JP6149766B2 - Fuel injection valve - Google Patents

Description

  The present invention relates to a fuel injection valve for injecting fuel into 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 includes a valve member that opens and closes a nozzle hole, and a control valve member that opens and closes between a pressure control chamber and a low-pressure portion, and the valve member is driven by fuel pressure in the pressure control chamber. It is energized in the valve closing direction. When the control valve member opens (that is, the pressure control chamber communicates with the low pressure portion) and the pressure in the pressure control chamber decreases, the valve member moves in the valve opening direction to open the nozzle hole, Fuel is injected.

  Further, the actuator is driven by the actuator to generate a pressure at the hydraulic pressure generating unit, and the control valve member is opened by the pressure of the hydraulic pressure generating unit.

  Specifically, the displacement take-out part includes a piston part that pressurizes the fuel filled in the hydraulic pressure generating part. Further, in order to make the movement direction of the displacement take-out part and the movement direction of the control valve member opposite, the control valve member is arranged in the large-diameter part that receives the pressure of the hydraulic pressure generating part and the hydraulic pressure generating part. And a small diameter portion. The pressure receiving area of the control valve member is an area obtained by subtracting the cross-sectional area of the small diameter portion from the cross-sectional area of the large diameter portion.

  Then, the pressure receiving area of the control valve member is made smaller than the pressure receiving area of the displacement extracting portion, and the expansion / contraction amount (that is, the displacement amount) of the actuator is enlarged and transmitted to the control valve member.

JP 2010-236375 A

  However, in the conventional fuel injection valve, since the small diameter portion of the control valve member is disposed in the hydraulic pressure generating portion, the pressure receiving area of the control valve member and the pressure receiving area of the displacement extracting portion cannot be increased. Further, since the control valve member and the displacement take-out portion are arranged in parallel, the outer diameters of the control valve member and the displacement take-out portion have to be reduced, and also from this point, the pressure receiving area of the control valve member and the displacement take-out portion The pressure receiving area cannot be increased.

  Therefore, the pressure of the hydraulic pressure generation unit necessary for opening the control valve member increases. This increase in the pressure of the hydraulic pressure generation part causes an increase in fuel leakage from the sliding part and a concomitant decrease in the pressure of the hydraulic pressure generation part. In the worst case, the control valve member cannot keep the valve open state. The control valve member closes early. As a result, there is a problem that the fuel injection ends earlier than the original timing and the fuel injection period becomes unstable.

  In view of the above points, the present invention aims to stabilize the fuel injection period.

  In order to achieve the above object, according to the first aspect of the present invention, a nozzle body (21) having an injection hole (211) for injecting high-pressure fuel into a combustion chamber of an internal combustion engine, a first cylinder hole (511), and A movable cylinder (51) having a second cylinder hole (512) having a diameter larger than that of the first cylinder hole, a movable piston (52) slidably inserted into the first cylinder hole, and a slide in the second cylinder hole. A fixed piston (53) that is movably inserted and fixed in position, and an oil-tight chamber (57) that is defined by a movable cylinder, a movable piston, and a fixed piston and that is filled with fuel, and expands and contracts to move. The actuator (4) that moves the piston and raises the pressure of the oil-tight chamber by the movement of the movable piston accompanying extension, and opens and closes the nozzle hole by operating according to the movement of the movable cylinder The movable cylinder is provided with a cylinder pressure receiving surface (513) that is formed at a boundary portion between the first cylinder hole and the second cylinder hole and receives the pressure of the oil-tight chamber, and the movable piston has an oil-tight chamber. And a piston pressure receiving surface (521) having a pressure receiving area larger than that of the cylinder pressure receiving surface.

  According to this, since there is no small diameter part arranged in the hydraulic pressure generating part in the conventional fuel injection valve, and the movable cylinder and the movable piston are arranged coaxially, each of the cylinder pressure receiving surface and the piston pressure receiving surface The pressure receiving area can be increased.

  Therefore, the pressure in the oil tight chamber necessary for driving the movable cylinder can be reduced, fuel leakage from the sliding portion can be reduced, and the pressure drop in the oil tight chamber can be reduced. As a result, the predetermined state of the movable cylinder can be maintained for a long time, and the fuel injection period can be stabilized.

  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 structure of the fuel injection valve which concerns on 1st Embodiment of this invention. It is an expanded sectional view of the principal part in the fuel injection valve of FIG. It is an expanded sectional view of the A section of FIG. It is BB sectional drawing of FIG. It is a perspective view of the fixed piston in the fuel injection valve of FIG. It is a perspective view of the discharge valve in the fuel injection valve of FIG. It is a figure which shows the pressure change characteristic of the fuel injection valve which concerns on 1st Embodiment of this invention, and the conventional fuel injection valve. It is sectional drawing which shows the structure of the fuel injection valve which concerns on 2nd Embodiment of this invention. It is an expanded sectional view of the C section of FIG.

  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 this embodiment injects high-pressure fuel supplied from a common rail (not shown) into a combustion chamber of a compression ignition type internal combustion engine (hereinafter referred to as an internal combustion engine, not shown).

  As shown in FIGS. 1 to 3, the fuel injection valve includes an injector body 1, a nozzle 2, a control valve mechanism 3, an actuator 4, a displacement transmission mechanism 5, and a retaining nut 6 as main components.

  The substantially bottomed cylindrical injector body 1 is formed with a high-pressure fuel passage 11 through which high-pressure fuel supplied from a common rail flows, and a storage chamber 12 as a low-pressure portion in which the actuator 4 and the displacement transmission mechanism 5 are stored. Yes. The storage chamber 12 is connected to a fuel tank (not shown) and is always at a low pressure.

  The nozzle 2 includes a substantially bottomed cylindrical nozzle body 21, a substantially cylindrical nozzle needle 22 that is slidably inserted into the nozzle body 21, a nozzle spring 23 that biases the nozzle needle 22 in a valve-closing direction, and a nozzle cylinder 24. It has.

  The nozzle body 21 is formed with a nozzle hole 211 through which high-pressure fuel is injected into the combustion chamber of the internal combustion engine, and the nozzle hole 21 is brought into contact with and separated from the nozzle body 21 by the tip (ie, the nozzle hole side end) of the nozzle needle 21. Can be opened and closed.

  A fuel reservoir chamber 25 in which high pressure fuel is always supplied from the common rail is formed in the nozzle body 21, and the high pressure fuel from the common rail flows toward the injection hole 211 through the fuel reservoir chamber 25.

  The cylindrical nozzle cylinder 24 is pressed against an intermediate body 31 (to be described later) by a nozzle spring 23, and the rear end portion (that is, the end portion on the side of the injection hole) of the nozzle needle 22 is slidably inserted into the nozzle cylinder 24. Yes.

  A control chamber 26 in which the internal fuel pressure is switched between a high pressure and a low pressure is formed in the nozzle cylinder 24. The nozzle needle 22 is urged in the valve closing direction by the fuel pressure in the control chamber 26 and is urged in the valve opening direction by the fuel pressure in the fuel reservoir chamber 25.

  The control valve mechanism 3 that controls the pressure in the control chamber 26 includes an intermediate body 31, a discharge valve 32, a control plate 33, and a plate spring 34.

  The disc-shaped intermediate body 31 is sandwiched between the injector body 1 and the nozzle body 21. In addition, the intermediate body 31 is pinched | interposed between the injector body 1 and the nozzle body 21, and the injector body 1 and the retaining nut 6 are screwed together, and the components of the fuel injection valve are integrated.

  The storage chamber side seat surface 311 on the injector body 1 side in the intermediate body 31 is exposed in the storage chamber 12. The control chamber side seat surface 312 on the nozzle body 21 side of the intermediate body 31 is exposed to the fuel reservoir chamber 25 and the control chamber 26.

  Further, the intermediate body 31 has a high pressure fuel passage 313 for communicating the high pressure fuel passage 11 of the injector body 1 and the fuel reservoir chamber 25 in the nozzle body 21, and a high pressure supply passage 314 for communicating the high pressure fuel passage 313 and the control chamber 26. , And a discharge passage 315 that allows the storage chamber 12 and the control chamber 26 to communicate with each other.

  The nozzle cylinder 24 is pressed against the control chamber side sheet surface 312 by the nozzle spring 23.

  In the control chamber 26, a disc-shaped control plate 33 and a plate spring 34 that urges the control plate 33 toward the intermediate body 31 are disposed.

  In the nozzle cylinder 24, a stopper surface 241 is formed on the inner wall surface that defines the control chamber 26. The control plate 33 is configured to reciprocate between the stopper surface 241 and the control chamber side sheet surface 312.

  When the control plate 33 is in contact with the stopper surface 241, the control chamber 26 is separated into two spaces by the control plate 33. Specifically, it is separated into an intermediate body side control chamber 26a which is a space on the intermediate body 31 side, and a needle side control chamber 26b which is a space on the nozzle needle 2 side. Hereinafter, the control chamber 26, the intermediate body side control chamber 26a, and the needle side control chamber 26b are properly used as necessary.

  A communication hole 331 penetrating in the axial direction of the control plate 33 is formed in the central portion of the control plate 33 in the radial direction.

  When the control plate 33 abuts against the control chamber side seat surface 312, the high pressure supply passage 314 is closed, and the communication between the high pressure fuel passage 313 and the control chamber 26 is blocked. Further, when the control plate 33 is in contact with the control chamber side sheet surface 312, the communication hole 331 and the discharge passage 315 are in communication.

  The discharge valve 32 includes a valve body 321 (details will be described later) and a valve body 322. The discharge valve 32 is disposed in the storage chamber 12, and the valve body 322 contacts and separates from the storage chamber side seat surface 311 to open and close between the storage chamber 12 and the discharge passage 315.

  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.

  The displacement transmission mechanism 5 as a transmission means includes a piezo spring 50, a movable cylinder 51, a movable piston 52, a fixed piston 53, a spacer 54, a first valve spring 55, and a second valve spring 56.

  In the cylindrical movable cylinder 51, a first cylinder hole 511 which is a columnar space, a second cylinder hole 512 which is a columnar space having a diameter larger than the first cylinder hole 511, and the first cylinder hole 511 and the first cylinder hole 511 are provided. A cylinder pressure receiving surface 513 is formed at the boundary with the two cylinder holes 512 and receives the pressure of an oil tight chamber 57 described later. The movable cylinder 51 is in contact with the valve body 321 of the discharge valve 32 at the end on the second cylinder hole 512 side.

  A cylindrical movable piston 52 is slidably inserted into the first cylinder hole 511. A piston pressure receiving surface 521 that receives the pressure of the oil-tight chamber 57 is formed at the end of the oil-tight chamber 57 in the movable piston 52. The pressure receiving area of the piston pressure receiving surface 521 is set larger than the pressure receiving area of the cylinder pressure receiving surface 513. The movable piston 52 is in contact with the actuator 4 at the end opposite to the oil-tight chamber 57.

  A cylindrical fixed piston 53 (detailed later) is slidably inserted into the second cylinder hole 512. The movable cylinder 51, the movable piston 52, and the fixed piston 53 define an oil-tight chamber 57 that is filled with fuel.

  The spacer 54 has a cylindrical shape, and the discharge valve 32 and the second valve spring 56 are disposed inside the spacer 54. The spacer 54 has one end abutting on the intermediate body 31 and the other end abutting on the fixed piston 53. The fixed piston 53 is pressed against the spacer 54 by the piezo spring 50 sandwiched between the movable piston 52 and the fixed piston 53, and the spacer 54 is pressed against the intermediate body 31. In other words, the fixed piston 53 is positioned and fixed with respect to the intermediate body 31.

  The first valve spring 55 is sandwiched between the movable cylinder 51 and the movable piston 52. The first valve spring 55 urges the movable piston 52 toward the actuator 4, whereby the movable piston 52 operates integrally with the actuator 4 as the actuator 4 expands and contracts. Further, the first valve spring 55 urges the discharge valve 32 through the movable cylinder 51 in the valve closing direction.

  The second valve spring 56 is sandwiched between the intermediate body 31 and the discharge valve 32. The second valve spring 56 biases the discharge valve 32 in the valve opening direction.

  When the discharge valve 32 is closed, there is a gap L between the discharge valve 32 and the fixed piston 53 corresponding to the maximum lift amount of the discharge valve 32.

  As shown in FIGS. 2 and 5, the fixed piston 53 is formed with a columnar fixed piston portion 531 inserted into the second cylinder hole 512, and on the opposite side of the fixed piston portion 531 from the oil-tight chamber 57. Are formed with three fixed piston arm portions 532 protruding radially outward. Between the fixed piston arm portions 532, three fixed piston notch portions 533 are formed along the circumferential direction.

  As shown in FIGS. 2 and 6, the valve body 321 of the discharge valve 32 is formed with three discharge valve leg portions 321 a protruding in the axial direction at the end opposite to the valve body 322. Three discharge valve notches 321b are formed between the discharge valve legs 321a along the circumferential direction.

  As shown in FIGS. 2 and 4, the fixed piston arm 532 is inserted into the discharge valve notch 321 b and the discharge valve leg 321 a is inserted into the fixed piston notch 533.

  Next, the operation of the fuel injection valve will be described. First, when the actuator 4 is charged when the needle valve is closed as shown in FIGS. 1 and 2, that is, when the discharge valve 32 is in contact with the storage chamber side seat surface 311, the actuator 4 expands. . Accordingly, the movable piston 52 is driven away from the actuator 4, and the pressure in the oil tight chamber 57 is increased by the movable piston 52.

  Further, the pressure in the oil tight chamber 57 that has been increased in pressure acts on the cylinder pressure receiving surface 513, and the movable cylinder 51 is driven toward the actuator 4 side. Further, the discharge valve 32 is urged by the second valve spring 56 and moves toward the actuator 4 following the movable cylinder 51.

  As described above, in the fuel injection valve of the present embodiment, the moving direction of the movable piston 52 and the moving direction of the movable cylinder 51 are reversed in accordance with the extension of the actuator 4, and the discharge valve 32 is accommodated in the storage chamber as the actuator 4 is extended. It is driven in a direction away from the side sheet surface 311.

  When the discharge valve 32 moves and the valve body 322 moves away from the storage chamber side seat surface 311 and the discharge passage 315 is opened, the fuel in the discharge passage 315 flows out into the storage chamber 12 and the discharge passage 315 and the intermediate body side. The pressure in the control chamber 26a decreases. Thereby, the control plate 33 is moved to the intermediate body 31 side by the pressure of the needle side control chamber 26b, rather than the force that the control plate 33 is urged toward the nozzle needle 2 side by the pressure of the intermediate body side control chamber 26a. Since the force urged toward becomes larger, the control plate 33 moves toward the intermediate body 31 side.

  As a result, the control plate 33 contacts the control chamber side seat surface 312, the high pressure supply passage 314 is closed by the control plate 33, and the communication between the high pressure fuel passage 11 and the control chamber 26 is blocked. Further, the fuel in the control chamber 26 flows out into the storage chamber 12 through the communication hole 331 and the discharge passage 315, and the pressure in the control chamber 26 is reduced. As a result, the force for urging the nozzle needle 22 in the valve closing direction is reduced, so that the nozzle needle 22 moves in the valve opening direction and fuel is injected from the injection hole 211.

  The displacement enlargement ratio, which is the ratio of the amount of change in the length of the actuator 4 (≈the amount of displacement of the movable piston 52) and the amount of displacement of the movable cylinder 51, is the pressure receiving area Slarge (see FIG. 3) of the piston pressure receiving surface 521. It is determined by the ratio (Slurge / Ssmall) to the pressure receiving area Ssmall (see FIG. 3) of the cylinder pressure receiving surface 513.

  The force with which the movable cylinder 51 is pushed by the pressure in the oil tight chamber 57 when the actuator 4 extends is expressed by the product of the pressure in the oil tight chamber 57 and the pressure receiving area Ssmall of the cylinder pressure receiving surface 513. Therefore, if the pressure receiving area Ssmall of the cylinder pressure receiving surface 513 can be increased, the pressure in the oil tight chamber 57 necessary for opening the discharge valve 32 can be reduced. As a result, the amount of fuel leakage during valve opening retention from the sliding portion between the movable cylinder 51 and the movable piston 52 and the sliding portion between the movable cylinder 51 and the fixed piston 53 is reduced.

  Here, the performance comparison was performed about the fuel injection valve which concerns on this embodiment, and the conventional fuel injection valve. The comparison target product has the same physique of the fuel injection valve and the displacement expansion rate is unified to 1.67, and under the conditions, the cylinder pressure in the fuel injection valve according to the present embodiment (hereinafter referred to as the embodiment product). The pressure receiving area Ssmall of the surface 513 was maximized, and the pressure receiving area of the control valve member in the conventional fuel injection valve (hereinafter referred to as a conventional product) was maximized. In this comparison target product, the pressure receiving area Ssmall of the cylinder pressure receiving surface 513 in the embodiment product is 1.17 times the pressure receiving area of the control valve member in the conventional product.

  Incidentally, the present embodiment does not include a small-diameter portion disposed in the hydraulic pressure generating portion in the conventional fuel injection valve, and the movable cylinder 51 and the movable piston 52 are disposed coaxially. And it is easy to enlarge each pressure receiving area of the piston pressure receiving surface 521.

  FIG. 7 shows the pressure change characteristics of the oil-tight chamber after the start of fuel injection in the above-mentioned comparison target product. In FIG. 7, the solid line indicates the pressure change characteristic of the embodiment product, and the alternate long and short dash line indicates the pressure change characteristic of the conventional product.

  As shown in FIG. 7, the pressure in the oil tight chamber after the start of fuel injection in the embodiment product decreases more slowly than in the conventional product, and the valve opening holdable limit pressure in the embodiment product is lower than that in the conventional product. Become. Therefore, in combination, the valve-openable period in the embodiment product is significantly (about 50%) longer than that in the conventional product.

  On the other hand, when the charge of the actuator 4 is discharged in the needle open state, that is, when the discharge valve 32 is away from the storage chamber side seat surface 311, the actuator 4 contracts. Accordingly, the movable piston 52 urged by the first valve spring 55 follows the actuator 4 and moves toward the actuator 4 side, and the pressure in the oil-tight chamber 57 decreases.

  Therefore, the movable cylinder 51 and the discharge valve 32 move toward the intermediate body 31 by the urging force of the first valve spring 55. As described above, in the fuel injection valve of the present embodiment, the moving direction of the movable piston 52 and the moving direction of the movable cylinder 51 are opposite to each other when the actuator 4 contracts.

  When the discharge valve 32 comes into contact with the storage chamber side seat surface 311 and the discharge passage 315 is closed by the movement of the discharge valve 32, the outflow of fuel in the discharge passage 315 stops, and the discharge passage 315 and the control chamber 26 have the same pressure. become. Thereby, the control plate 33 is moved to the nozzle needle 2 side by the pressure of the discharge passage 315 and the high pressure supply passage 314 rather than the force that the control plate 33 is urged toward the intermediate body 31 side by the pressure of the control chamber 26. Since the force urged toward the head increases, the control plate 33 moves toward the nozzle needle 2 side.

  Then, the control plate 33 contacts the stopper surface 241, and the high-pressure fuel that has flowed into the intermediate body-side control chamber 26 a from the high-pressure supply passage 314 flows into the needle-side control chamber 26 b through the communication hole 331.

  Thus, when high pressure fuel flows into the needle side control chamber 26b, the nozzle needle 2 moves in the valve closing direction, the injection hole 211 is closed, and fuel injection is completed.

  Here, the set load of the first valve spring 55 is F1, the set load of the second valve spring 56 is F2, and the maximum biasing force that biases the discharge valve 32 in the valve opening direction by the fuel pressure in the control chamber 26 is F3. F1> F2 and F1-F2> F3. Thereby, when the actuator 4 contracts, the movable cylinder 51 and the discharge valve 32 can be integrally moved toward the intermediate body 31 side.

  As described above, in the present embodiment, the pressure receiving areas of the cylinder pressure receiving surface 513 and the piston pressure receiving surface 521 can be increased. Therefore, the pressure in the oil tight chamber 57 necessary for opening the discharge valve 32 (that is, the pressure in the oil tight chamber 57 necessary for driving the movable cylinder 51) can be reduced, and the fuel from the sliding portion can be reduced. Leakage can be reduced and the pressure drop in the oil tight chamber 57 can be reduced. As a result, the open state of the discharge valve 32 can be maintained for a long time. Therefore, it is possible to avoid the problem that the fuel injection ends earlier than the original timing and the fuel injection period becomes unstable.

(Second Embodiment)
A second embodiment of the present invention will be described. In this embodiment, the nozzle needle and the movable cylinder are integrally operated, and the other parts are the same as those in the first embodiment. Therefore, only the parts different from the first embodiment will be described.

  As shown in FIGS. 8 and 9, in this embodiment, the control valve mechanism 3, the nozzle cylinder 24, and the second valve spring 56 in the first embodiment are omitted.

  The storage chamber 12 is not connected to the fuel tank but communicates with the fuel reservoir chamber 25 and is always at a high pressure. The nozzle needle 22 is urged toward the valve closing direction by the pressure of the high-pressure fuel.

  Three nozzle legs 221 projecting in the axial direction are formed at the rear end of the nozzle needle 22 (that is, the end opposite to the injection hole). Three nozzle notches 222 are formed between the nozzle legs 221 along the circumferential direction. In addition, the nozzle leg part 221 and the nozzle notch part 222 are the structures similar to the discharge valve leg part 321a and the discharge valve notch part 321b in 1st Embodiment.

  The fixed piston arm 532 is inserted into the nozzle notch 222 and the nozzle leg 221 is inserted into the fixed piston notch 533. Further, the tip of the nozzle leg 221 is in contact with the end of the movable cylinder 51 on the second cylinder hole 512 side.

  The nozzle 2 includes a substantially bottomed cylindrical nozzle body 21, a substantially cylindrical nozzle needle 22 that is slidably inserted into the nozzle body 21, and a nozzle spring 23 that urges the nozzle needle 22 toward the valve closing direction. .

  The nozzle spring 23 is sandwiched between the nozzle body 21 and the nozzle needle 22. The nozzle spring 23 biases the nozzle needle 22 in the valve opening direction. Further, the nozzle spring 23 biases the nozzle needle 22 toward the movable cylinder 51, whereby the nozzle needle 22 and the movable cylinder 51 operate integrally.

  When the nozzle needle 22 is in a closed state, there is a gap between the nozzle needle 22 and the fixed piston 53.

  Next, the operation of the fuel injection valve will be described. First, when the actuator 4 is charged when the needle is closed, the actuator 4 extends. Accordingly, the movable piston 52 is driven away from the actuator 4, and the pressure in the oil tight chamber 57 is increased by the movable piston 52.

  Further, the pressure in the oil tight chamber 57 that has been increased in pressure acts on the cylinder pressure receiving surface 513, and the movable cylinder 51 is driven toward the actuator 4 side.

  Accordingly, the nozzle needle 22 biased by the nozzle spring 23 follows the movable cylinder 51 and moves toward the actuator 4 side. That is, the nozzle needle 22 moves in the valve opening direction, and fuel is injected from the nozzle hole 211.

  On the other hand, when the charge of the actuator 4 is discharged in the needle open state, the actuator 4 contracts. Accordingly, the movable piston 52 urged by the first valve spring 55 follows the actuator 4 and moves toward the actuator 4 side, and the pressure in the oil-tight chamber 57 decreases.

  Therefore, the movable cylinder 51 and the nozzle needle 22 are moved in the valve closing direction by the force for biasing the nozzle needle 22 in the valve closing direction by the pressure of the high pressure fuel and the biasing force of the first valve spring 55, and the nozzle hole 211 is moved. It is closed and fuel injection ends.

  Here, when the set load of the first valve spring 55 is F1, the set load of the nozzle spring 23 is F4, and the maximum biasing force by which the nozzle needle 22 is biased in the valve closing direction by the pressure of the high-pressure fuel is F5, F4> F5 and F1> F4-F5. Thereby, when the actuator 4 contracts, the movable cylinder 51 and the nozzle needle 22 can be moved integrally in the valve closing direction.

  As described above, in the present embodiment, the pressure receiving areas of the cylinder pressure receiving surface 513 and the piston pressure receiving surface 521 can be increased as in the first embodiment. Therefore, the pressure in the oil tight chamber 57 necessary for opening the nozzle needle 22 (that is, the pressure in the oil tight chamber 57 necessary for driving the movable cylinder 51) can be reduced, and the fuel from the sliding portion can be reduced. Leakage can be reduced and the pressure drop in the oil tight chamber 57 can be reduced. As a result, the open state of the nozzle needle 22 can be maintained for a long time. Therefore, it is possible to avoid the problem that the fuel injection ends earlier than the original timing and the fuel injection period becomes unstable.

(Other embodiments)
In each of the above embodiments, a piezo element is used as the actuator 4.

  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.

4 Actuator 21 Nozzle body 22 Nozzle needle 51 Movable cylinder 52 Movable piston 53 Fixed piston 57 Oil tight chamber 211 Injection hole 511 First cylinder hole 512 Second cylinder hole 513 Cylinder pressure receiving surface 521 Piston pressure receiving surface

Claims (6)

A nozzle body (21) having an injection hole (211) for injecting high pressure fuel into the combustion chamber of the internal combustion engine;
A movable cylinder (51) having a first cylinder hole (511) and a second cylinder hole (512) having a larger diameter than the first cylinder hole;
A movable piston (52) slidably inserted into the first cylinder hole;
A fixed piston (53) that is slidably inserted into the second cylinder hole and fixed in position;
An oil tight chamber (57) defined by the movable cylinder, the movable piston and the fixed piston and filled with fuel;
An actuator (4) that expands and contracts to move the movable piston and raises the pressure of the oil-tight chamber by the movement of the movable piston accompanying expansion;
A nozzle needle (22) that operates according to the movement of the movable cylinder to open and close the nozzle hole;
The movable cylinder includes a cylinder pressure receiving surface (513) that is formed at a boundary portion between the first cylinder hole and the second cylinder hole and receives the pressure of the oil tight chamber,
The fuel injection valve, wherein the movable piston is provided with a piston pressure receiving surface (521) that receives the pressure of the oil tight chamber and has a pressure receiving area larger than that of the cylinder pressure receiving surface. A nozzle cylinder (24) forming a control chamber (26) in which one end side of the nozzle needle is slidably inserted, and a fuel pressure is applied to the nozzle needle in a valve closing direction;
An intermediate body (31) having a discharge passage (315) for discharging the fuel in the control chamber to the low pressure section (12);
A discharge valve (32) that opens and closes the discharge passage by following the movable cylinder and moving toward and away from the intermediate body;
A first valve spring (55) for biasing the discharge valve toward the valve closing direction via the movable cylinder;
The fuel injection valve according to claim 1, further comprising a second valve spring (56) for urging the discharge valve in the valve opening direction.   When the set load of the first valve spring is F1, the set load of the second valve spring is F2, and the maximum biasing force that biases the discharge valve in the opening direction by the fuel pressure in the control chamber is F3. F1> F2 and F1-F2> F3. 3. The fuel injection valve according to claim 2, wherein F1-F2> F3. A first valve spring (55) for urging the nozzle needle through the movable cylinder in a valve closing direction;
A nozzle spring (23) for urging the nozzle needle in the valve opening direction;
The nozzle needle is urged toward the valve closing direction by the pressure of the high-pressure fuel, and is configured to move in a direction to open the nozzle hole by following the movable cylinder when the actuator extends. The fuel injection valve according to claim 1.   Assuming that the set load of the first valve spring is F1, the set load of the nozzle spring is F4, and the maximum biasing force that biases the nozzle needle in the valve closing direction by the pressure of the high-pressure fuel is F5, F4> F5 The fuel injection valve according to claim 4, wherein F1> F4-F5.   6. The fuel injection valve according to claim 1, wherein the actuator is a piezoelectric element laminated body that expands and contracts due to charge and discharge of electric charges.

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