JP4294671B2 - Fuel injection device - Google Patents

Description

  The present invention relates to a fuel injection device used for injecting and supplying fuel to an internal combustion engine such as a diesel engine, and more particularly to a fuel injection device including 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 device 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 Document 1).
JP 2005-320904 A

  The variable nozzle hole disclosed in Patent Document 1 is configured to slidably hold a nozzle needle in a cylindrical nozzle body and open and close a plurality of nozzle holes formed in the axial direction at the tip of the nozzle body. . The nozzle needle is a twin needle type in which an inner needle is slidably provided inside a hollow cylindrical outer needle. The outer needle and the inner needle are urged in the valve closing direction by spring members arranged on the upper portions thereof. ing. A pressure control chamber is provided above the nozzle needle, and back pressure is applied to the outer needle and the inner needle by high-pressure fuel supplied from a high-pressure passage. The pressure control chamber communicates with the low pressure passage through the out orifice, and the pressure is increased or decreased by opening and closing a control valve provided at the outlet of the pressure control chamber.

  In the above configuration, when the control valve is driven to connect the pressure control chamber to the low pressure passage, the fuel in the pressure control chamber is discharged, and the back pressure acting on the nozzle needle is reduced. Along with this, the outer needle precedes to start the lift, and the tip side of the plurality of nozzle holes is opened. When the outer needle is further lifted and comes into contact with the inner needle, thereafter, both needles are lifted together to open the remaining nozzle holes. As a result, only the outer needle can be lifted to perform a small amount of fuel injection when the load is low, and both the outer needle and the inner needle can be lifted to increase the fuel injection amount when the load is high. Advanced injection amount control becomes possible.

  However, in the configuration of the above prior art, when the outer needle collides with the inner needle and pushes it up, a phenomenon occurs in which the inner needle bounces due to an impact received from the outer needle. Due to this phenomenon, the opening / closing operation of the injection hole is likely to be unstable, and the injection amount fluctuates when the inner needle is once lifted to open the injection hole and then lowered to close the injection hole again. For this reason, there has been a problem that the injection amount varies when the inner needle is opened or before and after.

  Therefore, an object of the present invention is to suppress bounce of the inner needle due to the collision of the outer needle and reduce the variation in the injection amount when the nozzle needle is opened in the fuel injection device having the twin needle type variable injection hole nozzle. Thus, an object of the present invention is to provide a high-performance fuel injection device capable of performing advanced injection amount control according to the operating state.

  According to a first aspect of the present invention, there is provided a fuel injection device including a variable nozzle hole that opens and closes a plurality of nozzle holes provided at a tip of a nozzle body by a first nozzle needle and a second nozzle needle that are coaxially disposed. The lift of the first nozzle needle and the second nozzle needle is controlled by increasing / decreasing the pressure of the control chamber acting in the valve closing direction by the needle drive unit, and the first nozzle needle is advanced as the pressure in the control chamber decreases. It is configured to lift and abut against the second nozzle needle to lift it. Furthermore, an impact mitigating means is provided that absorbs the impact caused by the contact between the first nozzle needle and the second nozzle needle and suppresses the variation in the lift amount of the second nozzle needle.

  According to the above configuration, since the impact that occurs when the first nozzle needle that is lifted in advance collides with the second nozzle needle is absorbed by the impact relaxation means, it is possible to prevent the second nozzle needle from floating and bouncing. Accordingly, the controllability of the lift amount of the nozzle needle is improved, the variation in the injection amount is improved, and a stable operation can be realized.

  According to a second aspect of the present invention, the impact mitigating means is a damper chamber that mitigates the impact force by an increase in pressure, or a buffer member that is made of a soft material or an elastic material and can absorb the impact force.

  Specifically, the shock when the first nozzle needle collides with the second nozzle needle due to the oil pressure in the damper chamber is reduced, or a buffer member made of an elastic material or a soft material is disposed between both needles, Can absorb impact force.

  In the invention of claim 3, the impact reducing means is a damper chamber provided on the back side of the second nozzle needle.

  By providing a hydraulic chamber serving as a damper chamber on the back side of the second nozzle needle and applying a pressure in the direction opposite to the lift, the rising force by the first nozzle needle can be suppressed, and bounce due to collision can be easily reduced. .

  According to a fourth aspect of the present invention, the impact mitigating means is a buffer member provided on a contact end surface of the first nozzle needle with the second nozzle needle.

  For example, a part of the first nozzle needle that comes into contact with the second nozzle needle is made of a soft material, so that it can function as a buffer member that absorbs an impact force when coming into contact with the second nozzle needle.

  In the invention of claim 5, the damper chamber of claim 2 is provided in the control chamber in which the pressure in the valve closing direction is applied. At this time, as in the sixth aspect of the invention, it is possible to provide an orifice for limiting the amount of fluid flowing from the damper chamber to the control chamber and adjusting the pressure of the damper chamber.

  Specifically, in the control chamber, the space above the second nozzle needle can be partitioned from the control chamber via an orifice and function as a damper chamber. At this time, by properly setting the orifice and restricting the fluid outflow, the pressure is increased at the time of the collision of the first nozzle needle, and the lift is effectively suppressed by acting in the direction opposite to the lift of the second nozzle needle. it can.

  In the invention of claim 7, the damper chamber is a chamber provided between the one-end-closed cylindrical container body installed in the control chamber and the back surface of the second nozzle needle slidably inserted into the opening. .

  By using a cylindrical container as a constituent member of the damper chamber, the damper chamber can be easily set.

  According to an eighth aspect of the present invention, the damper chamber is a chamber provided between the one-end closed space formed in the body member and the back surface of the second nozzle needle slidably inserted into the opening.

  By providing the damper chamber integrally with the body member, the posture retention of the second nozzle needle is improved.

  According to a ninth aspect of the present invention, the impact mitigating means is one or both of a damper chamber and a buffer member interposed between contact portions of the first nozzle needle and the second nozzle needle.

  A hydraulic chamber serving as a damper chamber may be provided between the contact portions of the first nozzle needle and the second nozzle needle, or a buffer member capable of absorbing an impact may be provided. By interposing one or both of the damper chamber and the buffer member, the impact transmitted to the second nozzle needle is reduced, and the same effect of suppressing bounce can be obtained.

  In the invention of claim 10, the damper chamber of claim 4 is constituted by a movable member disposed between the opposed end surfaces of the first nozzle needle and the second nozzle needle in the control chamber.

  A movable member is disposed between the opposed end surfaces of the first nozzle needle and the second nozzle needle, and the pressure of the space formed between the movable member and the second nozzle needle is increased by the lift of the first nozzle needle. Thus, it can function as a damper chamber.

  In the invention of claim 11, the damper chamber of claim 2 is communicated with the high-pressure passage, and a high pressure is always applied to the back surface of the second nozzle needle.

  A high-pressure damper chamber may be provided above the second nozzle needle so that the high pressure of the damper chamber is always applied, and the same effect of suppressing lift lifting force and bounce can be obtained.

  As in the twelfth aspect of the present invention, preferably, the first nozzle needle is formed in a cylindrical shape, and the second nozzle needle is slidably disposed therein. At this time, by providing a first spring and a second spring for urging the first nozzle needle and the second nozzle needle in the valve closing direction, the first nozzle needle and the second nozzle needle are quickly closed when the valve is closed. It can be moved to the valve position.

  Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing an overall configuration of a common rail fuel injection device for a diesel engine to which the present invention is applied, and FIG. 2 shows an enlarged view of a variable injection nozzle 1 which is a main part thereof. In FIG. 1, the fuel injection device includes a variable nozzle hole nozzle 1 having a twin needle type nozzle needle 2, and opens and closes a nozzle hole group 3 provided at the nozzle tip as the nozzle needle 2 is driven. It has become. A needle drive mechanism 6 as a needle drive unit for driving the nozzle needle 2 includes a control valve 7 and a piezo drive unit 8 and is controlled by the ECU 10.

  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 so as to be maintained at a predetermined high pressure.

  The body B of the variable nozzle hole 1 is formed by laminating a plate-shaped flow path forming member B2 on the nozzle body B1 in which the nozzle hole group 3 is formed at the tip cone portion, and tightening the outer periphery of these body members with a retaining nut B3. It is fixed. The nozzle body B1 is formed with a vertical hole 1a for accommodating the nozzle needle 2, and a plurality of first injection holes 31 and a plurality of second injection holes 32 constituting the injection hole group 3 are opened on the inner peripheral surface of the front end portion of the vertical hole 1a. is doing. The plurality of first injection holes 31 are disposed above the plurality of second injection holes 32.

  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 and corresponds to a first nozzle needle and a second nozzle needle, respectively. The outer needle 21, which is the first nozzle needle, is slidably held by a cylinder member 23 having an upper end portion disposed in the vertical hole 1a, and a lower end portion extends to the tip conical portion of the nozzle body B1 to be a plurality of second needles. It faces one nozzle hole 31. The lower end portion of the inner needle 22 that is the second nozzle needle protrudes downward from the lower end opening of the outer needle 21 and faces the plurality of second injection holes 32. 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.

  A fuel reservoir 16 is formed on the outer periphery of the intermediate portion 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. Spaces communicating with the internal space of the cylinder member 23 are formed in the flow path forming member B2, and the hydraulic pressure control chamber 4 serving as a control chamber is configured in these spaces to generate the back pressure of the nozzle needle 2. A return spring 24 as a first spring member is disposed on the outer periphery of the upper end portion of the outer needle 21, and a return spring 25 as a second spring member is disposed on the outer periphery of the upper end portion of the inner needle 22. The outer needle 21 and the inner needle 22 are urged downward, respectively.

  The hydraulic pressure in the hydraulic control chamber 4 is controlled by the control valve 7 of the needle drive mechanism 6. The control valve 7 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 selected as the hydraulic control chamber 4. Communicate. A communication path 74 to the control valve 7 is opened on the top surface of the hydraulic control chamber 4, and high-pressure fuel in the common rail 9 passes through the communication path 74 from the high-pressure path 72 at the illustrated position where the high-pressure path 72 is opened. It will flow in after that. For this reason, the pressure of the hydraulic control chamber 5 that is high pressure and the urging force of the return springs 24 and 25 act in the valve closing direction to press the nozzle needle 2 against the nozzle holes 31 and 32.

  The piezo drive unit 8 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 hydraulic control chamber 4 communicate with each other, the pressure in the hydraulic control chamber 4 decreases, so that the nozzle needle 2 opens.

Here, the impact mitigation means which is a characteristic part of the present invention will be described with reference to FIG. FIG. 2 schematically shows the structure of the variable nozzle nozzle 1 in FIG. 1, and there is no substantial difference from FIG.
In the twin needle type variable injection nozzle 1 employed by the present invention, when the fuel pressure in the hydraulic control chamber 4 decreases, the outer needle 21 first lifts to open the first injection hole 31 and then pushes up to the outer needle 21. Thus, the inner needle 22 is lifted to open the second injection hole 32. At this time, bounce due to the collision between the outer needle 21 and the inner needle 22 is likely to occur, and in order to suppress this, in this embodiment, the damper chamber 5 is provided on the back side of the inner needle 22 as shock absorbing means. This back side is located above the inner needle 22 in the lift direction (on the opposite injection hole side) in FIG.

  Specifically, a cylindrical container body 26 closed at the upper end is accommodated in the hydraulic control chamber 4, and the inner needle 22 is slidably inserted from the lower end opening with the inner periphery thereof as a cylinder. At this time, a space surrounded by the inner peripheral surface of the cylindrical container body 26 and the upper end surface of the inner needle 22 is defined as a damper chamber 5. In the present embodiment, the damper chamber 5 is configured to communicate with the hydraulic control chamber 4 via an orifice 51 provided on the upper cylindrical wall of the cylindrical container body 26. The diameter of the orifice 51 is set to be smaller than the orifice provided in the communication passage 74 between the hydraulic control chamber 4 and the control valve so that the damper effect can be sufficiently exerted, and the hydraulic control chamber 4 is opened when the nozzle needle 2 is opened. The pressure drops with a delay. A flange 261 is provided on the outer periphery of the cylindrical wall of the cylindrical container body 26, and a return spring 25 that biases the inner needle 22 in the valve closing direction is disposed between the flange 261 and the flange 221 on the outer periphery of the inner needle 22. Has been. The return spring 24 that urges the outer needle 21 in the valve closing direction is disposed between the cylinder member 23 constituting the hydraulic control chamber 4 and the flange 211 on the outer periphery of the outer needle 21.

  Next, the operation of the fuel injection device having the above configuration will be described. In the state of FIG. 1 in which the piezo drive unit 8 of the needle drive mechanism 6 does not operate, the control valve 7 is in a position where the hydraulic control chamber 4 and the high pressure passage 72 are communicated with each other. Thus, high pressure fuel is introduced into the hydraulic control chamber 4. The damper chamber 5 communicating with the hydraulic control chamber 4 via the orifice 51 is also at a high pressure. At this time, the outer needle 21 is pressed against the first injection hole 31 by the fuel pressure of the hydraulic control chamber 4 and the spring force of the return spring 24, and the inner needle 22 is pressed by the fuel pressure of the damper chamber 5 and the spring of the return spring 25. The nozzle needle 2 is closed by the force and is pressed against the second nozzle hole 32.

  When the piezo stack 81 of the piezo drive unit 8 is extended by energization according to a command from the ECU 10 and the drive piston 82 increases the pressure in the hydraulic chamber 83, the control valve 7 communicates with the hydraulic control chamber 4 and the low pressure passage 73. Can be switched to. As a result, the fuel in the hydraulic control chamber 4 is discharged from the communication passage 74 to the low pressure passage 73, and the control pressure gradually decreases. When the fuel pressure in the hydraulic control chamber 4 falls below a predetermined pressure, the outer needle 21 starts to lift and opens the first injection hole 31 due to the high pressure fuel pressure acting upward on the outer needle 21.

  The left half of FIG. 2 shows a state where only the outer needle 21 is lifted and fuel is injected from the first injection hole 31. Here, as the pressure in the hydraulic control chamber 4 decreases, the pressure in the damper chamber 5 also decreases. However, since the outflow of fuel is restricted by the orifice 51, the pressure in the damper chamber 5 is kept relatively high. When the outer needle 21 is further lifted, the upper end surface of the outer needle 21 collides with the flange 221 of the inner needle 22, and the inner needle 22 starts to be lifted to push it up.

  At this time, as the outer needle 21 collides with the inner needle 22, the upper end surface of the inner needle 22 moves upward, and the pressure in the damper chamber 5 using this as the chamber wall is increased. The oil pressure in the damper chamber 5 acts to suppress the ascending force of the inner needle 22 and prevents bounce. Therefore, the outer needle 21 and the inner needle 22 are united and smoothly raised, and the second injection hole 32 is opened. The right half of FIG. 2 shows this state. The outer needle 21 and the inner needle 22 are lifted, and fuel is injected from both the first injection hole 31 and the second injection hole 32.

  When the injection is stopped, the control valve 7 is switched to the initial position by the piezo drive unit 8 in FIG. 1, and high-pressure fuel is introduced from the common rail 9 into the hydraulic control chamber 4 through the control valve 7 and the communication path 74. As a result, the pressure in the hydraulic control chamber 4 rises again, and when the pressure exceeds a predetermined pressure, the outer needle 21 and the inner needle 22 are lowered. When the inner needle 22 closes the second injection hole 32, the outer needle 21 moves further away from the flange 221 of the inner needle 22 and closes the first injection hole 31.

  As described above, according to the present embodiment, the damper chamber 5 provided in the hydraulic control chamber 4 has a damper function to alleviate the impact caused by the collision between the outer needle 21 and the inner needle 22, so that bounce of the inner needle 22 is suppressed. can do. Therefore, it becomes possible to prevent unstable operation when the inner needle 22 is opened and before and after the valve opening, thereby enabling stable fuel injection control.

  Further, since the hydraulic control chamber 4 for the outer needle 21 is reduced by the volume of the damper chamber 5, the diameter of the communication passage 74 can be reduced accordingly. For example, it is desired to reduce the valve opening speed at the initial rise of the outer needle 21, and the lift speed of the outer needle 21 can be suppressed by reducing the diameter of the communication path 74 and suppressing fuel outflow. Further, the decrease in pressure in the hydraulic control chamber 4 is mitigated by the outflow of fuel from the damper chamber 5 to the hydraulic control chamber 4.

  In this way, by suppressing the lift increase of the outer needle 21, the inclination of the diagram indicated by the injection pulse T and the injection amount Q can be reduced. As a result, the controllability of the minute injection amount such as pilot injection is improved, which is effective in improving the fuel consumption during light load operation and reducing the combustion noise.

  FIG. 3 shows a second embodiment of the present invention. In the first embodiment, the damper chamber 5 is provided above the inner needle 22 in the lift direction as impact mitigating means. However, in this embodiment, a buffer member is provided above the outer needle 21 in the lift direction. The basic structure of the variable nozzle nozzle 1 shown schematically in FIG. 3 is the same as that of the first embodiment, and the following description will be focused on the differences. In FIG. 3, a substantially cylindrical outer needle 21 is configured such that an upper end 21 </ b> A facing the flange 221 on the outer periphery of the inner needle 22 is made of a softer material than the base material of the outer needle 21, It is functioning as. Specifically, when heat treatment is performed in the manufacturing process of the outer needle 21, only the upper end portion 21 </ b> A is masked and subjected to a carbon-proof treatment, so that it can be softer than the base material and have a buffer function. Preferably, the outer needle 21 base material can be SKH2 (heat treatment QT: HRC60 vicinity) and the upper end 21A can be 45C (raw material: HRC30 vicinity), and the impact absorption effect is high.

  From this state, when the hydraulic control chamber 4 is communicated with the low pressure passage 73 by the needle drive mechanism 6 of FIG. 1, the pressure in the hydraulic control chamber 4 decreases, the outer needle 21 starts to lift, and the first injection hole 31 is opened. Open (see left half of FIG. 3). When the outer needle 21 is further lifted, the upper end 21A pushes up the flange 221 on the outer periphery of the inner needle 22 (see the right half of FIG. 3). At this time, bounce of the inner needle 22 can be suppressed because the upper end portion 21A made of a soft material alleviates the impact force caused by the collision.

  Thus, even with the configuration in which the buffer member is provided on the outer needle 21 side, the operation before and after the inner needle 22 is opened is prevented from becoming unstable, and the same effect as in the first embodiment can be obtained. . Moreover, although the buffer member is provided integrally with the outer needle 21 here, it may be a separate body. In this case, a ring-shaped member that is softer than the outer needle 21 and the base material, for example, made of soft rope (or a member made of the same material as the outer needle 21 may be softened and softened) is inserted and arranged. Can do.

  FIG. 4 shows a third embodiment of the present invention. In the present embodiment, a damper chamber 5 </ b> A serving as an impact mitigating means is disposed between the contact portions of the outer needle 21 and the inner needle 22. The basic structure of the variable nozzle nozzle 1 schematically shown in FIG. 4 is the same as that of the first embodiment, and the following description will focus on the differences. In FIG. 4, a ring-shaped movable plate 52 serving as an impact reducing means is accommodated in the hydraulic control chamber 4 between the upper end surface of the outer needle 21 and the flange 221 on the outer periphery of the inner needle 22. The movable plate 52 is formed to have an outer diameter slightly larger than the flange 221 on the outer periphery of the inner needle 22 and constitutes the damper chamber 5A and functions as a buffer member. As the material of the movable plate 42, for example, a metal material having high elasticity is preferably used.

  When the nozzle needle 2 is at the lower end position, the damper chamber 5A is configured in a space formed between the movable plate 52 and the flange 221 above it. At this time, the damper chamber 5A communicates with the hydraulic control chamber 4 thereabove via the clearance on the outer periphery of the flange 221. The outer peripheral edge of the outer needle 21 is chamfered so that the contact area with the movable plate 52 is reduced.

  From this state, when the hydraulic control chamber 4 is communicated with the low pressure passage 73 by the needle drive mechanism 6, the pressure in the hydraulic control chamber 4 decreases, the outer needle 21 starts to lift, and the first injection hole 31 is opened ( (See the left half of FIG. 4). When the outer needle 21 lifts and pushes up the movable plate 52 (see the right half of FIG. 4), the pressure in the damper chamber 5A rises to generate a damper effect, and the outer needle 21 collides with the elastic force of the movable plate 52. Relieve power. Therefore, when the outer needle 21 collides with the inner needle 22, a downward acting force can be generated to prevent the inner needle 22 from being lifted.

  According to the above configuration, the damper chamber 5A can be configured relatively simply using the movable plate 52, and the same effect as in the first embodiment can be obtained. Further, since the outer needle 21 presses the movable plate 52 against the inner needle 22, the squeeze force makes it difficult for the movable plate 52 to be separated from the inner needle 22 when the valve is closed. Since the upper end surface is chamfered and the generation of the squeeze force is suppressed, the outer needle 21 is easily separated from the movable plate 52 to perform the valve closing operation. For this reason, it is possible to control the lift of the nozzle needle 2 with high accuracy.

  FIG. 5 shows a fourth embodiment of the present invention. In the present embodiment, the damper chamber 5A serving as an impact mitigation means is disposed between the contact portions of the outer needle 21 and the inner needle 22 and is substantially disposed so as to cover the flange 221 on the outer periphery of the inner needle 22. It is composed of a letter-shaped movable member 53. The basic structure of the variable nozzle nozzle 1 shown schematically in FIG. 5A is the same as that of the first embodiment, and the differences will be mainly described below. 5A, the movable member 53 includes a ring-shaped lower member 53a having a substantially L-shaped cross section and a plate ring-shaped upper member 53b. The lower member 53a is located between the upper end surface of the outer needle 21 and the flange 221 on the outer periphery of the inner needle 22, and a vertical wall extending upward from the outer peripheral edge thereof is in contact with the outer surface of the flange 221. The upper member 53b is disposed on the upper surface of the flange 221, and is pressed against the upper surface of the flange 221 by a return spring 25 disposed above the upper member 53b. The damper chamber 5 </ b> A includes a space formed between the upper member 53 b and the lower member 53 a and the flange 221.

  As shown in FIGS. 5B and 5C, the space that becomes the damper chamber 5 </ b> A is alternately formed at the lower position and the upper position of the flange 221 by the change in the relative position of the outer needle 21 and the inner needle 22. The clearance L1 formed at the lower part of the flange 221 at the time of the outer seat (FIG. 5B) is the same as the clearance L1 formed at the upper part of the flange 221 at the time of full lift (FIG. 5C).

  The operation of this embodiment will be described. As in the above embodiment, when the pressure in the hydraulic control chamber 4 decreases, the outer needle 21 first starts to lift and opens the first injection hole 31 (see the left half of FIG. 5A). Next, the outer needle 21 lifts and pushes up the movable member 53 (see the right half of FIG. 5A). Here, the damper chamber 5A is at the lower position of the flange 221 at the time of the outer seat shown in FIG. 6B, and its volume decreases with the lift. Along with this, the volume of the damper chamber 5A formed at the upper position of the flange 221 expands and becomes maximum at the time of the full lift shown in FIG.

  Thus, in this embodiment, the damper chamber 5A formed above and below the flange is alternately expanded and contracted by the relative position change (any movement) of the outer needle 21 and the inner needle 22. With this configuration, a braking effect can be produced in all steps in which the outer needle 21 and the inner needle 22 change relative positions, and the collision force between the outer needle 21 and the inner needle 22 is alleviated, so that the bounce of the inner needle 22 is achieved. A similar effect can be obtained. Moreover, since the substantially U-shaped movable member 53 is used, the volume of the damper chamber 5A and the clearance L1 can be easily set, and the damper effect is enhanced. Furthermore, since the biasing force from the return spring 25 is received when the injection is stopped, the movable member 53 can be forcibly returned to the initial position.

  FIG. 6 shows a fifth embodiment of the invention. In the first embodiment, the orifice 51 that communicates the damper chamber 5 and the hydraulic control chamber 4 serving as the impact reducing means is provided. However, the orifice 51 may not be provided. The basic structure of the variable nozzle hole 1 shown schematically in FIG. 6 is the same as that of the first embodiment, and includes a cylindrical container body 26 closed in the hydraulic control chamber 4 and a lower end opening thereof. The damper chamber 5 is formed by a space surrounded by the inserted inner needle 22. At this time, the orifice can be omitted by setting the gap between the inner peripheral surface of the cylindrical container body 26 and the outer peripheral surface of the inner needle 22 to an appropriate size that allows fluid to flow in and out.

  The operation in the above configuration is the same as in the first embodiment. When the outer needle 21 collides with the inner needle 22 and moves the inner needle 22 upward, the pressure in the damper chamber 5 rises and the inner needle The ascending force of 22 is suppressed. Therefore, the bounce of the inner needle 22 can be prevented, and the inner needle 22 can be raised smoothly together with the outer needle 21. According to the configuration of the present embodiment, the same effect can be obtained with a simple configuration by using the gap on the outer periphery of the inner needle 22 as a fluid flow path corresponding to the orifice.

  FIG. 7 shows a sixth embodiment of the present invention. In the present embodiment, the damper chamber 5 serving as an impact reducing means is provided integrally with the body B on the back side of the inner needle 22. The basic structure of the variable nozzle nozzle 1 schematically shown in FIG. 7 is the same as that of the first embodiment, and the following description will be focused on the differences. In FIG. 7, a space serving as a damper chamber 5 is formed above the inner needle 22 by recessing a part of the body B member that forms the top surface of the hydraulic control chamber 4. The upper end portion of the inner needle 22 is slidably inserted into the recessed portion from below, and an appropriate size corresponding to an orifice is provided between the outer peripheral portion of the inner needle 22 and the inner peripheral surface of the recessed portion. A gap is formed to allow fuel to flow into and out of the hydraulic control chamber 4. Instead of providing the recessed portion, a cylindrical portion that protrudes from the top surface of the hydraulic control chamber 4 to the control chamber 4 may be provided integrally with the body B member.

  Also with the above configuration, the same effect as in the first embodiment can be obtained. When the outer needle 21 collides with the inner needle 22 and moves the inner needle 22 upward, the pressure in the damper chamber 5 increases. The rising force of the inner needle 22 is suppressed. Therefore, the bounce of the inner needle 22 can be prevented, and the inner needle 22 can be raised smoothly together with the outer needle 21. Moreover, according to the structure of this embodiment, it is not necessary to provide the structural member of the damper chamber 5 separately, and the attitude | position retainability of the inner needle 22 improves because the damper chamber 5 is fixed. Moreover, the leak between the damper chamber 5 and other parts can be reduced.

  FIG. 8 shows a seventh embodiment of the present invention. In the present embodiment, the damper chamber 5 </ b> B serving as an impact reducing means is provided independently of the hydraulic control chamber 4. The basic structure of the variable nozzle nozzle 1 schematically shown in FIG. 8 is the same as that of the first embodiment, and the following description will focus on the differences. In FIG. 8, a cylinder member 41 having openings at both ends is provided in the hydraulic control chamber 4 so that the upper end portion of the inner needle 22 is slidably inserted. The space in the cylinder member 41 constitutes a damper chamber 5B, and a high-pressure passage 18 reaching the common rail 9 is opened on the top surface. The damper chamber 5 </ b> B does not communicate with the hydraulic control chamber 4, and fuel does not flow out into the hydraulic control chamber 4. As a result, the high pressure from the common rail 9 always acts on the upper end surface of the inner needle 22.

  In the configuration of the present embodiment, the pressure in the damper chamber 5B acts only on the inner needle 22, and the pressure in the hydraulic control chamber 4 acts on both the inner needle 22 and the outer needle 21. Similarly to the above embodiment, the nozzle needle 2 is opened by driving the needle driving mechanism 6 to reduce the pressure in the hydraulic control chamber 4. First, the outer needle 21 starts to lift, and the first injection hole 31 is opened (see the left half of FIG. 8). Next, when the outer needle 21 is further lifted to push up the inner needle 22, the second injection hole 32 is opened (see the right half of FIG. 8). At this time, since the pressure in the high-pressure damper chamber 5B always acts downward on the inner needle 22, the ascending force of the inner needle 22 is suppressed, and the effect of reducing the collision force is enhanced. Therefore, the inner needle 22 is hardly lifted at the time of collision, and the bounce of the inner needle 22 is prevented, thereby realizing a stable operation.

  If comprised as mentioned above, in a twin needle type variable injection hole nozzle, the bounce of an inner needle can be suppressed, the dispersion | variation in the injection amount with respect to an injection command can be reduced, and the stable driving | operation can be performed.

  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.

1 is an overall configuration schematic diagram of a fuel injection device for a diesel engine showing a first embodiment to which the present invention is applied. It is a principal part expanded sectional view of the fuel-injection apparatus in 1st Embodiment. It is a principal part expanded sectional view of the fuel-injection apparatus in 2nd Embodiment. It is a principal part expanded sectional view of the fuel-injection apparatus in 3rd Embodiment. It is a principal part expanded sectional view of the fuel-injection apparatus in 4th Embodiment. It is a principal part expanded sectional view of the fuel-injection apparatus in 5th Embodiment. It is a principal part expanded sectional view of the fuel-injection apparatus in 6th Embodiment. It is a principal part expanded sectional view of the fuel-injection apparatus in 7th Embodiment.

Explanation of symbols

B1 Nozzle body 1 Variable 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 (first nozzle needle)
21A Upper end (buffer member)
22 Inner needle (second nozzle needle)
221 Flange 23 Cylinder member 24 Return spring (first spring member)
25 Return spring (second spring member)
26 cylindrical container 3 nozzle hole group 31 first nozzle hole 32 second nozzle hole 4 hydraulic control room (control room)
5, 5A, 5B Damper chamber 51 Orifice 52 Movable plate (buffer member)
53 Movable member 6 Needle drive mechanism (needle drive)
7 Control valve 71, 72 High-pressure passage 73 Low-pressure passage 74 Communication passage 8 Piezo drive 9 Common rail

Claims (12)

In a fuel injection device including a variable nozzle hole that opens and closes a plurality of nozzle holes provided at a nozzle body tip with a plurality of nozzle needles,
A first nozzle needle and a second nozzle needle arranged coaxially;
A control chamber for applying pressure in the valve closing direction to the first nozzle needle and the second nozzle needle by high-pressure oil supplied from a high-pressure passage;
A needle driving unit for controlling the lift of the first nozzle needle and the second nozzle needle by increasing or decreasing the pressure in the control chamber;
The first nozzle needle is lifted in advance as the pressure in the control chamber decreases, and the first nozzle needle contacts the second nozzle needle to lift it,
In addition, a fuel injection device is provided that includes an impact mitigation means that absorbs an impact caused by contact between the first nozzle needle and the second nozzle needle and suppresses a variation in the lift amount of the second nozzle needle. .   2. The fuel injection device according to claim 1, wherein the impact mitigating means is a damper chamber for mitigating an impact force by an increase in pressure, or a buffer member made of a soft material or an elastic material and capable of absorbing the impact force.   3. The fuel injection device according to claim 2, wherein the impact relaxation means is the damper chamber provided on the back side of the second nozzle needle.   3. The fuel injection device according to claim 2, wherein the impact relaxation means is the buffer member provided on a contact end surface of the first nozzle needle with the second nozzle needle.   The fuel injection device according to claim 3, wherein the damper chamber is provided in the control chamber.   6. The fuel injection device according to claim 5, further comprising an orifice for adjusting a pressure in the damper chamber by restricting an amount of fluid flowing from the damper chamber to the control chamber.   7. The damper chamber is a chamber provided between a cylindrical container body with one end closed installed in the control chamber and a back surface of the second nozzle needle slidably inserted into the opening. The fuel injection device described.   7. The fuel according to claim 5, wherein the damper chamber is a chamber provided between a one-side-closed space formed in the body member and a back surface of the second nozzle needle slidably inserted into the opening. Injection device.   3. The fuel injection device according to claim 2, wherein the impact relaxation means is one or both of a damper chamber and a buffer member interposed between contact portions of the first nozzle needle and the second nozzle needle.   10. The fuel injection device according to claim 9, wherein the damper chamber is constituted by a movable member disposed between opposing end surfaces of the first nozzle needle and the second nozzle needle in the control chamber.   The fuel injection device according to claim 3, wherein the damper chamber is communicated with a high-pressure passage so that a high pressure is constantly applied to the back surface of the second nozzle needle.   The first nozzle needle is formed in a cylindrical shape, the second nozzle needle is slidably disposed therein, and the first spring member and the second nozzle needle for urging the first nozzle needle in the valve closing direction are provided. The fuel injection device according to any one of claims 1 to 11, further comprising a second spring member that urges the valve in a valve closing direction.