JP2010209794A - Fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection device immediately returning a closing assist piston to an initial position and efficiently controlling fuel injection. <P>SOLUTION: This fuel injection device 1 includes a nozzle body 40 and an injection control valve 20 advancing and retreating in a first fuel storage chamber 41. When the injection control valve 20 advances to a first position, a first fuel passage 51 communicates with the first fuel storage chamber 41, and also the first fuel storage chamber 41 is disconnected from a third fuel passage 53. When the injection control valve retreats to a second position, the first fuel passage 51 is disconnected from the first fuel storage chamber 41, and also the first fuel storage chamber 41 communicates with the third fuel passage 53. A needle valve closing chamber 43 communicating with the third fuel passage 53 has the closing assist piston 30, a closing assist pressure chamber 432, a return pressure chamber 433, and a communication passage 434 for allowing the closing assist pressure chamber 432 to communicate with the return pressure chamber 433 when the closing assist piston 30 advances by a predetermined distance. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel injection device. In particular, the present invention relates to a fuel injection device that is used in a diesel engine and injects fuel supplied at a high pressure from a fuel supply source.

Conventionally, a fuel injection device that injects fuel is used for a diesel engine.
FIG. 11 is a cross-sectional view of a fuel injection device 701 according to a conventional example.
The fuel injection device 701 has a first fuel storage chamber 741, a second fuel storage chamber 742, a needle valve closing chamber 743, and an injection hole 745 extending from the second fuel storage chamber 742 to the outside of the fuel injection device 701. The nozzle body 740, the needle valve 710 held by the needle valve holding portion 746 inside the nozzle body 740, the closing auxiliary piston 730 provided inside the needle valve closing chamber 743 of the nozzle body 740, and the nozzle body 740 And an injection control valve 720 that is held by the injection control valve holding part 744 and can advance and retreat in the first fuel storage chamber 741.

  The nozzle body 740 includes a first fuel passage 751 extending from the fuel supply source to the first fuel storage chamber 741, a second fuel passage 752 extending from the first fuel storage chamber 741 to the second fuel storage chamber 742, and a first fuel storage chamber. A third fuel passage 753 from 741 to the needle valve closing chamber 743 and a fourth fuel passage 754 from the needle valve closing chamber 743 to the low pressure portion outside the fuel injection device 701 are formed.

The injection control valve 720 moves to the first position where the injection control valve 720 moves forward and contacts the inner wall of the first fuel storage chamber 741 on the third fuel passage 753 side. The housing chamber 741 is communicated, and the first fuel housing chamber 741 and the third fuel passage 753 are shut off. Further, the injection control valve 720 moves backward to the second position where the injection control valve 720 contacts the inner wall near the first fuel passage 751, thereby blocking the first fuel passage 751 and the first fuel storage chamber 741, and the first The fuel storage chamber 741 and the third fuel passage 753 are communicated.
The injection control valve 720 includes a substantially cylindrical guide portion 722 that can slide in the injection control valve holding portion 744, and a substantially disk-shaped bowl-shaped enlarged diameter portion 723 that is provided on the distal end side of the guide portion 722. And a substantially cylindrical closing portion 724 provided on the distal end side of the enlarged diameter portion 723.

  The needle valve 710 moves forward and is seated on the nozzle body 740, thereby blocking the second fuel storage chamber 742 and the injection hole 745, and retreating and separating from the nozzle body 740, thereby 742 and the nozzle hole 745 are communicated.

The operation of the fuel injection device 701 is as follows.
Fuel is supplied to the first fuel passage 751 from the fuel supply source. In this state, when the injection control valve 720 is advanced to the first position, the first fuel passage 751 and the first fuel storage chamber 741 communicate with each other, and the first fuel storage chamber 741 and the third fuel passage 753 are blocked. Is done. Therefore, fuel flows from the first fuel passage 751 through the first fuel storage chamber 741 and the second fuel passage 752 into the second fuel storage chamber 742, and the fuel pressure in the second fuel storage chamber 742 increases. Then, due to the fuel pressure in the second fuel storage chamber 742, the needle valve 710 moves backward and separates from the nozzle body 740. As a result, the fuel in the second fuel storage chamber 742 is injected from the injection hole 745.

  On the other hand, when the injection control valve 720 is retracted to the second position, the first fuel passage 751 and the first fuel storage chamber 741 are blocked, and the first fuel storage chamber 741 and the third fuel passage 753 communicate with each other. . Therefore, fuel flows from the second fuel passage 752 through the first fuel storage chamber 741 and the third fuel passage 753 into the needle valve closing chamber 743, and the fuel pressure in the needle valve closing chamber 743 increases. Then, the closing assist piston 730 advances due to the fuel pressure in the needle valve closing chamber 743. As the closing auxiliary piston 730 moves forward, the inside of the needle valve closing chamber 743 is partitioned by the closing auxiliary piston 730 into a closing auxiliary pressure chamber 7432 communicating with the third fuel passage 753 and a return pressure chamber 7433 on the needle valve 710 side. Is done. Further, the advanced closing assist piston 730 pushes the needle valve 710 forward. As a result, the needle valve 710 is seated on the nozzle body 740 and fuel injection stops.

At this time, the fuel in the closed auxiliary pressure chamber 7432 flows out into the return pressure chamber 7433 formed under the closed auxiliary piston 730 through the minute communication passage 7331 formed in the closed auxiliary piston 730. Then, as the fuel pressure in the closed auxiliary pressure chamber 7432 decreases, the closed auxiliary piston 730 moves backward toward the third fuel passage 753 and returns to the initial position.
Thus, when fuel injection is stopped (when the injection control valve 720 shifts from the first position to the second position), the fuel in the first fuel storage chamber 741 is transferred to the third fuel passage 753, the needle valve closing chamber 743, And outflow to the outside through the fourth fuel passage 754 is suppressed.

Japanese Patent Application No. 2008-159266

  In order to increase the number of fuel injections or shorten the injection interval, the needle valve 710 needs to be moved quickly. For this purpose, the closing assist piston 730 is operated after the needle valve 710 is pressed. Therefore, it is required to quickly retreat and return to the initial position. That is, the retraction of the closing auxiliary piston 730 is completed by the time when fuel injection is stopped after the fuel injection is stopped, and the closing auxiliary piston 730 blocks the third fuel passage 753 and the needle valve closing chamber 743. It needs to be in a state.

  Also in Patent Document 1, a minute communication path 7331 for returning the closing assist piston 730 to the initial position at an early stage is provided, but the minute communication path 7331 is in a state in which the closing assist pressure chamber 7432 and the return pressure chamber 7433 are always in communication. ing. Since the closing auxiliary piston 730 needs to advance by the pressure of the fuel flowing in from the third fuel passage 753 and press the needle valve 10, the fuel pressure necessary to advance the closing auxiliary piston 730 is obtained. Needs to maintain the inflowing fuel in the closed auxiliary pressure chamber 7432 to some extent. For this reason, the passage area of the minute communication passage 7331 cannot be increased to increase the amount of fuel passing therethrough.

  An object of the present invention is to provide a fuel injection device capable of quickly returning a closing assist piston to an initial position and performing efficient fuel injection control.

  (1) A fuel injection device of the present invention (for example, a fuel injection device 1 described later) includes a first fuel storage chamber (for example, a first fuel storage chamber 41 described later) and a second fuel storage chamber (for example, a first fuel storage device described later). 2 fuel storage chamber 42), a third fuel storage chamber (for example, a needle valve closing chamber 43 described later), and an injection hole (for example, an injection hole 45 described later) from the second fuel storage chamber to the outside of the fuel injection device. ) Formed in a nozzle body (for example, a nozzle body 40 described later) and a needle valve (for example, a needle valve holding unit 46 described later) formed in the nozzle body (for example, a needle valve) Needle valve 10), which will be described later, and needle valve opening means (for example, a second fuel storage chamber 42 which will be described later) provided on the tip side of the needle valve holding portion inside the nozzle body and having the second fuel storage chamber. Step 13 and A fuel reservoir portion 421) and a needle valve closing means (for example, a needle valve closing chamber 43, which will be described later), which is provided on the proximal end side with respect to the needle valve holding portion inside the nozzle body and has the third fuel storage chamber. An auxiliary piston 30) and an injection control valve (for example, an injection control valve 20 described later) that is held inside the nozzle body and can be advanced and retracted, and the nozzle body supplies fuel. A first fuel passage (for example, a first fuel passage 51 described later) from a source to the first fuel storage chamber, and a second fuel passage (for example, described later) from the first fuel storage chamber to the second fuel storage chamber Second fuel passage 52), a third fuel passage from the first fuel storage chamber to the third fuel storage chamber (eg, a third fuel passage 53 described later), and the fuel from the third fuel storage chamber. Low outside the injector A fourth fuel passage (for example, a fourth fuel passage 54 described later), and the injection control valve moves forward to the first position, whereby the first fuel passage and the first fuel storage And the first fuel storage chamber and the third fuel passage are shut off and retracted to the second position to shut off the first fuel passage and the first fuel storage chamber. The first fuel storage chamber communicates with the third fuel passage, and the needle valve advances and seats on the nozzle body, thereby shutting off the second fuel storage chamber and the injection hole, By retreating and separating from the nozzle body, the second fuel storage chamber communicates with the nozzle hole, and the needle valve opening means retracts the needle valve by the fuel pressure in the second fuel storage chamber. The needle valve closing / releasing means is The needle valve is advanced by the fuel pressure in the second fuel storage chamber, and the needle valve closing means is a closing auxiliary piston (for example, a closing auxiliary piston 30 described later) provided to be able to advance and retreat in the third fuel storage chamber. The closing auxiliary piston shuts off the third fuel passage and the third fuel storage chamber at the last retracted position, and shifts to the forward movement state to thereby move the third fuel passage and the third fuel storage chamber. The third fuel storage chamber is in a closed auxiliary pressure chamber (for example, a closing auxiliary pressure chamber 432 described later) that communicates with the third fuel passage by the closing auxiliary piston when the closing auxiliary piston moves forward. ) And a return pressure chamber (for example, a return pressure chamber 433 described later) that communicates with the fourth fuel passage, and the closing assist piston is a fuel in the closing assist pressure chamber. A pressing force due to pressure can be transmitted in the forward direction to the needle valve, and the closing assist piston moves from the advanced state to the last retracted position, and the third fuel passage and the closing assist pressure chamber And the fuel in the first fuel storage chamber is suppressed from flowing into the third fuel storage chamber through the third fuel passage, and the fuel in the first fuel storage chamber is prevented from flowing into the fuel. An outflow suppression means for suppressing outflow from the outside of the injection device, wherein the closing assist piston moves forward a predetermined distance in a wall portion forming the third fuel storage chamber in the nozzle body. A communication path (for example, a communication path 434 described later) that connects the pressure chamber and the return pressure chamber is provided.

According to the invention of (1), the operation of the fuel injection device is as follows.
That is, fuel is supplied from the fuel supply source to the first fuel passage. When the injection control valve is advanced to the first position in this state, the first fuel passage and the first fuel storage chamber communicate with each other, and the first fuel storage chamber and the third fuel passage are blocked. Therefore, fuel flows from the first fuel passage through the first fuel storage chamber and the second fuel passage into the second fuel storage chamber, and the fuel pressure in the second fuel storage chamber increases. Then, the needle valve opening means operates, and the needle valve is retracted by the fuel pressure in the second fuel storage chamber and is separated from the nozzle body. Thereby, the fuel in the second fuel storage chamber is injected from the injection hole. At this time, the closing assist piston of the needle valve closing means is in a state of blocking the third fuel passage and the closing assist pressure chamber in the third fuel storage chamber.

  On the other hand, when the injection control valve is retracted to the second position, the first fuel passage and the first fuel storage chamber are shut off, and the first fuel storage chamber and the third fuel passage communicate with each other. Accordingly, the fuel flows into the closing auxiliary pressure chamber of the third fuel holding chamber through the first fuel holding chamber and the third fuel passage, the fuel pressure in the closing auxiliary pressure chamber rises, and a pressing force against the closing auxiliary piston is generated. To do. Then, the closing assist piston moves forward and transmits the pressing force by the fuel pressure in the closing assist pressure chamber to the needle valve, and the needle valve moves forward. As a result, the needle valve is seated on the nozzle body, and fuel injection stops.

At this time, when the closing auxiliary piston moves forward by a predetermined distance, a communication passage formed in the wall portion forming the third fuel storage chamber communicates the closing auxiliary pressure chamber and the return pressure chamber. Then, the fuel in the closed auxiliary pressure chamber flows out from the closed auxiliary pressure chamber to the return pressure chamber through the communication path. Thus, the closing auxiliary pressure chamber and the return pressure chamber are not communicated by the communication path until the closing assist piston moves forward by a predetermined distance. Therefore, the fuel pressure in the closing assist pressure chamber is unlikely to decrease until the closing assist piston communicates by the communication path. Therefore, the closing assist piston can be reliably advanced by the fuel pressure in the closing assist pressure chamber to press the needle valve, and the needle valve can be advanced quickly and surely by a predetermined distance.
Further, when the closing auxiliary piston moves forward by a predetermined distance and the closing auxiliary pressure chamber communicates with the return pressure chamber, the fuel in the closing auxiliary pressure chamber quickly flows out into the return pressure chamber, and the fuel pressure in the closing auxiliary pressure chamber rapidly increases. And the pressing force with which the auxiliary closing piston advances the needle valve also decreases rapidly. As a result, the closing assist piston can quickly move to the last retracted position, which is the initial position.
As described above, since the closing auxiliary piston and the needle valve can be moved forward and backward quickly and reliably, the fuel injection by the fuel injection device can be controlled accurately and the fuel injection device can be controlled. It is possible to shorten the fuel injection interval when the fuel injection is continuously performed a plurality of times.
Further, since the closing auxiliary piston can quickly return to the last retracted position, which is the initial position, by the communication passage, the third fuel passage and the needle valve closing chamber can be quickly shut off, and the fuel flows out from the fourth fuel passage to the outside. The amount of fuel to be reduced can be reduced.

  (2) When the closing auxiliary piston moves forward by the predetermined distance and the communication path connects the closing auxiliary pressure chamber and the return pressure chamber, the injection amount from the injection hole is half of the maximum injection amount. 1 or less.

According to the invention of (2), the communication path of the fuel injection device communicates between the closed auxiliary pressure chamber and the return pressure chamber because the injection amount from the injection hole is less than half of the maximum injection amount. Sometimes.
If the closing auxiliary pressure chamber communicates with the return pressure chamber before the injection amount from the nozzle hole becomes half of the maximum injection amount, the fuel pressure in the closing auxiliary pressure chamber that presses the closing auxiliary piston decreases. As a result, the retracting of the closing auxiliary piston is started, and the retraction of the needle valve may be started before the needle valve is seated on the nozzle body.
By making the closed auxiliary pressure chamber and the return pressure chamber communicate with each other through the communication path less than one half of the maximum injection amount, the needle valve can surely reach the most advanced position and the injection from the nozzle hole is stopped. In addition, the closing assistance piston can be quickly moved to the last retracted position, which is the initial position.

  (3) When the closing auxiliary piston is located at the most advanced position, the communication path has an end on the return pressure chamber side in the communication path that is a sliding portion of the closing auxiliary piston (for example, a partition described later). The portion 33) is formed so as to be positioned closer to the needle valve side than the end portion on the return pressure chamber side.

  According to the invention of (3), when the closing assist piston is located at the most advanced position, the end of the return passage on the return pressure chamber side of the communicating passage is on the return pressure chamber side in the sliding portion of the closing assist piston. It was made to be located in the needle valve side rather than the edge part. As a result, even when the closing assist piston is located at the most advanced position, the end of the communication passage on the return pressure chamber side is not blocked, and the pressure in the closing assist pressure chamber can be reliably reduced.

  (4) The closing assist piston further includes a minute communication path (for example, a minute communication path 331 described later) that communicates the closing assist pressure chamber and the return pressure chamber.

  According to the invention of (4), the closing auxiliary piston further has a minute communication path that connects the closing auxiliary pressure chamber and the return pressure chamber. Thereby, the fuel in the closed auxiliary pressure chamber is allowed to flow out to the return pressure chamber through the minute communication path, so that the closed auxiliary piston can be reliably retracted to the last retracted position that is the initial position. Therefore, the third fuel passage and the needle valve closing chamber can be quickly shut off, and the flow rate of the fuel flowing out from the fourth fuel passage can be further reduced.

  (5) The closing assist piston includes a plurality of the communication passages and the minute communication passages, and each of the plurality of communication passages and the minute communication passages in a cross-sectional view perpendicular to the advancing / retreating direction of the closing assist piston. Are equally arranged in the circumferential direction.

  According to the invention of (5), the closing assist piston is provided with a plurality of communication passages and a plurality of minute communication passages. Further, in the cross-sectional view perpendicular to the advance / retreat direction of the closing assist piston, the plurality of communication passages and the minute communication passages are equally arranged in the circumferential direction. Thereby, the passage of the fuel in the minute communication passage can be made smooth, and by arranging the plurality of passages equally in the circumferential direction, the closing auxiliary piston is pressed in one direction in the third fuel storage chamber, and is advanced and retracted. It can suppress that the movement of a direction is inhibited.

  (6) The communication path is formed by denting a part of the inner peripheral surface of the wall portion forming the third fuel storage chamber, and the micro communication path is a part of the outer peripheral surface of the closing assist piston. It is formed by denting.

  According to the invention of (6), the communication passage is formed by denting a part of the inner peripheral surface of the wall portion forming the third fuel storage chamber, and the micro communication passage is formed on the outer peripheral surface of the closing auxiliary piston. It was supposed to be formed with the part recessed. Therefore, the communication path and the minute communication path are formed as grooves on the inner peripheral surface of the third fuel storage chamber and the outer peripheral surface of the closing assist piston. For this reason, processing and manufacture become easier than forming as a hole inside each member, and a communicating path or a minute communicating path can be formed with high processing accuracy.

  (7) The number of the communication paths and the number of the micro communication paths do not have a common prime factor.

According to the invention of (7), the number of communication passages and the number of minute communication passages do not have a common prime factor. Thereby, it is possible to suppress the communication path and the minute communication path from having the same position in the circumferential direction at a maximum of one place.
When the communication path and the minute communication path are in the same position in the circumferential direction, the communication between the close auxiliary pressure chamber and the return pressure chamber when the close auxiliary piston moves forward by a predetermined distance is compared with the case where the communication is not the same position. The size of the entire passage is increased. For example, when the number of communication paths is the same number, a multiple, or a divisor with respect to the number of micro communication paths, the number of communication paths and micro communication paths at the same position is plural, and the closed auxiliary pressure chamber and the return There may be an excessive communication with the pressure chamber and an excessive pressure drop in the closed auxiliary pressure chamber. Then, the needle valve pressed by the closing assist piston reaches the most advanced position, and the needle valve may start to be retracted before the injection from the injection hole stops. In this way, by preventing the number of communication paths and the number of micro communication paths from having a common prime factor, the communication path and the micro communication path are at the same position in the circumferential direction at a maximum of one place. Can be suppressed.

  (8) The total cross-sectional area of the communication path is formed to be larger than the total cross-sectional area of the minute communication path.

  According to the invention of (8), the total cross-sectional area of the communication path is made larger than the total cross-sectional area of the minute communication path. By reducing the total cross-sectional area of the micro communication path, the closed auxiliary pressure chamber and the return pressure chamber are always in communication, so that the closing auxiliary piston moves forward and presses the needle valve in the forward direction. It is possible to prevent the pressure in the pressure chamber from dropping too much. Further, by increasing the total cross-sectional area of the communication passage, the pressure in the closing auxiliary pressure chamber can be quickly reduced when communicating. As a result, the closing assist piston can reliably push the needle valve so as to advance to the most advanced position, and the closing assist piston can be quickly moved to the last retracted position, which is the initial position.

  (9) An elastic member (for example, a spring to be described later) disposed between the closing auxiliary piston and the needle valve in the third fuel storage chamber and biasing in a direction in which the closing auxiliary piston and the needle valve are separated from each other. 31) is further provided.

  According to the invention of (9), the elastic member is arranged between the closing assist piston and the needle valve. The elastic member biases the closing assist piston and the needle valve in a direction away from each other. As a result, the closing auxiliary piston can be quickly retracted to the last retracted position, which is the initial position, so that the third fuel passage and the closing auxiliary pressure chamber can be quickly shut off, so that the flow rate of the fuel flowing out from the fourth fuel passage can be reduced. It can be reduced more.

  (10) The elastic member includes an annular elastic adjustment portion (for example, an elastic adjustment portion 311 described later) on the elastic member on the contact portion side of the auxiliary closing piston.

  According to the invention of (10), the elastic member is provided with the annular elastic adjustment portion on the contact portion side of the elastic member with the auxiliary closing piston. By providing the elastic adjustment part on the needle valve side, the inertia weight of the needle valve is increased, and the forward / backward movement of the needle valve can be suppressed from becoming dull.

  (11) The micro communication path is formed so that the position of the end portion on the return pressure chamber side in the micro communication path does not coincide with the position of the elastic adjustment section.

  According to the invention of (11), the minute communication passage is formed so that the position of the return pressure chamber side end portion in the minute communication passage does not coincide with the position of the elastic adjustment portion. Thereby, it can suppress that the communication state of the closing auxiliary | assistant pressure chamber and return pressure chamber by a microcommunication channel changes because the microcommunication channel and the position of an elastic adjustment part correspond.

  According to the present invention, it is possible to provide a fuel injection device that can quickly return the closing auxiliary piston to the last retracted position, which is the initial position, and perform efficient fuel injection control.

It is sectional drawing which shows the structure of the fuel-injection apparatus which concerns on one Embodiment of this invention. It is an expanded sectional view of the needle valve closed chamber of the fuel injection device concerning the embodiment. It is the figure which showed the relationship between the injection quantity from the nozzle hole of the fuel-injection apparatus which concerns on the said embodiment, and the movement amount of a needle valve. It is AA sectional drawing of FIG. FIG. 6 is a diagram (No. 1) for explaining the operation of the fuel injection device according to the embodiment; FIG. 6 is a diagram (No. 2) for explaining the operation of the fuel injection device according to the embodiment; FIG. 6 is a view (No. 3) for explaining the operation of the fuel injection device according to the embodiment. It is an expanded sectional view of the needle valve closed chamber of the fuel injection device concerning a 2nd embodiment of the present invention. It is an expanded sectional view of the needle valve closed chamber of the fuel injection device concerning a 3rd embodiment of the present invention. It is an expanded sectional view of the needle valve closed room of the fuel injection device concerning a 4th embodiment of the present invention. It is sectional drawing which shows the structure of the fuel-injection apparatus which concerns on the prior art example of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
An overall outline of the fuel injection device 1 will be described with reference to FIG.
FIG. 1 is a cross-sectional view showing a configuration of a fuel injection device 1 according to an embodiment of the present invention. 1, 2, and 5 to 7 below, the movement stroke amounts and dimensions of the needle valve 10, the injection control valve 20, and the closing assist piston 30 are exaggerated from the actual ones for easy understanding. It is drawn.

The fuel injection device 1 is accommodated in a housing (not shown), and injects fuel supplied at a high pressure from a fuel supply source according to the operation of the actuator 60.
The fuel injection device 1 includes a needle valve 10, an injection control valve 20, a spring 21 that biases the injection control valve, a closing assist piston 30 as a needle valve closing means, and a biasing force for the closing assist piston 30. A spring 31 serving as an elastic member, and a cylindrical nozzle body 40 that accommodates the spring 31.

  The nozzle body 40 is composed of three members, and the nozzle body 40 includes a first fuel storage chamber 41, a needle valve closing means, and a third fuel in order from the proximal end side to the distal end side. A needle valve closing chamber 43 as a storage chamber and a second fuel storage chamber 42 as a needle valve opening means are formed.

The nozzle body 40 includes a first fuel passage 51 extending from a fuel supply source (not shown) to the first fuel storage chamber 41, a second fuel passage 52 extending from the first fuel storage chamber 41 to the second fuel storage chamber 42, A third fuel passage 53 extending from the one fuel storage chamber 41 to the needle valve closing chamber 43 and a fourth fuel passage 54 extending from the needle valve closing chamber 43 to a low pressure portion (not shown) outside the nozzle body 40 are formed.
Here, examples of the fuel supply source include a high-pressure pump connected via a common rail.
Examples of the low pressure section include a fuel tank, a fuel passage between the low pressure pump and the high pressure pump, and a fuel passage upstream of the pressurizing chamber in the high pressure pump.

The first fuel storage chamber 41 is a substantially cylindrical space extending along the extending direction of the nozzle body 40.
A through hole having a circular cross section reaching the base end surface of the nozzle body 40 is formed in the base end surface of the first fuel storage chamber 41, and this through hole includes an injection control valve holding portion 44 that holds the injection control valve 20 and It has become.
The inner diameter of the injection control valve holding portion 44 is smaller than the inner diameter of the first fuel storage chamber 41, whereby a step portion 411 is formed on the base end surface of the first fuel storage chamber 41.

  The first fuel passage 51 extends from the proximal end surface of the nozzle body 40 to the inner peripheral surface on the distal end side of the through hole that is the injection control valve holding portion 44.

The needle valve closing chamber 43 is a substantially cylindrical space extending along the extending direction of the nozzle body 40. A stepped portion 431 is formed on the distal end side of the needle valve closing chamber 43 along the circumferential direction. The needle valve closing chamber 43 is formed with a communication passage 434 in which a part of the inner peripheral surface of the wall portion of the needle valve closing chamber 43 is recessed. Details will be described later.
The third fuel passage 53 is a through hole that extends from approximately the center of the distal end surface of the first fuel storage chamber 41 to approximately the center of the proximal end surface of the needle valve closing chamber 43.
The fourth fuel passage 54 extends from the inner peripheral surface on the distal end side of the needle valve closing chamber 43 to the proximal end surface of the nozzle body 40 and is connected to a low pressure portion (not shown).

The second fuel storage chamber 42 is a substantially cylindrical space that is formed on the tip side of the needle valve closing chamber 43 and extends along the extending direction of the nozzle body 40.
A through hole extending to the outside of the nozzle body 40 is formed on the distal end side of the second fuel storage chamber 42, and this through hole is a nozzle hole 45.
On the proximal end side in the extending direction of the second fuel storage chamber 42, a fuel reservoir portion 421 is formed as a needle valve opening means whose inner periphery is expanded.

A through hole from the needle valve closing chamber 43 to the second fuel storage chamber 42 is formed in the nozzle body 40, and this through hole serves as a needle valve holding portion 46 that holds the needle valve 10.
The second fuel passage 52 extends from the inner peripheral surface of the portion on the tip side of the step portion 411 of the first fuel storage chamber 41 to the fuel reservoir portion 421 of the second fuel storage chamber 42.

The needle valve 10 is held by a needle valve holding portion 46 of the nozzle body 40, and the distal end side of the needle valve 10 extends in the second fuel storage chamber 42 along the extending direction of the second fuel storage chamber 42. It is possible to advance and retreat.
The needle valve 10 includes a cylindrical needle valve main body 11 that is slidably held by the needle valve holding portion 46, and a movement restricting portion 12 that is formed in a bowl shape on the proximal end side of the needle valve main body 11. Prepare.

The proximal end side of the needle valve main body 11 with respect to the needle valve holding portion 46 is exposed in the needle valve closing chamber 43.
The movement restricting portion 12 is formed in a portion of the needle valve main body 11 exposed in the needle valve closing chamber 43.

  The outer diameter of the movement restricting portion 12 of the needle valve 10 is larger than the inner diameter of the portion closer to the proximal end than the stepped portion 431 of the needle valve closing chamber 43. Therefore, when the needle valve 10 is retracted, the movement restricting portion 12 hits the stepped portion 431, and the retreat of the needle valve 10 is restricted.

A step portion 13 as a needle valve opening means is formed in a ring shape along the circumferential direction in a portion of the outer peripheral surface of the needle valve main body 11 located in the vicinity of the fuel reservoir portion 421.
The outer diameter of the portion on the distal end side of the step portion 13 of the needle valve body 11 is smaller than the outer diameter of the portion on the proximal end side of the step portion 13 of the needle valve body 11. A gap through which fuel flows is formed between the outer peripheral surface of the tip side of the step portion 13 and the inner peripheral surface of the second fuel storage chamber 42.

  In the needle valve 10 described above, the distal end surface of the needle valve main body 11 is separated from the distal end side of the second fuel storage chamber 42, so that the fuel reservoir portion 421 of the second fuel storage chamber 42 and the injection hole 45 communicate with each other. When the tip end surface of the needle valve main body 11 is seated on the tip end side of the second fuel storage chamber 42, the fuel reservoir portion 421 and the injection hole 45 of the second fuel storage chamber 42 are shut off.

Details of each part will be described below.
The injection control valve 20 is held by the injection control valve holding portion 44 of the nozzle body 40, and the inside of the first fuel storage chamber 41 is extended by the piezoelectric actuator 60 along the extending direction of the first fuel storage chamber 41. It is possible to advance and retreat.
The injection control valve 20 includes a columnar injection control valve main body 22 and a passage closing portion 23 formed in a bowl shape on the injection control valve main body 22.
The passage closing portion 23 is formed in a portion of the injection control valve main body 22 exposed to the first fuel storage chamber 41.
The injection control valve main body 22 is slidably held by the injection control valve holding portion 44. A reduced diameter portion 221 is formed in a portion from the portion facing the first fuel passage 51 to the passage closing portion 23 on the outer peripheral surface of the injection control valve main body 22.

  The spring 21 is provided between the front end surface of the first fuel storage chamber 41 and the passage closing portion 23 of the injection control valve 20 and biases the injection control valve 20 in the backward direction.

The state in which the above injection control valve 20 moves forward against the biasing force of the spring 21 and the front end surface of the injection control valve main body 22 is in contact with the front end surface of the first fuel storage chamber 41 is The first position.
When the injection control valve 20 is positioned at the first position, the front end surface of the injection control valve main body 22 abuts on the front end surface of the first fuel storage chamber 41, and the step portion 411 between the passage closing portion 23 and the first fuel storage chamber 41. A gap is formed between the two.

  Since the first fuel passage 51 communicates with the distal end side of the through hole that is the injection control valve holding portion 44, and the third fuel passage 53 communicates with the distal end surface of the first fuel storage chamber 41, in this state The first fuel storage chamber 41 and the third fuel passage 53 are blocked, and the first fuel passage 51 and the first fuel storage chamber 41 are communicated with each other.

On the other hand, the state where the injection control valve 20 is retracted and the passage closing portion 23 is in contact with the step portion 411 of the first fuel storage chamber 41 is defined as the second position of the injection control valve 20.
When the injection control valve 20 is located at the second position, the front end surface of the injection control valve main body 22 and the front end surface of the first fuel storage chamber 41 are separated from each other to form a gap, and the passage closing portion 23 serves as the first fuel. It abuts on the step portion 411 of the storage chamber 41. In this state, the first fuel passage 51 and the first fuel storage chamber 41 are blocked, and the first fuel storage chamber 41 and the third fuel passage 53 are communicated.
FIG. 1 shows a state where the injection control valve 20 is located at the second position.

  The inside of the needle valve closing chamber 43 will be described in detail with reference to FIGS. FIG. 2 is an enlarged cross-sectional view of the needle valve closing chamber 43. FIG. 3 is a diagram showing the relationship between the injection amount from the injection hole 45 of the fuel injection device 1 and the movement amount of the needle valve 10. FIG. 4 is an enlarged view showing the positional relationship between the closing auxiliary piston 30 and the communication passage 434 of the fuel injection device 1.

  The needle valve closing chamber 43 includes a closing auxiliary piston 30, a spring 31 that biases the closing auxiliary piston 30 toward the proximal end side of the nozzle body 40, and the needle valve closing chamber 43 within the needle valve closing chamber 43 on the proximal end side of the nozzle body 40. A closed auxiliary pressure chamber 432 formed, a return pressure chamber 433 formed in the needle valve closing chamber 43 on the front end side of the nozzle body 40, and a communication passage 434 formed in the inner wall of the needle valve closing chamber 43 Have.

  The closing assist piston 30 is provided so as to be able to advance and retreat in the needle valve closing chamber 43, and has a substantially cylindrical partition portion 33 that slides on the inner wall surface of the needle valve closing chamber 43, and the needle valve 10 side of the partition portion 33. And an auxiliary force transmission portion 32 extending in a rod shape from the end portion.

  The closing auxiliary pressure chamber 432 and the return pressure chamber 433 are formed by being partitioned by the partition portion 33 of the advanced closing auxiliary piston 30 in the needle valve closing chamber 43. Further, the auxiliary closing pressure chamber 432 located on the proximal end side with respect to the partition portion 33 communicates with the third fuel passage 53, and the return pressure chamber 433 located on the distal end side with respect to the partition portion 33 communicates with the fourth fuel passage 54. To do.

A portion on the base end side of the partition portion 33 has a substantially conical shape protruding toward the third fuel passage 53 side.
In addition, the partition portion 33 is formed with a minute communication path 331 that allows the closing auxiliary pressure chamber 432 and the return pressure chamber 433 to communicate with each other (see FIG. 4). The minute communication path 331 is formed between the closing assist piston 30 and the needle valve closing chamber 43 by denting the outer peripheral surface of the partition portion 33 of the closing assist piston 30. The closing assist piston 30 is rotatable within the needle valve closing chamber 43. For this reason, the position of the minute communication path 331 and the position of the communication path 434 may coincide with each other (the lower left state in FIG. 4) and may not coincide. Although FIG. 1 and FIG. 2 do not show the micro communication path 331, as shown on the right side of FIG. 4, a cross section in which the micro communication path 331 and the communication path 434 do not coincide is shown. In FIG. 4, the dimensions of the minute communication path 331 and the communication path 434 are exaggerated from the actual size for easy understanding.

  The spring 31 is provided between the closing assist piston 30 in the needle valve closing chamber 43 and the proximal end side of the needle valve 10, and biases the closing assist piston 30 and the needle valve 10 in a separating direction.

The communication passage 434 is formed by denting a part of the inner peripheral surface of the wall portion of the needle valve closing chamber 43 over a predetermined length along the advance / retreat direction of the closing assist piston 30.
The communication passage 434 is formed at a position where the close assist pressure chamber 432 and the return pressure chamber 433 communicate with each other when the close assist piston 30 moves forward by a predetermined distance.
In addition, the communication passage 434 has a partition portion even when the end of the communication passage 434 on the return pressure chamber 433 side is located at the most advanced position (when the closing auxiliary piston 30 is in the mode shown in FIG. 2). It is formed so as to be positioned closer to the needle valve 10 than the end portion of the 33 return pressure chamber 433 side.

Similarly, the end of the communication passage 434 on the side of the auxiliary closing pressure chamber 432 has a third fuel passage 53 more than the end of the partition portion 33 on the side of the auxiliary closing pressure chamber 432 when the auxiliary closing piston 30 advances a predetermined distance. It is formed to be located on the side. More specifically, the end of the communication passage 434 on the closing auxiliary pressure chamber 432 side is such that after the needle valve 10 is retracted and fuel injection is started from the injection hole 45, the needle valve 10 starts to advance again. When the fuel injection amount from the nozzle hole 45 is less than or equal to one-half of the maximum injection amount, and preferably less than one-tenth, it is more than the end of the partition portion 33 on the closing auxiliary pressure chamber 432 side. 3 is formed so as to be positioned on the fuel passage 53 side (see FIG. 3).
In other words, the communication passage 434 has a closed auxiliary pressure chamber 432 and a return pressure chamber when the fuel injection amount from the injection hole 45 is less than or equal to one half of the maximum injection amount, preferably less than one tenth. It is formed at a position where 433 communicates.
When the fuel injection amount from the nozzle hole 45 is at least one-half or less of the maximum injection amount, the needle valve 10 has advanced a predetermined distance, and the tip of the needle valve 10 and the nozzle hole 45 The pressure in the space between is also low. For this reason, since the pressure in the space pushes the needle valve 10 in the backward direction is sufficiently weak, the fuel pressure in the closed auxiliary pressure chamber 432 is made to communicate with the closed auxiliary pressure chamber 432 by communicating with the return auxiliary pressure chamber 433. Even if the closing assist piston 30 weakens the force that pushes the needle valve 10 in the forward direction, the needle valve 10 can move forward quickly.

With reference to FIG. 4, the relationship between the minute communication path 331 and the communication path 434 will be described.
It is preferable that two or more micro communication paths 331 are formed evenly in the circumferential direction. This is to balance the pressure. For example, when only one minute communication passage 331 is formed in the closing assist piston 30, the cross-sectional area greatly changes within the tolerance range in which the minute communication passage 331 is formed, and the amount of fuel passing through the minute communication passage 331. This is because may change.

  It is preferable that two or more communication paths 434 are formed evenly in the circumferential direction. When the number of the communication passages 434 is one or is formed so as to be biased in the circumferential direction, the closing assist piston 30 is caused to be in the inner wall of the needle valve closing chamber 43 by a pressure difference between the communication passage 434 portion and the other portions. This is because the movement of the closing assisting piston 30 is suppressed because it is pressed against the portion.

  The numbers of the micro communication paths 331 and the communication paths 434 are preferably numbers that do not have a common prime factor. Specifically, as shown in FIG. 4, when two micro communication paths 331 are formed, three communication paths 434 are formed. For example, when two micro communication paths 331 and two communication paths 434 are formed, the closing assist piston 30 rotates in the needle valve closing chamber 43, and the two micro communication paths 331 and two The communication path 434 may overlap each other at the same time. In such a case, the size of the entire communication path is increased and the amount of fuel passing therethrough is increased, so that the pressure in the closed auxiliary pressure chamber 432 is excessively reduced. For this reason, in the closing auxiliary pressure chamber 432, the closing auxiliary piston 30 is advanced to press the needle valve 10 and the load for moving the needle valve 10 forward may be insufficient. It is necessary to reduce the possibility that the minute communication path 331 and the communication path 434 overlap each other as much as possible.

  In the present embodiment, as shown in FIG. 4, two micro communication paths 331 are formed at positions facing each other, and the communication paths 434 are equally 3 in the circumferential direction on the inner peripheral surface of the needle valve closing chamber 43. Formed. In this case, even when the closing assist piston 30 rotates in the needle valve closing chamber 43, the minute communication path 331 and the communication path 434 overlap at only one place at the maximum. Moreover, since the size per one of the micro communication path 331 and the communication path 434 can be reduced as the number of formations increases, even if the micro communication path 331 and the communication path 434 overlap, the closing assist piston 30 A large change in behavior can be avoided.

  Further, when a plurality of the micro communication paths 331 and the communication paths 434 are formed, it is preferable that the total cross sectional area of the communication paths 434 is larger than the total cross sectional area of the micro communication paths 331.

The above-mentioned closing assist piston 30 operates as follows (see FIGS. 1 and 4).
That is, first, the injection control valve 20 is located at the first position, the first fuel storage chamber 41 and the third fuel passage 53 are shut off, and the position where the closing auxiliary piston 30 is most retracted by the spring 31. It is assumed that the conical portion of the partition portion 33 closes the third fuel passage 53 on the base end surface of the needle valve closing chamber 43. This state is the last retracted position of the closing assist piston 30.

In the state where the closing auxiliary piston 30 is located at the last retracted position, the conical portion of the partition portion 33 closes the third fuel passage 53 and blocks the third fuel passage 53 and the closing auxiliary pressure chamber 432. At this time, the communication path 434 does not connect the closing auxiliary pressure chamber 432 and the return pressure chamber 433.
Further, in the state where the closing assist piston 30 is located at the last retracted position, even if the needle valve 10 is retracted until it is regulated by the movement restricting portion 12, the tip surface of the assist force transmitting portion 32 of the closing assist piston 30 and the needle The movement strokes and lengths of the closing assist piston 30 and the needle valve 10 are set so that a gap is formed between the base end surface of the valve 10 and the valve 10.

Next, when the injection control valve 20 moves backward from the first position, the first fuel storage chamber 41 and the third fuel passage 53 communicate with each other, and the fuel in the first fuel storage chamber 41 flows into the third fuel passage 53.
The second fuel passage 52 and the third fuel passage 53 communicate with each other, and the fuel in the second fuel passage 52 flows into the third fuel passage 53.
Then, due to the fuel pressure in the third fuel passage 53, the closing auxiliary piston 30 moves forward against the biasing force of the spring 21, and the distal end surface of the auxiliary force transmitting portion 32 comes into contact with the proximal end surface of the needle valve 10.

In this state, the fuel in the third fuel passage 53 flows into the closing auxiliary pressure chamber 432 of the needle valve closing chamber 43, and the fuel pressure in the fuel reservoir portion 421 of the second fuel storage chamber 42 and the needle valve closing chamber. The fuel pressure in the 43 closed auxiliary pressure chambers 432 is equal.
Then, the conical portion of the partition portion 33 of the closing assist piston 30 receives the fuel pressure from the closing assist pressure chamber 432 as a pressure receiving portion, so that the needle valve 10 moves forward through the closing assist piston 30. Power is added to.
At the same time, the annular step portion 13 of the needle valve 10 receives the fuel pressure from the fuel reservoir portion 421 as a pressure receiving portion, so that a force is applied to the needle valve 10 in the backward direction.

  Here, the maximum diameter of the partition portion 33 of the closing assist piston 30 is larger than the maximum diameter of the step portion 13 of the needle valve 10, and the pressure receiving area of the partition portion 33 of the close assist piston 30 is the step portion 13 of the needle valve 10. It is larger than the pressure receiving area. Therefore, the force for moving the closing assist piston 30 forward becomes larger than the force for moving the needle valve 10 backward, and the proximal end side of the needle valve 10 is pressed by the distal end surface of the assist force transmitting portion 32 of the closing assist piston 30. The needle valve 10 is advanced.

  At this time, the fuel that has flowed into the closing auxiliary pressure chamber 432 gradually flows out to the return pressure chamber 433 through the minute communication path 331 (see FIG. 4). Further, when the closing assist piston 30 advances the needle valve 10 to advance to a position where the injection amount from the nozzle hole 45 is at least half or less, the closing assist pressure chamber 432 and the return pressure chamber 433 are connected. The passage 434 communicates. Then, the fuel in the closing auxiliary pressure chamber 432 flows out into the return pressure chamber 433 through the communication passage 434 at a stretch, and the fuel pressure in the closing auxiliary pressure chamber 432 rapidly decreases. Retreat quickly due to power.

Hereinafter, the operation of the fuel injection device 1 will be described with reference to FIGS.
ST1 is in an initial state as shown in FIG. That is, fuel is supplied from the fuel supply source to the first fuel passage 51 at a high pressure, and the injection control valve 20 is moved backward by the urging force of the spring 21 to be in the second position. As a result, the passage closing portion 23 of the injection control valve 20 contacts the step portion 411 of the first fuel storage chamber 41, so that the high-pressure fuel in the first fuel passage 51 is separated from the reduced diameter portion 221 of the injection control valve 20. It remains in the gap with the inner peripheral surface of the injection control valve holding portion 44.

  Further, the urging force of the spring 31 causes the needle valve 10 to move forward and be seated on the front end side of the second fuel storage chamber 42, and the closing assist piston 30 moves backward and is located at the last retracted position so as to pass through the third fuel passage 53. It is closed. As a result, the fuel that has flowed in by the previous injection operation is confined in the second fuel storage chamber 42, the second fuel passage 52, the first fuel storage chamber 41, and the third fuel passage 53 at a certain pressure. At this time, the communication passage 434 is not in a state where the auxiliary closing pressure chamber 432 and the return pressure chamber 433 communicate with each other.

  In ST2, when the actuator 60 is driven from this state as shown in FIG. 5B, the injection control valve 20 moves forward and is positioned at the first position in resistance to the urging force of the spring 21.

Then, the front end surface of the injection control valve main body 22 contacts the front end surface of the first fuel storage chamber 41 and the first fuel storage chamber 41 and the third fuel passage 53 are shut off. The supply of high-pressure fuel is cut off.
Further, since the passage closing portion 23 is separated from the step portion 411 of the first fuel storage chamber 41 and a gap is formed between the passage closing portion 23 and the step portion 411 of the first fuel storage chamber 41, the first fuel The high-pressure fuel in the passage 51 passes through the gap between the reduced diameter portion 221 of the injection control valve 20 and the inner peripheral surface of the injection control valve holding portion 44, the first fuel storage chamber 41, and the second fuel passage 52, The fuel flows into the fuel reservoir 421 of the second fuel storage chamber 42. As described above, since the fuel in the fuel reservoir portion 421 is already at a certain pressure, the fuel pressure in the second fuel storage chamber 42 is increased by supplying high-pressure fuel in the first fuel passage 51. It rises.

  In ST3, as shown in FIG. 5 (c), as the fuel pressure in the fuel reservoir portion 421 increases, the annular step portion 13 of the needle valve 10 serves as a pressure receiving portion and the fuel pressure from the fuel reservoir portion 421. In response, a force for reversing the needle valve 10 is applied, and the needle valve 10 gradually retreats.

  In ST4, as shown in FIG. 6A, when the fuel pressure in the fuel reservoir 421 reaches a predetermined pressure, the movement restricting portion 12 of the needle valve 10 is stepped by the fuel pressure in the fuel reservoir 421. The needle valve 10 moves backward against the spring 31 until it hits the portion 431. Thereby, the needle valve 10 is separated from the front end side of the second fuel storage chamber 42, and the fuel in the second fuel storage chamber 42 is injected through the injection hole 45.

In ST5, the driving of the actuator 60 is stopped and the pressing force on the injection control valve 20 is released. Then, as shown in FIG. 6 (b), the injection control valve 20 moves backward and is positioned at the second position by the biasing force of the spring 21. Then, the passage closing portion 23 comes into contact with the step portion 411 of the first fuel storage chamber 41 and closes the injection control valve holding portion 44. As a result, the first fuel passage 51 and the first fuel storage chamber 41 are blocked, and the first fuel storage chamber 41 and the third fuel passage 53 communicate with each other. Therefore, the fuel in the first fuel storage chamber 41 flows into the third fuel passage 53 through the gap between the front end surface of the injection control valve body 22 and the front end surface of the first fuel storage chamber 41, and the third fuel passage The pressure in 53 rises.
At this time, since the closing auxiliary piston 30 is located at the last retracted position, the third fuel passage 53 is closed by the partition 33, but due to the fuel pressure flowing into the third fuel passage 53, Of the conical portion of the partition portion 33, the portion exposed to the third fuel passage 53 is pressed, and the closing assist piston 30 starts to advance.

In ST6, as shown in FIG. 6C, the closing assist piston 30 has moved forward, so that the blocking of the third fuel passage 53 by the partition 33 is released, and the fuel that has flowed into the third fuel passage 53 is closed by the needle valve. It flows into the closing auxiliary pressure chamber 432 of the chamber 43 and the pressure in the closing auxiliary pressure chamber 432 rises. When the pressure inside the closed auxiliary pressure chamber 432 reaches a predetermined pressure, the entire conical portion of the partition 33 is pressed by the fuel pressure flowing into the closed auxiliary pressure chamber 432, and the closed auxiliary piston 30 moves forward. Then, the distal end surface of the auxiliary force transmitting portion 32 of the closing assist piston 30 comes into contact with the proximal end surface of the needle valve 10.
Here, the force applied in the direction in which the closing assist piston 30 moves forward is more than the force applied in the direction in which the fuel in the fuel reservoir portion 421 of the second fuel storage chamber 42 presses the step portion 13 and moves backward to the needle valve 10. Is also big. Accordingly, the advancement of the needle valve 10 is started as the closing assist piston 30 moves forward.

In ST7, as shown in FIG. 7A, the closing assist piston 30 moves forward together with the needle valve 10. As the needle valve 10 moves forward, the fuel injection amount from the nozzle hole 45 gradually decreases.
Here, the fuel that has flowed into the closing auxiliary pressure chamber 432 from the third fuel passage 53 gradually flows out into the return pressure chamber 433 through the minute communication passage 331 (see FIG. 4) formed in the partition portion 33. . In addition, when the closing assist piston 30 and the needle valve 10 advance by a predetermined distance, the closing assist pressure chamber 432 and the return pressure chamber 433 communicate with each other through the communication passage 434. The communication path 434 communicates when the fuel injection amount from the injection hole 45 has advanced to a position where it is less than or equal to one half of the maximum injection amount. When the closing auxiliary pressure chamber 432 and the return pressure chamber 433 communicate with each other by the communication path 434, the fuel in the closing auxiliary pressure chamber 432 flows at once into the return pressure chamber 433 through the communication path 434 and flows into the closing auxiliary pressure chamber 432. The fuel pressure drops rapidly.

  In ST8, as shown in FIG. 7B, the closing assist piston 30 further advances together with the needle valve 10, and the needle valve 10 is seated on the front end side of the second fuel storage chamber 42, so Fuel injection stops. During this time, the fuel in the closed auxiliary pressure chamber 432 flows out to the return pressure chamber 433 through the minute communication path 331 or the communication path 434, and the fuel pressure in the closed auxiliary pressure chamber 432 decreases. Further, the fuel that has flowed out of the auxiliary closing pressure chamber 432 into the return pressure chamber 433 is discharged to the outside of the nozzle body 40 through the fourth fuel passage 54.

  In ST9, as shown in FIG. 7C, when the pressure inside the closing auxiliary pressure chamber 432 becomes less than a predetermined pressure, the closing auxiliary piston 30 moves backward to the last retracted position by the biasing force of the spring 31. To do. As a result, the fuel is trapped in the second fuel storage chamber 42, the second fuel passage 52, the first fuel storage chamber 41, and the third fuel passage 53 with a certain level of pressure, and returns to the initial state.

  A second embodiment will be described with reference to FIG. FIG. 8 is an enlarged cross-sectional view of the needle valve closing chamber 43 according to the second embodiment. The second embodiment is different from the first embodiment in the shape of the communication path 434. The following description will focus on the differences from the first embodiment, and description of the same parts as in the first embodiment will be omitted. In addition, the same code | symbol is attached | subjected in the case similar to 1st Embodiment.

The communication path 434 of the fuel injection device 1 according to the second embodiment is formed in a U-shaped cross section. The end portion of the communication passage 434 on the return pressure chamber 433 side is positioned closer to the needle valve 10 than the end portion of the partition portion 33 on the return pressure chamber 433 side when the auxiliary closing piston 30 is positioned at the most advanced position. Formed.
Further, the end of the communication passage 434 on the side of the closing auxiliary pressure chamber 432 is closed by the partition 33 when the closing auxiliary piston 30 is located at the last retracted position, and is closed when the closing auxiliary piston 30 moves forward by a predetermined distance. The auxiliary pressure chamber 432 and the return pressure chamber 433 are formed at a position where they communicate with each other.

  A third embodiment will be described with reference to FIG. FIG. 9 is an enlarged cross-sectional view of the needle valve closing chamber 43 according to the third embodiment. The third embodiment differs from the first embodiment in the shape of the communication path 434. The following description will focus on the differences from the first embodiment, and description of the same parts as in the first embodiment will be omitted. In addition, the same code | symbol is attached | subjected in the case similar to 1st Embodiment.

  In the communication passage 434 of the fuel injection device 1 according to the third embodiment, the end on the side of the closing auxiliary pressure chamber 432 is formed in a direction perpendicular to the extending direction of the nozzle body 40, and straight from the end in the outer direction. It is formed so as to communicate with the return pressure chamber 433 side.

  The fourth embodiment will be described with reference to FIG. FIG. 10 is an enlarged cross-sectional view of the needle valve closing chamber 43 according to the fourth embodiment. The fourth embodiment is different from the first embodiment in that the spring 31 includes an elastic adjustment unit 311. The following description will focus on the differences from the first embodiment, and description of the same parts as in the first embodiment will be omitted. In addition, the same code | symbol is attached | subjected in the case similar to 1st Embodiment.

  The spring 31 that biases the closing assist piston 30 and the needle valve 10 apart from each other includes an elastic adjustment portion 311 at the end on the closing assist piston 30 side. The elastic adjustment unit 311 can adjust the elastic force of the spring 31 by adjusting the thickness of the elastic adjustment unit 311.

  The elastic adjustment portion 311 is formed in an annular shape so as to surround the auxiliary force transmission portion 32 of the closing auxiliary piston 30, and the outer shape thereof is the same as the shape of the end portion of the partition portion 33 on the needle valve 10 side or the end portion thereof. It is formed in a shape smaller than the shape. Specifically, the outer peripheral shape of the elastic adjustment portion 311 is formed in a shape that does not block the minute communication path 331 formed in the partition portion 33. That is, the end of the minute communication passage 331 on the return pressure chamber 433 side is formed so as not to contact the elastic adjustment portion 311.

According to this embodiment, there are the following effects.
(1) When the closing auxiliary piston 30 moves forward by a predetermined distance, the communication passage 434 formed in the wall portion forming the needle valve closing chamber 43 communicates with the closing auxiliary pressure chamber 432 and the return pressure chamber 433. The fuel in the auxiliary pressure chamber 432 flows out from the closed auxiliary pressure chamber 432 to the return pressure chamber 433 through the communication path 434. As a result, the closing auxiliary pressure chamber 432 and the return pressure chamber 433 are not communicated with each other by the communication path 434 until the closing auxiliary piston 30 moves forward by a predetermined distance. Fuel pressure is unlikely to drop. Therefore, it is possible to reliably advance the closing assist piston 30 by the fuel pressure in the closing assist pressure chamber 432 to press the needle valve 10 and to reliably advance the needle valve 10 by a predetermined distance.
Further, when the closing assist piston 30 moves forward by a predetermined distance and the closing assist pressure chamber 432 and the return pressure chamber 433 communicate with each other, the fuel in the closing assist pressure chamber 432 rapidly flows into the return pressure chamber 433, and the closing assist pressure is increased. As the fuel pressure in the chamber 432 rapidly decreases, the pressing force with which the auxiliary closing piston 30 advances the needle valve 10 also decreases rapidly. As a result, the closing assist piston 30 can quickly move to the last retracted position, which is the initial position.
As described above, since the closing auxiliary piston 30 and the needle valve 10 can be moved forward and backward quickly and reliably, the fuel injection device 1 can accurately control the injection and stop of the fuel. It is possible to shorten the fuel injection interval when the injection device 1 performs fuel injection a plurality of times.
Further, since the closing auxiliary piston 30 can quickly return to the last retracted position, which is the initial position, by the communication passage 434, the third fuel passage 53 and the needle valve closing chamber 43 can be quickly shut off, and the fourth fuel passage. The amount of fuel flowing out from 54 can be reduced.

  (2) The communication passage 434 of the fuel injection device 1 communicates between the closing assist pressure chamber 432 and the return pressure chamber 433 when the injection amount from the injection hole 45 is equal to or less than half of the maximum injection amount. . Thus, the fuel pressure in the closing auxiliary pressure chamber 432 does not decrease until the injection amount from the injection hole 45 becomes half of the maximum injection amount, and the closing auxiliary piston 30 surely advances by the pressing force. Therefore, the needle valve 10 can be reliably reached to the most advanced position, and the injection from the injection hole 45 can be stopped. Further, when the injection amount from the injection hole 45 becomes one half of the maximum injection amount and the closing auxiliary pressure chamber 432 and the return pressure chamber 433 communicate with each other through the communication path 434, the fuel pressure in the closing auxiliary pressure chamber 432 is quickly increased. Therefore, the closing assist piston 30 can be quickly moved to the last retracted position that is the initial position.

  (3) The communication passage 434 has an end on the return pressure chamber 433 side of the communication passage 434 at the return pressure chamber 433 side in the partition portion 33 of the closure auxiliary piston 30 when the closing auxiliary piston 30 is located at the most advanced position. It is located in the needle valve 10 side rather than the edge part. Thus, even when the closing assist piston 30 is located at the most advanced position, the end of the communication passage 434 on the return pressure chamber 433 side is not blocked, and the pressure in the closing assist pressure chamber 432 is reliably reduced. Thus, the closing assist piston 30 can be retracted quickly.

  (4) The closing assist piston 30 further includes a minute communication passage 331 that allows the closing assist pressure chamber 432 and the return pressure chamber 433 to communicate with each other. For this reason, by allowing the fuel in the closing auxiliary pressure chamber 432 to flow out to the return pressure chamber 433 through the minute communication path 331, the closing auxiliary piston 30 can be reliably retracted to the last retracted position which is the initial position. Therefore, the third fuel passage 53 and the needle valve closing chamber 43 can be quickly shut off, and the flow rate of the fuel flowing out from the fourth fuel passage 54 can be further reduced.

  (5) The closing assist piston 30 includes a plurality of communication passages 434 and a plurality of minute communication passages 331. For this reason, the passage of the fuel in the minute communication path 331 can be made smooth. In addition, the plurality of communication passages 434 and the minute communication passages 331 are equally arranged in the circumferential direction, respectively, in a cross-sectional view perpendicular to the advance / retreat direction of the closing assist piston 30. Therefore, it is possible to suppress the closing assist piston 30 from being pressed in one direction in the needle valve closing chamber 43 and hindering the movement in the forward / backward direction.

  (6) The communication path 434 is formed by recessing a part of the inner wall of the needle valve closing chamber 43, and the micro communication path 331 is formed by recessing a part of the outer peripheral surface of the partition portion 33 of the closing assist piston 30. Then. Accordingly, the communication passage 434 and the minute communication passage 331 are formed as grooves on the inner peripheral surface of the needle valve closing chamber 43 and the outer peripheral surface of the partition portion 33. For this reason, processing and manufacture become easier than forming as a hole inside each member, and the communication path 434 and the minute communication path 331 can be formed with high processing accuracy.

  (7) The number of communication paths 434 and the number of minute communication paths 331 do not have a common prime factor. Thereby, it is possible to suppress the communication path 434 and the minute communication path 331 from having the same position in the circumferential direction at a maximum of one place.

  (8) The total cross-sectional area of the communication path 434 is formed to be larger than the total cross-sectional area of the minute communication path 331. By reducing the total cross-sectional area of the micro communication path 331, the pressure in the closing auxiliary pressure chamber 432 can be prevented from being excessively reduced. Further, by increasing the total cross-sectional area of the communication passage 434, the pressure in the closing auxiliary pressure chamber 432 can be quickly reduced when the closing auxiliary pressure chamber 432 and the return pressure chamber 433 communicate with each other. For this reason, while closing auxiliary piston 30 pushes needle valve 10 forward to the most advanced position reliably, closing auxiliary piston 30 can be quickly moved to the last retreat position which is an initial position.

  (9) A spring 31 is disposed between the closing assist piston 30 and the needle valve 10 to bias the closing assist piston 30 and the needle valve 10 in a direction away from each other. For this reason, since the closing auxiliary piston 30 can be quickly retracted to the last retracted position, which is the initial position, and the third fuel passage 53 and the closing auxiliary pressure chamber 432 can be quickly shut off, the fuel flows out from the fourth fuel passage 54 to the outside. The flow rate of fuel can be further reduced.

  (10) The spring 31 includes an annular elastic adjustment portion 311 on the contact portion side of the spring 31 with the closing assist piston 30. By providing the elastic adjustment part 311 on the needle valve 10 side, it is possible to suppress the inertia weight of the needle valve 10 from increasing and the forward / backward movement of the needle valve 10 from becoming dull.

  (11) The minute communication passage 331 is formed so that the position of the end portion on the return pressure chamber 433 side in the minute communication passage 331 does not coincide with the position of the elastic adjustment portion 311. Therefore, the minute communication path 331 and the position of the elastic adjustment unit 311 coincide with each other, so that it is possible to suppress a change in the communication state between the closing auxiliary pressure chamber 432 and the return pressure chamber 433 by the minute communication path 331.

It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within a scope that can achieve the object of the present invention are included in the present invention.
For example, in this embodiment, the injection control valve 20 is driven by the piezo-type actuator 60. However, the present invention is not limited to this, and it may be driven by an electromagnetic or hydraulic actuator.
In the present embodiment, the minute communication path 331 is formed by denting the outer peripheral surface of the partition portion 33 of the closing assist piston 30, but the present invention is not limited to this. You may set up.

DESCRIPTION OF SYMBOLS 1 Fuel injection apparatus 10 Needle valve 20 Injection control valve 21 Spring 23 Passage closing part 30 Closure auxiliary piston 31 Spring 33 Partition part 40 Nozzle body 41 1st fuel storage chamber 42 2nd fuel storage chamber 43 Needle valve closing chamber 45 Injection hole 51 First fuel passage 52 Second fuel passage 53 Third fuel passage 54 Fourth fuel passage 60 Actuator 311 Elasticity adjustment portion 331 Small communication passage 421 Fuel reservoir portion 432 Closed auxiliary pressure chamber 433 Return pressure chamber 434 Communication passage

Claims (11)

A fuel injection device,
A nozzle body having a first fuel storage chamber, a second fuel storage chamber, a third fuel storage chamber, and an injection hole formed from the second fuel storage chamber to the outside of the fuel injection device;
A needle valve held in a needle valve holding portion formed inside the nozzle body;
A needle valve opening means provided on the tip side of the needle valve holding portion inside the nozzle body and having the second fuel storage chamber;
A needle valve closing means provided on the base end side of the needle valve holding portion inside the nozzle body and having the third fuel storage chamber;
An injection control valve held inside the nozzle body and capable of advancing and retreating in the first fuel storage chamber,
The nozzle body is
A first fuel passage from a fuel supply source to the first fuel storage chamber;
A second fuel passage from the first fuel storage chamber to the second fuel storage chamber;
A third fuel passage from the first fuel storage chamber to the third fuel storage chamber;
A fourth fuel passage from the third fuel storage chamber to a low pressure portion outside the fuel injection device,
The injection control valve is
By advancing to the first position, the first fuel passage and the first fuel storage chamber communicate with each other, and the first fuel storage chamber and the third fuel passage are shut off,
By retracting to the second position, the first fuel passage and the first fuel storage chamber are shut off, and the first fuel storage chamber and the third fuel passage are communicated with each other.
The needle valve is
By moving forward and seating on the nozzle body, the second fuel storage chamber and the nozzle hole are shut off,
By retreating and separating from the nozzle body, the second fuel storage chamber communicates with the nozzle hole,
The needle valve opening means retracts the needle valve by the fuel pressure in the second fuel storage chamber,
The needle valve closing means advances the needle valve by the fuel pressure in the second fuel storage chamber,
The needle valve closing means includes a closing auxiliary piston provided to be able to advance and retreat in the third fuel storage chamber,
The closing assist piston shuts off the third fuel passage and the third fuel storage chamber at the last retracted position, and makes the third fuel passage and the third fuel storage chamber communicate with each other by shifting to the forward movement state. ,
The third fuel storage chamber has a closed auxiliary pressure chamber that communicates with the third fuel passage and a return pressure chamber that communicates with the fourth fuel passage by the closing auxiliary piston when the closing auxiliary piston moves forward. Divided into
The closing assist piston is capable of transmitting a pressing force due to fuel pressure in the closing assist pressure chamber to the needle valve in a forward direction,
The closing auxiliary piston shifts from the advanced state to the last retracted position, and shuts off the third fuel passage and the closing auxiliary pressure chamber, so that the fuel in the first fuel storage chamber becomes the third fuel. An outflow suppression means for suppressing the flow of fuel into the third fuel storage chamber through the passage and suppressing the fuel in the first fuel storage chamber from flowing out of the fuel injection device;
A wall that forms the third fuel storage chamber in the nozzle body includes a communication passage that communicates the close auxiliary pressure chamber and the return pressure chamber when the close assist piston moves forward a predetermined distance. A fuel injection device. The fuel injection device according to claim 1,
When the closing auxiliary piston moves forward by the predetermined distance and the communication path communicates the closing auxiliary pressure chamber and the return pressure chamber, the injection amount from the injection hole is less than half of the maximum injection amount. There is provided a fuel injection device. The fuel injection device according to claim 1 or 2,
In the communication passage, when the closing auxiliary piston is located at the most advanced position, the end portion on the return pressure chamber side in the communication passage is the end portion on the return pressure chamber side in the sliding portion of the closing auxiliary piston. It is formed so that it may be located in the needle valve side rather than. The fuel injection device according to any one of claims 1 to 3,
The fuel injection apparatus according to claim 1, wherein the closing assist piston further includes a minute communication path that connects the closing assist pressure chamber and the return pressure chamber. The fuel injection device according to claim 4,
The closing assist piston includes a plurality of the communication passages and the micro communication passages,
The fuel injection device according to claim 1, wherein the plurality of communication passages and the minute communication passages are equally arranged in a circumferential direction in a cross-sectional view perpendicular to the advancing and retreating direction of the closing auxiliary piston. The fuel injection device according to claim 5,
The communication path is formed by denting a part of the inner peripheral surface of the wall portion forming the third fuel storage chamber,
The fuel injection device according to claim 1, wherein the minute communication path is formed by denting a part of an outer peripheral surface of the closing auxiliary piston. The fuel injection device according to claim 6,
The number of the said communicating path and the number of the said minute communicating path do not have a common prime factor, The fuel-injection apparatus characterized by the above-mentioned. The fuel injection device according to claim 4 or 7,
The fuel injection device according to claim 1, wherein a total cross-sectional area of the communication path is formed to be larger than a total cross-sectional area of the minute communication path. The fuel injection device according to any one of claims 4 to 8,
The fuel further comprising an elastic member disposed between the closing auxiliary piston and the needle valve in the third fuel storage chamber and biasing in a direction in which the closing auxiliary piston and the needle valve are separated from each other. Injection device. The fuel injection device according to claim 9, wherein
The fuel injection device according to claim 1, wherein the elastic member includes an annular elastic adjustment portion on a contact portion side of the closing auxiliary piston in the elastic member. The fuel injection device according to claim 10,
The fuel injection device, wherein the minute communication passage is formed such that a position of the end portion on the return pressure chamber side in the minute communication passage does not coincide with a position of the elastic adjustment portion.

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