel injection device, the injection rate is low at the early stage of injection and increases toward the latter stage of injection. As a result, the amount of NOX generated and noise can be reduced.

Note that the injection start time is slightly delayed from the start time of energization to the solenoid 55;
This problem can be solved by advancing the timing of starting energization for No. 5 in advance.

At the end of the downward movement of the pump blunt gear 36, the control unit determines that fuel injection should be terminated, and based on that determination, the energization to the solenoid 55 is stopped, as shown in FIG.
), the electromagnetic switching valve 5 is opened, and the bone storage chamber 42a is communicated with the fuel pressurizing chamber 33 via the communication path 6.

Then, high-pressure fuel is pumped into the spring storage chamber 42a. The needle valve 446 is pressed downward by this pressure-fed fuel. This downward pressing force cancels the upward pressing force on the needle valve 446. Therefore, without waiting for the pressure in the fuel reservoir chamber 445 to decrease, the needle valve 446 is activated to the nozzle 1! It is rapidly moved downward by the biasing force of the spring 46 and is seated on the valve seat 443. As a result, as shown in FIG. 3, the fuel injection rate is rapidly reduced from a high state, and the fuel injection rate is improved. Therefore, generation of smoke can be suppressed.

When the pump plunger 36 moves further down and its annular groove 36a faces the fuel supply boat 37 as shown in FIG. 2(D), the fuel in the fuel pressurizing chamber 33 flows back into the fuel supply boat 37. As a result, the pressure of the fuel in the fuel reservoir chamber 445 and the spring storage chamber 42a decreases.

When the pump plunger 36 moves upward, fuel is sucked into the fuel pressurizing chamber 33 from the fuel supply boat 37.

Thereafter, the above operation is repeated.

It should be noted that the present invention is not limited to the above-described embodiments, and can be modified in various ways without departing from the essential aspects thereof.

For example, the fuel injection device shown in FIG. 4 has an orifice 7 at the connection between the communication passage 6 and the bone storage chamber 42a, thereby further reducing the lift speed of the needle valve 446. be.

Further, in the fuel injection device shown in FIG. 5, the bone storage chamber 42a is also used as the fuel introduction chamber in the above-described embodiment, whereas the orifice 7 and the communication passage are provided separately from the bone storage chamber 42a. 1. A fuel introduction chamber 8 is provided which communicates with the fuel pressurizing chamber 33 via the fuel pressurizing chamber 33. A plunger 9 that abuts against the needle valve 446 via a spring receiver 47 is slidably provided in the fuel introduction chamber 8 of -, and the diameter of the plunger 9 is larger than the diameter of the needle valve 446. .

In this fuel injection device, since the diameter of the plunge +9 is larger than the diameter of the needle valve 446, a larger damping effect can be obtained due to the larger diameter.

Due to the synergistic effect of this and the orifice 7, the moving speed of the needle valve 446 can be further reduced. Moreover, since the diameter of the blunt gear 9 is larger than the diameter of the needle valve 51, the repressing force of the seating movement force \\ against the needle valve 446 by the fuel becomes larger than the pressing force in the lift movement direction. Then, due to the difference in the pressing force, the needle valve 446
is pressed in the direction of seating movement. Therefore, the needle valve 51
The needle valve 4
46 can be moved at a higher speed, thereby further improving fuel injection.

Furthermore, the fuel injection device shown in FIG.
A plunger 10 having a diameter larger than that of the needle valve 4/i6 is provided in the fuel injection device 2a, and the same effect as that of the fuel injection device shown in FIG. 5 can be obtained.

Further, in the above embodiment, the valve body 51 of the electromagnetic switching valve 5 is directly assembled into the apparatus main body 1, but a previously completed electromagnetic valve may be assembled into the apparatus main body 1. It goes without saying that other configurations may be used as the on-off switching valve.

Effects of the Invention 1 As explained above, according to the fuel injection device of the present invention, the fuel injection part is communicated with the fuel pressurizing chamber, and the needle valve is moved in its seating position by the fuel introduced from the fuel pressurizing chamber. A fuel introduction chamber that presses in the direction is provided, and an on-off switching valve is provided between the fuel introduction i and the fuel pressurizing chamber to switch between a communication state and a cutoff state, so that when the valve is opened, the needle valve is The needle valve can be held at a low speed, and the needle valve can be seated without waiting for the fuel pressure to drop when the valve is closed, thereby improving the ability to inject the fuel.

Therefore, effects such as reducing NOx concentration and noise, and suppressing the generation of smoke can be obtained.

[Brief explanation of the drawing]

Figures 1 and 2 show an embodiment of the present invention, with Figure 1 being a longitudinal sectional view and Figure 2 (A). (B), (C), and (D) are diagrams for explaining the effects, FIG. 3 is a diagram showing the fuel injection rates of the conventional fuel injection device and the fuel injection device according to the present invention, and FIG. 5 and 6 are schematic configuration diagrams showing a part of an embodiment of the pond of the present invention, respectively. 3...Fuel pressurizing part, 4...Fuel injection part, 5...Solenoid switching valve (on/off switching valve), 6...Communication path, 8...
・Fuel introduction chamber, 33...Fuel pressurization chamber, 36...Pump plunger, 42a...Spring storage chamber (fuel introduction chamber)
, 44... Injection nozzle, 46... Nozzle spring, 44
3... Valve seat, 444... Injection hole, 446... Needle valve.

Claims (1)

[Claims] a fuel pressurizing section having a fuel pressurizing chamber to which fuel is supplied and a pump plunger pressurizing the fuel in the fuel pressurizing chamber; an injection hole communicating with the fuel pressurizing chamber via a valve seat; and the valve. The fuel injection unit includes a needle valve that is seated on a seat and blocks a connection between the fuel pressurizing chamber and the injection hole, and a fuel injection section that has a nozzle spring that biases the needle valve in a seating movement direction. In the fuel injection device, the fuel is injected from the injection hole by lifting the needle valve against the biasing force of the nozzle spring by the fuel applied to the nozzle spring. A fuel introduction chamber is provided which communicates with the fuel pressurization chamber and presses the needle valve in the seating movement direction by the fuel introduced from the fuel pressurization chamber, and the pump plunger is provided between the fuel introduction chamber and the fuel pressurization chamber. At the beginning of the pressurization movement of the pump plunger and before the needle valve lifts, the fuel introduction chamber and the fuel pressurization chamber are switched from a communication state to a disconnection state, and at the end of the pressurization movement of the pump plunger and before the needle valve lifts, 1. A fuel injection device comprising an on-off switching valve for switching the fuel introduction chamber and the fuel pressurizing chamber from a cutoff state to a communication state before the fuel injection chamber and the fuel pressurization chamber are seated.