JP2010223194A - Fuel injection valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the reliability of a piezo actuator while improving energy efficiency in a direct-acting fuel injection valve having a variable displacement magnification which is opened when the piezo actuator extends (i.e., when charged). <P>SOLUTION: When a piezo actuator 14 extends, a cylinder 22 is driven in the direction in which a second guide hole 221 is apart from a piston part 210, the volume of a first oil-tight chamber 26 is increased, and the pressure in the first oil-tight chamber 26 lowers. When the pressure in the first oil-tight chamber 26 lowers, a raising member 23 drives a nozzle needle 13 in the valve opening direction. When the raising member 23 is moved, the volume of a second oil-tight chamber 27 is increased, the pressure in the second oil-tight chamber 27 lowers, and the nozzle needle 13 is driven in the valve opening direction continuously due to a reduction in the pressure in the second oil-tight chamber 27. The displacement magnification is set so that the movement amount of the nozzle needle 13 is larger than that of the raising member 23. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fuel injection valve for injecting fuel into an internal combustion engine.

  A fuel injection valve that drives a nozzle needle by transmitting a driving force of a piezo actuator to the nozzle needle via a hydraulic or mechanical mechanism is called a direct acting type. In a direct acting fuel injection valve, a large force is required to drive the nozzle needle at the start of valve opening. In addition, when the nozzle is lifted after opening the valve, the pressure that urges the nozzle needle toward the valve closing balances with the pressure that urges the nozzle needle toward the valve opening. It is necessary to secure a large amount of displacement.

  The fuel injection valve disclosed in Patent Document 1 is a direct-acting fuel injection valve, which charges a charge and extends a piezo actuator to drive a nozzle needle in a valve closing direction, thereby discharging the charge and discharging the piezo. The nozzle needle is driven in the valve opening direction by contracting the actuator.

  In addition, the fuel injection valve disclosed in Patent Document 1 has a displacement expansion ratio after opening the valve rather than a displacement expansion ratio at the start of the valve opening (where the displacement expansion ratio is the displacement amount of the nozzle needle / the expansion / contraction amount of the piezo actuator). Since the rate is increased, a large driving force can be obtained at the start of the valve opening, and a large displacement amount of the nozzle needle can be ensured at the time of the nozzle lift after the valve opening. As a result, the charging energy to the piezo actuator can be reduced as compared with the fuel injection valve having a constant displacement expansion rate. That is, energy efficiency can be improved.

US Pat. No. 6,776,354

  However, in the case of the method of charging and closing the valve as in the fuel injection valve disclosed in Patent Document 1, during the operation of the internal combustion engine, the time during which the piezoelectric actuator is at a high voltage is Since it is longer than the time during which the voltage is low, the piezo actuator is liable to cause dielectric breakdown, which is undesirable in terms of reliability (durability, etc.) of the piezo actuator.

  The present invention has been made in view of the above points, and it is an object of the present invention to improve the reliability of a piezo actuator in a direct-acting fuel injection valve that improves energy efficiency by changing a displacement magnification rate.

  In order to achieve the above object, in the invention described in claim 1, a piezo actuator (14) that expands and contracts due to charge and discharge of electric charge, and a driven member (22, 30) driven by the piezo actuator (14), The position of the body (10, 11, 11a, 11b) is fixed, and the fixed member (21, 31) slidably assembled to the driven member (22, 30) and the extension of the piezo actuator (14) The first oil-tight chamber (26, 35) to be decompressed along with the driven member (22, 30) and the fixing member (21, 31) is formed in cooperation with the first oil-tight chamber (26, 35). And a pull-up member (23, 32) that engages with the nozzle needle (13) to drive the nozzle needle (13) in the valve-opening direction when the pressure decreases, and the pressure in the first oil-tight chamber (26, 35) The second oil-tight chambers (27, 36) that are depressurized in accordance with the movement of the lifting members (23, 32) due to the lowering are defined by the members including the lifting members (23, 32), and the second oil-tight chambers (27, 36) are formed. ) Is inserted into the rear end of the nozzle needle (13), and when the pressure in the second oil-tight chamber (27, 36) decreases, the nozzle needle (13) is driven in the valve opening direction. The area of the driven member (22, 30) that receives the pressure of the first oil-tight chamber (26, 35) is defined as the first pressure-receiving area, and the lifting member (23, 32) includes the first oil-tight chamber (26, 35). ) Is the second pressure receiving area, the area of the lifting member (23, 32) that is receiving the pressure of the second oil tight chamber (27, 36) is the third pressure receiving area, and the nozzle needle (13). Of the second oil-tight chamber (27, 36) The area of the force receiving part is the fourth pressure receiving area, the first pressure receiving area / the second pressure receiving area = the first displacement enlargement ratio, the first displacement enlargement ratio × the third pressure receiving area / the fourth pressure receiving area = the second displacement enlargement ratio. In this case, the second displacement magnification rate is set larger than the first displacement magnification rate.

  According to this, since the direct-acting fuel injection valve that changes the displacement expansion rate is realized by a method of opening the valve with the extension of the piezo actuator (14) (that is, by charging the electric charge), The reliability of the piezoelectric actuator (14) can be improved while improving the efficiency.

  According to a second aspect of the present invention, in the fuel injection valve according to the first aspect, the driven member (22) is a cylindrical member, and the driven member first guide hole (220) and the driven member A driven member second guide hole (221) having a smaller diameter than the first guide hole (220) is formed, and the fixed member (21) has a columnar piston portion (210) having a driven member first guide hole (220). The lifting member (23) is a bottomed cylindrical member, and the bottom cylindrical portion (230) is slidable in the driven member second guide hole (221). When the piezoelectric actuator (14) is inserted, the driven member (22) is configured so that the driven member second guide hole (221) is driven in a direction away from the piston portion (210). It is characterized by.

  According to this, as the piezo actuator (14) extends, the volume of the first oil-tight chamber (26) is expanded, and the first oil-tight chamber (26) is decompressed.

  According to a third aspect of the present invention, in the fuel injection valve according to the second aspect, the lifting member (23) is larger in diameter than the first cylindrical portion (230) and the first cylindrical portion (230) having a bottom portion. A second cylindrical portion (231) is formed, the first cylindrical portion (230) is slidably inserted into the driven member second guide hole (221), and the second cylindrical portion (231) is inserted into the body (10). , 11a, 11b), and the second oil-tight chamber (27) is defined by the lifting member (23) and the body (10, 11a, 11b), and is fourth than the third pressure-receiving area. The pressure receiving area is set small.

  According to this, since the second displacement magnification rate becomes larger than the first displacement magnification rate, the movement amount of the nozzle needle (13) becomes larger than the movement amount of the lifting member (23) from the middle of the valve opening stroke, A sufficient amount of displacement of the nozzle needle (13) can be ensured.

  According to a fourth aspect of the present invention, in the fuel injection valve according to the first aspect, the fixing member (31) is a bottomed cylindrical member, and the fixing member first guide hole (310) is provided in the cylindrical portion. The fixing member second guide hole (311) having a smaller diameter than the fixing member first guide hole (310) is formed at the bottom, and the lifting member (32) is formed from the fixing member second guide hole (311). Is a cylindrical member formed with a large-diameter lifting member guide hole (320), which is slidably inserted into the fixed member first guide hole (310), and the driven member (30) has a columnar shape. The first piston portion (300) that is slidably inserted into the lifting member guide hole (320) and the fixed member second guide hole (311), and one end is fixed Projecting from the member second guide hole (311) A second piston portion (301) that abuts the piezo actuator (14) is provided, and the driven member (30) has a first piston portion (300) as a fixed member second guide hole (30) as the piezo actuator (14) extends. 311) is configured to be driven in a direction away from 311).

  According to this, as the piezo actuator (14) extends, the volume of the first oil-tight chamber (35) is expanded and the first oil-tight chamber (35) is decompressed.

  According to a fifth aspect of the present invention, in the fuel injection valve according to the fourth aspect, the fixing member (31) has an opening end surface on the opposite bottom side abutting on the body (10), and the second oil-tight chamber (36) is The partition member is formed by the fixing member (31), the lifting member (32), and the body (10), and the fourth pressure receiving area is set smaller than the third pressure receiving area.

  According to this, since the second displacement magnification rate becomes larger than the first displacement magnification rate, the movement amount of the nozzle needle (13) becomes larger than the movement amount of the lifting member (32) from the middle of the valve opening stroke, A sufficient amount of displacement of the nozzle needle (13) can be ensured.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

It is front sectional drawing which shows the structure of the fuel injection valve which concerns on 1st Embodiment of this invention. (A) is a front view of the push plate 20 of FIG. 1, (b) is a bottom view of (a). It is a bottom view of the piston 21 of FIG. It is a figure which shows the relationship between the load which acts on a nozzle opening direction with respect to a nozzle needle, and the displacement amount of a nozzle needle. It is front sectional drawing which shows the structure of the fuel injection valve which concerns on 2nd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.

(First embodiment)
The fuel injection valve of the present embodiment is mounted on a cylinder head of an internal combustion engine (more specifically, a diesel engine, not shown), and high-pressure fuel stored in a pressure accumulator (not shown) is transferred into the cylinder of the internal combustion engine. It is to be sprayed on.

  As shown in FIG. 1, the body of the fuel injection valve is divided into a substantially cylindrical nozzle body 10, a substantially cylindrical first piezo body 11a, and a substantially cylindrical second piezo body 11b, and these bodies 10, 11a. , 11b are arranged in series in the injection valve axial direction and are integrally held by a substantially cylindrical retaining nut 12.

  In the piezo bodies 11a and 11b, an upstream high-pressure fuel passage 110 through which high-pressure fuel supplied from the pressure accumulator flows is formed. The nozzle body 10 is formed with a downstream high-pressure fuel passage 100 that guides the high-pressure fuel supplied via the upstream high-pressure fuel passage 110 to the tip end side of the nozzle body 10.

  A nozzle hole 101 through which high-pressure fuel supplied via the downstream high-pressure fuel passage 100 is injected into the cylinder of the internal combustion engine is formed at the tip side of the nozzle body 10. Further, a body sheet portion 102 is formed on the upstream side of the nozzle hole 101 on the tip side of the nozzle body 10.

  The substantially cylindrical nozzle needle 13 that opens and closes the nozzle hole 101 has a cylindrical needle first piston portion 130 slidably held in the nozzle body guide hole 103 of the nozzle body 10. The nozzle needle 13 is formed with a tapered needle seat portion 131 at an end portion (that is, a tip portion) on the nozzle hole 101 side, and the needle seat portion 131 becomes the body sheet portion 102 as the nozzle needle 13 reciprocates. The nozzle hole 101 is opened and closed by contacting and separating.

  The end of the nozzle needle 13 on the side opposite to the injection hole (that is, the rear end) protrudes from the end surface on the side opposite to the injection hole 104 of the nozzle body 10 (hereinafter referred to as the nozzle body rear end surface). The part is formed with a needle flange part 132 projecting radially outward.

  The upstream high-pressure fuel passage 110 houses a piezo actuator 14 in which a large number of piezo elements are stacked and expands and contracts due to charge / discharge. A push plate 20, a piston 21, a cylinder 22, and a lifting member 23 are arranged in the upstream high pressure fuel passage 110.

  As shown in FIG. 2, the push plate 20 includes a columnar disc portion 200 and a columnar leg portion 201 protruding in the axial direction from one end surface of the disc portion 200. Three leg portions 201 are provided along the circumferential direction.

  As shown in FIG. 3, the piston 21 as a fixing member includes a columnar piston portion 210 and a flange portion 211 that protrudes radially outward from the piston portion 210. In the flange portion 211, leg portion through holes 212 are formed at three locations along the circumferential direction.

  As shown in FIG. 1, in the piston 21, the outer peripheral portion of the flange portion 211 is sandwiched between a first piezoelectric body 11a and a second piezoelectric body 11b, whereby the piston 21 is positioned and fixed with respect to the piezoelectric bodies 11a and 11b.

  In the push plate 20, the disc portion 200 is in contact with the piezo actuator 14. Further, the leg portion 201 penetrates the leg passage hole 212 of the piston 21, and the tip portion is in contact with the cylinder 22. When the piezo actuator 14 is extended, the cylinder 22 is driven by the piezo actuator 14 via the push plate 20.

  The cylinder 22 as the driven member is cylindrical, and the driven member first guide hole 220 and the driven member second guide hole 221 having a smaller diameter than the driven member first guide hole 220 are formed in the cylinder 22. Has been. The piston portion 210 of the piston 21 is slidably inserted into the driven member first guide hole 220.

  The lifting member 23 is formed with a first cylindrical portion 230 and a second cylindrical portion 231 having a larger diameter than the first cylindrical portion 230. The lifting member 23 has a bottomed cylindrical shape, has a bottom portion at one end of the first cylindrical portion 230, and opens one end of the second cylindrical portion 231. The first cylindrical portion 230 is slidably inserted into the driven member second guide hole 221 of the cylinder 22. The second cylindrical portion 231 is slidably inserted into a piezo body guide hole 111 formed in the second piezo body 11b. Further, a claw portion 232 that protrudes radially inward is formed on the opening end side of the second cylindrical portion 231.

  A first spring 24 is sandwiched between the cylinder 22 and the lifting member 23, and the first spring 24 biases the cylinder 22 toward the piezo actuator 14. A second spring 25 is sandwiched between the lifting member 23 and the nozzle needle 13, and the second spring 25 urges the lifting member 23 toward the piston part 210 side.

  A first oil-tight chamber 26 is formed by the cylinder 22, the piston portion 210 of the piston 21, and the first cylindrical portion 230 of the lifting member 23. A second oil-tight chamber 27 is formed by the lifting member 23, the piezo body guide hole 111, and the nozzle body rear end surface 104.

  The rear end of the nozzle needle 13 is inserted into the second oil tight chamber 27. Further, the needle flange portion 132 of the nozzle needle 13 enters the internal space of the lifting member 23 in the second oil tight chamber 27, and the claw portion 232 of the lifting member 23 can be engaged with the needle flange portion 132. .

  Here, the inner diameter of the driven member first guide hole 220 (= the outer diameter of the piston part 210) is d1, the inner diameter of the driven member second guide hole 221 (= the outer diameter of the first cylindrical part 230) is d2, and the second. The outer diameter of the two cylindrical portions 231 (= the inner diameter of the piezoelectric body guide hole 111) is d3, and the outer diameter of the needle first piston portion 130 is d4.

Further, the area of the cylinder 22 that receives the pressure of the first oil-tight chamber 26 is the first pressure receiving area A1, and the area of the lifting member 23 that receives the pressure of the first oil-tight chamber 26 is the second pressure receiving area A2. The area of the member 23 that receives the pressure of the second oil-tight chamber 27 is referred to as a third pressure receiving area A3, and the area of the nozzle needle 13 that receives the pressure of the second oil-tight chamber 27 is referred to as a fourth pressure receiving area A4. Incidentally, A1 = π / 4 × (d1 ² −d2 ² ), A2 = π / 4 × d2 ² , A3 = π / 4 × d3 ² , A4 = π / 4 × d4 ² .

  Further, A1 / A2 is a first displacement magnification factor λ1, and λ1 × A3 / A4 is a second displacement magnification factor λ2. In this embodiment, the outer diameter d4 of the needle first piston portion 130 is smaller than the outer diameter d3 of the second cylindrical portion 231, that is, the fourth pressure receiving area A4 is smaller than the third pressure receiving area A3. The second displacement magnification rate λ2 is larger than the first displacement magnification rate λ1.

  Next, the operation of the fuel injection valve will be described. FIG. 1 shows a closed state of the fuel injection valve. At this time, the piezoelectric actuator 14 is contracted due to discharge of electric charge. The nozzle needle 13 is urged toward the valve closing direction by the pressure of the second oil tight chamber 27, and the needle seat portion 131 abuts the body seat portion 102 to close the injection hole 101.

  Next, when the piezo actuator 14 is charged, the piezo actuator 14 extends and the cylinder 22 is driven via the push plate 20. More specifically, as the piezoelectric actuator 14 extends, the cylinder 22 is driven in a direction in which the driven member second guide hole 221 moves away from the piston portion 210.

  Since the inner diameter d2 of the driven member second guide hole 221 is smaller than the inner diameter d1 of the driven member first guide hole 220, the volume of the first oil-tight chamber 26 is expanded as the cylinder 22 moves, 1 The pressure in the oil tight chamber 26 decreases.

  Due to the pressure drop in the first oil-tight chamber 26, the lifting member 23 is driven toward the piston part 210 side. Since the claw portion 232 of the lifting member 23 is engaged with the needle flange portion 132, the nozzle needle 13 is driven in the valve opening direction with the movement of the lifting member 23, and the needle seat portion 131 is moved to the body seat portion. The nozzle hole 101 is opened away from 102, and fuel injection into the cylinder of the internal combustion engine is started.

  As the lifting member 23 moves, the volume of the second oil-tight chamber 27 is increased and the pressure of the second oil-tight chamber 27 is reduced. The pressure drop in the second oil-tight chamber 27 causes the nozzle needle 13 to continue to open. Driven. Since the second displacement magnification rate λ2 is larger than the first displacement magnification rate λ1, the movement amount of the nozzle needle 13 becomes larger than the movement amount of the lifting member 23, and the nozzle needle 13 moves away from the claw portion 232. Move to the fully open position.

  Thereafter, when the electric charge is discharged from the piezo actuator 14, the piezo actuator 14 contracts, and the push plate 20 and the cylinder 22 are pushed back toward the piezo actuator 14 by the first spring 24. As a result, the volume of the first oil-tight chamber 26 is reduced, the pressure in the first oil-tight chamber 26 is increased, and the lifting member 23 is driven toward the anti-piston portion side. As the lifting member 23 moves, the volume of the second oil-tight chamber 27 is reduced to increase the pressure of the second oil-tight chamber 27, the nozzle needle 13 is driven in the valve closing direction, and the needle seat portion 131 is moved to the body seat portion. The nozzle hole 101 is closed in contact with 102, and fuel injection is completed.

  Next, the fuel that changes the displacement expansion rate with respect to the characteristics related to the load acting on the nozzle needle 13 in the valve opening direction (valve opening driving force) and the displacement amount of the nozzle needle 13 when the piezo actuator 14 is charged. The characteristics in the case of an injection valve and the characteristics in the case of a fuel injection valve with a constant displacement magnification will be described.

  As shown in FIG. 4, a large load is required as indicated by point a at the start of valve opening, and a large displacement amount of the nozzle needle 14 is required as indicated by point b when the nozzle is lifted after the valve is opened.

  In the fuel injection valve of the present embodiment, when the charging energy to the piezo actuator 14 is controlled to a predetermined value, the first displacement enlargement ratio λ1 is obtained at the start of valve opening, so that a large load such as line c is obtained. When the nozzle is lifted after the valve is opened, the second displacement enlargement ratio λ2 is obtained, so that a large displacement amount of the nozzle needle 14 as shown by the line d is obtained. Then, by appropriately setting the first displacement magnification rate λ1 and the second displacement magnification rate λ2, it is possible to set the characteristic passing through the point a and the characteristic passing through the point b.

  On the other hand, in the case of a fuel injection valve with a constant displacement expansion rate, if the charging energy for the piezo actuator is set to the same value as in the present embodiment, the required load at the start of valve opening and None of the required displacement during the nozzle lift can be achieved. Then, in the fuel injection valve having a constant displacement expansion rate, when trying to obtain the characteristic f passing through both points a and b, the charging energy for the piezo actuator must be made larger than in the case of this embodiment.

  Therefore, the fuel injection valve that changes the displacement expansion rate can reduce the charging energy to the piezo actuator 14 than the fuel injection valve with a constant displacement expansion rate.

  As described above, in the present embodiment, since the second displacement magnification rate λ2 is set larger than the first displacement magnification rate λ1, a large driving force can be obtained at the start of valve opening, A sufficient amount of displacement of the nozzle needle 13 can be ensured during the nozzle lift. As a result, the charging energy to the piezo actuator 14 can be reduced as compared with the fuel injection valve having a constant displacement expansion rate. That is, energy efficiency can be improved.

  Further, since the direct-acting fuel injection valve that changes the displacement expansion rate is realized by opening the piezo actuator 14 with the extension of the piezo actuator 14 (that is, by charging the electric charge), energy efficiency is improved. However, the reliability of the piezo actuator 14 can be improved.

(Second Embodiment)
This embodiment is different from the first embodiment in the configuration of the members forming the first oil-tight chamber and the second oil-tight chamber. In addition, since it is the same as that of 1st Embodiment regarding others, only a different part is demonstrated.

  As shown in FIG. 5, the nozzle needle 13 is divided into a substantially cylindrical needle first member 13 a and a needle second member 13 b that open and close the nozzle hole 101. A needle second piston portion 133 that is slidably inserted into a lifting member 32 (described later in detail) is formed at the end of the needle first member 13a on the side opposite to the injection hole (that is, the rear end). The needle second member 13 b includes a needle flange portion 132 that can be engaged with the lifting member 32 and a needle third piston portion 134 that is slidably inserted into the lifting member 32. The piezo body 11 is divided into two in the first embodiment, but is integrated in the present embodiment.

  A piston 30 as a driven member that is driven by the piezo actuator 14 is disposed in the upstream high-pressure fuel passage 110. The piston 30 includes a columnar first piston part 300 and a second piston part 301 having a smaller diameter than the first piston part 300.

  A cylinder 31 as a fixing member is disposed in the upstream high-pressure fuel passage 110. The cylinder 31 has a bottomed cylindrical shape. The cylinder 31 has a fixing member first guide hole 310 formed in the cylinder portion, and a fixing member second guide hole having a smaller diameter than the fixing member first guide hole 310 in the bottom portion. 311 is formed. The fixing member second guide hole 311 passes through the bottom. A fixing member communication hole 312 for communicating the inside and the outside of the cylinder portion is formed at an axially intermediate portion of the cylinder portion of the cylinder 31. The bottom of the cylinder 31 is positioned on the piezo actuator 14 side, and the opening end surface on the side opposite to the bottom is in airtight contact with the rear end surface 104 of the nozzle body.

  The second piston portion 301 of the piston 30 is slidably inserted into the fixed member second guide hole 311. One end of the second piston portion 301 protrudes from the fixed member second guide hole 311 and is in contact with the piezoelectric actuator 14.

  A cylindrical lifting member 32 is slidably inserted into the first fixing member guide hole 310. The lifting member 32 has an axial length shorter than the axial length of the fixed member first guide hole 310, and the entire lifting member 32 is accommodated in the fixed member first guide hole 310.

  The lifting member 32 is formed with a lifting member first guide hole 320 having a larger diameter than the fixed member second guide hole 311 and a lifting member second guide hole 321 having a smaller diameter than the lifting member first guide hole 320. . Hereinafter, the cylindrical portion in which the lifting member first guide hole 320 is formed in the lifting member 32 is referred to as a first cylindrical portion 322, and the cylindrical portion in which the lifting member second guide hole 321 is formed in the lifting member 32 is the second cylindrical portion. It is called 323.

  The lifting member 32 is disposed such that the first cylindrical portion 322 is positioned on the bottom side of the cylinder 31 and the second cylindrical portion 323 is positioned on the opening side of the cylinder 31. The first cylindrical portion 322 is formed with a lifting member communication hole 324 that allows the inside and outside of the lifting member 32 to communicate with each other. The lifting member communication hole 324 is always in communication with the fixed member communication hole 312.

  The first piston portion 300 of the piston 30 is slidably inserted into the lifting member first guide hole 320. In the lifting member first guide hole 320, the needle flange portion 132 of the needle second member 13b is disposed closer to the lifting member second guide hole 321 than the first piston portion 300 is. The needle second piston portion 133 of the needle first member 13a is slidably inserted into the lifting member second guide hole 321 and the needle third piston portion 134 of the needle second member 13b is slidably inserted. ing. A boundary portion between the lifting member first guide hole 320 and the lifting member second guide hole 321 has a stepped shape, and the stepped portion 325 can be engaged with the needle flange portion 132.

  A first spring 33 is sandwiched between the piezo actuator 14 and the cylinder 31, and the first spring 33 urges the cylinder 31 toward the nozzle body 10. A second spring 34 is sandwiched between the lifting member 32 and the nozzle body 10, and the second spring 34 moves the lifting member 32 in a direction in which the stepped portion 325 engages with the needle flange portion 132. Energized. Further, a third spring 39 is sandwiched between the piston 30 and the needle second member 13b. The third spring 39 biases the needle second member 13b toward the needle first member 13a. ing.

  The piston 30, the cylinder 31, and the lifting member 32 form a first oil tight chamber 35. A second oil-tight chamber 36 is formed by the cylinder 31, the lifting member 32, the nozzle body 10, and the needle first member 13a. A part of the needle first piston part 130 and a part of the needle second piston part 133 are inserted into the second oil tight chamber 27.

  A third oil-tight chamber 37 is formed by the lifting member 32, the needle first member 13a, and the needle second member 13b. An oil chamber 38 is formed by the lifting member 32, the piston 30, and the needle second member 13b. The needle flange portion 132 is disposed in the oil chamber 38, and the oil chamber 38 is always in communication with the upstream high-pressure fuel passage 110 through the lifting member communication hole 324 and the fixing member communication hole 312.

  Here, the inner diameter of the fixed member first guide hole 310 (= the outer diameter of the lifting member 32) is d11, the inner diameter of the fixed member second guide hole 311 (= the outer diameter of the second piston portion 301) is d12, The inner diameter of the one guide hole 320 (= the outer diameter of the first piston part 300) is d13, the inner diameter of the second guide hole 321 of the lifting member (= the outer diameter of the needle second piston part 133) is d14, and the needle first piston part 130. Let d15 be the outer diameter.

Further, the area of the needle first piston portion 130 that receives the pressure of the first oil-tight chamber 35 is the first pressure-receiving area A11, and the area of the lifting member 32 that receives the pressure of the first oil-tight chamber 35 is the second pressure-receiving area. Area A12, the area of the lifting member 32 that receives the pressure of the second oil-tight chamber 36 is the third pressure receiving area A13, and the area of the nozzle needle 13 that receives the pressure of the second oil-tight chamber is the fourth pressure receiving area A14. To do. Incidentally, A11 = π / 4 × (d13 ² −d12 ² ), A12 = π / 4 × (d11 ² −d13 ² ), A13 = π / 4 × (d11 ² −d14 ² ), A14 = π / 4 × (D15 ² -d14 ² ).

  Furthermore, let A11 / A12 be the first displacement magnification factor λ11, and let λ11 × A13 / A14 be the second displacement magnification factor λ12. In the present embodiment, since the outer diameter d15 of the needle first piston portion 130 is smaller than the outer diameter d11 of the lifting member 32, that is, the fourth pressure receiving area A14 is smaller than the third pressure receiving area A13, the first The second displacement magnification rate λ12 is larger than the displacement magnification rate λ11.

  Next, the operation of the fuel injection valve will be described. FIG. 5 shows the closed state of the fuel injection valve. At this time, the piezoelectric actuator 14 is contracted due to discharge of electric charge. The slew needle 13 is urged toward the valve closing direction by the pressure of the second oil tight chamber 36, and the needle seat portion 131 abuts the body seat portion 102 to close the injection hole 101. Further, the second needle member 13b is biased by the third spring 39 and is in contact with the first needle member 13a.

  Next, when the piezo actuator 14 is charged, the piezo actuator 14 extends and the piston 30 is driven. More specifically, as the piezo actuator 14 extends, the piston 30 is driven in a direction in which the first piston portion 300 moves away from the fixed member second guide hole 311.

  Since the outer diameter 13 of the first piston portion 300 is larger than the outer diameter d12 of the second piston portion 301, the volume of the first oil-tight chamber 35 is increased with the movement of the piston 30, and the first oil-tight chamber 35 is expanded. The pressure drops.

  Due to the pressure drop in the first oil tight chamber 35, the lifting member 32 is driven toward the fixed member second guide hole 311 side (that is, the bottom side of the cylinder 31). Since the stepped portion 325 of the lifting member 32 is engaged with the needle flange portion 132, the needle second member 13 b is driven toward the fixed member second guide hole 311 side with the movement of the lifting member 32. Is done.

  With the movement of the needle second member 13b, the pressure in the third oil-tight chamber 37 is lowered, and due to the pressure drop in the third oil-tight chamber 37, the needle first member 13a is driven in the valve opening direction, and the needle seat portion 131 is moved. The nozzle hole 101 is opened away from the body seat portion 102, and fuel injection into the cylinder of the internal combustion engine is started.

  As the lifting member 32 moves, the volume of the second oil-tight chamber 36 is increased and the pressure of the second oil-tight chamber 36 is reduced. The pressure reduction in the second oil-tight chamber 36 causes the needle first member 13a to continue to open. Driven in the direction. Since the second displacement magnification rate λ12 is larger than the first displacement magnification rate λ11, the movement amount of the needle first member 13a becomes larger than the movement amount of the lifting member 32, and the needle first member 13a is in the fully open position. Move up. At this time, since the pressure in the third oil tight chamber 37 increases with the movement of the needle first member 13 a, the needle flange portion 132 of the needle second member 13 b moves away from the stepped portion 325, and the fixed member second guide hole 311. Move towards the side.

  Thereafter, when the electric charge is discharged from the piezo actuator 14, the piezo actuator 14 contracts and the piston 30 is pushed back to the piezo actuator 14 side by the pressure of the oil chamber 38. As a result, the volume of the first oil-tight chamber 35 is reduced, the pressure of the first oil-tight chamber 35 is increased, and the lifting member 32 is driven toward the opening side of the cylinder 31. As the lifting member 32 moves, the volume of the second oil-tight chamber 36 is reduced and the pressure of the second oil-tight chamber 36 increases, the needle first member 13a is driven in the valve-closing direction, and the needle seat portion 131 is moved to the body. The nozzle hole 101 is closed in contact with the seat portion 102, and fuel injection is completed. At this time, since the pressure in the third oil-tight chamber 37 decreases as the needle first member 13a moves, the needle second member 13b moves following the needle first member 13a.

  In the present embodiment, since the second displacement magnification rate λ12 is set larger than the first displacement magnification rate λ11, a large driving force can be obtained at the start of valve opening, and the nozzle needle 13 can be used at the time of nozzle lift after the valve opening. A sufficient amount of displacement can be secured. As a result, the charging energy to the piezo actuator 14 can be reduced as compared with the fuel injection valve having a constant displacement expansion rate. That is, energy efficiency can be improved.

  Further, since the direct-acting fuel injection valve that changes the displacement expansion rate is realized by opening the piezo actuator 14 with the extension of the piezo actuator 14 (that is, by charging the electric charge), energy efficiency is improved. However, the reliability of the piezo actuator 14 can be improved.

10 Nozzle body 11 Piezo body 11
13 Nozzle needle 14 Piezo actuator 21 Piston (fixing member)
22 Cylinder (driven member)
23 Lifting member 26 First oil-tight chamber 27 Second oil-tight chamber 30 Piston 30 (driven member)
31 Cylinder (fixing member)
32 Lifting member 35 First oil tight chamber 36 Second oil tight chamber 100 Downstream high pressure fuel passage 101 Injection hole 110 Upstream high pressure fuel passage 11a First piezo body 11b Second piezo body

Claims (5)

High pressure fuel passages (100, 110) through which high pressure fuel flows and injection holes (101) connected to the high pressure fuel passages (100, 110) are formed in the body (10, 11, 11a, 11b). A fuel injection valve that opens and closes (101) at the tip surface of the nozzle needle (13),
A piezo actuator (14) that expands and contracts by charge and discharge of electric charge;
Driven members (22, 30) driven by the piezoelectric actuator (14);
A fixing member (21, 31) fixed to the body (10, 11, 11a, 11b) and slidably assembled to the driven member (22, 30);
Forming the first oil-tight chamber (26, 35), which is depressurized as the piezoelectric actuator (14) extends, in cooperation with the driven member (22, 30) and the fixing member (21, 31); A lifting member (23, 32) that engages with the nozzle needle (13) to drive the nozzle needle (13) in the valve opening direction when the pressure in the first oil-tight chamber (26, 35) decreases; Prepared,
The second oil-tight chamber (27, 36) that is depressurized as the lifting member (23, 32) moves due to the pressure drop in the first oil-tight chamber (26, 35) includes the lifting member (23, 32). Defined by members,
When the rear end of the nozzle needle (13) is inserted into the second oil-tight chamber (27, 36) and the pressure in the second oil-tight chamber (27, 36) decreases, the nozzle needle (13) It is configured to drive in the valve opening direction,
Further, the area of the driven member (22, 30) that receives the pressure of the first oil tight chamber (26, 35) is the first pressure receiving area, and the first oil of the lifting members (23, 32). The area of the portion receiving the pressure of the closed chamber (26, 35) is the second pressure receiving area, and the area of the portion of the lifting member (23, 32) receiving the pressure of the second oil tight chamber (27, 36) is the third pressure receiving area. The area of the portion that receives the pressure of the second oil tight chamber (27, 36) in the nozzle needle (13) is the fourth pressure receiving area, the first pressure receiving area / the second pressure receiving area = the first displacement expansion rate, A fuel injection valve characterized in that the second displacement enlargement ratio is set larger than the first displacement enlargement ratio when 1 displacement enlargement ratio × third pressure receiving area / fourth pressure receiving area = second displacement enlargement ratio . The driven member (22) is a cylindrical member, and a driven member first guide hole (220) and a driven member second guide hole having a smaller diameter than the driven member first guide hole (220). (221) is formed,
The fixing member (21) has a columnar piston portion (210) slidably inserted into the driven member first guide hole (220),
The lifting member (23) is a bottomed cylindrical member, and a cylindrical portion (230) on the bottom side is slidably inserted into the driven member second guide hole (221),
As the piezoelectric actuator (14) extends, the driven member (22) is configured so that the driven member second guide hole (221) is driven in a direction away from the piston portion (210). The fuel injection valve according to claim 1. The lifting member (23) is formed with a first cylindrical part (230) having a bottom and a second cylindrical part (231) having a larger diameter than the first cylindrical part (230),
The first cylindrical portion (230) is slidably inserted into the driven member second guide hole (221), and the second cylindrical portion (231) is slid onto the body (10, 11a, 11b). Inserted freely,
The second oil-tight chamber (27) is defined by the lifting member (23) and the body (10, 11a, 11b),
The fuel injection valve according to claim 2, wherein the fourth pressure receiving area is set smaller than the third pressure receiving area. The fixing member (31) is a bottomed cylindrical member, and a fixing member first guide hole (310) is formed in the cylinder portion, and at the bottom portion than the fixing member first guide hole (310). A small-diameter fixing member second guide hole (311) is formed,
The lifting member (32) is a cylindrical member in which a lifting member guide hole (320) having a diameter larger than that of the fixing member second guide hole (311) is formed, and the fixing member first guide hole ( 310) is slidably inserted,
The driven member (30) is a columnar member, and includes a first piston part (300) slidably inserted into the lifting member guide hole (320), and the fixed member second guide hole (311). ) And a second piston portion (301) whose one end protrudes from the fixed member second guide hole (311) and contacts the piezoelectric actuator (14),
As the piezoelectric actuator (14) extends, the driven member (30) is configured such that the first piston portion (300) is driven in a direction away from the fixed member second guide hole (311). The fuel injection valve according to claim 1, wherein: The fixing member (31) has an opening end surface on the opposite bottom side abutting on the body (10),
The second oil-tight chamber (36) is defined by the fixing member (31), the lifting member (32), and the body (10),
The fuel injection valve according to claim 4, wherein the fourth pressure receiving area is set smaller than the third pressure receiving area.

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