JP2016176422A - Fuel injection valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce energizing force of a needle spring and a driving force of an actuator.SOLUTION: In an outward-opening type fuel injection valve, an end on an actuator 4 side of a nozzle needle 32 is disposed in low-pressure sections 12, 22 filled with low-pressure fuel. This configuration prevents pressure of high-pressure fuel from being applied to an end surface on the actuator 4 side of the nozzle needle 32, so that energizing force in the valve opening direction applied to the nozzle needle in the closed state is drastically reduced compared to the case where high-pressure fuel pressure is applied. Therefore, energizing force of a needle spring 33 for energizing the nozzle needle 32 in the valve closing direction can be reduced, which enables reduction of the driving force of an actuator 4 for driving the nozzle needle 32 in the valve opening direction.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel injection valve for injecting fuel into a combustion chamber of an internal combustion engine.

  Conventionally, as this type of fuel injection valve, for example, there is one described in Patent Document 1. The fuel injection valve described in Patent Document 1 is an outward-opening type fuel injection valve, in which a nozzle hole and a body seat portion are formed in a body, and a needle seat portion formed in a nozzle needle is a body seat portion. The nozzle hole is opened and closed by contact and separation.

  The nozzle needle is urged in the valve closing direction by a needle spring and is driven in the valve opening direction by an actuator.

German Patent Application No. 102005063010

  However, the nozzle needle is disposed in a high-pressure portion through which high-pressure fuel flows, and a biasing force in the valve opening direction acts on the nozzle needle in the valve-closed state due to the pressure of the high-pressure fuel. More specifically, since the pressure of the high-pressure fuel acts not only on the needle seat portion but also on the end surface of the nozzle needle on the actuator side, the urging force in the valve opening direction due to the pressure of the high-pressure fuel Will be big.

  Therefore, it is necessary to increase the urging force of the needle spring in order to maintain the valve closing state against the urging force in the valve opening direction due to the pressure of the high-pressure fuel. Further, since the actuator drives the nozzle needle in the valve opening direction against the urging force of the needle spring, it becomes necessary to increase the driving force of the actuator as the urging force of the needle spring increases. And the problem of increased driving energy occurs.

  The present invention has been made in view of the above points, and an object thereof is to reduce the urging force of a needle spring and the driving force of an actuator.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided an outwardly-opening fuel injection valve, wherein the high pressure fuel supplied to the high pressure section (11, 21, 311 and 312) is supplied to the combustion chamber of the internal combustion engine. The body (1, 2, 31) having an injection hole (318) for injecting into the body and the needle seat part (324) that opens and closes the injection hole by contacting and separating from the body sheet part (316) formed on the body are at one end. A nozzle needle (32) disposed in a low pressure portion (12, 22) formed on the other side and filled with low pressure fuel at the other end, an actuator (4) for driving the nozzle needle in a valve opening direction, and a nozzle needle And a needle spring (33) that urges the valve in the valve closing direction.

  According to this, since the pressure of the high pressure fuel does not act on the end surface of the nozzle needle opposite to the needle seat portion, the biasing force acting in the valve opening direction acting on the nozzle needle in the valve closing state becomes small. Therefore, the urging force of the needle spring can be reduced and the driving force of the actuator can be reduced accordingly.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

It is sectional drawing which shows the fuel injection valve which concerns on 1st Embodiment of this invention. It is an expanded sectional view of the nozzle needle periphery in the fuel injection valve concerning a 1st embodiment. It is an expanded sectional view of the nozzle needle tip part periphery in the fuel injection valve concerning a 1st embodiment. It is sectional drawing of the nozzle needle front-end | tip part periphery in the fuel injection valve which concerns on 2nd Embodiment of this invention. It is sectional drawing of the nozzle needle periphery in the fuel injection valve which concerns on 3rd Embodiment of this invention. It is sectional drawing which shows the fuel injection valve which concerns on 4th Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.

(First embodiment)
A first embodiment of the present invention will be described. The fuel injection valve of the present embodiment is an externally-open fuel injection valve having an externally-opening nozzle, and high-pressure fuel supplied from a common rail is supplied to a combustion chamber of a compression ignition internal combustion engine (hereinafter referred to as an internal combustion engine). It is to be jetted.

  As shown in FIGS. 1 to 3, the fuel injection valve includes an injector body 1, an intermediate body 2, a nozzle 3, an actuator 4, and a retaining nut 5 as main components.

  The substantially cylindrical injector body 1 includes a first high-pressure fuel passage 11 through which high-pressure fuel supplied from a common rail (not shown) flows, and a first storage chamber 12 in which the actuator 4 is stored. The first storage chamber 12 is connected to a fuel tank (not shown) and is always filled with low-pressure fuel.

  The substantially cylindrical intermediate body 2 includes a second high-pressure fuel passage 21 that communicates with the first high-pressure fuel passage 11 and a second storage chamber 22 that communicates with the first storage chamber 12. In addition, the 1st storage chamber 12 and the 2nd storage chamber 22 comprise the low voltage | pressure part of this invention.

  The nozzle 3 includes a substantially cylindrical nozzle body 31, a substantially cylindrical nozzle needle 32 that is reciprocally inserted into the nozzle body 31, a needle spring 33 that biases the nozzle needle 32 in a valve closing direction, and one end of the needle spring 33. A spring seat 34 for supporting the side is provided.

  The injector body 1, the intermediate body 2, and the nozzle body 31 are integrated by screwing the injector body 1 and the retaining nut 5 in a state where the intermediate body 2 is disposed between the injector body 1 and the nozzle body 31. Has been. The injector body 1, the intermediate body 2, and the nozzle body 31 constitute the body of the present invention.

  The nozzle body 31 is connected to a third high-pressure fuel passage 311 that communicates with the second high-pressure fuel passage 21 and a fuel reservoir chamber 312 that is constantly supplied with high-pressure fuel from a common rail. . The first high-pressure fuel passage 11, the second high-pressure fuel passage 21, the third high-pressure fuel passage 311 and the fuel reservoir chamber 312 constitute the high-pressure part of the present invention.

  The nozzle body 31 has a partition wall 313 that separates the fuel reservoir chamber 312 and the second storage chamber 22 from a portion adjacent to the intermediate body 2. A needle sliding hole 314 that penetrates from the fuel reservoir chamber 312 to the second storage chamber 22 is formed in the partition wall 313.

  The first cylindrical portion 321 of the nozzle needle 32 is slidably inserted into the needle sliding hole 314. A part of the first cylindrical portion 321 is disposed in the first storage chamber 12 and the second storage chamber 22, and an end portion of the first cylindrical portion 321 is exposed to the first storage chamber 12.

  The nozzle body 31 is formed with a fuel passage hole 315 extending from the fuel reservoir chamber 312 toward the side opposite to the intermediate body 2 (that is, a nozzle hole side described later). The second cylindrical portion 322 of the nozzle needle 32 is inserted into the fuel passage hole 315.

  Here, the inner diameter of the needle sliding hole 314 and the inner diameter of the fuel passage hole 315 are equal. Further, the outer diameter of the second cylindrical portion 322 is smaller than the outer diameter of the first cylindrical portion 321. Therefore, a gap through which high-pressure fuel flows is formed between the fuel passage hole 315 and the second cylindrical portion 322. The fuel supplied to the fuel reservoir 312 flows through a gap between the fuel passage hole 315 and the second cylindrical portion 322 toward an injection hole described later.

  In the nozzle body 31, a body sheet portion 316 is formed at a portion of the fuel passage hole 315 on the downstream side of the fuel flow (a nozzle hole side described later). The body seat portion 316 has a tapered shape whose diameter increases toward the downstream side of the fuel flow.

  The nozzle body 31 has a cylindrical injection hole cylinder part 317 on the downstream side of the fuel flow from the body sheet part 316, and an injection hole 318 for injecting high-pressure fuel into the combustion chamber of the internal combustion engine is formed in the injection hole cylinder part 317. ing. The nozzle holes 318 are through holes that allow the inner peripheral side and the outer peripheral side of the nozzle hole cylinder part 317 to communicate with each other, and a plurality of the nozzle holes 318 are arranged along the circumferential direction.

  A needle guide hole 319 into which the third cylindrical portion 323 of the nozzle needle 32 is slidably inserted is formed on the tip side of the nozzle hole portion 317 in the nozzle hole portion 317. The inner diameter of the needle guide hole 319 is larger than the inner diameter of the fuel passage hole 315.

  In the nozzle needle 32, a needle seat portion 324 that opens and closes the injection hole 318 by contacting and separating from the body seat portion 316 is formed at a boundary portion between the second cylindrical portion 322 and the third cylindrical portion 323. The needle seat portion 324 has a tapered shape that expands toward the downstream side of the fuel flow.

  More specifically, the needle seat portion 324 contacts and separates from the inner peripheral side edge portion of the body seat portion 316. Therefore, the seat diameter Ds, which is the diameter of the portion where the body seat portion 316 and the needle seat portion 324 abut, is equal to the inner diameter of the fuel passage hole 315.

  Further, when the outer diameter of the first cylindrical portion 321 that is the portion inserted into the needle sliding hole 314 in the nozzle needle 32 is the needle sliding portion diameter Dn, the needle sliding portion diameter Dn and the seat diameter Ds are equal. ing.

  The actuator 4 is composed of a cylindrical piezo element laminate in which a large number of piezo elements are stacked and expanded and contracted by charge and discharge. A fixed end 41, which is one end side end of the actuator 4, is positioned on the injector body 1. The free end 42, which is the other end side end of the actuator 4, faces the end of the first cylindrical portion 321 of the nozzle needle 32. The free end 42 of the actuator 4 is displaced in the actuator axial direction as the actuator 4 expands and contracts.

  Next, the operation of the fuel injection valve will be described. First, in the needle valve closed state shown in FIGS. 1 to 3 (that is, the nozzle hole 318 is closed), the electric charge of the actuator 4 is discharged and the actuator 4 contracts.

  When the actuator 4 is charged when the needle is closed, the actuator 4 extends and the free end 42 is displaced downward in the drawing of FIG. The extension of the actuator 4 causes the free end 42 to abut the end of the first cylindrical portion 321 of the nozzle needle 32, and then the nozzle needle 32 moves toward the downstream side of the fuel flow against the urging force of the needle spring 33. The needle seat portion 324 is driven away from the body seat portion 316 to be in a valve opening state, and fuel is injected from the injection hole 318 into the combustion chamber of the internal combustion engine.

  As described above, the nozzle 2 of the present embodiment is a so-called externally open nozzle in which the nozzle needle 32 moves toward the fuel flow downstream side and opens.

  Here, in the case of the fuel injection valve described in Patent Document 1, since the spray shape of the injected fuel has an umbrella shape, mixing with air is poor, combustion is worsened, and the amount of smoke generated is increased. There's a problem. On the other hand, in this embodiment, since the nozzle hole 318 is a through-hole, it becomes a needle-like spray, and the generation of smoke due to the deterioration of combustion can be suppressed.

  On the other hand, when the electric charge of the actuator 4 is discharged while the needle is open, the actuator 4 contracts and the free end 42 is displaced upward in FIG. When the actuator 4 contracts, the nozzle needle 32 is urged by the needle spring 33 to follow the displacement of the free end 42, the needle seat portion 324 comes into contact with the body seat portion 316, and the needle valve is closed. 318 is closed and fuel injection ends.

  Here, since the end portion of the first cylindrical portion 321 of the nozzle needle 32 is exposed to the low-pressure first storage chamber 12, the end surface of the first cylindrical portion 321 (that is, the needle seat portion 324 in the nozzle needle 32) The pressure of the high-pressure fuel does not act on the opposite end surface), but the low pressure acts. Therefore, the force that urges the nozzle needle 32 in the valve opening direction by the pressure acting on the end surface of the first cylindrical portion 321 is significantly smaller than that in the case where the pressure of the high pressure fuel acts on the end surface of the first cylindrical portion 321. Become.

  As a result, the urging force in the valve opening direction acting on the nozzle needle 32 in the valve-closed state is reduced, the urging force of the needle spring 33 can be reduced, and the driving force of the actuator 4 can be reduced accordingly. .

  Further, since the needle sliding part diameter Dn and the seat diameter Ds are made equal, in the valve closing state, the pressure of the high pressure fuel biases the nozzle needle 32 in the valve opening direction and the valve closing direction. Power is equal.

  As a result, the urging force in the valve opening direction that acts on the nozzle needle 32 in the valve-closed state is further smaller than when the needle sliding portion diameter Dn is smaller than the seat diameter Ds, and the urging force of the needle spring 33 is further increased. While being able to make it small, the driving force of the actuator 4 can further be made small in connection with it.

  As described above, according to the present embodiment, the urging force of the needle spring 33 can be reduced, and the driving force of the actuator 4 can be reduced accordingly. Moreover, it becomes needle-like spraying and can suppress the generation of smoke due to deterioration of combustion.

(Second Embodiment)
A second embodiment of the present invention will be described. Only the parts different from the first embodiment will be described below.

  As shown in FIG. 4, a cylindrical cover portion 325 having an outer diameter larger than that of the third cylindrical portion 323 is formed on the distal end side of the third cylindrical portion 323 in the nozzle needle 32. The cover 325 covers the open end of the needle guide hole 319 on the combustion chamber side.

  Since the nozzle hole cylinder portion 317 is disposed in the combustion chamber, there is a possibility that soot, foreign matter, etc. generated by combustion may enter the sliding portion between the needle guide hole 319 and the third cylindrical portion 323 and cause a sliding failure. However, it is possible to prevent inadequate sliding by preventing the soot and foreign matter from entering the sliding portion with the cover portion 325.

  According to this embodiment, the same effect as that of the first embodiment can be obtained. Moreover, the sliding failure of the 3rd cylindrical part 323 can be avoided.

(Third embodiment)
A third embodiment of the present invention will be described. Only the parts different from the first embodiment will be described below.

  As shown in FIG. 5, a cylindrical cylinder 6 is slidably inserted into the needle sliding hole 314. One end side of the cylinder 6 is exposed in the fuel reservoir chamber 312, and the other end side of the cylinder 6 is exposed in the first storage chamber 12.

  Further, the first cylindrical portion 321 of the nozzle needle 32 is slidably inserted into the cylinder 6. The end of the first cylindrical portion 321 is exposed to the first storage chamber 12.

  When the outer diameter of the part inserted into the needle sliding hole 314 in the cylinder 6 is the cylinder sliding part diameter Dc, the cylinder sliding part diameter Dc and the seat diameter Ds are equal. Further, when the outer diameter of the first cylindrical portion 321 that is the portion inserted into the cylinder 6 in the nozzle needle 32 is the needle sliding portion diameter Dn, the needle sliding portion diameter Dn is smaller than the seat diameter Ds. .

  Thus, when the needle sliding part diameter Dn is made smaller than the seat diameter Ds, the force for urging the nozzle needle 32 in the valve opening direction by the pressure of the high-pressure fuel increases.

  On the other hand, the cylinder 6 is urged toward the actuator 4 by the pressure of the high-pressure fuel in the fuel reservoir chamber 312 (that is, upward in the drawing of FIG. 5), and the nozzle needle 32 via the spring seat 34 is urged by the urging force. Is energized in the valve closing direction.

  Therefore, the increase in the force for urging the nozzle needle 32 in the valve opening direction can be canceled by the urging force in the valve closing direction due to the pressure of the high-pressure fuel acting on the cylinder 6, while ensuring the fuel shut-off property, An increase in the driving force of the actuator 4 can be suppressed.

  Here, the force for biasing the nozzle needle 32 in the valve opening direction is the valve opening biasing force Fop, the force for biasing the nozzle needle 32 in the valve closing direction is the valve closing biasing force Fsh, and the spring force of the needle spring 33 is Fsp, When the pressure of the high-pressure fuel is Pc, the force for urging the nozzle needle 32 when Ds = Dc> Dn is as follows.

When opening the valve, Fop = π / 4 (Ds ² −Dc ² ) × Pc, and when closing the valve, Fop = 0.

Further, both when the valve is opened and when the valve is closed, Fsh = π / 4 (Dc ² −Dn ² ) × Pc + Fsp.

When the force by which the cylinder 6 is urged by the pressure of the high-pressure fuel, that is, π / 4 (Dc ² −Dn ² ) × Pc is set to about ½ Fop, the valve opening due to the fuel pressure at the time of valve opening is performed. The direction biasing force can be halved.

  According to this embodiment, the same effect as that of the first embodiment can be obtained.

(Fourth embodiment)
A fourth embodiment of the present invention will be described. Only the parts different from the first embodiment will be described below.

  As shown in FIG. 6, the actuator 4 of this embodiment is configured by a solenoid. Specifically, the actuator 4 includes a coil 41 that forms a magnetic field when energized, a stator core 42 that generates a magnetic attractive force when the coil 41 is energized, and an armature 43 that is attracted to the stator core 42 side by the magnetic attractive force. ing. One end of the armature 43 faces the end of the first cylindrical portion 321 of the nozzle needle 32.

  When the coil 41 is energized, the armature 43 is displaced downward in FIG. 6, and the nozzle needle 32 is driven toward the downstream side of the fuel flow against the urging force of the needle spring 33, and the needle seat portion 324. 3 (see FIG. 3) is separated from the body seat portion 316 (see FIG. 3) to open the needle valve, and fuel is injected from the injection hole 318 (see FIG. 3) into the combustion chamber of the internal combustion engine.

  According to this embodiment, the same effect as that of the first embodiment can be obtained.

(Other embodiments)
In addition, this invention is not limited to above-described embodiment, In the range described in the claim, it can change suitably.

  Further, the above embodiments are not irrelevant to each other, and can be combined as appropriate unless the combination is clearly impossible.

  In each of the above-described embodiments, it is needless to say that elements constituting the embodiment are not necessarily essential unless explicitly stated as essential and clearly considered essential in principle. Yes.

  Further, in each of the above embodiments, when numerical values such as the number, numerical value, quantity, range, etc. of the constituent elements of the embodiment are mentioned, it is clearly limited to a specific number when clearly indicated as essential and in principle. The number is not limited to the specific number except for the case.

  Further, in each of the above embodiments, when referring to the shape, positional relationship, etc. of the component, etc., the shape, unless otherwise specified and in principle limited to a specific shape, positional relationship, etc. It is not limited to the positional relationship or the like.

1 Injector body (body)
2 Intermediate body
4 Actuator 11 1st high pressure fuel passage (high pressure part)
12 First storage room (low pressure part)
21 Second high-pressure fuel passage (high-pressure section)
22 Second storage room (low pressure part)
31 Nozzle body
32 Nozzle needle 33 Needle spring 311 Third high pressure fuel passage (high pressure section)
312 Fuel reservoir (high pressure part)
316 Body seat portion 318 Injection hole 324 Needle seat portion

Claims (3)

An outward-opening fuel injection valve,
Bodies (1, 2, 31) having injection holes (318) for injecting high-pressure fuel supplied to the high-pressure sections (11, 21, 311, 312) into the combustion chamber of the internal combustion engine;
A low pressure portion (12, 22) is formed on one end side of a needle seat portion (324) that opens and closes the injection hole by contacting and separating from the body seat portion (316) formed on the body, and the other end side is filled with low pressure fuel. Nozzle needle (32) arranged in
An actuator (4) for driving the nozzle needle in a valve opening direction;
A fuel injection valve, comprising: a needle spring (33) for urging the nozzle needle in a valve closing direction. Separating the high pressure part and the low pressure part, and comprising a partition part (313) in which a needle sliding hole (314) into which the nozzle needle is slidably inserted is formed,
The diameter of a needle sliding portion that is a diameter of a portion inserted into the needle sliding hole in the nozzle needle is equal to a seat diameter that is a diameter of a portion where the body sheet portion and the needle seat portion are in contact with each other. The fuel injection valve according to claim 1. The body has an injection hole cylinder part (317) on the downstream side of the fuel flow from the body sheet part,
3. The fuel injection valve according to claim 1, wherein the injection hole is formed in the injection hole cylinder part so as to communicate an inner peripheral side and an outer periphery side of the injection hole cylinder part. 4. .

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