JP3885804B2 - FUEL INJECTION VALVE HAVING EXPANSION DIFFERENTIAL ABSORPTION MECHANISM AND ITS MANUFACTURING METHOD - Google Patents

Description

The present invention relates to a fuel injection valve provided with an expansion difference absorbing mechanism for absorbing a difference in thermal expansion between components, and a method for manufacturing the same.

  In a mechanism having a relatively long member, a difference in thermal expansion coefficient (material) of each member and a difference in temperature of each member cause a large difference in thermal expansion between the members, and a desired operation can be obtained. There may be no cases. As a mechanism including such a long member, a fuel injection valve mounted on an engine cylinder head or the like can be cited.

For example, as shown in FIG. 5, a fuel injection valve 100 for gaseous fuel under development by the present inventors includes a cylinder 102 slidably accommodated in a relatively long barrel 101, and a cylinder 102. Connected to the piston 105, which is divided into the upper chamber 103 and the lower chamber 104, the viscous fluid (represented by dots) filled in the upper chamber 103 and the lower chamber 104, the actuator 106 for sliding the cylinder 102, and the piston 105 The needle valve 107 is lifted by the actuator 106, the piston 105 is lifted via the viscous fluid in the lower chamber 104 , and the needle valve 107 connected to the piston 105 is lifted. An injection hole 108 formed at the tip (lower end) of 101 is opened.

  Specifically, the cylinder 102 is accommodated in the barrel 101 so as to be slidable in the vertical direction, and includes a cylinder body 102a having a bottomed cylindrical shape and a cylinder cap 102b that covers the upper portion by screwing. The 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 with respect to the barrel 101. The upper chamber 103 and the lower chamber 104 partitioned by the piston 105 are accommodated in the cylinder 102. Filled with incompressible viscous fluid. The viscous fluid is filled via an injection passage (not shown), and the upper chamber 103 and the lower chamber 104 are completely deaerated. The viscous fluid injection passage is closed with a stopper after the viscous fluid is injected.

  A needle valve 107 is connected to the lower surface of the piston 105, and this needle valve 107 extends downward through a through hole 109 provided in the bottom wall of the cylinder body 102 a, and its lower end is inside the tip of the barrel 101. The sheet portion 110 is formed in contact with the sheet portion 110. The through hole 109 is provided with a seal member 111 (O-ring) that seals between the through hole 109 and the needle valve 107 in a liquid-tight manner. Further, the fuel supplied into the barrel 101 from the fuel supply port 122 provided at the upper end of the barrel 101 flows into the seat portion 110 through each member.

  A rod 112 is provided on the upper surface of the piston 105. The rod 112 is slidably inserted into a through hole 113 formed in the cylinder cap 102a, and is urged downward by a disc spring 115 via an intermediate member 114. Has been. The through hole 113 is provided with a seal member 116 (O-ring) for liquid-tight sealing between the through hole 113 and the rod 112. When the needle valve 107 is urged downward by the disc spring 115, the lower end portion of the needle valve 107 is seated on the seat portion 110 with a predetermined force, and the injection hole 108 is closed.

  The actuator 106 includes a magnetostrictive element 106a disposed outside the needle valve 107, and a coil 106b disposed outside the magnetostrictive element 106a. The magnetostrictive element 106 a has an upper end in contact with the lower surface of the cylinder body 102 a via the seat 117, and a lower end in contact with the step surface portion 119 in the barrel 101 via the seat 118. Further, a disc spring 120 is disposed above the cylinder 102 to urge the cylinder 102 downward and press the cylinder 102 against the magnetostrictive element 106a via the seat 117. The biasing force of the disc spring 120 is larger than the biasing force of the disc spring 115.

  When the coil 106 b is not energized from the external terminal 121 provided on the barrel 101, the needle valve 107 is biased downward by the disc spring 115, so that the lower end portion of the needle valve 107 is applied to the seat portion 110 at a predetermined pressure. It is pressed and the injection hole 108 is closed. Therefore, the fuel does not reach the injection hole 108 and fuel injection is not performed.

  When a predetermined power is supplied to the external terminal 121, the coil 106b is magnetized, and the magnetostrictive element 106a expands according to the magnetic force (magnetic field). At this time, since the lower end of the magnetostrictive element 106 a is in contact with the stepped surface portion 119 via the sheet 118, the magnetostrictive element 106 a extends so as to push up the cylinder 102 against the urging force of the disc spring 120. When the cylinder 102 is pushed up, the piston 105 is lifted via the viscous fluid in the lower chamber 104, the needle valve 107 connected to the piston 105 is lifted, the injection hole 108 is opened, and fuel injection is performed.

  Such a fuel injection valve 100 is also disclosed in Patent Document 1, for example.

  In the fuel injection valve 100, in order to secure the maximum lift amount required for the needle valve 107, it is necessary to lengthen the length (vertical dimension) of the magnetostrictive element 106a to some extent. As a result, it is necessary to lengthen the dimensions of the barrel 101, the needle valve 107 and the like in accordance with the dimensions of the magnetostrictive element 106a.

  As described above, in a mechanism including a long member, a difference in thermal expansion (difference in dimensional change caused by thermal expansion or contraction) between the members 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 106a) and the like are relatively small (several tens of μm). There is a risk of giving.

  Therefore, in the fuel injection valve 100 shown in FIG. 5, when a difference in thermal expansion occurs between the members, 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. It is possible to move between the upper chamber 103 and the lower chamber 104.

  For example, when the thermal expansion of the magnetostrictive element 106 a is larger than the thermal expansion of the needle valve 107, the cylinder 102 rises at a very slow speed, and the pressure rise speed of the viscous fluid in the lower chamber 103 is extremely small. 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 relative to the piston 105 upward, and the thermal expansion difference between the needle valve 107 and the magnetostrictive element 106a 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.

  On the other hand, when the magnetostrictive element 106a is extended and the cylinder 102 is lifted upward in order to inject fuel from the injection hole 108, the cylinder 102 is raised at a speed much faster than the above speed. The pressure increase rate of the viscous fluid is significantly larger than the pressure increase rate during the thermal expansion described above. At this time, the viscous fluid in the lower chamber 104 functions as a solid, does not move to the upper chamber 103 through the clearance between the cylinder 102 and the piston 105, and the piston 105 and the needle valve 107 lift together with the cylinder 102. The fuel is then injected.

Special table 2003-512555 gazette

  Incidentally, in the fuel injection valve 100, the total volume of the upper chamber 103 and the lower chamber 104 in the cylinder 102 is constant even if the piston 105 moves. Therefore, when the viscous fluid thermally expands to more than the cylinder 102, the pressure of the viscous fluid in the cylinder 102 increases, and the sealing members 111 and 116 are detached or chipped, so that the viscous fluid flows from the upper chamber 103 and the lower chamber 104. The problem of flowing out and the problem that the viscous fluid flows out due to the removal of the plug that closes the injection passage for injecting the viscous fluid occur.

  More specifically, the volume change due to the thermal expansion of the viscous fluid and the total volume change of the upper chamber 103 and the lower chamber 104 due to the thermal expansion of the cylinder 102 actually differ by almost two orders of magnitude. For this reason, when the temperature of the viscous fluid and the cylinder 102 rises to substantially the same temperature, for example, when the temperature of the viscous fluid and the cylinder 102 rises to substantially the same temperature due to the heat received from the cylinder head or the like as a whole, Since the cylinder 102 does not expand so much, the total volume of the upper chamber 103 and the lower chamber 104 does not increase so much, and the viscous fluid which is basically incompressible looks for a escape place in the upper chamber 103 and the lower chamber 104.

  Here, since the inside of the upper chamber 103 and the lower chamber 104 is completely deaerated, the internal pressure of the cylinder 102 rises, and the expanded viscous fluid forms the inside of the upper chamber 103 and the lower chamber 104 as a sealed space. The seal members 111 and 116, which are relatively weak parts, and plugs that block the injection passage are damaged and overflow. The reason why the upper chamber 103 and the lower chamber 104 are completely evacuated is that, if bubbles exist in the upper chamber 103 and the lower chamber 104, the bubbles are generated when the magnetostrictive element 106a is extended to raise the cylinder 102. This is because the piston 105 is compressed and does not rise integrally with the cylinder 102, and the lift of the needle valve 107 is delayed or difficult.

  As a countermeasure for preventing overflow of such viscous fluid due to thermal expansion, it is conceivable to employ a viscous fluid and a cylinder 102 having substantially the same thermal expansion coefficient. do not do. In fact, in the viscous fluid and the substance / material used as the cylinder 102, there is firstly a thermal expansion difference between the viscous fluid and the cylinder 102 by one digit.

Accordingly, an object of the present invention is to solve the above-described problems and provide a fuel injection valve having a thermal expansion difference absorption mechanism capable of preventing overflow from the room when a viscous fluid is thermally expanded and a method for manufacturing the same. is there.

In order to achieve the above object, the invention according to claim 1 includes a cylinder accommodated in a barrel so as to be vertically slidable, a piston for partitioning the inside of the cylinder into an upper chamber and a lower chamber, and the upper chamber and the lower chamber. Each of the viscous fluids filled with each other, an actuator for sliding the cylinder upward, and a needle valve connected to the lower part of the piston, and the cylinder is slid upward by the actuator, And a fuel injection valve having an expansion difference absorbing mechanism that lifts the needle valve via a piston , wherein the first throttle is placed in the lower chamber where the internal pressure rises when the cylinder is slid upward by the actuator. communicated with the upper chamber through the parts, to the upper chamber, it communicates the air chamber via a second throttle section, Nagarero抵of the first throttle portion Is the pressure rise rate resulting in the cylinder to the lower chamber when the slide upward by the actuator without passing through the viscous fluid in the first throttle portion, the thermal expansion difference between the needle valve and the actuator resulting in the lower chamber and the upper chamber by the slow pressure increase speed than the speed set as expanded viscous fluid passes through the first throttle portion, when the viscous fluid thermally expands, the viscous fluid Is absorbed into the air chamber via the second restrictor.

According to a second aspect of the present invention, the flow path resistance of the first throttle part is set smaller than the flow path resistance of the second throttle part.

According to a third aspect of the present invention, the first throttle portion is provided in the piston, the second throttle portion is provided in the thickness of the cylinder or in the piston, and the air chamber is It is provided within the wall thickness of the cylinder or inside the piston.

According to a fourth aspect of the present invention, the first throttle portion is provided in the piston, and the second throttle portion is provided in the thickness of the cylinder or in the piston, and the cylinder or the piston Further, a screw hole communicating with the second throttle portion is formed, and the air chamber is formed inside a plug screwed into the screw hole .

According to a fifth aspect of the present invention, the first throttle portion is provided in the piston, and the cylinder includes a bottomed cylindrical cylinder body and a cylinder cap screwed to the upper end of the cylinder body. The cylinder cap is formed with the second throttle portion, a screw hole extending downward from the upper surface of the cylinder cap and communicating with the second throttle portion is formed, and the plug screwed into the screw hole The air chamber is formed in the interior of the chamber .

According to a sixth aspect of the present invention, there is provided a method of manufacturing a fuel injection valve including an expansion difference absorbing mechanism , wherein the cylinder body is arranged vertically, the upper chamber and the lower chamber in the cylinder body are filled with a viscous fluid, The cylinder cap, in which the plug is not attached to the screw hole, is screwed into the upper end of the cylinder body while the viscous fluid overflows, and the plug is screwed into the screw hole formed in the cylinder cap. It is a thing.

  ADVANTAGE OF THE INVENTION According to this invention, the outstanding effect that the overflow from a room | chamber interior when a viscous fluid thermally expands can be 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 is disposed substantially vertically on a cylinder head of an engine (not shown), 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 barrel body. And a cap 2c screwed to the upper end of 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.

  A 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. The cylinder body 3a and the cylinder cap 3b are liquid-tightly sealed by a seal member 33 (here, an O-ring).

  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, passes through a through hole 14 formed in the bottom wall of the cylinder body 3a, and extends downward, and a needle 10b integrally attached to the lower end of the rod 10a. It consists of. The lower end portion of the needle 10b is in contact with the sheet portion 30 formed in the tip 2b. The through hole 14 is provided with a seal member 17 (here, an O-ring) that seals the space between the through hole 14 and the rod 10a in a liquid-tight manner.

  A large-diameter rod 15 that extends upward through a through hole 18 formed in 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. Is formed. The through hole 18 is provided with a seal member 19 (here, an O-ring) that seals between the through hole 18 and the large-diameter rod 15 in a liquid-tight manner.

  An actuator 9 is provided between the needle valve 10 and the barrel body 2a. The actuator 9 includes a magnetostrictive element 9a arranged at a peripheral portion of the rod 10a of the needle valve 10 with a predetermined gap from the rod 10a, and a coil arranged at a peripheral portion of the magnetostrictive element 9a with a predetermined gap from the magnetostrictive element 9a. 9b. The lower end of the magnetostrictive element 9 a comes into contact with the stepped surface portion 20 in the barrel body 2 a through the seat 22, and the upper end comes into 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 biasing member 25 (here, a coil spring) that biases the cylinder 3 downward and presses it against the seat 23 , and a large-diameter rod 15 are biased downward. A second urging member 26 (here, a coil spring) that urges the needle valve 10 downward (in the valve closing direction) via the piston 7 is provided. The springs 25 and 26 are provided in a state compressed by a predetermined load by the cap 2 c, and the urging force of the spring 25 is larger than the urging force of the spring 26.

  The features of this embodiment will be described with reference to FIG.

  An air chamber 40 is disposed above the upper chamber 5, and the air chamber 40 communicates with the lower chamber 6 through a throttle portion 41. The lower chamber 6 is a chamber on the side of the two chambers 5 and 6 in which the viscous fluid is compressed and the internal pressure rises when the cylinder 3 is slid upward. As will be described later, a part of the thermally expanded viscous fluid in the chambers 5 and 6 is accommodated in the air chamber 40 through the throttle portion 41.

  The air chamber 40 and the throttle part 41 will be described in detail. The air chamber 40 is formed within the thickness of the cylinder cap 3b. On the other hand, the throttle 41 communicates the first throttle 41a (pore) formed by communicating the lower chamber 6 and the upper chamber 5 with the piston 7 and the upper chamber 5 and the air chamber 40 with the cylinder cap 3b. For this purpose, the second throttle part 41b (pore) is formed.

  The second throttle portion 41 b communicates with the air chamber 40 through the intermediate hole 42. That is, the cylinder cap 3b is formed with a second throttle portion 41b communicating with the upper chamber 5, and an intermediate hole 42 having a diameter larger than that of the second throttle portion 41b is formed by being connected to the second throttle portion 41b. Further, a screw hole 43 having a diameter larger than that of the intermediate hole 42 is formed so as to open to the upper surface of the cylinder cap 3b.

  A plug (plug) 44 having an air chamber 40 formed on the lower surface is screwed into the screw hole 43. Thereby, the air chamber 40 is connected to the upper chamber 5 through the intermediate hole 42 and the second throttle portion 41b. Viscous fluid (represented by dots) in the upper chamber 5 is infiltrated into a part of the second throttle portion 41b, the intermediate hole 42, and the screw hole 43, but in the air chamber 40 positioned above it, Viscous fluid is not infiltrated by the action of gravity.

  Since the first throttle part 41a is formed in the piston 7 as described above, the lower chamber 6 is communicated with the upper chamber 5 via the first throttle part 41a, and further via the second throttle part 41b. The air chamber 40 is communicated.

  In the example shown in the figure, two first diaphragm portions 41a and second diaphragm portions 41b are formed at intervals of 180 degrees.

  Further, a seal member 27 is provided between the outer peripheral surface of the piston 7 and the inner peripheral surface of the cylinder body 3a for sealing the space therebetween. Therefore, the viscous fluid in the upper chamber 5 and the viscous fluid in the lower chamber 6 go back and forth only through the first throttle part 41a.

  The flow path resistance (size / shape) of the first restrictor 41a is expanded at a relatively slow pressure increase rate generated in the chambers 5 and 6 when the viscous fluid in the upper chamber 5 and the lower chamber 6 is thermally expanded. At a pressure increase speed higher than the above speed generated in the lower chamber 6 when the viscous fluid passes through the first throttle portion 41a and the cylinder 3 is lifted upward by the actuator 9 (extension of the magnetostrictive element 9a), It is set so that the viscous fluid in the chamber 6 does not pass through the first throttle part 41a. Actually, the size, shape, number, and the like of the first restrictor 41a are determined by appropriate experiments, simulations, and the like based on the driving characteristics (driving speed, etc.) of the actuator 9 and the characteristics (viscosity, etc.) of the viscous fluid. .

  The channel resistance of the first throttle unit 41a is set smaller than the channel resistance of the second throttle unit 41b. Specifically, the hole diameter of the first throttle part 41a is larger than the hole diameter of the second throttle part 41b.

  The method of injecting the viscous fluid into the cylinder 3 will be described. The cylinder body 3a is set vertically, the upper chamber 5 and the lower chamber 6 are filled with the viscous fluid, and the plug 44 is not attached to the screw hole 43. 3b is screwed into the cylinder body 3a while overflowing the viscous fluid. Thereby, the presence chance of the bubbles in the upper chamber 5 and the lower chamber 6 becomes substantially zero. Thereafter, a viscous fluid is additionally injected into the upper chamber 5 from the screw hole 43, and the cylinder 3 is completely deaerated. Finally, the plug 44 is screwed into the screw hole 43 and fixed. Thereby, the assembly (assembly) of the cylinder 3 and the piston 7 is completed.

  The injection of the fuel injection valve 1 and the absorption of the thermal expansion difference of each member will be described.

  The fuel introduced into the barrel body 2a from the fuel inlet 13 of the cap 2c shown in FIG. 1 is the gap between the small diameter rod 16 and the cap 2c, the gap between the cylinder 3 and the barrel body 2a, the needle valve 10 and the magnetostrictive element 9a. Through the gap between the needle valve 10 and the tip 2b and the like to the seat portion 30 of the tip 2b. The pressure of the supplied fuel is, for example, about 100 to 250 Bar.

  When the coil 9b 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 (such as an ECU) (not shown) is supplied to the coil 9b via the external terminal 31 provided on the barrel body 2a, the coil 9b has strength corresponding to the supplied electric power. Generate a magnetic field.

  When the coil 9b is magnetized, the magnetostrictive element 9a 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 9a is in contact with the stepped surface portion 20 of the barrel body 2a via the seat 22, the magnetostrictive element 9a moves the cylinder 3 upward against the urging force of the springs 25 and 26. Stretch to push up. The expansion speed of the magnetostrictive element 9a, that is, the driving speed of the cylinder 3 by the actuator 9 is relatively quick (for example, about several μm / μs).

  In this case, as described above, the pressure increase rate in the lower chamber 6 becomes a predetermined value or more, and the viscous fluid in the lower chamber 6 does not pass through the first throttle portion 41a and functions as a solid. Accordingly, when the cylinder 3 is pushed up by the magnetostrictive element 9a, the piston 7 and the needle valve 10 are lifted up (lifted) together via the viscous fluid in the lower chamber 6, and the springs 25 and 26 are 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.

Further, a difference in thermal expansion occurs in each member. For example, when the thermal expansion of the magnetostrictive element 9a is larger than the thermal expansion of the needle valve 10, a force that lifts the cylinder 3 by the thermal expansion of the magnetostrictive element 9a is generated. The internal pressure rises slowly (at a speed equal to or lower than the pressure increase speed by the actuator 9). At this time, the viscous fluid in the lower chamber 6 passes through the first throttle portion 41a and flows out into the upper chamber 5, and only the cylinder 3 is lifted without moving the position of the piston 7. Therefore, the needle valve 10 connected to the piston 7 does not lift due to the difference in thermal expansion between the magnetostrictive element 9 a and the needle valve 10.

  The operation of the fuel injection valve 1 according to this embodiment will be described.

  For example, when the entire fuel injection valve 1 is heated by receiving heat from a cylinder head or the like, the cylinder 3 and the viscous fluid in the cylinder 3 are heated to substantially the same temperature. Then, the viscous fluid (silicon oil or the like) has a thermal expansion coefficient that is about two orders of magnitude greater than that of the cylinder 3 (iron-based metal), so that the volume of the viscous fluid can be contained in the upper chamber 5 and the lower chamber 6. The internal pressure of the upper chamber 5 and the lower chamber 6 gradually increases.

  Here, since the upper chamber 5 and the lower chamber 6 are communicated with each other via the first throttle portion 41a having a diameter larger than that of the second throttle portion 41b, the viscous fluid in the upper chamber 5 and the lower chamber 6 is substantially integrated. The internal pressure of the upper chamber 5 and the lower chamber 6 gradually rises. As described above, when the pressure increase rate in the upper chamber 5 and the lower chamber 6 is relatively slow, a part of the expanded viscous fluid enters the air chamber 40 through the second throttle portion 41b as described above. To do. Thereby, the pressure in the upper chamber 5 and the lower chamber 6 is relieved, so that damage to the seals 17 and 19 and the plug 44 due to thermal expansion of the viscous fluid can be avoided.

  On the other hand, when the cylinder 3 is lifted by the magnetostrictive element 9a to open the needle valve 10, the pressure of the viscous fluid in the lower chamber 6 quickly rises at a speed faster than the pressure increase rate due to the thermal expansion of the viscous fluid. Then, as described above, the viscous fluid in the lower chamber 6 does not pass through the first throttle portion 41a, and the piston 7 is lifted integrally with the cylinder 3. Accordingly, at this time, the pressure rise hardly occurs in the upper chamber 5, and the viscous fluid in the upper chamber 5 does not flow out into the air chamber 40 through the second throttle portion 41 b.

  By the way, when the viscous fluid thermally expands, if there is a difference in internal pressure between the upper chamber 5 and the lower chamber 6, the viscous fluid in the upper chamber 5 and the lower chamber 6 passes through the first throttle portion 41a. When flowing so as to balance the internal pressure difference between the upper and lower sides, the air flows out into the air chamber 40 through the second throttle portion 41b substantially simultaneously. Here, since the first throttle part 41a has a larger diameter than the second throttle part 41b and flows easily, the flow rate increases, and the balance of the internal pressure difference caused by passing through the first throttle part 41a is the second. This is given priority over absorption of thermal expansion caused by passing through the throttle 41b. Therefore, the lift of the needle valve 10 or the down of the needle valve 10 (excessive pressing of the needle valve 10 against the seat portion 30) caused by the internal pressure difference can be avoided.

  When the assembly of the cylinder 3 and the piston 7 is assembled, the viscous fluid is filled into the upper chamber 5 and the lower chamber 6 from the screw hole 43 without bubbles, and the plug 44 is screwed into the screw hole 43 so that the viscous fluid is filled. Since the viscous fluid in the upper chamber 5 and the lower chamber 6 is sealed through the air in the air chamber 40 of the plug 44, the viscous fluid in the upper chamber 5 and the lower chamber 6 is sealed. The pressure can be controlled to be substantially constant for each individual (cylinder, piston, assembly).

  In this regard, in the type shown in FIG. 5 described in the background art section, the cylinder 102 is filled with a viscous fluid (incompressible) and the injection passage is covered with a stopper. In order to cover the cylinder 102, the cylinder 102 must be closed in the presence of internal pressure. This internal pressure differs for each individual (piston, cylinder, assembly) due to variations in the sealing start point of the internal pressure at which the viscous fluid can be sealed by the stopper in the step of attaching the stopper to the injection passage. Therefore, the overflow limit temperature of the viscous fluid varies due to the difference in thermal expansion between the viscous fluid and the cylinder 102.

  On the other hand, in this embodiment, since the viscous fluid is sealed through the air in the air chamber 40, the variation in the internal pressure in the cylinder 3 for each individual is appropriately compressed. As a result, a substantially constant internal pressure of the viscous fluid is achieved for each individual. Therefore, the overflow limit temperature can be easily managed. Note that the air in the air chamber 40 does not affect the lift of the piston 7 and the needle valve 10 when the cylinder 9 is lifted by the actuator 9 as described above.

  A modification of the air chamber 40 and the second throttle part 41b is shown in FIG.

  In this modification, the cylinder cap 3b is formed with a pore as the second throttle portion 41b ′, and a screw hole 43 ′ is formed in the upper portion of the second throttle portion 41b ′, and the second throttle is formed in the screw hole 43 ′. The plug 44 'in which the pore 45 and the air chamber 40' connected to the portion 41b 'are formed is screwed. A part of the viscous fluid in the upper chamber 5 is infiltrated into a part of the second throttle portion 41b ', the pore 45, and the air chamber 40'. Since this modification has the same configuration as the above embodiment, the same effects as the above embodiment can be obtained.

  Another modification is shown in FIG.

  This modification is only that the second throttle portion 41b, the intermediate hole 42, the screw hole 43 and the plug 44 of the embodiment shown in FIG. 2 are formed in the large-diameter rod 15 of the piston 7 instead of the cylinder cap 3b. Different from the embodiment shown in FIG. This modification also has the same effects as the above embodiment.

The present invention is not limited to the above embodiment .

For example , the number of the first diaphragm portions 41a and the second diaphragm portions 41b is not limited to two, and may be one or three or more. Further, the present invention can also be applied to a type in which the first throttle portion 41a is not formed on the piston 105 shown in FIG. 5, and in this case, the clearance between the piston 105 and the cylinder 102 corresponds to the first throttle portion 41a. That is, the first throttle part 41a and the seal member 27 formed in the piston 7 shown in FIGS. 1, 2, and 4 are omitted, and a predetermined clearance is set between the piston 7 and the cylinder 3, and this clearance is set. It is good also as the 1st aperture | diaphragm | squeeze part 41a of Claim 1 .

  Further, the actuator 9 is not limited to the one using the magnetostrictive element 9a, and an electrostrictive element or the like that expands according to the supplied power may be used. Further, the seal members 13, 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 which shows the modification of a throttle part and an air chamber. It is a partial expanded sectional view which shows another modification (equivalent to FIG. 2). It is sectional drawing of the fuel injection valve which this inventor developed previously.

Explanation of symbols

1 Fuel injection valve 2 Barrel (casing)
3 Cylinder 5 Upper chamber 6 Lower chamber 7 Piston 9 Actuator 9a Magnetostrictive element 9b Coil 10 Needle valve (actuating member)
11 Injection hole 25 First urging means (spring)
26 Second urging means (spring)
29 communication hole 40 air chamber 41 throttle part 41a first throttle part 41b second throttle part

Claims (6)

A cylinder housed in a barrel so as to be vertically slidable,
A piston that partitions the cylinder into an upper chamber and a lower chamber ;
A viscous fluid filled in each of the upper and lower chambers ;
An actuator that slides the cylinder upward;
A needle valve connected to the lower part of the piston,
A fuel injection valve provided with an expansion difference absorbing mechanism that lifts the needle valve through the viscous fluid and a piston by sliding the cylinder upward by the actuator ,
The upper chamber communicates with the lower chamber through which the internal pressure rises when the cylinder is slid upward by the actuator via the first throttle portion, and the air is communicated with the upper chamber via the second throttle portion. Communicate the room,
The flow path resistance of the first throttle part is
The pressure rise rate resulting in the lower chamber when the cylinder is slid upward by the actuator the viscous fluid does not pass through the first throttle portion,
Occurring to the lower chamber and the upper chamber by the thermal expansion difference between the needle valve and the actuator, the slow pressure increase speed than the speed set as expanded viscous fluid passes through the first throttle portion,
A fuel injection valve provided with an expansion difference absorbing mechanism , wherein when the viscous fluid is thermally expanded, the viscous fluid is absorbed into the air chamber via the second throttle portion . 2. The fuel injection valve having the expansion difference absorbing mechanism according to claim 1, wherein a flow path resistance of the first throttle portion is set smaller than a flow path resistance of the second throttle portion . The first throttle portion is provided inside the piston;
The second throttle portion is provided in the thickness of the cylinder or in the piston;
The fuel injection valve provided with the expansion difference absorption mechanism according to claim 1 or 2 , wherein the air chamber is provided within a thickness of the cylinder or inside the piston . The first throttle portion is provided inside the piston;
The second throttle portion is provided in the thickness of the cylinder or in the piston;
A screw hole communicating with the second throttle part is formed in the cylinder or the piston,
The fuel injection valve provided with the expansion difference absorbing mechanism according to claim 1 or 2, wherein the air chamber is formed inside a plug screwed into the screw hole . The first throttle portion is provided inside the piston;
The cylinder is composed of a bottomed cylindrical cylinder body and a cylinder cap screwed to the upper end of the cylinder body.
In the cylinder cap, the second throttle portion is formed, and a screw hole extending downward from the upper surface of the cylinder cap and communicating with the second throttle portion is formed.
The fuel injection valve provided with the expansion difference absorbing mechanism according to claim 1 or 2, wherein the air chamber is formed inside a plug screwed into the screw hole . Place the cylinder body vertically,
Fill the upper and lower chambers in the cylinder body with a viscous fluid,
At the upper end of the cylinder body, screw the cylinder cap not fitted with the plug into the screw hole while overflowing the viscous fluid,
The plug was screwed into the screw hole formed in the cylinder cap.
A method for manufacturing a fuel injection valve having an expansion difference absorbing mechanism according to claim 5 .

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