JPH0666219A - Fuel injector for diesel engine - Google Patents

Abstract

PURPOSE:To facilitate setting work of a pre-lift quantity of a nozzle needle for determining an injection ratio and fixing work of parts. CONSTITUTION:A reciprocating nozzle needle 5 is guided slidably in the axial direction by a valve casing 1d, and is controlled via a first piston 11 and a second piston 12 by each pressure control of a first pressure control chamber and a second pressure control chamber 50. The connecting portion 7 of the nozzle needle 5 is slidably fitted to a small-diameter cylinder disposed in the second piston 12. A spacer 1b for determining a pre-lift quantity of the nozzle needle 5 is interposed between a lower body 1a and a distance piece 1c. A pre-lift quantity of the nozzle needle 5 is determined according to a step difference between the spacer 1b and the top of the second piston 12. Consequently, it is possible to easily manage a vertical dimension of parts constituting an injector, thus making unnecessary estimation of vertical deformation of the parts due to an oil pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device for a diesel engine, and more particularly to a fuel injection device for a diesel engine which facilitates setting of a pre-lift amount of a nozzle needle.

[0002]

As a fuel injection device for a diesel engine,
It is known that a common pressure accumulating pipe called a common rail for accumulating high-pressure fuel and an injector for injecting fuel are known. A nozzle needle that opens and closes the injection hole is slidably arranged in this injector, and a back pressure chamber that holds the fuel pressure acting on the nozzle needle is formed. Is controlled to be switched between the high-pressure side fuel pressure and the low-pressure side fuel pressure by the three-way solenoid valve, so that the high-pressure fuel supplied from the pressure accumulating pipe is injected from the injection hole. In order to improve engine performance, the initial injection amount is constant and rises again.After that, the injection amount becomes almost constant, and the injection end is instantaneously ended. Is set.

[0003]

However, in the conventional fuel injection device for a diesel engine having this kind of structure, the pre-lift amount of the nozzle needle that determines the initial injection rate is the maximum of the parts group that moves integrally with the nozzle needle. Since it is determined by the upper part, there is a problem that it is very difficult to control the dimension in the vertical direction of a plurality of parts and estimate the longitudinal deformation of the parts by hydraulic pressure.

An object of the present invention is to provide a structure in which the pre-lift amount in boot type injection is set by the gap between the nozzle needle and the piston above it.
It is to improve the workability of setting the pre-lift amount of the nozzle needle and the workability of assembling.

[0005]

A fuel injection device for a diesel engine according to the present invention is capable of contacting a pressure accumulating pipe for accumulating high-pressure fuel, a guide hole for axially slidably holding a nozzle needle, and the nozzle needle. And a low pressure fuel pressure in the accumulator pipe, which is a high pressure side of the valve casing having a valve seat portion and a nozzle hole, and the pressures of the first pressure control chamber and the second pressure control chamber that hold the pressure for operating the nozzle needle. Control valve for switching to the fuel pressure on the side, delay means provided between the control valve and the first pressure control chamber for delaying a decrease in the pressure of the first pressure control chamber, and the first pressure control chamber. A first piston that moves the nozzle needle in the valve closing direction in response to an increase in pressure of the first piston, a lower body having a cylinder that reciprocally guides the first piston, and a nozzle knee of the first piston. A spacer having a stopper for restricting the closing position of the valve, a second piston slidably guided by a cylinder formed in the spacer and abutting the first piston, the valve casing and the lower body. A distance piece that determines a distance together with the spacer and the second pressure control chamber are provided, one end of which abuts on the distance piece and the other end of which abuts on the nozzle needle, and urges the nozzle needle in a closing direction. And a pre-lifting amount determining device for connecting the second piston and the nozzle needle so as to variably change the axial distance within a certain range and determining a pre-lifting amount of the nozzle needle. .

In the above configuration of the present invention, the pre-lift amount determining means is, for example, configured such that the connecting portion of the nozzle needle is slidably fitted in a cylinder portion formed in the piston. In the above configuration of the present invention,
The delay means is, for example, a one-way orifice.

[0007]

According to the fuel injection device for a diesel engine of the present invention, the prelift amount of the nozzle needle is determined by the prelift amount determining means formed between the piston and the nozzle needle. It becomes easy to control the vertical dimension of the constituent parts, and it becomes unnecessary to estimate the vertical deformation of the parts due to hydraulic pressure.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 1, the casing member 1 of the injector 100 includes a body lower 1a, a spacer 1b, a distance piece 1c, and a valve casing 1d.
The members 1a and 1b are integrally connected by the retaining ring 1e, and the members 1b, 1c, 1d are integrally connected by the second retaining ring 1f. A valve body sliding hole 2 and a fuel storage chamber 3 are formed in the valve casing 1d, and a large diameter portion 6 of a nozzle needle 5 is slidable in the valve body sliding hole 2 communicating with the fuel storage chamber 3. It is fitted. The large diameter portion 6 of the nozzle needle 5 has a connecting portion 7
The small diameter portion 8 and the valve body portion 9 are integrally formed further downward. Then, the seat portion x is opened and closed by the valve body portion 9, and the injection from the injection hole 4 is turned on / off.

Cylinder 14 formed in body lower 1a
A first piston 11 is slidably fitted therein, and the first piston 11 contacts one end of a second piston 12. As shown in FIG. 3, a small diameter portion 54 is formed at the other end of the second piston 12, and a connecting portion 7 of the nozzle needle 5 is connected to a cylinder portion 55 formed in the small diameter portion 54.
Has a slidably fitted tip.

As shown in FIG. 5, the first pressure control chamber 15 is formed in the cylinder 14 and forms a one-way orifice 38. The first pressure control chamber 15 has a valve body 29.
The narrowed passage 35 formed at the end communicates with the passage 36.
One end 32a of the compression coil spring 32 abuts on the valve body 29, and the other end 32b of the compression coil spring 32 passes through the valve seat 34 and the first piston 1
Abut 1. When high pressure is introduced from the passage 22 to the passage 36 via the inner valve 19 and the outer valve 18, the valve body 29 is pushed down, and the compression coil spring 32 and the valve body 29 come into contact with the piston 11 to move the first piston 11 to the first piston 11. Push down. At this time, the high-pressure fuel flows into the first pressure control chamber 15 from the throttle passage 35, and the pressure in the first pressure control chamber 15 eventually becomes high. Next, when the passage 36 is switched to the low pressure, the fuel flows out from the throttle passage 35 until the pressure balance of the first pressure control chamber 15 is lost, and the first piston 11 is held in the depressed state. After that, when the first pressure control chamber 15 becomes low in pressure, the pressure balance of the first pressure control chamber 15 is lost, and the first piston 11 lifts.

The second pressure control chamber 50 has a high pressure fuel passage 56.
Communicates with the passage 36. As shown in FIG. 3, an annular spring material 51 is housed inside the second pressure control chamber 50, and one end 51a of the annular spring material 51 abuts on an annular groove 52 formed on the bottom surface of the distance piece 1c. The end 51b is in contact with a large-diameter spring seat portion 53 formed at the rear end of the nozzle needle 5. The connecting portion 7 is vertically slidable in a cylinder portion 55 formed in a small diameter solid cylindrical portion 54 formed at the rear end of the second piston 12. Here, as shown in FIG. 3, the full lift amount and the pre-lift amount of the nozzle needle 5 are determined. This pre-lift amount H is determined by the step difference between the spacer 1b and the top of the second piston 12 shown in FIG.

A three-way solenoid valve (control valve) 16 is provided above the first piston 11, and this three-way solenoid valve (control valve) 16 is provided.
Reference numeral 16 is composed of valve means and exciting means. The valve means includes an outer valve 18 slidably guided by a cylinder 17,
The inner valve 19 is slidably guided in the inner hole 18a of the outer valve 18. The exciting means includes a coil 20 attached to a solenoid housing 63, a stator 60 fixed to a case 62 via the solenoid housing 63, a movable iron core fixed to the outer valve 18 and attracted to the stator 60 when energized. 61
And a compression coil spring 21 that urges the outer valve 18 to the side opposite to the suction side.

When the coil 20 is demagnetized, the outer valve 18 is at the lower position due to the urging force of the compression coil spring 21, and the passage 22 and the first pressure control chamber 1
It is in a state of communicating with 5 through the passage 36. Further, when the coil 20 is excited, the outer valve 18 moves upward, and the first pressure control chamber 15 and the drain passage 23 are in communication with each other. The fuel in the drain passage 23 is
It can be drained to a drain tank (not shown) via the passages 43 and 44 and the outlet 27.

A fuel supply passage 24 is formed in the casing member 1, and one end of the fuel supply passage 24 has a fuel reservoir 3
And the other end is connected to the passage 2 of the three-way solenoid valve 16.
It is connected to 2. The pressure accumulating pipe 26 accumulates the high pressure fuel supplied from a high pressure supply pump (not shown), and the pressure accumulating pipe 26 is provided for each cylinder.
High-pressure fuel is supplied to 00 through the inlet 25. The controller 28 inputs signals from the cylinder discrimination sensor, the cam angle sensor, and the accelerator opening sensor, and controls the three-way solenoid valve 16 at a predetermined fuel injection timing.

Next, the operation will be described. Accumulation pipe 2
The high-pressure fuel 6 is supplied into the injector 100 via the inlet 25. This fuel is supplied to the fuel reservoir chamber 3 and the three-way solenoid valve 16 via the fuel supply passage 24. At this time, when the three-way solenoid valve 16 is demagnetized, the outer valve 18 is seated by the compression coil spring 21, and the fuel supplied to the three-way solenoid valve 16 causes the inner valve 19 to move upward in the figure and to pass through the passage. Flows into 36.

The fuel flowing into the passage 36 flows into the throttle passage 35.
The first pressure control chamber 15 is filled with high-pressure fuel in a state where it flows into the first pressure control chamber 15 for a predetermined time. At this time, the first pressure control chamber 15 and the second pressure control chamber 5
0 and the fuel storage chamber 3 are at high pressure, the first piston 11 contacts the stopper portion 45, and the second piston 1
2 contacts the first piston 11, and the nozzle needle 5 is seated on the seat portion x due to the difference between the pressure receiving area of the second control chamber and the pressure receiving area of the fuel reservoir chamber 3 and the setting force of the annular spring member 51.

When the three-way solenoid valve 16 is excited, the outer valve 18 is sucked upward in the figure, and the fuel in the first pressure control chamber 15 is released to the low pressure side via the passage 36 and the drain passage 23. However, at this time, in the first pressure control chamber 15, the outflow of fuel is restricted by the throttle passage 35, so that
The pressure in the pressure control chamber 15 does not immediately drop and is kept high for a predetermined period. As a result, the first piston 11 is held in contact with the stopper portion 45. At this time, the second
The piston 12 is still in contact with the first piston 11. The nozzle needle 5 is shown in FIG. 3 by the difference between the pressure (low pressure) received by the pressure receiving area of the second pressure control chamber 56 and the pressure (high pressure) received by the pressure receiving area of the fuel reservoir chamber 3 and the set pressure of the annular spring member 51. Increase by the amount of pre-lift.

After that, the pressure in the first pressure control chamber 15 is changed to the first pressure.
When the piston 11 and the second piston 12 are lowered to a level enough to rise, the first piston 11 and the second piston 12 are in a full lift state. Next, when the three-way solenoid valve 16 is demagnetized, the high pressure fuel is transferred to the three-way solenoid valve
6, when supplied to the first pressure control chamber 15 and the second pressure control chamber 50 through the passage 36, the first piston 11 receives the pressure of the first pressure control chamber 15 and instantly moves downward in the drawing. The second piston 12 and the nose needle 5 are accompanied by this.
Drops and the injection ends immediately.

Incidentally, FIG. 6 shows the passage 36,
FIG. 7 is a time chart showing pressure changes in the second pressure control chamber 50 and the first pressure control chamber 15, and FIG. 7 is a time chart showing displacements of the first piston 11, the second piston 12, and the nozzle needle 5 in the above operation. is there. As shown in FIG. 8, the pre-lift amount can be adjusted by the axial lengths of the distance piece 1c and the spacer 1b shown in FIG. 4, and as shown in FIG. 9, by adjusting the throttle diameter of the throttle passage 35, the nozzle can be adjusted. The inclination of the full lift of the needle 5 can be controlled. Further, as shown in FIG. 10, compared with the conventional delta type injection, the injection amount during the ignition delay period can be reduced, so that the burst combustion is prevented,
Nitrogen oxide can be reduced.

According to the configuration of the above embodiment, when assembled,
As shown in FIG. 4, the second piston 12 is brought into contact with the nozzle needle 5, and the pre-lift amount H is set by the step between the second piston 12 and the spacer 1b. The pre-lift amount H of the nozzle needle 5 is set by setting the spacer 1 shown in FIG.
It can be managed only by b and the step H at the top of the second piston 12. Conventionally, the vertical dimension of the body lower governs the pre-lift amount, but in the present embodiment, the dimensional control of the body lower 1a is not required to determine the pre-lift amount.
The pre-lift amount can be set easily. Moreover, pre-lift amount adjustment work and maintenance inspection work can be performed simply by reassembling each part shown in FIG. 4 with the retaining ring 1e, which has the effect of improving serviceability.

When the annular spring member 51 of the above embodiment is assembled, since the elastic deformation of the annular spring member 51 is relatively smaller than that of the compression coil spring, there is also an effect that the pre-lift amount can always be maintained properly.

[0022]

As described above, according to the fuel injection device for a diesel engine of the present invention, a boot type injection is made possible, and the pre-lift amount of the nozzle needle that determines the injection rate moves together with the nozzle needle. Since it is decided in the middle part of the above, there is an effect that the setting work of the pre-lift amount becomes easy and the workability at the time of maintenance and inspection is improved. Further, when determining the pre-lift amount of the nozzle needle, there is an effect that it becomes easy to control the dimension in the vertical direction of the plurality of components that form the injector, and it becomes easy to estimate the vertical deformation of the components due to hydraulic pressure.

[Brief description of drawings]

FIG. 1 is a sectional view showing a fuel injection device for a diesel engine according to an embodiment of the present invention.

2 is a cross-sectional view showing the fuel injection device for a diesel engine shown in FIG. 1, taken along a section different from the section shown in FIG.

FIG. 3 is an enlarged cross-sectional view showing a portion B shown in FIG.

FIG. 4 is a cross-sectional view showing the fuel injection device for a diesel engine shown in FIG. 1, illustrating an operation of setting a pre-lift amount before the completion of assembly.

5 is an enlarged cross-sectional view of a portion A shown in FIG.

FIG. 6 is a time chart showing pressure change characteristics of the above-mentioned embodiment of the present invention.

FIG. 7 is a time chart showing a displacement characteristic of the embodiment of the present invention.

FIG. 8 is a diagram for explaining injection characteristics of the embodiment of the present invention.

FIG. 9 is a diagram for explaining injection characteristics of the embodiment of the present invention.

FIG. 10 is a diagram for explaining injection characteristics of the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Casing member 1a Lower body 1b Spacer 1c Distance piece 1d Valve casing 2 Valve body sliding hole (guide hole) 4 Injection hole 5 Nozzle needle 7 Connecting part (pre-lift amount determining means) 11 First piston 12 Second piston 14 Cylinder 15 first pressure control chamber 16 three-way solenoid valve (control valve) 18 outer valve (control valve) 19 inner valve (control valve) 20 coil (control valve) 21 compression coil spring (control valve) 22 high pressure fuel passage 26 pressure accumulation pipe 35 throttle passage 38 One-way orifice 45 Stopper 50 Second pressure control chamber 51 Annular spring material (biasing means) 55 Cylinder part 60 Stator (control valve) 61 Movable iron core (control valve) 100 Injector X Seat part (valve seat part)

Claims (3)

[Claims] 1. A valve casing having a pressure accumulating pipe for accumulating high-pressure fuel, a guide hole for holding a nozzle needle slidably in an axial direction, a valve seat portion with which the nozzle needle can come into contact, and an injection hole, A control valve for switching the pressures of the first pressure control chamber and the second pressure control chamber, which hold the pressure to be applied to the nozzle needle, between the fuel pressure of the accumulator pipe on the high pressure side and the fuel pressure on the low pressure side; Delay means provided between the first pressure control chambers for delaying a decrease in the pressure of the first pressure control chambers; and the nozzle needle in the valve closing direction in response to an increase in the pressure of the first pressure control chambers. A first piston that moves, a lower body that has a cylinder that guides the first piston so that the first piston can reciprocate, and a spacer that has a stopper that restricts the nozzle needle closing side position of the first piston, A second piston slidably guided by a cylinder formed in the spacer and abutting the first piston; a distance piece that determines a distance between the valve casing and the lower body together with the spacer; Two pressure control chambers, one end of which abuts on the distance piece and the other end of which abuts on the nozzle needle, and biases the nozzle needle in a closing direction; and the second piston and the nozzle. A fuel injection device for a diesel engine, comprising: a pre-lift amount determining means for connecting a needle and a variable distance in an axial direction within a certain range to determine a pre-lift amount of the nozzle needle. 2. The pre-lift amount determining means is characterized in that a connecting portion of the nozzle needle is slidably fitted in a cylinder portion formed in the piston.
The fuel injection device for a diesel engine described. 3. The fuel injection device for a diesel engine according to claim 1, wherein the delay means is a one-way orifice.