JP2001227434A - Fuel injection nozzle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accelerate atomization of spray by introducing air within a cylinder into a suck chamber 22 at the low lift and enable fuel injection of a large flow rate at the high lift. SOLUTION: A first nozzle 19 and a second nozzle 20 are provided so as to pass through a circular top wall part 3a of a body lower end part forming a suck chamber 22. In the first nozzle 19, an opening part (entrance 19a) on the side of the suck chamber 22 is opened on an inner wall surface of the suck chamber 22 close to a sheet surface 21. In the second nozzle 20, an opening part on the side of the suck chamber 22 is opened in the downstream of the opening part of the first nozzle 19. A needle lift amount is set into two stages. The low lift amount is set in an area where suck inlet flow passage area becomes smaller than sheet part flow passage area and smaller than opening area of the second nozzle 20. The high lift amount is set in an area where suck inlet flow passage area becomes larger than opening area that the first nozzle 19 and the second nozzle 20 are summed up.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel injection nozzle having a suck chamber at a downstream end of a fuel passage.

[0002]

2. Description of the Related Art Conventionally, in a diesel engine, the particle size of a fuel spray injected from a fuel injection nozzle has a great influence on discharged graphite. That is, if the atomization of the injected fuel is promoted, the ignitability of the fuel is improved and good combustion is ensured, so that harmful components in the exhaust gas can be reduced and the fuel efficiency is also improved. As a conventional technique for atomizing the injected fuel, for example, there is a fuel injection valve disclosed in Japanese Patent Application Laid-Open No. 7-145767. This fuel injection valve has a suck chamber at the tip of a nozzle body, and is provided with an air intake passage communicating the suck chamber with an external space. The air suction passage is open to a low-pressure portion generated in the suck chamber when the needle lifts and fuel flows into the suck chamber. As a result, air is introduced into the sack chamber from the external space through the air suction passage, and the air is mixed with the fuel in the sack chamber and injected from the injection holes. As a result, the fuel spray is atomized, the ignitability of the fuel is improved, and good combustion becomes possible.

[0003]

However, in the structure of the fuel injection valve disclosed in the above prior art, the injection rate cannot be changed stepwise, so that it is possible to obtain the optimum injection rate for the engine. Have difficulty. That is, in the above fuel injection valve, the air suction passage cannot be used as an injection hole. Therefore, even if the needle lift amount is controlled in a stepwise manner, the injection hole area is constant, and the injection rate cannot be changed. Can not. The present invention has been made based on the above circumstances, and its object is to control the amount of needle lift stepwise to introduce air in a cylinder into a suck chamber at a low lift to promote atomization of spray. It is another object of the present invention to provide a fuel injection nozzle capable of injecting a large amount of fuel during a high lift.

[0004]

Means for Solving the Problems The flow area of the inner periphery of the inlet of the sac chamber is called the sac inlet flow area, and the flow area of the outer periphery of the seat is called the seat flow area. In some cases, the lift amount at the time of low lift is set in a region where the sac inlet passage area is smaller than the seat part passage area and smaller than the opening area of the second injection hole, and the sac inlet passage area is set to the first area. The lift amount at the time of high lift is set in a region larger than the sum of the opening area of the injection hole and the opening area of the second injection hole.

According to this configuration, when the needle is at a low lift, the sack inlet passage area is smaller than the seat passage area and smaller than the opening area of the second injection hole. The flow rate of the incoming fuel increases. In this case, a vortex is generated near the inner wall surface of the sack chamber close to the seat surface, and the opening of the first injection hole has a low pressure (lower than the inside of the engine cylinder) due to the influence of the vortex. As a result, air is introduced into the sack chamber from the outer space (inside the engine cylinder) of the nozzle body through the first injection hole, and the air is mixed with fuel in the sack chamber and injected from the second injection hole. Further, at the time of high lift of the needle, the sack inlet flow path area becomes larger than the sum of the opening area of the first injection hole and the opening area of the second injection hole, so that the flow velocity of the fuel flowing into the sac chamber is reduced. Slower than at low lift. in this case,
Since the fuel pressure is also applied to the inner wall surface of the sack chamber near the seat surface, the opening of the first injection hole becomes high pressure (higher than the inside of the engine cylinder), and the first injection hole and the second injection hole both receive the fuel pressure. Fuel is injected.

(Section 2) The sack chamber side opening of the first injection hole is called a first opening, and the sack chamber side opening is called a second opening. When the pressure inside the chamber is called the internal pressure, and the external pressure applied to the second opening is called the external pressure, when the needle lifts low,
When the internal pressure applied to the first opening becomes lower than the external pressure applied to the opening, and the needle lifts high,
The lift amount at the time of the low lift and the lift amount at the time of the high lift are set so that the internal pressure applied to the first opening is higher than the external pressure applied to the opening.

With this configuration, when the needle is at a low lift, the internal pressure applied to the first opening is lower than the external pressure (pressure in the engine cylinder) applied to the second opening of the first injection hole. Therefore, air is introduced into the sack chamber from the external space (in the engine cylinder) of the nozzle body through the first injection hole, and the air is mixed with fuel in the sack chamber and injected from the second injection hole. When the needle is at a high lift, the first pressure is applied to the first injection hole from the external pressure applied to the second opening of the first injection hole.
Since the internal pressure applied to the opening is higher, fuel is injected from both the first injection hole and the second injection hole.

[0008]

Next, a fuel injection nozzle according to the present invention will be described with reference to the drawings. (First Embodiment) FIG. 1 is a sectional view of the tip of a fuel injection nozzle. The fuel injection nozzle 1 of this embodiment (hereinafter referred to as nozzle 1
3), as shown in FIG. 3, is for injecting fuel into the cylinder 2 of the diesel engine, and is composed of a nozzle body 3 and a needle 4 which will be described later.
To the nozzle holder 6.

In the nozzle holder 6, a fuel passage 8 for guiding the fuel supplied from the fuel pump 7 to the nozzle 1 is formed, and two springs (a first spring 9 and a first spring 9) for setting the valve opening pressure of the nozzle 1 are provided. A second spring 10) is incorporated. The upper end of the first spring 9 is the adjusting screw 1.
1, the lower end abuts on the head 12 a of the rod 12, the set load is adjusted by the adjusting screw 11, and the set load is applied to the needle 4 via the rod 12. The second spring 10 has an upper end supported by the shim 13 and a lower end supported by the spacer 14, and the set load is adjusted by changing the thickness of the shim 13.

[0010] As shown in FIG.
A large-diameter portion 14a for receiving the lower end of the spring 10, and a small-diameter portion 14b provided below the large-diameter portion 14a;
A through-hole 14c is formed through the center of the large diameter portion 14a and the small diameter portion 14b in the vertical direction. The large diameter portion 14a
It is supported by a tip packing 15 sandwiched between the lower end surface of the nozzle holder 6 and the upper end surface of the nozzle body 3.
The small-diameter portion 14b is slidably inserted into a round hole 15a formed at the center of the chip packing 15, and the lower end surface protrudes downward from the lower end surface of the chip packing 15.

Next, the configuration of the nozzle 1 according to the present invention will be described. As shown in FIG. 2, the nozzle body 3 has a guide hole 16 into which the needle 4 is slidably inserted, a fuel passage 17 extending below the guide hole 16, and a fuel conduit for guiding fuel to the fuel passage 17. 18 and injection holes 19 and 20 for injecting fuel. A conical seat surface 21 is formed at the lower end of the fuel passage 17, and a suck chamber 22 is provided continuously to the lower end of the seat surface 21. An annular fuel reservoir 23 is formed at the upper end of the fuel passage 17, and the fuel conduit 18 communicates with the fuel reservoir 23.

As shown in FIG. 1, the injection holes 19 and 20 are located at different positions in the axial direction (vertical direction in FIG. 1).
And a second injection hole 20, which is provided through the circular top wall 3 a at the lower end of the body forming the sack chamber 22. However, the opening of the first injection hole 19 on the side of the suck chamber 22 is opened on the inner wall surface of the suck chamber 22 close to the seat surface 21. In the second injection hole 20, the opening on the side of the sac chamber 22 is opened downstream from the opening of the first injection hole 19. Hereinafter, the opening of the first injection hole 19 on the suck chamber 22 side is referred to as an inlet 19a, and the opening on the cylinder side is referred to as an outlet 19b. A plurality of the first injection holes 19 and the second injection holes 20 are respectively provided in the circumferential direction. However, the positions of the first injection holes 19 and the second injection holes 20 in the circumferential direction are different. Is also good.

As shown in FIG. 2, the needle 4 has a sliding portion 24 inserted into the guide hole 16 with a clearance of several μm.
A projection 25 projecting upward from the upper end surface of the sliding portion 24; a pressure receiving surface 26 formed below the sliding portion 24 to receive the fuel pressure in the fuel storage chamber 23; And a shaft portion 27 extending downward. Shaft 2
As shown in FIG. 1, the lower end portion 7 is constituted by two conical surfaces 28 and 29 having different conical angles, the upper conical surface 28 having a small conical angle and the lower conical surface 2 having a large conical angle.
The boundary line (ridge line) with the nozzle surface 9 is the seat surface 21 of the nozzle body 3.
Is provided as a sheet portion 30 facing the front side.

As shown in FIG. 4, the needle 25 has a projection 25 inserted into the through hole 14c of the spacer 14 to face the rod 12, and receives the urging force of the first spring 9 via the rod 12. ing. In the state where the seat portion 30 is seated (contacted) on the seat surface 21, the sliding portion 24
Is set as the low lift amount HD1 of the needle 4, and the distance between the upper end surface 24a of the sliding portion 24 and the lower end surface of the tip packing 15 is set as the distance between the needle 4 and the lower end of the small diameter portion 14b of the spacer 14. Is set as the high lift amount HD2. However, low lift HD1 and high lift HD
2 are set as follows based on the relationship with the flow path area of each part shown in FIG. Graph a in the figure is the sack inlet flow path area, graph b is the sheet part flow area, graph c is the opening area of the second injection hole 20, and graph d is the opening area of the first injection hole 19 and the second. The opening area is the sum of the opening area of the injection hole 20 and the opening area.

The sack inlet flow path area is defined as the inner circumference of the inlet of the sack chamber 22 (the boundary line between the seat surface 21 and the sack chamber 22) and the outer peripheral surface of the needle 4 (lower conical surface 2).
9), and the area of the sheet passage is the area of the annular space formed between the outer periphery of the seat portion 30 and the seat surface 21. Low lift HD
1 is set to a region (between a and b in FIG. 5) in which the sack inlet flow path area is smaller than the sheet part flow path area and smaller than the opening area of the second injection hole 20. The high lift HD2 is
The sack inlet flow passage area is different between the first injection hole 19 and the second injection hole 2.
0 (c of FIG. 5)
After).

Next, the operation of this embodiment will be described. Fuel pumped from the fuel pump 7 is stored in the fuel storage chamber 23,
When the fuel pressure in the fuel storage chamber 23 (the pressure applied to the pressure receiving surface 26) becomes larger than the first valve opening pressure set by the first spring 9, the needle 4 is pushed up, and the low lift amount is increased.
Lift only HD1. At the time of this low lift, the sack inlet flow path area is smaller than the seat part flow path area and smaller than the opening area of the second injection hole 20, so that the flow velocity of the fuel flowing into the sack chamber 22 along the seat surface 21 is high. Become. In this case, a vortex is generated near the inner wall surface of the sack chamber 22 near the seat surface 21, and the first injection hole 1 is formed by the influence of the vortex.
9 has a low pressure (lower than the pressure in the engine cylinder 2) at the inlet 19a. As a result, air is introduced into the suck chamber 22 from the outer space (inside the engine cylinder 2) of the nozzle body 3 through the first injection holes 19, and the air is mixed with fuel in the suck chamber 22 to form the second injection holes. Injected into cylinder 2 from 20.

When the fuel pressure in the fuel storage chamber 23 further increases and the fuel pressure becomes higher than a second valve opening pressure set by the resultant force of the first spring 9 and the second spring 10, the needle 4 is further pushed up. High lift HD2
Lift up to. At this time, the sack inlet flow passage area is larger than the sum of the opening area of the first injection hole 19 and the opening area of the second injection hole 20, so that the flow velocity of the fuel flowing into the sac chamber 22 is low. Slower than time. In this case, since the fuel pressure is also applied to the inner wall surface of the sack chamber 22 near the seat surface 21, the inlet 19a of the first injection hole 19 has a high pressure (higher than the inside of the engine cylinder 2). Second
The fuel is injected into the cylinder 2 from both of the injection holes 20.

Here, the reason why the inlet pressure of the first injection hole 19 changes between when the needle 4 is at a low lift and when the needle 4 is at a high lift will be described with reference to FIGS. 6 and 7. FIG. FIG. 6B shows FIG.
It shows the flow area of each part (the seat part 30, the entrance of the sack chamber 22, the injection hole entrance) shown in FIG. This is represented by a broken line graph. FIG. 7B shows the result of actually measuring the pressure of each part (1 to 10) shown in FIG. 7A using an enlarged model of the nozzle 1, and the pressure value at the time of low lift is shown by a solid line graph. The pressure value at the time of high lift is represented by a broken line graph.

At the time of low lift, as shown in FIG. 6B, the flow path area at the inlet of the suck chamber 22 is minimized, and the flow path is narrowed here. , The flow path area is rapidly increased. For this reason, the fuel flowing into the suck chamber 22 has the highest flow velocity in the inlet flow path of the suck chamber 22, and flows into the suck chamber 22 along the seat surface 21 vigorously. At this time, the sheet surface 21
There is an angle difference between the inner surface of the suck room 22 and the inner wall surface of the suck room 22 close to the seat surface 21 because there is an angle difference between the inner surface of the suck room 22 and the inlet side inner wall surface. As a result of the actual measurement, as shown in FIG.
It can be confirmed that the pressure shows a negative value at the measurement points (6 and 7) on the inner wall surface of the sack chamber 22 near the seat surface 21.

At the time of high lift, as shown in FIG. 6B, the flow path area (opening area) at the injection hole inlet is minimized, and the flow path is narrowed here.
The fuel flow rate at the inlet decreases. In this case, even if there is an angle difference between the seat surface 21 and the inner wall surface on the entrance side of the suck room 22, substantially the entire area in the suck room 22 is maintained at a high pressure. As a result of the actual measurement, as shown in FIG. 7B, it can be confirmed that the high pressure is maintained at all the measurement points.

(Effects of the present embodiment) As is clear from the results shown in FIGS. 6 and 7, by opening the inlet 19a of the first injection hole 19 on the inner wall surface of the sack chamber 22 close to the seat surface 21. When the lift is low, the inlet 19 of the first injection hole 19
Since a becomes a negative pressure and becomes lower than the outlet 19 b to which the pressure in the cylinder 2 is applied, the air in the cylinder 2 is automatically sucked into the suck chamber 22 from the first injection hole 19. In addition, at the time of high lift, the inlet 19a of the first injection hole 19 has a positive pressure,
Further, since the pressure becomes higher than the outlet 19 b to which the pressure in the cylinder 2 is applied, the fuel flowing into the suck chamber 22 is also injected from the first injection holes 19. Thereby, the injection amount can be controlled in two stages according to the lift amount of the needle 4, and at the time of a low lift, the air in the cylinder 2 is sucked from the first injection hole 19 into the suck chamber 22.
Therefore, atomized fuel can be injected into the cylinder 2 at an appropriate injection rate.

(Second Embodiment) FIG. 8 is a sectional view of the tip of the nozzle 1. As shown in FIG. As shown in FIG. 8, the nozzle 1 of this embodiment is an example in which the inclination angle α of the sheet surface 21 with respect to the axis is large (for example, 80 degrees or more). In this case, when the inclination angle of the seat surface 21 is small (for example, 60
(Before and after), the angle between the flow direction of the fuel flowing into the sack chamber 22 at the time of low lift and the inner wall surface on the inlet side of the sack chamber 22 becomes larger, so that the first injection hole 19 can more effectively serve. The air in the cylinder 2 can be introduced into the suck chamber 22.

(Third Embodiment) FIG. 9 is a sectional view of the tip of the nozzle 1. As shown in FIG. 9, the nozzle 1 of this embodiment is provided with an inclined surface 31 that is inclined in a direction opposite to the seat surface 21 at the entrance of the suck chamber 22, and the entrance of the first injection hole 19 is formed on the inclined surface 31. This is an example when 19a is provided. In this case, the flow direction of the fuel flowing into the sack chamber 22 at the time of low lift and the inclined surface 31 on which the inlet 19a of the first injection hole 19 is opened.
Therefore, the air in the cylinder 2 can be more effectively introduced into the suck chamber 22 through the first injection hole 19.

The fuel injection nozzle 1 of the present invention relates to the nozzle body 3 and the needle 4 and includes a nozzle holder 6.
Is not limited to the configuration described in the above embodiment. For example, the present invention can be applied to an injector capable of arbitrarily varying a needle lift amount by driving a piezo element, or an injector capable of gradually varying a needle lift amount by driving an electromagnetic valve.

[Brief description of the drawings]

FIG. 1 is a sectional view of a tip portion of a fuel injection nozzle (first example).
Example).

FIG. 2 is a sectional view of a nozzle.

FIG. 3 is an overall view of a fuel injection system.

FIG. 4 is an enlarged cross-sectional view of a portion defining a needle lift amount.

FIG. 5 is a correlation diagram between a needle lift amount and a flow path area.

6A is a cross-sectional view of a nozzle tip portion, and FIG. 6B is a characteristic diagram showing a flow path area.

FIGS. 7A and 7B are a cross-sectional view of a nozzle tip portion showing a pressure measurement site and a diagram showing a pressure measurement result at each measurement site; FIGS.

FIG. 8 is a sectional view of a tip portion of a fuel injection nozzle (second example).
Example).

FIG. 9 is a sectional view of a tip portion of a fuel injection nozzle (third section).
Example).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuel injection nozzle 3 Nozzle body 4 Needle 17 Fuel passage 19 First injection hole 19a Inlet (first opening) 19b Exit (second opening) 20 Second injection hole 21 Seat surface 22 Suck chamber 30 Seat portion

Claims (2)

[Claims] 1. A first seat having a conical seat surface downstream of a fuel passage, a sack chamber continuous downstream of the seat surface, and opening to an inner wall surface of the sack chamber near the seat surface.
A nozzle body having a second injection hole opening downstream of the first injection hole and a second injection hole. The nozzle body is slidably fitted into the nozzle body and faces the seat surface at its lower end. A needle provided with a seat portion, wherein when the needle is lifted, a low lift having a small lift amount and a high lift having a large lift amount are set. When the peripheral flow path area is referred to as a sac inlet flow path area, and the flow path area of the outer periphery of the seat portion is referred to as a seat flow path area, the sac inlet flow path area is smaller than the seat flow path area and The lift amount at the time of the low lift is set in a region smaller than the opening area of the second injection hole, and the sack inlet passage area is determined by the opening area of the first injection hole and the opening area of the second injection hole. Greater than the sum of A fuel injection nozzle, characterized in that the Kunar region lift amount during the high lift is set. 2. A first seat having a conical seat surface downstream of a fuel passage, a sack chamber continuous downstream of the seat surface, and opening to an inner wall surface of the sack chamber close to the seat surface.
A nozzle body having a second injection hole opening downstream of the first injection hole and a second injection hole. The nozzle body is slidably fitted into the nozzle body and faces the seat surface at its lower end. A fuel injection nozzle comprising a needle provided with a seat portion, wherein when the needle lifts, a low lift having a small lift amount and a high lift having a large lift amount are set; The sack chamber side opening is referred to as a first opening, the anti-sack chamber side opening is referred to as a second opening, the pressure in the sac chamber applied to the first opening is referred to as an internal pressure, and the second When the external pressure applied to the opening is referred to as an external pressure, when the needle has a low lift, the internal pressure applied to the first opening is lower than the external pressure applied to the second opening, and the needle When he lifts high, The lift amount at the time of the low lift and the lift amount at the time of the high lift are set such that the internal pressure applied to the first opening is higher than the external pressure applied to the second opening. Fuel injection nozzle.