JP3931329B2 - Fuel injection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection device for an internal combustion engine (hereinafter referred to as an engine).
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there is known a fuel injection device that opens and closes a nozzle hole by a valve member that moves integrally with a movable core by attracting and separating the movable core from a fixed core using magnetic flux generated by a coil portion. . In this fuel injection device, a movable core is accommodated in a cylindrical valve body so as to be able to reciprocate, a fixed core is immovably accommodated in the valve body, and a downstream end face of the fixed core is located upstream of the movable core. Opposite the end face. In this fuel injection device, the coil portion is energized to form a magnetic flux that passes through the fixed core, the movable core, and the valve body, whereby the movable core is driven by suction to the fixed core and the nozzle hole is opened. Further, by stopping energization of the coil portion, the movable core is allowed to be separated from the fixed core, and the nozzle hole is closed. Hereinafter, in the fuel injection device, opening of the nozzle hole by the valve member is referred to as “valve opening”, and closing of the nozzle hole by the valve member is referred to as “valve closing”.
[0003]
In the fuel injection device described above, for example, as disclosed in Japanese Patent Laid-Open No. 8-506876, it is considered that a recess is provided on the outermost peripheral edge of the upstream end surface of the movable core facing the fixed core. By providing such a recess, when the valve is opened, fuel stays in a space formed between the fixed core and the movable core (hereinafter referred to as the core chamber), so that it can move due to the hydraulic damping effect of the fuel in the core chamber. The collision speed of the core to the fixed core is suppressed, and the valve opening bounce of the valve member is reduced.
[0004]
[Problems to be solved by the invention]
In the fuel injection device in which the concave portion is provided in the movable core, a side gap 4 is formed between the outer peripheral wall of the movable core 1 and the inner peripheral wall of the valve body 2 as shown in FIG. According to the research results of the present inventor, it is necessary to make the distance between the side gaps 4 as narrow as possible in order to obtain an effective hydraulic damping effect. However, conventionally, the side gap 4 is formed so as to have a constant interval in the axial direction. Therefore, if the interval between the side gaps 4 is narrowed, the fuel flows into the core chamber 5 from the side gap 4 when the valve is closed. It becomes difficult to do. In that case, it becomes difficult for the movable core 1 to be separated from the fixed core 6, and the time required for closing the nozzle hole of the valve member increases, so that the valve closing response is deteriorated. Further, when narrowing the gaps of the side gaps 4 at a constant interval in the axial direction, the magnetic flux formed in the coil portion so as to pass through the fixed core 6, the movable core 1 and the valve body 2 when the valve is opened (see FIG. It is difficult to reduce the density (shown schematically by a dotted line arrow) when the valve is closed. In this case, since the magnetic attractive force acting between the cores 1 and 6 with a magnitude according to the magnetic flux density is less likely to decrease, the time lag from when the energization to the coil portion is stopped until the valve member actually starts to move increases. The valve closing response deteriorates.
[0005]
By the way, in the fuel injection device mounted on the engine of the vehicle, it is required to reduce the lower limit of the injection amount that can be stably obtained in response to the energization to the coil portion (hereinafter referred to as the stable injection amount). It has been. However, as described above, when the valve closing response is deteriorated, there arises a problem that the lower limit value of the stable injection amount cannot be sufficiently lowered.
[0006]
The objective of this invention is providing the fuel-injection apparatus which is excellent in valve-closing responsiveness while reducing the valve-opening bounce of a valve member.
Another object of the present invention is to provide a fuel injection device that reduces the lower limit value of the stable injection amount.
[0007]
[Means for Solving the Problems]
According to the fuel injection device of the first aspect of the present invention, the upstream end surface of the movable core facing the downstream end surface of the fixed core is formed with a recessed portion on the outermost peripheral edge or a flat surface. As a result, when the valve is opened, the fuel stays in the core chamber between the fixed core and the movable core, so that the collision speed of the movable core to the fixed core is suppressed by the hydraulic damping effect produced by the fuel in the core chamber, and the valve member The valve opening bounce can be reduced.
[0008]
  Further, according to the fuel injection device of the first aspect, the outer peripheral wall of the movable core forms a side gap with the inner peripheral wall of the valve body. However, the movable core has an enlarged portion on the outer peripheral wall that enlarges the gap of the side gap on the outer periphery of the downstream end than the interval on the outer periphery of the upstream end. Therefore, when the valve is closed, the flow coefficient of the side gap whose interval is increased on the outer periphery of the downstream end of the movable core increases, so that fuel easily flows into the core chamber from the side gap. Thereby, when the valve is closed, the movable core is easily separated from the fixed core, and the time required for the valve member to close the nozzle hole is shortened, so that the valve closing response is improved. Moreover, since the gap of the side gap is enlarged on the outer periphery of the downstream end of the movable core, the density of the magnetic flux formed by the coil portion by energization tends to decrease when no current is applied. Therefore, when the valve is closed when energization to the coil portion is stopped due to the injection hole closing, the magnetic attractive force acting between the fixed core and the movable core is likely to decrease. The valve responsiveness can be improved by reducing the time lag until the member actually starts moving.
Further, the enlarged portion is formed in a taper shape that is reduced in diameter as it approaches the downstream end portion of the movable core.
  Thus, according to the fuel injection device of the first aspect, since excellent valve closing response can be obtained, the lower limit value of the stable injection amount can be reduced.
[0009]
According to the fuel injection device of the second aspect of the present invention, the enlarged portion extends a predetermined length from the downstream end portion of the movable core toward the upstream side. The movable core has a guide portion on the outer peripheral wall that extends straight in the axial direction from the upstream end portion toward the downstream side and continues to the enlarged portion, and the guide portion is guided in the axial direction by the inner peripheral wall of the valve body. . Thereby, since the reciprocating movement of the movable core is stabilized, a desired fuel injection amount can be obtained with certainty.
[0010]
According to the fuel injection device of the third aspect of the present invention, the axial length L of the enlarged portion is set to be equal to or longer than the axial length L ′ of the guide portion. Both the reduction of valve opening bounce and the improvement of valve closing response can be realized with certainty.
[0011]
According to the fuel injection device of the fourth aspect of the present invention, the distance D between the side gaps at the outer periphery of the downstream end of the movable core is set to 0.2 to 0.6 mm. As a result, it is possible to sufficiently lower the lower limit value of the stable injection amount while ensuring the magnetic attraction force necessary for attracting the movable core to the fixed core when the valve is opened.
[0012]
  By the fuel-injection apparatus of Claim 5 of this inventionAnd expansionL / D, which is the ratio between the most axial length L and the gap D of the side gap at the outer periphery of the downstream end of the movable core, is set within a range of 10 / 3-30. By adopting such a configuration, the valve closing response can be enhanced with a simple configuration.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a plurality of examples showing embodiments of the present invention will be described with reference to the drawings.
(First Example)
1 and 2 show a fuel injection device according to a first embodiment of the present invention. The housing 11 of the fuel injection device 10 is formed in a straight cylindrical shape. The housing 11 includes a first magnetic cylinder part 11a, a nonmagnetic cylinder part 11b, and a second magnetic cylinder part 11c. The nonmagnetic cylindrical portion 11b is sandwiched between the first magnetic cylindrical portion 11a and the second magnetic cylindrical portion 11c in the axial direction, and the outer periphery of the downstream end 13 of the fixed core 12 and the upstream end 15 of the movable core 14. It is arranged on the side. Thereby, the leakage of the magnetic flux which the coil part 43 forms is prevented.
[0014]
The fixed core 12 is formed of a magnetic material in a cylindrical shape, and forms a fuel passage therein. The fixed core 12 is coaxially accommodated and fixed to the upstream portion of the housing 11, and is not movable relative to the housing 11. The outer peripheral wall of the downstream end 13 of the fixed core 12 is in close contact with the inner peripheral wall of the housing 11. The downstream end face 13 a of the fixed core 12 is formed in a flat surface shape perpendicular to the central axis of the fixed core 12.
[0015]
The movable core 14 is formed of a magnetic material in a cylindrical shape, and forms a fuel passage therein. The movable core 14 is accommodated coaxially in the housing 11 so that the upstream end face 15a faces the downstream end face 13a of the fixed core 12, and can move back and forth in the axial direction. The outflow hole 25 that penetrates the cylindrical wall of the movable core 14 forms a fuel passage that communicates inside and outside the cylinder. A joining sleeve 22 is integrally provided on the downstream end portion 16 side of the movable core 14.
[0016]
As shown in FIGS. 1 and 3, the movable core 14 has a protrusion 50 and a recess 52 at the upstream end 15.
The protrusion 50 is formed in an annular shape on the outer peripheral side of the inner hole 54 of the movable core 14 and protrudes toward the fixed core 12. The protruding end surface 56 of the protruding portion 50 constituting the upstream end surface 15 a of the movable core 14 is formed in a flat surface shape perpendicular to the central axis of the movable core 14. The protruding end face 56 abuts on the downstream end face 13a of the fixed core 12 as shown in FIG. 4 when the valve member 20 is fully lifted upstream, and otherwise the downstream end face of the fixed core 12 as shown in FIG. A core chamber 80 is formed opposite to 13a with a gap. The inner peripheral side of the protrusion 50 is continuous with the inner hole 54.
[0017]
The recessed portion 52 is formed in an annular shape on the outer peripheral side of the protruding portion 50, and is recessed from the protruding portion 50 toward the side opposite to the fixed core 12. The bottom surface 57 of the recess 52 that constitutes the upstream end surface 15a of the movable core 14 is continuous with the outer peripheral wall of the movable core 14 on the outer peripheral side. That is, the recessed part 52 is formed in the outermost periphery of the upstream end surface 15a. The bottom surface 57 of the recessed portion 52 faces the downstream end surface 13a of the fixed core 12 with a space therebetween to form a core chamber 80. The inner peripheral side of the recessed part 52 is connected to the outer peripheral side of the protruding part 50 in a stepped manner.
[0018]
As shown in FIG. 1, the movable core 14 forms an annular cross-sectional side gap 70 between the outer peripheral wall of the movable core 14 and the inner peripheral wall of the housing 11 at an arbitrary movement position. The interval of the side gap 70 changes in the axial direction due to the outer peripheral wall of the movable core 14.
Specifically, the movable core 14 has a guide portion 60 that keeps the interval between the side gaps 70 constant and an enlarged portion 62 that changes the interval between the side gaps 70 on the outer peripheral wall thereof.
[0019]
The guide part 60 is formed in a rotating columnar shape extending straight in the axial direction from the upstream end 15 of the movable core 14 toward the downstream side. A distance D 'between side gaps 70a formed on the outer periphery of the guide portion 60 (hereinafter referred to as guide portion side gap) 70a is constant in the axial direction. Thereby, since the guide part 60 is reliably guided in the axial direction by the inner peripheral wall of the housing 11 when the movable core 14 moves, the movement stability of the movable core 14 is enhanced.
[0020]
The enlarged portion 62 extends from the downstream end 16 of the movable core 14 toward the upstream side, and continues to the downstream side of the guide portion 60. The enlarged portion 62 is formed in a tapered shape that decreases in diameter as it approaches the downstream end portion 16 of the movable core 14 from the guide portion 60 side. As a result, the interval between the side gaps 70b formed on the outer periphery of the enlarged portion 62 (hereinafter referred to as the enlarged portion side gap) 70b gradually increases toward the downstream side in the axial direction, and the side at the outer periphery of the upstream end 15 of the movable core 14 is increased. The gap 70 is larger than the gap D, that is, the gap D ′ of the guide side gap 70a. About the enlarged part 62 of a present Example, the bus-line of a taper surface is comprised by the straight line.
[0021]
The valve body 17 is formed in a cylindrical shape. The downstream end of the housing 11 is coaxially fixed to the upstream end of the valve body 17. A cylindrical valve body body 18 is caulked coaxially at the downstream end of the valve body 17. A nozzle hole 18 b is formed at the downstream end of the valve body 18. Further, a valve seat 18a is formed in the valve body main body 18 on the upstream side of the nozzle hole 18b.
[0022]
The valve member 20 is coaxially accommodated in the housing 11, the valve body 17, and the valve body main body 18 so as to be reciprocally movable. The valve member 20 is joined and fixed to the joining sleeve 22 of the movable core 14 at the upstream end thereof, and reciprocates integrally with the movable core 14. The housing 11, the valve body 17, and the valve body main body 18 form a fuel passage between each inner peripheral wall and the outer peripheral wall of the valve member 20. The seat portion 21 provided at the downstream end portion of the valve member 20 can be seated on the valve seat 18 a of the valve body main body 18. The valve member 20 moves to the downstream side where the movable core 14 is separated from the fixed core 12, and the seat portion 21 is seated on the valve seat 18a, whereby the nozzle hole 18b is closed. On the other hand, the valve member 20 moves to the upstream side where the movable core 14 approaches the fixed core 12 and the seat portion 21 is separated from the valve seat 18a, whereby the nozzle hole 18b is opened.
The housing 11, the valve body 17 and the valve body main body 18 constitute a “valve body” recited in the claims.
[0023]
The adjusting pipe 32 is press-fitted and fixed in the fixed core 12 and forms a fuel passage therein. The coil spring 31 that is an urging means is locked to the adjusting pipe 32 at one end and is locked to the movable core 14 at the other end. As a result, the coil spring 31 urges the movable core 14 and the valve member 20 toward the downstream side. The load of the coil spring 31 can be changed by adjusting the press-fitting amount of the adjusting pipe 32 to the fixed core 12.
[0024]
The cylindrical connector 36 is fixed to the upstream end portion of the housing 11 and forms a fuel passage therein. The fuel passage in the connector 36 communicates with the fuel passage in the adjusting pipe 32. The filter 35 is accommodated in a fuel passage in the connector 36. The filter 35 removes foreign matter in the fuel that is pumped by the high-pressure pump and flows into the connector 36. The fuel that has passed through the filter 35 is the fuel passage in the adjusting pipe 32, the fuel passage in the fixed core 12, the fuel passage in the movable core 14, the fuel passage formed by the outflow hole 25, the outer peripheral wall of the valve member 20 and the housing. 11. Formed between the seat portion 21 and the valve seat 18a when passing through the fuel passages between the valve body 17 and the inner peripheral walls of the valve body main body 18 in sequence and the valve member 20 is separated from the valve seat 18a. It passes through the opening to be guided to the nozzle hole 18b. The fuel that has passed through the fuel passage in the fixed core 12 flows into the core chamber 80 between the fixed core 12 and the movable core 14.
[0025]
The driving device 40 is fixed to the outer periphery of the housing 11. The drive device 40 includes a spool 41, a coil portion 43, a connector 45, a terminal 46, and the like. The spool 41 is formed of a resin in a cylindrical shape and is attached to the outer peripheral wall of the housing 11. The coil part 43 is wound around the spool 41 and surrounds the outer peripheral sides of the first magnetic cylinder part 11a and the nonmagnetic cylinder part 11b of the housing 11. The outer periphery of the spool 41 and the coil part 43 is covered with a resin-molded connector 45. The terminal 46 is embedded in the connector 45 and is electrically connected to the coil portion 43.
[0026]
In this embodiment, a drive circuit (not shown) supplies a current corresponding to a drive pulse input from a control device (not shown) to the coil unit 43 through the terminal 46. Specifically, the drive circuit energizes the coil unit 43 for a time corresponding to the pulse width W of the drive pulse shown in FIG. The energization causes the coil portion 43 to form a magnetic flux that passes through the fixed core 12, the movable core 14, and the housing 11 as schematically indicated by a two-dot chain line arrow in FIG. 4. Then, a magnetic attractive force corresponding to the magnetic flux density is generated between the fixed core 12 and the movable core 14. On the other hand, the drive circuit has a falling T of the drive pulse shown in FIG._fIn response to this, the energization to the coil portion 43 is stopped. By stopping the energization, the density of the magnetic flux formed at the time of energization decreases, and the magnetic attractive force between the cores 12 and 14 decreases.
[0027]
Here, the operation of the fuel injection device 10 will be described.
(I) When a drive pulse is input from the control device to the drive circuit and the coil portion 43 of the drive device 40 is energized by the drive circuit, a magnetic attractive force is generated between the cores 12 and 14 by the magnetic flux generated by the coil portion 43. To do. Then, this magnetic attractive force overcomes the urging force of the coil spring 31, and the movable core 14 is attracted toward the fixed core 12 and driven upstream. As a result, the valve member 20 is lifted to the upstream side and the seat portion 21 is separated from the valve seat 18a, so that the fuel flows into the nozzle hole 18b from between the seat portion 21 and the valve seat 18a, and then from the nozzle hole 18b. Be injected.
[0028]
(Ii) When the input of the drive pulse from the control device to the drive circuit is stopped and the energization of the coil unit 43 by the drive circuit is stopped, the core 12, The magnetic attractive force acting between 14 is reduced. Then, the movable core 14 is allowed to be separated from the fixed core 12, and the movable core 14 is driven downstream by the urging force of the coil spring 31. As a result, the valve member 20 moves downstream and the seat portion 21 is seated on the valve seat 18a, so that fuel injection from the injection hole 18b is blocked.
[0029]
FIG. 6 shows the relationship between the fuel injection amount injected from the fuel injection device 10 by the operations (i) and (ii) above and the pulse width of the drive pulse (that is, the energization time) by a solid line graph α. The fact that the pulse width of the drive pulse and the fuel injection amount are in a direct proportional relationship as shown by the straight line portion of the solid line graph α means that the fuel injection amount can be stably obtained in accordance with the energization to the coil unit 43. . Further, as shown in FIG. 6, the lower limit value of the stable injection amount is the minimum width W of the pulse width in which the fuel injection amount is directly proportional._minInjection quantity Q corresponding to_minMeans.
[0030]
According to the fuel injection device 10 described above, since the recessed portion 52 is formed on the outermost peripheral edge of the upstream end face 15a of the movable core 14, the fixed core 12 and the movable core 14 are opened during the valve opening operation (i). A large core chamber 80 can be secured between the two and fuel can be retained in the core chamber 80. Therefore, the fuel accumulated in the core chamber 80 can exert a hydraulic damping effect and suppress the collision speed of the movable core 14 to the fixed core 12, so that the valve opening bounce of the valve member 20 can be suppressed. The suppression effect of the valve opening bounce makes it possible to control the fuel injection amount with high accuracy.
[0031]
Furthermore, according to the fuel injection device 10, since the gap of the side gap 70 on the outer periphery of the movable core 14 is larger on the enlarged portion side 70 b than on the guide portion side 70 a, the density of the magnetic flux formed by energizing the coil portion 43 is It tends to decrease when energization of the coil portion 43 is stopped. Therefore, at the time of the valve closing operation of (ii) above, the magnetic attractive force acting between the cores 12 and 14 tends to decrease, so that the drive pulse falls (that is, when the energization is stopped) T as shown in FIG._fStart of movement of the valve member 20 from the downstream side to the downstream side T_sTime lag until₁However, it becomes smaller than the case of the conventional apparatus shown in FIG. Moreover, in the fuel injection device 10, the enlarged portion side gap 70b is larger than the guide portion side gap 70a, so that the flow coefficient in the enlarged portion side gap 70b is large. Therefore, when the valve is closed, the fuel easily flows into the core chamber 80 from the side gap 70, so that the movable core 14 is easily separated from the fixed core 12. Thereby, as shown in FIG. 5, the movement start T of the valve member 20 to the downstream side is started._sT from which the valve member 20 closes the nozzle hole 18b_eValve closing time t until₂Is shorter than that of the conventional device.
[0032]
Thus, according to the fuel injection device 10, the time lag t₁And valve closing time t₂Therefore, the valve closing response (t₁+ T₂) Will improve. Therefore, according to the fuel injection device 10, the lower limit value Q of the stable injection amount shown in FIG._minIn the case of the conventional apparatus in which the relationship between the fuel injection amount and the pulse width is indicated by a one-dot chain line graph β in FIG._minSmaller values can be realized.
[0033]
Next, an example of setting the dimensions of each part of the movable core 14 and the interval of the side gap 70 in the fuel injection device 10 according to the first embodiment will be described with reference to FIGS. 1 and 7.
The interval between the side gaps 70 on the outer periphery of the downstream end 16 of the movable core 14, that is, the interval between the downstream ends that is the maximum interval in the enlarged portion side gap 70 b (hereinafter referred to as the downstream end interval) D is determined in the fuel injection device 10. Target lower limit value Q of required stable injection amount_minAnd the lower limit F of the magnetic attractive force necessary for attracting the movable core 14 to the fixed core 12_minAnd is set based on As shown in FIG. 7A, the lower limit value of the stable injection amount obtained under the same driving conditions becomes smaller as the downstream end interval D of the enlarged portion side gap 70b becomes larger. In this setting example, as shown in FIG. 7A, the target lower limit value Q of the stable injection amount_minIs a lower limit D of the downstream end interval D of the enlarged portion side gap 70b to a value that can be realized._minIs set, specifically, 0.2 mm. Further, as shown in FIG. 7B, the magnetic attractive force generated between the cores 12 and 14 with the same energization amount becomes smaller as the downstream end distance D of the enlarged portion side gap 70b becomes larger. In this setting example, as shown in FIG._minThe upper limit value D of the downstream end interval D of the enlarged portion side gap 70b to a value that can secure_maxIs set, specifically, 0.6 mm.
[0034]
Further, the downstream end interval D of the enlarged portion side gap 70b and the axial length L of the enlarged portion 62 are set so that the ratio L / D thereof falls within the range of 10/3 to 30. When the ratio L / D is less than 10/3 or exceeds 30, the effect of improving the valve closing response is reduced.
Further, the axial length L of the enlarged portion 62 and the axial length L ′ of the guide portion 60 are set so that the former L is longer than the latter L ′. When the length L of the enlarged portion 62 is shorter than the length L ′ of the guide portion 60, the effect of improving the valve closing response is reduced.
[0035]
Furthermore, the interval D 'of the guide portion side gap 70a is set to 15 to 80 m in order to realize high valve opening response and low valve opening bounce amount.
In addition to the setting example described above, the dimensions of each part of the movable core 14 and the interval between the side gaps 70 are appropriately set to values at which desired characteristics can be obtained in each fuel injector according to the specifications of the fuel injector. Can do.
[0036]
(Second, third and fourth embodiments)
The fuel injection devices according to the second, third and fourth embodiments of the present invention are shown in FIGS. 8, 9 and 10, respectively. In each embodiment, components that are substantially the same as those in the first embodiment are denoted by the same reference numerals.
[0037]
In the fuel injection device 100 of the second embodiment shown in FIG. 8, the generatrix of the tapered surface forming the enlarged portion 102 of the movable core 14 is configured by a curve that curves to the outer peripheral side.
In the fuel injection device 150 of the third embodiment shown in FIG. 9, the generatrix of the tapered surface forming the enlarged portion 152 of the movable core 14 is composed of two straight lines having different inclination angles with respect to the central axis. However, the inclination angle with respect to the central axis of the straight line on the downstream side of the two straight lines constituting the bus is set larger than that of the straight line on the upstream side.
[0038]
In the fuel injection device 200 of the fourth embodiment shown in FIG. 10, the enlarged portion 202 of the movable core 14 includes a tapered portion 204 and a straight portion 206. The tapered portion 204 is formed in a tapered shape that decreases in diameter as it approaches the downstream end portion 16 of the movable core 14 from the downstream end portion of the guide portion 60. Thereby, the space | interval in the outer periphery of the taper part 204 among the expansion part side gaps 70b is gradually expanded as it goes to an axial direction downstream side, and is expanded rather than the space | interval D 'of the guide part side gap 70a. The straight portion 206 is formed in a rotating columnar shape extending straight in the axial direction from the downstream end portion 16 of the movable core 14 toward the upstream side, and is connected to the downstream side of the tapered portion 204. Thereby, the space | interval in the outer periphery of the straight part 206 among the expansion part side gaps 70b is larger than the space | interval D 'of the guide part side gap 70a.
[0039]
According to the second to fourth embodiments described above, the valve opening bounce of the valve member 20 is suppressed and the valve closing response is improved by the same principle as the first embodiment. Further, according to the second to fourth embodiments, since the guide portion 60 is guided by the housing 11, the movement stability of the movable core 14 is improved. In the second to fourth embodiments, the downstream end interval D of the enlarged portion side gap 70b, the axial length L of the enlarged portions 102, 152, 202, the axial length L ′ of the guide portion 60, and the guide About the space | interval D 'of the part side gap 70a, it can set similarly to the setting example regarding a 1st Example.
[0040]
(Fifth embodiment)
A fuel injection apparatus according to a fifth embodiment of the present invention is shown in FIG. In addition, the same code | symbol is attached | subjected to the component substantially the same as a 1st Example.
In the fuel injection device 250 of the fifth embodiment, no guide portion is provided in the movable core 14, and the enlarged portion 252 corresponding to the enlarged portion 62 of the first embodiment is located upstream from the downstream end 16 of the movable core 14. It extends to the part 15.
[0041]
According to the fifth embodiment, valve opening bounce of the valve member 20 is suppressed and valve closing response is improved by the same principle as in the first embodiment. In the fifth embodiment, the downstream end interval D of the enlarged portion side gap 70b and the ratio L / D between the downstream end interval D and the axial length L of the enlarged portion 252 are set for the first embodiment. It can be set in the same way.
[0042]
In the plurality of embodiments described above, the recessed portions 52 are formed in an annular shape on the outer peripheral side of the protruding portion 50, but a predetermined number of recessed portions 52 are spaced apart from each other in the circumferential direction on the outer peripheral side of the protruding portion 50. You may open and form. Further, in the above-described embodiments, the protruding portion 50 and the recessed portion 52 are connected in a stepped manner, but the recessed portion 52 is gradually recessed from the outer peripheral edge of the protruding portion 50 toward the outer peripheral edge of the movable core 14. May be formed. Further, the entire upstream end face 15a of the movable core 14 may be formed in a flat surface perpendicular to the central axis without forming the recess 52 in the movable core 14 as in the above-described embodiments.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view schematically showing a main part of a fuel injection device according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a fuel injection device according to a first embodiment of the present invention.
3 is a plan view schematically showing an upstream end portion of the movable core shown in FIG. 1. FIG.
4 is a cross-sectional view for explaining the operation of the fuel injection device according to the first embodiment of the present invention, corresponding to FIG. 1. FIG.
FIG. 5 is a characteristic diagram for comparing the operation of the fuel injection device according to the first embodiment of the present invention and the operation of the conventional device shown in FIG. 12;
FIG. 6 is a characteristic diagram for explaining a fuel injection amount of the fuel injection device according to the first embodiment of the present invention.
FIG. 7 is a characteristic diagram for explaining a setting example of a side gap interval of the fuel injection device according to the first embodiment of the present invention.
FIG. 8 is a cross-sectional view schematically showing a main part of a fuel injection device according to a second embodiment of the present invention.
FIG. 9 is a cross-sectional view schematically showing a main part of a fuel injection device according to a third embodiment of the present invention.
FIG. 10 is a cross-sectional view schematically showing a main part of a fuel injection device according to a fourth embodiment of the present invention.
FIG. 11 is a cross-sectional view schematically showing a main part of a fuel injection device according to a fifth embodiment of the present invention.
FIG. 12 is a cross-sectional view schematically showing a main part of a conventional fuel injection device.
[Explanation of symbols]
10, 100, 150, 200, 250 Fuel injection device
11 Housing (Valve body)
12 Fixed core
13 Downstream end of fixed core
13a Downstream end face of fixed core
14 Movable core
15 Upstream end of movable core
15a Upstream end face of movable core
16 Downstream end of movable core
17 Valve body
18b nozzle hole
18 Valve body (valve body)
20 Valve member
40 Drive unit
43 Coil part
50 Protrusion
52 dent
56 Projecting end face of projecting part
57 Bottom of recess
60 Guide
62,102,152,202,252 Enlarged part
70 Side gap
70a Guide side gap
70b Gap on the enlarged side
80 core room
204 Taper
206 Straight section

Claims (5)

A cylindrical valve body forming a fuel passage for supplying fuel to the nozzle hole;
A movable core accommodated in the valve body so as to be reciprocally movable;
A stationary core that is immovably accommodated in the valve body, and whose downstream end surface faces the upstream end surface of the movable core;
The valve body is housed in the valve body so as to be able to reciprocate integrally with the movable core, and the movable core moves upstream to approach the fixed core, thereby opening the nozzle hole, and the movable core is separated from the fixed core. A valve member that closes the nozzle hole by moving to the downstream side,
By energizing to open the nozzle hole, a magnetic flux passing through the fixed core, the movable core, and the valve body is formed, and the movable core is driven to be sucked toward the fixed core to close the nozzle hole. A coil portion that allows the movable core to be separated from the fixed core when the energization is stopped,
A fuel injection device comprising:
The upstream end surface of the movable core forms a recess in the outermost periphery,
The outer peripheral wall of the movable core forms an annular side gap in cross section with the inner peripheral wall of the valve body,
The movable core has, on the outer peripheral wall, an enlarged portion that enlarges the interval of the side gap on the outer periphery of the downstream end than the interval on the outer periphery of the upstream end,
The enlarged portion is formed in a tapered shape having a diameter that decreases as it approaches the downstream end of the movable core, and fuel flows into the recess through the outer peripheral side of the enlarged portion. apparatus. The enlarged portion extends a predetermined length from the downstream end of the movable core toward the upstream side,
The movable core has a guide portion on the outer peripheral wall that extends straight in the axial direction from the upstream end to the downstream and continues to the enlarged portion.
The fuel injection device according to claim 1, wherein the guide portion is guided in an axial direction by an inner peripheral wall of the valve body. 3. The fuel injection device according to claim 2, wherein an axial length L of the enlarged portion is set to be equal to or longer than an axial length L ′ of the guide portion. 4. The fuel injection device according to claim 1, wherein an interval D of the side gap in the outer periphery of the downstream end portion of the movable core is set to 0.2 to 0.6 mm. L / D is the ratio between the distance D of the side gap at the downstream side end portion outer periphery of the movable core and the axial length L of the front Symbol enlargements, be in the range of 10 / 3-30 The fuel-injection apparatus as described in any one of Claims 1-4 characterized by these.

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