JP4645636B2 - Fuel injection valve - Google Patents

Description

  The present invention relates to a fuel injection valve that injects fuel into a combustion chamber of an internal combustion engine.

Conventionally, the force acting on the control piston is controlled by controlling the fuel pressure in the pressure control chamber that accumulates the fuel pressure acting on the end of the control piston that controls the opening and closing operation of the needle that opens and closes the nozzle hole. A fuel injection valve that controls the opening / closing operation is known (see Patent Document 1). The fuel injection valve includes a nozzle body having a needle housing hole that houses a needle, and a lower body that supports the nozzle body and communicates with the pressure control chamber and has a piston housing hole that houses a control piston. The piston housing hole is configured by a sliding hole that slidably supports a sliding portion formed on the pressure control chamber side of the control piston, and a large-diameter housing hole having a diameter larger than the sliding hole. . Generally, the accommodation hole is formed by drilling.
JP 2002-147310 A

  Now, with the recent tightening of automobile exhaust gas regulations, reduction of emissions such as Nox (nitrogen oxide), PM (particulate matter), CO2 (carbon dioxide) has become an issue. In response to this problem, a fuel injection valve is required to reduce variations in injection amount.

  One of the causes of variation in the injection amount in the fuel injection valve is an improvement in the sliding resistance of the sliding portion of the control piston. It is considered that the operation of the control piston is stabilized by reducing the sliding resistance, and variation in the injection amount can be reduced. Generally, the sliding resistance is reduced by increasing the machining accuracy of the sliding hole and the sliding portion of the control piston.

  However, there is a limit even if the processing accuracy of the sliding hole and the sliding portion of the control piston is increased. For this reason, it is anticipated that it will no longer be possible to meet the desire to reduce further variations in the injection amount.

  Therefore, the inventor of the present application has studied in detail the shape of the accommodation hole and the like in order to find the cause of the sliding resistance of the control piston, and as a result, vibration generated when machining the sliding hole, or a tool for drilling Through a sliding gap between the sliding hole and the sliding portion of the control piston in the enlarged diameter portion (hereinafter referred to as a machining sag portion) formed at the end of the sliding hole on the large-diameter receiving hole side due to the shaft runout of It was found that the fuel flow of high-pressure fuel from the pressure control chamber discharged into the large-diameter accommodation hole is one of the causes of increased sliding resistance. The inventor has come up with the idea that the sliding resistance of the control piston can be further reduced by improving the fuel flow that flows in the vicinity of the machining sag portion that is formed during drilling.

  The present invention has been made on the basis of the above-described idea, and an object thereof is to provide a fuel injection valve capable of reducing injection amount variation.

According to a first aspect of the present invention, in a fuel injection valve that injects high-pressure fuel to be supplied from a nozzle hole into a combustion chamber of an internal combustion engine, a needle that opens and closes the nozzle hole, a control piston that controls the opening and closing operation of the needle, Pressure control chamber for generating a force for closing the needle of the control piston by accommodating high-pressure fuel on the end of the control piston, and the housing hole for containing the nozzle and the needle and the control piston and communicating with the nozzle hole A fuel injection valve comprising: a housing formed with:
The accommodation hole has a larger diameter than the needle accommodation hole that accommodates the needle so as to be movable in the axial direction, the slide hole that supports the control piston in a slidable manner, and communicates with the pressure control chamber. It is arranged between the hole and the sliding hole, and is composed of a large-diameter receiving hole that accommodates a part of the control piston. The diameter-enlarged part is formed by the vibration of the tool tool for vibration or the vibration that occurs at the time of sliding hole processing.
The control piston has a sliding portion that is slidably supported in the sliding hole, and a rod portion that has a smaller diameter than the sliding portion that is accommodated in the large-diameter accommodation hole, and the sliding portion is at least the control piston. Is a moving range in which the needle is driven to open and close, and is arranged closer to the pressure control chamber than the enlarged diameter portion.

  Here, the diameter-enlarged portion is a portion formed by shaft runout of a drilling tool generated when the sliding hole is formed by drilling or vibration generated during processing. For this reason, the processing accuracy of the enlarged diameter portion is lower than that of the other portions, and the roundness of the cross section of the hole of the enlarged diameter portion is low. That is, the distance from the central axis of the sliding hole to the enlarged diameter portion is not uniform in the circumferential direction.

  For this reason, when the control piston is housed in the housing hole including the sliding hole and the large-diameter housing hole, the gap between the diameter-enlarged portion of the sliding hole and the control piston facing it is not uniform in the circumferential direction. . Depending on the location, the gap is widened or narrowed.

  Since the gap with the control piston in the enlarged diameter portion is not uniform in the circumferential direction, when the high-pressure fuel in the pressure control chamber is discharged from the sliding gap into the large-diameter receiving hole, the flow of fuel in the enlarged diameter portion is also circumferential. It is not uniform in the direction, and the balance of the fuel pressure in the enlarged diameter portion is lost. Thereby, radial force acts on the control piston, and the control piston comes into contact with the sliding hole. Therefore, the sliding resistance of the control piston increases, the operation of the control piston becomes unstable, and the injection amount varies.

  According to this invention, the sliding portion of the control piston is at least as large as the diameter-enlarged portion at the end of the sliding hole on the large-diameter receiving hole side that is formed during processing in the moving range in which the control piston drives to open and close the needle. It is arranged on the pressure control chamber side. For this reason, a diameter expansion part will oppose the rod part whose diameter is smaller than a sliding part among control pistons. Since the rod portion has a smaller diameter than the sliding portion, the gap between the sliding hole and the enlarged diameter portion is larger than the gap formed when the sliding portion and the enlarged diameter portion face each other.

  For this reason, it becomes difficult to generate a difference in the circumferential pressure in the diameter-enlarged portion, and the influence of the pressure fuel is reduced as compared with the case where the diameter-enlarged portion and the sliding portion are arranged to face each other. As a result, the sliding resistance of the control piston can be reduced, the operation of the control piston can be stabilized, and the variation in the injection amount can be reduced.

According to a second aspect of the present invention, there is provided a fuel injection valve that injects a high-pressure fuel supplied from a nozzle hole into a combustion chamber of an internal combustion engine, a needle that opens and closes the nozzle hole, a control piston that controls an opening and closing operation of the needle, Pressure control chamber for generating a force for closing the needle of the control piston by accommodating high-pressure fuel on the end of the control piston, and the housing hole for containing the nozzle and the needle and the control piston and communicating with the nozzle hole A fuel injection valve comprising: a housing formed with:
The accommodation hole has a larger diameter than the needle accommodation hole that accommodates the needle so as to be movable in the axial direction, the slide hole that supports the control piston in a slidable manner, and communicates with the pressure control chamber. It is arranged between the hole and the sliding hole, and is composed of a large diameter accommodation hole that accommodates a part of the control piston,
The end of the sliding hole on the large-diameter receiving hole side is formed with a diameter-enlarged portion due to shaft runout of the drilling tool during sliding hole processing or vibration generated during processing of the sliding hole. Of these, a circumferential groove is formed in a portion facing the enlarged diameter portion.

  According to this configuration, since the circumferential groove is formed in the portion of the control piston that faces the enlarged diameter portion, all the high-pressure fuel from the pressure control chamber that has flowed into the vicinity of the enlarged diameter portion passes through the circumferential groove. It can be distributed around the lap. Thereby, the fuel pressure in a diameter expansion part can be made substantially uniform over a perimeter.

  As a result, the balance of fuel pressure in the enlarged diameter portion can be prevented from being lost. As a result, the sliding resistance of the control piston can be reduced, the operation of the control piston can be stabilized, and the variation in the injection amount can be reduced.

  The invention according to claim 3 is characterized in that the diameter-enlarging portion faces the sliding portion of the control piston, and the circumferential groove is formed in the sliding portion. According to this structure, since the axial direction length of a sliding part can be lengthened as much as possible, the control piston in an accommodation hole can be guided stably.

  The invention according to claim 4 is characterized in that the sliding gap between the sliding portion slidably supported by the sliding hole of the control piston and the sliding hole becomes larger toward the pressure control chamber. Yes.

  According to this configuration, the high-pressure fuel in the pressure control chamber flows from the pressure control chamber side into the gap formed between the sliding portion and the sliding hole, so that a force toward the central axis acts on the control piston. . As a result, the control piston tends to stay on the central axis of the sliding hole, so that the sliding portion of the control piston is difficult to contact the sliding hole, and an increase in the sliding resistance of the control piston can be suppressed.

  The invention according to claim 5 is characterized in that the sliding portion of the control piston has an inclined portion whose outer diameter decreases toward the pressure control chamber. According to this configuration, it is possible to easily form a configuration in which the sliding gap between the sliding portion and the sliding hole according to claim 4 is increased toward the pressure control chamber.

  Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 shows a cross section of the fuel injection valve according to the first embodiment of the present invention. FIG. 2 shows an enlarged cross-sectional view of the main part of the fuel injection valve according to the first embodiment.

  The fuel injection valve 10 is used, for example, in a common rail fuel injection device for a diesel engine. The fuel injection valve 10 is mounted on an engine head (not shown) of the engine and configured to directly inject high-pressure fuel supplied from a common rail (not shown) that accumulates high-pressure fuel into each cylinder of the engine.

  The fuel injection valve 10 includes a nozzle unit 11, a nozzle holder unit 12, a pressure control unit 13, and the like. The nozzle portion 11 and the nozzle holder portion 12 are coupled by a retaining nut 14. The nozzle holder unit 12 and the pressure control unit 13 are coupled by a body upper 15.

  The nozzle unit 11 includes a nozzle body 20 and a nozzle needle 30. The nozzle body 20 is formed in a rod shape, and a needle accommodation hole 21 extending in the axial direction is formed inside. A nozzle hole 22 that communicates the inner wall of the needle housing hole 21 and the outer wall of the nozzle body 20 is formed at the bottom of the needle housing hole 21. In the needle accommodation hole 21, a valve seat 23 on which the nozzle needle 30 is seated is formed above the injection hole 22. The nozzle body 20 has a fuel supply passage 24 for supplying high-pressure fuel in the common rail to the needle accommodation hole 21.

  The nozzle needle 30 is formed in a rod shape and is accommodated in the needle accommodation hole 21. When the nozzle needle 30 is accommodated in the needle accommodation hole 21, a fuel reservoir chamber 25 that is surrounded by the outer wall of the nozzle needle 30 and the inner wall of the needle accommodation hole 21 and communicates with the fuel supply passage 24 is formed. The fuel reservoir chamber 25 communicates with the nozzle hole 22 in a state where the nozzle needle 30 is separated from the valve seat 23.

  The nozzle needle 30 has a pressure receiving portion 31 at an intermediate portion in the axial direction. The pressure receiving portion 31 is accommodated in the fuel reservoir chamber 25. When the fuel pressure of the high pressure fuel in the fuel reservoir chamber 25 acts on the pressure receiving portion 31, a force that pushes the nozzle needle 30 in the valve opening direction acts on the nozzle needle 30.

  When the nozzle needle 30 is seated on the valve seat 23, the communication between the fuel reservoir chamber 25 and the injection hole 22 is blocked. For this reason, even if the high pressure fuel is supplied to the fuel reservoir 25, the fuel is not injected from the nozzle hole 22. When the nozzle needle 30 moves away from the valve seat 23, the fuel reservoir chamber 25 and the injection hole 22 communicate with each other, so that fuel is injected from the injection hole 22.

  The nozzle holder unit 12 supports the nozzle unit 11 at one end and supports the pressure control unit 13 at the other end. The nozzle holder portion 12 includes a lower body 40, a command piston 50, a rod pressure 60, a coil spring 61, an orifice plate 70, and the like.

  The lower body 40 is formed in a rod shape and supports the nozzle body 20 at the lower end. The lower body 40 has a high-pressure port 43 to which a fuel pipe extending from the common rail is connected. The high-pressure port 43 is provided with a filter member 49 that suppresses entry of foreign matter contained in the fuel into the fuel injection valve 10. The lower body 40 is formed with a fuel supply passage 45 that supplies the high-pressure fuel flowing into the high-pressure port 43 to the fuel supply passage 24 of the nozzle body 20.

  A recess 41 that is recessed downward is formed at the upper end of the lower body 40. A branch passage 451 that branches from the fuel supply passage 45 is formed in the lower body 40. The branch passage 451 opens at the bottom of the recess 41.

  The lower body 40 is formed with a piston accommodation hole 47 extending in the axial direction. One end of the piston accommodation hole 47 opens to the bottom of the recess 41, and the other end opens to the support surface 42 that supports the nozzle body 20.

  The piston accommodation hole 47 is arranged coaxially with the needle accommodation hole 21 and communicates with the needle accommodation hole 21. The piston accommodation hole 47 is formed in a rod shape, and accommodates a command piston 50 having a sliding portion 51 that slides in the piston accommodation hole 47 and a rod portion 52 having a smaller diameter than the sliding portion 51 so that the piston can reciprocate. ing. The command piston 50 is accommodated in the piston accommodation hole 47 so that the sliding portion 51 is disposed on the concave portion 41 side. The piston accommodation hole 47 and the needle accommodation hole 21 in this embodiment correspond to the accommodation hole described in the claims.

  A rod pressure 60 formed in a substantially cylindrical shape is provided between the distal end portion of the rod portion 52 and the end portion of the nozzle needle 30 on the lower body 40 side. The rod pressure 60 indirectly connects the command piston 50 and the nozzle needle 30, and can move in the axial direction together with the command piston 50 and the nozzle needle 30.

  A coil spring 61 that urges the rod pressure 60 toward the nozzle needle 30 via the rod pressure 60 is disposed at the end of the rod pressure 60 on the concave portion 41 side. The end of the coil spring 61 opposite to the end that contacts the rod pressure 60 is supported by a stepped portion 473 formed in the piston accommodation hole 47 via a spacer 62.

  As shown in FIG. 1, a fuel passage 46 is formed between the rod portion 52 and the piston accommodation hole 47 through which fuel discharged from the sliding gap H between the sliding portion 51 and the piston accommodation hole 47 flows. The

  The lower body 40 is formed with a leak passage 461, one of which communicates with the fuel passage 46 via the support surface 42 and the other of which opens at the bottom of the recess 41. The leak passage 461 branches off in the middle and communicates with the low pressure port 44 formed in the lower body 40. The fuel discharged from the sliding gap H is discharged from the low pressure port 44 to the outside of the fuel injection valve 10 through the fuel passage 46 and the leak passage 461.

  The orifice plate 70 is formed in a substantially disc shape, and is provided at the bottom of the recess 41 so as to cover the piston accommodation hole 47. A pressure control chamber 71 that communicates with the piston accommodation hole 47 is formed on the bottom end surface of the recess 41 of the orifice plate 70. Further, the orifice plate 70 has an out-orifice 72 that communicates the pressure control chamber 71 and the end surface of the orifice plate 70 opposite to the concave portion 41, and an in-orifice 73 that communicates the branch passage 451 and the pressure control chamber 71. Is formed. The passage diameter of the out orifice 72 is larger than the passage diameter of the in orifice 73.

  The high pressure fuel accumulated in the common rail is supplied to the pressure control chamber 71 through the branch passage 451, and the fuel pressure of the high pressure fuel acts on the upper end portion of the command piston 50. As a result, the command piston 50 has a force that pushes the nozzle needle 30 downward, that is, pushes the nozzle needle 30 in the valve closing direction.

  The outer diameter of the orifice plate 70 is smaller than the inner diameter of the recess 41. Therefore, a fuel passage 74 is formed between the outer wall of the orifice plate 70 and the inner wall of the recess 41. The fuel passage 74 communicates with the leak passage 461. The nozzle body 20, the lower body 40, and the orifice plate 70 described above constitute the housing described in the claims.

  The pressure control unit 13 is provided on the side of the recess 41 of the lower body 40 and adjusts the fuel pressure in the pressure control chamber 71. The pressure control unit 13 includes a valve body 80, a valve member 85, a solenoid 90, and the like. The valve body 80 is formed in a substantially cylindrical shape and is provided on the out orifice 72 side of the orifice plate 70. A vertical hole 81 is formed in the valve body 80. A valve chamber 82 communicating with the out orifice 72 is formed at the end of the vertical hole 81 on the orifice plate 70 side.

  The valve body 80 is formed with a fuel passage 83 passing through the end surface of the body 80 on the orifice plate 70 side and the end surface on the opposite side at a position shifted in the radial direction from the vertical hole 81. Further, the valve body 80 is formed with a communication passage 84 that allows the fuel passage 83 and the valve chamber 82 to communicate with each other.

  The valve member 85 includes a valve body 86 formed in a hemispherical shape and an armature 87 that supports the valve body 86. The valve body 86 is accommodated in the valve chamber 82 such that the hemispherical plane portion faces the opening of the out orifice 72. The out orifice 72 is closed when the valve body 86 is seated on the orifice plate 70, and the out orifice 72 is opened when the valve body 86 is separated from the orifice plate 70. The armature 87 includes a disk portion and a columnar portion that extends from the center portion of the disk portion, is supported by the vertical hole 81 so as to be movable in the axial direction, and supports the valve body 86 at the end.

  When the valve body 86 is separated from the orifice plate 70 and the out orifice 72 is opened, the high-pressure fuel that has flowed into the pressure control chamber 71 is discharged to the valve chamber 82 on the low-pressure side, Fuel pressure decreases. The fuel discharged to the valve chamber 82 is discharged from the low pressure port 44 through the communication passage 84, the fuel passage 83, the fuel passage 74, and the leak passage 461.

  The solenoid 90 includes a stator 91, a coil 95, a coil spring 96, and the like. The stator 91 is formed in a substantially cylindrical shape, and is provided on the opposite side of the valve body 80 from the orifice plate 70. Between the stator 91 and the valve body 80, an armature chamber 94 for accommodating the disk portion of the armature 87 is formed. The armature chamber 94 communicates with the fuel passage 83.

  A vertical hole 92 extending in the axial direction is formed in the stator 91. A coil spring 96 that biases the armature 87 downward is accommodated in the vertical hole 92. A coil 95 is provided on the outer peripheral side of the vertical hole 92 and receives electric power from an external power source (not shown) via the connector 97. When the coil 95 is energized, a magnetic flux passing through the stator 91 and the armature 87 is generated, and a magnetic attraction force acts between the attraction portion 93 and the armature 87. Thereby, the armature 87 and the valve body 86 move in the valve opening direction, and the out orifice 72 opens. When energization of the coil 95 is stopped, the armature 87 and the valve body 86 are moved in the valve closing direction by the biasing force of the coil spring 96, and the out orifice 72 is closed.

  Next, the operation of the fuel injection valve 10 will be described. High pressure fuel pressurized by a fuel injection pump (not shown) is supplied to the fuel supply passage 45 through a pipe connected to the high pressure port 43. The high pressure fuel supplied to the fuel supply passage 45 flows into the fuel reservoir chamber 25 through the fuel supply passage 24 and flows into the pressure control chamber 71 through the branch passage 451 and the in-orifice 73.

  When the coil 95 is not energized, the valve body 86 closes the out orifice 72 by the urging force of the coil spring 96. For this reason, the fuel pressure in the pressure control chamber 71 is substantially the same as the fuel pressure of the high-pressure fuel. At this time, the force in the valve closing direction toward the nozzle needle 30 corresponding to the fuel pressure in the pressure control chamber 71 acts on the command piston 50.

  The nozzle needle 30 has a force in the valve opening direction due to the fuel pressure in the fuel reservoir chamber 25 acting on the pressure receiving portion 31, a force in the valve closing direction from the coil spring 61 applied via the rod pressure 60, and A force in the valve closing direction from the command piston 50 applied via the rod pressure 60 acts.

  In the state where the valve body 86 closes the out orifice 72, the force in the valve closing direction acting on the nozzle needle 30 exceeds the force in the valve opening direction, so the nozzle needle 30 is seated on the valve seat 23. Then, the nozzle hole 22 is closed. For this reason, fuel is not injected from the nozzle hole 22.

  When the coil 95 is energized, the armature 87 is sucked into the suction portion 93 of the stator 91, and the valve body 86 opens the out orifice 72. Then, the high-pressure fuel in the pressure control chamber 71 is discharged to the valve chamber 82 through the out orifice 72. The high-pressure fuel discharged to the valve chamber 82 is discharged from the low-pressure port 44 to the outside of the fuel injection valve 10 through the communication passage 84, the fuel passage 83, the fuel passage 74, and the leak passage 461. As a result, the fuel pressure in the pressure control chamber 71 gradually decreases. As a result, the force in the valve closing direction acting on the command piston 50 also decreases.

  When the force in the valve closing direction acting on the nozzle needle 30 becomes weak and falls below the force in the valve opening direction, the nozzle needle 30 starts to move in the valve opening direction, moves away from the valve seat 23, and opens the nozzle hole 22. To do. Thereby, the fuel in the fuel reservoir 25 is injected from the injection hole 22.

  When the energization to the coil 95 is stopped again, the fuel pressure in the pressure control chamber 71 rises, the force in the valve closing direction acting on the nozzle needle 30 exceeds the force in the valve opening direction, and the nozzle needle 30 The user sits on the seat 23 and closes the nozzle hole 22.

  Next, the characteristic part of this embodiment is demonstrated in detail using FIG. The piston accommodation hole 47 for accommodating the command piston 50 includes two sliding holes 471 for slidably supporting the sliding portion 51 of the command piston 50 and a rod accommodation hole 472 for accommodating the rod portion 52 of the command piston 50. It consists of parts. The sliding hole 471 and the rod receiving hole 472 are arranged coaxially, and the inner diameter of the rod portion 52 is larger than the inner diameter of the sliding hole 471.

  Here, a method of forming the piston accommodation hole 47 will be described. The piston accommodation hole 47 is formed by drilling. Specifically, first, the rod housing hole 472 is formed from the support surface 42 of the rod-shaped lower body 40 using a tool such as a drill. When forming the rod receiving hole 472, the drill does not penetrate the lower body 40 and stops at the axially intermediate portion. Next, the sliding hole 471 is formed using a drill having a smaller diameter than the drill used when forming the rod housing hole 472. The sliding hole 471 is formed from the bottom side of the recess 41. Thereafter, the connecting portion between the sliding hole 471 and the rod receiving hole 472 is subjected to processing (for example, honing processing) for removing burrs and the like generated during processing. In the present embodiment, an example in which the sliding hole 471 is processed from the bottom side of the concave portion 41 has been described. However, the sliding hole 471 may be processed from the rod accommodation hole 472 side.

  As shown in FIG. 2, when machining the sliding hole 471, the end of the sliding hole 471 on the rod receiving hole 472 side is a shaft runout of the drill, processing equipment generated during the machining of the sliding hole 471, A machining sag portion 48 is formed by vibration of a workpiece (lower body) or the like. Since the processing sag portion 48 is formed by the phenomenon described above, the hole diameter is larger than the sliding holes 471 other than the processing sag portion 48. Further, the processing accuracy of the processing sag portion 48 is lower than that of other portions, and the roundness of the cross section of the hole of the processing sag portion 48 is lower than that of the other portions.

  The command piston 50 includes the sliding part 51 and the rod part 52 as described above. The sliding part 51 is supported by the sliding hole 471 so as to be slidable in the axial direction. The sliding portion 51 is disposed closer to the pressure control chamber 71 than the processing sag portion 48 in at least the axial movement range in which the command piston 50 drives the nozzle needle 30 to open and close.

  Next, the effect of the characteristic part of this embodiment is demonstrated using FIG. 3 and FIG. 4, comparing with a comparative example. FIG. 3 is a diagram schematically showing a characteristic part of the present embodiment, and FIG. 4 is a diagram schematically showing a comparative example. FIGS. 3 and 4 both show a state where the command piston has the nozzle needle seated on the valve seat.

  First, the comparative example shown in FIG. 4 will be described. When the sliding hole 471a is formed by drilling, the processing sag portion 48a is formed at the end of the sliding hole 471a on the rod receiving hole 472a side as described above. The processing accuracy of the processing sag portion 48a is low, and the roundness of the cross section of the hole of the processing sag portion 48a is lower than other portions. For example, in FIG. 4, the distance from the central axis of the sliding hole 471a to the processing sag portion 48a on the left side in the drawing is longer than the distance from the central axis to the processing sag portion 48a on the right side in the drawing.

  In the comparative example shown in FIG. 4, the sliding portion 51a of the command piston 50a is arranged so that the end portion on the rod portion 52a side of the sliding portion 51a overlaps with the processing sag portion 48a in the axial direction. When the sliding portion 51a is arranged in the sliding hole 471a as described above, the distance from the central axis of the sliding hole 471a to the processing sag portion 48a is different on the left and right as described above. The spacing between the sliding portion 51a facing it and the spacing between the right processing sag portion 48a and the sliding portion 51a facing it are different. In the present embodiment, the interval at the left machining sag portion 48a is wider than the interval at the right machining sag portion 48a.

  The high-pressure fuel in the pressure control chamber 71a flows into the fuel passage 46a through the sliding gap H formed between the sliding portion 51a and the sliding hole 471a. Since the interval in the left processing sag portion 48a in the drawing is wider than the interval in the right processing sag portion 48a, the fuel flowing through the sliding gap H flows toward the left processing sag portion 48a in the drawing. As a result, the fuel pressure near the left processing sag portion 48a becomes larger than the fuel pressure near the right processing sag portion 48a.

  For this reason, the sliding part 51a is drawn toward the right side processing sag part 48a where the fuel pressure is low, and comes into contact with the sliding hole 471a. As a result, the sliding resistance of the command piston 50a increases.

  At this time, the radial force F acting on the command piston 50a is such that the diameter of the sliding portion 51a is D, the axial length of the processing sag portion 48a is L, and the pressure control chamber 71a side of the processing sag portion 48a is ΔP (= P1−P2) is defined as the difference between the fuel pressure P1 at the side and the fuel pressure P2 at the rod accommodating hole 472a side of the machining sag portion 48a, and the gap between the machining sag portion 48a and the sliding portion 51a at the rod accommodation hole 472a side. When the value of the ratio between h2 and the gap h1 between the machining sag portion 48a and the sliding portion 51a on the pressure control chamber 71a side is ε (= h2 / h1), the following equation (1) is obtained.

(1) F = π / 4 × D × L × ΔP {(ε + 1) × √ ((ε−1) / (ε + 3)) + (ε−1)}
Further, this force F becomes maximum in the vicinity of ε = 1.8.

  Next, the present embodiment shown in FIG. 3 will be described. The shape of the processed sag portion 48 shown in FIG. 3 is the same as the processed sag portion 48a shown in FIG.

  As shown in FIG. 3, in this embodiment, as described with reference to FIG. 2, the sliding portion 51 of the command piston 50 is more than the pressure control chamber 71 than the machining sag portion 48 within the axial movement range. Arranged on the side. In this case, the portion of the command piston 50 that faces the processing sag portion 48 is a rod portion 52 that has a smaller diameter than the sliding portion 51.

  In the command piston 50 shown in FIG. 3 as well, the high-pressure fuel in the pressure control chamber 71 passes through the sliding gap H between the sliding portion 51 and the sliding hole 471 as in FIG. As shown in FIG. 3, in the case where the sliding portion 51 is arranged, the flow of fuel at the end of the sliding portion 51 on the rod portion 52 side is substantially uniform over the entire circumference unlike FIG. .

  The fuel discharged from the end portion of the sliding portion 51 on the rod portion 52 side passes through the rod portion 52 and the machining sag portion 48. At this time, the fuel flowing in the vicinity of the machining sag portion 48 tends to flow in the direction where the distance between the rod portion 52 and the machining sag portion 48 is wider as in FIG. 4, but this interval is the machining sag portion 48 shown in FIG. Since it is larger than the distance between the sliding part 51 and the sliding part 51, it flows toward the nozzle part 11 without flowing into the wider part.

  For this reason, the pressure difference between the fuel pressure in the vicinity of the processing sag 48 on the left side and the fuel pressure in the vicinity of the processing sag 48 on the right side becomes smaller than the pressure difference in FIG.

  Here, the fuel pressure P1 on the pressure control chamber 71 side of the processing sag portion 48 and the fuel pressure P2 on the rod accommodation hole 472 side are substantially wide because the distance between the rod portion 52 and the processing sag portion 48 in this portion is very wide. The pressure is the same as the fuel pressure in the leak passage 461. For this reason, ΔP (= P1−P2) is a very small value.

  When the value of ΔP described above is substituted into the above equation (1) and the radial force acting on the command piston 50 is obtained, ΔP is a very small value, so the force F is the comparative example shown in FIG. Compared to, the value is very small. In this case, D in Formula (1) is the diameter of the rod portion 52, h1 is a gap between the machining sag portion 48 and the rod portion 52 on the pressure control chamber 71 side, and h2 is the machining sag portion 48. It is a clearance with the rod part 52 in the rod accommodating hole 472 side.

  By disposing the sliding part 51 on the pressure control chamber 71 side with respect to the machining sag part 48 within the axial movement range, the flow of fuel near the machining sag part 48 is improved, and the sliding resistance of the command piston 50 is reduced. The increase can be suppressed. As a result, the operation of the command piston 50 is stabilized, and as a result, variations in the injection amount of the fuel injection valve 10 can be reduced.

(Second Embodiment)
FIG. 5 shows a second embodiment. Components that are substantially the same as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted. Here, only the characteristic structure of the second embodiment will be described.

  In the second embodiment shown in FIG. 5, unlike the first embodiment in which the end portion on the rod portion 52a side of the sliding portion 51a is disposed closer to the pressure control chamber 71 than the processing sag portion 48, FIG. It arrange | positions in the position facing the process | sagging part 48 shown in FIG. As shown in FIG. 5, the present embodiment is characterized in that a circumferential groove 511 is formed over the entire circumference in a portion of the sliding portion 51a that faces the processing sag portion 48.

  Next, the effect of the characteristic part of this embodiment is demonstrated using FIG. FIG. 6 is a diagram schematically showing the characteristic part of the present embodiment. In this figure, the piston accommodation hole 47 is the same as the piston accommodation hole 47 shown in FIGS. Further, in this drawing, the command piston 50a shows a state when the nozzle needle 30 is seated on the valve seat 23.

  The high-pressure fuel in the pressure control chamber 71 flows into the fuel passage 46 through a sliding gap H formed between the sliding portion 51a and the sliding hole 471. As described with reference to FIG. 4, the fuel flowing through the sliding gap H flows toward the processing sag portion 48 on the left side in the drawing with a wide interval.

  However, in the present embodiment, since the circumferential groove 511 is formed at a portion of the sliding portion 51a that faces the machining sag portion 48, a part of the fuel that flows into the vicinity of the left machining sag portion 48 is part of the circumferential groove. It flows into the vicinity of the processing sag portion 48 on the right side having a low pressure through 511. As a result, the fuel pressure in the vicinity of the left and right machining sag portions 48 is adjusted and becomes substantially uniform over the entire circumference. As a result, an increase in sliding resistance of the command piston 50a can be suppressed.

(Third embodiment)
7 and 8 show a third embodiment. Components that are substantially the same as those in the first and second embodiments are denoted by the same reference numerals, and description thereof is omitted. Here, only the characteristic structure of the third embodiment will be described.

  In the third embodiment shown in FIG. 7, the sliding portion 51 of the command piston 50 of this embodiment is formed with an inclined portion 512 whose outer diameter decreases toward the pressure control chamber 71 side. Other parts are the same as those of the first embodiment shown in FIG.

  By accommodating the command piston 50 having the inclined portion 512 in the piston accommodation hole 47, the sliding gap H formed in the sliding portion 51 and the sliding hole 471 is formed in the pressure control chamber 71 as shown in FIG. 7. It gets wider as you go.

  According to this configuration, the high-pressure fuel in the pressure control chamber 71 is smaller than the case where the outer diameter of the sliding portion 51 on the pressure control chamber 71 side is substantially the same as the end of the sliding portion 51 on the rod portion 52 side. It becomes easy to flow into the sliding gap H. For this reason, a force toward the central axis acts on the sliding portion 51 by the action of the fuel pressure of the high-pressure fuel. As a result, the command piston 50 is automatically aligned with the central axis of the piston accommodation hole 47, and an increase in sliding resistance of the command piston 50 can be suppressed.

  In order to increase the sliding clearance H toward the pressure control chamber 71, the inner diameter of the sliding hole 471 can be increased toward the pressure control chamber 71. However, as in the present embodiment, the sliding portion This is achieved by forming an inclined portion 512 in 51 so that the outer diameter decreases toward the pressure control chamber 71. Since the command piston 50 is made of a material having lower hardness than the lower body 40 in which the sliding hole 471 is formed, an inclined portion for forming a sliding gap H that becomes wider toward the pressure control chamber 71. 512 can be formed easily.

  FIG. 8 shows an example applied to the second embodiment shown in FIG. As in FIG. 7, the sliding portion 51a of the command piston 50a is formed with an inclined portion 512 whose outer diameter decreases toward the pressure control chamber 71 side. Also in this embodiment, since the force toward the central axis acts on the sliding portion 51a as described above, the command piston 50a is automatically aligned with the central axis of the piston accommodation hole 47. As a result, an increase in sliding resistance of the command piston 50a can be suppressed.

It is sectional drawing of the fuel injection valve by 1st Embodiment of this invention. It is sectional drawing to which the principal part of the fuel injection valve of FIG. 1 was expanded. It is sectional drawing which showed typically the principal part of the fuel injection valve of FIG. It is sectional drawing which showed typically the principal part of the fuel injection valve in a comparative example. It is sectional drawing of the fuel injection valve by 2nd Embodiment of this invention. It is sectional drawing to which the principal part of the fuel injection valve of FIG. 5 was expanded. It is sectional drawing to which the principal part of the fuel injection valve by 3rd Embodiment of this invention was expanded. It is sectional drawing to which the principal part of the fuel injection valve of other embodiment by 3rd Embodiment of this invention was expanded.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Fuel injection valve, 11 Nozzle part, 12 Nozzle holder part, 13 Pressure control part, 14 Retaining nut, 15 Body upper, 20 Nozzle body (housing), 21 Needle accommodation hole, 22 Injection hole, 23 Valve seat, 24 Fuel supply passage , 25 Fuel reservoir, 30 Nozzle needle (needle), 40 Lower body (housing), 43 High pressure port, 44 Low pressure port, 45 Fuel supply passage, 451 Branch passage, 46 Fuel passage, 461 Leak passage, 47 Piston housing hole, 471 Sliding hole, 472 Rod housing hole (large diameter housing hole), 473 Stepped portion, 48 Processing sag portion (diameter enlarged portion), 49 Filter member, 50 Command piston (control piston), 51 Sliding portion, 511 Circumferential groove, 512 Inclined part, 52 Rod part, 60 Rod pressure, 61 Carp Spring, 70 Orifice plate (housing), 71 Pressure control chamber, 72 Out orifice, 73 In orifice, 74 Fuel passage, 80 Valve body, 82 Valve chamber, 83 Fuel passage, 84 Communication passage, 85 Valve member, 86 Valve body, 87 Armature, 90 Solenoid, 91 Stator, 95 Coil, 96 Coil Spring, 97 Connector

Claims (5)

In a fuel injection valve for injecting high-pressure fuel to be supplied into a combustion chamber of an internal combustion engine from an injection hole,
A needle for opening and closing the nozzle hole;
A control piston for controlling the opening and closing operation of the needle;
The needle is closed to drive the control piston by causing the high-pressure fuel to act on the nozzle hole, the needle and the control piston, and the communication hole communicating with the nozzle hole, and the end of the control piston. A fuel injection valve comprising a housing in which a pressure control chamber for generating a force to be generated is formed,
The accommodation hole includes a needle accommodation hole that accommodates the needle so as to be movable in the axial direction, a sliding hole that slidably supports the control piston and communicates with the pressure control chamber, and a diameter larger than the sliding hole. Is arranged between the needle accommodation hole and the sliding hole, and is composed of a large diameter accommodation hole that accommodates a part of the control piston,
An end portion of the sliding hole on the large-diameter receiving hole side is formed with a diameter-enlarged portion due to a shaft runout of a drilling tool at the time of machining the sliding hole or vibration generated at the time of machining the sliding hole. And
The control piston has a sliding portion that is slidably supported in the sliding hole, and a rod portion having a smaller diameter than the sliding portion that is accommodated in the large-diameter accommodation hole,
The fuel injection valve according to claim 1, wherein the sliding portion is disposed at a position closer to the pressure control chamber than the enlarged-diameter portion in a moving range where at least the control piston drives the needle to open and close. In a fuel injection valve for injecting high-pressure fuel to be supplied into a combustion chamber of an internal combustion engine from an injection hole,
A needle for opening and closing the nozzle hole;
A control piston for controlling the opening and closing operation of the needle;
The needle is closed to drive the control piston by causing the high-pressure fuel to act on the nozzle hole, the needle and the control piston, and the communication hole communicating with the nozzle hole, and the end of the control piston. A fuel injection valve comprising a housing in which a pressure control chamber for generating a force to be generated is formed,
The accommodation hole includes a needle accommodation hole that accommodates the needle so as to be movable in the axial direction, a sliding hole that slidably supports the control piston and communicates with the pressure control chamber, and a diameter larger than the sliding hole. Is arranged between the needle accommodation hole and the sliding hole, and is composed of a large diameter accommodation hole that accommodates a part of the control piston,
An end portion of the sliding hole on the large-diameter receiving hole side is formed with a diameter-enlarged portion due to a shaft runout of a drilling tool at the time of machining the sliding hole or vibration generated at the time of machining the sliding hole. And
A fuel injection valve characterized in that a circumferential groove is formed in a portion of the control piston facing the enlarged diameter portion. The diameter enlarged portion is opposed to the sliding portion of the control piston,
The fuel injection valve according to claim 2, wherein the circumferential groove is formed in the sliding portion.   4. The sliding gap between the sliding portion that is slidably supported by the sliding hole of the control piston and the sliding hole becomes larger toward the pressure control chamber. The fuel injection valve according to any one of the above.   The fuel injection valve according to claim 3, wherein the sliding portion of the control piston has an inclined portion whose outer diameter decreases toward the pressure control chamber.

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