JP2511188Y2 - Fuel injection valve - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a fuel injection valve of a diesel engine, and in particular to a fuel injection with improved injection performance in the low speed range and the medium speed range of the diesel engine. Regarding the valve.

[Prior Art] Generally, in a diesel engine, in order to reduce the emission amount of nitrogen oxides, it is necessary to make the injection mist particle size of the fuel as small as possible and to mix the fuel and the air after injection in a short time. is there. For this purpose, it is required to increase the valve opening pressure of the fuel injection valve and inject fuel at a high injection pressure. In order to satisfy this requirement, there is a method of increasing the valve opening pressure by increasing the spring force of the pressure spring that biases the needle valve in the valve closing direction.

However, if the valve opening pressure is increased by increasing the spring force of the pressure spring, the needle valve will hit the valve seat with a strong force when closing the valve immediately after fuel injection. From the aspect of performance, there is a limit to the performance improvement of the fuel injection valve.

As a conventional technique to improve such a point, there is, for example, a fuel injection valve disclosed in JP-A-60-122269. In this fuel injection valve, a central plunger is provided above the needle valve, and the pressure in the injection pipe is applied to this central plunger to add the spring force of the pressure spring to keep the valve opening pressure high. At the end of fuel injection, the force of pressing the central plunger decreases before the fuel pool chamber in the nozzle body due to the decrease in pressure in the injection pipe, and the force of pressing the needle valve against the valve seat is compared when the valve is opened. Therefore, the valve closing pressure is kept low, the valve opening pressure is increased and the durability is improved.

In recent years, however, it has been desired to reduce the combustion noise in the low speed range and the medium speed range and to improve the output in the high speed range with the direct injection of the diesel engine. In the valve, it is possible to increase the valve opening pressure overall from the low speed rotation range to the high speed rotation range, but since the valve opening pressure cannot be changed according to the change in the rotation speed of the diesel engine, In the low speed rotation range, combustion noise was large, and fuel supercharging at the time of starting was difficult, so that the hunting phenomenon due to the irregular injection in the low speed rotation / low injection range could not be prevented. Furthermore, there is a problem that atomization of the spray cannot be promoted in the high speed rotation range, and the output of the diesel engine cannot be improved.

[Problems to be Solved by the Invention] The present invention has been made in consideration of the above problems, and maintains the valve opening pressure of the fuel injection valve at a high level and the valve opening pressure according to the rotational speed of the diesel engine. By making variable, it is possible to realize good fuel injection performance over the entire rotation range, and particularly to achieve high pressure injection after injection in the low speed rotation range and the medium speed rotation range. At the same time, needle valve overshoot,
An object of the present invention is to provide a fuel injection valve capable of suppressing bouncing.

[Means for Solving the Problems] That is, the present invention is directed to a fuel inlet for introducing high-pressure fuel from a fuel injection pump, and a pressure in the high-pressure fuel chamber of the fuel injection pump, which changes substantially in proportion to the engine speed. A fuel injection pump having a nozzle holder having a pressure introducing port for introducing a pressure, and a valve opening pressure is obtained by causing the pressure in the high pressure fuel chamber to act on the needle valve in the nozzle body together with the spring force of the pusher spring. A pressure receiving piston capable of receiving the pressure in the high pressure fuel chamber and capable of transmitting this pressure to a central plunger, a movable flat valve provided between the pressure receiving piston and the pressure introducing port, and the flat valve. Has a valve seat for seating, and these flat valves and valve seats have By providing the flat damping mechanism having the orifices (first and second orifices), the damper effect when the pressure receiving piston moves up and down is realized, and the pulsation of the pressure in the high pressure fuel chamber of the fuel injection pump is realized. The fuel injection valve is characterized in that the needle valve is smoothed and a needle valve in the middle of lifting is pressed down.

[Operation] In the fuel injection valve according to the present invention, even when the pressure in the high pressure fuel chamber of the fuel injection pump pulsates when the needle valve is in the seated state, it is smoothed by the first orifice of the flat valve, and the needle is also smoothed. When the valve is lifted, the pressure-receiving piston also rises in response to this lift. At this time, the second orifice of the valve seat on which the flat valve is seated causes a damper effect on the pressure-receiving piston and further on the needle valve, and This prevents the rise, realizes high pressure injection after injection, prevents overshoot of the needle valve, and suppresses bouncing during seating. Therefore, even in the low speed rotation range or the like, the pressure for pressing the needle valve, that is, the valve opening pressure can be controlled according to the rotation speed.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 to 8.

FIG. 1 is a vertical sectional view of a fuel injection valve 1 according to the present invention. The fuel injection valve 1 has a nozzle holder head 2 integrated with a nozzle holder body 3 via a cylinder 19 (described later) by a tightening nut 4. The main components are a nozzle holder 5 that is configured by tightening the retaining nut 6, and a nozzle body 7 that is fixed to the lower end of the nozzle holder body 3 by tightening a retaining nut 6.

A fuel inlet 2A and a pressure inlet 2B are formed at the upper end of the nozzle holder body 3. At the fuel inlet 2A, high-pressure fuel distributed under pressure by vertical movement of a plunger (not shown) of a fuel injection pump 8 (for example, a well-known distribution type fuel injection valve) is delivered from a delivery valve holder 9 through an injection pipe 10. It is supposed to be supplied. Further, the pressure introducing port 2B has a hydraulic pressure in the high-pressure fuel chamber communicating with the discharge side of the feed pump (not shown) of the fuel injection pump 8 (pressure Pt that changes substantially in proportion to the rotational speed of the diesel engine).
Are supplied via a conduit 11.

A distance piece 12 is interposed between the nozzle holder body 3 and the nozzle body 7. Further, the needle valve 13 is fitted in the guide hole 7A of the nozzle body 7 so as to be vertically slidable. The pressure pin 14 is brought into contact with the journal portion of the needle valve 13 protruding upward from the center hole of the distance piece 12, and the needle seat surface 13A at the tip of the needle valve 13 is caused to contact the body of the nozzle body 7 by the pressure spring 15. The seat surface 7B is seated and biased toward the nozzle 7C, and the needle valve 13 is moved up and down to open and close the nozzle 7C. Note that reference numeral 16
Indicates a fixed spring seat.

A central plunger 17 slidable in the fitting hole 3A of the nozzle holder body 3 is brought into contact with the top of the pressure pin 14, and a pressure receiving piston 18 is brought into contact with the central plunger 17. The pressure receiving piston 18 is slidable in the fitting hole 19A of the cylinder 19.

The pressure receiving piston 18 is supplied with the above-mentioned oil pressure Pt in the high-pressure fuel chamber through the pressure introducing port 2B, the pressure passage 2C, and a flat damping mechanism 30 (described later), so as to match the spring force of the pressure spring 15 with the central force. The needle seat surface 13A of the needle valve 13 is seated on the body seat surface 7B of the nozzle body 7 with a predetermined pressure via the plunger 17.

Fuel passages 2D, 19B, 3B, 12A and 7D are formed in the nozzle holder head 2, the cylinder 19, the nozzle holder body 3, the distance piece 12 and the nozzle body 7 so as to communicate with the fuel inlet 2A. . Fuel passage
7D communicates with the fuel storage chamber 7E. Therefore, when the pressure stage 13B of the needle valve 13 receives the pressure of the fuel pumped from the fuel injection pump 8, the needle valve 1
When 3 is lifted, the needle seat surface 13A becomes the body seat surface
7B is separated, the injection port 7C is opened, and a predetermined amount of fuel is injected at a predetermined pressure. The maximum lift amount is indicated by L in the figure.

The nozzle holder body 3, the cylinder 19 and the nozzle holder head 2 are respectively provided with leak oil passages 3C,
19C and 2E are respectively formed and communicated with the leak oil outlet 20 of the nozzle holder head 2.

Next, the structure of the flat damping mechanism 30 will be described with reference to FIGS.

FIG. 2 shows the needle valve of the flat damping mechanism 30.
13 is an enlarged cross-sectional view of the seat state of FIG. 13, in which the flat damping mechanism 30 is connected to the pressure passage 2C.
This is installed in the mounting hole 2F.

The flat damping mechanism 30 includes a valve body 31 and
Flat valve 32, valve seat 33, and mounting bolt
34.

The valve body 31 has a through hole 31A communicating with the pressure passage 2C, a through hole 31B having a larger diameter than the through hole 31A, and a flat valve stopper surface 31C.

The flat valve 32 has a first orifice 32A at its center and is loosely fitted in the large-diameter through hole 31B so as to be vertically movable.

The valve seat 33 has a through hole 33A communicating with the first orifice 32A at the center thereof, and the flat valve 32
Is a sheet. However, a second orifice 33B is formed in the through hole 33A on the mounting bolt 34 side.

The mounting bolt 34 is for mounting and fixing the valve body 31, the flat valve 32, and the valve seat 33 into the mounting hole 2F by screwing, and communicates with the through hole 33A and the fitting hole 19A of the cylinder 19. Through holes 34A, 34
B and 34C are formed. The through hole 34C has a hexagonal cross section so that a mounting tool (not shown) used for fixing the mounting bolt 34 to the mounting hole 2F can be fitted therein.

The flat valve 32 is shown in FIG. 3 (III in FIG. 2).
-III cross section) and FIG. 4, the plane shape is formed in a cross shape. And the central plane 32
B indicates that the flat valve 32 is seated on the upper surface of the valve seat 33 as shown in FIG.
Is larger than the through hole 33A so as to close the through hole 33A, and the flat valve 32 has a valve body as shown in FIG.
When the flat valve stopper surface 31C of 31 is abutted, four fuel return passages 35 (FIG. 3) are formed between the through hole 31A of the valve body 31 and the central flat surface portion 32B so as to penetrate therethrough. It should be formed in a size smaller than the hole 31A.

Next, the operation of the fuel injection valve 1 having the above-described configuration will be described below centering on the operation of the flat damping mechanism 30.

When the hydraulic pressure Pt in the high-pressure fuel chamber is introduced into the pressure introducing port 2B, this pressure Pt is applied to the pressure passage 2C and the valve body.
By acting on the upper surface of the flat valve 32 through the through hole 31A of 31, the flat valve 32 seats on the upper surface of the valve seat 33 as shown in FIG. At this time,
The pressure Pt is a flat valve as shown by the arrow in FIG.
32 1st orifice 32A and 2nd valve seat 33
Since it passes only through the orifice 33B of No. 3, even if there is pulsation in the pressure Pt, this pulsation is relaxed and smoothed by the orifices 32A, 33B, and this smoothed pressure Pt is passed through the through holes 34A, 34B of the mounting bolt 34. , 34C and the fitting hole 19A of the cylinder 19 to act on the upper surface of the pressure receiving piston 18.

That is, a pressure without pulsation acts on the upper surface of the pressure receiving piston 18, and this pressure acts on the needle valve 13 via the central plunger 17 and the pressure pin 14, and the resultant force of the pressure and the spring force of the pressure spring 15. The needle valve 13 is pressed by the valve closing position (see FIG. 1). Therefore, the valve opening pressure of the needle valve 13 is prevented from fluctuating due to the pulsation of the pressure Pt.

Next, when the needle valve 13 is lifted from the valve opening position and fuel is injected, the pressure receiving piston 18 is pushed up by the central plunger 17 and rises while the needle valve 13 is fully lifted to the valve opening position. A shock wave propagates from the upper surface of the pressure receiving piston 18 to the lower surface of the flat valve 32 due to the rise, and the shock wave displaces the flat valve 32 to the position shown in FIG. 5, and the upper end surface of the flat valve 32 is the flat valve of the valve body 31. Contact the stopper surface 31C. In this state, the through hole of the valve body 31
A fuel return passage 35 (FIG. 3) is formed between 31A and the central flat portion 32B of the flat valve 32.

Therefore, as shown by the arrow in FIG. 5, the shock wave is throttled by the second orifice 33B of the valve seat 33, that is, the dead volume corresponding to the rise of the pressure receiving piston 18 is directly returned to the conduit 11. Without the fuel return passage 35 and the first orifice 32A.
Through the through hole 31A, the pressure passage 2C, and the pressure introducing port 2B, and is released to the outside of the fuel injection valve 1.

Thus, when the pressure due to the shock wave escapes to the outside of the fuel injection valve 1 and the pressure Pt again acts on the upper surface of the flat valve 32, the flat valve 32 is displaced again from the position shown in FIG. 5 to the position shown in FIG. As described above, the pulsation of the pressure Pt is relaxed and smoothed by the first orifice 32A, and the smoothed pressure Pt and the spring force of the pressure spring 15 push down the needle valve 13 to the closed position, and the injection is completed. .

As shown in FIG. 6, the pressure Pt in the high-pressure fuel chamber of the fuel injection pump 8 rises substantially in proportion to the pump rotation speed in a rotation speed range above a certain low speed rotation speed. In addition, as shown in FIG. 7, the force pressing the needle valve 13 is the resultant force of the spring force and the pressure Pt by the pressure spring 15, and as in the case shown in FIG. In, the value increases in proportion to the pump rotation speed. In FIG. 7, the constant spring force of the pressure spring 15 is shown by the dotted line.

Then, by pressing the needle valve 13 in the middle of the lift by the damper effect by the second orifice 33B of the valve seat 33, as shown in FIG. Along with the lift of 13, the force pressing the needle valve 13 is increased more greatly (solid line in the figure) compared to the case where only the pressure spring 15 is used (dotted line in the figure).

Therefore, the following effects occur in each rotation region.

That is, first, at the time of idling, as a result of suppressing the overshoot of the needle valve 13 and extending the injection period, the injection rate (injection amount per unit time or pump shaft unit angle) decreases, and This is a so-called trailing injection in which the rise time of the curve is delayed. Moreover, the injection is performed at a higher pressure than in the case without the damper effect.

Further, the above tendency is maintained in the low speed range to the medium speed range, and the high pressure injection, the injection period extension and the post injection are performed.

Further, in the high speed rotation range, as shown in FIG. 7, the resultant force for pressing the needle valve 13 increases, so the nozzle opening pressure rises and the second orifice 33B as described above is used. Although the injection pressure increases due to the damper effect, the injection period is the same as that of the conventional fuel injection valve. In addition, the so-called pre-injection is performed in which the rising timing of the injection rate curve after the start of injection is advanced.

Thus, it is possible to expect suppression of the initial injection rate due to the damper effect mainly in the low speed rotation range and the medium speed rotation range, and in the high speed rotation range, the atomization of fuel is promoted by the high pressure injection by improving the valve opening pressure. Can be realized.

In the above-mentioned embodiment, the fuel injection valve of the hall type nozzle has been described as an example, but it can be applied to a fuel injection valve having a pin type nozzle such as a piston nozzle or a throttle nozzle.

[Effects of the Invention] As described above, according to the present invention, since the flat damping mechanism having the first and second orifices having the throttling effect in the seated state and the lifted state of the needle valve is provided, the hydraulic pressure is positively applied. By using the damper, it is possible to reduce the influence of pressure pulsation in the high-pressure fuel chamber, hold down the needle valve in the middle of the lift, and increase the throttling effect, especially in the low speed range, to suppress combustion noise and reduce fuel injection. After that, high-pressure injection can be realized.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a fuel injection valve 1 according to an embodiment of the present invention, FIG. 2 is an enlarged sectional view of an essential part of a flat damping mechanism 30, and FIG. 3 is a III-III line in FIG. Sectional view, 4th
FIG. 7 is a perspective view of the flat valve 32, FIG. 5 is an enlarged cross-sectional view of an essential part of the flat damping mechanism 30 in an operating state, FIG. 6 is a graph showing the relationship between the rotational speed of the pump and the pressure Pt in the high pressure fuel chamber, and FIG. Similarly, FIG. 8 is a graph showing the relationship between the pump rotation speed and the resultant force pressing the needle valve 13, and FIG. 8 is a graph showing the relationship between the lift amount of the needle valve 13 and the force pressing the needle valve 13. 1 ... Fuel injection valve 2 ... Nozzle holder head 2A ... Fuel inlet 2B ... Pressure inlet 2C ... Pressure passage 2D ... Fuel passage 2E ... Leak oil passage 2F ... Mounting hole for flat damping mechanism 30 3 Nozzle holder body 3A Fitting hole 3B Fuel passage 3C Leak oil passage 4 Tightening nut 5 Nozzle holder 6 Retaining nut 7 Nozzle body 7A Guide hole 7B …… Body seat surface 7C …… Injection port 7D …… Fuel passage 7E …… Fuel reservoir 8 …… Fuel injection pump 9 …… Delivery valve holder 10 …… Injection pipe 11 …… Conduit 12 …… Distance piece 12A …… Fuel Passage 13 …… Needle valve 13A …… Needle seat surface 13B …… Pressure stage 14 …… Pressure pin 15 …… Pressure spring 16 …… Fixed spring seat 17 …… Central plunger 18 …… Receiver Pressure piston 19 …… Cylinder 19A …… Fit hole 19B …… Fuel passage 19C …… Leak oil passage 20 …… Leak oil outlet 30 …… Flat damping mechanism 31 …… Valve body 31A …… Through hole 31B …… Large diameter Through hole 31C …… Flat valve stopper surface 32 …… Flat valve 32A …… First orifice 32B …… Central plane part 33 …… Valve seat 33A …… Through hole 33B …… Second orifice 34 …… Mounting bolt 34A, 34B, 34C …… Through hole 35 …… Fuel return passage Pt …… Hydraulic pressure in the high pressure fuel chamber L …… Maximum lift amount

Claims (1)

(57) [Scope of utility model registration request] 1. A nozzle holder having a fuel inlet for introducing high-pressure fuel from a fuel injection pump, and a pressure inlet for introducing a pressure in a high-pressure fuel chamber of the fuel injection pump which changes substantially in proportion to the number of revolutions of an engine. A nozzle body supported by the nozzle holder and having a fuel injection port communicating with the fuel inlet; and a needle valve slidably accommodated in the nozzle body and biased by a pressure spring in a direction to close the injection port. A fuel injection valve having a central plunger slidable integrally with the needle valve, the pressure receiving piston capable of receiving the pressure in the high-pressure fuel chamber and transmitting the pressure to the central plunger, The pressure in the high-pressure fuel chamber is movable while being movable between the pressure receiving piston and the pressure introducing port. A flat valve having a smoothed first orifice, and a valve seat having the flat valve seating on the downstream side of the pressure in the high-pressure fuel chamber and having a second orifice further downstream of the seat portion. And a fuel return passage communicating from the valve seat to the high pressure fuel chamber through the flat valve when the flat valve moves upstream of the pressure in the high pressure fuel chamber. A fuel injection valve comprising a flat damping mechanism that can be formed upstream of a second orifice.