JP2008215170A - Injector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a margin with respect to high-pressure sealing property between a nozzle body and a valve body by reducing frictional force in fastening a retaining nut to reduce variation in fastening torque. <P>SOLUTION: A plurality of spherical bodies 18 is interposed and fastened between the axial force receiving surface 48A of the nozzle body 48 and the axial force applying surface 25A of the retaining nut 25 which axially screws and tightens the nozzle body 48 and valve body 20. Thereby, the frictional force in fastening the retaining nut 25 is reduced, and the sufficient axial force is generated with a small fastening torque. A torsional moment acting on the nozzle body 48 is also reduced by frictional force reduction, and eccentric wear with deformation of a high precision sliding part structure such as a needle is suppressed. Further, since variation in frictional force is reduced, variation in fastening torque is reduced, and the margin with respect to the high-pressure sealing property between the nozzle body 48 and the valve body 20 is improved. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an injector that receives fuel from a predetermined fuel supply source and injects it into an engine.

[Conventional technology]
Conventionally, an injector is mounted on a direct-injection engine such as a diesel engine, and is used to receive high-pressure fuel from a fuel supply source such as a common rail and to inject fuel directly into each cylinder of the engine. It has been.

  In recent years, regulations on engine exhaust gas have been strengthened to improve the environment, and while CO2 emission reduction and exhaust gas purification are being promoted, especially in diesel engines, fuel spray injected from the injector is further reduced. In order to improve the combustion by atomizing, the fuel injection pressure is increased by the injector, the multistage injection is being advanced, and the like. In particular, the trend toward higher pressures in injected fuel is expected to accelerate further in the future with the tightening of exhaust gas regulations.

  The structure of an injector used in a diesel engine fuel injection device is composed of a nozzle body that slidably accommodates a needle, and a valve body that includes a control piston and a pressure control chamber. One having a structure that ensures sealing performance by fastening axial force is known (for example, see Patent Document 1).

  FIG. 5 shows a configuration of a conventional injector 100 disclosed in Patent Document 1, and is an enlarged cross-sectional view of a main part. As shown in FIG. 5, a nozzle hole 103 is provided at the tip of the nozzle body 102, a needle 104 is provided in the nozzle body 102 so as to be slidable in the axial direction, and opens and closes the nozzle hole 103. A nozzle chamber 106 that receives high-pressure fuel from a fuel supply source such as a common rail via a high-pressure fuel passage 105 is provided. The control piston 110 is slidably accommodated inside the valve body 101, and the tip of the control piston 110 is in contact with the shaft end portion of the needle 104 on the side opposite to the injection hole.

  Further, the shaft end of the control piston 110 on the side opposite to the needle communicates with a pressure control chamber (not shown) and receives pressure, and the supply of high-pressure fuel causes the control piston 110 to generate a biasing force in the valve closing direction. The pressure control chamber controls the urging force in the valve closing direction of the control piston 110 by supplying (pressurizing) fuel and the urging force in the valve opening direction of the control piston 110 by discharging (depressurizing) fuel. 110 is disposed on the other end side. In addition, a spring 111 is provided at the tip of the pressure control chamber, and the needle 104 is always urged in the valve closing direction. An open / close valve mechanism that is controlled by opening / closing an electromagnetic valve (not shown) that switches supply and discharge of high-pressure fuel from a common rail to the pressure control chamber is provided.

  The opposite end surfaces of the valve body 101 and the nozzle body 102 are precisely machined and fastened by a retaining nut 125 to form an injector 100 that ensures sealing performance. This injector 100 has a biasing force in the valve opening direction of the nozzle hole 103, a biasing force of the spring 111 in the valve closing direction of the nozzle hole 103, and a pressure control chamber by the fuel pressure introduced into the nozzle chamber 106 with respect to the needle 104. The fuel pressure is controlled by the balance of the urging force in the valve closing direction of the nozzle hole 103 acting on the control piston 110.

[Problems with conventional technology]
However, as the fuel pressure increases in recent years, it is necessary to further increase the tightening axial force of the retaining nut 125 in order to improve the sealing performance between the seal surfaces of the nozzle body 102 and the valve body 101. However, increasing the tightening axial force requires increasing the tightening torque. When the tightening torque is increased, an excessive torsional moment generated by the high tightening torque is applied to the nozzle body 102, which is a member to be tightened, so that the highly precise sliding part structure provided in the nozzle body 102 is deformed. As a result, abnormal uneven wear is generated in the needle sliding portion 109. For this reason, when designing the injector 100, it is necessary to define the upper limit value of the tightening torque of the retaining nut 125.

  In the conventional structure disclosed in Patent Document 1, the axial force applying surface 126 of the retaining nut 125 and the axial force receiving surface 108 of the nozzle body 102 come into contact with each other in a plane to generate a large frictional force, and a torsional moment. Is a structure that strongly generates.

This frictional force varies greatly depending on the surface roughness, flatness, and the like of the axial force receiving surface 108 and the axial force applying surface 126, and therefore the variation in tightening torque is very large. When designing, it is necessary to set the design value so that there is a sufficient margin for variations in the tightening torque. As a result, the margin for the required sealing performance of the tightening axial force is lower than the margin for torque. . For this reason, there is a problem that the margin of the tightening axial force becomes lower and lower with respect to the further trend toward higher fuel pressure in the future.
JP 2002-147310 A

  The present invention has been made to solve the above-described problems, and its object is to reduce the variation in the tightening torque by reducing the friction of the retaining nut tightening when assembling the injector. This is to improve the margin for high-pressure sealing between the nozzle body and the valve body.

[Means of Claim 1]
According to the injector of the first aspect, the nozzle hole provided at the tip for ejecting the fuel, the needle slidably disposed therein and opening and closing the nozzle hole, and the valve opening or closing direction with respect to the needle A nozzle body that forms a nozzle chamber into which fuel flows in and out so as to supply fuel to the nozzle hole when the needle is opened, and is provided on the side opposite to the nozzle hole of the needle and is open to the needle Alternatively, a pressure control chamber that accommodates a control piston that is interlocked and displaced in the valve closing direction, generates a control pressure that biases the control piston in the distal direction, and an opening / closing means that opens and closes communication between the pressure control chamber and the low pressure passage. An injector having a valve body to be accommodated, and a retaining nut for screwing and fastening the nozzle body and the valve body in the axial direction, the axial force application surface of the retaining nut and the nozzle body Between the force receiving surface is characterized by providing a plurality of spheres.

  Thereby, when tightening the retaining nut, the frictional force of tightening can be reduced, and a sufficient axial force can be generated with a small tightening torque (improvement of axial force generation efficiency). Further, the torsional moment acting on the nozzle body is also reduced by reducing the frictional force, and uneven wear due to the deformation of the high precision sliding part structure such as the needle is suppressed (the effect of reducing torsional deformation). Furthermore, since the variation in friction force is reduced, the variation in tightening torque can be reduced, and a margin for the upper limit of the tightening torque of the retaining nut can be secured, resulting in a high pressure between the nozzle body and the valve body. The margin for sealing performance can be improved (margin improvement effect due to variations).

[Means of claim 2]
According to the injector of the second aspect of the present invention, an annular groove structure continuous in the circumferential direction is provided on one of the axial force applying surface of the retaining nut and the axial force receiving surface of the nozzle body. .

  As a result, the sphere is guided at least in the groove on either the retaining nut side or the nozzle body side and can be aligned on a concentric circle, so that the sphere is unevenly distributed and the retaining nut can be uniformly tightened without being offset. Thus, variation in tightening torque can be further reduced.

[Means of claim 3]
According to the injector of the third aspect, the groove structure is characterized by including at least one row of annular grooves.
As a result, the tightening load is applied by a larger number of spheres, so that it is easy to ensure a margin for the upper limit value of the tightening torque of the retaining nut.

[Means of claim 4]
According to the injector of claim 4, the groove structure has a shape in which the cross-sectional shape of the groove structure is an arc shape, a semi-elliptical shape, or a triangular shape, and has a point or line contact so as to make a spherical pointed contact. It is characterized by being.
Thereby, since the sphere can move without rolling, the coefficient of friction can be further reduced, and it is easy to secure a margin for the upper limit value of the tightening torque of the retaining nut.

[Means of claim 5]
According to the injector of the fifth aspect, the sphere is provided with a lubricant attached thereto.
Thereby, rolling contact becomes smoother and it becomes easy to ensure the margin with respect to the tightening torque upper limit value of the retaining nut tightening.

[Means of claim 6]
According to the injector of the sixth aspect, a plurality of columnar bodies are provided radially between the axial force applying surface of the retaining nut and the axial force receiving surface of the nozzle body.
As a result, the radial load points can be widened, the load at the load points can be reduced, and the radial bias can be eliminated, so it is easier to secure a margin for the upper limit of the tightening torque of the retaining nut. In addition, the structure can be simplified and made compact.

  The best mode of the present invention will be described together with Example 1 shown in the drawings.

[Configuration of Example 1]
FIG. 1 is an overall cross-sectional view of the injector according to the first embodiment of the present invention, and FIG. 2 is an enlarged cross-sectional view showing a main part of the injector shown in FIG.
The injector 1 includes an injection valve main body 2, an electromagnetic valve 3 attached to the rear end of the injection valve main body 2, and a fuel injection nozzle 4 fastened to the front end. The solenoid valve 3 is controlled by a control signal sent from an engine control unit (ECU) (not shown). In the following description, the injection nozzle side of the injector is referred to as one end side or the front end side, and the solenoid valve side is referred to as the other end side or the rear end side.

  The injection valve main body 2 has a rod-like shape and is provided with a cylinder 21 penetrating the shaft center. A high-pressure fuel passage 22 and a low-pressure fuel passage 23 are provided in parallel with the cylinder 21, and high-pressure fuel is supplied to the high-pressure fuel passage 22. A valve body 20 having a cylindrical inlet portion 26 to be supplied and a control piston 41 and a control piston 41 which are accommodated in a cylinder 21 of the valve body 20 and transmit a biasing force in a valve closing direction of a needle 42 which will be described later. It comprises a pressure control chamber 40 for controlling the magnitude of the urging force. A cylindrical electromagnetic valve installation chamber 10 is provided at the rear end of the valve body 20, and the electromagnetic valve 3 is mounted in the electromagnetic valve installation chamber 10 and fastened by a retaining nut 24. The injection nozzle 4 is fastened to the tip of the valve body 20 by a retaining nut 25.

  The electromagnetic valve 3 includes an electromagnetic solenoid 30 installed at the rear end of the electromagnetic valve installation chamber 10 and an on-off valve mechanism 50 installed at the front end of the electromagnetic valve installation chamber 10. The on-off valve mechanism 50 includes a mover 5 and a mover holder 6 that holds the mover 5. The tip of the mover holder 6 (the tip of the solenoid valve installation chamber 10) is a slightly small-diameter plate chamber 70 in which a substantially disc-shaped orifice plate 7 is accommodated.

  The electromagnetic solenoid 30 has a magnetic core in which a composite magnetic material is laminated on the outer periphery of a cylinder made of a ferromagnetic material and has a bowl-shaped rear end, and the outer periphery of the magnetic core is surrounded by an outer cylinder made of a ferromagnetic material. The electromagnetic coil 35 is disposed inside. The front end surface of the electromagnetic solenoid 30 is a suction surface that sucks the mover 5, and the front end portion of the bowl-shaped cylinder is a stopper surface on which the mover 5 abuts.

  The mover 5 has a flat plate portion and a shaft portion. The flat plate portion has a substantially flat upper surface and is an adsorption surface that is adsorbed to the front end surface of the electromagnetic solenoid 30, and is arranged in the mover chamber 60. It is installed. The shaft portion has a columnar shape and is slidably fitted into the center hole of the mover holder 6. The mover holder 6 is screwed to the inner periphery of the electromagnetic valve installation chamber 10 to generate a fastening axial force, and joins the orifice plate 7 to the end surface of the plate chamber 70.

  A valve body chamber 77 composed of a cylindrical portion and a conical portion is provided at the center of the front end surface of the shaft portion, and a ball valve 78 made of silicon nitride is accommodated in the valve body chamber 77. The ball valve 78 has a spherical upper surface, and the lower surface has a sealing flat shape that closes the outlet orifice 73 on the upper surface of the orifice plate 7. The mover 5 is urged in the distal direction (valve closing direction) by a spring 36 disposed in the axial center of the electromagnetic solenoid 30, and is attracted in the rear end direction (valve opening direction) by the magnetic force generated by the electromagnetic coil 35. Displacement in the front-rear direction (up and down in the figure).

  The orifice plate 7 is a substantially circular disk having a notch in a part of its outer peripheral end surface. A conical recess is formed at the center of the tip surface to form a pressure control chamber 40. An exit orifice 73 is provided on the center rear end side.

  A high-pressure fuel inflow passage 11 is provided inside the inlet portion 26 and branches into and communicates with the high-pressure fuel passages 22 and 28. The high-pressure fuel passage 22 communicates with the nozzle chamber 45C via an inclined high-pressure fuel passage 46 provided in the nozzle body 48, and supplies high-pressure fuel for injection. It acts on the pressure receiving surface and generates an urging force in the valve opening direction. The high-pressure fuel passage 28 communicates with an inlet orifice 74 provided in the orifice plate 7 and controls the recovery pressure in the pressure control chamber 40.

  In addition, the drain pipe 31 constituting the outlet portion has surplus fuel that flows via a plate chamber 70 and a mover chamber 60 communicating with the low-pressure fuel passage 23 and via a spring chamber 36 </ b> A disposed at a substantially central portion of the electromagnetic valve 3. Is returned to a drain tank (not shown), the control fuel flowing out from the outlet orifice 73 provided in the pressure control chamber 40 via the outflow passage 13, and the needle 42 flowing through the low pressure fuel passage 23. Excess fuel that has leaked from the sliding portion and was not injected is collectively discharged to the outside.

  A cylinder 21 passes through the center of the valve body 20. The cylinder 21 houses a control piston 41. The control piston 41 includes a clearance seal type sliding portion 41A that can slide in the cylinder 21, and a cylindrical movable pressure pin portion 41B that does not have a sliding portion. The tip of the pressure pin portion 41B is It has a spherical joint surface that can be contacted in the normal direction, and is always in contact with the rear end of the needle 42. The rear end of the control piston 41 has a truncated cone shape or the like, faces the pressure control chamber 40, and receives the pressure of the high-pressure fuel supplied to the pressure control chamber 40 to generate a biasing force in the valve closing direction. .

  Further, in the distal end region of the valve body 20, a spring chamber 44A having a diameter larger than the inner diameter of the cylinder 21 is provided at the center thereof, and the spring 44 has a spring seat 44B and an annular inner diameter portion in the spring chamber 44A. It is interposed between the annular member 44C and always urges the needle 42 in the distal direction (valve closing direction) via the annular member 44C. Accordingly, in the cylinder 21, the pressure control chamber 40 communicates with the spring chamber 44A, a space surrounded by the annular member 44C on the distal end side of the spring chamber 44A and the rear end surface of the needle 42, and the pressure control chamber The control pressure (back pressure) 40 can be applied to the rear end face of the needle 42 evenly. A screw 16 for fastening the nozzle body 48 to the distal end surface of the valve body 20 by the retaining nut 25 is formed on the outer peripheral portion of the distal end region of the valve body 20.

  The injection nozzle 4 has a two-stage cylinder shape having a nozzle body 48 having a large diameter portion and a nozzle 49 having a small diameter portion. A needle hole 45 for accommodating the needle 42 is formed at the center of the nozzle body 48, and the needle 42 is slid. A clearance seal type needle sliding portion 45A that can be moved and a needle fuel passage portion 45B that is a passage for high-pressure fuel that does not have a sliding portion are configured. In addition, a nozzle chamber 45C having a large diameter and a large volume is provided at an intermediate position of the needle hole 45 on the upstream side of the needle fuel passage portion 45B so as to intersect with the inclined high pressure fuel passage 46.

  Further, a nozzle tip chamber 49A having an appropriately thin taper structure that closes the tip of the needle hole 45 is formed on the downstream side of the needle fuel passage portion 45B, and one or a plurality of nozzle tip chambers 49A have an appropriate number. Nozzle holes 43 are provided at appropriate positions to spray high-pressure fuel. The nozzle body 48 is fastened to the distal end of the valve body 20 by the retaining nut 25 to constitute the injector 1. Here, in the present embodiment according to the present invention, a plurality of spheres 18 are interposed between the axial force receiving surface 48A of the nozzle body 48 and the axial force applying surface 25A of the retaining nut 25 and fastened. It is said. Hereinafter, this configuration will be described in detail with reference to FIG.

  As shown in FIG. 2, the injection nozzle 4 has a two-stage cylindrical shape having a large-diameter nozzle body 48 and a small-diameter nozzle 49, and a step portion formed by the large-diameter portion and the small-diameter portion has a circular shape. An axial force receiving surface 48A which is an annular flat plane is formed. On the other hand, the retaining nut 25 has an axial force applying surface 25A that forms an annular flat plane that is paired with the annular flat axial force receiving surface 48A, and has a tip having a diameter difference in three steps. Has a cylindrical shape having a stepped shape with different diameters with a small diameter and a large rear end.

  In the rear end large diameter portion 25B of the three-stage retaining nut 25, a screw 16 formed on the outer peripheral portion of the tip of the valve body 20 and a female screw 17 constituting the screw mechanism are processed to a predetermined depth on the inner peripheral side, Further, the small diameter portion 25D has an inner diameter portion that forms an axial force application surface 25A that can be brought into contact with an axial force pressure receiving surface 48A formed in the nozzle body 48 by inserting the nozzle 49 of the injection nozzle 4. The outer diameter portion has a hexagonal shape or a two-chamfered shape so that a tightening torque of the screw mechanism can be applied. Further, the inner diameter shape of the intermediate middle diameter portion 25 </ b> C is determined so that the outer periphery of the nozzle body 48 is properly fitted and the axial centers of the nozzle body 48 and the valve body 20 are aligned. Note that a knock pin method may be used to align the axial centers of the nozzle body 48 and the valve body 20.

  A plurality of spheres 18 are previously arranged in an annular shape on the axial force applying surface 25A of the retaining nut 25, and the small diameter portion of the nozzle 49 of the injection nozzle 4 is inserted as a guide, and this is further inserted into the valve body. Tighten to 20 and install. At this time, the tightening torque applied to the hexagonal head of the retaining nut 25 significantly reduces the frictional force by interposing the spherical body 18 between the axial force receiving surface 48A and the axial force applying surface 25A. Thus, a predetermined sealing pressure can be secured with a small torque, and the variation in the frictional force is reduced, so that the variation in torque can be reduced. The plurality of spheres 18 to be interposed are at least three or more, and a predetermined number determined by the size (diameter) of the spheres 18 is preferable. The plurality of spheres 18 may be provided with a lubricant attached in advance.

[Operation of Example 1]
The operation of the injector 1 having such a configuration is such that the needle 42 is applied in the valve closing direction by the control pressure of the pressure control chamber 40 and in the tip direction (valve closing direction) by the spring load of the spring 44. It moves in the direction of the front and rear end (up and down in the figure) by the balance between the urging force and the urging force applied to the needle 42 by the fuel pressure in the nozzle chamber 45C in the injection nozzle 4 (up and down in the figure). Open and close.

  That is, when the electromagnetic solenoid 30 is energized, the mover 5 is attracted by the electromagnetic force and moves in the rear end direction, and the ball valve 78 is displaced upward in conjunction with the mover 5, and the outlet orifice 73 is moved. Since it is opened and communicated with the low-pressure fuel outflow passage 13, the pressure in the pressure control chamber 40 becomes a low pressure almost instantaneously. This pressure immediately acts on the spring chamber 44A, and the urging force balance acting on the needle 42 is lost. The needle 42 moves in the rear end direction together with the control piston 41 to open the injection hole 43, and high-pressure fuel from the nozzle chamber 45 </ b> C is sprayed from the injection hole 43. At this time, the inlet orifice 74 having a diameter smaller than the orifice diameter of the outlet orifice 73 starts the pressure recovery of the pressure control chamber 40 while supplying the high-pressure fuel, and this pressure recovery pattern determines the injection rate profile of the fuel injection. .

  When the energization of the electromagnetic solenoid 30 is turned off, the mover 5 is moved in the distal direction by the biasing force of the spring 36, the ball valve 78 closes the outlet orifice 73, and the high pressure fuel pressure is supplied from the inlet orifice 74 to the pressure control chamber. The pressure is immediately transmitted to the spring chamber 44A, and the needle 42 moves in the distal direction together with the control piston 41, closes the injection hole 43, and the fuel injection ends. Excess fuel that has not been used for injection is discharged from the drain pipe 31 through the low-pressure fuel passage 23 together with the control fuel flowing out from the outlet orifice 73. At this time, since the sealing performance between the valve body 20 and the nozzle body 48 is kept high, leakage from the sealing surface to the low-pressure passage side hardly occurs.

[Effect of Example 1]
In the present embodiment, a plurality of spheres 18 are formed between the axial force applying surface 25A of the retaining nut and the axial force receiving surface 48A of the nozzle body, which are screwed and fastened in the axial direction to the nozzle body and the valve body. Since it is configured to be interposed and fastened, the frictional force of tightening the retaining nut 25 can be reduced, and a sufficient axial force can be generated with a small tightening torque (improvement of axial force generation efficiency). In addition, the torsional moment acting on the nozzle body 48 is also reduced due to the reduction of the frictional force, and uneven wear due to the deformation of the high-precision sliding part structure such as the needle 42 is suppressed (the effect of reducing the torsional deformation). ). Further, since the variation of the frictional force is reduced, the variation of the tightening torque can be reduced, and a margin for the upper limit value of the tightening torque of the retaining nut can be secured. The margin for high-pressure sealability can be improved (margin improvement effect due to variation reduction). In addition, by applying a lubricant to the sphere, the frictional force can be further reduced, and the margin for high-pressure sealability can be further improved.

[Configuration of Example 2]
A second embodiment of the present invention is shown in FIG. FIG. 3 is an enlarged cross-sectional view showing the main part of the injector in the second embodiment. Components that are substantially the same as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the injector 1 according to the first embodiment, the axial force applying surface 25 </ b> A that becomes an annular flat plane of the stepped portion of the retaining nut 25 and the axial force pressure receiving surface 48 </ b> A that becomes an annular flat plane of the stepped portion of the nozzle body 48. However, the present invention is not limited to this, and any one of the axial force application surface 25A and the axial force pressure receiving surface 48A is connected to the annular groove in the circumferential direction. A structure is provided.

  In the present embodiment shown in FIG. 3, a groove 19 that is continuous in the circumferential direction is provided at the substantially annular center of an annular axial force imparting surface 25 </ b> A provided in the tip small diameter portion 25 </ b> D of the retaining nut 25. The cross-sectional shape of the groove 19 is a V-shaped triangular shape having a wide apex angle. The groove 19 is in contact with the outer peripheral surface of the sphere 18 held in the groove 19 at at least two points, and the sphere 18 rolls and contacts in the circumferential direction to move. Even so, it has an apex angle that does not deviate from the track of the groove structure. The groove depth is such that when the sphere 18 is supported at two points, the other end side of the sphere 18, that is, the upper side protrudes at least from the axial force application surface 25 A, and conversely, one end side of the sphere 18, that is, the lower side The depth is such that at least a lower position below the spherical position of the sphere 18 is secured.

  This is the main difference between the present embodiment and the first embodiment, and other configurations are not changed. Accordingly, similarly to the assembly in the first embodiment, a plurality of spheres 18 are arranged in the groove 19 and the nozzle body 48 is inserted and then assembled to the valve body 20 to constitute the injector 1. The groove structure is not limited to a triangular shape in cross section, but may be an arc shape or a semi-elliptical shape. As described above, the spherical body 18 disposed in the groove 19 has two points so as to make rolling contact. Alternatively, other shapes may be used as long as the cross-sectional shape has line contact. Further, a two-row groove structure may be formed in conjunction with the size of the sphere 18 to be used and the load applied to the axial force applying surface 25A.

  Accordingly, the sphere 18 is guided at least in the groove 19 on the side of the retaining nut 25 and can be aligned on the concentric circle, so that the sphere 18 is unevenly distributed and the retaining nut 25 can be uniformly tightened without being offset. The variation in attached torque can be further reduced. Further, since the tightening load is applied by a larger number of spheres 18, it is easy to ensure a margin for the upper limit value of the tightening torque of the retaining nut. Furthermore, since the sphere 18 can move without rolling, the friction coefficient can be further reduced, and it is easy to secure a margin for the upper limit value of the tightening torque of the retaining nut.

[Configuration of Example 3]
A third embodiment of the present invention is shown in FIG. FIG. 4 is an enlarged cross-sectional view showing the main part of the injector in the third embodiment. Components that are substantially the same as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the injector 1 according to the first embodiment, the axial force applying surface 25 </ b> A that becomes an annular flat plane of the stepped portion of the retaining nut 25 and the axial force pressure receiving surface 48 </ b> A that becomes an annular flat plane of the stepped portion of the nozzle body 48. A plurality of spheres 18 are interposed and fastened to each other, but the present invention is not limited to this, and a plurality of columnar bodies (needles) 15 are arranged radially instead of the spheres 18.

  In the present embodiment shown in FIG. 3, the axial force application surface 25 </ b> A that is an annular flat plane of the stepped portion of the retaining nut 25 and the axial force pressure receiving surface that is an annular flat plane of the stepped portion of the nozzle body 48. A plurality of columnar bodies 15 are arranged radially between 48A and fastened by interposing them. The columnar body 15 has a sufficiently long length compared to its diameter, and is generally a columnar body called a needle, which is substantially equal to the annular width of either the annular axial force applying surface 25A or the axial force receiving surface 48A, which is smaller. It has a length. After the plurality of columnar bodies 15 are radially arranged at equal intervals in the circumferential direction on the axial force applying surface 25A of the retaining nut 25, the nozzle body 48 is inserted into the valve body 20 as in the first embodiment. The assembly 1 constitutes the injector 1. This is the main difference between the present embodiment and the first embodiment, and other configurations are not changed.

  Therefore, since the assembly of the columnar body 15 can increase the length of the columnar body 15, the entire width of the annular axial force applying surface 25A and the axial force receiving surface 48A from the inner side to the outer side is in line contact. The load surface pressure can be reduced, the load point can be prevented from being biased, and the frictional force can be reduced by easily rolling in the circumferential direction.

  Further, unlike the sphere 18, there is no need for a groove structure as a guide so as not to bias the load point, and there is no need to double the groove structure in order to reduce the load surface pressure, and the columnar body 15. Since the degree of freedom in reducing the diameter is large, the structure can be simplified and the structure can be made compact.

[Modification]
In the injector according to the first embodiment, the present invention has been described with respect to an example in which the pressure control chamber communicates with a common rail that accumulates fuel in a high-pressure state. The present invention can be adopted in any case, even in the case of an injector that has a pressure-increasing mechanism for increasing the pressure to a high pressure and supplying it to the nozzle chamber, or in an injector that does not communicate with the pressure control chamber and the common rail. Similar effects can be obtained.
In the injector according to the first embodiment, the pressure control in the pressure control chamber is adjusted by opening and closing the electromagnetic valve. However, the present invention is not limited to this. For example, an opening / closing means that opens and closes by the driving force of a piezoelectric actuator may be used. Good.

1 is an overall configuration cross-sectional view of an injector (Example 1). (Example 1) which is an expanded sectional view which shows the principal part of an injector. (Example 2) which is an expanded sectional view which shows the principal part of an injector. (Example 3) which is an expanded sectional view which shows the principal part of an injector. It is an expanded sectional view which shows the principal part of an injector (conventional example).

Explanation of symbols

1 Injector 2 Injection valve body 3 Solenoid valve (opening / closing means)
4 injection nozzle 15 columnar body 18 sphere 19 groove (groove structure)
20 Valve body 21 Cylinders 22 and 28 High pressure fuel passage 23 Low pressure fuel passage 25 Retaining nut 25A Axial force imparting surface 30 Electromagnetic solenoids 36 and 44 Spring 40 Pressure control chamber 41 Control piston 42 Needle 43 Injection hole 45 Needle hole 45C Nozzle chamber 48 Nozzle body 48A Axial pressure receiving surface 49 Nozzle

Claims (6)

A nozzle hole provided at the tip for ejecting fuel, a needle that is slidably disposed inside and opens and closes the nozzle hole, applies pressure to the needle in a valve opening or closing direction, and opens the needle. A nozzle body that forms a nozzle chamber through which fuel flows in and out so as to supply fuel to the nozzle hole at the time of valve; and
A pressure control chamber that is provided on the side opposite to the injection hole of the needle, accommodates a control piston that moves in conjunction with the needle in the valve opening or closing direction, and generates a control pressure that biases the control piston in the distal direction; An opening and closing means for opening and closing the communication between the pressure control chamber and the low pressure passage;
A retaining nut for axially screwing and fastening the nozzle body and the valve body;
In an injector having
An injector comprising a plurality of spheres between an axial force applying surface of the retaining nut and an axial force receiving surface of the nozzle body. The injector according to claim 1, wherein
An injector having an annular groove structure continuous in a circumferential direction on one of an axial force applying surface of the retaining nut and an axial force receiving surface of the nozzle body. Injector according to claim 1 or 2,
The said groove | channel structure is provided with the annular groove | channel of at least 1 row or more, The injector characterized by the above-mentioned. The injector according to any one of claims 1 to 3,
The groove structure has an arc shape, a semi-elliptical shape, or a triangular shape, and has a shape having a point or line contact so as to make the spherical point contact. Injector according to any one of claims 1 to 4,
The sphere is provided with a lubricant attached thereto. The injector according to claim 1, wherein
An injector, wherein a plurality of columnar bodies are provided radially between an axial force applying surface of the retaining nut and an axial force receiving surface of the nozzle body.

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