JP2006299889A - Fuel injection valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection valve achieving prevention of unintended lift of a needle valve caused by thermal expansion difference between a displacement element and a needle valve with receiving no restriction of material and dimension, increasing degree of freedom in design and reducing cost in the fuel injection valve lifting the needle valve by the displacement element such as a piezoelectric element. <P>SOLUTION: This valve is provided with the displacement element 7 stored in an injector body 2 for lifting the needle valve 5 and extending in operation, and an intermediate body 8 put between the displacement element 7 and the needle valve 5 and not transmitting extension of the displacement element 7 to the needle valve 5 when the displacement element 7 slowly extends by thermal expansion. The intermediate body 8 consists of a drive member 9 moving the needle valve 5 in a slide direction S, a driven member 10 separated from the drive member 9 by a predetermined gap Tc, liquid filled in the predetermined gap Tc, and a restrictor 11 giving predetermined resistance on liquid leaving from the predetermined gap Tc when the drive member 9 gets close to the driven member 10. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel injection valve that lifts a needle valve in an injector body by a displacement element such as a piezoelectric element, and in particular, prevents unintentional lift of the needle valve due to a difference in thermal expansion between the displacement element and the needle valve. However, the present invention relates to a fuel injection valve that applies an appropriate load to the displacement element and the needle valve.

  As a fuel injection valve, one that lifts a needle valve in an injector body using a displacement element such as a piezoelectric element is known. One end of the displacement element is engaged with a reaction force receiving portion formed in the injector body, and the other end is engaged with the needle valve. When the displacement element is actuated, the displacement element extends by taking a reaction force on the reaction force receiving portion, and lifts the needle valve pressed against the valve seat portion by a spring or the like from the valve seat portion. Thereby, the injection hole formed in the said valve seat part is open | released, and fuel is injected.

  As described above, as a problem of the type in which the displacement element is abutted against the reaction force receiving portion in the injector body and is extended to lift the needle valve, the needle valve is intended due to the difference in thermal expansion between the displacement element and the needle valve. The lift that does not occur is mentioned. That is, dimensional changes due to thermal expansion can occur in the displacement element and the needle valve due to heat generated when the displacement element is driven and temperature rise due to changes in fuel and ambient temperature. If it is larger, the needle valve is lifted by the thermal expansion of the displacement element without opening the displacement element, and the injection hole is opened.

  As a countermeasure against this, as described in Patent Document 1, a giant magnetostrictive actuator is known in which materials having different thermal expansion coefficients are appropriately combined to absorb thermal expansion of a displacement element.

Japanese Utility Model Publication No. 6-50368

  However, when absorbing the thermal expansion of the displacement element by appropriately combining materials having different thermal expansion coefficients, such as the above-mentioned giant magnetostrictive actuator, the degree of freedom in design is reduced due to restrictions on the material and dimensions, and the cost also increases .

  Accordingly, an object of the present invention is to prevent unintentional lift of the needle valve caused by a difference in thermal expansion between the displacement element and the needle valve in a fuel injection valve in which the needle valve in the injector body is lifted by a displacement element such as a piezoelectric element. Another object of the present invention is to provide a fuel injection valve that can be achieved by appropriately combining materials having different coefficients of thermal expansion, that is, without being restricted by materials and dimensions, and increasing the degree of design freedom and reducing the cost.

  The present invention devised to achieve the above object includes a needle valve accommodated in an injector body and slidable in a lift direction from a seated state in a valve seat portion formed in the vicinity of an injection hole, and the injector body A displacement element that is accommodated to lift the needle valve in the interior thereof and extends by taking a reaction force in the reaction force receiving portion during operation, and the displacement element is interposed between the displacement element and the needle valve. When the actuator is actuated and quickly extended, the extension is transmitted to the needle valve to lift the valve, and when the displacement element is slowly expanded by thermal expansion, heat is not transferred to the needle valve without transmitting the extension to the needle valve. An intermediate body having an expansion absorption mechanism, the intermediate body moving in the sliding direction of the needle valve in conjunction with the extension of the displacement element; A driven member provided in a dollar valve and having a predetermined gap in the sliding direction with respect to the driving member; a liquid interposed in the predetermined gap; and the predetermined gap when the driving member approaches the driven member And a diaphragm for giving a predetermined resistance to the liquid escaping from the liquid.

  The predetermined resistance is set in consideration of the viscosity of the liquid so that the liquid does not escape from the predetermined gap when the displacement element is operated and the driving member approaches the driven member at a speed higher than a predetermined speed. In addition, when the displacement element is thermally expanded and the driving member approaches the driven member at a speed lower than the predetermined speed, the liquid is set to escape from the predetermined gap.

  The predetermined gap is set to be larger than a maximum thermal expansion difference along the sliding direction between the displacement element and the needle valve.

  A plurality of the driving members and the driven members are alternately arranged in the sliding direction, the predetermined gaps are formed between the driving members and the driven members, and the predetermined gaps are adjacent to each other in the sliding direction. Communication passages that communicate with each other were provided, and each of the communication passages was used as the throttle.

  The liquid is fuel introduced into the injector body.

  According to the present invention, in a fuel injection valve in which a needle valve in an injector body is lifted by a displacement element such as a piezoelectric element, unintentional lift prevention of the needle valve due to a thermal expansion difference between the displacement element and the needle valve is prevented. It is possible to provide a fuel injection valve that can be achieved by appropriately combining materials having different expansion coefficients, that is, without being restricted by materials and dimensions, and increasing the degree of design freedom and reducing the cost.

  Preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  First, the outline of the fuel injection valve according to the present embodiment will be described with reference to FIG.

  As shown in FIG. 1, the fuel injection valve 1 is housed in an injector body 2, and a needle valve 5 slidable in a lift direction from a seated state on a valve seat portion 4 formed in the vicinity of an injection hole 3. The displacement element 7 is accommodated in the injector body 2 for lifting the needle valve 5 and extends by taking the reaction force on the reaction force receiving portion 6 during operation. The displacement element 7 is interposed between the displacement element 7 and the needle valve 5. When the displacement element 7 is actuated and quickly expanded, the expansion is transmitted to the needle valve 5 to lift the valve 5, and when the displacement element 7 is slowly expanded by thermal expansion, the expansion is transmitted to the needle valve 5. And an intermediate body 8 having a thermal expansion absorption mechanism that does not lift the valve 5.

  The intermediate body 8 includes a driving member 9 that moves in the sliding direction S of the needle valve 5 in conjunction with the extension of the displacement element 7, and a predetermined gap Tc that is provided in the needle valve 5 in the sliding direction S with respect to the driving member 9. When the driven member 10 approaches the driven member 10 when the driven member 10 approaches the driven member 10, the liquid interposed in the predetermined gap Tc (the compression ratio is very small: a white portion in the figure) and the driven member 9. It comprises an aperture 11 for giving a predetermined resistance to the liquid.

  The predetermined resistance of the diaphragm 11 is determined in consideration of the viscosity of the liquid so that the liquid does not escape from the predetermined gap Tc when the displacement element 7 is actuated and the driving member 9 approaches the driven member 10 at a speed higher than the predetermined speed. It is set so that the liquid escapes from the predetermined gap Tc when the displacement element 7 is thermally expanded and the driving member 9 approaches the driven member 10 at a speed lower than the predetermined speed. The predetermined gap Tc is set to be larger than the maximum thermal expansion difference along the sliding direction S between the displacement element 7 and the needle valve 5.

  According to the above configuration, in the fuel injection valve 1 that lifts the needle valve 5 in the injector body 2 using the displacement element 7 such as a piezoelectric element or a giant magnetostrictive element, the thermal expansion difference between the displacement element 7 and the needle valve 5. Prevention of unintentional lift of the needle valve 5 due to the above can be realized without appropriately combining materials having different thermal expansion coefficients, that is, without being restricted by materials and dimensions, increasing design freedom and reducing cost.

  Hereinafter, the fuel injection valve 1 which concerns on this embodiment is explained in full detail using FIGS.

  As shown in FIG. 1, a nozzle 12 having an injection hole 3 opened at the tip is attached to one end of an injector body 2 formed in a cylindrical shape by a nozzle fixing nut 13. A valve seat portion 4 is formed on the inner surface of the nozzle 12 so as to be positioned in the vicinity of the injection hole 3 and on which the tip of the needle valve 5 is seated. A spring pressing member 14 is attached to the other end portion of the injector body 2 via a screw or the like. One end of an element pressurizing spring 15 and one end of a needle pressurizing spring 16 which will be described later are brought into contact with each other in a compressed state.

  A needle valve 5 is accommodated inside the injector body 2 so as to be slidable in the longitudinal direction of the body 2. One end portion (tip portion) of the needle valve 5 is seated on the valve seat portion 4 and the other end portion is in contact with the needle pressurizing spring 16 via the flange 17. It is pressed with the power of. The needle valve 5 is moved upward in the longitudinal direction as the displacement element 7 (piezoelectric element, giant magnetostrictive element, etc.) accommodated in the injector body 2 is extended, and is lifted from the valve seat portion 4. The

  The displacement element 7 has one end abutted against a reaction force receiving portion 6 formed in a step shape inside the injector body 2 and the other end freely moved in the longitudinal direction (sliding direction S of the needle valve 5). It is supposed to be. In the illustrated example, the displacement element 7 is formed in a cylindrical shape so as to surround the needle valve 5 with a predetermined interval therebetween, and the outer diameter thereof is formed in the injector body 2 along the slide direction S. It is set to be slightly smaller than the accommodation hole 18 (slide hole), and is extended along the slide hole 18 by applying a reaction force to the reaction force receiving portion 6 when extended during operation.

  On the upper end surface of the displacement element 7, a slider 19 guided by the slide hole 18 and movable in the vertical direction is placed. The element pressurizing spring 15 is in contact with the upper end surface of the slider 19, and the element pressurizing spring 15 presses the displacement element 7 against the reaction force receiving portion 6 through the slider 19 with a predetermined force. The slider 19 is formed of a substantially cylindrical body, and the outer diameter thereof is set to be slightly smaller than the diameter of the slide hole 18. When the displacement element 7 is operated, the slider 19 is super-high-speed with the rapid extension of the element 7. At the time of thermal expansion, the element 7 moves along the slide hole 18 at a very low speed as the element 7 slowly extends.

  Between the slider 19 and the needle valve 5, when the displacement element 7 is actuated and quickly expanded, the expansion is transmitted to the needle valve 5 to lift the valve 5, and the displacement element 7 is slowly expanded by thermal expansion. An intermediate body 8 having a thermal expansion absorbing mechanism that does not lift the valve 5 without transmitting the extension to the needle valve 5 is interposed. The intermediate body 8 is interposed between the drive member 9 provided on the slider 19, the driven member 10 provided on the needle valve 5 and spaced apart from the drive member 9 in the slide direction S by the predetermined gap Tc, and the predetermined gap Tc. And a diaphragm 11 for giving a predetermined resistance to the liquid that escapes from the predetermined gap Tc when the driving member 9 approaches the driven member 10.

  Specifically, as shown in FIG. 6, the driving member 9 is a disk provided on the inner peripheral surface of the slider 19 and extending inward, and the driven member 10 is a disc mounted on the upper portion of the needle valve 5. The driving member 9 and the driven member 10 are alternately arranged in the sliding direction S. Between each drive member 9 and the driven member 10, the needle valve 5 is seated on the valve seat portion 4 by the needle pressurizing spring 16, and the displacement element 7 is pressed against the reaction force receiving portion 6 by the element pressurizing spring 15. In this state, the predetermined gap Tc is formed.

  The predetermined gap Tc is set to be larger than the maximum thermal expansion difference along the sliding direction S between the displacement element 7 and the needle valve 5 due to heat generated when the displacement element 7 is driven, or changes in fuel and ambient temperature. . In addition, the predetermined gap Tc has a size (about several tens of microns) that allows liquid (here, fuel) to be stored (entered).

  The predetermined gap Tc does not necessarily have the same dimension on the upper surface side and the lower surface side of each drive member 9. In short, when the displacement element 7 and the needle valve 5 take the reaction force on the reaction force receiving portion 6 and the valve seat portion 4 respectively and thermally expand and contract in the sliding direction S, the driving member 9 and the driven member 10 As long as the dimensions do not contact each other. Assuming that the interval between the adjacent drive members 9 is Ta and the plate thickness of the driven member 10 sandwiched between them is Tb, Ta−Tb = T is the thermal expansion difference in the sliding direction S between the displacement element 7 and the needle valve 5. It becomes the dimension to absorb.

  Adjacent ones of the predetermined gaps Tc communicate with each other through an inner diameter side communication path Ra or an outer diameter side communication path Rb. As shown in FIG. 3, the inner diameter side communication path Ra is formed in a ring shape between the inner diameter end of the drive member 9 (flange) and the outer periphery of the needle valve 5, and the outer diameter side communication path Rb is As shown in FIG. 2, it is formed in a ring shape between the outer diameter end portion of the driven member 10 (disk) and the inner peripheral surface of the slider 19 (cylindrical body).

  The communication path Ra on the inner diameter side and the communication path Rb on the outer diameter side connect the predetermined gaps Tc adjacent to each other in a zigzag alternately in the sliding direction S, and the predetermined gap when the driving member 9 approaches the driven member 10. A diaphragm 11 is provided to give a predetermined resistance to the liquid escaping from Tc.

  The predetermined resistance of the restrictor 11, that is, the radial gaps of the communication paths Ra and Rb, is a total. When the displacement element 7 is actuated and the driving member 9 approaches the driven member 10 at a speed higher than the predetermined speed, the liquid can be removed. It is set in consideration of the viscosity of the liquid so as not to escape from the predetermined gap Tc, and when the displacement element 7 is thermally expanded and the driving member 9 approaches the driven member 10 at a speed lower than the predetermined speed, the liquid is set to the predetermined gap. It is set to escape from Tc. The radial gap between the communication passages Ra and Rb is specifically smaller than the predetermined gap Tc and is about 1 to 5 microns.

  As shown in FIG. 1, the fuel (incompressible fluid) that enters the predetermined gap Tc and the like is introduced from the inlet 20 formed in the spring pressing member 14 into the spring accommodating chamber 21 in the injector body 2. It is burned. As shown in FIGS. 2 and 3, the fuel in the spring accommodating chamber 21 has a passage portion 22 formed so as to cut out a part of the outer periphery of the slider 19, and a lower end portion of the slider 19 as shown in FIG. 1 is guided to a clearance 24 between the needle valve 5 and the displacement element 7 shown in FIG. Thereafter, the fuel reaches the vicinity of the valve seat portion 4 through a passage portion 26 formed as shown in FIG. 4 on the outer peripheral portion of the guide portion 25 provided at the lower portion of the needle valve 5. As a result, the fuel injection valve 1 is filled with fuel without voids.

  The operation of this embodiment will be described.

  When the displacement element 7 is operated to inject fuel, the displacement element 7 takes a reaction force against the reaction force receiving portion 6 and quickly expands, the slider 19 is quickly pushed upward, and the driving member 9 is moved to the driven member 10. It tries to approach at an ultra-high speed above a predetermined speed. Then, the driven member 10 is quickly pushed up through the fuel interposed in the predetermined gap Tc, the needle valve 5 is lifted from the valve seat portion 4 and the fuel is injected from the injection hole 3. This is because the fuel interposed in the predetermined gap Tc cannot move so as to escape by the throttle function of the communication passages Ra and Rb when the driving member 9 moves at a high speed equal to or higher than the predetermined speed. That is, at this time, the driving member 9 and the driven member 10 are raised together with the fuel interposed in the predetermined gap Tc.

  On the other hand, when the displacement element 7 thermally expands larger than the needle valve 5 due to heat generated when the displacement element 7 is driven or a temperature rise due to changes in fuel or ambient temperature, the displacement element 7 is in an inoperative state. However, the slider 19 is slowly pushed up by the thermal expansion of the displacement element 7, and the driving member 9 approaches the driven member 10 at an extremely low speed less than the predetermined speed. In this case, since the fuel interposed in the predetermined gap Tc gradually escapes through the communication paths Ra and Rb, the driven member 10 is not pushed up and the needle valve 5 is not lifted. Therefore, the lift (fuel injection) of the needle valve 5 against the intention due to the difference in thermal expansion between the displacement element 7 and the needle valve 5 does not occur.

  As described above, the fuel injection valve 1 according to the present embodiment appropriately sets the radial gaps (correlating to the predetermined resistance of the throttle 11) of the communication paths Ra and Rb in consideration of the viscosity of the fuel. When the element 7 is actuated and the drive member 9 tries to approach the driven member 10 quickly, the fuel cannot escape from the predetermined gap Tc. 5 lifts. On the other hand, when the displacement element 7 thermally expands and the driving member 9 tries to approach the driven member 10 slowly, the fuel escapes from the predetermined gap Tc. The needle valve 5 is prevented from being lifted in an idling state. As a result, an appropriate lift of the needle valve 5 when the displacement element 7 is operated, that is, fuel injection, can be secured, and the lift of the needle valve 5 that is contrary to the intention due to the difference in thermal expansion between the displacement element 7 and the needle valve 5 is not intended. The fuel injection can be prevented in advance, and the fuel injection valve 1 capable of stable driving regardless of the temperature condition can be realized.

  Since the predetermined gap Tc is set to be larger than the maximum thermal expansion difference along the sliding direction S between the displacement element 7 and the needle valve 5, the driving member 9 and the driven member 10 have the above thermal expansion difference. There will be no contact. That is, when the thermal expansion along the sliding direction S of the displacement element 7 is larger than that of the needle valve 5, the needle valve 5 can be generated by pushing up the driven member 10 as described above. Lift (unintended fuel injection) can be prevented in advance. Conversely, when the thermal expansion along the sliding direction S of the needle valve 5 is larger than that of the displacement element 7, the predetermined gap Tc is the maximum thermal expansion difference along the sliding direction S between the displacement element 7 and the needle valve 5. If it is set to be smaller than that, the driven member 10 of the needle valve 5 that extends by taking a reaction force on the valve seat portion 4 pushes up the driving member 9, and the slider 19 is separated from the displacement element 7 (displacement element 7). However, in this embodiment, such a situation does not occur.

  The predetermined resistance of the diaphragm 11 can be finely adjusted as a whole by appropriately setting the size of the gaps in the radial direction of the communication paths Ra and Rb and the number of combinations along the sliding direction S at the design stage. . Therefore, the degree of freedom of design is expanded. Further, since the plurality of communication paths Ra and Rb are arranged in a zigzag manner in the sliding direction S, the predetermined resistance of the diaphragm 11 can be efficiently obtained.

  According to the present embodiment, in the fuel injection valve 1 that lifts the needle valve 5 in the injector body 2 using the displacement element 7, the intention of the needle valve 5 due to the thermal expansion difference between the displacement element 7 and the needle valve 5. Lift prevention that is not performed can be realized without appropriately combining materials having different thermal expansion coefficients, that is, without being restricted by materials and dimensions, increasing the degree of freedom in design, and reducing the cost.

  Embodiments of the present invention are not limited to the above types. The liquid interposed in the predetermined gap Tc is not limited to fuel, and an incompressible fluid such as oil may be used. Further, the slider 19 may be omitted, and the driving member 9 may be attached to the upper part of the displacement element 7. Further, the displacement element 7 is not limited to the cylindrical one, and a plurality of rod-shaped elements may be arranged at intervals in the circumferential direction so as to surround the needle valve 5.

It is a sectional side view of the fuel injection valve concerning one embodiment of the present invention. It is the II-II sectional view taken on the line of FIG. It is the III-III sectional view taken on the line of FIG. It is the IV-IV sectional view taken on the line of FIG. It is the VV sectional view taken on the line of FIG. It is a principal part enlarged view of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel injection valve 2 Injector body 3 Injection hole 4 Valve seat part 5 Needle valve 6 Reaction force receiving part 7 Displacement element 8 Intermediate body 9 Drive member 10 Driven member 11 Restriction Ra Communication path Rb Communication path Tc Predetermined gap

Claims (5)

A needle valve that is accommodated in the injector body and is slidable in the lift direction from a seated state on a valve seat portion formed in the vicinity of the injection hole;
A displacement element that is accommodated in the injector body for lifting the needle valve, and that extends by taking a reaction force in the reaction force receiving portion during operation;
When interposed between the displacement element and the needle valve, when the displacement element is actuated and quickly extended, the extension is transmitted to the needle valve to lift the valve, and the displacement element is slowly expanded by thermal expansion. An intermediate body having a thermal expansion absorption mechanism that does not lift the valve without transmitting the extension to the needle valve when extended,
The intermediate body includes a driving member that moves in the sliding direction of the needle valve in conjunction with the extension of the displacement element, and a driven member that is provided in the needle valve and that is spaced apart from the driving member in the sliding direction by a predetermined gap. A fuel injection system comprising: a member; a liquid interposed in the predetermined gap; and a throttle for giving a predetermined resistance to the liquid that escapes from the predetermined gap when the driving member approaches the driven member. valve.   The predetermined resistance is set in consideration of the viscosity of the liquid so that the liquid does not escape from the predetermined gap when the displacement element is operated and the driving member approaches the driven member at a speed higher than a predetermined speed. 2. The fuel according to claim 1, wherein the liquid is set to escape from the predetermined gap when the displacement element is thermally expanded and the driving member approaches the driven member at a speed lower than the predetermined speed. Injection valve.   The fuel injection valve according to claim 1 or 2, wherein the predetermined gap is set to be larger than a maximum thermal expansion difference along the sliding direction between the displacement element and the needle valve.   A plurality of the driving members and the driven members are alternately arranged in the sliding direction, the predetermined gaps are formed between the driving members and the driven members, and the predetermined gaps are adjacent to each other in the sliding direction. The fuel injection valve according to any one of claims 1 to 3, wherein communication passages for communicating things are provided respectively, and each of the communication passages is the throttle. The fuel injection valve according to any one of claims 1 to 4, wherein the liquid is fuel introduced into the injector body.

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