JP2008267164A - Fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection device capable of controlling an increase in sliding resistance of a sliding portion of a piston member even in a case that an unbalanced load is imposed when mounting onto an engine. <P>SOLUTION: In the fuel injection device including an actuator 5 having a piezoelectric stack of piezoelectric elements as a displacement generating source; a piston member 7 having a first piston 71 and a second piston 73 axially movably supported in a guide hole 6a and transmitting displacement of the actuator 5 to the first piston 71 and the second piston 73 in this order; a nozzle needle 31 for opening and closing an injection hole 33 in accordance with the displacement of the piston member 7; and housings 2, 6 and 32 respectively containing the actuator 5, the piston member 7 and the nozzle needle 31, a side face (surface) 71a of the first piston 71 running along the guide hole 6a is shaped into an axially directed spherical surface (a curved surface). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel injection device, and is suitably applied to, for example, an accumulator fuel injection device that injects and supplies fuel to an internal combustion engine.

  2. Description of the Related Art Conventionally, as a fuel injection device, for example, in a pressure accumulating fuel injection device for a diesel engine, a fuel injection valve that is provided in each cylinder of an internal combustion engine and supplies fuel to a combustion chamber of the cylinder is known (Patent Document 1). reference). This type of fuel injection valve is a piezo injector that uses a piezo actuator with excellent responsiveness as a drive unit, and the drive unit usually includes a hydraulic pressure transmission device that transmits the displacement of the piezo injector via hydraulic pressure. (See Patent Document 1).

  In the technique disclosed in Patent Document 1, a small-diameter piston is held in a small-diameter portion in a stepped cylinder, and a large-diameter piston is slidably held in a large-diameter portion, and a hydraulic chamber is provided between the small-diameter piston and the large-diameter piston. Is formed. This technology has a displacement expansion function that expands the displacement of the piezoelectric actuator by combining a hydraulic chamber and a large and small piston.

In Patent Document 2, a sliding gap between piston members of a large-diameter piston and a small-diameter piston and a guide hole of a cylinder (casing) that supports them is formed in a hydraulic chamber (combined chamber) by a piezoelectric actuator operation at the time of injection. A technique for setting the gap amount for refilling the liquid loss is disclosed.
JP 2002-202022 A JP 2001-512547 A

  In the prior art, for example, in the case where the fuel injection valve is attached to the engine with a clamp member, the clamping force does not act uniformly and an uneven load may be applied to the fuel injection valve. When an unbalanced load is applied to the fuel injection valve, misalignment may occur in components such as the nozzle body of the fuel injection valve and the sliding member in the lower body due to deformation due to bending, tilting, or axis misalignment.

  In particular, when the piston member is tilted or the guide hole of the cylinder supporting the piston member is deformed, the sliding resistance of the sliding portion between the piston member and the guide hole may increase. In some cases, the sliding portion cannot be smoothly slid, and a predetermined amount of displacement cannot be obtained and proper injection may not be performed.

  The present invention has been made in consideration of such circumstances, and the object of the present invention is to slide the piston member at the sliding portion even when an unbalanced load may be applied during assembly to the engine. An object of the present invention is to provide a fuel injection device that suppresses an increase in dynamic resistance.

  In order to achieve the above object, the present invention comprises the following technical means.

  That is, the invention according to any one of claims 1 to 9 includes an actuator using a piezoelectric element or a magnetostrictive element as a displacement generation source, and a first piston and a second piston supported in the guide hole so as to be movable in the axial direction. A piston member that transmits the displacement of the first piston and the second piston in order, a nozzle needle that opens and closes the nozzle hole according to the displacement of the piston member, and a housing that houses the actuator, the piston member, and the nozzle needle In the injection device, the first piston is characterized in that a side surface along the guide hole is formed into a curved surface directed in the axial direction.

  According to this, the piston member has the first piston and the second piston supported in the guide hole so as to be movable in the axial direction, and transmits the displacement of the actuator in the order of the first piston and the second piston. In the piston member, the first piston is formed as a curved surface in the axial direction at the side surface along the guide hole.

  That is, the first piston, which is disposed between the actuator and the second piston and transmits the displacement of the actuator to the second piston, has a side surface along the guide hole formed in a curved surface directed in the axial direction. The clearance margin with the guide hole is enlarged at both ends in the axial direction. Thereby, even when an unbalanced load may be applied to the housing, when the displacement is transmitted to the first piston between the actuator and the second piston, the sliding portion between the first piston and the guide hole is An increase in sliding resistance due to, for example, contact with the guide hole at the axial end as in the conventional cylindrical shape can be avoided.

  In the side surface of the first piston, the curved surface may have the same or different curvature radius in the axial direction and the circumferential direction.

  Here, the sliding resistance increases when the first piston of the prior art hits against the guide hole because the displacement is transmitted by the extension of the actuator and the driving force is applied by the extension. This is because, in the driving force applied to the first piston, a component force in a substantially radial direction acts toward the guide hole that contacts one piece.

  On the other hand, as in the invention described in claim 2, the first piston is preferably a sphere.

  Thereby, even if the position of an action point with the both contact parts on the actuator side and the second piston side may be shifted, for example, the first piston has a spherical first piston without changing the position of the action point. It is possible to absorb the above-mentioned component force by rotating the lens.

  Therefore, even if an uneven load is applied to the housing, the sliding portion between the first piston and the guide hole can prevent an increase in sliding resistance.

  In the case where the guide hole is formed in a cylinder member provided in the housing and supporting the first piston and the second piston so as to be movable in the axial direction, as in the invention according to claim 3, the first of the actuator The axial end of the piston side is preferably in contact with the first piston.

  Since the first piston according to the first aspect of the present invention has a side surface along the guide hole formed into a curved surface that extends in the axial direction, an increase in the sliding resistance is avoided, so that the first piston is extended by the extension of the actuator. When transmitting displacement to one piston, the reaction force to the actuator due to sliding resistance can be kept relatively small.

  Accordingly, in the invention described in claim 3, since the reaction force applied to the actuator by displacing the first piston is relatively small, the axial end of the actuator on the first piston side is brought into direct contact with the first piston. Can do. Thereby, for example, it is possible to avoid damage to the piezoelectric element or the magnetostrictive element of the actuator due to an excessive reaction force applied to the actuator.

  Further, in the case where the guide hole is formed in the cylinder member, as in the inventions according to claims 4 to 5, there is a gap between the axial end of the actuator on the first piston side and the first piston. It is preferable to include a third piston that can be inserted into the guide hole of the cylinder and is in contact with the axial end and the first piston.

  As a result, when the displacement is transmitted to the first piston by the extension of the actuator, the axial end portion on the first piston side of the actuator does not directly contact the first piston, so the first piston is connected via the third piston. It is possible to absorb misalignment between the piston and the actuator.

  Particularly, in the third piston, as in the invention described in claim 5, it is preferable that the contact portion on the first piston side is formed in a curved surface along the first piston.

  According to this, since the 3rd piston inserted | pinched between an actuator and a 1st piston forms the contact part by the side of a 1st piston in the curved surface along a 1st piston, in 3rd piston The misalignment between the first piston and the actuator can be absorbed by using the curved surface along the first piston.

  According to a sixth aspect of the present invention, the end of the second piston on the first piston side is formed in a curved surface along the first piston. According to this, the contact part with which a 2nd piston contact | abuts to a 1st piston can be formed in the curved surface along a 1st piston. Therefore, since the contact state between the first piston and the second piston is a surface contact, it is possible to suppress wear of both contact portions of the first piston and the second piston, and from the first piston to the second piston. The displacement can be transmitted smoothly.

  Further, the curved surface is preferably a spherical surface as in the invention described in claim 7.

  Thereby, even if the posture of the first piston may be changed due to the offset load applied to the housing, the curved surface is a spherical surface, so that the contact state between the first piston, the guide hole, and the second piston is Without change, it is possible to prevent an increase in sliding resistance at the sliding portion between the first piston and the guide hole.

  The third piston is integrally formed with the first piston as in the invention described in claim 8.

  According to this, since the third piston is inserted into the guide hole, the contact state between the guide hole and the second piston can be determined only by the first piston. Thereby, the number of parts can be reduced by integrating the first piston and the third piston.

  The housing according to any one of claims 1 to 8, as in the invention according to claim 9, has a lower body that accommodates an actuator and a piston member so as to be movable therein, an injection hole, and a nozzle. A lower body that includes a nozzle body that slidably houses a needle, and a lower body and a fixing member that hermetically fixes the nozzle body, and the housing is inserted into a mounting hole of an internal combustion engine or the like as a mounted member and protrudes from the mounting hole It is characterized in that a clamping force is applied to.

  Since such a housing is applied to a fuel injection device in which a clamping force is applied to a lower body that is inserted into a mounting hole of an internal combustion engine or the like as a mounted member and protrudes from the mounting hole, a clamping force is applied from the outside of the fuel injection device. Even if an unbalanced load is applied by such an external force, an increase in sliding resistance at the sliding portion of the piston member can be suppressed.

  Hereinafter, embodiments in which the fuel injection device of the present invention is applied to a fuel injection valve used in an accumulator fuel injection device will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a cross-sectional view showing a sliding portion of a piston member according to the fuel injection device of the present embodiment. FIG. 2 is a partial cross-sectional view when the fuel injection device of the present embodiment is mounted on the engine head. FIG. 3 is a schematic cross-sectional view showing an example of a contact state of the end portion of the actuator, the first piston, the second piston, and the guide hole in FIG.

  As shown in FIG. 2, the fuel injection valve 1 is used in, for example, a pressure accumulation fuel injection device for a diesel engine (hereinafter referred to as an engine), and a high pressure fuel supplied from a pressure accumulation device (not shown) is used as a combustion chamber of the engine. It is to be sprayed on. The fuel injection valve 1 includes a fuel injection nozzle (hereinafter simply referred to as an injection nozzle) 3, a lower body 2, a piston member 7, a cylinder 6, and an actuator 5.

  In the injection nozzle 3, a nozzle hole 35 is formed from the upper end surface to the vicinity of the lower end in FIG. 2, and a nozzle body 32 having an injection hole 33 at the lower end (bottom) 34 and a slidable support inside the nozzle hole 35. It consists of a nozzle needle 31. The nozzle needle 31 is urged downward (in the valve closing direction) by a coil spring 39 disposed around the upper portion of the nozzle needle 31. The injection nozzle 3 is fastened to the lower body 2 indirectly or directly by being fastened to the lower body 2 by a retaining nut 4 so as to be airtightly fixed.

  The lower body 2 is formed in a substantially rod shape, and the lower body 2 is formed with a cylinder hole 21 into which the actuator 5 and the cylinder 6 are inserted, a high pressure passage 22 for guiding the high pressure fuel supplied from the pressure accumulator to the injection nozzle 3 and the like.

  The cylinder 6 has a guide hole 21 that supports the first piston 71 and the second piston 73 as the piston member 7 so as to be movable in the axial direction. The guide hole 21 is formed so as to be coaxial with the cylinder hole 21, and the first piston 71 and the second piston 73 are disposed coaxially with respect to the actuator 5. The details of the piston member 7 having the first piston 71 and the second piston 73 will be described later.

  The actuator 5 is composed of a piezo stack in which piezoelectric elements such as PZT are laminated in the axial direction. The actuator 5 extends downward in FIG. 2 by receiving external energy supply, and contracts upward by releasing injected energy. Is a well-known one. Specifically, when the actuator 5 is energized through a connector 59 having a terminal from an energization circuit (not shown), the piezo stack is extended by receiving high-voltage electrical energy, and the energization is stopped. When it is done, electrical energy is released and the piezo stack contracts.

  The actuator 5 has a movable end 5a and a fixed end 5b across the piezo stack, and the fixed end 5b is fixed to the cylinder hole 21 so as not to be displaced. On the other hand, the movable end 5a is brought into contact with the lower end of the piezo stack and is displaced in the axial direction as the piezo stack expands and contracts.

  Since the actuator 5 is mounted in the cylinder hole 21 in which the piston member 7 is disposed, the actuator 5 has a structure that prevents the fuel from entering the piezo stack. Specifically, the piezo stack, the movable end portion 5a, and the fixed end portion 5b are formed of a cylindrical metal stack case (not shown) that forms a stack chamber therein, and a side wall is formed. The end portion on the side of the portion 5a and the movable end portion 5a are airtightly connected by a diaphragm. In FIG. 1 and FIG. 2, the movable end portion 5 a is only shown in a portion that is exposed from the diaphragm and protrudes downward in the axial direction, among those sealed by the diaphragm.

  The distal end surface (hereinafter referred to as a contact surface) 5as of the movable end 5a may be a flat surface or a curved surface such as a spherical surface. In the following examples, a flat surface is used.

  Further, a control valve member (not shown) for accommodating the control valve 8 is disposed between the lower body 2 and the nozzle body 32, and the lower body 2, the nozzle body 32, and the control valve member are arranged in the retaining nut 4. It is fixed more tightly.

  A space defined by using the upper end surface of the nozzle needle 31 as a chamber wall forms a control hydraulic chamber 9, and the control valve 8 is disposed in the control hydraulic chamber 9, and the pressure in the control hydraulic chamber 9 (oil pressure) ) To control. The control valve 8 is driven via the piston member 7 by the expansion and contraction of the actuator 5, and the control valve 8 increases or decreases the hydraulic pressure in the control hydraulic chamber 9. Thereby, the back pressure (acting force in the valve closing direction) of the nozzle needle 31 is controlled, and the nozzle needle 31 opens and closes the injection hole 33. In FIG. 2, the control valve 8, the control hydraulic chamber 9, and the fuel circuit communicating therewith are shown in a simplified manner for convenience of explanation.

  Next, details of the piston member 7 will be described with reference to FIGS. 1 and 2. The piston member 7 includes a first piston 71 and a second piston 73, and the first piston 71 and the second piston 73 are supported in the guide hole 6a so as to be movable in the axial direction. The piston member 7 transmits the displacement due to the expansion and contraction of the actuator 5 to the control valve 8 in the order of the first piston 71 and the second piston 73, and drives the control valve 8.

  The guide hole 6a is formed in a stepped circular inner periphery, and houses the second piston 73 and the first piston 71 having a diameter D1 larger than the diameter D3 of the second piston 73. .

  As shown in FIGS. 1 and 2, the first piston 71 is formed in a spherical shape, and the second piston 73 is formed in a columnar shape.

  The second piston 73 is formed with a sliding gap (hereinafter referred to as a second sliding gap) between the second piston 73 and the guide hole 6a, and the second sliding gap is disposed on the fuel upstream side. In order to suppress the leaked fuel leaking from the control hydraulic pressure chamber 9 side to the fuel low pressure side through the second sliding gap, the gap amount is set to be relatively small.

  The first piston 71 has a sliding gap (hereinafter referred to as a first sliding gap) between the first piston 71 and the guide hole 6a. The first sliding gap is more than the second sliding gap. Largely formed. That is, in the first sliding gap, the gap portion in the diameter direction of the first piston 71 that is a sphere (hereinafter, the diameter gap portion) is larger than the gap amount of the second sliding gap, and the shaft of the first piston 71 The gap portion formed between the spherical surface and the guide hole 6a in the direction cross section (hereinafter referred to as the axial gap portion) increases as the distance from the diameter gap portion increases in the axial direction, and the clearance margin increases. Is done. When the first piston 71 and the guide hole 6a are in contact with each other, line contact or point contact is always made in the diameter gap portion.

  As shown in FIG. 1, the first piston 71 is in contact with the movable end 5a of the actuator 5, and the spherical surface 71a of the first piston 71 makes point contact with the contact surface 5as of the movable end 5a. ing. The first piston 71 is in contact with the second piston 73, and the surface 71 a of the first piston 71 is in point contact with the contact surface 73 s of the second piston 73.

  Further, as a method of mounting the fuel injection valve 1 on the engine 100, the following method is generally used. That is, as shown in FIG. 2, the engine head (cylinder head) 101 is formed with a mounting hole 102 into which the fuel injection valve 1 can be inserted and accommodated so that the injection nozzle 3 faces the combustion chamber 104. . The fuel injection valve 1 is mounted in the mounting hole 102, and a clamping force is applied to the lower body 2 protruding from the mounting hole 102 by a clamping member (not shown). By applying this clamping force in the axial direction of the fuel injection valve 1, the fuel injection valve 1 is attached and fixed to the engine head 101. This clamping force is applied to both receiving portions on the lower body 2 side by a bifurcated clamp member.

  The mounting hole 102 is formed in a stepped inner periphery, and the gasket 103 is sandwiched between the stepped inner peripheral stepped portion and the retaining nut 4 on the tip end side of the fuel injection valve 1 for airtightness. Is sealed.

  Here, in order to explain the effect of the piston member 7 according to the present invention, a comparative example shown in FIG. 7 will be described. In general, as shown in FIG. 7A, as the piston member 907, a first piston 971 and a second piston 973 are formed in a columnar shape, and between the first piston 971 and the second piston 973 and the guide hole 906a. The first sliding gap and the second sliding gap formed in the above are both set to a slight gap amount in order to suppress leak fuel. When the clamping force is applied to the fuel injection valve 1 without being an uneven load as shown in FIG. 7A, the sliding portions of the first piston 971, the second piston 973, and the guide hole 6a The proper sliding resistance is formed without narrowing. That is, the side surfaces 971a and 973a of the first piston 971 and the second piston 973 are in surface contact with the inner peripheral surface of the guide hole 906a, and the sliding resistance according to the surface contact state between the side surfaces 971a and 973a and the inner periphery 906a. It was happening.

  However, as shown in FIG. 7B, in the fuel injection valve 1 having the piston member 907 of the comparative example, when an unbalanced load (F1 <F2 or F1> F2) occurs in the clamping forces F1 and F2, the fuel injection valve 1 The lower body 2 may be deformed, and the movable end 5a of the actuator 5 may be displaced. The contact portion between the axially displaced movable end portion 5a and the first piston 971 is shifted to the right side of the contact surface 971s of the upper end portion of the first piston 973, and thus the side surface 971a on the upper end portion side of the first piston 971. And the guide hole 906a may cause contact with each other.

  If the first piston 971 and the guide hole 906a come into contact with each other, an appropriate surface contact state cannot be maintained, and the sliding resistance may increase due to line contact or point contact at the piece contact portion in the sliding portion. was there.

  On the other hand, in the present embodiment, the first piston 71 is a sphere, and the side surface along the guide hole 6a, that is, the surface 71a is formed in a curved surface along the axial direction such as a spherical surface. In the first sliding gap with the guide hole 6a, the gap amount in the axial gap portion is larger than that in the diameter gap portion as it is separated from the diameter gap portion in the axial direction. That is, the clearance margin is enlarged toward the both shaft ends of the first piston 71. Due to the enlarged clearance margin, the first piston 71 does not come into contact with the guide hole 6a. When the first piston 71 and the guide hole 6a are in contact with each other, the line contact or the point is always in the diameter clearance portion. Contact.

  As a result, even if an unbalanced load due to external forces such as the clamping forces F1 and F2 is applied to the fuel injection valve 1, the displacement is transmitted to the first piston 71 between the actuator 5 and the second piston 73. In this case, the sliding portion between the first piston 71 and the guide hole 6a is caused by the sliding resistance generated when the first piston 907 having a cylindrical shape as shown in FIG. 7B contacts the guide hole 906a. The increase of can be avoided.

  Here, the sliding resistance increases when the first piston 907 of the comparative example comes into contact with the guide hole 906a because the displacement is transmitted by the extension of the actuator and the driving force is applied by the extension. This is because, in the driving force applied to the first piston 971, a component force in a substantially radial direction acts toward the guide hole 906a that contacts one piece.

  On the other hand, in the present embodiment, since the first piston 71 is a sphere, the position of the point of action between the contact portions 5as and 73s on the actuator 5 side and the second piston 73 side may shift. However, it is possible to absorb the above component force by rotating the spherical first piston 71 without changing the position of the action point.

  That is, an example of misalignment is shown in which the movable end portion 5a of the actuator 5 in FIG. 3 and the contact portions 5as and 73s of the second piston 73 are displaced from each other by the axis of action of the contact portions 5as and 73s. Has been. As shown in FIG. 3, the driving force N <b> 1 that attempts to displace the second piston 71 downward along with the extension of the actuator 5 is received by the second piston 73 via the first piston 71. A reaction force N2 is applied to the piston 71. Further, the first piston 71 has an acting force Nr1 that opposes the driving force N1, an acting force Nr2 that opposes the reaction force N2, and a couple of forces is generated by the acting force Nr1 and the acting force Nr2. A rotational moment acts in the direction of the white arrow.

  The first piston 71, which is such a sphere, rotates by the rotational moment. Thereby, even in the case where the misalignment occurs, the driving force that drives the first piston 71 consumes and absorbs the component force that causes the increase in sliding resistance as in the comparative example as the rotational motion of the rotational moment. be able to.

  Therefore, even if the above-described uneven load is applied to the fuel injection valve 1, the sliding portion between the first piston 71 and the guide hole 6a can reliably prevent an increase in sliding resistance.

  In the present embodiment described above, since the first piston 71 is a sphere, an increase in sliding resistance is prevented. Therefore, when the displacement is transmitted to the first piston 71 by the extension of the actuator 5, the sliding resistance is increased. The reaction force to the actuator 5 can be kept relatively small. That is, since the reaction force applied to the actuator 5 by displacing the first piston 71 is relatively small, the movable end 5a of the actuator 5 can be brought into direct contact with the first piston 71 as shown in FIG. . Thereby, for example, it is possible to avoid damaging the piezo stack of the actuator 5 due to an excessive reaction force applied to the actuator 5.

  Here, the lower body 2, the nozzle body 32, and the cylinder 6 correspond to the housing described in the claims. The retaining nut 4 corresponds to the fixing member described in the claims. The movable end 5a corresponds to an axial end on the first piston side of the actuator 5 described in the claims. The engine head (cylinder head) corresponds to the mounted member described in the claims.

(Second Embodiment)
Hereinafter, other embodiments to which the present invention is applied will be described. In the following embodiments, the same or equivalent components as those in the first embodiment are denoted by the same reference numerals, and description thereof will not be repeated.

  A second embodiment is shown in FIG. The second embodiment shows an example in which the first piston 171 has different radii of curvature in the axial direction and the circumferential direction. FIG. 4 is a cross-sectional view showing a sliding portion of the piston member according to this embodiment.

  As shown in FIG. 4, the piston member 7 includes a first piston 171 and a second piston 73. The first piston 171 is not a sphere having a radius of curvature in both the axial direction and the circumferential direction, and is substantially egg-shaped. It is formed in a shape. In the axial cross section (longitudinal cross section) of FIG. 4, the cross-sectional shape of the first piston 171 is an ellipse, and the ellipse has a major axis D2 in the axial direction and a minor axis D1 in the radial direction. That is, in the curved surface formed on the side surface (surface) 171a of the first piston 171, the curved surface shape toward the axial direction, that is, the radius of curvature in the axial direction is represented by 1/2 of the major axis D1, and the curved surface shape toward the circumferential direction, that is, the circumferential shape. The curvature radius in the direction is represented by 1/2 of the minor axis D2.

  The first piston 171 has a curvature radius in the circumferential direction that is larger than the curvature radius (same as 1/2 of the minor axis D2) in the case of a spherical spherical surface.

  Also in the first piston 171 having such a shape, the gap amount increases from the short diameter gap portion as the axial gap portion in the first sliding gap moves away from the short diameter (diameter) gap portion in the axial direction. That is, the clearance margin is enlarged toward the both shaft ends of the first piston 171.

(Third embodiment)
A third embodiment is shown in FIG. The third embodiment shows an example in which the third piston 75 is sandwiched between the actuator 5 and the first piston 71. FIG. 5 is a cross-sectional view showing a sliding portion of the piston member according to the present embodiment.

  As shown in FIG. 5, a gap between the movable end 5 a of the actuator 5 and the first piston 71 can be inserted into the guide hole 6 a of the cylinder 6 and is in contact with the movable end 5 a and the first piston 71. Three pistons 75 are provided.

  Thus, when the displacement is transmitted to the first piston 71 due to the extension of the actuator 5, the movable end portion 5a of the actuator 5 does not directly contact the first piston 71, and the third piston 75 is interposed. The misalignment between the first piston 71 and the actuator 5 can be absorbed via the third piston 75.

  In particular, in the third piston 75, it is preferable that a front end surface (hereinafter referred to as a contact surface) 75s on the first piston 71 side is a spherical surface along the surface 71a of the first piston 71. According to this, the third piston 75 sandwiched between the actuator 5 and the first piston 71 forms a contact surface 75 on the first piston 71 side as a spherical surface along the first piston 71. Therefore, the misalignment between the first piston 71 and the actuator 5 can be absorbed by using the spherical contact surface 75s along the first piston 71 in the third piston 75.

  In the present embodiment, the contact state of the contact portion between the third piston 75 and the first piston 71 is the surface contact because the contact surface 75s of the third piston 75 is formed into a spherical surface along the first piston 71. Become. Thereby, the wear of the contact portion between the third piston 75 and the first piston 71 is reduced.

  Here, the contact surface 75s of the third piston 75 is a spherical surface because the first piston 71 is a sphere, but the first piston 71 is not a sphere but a curved surface such as a substantially egg shape. For things, it is a curved surface.

(Fourth embodiment)
A fourth embodiment is shown in FIG. 4th Embodiment shows the modification of the contact state of the contact part of the 1st piston 71 and the 2nd piston 73. FIG. FIG. 6 is an enlarged cross-sectional view showing a part of the piston member according to the present embodiment.

  As shown in FIG. 6, in the second piston 73, a front end surface (hereinafter referred to as a contact surface) 73 s on the first piston 71 side is formed into a spherical surface along the surface 71 a of the first piston 71.

  According to this, the contact state of the contact portion between the second piston 73 and the first piston 71 is a surface contact because the contact surface 73 s of the second piston 73 is formed into a spherical surface along the first piston 71. Thereby, wear of the contact portion between the second piston 73 and the first piston 71 is reduced.

  Therefore, wear of both contact portions of the first piston 71 and the second piston can be suppressed, and displacement from the first piston 71 to the second piston 73 can be smoothly transmitted.

  Here, the contact surface 73s of the second piston 73 is a spherical surface because the first piston 71 is a sphere, but the first piston 71 is not a sphere, but is a curved surface such as a substantially egg shape. For things, it is a curved surface.

(Other embodiments)
(1) In the present embodiment described above, the surface (side surface) 71a of the first piston 71 in the first, third, and fourth embodiments is a spherical surface, and the surface (side surface) of the first piston 171 in the second embodiment. ) 171a is a curved surface. The surface (side surface) of the first piston 71 is preferably a spherical surface rather than merely a curved surface.

  Thereby, even if the posture of the first piston 71 may be changed due to the offset load applied to the fuel injection valve 1, the curved surface of the first piston 71 is a spherical surface. Without increasing the contact state between the guide hole 6a and the second piston 73, it is possible to effectively prevent an increase in sliding resistance at the sliding portion between the first piston 71 and the guide hole 6a.

  (2) In the third embodiment described above, the third piston 75 is provided between the movable end 5a of the actuator 5 and the first piston 71. The third piston 75 and the first piston 71 are separate members. It was. The third piston is not limited to this, and may be integrally formed with the first piston.

  In this case, the third piston is set to a size that can be inserted into the guide hole. Therefore, in the case where the third piston and the first piston are integrally formed, the contact state between the guide hole and the second piston can be determined only by the first piston portion regardless of the third piston portion. Thereby, the number of parts can be reduced by integrating the first piston and the third piston.

(3) In this embodiment described above, a fuel injection device having a piston member according to the present invention is provided.
Lower body 2 that accommodates actuator 5 and piston member 7 so as to be movable therein, nozzle hole 33 in which nozzle hole 33 is formed and slidably accommodates nozzle needle 31 and lower body 2 and nozzle body 32 are indirectly or A fuel injection valve 1 having a retaining nut that is directly butted and fastened tightly, and the fuel injection valve is inserted into the mounting hole 102 of the engine head 102 and clamped to the lower body 2 protruding from the mounting hole 102 Applied to those to which power is granted.

In such a fuel injection valve 1, even if an unbalanced load is applied from the outside of the fuel injection device by an external force such as a clamping force, an increase in sliding resistance at the sliding portion of the piston member can be suppressed. it can.
(4) In the present embodiment described above, an explanation has been given of an actuator composed of a piezo stack in which piezoelectric elements are stacked as a displacement generation source for displacing the piston member 7 by expansion and contraction, but an actuator composed of a magnetostrictive element may be used. .

It is sectional drawing which shows the sliding part of the piston member concerning the fuel-injection apparatus of 1st Embodiment of this invention. It is a fragmentary sectional view when the fuel-injection apparatus of 1st Embodiment of this invention is mounted | worn with an engine head. It is typical sectional drawing which shows an example of the contact state of the edge part of an actuator in FIG. 1, a 1st piston, a 2nd piston, and a guide hole. It is sectional drawing which shows the sliding part of the piston member concerning 2nd Embodiment. It is sectional drawing which shows the sliding part of the piston member concerning 3rd Embodiment. It is an expanded sectional view showing a part of piston member concerning a 4th embodiment. FIGS. 7A and 7B are diagrams showing a sliding portion of a piston member of a comparative example, in which FIG. 7A is a cross-sectional view showing a state in which a bias load is not applied to the fuel injection device, and FIG. It is sectional drawing which shows the state in which the load is provided.

Explanation of symbols

1 Fuel injection valve (fuel injection device)
2 Lower body (housing)
3 Injection nozzle (fuel injection nozzle)
31 Nozzle Needle 32 Nozzle Body (Housing)
33 Injection hole 4 Retaining nut (fixing member)
5 Actuator 5a Movable end 5as Contact surface 5b Fixed end 6 Cylinder (housing)
6a Guide hole 7 Piston member 71 First piston 71a Surface (side surface)
73 Second piston 73a Side surface 73s Contact surface 9 Control valve 100 Engine (internal combustion engine)
101 Engine head 102 Mounting hole 104 Combustion chamber

Claims (9)

An actuator using a piezoelectric element or a magnetostrictive element as a displacement generation source;
A piston member having a first piston and a second piston supported in the guide hole so as to be axially movable, and transmitting a displacement of the actuator in the order of the first piston and the second piston;
A nozzle needle that opens and closes the nozzle hole according to the displacement of the piston member;
A housing that houses the actuator, the piston member, and the nozzle needle;
In a fuel injection device comprising:
The fuel injection device according to claim 1, wherein the first piston is formed with a curved surface directed in the axial direction at a side surface along the guide hole.   The fuel injection device according to claim 1, wherein the first piston is a sphere. The guide hole is provided in the housing, and is formed in a cylinder member that supports the first piston and the second piston so as to be axially movable.
3. The fuel injection device according to claim 1, wherein an axial end portion of the actuator on the first piston side is in contact with the first piston. 4. The guide hole is provided in the housing, and is formed in a cylinder member that supports the first piston and the second piston so as to be axially movable.
Between the axial end of the actuator on the first piston side and the first piston, the actuator can be inserted into the guide hole of the cylinder, and is in contact with the axial end and the first piston. The fuel injection device according to claim 1, further comprising three pistons.   2. The fuel injection device according to claim 1, wherein the first piston-side contact portion of the third piston is formed in a curved surface along the first piston.   The fuel injection device according to any one of claims 1 to 5, wherein an end portion of the second piston on the first piston side is formed in a curved surface along the first piston. .   The fuel injection device according to any one of claims 1 to 6, wherein the curved surface is formed into a spherical surface.   The fuel injection device according to claim 4, wherein the third piston is integrally formed with the first piston. The housing is
A lower body for accommodating the actuator and the piston member movably therein;
A nozzle body in which the nozzle hole is formed and slidably accommodates the nozzle needle;
A fixing member for hermetically fixing the lower body and the nozzle body;
With
The housing is inserted into the mounting hole of the mounted member;
The fuel injection device according to any one of claims 1 to 8, wherein a clamping force is applied to the lower body projecting from the mounting hole.

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