JP2841808B2 - Fuel injection device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel injection device that accumulates high-pressure fuel in a common rail and supplies the accumulated fuel to an internal combustion engine.

[Prior art] Conventionally, in a fuel injection device, particularly in a nozzle,
A predetermined clearance is formed between the outer periphery of the needle and the inner periphery of the nozzle body in order to ensure good sliding of the needle. In the nozzle, the pressure in the fuel passage in the nozzle body becomes high during a very short period including the injection period. Therefore, fuel leakage from the clearance to the low-pressure fuel line was small.

Here, in JP-A-59-165858, a high-pressure fuel supplied from a pump driven by an internal combustion engine is accumulated in a fuel passage of a nozzle body, and the accumulated fuel is used to open and close an injection valve by an electromagnetic actuator. Discloses an electromagnetic fuel injection device that supplies fuel to an internal combustion engine.

As the injection valve of this electromagnetic fuel injection device, one using the above-described nozzle (prior art) is conceivable (see FIG. 6).

[Problems to be Solved by the Invention] However, in the prior art, as shown in FIG. 6, the high-pressure fuel from a predetermined clearance 103 formed between the outer periphery of the needle 101 and the inner periphery of the nozzle body 102. Is increased due to the expansion of the clearance 103 due to the high pressure fuel always present in the fuel passage 104 penetrating into the clearance 103.

As a result, in the related art, the fuel leakage of the high-pressure fuel increases, so that the driving torque loss of the pump increases. For this reason, there is a problem that the driving torque loss of the internal combustion engine that drives the pump increases.

An object of the present invention is to provide a fuel injection device that can prevent an increase in drive torque loss of an internal combustion engine due to a fuel leak of high-pressure fuel.

Means for Solving the Problems A fuel injection device according to the present invention includes a nozzle body having a fuel passage to which high-pressure fuel is constantly supplied, a nozzle body fitted into the nozzle body, slidably held by the nozzle body, Between the inner circumference of the fuel passage, and a needle formed with a clear rinse for ensuring good sliding, and an electromagnetic actuator for driving the needle, the nozzle body, A technical means is provided on the outer periphery of the clearance, a high-pressure chamber in which high-pressure fuel is guided from a fuel passage is formed on the outer periphery, and a cylindrical holding portion that slidably holds the needle on the inner periphery. Adopted.

[Operation] Even if high-pressure fuel constantly supplied into the fuel passage enters the clearance formed between the inner periphery of the cylindrical holding portion of the nozzle body and the outer periphery of the needle, the cylindrical holding of the nozzle body is maintained. High-pressure fuel is guided from the fuel passage to a high-pressure chamber formed on the outer periphery of the section.

As a result, a pressure corresponding to the high-pressure fuel is applied from the outer periphery of the cylindrical holding portion of the nozzle body, so that an increase in clearance is prevented, and an increase in fuel leakage of the high-pressure fuel to the low-pressure fuel line is suppressed.

[Effect of the Invention] Since an increase in fuel leakage of high-pressure fuel can be suppressed, an increase in drive torque loss of the internal combustion engine can be suppressed.

Embodiment A fuel injection device according to the present invention will be described based on an embodiment shown in FIGS.

1 and 2 show a first embodiment of the present invention. FIG. 1 is a view showing a common rail type fuel injection device, and FIG.
The figure is an enlarged view of the main part of FIG.

The common rail type fuel injection device 1 is attached to each cylinder of a diesel engine (not shown), and is an introduction pipe (not shown) branched from a common surge tank (not shown).
It is connected to the. In the fuel injection device 1, high-pressure fuel pumped from a surge tank by a pump driven by a diesel engine is constantly supplied from an introduction pipe.

The fuel injection device 1 includes a nozzle body 2, a nozzle holder 3, a needle 4, a pressure pin 5, and an electromagnetic actuator 6.

The nozzle body 2 includes a nozzle body 21 and a tip packing 22.

The nozzle body 21 has a tubular shape, for example, made of alloy steel or carbon steel through SCM 420, and holds the needle 4 slidably on the inner periphery. The nozzle body 21 has a fuel passage 23 and a fuel reservoir 24 formed therein. High-pressure fuel is constantly supplied to the fuel passage 23 and the fuel reservoir 24 from a surge tank via an introduction pipe.

The tip packing 22 is, for example, the same SC as the nozzle body 21.
An annular portion 26 made of alloy steel such as M420 or carbon steel and having an annular passage 25 communicating with the fuel passage 23, and the annular portion 26
And a cylindrical holding portion 27 provided to protrude in the axial direction from the inner peripheral side toward the inner periphery of the nozzle body 21.

As shown in FIG. 2, the holding portion 27 is a portion that slidably holds the needle 4 on the inner periphery.

Further, a clearance 28 is formed between the outer periphery of the needle 4 and the inner periphery of the holding portion 27 so as to communicate with the fuel reservoir 24 and to ensure good sliding of the needle 4. The clearance 28 is a portion where the high-pressure fuel in the fuel reservoir 24 leaks to the low-pressure fuel unit 30. Further, between the inner periphery of the nozzle body 21 and the outer periphery of the holding portion 27, a fuel reservoir 24 is provided.
A high-pressure chamber 29 through which high-pressure fuel is guided is formed. The high-pressure chamber 29 has a function of pressing the holding portion 27 of the tip packing 22 inward to prevent the clearance 28 from expanding.

The relationship between the axial length L of the holding portion 27 and the outer diameter D is preferably about 2 to 4 in L / D. In addition, the holding portion 27
Is formed so that the outer periphery is tapered downward in the drawing so that a large amount of high-pressure fuel penetrates into the high-pressure chamber 29 side from the clearance. For this reason,
The pressure applied to the outer circumference of the holding section 27 is slightly larger than the pressure applied to the inner circumference of the holding section 27.

The nozzle holder 3 is made of, for example, alloy steel such as SCM420 or carbon steel, has a tubular shape, and has a pressure chamber 31 and a fuel passage 32. The pressure chamber 31 has a high pressure when the high-pressure fuel is supplied to the inside, and has a low pressure when the high-pressure fuel is discharged from the inside. The fuel passage 32 communicates the fuel passage 23, the fuel reservoir 24, the annular passage 25, and the pressure chamber 31 with the introduction pipe.
The high-pressure fuel is guided to the fuel reservoir 24, the annular passage 25, and the pressure chamber 31.

Further, the nozzle holder 3, the nozzle body 21, and the tip packing 22 are provided with a sleeve 33 fitted around the outer periphery thereof.
Are held in a state where the end faces are in close contact with each other.

The needle 4 has a nozzle body 21 and a tip packing 22.
Is slidably held on the inner periphery of the holding portion 27 of the first member. The needle 4 is connected at its upper end to the pressure pin 5 in the figure, opens when the pressure pin 5 moves upward in the figure, and closes when the pressure pin 5 returns to its original position.

When the pressure chamber 31 of the nozzle holder 3 becomes low pressure, the pressure pin 5 overcomes the urging force of the spring 51 and moves upward in the figure when the pressure chamber 31 of the nozzle holder 3 becomes low pressure. When the pressure chamber 31 has a high pressure, it moves downward in the figure by overcoming the pressure in the nozzle body 21 and the urging force of the spring 51 due to the difference in the pressure receiving area.

The electromagnetic actuator 6 includes a coil 61 and a valve 62. When the coil 61 is energized, the electromagnetic actuator 6 moves the valve 62 upward in the drawing to cut off the communication between the fuel passage 32 and the pressure chamber 31 of the nozzle holder 3, and removes the high-pressure fuel in the pressure chamber 31. Discharge to low pressure fuel line. When the power supply to the coil 61 stops, the valve
The fuel passage 32 and the nozzle holder 3
With the pressure chamber 31.

FIGS. 1 and 2 show the operation of the fuel injection device 1 of the present embodiment.
A description will be given based on the drawings.

In the fuel reservoir 24, high-pressure fuel is constantly supplied from the surge tank through the introduction pipe, the fuel passage 32, the annular passage 25, and the fuel passage 23.

For this reason, the high pressure fuel infiltrates from the fuel reservoir 24 also into the clearance 28 between the inner periphery of the holding portion 27 of the tip packing 22 and the outer periphery of the needle 4 for ensuring good sliding of the needle 4. come. Further, the high-pressure fuel enters the high-pressure chamber 29 formed between the inner periphery of the nozzle body 21 and the outer periphery of the holding portion 27 of the chip packing 22 from the fuel reservoir 24.

Therefore, as shown in FIG. 2, the pressure on the inner periphery of the holding portion 27 of the tip
And the pressure toward the inner circumference side of arrow b. Both of these pressures are generated by the high-pressure fuel that has entered the clearance 28 and the high-pressure fuel that has entered the high-pressure chamber 29, and the high-pressure chamber 29 has a higher pressure than the clearance 28.
The volume is slightly larger. For this reason, the pressure of the arrow b for decreasing the clearance 28 slightly exceeds the pressure of the arrow a for increasing the clearance 28, so that the holding portion 27 is slightly changed to the inside, thereby increasing the clearance 28. Can be prevented.

As a result, an increase in fuel leakage of the high-pressure fuel to the low-pressure fuel section 30 can be suppressed, and thus a pump driving torque loss due to the fuel leakage of the high-pressure fuel does not increase. This prevents an increase in drive torque loss of the diesel engine that rotationally drives the pump.

FIG. 3 shows a second embodiment of the present invention and is a view showing a common rail type fuel injection device.

The fuel injection device 1 includes a holding portion 27 of the tip packing 22.
By extending the axial dimension of the first embodiment from that of the first embodiment,
This type does not hold the needle 4 slidably on the inner periphery of the nozzle body 21.

FIG. 4 shows a third embodiment of the present invention and is a view showing a common rail type fuel injection device.

This fuel injection device 1 is a tip packing of the first embodiment.
This is a type in which 22 is divided into an annular tip packing 71 and a collar 72. Annular passages 73 and 74 are formed in the tip packing 71 and the collar 72, respectively. Also,
The cylindrical holding portion 75 of the collar 72 has an axial dimension that is longer than that of the first embodiment, as in the second embodiment.

FIG. 5 shows a fourth embodiment of the present invention and is a diagram showing a common rule type fuel injection device.

The fuel injection device 1 is of a type in which a cylindrical groove-shaped pressure chamber 82 is formed in a nozzle body 81, and a cylindrical holding portion 83 is provided integrally with the nozzle body 81. The holding part 83 is a nozzle body
It is formed in a shape protruding upward from the inner periphery of 81 in the figure.

(Modification) In the present embodiment, the holding portion is deformed inward due to the presence of the high-pressure chamber to prevent the expansion of the clearance, but the pressure applied to the outer circumference and the inner circumference of the holding portion by the high-pressure chamber and the clearance is balanced. Alternatively, the shapes of the outer peripheral surfaces of the high-pressure chamber and the holding portion may be changed.

[Brief description of the drawings]

1 and 2 show a first embodiment of the present invention. First
The figure is a sectional view showing a common rail type fuel injection device.
The figure is an enlarged sectional view of the main part of FIG. FIG. 3 shows a second embodiment of the present invention, and is a sectional view showing a common rail type fuel injection device. FIG. 4 is a sectional view showing a third embodiment of the present invention, showing a common rail type fuel injection device. FIG. 5 is a sectional view showing a fourth embodiment of the present invention and showing a common rail type fuel injection device. FIG. 6 is a sectional view showing a fuel injection device used as a prior art. In the drawing, 1 ... common rail type fuel injection device, 2 ... nozzle body, 4 ... needle, 6 ... electromagnetic actuator, 23
… Fuel passage, 24… Fuel pool, 27… Holding part, 28…
Clearance, 29 …… High pressure chamber

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F02M 51/06 F02M 47/00-47/02 F02M 47/06 F02M 61/10-61/12

Claims (1)

(57) [Claims] (A) a nozzle body having a fuel passage through which high-pressure fuel is constantly supplied; and (b) a nozzle body fitted in the nozzle body and slidably held by the nozzle body, and between an inner periphery of the nozzle body. And (c) an electromagnetic actuator for driving the needle, the nozzle body being provided with a clearance communicating with the fuel passage and ensuring good sliding. And a high-pressure chamber through which high-pressure fuel is guided from the fuel passage is formed on the outer periphery, and a cylindrical holding portion that slidably holds the needle on the inner periphery is provided. Injection device.