JPH09195881A - Fuel injection equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection device in which the volume change of a pressure control chamber against the movement of a control piston is lessened so that a fuel flow rate can follow. SOLUTION: When the pressure of a control chamber 81 is changed from high pressure to low pressure, a control 22 is lifted and a nozzle needle is lifted so as to inject fuel from a nozzle hole. When an outer valve 54 is seated on the valve seat 32a by a solenoid valve in the low pressure of the control chamber 81, high pressure fuel is gradually introduced into the control chamber 81 via a fuel through hole 54b, an oil pressure chamber 88, and an orifice hole 10, and one part of the high pressure fuel of the control chamber 81 is introduced into an oil storing chamber 82 through the orifice hole 84 so that the pressure of the oil storing chamber 82 is gradually raised. Thereby, the moving orifice 83 acts as buffer material, the pressure of the control chamber 81 is slowly raised, and the rapid rise, the rapid drop and the pressure pulsation of the control chamber pressure are eliminated so that the returning behavior of the control piston 22 and the nozzle needle is avoided and the stable fuel injection amount during an injection period can be secured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-accumulation type fuel injection device which is supplied with high pressure fuel accumulated in a common rail and injects it into a diesel engine.

[0002]

2. Description of the Related Art Conventionally, there has been known a fuel injection device for accumulating high pressure fuel in a kind of surge tank called a common rail and injecting the accumulated high pressure fuel into a diesel engine. In this pressure-accumulation fuel injection device, as a means for lowering the initial injection rate, there is a structure in which a movable valve element is arranged in a control chamber that controls the back pressure of the hydraulic piston. The movable valve body is provided with an orifice for suppressing the flow rate of fuel flowing out of the control chamber. Further, the movable valve body is pressed by a spring in the control chamber in a direction to close the communication passage communicating with the control chamber.

Therefore, at the start of fuel injection, the fuel in the control chamber is discharged from the communication passage through the orifice of the movable valve body, so that the outflow rate of the fuel flowing out of the control chamber is suppressed. As a result, the needle driven by the hydraulic piston slowly rises, resulting in a low initial injection rate. At the end of fuel injection, high-pressure fuel is introduced into the control chamber through the communication passage.
Since the pressure of the high-pressure fuel that flows in exceeds the biasing force of the spring, it is pushed down in the control chamber to open the communication passage. As a result, the high-pressure fuel is instantaneously introduced into the control chamber, so that the needle descends at a stretch together with the hydraulic piston, and the fuel injection ends.

After the injection is completed, the control chamber is filled with high-pressure fuel, and the internal pressure of the control chamber becomes equal to the internal pressure of the communication passage, so that the movable valve body closes the communication passage again by the urging force of the spring. Return to.

[0005]

By the way, the applicant of the present invention has found that when the pressure of the control chamber is switched from the high pressure side to the low pressure side in this pressure-accumulation type fuel injection device, depending on the behavior of the movable valve body, In order to make the pressure unstable, a fuel injection device has been proposed in which the movable valve element is eliminated and a fixed orifice having a small passage cross-sectional area is provided in the middle of the fuel discharge passage communicating with the control chamber. In the pressure accumulating fuel injection device provided with this fixed orifice, the pressure in the control chamber tends to become unstable due to the combination of the flow rate of the orifice and the volume of the control chamber. For example, since the orifice flow rate cannot follow the change in the volume of the control chamber due to the movement of the hydraulic piston, the phenomenon that the pressure in the control chamber becomes unstable may occur.

This phenomenon will be described in detail with reference to the conventional example shown in FIG. 6 and the injection characteristic shown in FIG. The control piston 22 is controlled in the needle opening direction by the force that acts on the control piston 22 in the needle closing direction by the pressure of the control pressure chamber 64 of the injector body 13 and the pressure in the lower fuel puddle (not shown) of the control piston 22. The sum of the force pushing the piston 22 and the force acting in the needle closing direction by the spring force (not shown) is in a balanced position. Further, when the outer valve 54 that comes into contact with the valve body 32 is in the position shown in FIG. 6, the outer valve 54 comes into contact with the valve seat 32a so that high-pressure fuel is supplied from the fuel passage hole 54b to the hydraulic chamber 88. When the outer valve 54 is separated from the valve body 32, the hydraulic chamber 88 communicates with the low pressure passage 63, and the hydraulic chamber 88 has a low pressure. The control pressure chamber 64 communicates with the hydraulic chamber 88 via the orifice hole 10 of the fixed orifice 9.

In the fuel injection device having the fixed orifice 9, the flow rate of the orifice hole 10 cannot follow the volume change of the control pressure chamber 64 due to the vertical movement of the control piston 22. May become unstable. Therefore, the behavior of the control piston 22 becomes unstable, and, for example, as shown in FIG. 8, when the outer valve 54 shifts from the state where it is seated on the valve seat 32a of the valve body 32 to the state where it is separated, The high-pressure fuel in the hydraulic chamber 88 is led out from the low-pressure passage 63, and the outer valve 54
When the fuel cell moves from the state of being separated from the valve seat 32a of the valve body 32 to the state of being seated, high-pressure fuel is introduced into the hydraulic chamber 88 from the fuel passage hole 54b. The pressure in the pressure control chamber 64 that communicates via the hole 10 tends to become unstable. Such an unstable pressure behavior of the pressure control chamber 64 induces an unstable behavior of the needle lift amount.

The present invention has been made from such a point of view, and it is an object of the present invention to provide a fuel injection device in which the volume change of the pressure control chamber is reduced with respect to the movement of the control piston, and the fuel flow rate can be followed. To aim. Another object of the present invention is to provide a fuel injection device for an internal combustion engine in which a pressure change in the control chamber, which greatly contributes to determining the position of the control piston, is stabilized for each injection.

[0009]

A fuel injection device for an internal combustion engine according to the present invention employs the technical means described in claim 1.
According to the fuel injection device for an internal combustion engine of claim 1, since the control chamber volume varying means for suppressing the pressure pulsation of the control chamber when the high pressure fuel flows into the control chamber and flowing into the control chamber is provided, during the injection period by a simple means. It is possible to prevent a sudden change in the pressure of the control chamber, prevent backward movement of the valve member, and stabilize the injection amount for each injection.

According to another aspect of the fuel injection device for an internal combustion engine of the present invention, a fixed orifice provided in a passage connecting the solenoid valve and the control chamber, one end face of the control orifice defines a part of the control chamber, and the other end face of the fixed orifice is provided. Since the movable orifice that partitions a part of the oil reservoir together with the end surface of the valve member opposite to the injection side and the elastic body that suppresses the sudden increase in the volume of the control chamber when the pressure in the control chamber increases, the fixed orifice, the movable orifice, and the elastic orifice are provided. Due to the organic mechanical behavior with the body, there is no abrupt increase, abrupt drop and pressure pulsation of the pressure of the control chamber when high pressure fuel is introduced or discharged into the control chamber, thus avoiding the backward movement of the valve member, It is possible to secure a stable fuel injection amount during the injection period.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIGS. 1 to 3 show a first embodiment of a fuel injection device for an internal combustion engine in which the present invention is applied to an injector attached to each cylinder of a multi-cylinder internal combustion engine.

As shown in FIG. 1, a nozzle needle 20 for opening and closing the injection hole 3 is reciprocally accommodated in a nozzle body 11 of an injection nozzle 2 provided at a lower end portion of an injector 1. The nozzle body 11 and the injector body 13 are joined by a retaining nut 14 with the distance piece 12 interposed therebetween. Nozzle needle 2
A pressure pin 21 and a control piston 22 that is in contact with or connected to the pressure pin 21 on the side opposite to the injection side are arranged on the side opposite to 0. The pressure pin 21 is inserted into the compression coil spring 23, and the compression coil spring 23 urges the pressure pin 21 downward in FIG. 1. A control chamber 81 is provided on the side opposite to the injection side of the control piston 22. The nozzle needle 20, the pressure pin 21, and the control piston 22 form an injection side valve member that connects and disconnects the fuel supply passage 61 and the injection hole 3 described later.

High-pressure fuel is supplied to the fuel supply passage 61 from a common rail (not shown) through a fuel filter 71 housed in the fuel inlet 70. Excess fuel in the injector 1 is discharged from the fuel outlet 72 to the outside of the injector. The electromagnetic coil portion 51 and the valve body 32 of the electromagnetic valve 50 are connected to the injector body 13 by the retaining nut 17. An outer valve 54 is housed in the valve body 32 so as to be capable of reciprocating, and an inner valve 55 is housed in the outer valve 54. The outer valve 54 is connected to the armature 56, and the spring 30 biases the armature 56 downward in FIG. 1, whereby the outer valve 54 is seated on the valve seat 32 a formed on the inner wall of the valve body 32.

When the energization of the electromagnetic coil portion 51 is turned off, the outer valve 54 is urged by the spring 30 so that the valve seat 32a is actuated.
There is a clearance between the valve seat 54a formed on the inner wall of the outer valve 54 and the inner valve 55. Therefore, the high-pressure fuel supplied to the fuel supply passage 61 is supplied to the hydraulic chamber 88 via the fuel passage hole 54b formed by penetrating the outer valve 54 in the axial direction. When the high-pressure fuel is supplied to the control chamber 81 when the electromagnetic coil portion 51 is deenergized, the nozzle needle 20 receives the urging force from the compression coil spring 23 toward the valve seat 2a near the injection hole 3 and the control chamber 81. From the fuel pressure inside the valve seat 2a
The sum of the force applied to the nozzle needle 20 is larger than the force applied to the lift direction due to the fuel pressure around the nozzle needle 20, so the nozzle needle 20 is seated on the valve seat 2a and is in the valve closed state.

When the electromagnetic coil portion 51 is energized, the outer valve 54 is lifted and the high pressure fuel in the control chamber 81 is discharged from the low pressure passage 63. When the fuel pressure in the control chamber 81 decreases, the nozzle needle 20 moves the valve seat 2a. Sit away and lift. Next, the structure near the control room 81 will be described in detail with reference to FIG. Here, the pressure stabilizing means and the volume varying means described in the claims are the fixed orifice 9, the movable orifice 83, the control chamber 81, the oil reservoir chamber 82, the first compression coil spring 85, and the second compression coil shown in FIG. It is composed of a spring 86 and the like.

As shown in FIG. 1, a fixed orifice 9 is provided between the valve body 32 and the injector body 13. The fixed orifice 9 is formed with an orifice hole 10 penetrating the plate thickness in the axial direction. The upper side of the orifice hole 10 in FIG. 1 communicates with the hydraulic chamber 88, and the lower side communicates with the control chamber 81. The movable orifice 83 is
Cylindrical inner wall surface 22 formed at the upper end of the control piston 22
It is accommodated in a so as to be slidable in the axial direction. An oil sump chamber 82 is provided between the lower surface of the movable orifice 83 and the control piston 22.
Are formed. A control chamber 81 is defined by the inner wall of the injector body 13 between the movable orifice 83 and the fixed orifice 9. The movable orifice 83 is formed with an orifice hole 84 that constantly connects the control chamber 81 and the oil reservoir chamber 82.

One end of the first compression coil spring 85 is in contact with the fixed orifice 9 and the other end is in contact with the upper surface of the movable orifice 83. Further, one end of the second compression coil spring 86 is in contact with the lower surface of the movable orifice 83, and the other end is in contact with the upper surface of the control piston 22. The urging force of the second compression coil spring 86 is set to such an extent that the movable orifice 83 does not always collide with the control piston 22 in a range in which the movable orifice 83 behaves due to the pressure difference between the control chamber 81 and the oil reservoir chamber 82. ing. Also, the first
Similarly, the compression coil spring 85 has the fixed orifice 9
And the movable orifice 83 do not collide with each other.

When the solenoid valve 50 is excited, the outer valve 54 is lifted from the valve seat 32a of the valve body 32, the hydraulic chamber 88 and the low pressure passage 63 communicate with each other, and the high pressure fuel in the hydraulic chamber 88 flows to the low pressure passage 63. Is discharged. Along with this,
The high-pressure fuel in the control chamber 81 is discharged to the low-pressure passage 63 through the orifice hole 10 and the hydraulic chamber 88, and the pressure in the control chamber 81 gradually decreases. At this time, the high-pressure fuel in the oil reservoir 82 also flows into the control chamber 81 through the orifice hole 84. When the pressure in the control chamber 81 drops to a certain value,
The nozzle needle 20 rises as the control piston 22 rises. At this time, when the ascending speed of the control piston 22 increases and the flow rate flowing out from the control chamber 81 to the hydraulic chamber 88 through the orifice hole 10 cannot follow the volume change of the control chamber 81, the oil sump is higher than the pressure in the control chamber 81. Since the pressure in the chamber 82 becomes relatively low, the movable orifice 83 is pushed down to reduce the volume change of the control chamber 81. Therefore, the outflow rate of the high-pressure fuel flowing out of the control chamber 81 through the orifice hole 10 of the fixed orifice 9 can follow the volume change of the control chamber 81, so that the stable pressure behavior of the control chamber 81 can be obtained. That is, the unstable behavior does not occur when the lift amount of the needle 20 as shown in FIG. 7 increases. Therefore, as shown in FIG. 3, stable movement of the control piston 22 can be ensured. As a result, there is an effect that variations in fuel injection amount are small and a stable fuel injection amount can be secured.

When the solenoid valve 50 is demagnetized, it passes through the fuel supply passage 61 and the high-pressure passage 62 and the fuel passage 54b to the hydraulic chamber 8.
The high-pressure fuel is introduced into the control chamber 81, the high-pressure fuel flows into the control chamber 81 through the orifice hole 10, and the pressure in the control chamber 81 rises. Then, at the initial stage of the pressure rise in the control chamber 81, the control piston 22 is pushed down due to the pressure rise in the control chamber 81. At this time, a part of the high-pressure fuel flowing from the hydraulic chamber 88 into the control chamber 81 through the orifice hole 10 flows into the oil reservoir chamber 82 through the orifice hole 84. At this time, the descent rate of the control piston 22 becomes faster, and if the flow rate flowing from the hydraulic chamber 88 into the control chamber 81 through the orifice hole 10 cannot follow the volume change of the control chamber 81, the oil sump chamber 82 is higher than the pressure in the control chamber 81. Since the pressure of is relatively high, the movable orifice 83 is pushed up to reduce the volume change of the control chamber 81. Therefore, the inflow flow rate of the high-pressure fuel flowing into the control chamber 81 through the orifice hole 10 of the fixed orifice 9 can follow the volume change of the control chamber 81, so that the stable pressure increase of the control chamber 81 can be obtained. That is, the pressure drop phenomenon after the pressure rise in the control chamber 81 as shown in FIG. 8 does not occur. Therefore, as shown in FIG. 3, the stable movement of the control piston 22 can be ensured.
The movement of the control piston 22 is stable, and the sharp cut can be realized by the rapid lowering of the control piston 22. As a result, there is an effect that the variation in fuel injection amount is small and a stable fuel injection amount can be secured.

In the injection characteristic of the first embodiment shown in FIG. 3, when the pressure in the control chamber 81 gradually rises from the minimum value, the pressure change in the control chamber 81 is stepwise as shown in FIG.
It becomes smooth, and unstable parts such as pressure drop do not occur in the transient state. Due to such pressure behavior of the control chamber, when the needle lift amount increases, the nozzle needle rises smoothly, the variation in the injection amount decreases, and when the needle lift amount decreases, the nozzle needle immediately moves to the valve seat. The seat can be seated and the fuel can be stabilized by sharp cutting.

(Second Embodiment) FIG. 4 shows a second embodiment of the present invention.
Shown in In the second embodiment shown in FIG. 4, the movable orifice 8
An elastic body 88 is provided at a contacting portion of the control piston 3 in order to absorb an impact when the contacting end of the control piston 22 is abutted.
The elastic body 88 is annularly inserted into the lower end of the flange of the movable orifice 83. No compression coil spring exists in the control chamber 81, and no compression coil spring exists in the oil sump chamber 82. The movable orifice 83 moves up and down due to the pressure difference between the pressure in the control chamber 81 and the pressure in the oil reservoir chamber 82.

In the second embodiment, in addition to the effect of the vertical movement of the movable orifice 83 of the first embodiment, the elastic member 8
8 is provided, when the pressure in the control chamber 81 suddenly rises as compared with the pressure in the oil sump chamber 82, the movable orifice 83
The elastic body 88
Is suppressed, the rebound of the movable orifice 83 due to the impact and the asymmetrical behavior of the control piston 22 accompanying it are suppressed. There is no phenomenon in which the needle moves in the opposite direction in the process of reaching zero lift in the valve closed state. Therefore, the fuel cut is properly performed.

(Third Embodiment) FIG. 5 shows a third embodiment of the present invention.
Shown in The third embodiment shown in FIG. 5 is the second embodiment shown in FIG.
This is an example in which a compression coil spring 85 is provided in the control chamber 81 of the embodiment. One end of the compression coil spring 85 contacts the fixed orifice 9 and the other end contacts the movable orifice 83.

In the third embodiment, when the solenoid valve 50 is excited, the outer valve 54 lifts to connect the hydraulic chamber 88 and the low pressure passage 63, so that the high pressure fuel in the hydraulic chamber 88 flows out to the low pressure side. With this outflow of fuel, the control room 8
Although the pressure of No. 1 gradually drops through the orifice hole 10, the compression coil spring 85 biases the movable orifice 83 toward the control piston 22 side, so that the rising speed of the control piston 22 is suppressed and the needle lift amount becomes slow. Since it becomes large, there is an effect that the initial injection rate can be suppressed.

Also in the third embodiment, since the elastic body 88 is provided, the impact is reduced when the movable orifice 83 and the control piston 22 come into contact with each other. Therefore, when the nozzle needle 20 is seated, a phenomenon in which the nozzle needle once lifts in the opposite direction is prevented.
Therefore, the fuel can be cut properly and the injection amount can be stabilized.

As described above, in the above embodiment, the volume change amount of the control chamber 81 is made relatively small by providing the oil reservoir chamber 82 and the movable orifice 83, and the control chamber due to the introduction and introduction of fuel is introduced. The pressure change of 81 can be stabilized. Therefore, when high-pressure fuel is discharged and introduced into the control chamber, the nozzle needle is quickly raised and lowered at the time of transition from the closed state of the nozzle needle to the open state and from the open state to the closed state, and the injection amount is changed. Can be stable.

Although the present description is given by taking the three-way valve system as an example, the present invention can be applied to other injection devices by pressure control of the control chamber, for example, a two-way valve system.

[Brief description of the drawings]

FIG. 1 shows an essential part of a first embodiment of the present invention and is an enlarged view of a portion I shown in FIG.

FIG. 2 is a sectional view of the injector according to the first embodiment of the present invention.

FIG. 3 is a time chart showing the fuel injection characteristics of the first embodiment of the present invention.

FIG. 4 shows a main part of a second embodiment of the present invention and corresponds to FIG.

FIG. 5 shows a main part of a third embodiment of the present invention and is a view corresponding to FIG.

FIG. 6 is a sectional view showing a main part of a conventional example.

FIG. 7 is a time chart showing a fuel injection characteristic of a conventional example.

[Explanation of symbols]

1 injector 2 injection nozzle 9 fixed orifice 10 orifice hole 13 injector body (valve body) 20 nozzle needle (valve member) 22 control piston (valve member) 32 valve body (valve body) 50 solenoid valve 81 control chamber 82 oil sump chamber ( Pressure stabilizing means, control chamber volume varying means) 83 movable orifice 84 orifice hole 85 first compression coil spring (elastic body) 86 second compression coil spring (elastic body) 88 elastic body

Claims (2)

[Claims] 1. A reciprocating valve member, a housing hole for housing the valve member, a nozzle hole for communicating the housing hole with the outside, and a sliding portion for slidably guiding the valve member, A valve body having a valve seat that is brought into a valve closed state by abutting the valve member, a control chamber that pushes the valve member in a direction to abut the valve seat when the internal pressure increases, and a pressure in the control chamber that is high. An electromagnetic valve capable of switching to a low pressure and a pressure stabilizing means for reducing a pressure change in the control chamber are provided, and the pressure stabilizing means controls the pressure pulsation of the control chamber when high pressure fuel flows into and out of the control chamber. A fuel injection device comprising a control chamber volume changing means for suppressing the fuel injection amount. 2. The control chamber volume varying means comprises a fixed orifice provided in a passage connecting the solenoid valve and the control chamber, one end surface of which defines a part of the control chamber, and the other end surface of which is the valve. A movable orifice that partitions a part of the oil reservoir together with the end surface of the member opposite to the injection side, and is provided between the movable orifice and the end surface of the valve member opposite the injection side, and when the pressure in the control chamber rises, The fuel injection device according to claim 1, further comprising an elastic body that suppresses a sudden increase in volume.