JP2010043542A - Fuel injection valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection valve stabilizing a fuel injection quantity while inhibiting a rise of manufacturing cost. <P>SOLUTION: The fuel injection valve 1 includes an actuator 2 including a piezoelectric element 22 and a displacement take out part 24 transmitting expansion and contraction of the piezoelectric element 22 to an outside, and a valve element 3 actuated by the actuator 2. A movement regulation part 45 regulating movement of the displacement take out part 24 when the piezoelectric element 22 reaches a prescribed expansion quantity is provided at an outside of the actuator 2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel injection valve.

  A fuel injection valve using a piezo element is known as an actuator that controls driving of a valve element that opens and closes a nozzle hole. An actuator is a stack formed by laminating a plurality of plate-like piezoelectric elements in the thickness direction, and the displacement of the piezoelectric element that expands and contracts by applying a voltage to one end of the stack is external to the actuator. And a displacement extracting portion for transmitting the displacement to the valve element.

  However, when the piezo element is extended, the piezo element is vibrated by extending more than necessary due to inertia. The vibration is transmitted to the valve element via the displacement extraction portion. If the vibration generated by the piezo element is transmitted to the valve element, the position of the valve element when it is closed is not stable and the fuel injection amount is not stable.

For example, Patent Document 1 and Patent Document 2 disclose a damping element that absorbs shock at one end of a stacked piezo element provided inside an actuator casing, and a piezo element machine between stacked piezo elements. A structure that suppresses vibration by providing an absorption layer that absorbs vibration is disclosed.
European Patent Application No. 1647703 International Publication No. 2006/131106 Pamphlet

  However, the actuators disclosed in each of the documents 1 and 2 have a structure in which a member that absorbs vibration is accommodated inside the actuator, so that the structure of the actuator becomes complicated and the cost of the actuator increases. For this reason, the manufacturing cost of the fuel injection valve using this actuator will rise.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a fuel injection valve capable of stabilizing the fuel injection amount while suppressing an increase in manufacturing cost.

  According to a first aspect of the present invention, in a fuel injection valve that injects fuel, a housing in which an injection hole is formed, a valve element that is accommodated in the housing and opens and closes the injection hole, and an opening and closing operation of the valve element is controlled. An actuator, and the actuator has a piezoelectric element that expands and contracts when a voltage is applied, and a displacement extraction unit that extracts a displacement when the piezoelectric element expands and contracts to the outside of the actuator and transmits the displacement to the valve element. The outside is characterized in that a movement restricting portion for restricting the movement of the displacement extracting portion when the piezoelectric element reaches a predetermined extension amount is provided.

  According to the present invention, the movement restricting portion that restricts the movement of the displacement extracting portion when the predetermined voltage is applied to the piezoelectric element and the piezoelectric element reaches the predetermined extension amount is provided outside the actuator. The element can be prevented from extending beyond a predetermined extension amount. As a result, when the element is extended, vibration of the element that is generated due to inertia exceeding the predetermined extension amount is suppressed, and transmission to the displacement extraction portion can be suppressed as much as possible.

  Since the vibration of the displacement extraction portion when the element is extended can be suppressed, the operation of the valve element can be stabilized, and consequently the injection amount can be stabilized. In addition, since this movement restricting portion is provided outside the actuator, the structure of the actuator can be simplified compared to the conventional technique in which a member that absorbs vibration during expansion of the piezo element is provided in the actuator. As a result, an increase in the manufacturing cost of the fuel injection valve can be suppressed. Thereby, it is possible to provide a fuel injection valve capable of stabilizing the fuel injection amount while suppressing an increase in manufacturing cost.

  According to the second aspect of the present invention, the valve element opens and closes the nozzle hole using the hydraulic pressure generating unit that converts the displacement of the displacement extracting unit into the hydraulic pressure, and the hydraulic pressure generated at the hydraulic pressure generating unit as a drive source. The hydraulic pressure generating unit includes a piston and a cylinder that slidably supports the piston in the axial direction and forms a hydraulic pressure chamber between the piston and the movement restricting member. It is characterized by being provided between the cylinder and the cylinder.

  In a fuel injection valve having a valve element that converts the displacement of the displacement extraction portion into a hydraulic pressure at the hydraulic pressure generation portion and drives the valve member using the converted hydraulic pressure as a drive source, the vibration is caused by the vibration of the piston of the hydraulic pressure generation portion. The pulsation of the generated hydraulic pressure is one of the causes that impairs the driving stability of the valve member.

  According to this invention, since the movement restricting portion is provided between the piston and the cylinder of the hydraulic pressure generating portion, the vibration of the displacement extracting portion of the actuator is suppressed and the pulsation of the hydraulic pressure in the hydraulic pressure chamber is directly caused. Can be suppressed. Thereby, the operation of the valve member driven by the hydraulic pressure can be stabilized, and the fuel injection amount can be stabilized.

  The invention according to claim 3 is characterized in that the movement restricting portion is fixed to either the piston or the cylinder.

  According to the present invention, since the movement restricting portion is fixed to either the piston or the cylinder, when the movement restricting portion does not restrict the movement of the piston and the cylinder, the movement restricting portion includes the piston and the cylinder. It is possible to prevent generation of noise due to floating between the cylinders and colliding with the piston or the cylinder.

  The invention according to claim 4 is characterized in that the movement restricting portion is formed integrally with either the piston or the cylinder.

  According to this invention, since the movement restricting portion is formed integrally with either the piston or the cylinder, when the movement restricting portion does not restrict the movement of the piston and the cylinder, the movement restricting portion is connected to the piston. It is possible to prevent generation of noise due to floating with the cylinder and colliding with the piston or the cylinder. Further, since it is not necessary to provide the movement restricting part as a separate part, the structure of the hydraulic pressure generating part can be simplified.

  The invention according to claim 5 is characterized in that the movement restricting portion is accommodated in the hydraulic pressure chamber of the hydraulic pressure generating portion.

  Here, when the movement restricting portion collides with either the piston or the cylinder so as to restrict the movement of the displacement extracting portion, there is a possibility that a problem that noise is generated is generated.

  With respect to this problem, according to the invention described in claim 5, since the movement restricting portion is housed in the hydraulic pressure chamber of the hydraulic pressure generating portion, the noise when the movement restricting portion collides with the piston or the cylinder is reduced. As much as possible, it can be prevented from being discharged outside the fuel injection valve.

  The invention according to claim 6 is characterized in that the elastic coefficient of the movement restricting portion is lower than the elastic coefficient of any one of the piston or cylinder that the movement restricting portion collides.

  According to this invention, since the elastic coefficient of the movement restricting portion is lower than the elastic coefficient of any one of the piston or cylinder that collides with the movement restricting portion, when the movement restricting portion and the piston or cylinder collide. The generated noise can be suppressed as much as possible.

  The elastic coefficient here means not only the elastic coefficient of the material itself of the movement restricting part, but also the elastic coefficient due to the shape change accompanied by twisting or bending of the movement restricting part when colliding with the piston or the cylinder. Contains.

  The invention described in claim 7 is characterized in that the movement restricting portion is fixed to the housing and directly restricts the movement of the displacement extracting portion.

  According to this invention, since the movement restricting portion is fixed to the housing which is a member having a larger physique than the hydraulic pressure generating portion, the movement restricting portion is assembled to the hydraulic pressure generating portion or formed in the hydraulic pressure generating portion. Compared to the case, an increase in manufacturing cost can be suppressed as much as possible.

  The invention according to claim 8 is characterized in that the elastic coefficient of the movement restricting portion is lower than the elastic coefficient of the displacement extracting portion with which the movement restricting portion collides.

  According to this invention, since the elastic coefficient of the movement restricting portion is lower than the elastic coefficient of the displacement extracting portion that collides with the movement restricting portion, the noise generated when the movement restricting portion and the displacement extracting portion collide is suppressed as much as possible. be able to.

  As in the sixth aspect, the elastic coefficient here indicates the elastic coefficient of the material of the movement restricting portion itself, and the elastic coefficient due to the change in shape when the movement restricting portion collides with the piston or the cylinder. Contains.

  Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
1 and 2 are cross-sectional views of the fuel injection valve 1 in the first embodiment. The fuel injection valve 1 in FIG. 1 shows a state where the injection hole 57 is closed, and the fuel injection valve 1 in FIG. 2 shows a state where the injection hole 57 is opened. The fuel injection valve 1 is attached so that fuel can be directly supplied to each cylinder of an internal combustion engine (not shown).

  The fuel injection valve 1 includes an actuator 2 and a valve element 3. The actuator 2 and the valve element 3 are accommodated in a rod-shaped housing 5 side by side in the axial direction.

  The housing 5 includes a holder body 51 that houses a part of the actuator 2 and the valve element 3, and a nozzle body 55 that houses a part of the valve element 3.

  The holder body 51 is formed in a cylindrical shape having a cavity inside, and the upper end 52 (the end opposite to the nozzle body 55) is closed. The upper end portion 52 supports the upper end portion of the actuator 2. A valve element 3 is disposed at the lower end of the actuator 2. The lower end is open and the nozzle body 55 is connected. A suction port 54 for supplying fuel into the holder body 51 is formed in the side wall 53 of the holder body 51.

  The nozzle body 55 is formed in a cylindrical shape having a hollow inside, and the lower end portion 56 (the side opposite to the holder body 51) is closed. The cavity of the nozzle body 55 is connected to the cavity of the holder body 51. The lower end portion 56 is formed with a nozzle hole 57 that communicates the inside of the nozzle body 55 and the outside of the nozzle body 55. The fuel that has flowed into the holder body 51 flows into the nozzle body 55 and is injected through the injection holes 57. The opening and closing of the nozzle hole 57 is controlled by the valve element 3.

  The actuator 2 includes a piezo stack 21, a fixing member 23, a displacement extraction portion 24, a diaphragm 25, a casing 26, and the like. The piezo stack 21 is formed by stacking a plurality of plate-like piezo elements 22 in the plate thickness direction, and is housed in a cylindrical casing 26. As shown in FIG. 1, when a voltage is applied from the outside of the fuel injection valve 1, the piezo stack 21 extends in the thickness direction of the piezo element 22 in accordance with the magnitude of the applied voltage. When released, the piezo element 22 contracts and returns almost to the state before the voltage is applied.

  The fixing member 23 is fixed to one end of the casing 26. The inner side of the fixing member 23 supports one end of the piezo stack 21 opposite to the valve element 3. The outer side of the fixing member 23 is supported by the upper end portion 52 of the holder body 51.

  The displacement extraction portion 24 is supported on the inner peripheral side of the casing 26 so as to be slidable in the axial direction. The displacement extraction part 24 is supported by the other end of the piezo stack 21. The end of the displacement extraction portion 24 on the valve element 3 side protrudes downward from the end of the casing 26. The lower end portion of the displacement extraction portion 24 is always in contact with a hydraulic pressure generation portion 36 that is a part of the valve element 3.

  The diaphragm 25 is formed in an annular shape and is fixed to an end portion of the casing 26 on the displacement extraction portion 24 side. The outer peripheral end of the diaphragm 25 is fixed to the end of the casing 26, and the inner peripheral end is always in contact with the side wall of the displacement extracting portion 24. Thereby, even if the displacement extraction part 24 reciprocates in an axial direction, it can suppress that the fuel with which the exterior of the casing 26 was filled in the inside of the casing 26 penetrate | invades.

  When a predetermined voltage is applied to the piezo stack 21 of the actuator 2, the piezo stack 21 extends a predetermined length according to the magnitude of the applied voltage. Since the movement of the upper portion of the piezo stack 21 is restricted by the fixing member 23, when the piezo stack 21 is extended, the other end of the piezo stack 21 with which the displacement extraction portion 24 is in contact is extended downward. Move by the amount corresponding to. Along with this, the displacement extraction unit 24 also moves downward by an amount corresponding to the extension amount of the piezo stack 21.

  Thereafter, when the application of the voltage is released, the piezo stack 21 contracts and returns almost to the state before the voltage is applied. Along with this, the displacement extraction unit 24 also moves to the original position.

  The valve element 3 disposed below the actuator 2 includes a valve member 31 and a hydraulic pressure generator 36.

  The valve member 31 controls the injection and non-injection of fuel from the injection hole 57 by the tip 32 being seated on the inner wall of the lower end portion of the nozzle body 55. The valve member 31 is formed in a cylindrical shape. The outer diameter of the valve member 31 decreases toward the tip 32, and two stepped portions 33 and 34 are formed in the middle. A side wall between the stepped portion 33 of the valve member 31 and the stepped portion 34 is supported on the inner wall of the nozzle body 55 so as to be slidable in the axial direction. A passage 35 extending in the axial direction is formed in the valve member 31 from the upper end portion to the vicinity of the lower step portion 34. The passage 35 on the distal end 32 side communicates with the side wall of the lower step portion 34.

  The nozzle body 55 forms an accommodation chamber 58 that surrounds the upper stepped portion 33 between the upper end portion of the valve member 31. An interior cylinder 47 and a spring 48 are accommodated in the accommodation chamber 58. The internal cylinder 47 supports the side wall of the valve member 31 above the step portion 33 so as to be slidable in the axial direction. The upper end portion of the interior cylinder 47 abuts on the outer wall of the lower end portion of a cylinder 39 described later. The spring 48 is disposed between the bottom of the storage chamber 58 and the lower end of the interior cylinder 47, and always urges the interior cylinder 47 upward.

  When the internal cylinder 47 comes into contact with the outer wall of the lower end portion of the cylinder 39, the passage 35 and the storage chamber 58 are partitioned. The nozzle body 55 forms a fuel reservoir chamber 59 below the lower step 34.

  The fuel that has flowed in from the upper side of the passage 35 passes through the passage 35 and is discharged into the fuel reservoir 59. In a state where the nozzle hole 57 is closed by the valve member 31, the fuel that has flowed into the fuel reservoir 59 remains there. When the injection hole 57 is opened by the valve member 31, the fuel in the fuel reservoir chamber 59 is injected outside through the injection hole 57. A spring 49 for biasing the valve member 31 in the valve closing direction is accommodated on the upper side of the passage 35.

  The fuel that has flowed into the holder body 51 flows into the passage 35. The hydraulic pressure generated by the hydraulic pressure generator 36 described later flows into the storage chamber 58. The hydraulic pressure generated by the hydraulic pressure generator 36 acts on the upper step 33.

  The hydraulic pressure generating unit 36 is a mechanism that is disposed between the valve member 31 and the actuator 2 and increases the amount of displacement of the displacement extracting unit 24 of the actuator 2. The hydraulic pressure generating unit 36 includes a piston 37, a cylinder 39, a slit spring 44, a movement restricting unit 45, and the like.

  The piston 37 is formed in a columnar shape, and the outer wall of the upper end portion is disposed in contact with the displacement extraction portion 24. The lower end side of the piston 37 is accommodated in a cylinder 39 formed in a cylindrical shape having a bottom 41 so as to be slidable in the axial direction. The cylinder 39 forms a hydraulic chamber 46 between the lower end portion of the piston 37, that is, the top portion. The cylinder 39 is supported on the upper end portion of the nozzle body 55 and is accommodated in the holder body 51.

  The hydraulic chamber 46 is always filled with fuel, and when the piston 37 moves downward, the volume of the hydraulic chamber 46 is reduced and the pressure of the hydraulic chamber 46 is increased. When the piston 37 moves upward, the pressure in the hydraulic chamber 46 decreases. The hydraulic pressure chamber 46 has a sliding gap between the piston 37 and the cylinder 39 due to a hydraulic pressure difference generated between the hydraulic pressure chamber 46 and the periphery of the hydraulic pressure generating portion 36 when the piston 37 moves upward. Via which the fuel is filled.

  A lower end portion of the cylinder 39 is formed with a first series passage 42 that communicates the fluid pressure chamber 46 and the storage chamber 58 and a second communication passage 43 that communicates the passage 35 of the valve member 31 and the outside. . In FIG. 1, the first series passage 42 and the second communication path 43 appear to be connected, but the first series path 42 and the second communication path 43 are not connected.

  A slit spring 44 is disposed around the cylinder 39. The slit spring 44 has a known configuration and exhibits spring characteristics by, for example, forming a plurality of slits extending in the circumferential direction on a cylindrical member. The upper end portion of the slit spring 44 is supported by the piston 37 and the lower end portion is supported by the cylinder 39. The slit spring 44 urges the cylinder 39 and the piston 37 in a direction that always separates them while being accommodated in the fuel injection valve 1. The slit spring 44 applies a preload to the piezo stack 21 via the piston 37 and the displacement extraction portion 24. The preliminary load is set to such an extent that it does not hinder the piezo stack 21 from extending.

  When the piston 37 moves downward, the pressure of the fuel in the hydraulic chamber 46 increases. The pressure flows into the accommodation chamber 58 through the first series, and acts on the stepped portion 33 on the upper side of the valve member 31.

  Next, the mechanism of the opening / closing operation of the valve member 31 will be described.

  The opening / closing operation of the valve member 31 includes the pressure of the fuel supplied from the suction port 54 into the fuel injection valve 1, the force generated by the pressure of the fuel generated by the hydraulic pressure generator 36, and the attachment of the spring 49. Determined by the balance of power.

  In the valve member 31, an upward force (hereinafter referred to as “upward force”) is generated when the fuel pressure acts on the step portion 33. The upward force is determined by the pressure receiving area of the stepped portion 33 on which the fuel pressure acts and the fuel pressure in the storage chamber 58.

  In the valve member 31, fuel pressure acts on the passage 35 and a downward force (hereinafter referred to as “downward force”) is generated by the biasing force of the spring 49. The downward force is determined by the pressure receiving area in the passage 35 where the fuel pressure acts, the pressure of the fuel in the passage 35, and the biasing force of the spring 49.

  When the upper force wins over the lower force, the valve member 31 moves in the valve opening direction, and when the lower force wins over the upper force, the valve member 31 moves in the valve closing direction.

  The pressure of the fuel in the fuel reservoir 59 and the passage 35 is substantially the same as the pressure of the fuel flowing in from the suction port 54, and shows a substantially constant value. The pressure of the fuel in the storage chamber 58 is intentionally increased or decreased by the hydraulic pressure generator 36 that operates the actuator 2. The pressure of the fuel in the storage chamber 58 can be made higher than the pressure of the fuel in the fuel pool chamber 59 and the passage 35 by operating the actuator 2 and moving the piston 37 downward. When the pressure of the fuel in the storage chamber 58 increases and the upper force exceeds the lower force, the valve member 31 moves in the valve opening direction.

  Next, operation | movement of the fuel injection valve 1 is demonstrated based on FIGS. 1-3. FIG. 3 is a time chart for explaining the operation of the fuel injection valve 1. FIG. 3A shows a state of drive pulses transmitted from the control device (not shown) to the actuator 2. In the drawing, a predetermined voltage is applied to the actuator 2 when it is in the ON state, and the application of the predetermined voltage to the actuator 2 is completed when it is in the OFF state. FIG. 3B shows the displacement of the piston 37. In the figure, the zero state indicates a state where the piston 37 is positioned above. FIG. 3C shows the fuel pressure state in the hydraulic chamber 46. FIG. 3D shows the lift amount of the valve member 31.

  Until time t1, that is, until the pulse is switched from OFF to ON, the position of the piston 37 is upward (see FIG. 3B). For this reason, the pressure of the fuel in the hydraulic pressure chamber 46 is substantially the same as the pressure of the fuel in the passage 35 of the valve member 31 (see FIG. 3C). In this state, since the upward force generated in the valve member 31 is lower than the downward force, the tip 32 of the valve member 31 is kept seated on the nozzle body 55 and fuel is not injected from the injection hole 57.

  When the pulse is turned on at time t1, the piston 37 is moved downward by the displacement extraction portion 24. Then, the piston 37 is pushed downward, and the fuel pressure in the hydraulic chamber 46 begins to rise.

  When the fuel pressure in the hydraulic pressure chamber 46 rises to some extent and time t2 is reached, the increased pressure acts on the upper step portion 33, so the upper force generated in the valve member 31 is superior to the lower force. Thereby, the valve member 31 begins to lift in the valve opening direction. When the valve member 31 is lifted in the valve opening direction, as shown in FIG. 2, the fuel in the fuel reservoir 59 is injected from the injection hole 57 (see FIG. 2).

  From time t2 to time t3, the pressure in the hydraulic chamber 46 slightly decreases as the position of the piston 37 moves downward. This is because the valve member 31 is lifted upward and the volume in the storage chamber 58 is increased.

  When the pulse is switched from ON to OFF at time t3, the piston 37 starts to move upward due to the fuel pressure in the hydraulic chamber 46 and the biasing force of the slit spring 44. At this time, the lift of the valve member 31 remains in the open state.

  From time t3 to time t4, as the position of the piston 37 moves upward, the pressure in the hydraulic chamber 46 becomes lower than the pressure of the fuel in the passage 35.

  When the pressure of the fuel in the hydraulic pressure chamber 46 is lowered to a predetermined value at time t4, the downward force generated in the valve member 31 is superior to the upward force. Thereby, the valve member 31 begins to move in the valve closing direction. Thereafter, the tip 32 of the valve member 31 is seated on the nozzle body 55, and fuel injection from the injection hole 57 is stopped (see FIG. 1).

  Next, the characteristic part of this embodiment is demonstrated in detail based on FIG. 4 and FIG.

  FIG. 4 is an enlarged view of the hydraulic pressure generator 36 having the characteristic configuration of the present embodiment, and shows a state where the actuator 2 is contracted. FIG. 5 is an enlarged view of the hydraulic pressure generation unit 36 and shows a state where the actuator 2 is extended.

  In the present embodiment, the piston 37 moves downward between the upper end portion 40 of the cylinder 39 of the hydraulic pressure generating portion 36 (the portion facing the stepped portion 38 of the piston 37) and the stepped portion 38 of the piston 37. A movement restricting portion 45 for restricting the movement is provided.

  The movement restricting portion 45 is formed in an annular shape from a metal material having a lower elastic coefficient than the piston 37. As shown in FIG. 4, one end of the movement restricting portion 45 is fixed to the upper end portion 40 of the cylinder 39 by welding or the like.

  Between the other end of the movement restricting portion 45 and the stepped portion 38 of the piston 37 facing this end, the state shown in FIG. 4 (the state in which the actuator 2 is contracted) is a predetermined distance L. Only gaps are formed. As shown in FIG. 5, the predetermined interval L is substantially the same as the movement amount of the displacement extraction portion 24 when a predetermined voltage is applied to the actuator 2.

  According to this, when a predetermined voltage is applied to the actuator 2 and a predetermined extension amount corresponding to the magnitude of the voltage applied to the piezo element 22 is reached, that is, the piston 37 and the displacement extracting portion 24 move by a predetermined amount. When this occurs, the movement restricting portion 45 restricts further movement of the piston 37 and the displacement extracting portion 24. Extra extension due to the inertia of the piezoelectric element 22 when a predetermined voltage is applied to the actuator 2 is limited. In this way, the vibration of the piezo stack 21 is suppressed.

  Next, the effect which the said characteristic part show | plays is demonstrated in detail based on FIGS. 6-9.

  FIG. 6 is a time chart in the fuel injection valve 1 of the present embodiment having the movement restricting portion 45. The items in the time chart are the same as those in FIG. FIG. 7 is a tq characteristic diagram of the fuel injection valve 1 according to this embodiment having the movement restricting portion 45.

  FIG. 8 is a time chart in the fuel injection valve 1 of the comparative example without the movement restricting portion 45. The items in the time chart are the same as those in FIG. FIG. 9 is a tq characteristic diagram of the fuel injection valve 1 of the comparative example in which the movement restricting portion 45 is not provided.

  First, the fuel injection valve of the comparative example will be described. When describing the fuel injection valve of the comparative example, members common to the fuel injection valve of the present embodiment will be described using the same member names and numbers as those of the fuel injection valve of the present embodiment.

  As shown in FIG. 8A, a case where the pulse ON time is relatively short will be described. As shown in FIG. 8B, when the pulse is switched to ON at time t1, the piston 37 is pushed by the displacement extraction portion 24 and starts to move downward. Along with this, as shown in FIG. 8C, the fuel pressure in the hydraulic chamber 46 begins to rise as the piston 37 moves.

  When the fuel pressure in the hydraulic pressure chamber 46 rises to some extent and at time t2, the increased pressure acts on the step portion 33, and the valve member 31 begins to lift in the valve opening direction (see FIG. 8D). However, since the hydraulic pressure generating part 36 in the comparative example does not have the movement restricting part 45, the movement of the piston 37 vibrates without being restricted. This is because vibration generated when the piezo element 22 is excessively extended due to inertia is transmitted to the piston 37 via the displacement extraction portion 24.

  The vibration of the piston 37 is also transmitted to the pressure of the fuel in the hydraulic chamber 46 of the hydraulic pressure generator 36, and the pressure of the fuel in the hydraulic chamber 46 pulsates. This pressure pulsation subsides with time, but when the pulse ON time is relatively short as in this comparative example, the pressure pulsation is switched from ON to OFF before the pressure pulsation subsides (FIG. 8A and FIG. 8). (See (c)).

  If the pulse is switched to the OFF state before the pressure pulsation of the hydraulic chamber 46 is subsided, the valve closing response of the valve member 31 changes depending on the pressure state of the hydraulic chamber 46 at the time of switching. As shown in FIG. 8D, the valve closing timing of the valve member 31 does not become the timing corresponding to the switching timing of the pulses. As a result, as shown in FIG. 9, the relationship between the pulse ON time t and the fuel injection amount q is not a proportional relationship, and the fuel injection amount becomes unstable.

  As shown in FIG. 8A, when the switching timing of the pulse from ON to OFF is gradually delayed at times t3, t4, and t5, that is, when the ON time of the pulse is gradually increased, the piston at that time The valve closing timing of the valve member 31 is changed by the operation of 37.

  For example, at time t3 when the switching timing is earlier than time t4, the piston 37 is moving downward. For this reason, even if the pulse is turned OFF at this timing, the piston 37 continues to drop due to inertia, and the pressure in the hydraulic chamber 46 does not drop immediately but rises slightly and then drops. Based on time t4, which is the next later than the switching timing, the pressure curve of the hydraulic chamber 46 at time t3 indicated by the one-dot chain line approaches the pressure curve at time t4 indicated by the solid line (see the one-dot chain line in FIG. 8C). ).

On the other hand, at time t5 when the switching timing is later than time t4, the piston 37 is moving upward unlike the case of time t3. For this reason, when the pulse is turned OFF at this timing, the piston 37 continues to rise due to inertia, and the pressure in the hydraulic chamber 46 falls relatively quickly. The pressure curve of the hydraulic chamber 46 at time t5 indicated by the two-dot chain line approaches the pressure curve at time t4 indicated by the solid line (see the two-dot chain line in FIG. 8C).
Therefore, as shown in FIG. 9, when the ON time of the pulse is relatively short, the relationship between the ON time t and the fuel injection amount q is not a proportional relationship compared to when the ON time is long. The fuel injection amount when a minute fuel injection amount is required is not stable.

  On the other hand, in this embodiment, since the movement restricting portion 45 is provided between the piston 37 and the cylinder 39 to restrict the movement of the piston 37 when the piston 37 moves by a predetermined amount, extra movement due to the inertia of the piezo element 22 is caused. Elongation can be restricted via the displacement extraction part 24. According to this, since the vibration to the piston 37 transmitted through the displacement extraction portion 24 is suppressed (see FIG. 6B), the time until the pressure pulsation in the hydraulic chamber 46 is stabilized is increased. It can be shortened (see FIG. 6C).

  According to this, even if the timing of switching the pulse to OFF is advanced for the purpose of injecting the minute fuel, the pressure in the hydraulic pressure chamber 46 is already stable at the timing of switching. For this reason, as shown in FIG.6 (d), the valve closing timing of the valve member 31 can be made into the timing according to the ON time of the pulse. As a result, as shown in FIG. 7, even when the ON time is relatively short, the fuel injection amount q can be set to an amount corresponding to the ON time t, and the fuel injection amount is stabilized.

  Here, in order to suppress the vibration of the piezo stack 21 due to excessive extension of the piezo elements 22, it is conceivable to increase the preload applied to the piezo stack 21. In the present embodiment, the preliminary load can be achieved mainly by changing the urging force of the slit spring 44 of the hydraulic pressure generator 36.

  However, if the preliminary load is increased in order to suppress the excessive extension of the piezo element 22, the extension amount of the piezo stack 21 itself becomes extremely small as described above, and the displacement amount of the displacement extraction portion 24 is reduced. Get smaller. In this case, the piston 37 of the fluid pressure generating unit 36 cannot be moved sufficiently, and the fuel pressure sufficient to move the valve member 31 in the valve opening direction cannot be generated in the fluid pressure chamber 46.

  In the present embodiment, the movement restricting portion 45 does not restrict the movement of the piston 37 so as not to prevent the expansion of the piezoelectric element 22 until the expansion amount according to the magnitude of the voltage applied by the piezoelectric element 22 is reached. ing. As a result, vibration after stretching can be effectively suppressed while securing a sufficient amount of stretching of the piezo stack 21.

  As in the present embodiment, a hydraulic pressure generating unit 36 that changes the displacement of the displacement extracting unit 24 of the actuator 2 to a fuel pressure, and a valve member 31 that uses the fuel pressure generated by the hydraulic pressure generating unit 36 as a drive source. In such a fuel injection valve 1, there is a possibility that pulsation may occur in the pressure of the fuel in the hydraulic pressure chamber 46 due to vibration due to the inertia of the piston 37 of the hydraulic pressure generating portion 36. This pulsation may impair the driving stability of the valve member 31.

  In this embodiment, since the movement restricting portion 45 is provided between the piston 37 and the cylinder 39 of the fluid pressure generating portion 36, the pressure pulsation of the fuel in the fluid pressure chamber 46 described above is directly suppressed. Can do. Thereby, while suppressing the vibration of the displacement extraction part 24, the pulsation of the pressure of a fuel can be suppressed effectively.

  In the present embodiment, the movement restricting portion 45 is formed of a metal material having a lower elastic coefficient than the piston 37. According to this, the impact sound when the movement restricting portion 45 collides with the piston 37 can be suppressed as much as possible. Further, wear of the piston 37 can be suppressed.

  As shown in FIG. 10, the movement restricting portion 45 may be fixed to the piston 37 instead of the cylinder 39. The effect by this is completely the same as the above-mentioned thing. In the case of being fixed to the piston 37, the movement restricting portion 45 is preferably formed of a metal material having a lower elastic coefficient than that of the cylinder 39.

  Moreover, the movement control part 45 is not restricted to metal. The movement restricting portion 45 may be made of a material such as rubber having a lower elastic coefficient than the piston 37 or the cylinder 39 that contacts when the movement of the piston 37 is restricted.

(Second Embodiment)
Next, a second embodiment will be described. Components that are substantially the same as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted. Here, only characteristic parts of the second embodiment will be described.

  In the second embodiment, the movement restricting portion 45 is not provided between the upper end portion 40 of the cylinder 39 and the stepped portion 38 of the piston 37 as in the first embodiment, but as shown in FIGS. It is provided in the hydraulic chamber 46.

  In FIG. 11, a plate-like movement restricting portion 45 a is provided in the central portion of the hydraulic chamber 46. The clearance between the movement restricting portion 45a and the piston 37 is the same size as the clearance L in the first embodiment. Further, as shown in FIG. 12, the movement restricting portion 45b provided in the hydraulic chamber 46 may be a ring-shaped member. In this case, it is necessary to make the opening of the first series passage 42 connected to the hydraulic pressure chamber 46 so as not to be blocked. The clearance between the movement restricting portion 45a and the piston 37 is also the same size as the clearance L in the first embodiment.

  According to the embodiment shown in FIGS. 11 and 12, since the movement restricting portions 45a and 45b are provided in the hydraulic pressure chamber 46, the movement restricting portions 45a and 45b and the piston 37 or the cylinder 39 come into contact with each other. The impact sound is difficult to leak outside. By making the material of the movement restricting portions 45a and 45b lower than the elastic coefficient of the piston 37 or the cylinder 39 that abuts when restricting the movement of the piston 37, the impact sound can be further reduced.

  Further, as described in the first embodiment, the movement restricting portions 45a and 45b may be fixed to either the piston 37 or the cylinder 39.

(Third embodiment)
Next, a third embodiment will be described. Components that are substantially the same as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted. Here, only the characteristic part of the third embodiment will be described.

  In the third embodiment, instead of forming the movement restricting portions 45, 45a, 45b in an annular or plate shape as in the first and second embodiments, as shown in FIG. The movement restricting portion 45c is formed so as to act as a shape that deforms when restricting the movement of the piston 37, for example, a leaf spring.

  By forming the movement restricting portion 45c in this way, the elastic modulus of the movement restricting portion 45c can be lowered while increasing the elastic modulus of the material to be used. As a result, it is possible to reduce the impact sound when the movement restricting portion 45c comes into contact with the piston 37 or the cylinder 39, and to delay the progress of wear of the movement restricting portion 45c itself.

(Fourth embodiment)
Next, a fourth embodiment will be described. Components that are substantially the same as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted. Here, only the characteristic part of the fourth embodiment will be described.

  In the first to third embodiments, the movement restricting portions 45, 45a to c are separate from the piston 37 and the cylinder 39, whereas in the fourth embodiment, as shown in FIGS. 45d and 45e are formed as part of the piston 37 or the cylinder 39.

  FIG. 14 shows an example in which the movement restricting portion 45 d is integrally formed as a part of the upper end portion 40 of the cylinder 39. The dimensions of the cylinder 39 are determined so that the gap between the upper end portion 40 and the stepped portion 38 of the opposing piston 37 is L.

  FIG. 15 shows an example in which the movement restricting portion 45 e is integrally formed as a part of the step portion 38 of the piston 37. The piston 37 is dimensioned such that the gap between the stepped portion 38 and the upper end portion 40 of the opposing cylinder 39 is L.

  According to this, since it becomes unnecessary to prepare the movement restricting portions 45d and 45e as separate parts, the number of parts of the fuel injection valve 1 is reduced, and an increase in manufacturing cost can be suppressed.

(Fifth embodiment)
Next, a fifth embodiment will be described. Components that are substantially the same as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted. Here, only the characteristic part of the fifth embodiment will be described.

  In the fifth embodiment, unlike the first to fourth, as shown in FIG. 16, the movement restricting portion 45 f is formed so as to protrude from the inner wall of the holder body 51 toward the displacement extracting portion 24. The movement restricting portion 45f directly restricts the movement of the displacement extracting portion 24. The movement restricting portion 45f is formed at a position where the displacement extracting portion 24 contacts when the displacement extracting portion 24 moves downward by L.

  According to this configuration, since the movement restricting portion 45f is formed in the holder body 51 having larger parts than the hydraulic pressure generating portion 36, the movement restricting portion is assembled to the hydraulic pressure generating portion 36, or the movement restricting portion is generated by the hydraulic pressure. Compared with the case of forming in the portion 36, an increase in manufacturing cost can be suppressed as much as possible, and an increase in manufacturing cost of the fuel injection valve 1 can be suppressed. Moreover, according to this structure, it is applicable also to the fuel injection valve of the type which does not have the hydraulic pressure generation part 36.

It is sectional drawing which showed the valve closing state of the fuel injection valve by 1st Embodiment of this invention. It is sectional drawing which showed the valve opening state of the fuel injection valve shown in FIG. It is a time chart for demonstrating the principle of operation of the fuel injection valve shown in FIG. It is sectional drawing to which the principal part when the fuel injection valve shown in FIG. 1 exists in a valve closing state was expanded. It is sectional drawing to which the principal part when the fuel injection valve shown in FIG. 1 is a valve opening state was expanded. It is a time chart which shows the actual operation | movement of the fuel injection valve shown in FIG. It is a tq characteristic view of the fuel injection valve shown in FIG. It is a time chart which shows operation | movement of the fuel injection valve in a comparative example. It is a tq characteristic view of a fuel injection valve in a comparative example. It is sectional drawing to which the principal part of the fuel injection valve by the modification of 1st Embodiment was expanded. It is sectional drawing to which the principal part of the fuel injection valve by 2nd Embodiment was expanded. It is sectional drawing to which the principal part of the fuel injection valve by the modification of 2nd Embodiment was expanded. It is sectional drawing to which the principal part of the fuel injection valve by 3rd Embodiment was expanded. It is sectional drawing to which the principal part of the fuel injection valve by 4th Embodiment was expanded. It is sectional drawing to which the principal part of the fuel injection valve by the modification of 4th Embodiment was expanded. It is sectional drawing to which the principal part of the fuel injection valve by 5th Embodiment was expanded.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Fuel injection valve, 2 Actuator, 3 Valve element, 5 Housing, 21 Piezo stack, 22 Piezo element, 23 Fixed member, 24 Displacement extraction part, 26 Casing, 31 Valve member (valve element), 36 Fluid pressure generation part (Valve) Element), 37 piston, 39 cylinder, 44 slit spring, 45 movement restricting part, 46 hydraulic chamber, 47 internal cylinder, 48 spring, 49 spring, 51 holder body (housing), 55 nozzle body (housing), 57 nozzle hole, 58 Containment chamber, 59 Fuel reservoir

Claims (8)

In a fuel injection valve that injects fuel,
A housing in which a nozzle hole is formed;
A valve element housed in the housing and opening and closing the nozzle hole;
An actuator for controlling the opening and closing operation of the valve element,
The actuator has a piezo element that expands and contracts by applying a voltage, and a displacement extraction unit that takes out a displacement when the piezo element expands and contracts to the outside of the actuator and transmits the displacement to the valve element.
A fuel injection valve characterized in that a movement restricting portion for restricting movement of the displacement extracting portion when the piezoelectric element reaches a predetermined extension amount is provided outside the actuator. The valve element includes a hydraulic pressure generating unit that converts the displacement of the displacement extracting unit into a hydraulic pressure, and a valve member that opens and closes the nozzle hole using a hydraulic pressure generated in the hydraulic pressure generating unit as a drive source. And
The fluid pressure generating unit includes a piston and a cylinder that supports the piston so as to be slidable in the axial direction, and forms a fluid pressure chamber between the piston and the piston.
The fuel injection valve according to claim 1, wherein the movement restricting member is provided between the piston and the cylinder.   The fuel injection valve according to claim 2, wherein the movement restricting portion is fixed to either the piston or the cylinder.   The fuel injection valve according to claim 2, wherein the movement restricting portion is formed integrally with either the piston or the cylinder.   The fuel injection valve according to any one of claims 2 to 4, wherein the movement restricting portion is accommodated in the hydraulic pressure chamber of the hydraulic pressure generating portion.   6. The elastic coefficient of the movement restricting portion is lower than an elastic coefficient of any one of the piston and the cylinder with which the movement restricting portion collides. 6. Fuel injection valve.   The fuel injection valve according to claim 1, wherein the movement restricting portion is fixed to the housing and directly restricts the movement of the displacement extracting portion.   8. The fuel injection valve according to claim 7, wherein an elastic coefficient of the movement restricting portion is lower than an elastic coefficient of the displacement extraction portion with which the movement restricting portion collides.

Images