JP6293586B2 - Fuel injection valve and fuel injection device - Google Patents

Description

  The present invention relates to a fuel injection valve and a fuel injection device applied to an internal combustion engine.

  The fuel injection device is applied to an internal combustion engine such as a diesel engine, pressurizes the fuel, and injects the fuel into the cylinder. The fuel injection device includes a fuel injection valve provided in a cylinder head and a fuel injection pump that pumps fuel to the fuel injection valve via a fuel injection pipe. The fuel is supplied from the fuel tank and the fuel supply pump to the fuel injection pump through the fuel supply pipe, and a predetermined amount of fuel accumulated in the plunger barrel of the fuel injection pump is pressurized by the plunger of the fuel injection pump, Pumped to the injection valve.

  Patent Document 1 is an invention of a fuel injection control device for a marine engine. In order to improve the accuracy of fuel injection, a servo valve for fuel injection and a valve control unit are integrally formed, and the valve control unit is another device. There is disclosed a technique for forming a desired injection pattern without being affected by the above and without causing a deviation in injection timing.

JP 2012-52428 A JP 2002-61550 A

  As shown in FIG. 4, in general, the higher the fuel injection rate, which is the amount of fuel injected per unit time, the lower the fuel consumption rate (fuel consumption), but the higher the NOx emission concentration. On the other hand, the lower the fuel injection rate, the lower the NOx emission concentration, but the higher the fuel consumption rate. Therefore, as shown by the solid line in the upper graph of FIG. 5, the two-stage injection control in which the fuel injection pressure at the initial stage of fuel injection is lowered (first stage) and then the fuel injection pressure is raised (second stage). May be implemented. As a result, as indicated by the broken line or the alternate long and short dash line in FIG. 4, the NOx emission concentration can be lowered while reducing the fuel consumption rate at the initial stage of fuel injection as compared with the conventional injection control indicated by the solid line.

  However, the amount of fuel supplied from the fuel injection pump to the fuel injection valve is small, such as in the initial stage of two-stage injection, and the fuel supply pressure is not sufficiently high compared to the valve opening pressure of the needle valve in the fuel injection valve. As shown by the broken line in the lower graph of FIG. 5, the behavior of the needle valve becomes unstable. As a result, there is a problem that the robustness of the fuel injection control cannot be ensured.

  FIG. 6 is a longitudinal sectional view showing a fuel injection valve 32 of a conventional fuel injection device. In addition, the component which a structure and an action overlap with the fuel injection valve 2 which concerns on one Embodiment of this invention mentioned later is shown with the same code | symbol. In the fuel injection valve 32, a spring accommodating portion 34 is formed above the needle valve 11 in the housing 6. The spring accommodating portion 34 accommodates a coil spring 35 and a support portion 37. The spring accommodating portion 34 has, for example, a cylindrical inner surface. The coil spring 35 has a lower end in contact with the upper surface of the needle valve 11 and an upper end in contact with the upper surface of the spring accommodating portion 34. Thereby, the coil spring 35 urges the needle valve 11 against the upper surface of the spring accommodating portion 34.

  The needle valve 11 is pushed downward by the coil spring 35, and the needle valve 11 closes the fuel injection hole 8. When the needle valve 11 is pushed down completely, a gap L3 corresponding to the full lift amount exists between the upper surface of the needle valve 11 and the lower surface of the support portion 37. The distance that the needle valve 11 can move upward is the full lift amount and is the gap L3. In such a conventional fuel injection valve 32, when the two-stage injection control is performed, the amount of fuel supplied from the fuel injection pump to the fuel injection valve is small, such as in the initial stage of the two-stage injection, and the fuel supply pressure is If the valve opening pressure of the needle valve 11 in the injection valve is not sufficiently high, the needle valve 11 remains seated, etc. As shown by the broken line in the lower graph of FIG. It becomes unstable.

  The present invention has been made in view of such circumstances, and is a fuel injection valve capable of stabilizing the behavior of a needle valve in a fuel injection valve in a state where the fuel injection pressure at the initial stage of fuel injection is low. And it aims at providing a fuel-injection apparatus.

In order to solve the above problems, the fuel injection valve and the fuel injection device of the present invention employ the following means.
That is, the fuel injection valve according to the present invention includes a housing in which a fuel flow path is formed and a fuel injection hole is formed in a tip portion, and the fuel injection valve is disposed in the housing, and the fuel flow according to the fuel supply pressure. A needle valve that opens and closes the path; a rod-shaped portion; and a protrusion formed on an outer peripheral surface of the rod-shaped portion, and a lower end of the rod-shaped portion is disposed so as to be in contact with the upper surface of the needle valve. A first support portion that defines a first lift amount of the needle valve ; a lower end is in contact with an upper surface of the needle valve; an upper end is in contact with a lower surface of the projecting portion of the first support portion; A first elastic part that urges the needle valve against the first support part, and a rod-like member that extends downward from the upper surface of the housing part formed above the needle valve inside the housing, lower end disposed top and can contact opposite of the bar-shaped portion of the first supporting portion, the needle A second support portion defining a second lift amount of the lower end contacts the upper surface of the projecting portion of the first supporting portion and contacts the upper surface of the receiving portion upper end, relative to said housing A second elastic portion that biases the needle valve and the first support portion.

According to this configuration, when the fuel supply pressure is low, only the first elastic portion urges the needle valve, and when the needle valve increases by the first lift amount as the fuel supply pressure increases, The needle valve hits the first support part. When the fuel supply pressure further increases, the second elastic portion receives the needle valve and the first support portion, and the needle valve and the first support portion increase by the second lift amount. When the first support portion hits the second support portion, the needle valve finishes raising the first lift amount and the second lift amount.
Therefore, even if the fuel supply pressure is low, if the valve opening pressure determined by the spring force of the first elastic portion is exceeded, the needle valve lifts by the first lift amount, so that the behavior of the needle valve is stabilized. Can do.

A fuel injection device according to the present invention includes the fuel injection valve and a fuel injection pump that supplies fuel to the fuel injection valve while adjusting the fuel supply pressure.
According to this configuration, the fuel supply pressure of the fuel supplied to the fuel injection valve is adjusted by the fuel injection pump.

In the above invention, the fuel supply pressure includes a first stage in which the fuel supply pressure is set low, and a second stage in which the fuel supply pressure is set high after the first stage.
According to this configuration, even when the fuel supply pressure is low, the needle valve lifts by the first lift amount if the valve opening pressure determined by the spring force of the first elastic portion is exceeded. Can be stabilized.

  According to the present invention, in a state where the fuel injection pressure at the initial stage of fuel injection is low, the behavior of the needle valve in the fuel injection valve can be stabilized, and the robustness of the fuel injection control can be ensured. Further, since the fuel injection pressure at the initial stage of fuel injection can be reliably lowered, the NOx emission concentration can be lowered while reducing the fuel consumption rate.

1 is a schematic configuration diagram illustrating an internal combustion engine and a fuel injection device according to an embodiment of the present invention. It is a longitudinal section showing a fuel injection valve of a fuel injection device concerning one embodiment of the present invention. It is a block diagram which shows the fuel-injection pump of the fuel-injection apparatus which concerns on one Embodiment of this invention. It is a graph which shows the relationship between NOx discharge density | concentration and a fuel consumption rate. 4 is a graph (upper stage) showing the relationship between the fuel injection pressure and the crank angle, and a graph (lower stage) showing the relationship between the needle valve lift amount and the crank angle. It is a longitudinal cross-sectional view which shows the fuel injection valve of the conventional fuel injection apparatus.

Embodiments according to the present invention will be described below with reference to the drawings.
A fuel injection device 1 according to an embodiment of the present invention will be described. As shown in FIG. 1, the fuel injection device 1 is applied to an internal combustion engine 10 such as a two-cycle marine diesel engine.
As shown in FIG. 1, the fuel injection device 1 includes a fuel injection valve 2, a fuel injection pump 3, and a fuel injection pipe 4. In the fuel injection valve 2, a cylindrical housing 6 is installed in a cylinder head of the internal combustion engine 10.

  A fuel supply pump (not shown) is connected to a plunger barrel (not shown) of the fuel injection pump 3 via a fuel supply pipe 5. The plunger barrel is connected to one end of the fuel injection pipe 4, and the other end of the fuel injection pipe 4 is connected to a fuel flow path 7 (see FIG. 2) formed in the housing 6 of the fuel injection valve 2. A plunger (not shown) that reciprocates by hydraulic control of the hydraulic oil is provided inside the plunger barrel. Fuel is supplied from the fuel supply pump to the plunger barrel, and the fuel in the plunger barrel is supplied to the fuel flow path 7 as the plunger moves up.

  The housing 6 is provided with a plurality of fuel injection holes 8 at the distal end portion 6a. In the internal combustion engine 10, the tip portion 6a protrudes from the lower surface of the cylinder head into the combustion chamber. In the housing 6, a cylindrical center hole 9 is formed inside along the axis, and a needle valve 11 is accommodated in the center hole 9. As an example, the center hole 9 inside the housing 6 is cylindrical, but is not limited thereto, and may be, for example, a rectangular tube.

  A fuel flow path 7 is formed from the upper part to the lower part of the housing 6, and the fuel flow path 7 communicates with the chamber 12. In addition, a leak oil passage 13 is formed in the housing 6, and the leak oil passage 13 is connected to a spring accommodating portion 14 and an external leak oil recovery pipe (not shown).

  In the housing 6, a spring accommodating portion 14 is formed above the needle valve 11. The spring accommodating portion 14 accommodates the first coil spring 15, the second coil spring 16, the first support portion 17, and the second support portion 18. The spring accommodating portion 14 has, for example, a cylindrical inner surface.

  The first coil spring 15 is an example of a first elastic portion, the lower end is in contact with the upper surface of the needle valve 11, and the upper end is in contact with the lower surface of the protruding portion 17 a of the first support portion 17.

  The second coil spring 16 is an example of a second elastic portion, the lower end is in contact with the upper surface of the protruding portion 17 a of the first support portion 17, and the upper end is in contact with the upper surface of the spring accommodating portion 14. Accordingly, the second coil spring 16 biases the needle valve 11 and the first support portion 17 against the upper surface of the spring accommodating portion 14.

  The 1st support part 17 has the protrusion part 17a and the rod-shaped part 17b, and the protrusion part 17a is formed in disk shape on the outer peripheral surface of the rod-shaped part 17b. The lower end of the rod-shaped portion 17 b faces the upper surface of the needle valve 11, and the upper end of the rod-shaped portion 17 b faces the lower end of the second support portion 18. The first coil spring 15 is inserted into the rod-shaped portion 17b below the protruding portion 17a of the first support portion 17, and the first portion around the rod-shaped portion 17b below the protruding portion 17a of the first support portion 17 is the first. A coil spring 15 is installed.

The second support portion 18 is a rod-like member, extends downward from the upper surface of the spring accommodating portion 14, and is fixed to the housing 6. The second coil spring 16 is inserted into the second support portion 18, and the second coil spring 16 is installed around the second support portion 18.
The 1st support part 17 and the 2nd support part 18 are installed substantially coaxially. The outer diameter of the rod-shaped portion 17 b of the first support portion 17 and the outer diameter of the second support portion 18 are substantially the same and are smaller than the inner diameter of the spring accommodating portion 14.

  In a state where the fuel supply pressure is low, the first coil spring 15 and the second coil spring 16 push the needle valve 11 and the first support portion 17 downward, and the needle valve 11 closes the fuel injection hole 8. . When the needle valve 11 and the first support portion 17 are completely pushed down, there is a gap L1 corresponding to the first lift amount between the upper surface of the needle valve 11 and the lower surface of the first support portion 17. There is a gap L2 corresponding to the second lift amount between the upper surface of the first support portion 17 and the lower surface of the second support portion.

The needle valve 11 moves upward according to the hydraulic pressure of the fuel supplied to the fuel flow path 7, that is, the supply pressure, and the fuel flow path 7, the chamber 12, and the fuel injection hole 8 communicate with each other. As a result, fuel is injected from the fuel injection hole 8. The distance that the needle valve 11 can move upward is the total value of the first lift amount and the second lift amount, and is the total value of the gap L1 and the gap L2. The distance that the first support portion 17 can move upward is the second lift amount, which is the gap L2.
Note that the gap L2 is approximately half the total value of the first lift amount and the second lift amount, that is, the gap L1 and the gap L2 are substantially the same, thereby suppressing the fuel injection rate at the initial stage of fuel injection, The NOx emission concentration can be lowered while reducing the fuel consumption rate.

The elastic force of the first coil spring 15 is determined in relation to the supply pressure for starting the opening operation of the first stage of the needle valve 11, and the total elastic force of the first coil spring 15 and the second coil spring 16 is It is determined in relation to the supply pressure for starting the second stage opening operation of the needle valve 11. The elastic force of the first coil spring 15 is a relatively small value as long as the needle valve 11 can be operated in a state where the supply pressure is low.
The elastic force of the second coil spring 16 is set to a value that starts the opening operation of the second stage of the needle valve 11 when the supply pressure becomes as high as possible. The NOx emission concentration can be reduced. However, if the period during which the fuel injection rate is suppressed becomes too long, the injection period will be extended, so it is necessary to select an appropriate supply pressure.

  When the fuel supply pressure starts to rise from the state where the fuel injection hole 8 is closed by the needle valve 11, the needle valve 11 rises along the center hole 9 against the elastic force of the first coil spring 15. At this time, since the first coil spring 15 absorbs the force applied to the needle valve 11, the second coil spring 16 hardly contracts, and the position of the first support portion 17 remains substantially constant. When the fuel supply pressure further increases, the upper surface of the needle valve 11 comes into contact with the lower surface of the first support portion 17.

  After the contact, the fuel supply pressure is directly transmitted to the needle valve 11 and the first support portion 17. When the fuel supply pressure rises above a predetermined pressure, the needle valve 11 and the first support portion 17 rise along the center hole 9 against the elastic force of the second coil spring 16. Accordingly, the first lift amount of the needle valve 11 is maintained until the fuel supply pressure reaches a predetermined pressure. After the needle valve 11 and the first support portion 17 start to rise, when the fuel supply pressure further rises, the upper surface of the first support portion 17 contacts the lower surface of the second support portion 18. As a result, the needle valve 11 and the first support portion 17 are raised by the second lift amount and do not rise beyond the second lift amount.

  On the other hand, when the fuel supply pressure decreases, the first coil spring 15 and the second coil spring 16 urge the needle valve 11 and the first support material, and finally the needle valve 11 closes the fuel injection hole 8. To do. As a result, fuel injection ends.

  As described above, according to the present embodiment, even when the fuel supply pressure is low, the needle valve 11 is lifted by the first lift amount if the valve opening pressure determined by the spring force of the first coil spring 15 is exceeded. The behavior of the valve 11 can be stabilized.

Next, the configuration and operation of the fuel injection pump 3 will be described with reference to FIG.
The fuel injection pump 3 is provided with a hydraulic oil passage 21 through which hydraulic oil flows. The hydraulic oil passage 21 is opened and closed by a main valve 22. The hydraulic oil is pressurized by a hydraulic oil pump (not shown), and when the main valve 22 is opened, the plunger of the fuel injection pump 3 is pushed up. As a result, fuel is supplied from the fuel injection pump 3 to the fuel injection valve 2. When in the closed state, the plunger is lowered. As a result, the supply of fuel from the fuel injection pump 3 is stopped.

  The main valve 22 is driven by the pilot oil pressure. Hereinafter, an example of a pilot oil system of the fuel injection pump 3 that enables two-stage injection of fuel will be described.

  The pilot oil system is provided with a main solenoid valve 23 and a sub solenoid valve 24. A connecting pipe 25 between the main solenoid valve 23 and the sub solenoid valve 24 is provided with a first orifice 26 that can flow a relatively large flow rate. The connecting pipe 25 between the main solenoid valve 23 and the sub solenoid valve 24 is provided with a branch pipe 27, and the branch pipe 27 has a second orifice whose flow rate is set to be smaller than that of the first orifice 26. 28 is installed.

  The opening / closing operation of the main valve 22 by the pilot oil system of this embodiment is as follows. First, the hydraulic pressure of the pilot oil on the back of the main valve 22 is lowered by opening the main solenoid valve 23. As a result, the main valve 22 starts to open, and the hydraulic pressure of the hydraulic oil below the plunger increases. As a result, the plunger is slowly pushed up, and fuel is supplied from the fuel injection pump 3 to the fuel injection valve 2. At this time, the first stage of injection with a relatively low fuel injection pressure is performed.

  Next, the hydraulic pressure of the pilot oil on the back surface of the main valve 22 is further lowered by opening the sub solenoid valve 24. As a result, the opening degree of the main valve 22 is increased, and the hydraulic pressure of the hydraulic oil below the plunger is further increased. As a result, the plunger is pushed up quickly, and fuel is supplied from the fuel injection pump 3 to the fuel injection valve 2 at a high supply pressure. At this time, the second-stage injection having an injection pressure higher than that of the first stage is performed.

  The fuel supply pressure is reduced by delaying the opening timing of the sub solenoid valve 24 relative to the opening timing of the main solenoid valve 23 and reducing the flow rate of pilot oil passing through the second orifice 28 provided in the branch pipe 27. The fuel injection rate can be suppressed. As a result, the NOx emission concentration can be lowered while reducing the fuel consumption rate at the initial stage of fuel injection.

  As described above, by using the fuel injection valve 2 described above while using the fuel injection pump 3 that enables the two-stage injection described above, the fuel supply pressure is lowered in the initial stage of fuel injection in which the fuel injection rate is suppressed. Even if it exists, the behavior of the needle valve 11 inside the fuel injection valve 2 can be stabilized as shown by the solid line in the lower graph of FIG.

  According to this embodiment, the unstable behavior of the needle valve 11 due to the needle valve 11 not being fully lifted can be eliminated, and the problem of not being raised while sitting can be eliminated or reduced, and the robustness of the fuel injection control can be ensured. . As a result, since the fuel injection pressure at the initial stage of fuel injection can be reliably reduced, the NOx emission concentration can be lowered while reducing the fuel consumption rate.

DESCRIPTION OF SYMBOLS 1 Fuel injection apparatus 2 Fuel injection valve 3 Fuel injection pump 4 Fuel injection pipe 6 Housing 6a Tip part 7 Fuel flow path 8 Fuel injection hole 10 Internal combustion engine 11 Needle valve 15 1st coil spring (1st elastic part)
16 2nd coil spring (2nd elastic part)
17 1st support part 18 2nd support part

Claims (3)

A housing in which a fuel flow path is formed inside, and a fuel injection hole is formed in a tip portion;
A needle valve that is disposed inside the housing and opens and closes the fuel flow path according to a fuel supply pressure;
A rod-shaped portion and a protruding portion formed on the outer peripheral surface of the rod-shaped portion, and a lower end of the rod-shaped portion is disposed so as to be in contact with an upper surface of the needle valve, and the first of the needle valve A first support that defines a lift amount;
A first elastic portion that has a lower end in contact with an upper surface of the needle valve, an upper end in contact with a lower surface of the protruding portion of the first support portion, and biases the needle valve with respect to the first support portion; ,
A rod-shaped member extending downward from the upper surface of the housing portion formed above the needle valve inside the housing, and having a lower end opposed to an upper end of the rod-shaped portion of the first support portion. And a second support part that defines a second lift amount of the needle valve;
A lower end is in contact with the upper surface of the protruding portion of the first support portion, an upper end is in contact with the upper surface of the accommodating portion, and a second force that biases the needle valve and the first support portion with respect to the housing . An elastic part;
A fuel injection valve comprising: A fuel injection valve according to claim 1;
A fuel injection pump for supplying fuel to the fuel injection valve while adjusting the fuel supply pressure;
A fuel injection device comprising: 3. The fuel supply pressure is controlled so as to have a first stage in which the fuel supply pressure is set low and a second stage in which the fuel supply pressure is set high after the first stage. The fuel injection device described in 1.

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