JP2005307936A - Expansion difference absorbing mechanism and fuel injection valve equipped with expansion difference absorbing mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an expansion difference absorbing mechanism having making difference in thermal expansion absorbing performance between individuals and certainly obtaining proper thermal expansion difference absorbing performance; and a fuel injection valve equipped with the expansion difference absorbing mechanism. <P>SOLUTION: The fuel injection valve moves a cylinder 3 by an actuator 9 to move a needle valve 10 through viscous fluid and a piston 7. The fuel injection valve comprises a sealing member 27 sealing between the cylinder 3 and the piston 7, and a communicating hole 29 formed on the piston 7 and communicating two chambers 5, 6 with each other. The size and/or shape of the communicating hole 29 is set to allow the viscous fluid pass through the communicating hole 29 to move between the tow chambers 5, 6 when force for moving the cylinder 3 or the piston 7 at speed slower than driving speed of the actuator 9 is generated by thermal expansion difference between members. On the other hand, the size and/or shape of the communicating hole 29 is set to prevent the viscous fluid from passing through the communicating hole 29 when force for moving the cylinder 3 at speed faster than force due to thermal expansion is generated by the actuator 9. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an expansion difference absorbing mechanism that absorbs a difference in thermal expansion between members, and a fuel injection valve including the same.

  As a problem common to a mechanism having a long member (for example, a long actuator, a rod, etc.), there is a physical deviation or malfunction due to a difference in thermal expansion between members. This is because if the member is long, a difference in thermal expansion (difference in dimensional change caused by thermal expansion or contraction) caused by a temperature difference between members or a difference in thermal expansion coefficient (difference in material) increases.

  As a mechanism having a long member, there is a fuel injection valve of an engine.

  For example, as shown in FIG. 3, a fuel injection valve for gaseous fuel includes a cylinder 102 that is movably accommodated in a relatively long barrel 101, and a cylinder 102 that is movably accommodated in the cylinder 102. The piston 105 partitioned into the upper chamber 103 and the lower chamber 104, the incompressible viscous fluid filled in the upper chamber 103 and the lower chamber 104, the actuator 106 for raising the cylinder 102, and the piston 105 are integrated. A needle valve 107 attached thereto, and by raising the cylinder 102 by the actuator 106, the needle valve 107 is raised via the viscous fluid in the lower chamber 104 and the piston 105, and the tip (lower end) of the barrel 101. The injection hole 108 formed in is opened.

  The barrel 101 includes a barrel main body 109, a chip 110 attached to the lower end of the barrel main body 109 via a lock nut 119, and a cap 112 screwed to the upper end of the barrel main body 109. A fuel injection hole 108 is formed at the lower end of the chip 110, and a fuel inlet 111 is formed in the cap 112.

  A cylinder 102 is held in the barrel body 109 so as to be slidable in the longitudinal direction (vertical direction). The cylinder 102 includes a cylinder body 117 and a cylinder cap 118.

  A piston 105 is accommodated in the cylinder 102 so as to be slidable in the same direction (vertical direction) as the sliding direction of the cylinder 102, and the piston 105 divides the space in the cylinder 102 into an upper chamber 103 and a lower chamber 104. Is done. The upper chamber 103 and the lower chamber 104 are filled with an incompressible viscous fluid.

  A needle valve 107 extending through the cylinder body 117 and extending downward is integrally connected to the lower end of the piston 105. A rod 120 that partially penetrates the cylinder cap 118 is formed at the upper end of the piston 105.

  An actuator 106 is provided between the needle valve 107 and the barrel main body 109, and the actuator 106 includes a magnetostrictive element 113 disposed on the peripheral portion of the needle valve 107, and a coil 114 disposed on the peripheral portion of the magnetostrictive element 113. Is provided. The lower end of the magnetostrictive element 113 is in contact with the bottom wall of the barrel body 109 via the seat 115 and the upper end is in contact with the lower surface of the cylinder 102 via the seat 116.

  Above the cylinder 102, a disc spring 121 that biases the cylinder 102 downward and presses it against the seat 116 and the magnetostrictive element 113, and a disc spring 123 that biases the piston 105 and the needle valve 107 downward via the pressing member 122. And are provided.

  The fuel introduced into the barrel main body 109 from the fuel introduction port 111 of the cap 112 flows into the seat portion 125 of the chip 110 through the gap between the members.

  When the coil 114 of the actuator 106 is not energized, since the needle valve 107 is biased downward by the disc spring 123, the lower end portion of the needle valve 107 is pressed against the seat portion 125 of the chip 110 with a predetermined pressure and injected. The hole 108 is closed. Therefore, the fuel does not reach the injection hole 108 and fuel injection is not performed.

  On the other hand, when the coil 114 is energized through the terminal 126, the coil 114 is magnetized, and the magnetostrictive element 113 is expanded by the magnetic force (magnetic field). At this time, since the lower end of the magnetostrictive element 113 is in contact with the bottom wall of the barrel main body 109 via the seat 115, the magnetostrictive element 113 extends so as to push up the cylinder 102 against the biasing force of the disc spring 121. To do. When the cylinder 102 is pushed up, the piston 105 and the needle valve 107 are integrally lifted (lifted) via the viscous fluid in the lower chamber 104. As a result, the lower end of the needle valve 107 is separated from the seat portion 125 of the tip 110, the injection hole 108 is opened, and fuel injection is performed. Such a fuel injection valve is also disclosed in Patent Document 1, for example.

  In such a fuel injection valve 100, in order to ensure the maximum lift amount required for the needle valve 107, it is necessary to lengthen the length (vertical dimension) of the magnetostrictive element 113 to some extent. As a result, it is necessary to lengthen the dimensions of the barrel 101, the needle valve 107, etc. in accordance with the dimensions of the magnetostrictive element 113.

  As described above, in a mechanism including a long member, a difference in thermal expansion between components (a difference in dimensional change caused by thermal expansion or thermal contraction) becomes a problem. In particular, in the fuel injection valve 100, the lift amount of the needle valve 107, that is, the displacement amount of the actuator 106 (the extension amount of the magnetostrictive element 113) and the like are relatively small, so that a slight difference in thermal expansion may affect the operation. There is.

  Therefore, in the fuel injection valve 100 shown in FIG. 3, when a difference in thermal expansion occurs, the viscous fluid passes through a slight gap (clearance) between the inner surface of the cylinder 102 and the outer surface of the piston 105. And the lower chamber 104 can be moved.

  For example, when the magnetostrictive element 113 is larger in thermal expansion than the needle valve 107, the force that raises the cylinder 102 at a very slow speed compared to the driving speed of the actuator 106 (the extension speed of the magnetostrictive element 113 due to a change in the magnetic field). At this time, the viscous fluid in the lower chamber 104 moves to the upper chamber 103 through the clearance between the cylinder 102 and the piston 105. As a result, the cylinder 102 moves upward relative to the piston 105, and the thermal expansion difference is absorbed. As a result, the positions of the piston 105 and the needle valve 107 are not changed and do not affect the operation.

Special table 2003-512555 gazette

  However, in the conventional fuel injection valve 100 that moves the viscous fluid through the clearance between the cylinder 102 and the piston 105 in this way, there is a problem that a difference occurs in the thermal expansion difference absorption performance between each individual (each fuel injection valve). It was.

  The reason for this is as follows.

  Reason 1: Since it is difficult to control and manage the clearance between the inner surface of the cylinder 102 and the outer surface of the piston 105 with high accuracy, the clearance difference between the individual members increases. As measures against this, it is conceivable to increase the processing accuracy of the cylinder 102 and the piston 105, or to measure the dimensions of the cylinder 102 and the piston 105 and to select a combination thereof, thereby making the clearance uniform. In these cases, adverse effects on production such as cost increase and man-hour increase cannot be avoided.

  Reason 2: Deviation in cylindricity (roundness) between the inner surface of the cylinder 102 and the outer surface of the piston 105, deviation in concentricity between the cylinder 102 and the piston 105 (offset), the central axis of the cylinder 102 and the central axis of the piston 105 As a result, a difference in clearance (inclination) or the like varies between individuals, resulting in a difference in clearance between individuals.

  Reason 3: Since the dimensional change over time due to the sliding of the cylinder 102 and the piston 105 is different for each individual, the clearance difference between the individual increases as the use proceeds.

  Reason 4: The viscosity of the viscous fluid changes due to the wear powder generated by sliding between the cylinder 102 and the piston 105 entering the viscous fluid. However, since this viscosity change varies among individuals, the difference in thermal expansion as the use proceeds. A difference occurs in the absorption performance.

  Accordingly, an object of the present invention is to solve the above-mentioned problems, to reduce a difference in thermal expansion difference absorption performance between individuals, and to obtain a thermal expansion difference absorption mechanism that can surely obtain an appropriate thermal expansion difference absorption performance and It is providing the fuel injection valve provided.

  To achieve the above object, the present invention provides a cylinder movably accommodated in a casing, a piston movably accommodated in the cylinder and dividing the cylinder into two chambers, and the two chambers. The casing, the actuator, and the operating member are provided with a filled viscous fluid, an actuator for moving the piston via the viscous fluid by moving the cylinder, and an operating member connected to the piston. An expansion difference absorbing mechanism for absorbing a difference in thermal expansion between the cylinder and the piston, and a communication hole formed in the piston for communicating the two chambers with each other. And the size and / or shape of the communication hole is slower than the driving speed of the actuator due to the thermal expansion difference. When a force for moving the cylinder or the piston is generated, the viscous fluid passes through the communication hole and moves between the two chambers, so that the cylinder and the piston move relative to each other and the thermal expansion difference is obtained. On the other hand, when the actuator generates a force that moves the cylinder at a speed faster than the force due to the thermal expansion difference, the viscous fluid cannot pass through the communication hole, and the piston is integrated with the cylinder. The size and / or shape is set so as to move.

  The present invention also includes a cylinder movably accommodated in the barrel, a piston movably accommodated in the cylinder and dividing the cylinder into two chambers, and a viscous fluid filled in the two chambers. An actuator for moving the cylinder; and a needle valve connected to the piston, and the cylinder is moved by the actuator to move the needle valve via the viscous fluid and the piston. An injection valve, comprising: a seal member that seals between the cylinder and the piston; and a communication hole that is formed in the piston and communicates the two chambers with each other, and the size and / or shape of the communication hole is , Due to the difference in thermal expansion of the barrel, actuator, needle valve, etc., at a speed slower than the driving speed of the actuator When a force for moving the cylinder or piston is generated, the viscous fluid enters the communication hole and moves between the two chambers, whereby the cylinder and the piston move relative to each other to cause the thermal expansion difference. On the other hand, when a force for moving the cylinder at a speed faster than the force due to the thermal expansion difference is generated by the actuator, the viscous fluid cannot enter the communication hole, and the piston and the needle valve Is set to a size and / or shape that moves integrally with the cylinder.

  Here, the actuator may include a magnetostrictive element or an electrostrictive element.

  Moreover, you may provide the 1st biasing means which presses the said cylinder and the said actuator, and the 2nd biasing means which urges | biases the said needle valve in a valve closing direction.

  According to the present invention, the difference in thermal expansion difference absorption performance between individuals is small, and an excellent effect that an appropriate thermal expansion difference absorption performance can be obtained with certainty is exhibited.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  In this embodiment, the expansion difference absorption mechanism of the present invention is applied to a fuel injection valve for injecting gaseous fuel such as compressed natural gas (CNG), propane gas, or hydrogen into a combustion chamber of an engine.

  FIG. 1 is a sectional view of a fuel injection valve provided with an expansion difference absorbing mechanism of the present embodiment, and FIG. 2 is a partially enlarged view of FIG.

  As shown in FIG. 1, the fuel injection valve 1 according to this embodiment includes a cylinder (chamber) 3 movably accommodated in a relatively long barrel (casing) 2, and is movable in the cylinder 3. The piston 7 that is housed and divides the inside of the cylinder 3 into an upper chamber 5 and a lower chamber 6, an incompressible viscous fluid filled in the upper chamber 5 and the lower chamber 6, and the cylinder 3 is raised (moved). And a needle valve 10 connected to the piston 7. The cylinder 9 is lifted by the actuator 9 to lift (lift) the needle valve 10 through the viscous fluid in the lower chamber 6 and the piston 7. And the injection hole (orifice) 11 formed at the tip (lower end) of the barrel 2 is opened to inject fuel.

  The barrel 2 includes a barrel body 2a, a tip 2b integrally attached to the lower end of the barrel body 2a via a lock nut 12, and a cap 2c screwed to the upper end of the barrel body 2a. A plurality of fuel injection holes 11 are formed radially at the lower end of the tip 2b, and a fuel introduction port 13 for introducing fuel into the barrel body 2a is formed in the cap 2c.

  The cylinder 3 is held in the barrel body 2a so as to be slidable in the longitudinal direction (vertical direction). The cylinder 3 includes a cylinder body 3a having a bottomed cylindrical shape and a cylinder cap 3b screwed to the upper end of the cylinder body 3a. A seal member 14 (here, an O-ring) is sealed between the cylinder body 3a and the cylinder cap 3b.

  A piston 7 is accommodated in the cylinder 3 so as to be slidable in the same direction (vertical direction) as the sliding direction of the cylinder 3. The piston 7 divides the space in the cylinder 3 into an upper chamber 5 and a lower chamber 6. Is done. The upper chamber 5 and the lower chamber 6 are filled with an incompressible viscous fluid (for example, silicon oil).

  The needle valve 10 is connected to the lower end of the piston 7, and includes a rod 10a penetrating the bottom wall of the cylinder body 3a and extending downward, and a needle 10b integrally attached to the lower end of the rod 10a. A large-diameter rod 15 that extends upward through the cylinder cap 3 b and a small-diameter rod 16 that extends upward from the upper end of the large-diameter rod 15 are integrally formed at the upper end of the piston 7. Seals between the rod 10a of the needle valve 10 and the cylinder body 3a and between the large-diameter rod 15 and the cylinder cap 3b are respectively sealed by seal members 17 and 19 (here, O-rings).

  An actuator 9 is provided between the needle valve 10 and the barrel body 2a, and the actuator 9 is disposed on the periphery of the rod 10a of the needle valve 10 and on the periphery of the magnetostrictive element 20. A coil 21. The lower end of the magnetostrictive element 20 is in contact with the bottom wall of the barrel main body 2 a through the seat 22, and the upper end is in contact with the lower surface of the cylinder 3 through the seat 23.

  Between the upper surface of the cylinder 3 and the cap 2c, a first urging member 25 (here, a coil spring) that urges the cylinder 3 downward to press it against the seat 23 and the magnetostrictive element 20, a large-diameter rod 15 and a piston. A second biasing member 26 (here, a coil spring) that biases the needle valve 10 downward (in the valve closing direction) via 7 is provided. These springs 25 and 26 are provided in a state compressed by a predetermined load by the cap 2c.

  Next, the feature point of the fuel injection valve 1 of this embodiment is demonstrated using FIG.

  As shown in the figure, the fuel injection valve 1 of the present embodiment includes a seal member 27 that completely seals between the inner surface of the cylinder 3 (cylinder body 3a) and the outer surface of the piston 7. That is, in the fuel injection valve 1, the viscous fluid is completely prohibited from moving between the upper chamber 5 and the lower chamber 6 through the clearance between the cylinder 3 and the piston 7. Any type of seal member 27 can be used as long as it seals between the cylinder 3 and the piston 7 and allows relative movement between the cylinder 3 and the piston 7. For example, a rubber O-ring, packing, metal seal, diaphragm / bellow seal, or the like can be used.

  The fuel injection valve 1 further includes a communication hole 29 that is formed so as to penetrate the piston 7 in the vertical direction and communicates the upper chamber 5 and the lower chamber 6. In the present embodiment, two communication holes 29 are provided in the circumferential direction of the piston 7 with an interval of 180 °. That is, instead of completely closing (sealing) the clearance between the cylinder 3 and the piston 7, a viscous fluid moving passage (communication hole 29) is separately formed in the piston 7.

  The size and / or shape of the communication hole 29 is a thermal expansion difference (heat) caused by a temperature difference or a thermal expansion coefficient difference (material difference) among members such as the barrel 2, the actuator 9 (particularly the magnetostrictive element 20), and the needle valve 10. When a force for moving the cylinder 3 or the piston 7 is generated at a speed slower than the driving speed of the actuator 9 (extension speed of the magnetostrictive element 20 due to a magnetic field change) due to a dimensional change caused by expansion or thermal contraction, the viscous fluid Can move between the upper chamber 5 and the lower chamber 6 through the communication hole 29, and the actuator 9 generates a force for moving the cylinder 3 at a speed faster than the force due to the difference in thermal expansion. The size and / or shape is set so that the viscous fluid cannot pass through the communication hole 29. The size, shape, number, etc. of the communication holes 29 are appropriately set based on the drive characteristics (drive speed, etc.) of the actuator 9 and the characteristics (viscosity, etc.) of the viscous fluid.

  Hereinafter, the operation of the fuel injection valve 1 of the present embodiment will be described.

  The fuel introduced into the barrel body 2a from the fuel inlet 13 of the cap 2c is a gap between the small diameter rod 16 and the cap 2c, a gap between the cylinder 3 and the barrel body 2a, a gap between the needle valve 10 and the magnetostrictive element 20, It flows into the seat portion 30 of the tip 2b through a gap between the needle valve 10 and the tip 2b. The pressure of the supplied fuel is, for example, about 100 to 250 Bar.

  When the coil 21 of the actuator 9 is not energized, the needle valve 10 is urged downward by the spring 26. Therefore, the lower end portion of the needle valve 10 is pressed against the seat portion 30 of the tip 2b with a predetermined pressure, and the injection hole 11 is closed. Therefore, the fuel does not reach the injection hole 11 and fuel injection is not performed.

  On the other hand, when electric power controlled to a desired value by a controller (ECU or the like) (not shown) is supplied to the coil 21 via the terminal 31, the coil 21 generates a magnetic field having an intensity corresponding to the supplied electric power.

  When the coil 21 is magnetized, the magnetostrictive element 20 extends in the vertical direction by a length corresponding to the magnetic field strength. At this time, since the lower end of the magnetostrictive element 20 is in contact with the bottom wall of the barrel body 2 a via the sheet 22, the magnetostrictive element 20 pushes the cylinder 3 upward against the urging force of the spring 25. Elongate. The extension speed of the magnetostrictive element 20, that is, the driving speed of the cylinder 3 by the actuator 9 is relatively quick (for example, about several μm / μs). As described above, the size and / or shape of the communication hole 29 is set so that the viscous fluid cannot flow into the communication hole 29 when the cylinder 3 is driven by the actuator 9. When raising the cylinder 3, the incompressible viscous fluid acts as a solid. Accordingly, when the cylinder 3 is pushed up by the magnetostrictive element 20, the piston 7 and the needle valve 10 are integrally lifted (lifted) via the viscous fluid in the lower chamber 6, and the spring 26 is bent. As a result, the lower end of the needle valve 10 is separated from the seat portion 30 of the tip 2b to open the injection hole 11, and the high-pressure fuel supplied up to the seat portion 30 is sprayed from the injection hole 11 to the outside (combustion chamber). Be injected.

  By the way, due to the heat generated in the coil 21, heat in the combustion chamber transmitted through the chip 2b, or the like, a temperature difference occurs between the members, or a difference in thermal expansion coefficient between the members causes a difference in thermal expansion between the members. Occurs, a force is generated to move the cylinder 3 or the piston 7 opposite to the urging force of the springs 25 and 26 at a very gentle speed (for example, about several μm / min) compared to the driving speed of the actuator 9. There is a case.

  For example, when the magnetostrictive element 20 is larger in thermal expansion than the needle valve 10, a force for moving the cylinder 3 upward at a very gentle speed is generated. At this time, when the pressure in the lower chamber 6 increases, the viscous fluid in the lower chamber 6 moves to the upper chamber 5 side through the communication hole 29. This is because, as described above, the size and / or shape of the communication hole 29 is set so that viscous fluid can flow into the communication hole 29 when a gentle driving force is generated due to a difference in thermal expansion between the members. Because. As a result, the cylinder 3 relatively moves upward with respect to the piston 7, and the thermal expansion difference is absorbed by this relative movement. Therefore, the positions of the piston 7 and the needle valve 10 are not changed, and there is no adverse effect on the operation such as erroneous injection. In addition, since the gap between the cylinder 3 and the piston 7 is sealed by the seal member 27, the viscous fluid does not move between them.

  On the other hand, when the needle valve 10 is thermally expanded larger than the magnetostrictive element 20 on the contrary, a force that raises the piston 7 at a very moderate speed is generated. Then, the viscous fluid in the upper chamber 5 moves to the lower chamber 6 side through the communication hole 29. Thereby, the piston 7 moves upward relative to the cylinder 3 and can absorb the thermal expansion difference.

  As described above, in the fuel injection valve 1 of the present embodiment, the viscous fluid is moved through the communication hole 29 formed in the piston 7 when a difference in thermal expansion occurs between the members. The area (cross-sectional area of the communication hole 29) can be controlled and managed relatively easily and with high accuracy. Therefore, the difference in thermal expansion difference absorption performance between each individual (for each fuel injection valve) can be reduced, and appropriate thermal expansion difference absorption performance can be reliably obtained.

  The reason why the difference in thermal expansion difference absorption performance between individual individuals is reduced will be described using specific numerical values.

  First, in the conventional fuel injection valve 100 as shown in FIG. 3, for example, the inner diameter of the cylinder 102 and the nominal (reference) diameter of the outer diameter of the piston 105 are set to φ16 mm, and the machining accuracy of the cylinder 102 is set to φ16 mm + 10 to 20 μm (16 .015 mm ± 5 μm) and the processing accuracy of the piston 105 is φ16 mm−0 to −5 μm (15.9975 mm ± 2.5 μm), the clearance between them in the radial direction is 17.5 μm ± 7.5 μm (10 to 25 μm). Become. Here, when the total clearance area is calculated and converted as the area of one hole, the diameter of the hole is φ0.566 mm at the minimum clearance (10 μm), and φ0 .0 at the maximum clearance (25 μm). 895 mm. That is, when the fuel injection valve 1 is replaced with the communication hole 29 of the present embodiment, a manufacturing error of about 0.25 mm in diameter occurs. Of course, if the machining accuracy of the cylinder 102 and the piston 105 is increased, the error is reduced, but the manufacturing cost is greatly increased, and there is a limit to the accuracy.

  On the other hand, in the fuel injection valve 1 of the present embodiment, when the nominal diameter of the communication hole 29 is 0.5 mm, the processing is performed with an accuracy of, for example, about 0.5 mm ± 0.05 mm using a general processing device. It is relatively easy. Actually, the injection hole of the fuel injection valve of the diesel engine is processed with higher accuracy. In this case, the manufacturing error of the communication hole 29 is 0.10 mm, which is less than half that of the conventional fuel injection valve 100. Thus, in the fuel injection valve 1 of the present embodiment, the error in the passage area of the viscous fluid can be made extremely small as compared with the conventional fuel injection valve 100. This is because the conventional fuel injection valve 100 needs to manage the dimensions of the two members of the cylinder 102 and the piston 105, whereas the fuel injection valve 1 of the present embodiment manages only the dimensions of the communication hole 29. This is because it only has to be done. As a result, the difference in thermal expansion difference absorption performance between individual individuals is reduced.

  For reference, when the error (0.5 mm ± 0.05 mm) of the communication hole 29 described above is converted into the clearance error of the conventional fuel injection valve 100, when the nominal diameter of the cylinder 102 and the piston 105 is φ16 mm, It is about 4 μm (± 2 μm), and it can be seen from this point that the difference between each individual is small.

  Further, in the fuel injection valve 1 of the present embodiment, the cross-sectional area (passage area of the viscous fluid) of the communication hole 29 can be processed with high accuracy, so that the passage area suitable for the characteristics of the actuator 9 and the viscous fluid is ensured. Can get to. Therefore, the thermal expansion difference absorption performance can be obtained reliably and effectively. On the other hand, in the conventional fuel injection valve 100 as shown in FIG. 3, since the manufacturing error of the clearance is large, a mismatch occurs between the clearance and the characteristics of the actuator 106 and the viscous fluid, and sufficient thermal expansion difference absorption performance can be obtained. There is a possibility of disappearing.

  Furthermore, in the fuel injection valve 1 of the present embodiment, the clearance between the cylinder 3 and the piston 7 is sealed by the seal member 27, so that the machining accuracy of the cylinder 3 and the piston 7 can be lowered and the manufacturing cost can be reduced.

  Further, since the clearance between the cylinder 3 and the piston 7 is not used as a moving path for the viscous fluid, the cylinder 3 and the piston 7 are displaced in cylindricity (roundness), and the cylinder 3 and the piston 7 are displaced in concentricity. (Offset), a deviation (inclination) between the center axis of the cylinder 3 and the center axis of the piston 7 does not affect the thermal expansion difference absorption performance. Also from this point, it can be seen that the difference in thermal expansion difference absorption performance between individual individuals becomes small.

  Further, since the clearance between the cylinder 3 and the piston 7 is not used as a moving path for the viscous fluid, the dimensional change over time due to sliding between the cylinder 3 and the piston 7 affects the thermal expansion difference absorption performance. There is no. Also from this point, it can be seen that the difference in thermal expansion difference absorption performance between individual individuals becomes small.

  Further, since sliding between the cylinder 3 and the piston 7 is performed via the seal member 27, no abrasion powder is generated. Therefore, there is no difference in thermal expansion difference absorption performance that accompanies the change in viscosity of the viscous fluid due to the mixing of wear powder.

  Furthermore, since the sliding movement between the cylinder 3 and the piston 7 is performed via the seal member 27, it is possible to avoid the occurrence of malfunction due to wear powder or adhesion.

  Further, in the conventional fuel injection valve 100, since the outer surface of the piston 105 needs to function as a sliding portion and a function of forming a moving passage for viscous fluid, the length of the piston 105 (vertical dimension) However, in the fuel injection valve 1 of the present embodiment, the outer surface of the piston 7 only needs to function as a sliding portion, so that the length of the piston 7 can be shortened as compared with the prior art. Therefore, the fuel injection valve 1 can be reduced in size and weight.

  Further, in the fuel injection valve 1 of the present embodiment, the cylinder 3 is pressed against the magnetostrictive element 20 by the spring 25 via the seat 23, so that the cylinder 3 and the magnetostrictive element 20 can always be maintained in an appropriate positional relationship. For example, even when the length of the magnetostrictive element 20 is shortened due to a dimensional change over time (such as a sag), the cylinder 3 follows and moves by the biasing force of the spring 25 to absorb the dimensional change. be able to.

  The present invention is not limited to the above embodiment.

  For example, the number of communication holes 29 is not limited to two, and may be one or three or more.

  In addition, the actuator 9 is not limited to the one using the magnetostrictive element 20, and an electrostrictive element or the like that expands according to the supplied power may be used.

  The seal members 14, 17, 19, and 27 are not limited to O-rings, and other seal members may be used.

  The first urging means 25 and the second urging means 26 are not limited to coil springs, and other urging means such as a disc spring may be used.

  Moreover, although the example applied to the fuel injection valve for gaseous fuel was shown in the said embodiment, of course, this invention is applicable also to the fuel injection valve for light oil, gasoline, etc.

  Furthermore, the above-described expansion difference absorbing mechanism can be used to absorb the difference in thermal expansion of mechanisms other than the fuel injection valve.

It is sectional drawing of the fuel injection valve provided with the expansion difference absorption mechanism which concerns on one Embodiment of this invention. It is a partial expanded sectional view of FIG. It is sectional drawing of the conventional fuel injection valve.

Explanation of symbols

1 Fuel injection valve 2 Barrel (casing)
3 Cylinder 5 Upper chamber 6 Lower chamber 7 Piston 9 Actuator 10 Needle valve 11 Injection hole 20 Magnetostrictive element 21 Coil 25 First biasing means (spring)
26 Second urging means (spring)

Claims (4)

A cylinder movably accommodated in the casing, a piston movably accommodated in the cylinder and partitioning the cylinder into two chambers, a viscous fluid filled in the two chambers, and the cylinder moving An actuator for moving the piston via the viscous fluid, and an operating member connected to the piston to absorb a difference in thermal expansion between the casing, the actuator, the operating member, and the like. The differential expansion absorption mechanism of
A seal member that seals between the cylinder and the piston; and a communication hole that is formed in the piston and communicates the two chambers with each other.
The size and / or shape of the communication hole is
When the force for moving the cylinder or piston is generated at a speed slower than the driving speed of the actuator due to the difference in thermal expansion, the viscous fluid passes between the communication holes and moves between the two chambers. The cylinder and the piston move relative to each other to absorb the thermal expansion difference,
On the other hand, when the force for moving the cylinder at a speed faster than the force due to the thermal expansion difference is generated by the actuator, the viscous fluid cannot pass through the communication hole, and the piston moves integrally with the cylinder. An expansion difference absorption mechanism characterized by being set to such a size and / or shape. A cylinder movably accommodated in the barrel, a piston movably accommodated in the cylinder and dividing the cylinder into two chambers, a viscous fluid filled in the two chambers, and the cylinder moving And a fuel injection valve that moves the needle valve via the viscous fluid and the piston by moving the cylinder by the actuator. ,
A seal member that seals between the cylinder and the piston; and a communication hole that is formed in the piston and communicates the two chambers with each other.
The size and / or shape of the communication hole is
When a force for moving the cylinder or piston is generated at a speed slower than the driving speed of the actuator due to a difference in thermal expansion between the barrel, the actuator and the needle valve, the viscous fluid passes through the communication hole. Moving between the two chambers, the cylinder and the piston move relative to each other to absorb the thermal expansion difference,
On the other hand, when the force that moves the cylinder at a speed faster than the force due to the thermal expansion difference is generated by the actuator, the viscous fluid cannot pass through the communication hole, and the piston and the needle valve are integrated with the cylinder. A fuel injection valve provided with an expansion difference absorbing mechanism, characterized in that it is set to a size and / or shape that moves in a moving manner.   The fuel injection valve provided with an expansion difference absorbing mechanism according to claim 2, wherein the actuator includes a magnetostrictive element or an electrostrictive element. 4. A fuel having an expansion difference absorbing mechanism according to claim 2, further comprising: a first urging unit that presses the cylinder and the actuator; and a second urging unit that urges the needle valve in a valve closing direction. Injection valve.

Images