JP2007218175A - Fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection device having a twin-needle type variable hole nozzle and inhibiting eccentricity of an inner needle to reduce variations between holes in fuel spray injected from the second holes. <P>SOLUTION: The plurality of holes 31, 32 provided in a tip of a nozzle body B of the variable hole nozzle 1 are opened and closed by the outer needle 21 and the inner needle 22 which are coaxially arranged. When pressure of a control chamber 4 decreases, the outer needle 21 on an outer peripheral side opens the first holes 31 and then the inner needle 22 on an inner peripheral side is pushed up by the outer needle 21 and opens the second holes 32. The inner needle 22 is lifted under guidance of a second guide 52 provided in a sliding portion with the outer needle 21 and a third guide portion 53 provided on an inner periphery of a tip portion B1 of the nozzle body B, an axis shift is inhibited and the fuel spray injected from the plurality of second holes 32 is inhibited from causing variations. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel injection valve used for injecting and supplying fuel to an internal combustion engine such as a diesel engine, and more particularly to a fuel injection valve having a twin needle type variable injection nozzle.

  An internal combustion engine for automobiles is desired to improve exhaust emission and fuel consumption from the viewpoint of environmental and resource protection, and to realize output performance in response to a driver's request. In order to achieve both of these, more advanced fuel injection control is required. For example, in a diesel engine, a fuel injection valve that injects high-pressure fuel supplied from a common rail from a variable nozzle is proposed. The variable injection hole nozzle has a plurality of injection holes at the tip of the nozzle, and the fuel injection rate can be made variable by sequentially opening the plurality of injection holes in accordance with the lift amount of the nozzle needle.

As a prior art of such a variable nozzle hole, there is a twin needle type variable nozzle nozzle (for example, Patent Documents 1 and 2).
JP 2005-320904 A JP 2001-241370 A

  As shown in an example in FIG. 7A, such a variable nozzle has a plurality of second nozzles that are slidably held in a cylindrical nozzle body 101 and are formed in the axial direction at the tip of the nozzle body 101. The first nozzle hole 105 and the second nozzle hole 106 are opened and closed. The nozzle needle 102 is a twin needle type in which an inner needle 104 is slidably provided inside a hollow cylindrical outer needle 103. The outer needle 103 and the inner needle 104 are first and second arranged at the upper part thereof. The springs 107 and 108 are urged in the valve closing direction. A control chamber 109 is provided in the spacer 112 that holds the upper end portion of the nozzle needle 102, and back pressure is applied to the outer needle 103 and the inner needle 104 by the high-pressure fuel supplied from the high-pressure passage 110. The control chamber 109 communicates with the low pressure passage via the control passage 111, and the pressure is increased or decreased by opening and closing a control valve (not shown) provided at the outlet portion.

  In the above configuration, when the control valve is driven to connect the control chamber 109 to the low pressure passage, the fuel in the control chamber 109 is discharged, and the back pressure acting on the nozzle needle 102 is reduced. Along with this, the outer needle 103 precedes and starts the lift, and the first sheet 113 and the second sheet 114 shown in FIG. 7B are separated from each other to open the first injection hole 105 on the upstream side. When the outer needle 103 is further lifted and comes into contact with the inner needle 104, both needles are lifted together thereafter, and the third seat 115 is separated to open the second injection hole 106 on the downstream side. . As a result, only the outer needle 103 is lifted to perform a small amount of fuel injection when the load is low, and both the outer needle 103 and the inner needle 104 are lifted to increase the fuel injection amount when the load is high. Therefore, advanced injection amount control is possible.

  In the configuration of the above prior art, when the outer needle 103 is opened, the first guide 117 provided on the inner peripheral surface of the spacer 112 constituting the control chamber 109, and the sliding portion of the outer needle 103 and the inner needle 104 are provided. Since the lift is performed while being guided at two locations of the second guide 116, the shaft center of the outer needle 103 can be lifted without being eccentric with respect to the shaft center of the nozzle body 101. Actually, since the guide is provided in a slidable state, there is a slight sliding clearance, and although there is a corresponding axial deviation, there is no functional problem.

  On the other hand, since the inner needle 104 is in a state in which only the upper end is held at one position by the second guide 116 as soon as the tip is lifted from the third sheet 115 of the nozzle body 101, an axis deviation is likely to occur. When the axial deviation occurs, the cross-sectional area of the passage between the seat portion of the nozzle body 101 and the tip of the inner needle 104 changes in the circumferential direction, and the fuel injected from the plurality of second injection holes 106 arranged on the circumference. Variation in spraying occurs. As a result, the state of spray in the combustion chamber becomes non-uniform and the exhaust state may be deteriorated.

  Accordingly, an object of the present invention is to suppress the eccentricity of the inner needle in a fuel injection device having a twin needle type variable injection hole nozzle, and to reduce the variation between the injection holes of the fuel spray injected from the second injection hole. In order to achieve good combustion.

  According to another aspect of the present invention, a fuel injection valve includes a variable injection nozzle that opens and closes a plurality of injection holes provided at a tip portion of a nozzle body with an outer needle and an inner needle arranged coaxially. The outer needle is slidably disposed in the nozzle body to open and close the first nozzle hole, and the inner needle is slidably disposed in the outer needle to open and close the second nozzle hole. A control chamber that acts on the outer needle and the inner needle in the valve closing direction is provided. As the pressure in the control chamber decreases, the outer needle first lifts and abuts against the inner needle to lift it. Further, a guide portion is provided on the inner periphery of the tip portion of the nozzle body, and the tip shaft portion of the inner needle is slidably held by this guide portion.

  In the above configuration, when the control chamber pressure decreases, the outer needle first opens the first nozzle hole, and then is pushed up by the outer needle, so that the inner needle opens the second nozzle hole. At this time, since the inner needle is guided at two places, that is, the sliding portion with the outer needle and the guide portion at the tip of the nozzle body, it is possible to prevent the occurrence of axial deviation. Therefore, even if a plurality of second injection holes are formed, it is possible to suppress variation in the fuel spray injected from each injection hole, so that good combustion can be realized and exhaust emission can be reduced.

  In the invention of claim 2, the tip shaft portion of the inner needle held by the guide portion has a shape in which a part of the outer peripheral surface is notched in the axial direction.

  When the inner needle is closed, there is a risk that the fuel in the space on the tip side will be compressed as the tip shaft descends, resulting in instability of the valve closing operation. The fuel can flow out to the upstream side through the gap between the guide portion and the guide portion, and the pressure fluctuation can be suppressed and the operation of the inner needle can be stabilized.

  According to a third aspect of the present invention, a communication hole is provided in the tip shaft portion of the inner needle to communicate the inner space of the tip portion of the nozzle body with the upstream side of the tip shaft portion.

  When the tip shaft is lowered when the inner needle is closed, the fuel in the inner space of the tip of the nozzle body flows out from the communication hole. When the seat portion of the inner needle is seated, the communication between the communication hole and the upstream side of the seat portion is blocked. Thus, even if it is the structure which provided the communicating hole inside the front-end | tip shaft part, the same effect which suppresses a pressure fluctuation and stabilizes the action | operation of an inner needle is acquired.

  According to a fourth aspect of the present invention, the second nozzle hole is formed in the tip wall of the nozzle body where the guide portion is formed, and the opening of the second nozzle hole is controlled by the lift of the tip shaft portion of the inner needle. It was set as the structure to do.

  The second injection hole may be provided at the position where the guide part is formed, and may be configured to open and close at the tip shaft part of the inner needle, and the lift amount from the start of the inner needle to the start of valve opening of the second injection hole is arbitrary. Can be set.

  In the invention of claim 5, the tip shaft portion of the inner needle is used as the seal portion of the second nozzle hole.

  Specifically, if the second injection hole is sealed at the distal end shaft portion when the inner needle is closed, the seat portion is unnecessary and processing becomes easy.

  In a sixth aspect of the present invention, the gap between the outer needle and the inner needle is opened to a low pressure portion provided in the nozzle body.

  When the outer needle is lifted, high-pressure fuel flows between the inner needle and the fuel, which may leak to the second nozzle hole side. As in the above configuration, by allowing the gap formed between the outer needle and the inner needle to communicate with the low pressure portion, fuel can escape and leakage to the second injection hole can be prevented.

  Preferably, the inner needle has a seat portion on the upstream side of the first nozzle hole, and covers the downstream side of the seat portion when the inner needle is closed. And

  If the seat portion is provided only on the upstream side of the first nozzle hole, and the first nozzle hole is substantially closed by covering the downstream side of the seat portion when the valve is closed, fuel leakage to the nozzle hole can be easily suppressed. And easy to process.

  Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1A is a schematic diagram showing the configuration of a common rail fuel injection system of a diesel engine including a fuel injection valve of the present invention, and FIG. 1B is a front end portion of a variable injection hole nozzle 1 (the main portion). It is an enlarged view of (shown as part A in the figure). In FIG. 1A, the variable nozzle hole 1 includes a twin needle type nozzle needle 2, and opens and closes the nozzle hole group 3 provided at the nozzle tip as the nozzle needle 2 is driven. Yes. The needle drive mechanism 6 that drives the nozzle needle 2 includes a control valve 7 and a piezo drive unit 8 in this example, and is controlled by the ECU 10. The drive unit is not limited to a piezo.

  The injected fuel is supplied from a common rail 9 common to each cylinder of the engine. A high-pressure pump 12 is connected to the common rail 9, and the fuel in the fuel tank 11 is pressurized by the high-pressure pump 12 and is pumped through the fuel passage 13 to be held at a predetermined high pressure.

  The variable nozzle hole 1 includes a nozzle body B in which a nozzle hole group 3 is formed at a conical tip B1, and a plate-shaped flow path forming member B2 stacked on top of the nozzle body B. And oil-tight. The nozzle body B is formed with a vertical hole 1a for accommodating the nozzle needle 2, and the inner peripheral surface of the front end portion of the vertical hole 1a has a conical shape along the shape of the front end portion B1. A plurality of first nozzle holes 31 and a plurality of second nozzle holes 32 constituting the nozzle hole group 3 are opened on the conical surface. The plurality of first injection holes 31 are arranged on the outer peripheral side of the conical surface, and the plurality of second injection holes 32 are arranged on the same surface on the inner peripheral side.

  The nozzle needle 2 includes a substantially cylindrical outer needle 21 and a shaft-shaped inner needle 22 that slides inside the outer needle 21. The outer needle 21 is inserted into a cylindrical spacer 23 whose upper end is disposed in the vertical hole 1a, and is held in a slidable state with respect to the first guide 51 on the inner peripheral surface of the spacer 23. The outer needle 21 is slidable with the outer peripheral surface of the sliding portion of the inner needle 22 as the second guide 52.

  The lower end portion of the outer needle 21 is opposed to a plurality of first injection holes 31 that extend to the tip end portion B1 of the nozzle body B and open to the inner peripheral conical surface. The lower end portion of the inner needle 22 protrudes from the lower end opening of the outer needle 21 toward the distal end side, and faces a plurality of second injection holes 32 that are opened at positions below the first injection holes 31. Therefore, when the nozzle needle 2 is at the lower end position, the outer needle 21 closes the plurality of first injection holes 31 and the inner needle 22 closes the plurality of second injection holes 32. Details of the configuration of the sheet portion of the variable nozzle hole 1 will be described later.

  A fuel reservoir 16 is formed on the outer peripheral side of the outer needle 21, and high-pressure fuel is supplied from a high-pressure passage 17 provided in the flow path forming member B2 through a space in the vertical hole 1a. The high pressure passage 17 communicates with the fuel supply passage 14 that reaches the common rail 9 via the high pressure passage 71 in the needle drive mechanism 6. In the flow path forming member B2, spaces communicating with the spaces in the spacer 23 are formed, and the control chamber 4 is configured in these spaces to generate the back pressure of the nozzle needle 2. A first spring 24 is disposed between the spacer 23 constituting the control chamber 4 and the flange 211 on the outer periphery of the outer needle 21 to urge the outer needle 21 in the valve closing direction. Further, in the control chamber 4, a second spring 25 that is supported on a flange 221 provided at the upper end of the inner needle 22 and urges the inner needle 22 in the valve closing direction is disposed.

  The hydraulic pressure in the control chamber 4 is controlled by the control valve 7 of the needle drive mechanism 6. The control valve 7 in this example has a two-position three-way valve structure, and either the high pressure passage 72 branched from the high pressure passage 71 or the low pressure passage 73 connected to the fuel discharge passage 15 to the fuel tank 11 is connected to the control chamber 4. Selectively communicate with. A control passage 41 communicating with the control valve 7 is opened on the top surface of the control chamber 4, and the high-pressure fuel in the common rail 9 passes through the control passage 41 from the high-pressure passage 72 at the illustrated position where the high-pressure passage 72 is opened. It will flow in after that. For this purpose, the outer needle 21 and the inner needle 22 are moved into the first injection hole 31 and the second injection hole 32 by the resultant force of the pressure of the control chamber 4 that is high pressure and the urging force of the first spring 24 and the second spring 25. The nozzle needle 2 is closed by being pressed.

  The piezo drive unit 8 of this example drives the control valve 7 by displacing the drive piston 82 by the drive force of the piezo actuator 81 and increasing or decreasing the pressure in the hydraulic chamber 83. The piezo actuator 6 includes, for example, a piezo stack formed by stacking piezoelectric bodies, and generates a displacement by extending the piezo stack by energization. Accordingly, when the position of the control valve 7 is switched and the low-pressure passage 73 and the control chamber 4 communicate with each other, the pressure in the control chamber 4 decreases, and the nozzle needle 2 opens.

  Here, the tip structure of the variable nozzle hole 1 which is a characteristic part of the present invention will be described with reference to FIG. In FIG. 1A, the tip B1 of the nozzle body B has a conical apex protruding toward the tip, and a sac chamber 5 is formed therein. As shown in FIG. 1 (b), the first nozzle hole 31 and the second nozzle hole 32 constituting the nozzle hole group 3 are provided so as to penetrate the tip B1 wall upstream of the sack chamber 5.

  The distal end surface of the outer needle 21 that closes the upstream first injection hole 31 is formed as a substantially conical surface along the inner peripheral conical surface of the distal end portion B1, and the opposite position of the first injection hole 31 is set in the circumferential direction. The first sheet 2a and the second sheet 2b are formed by edges on both sides thereof. Thus, when the outer needle 21 is closed, the first seat 2a is seated on the upstream side of the first injection hole 31, the second seat 2b is seated on the downstream side of the first injection hole 31, and the fuel is supplied to the first injection hole. It is prevented from flowing out to 31.

  The inner needle 22 that closes the second nozzle hole 32 on the downstream side has a lower end projecting downward from the outer needle 21 and has a stepped diameter reduction, and a small-diameter tip shaft portion 222 is located in the sac chamber 5. . The sac chamber 5 has a third guide 53 as a guide portion with the inner peripheral surface of the upper half portion having a constant diameter, and slidably holds the tip shaft portion 222 of the inner needle 22. The edge of the stepped portion of the inner needle 22 forms the third seat 2c and sits on the upstream side of the second injection hole 32 when the inner needle 22 is closed.

  Next, the operation of the fuel injection valve configured as described above will be described. 1A and 1B, when the piezo drive unit 8 of the needle drive mechanism 6 is not operated, the control valve 7 is in a position where the control chamber 4 and the high-pressure passage 72 are communicated with each other. At this time, since the high pressure fuel is introduced from the common rail 9 into the control chamber 4 via the control valve 7 and the control passage 41, the nozzle needle 2 is closed. In the outer needle 21, the first seat 2a and the second seat 2b are pressed against the seat surface by the resultant force of the fuel pressure in the control chamber 4 and the spring force of the first spring 24, and the first injection hole 31 is closed. To do. Similarly, the third seat 2c of the inner needle 22 is seated by the resultant force of the fuel pressure in the control chamber 4 and the spring force of the second spring 25, and the second injection hole 32 is closed.

  When the piezo stack 81 of the piezo drive unit 8 is energized and extended by a command from the ECU 10 and the drive piston 82 increases the pressure of the hydraulic chamber 83, the control valve 7 communicates with the control chamber 4 and the low pressure passage 73. Can be switched to. Thereby, the fuel in the control chamber 4 is discharged from the control passage 41 to the low pressure passage 73, and the control pressure gradually decreases. When the fuel pressure in the control chamber 4 falls below a predetermined pressure, the first seat 2a and the second seat 2b are separated from each other by the fuel pressure of the fuel reservoir 16 acting upward on the tip surface of the outer needle 21, and the outer needle 21 is Start the lift. Accordingly, the first injection hole 31 is opened and fuel is injected.

  Since the outer needle 21 is lifted while being guided at two locations of the first guide 51 and the second guide 52, the outer needle 21 can be lifted without being eccentric with respect to the axis center of the nozzle body B. Therefore, the spray injected from the plurality of first injection holes 31 is uniform and a good combustion state is obtained. When the outer needle 21 is further lifted, its upper end surface collides with the flange 221 of the inner needle 22 and pushes it up. For this reason, the 3rd sheet | seat 2c of the inner needle 22 leaves | separates, and a lift is started. Thereafter, the outer needle 21 and the inner needle 22 are lifted together.

  As shown in FIG. 2, the second injection hole 31 is opened with the lift of the inner needle 22, and fuel is injected from both injection holes 31 and 32. Here, the inner needle 22 is configured such that the tip shaft portion 222 having a small diameter slides in the sac chamber 5, and the third guide 53 and the second guide of the sac chamber 5 after the third seat 2 c is separated. Since the lift is performed while being guided at two positions 52, the lift can be performed without being eccentric with respect to the center of the axis of the nozzle body B. Therefore, unlike the conventional configuration, there is no possibility of axis deviation, and uniform spray is injected from the plurality of second injection holes 32, so that a good combustion state is realized.

  When the injection is stopped, the control valve 7 is switched to the initial position by the piezo drive unit 8 in FIG. 1A, and high-pressure fuel is introduced from the common rail 9 into the control chamber 4 through the control valve 7 and the control passage 41. When the pressure in the control chamber 4 rises again and exceeds the predetermined pressure, the outer needle 21 and the inner needle 22 are lowered. At this time, first, the inner needle 22 is lowered while being guided at two locations of the third guide 53 and the second guide 52, and the third seat 2 c is seated on the upstream side of the second injection hole 32. As a result, the gap between the fuel reservoir 16 and the second injection hole 32 is cut off, and fuel injection from the second injection hole 32 is stopped.

  On the other hand, the outer needle 21 is further lowered while being separated from the flange 221 of the inner needle 22 and being guided at two locations of the first guide 51 and the second guide 52. When the first seat 2a and the second seat 2b of the inner needle 22 are seated and the first injection hole 31 is closed, the fuel injection is stopped. At this time, the first seat 2a sits on the upstream side of the first injection hole 31 and blocks the fuel reservoir 16, and the second sheet 2b blocks the downstream side of the first injection hole 31. It is possible to prevent fuel leaking from the outer needle 21 and the inner needle 22 from being injected into the first injection hole 31.

  Thus, according to the present embodiment, the third guide 53 as the guide portion is formed in the sack chamber 5 to guide the distal end shaft portion 222 of the inner needle 22, so that the nozzle needle 2 is opened. Misalignment of the spray nozzles can be prevented, and variations in spray spray holes can be reduced. Therefore, an effect of forming stable fuel spray and reducing exhaust emission and the like can be obtained.

  FIG. 3 shows the configuration of the tip of the variable nozzle nozzle 1 in the second embodiment of the present invention. The basic structure of the fuel injection valve of the present embodiment is the same as that of the first embodiment shown in FIG. 1 and will be described below with a focus on the differences. In the variable nozzle nozzle 1 of the present embodiment, the tip shaft portion 222 of the inner needle 22 that slides in the sac chamber 5 is formed by cutting out a part of the outer peripheral surface. Specifically, as shown in FIG. 3, three portions on the outer peripheral surface of the tip shaft portion 222 are cut out in the axial direction to form a flat surface, and a communication hole is formed between the third guide 53 on the inner peripheral surface of the sack chamber 5. 223 is formed.

  The upper end of the communication hole 223 opens to the space 54 between the inner peripheral conical surface of the distal end B1 reaching the sack chamber 5 and the stepped portion of the inner needle 22 on the downstream side of the third seat 2c. It opens to the sack chamber 5 below the tip shaft portion 222. The space 54 communicates with the upstream fuel reservoir 16 when the inner needle 22 is opened, and becomes a closed space when the third seat 2c is seated when the inner needle 22 is closed.

  In the configuration that does not have the communication hole 223, when the inner needle 22 is closed, the fuel in the lower sac chamber 5 is compressed as the distal end shaft portion 222 is lowered, so that the valve closing speed is reduced. The operation of 22 may become unstable. On the other hand, in the configuration of the present embodiment, the suck chamber 5 and the space 54 upstream of the tip shaft portion 222 are always in communication with each other through the communication hole 223, and the initial valve closing of the inner needle 22 is performed through the third seat 2c. Since the fuel reservoir 16 is also communicated, the fuel can flow out of the sac chamber 5 as the tip shaft portion 222 is lowered. Therefore, the pressure fluctuation in the sac chamber 5 is suppressed, and the inner needle 22 can be operated stably.

  FIG. 4 shows a third embodiment of the present invention. The basic structure of the present embodiment is the same as that of the second embodiment, and the differences will be mainly described below. The variable injection hole nozzle 1 of the present embodiment communicates with the space 54 between the third seat 2 c and the tip shaft portion 222 and the space in the sack chamber 5 at all times inside the tip shaft portion 222 of the inner needle 22. A hole 224 is provided. Specifically, as shown in FIG. 3, a T-shaped hole is provided in the tip shaft portion 222 to form a communication hole 224, the lower end thereof is opened to the sack chamber 5, and both upper ends are opened to the space 54.

  As in this embodiment, instead of the communication hole 223 in the second embodiment, the communication hole 224 may be provided inside the distal end shaft portion 222. Also in this case, when the inner needle 22 is closed, the fuel in the sac chamber 5 can flow out through the space 54 upstream of the communication hole 224 and the tip shaft portion 222. Therefore, the pressure fluctuation in the sac chamber 5 is suppressed, and the inner needle 22 can be operated stably.

  FIG. 5 shows a fourth embodiment of the present invention. The basic structure of the present embodiment is the same as that of the third embodiment, and the differences will be mainly described below. As shown in FIG. 5A, the variable nozzle hole 1 of the present embodiment does not have the third sheet 2c and the space 54 at the lower end portion of the inner needle 22, and has a conical surface that continues to the small-diameter tip shaft portion 222 at the tip. The shape is along the inner peripheral conical surface of the part B1. A T-shaped communication hole 224 that opens into the space inside the sac chamber 5 is provided in the distal end shaft portion 222, and both upper ends thereof are opened at positions facing the upper end edge of the sack chamber 5. Further, the second injection hole 32 is opened on the inner peripheral surface of the sack chamber 5 constituting the third guide 53.

  According to this embodiment, when the inner needle 22 in FIG. 5A is in the valve closing position, the second injection hole 32 is closed by the distal end shaft portion 222. As shown in FIG. 5B, when the inner needle 22 is lifted, the communication passage 224 and the second injection hole 32 are opened, and the fuel flowing into the sac chamber 5 from the fuel reservoir 16 through the communication hole 224 becomes the first. The two injection holes 32 are injected.

  At this time, a lift amount L (a distance from the outer peripheral edge of the lower end of the tip shaft portion 222 to the second nozzle hole 32) from when the inner needle 22 starts to lift to when the second nozzle hole 32 starts to be lifted is arbitrarily set. Thus, the second nozzle hole opening timing can be freely set. In the configuration of each of the above embodiments, the second nozzle hole opening timing is set by the lift amount until the outer needle 21 contacts the inner needle 22, the position of the top of the outer needle 21 with respect to the nozzle body B, Since it is necessary to manage the gap from the position of the flange 221 of the inner needle 22, there are three related parts, which takes time and trouble. On the other hand, in the configuration of the present embodiment, only the lift amount L dimension with respect to the nozzle body B needs to be managed, and the adjustment is made only by the inner needle 22, so that it can be simplified. Therefore, the injection timing from the second injection hole 32 can be easily controlled.

  FIG. 6 shows a fifth embodiment of the present invention. The basic structure of the present embodiment is the same as that of the fourth embodiment, and the differences will be mainly described below. As shown in FIG. 6A, the variable nozzle nozzle 1 of the present embodiment extends the spacer 23 below the second guide 52 of the outer needle 21 and the inner needle 22, and forms an annular groove on the inner periphery of the lower end of the spacer 23. A low pressure chamber 43 is formed between the outer needle 21 and the outer needle 21. The low pressure chamber 43 communicates with the fuel discharge passage 15 of FIG. 1 through a low pressure passage 44 formed in the axial direction in the spacer 23 and the flow path forming member B2, and constitutes a low pressure portion in the nozzle body B. In addition, the outer needle 21 is provided with a radial through hole at a position adjacent to the low pressure chamber 43 to form a communication path 42 between the outer needle 21 and the inner needle 22 and the low pressure chamber 43.

  According to the present embodiment, since the gap between the outer needle 21 and the inner needle 22 communicates with the low pressure chamber 43 via the communication path 42, the fuel in the fuel reservoir 16 moves toward the inner needle 22 after the outer needle 21 is opened. Leakage can be suppressed. In the configuration of the inner needle 22 of the fourth embodiment (see FIG. 5), the third seat 2c is omitted, and the fuel in the fuel reservoir 16 passes from the sliding portion of the tip shaft portion 222 to the second injection hole 32. There is a risk of leakage. The amount of leakage of the sliding portion is generated from a slight clearance with the third guide 53 and is not a large amount of leakage, but can be further reduced by configuring the low pressure chamber 43.

  Further, as shown in FIG. 6B, the seat portion of the outer needle 21 is configured only by the first seat 2 a upstream of the first injection hole 31, and the first seat 2 a is closed when the outer needle 21 is closed. The downstream outer needle 21 tip surface is close to the inner peripheral surface of the nozzle body tip B1 and substantially covers the inlet of the first injection hole 31 (so-called VCO method). In this way, it is possible to provide a single-sheet configuration in which a sheet is provided only on the upstream side and the downstream sheet is omitted as a VCO system, and complicated processing is not required, so that manufacture is facilitated.

  If comprised as mentioned above, in a twin needle type variable nozzle hole nozzle, the dispersion | variation between the nozzle holes of the spray by the axial shift of an inner needle can be reduced, favorable combustion can be implement | achieved, and an exhaust state can be improved. .

  Note that the configurations of the needle drive mechanism, for example, the control valve and the piezo drive unit in the above embodiment are not limited to this, and other configurations may be employed. Further, an electromagnetic drive unit having a solenoid may be used instead of the piezo drive unit.

BRIEF DESCRIPTION OF THE DRAWINGS (a) is the whole structure schematic diagram of the fuel injection system of the diesel engine containing the fuel injection valve of the 1st Embodiment of this invention, (b) is a principal part expansion of the variable injection hole nozzle in 1st Embodiment. It is sectional drawing and is the A section enlarged view of (a). It is a principal part expanded sectional view of the variable nozzle hole nozzle in 1st Embodiment, and is a figure which shows the state at the time of nozzle needle valve opening. It is a principal part expanded sectional view of the variable nozzle hole nozzle in 2nd Embodiment. It is a principal part expanded sectional view of the variable nozzle hole in 3rd Embodiment. (A) is a principal part expanded sectional view of the variable injection hole nozzle in 4th Embodiment, and is a figure which shows the state at the time of valve closing, (b) is a principal part expanded sectional view which shows the state at the time of valve opening. (A) is the upper expanded sectional view of the variable nozzle hole nozzle in 5th Embodiment, (b) is the principal part expanded sectional view. (A) is the principal part expanded sectional view of the variable injection hole nozzle in the conventional fuel injection valve, (b) is the principal part expanded sectional view, and is the A section enlarged view of (a).

Explanation of symbols

B Nozzle body B1 Tip portion 1 Variable nozzle nozzle 1a Vertical hole 14 Fuel supply passage 15 Fuel discharge passage 16 Fuel reservoir 17 High pressure passage 2 Nozzle needle 21 Outer needle 211 Flange 22 Inner needle 221 Flange 222 Tip shaft portion 223 Communication hole 224 Communication hole 23 Spacer 24 First spring 25 Second spring 26 Orifice passage 27 Groove 3 Injection hole group 31 First injection hole 32 Second injection hole 4 Control chamber 41 Control passage 43 Low pressure chamber (low pressure portion)
44 Low pressure passage (low pressure section)
45 Communication passage 5 Suck chamber 51 First guide 52 Second guide 53 Third guide 6 Needle drive mechanism 7 Control valve 71, 72 High pressure passage 73 Low pressure passage 8 Piezo drive 9 Common rail

Claims (7)

A fuel injection valve comprising a variable nozzle nozzle that opens and closes a plurality of nozzle holes provided at the tip of a nozzle body with a plurality of needles,
An outer needle that is slidably disposed in the nozzle body and opens and closes the first nozzle hole;
An inner needle that is slidably disposed in the outer needle and opens and closes the second nozzle hole;
A control chamber for applying pressure in the valve closing direction to the outer needle and the inner needle;
With the pressure drop in the control chamber, the outer needle is lifted in advance, the outer needle is in contact with the inner needle and lifts it,
A fuel injection valve characterized in that a guide portion for slidably holding the tip shaft portion of the inner needle is provided on the inner periphery of the tip portion of the nozzle body.   2. The fuel injection valve according to claim 1, wherein the tip end shaft portion of the inner needle held by the guide portion has a shape in which a part of the outer peripheral surface is notched in the axial direction.   2. The fuel injection valve according to claim 1, wherein the inner needle is provided with a communication hole that communicates the inner space of the tip of the nozzle body and the upstream side of the tip shaft in the tip shaft.   The second nozzle hole is formed in a tip wall of the nozzle body in which the guide part is formed, and the opening of the second nozzle hole is controlled by a lift of a tip shaft part of the inner needle. The fuel injection valve as described.   The fuel injection valve according to claim 4, wherein a tip shaft portion of the inner needle is a seal portion of the second injection hole.   The fuel injection valve according to any one of claims 1 to 5, wherein a gap between the outer needle and the inner needle is opened to a low pressure portion provided in a nozzle body. The said outer needle has a sheet | seat part in the upstream of the said 1st nozzle hole, and is a shape which covers the said sheet | seat part downstream side at the time of valve closing of the said outer needle. Fuel injection valve.