JP5240158B2 - Fuel injection device - Google Patents

Description

  The present invention relates to a fuel injection device that injects and supplies fuel to an internal combustion engine.

  A conventional fuel injection device includes a valve member that moves back and forth in the axial direction to open and close the nozzle hole, an actuator that expands and contracts in the axial direction, a piston that moves back and forth in the axial direction in response to the expansion and contraction of the actuator, A control chamber in which the pressure is increased and decreased, and a back pressure chamber into which high-pressure fuel received in the body from a fuel tank or the like flows in and out. Further, the valve member is configured to receive the fuel pressure of the control chamber in the valve opening direction and to receive the fuel pressure of the back pressure chamber in the valve closing direction (see, for example, Patent Document 1). In such a fuel injection device, it is required to increase the pressure of the fuel from the viewpoints of high combustion efficiency, suppression of discharge of soot and unburned components, and the like.

JP 2008-255869 A

  However, in the above-described conventional fuel injection device, the higher the fuel in the device, the greater the valve closing force that acts in the closing direction with respect to the valve member. When the valve closing force increases in this way, it is necessary to set the valve opening force for opening the valve member so as to overcome the valve closing force in order to ensure valve opening and valve closing responsiveness. . In order to set such a valve opening force, for example, it is necessary to strengthen a mechanism for forcibly driving the valve member, which leads to an increase in size of a device including the mechanism.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a fuel injection device capable of suppressing a required valve opening force with respect to a valve closing force acting on a valve member. is there.

The present invention employs the following technical means to achieve the above object. That is, the invention of the fuel injection device according to claim 1 is provided with a housing in which an injection hole for injecting fuel is formed, and provided in the housing, and is reciprocated in the axial direction to open and close the injection hole, A valve member that allows and stops fuel injection from the hole, and an internal member of the housing that extends and contracts in the axial direction to reciprocate the first piston to control the internal pressure of the pressure control chamber to control the valve member. An actuator for reciprocating displacement, a second piston connected to the valve member and displaced together with the valve member in a closed state closing the nozzle hole, and a second piston in the valve opening direction in which the valve member is away from the nozzle hole The pressure balance means that is compressed so as to balance with the force acting on the valve, the integral displacement state in which the second piston is displaced without relative displacement with respect to the valve member, and the integral displacement state are released And a integral displacement and release generation means for generating an integral displacement state,
The integral displacement / release generating means maintains the integral displacement state when the valve is closed,
When the valve member moves from the closed state to the open state where the valve member is displaced maximum in the valve opening direction, the integral displacement / release generation means releases the integral displacement state, and the pressure balance means opens the second piston. The second piston is supported in the valve closing direction by being compressed so as to be balanced with the force acting in the direction.

  According to the present invention, the integrated displacement / release generating means for generating an integrally displaced state in which the second piston is integrally displaced without relative displacement with respect to the valve member and a non-integrated displaced state in which the integrally displaced state is canceled. The integrated displacement / release generating means maintains the integrated displacement state in the closed state and releases the integrated displacement state when moving from the closed state to the open state to become a non-integrated displacement state. A structure in which the force acting on the valve member when the member moves from the valve closed state to the valve open state does not interlock with the second piston is enabled. Thereby, the pressure balance means is compressed without receiving the acting force acting on the valve member and supports the second piston, so that the action of the force for closing the valve member due to the fuel pressure is canceled. The present invention can implement the valve open state while approaching the balance state while having such a mechanism. Therefore, a fuel injection device that can suppress the valve opening force generated by the actuator or the like to overcome the valve closing force acting on the valve member is obtained. Further, since the valve opening force can be suppressed, the mechanism for driving the valve member in the valve opening direction can be prevented from being strengthened and increased in size, which can contribute to improvement in cost performance and size reduction of the fuel injection device.

  According to a second aspect of the present invention, the fuel injection device further includes a connecting rod for connecting the second piston and the valve member, and the integral displacement / release generating means is configured such that one side of the connecting rod has the second piston and the valve. One of the members is fixed so as to be displaced integrally without relative displacement, and the other side of the connecting rod can be displaced integrally without relative displacement with respect to the other member when the valve is closed. When the valve is closed from the closed state to the open state, it is constituted by relative displacement with respect to the other counterpart member.

  According to this invention, since the integral displacement / release generating means is constituted by the integral displacement structure of the connecting rod and one of the second piston or the valve member and the relative displacement structure of the other, a simple mechanical structure is realized. This can greatly contribute to improvement in cost performance and miniaturization of the fuel injection device.

According to a third aspect of the present invention, in the second aspect, the other mating member is formed with a sliding space portion that extends in the axial direction and slidably accommodates the other end portion of the connecting rod. Has been
When the valve is closed, the other end of the connecting rod is in axial contact with the inner wall surface forming the sliding space, and the other mating member and connecting rod are displaced together without relative displacement.
When moving from the closed state to the open state, the contact between the inner wall surface of the sliding space and the other end of the connecting rod is released, and the connecting rod is displaced relative to the other counterpart member. Features.

  According to this invention, the sliding space portion that slidably accommodates the other end portion of the connecting rod is provided, and the other end portion of the connecting rod comes into contact with the inner wall surface of the sliding space portion in a valve-closed state. As a result, the movement in the axial direction is restricted to be in an integrally displaced state, and when going from the valve-closed state to the valve-opened state, the restriction is released and a relative displacement is possible. Thus, by forming a sliding space having the above-mentioned shape on the other member, a useful integrated displacement / release generating means that is a simple mechanism with a small number of parts and few malfunctions can be obtained.

  According to the invention described in claim 4, the pressure balance means is provided adjacent to the second piston on the side in the valve opening direction, and is a sealed chamber whose volume changes in accordance with the displacement of the second piston. The pressure balance chamber is filled with a liquid.

  According to the present invention, if a material having a preferable bulk modulus as a liquid that fills the pressure balance chamber is adopted, the displacement amount of the second piston from the valve closing state to the valve opening state is set to the displacement amount of the valve member. An appropriate range can be set. Therefore, it is possible to provide a fuel injection device that is easy to manufacture according to product specifications and has excellent productivity with a simple mechanism with a small number of parts.

  According to the fifth aspect of the present invention, in the second aspect, the second piston has a diameter dimension of a portion that applies an axial force to the liquid in the pressure balance chamber, and the inner wall surface of the housing is in a closed state. It is characterized by being configured to be equal to the diameter dimension of the valve member seated on.

  According to this invention, it is easy to produce a product that easily cancels the valve closing force due to fuel pressure, and it becomes easy to maintain a good balance between the liquid pressure in the pressure balance chamber and the force acting on the valve member, A fuel injection device with excellent product performance and productivity can be provided.

  According to a sixth aspect of the present invention, in the fourth or fifth aspect, the second piston is provided with a seal member that prevents the liquid sealed in the pressure balance chamber from leaking to the outside. Features. According to this invention, since the liquid pressure in the pressure balance chamber is appropriately maintained by providing the seal member, the function of the pressure balance chamber can be exerted stably for a long time.

It is a longitudinal cross-sectional view which shows the structure of the fuel injection valve which concerns on 1st Embodiment, and has shown the state which a needle closes a nozzle hole. It is a longitudinal cross-sectional view which shows the structure of the fuel injection valve which concerns on 1st Embodiment, and has shown the state in which a needle opens a nozzle hole. It is the elements on larger scale which expand and show the valve opening state of FIG. It is a longitudinal cross-sectional view which partially expands and shows the structure of the fuel injection valve which concerns on 2nd Embodiment, and has shown the state in which a needle opens a nozzle hole.

  A plurality of modes for carrying out the present invention will be described below with reference to the drawings. In each embodiment, parts corresponding to the matters described in the preceding embodiment may be denoted by the same reference numerals, and redundant description may be omitted. When only a part of the configuration is described in each mode, the other modes described above can be applied to the other parts of the configuration. Not only combinations of parts that clearly show that combinations are possible in each embodiment, but also combinations of the embodiments even if they are not specified, unless there is a particular problem with the combination. Is also possible.

(First embodiment)
Hereinafter, a first embodiment as an example of a fuel injection device according to the present invention will be described with reference to FIGS. The fuel injection device is, for example, a device used for a direct injection type engine that directly injects a cylinder of an in-cylinder injection spark ignition internal combustion engine (hereinafter referred to as a direct injection gasoline engine). A fuel injection valve 1 as an example of a fuel injection device is attached to a cylinder head such that an injection hole 9 formed at a tip for injecting fuel is connected to a combustion chamber in a cylinder (not shown). FIG. 1 is a longitudinal sectional view showing the configuration of the fuel injection valve 1 and shows a state where the needle 7 closes the injection hole 9 (valve closed state). FIG. 2 shows a state in which the needle 7 opens the nozzle hole 9 to the maximum in the fuel injection valve 1 (valve open state). FIG. 3 is a partially enlarged view showing the valve opening state shown in FIG. 2 in an enlarged manner.

  As shown in FIG. 1, the fuel injection valve 1 includes a housing body 2, a nozzle body 3 that forms a housing together with the housing body 2, a needle 7 as a valve member, a needle guide cylinder 71, and a first piston 6. And a second piston 8, a piston guide cylinder 61, an actuator 5, a stack housing 10 as a support member for supporting the actuator, and a lid member 4 as a closing member for closing the housing. Yes.

  The housing of the fuel injection valve 1 is composed of a housing body 2 and a nozzle body 3. The housing body 2 is a cylindrical body that is open at both ends, and mainly accommodates the stack housing 10, the actuator 5, the first piston 6, and the piston guide cylinder 61 therein. The housing main body 2 has an axial lower end connected to the nozzle body 3 and an axial upper end sandwiched between the lid member 4 and the stack housing 10. The nozzle body 3 is a component constituting the nozzle portion of the fuel injection valve 1 and is a cylindrical body that mainly accommodates the needle 7 and the needle guide cylinder 71 therein. The nozzle body 3 is connected to the nozzle body 3 at the upper end portion in the axial direction, and the injection hole 9 is formed at the lower end portion in the axial direction.

  The nozzle hole 9 is a pore that communicates the inner wall surface and the outer wall surface of the nozzle body 3, and the inner wall surface around the nozzle hole 9 (the inner wall surface located at the periphery of the inlet of the nozzle hole 9) is closed when the valve is closed. A valve seat 91 on which the needle 7 is seated is provided. A fuel reservoir chamber 75 is formed between the needle 7 and the inner wall surface of the nozzle body 3 inside the nozzle body 3 and around the inlet portion of the nozzle hole 9. The valve seat 91 is a seating surface located on the inner wall surface between the fuel reservoir 75 and the inlet portion of the injection hole 9.

  The housing main body 2 has an inlet 21 through which high-pressure fuel flows in a side surface, and a fuel passage 11 through which the fuel flows. In the fuel passage 11, fuel having substantially the same pressure as the fuel flowing into the inlet 21 flows. The fuel reservoir 75 constitutes a part of the fuel passage 11.

  The needle 7 is accommodated inside the housing body 2 so as to be reciprocally movable, and is a valve member that reciprocally displaces to open and close the injection hole 9 and allow and stop fuel injection from the injection hole 9. The needle 7 is formed with a communication hole 74 that allows the back pressure chamber 73 communicating with the fuel passage 11 and the fuel reservoir chamber 75 to communicate with each other. The tip side surface portion 78 of the needle (the lower end portion of the needle 7 shown in FIG. 1) is a portion that is seated in contact with the valve seat 91. When the tip side surface portion 78 of the needle is separated from the state where it is seated in close contact with the valve seat 91, the fuel reservoir chamber 75 and the injection hole 9 come to communicate with each other, that is, the injection hole 9 and the fuel passage 11 are connected. Since the communication is made through the back pressure chamber 73 and the like, fuel injection from the injection hole 9 is allowed. On the other hand, when the tip side surface portion 78 of the needle is seated on the valve seat 91, the fuel passage 11 and the injection hole 9 are shut off, and fuel injection from the injection hole 9 is stopped (the state shown in FIG. 1). ). Further, the state in which the needle 7 is displaced from the valve closed state to the valve opening direction in which the tip side surface portion 78 of the needle is away from the valve seat 91 is the valve opened state (the state shown in FIG. 2).

  The needle guide cylinder 71 is a cylindrical body, and the upper end in the axial direction is fixed to the piston guide cylinder 61, and the lower end in the axial direction is arranged to provide a predetermined distance from the inner wall surface of the nozzle body 3 on the nozzle hole 9 side. Has been. An annular pressure control chamber 77 is formed between the outer wall of the needle 7 on the nozzle hole 9 side, the inner peripheral wall of the needle guide cylinder 71, and the inner wall surface of the nozzle body 3.

  The back pressure chamber 73 is installed with the axial upper end of the needle guide cylinder 71 and the axial lower end of the piston guide cylinder 61 in contact with each other. A space formed between the upper end portion in the axial direction). The back pressure chamber 73 communicates with the fuel passage 11 through a passage 65 that passes through the piston guide cylinder 61.

  The outer peripheral wall of the needle 7 is in contact with the inner peripheral wall of the needle guide cylinder 71 (the needle 7 can slide in the axial direction with respect to the needle guide cylinder 71). As a result, the needle 7 is guided by the needle guide cylinder 71 so as to be reciprocally movable in the axial direction, and therefore can be reciprocally displaced. When the needle 7 is seated on the valve seat 91, a predetermined gap is formed between the axial upper end portion of the needle 7 and the axial lower end portion of the piston guide cylinder 61. By this gap, the needle 7 can move from a position where the tip side surface portion 78 of the needle contacts the valve seat 91 to a position where the upper end in the axial direction of the needle 7 contacts the lower end in the axial direction of the piston guide cylinder 61. That is, the maximum lift amount of the needle 7 is defined by the gap.

  The back pressure chamber 73 accommodates a first spring 72 as a first urging member. The first spring 72 has a lower end in the axial direction in contact with the needle 7, and an upper end in the axial direction is in contact with the lower end in the axial direction of the piston guide cylinder 61, so that the needle 7 moves toward the valve seat 91, that is, in the valve closing direction. Energize. Fuel flows into the fuel reservoir 75 from the back pressure chamber 73 through the communication hole 74.

  The piston guide cylinder 61 has a first piston 6 slidably guided on its inner peripheral wall. The first piston 6 is a columnar body, and includes a flange portion 63 that extends radially outward at an upper end portion in the axial direction of the first piston 6. The first piston 6 is inserted into the inner peripheral wall surface of the piston guide cylinder 61 from the upper end side in the axial direction of the piston guide cylinder 61 toward the lower side in the axial direction (downward in FIG. 1). A pressurizing chamber 64 is formed between the lower end of 6 and the inner peripheral wall surface of the piston guide cylinder 61. The outer peripheral wall of the first piston 6 can slide in the axial direction with respect to the inner peripheral wall of the piston guide cylinder 61 (the first piston 6 can slide in the axial direction with respect to the piston guide cylinder 61). Is in contact) Since the first piston 6 is guided by the inner peripheral wall of the piston guide cylinder 61 so as to be reciprocally movable in the axial direction, the first piston 6 can be reciprocally displaced.

  A second spring 62 as a second urging member is provided on the outer peripheral side of the piston guide cylinder 61. The second spring 62 has an upper end in the axial direction in contact with the piston guide cylinder 61 and a lower end in the axial direction in contact with the flange 63 of the first piston 6. (Upward), that is, in a direction in which the volume of the pressurizing chamber 64 increases. When the first piston 6 moves in the direction in which the volume of the pressurizing chamber 64 increases due to the urging force of the second spring 62, the pressure in the pressurizing chamber 64 decreases.

  The pressurizing chamber 64 communicates with the pressure control chamber 77 by a passage 66 formed in the piston guide cylinder 61 and a passage 76 formed so as to penetrate the needle guide cylinder 71 in the axial direction. As a result, when the first piston 6 moves downward in the axial direction (in the direction toward the injection hole 9, that is, in the valve closing direction), the volume of the pressurizing chamber 64 decreases and the pressure increases, The pressure is transmitted to the pressure control chamber 77 through the passage 76 to increase the pressure in the pressure control chamber 77, and the needle 7 is against the elastic force of the first spring 72 in the axial direction (the direction away from the injection hole 9, that is, the valve opening direction). ). When the needle 7 moves upward in the axial direction, the nozzle hole 9 and the fuel passage 11 communicate with each other via the back pressure chamber 73 and the like when the tip side surface portion 78 of the needle is separated from the seated state on the valve seat 91. Thus, fuel injection from the nozzle hole 9 is allowed.

  The piston guide cylinder 61 is provided with a concave portion 67 whose central portion is recessed in a cylindrical shape upward in the axial direction at the lower end portion in the axial direction. A cylindrical second piston 8 is accommodated in the recess 67 so as to be slidable in the axial direction. The second piston 8 can be displaced in the axial direction, and is connected to the needle 7 by a connecting rod 12, and can be displaced together with the needle 7 in a valve-closing state that closes the injection hole 9. Furthermore, the outer peripheral surface of the second piston 8 has a shape inscribed in the inner peripheral surface of the concave portion 67, and a gap between the outer peripheral surface and the inner peripheral surface by an O-ring 82 fitted outside as a seal member. Is sealed.

  The second piston 8 is arranged so as to form a space portion having a predetermined volume between the bottom portion on the axially upper side of the recess 67 and the upper end portion in the axial direction of the second piston 8. This space portion is a sealed chamber provided adjacent to the second piston 8 in the valve opening direction (upward in the axial direction) and whose volume changes in accordance with the displacement of the second piston 8. The pressure balance chamber 81 is filled with a predetermined liquid. That is, the pressure balance chamber 81 functions as a pressure balance means that is compressed so as to balance the force acting on the second piston 8 in the valve opening direction in which the needle 7 moves away from the nozzle hole 9. As the predetermined liquid, water or light oil can be employed from the viewpoint of the bulk modulus K (Pa).

  The connecting rod 12 that connects the second piston 8 and the needle 7 is accommodated in the upper end portion 12 a of the connecting rod fixed to the second piston 8 and the sliding space portion 13 formed in the needle 7. The connecting rod includes a lower end portion 12b, and an upper end portion 12a and a shaft portion 12c that connects the lower end portion 12b. The upper end portion 12a of the connecting rod is an end portion on one side of the connecting rod 12, and the connecting rod 12 is integrally displaced without being displaced relative to the second piston 8 which is a counterpart member on one side. It is fixed to the second piston 8. That is, the upper end portion 12a of the connecting rod is always displaced in the axial direction with the second piston 8 at the same time. Further, the lower end portion 12b of the connecting rod is the other end portion of the connecting rod 12 having a spherical shape with a diameter larger than the shaft diameter of the shaft portion 12c. When the valve is closed, the connecting rod 12 is on the other side. In the sliding space 13 of the needle 7, it can be displaced integrally without relative displacement with respect to the needle 7, which is a counterpart member, and is displaced relative to the needle 7 when moving from the closed state to the open state. Contained.

  The sliding space portion 13 is opened at the axial upper end portion of the needle 7 corresponding to the axially lower bottom wall portion of the back pressure chamber 73, and is a cylindrical concave portion formed so as to extend a predetermined length downward in the axial direction. It is. The sliding space portion 13 includes a cylindrical sliding recess 13b in which a part of the outer peripheral surface of the lower end portion 12b of the connecting rod is inscribed so that the lower end portion 12b of the connecting rod can slide, and the sliding recess portion 13b. A connecting portion between a sliding cylindrical portion 13c having a small inner diameter and in which the shaft portion 12c of the connecting rod 12 is slidably inscribed, and a sliding concave portion 13b and the sliding cylindrical portion 13c, the lower end portion 12b of the connecting rod A cylindrical shape formed integrally with a stopper portion 13a that is formed by an inner wall surface that conforms to the outer shape of the inner wall and abuts against the inner wall surface to prevent the lower end portion 12b of the connecting rod from moving upward in the axial direction. It is a recessed part.

  The sliding cylinder portion 13c has an inner cylindrical shape that has an inner diameter slightly larger than the outer diameter of the shaft portion 12c of the connecting rod 12 and opens in the axial upper end portion of the needle 7 and extends downward in the axial direction. It is connected. The sliding recess 13b is a bottomed inner cylindrical portion formed by an inner wall surface having an axial length longer than the axial displacement length of the lower end portion 12b of the connecting rod that is integrally displaced with the second piston 8. There is no. That is, the stopper portion 13a is a portion that transitions from the sliding cylinder portion 13c to the sliding recess portion 13b, is formed by an inner wall surface portion that gradually increases in inner diameter, and is also a seating surface of the lower end portion 12b of the connecting rod. .

  With the above-described configuration, the connecting rod 12 and the sliding space 13 are in an integrated displacement state in which the second piston 8 is integrally displaced without relative displacement with respect to the needle 7 and a non-integrated displacement state in which the integrated displacement state is released. And function as an integral displacement / cancellation generating means for generating The integral displacement state is a state in which the lower end portion 12b of the connecting rod is in contact with the stopper portion 13a, and both are integrally displaced while maintaining the state in the axial direction. In this state, the needle 7, the connecting rod 12, and the second piston 8 are displaced together without being displaced relative to each other. That is, in the integrally displaced state, the displacement lengths of the needle 7, the connecting rod 12, and the second piston 8 with respect to the nozzle body 3 are equal.

  The non-integral displacement state is a state generated when the lower end portion 12b of the connecting rod does not contact the stopper portion 13a, and the connecting rod 12, the second piston 8 and the needle 7 are relatively displaced. In this state, the connecting rod 12 and the second piston 8 are integrally displaced with a short displacement length with respect to the displacement length of the needle 7. That is, when the needle 7 is displaced in the valve opening direction, the displacement amount of the connecting rod 12 and the second piston 8 is smaller than the displacement amount. This is because the force that pushes up the second piston 8 upward in the axial direction balances the pressure of the liquid in the pressure balance chamber 81, and the pressure balance chamber 81 becomes smaller due to the displacement of the second piston 8. This is because the liquid sealed in 81 is compressed.

  The connecting rod 12 and the sliding space portion 13 constituting the integral displacement / release generating means maintain the integral displacement state when the valve is closed, and the needle 7 is opened to the maximum in the valve opening direction from the valve closed state. When moving to the valve state, the integral displacement state is canceled to generate a non-integral displacement state. In this non-integral displacement state, the pressure balance chamber 81 is further compressed so as to balance the force pushing up the second piston 8 upward in the axial direction, and supports the second piston 8 so as to push it back in the valve closing direction. The displacement amount of the second piston 8 is determined.

  Further, the second piston 8 is a needle in which the diameter dimension DP of the portion that applies the axial force to the liquid sealed in the pressure balance chamber 81 is seated on the inner wall surface of the nozzle body 3 when the valve is closed. 7 is preferably configured to be equal to a diameter dimension DN of 7, that is, a seat diameter dimension DS of a valve member.

  The actuator 5 is provided on the upper side in the axial direction than the first piston 6 (on the side opposite to the injection hole 9). The actuator 5 has a piezo stack 51 made of a piezoelectric element as an electric drive unit, and drives the first piston 6 by expansion and contraction of the piezo stack 51. The piezo stack 51 is formed by alternately stacking piezoelectric ceramic layers such as PZT and electrode layers, and extends in the stacking direction, that is, in the axial direction of the housing body 2 when charged with electrical energy. On the other hand, the electric energy is discharged from the piezo stack 51 and contracts in the axial direction.

  The piezo stack 51 expands and contracts while the side portion is supported by the casing 52. A push rod 53 that is in contact with the other axial end of the first piston 6 is provided at the end of the piezo stack 51 in the lower axial direction (the direction toward the injection hole 9). The push rod 53 applies an acting force corresponding to the expansion and contraction of the piezo stack 51 to the first piston 6.

  A stack housing 10 that supports the piezo stack 51 together with the casing 52 is provided at the end of the piezo stack 51 in the upper axial direction (opposite to the injection hole 9). The stack housing 10 includes a male screw portion 101 formed at the upper end in the axial direction, and a stack housing that protrudes in a bowl shape radially outward toward the lower side in the axial direction (direction toward the injection hole 9) than the male screw portion 101. A flange portion 102 and an electrode passage 103 penetrating in the axial direction at the central portion for passing a lead wire connected to the electrode portion of the piezo stack 51 are provided. The lid member 4 fastened to the stack housing 10 is formed with a through-hole 43 communicating with the electrode passage 103, and the lead wire passes through the electrode passage 103 and the through-hole 43 to the outside of the housing body 2. It is taken out and connected to the drive circuit of the piezo stack 51.

  An inward protruding portion 22 that protrudes inward in the radial direction is formed at the upper end portion in the axial direction of the housing body 2. When the female thread portion 41 of the lid member 4 is screwed (screwed) to the male thread portion 101 of the stack housing 10, the inwardly projecting portion 22 and the flange portion 42 projecting radially outward of the lid member 4 are stacked. The lid member 4 and the stack housing 10 are fixed to the housing body 2 because they are sandwiched from both sides by the flange portion 102 of the housing.

  When assembling the components of the fuel injection valve 1, the needle 7, the connecting rod 12, the second piston 8, the first piston 6, and the piston guide cylinder 61 are integrated with the needle guide cylinder 71 installed inside. These are installed in a predetermined position in the nozzle body 3, and the housing body 2 in which the actuator 5 and the like are arranged in a predetermined position is combined to fix them together. Then, the lid member 4 is fastened to sandwich the upper end of the housing body 2 in the axial direction between the stack housing 10 and the lid member 4, and the components are assembled together. For an assembly in which the needle 7, the connecting rod 12, the second piston 8, the first piston 6 and the piston guide cylinder 61 are integrated, before installing the assembly in the nozzle body 3, It is necessary to enclose the predetermined liquid in the pressure balance chamber 81. That is, a predetermined amount of the predetermined liquid is injected into the pressure balance chamber 81 of the assembly, and the plug member 83 is plugged from the outside and sealed.

  Next, the operation of the fuel injection valve 1 will be described. When the piezo stack 51 is not charged, the piezo stack 51 is contracted. At this time, since the first piston 6 is biased upward in FIG. 1 by the second spring 62, the pressure in the pressurizing chamber 64 is not high, and the pressure in the pressure control chamber 77 communicating with the pressurizing chamber 64 is also equal. It is. Further, the pressure of the fuel in the fuel passage 11 also acts on the back pressure chamber 73, and the needle 7 is pushed downward in FIG. 1 by this pressure. Therefore, the force of the needle 7 urged downward in FIG. 1 by the first spring 72 and the pressure by the fuel in the back pressure chamber 73 rather than the force pushed upward in FIG. Since it is larger, it moves downward in FIG. 1, and the tip side surface portion 78 of the needle is in contact with the valve seat 91 and is seated. Therefore, when the piezo stack 51 is not charged, the valve is closed and fuel injection from the nozzle hole 9 is stopped (see FIG. 1 above).

  At this time, the lower end portion 12b of the connecting rod is held by a stopper portion 13a formed on the needle 7, and the second piston 8 is prevented from moving upward in the axial direction. The needle 7 and the second piston 8 are in an integrally displaced state in which the needle 7 and the second piston 8 are displaced relative to each other via the rod 12. Further, when in such a valve-closed state (integral displacement state), the pressure balance chamber 81 has an axial length of LP1, and the sealed liquid acts on the second piston 8 in the axially upper direction. Balance with power.

  When charging of the piezo stack 51 is started, the piezo stack 51 extends, and the first piston 6 moves downward in FIG. 1 against the urging force of the second spring 62 by the push rod 53. As the first piston 6 moves, the fuel in the pressurizing chamber 64 is pressurized, and the pressure in the pressure control chamber 77 communicating with the pressurizing chamber 64 increases. And the force which pushes the needle 7 upward of FIG. 1 by the pressure of the pressure control chamber 77 becomes large. When the force pushing the needle 7 upward as shown in FIG. 2 becomes larger than the urging force of the first spring 72 and the like, the needle 7 moves upward in FIG. Leave. As a result, the nozzle hole 9 is opened, and the fuel in the back pressure chamber 73 flows from the fuel reservoir chamber 75 to the nozzle hole 9 through the communication hole 74. Accordingly, when the piezo stack 51 is charged, the valve 7 is in the valve opening state (the needle 7 is at the highest point) in which the displacement amount of the needle 7 in the axial direction upward (valve opening direction) is maximized. It is opened and fuel is injected from the injection hole 9 (see FIGS. 2 and 3).

  At this time, the lower end portion 12b of the connecting rod moves upward in the axial direction with respect to the sliding space portion 13 rather than the state of FIG. 1 and is not in contact with the stopper portion 13a. In this state, the second piston 8 is allowed to move upward in the axial direction. That is, the second piston 8 and the connecting rod 12 are in a non-integral displacement state that can be displaced in the axial direction with respect to the needle 7. Further, when the valve 7 is in the valve opening state in which such a non-integral displacement state is maintained, the needle 7 is displaced in the axial direction by a dimension ΔLN from the valve closing state, and the pressure balance chamber 81 has an axial length dimension from the LP1. Becomes a short LP2 and balances with the force of the sealed liquid acting on the second piston 8 in the axial direction upward. Therefore, the displacement amount ΔLP of the second piston 8 from the closed state of FIG. 1 to the opened state of FIG. 2 is a value obtained by subtracting LP2 from LP1, and during this time, the needle 7 is displaced by ΔLN, = LP1-LP2 <ΔLN.

  Next, the displacement amount of the second piston 8 in the valve open state shown in FIGS. 2 and 3 will be further described. The relationship between the pressure and volume of the sealed liquid in the pressure balance chamber 81 satisfies the following formula 1.

(Formula 1)
ΔP = K · (ΔV / V ₀ )
However, [Delta] P is the pressure (Pa), K is the bulk modulus (Pa), [Delta] V volume to be compressed liquid ^(m 3), _{V 0} is the liquid volume in the valve opening state ^{(m 3).}

For example, in the fuel injection valve 1, ΔP = 40 (MPa), K = 2 (GPa), the diameter dimension of the second piston 8 is 2 (mm), and the axial length of the pressure balance chamber in the initial state is 0. Set to 5 (mm). And the result of calculating ΔV by substituting these values into the above equation 1 is
ΔV = 1.0 × 10 ⁻¹¹ · π (m ³ ).

  Furthermore, the displacement amount ΔLP of the second piston 8 from the valve closing state to the valve opening state is 10 (μm) by dividing the calculated ΔV by the cross-sectional area of the second piston 8. If the lift amount (displacement amount) ΔLN of the needle 7 from the valve closing state to the valve opening state is set to be larger than ΔLP, the integral displacement state is not changed during the transition from the valve closing state to the valve opening state. It becomes possible to make a transition to the integral displacement state. In addition, ΔLN is preferably set in a range of 60 to 100 (μm). In this embodiment, ΔLN is set in this way, so that simultaneous displacement of the needle 7 and the second piston 8 in the valve-opened state is ensured. Therefore, the needle 7 can be displaced relative to the second piston 8, and the increase in the valve closing force acting on the needle 7 that tends to increase due to the high-pressure fuel can be mitigated. Accordingly, it is possible to reduce an increase in the force forcibly driving the needle 7 in the valve opening direction in the fuel injection valve 1.

  When discharging starts after the piezo stack 51 is charged, the piezo stack 51 contracts. As the piezo stack 51 contracts, the first piston 6 moves upward together with the piezo stack 51 by the urging force of the second spring 62. As the first piston 6 moves upward, the hydraulic pressure in the pressurizing chamber 64 decreases and the pressure in the pressure control chamber 77 also decreases. When the force pushing the needle 7 upward by the pressure in the pressure control chamber 77 becomes smaller than the urging force or the like of the first spring 72, the needle 7 moves downward, and the tip side surface portion 78 of the needle again moves to the valve seat 91. Sit down. Therefore, the communication between the fuel reservoir chamber 75 and the injection hole 9 is closed, and the fuel injection from the injection hole 9 ends (the state shown in FIG. 1).

  The effect which the fuel injection valve 1 of this embodiment brings is described. The fuel injection valve 1 is reciprocally displaced in the axial direction inside the nozzle body 3 to open and close the injection hole, and the needle 7 that allows and stops the injection of fuel from the injection hole and the first and second expansion and contraction in the axial direction. An actuator 5 that reciprocally displaces the needle 7 by controlling the internal pressure of the pressure control chamber 77 by reciprocally displacing the piston 6, and a second piston 8 that is connected to the needle 7 and is displaced together with the needle 7 in the valve-closed state. The pressure balance chamber 81 as pressure balance means compressed so as to balance with the force acting on the second piston 8 in the valve opening direction, and the second piston 8 are integrated with each other without being displaced relative to the needle 7. And an integral displacement / cancellation generating means for generating a non-integral displacement state in which the integral displacement state is released.

  The integral displacement / release generation means maintains the integral displacement state when the valve is closed, releases the integral displacement state when moving from the closed state to the open state, and the pressure balance chamber 81 further includes the second The second piston 8 is supported in the valve closing direction by being compressed so as to balance with the force acting on the piston 8 in the valve opening direction.

  In the above-described prior art, the valve closing force acting on the needle increases as the fuel in the fuel injection valve is increased in pressure to suppress the discharge of unburned components and the like. When the valve closing force increases, it is necessary to strengthen the forcible valve opening force for opening the valve member in order to ensure the responsiveness of opening and closing of the needle. Therefore, according to the present embodiment, since the integrated displacement / release generating means for generating the integral displacement state and the non-integral displacement state between the second piston 8 and the needle 7 is provided, The integral displacement state can be maintained when the valve is closed, and the integral displacement state can be released to the non-integral displacement state when moving from the closed state to the open state. A structure can be realized in which the force acting on the needle 7 does not interlock with the second piston 8 when the needle 7 moves from the closed state to the open state.

  Thereby, the pressure balance chamber 81 is compressed and balanced without being affected by the acting force acting on the needle 7 and supports the second piston 8. For this reason, the action of the force for closing the needle 7 due to the fuel pressure is canceled, and the valve 7 can be opened while approaching the balanced state. Therefore, the valve opening force generated by the actuator 5 or the like to overcome the valve closing force acting on the needle 7 can be suppressed. Since the valve opening force can be suppressed, the mechanism for driving the needle 7 in the valve opening direction can be prevented from being strengthened and increased in size, and thus the fuel injection valve 1 can be greatly improved in cost performance and size.

  Since the valve 7 is in a non-integral displacement state, the needle 7 is not affected by the pressure of the pressure balance chamber 81 when the needle 7 is displaced in the valve closing direction (downward in the axial direction). 7 is not hindered. Therefore, it is possible to contribute to improving the responsiveness of closing and opening the needle 7.

  As described above, according to the fuel injection valve 1 of the present embodiment, since the above problem can be solved even when the fuel pressure is set to a high pressure, the soot and unburned components are suppressed and the combustion is efficiently performed by increasing the pressure of the fuel. High output can be obtained.

  Further, in the fuel injection valve 1, the integral displacement / release generating means does not relatively displace the one side of the connecting rod 12 that connects the second piston 8 and the needle 7 with respect to the second piston 8 that is one counterpart member. The connecting rod 12 is fixed so as to be displaced integrally, and the other side of the connecting rod 12 can be displaced integrally without relative displacement with respect to the needle 7 as the other member when the valve is closed. It is comprised by making relative displacement with respect to the needle 7 when heading to.

  According to this configuration, the integral displacement / release generating means is configured by the integral displacement structure of the connecting rod 12 and the second piston 8 and the relative displacement structure of the needle 7. For this reason, the integrated displacement / release generating means can be realized by a simple mechanical structure, and a great effect can be expected in improving the cost performance and downsizing of the product.

  The needle 7 which is the other member has a sliding space 13 which is formed so as to extend in the axial direction and slidably accommodates the lower end 12b of the connecting rod (the other end of the connecting rod). Is formed. When the valve is closed, the lower end portion 12b of the connecting rod comes into contact with the stopper portion 13a of the sliding space portion 13 in the axial direction, and the needle 7 and the connecting rod 12 are integrally displaced without being relatively displaced. When moving from the closed state to the open state, the contact between the stopper portion 13 a and the lower end portion 12 b of the connecting rod is released, and the connecting rod 12 is displaced relative to the needle 7.

  According to this, when the lower end portion 12b of the connecting rod comes into contact with the stopper portion 13a in the valve-closed state, the movement in the axial direction is restricted, and an integral displacement state is obtained. The restriction is released and a relative displacement is possible. Thus, by forming the sliding space portion 13 having the above-described shape in the needle 7, a useful integrated displacement / release generating means that is a simple mechanism with a small number of parts and can reduce malfunctions can be obtained.

  The pressure balance means is a sealed chamber that is provided adjacent to the second piston 8 on the side in the valve opening direction, and whose volume changes according to the displacement of the second piston 8. The pressure balance chamber 81 is enclosed.

  According to this, if a substance (for example, water, light oil) having a preferable bulk modulus as a liquid that fills the pressure balance chamber 81 is adopted, the degree of compression of the pressure balance chamber 81 can be easily adjusted, and the valve is closed. It becomes easy to set the displacement amount of the second piston 8 from the state to the valve open state to an appropriate range with respect to the lift amount of the needle 7. Therefore, it is possible to obtain the fuel injection valve 1 that is easy to manufacture according to the product specifications and excellent in productivity with a simple mechanism having a small number of parts.

  Further, the second piston 8 has a diameter dimension DP of a portion where an axial force is applied to the liquid in the pressure balance chamber 81, and the diameter dimension of the needle 7 seated on the inner wall surface of the nozzle body 3 in the closed state. It is configured to be equal to DN (sheet diameter diameter DS).

  If the diameter dimension of the second piston 8 is smaller than the diameter dimension (seat diameter) of the needle 7 in the fuel injection valve, the force acting in the valve closing direction in the apparatus tends to increase. When the diameter of the piston 8 is large, the force acting in the valve opening direction tends to increase in the apparatus. Therefore, by making the seat diameter of the needle 7 and the diameter dimension of the second piston 8 equal, product production that easily cancels the valve closing force caused by the fuel pressure is facilitated. Further, it becomes easy to maintain a good balance between the liquid pressure in the pressure balance chamber 81 and the force acting on the valve member, and the fuel injection valve 1 excellent in product performance and productivity can be provided.

  The second piston 8 is provided with an O-ring 82 as a seal member that prevents the liquid sealed in the pressure balance chamber 81 from leaking outside. According to this, the liquid pressure in the pressure balance chamber 81 is appropriately maintained by providing the seal structure with the O-ring 82. For this reason, the pressure balance chamber 81 can exert functions such as a canceling function of the valve closing force by the hydraulic pressure and the downward responsiveness of the needle 7 from the opened state in a long term and stably.

(Second Embodiment)
The second embodiment differs from the first embodiment in the configuration of the pressure balance means. FIG. 4 is a longitudinal sectional view showing a partially enlarged configuration of the fuel injection valve 1A according to the second embodiment, and shows a valve open state.

  As shown in FIG. 4, the connecting rod 14 for connecting the second piston 8A and the needle 7A has a lower end portion 14b of the connecting rod fixed to the needle 7A and a slide formed on the second piston 8A. The upper end part 14a of the connecting rod accommodated in the space part 15 and a shaft part 14c that connects the upper end part 14a and the lower end part 14b are configured. The lower end portion 14b of the connecting rod is an end portion on one side of the connecting rod 14, and is fixed to the needle 7A so that the connecting rod 14 is integrally displaced without being displaced relative to the needle 7A, which is a counterpart member on one side. Has been. That is, the lower end portion 14b of the connecting rod is always displaced in the axial direction with the needle 7A at the same time. The upper end portion 14a of the connecting rod is the other end portion of the connecting rod 14 having a spherical shape with a diameter larger than the shaft diameter of the shaft portion 14c, and when the valve is closed, the connecting rod 14 is on the other side. The second piston can be integrally displaced without being displaced relative to the second piston 8A, which is a side member, and is displaced relative to the second piston 8A when moving from the closed state to the opened state. It is accommodated in the sliding space 15 of 8A.

  The sliding space portion 15 is opened at the lower end portion in the axial direction of the second piston 8A corresponding to the ceiling wall portion in the axial direction above the back pressure chamber 73, and is formed to extend in the axial direction upward by a predetermined length. Shaped recess. The sliding space portion 15 includes a cylindrical sliding recess 15a in which a part of the outer peripheral surface of the upper end portion 14a of the connecting rod is inscribed so that the upper end portion 14a of the connecting rod can slide, and the sliding recess portion 15a. A connecting portion between a sliding cylinder 15c having a small inner diameter and in which the shaft portion 14c of the connecting rod 14 is slidably inscribed, and a sliding recess 15a and the sliding cylinder 15c, and an upper end 14a of the connecting rod A cylindrical portion formed integrally with a stopper portion 15b that is formed by an inner wall surface that conforms to the outer shape of the stopper and that prevents the upper end portion 14a of the connecting rod from moving upward in the axial direction by contacting the inner wall surface. It is a recessed part.

  The sliding cylinder portion 15c is an inner cylindrical shape that has an inner diameter slightly larger than the outer diameter of the shaft portion 14c of the connecting rod 14 and opens at the lower end in the axial direction of the second piston 8A and extends upward in the axial direction. It is connected to the recess 15a. The sliding recess 15a is a bottomed inner cylindrical portion formed by an inner wall surface having an axial length longer than the axial displacement length of the upper end portion 14a of the connecting rod that is displaced integrally with the needle 7A. . That is, the stopper portion 15b is a portion that transitions from the sliding cylinder portion 15c to the sliding recess portion 15a, is formed by an inner wall surface portion that gradually increases in inner diameter, and is also a seating surface of the upper end portion 14a of the connecting rod. .

  With the above-described configuration, the connecting rod 14 and the sliding space 15 are in an integrally displaced state in which the second piston 8A is integrally displaced without relative displacement with respect to the needle 7A, and in a non-integrally displaced state in which the integrally displaced state is released. And function as an integral displacement / cancellation generating means for generating The integrally displaced state is a state in which the upper end portion 14a of the connecting rod is in contact with the stopper portion 15b, and both are integrally displaced while maintaining the state in the axial direction. In this state, the needle 7A, the connecting rod 14, and the second piston 8A are displaced together without being displaced relative to each other. That is, in the integrally displaced state, the displacement lengths of the needle 7A, the connecting rod 14, and the second piston 8A with respect to the nozzle body 3 are equal.

  The non-integral displacement state is a state generated when the upper end portion 14a of the connecting rod does not contact the stopper portion 15b, and the connecting rod 14, the needle 7A, and the second piston 8A are relatively displaced. In this state, the second piston 8A is integrally displaced with a short displacement length with respect to the displacement length of the connecting rod 14 and the needle 7A. That is, when the needle 7A is displaced in the valve opening direction together with the connecting rod 14, the displacement amount of the second piston 8A is smaller than the displacement amount. This is because the force that pushes the second piston 8A upward in the axial direction and the pressure of the liquid in the pressure balance chamber 81 balance, and the pressure balance chamber 81 becomes smaller due to the displacement of the second piston 8A, and the pressure balance chamber This is because the liquid sealed in 81 is compressed.

  The connecting rod 14 and the sliding space portion 15 constituting the integral displacement / release generating means maintain the integral displacement state when the valve is closed, and open the needle 7A from the closed state to the maximum opening direction. When moving to the valve state, the integral displacement state is canceled to generate a non-integral displacement state. In this non-integral displacement state, the pressure balance chamber 81 is further compressed so as to balance the force pushing up the second piston 8A upward in the axial direction, and supports the second piston 8A so as to push it back in the valve closing direction. The displacement amount of the second piston 8A is determined.

  Next, the operation of the fuel injection valve 1A will be described. When the piezo stack 51 is not charged, the valve is closed as described in the first embodiment, and the fuel injection from the nozzle hole 9 is stopped. At this time, the upper end portion 14a of the connecting rod abuts against a stopper portion 15b formed on the second piston 8A and the movement is restricted, and the second piston 8A is prevented from moving upward in the axial direction. By closing the valve 7A, the needle 7A and the second piston 8A are not displaced relative to each other via the connecting rod 14, but are integrally displaced. Further, when in such a valve-closed state (integral displacement state), the pressure balance chamber 81 has an axial length dimension LP1 (see FIG. 1), and the sealed liquid is pivoted to the second piston 8A. Balance with the force acting upward.

  When the piezo stack 51 is charged, similarly to the description of the first embodiment, the valve 7 is in the valve open state in which the displacement amount in the upper axial direction (the valve opening direction) of the needle 7A is maximum (the needle 7A is at the highest point). The nozzle hole 9 is opened and fuel is injected from the nozzle hole 9 (see FIG. 4 above).

  At this time, the upper end portion 14a of the connecting rod moves upward in the axial direction with respect to the sliding space portion 15 and does not come into contact with the stopper portion 15b as compared with the valve closed state, so that it is released from the restriction by the stopper portion 15b. Thus, the second piston 8A is allowed to move upward in the axial direction. That is, the second piston 8A is in a non-integral displacement state that can be displaced in the axial direction with respect to the connecting rod 14 and the needle 7A. When the valve 7 is in the open state to maintain such a non-integral displacement state, the needle 7A is displaced in the axial direction by a dimension ΔLN from the closed state, and the pressure balance chamber 81 has an axial length dimension from LP1. Becomes a short LP2 and balances with the force that the sealed liquid acts on the second piston 8A in the axial direction upward.

  The effects brought about by the fuel injection valve 1A of the present embodiment will be described. In the fuel injection valve 1A, the integral displacement / cancellation generating means is configured so that one side of the connecting rod 14 that couples the second piston 8A and the needle 7A is integrally displaced without relative displacement with respect to the needle 7A that is one counterpart member. The other side of the connecting rod 14 can be integrally displaced without relative displacement with respect to the second piston 8A, which is the other counterpart member, in the valve-closed state, and moves from the valve-closed state to the valve-opened state. Sometimes it is constituted by relative displacement with respect to the second piston 8A.

  According to this configuration, the integral displacement / release generating means is constituted by the integral displacement structure of the connecting rod 14 and the needle 7A and the relative displacement structure of the second piston 8A. For this reason, the integrated displacement / release generating means can be realized by a simple mechanical structure, and a great effect can be expected in improving the cost performance and downsizing of the product.

  The second piston 8A, which is the other member, is a sliding space that is formed to extend in the axial direction and slidably accommodates the upper end portion 14a of the connecting rod (the other end portion of the connecting rod). A portion 15 is formed. When the valve is closed, the upper end portion 14a of the connecting rod comes into contact with the stopper portion 15b of the sliding space portion 15 in the axial direction, and the second piston 8A and the connecting rod 14 are displaced together without being relatively displaced. When moving from the closed state to the open state, the contact between the stopper portion 15b and the upper end portion 14a of the connecting rod is released, and the connecting rod 14 is displaced relative to the second piston 8A.

  According to this, when the upper end portion 14a of the connecting rod comes into contact with the stopper portion 15b in the valve-closed state, the movement in the axial direction is restricted to become an integral displacement state, and when moving from the valve-closed state to the valve-open state, The restriction is released and a relative displacement is possible. Thus, by forming the sliding space portion 15 having the above-described shape on the second piston 8A, a useful integrated displacement / release generating means that is a simple mechanism with a small number of parts and that can reduce malfunctions can be obtained. .

(Other embodiments)
In the above-described embodiment, the preferred embodiment of the present invention has been described. However, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. It is.

  The integral displacement / release generation means and the pressure balance means included as technical ideas in the present invention are not limited to the configurations described in the above embodiment, and other configurations are possible as long as the functions described above of each unit can be achieved. It may be.

  In the above embodiment, the first piston 6 is provided with a communication passage that allows the fuel passage 11 and the pressurizing chamber 64 to communicate with each other, and the communication passage is closed by a spring that is urged in the other axial direction by the communication passage. A check valve may be provided. When the volume of the pressurizing chamber 64 is increased to a negative pressure, the check valve is pushed by the fuel filled in the fuel passage 11 and moves in one axial direction (direction toward the injection hole 9). Release the blockage. As a result, the fuel in the fuel passage 11 flows into the pressurizing chamber 64 through the communication passage.

1 ... Fuel injection valve 2 ... Housing body (housing)
3. Nozzle body (housing)
5 ... Actuator 6 ... First piston 7, 7A ... Needle (valve member, mating member)
8, 8A ... Second piston (mating member)
9 ... nozzle hole 12, 14 ... connecting rod (integral displacement / release generating means)
12a: upper end of connecting rod (one side of connecting rod)
12b ... lower end of the connecting rod (the other end of the connecting rod)
13, 15 ... sliding space (integral displacement / release generation means)
13a ... Stopper (inner wall surface)
14a: upper end of the connecting rod (the other end of the connecting rod)
14b ... Lower end of connecting rod (one side of connecting rod)
15b ... Stopper (inner wall surface)
81 ... Pressure balance chamber (pressure balance means)
77 ... Pressure control chamber 82 ... O-ring (seal member)

Claims (6)

A housing in which a nozzle hole for ejecting fuel is formed;
A valve member provided inside the housing, reciprocally displaced in the axial direction to open and close the nozzle hole, and to permit and stop the ejection of the fuel from the nozzle hole;
An actuator that is provided inside the housing and that reciprocally displaces the valve member by controlling the internal pressure of the pressure control chamber by reciprocally displacing the first piston by extending and contracting in the axial direction;
A second piston coupled to the valve member and displaced together with the valve member in a closed state to close the nozzle hole;
Pressure balancing means that is compressed so as to balance the force acting on the second piston in the valve opening direction in which the valve member is away from the nozzle hole;
An integrated displacement / release generating means for generating an integrally displaced state in which the second piston is displaced integrally without relative displacement with respect to the valve member, and a non-integrated displaced state in which the integrated displaced state is released;
The integral displacement / release generation means maintains the integral displacement state when the valve is closed,
When the valve member moves from the closed state to a valve open state where the valve member is displaced maximum in the valve opening direction, the integrated displacement / release generating unit releases the integrated displacement state, and the pressure balance unit balances the valve member. The fuel injection device is so compressed that the second piston is supported in the valve closing direction. And a connecting rod for connecting the second piston and the valve member,
The integral displacement / cancellation generating means is
One side of the connecting rod is fixed so as to be integrally displaced without relative displacement with respect to one of the second piston and the valve member,
The other side of the connecting rod can be displaced integrally without relative displacement with respect to the other mating member when the valve is closed, and the other mating member can be displaced when moving from the valve closing state to the valve opening state. 2. The fuel injection device according to claim 1, wherein the fuel injection device is constituted by relative displacement. The other counterpart member is formed with a sliding space portion that extends in the axial direction and slidably accommodates the other side end portion of the connecting rod,
When the valve is closed, the other end of the connecting rod abuts against the inner wall surface forming the sliding space portion in the axial direction, and the other mating member and the connecting rod are integrated without relative displacement. Is displaced to
When moving from the valve-closed state to the valve-opened state, the contact between the inner wall surface of the sliding space portion and the other side end of the connecting rod is released, and the connecting rod is the other counterpart. The fuel injection device according to claim 2, wherein the fuel injection device is relatively displaced with respect to the member.   The pressure balance means is a sealed chamber which is provided adjacent to the second piston in the valve opening direction side and whose volume changes according to the displacement of the second piston. The fuel injection device according to any one of claims 1 to 3, wherein the fuel injection device is an enclosed pressure balance chamber.   In the second piston, the diameter dimension of the portion of the pressure balance chamber that applies an axial force to the liquid is equal to the diameter dimension of the valve member seated on the inner wall surface of the housing when the valve is closed. It is comprised so that it may become. The fuel-injection apparatus of Claim 4 characterized by the above-mentioned.   The fuel injection according to claim 4 or 5, wherein the second piston is provided with a seal member that prevents the liquid sealed in the pressure balance chamber from leaking to the outside. apparatus.

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