JP2010090774A - Fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection device in which a response time can be kept constant when fuel injection stops. <P>SOLUTION: The fuel injection device 1 is provided with: a nozzle body 40; an injection control valve 20; and an actuator 60. A first fuel storage chamber 41 and a needle valve closing chamber 43 are formed in the nozzle body 40. The fuel control valve 20 makes a first fuel passage 51 communicate with the first fuel storage chamber 41 and cuts off the first fuel storage chamber 41 from a third fuel passage 53 by moving forward to the first position, and cuts off the first fuel passage 51 from the first fuel storage chamber 41, and makes the first fuel storage chamber 41 communicate with the third fuel passage 53 by moving backward to the second position. When the injection control valve 20 is moved from the second position to the first position with a starting operation of fuel injection, the actuator 60 controls such that the injection control valve 20 reaches the first position before the needle valve 10 starts leaving from the nozzle body 40. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel injection device. Specifically, 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, fuel injection devices that inject fuel are used for diesel engines.
FIG. 6 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 are formed.

  The injection control valve 720 communicates with the first fuel passage 751 and the first fuel storage chamber 741 by moving forward to the first position, and shuts off the first fuel storage chamber 741 and the third fuel passage 753. By retracting 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 are communicated.

  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 starting the fuel injection 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, as shown in FIG. 7A, 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. 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, the operation of stopping the fuel injection of the fuel injection device 701 is as follows.
As shown in FIG. 7B, 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 first fuel storage chamber 741 are The three fuel passages 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, due to the fuel pressure in the needle valve closing chamber 743, the closing assist piston 730 moves forward, and pushes the needle valve 710 forward. As a result, the needle valve 710 is seated on the nozzle body 740 and fuel injection stops.
Japanese Patent Application No. 2008-159266

  By the way, in the fuel injection device 701 described above, the injection control valve 720 when stopping the fuel injection is controlled by the length of the transition time from the second position to the first position of the injection control valve 720 when starting the fuel injection. There is a problem that the response time from the operation to the actual stop of the fuel injection is affected.

  That is, when the transition from the second position to the first position of the injection control valve 720 at the start of fuel injection is slow, the period of the injection control valve 720 located at the intermediate position between the second position and the first position is prolonged. . In a state where the injection control valve 720 is located at the intermediate position, as shown in FIG. 8, the high-pressure fuel from the first fuel passage 751 flows into both the third fuel passage 753 and the second fuel passage 752, High-pressure fuel flows into the needle valve closing chamber 743 through the third fuel passage 753, and a force is applied in the forward direction to the closing assist piston 730. Accordingly, the backward force acting on the needle valve 710 is reduced, and fuel injection is started without the needle valve 710 fully retracting. Thereafter, when the injection control valve 720 is moved from the first position to the second position in order to stop fuel injection, the needle valve 710 is not sufficiently retracted, and therefore the needle is operated after the injection control valve 720 is operated. The response time until the valve 720 is seated on the nozzle body 740 is shortened.

  On the other hand, when the transition from the second position to the first position of the injection control valve 720 at the start of fuel injection is early, the period during which the injection control valve 720 is located at the intermediate position is shortened. Then, high-pressure fuel from the first fuel passage 751 hardly flows into the third fuel passage 753 or the needle valve closing chamber 743, and no force is applied to the closing assist piston 730 in the forward direction. Therefore, since the force in the backward direction acting on the needle valve 710 does not decrease, the needle valve 710 is sufficiently retracted to start injection. Thereafter, when the injection control valve 720 is moved from the first position to the second position in order to stop the fuel injection, the needle valve 710 is sufficiently retracted to be positioned at the predetermined last retracted position. The response time from when the control valve 720 is operated until the needle valve 720 is seated on the nozzle body 740 is constant.

  The present invention relates to a fuel injection device capable of making the response time from when the injection control valve is operated to when the needle valve is seated (that is, the response time until fuel injection actually stops) at the time of stopping fuel injection. The purpose is to provide.

  The 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 second fuel storage described later). Chamber 42), a third fuel storage chamber (for example, a needle valve closing chamber 43 described later), and a nozzle hole (for example, a nozzle hole 45 described later) extending from the second fuel storage chamber to the outside of the fuel injection device. A needle valve (for example, a later-described needle valve 10) held by a nozzle body (for example, a later-described nozzle body 40) and a needle valve retaining portion (for example, a later-described needle valve retaining portion 46) inside the nozzle body. And a needle valve opening means (for example, a second fuel storage chamber 42, a stepped portion 13 and a fuel reservoir, 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. 421) and needle valve closing means (for example, a needle valve closing chamber 43 and a closing auxiliary piston 30 to be described later) 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 (for example, an injection control valve 20 described later) that is held inside the nozzle body and can advance and retreat in the first fuel storage chamber, and an injection control valve control device that controls the injection control valve ( For example, an actuator 60 described later is provided, and the nozzle body includes a first fuel passage (for example, a first fuel passage 51 described later) from the fuel supply source to the first fuel storage chamber, and the first fuel. A second fuel passage (for example, a second fuel passage 52 described later) from the storage chamber to the second fuel storage chamber, and a third fuel passage (for example, the rear fuel passage) from the first fuel storage chamber to the third fuel storage chamber A third fuel passage 53) and a fourth fuel passage (for example, a fourth fuel passage 54 described later) extending from the third fuel storage chamber to a low pressure portion outside the fuel injection device, and the injection control valve Advances to a first position (for example, a first position to be described later), thereby communicating the first fuel passage and the first fuel storage chamber, and the first fuel storage chamber and the third fuel passage. And the first fuel passage and the first fuel storage chamber are shut off, and the first fuel storage chamber and the first fuel storage chamber are separated from each other by retreating to a second position (for example, a second position described later). The three fuel passages communicate with each other, and the needle valve moves forward and is seated on the nozzle body, thereby shutting off the second fuel storage chamber and the nozzle hole and moving backward to separate from the nozzle body. The second fuel storage chamber and the jet The needle valve opening means retreats the needle valve by the fuel pressure in the second fuel storage chamber, and the needle valve closing means is connected to the needle valve by the fuel pressure in the third fuel storage chamber. When the injection control valve shifts the injection control valve from the second position to the first position, the injection control valve control device performs the injection earlier than the needle valve starts to separate from the nozzle body. The control valve is controlled to reach the first position.

According to the present invention, the fuel injection start 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.

On the other hand, the fuel injection stopping operation of the fuel injection device is as follows.
That is, 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. Therefore, fuel flows from the second fuel passage through the first fuel storage chamber and the third fuel passage into the third fuel storage chamber, and the fuel pressure in the third fuel storage chamber increases. Then, the needle valve closing means operates, and the needle valve advances by the fuel pressure in the third fuel storage chamber. As a result, the needle valve is seated on the nozzle body, and fuel injection stops.

  Here, when the injection control valve is shifted from the second position to the first position in the fuel injection start operation, the injection control valve control device causes the injection control valve to move earlier than the needle valve starts to be separated from the nozzle body. Control is performed to reach the first position. Therefore, when the needle valve starts to be separated from the nozzle body due to the fuel pressure in the second fuel storage chamber, the injection control valve is already positioned at the first position, and therefore, the forward direction with respect to the needle valve. No power is added to the. Accordingly, since the retraction amount of the needle valve at the time of fuel injection is always constant, after that, even when the injection control valve is shifted from the first position to the second position in the fuel injection stop operation, the injection control valve is operated. The response time from when the needle valve is seated on the nozzle body is constant.

  A fuel injection device according to the present invention includes a first fuel storage chamber, a second fuel storage chamber, a third fuel storage chamber, and a nozzle body formed with injection holes extending from the second fuel storage chamber to the outside of the fuel injection device. A needle valve held by a needle valve holding portion inside the nozzle body, and 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 proximal side with respect to the needle valve holding portion inside the nozzle body and having the third fuel storage chamber; and being held inside the nozzle body, the first fuel storage chamber An injection control valve capable of advancing and retreating, and an injection control valve control device for controlling the injection control valve, wherein the nozzle body includes a first fuel passage extending from a fuel supply source to the first fuel storage chamber, 1 A second fuel passage from the 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, and a fuel injection device from the third fuel storage chamber to the fuel injection device. A fourth fuel passage leading to an external low pressure portion is formed, and the injection control valve advances to the first position, thereby communicating the first fuel passage with the first fuel storage chamber, and the first fuel passage. By shutting off the fuel storage chamber and the third fuel passage and moving backward 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 first fuel passage are separated. The three fuel passages communicate with each other, and the needle valve moves forward and is seated on the nozzle body, thereby shutting off the second fuel storage chamber and the nozzle hole and moving backward to separate from the nozzle body. The second fuel storage chamber and the front The needle valve opening means retreats the needle valve by the fuel pressure in the second fuel storage chamber, and the needle valve closing means is connected by the fuel pressure in the third fuel storage chamber. The total of the volumes of the first fuel storage chamber, the second fuel passage, and the second fuel storage chamber is calculated by moving the injection control valve from the second position by the injection control valve control device. When shifting to the position, the needle valve is set to start to be separated from the nozzle body after the injection control valve reaches the first position.

  According to this invention, when the total of the volumes of the first fuel storage chamber, the second fuel passage, and the second fuel storage chamber is transferred from the second position to the first position by the injection control valve control device, After the injection control valve reaches the first position, the needle valve is set so as to start to be separated from the nozzle body. Therefore, when the needle valve starts to be separated from the nozzle body due to the fuel pressure in the second fuel storage chamber, the injection control valve is already positioned at the first position, and therefore, the forward direction with respect to the needle valve. No power is added to the. Accordingly, since the retraction amount of the needle valve at the time of fuel injection is always constant, after that, even when the injection control valve is shifted from the first position to the second position in the fuel injection stop operation, the injection control valve is operated. The response time from when the needle valve is seated on the nozzle body is constant.

  According to the present invention, when the needle valve starts to be separated from the nozzle body due to the fuel pressure in the second fuel storage chamber, the injection control valve is already in the first position. On the other hand, no force is applied in the forward direction. Accordingly, since the retraction amount of the needle valve at the time of fuel injection is always constant, after that, even when the injection control valve is shifted from the first position to the second position in the fuel injection stop operation, the injection control valve is operated. The response time from when the needle valve is seated on the nozzle body is constant.

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

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 in accordance with the operation of a piezo actuator 60 serving as an injection control valve control device.
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. And a columnar nozzle body 40 that accommodates these springs 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 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.

The second fuel storage chamber 42 is a substantially cylindrical space extending 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.

  The injection control valve 20 is held by the injection control valve holding portion 44 of the nozzle body 40 and can advance and retreat in the first fuel storage chamber 41 along the extending direction of the first fuel storage chamber 41.

  The injection control valve 20 includes a substantially cylindrical guide portion 22 that can slide in the injection control valve holding portion 44, a disk-shaped bowl-shaped enlarged diameter portion 23 provided on the distal end side of the guide portion 22, A substantially cylindrical closing portion 24 provided on the distal end side of the enlarged diameter portion 23.

The guide part 22 is slidably held by the injection control valve holding part 44. A reduced diameter portion 221 having a circular cross section extending from the position adjacent to the enlarged diameter portion 23 toward the proximal end side is formed on the outer peripheral surface of the guide portion 22. A first fuel passage 51 is opened at a position facing the reduced diameter portion 221 in the injection control valve holding portion 44.
The enlarged diameter portion 23 and the closing portion 24 are exposed in the first fuel storage chamber 41. The base end surface of the enlarged diameter portion 23 is inclined with respect to a plane orthogonal to the central axis of the injection control valve 20.

  The spring 21 is provided between the distal end surface of the first fuel storage chamber 41 and the enlarged diameter portion 23 of the injection control valve 20, contacts the distal end side of the enlarged diameter portion 23, and retracts the injection control valve 20. Energize in the direction.

The above-described injection control valve 20 moves forward against the urging force of the spring 21, and the state in which the front end surface of the closing portion 24 abuts on the front end surface of the first fuel storage chamber 41 is the first of the injection control valve 20. Position.
When the injection control valve 20 is located at the first position, the front end surface of the closing portion 24 abuts on the front end surface of the first fuel storage chamber 41, and the enlarged diameter portion 23 and the step portion 411 of the first fuel storage chamber 41 are in contact with each other. A gap is formed between them.

  Further, 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, this In the 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.

On the other hand, the state in which the injection control valve 20 is retracted and the enlarged diameter portion 23 is in contact with the stepped 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 closing portion 24 and the front end surface of the first fuel storage chamber 41 are separated from each other to form a gap, and the enlarged diameter portion 23 is formed in the first fuel storage chamber. 41 is in contact with the stepped portion 411. 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 actuator 60 is provided on the base end side of the injection control valve holding portion 44 of the injection control valve 20 and can load the injection control valve 20 in the forward direction.

  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 needle valve closing chamber 43 is partitioned by the partition 33 into a closing auxiliary pressure chamber 432 that communicates with the third fuel passage 53 and a return pressure chamber 433 that communicates with the fourth fuel passage 54.

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. 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 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 above closing auxiliary piston 30 operates as follows.
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.
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 assist piston 30 moves forward against the biasing force of the spring 31, and the distal end surface of the assist 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, a force is applied to the needle valve 10 in a direction in which the annular step portion 13 of the needle valve 10 is retracted by receiving the fuel pressure from the fuel reservoir portion 421 as a pressure receiving portion.

  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.

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 enlarged diameter portion 23 of the injection control valve 20 abuts on 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.

  In ST2, when the actuator 60 is driven from this state as shown in FIG. 2B, the injection control valve 20 moves forward against the biasing force of the spring 21 and is positioned at the first position.

Then, the front end surface of the closing portion 24 of the injection control valve 20 comes into contact with 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 fuel supply to 53 is cut off.
Further, since the enlarged diameter portion 23 is separated from the step portion 411 of the first fuel storage chamber 41 and a gap is formed between the enlarged diameter 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. To rise.

  In ST3, 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 as shown in FIG. The needle valve 10 moves backward against the urging force of 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.

  Thus, when the actuator 60 moves the injection control valve 20 from the second position to the first position, the injection control valve 20 is moved to the first position earlier than the needle valve 10 starts to be separated from the nozzle body 40. Control to reach.

  In ST4, the driving force of the actuator 60 is stopped or the driving force is decreased to reduce the pressing force on the injection control valve 20. Then, the injection control valve 20 moves backward by the biasing force of the spring 21. At this time, the injection control valve 20 is positioned at the second position by the difference between the urging force of the spring 21 and the driving force of the actuator 60, and as shown in FIG. The injection control valve holding part 44 is closed in contact with the step part 411 of the fuel storage chamber 41. 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 second fuel storage chamber 42, the second fuel passage 52, and the first fuel storage chamber 41 passes through the gap between the front end surface of the closing portion 24 and the front end surface of the first fuel storage chamber 41, It flows into the 3rd fuel passage 53, and the pressure in the 3rd fuel passage 53 rises.

  Further, due to the fuel pressure flowing into the third fuel passage 53, a portion exposed to the third fuel passage 53 among the conical portions of the partition portion 33 is pressed, and the closing assist piston is resisted against the biasing force of the spring 31. 30 begins to move forward.

  In ST5, as shown in FIG. 3 (b), when the closing assist piston 30 moves forward, the closing of the third fuel passage 53 by the partition 33 is released, and the fuel that has flowed into the third fuel passage 53 further flows into the needle valve. It flows into the closing auxiliary pressure chamber 432 of the closing chamber 43 and the pressure in the closing auxiliary pressure chamber 432 rises. When the pressure inside the valve closing auxiliary pressure chamber 432 reaches a predetermined pressure, the whole conical portion of the partition 33 is pressed by the fuel pressure flowing into the closing auxiliary pressure chamber 432, and the closing auxiliary piston 30 is The front end surface of the auxiliary force transmitting portion 32 of the valve closing auxiliary piston 30 comes into contact with the base end surface of the needle valve 10 by moving forward.

  When the fuel in the second fuel storage chamber 42, the second fuel passage 52, and the first fuel storage chamber 41 flows into the third fuel passage 53 and the closing auxiliary pressure chamber 432, the second fuel storage chamber 42, the second fuel storage chamber 42, The pressure in the second fuel passage 52 and the third fuel passage 53 gradually decreases.

  In ST6, as shown in FIG. 3C, the fuel in the closing assist pressure chamber 432 presses the closing assist piston 30. Here, as described above, the force applied in the direction in which the closing assist piston 30 moves forward is 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. Greater than the force applied to Therefore, the valve closing assist piston 30 moves forward together with the needle valve 10, the needle valve 10 is seated on the distal end side of the second fuel storage chamber 42, and the fuel injection from the injection hole 45 is stopped.

In ST7, as shown in FIG. 4, the fuel inside the valve closing auxiliary pressure chamber 432 gradually flows out into the return pressure chamber 433 through the minute communication path 331 formed in the partition portion 33, and this return pressure. The fuel that has flowed into the chamber 433 is discharged to the outside of the nozzle body 40 through the fourth fuel passage 54.
Thereby, the pressure inside the valve closing auxiliary pressure chamber 432 gradually decreases, and when the pressure inside the valve closing auxiliary pressure chamber 432 becomes less than a predetermined pressure, the valve closing auxiliary piston 30 is urged by the biasing force of the spring 31. Moves backward to the last retracted position, and the communication between the valve closing auxiliary pressure chamber 432 and the third fuel passage 53 is cut off. 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.

FIG. 5 is a timing chart of the injection control valve 20 and the needle valve 10.
Time _{t 0} is the above-mentioned initial state (ST1).
Period between time _{t 1} from time _{t 0} corresponds to the ST2 described above. In this period, the actuator 60 is driven to shift the injection control valve 20 from the second position to the first position.
After a lapse of time _{t 1} a predetermined time period from the time _{t 3} from time _{t 2} corresponds to ST3 described above. During this period, the high-pressure fuel in the first fuel passage 51 flows into the second fuel storage chamber 42 via the first fuel storage chamber 41 and the second fuel passage 52, and enters the second fuel storage chamber 42. The needle valve 10 is retracted by the fuel pressure.

Depending on the fuel injection amount or the like, a predetermined time, after maintaining the injection control valve 20 to the first position, at time t _4, thereby driving the actuator 60 decreases the stopping or driving force.

Period between times _{t 5} from time _{t 4} corresponds to ST4 described above. In this period, the injection control valve 20 is retracted from the first position to the second position.
Period from the time _{t 6} from time _{t 5} corresponds to the above ST5, ST6. During this period, the fuel in the second fuel storage chamber 42, the second fuel passage 52, and the first fuel storage chamber 41 flows into the needle valve closing chamber 43, and the closing assist piston 30 moves forward to move the needle valve 10. Press. As a result, the needle valve 10 moves forward toward the distal end side of the second fuel storage chamber 42 and is seated on the distal end side of the second fuel storage chamber 42, and fuel injection stops.

According to this embodiment, there are the following effects.
(1) When the injection control valve 20 is shifted from the second position to the first position in the fuel injection start operation, the injection control valve 20 is earlier than the needle valve 10 starts to be separated from the nozzle body 40 by the actuator 60. Is controlled to reach the first position. Therefore, when the needle valve 10 starts to be separated from the nozzle body 40 due to the fuel pressure in the second fuel storage chamber 42, the injection control valve 20 is already in the first position. No force is applied to 20 in the forward direction. Accordingly, since the retraction amount of the needle valve 10 at the time of fuel injection is always constant, even if the injection control valve 20 is shifted from the first position to the second position in the fuel injection stop operation, the injection control valve 20 is not changed. The response time from when the needle valve 10 is operated until the needle valve 10 is seated on the nozzle body 40 is constant.

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 the above-described embodiment, the injection control valve 20 is controlled by the actuator 60 so that the injection control valve 20 reaches the first position earlier than the needle valve 10 starts to leave the nozzle body 40. However, it is not limited to this. That is, the total volume of the first fuel storage chamber 41, the second fuel passage 52, and the second fuel storage chamber 42 is determined so that the needle valve 10 is separated from the nozzle body 40 after the injection control valve 20 reaches the first position. May be set to start.

In the above-described embodiment, the injection control valve 20 is driven by the piezo-type actuator 60. However, the present invention is not limited to this and may be driven by an electromagnetic or hydraulic actuator.
Further, in each of the above-described embodiments, 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 not limited to this, the inner side of the partition portion 33 of the closing assist piston 30. The nozzle body 40 may be formed on the inner peripheral surface of the needle valve closing chamber 43.

Further, in the above-described embodiment, the proximal end side of the needle valve 10 is directly pressed by the auxiliary force transmission unit 32 of the closing auxiliary piston 30, but not limited to this, between the closing auxiliary piston 30 and the needle valve 10. A member may be provided on the proximal end side of the needle valve 10 via this member.
Moreover, in the above-mentioned embodiment, although the level difference part 13 was formed in one place of the outer peripheral surface of the needle valve main body 11, not only this but a level difference part is provided in several places, such as the front end side outer peripheral surface of the needle valve main body 11. May be.

  In the above-described embodiment, the spring 21 is disposed on the distal end side of the injection control valve holding portion 44 of the injection control valve 20, but not limited to this, the spring 21 is disposed on the proximal end side of the injection control valve holding portion 20. The injection control valve 20 may be urged in the backward direction.

It is sectional drawing which shows the structure of the fuel-injection apparatus which concerns on one Embodiment of this invention. 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 a timing chart which shows operation | movement of the fuel-injection apparatus which concerns on the said embodiment. It is sectional drawing which shows the structure of the fuel-injection apparatus which concerns on the prior art example of this invention. It is a figure for demonstrating operation | movement of the fuel-injection apparatus based on the said prior art example. It is an expanded sectional view in the middle position of the injection control valve of the fuel injection device concerning the above-mentioned conventional example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel injection apparatus 10 Needle valve 13 Level difference part (needle valve opening means)
20 Injection control valve 30 Close assist piston (needle valve closing means)
40 Nozzle body 41 First fuel storage chamber 42 Second fuel storage chamber (needle valve opening means)
43 Needle valve closing chamber (third fuel storage chamber, needle valve closing means)
45 Injection hole 46 Needle valve holding portion 51 First fuel passage 52 Second fuel passage 53 Third fuel passage 54 Fourth fuel passage 60 Actuator (injection control valve control device)
421 Fuel reservoir (needle valve opening means)

Claims (2)

A first fuel storage chamber, a second fuel storage chamber, a third fuel storage chamber, and a nozzle body in which nozzle holes extending from the second fuel storage chamber to the outside of the fuel injection device are formed;
A needle valve held in a needle valve holding portion inside the nozzle body;
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;
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 moving back and forth in the first fuel storage chamber;
An injection control valve control device for controlling the injection control valve,
The nozzle body includes 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, and from the first fuel storage chamber. A third fuel passage extending to the third fuel storage chamber and a fourth fuel passage extending from the third fuel storage chamber to a low pressure portion outside the fuel injection device are formed;
The injection control valve advances to the first position, thereby communicating the first fuel passage and the first fuel storage chamber, and blocking the first fuel storage chamber and the third fuel passage; 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 moves forward and is seated on the nozzle body, thereby shutting off the second fuel storage chamber and the nozzle hole, and retreating and moving away from the nozzle body, thereby the second fuel storage chamber. Communicating the chamber 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 third fuel storage chamber,
When the injection control valve shifts the injection control valve from the second position to the first position, the injection control valve controls the injection control valve before the needle valve starts to move away from the nozzle body. A fuel injection device controlled to reach a first position. A first fuel storage chamber, a second fuel storage chamber, a third fuel storage chamber, and a nozzle body in which nozzle holes extending from the second fuel storage chamber to the outside of the fuel injection device are formed;
A needle valve held in a needle valve holding portion inside the nozzle body;
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;
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 moving back and forth in the first fuel storage chamber;
An injection control valve control device for controlling the injection control valve,
The nozzle body includes 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, and from the first fuel storage chamber. A third fuel passage extending to the third fuel storage chamber and a fourth fuel passage extending from the third fuel storage chamber to a low pressure portion outside the fuel injection device are formed;
The injection control valve advances to the first position, thereby communicating the first fuel passage and the first fuel storage chamber, and blocking the first fuel storage chamber and the third fuel passage; 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 moves forward and is seated on the nozzle body, thereby shutting off the second fuel storage chamber and the nozzle hole, and retreating and moving away from the nozzle body, thereby the second fuel storage chamber. Communicating the chamber 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 third fuel storage chamber,
The total volume of the first fuel storage chamber, the second fuel passage, and the second fuel storage chamber is determined when the injection control valve is moved from the second position to the first position by the injection control valve control device. The fuel injection device is set so that the needle valve starts to be separated from the nozzle body after the injection control valve reaches the first position.

Images