JP2005240644A - Fuel injection valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection valve having improved mountability by reducing the axial length of the fuel injection valve. <P>SOLUTION: The fuel injection valve 11 comprises an actuator 28 consisting of a piezoelectric element, a displacement enlarging mechanism 30, and a needle valve 22. The displacement enlarging mechanism 30 has a first piston 31 and a second piston 32 arranged via a fixed-capacity displacement enlarging chamber 33 in which fuel is stored. The pressure receiving area of the second piston 32 is smaller than that of the first piston 31. The displacement enlarging mechanism 30 enlarges the displacement of the first piston 31 in the displacement enlarging chamber 33 with the expansion of the actuator 28 and transmits it to the second piston 32. In this fuel injection valve 11, both pistons 31, 32 are arranged so that the second piston 32 is displaced in the opposite direction to the first piston 31 and at least part of the movable range of the second piston 32 is overlapped with the movable range of the first piston 31. The displacement enlarging chamber 33 is provided at the ends (the lower ends) of both pistons 31, 32 on the same side. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel injection valve in which a needle valve is lifted using an actuator using a piezoelectric element or a magnetostrictive element as a displacement generation source, and fuel is injected from an injection hole.

  For example, as a fuel injection system for a diesel engine, a common rail system is known in which high pressure fuel pumped from a high pressure pump is accumulated in a common rail (accumulation chamber) common to each cylinder. As a fuel injection valve used in this system, for example, a needle valve that opens and closes a nozzle hole, a control chamber that applies a pressure (back pressure) in the valve closing direction to the needle valve, and a control chamber and a low-pressure fuel passage are opened and closed. And a control valve for adjusting the pressure in the control chamber. In this fuel injection valve, the control valve is driven in accordance with the operating state of the diesel engine to reduce the pressure in the control chamber. This pressure drop lifts the needle valve, opens the nozzle hole, and injects high-pressure fuel into the combustion chamber.

  In recent years, an actuator using a piezoelectric element or a magnetostrictive element excellent in responsiveness as a displacement generation source has attracted attention. In this case, since the amount of displacement of the actuator is small, this displacement is enlarged and efficiently transmitted to the control valve. For example, in Patent Document 1, a large-diameter first piston that displaces as the actuator expands and contracts, and a small-diameter second piston that can be displaced coaxially with the first piston via a displacement expansion chamber having a constant volume, The displacement expansion mechanism formed by arranging the first piston, the displacement expansion chamber, and the second piston in series is provided between the actuator and the control valve.

In addition, as a prior art document concerning this invention, the following patent document 2 is mentioned other than the patent document 1 mentioned above.
JP 2002-257002 (page 4-5, FIG. 1) Japanese Patent Laid-Open No. 11-166653

  However, the fuel injection valve described in Patent Document 1 employs a configuration in which the first piston, the displacement expansion chamber, and the second piston, which are components of the displacement expansion mechanism, are arranged in series. For this reason, the displacement enlarging mechanism becomes longer in the axial direction, and accordingly, the distance between the actuator and the control valve becomes wider. As a result, the dimension of the fuel injection valve in the axial direction becomes large, and the mountability to the diesel engine is reduced.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a fuel injection valve capable of improving the mountability by reducing the axial length.

In the following, means for achieving the above object and its effects are described.
According to the first aspect of the present invention, the actuator includes a piezoelectric element or a magnetostrictive element as a displacement generation source, and a first piston and a second piston arranged via a displacement expansion chamber having a constant volume in which liquid is stored. The pressure receiving area of the second piston is set smaller than the pressure receiving area of the first piston, and the displacement of the first piston accompanying expansion and contraction of the actuator is expanded in the displacement expansion chamber and transmitted to the second piston. And a needle valve that opens and closes the nozzle hole in accordance with the displacement of the second piston, and the second piston is displaced in the opposite direction to the first piston. And both pistons are arranged so that at least a part of the movable range of the second piston overlaps with the movable range of the first piston, and ends of the same pistons on the same side. It is provided with the displacement enlarging chamber.

  According to the above configuration, when the actuator expands and contracts, the first piston is displaced accordingly. This displacement is expanded in the displacement expansion chamber and transmitted to the second piston, and the second piston is displaced in the opposite direction to the first piston. Then, the needle valve is lifted according to the displacement of the second piston, the nozzle hole is opened and closed, and the fuel is injected or stopped.

  By the way, in the displacement enlarging mechanism, at least a part of the movable range of the second piston overlaps with the movable range of the first piston. Moreover, the displacement expansion chamber is provided at the end portions on the same side of both pistons. For this reason, the dimension in the axial direction of the displacement enlarging mechanism is shorter than when the first piston, the displacement enlarging chamber, and the second piston are arranged in series in the axial direction. As a result, the axial dimension of the fuel injection valve is reduced, and the mountability to the engine or the like is improved.

  According to a second aspect of the present invention, in the first aspect of the present invention, at least a part of the second piston is slidably provided in the cylinder using the first piston as a cylinder. .

  According to said structure, a 1st piston functions as a cylinder of a 2nd piston besides being displaced with the expansion-contraction of an actuator. Further, when the second piston is displaced, at least a part of the second piston slides in the first piston. As described above, since at least a part of the second piston is provided in the first piston, the displacement enlarging mechanism, and hence the fuel injection valve, can be compared with the case where the second piston is arranged in parallel outside the first piston. The size in the radial direction is reduced, and mountability is further improved.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, a control chamber for applying a back pressure for lift to the needle valve, and opening and closing according to displacement of both the pistons, the control chamber. A control valve for adjusting the pressure of the first piston or the second piston, and the control valve is provided on the second piston or the first piston, It is assumed that a valve body that is seated on or separated from the valve seat with displacement is provided.

  According to the above configuration, when the actuator expands and contracts, the first piston and the second piston are displaced in the opposite directions. With these displacements, the valve seat and the valve body are displaced, and the valve body is seated on or separated from the valve seat. In this way, the control valve opens and closes. At this time, the valve seat and the valve body are displaced in opposite directions. For this reason, compared with the case where it is set as the structure which displaces only one of a valve seat and a valve body, the relative speed of a valve seat and a valve body becomes quick, and the response of opening and closing of a control valve improves.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the valve seat is provided as a part of the first piston or the second piston, and the valve body is the second piston or the first piston. It is assumed that it is provided as a part of the piston.

  According to the above configuration, when the first piston and the second piston are displaced along with the expansion and contraction of the actuator, the valve seat and the valve body provided as a part thereof are also displaced. These displacements cause the valve body to be seated on or separated from the valve seat. Thus, since the valve body and the valve seat are provided as a part of both pistons, the valve seat is provided as a separate member from the first piston or the second piston, and the valve body is provided as the second piston or the first piston. Compared with the case where it is provided as a separate member, the number of parts of the control valve can be reduced.

  According to a fifth aspect of the present invention, in the first or second aspect of the present invention, a control chamber that applies a back pressure for lift to the needle valve, and the control chamber that opens and closes according to displacement of both the pistons. A control valve that adjusts the pressure of the valve, and the control valve includes a valve seat provided at a location away from the first piston and the second piston, and a valve body that is seated on or separated from the valve seat. And a transmission member for transmitting the displacement of the second piston to the valve body.

  According to the above configuration, when the actuator expands and contracts, the first piston and the second piston are displaced. The displacement of the second piston is transmitted to the valve body via the transmission member. The valve body is displaced and is seated on or separated from a valve seat provided at a location away from the first piston and the second piston. When the control valve opens and closes in this way, the pressure in the control chamber changes, the back pressure acting on the needle valve changes, and the needle valve lifts to open and close the nozzle hole.

  According to a sixth aspect of the present invention, in the fifth aspect of the present invention, a first biasing member that biases the first piston in a direction opposite to the extending direction of the actuator, and the same direction as the extending direction. And a second urging member that urges the second piston.

  According to the above configuration, when the actuator is extended, the first piston is displaced in the same direction as the extension direction of the actuator while contracting the first biasing member, and the second piston is contracting the second biasing member. It is displaced in the direction opposite to the extending direction. On the other hand, when the actuator contracts, the first urging member is extended and the first piston is displaced in the direction opposite to the extending direction of the actuator. Further, the second urging member is extended, and the second piston is displaced in the same direction as the extension direction of the actuator.

  By the way, as described above, the control valve is located at a position away from the displacement magnifying mechanism, and the high pressure in the control chamber does not act directly on the displacement magnifying mechanism. For this reason, as a 1st biasing member and a 2nd biasing member, what exhibits the biasing force which resists such a high pressure does not need to be used. Since a member having a small urging force may be used, the degree of freedom in designing both urging members is increased accordingly.

(First embodiment)
Hereinafter, a first embodiment in which the present invention is embodied in a fuel injection valve used in a common rail fuel injection system of a diesel engine will be described with reference to FIGS. 1 to 6.

  As shown in FIG. 1, the fuel injection valve 11 includes a bottomed cylindrical nozzle holder 12 having an open upper end. A nozzle body 13 is attached to the nozzle holder 12 so as to penetrate the bottom. Inside the nozzle holder 12, a plate 14 and a valve body 15 are sequentially stacked on the nozzle body 13. Further, the lower end of the housing 16 is screwed into the open end of the upper end of the nozzle holder 12.

  A nozzle hole 17 is formed at the tip (lower end in FIG. 1) of the nozzle body 13. The nozzle body 13, the plate 14, the valve body 15, and the housing 16 are provided with a high-pressure passage 18 that guides high-pressure fuel supplied from a high-pressure pump (not shown) to the injection hole 17. A fuel reservoir 19 is provided in the middle of the high-pressure passage 18. The plate 14, the valve body 15 and the housing 16 are provided with a drain passage 21 as a fuel return low-pressure passage for returning excess fuel to a fuel tank (not shown).

  A needle valve 22 is disposed in the nozzle body 13 so as to be able to lift in the axial direction (vertical direction in FIG. 1). A control chamber 23 for applying a back pressure to the needle valve 22 is provided between the needle valve 22 and the plate 14. A spring 24 that urges the needle valve 22 in the valve closing direction (downward in FIG. 1) is disposed in the control chamber 23. The valve body 15 and the plate 14 are provided with a high pressure port 25 that branches from the high pressure passage 18 and communicates with the control chamber 23.

  Therefore, the pressure of the fluid (here, fuel) in the control chamber 23 and the urging force of the spring 24 act on the needle valve 22 as force in the valve closing direction. Further, the pressure of the fuel in the fuel reservoir 19 acts on the needle valve 22 as a force in the valve opening direction. The needle valve 22 is lifted in the axial direction to open and close the nozzle hole 17 so that these two forces are balanced. When the needle valve 22 is lowered and seated on the valve seat 26 in the nozzle body 13, the nozzle hole 17 is closed. In this state, the high-pressure passage 18 is blocked and the injection of high-pressure fuel from the injection hole 17 is stopped. On the other hand, when the needle valve 22 is lifted and separated from the valve seat 26, the nozzle hole 17 is opened. In this state, the high-pressure fuel guided through the high-pressure passage 18 is injected from the injection hole 17 into the combustion chamber.

  The fuel injection valve 11 includes a control valve 27 that adjusts the pressure of fuel in the control chamber 23. This will be described later. An actuator 28 that incorporates a piezoelectric element as a displacement generation source and drives the control valve 27 to open and close to change the pressure of fuel in the control chamber 23 is incorporated in the housing 16. The actuator 28 is composed of a piezo stack in which piezoelectric materials such as PZT are laminated in the axial direction, and has a characteristic of expanding downward by receiving energy supply from the outside and contracting upward by releasing injected energy. .

  A low pressure chamber 29 is provided in the housing 16 between the actuator 28 and the valve body 15, and the low pressure chamber 29 is connected to the drain passage 21. In the low pressure chamber 29 and the valve body 15, a displacement enlarging mechanism 30 that expands and contracts the actuator 28 is provided. The displacement enlarging mechanism 30 includes a first piston 31 that is displaced in the axial direction as the actuator 28 extends and contracts, and a second piston that can be displaced coaxially with the first piston 31 via a displacement enlarging chamber 33 having a constant volume. 32.

  The lower half of the first piston 31 is accommodated in the cylinder so as to be slidable in the axial direction, with the valve body 15 as a cylinder. The upper half of the first piston 31 enters the low pressure chamber 29.

  In the low pressure chamber 29, between the first piston 31 and the actuator 28, transmission members 34 and 35 made of a rigid body for transmitting the expansion and contraction of the actuator 28 to the first piston 31 are interposed. The latter transmission member 35 has a substantially cylindrical shape with a lid, and the lower end portion of the transmission member 35 is in contact with the upper end portion of the first piston 31. The former transmission member 34 is not particularly limited as long as it transmits the displacement of the actuator 28 to the transmission member 35. For example, a rod can be used as a transmission member. However, even when the actuator 28 expands and contracts with its lower end surface inclined, from the viewpoint of reliably transmitting the expansion and contraction to the transmission member 35, the contact surface (lower surface) of the transmission member 34 with the transmission member 35 is provided. It is desirable to form it in a spherical shape.

  A spring 36 is provided between the upper end of the first piston 31 and the valve body 15 as a first urging member that urges the first piston 31 in a direction opposite to the extending direction of the actuator 28. Is arranged. The spring 36 is for displacing the first piston 31 following the contraction when the actuator 28 contracts.

  The first piston 31 has a cylindrical shape with both upper and lower ends open. A part of the second piston 32 is accommodated in the first piston 31 as a cylinder so as to be slidable in the axial direction. A valve body 37 having a larger diameter than other portions is provided as an upper part of the second piston 32 as a part of the second piston. The upper part of the second piston 32 including the valve body 37 is a transmission member 35. It is in the inside. Between the valve body 37 and the ceiling portion of the transmission member 35, a spring 38 is provided as a second urging member that constantly urges the second piston 32 in the same direction as the extension direction of the actuator 28 (downward in FIG. 1). Has been placed.

  The displacement expansion chamber 33 is a space surrounded by the plate 14, the first piston 31, and the second piston 32 inside the valve body 15, and is filled with a liquid (here, fuel). The volume of the displacement expansion chamber 33 needs to be always constant. On the other hand, the fuel in the displacement expansion chamber 33 may leak from the gap between the valve body 15 and the plate 14, the gap between the first piston 31 and the valve body 15, the gap between the first piston 31 and the second piston 32, and the like. There is. In view of this, contrivances have been made to maintain the volume of the displacement expansion chamber 33 substantially constant in spite of such leakage.

  Specifically, a part of the drain passage 21 is opened at a location facing the displacement expansion chamber 33 on the upper surface of the plate 14. A check valve 41 is provided to open and close this opening. The check valve 41 includes a valve seat provided around the opening portion of the drain passage 21 on the upper surface of the plate 14 and a valve body that is seated on or separated from the valve seat. The valve body is pushed down and seated on the valve seat when the first piston 31 descends as the actuator 28 extends. By this seating, the opening of the drain passage 21 is closed, and the inflow of fuel from the drain passage 21 to the displacement expansion chamber 33 is blocked. On the other hand, when the first piston 31 rises as the actuator 28 contracts, the valve body rises due to negative pressure and separates from the valve seat. The opening of the drain passage 21 is opened, and fuel can be supplied (supplemented) from the drain passage 21 to the displacement expansion chamber 33.

  Each lower end surface of the first piston 31 and the second piston 32 serves as a surface (pressure receiving surface) that receives the fuel pressure in the displacement expansion chamber 33. The pressure receiving area S1 of the lower end surface of the first piston 31 is set to a value (here, twice the value) larger than the pressure receiving area S2 of the lower end surface of the second piston 32. The ratio (S1 / S2) of these pressure receiving areas is the displacement magnification rate (= 2) by the displacement magnification mechanism 30.

  In order to adjust the fuel pressure in the control chamber 23, an oil passage 43 connecting the high pressure port 25 and the drain passage 21 is provided. In the present embodiment, a configuration is adopted in which the oil passage 43 passes between the first piston 31 and the second piston 32 and the low pressure chamber 29. Specifically, a part of the oil passage 43 is provided inside the valve body 15, one end (the left end in FIG. 1) is at the high-pressure port 25, and the other end (the right end in FIG. 1) is at the valve body 15. Each has an opening on the inner wall. On the outer periphery of the first piston 31, an annular groove 44 that always faces the opening is formed over the entire periphery. The first piston 31 is provided with a conduction hole 45 that extends in the radial direction and communicates the annular groove 44 and the inner wall surface of the first piston 31. 2A and 2B, a plurality of lands 46 extending in the axial direction (vertical direction in FIG. 2) and grooves 47 between adjacent lands 46 are formed on the outer periphery of the second piston 32, respectively. Each land 46 functions as a sliding guide of the second piston 32 with respect to the first piston 31, and the groove 47 functions as an oil passage that connects the conduction hole 45 and the internal space of the transmission member 35. As shown in FIG. 1, the transmission member 35 is provided with a communication hole 48 that allows the low-pressure chamber 29 and the internal space of the transmission member 35 to communicate with each other.

  The control valve 27 for adjusting the pressure in the control chamber 23 described above is provided as a part of the second piston 32 and a valve seat 49 provided as a part of the first piston 31 at the upper end opening of the first piston 31. And the valve body 37. The valve body 37 is separated from the valve seat 49 when the first piston 31 is lowered and the second piston 32 is raised as the actuator 28 is extended. By this separation (opening of the control valve 27), the fuel in the control chamber 23 can flow out to the drain passage 21 through the high pressure port 25, the oil passage 43 and the low pressure chamber 29, and the fuel in the control chamber 23 can be discharged. The pressure drops. On the other hand, the valve body 37 is seated on the valve seat 49 when the first piston 31 rises and the second piston 32 descends as the actuator 28 contracts. By this seating (the valve closing of the control valve 27), the fuel in the control chamber 23 is blocked from flowing out into the low pressure chamber 29 and the drain passage 21, and the pressure of the fuel in the control chamber 23 is increased.

Next, the operation of the fuel injection valve 11 of the present embodiment configured as described above will be described.
FIG. 1 shows the state of the fuel injection valve 11 when the actuator 28 is contracted. In this state, the first piston 31 urged upward by the spring 36 is pressed against the transmission member 35 and is positioned at the upper end of the movable range. The second piston 32 is located at a location where the downward biasing force of the spring 38 and the fuel pressure in the displacement expansion chamber 33 are balanced, and the valve body 37 is seated on the valve seat 49 and the control valve 27 is closed. doing. For this reason, the pressure of the fuel in the control chamber 23 is high due to the inflow of the high-pressure fuel from the high-pressure passage 18, and the downward force due to this pressure and the urging force of the spring 24 is the upward force due to the fuel pressure in the fuel reservoir 19. The force is overcome, the needle valve 22 is seated on the valve seat 26, and the nozzle hole 17 is closed. For this reason, high-pressure fuel is not injected from the injection hole 17.

  When a predetermined voltage is applied to the actuator 28 from the above state, the actuator 28 extends downward by an amount proportional to the voltage, as shown in FIG. With this extension, the transmission members 34 and 35 and the first piston 31 are displaced downward by the same amount as the actuator 28 against the urging force of the spring 36. Due to the downward displacement of the first piston 31, an amount obtained by multiplying the displacement amount by the displacement enlargement ratio (pressure receiving area ratio of the first piston 31 and the second piston 32: S1 / S2), Displaces upward against the biasing force.

  The valve seat 49 descends with the downward displacement of the first piston 31, while the valve body 37 rises with the upward displacement of the second piston 32. Due to the displacement in the opposite direction, the valve element 37 is separated from the valve seat 49 and the control valve 27 is opened. By opening the valve, the control chamber 23 and the low pressure chamber 29 are connected through the high pressure port 25 and the oil passage 43, and the pressure of the fuel in the control chamber 23 is reduced. The upward force due to the fuel pressure in the fuel reservoir 19 overcomes the downward force due to the fuel pressure in the control chamber 23 and the urging force of the spring 24, so that the needle valve 22 is separated from the valve seat 26 and the nozzle hole 17. Is released. For this reason, the high-pressure fuel supplied through the high-pressure passage 18 is injected from the injection hole 17.

  When the voltage application to the actuator 28 is stopped from the above state and the electric charge is released, the actuator 28 contracts by the same amount as the displacement at the time of voltage application and returns to the original length as shown in FIG. With this contraction, the transmission members 34 and 35 and the first piston 31 are displaced upward by the same amount as the actuator 28 by the spring 36. An amount obtained by multiplying the displacement amount of the first piston 31 by the displacement enlargement rate by the second piston 32 biased by the spring 38 due to the pressure of the fuel in the displacement expansion chamber 33 being lowered by the upward displacement of the first piston 31. Displaces downward.

  The valve seat 49 rises with the upward displacement of the first piston 31, while the valve element 37 descends with the downward displacement of the second piston 32. The valve body 37 is seated on the valve seat 49 by these displacements in the reverse direction, and the control valve 27 is closed. By closing the valve, the control chamber 23 and the low-pressure chamber 29 are shut off, and the fuel pressure in the control chamber 23 increases. The downward force due to the fuel pressure in the control chamber 23 and the biasing force of the spring 24 overcomes the upward force due to the fuel pressure in the fuel reservoir 19, so that the needle valve 22 is seated on the valve seat 26 and the nozzle hole 17. Is closed and the injection of the high-pressure fuel from the injection hole 17 is stopped.

According to the first embodiment described in detail above, the following effects can be obtained.
(1) Both pistons 31, 32 so that the second piston 32 is displaced in the opposite direction to the first piston 31 and at least a part of the movable range of the second piston 32 overlaps the movable range of the first piston 31. Is arranged. Further, a displacement expansion chamber 33 is provided at the end (lower end) on the same side of both pistons 31 and 32. For this reason, the dimension in the axial direction (vertical direction in FIG. 1) of the displacement enlarging mechanism 30 is larger than that in the case where the first piston, the displacement enlarging chamber and the second piston are arranged in series in the axial direction (corresponding to Patent Document 1) Shorter. Along with this, the axial dimension of the fuel injection valve 11 is reduced, and the mountability to the diesel engine is improved accordingly.

  (2) In the displacement enlarging mechanism 30, the first piston 31 is formed in a substantially cylindrical shape to function as a cylinder, and a part of the second piston 32 is slidably accommodated in the cylinder. As described above, since at least a part of the second piston 32 is provided in the first piston 31, compared to the case where the second piston is simply arranged in parallel outside the first piston, the displacement enlarging mechanism 30, As a result, the dimension of the fuel injection valve 11 in the radial direction is reduced, and the mounting property to the diesel engine is further improved.

  (3) The control valve 27 is provided with a valve seat 49 provided on the first piston 31 and a valve body 37 provided on the second piston 32 and seats on or separates from the valve seat 49 as the pistons 31 and 32 are displaced. The valve seat 49 and the valve body 37 are displaced in the opposite directions by the displacement of both the pistons 31 and 32 accompanying the expansion and contraction of the actuator 28. Therefore, the relative speed of the valve seat 49 and the valve body 37 is increased compared with the case where only one of the valve seat and the valve body is displaced (the other is not displaceable), and the control valve 27 is opened and closed. Responsiveness can be improved.

  5 and 6, the displacement speed of the actuator 28 is Vp (-Vp), the displacement speed of the valve seat 49 is Vs (-Vs), and the displacement speed of the valve body 37 is Vb (- Vb), the valve opening speed and the valve closing speed of the control valve 27 are expressed by the following equations (i) and (ii). These valve opening speed and valve closing speed are relative speeds of the valve seat 49 and the valve element 37. 5 and 6, for the sake of convenience, the direction in which the actuator 28 extends (downward in the figure) is positive (+), and the direction in which the actuator 28 contracts (upward in the figure) is negative (-). Since only the transmission members 34 and 35 made of a rigid body are interposed between the actuator 28 and the first piston 31, it can be said that “Vs = Vp” or “−Vs = −Vp”. If the displacement magnification rate is “2”, the displacement directions of the valve seat 49 and the valve element 37 are opposite, and therefore, it can be said that “−Vb = −2 Vs” or “Vb = 2 Vs”.

Valve opening speed = Vs − (− Vb)
= Vs-(-2Vs)
= 3Vs = | 3Vs | = | 3Vp | (i)
Valve closing speed = −Vs− (Vb)
= -Vs-2Vs
= -3Vs = | 3Vs | = | 3Vp | (ii)
On the other hand, if the valve seat is not displaced (corresponding to Patent Document 1), the valve seat displacement speed Vs is “0”, so that the valve opening speed and the valve closing speed are | 2 Vp | This is slower than this embodiment (| 3Vp |).

  Therefore, as shown by the solid line in the injection characteristic (time change of the injection rate) of the fuel injection valve 11 in FIG. 3, the injection rate suddenly rises at the start of fuel injection and sharply decreases when injection stops. The injection rate is an injection flow rate per unit time. In addition, the dashed-two dotted line in FIG. 3 has shown the injection characteristic at the time of setting it as the structure which does not displace a valve seat. It can be seen from FIG. 3 that the opening and closing speed of the control valve 27 is increased and the responsiveness is improved.

  (4) The valve seat 49 is provided as a part of the first piston 31, and the valve body 37 is provided as a part of the second piston 32. For this reason, compared with the case where a valve seat and a valve body are provided as members separate from both pistons, the number of parts of the control valve 27 can be reduced.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. The second embodiment differs from the first embodiment in which the control valve 27 is provided on the first piston 31 and the second piston 32 in that the control valve is provided at a location different from the displacement magnifying mechanism 30. Yes. Hereinafter, the second embodiment will be described focusing on this difference, and the same members as those in the first embodiment will be denoted by the same reference numerals and description thereof will be omitted.

  A lid portion 31 </ b> A is provided at the upper end portion of the first piston 31 of the displacement magnifying mechanism 30, and the lid portion 31 </ b> A is in direct contact with the transmission member 34. The lid portion 31A also functions as a transmission member. Therefore, the transmission member 35 used in the first embodiment is omitted. A communication hole 52 extending in the radial direction is formed in the first piston 31, and the inside and the outside (low pressure chamber 29) of the first piston 31 communicate with each other through the communication hole 52. The point that the spring 36 is provided between the outer peripheral portion of the lid portion 31A and the valve body 15 and the point that the second piston 32 is slidably accommodated in the first piston 31 as a cylinder are the first. This is the same as in the first embodiment. However, while the upper part of the second piston 32 is exposed upward from the first piston 31 in the first embodiment, the entire second piston 32 is accommodated in the first piston 31 in the present embodiment. . The spring 38 that biases the second piston 32 downward is disposed between the lid portion 31 </ b> A and the second piston 32.

  In order to adjust the pressure of the fuel in the control chamber 23, an oil passage 53 that connects the control chamber 23 and the drain passage 21 is provided, and a control valve 54 is provided in the middle of the oil passage 53. Specifically, a bottomed cylindrical member 55 is fitted in the lower part of the plate 14 and immediately above the control chamber 23. A space surrounded by the cylindrical member 55 and the plate 14 forms a valve chamber 56. A hole 57 for communicating the valve chamber 56 and the control chamber 23 is formed at the bottom of the cylindrical member 55. Further, the valve chamber 56 and the drain passage 21 are communicated by an oil passage 58 provided in the plate 14. A valve seat 59 is provided at a boundary portion between the valve chamber 56 and the hole 57. A spherical valve element 61 is accommodated in the valve chamber 56 so as to be displaceable in the axial direction of the fuel injection valve 11 (the vertical direction in FIG. 7). Between the second piston 32 and the valve body 61, a command piston 62 as a transmission member that transmits the displacement of the second piston 32 to the valve body 61 is interposed in a state of penetrating the plate 14.

  In the control valve 54 configured as described above, the downward displacement of the second piston 32 due to the contraction of the actuator 28 is transmitted to the valve body 61 via the command piston 62, and the valve body 61 is seated on the valve seat 59. To do. By this seating (closing of the control valve 54), the fuel in the control chamber 23 is blocked from flowing into the drain passage 21 through the oil passage 53, and the pressure of the fuel in the control chamber 23 increases. On the other hand, when the second piston 32 is displaced upward as the actuator 28 is extended, the valve body 61 is displaced upward and is separated from the valve seat 59. By this separation (opening of the control valve 54), the fuel in the control chamber 23 can flow out to the drain passage 21 through the valve chamber 56 and the oil passage 53, and the pressure of the fuel in the control chamber 23 decreases. .

  In addition, since the command piston 62 is in contact with the lower surface of the second piston 32 as described above, the pressure receiving area of the second piston 32 is narrowed by the contact amount in this embodiment. In addition, since the command piston 62 is located immediately below the second piston 32, the check valve 41 is disposed at a location away from the command piston 62 to the side in order to prevent interference with the command piston 62.

  The fuel injection valve 11 of the second embodiment configured as described above basically operates in the same manner as the fuel injection valve 11 of the first embodiment. That is, when the actuator 28 expands and contracts, the first piston 31 and the second piston 32 are displaced. The displacement of the second piston 32 is transmitted to the valve body 61 via the command piston 62. The valve body 61 is displaced and is seated on or separated from the valve seat 59 provided at a location away from the first piston 31 and the second piston 32. When the control valve 54 opens and closes in this way, the pressure in the control chamber 23 changes, the back pressure acting on the needle valve 22 changes, and the needle valve 22 lifts to open and close the nozzle hole 17.

  Therefore, according to the second embodiment, the same effects as (1) and (2) in the first embodiment described above can be obtained, and the following effects (5) and (6) can be obtained. In addition, the dimension reduction effect in the axial direction of (1) is slightly reduced by adding the command piston 62. However, depending on how the lengths of the command piston 62 and the overlapping portions of the movable ranges of the pistons 31 and 32 are set, the axial dimension may be made smaller than when both pistons are simply arranged in series. Is possible.

  (5) In the control chamber 23, it is necessary to take measures against fuel leakage in order to generate a high pressure. In this regard, in the second embodiment, the control valve 54 is disposed at a position away from the displacement enlarging mechanism 30 downward. For this reason, the displacement magnifying mechanism 30 does not need such a countermeasure against leakage of high-pressure fuel. As a result, it is not necessary to increase the processing accuracy of the components of the displacement magnifying mechanism 30, and the processing becomes easy.

  (6) Since the control valve 54 is located at a location away from the displacement magnifying mechanism 30, the high fuel pressure in the control chamber 23 does not act directly on the displacement magnifying mechanism 30. For this reason, as the spring 36 for urging the first piston 31 in the direction opposite to the extension direction of the actuator 28 (upward) and the spring 38 for urging the second piston 32 in the same direction (downward) as the extension direction. Therefore, it is not necessary to use one that exerts an urging force against such high pressure. Since a member having a small urging force may be used, the degree of freedom in designing the springs 36 and 38 is increased accordingly.

Note that the present invention can be embodied in another embodiment described below.
The actuator may be constituted by a magnetostrictive element instead of a piezoelectric element.
The check valve 41 in the first embodiment may be provided at a location different from the position directly below the second piston 32. The point is that the portion may face the displacement expansion chamber 33.

  -The present invention provides the position of both pistons on the condition that the second piston is displaced in the opposite direction to the first piston and that at least a part of the movable range of the second piston overlaps the movable range of the first piston. May be changed. Therefore, for example, the second piston may be arranged in parallel outside the first piston.

  In the first embodiment, the valve seat 49 of the control valve 27 may be provided in the second piston 32 instead of the first piston 31, and the valve body 37 may be provided in the first piston 31 instead of the second piston 32.

In 1st Embodiment of this invention, the fragmentary sectional view which shows the state at the time of the fuel injection stop of a fuel injection valve. (A) is sectional drawing of a 2nd piston, (B) is the YY sectional view taken on the line of (A). The characteristic view which shows the injection characteristic of a fuel injection valve. The fragmentary sectional view which shows the state at the time of the fuel injection of a fuel injection valve. The fragmentary sectional view for demonstrating the operating speed of each part of a control valve about the X section of FIG. The fragmentary sectional view for demonstrating the operating speed of each part of a control valve about the Z section of FIG. The fragmentary sectional view of the fuel injection valve in a 2nd embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Fuel injection valve, 17 ... Injection hole, 22 ... Needle valve, 23 ... Control chamber, 27, 54 ... Control valve, 28 ... Actuator, 30 ... Displacement expansion mechanism, 31 ... 1st piston, 32 ... 2nd piston, 33 ... Displacement expansion chamber, 36 ... Spring (first biasing member), 37, 61 ... Valve body, 38 ... Spring (second biasing member), 49, 59 ... Valve seat, 62 ... Command piston (transmission member) , S1, S2 ... pressure receiving area.

Claims (6)

An actuator using a piezoelectric element or a magnetostrictive element as a displacement generation source;
Having a first piston and a second piston arranged through a displacement expansion chamber of a constant volume in which liquid is stored, the pressure receiving area of the second piston is set smaller than the pressure receiving area of the first piston, A displacement enlarging mechanism for enlarging the displacement of the first piston accompanying expansion and contraction of the actuator in the displacement enlarging chamber and transmitting the displacement to the second piston;
A fuel injection valve comprising a needle valve that lifts and opens and closes the injection hole according to the displacement of the second piston,
Both pistons are disposed so that the second piston is displaced in the opposite direction to the first piston, and at least a part of the movable range of the second piston overlaps the movable range of the first piston. A fuel injection valve characterized in that the displacement expansion chamber is provided at the ends of both pistons on the same side. 2. The fuel injection valve according to claim 1, wherein at least a part of the second piston is slidably provided in the cylinder with the first piston as a cylinder. 3. A control chamber for applying a back pressure for lift to the needle valve;
A control valve that opens and closes according to the displacement of both pistons to adjust the pressure in the control chamber, and the control valve comprises:
A valve seat provided on the first piston or the second piston;
The fuel injection valve according to claim 1, further comprising: a valve body that is provided on the second piston or the first piston and is seated on or separated from the valve seat according to displacement of both pistons. The fuel injection valve according to claim 3, wherein the valve seat is provided as a part of the first piston or the second piston, and the valve body is provided as a part of the second piston or the first piston. . A control chamber for applying a back pressure for lift to the needle valve;
A control valve that opens and closes according to the displacement of both pistons to adjust the pressure in the control chamber, and the control valve comprises:
A valve seat provided at a location away from the first piston and the second piston;
A valve body seated on or away from the valve seat;
The fuel injection valve according to claim 1, further comprising: a transmission member that transmits the displacement of the second piston to the valve body. A first urging member that urges the first piston in a direction opposite to an extension direction of the actuator, and a second urging member that urges the second piston in the same direction as the extension direction. 5. The fuel injection valve according to 5.

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