JP2010203375A - Fuel injection valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection valve including a fixed core 32 achieving both high magnetic attraction and magnetic dissipation property. <P>SOLUTION: The fixed core 32 includes a first cylindrical portion 40 and a second cylindrical portion 41. The fixed core 32 has different magnetic characteristics in the first cylindrical portion 40 positioned in an inner peripheral portion and the second cylindrical portion 41 positioned in an outer peripheral portion. The second cylindrical portion 41 has a higher specific resistance than the first cylindrical portion 40. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel injection valve that injects and supplies fuel to an internal combustion engine.

  2. Description of the Related Art As a fuel injection device for an internal combustion engine, there is a fuel injection valve that controls opening and closing of a valve member provided in a fuel flow passage with an electromagnet. The fuel injection valve according to the prior art is opened by applying an electromagnetic force to a movable core integral with a valve member and magnetically attracting the movable core to a fixed core.

  In such a fuel injection valve, it is desirable to control the fuel injection amount with high accuracy, so that the timing for opening and closing the valve member is close to the rise and fall of the pulse waveform applied to the coil constituting the fuel injection valve. Is required. In other words, it is required to shorten the time from when the energization to the coil is turned on until the valve is opened, and to shorten the time from when the coil is energized to when the coil is closed.

  In response to such demands, in the conventional fuel injection valve, the opening time and closing time of the fuel injection valve are shortened by adjusting the arrangement and length of the non-magnetic portion, the movable core, the fixed core, and the coil. is doing. Specifically, it is configured such that the ratio occupied by the nonmagnetic portion is increased in the inner space of the coil. As a result, the inductance of the coil is reduced. Therefore, when energization of the coil is turned on, the value of the current flowing through the coil rises quickly and the valve opening time is shortened. In addition, when the power supply to the coil is turned off, the value of the current flowing through the coil is quickly reduced, so that the valve closing time is shortened (see, for example, Patent Document 1).

JP 2002-48031 A

  In the fuel injection valve described in Patent Document 1, the response to energization pulses is improved by reducing the inductance of the coil. However, in such a configuration, there is a problem that the magnetic attractive force is reduced (Patent Document). 1 (see FIG. 4).

  As means for improving the magnetic attractive force, a means for increasing the area of the portion where the fixed core opposes the movable core and a means using a high magnetic flux density material for the fixed core are mainly used. In the case of means for increasing the area of the portion where the fixed core faces the movable core, there is a problem that the size of the fixed core is increased. Further, in the case of means using a high magnetic flux density material for the fixed core, the magnetic attractive force can be increased, but there is a problem that the magnetic breakage is deteriorated due to the increased magnetic attractive force. Therefore, it has been difficult to achieve both high magnetic attractive force and magnetic severability.

  Accordingly, the present invention has been made in view of the above-described problems, and an object of the present invention is to provide a fuel injection valve having a fixed core that can achieve both high magnetic attraction force and magnetic breakability.

  The present invention employs the following technical means in order to achieve the aforementioned object.

In the invention according to claim 1, a cylindrical housing in which a nozzle hole for injecting fuel is formed;
A valve member that is provided in the housing, opens and closes the injection hole by reciprocating displacement, and intermittently injects fuel from the injection hole;
A movable core provided to reciprocate together with the valve member in the housing;
A cylindrical fixed core fixed at a predetermined position in the housing;
A coil that generates a magnetic force that attracts the movable core to the fixed core by being energized,
The fixed core is a fuel injection valve characterized in that the inner peripheral portion and the outer peripheral portion have different magnetic characteristics, and the outer peripheral portion of the fixed core has a higher specific resistance than the inner peripheral portion of the fixed core.

  According to the first aspect of the present invention, the fixed core has different magnetic characteristics between the inner peripheral portion and the outer peripheral portion, and the outer peripheral portion of the fixed core has a higher specific resistance than the inner peripheral portion of the fixed core. The inner peripheral portion of the fixed core has a larger amount of magnetic flux than the outer peripheral portion, and thus contributes greatly to the magnetic attraction characteristics. The outer peripheral portion of the fixed core easily generates eddy currents when the magnetic flux disappears, The Applicant has found that the influence of arcing extinction) is significant. Paying attention to the characteristics of the inner and outer peripheries of the fixed core, and increasing the specific resistance (electric resistance value) of the outer periphery of the fixed core as described above, the magnetic breakage of the fixed core is improved. Can do. Further, for example, by using a high magnetic flux density material for the inner peripheral portion of the fixed core, the amount of magnetic flux can be further increased, so that the magnetic attractive force can be increased and a high magnetic attractive force can be obtained. Further, the outer peripheral portion of the fixed core is also made of a magnetic material having a high specific resistance, so that the outer peripheral portion of the fixed core can also contribute to the magnetic attractive force. Therefore, the fixed core of the present invention can achieve both high magnetic attraction force and magnetic severance, and therefore the time for opening and closing the fuel injection valve can be shortened.

  As described above, when the opening time and closing time of the fuel injection valve are shortened, the characteristics of the fuel injection rate approach the waveform of the drive signal applied to the coil, so that the signal width of the drive signal and the fuel injection amount are approximately proportional. In addition, the fuel injection amount can be controlled with high accuracy. In particular, when the fuel injection amount is small, such as during idling, excessive fuel injection can be suppressed. Therefore, fuel consumption can be improved and the amount of harmful substances contained in the exhaust gas can be reduced.

  Further, the invention according to claim 2 is characterized in that the outer peripheral portion of the fixed core has a higher porosity than the inner peripheral portion of the fixed core.

  According to the second aspect of the present invention, since the outer peripheral portion of the fixed core has a higher porosity than the inner peripheral portion of the fixed core, the specific resistance of the outer peripheral portion can be increased by the pores. Therefore, for example, even when the outer peripheral portion and the inner peripheral portion are made of materials having the same magnetic characteristics, the specific resistance of the outer peripheral portion can be increased by the porosity. As a result, a fixed core having the above-described functions and effects can be realized.

  Further, the invention according to claim 3 is characterized in that the outer peripheral portion of the fixed core is formed by metal powder injection molding.

  According to the invention described in claim 3, since the outer peripheral portion of the fixed core is formed by metal powder injection molding, the porosity of the outer peripheral portion of the fixed core is increased. Therefore, as described above, the specific resistance of the outer peripheral portion of the fixed core can be increased.

  Further, the invention according to claim 4 is characterized in that the outer peripheral portion of the fixed core is a sintered body of metal powder.

  According to the invention described in claim 4, since the outer peripheral portion of the fixed core is a sintered body of metal powder, the porosity of the outer peripheral portion of the fixed core is increased. Therefore, as described above, the specific resistance of the outer peripheral portion of the fixed core can be increased.

It is sectional drawing which shows the injector 10 of 1st Embodiment. FIG. 2 is an enlarged cross-sectional view showing a part of an injector 10. 3 is a cross-sectional view showing a fixed core 32. FIG. FIG. 3 is a front view showing a first tube part 40. It is sectional drawing which shows the fixed core 32A of 2nd Embodiment.

  Hereinafter, a plurality of embodiments for carrying out the present invention will be described with reference to the drawings. In some embodiments, portions corresponding to the matters described in the preceding embodiments are denoted by the same reference numerals, and redundant descriptions may be omitted. In addition, when a part of the configuration is described in each embodiment, the other parts of the configuration are the same as those of the embodiment described in advance. In addition to the combination of parts specifically described in each embodiment, the embodiments may be partially combined as long as the combination does not hinder the combination.

(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS. A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view showing an injector 10 of the first embodiment. FIG. 2 is an enlarged cross-sectional view showing a part of the injector 10. The injector 10 is a fuel injection valve, and is applied to, for example, a port injection type gasoline engine. When the injector 10 is applied to a port injection type gasoline engine, the injector 10 is mounted on an engine head (not shown).

  The injector 10 includes a cylindrical member 11 extending in a predetermined axial direction Z (opening / closing direction Z), a filter member 12 provided inside the cylindrical member 11, a housing holder 13 covering the cylindrical member 11, and a resin housing 14 covering the cylindrical member 11. The needle 10 is accommodated in the injector 10 so as to be reciprocally displaceable in the axial direction Z, and the drive unit 16 drives the needle 15.

  Hereinafter, as the direction of the injector 10, the direction in which the cylindrical member 11 extends is referred to as an axial direction Z (up and down direction in FIG. 1), and one of the axial directions Z is referred to as a valve opening direction Z1 (upward in FIG. 1). May be referred to as a valve closing direction Z2 (downward in FIG. 1).

  The cylindrical member 11 is formed in a cylindrical shape extending in the axial direction Z. The cylindrical member 11 is open at an end located in the valve opening direction Z <b> 1 and serves as a fuel inlet 17. Fuel is supplied to the fuel inlet 17 from a fuel pump (not shown). The cylinder member 11 includes a first magnetic part 18 having magnetism, a second magnetic part 19, and a nonmagnetic part 20 having no magnetism. The first magnetic part 18 is located in the valve opening direction Z1 with respect to the nonmagnetic part 20. The second magnetic part 19 is located in the valve closing direction Z2 relative to the nonmagnetic part 20. Therefore, the end portion of the cylindrical member 11 located in the valve closing direction Z <b> 2 becomes the second magnetic portion 19. Such a nonmagnetic portion 20 prevents a magnetic short circuit between the first magnetic portion 18 and the second magnetic portion 19. The first magnetic part 18 and the second magnetic part 19 and the nonmagnetic part 20 are integrally connected, for example, by laser welding. Further, the cylindrical member 11 may be partly magnetized or non-magnetic by, for example, thermal processing after being integrally formed.

  A stepped portion 42 is formed in the outer peripheral surface portion of the cylindrical member 11 so as to expand radially outward. In other words, a stepped portion 42 that is convex outward in the radial direction is formed on the outer peripheral surface portion of the cylindrical member 11. Such a stepped portion 42 is a portion that contacts the housing holder 13. Specifically, the surface portion of the stepped portion 42 located in the valve closing direction Z2 contacts the surface portion of the housing holder 13 located in the valve opening direction Z1. In other words, the distal end portion of the housing holder 13 and the tubular member 11 are configured to abut the distal end portion of the housing holder 13 against the stepped portion 42 of the tubular member 11.

  The filter member 12 is press-fitted on the inner peripheral side of the cylindrical member 11. The filter member 12 removes foreign matters contained in the fuel. Therefore, the fuel supplied to the fuel inlet 17 flows down in the valve closing direction Z <b> 2 of the cylindrical member 11 via the filter member 12.

  The housing holder 13 is formed in a cylindrical shape. On the outer periphery of the housing holder 13, an enlarged diameter portion 22 is formed as a step for locking the injector 10 to an engine intake pipe (not shown). Moreover, the housing holder 13 has magnetism. The housing holder 13 is an outer frame member and covers the outer peripheral side of a coil 23 described later. The housing holder 13 is magnetically connected to the first magnetic part 18 and the second magnetic part 19. Specifically, as shown in FIG. 2, the end portion of the housing holder 13 positioned in the valve opening direction Z <b> 1 contacts the outer peripheral surface portion of the first magnetic portion 18. Further, the end portion of the housing holder 13 located in the valve closing direction Z2 is in contact with the outer peripheral surface portion of the second magnetic portion 19.

  The resin housing 14 is formed in a cylindrical shape and is made of resin. The resin housing 14 is provided on the side of the housing holder 13 in the valve opening direction Z1. The resin housing 14 covers the outer periphery of the cylindrical member 11 and covers the outer periphery of the housing holder 13 on the valve opening direction Z1 side.

  The nozzle body 21 is formed in a cylindrical shape, and is fixed to an end portion of the cylindrical member 11 positioned in the valve closing direction Z2, for example, by press fitting or welding. The nozzle body 21 has a valve seat portion 24 on the inner peripheral wall on which the needle 15 can be seated. A cup-shaped injection hole plate 25 is fixed to the outer peripheral wall of the nozzle body 21 by welding so as to cover the end of the nozzle body 21 located in the valve closing direction Z2. The nozzle hole plate 25 is formed in a thin plate shape, and a plurality of nozzle holes 26 communicating the inner wall surface and the outer wall surface are formed at the center. A plate holder 27 for maintaining the joined state between the nozzle hole plate 25 and the nozzle body 21 is mounted outside the nozzle hole plate 25. The plate holder 27 is opened so as not to close the nozzle hole 26.

  The needle 15 is a valve member and is accommodated on the inner peripheral side of the cylinder member 11 and the nozzle body 21 so as to be capable of reciprocating in the axial direction Z. The needle 15 reciprocates in the axial direction Z to open and close the nozzle hole 26 and intermittently inject fuel from the nozzle hole 26. The needle 15 is disposed substantially coaxially with the nozzle body 21. The needle 15 has a hollow bottomed cylindrical shape having a fuel passage 28 therein, and a contact portion 29 is formed on the bottom side (the lower side in FIG. 1). The contact portion 29 can be seated on a valve seat portion 24 formed on the nozzle body 21. When the contact portion 29 is seated on the valve seat portion 24, the injection hole 26 is closed and the fuel injection is shut off.

  A fuel hole 30 penetrating the side wall of the needle 15 is formed on the upstream side (the upper side in FIG. 1) of the contact portion 29. The fuel that has flowed into the fuel passage 28 of the needle 15 passes from the inside to the outside through the fuel hole 30 and flows into a passage defined by the contact portion 29 and the valve seat portion 24.

  Next, the drive unit 16 that drives the needle 15 will be described mainly with reference to FIG. The drive unit 16 drives the needle 15 along the axial direction Z. The drive unit 16 includes a coil device 31, a fixed core 32, a movable core 34, a connector 35, and a spring 36.

  The coil device 31 includes a coil 23 and a terminal 37. The coil 23 generates a magnetic force that attracts the movable core 34 to the fixed core 32 when energized. In other words, when the coil 23 is energized, the coil 23 sucks the movable core 34 in the suction direction that is the valve opening direction Z1. Therefore, the valve opening direction Z1 and the suction direction are the same direction. Further, the valve closing direction Z2 and the direction opposite to the suction direction are the same direction. The coil 23 has a cylindrical shape, and a fixed core 32 is disposed in the inner space thereof.

  The terminal 37 has conductivity and is electrically connected to the coil 23. The terminal 37 is pulled out to the connector 35 provided in the resin housing 14. The terminal 37 is electrically connected to an external electric circuit (not shown) attached to the connector 35, and the energization state of the coil 23 is controlled by the external electric circuit.

  The fixed core 32 is formed in a cylindrical shape from a magnetic material. The fixed core 32 is fixed to the non-magnetic portion 20 of the cylindrical member 11 and the inner wall of the first magnetic portion 18 by press-fitting. The fixed core 32 is provided on the valve opening direction Z1 side with respect to the movable core 34. The lower end surface portion of the fixed core 32 faces the upper end surface portion of the movable core 34 located on the side opposite to the injection hole 26. The lower end surface portion of the fixed core 32 and the upper end surface portion of the movable core 34 are separated from each other when the valve is closed.

  The lower end surface portion of the fixed core 32 located in the valve closing direction Z2 is arranged at a position where the nonmagnetic portion 20 exists in the axial direction Z. In other words, with respect to the axial direction Z, the end portion of the nonmagnetic portion 20 located in the valve opening direction Z1 is located in the valve opening direction Z1 and located in the valve closing direction Z2 with respect to the lower end surface portion of the fixed core 32. The end portion of 20 is positioned in the valve closing direction Z2 with respect to the axial direction Z rather than the lower end surface portion of the fixed core 32.

  The upper end surface portion of the fixed core 32 located in the valve opening direction Z1 is arranged at a position where the first magnetic portion 18 exists with respect to the axial direction Z. Further, the upper end surface portion of the fixed core 32 is disposed at a position facing the stepped portion 42 with respect to the axial direction Z. In other words, the upper end surface portion of the fixed core 32 is arranged at a position where the end portion of the housing holder 13 located in the valve opening direction Z <b> 1 exists with respect to the axial direction Z.

  The movable core 34 is fixed to the end of the needle 15 located in the valve opening direction Z1 by welding or the like. The movable core 34 is installed on the inner peripheral side of the cylindrical member 11 so as to be capable of reciprocating in the axial direction Z. Therefore, the movable core 34 is reciprocally displaced in the axial direction Z together with the needle 15. The movable core 34 is formed in a cylindrical shape from a magnetic material such as iron. The space inside the cylindrical movable core 34 communicates with the fuel passage 28 of the needle 15.

  The upper end surface portion of the movable core 34 located in the valve opening direction Z1 is arranged at a position where the nonmagnetic portion 20 exists with respect to the axial direction Z. In other words, with respect to the axial direction Z, the end portion of the nonmagnetic portion 20 located in the valve opening direction Z1 is located in the valve opening direction Z1 and located in the valve closing direction Z2 relative to the upper end surface portion of the movable core 34. The end portion 20 is positioned in the valve closing direction Z <b> 2 with respect to the axial direction Z rather than the lower end surface portion of the movable core 34. Further, the lower end surface portion of the movable core 34 located in the valve closing direction Z <b> 2 is arranged in a position where the second magnetic portion 19 exists in the axial direction Z.

  The spring 36 is provided on the inner peripheral side of the fixed core 32. One end of the spring 36 is in contact with the movable core 34, and the other end is in contact with the adjusting pipe 39. The spring 36 has a force that extends in the axial direction Z. Therefore, the needle 15 is pressed by the spring 36 in the valve closing direction Z2 seated on the valve seat portion 24.

  The adjusting pipe 39 is press-fitted on the inner peripheral side of the fixed core 32. Thereby, the load of the spring 36 is adjusted by adjusting the press-fitting amount of the adjusting pipe 39. When the coil 23 is not energized, the movable core 34 and the needle 15 are pressed in the valve closing direction Z <b> 2, and the contact portion 29 contacts the valve seat portion 24.

  The housing holder 13 is provided on the outer periphery of the coil 23 as described above. The end portion of the housing holder 13 located in the valve opening direction Z1 is located in the valve opening direction Z1 with respect to the axial direction Z rather than the end portion of the coil 23 located in the valve opening direction Z1. The enlarged diameter portion 22 of the housing holder 13 is substantially in the same position as the lower end surface portion of the movable core 34 in the axial direction Z. In other words, the enlarged diameter portion 22 is a portion constituting a magnetic circuit in the housing holder 13. Thus, the housing holder 13 is magnetically connected to the first magnetic part 18 and the second magnetic part 19. Therefore, the magnetic flux generated by the electromagnetic force generated by energizing the coil 23 is the first magnetic part 18 of the cylindrical member 11, the fixed core 32, the movable core 34, the second magnetic part 19 of the cylindrical member 11, the housing holder 13, and the cylindrical member 11 again. The magnetic circuit which flows in order of the first magnetic part 18 is configured.

  Of the members constituting the magnetic circuit, the members whose positions are fixed are preferably in close contact with each other. In other words, the remaining members except for the movable core 34 are preferably in close contact with each other. Therefore, in the present embodiment, the fixed core 32 is inserted inward of the cylindrical member 11, so that the fixed core 32 and the cylindrical member 11 are in close contact with each other. Moreover, since the part located in the valve closing direction Z2 among the housing holders 13 is provided so as to be in contact with the outer peripheral surface portion of the cylindrical member 11, it is in close contact. Furthermore, since the part located in the valve opening direction Z1 among the housing holders 13 is comprised so that the level | step-difference part 42 of the cylinder member 11 may be contact | abutted, it is contacting closely.

  Next, the configuration of the fixed core 32 will be further described with reference to FIGS. FIG. 3 is a cross-sectional view showing the fixed core 32. The fixed core 32 is formed in a cylindrical shape from a magnetic material. The fixed core 32 is configured so that the magnetic properties are different between the inner peripheral portion and the outer peripheral portion. The magnetic characteristics include, for example, magnetic permeability, magnetic flux density, and specific resistance. In the present embodiment, among the magnetic characteristics, the outer peripheral portion of the fixed core 32 is more specific than the inner peripheral portion of the fixed core 32 (electricity). (Resistance) is configured to be high. The fixed core 32 is a member having the greatest influence on the magnetic attraction characteristics in the magnetic circuit. Here, the magnetic attraction characteristics are, for example, magnetic attraction force and magnetism. In the present embodiment, in order to improve the magnetic attraction characteristics, the magnetic characteristics of the fixed core 32 are changed to two types corresponding to the locations, and the electromagnetic valve performance with good magnetic breakage is realized while having a high magnetic attraction force. .

  The fixed core 32 includes a first tube portion 40 and a second tube portion 41 having different magnetic characteristics. The fixed core 32 has two such cylindrical portions disposed coaxially, the first tubular portion 40 is disposed on the radially inner side of the fixed core 32, and the second tubular portion 41 is disposed radially outside the fixed core 32. It is arranged on the side. In such an arrangement state, the first tube portion 40 and the second tube portion 41 are integrally formed.

  A concave portion 45 that is concave inward in the radial direction is formed on the outer peripheral surface portion (radially outward surface portion) of the first cylindrical portion 40. The concave portion 45 is provided over the entire circumferential direction of the first cylindrical portion 40. The recess 45 is provided in an intermediate portion of the first tube portion 40 in the axial direction Z. Accordingly, the recess 45 is not provided in the vicinity of both end portions in the axial direction Z. In other words, the cross-sectional shape in the axial direction Z of the first cylindrical portion 40 is substantially I-shaped.

  The second cylinder portion 41 is provided in the recess 45. Therefore, the dimension in the axial direction Z of the second cylindrical portion 41 is equal to the dimension in the axial direction Z of the recess 45. The thickness dimension of the second cylinder portion 41 is equal to the depth dimension of the recess 45. Therefore, the outer peripheral surface portion of the second cylindrical portion 41 is flush with the outer peripheral surface portion of the first cylindrical portion 40. As a result, the fixed core 32 becomes a tubular member having an outer peripheral surface with no irregularities as a whole. In the present embodiment, the thickness dimension of the second cylinder portion 41 is smaller than the thickness dimension of the bottom portion of the recess 45. The thickness dimension of the second cylinder portion 41 is set to, for example, ¼ or more and ½ or less of the thickness of the fixed core 32.

  Next, the material of the 1st cylinder part 40 and the 2nd cylinder part 41 is demonstrated. In the present embodiment, the first tube portion 40 and the second tube portion 41 are made of materials having the same magnetic characteristics. The first tube portion 40 is made of, for example, ferritic stainless steel. Similarly, the second cylinder portion 41 is made of, for example, ferritic stainless steel. The first tube portion 40 and the second tube portion 41 are made of materials having the same magnetic characteristics. However, when the first tube portion 40 and the second tube portion 41 are formed as the first tube portion 40 and the second tube portion 41, the second tube portion 41 becomes the first tube. The specific resistance is higher than that of the portion 40. Specifically, the second cylinder part 41 is formed to have a higher porosity than the first cylinder part 40. Here, the porosity is a volume fraction occupied by pores in the molded body. Therefore, a large number of pores (not shown) exist in the second cylinder portion 41. Since such pores are portions that do not contribute to the magnetic properties, the specific resistance increases due to the presence of many pores.

  Next, a method for manufacturing the fixed core 32 will be described. FIG. 4 is a front view showing the first tube portion 40. As described above, the first cylindrical portion 40 is made of, for example, ferritic stainless steel. In order to form the first cylindrical portion 40, the concave portion 45 is formed in the cylindrical member that is a precursor of the first cylindrical portion 40 by processing such as shaving. Next, the 2nd cylinder part 41 is formed in the recessed part 45 by metal powder injection molding (Metal Injection Molding: Abbreviation MIM). Specifically, first, a metal powder as a raw material of the second cylinder portion 41 and a binder (binder) are mixed. Next, the aforementioned mixture is injection-molded in the recess 45. Finally, degreasing and sintering are performed by heating the injection-molded precursor of the second cylindrical portion 41. As a result, the second cylinder portion 41 is formed in the recess 45. Therefore, the 2nd cylinder part 41 is a sintered compact of metal powder. Such a sintered body is characterized in that it includes pores inside, and thus a large number of pores are formed inside the second cylindrical portion 41. The second cylinder part 41 has a larger porosity than the first cylinder part 40.

  Next, the positional relationship between the fixed core 32 and each part will be described with reference to FIG. As described above, the outer peripheral surface portion of the fixed core 32 includes a portion that is the outer peripheral surface portion of the first cylindrical portion 40 and a portion that is the outer peripheral surface portion of the second cylindrical portion 41.

  The upper end surface portion of the first tube portion 40 located in the valve opening direction Z <b> 1 is disposed at a position facing the step portion 42. In other words, the upper end surface portion of the first tube portion 40 is arranged at a position where the end portion of the housing holder 13 located in the valve opening direction Z1 exists with respect to the axial direction Z. Further, the portion where the outer peripheral surface portion of the first tube portion 40 located in the valve opening direction Z1 is exposed, and the cylindrical member 11 and the inner peripheral surface portion facing the exposed portion are close to the second tube portion 41. The remaining parts are in contact with each other, and the remaining parts are separated.

  Further, the outer peripheral surface portion of the second cylindrical portion 41 is in contact with the inner peripheral surface portion of the cylindrical member 11. Moreover, the site | part which the outer peripheral surface part of the 1st cylinder part 40 located in the valve closing direction Z2 is exposed, and the cylinder member 11 and the inner peripheral surface part which oppose the said exposed part are contacting. Thus, the portion in contact with the first tube portion 40 is the inner peripheral surface portion of the nonmagnetic portion 20.

  The upper end surface portion of the second cylindrical portion 41 located in the valve opening direction Z1 is arranged at a position where the first magnetic portion 18 exists with respect to the axial direction Z. Further, the lower end surface portion of the second cylinder portion 41 located in the valve closing direction Z2 is arranged at a position where the nonmagnetic portion 20 exists in the axial direction Z. Accordingly, the second cylindrical portion 41 is disposed so as to straddle the first magnetic portion 18 and the nonmagnetic portion 20.

  Next, the flow of fuel will be described. The fuel flowing in from the fuel inlet 17 of the cylindrical member 11 flows down the cylindrical member 11 toward the nozzle hole 26 (the lower side in FIG. 1). When the tube member 11 flows down, the filter member 12 removes foreign matter in the fuel. The fuel from which the foreign matter has been removed sequentially passes through the inner peripheral side of the adjusting pipe 39, the inner peripheral side of the fixed core 32, the inner peripheral side of the movable core 34, the fuel passage 28 of the needle 15, and the fuel hole 30. It flows to the passage defined by the contact portion 29 and the valve seat portion 24. Thus, when the valve is opened, fuel is injected from the nozzle hole 26.

  Next, the operation of the injector 10 will be described. When the coil 23 is turned off, no magnetic attractive force is generated between the movable core 34 and the fixed core 32. At this time, since the needle 15 is urged in the valve closing direction Z2 by the urging force of the spring 36, the needle 15 moves in the valve closing direction Z2, and the contact portion 29 is seated on the valve seat portion 24. Therefore, the fuel injection from the nozzle hole 26 is stopped.

  When energization of the coil 23 is turned on, magnetic flux flows through a magnetic circuit including the fixed core 32, the movable core 34, the first magnetic part 18, the housing holder 13, and the second magnetic part 19, and the fixed core 32 and the movable core 34 Magnetic attractive force is generated during Thereby, the movable core 34 is attracted to the fixed core 32, and the needle 15 integrated with the movable core 34 also moves to the fixed core 32 side. As the needle 15 moves, fuel is injected from the nozzle hole 26 where the contact portion 29 moves away from the valve seat portion 24. Then, when the movable core 34 and the fixed core 32 abut, the movement of the needle 15 toward the fixed core 32 is limited.

  At this time, the magnetic attractive force of the fixed core 32 is increased if the first cylindrical portion 40 and the second cylindrical portion 41 constituting the fixed core 32 are high magnetic flux density materials. Since the second cylinder part 41 has a large specific resistance as described above, the magnetic flux density is lower than that of the first cylinder part 40. However, the first cylindrical portion 40 located on the inner peripheral side of the fixed core 32 has a high contribution to the magnetic attractive force. Accordingly, since the first tube portion 40 is made of a ferritic stainless steel that is a high magnetic flux density material, and the second tube portion 41 is also made of a ferritic stainless steel that is the same high magnetic flux density material, the magnetic attraction force should be increased. Can do.

  Next, when the energization to the coil 23 is turned off again, the magnetic flux flowing through the magnetic circuit disappears, and the magnetic attractive force between the fixed core 32 and the movable core 34 also disappears. Therefore, the needle 15 is moved again in the valve closing direction Z2 by the urging force of the spring 36, and the contact portion 29 is seated on the valve seat portion 24. Thereby, the fuel injection from the nozzle hole 26 is stopped.

  When the energization is turned off, the magnetic flux flowing through the magnetic circuit disappears. However, the higher the magnetic flux density of the fixed core 32, the longer the magnetic flux disappearance time from when the energization is turned off until the magnetic flux disappears (magnetism breaks). . As described above, since both the first tube portion 40 and the second tube portion 41 are made of a high magnetic flux density material, it may be considered that the time until the magnetism is cut off is long, but the second tube portion 41 is the first tube portion. The specific resistance is higher than 40. Since the second cylindrical portion 41 is located on the outer peripheral portion of the fixed core 32, it is the portion of the fixed core 32 that is closest to the coil 23. Since the second cylindrical portion 41 close to the coil 23 is a portion in which magnetism tends to remain, the influence on the magnetic break is large. In the present embodiment, the second cylinder portion 41 increases the specific resistance and decreases the magnetic flux density. With such a second cylindrical portion 41, even when the second cylindrical portion 41 is made of a high magnetic flux density material, it is possible to improve the magnetic breakage. Therefore, the magnetic flux disappearance time can be made shorter than the configuration in which the second cylindrical portion 41 has the same high magnetic flux density as the first cylindrical portion 40.

  As described above, in the injector 10 of the present embodiment, the fixed core 32 has different magnetic characteristics between the inner peripheral portion and the outer peripheral portion, and the outer peripheral portion of the fixed core 32 is more in proportion than the inner peripheral portion of the fixed core 32. Resistance is high. In the present embodiment, the fixed core 32 includes the first cylindrical portion 40 located on the inner peripheral portion and the second cylindrical portion 41 located on the outer peripheral portion, so that the second cylindrical portion 41 is more than the first cylindrical portion 40. Is configured to have a high specific resistance.

  As described in the operation of the injector 10, the first cylinder portion 40 has a larger amount of magnetic flux than the second cylinder portion 41, and thus contributes greatly to the magnetic attraction characteristics. Of the causes that eddy currents are likely to occur when extinguishing and the magnetic break (arc extinction) is delayed, the influence is great. Paying attention to such characteristics of the first cylinder part 40 and the second cylinder part 41, and increasing the specific resistance (electric resistance value) of the second cylinder part 41 as described above, the eddy current disappearance at the time of magnetism disappearance. Time can be shortened and the magnetic break of the fixed core 32 can be improved. Moreover, since the amount of magnetic flux can be increased more by using high magnetic flux density materials, such as ferritic stainless steel, for the 1st cylinder part 40, magnetic attraction force can be enlarged and high magnetic attraction force is obtained. Obtainable. Furthermore, the 2nd cylinder part 41 can also contribute to a magnetic attraction force by making the 2nd cylinder part 41 into a magnetic material with high specific resistance. As a result, the fixed core 32 of the present embodiment can achieve both high magnetic attraction force and magnetic severability, and therefore the valve opening time and valve closing time of the injector 10 can be shortened.

  Thus, when the valve opening time and valve closing time of the injector 10 are shortened, the characteristics of the fuel injection rate approach the waveform of the drive signal applied to the coil, so that the signal width of the drive signal and the fuel injection amount are substantially proportional, The fuel injection amount can be controlled with high accuracy. In particular, when the fuel injection amount is small, such as during idling, excessive fuel injection can be suppressed. Therefore, fuel consumption can be improved and the amount of harmful substances contained in the exhaust gas can be reduced.

  In other words, in the present embodiment, paying attention to the fact that the inner diameter side of the fixed core 32 has a large contribution to the magnetic attraction characteristics, and the outer peripheral side of the fixed core 32 has a great influence on magnetic breakage (arc extinction). By using two types of materials and a material having a high specific resistance value (electric resistance value) on the surface of the fixed core 32, it is possible to achieve both a high magnetic attractive force and a magnetic break. As a result, the injector 10 can be injected more precisely, and the exhaust gas performance of the engine can be improved.

  In the present embodiment, since the second cylinder portion 41 has a larger porosity than the first cylinder portion 40, the first cylinder portion 40 and the second cylinder portion 41 have magnetic characteristics as in the present embodiment. Even if it consists of an equal material, the specific resistance of the 2nd cylinder part 41 can be made high with a porosity. Therefore, the fixed core 32 having the above-described functions and effects can be realized.

  Furthermore, in the present embodiment, since the second cylinder portion 41 is formed in the recess 45, which is the outer surface of the first cylinder portion 40, by metal powder injection molding, the porosity of the second cylinder portion 41 is increased. Therefore, as described above, the specific resistance of the second cylindrical portion 41 can be increased.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 5 is a cross-sectional view showing a fixed core 32A of the second embodiment. The present embodiment is characterized in that the configuration of the fixed core 32A is different from that of the first embodiment.

  In this Embodiment, the recessed part 45 is not formed in the outer peripheral surface part of 40 A of 1st cylinder parts, but an outer peripheral surface part is a flat cylindrical body. Similarly, a second cylindrical portion 41A having a cylindrical body is provided on the outer peripheral surface portion of the first cylindrical portion 40A. Accordingly, the second cylinder portion 41A is provided over the entire area in the axial direction Z of the outer peripheral surface portion of the first cylinder portion 40A.

  The lower end surface portion of the fixed core 32A is a portion where the upper end surface portion of the movable core 34 collides. Therefore, the lower end surface portion of the fixed core 32A is formed in a flat shape without irregularities so that the upper end surface portion of the movable core 34 does not come into contact with one piece. In the present embodiment, the lower end surface portion of the fixed core 32A is composed of the lower end surface portion of the first cylinder portion 40A and the lower end surface portion of the second cylinder portion 41A. Accordingly, the lower end surface portions of the first tube portion 40A and the second tube portion 41A are configured to be flush with each other.

  Thus, in the present embodiment, the second cylinder portion 41A is provided over the entire outer peripheral surface portion of the first cylinder portion 40A. Accordingly, the volume occupied by the second cylindrical portion 41A in the fixed core 32A is larger than that in the first embodiment. As a result, the effect of the magnetic cut by the second cylinder portion 41A can be increased. Therefore, the valve closing time of the injector 10 can be further shortened.

  In the present embodiment, the lower end surface portions of the first cylindrical portion 40A and the second cylindrical portion 41A are configured to be flush with each other so that the upper end surface portion of the movable core 34 does not come into contact with each other. It is not restricted to such a configuration. For example, you may comprise so that the lower end surface part of 40 A of 1st cylinder parts may be located in the valve closing direction Z2 side rather than the lower end surface part of 41 A of 2nd cylinder parts. As a result, the upper end surface portion of the movable core 34 collides with the lower end surface portion of the first cylindrical portion 40A, and the lower end surface portion of the first cylindrical portion 40A is flattened to prevent the movable core 34 from hitting one side. Can do. Moreover, you may plate on the lower end surface part of 40 A of 1st cylinder parts which protruded in such valve-opening direction Z1. By plating the lower end surface portion of the first cylindrical portion 40A protruding in the valve opening direction Z1, the strength can be increased, and the damage to the lower end surface portion of the first cylindrical portion 40A due to the collision of the movable core 34 can be suppressed. it can.

(Other embodiments)
The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  In the first embodiment described above, the injector 10 is applied to a port-injection gasoline engine. However, the injector 10 is not limited to a port-injection gasoline engine, and may be applied to a direct-injection gasoline engine or a diesel engine. May be.

  In the first embodiment described above, the first tube portion 40 and the second tube portion 41 are both made of a soft magnetic material such as ferritic stainless steel, which is a high magnetic flux density material. Instead, it may be formed of a magnetic material such as pure iron and low carbon steel, which are high magnetic flux density materials.

  In the first embodiment described above, the first cylinder portion 40 and the second cylinder portion 41 are made of the same high magnetic flux density material, but the present invention is not limited to such a configuration, and the second material can be obtained by using different materials. You may comprise so that the specific resistance of the cylinder part 41 may become larger than the 1st cylinder part 40. FIG. In such a configuration, the high magnetic flux density material forming the first tube portion 40 may be the above-described soft magnetic material and iron-cobalt alloy, and the high specific resistance material forming the second tube portion 41. May be an iron-nickel alloy (permalloy), an electromagnetic steel obtained by adding silicon to iron, or an iron-aluminum alloy obtained by adding aluminum to iron.

10 ... Injector (fuel injection valve)
11 ... Cylinder member (housing)
15 ... Needle (valve member)
DESCRIPTION OF SYMBOLS 23 ... Coil 32 ... Fixed core 34 ... Moving core 40 ... 1st cylinder part (inner peripheral part of the fixed core 32)
41 ... 2nd cylinder part (outer peripheral part of the fixed core 32)

Claims (4)

A cylindrical housing in which an injection hole through which fuel is injected is formed;
A valve member that is provided in the housing, opens and closes the nozzle hole by reciprocating displacement, and intermittently injects fuel from the nozzle hole;
A movable core provided to reciprocate together with the valve member in the housing;
A cylindrical fixed core fixed at a predetermined position in the housing;
A coil that generates a magnetic force that attracts the movable core to the fixed core by being energized,
The fuel injection valve, wherein the fixed core has different magnetic characteristics between an inner peripheral portion and an outer peripheral portion, and the specific resistance of the outer peripheral portion of the fixed core is higher than that of the inner peripheral portion of the fixed core.   The fuel injection valve according to claim 1, wherein the outer peripheral portion of the fixed core has a larger porosity than the inner peripheral portion of the fixed core.   The fuel injection valve according to claim 1, wherein the outer peripheral portion of the fixed core is formed by metal powder injection molding.   The fuel injection valve according to claim 1, wherein the outer peripheral portion of the fixed core is a sintered body of metal powder.

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