JP2005030336A - Electromagnetic drive device, and fuel injection valve using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnetic drive device of high responsiveness and durability. <P>SOLUTION: A magnetic part 32 is formed of a green compact material formed by pressurizing magnetic metal powder with a resin. The magnetic part 32 is large in electric resistance, and the eddy current is less liable to generate inside thereof even when a coil is energized or energization is stopped. Responsiveness of a movable core 15 to energization or non-energization to the coil is enhanced. The magnetic part 32, which is formed of the green compact material, is brittle and low in mechanical strength. Therefore, the magnetic part 32 is housed in a skeleton part 31 formed of electromagnetic stainless steel. Even when a fixed core 30 and the movable core 15 are repeatedly collided with each other, only the skeleton part 31 is collided with the movable core 15. Thus, damages to the fixed core 30 is prevented, and responsiveness and durability can be compatibly enhanced. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electromagnetic driving device driven by energizing a coil and a fuel injection valve using the electromagnetic driving device.

  An electromagnetic drive device in which a movable core is attracted to a fixed core by energizing a coil is known. The electromagnetic drive device is applied to a valve device such as a fuel injection valve, an ABS actuator, or a pressure control valve that repeatedly opens and closes at high speed (for example, refer to Patent Document 1 for a fuel injection valve). In such an electromagnetic drive device, the fixed core and the movable core are repeatedly contacted and separated. Therefore, a magnetic material having high mechanical strength such as electromagnetic stainless steel is used for the fixed core and the movable core.

JP 2002-310029 A

  However, a magnetic material such as electromagnetic stainless steel has a relatively small electric resistance. Therefore, an eddy current is generated inside the fixed core when the coil is energized or stopped. Thereby, there exists a problem that the responsiveness with respect to electricity supply to a coil or a stop of electricity supply deteriorates.

  On the other hand, in order to reduce the eddy current generated inside the fixed core, it is conceivable to use a magnetic material having a relatively large electric resistance. As a magnetic material having a large electric resistance, for example, a powder material obtained by solidifying pure iron powder with a resin can be considered. However, for example, a compacted material made of pure iron powder has a problem of low mechanical strength and low durability.

  Therefore, an object of the present invention is to provide an electromagnetic drive device having high responsiveness and durability.

  In the invention according to claim 1, at least one of the fixed core or the movable core has a skeleton part and a magnetic part. By accommodating the magnetic part in the skeleton part having high mechanical strength, the magnetic part is reinforced by the skeleton part. In addition, the magnetic part has a larger electrical resistance than the skeleton part. Therefore, generation of eddy current in the magnetic part is reduced. Accordingly, both responsiveness and durability can be improved.

  In the invention according to claim 2, the end portion of the skeleton portion that faces the fixed core or the movable core protrudes in the axial direction from the magnetic portion. Therefore, the fixed core and the movable core abut on the skeleton portion. Thereby, contact | abutting of the magnetic parts with low mechanical strength is prevented. Therefore, durability can be improved.

  In the invention according to claim 3 or 4, the skeleton has a radial or lattice-shaped contact surface on the side facing the fixed core or the movable core. As a result, the area of the side of the skeleton that faces the fixed core or the movable core is enlarged. Therefore, the force caused by the contact between the fixed core and the movable core acts in a distributed manner on the radial or lattice-shaped contact surface. Therefore, durability can be improved.

In the invention described in claim 5, the skeleton may be formed of a magnetic material. Since the magnetic part has a larger electric resistance than the skeleton part, even when the skeleton part is formed of a magnetic material, an eddy current hardly occurs in the magnetic part. Therefore, responsiveness can be improved.
In the invention of claim 6, the electric resistance of the magnetic part is 10 times or more that of the skeleton part. Therefore, eddy current is unlikely to occur in the magnetic part. Therefore, responsiveness can be improved.
In the invention according to claim 7, the magnetic part is formed of a dust material. Therefore, electrical resistance is large and mechanical strength is low. On the other hand, the magnetic part is reinforced by being accommodated in the skeleton part. Accordingly, both responsiveness and durability can be improved.

  According to an eighth aspect of the present invention, the fuel injection valve includes the electromagnetic drive device according to any one of the first to seventh aspects. Therefore, the responsiveness of the electromagnetic drive device is increased, and the valve opening or closing delay with respect to energization of the coil is reduced. Thereby, the fuel injection for a short period of time and the fuel injection amount can be reduced. Therefore, the degree of freedom of fuel injection can be increased.

Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 2 shows a first embodiment in which the electromagnetic drive device of the present invention is applied to a fuel injection valve (hereinafter, the fuel injection valve is referred to as an “injector”). The injector 10 according to the first embodiment is applied to, for example, a direct injection gasoline engine. The injector 10 is not limited to a direct-injection gasoline engine, but may be applied to a premixed gasoline engine, a diesel engine, or the like. When the injector 10 according to the first embodiment is applied to a direct injection gasoline engine, the injector 10 is mounted on an engine head (not shown).

The housing 11 of the injector 10 is formed in a cylindrical shape. The housing 11 has a first magnetic part 12, a nonmagnetic part 13, and a second magnetic part 14. The nonmagnetic part 13 prevents a magnetic short circuit between the first magnetic part 12 and the second magnetic part 14.
A spool 20 is mounted on the outer peripheral side of the housing 11. A coil 21 is wound around the spool 20. The outer peripheral sides of the spool 20 and the coil 21 are covered with a resin mold 22. The coil 21 is connected to a terminal 24 embedded in a connector 23 formed by a resin mold 22. When the coil 21 is energized via the terminal 24, a magnetic attractive force is generated between the fixed core 30 and the movable core 15. The fixed core 30, the movable core 15 and the coil 21 constitute an electromagnetic drive device. Both the fixed core 30 and the movable core 15 are formed in a cylindrical shape. The fixed core 30 is press-fitted on the inner peripheral side of the housing 11. The movable core 15 can reciprocate in the axial direction on the inner peripheral side of the housing 11. The movable core 15 is integrally formed of electromagnetic stainless steel that is a magnetic material.

  The adjusting pipe 16 is press-fitted on the inner peripheral side of the fixed core 30. A fuel passage 41 is formed on the inner peripheral side of the adjusting pipe 16. The adjusting pipe 16 is in contact with the spring 17 at the end on the movable core 15 side. One end of the spring 17 is in contact with the adjusting pipe 16, and the other end is in contact with the movable core 15. As a result, the spring 17 biases the movable core 15 toward the anti-fixed core. By adjusting the press-fitting amount of the adjusting pipe 16, the load of the spring 17 that biases the movable core 15 is adjusted.

The housing 11 has a fuel inlet 18. Fuel is supplied to the fuel inlet 18 from a fuel pump (not shown). The fuel flowing in from the fuel inlet 18 flows into the inner peripheral side of the housing 11 via the filter 19. The filter 19 removes foreign matters contained in the fuel.
The nozzle holder 50 is formed in a cylindrical shape and is connected to the end of the housing 11. A nozzle body 60 is fixed on the inner peripheral side of the nozzle holder 50. The nozzle body 60 is formed in a cylindrical shape, and is fixed to the nozzle holder 50 by, for example, press fitting or welding. The nozzle body 60 has a valve seat 61 on a conical inner wall surface whose inner diameter decreases as it approaches the tip. An injection hole plate 62 is installed between the end of the nozzle body 60 on the side opposite to the housing and the nozzle holder 50. The nozzle hole plate 62 has one or a plurality of nozzle holes 63. A plate housing 25 made of a magnetic material is installed on the outer peripheral side of the coil 21. The plate housing 25 is magnetically connected to the nozzle holder 50.

  A needle 51 as a valve member is accommodated on the inner peripheral side of the housing 11, the nozzle holder 50 and the nozzle body 60 so as to be reciprocally movable in the axial direction. The needle 51 is arranged coaxially with the nozzle body 60. One end of the needle 51 is connected to the movable core 15. Thereby, the needle 51 can reciprocate in the axial direction integrally with the movable core 15. The needle 51 has an abutting portion 52 that can be seated on the valve seat 61 of the nozzle body 60 at the end on the side opposite to the movable core. A fuel passage 42 through which fuel flows is formed between the needle 51 and the nozzle body 60.

  The fuel that has flowed into the inner peripheral side of the housing 11 from the fuel inlet 18 passes through the filter 19, the fuel passage 41 formed on the inner peripheral side of the adjusting pipe 16, and the inner peripheral side of the fixed core 30. 15 flows into the inner peripheral side. The fuel that has flowed into the inner peripheral side of the movable core 15 flows between the housing 11 and the needle 51 via the fuel hole 43 that communicates the inside and the outside of the movable core 15. The fuel flows into the fuel passage 42 formed between the nozzle body 60 and the needle 51 via the gap between the nozzle holder 50 and the needle 51.

  When the energization of the coil 21 is stopped, the needle 51 is moved downward in FIG. 2 together with the movable core 15 by the urging force of the spring 17. Therefore, the contact portion 52 is seated on the valve seat 61, and the flow of fuel between the fuel passage 42 and the nozzle hole 63 formed in the nozzle hole plate 62 is blocked. Therefore, fuel is not injected from the injection hole 63.

  When the coil 21 is energized, the nozzle holder 50, the first magnetic part 12 of the housing 11, the movable core 15, the fixed core 30, the second magnetic part 14 of the housing 11, and the plate housing 25 are generated by the magnetic flux generated in the coil 21. A magnetic circuit is formed. As a result, a magnetic attractive force is generated between the fixed core 30 and the movable core 15 that are separated from each other. Therefore, the movable core 15 and the needle 51 integral with the movable core 15 move upward in FIG. 2, that is, toward the fixed core 30 against the urging force of the spring 17. The movable core 15 moves until it comes into contact with the fixed core 30. As a result, the contact portion 52 is separated from the valve seat 61, and the fuel passage 42 and the injection hole 63 communicate with each other. Therefore, the fuel is injected from the injection hole 63.

  When energization of the coil 21 is stopped, the magnetic attractive force between the fixed core 30 and the movable core 15 disappears. Thereby, the movable core 15 and the needle 51 integral with the movable core 15 are moved downward in FIG. 2 by the urging force of the spring 17. Therefore, the contact portion 52 is seated on the valve seat 61 again, and the flow of fuel between the fuel passage 42 and the injection hole 63 is blocked. Therefore, the fuel injection ends.

Next, the fixed core 30 will be described in detail.
As shown in FIG. 1, the fixed core 30 is formed in a substantially cylindrical shape, and has a skeleton part 31 and a magnetic part 32. The fixed core 30 is fixed, for example, by being press-fitted into the inner peripheral side of the housing 11. The skeleton part 31 is made of a magnetic material having a mechanical strength higher than that of the magnetic part 32 and having a small electric resistance. The skeleton 31 is made of a magnetic metal such as electromagnetic stainless steel. As shown in FIGS. 1 and 3, the skeleton part 31 has an inner cylinder 33 and an outer cylinder 34. The outer cylinder 34 is substantially concentric with the inner cylinder 33 and is disposed on the radially outer side of the inner cylinder 33. That is, the skeleton part 31 is formed in a double ring shape.

  The inner cylinder 33 and the outer cylinder 34 are connected by spokes 35 that extend in the radial direction. The spokes 35 are formed radially from the inner cylinder 33 to the outer cylinder 34. The inner cylinder 33, the outer cylinder 34, and the spoke 35 constituting the skeleton part 31 are each formed from a thin plate of magnetic metal. The fixed core 30 is held by the housing 11 by the contact between the outer peripheral surface of the outer cylinder 34 and the inner peripheral surface of the housing 11.

  The magnetic part 32 is made of a magnetic material having a lower mechanical strength and a higher electric resistance than the skeleton part 31. In the case of the present embodiment, the magnetic part 32 is formed of a powder material obtained by solidifying magnetic powder with a binder resin. The magnetic substance powder is made of a metal powder. As the metal powder, for example, a magnetic metal powder such as iron or cobalt is used. The magnetic part 32 is formed of a magnetic metal powder such as iron or cobalt alone or mixed.

  The magnetic part 32 is brittle with low mechanical strength because the metal powder is hardened with a binder resin. On the other hand, although the magnetic part 32 solidifies the metal powder with a binder resin, a sufficient magnetic flux flows, but the electric resistance increases. The electric resistance of the magnetic part 32 is 10 times or more that of the skeleton part 31. For example, when pure iron powder is used as the magnetic part 32, the specific resistance of the magnetic part 32 is about 1000 μΩ · m. When electromagnetic stainless steel is used as the skeleton 31, the specific resistance of the skeleton 31 is about 60 μΩ · m. Therefore, in this embodiment, the electric resistance of the magnetic part 32 is about 17 times the electric resistance of the skeleton part 31.

  The magnetic part 32 formed from the dust material is molded into a predetermined shape and then accommodated in the skeleton part 31. As shown in FIG. 4, the skeleton part 31 is partitioned into a plurality of storage chambers 36 in the circumferential direction in a substantially sectoral column shape by an inner cylinder 33, an outer cylinder 34 and spokes 35. The magnetic part 32 is molded into a shape corresponding to the storage chamber 36 of the partitioned skeleton part 31 and is stored in the storage chamber 36. The length of the magnetic part 32 in the axial direction is shorter than that of the skeleton part 31. As a result, as shown in FIG. 1, the end of the skeleton 31 on the movable core 15 side protrudes from the magnetic part 32 toward the movable core 15.

  As described above, the skeleton 31 has the inner cylinder 33, the outer cylinder 34, and the spokes 35. Therefore, when the skeleton part 31 protrudes toward the movable core 15 from the magnetic part 32, a radial contact surface 37 is formed on the side of the skeleton part 31 facing the movable core 15 as shown in FIG. It is formed. The contact surface 37 contacts the end surface 15 a of the movable core 15 on the fixed core 30 side.

  In the first embodiment described above, the fixed core 30 includes the skeleton part 31 and the magnetic part 32. The magnetic part 32 is made of a dust magnetic material having a larger electrical resistance than the skeleton part 31. For this reason, the electrical resistance of the magnetic part 32 increases, and eddy currents are unlikely to occur inside the magnetic part 32 when the energization of the coil 21 is started or stopped. Therefore, the operation responsiveness of the movable core 15 to the start or stop of energization of the coil 21 can be enhanced. Further, since the operation responsiveness of the movable core 15 is increased, the operation responsiveness of the needle 51 to the energization of the coil 21 and the responsiveness of fuel injection from the injection hole 63 are enhanced. Thereby, fuel injection for a short period of time becomes possible, and the fuel injection amount per injection is reduced. Therefore, the injector 10 can increase the degree of freedom of fuel injection.

In the first embodiment, the magnetic part 32 is accommodated in the skeleton part 31. The skeleton part 31 protrudes toward the movable core 15 from the magnetic part 32, and the protruding skeleton part 31 and the movable core 15 come into contact with each other. The skeleton part 31 has higher mechanical strength than the magnetic part 32. Therefore, even if the collision between the fixed core 30 and the movable core 15 is repeated, the magnetic part 32 accommodated in the skeleton part 31 is not damaged. Therefore, even when the magnetic part 32 made of a dust material having a large electric resistance and a low mechanical strength is used, damage to the magnetic part 32 is prevented. Therefore, both improvement in responsiveness and improvement in durability can be achieved.
Further, by accommodating the magnetic part 32 in the skeleton part 31, the magnetic part 32 does not directly contact the movable core 15 even if the contact area between the fixed core 30 and the movable core 15 is increased. Therefore, the shape of the end face 15a on the fixed core 30 side of the movable core 15 can be freely changed, and the degree of freedom in design can be increased.

  In the first embodiment, the radial contact surface 37 is formed on the movable core 15 side of the skeleton 31 by connecting the inner cylinder 33 and the outer cylinder 34 with the spokes 35. As the movable core 15 reciprocates, the end surface of the movable core 15 on the fixed core 30 side repeats contact with the contact surface 37 of the skeleton 31. Therefore, the impact of the collision between the fixed core 30 and the movable core 15 is distributed to the contact surface 37, and the durability of the fixed core 30 and the movable core 15 can be improved.

(Second Embodiment)
An injector according to a second embodiment of the present invention is shown in FIG. Components that are substantially the same as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
In the first embodiment described above, the degree of freedom in designing the movable core 15 that faces the fixed core 30 is improved by housing the magnetic part 32 in the skeleton part 31. Therefore, in 2nd Embodiment, as shown in FIG. 5, the end surface 15a by the side of the fixed core 30 of the movable core 15 can be expanded to radial direction outer side.

  In the second embodiment, even when the end surface 15 a of the movable core 15 is expanded radially outward, the magnetic portion 32 of the fixed core 30 does not directly contact the movable core 15. Therefore, it is possible to achieve both improvement in durability of the fixed core 30 and improvement in design freedom of the movable core 15.

(Third and fourth embodiments)
The fixed core of the injector according to the third and fourth embodiments of the present invention is shown in FIG. 6 or FIG. Components that are substantially the same as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
As shown in FIG. 6, the skeleton 38 of the fixed core 30 according to the third embodiment has only the inner cylinder 33 and the spokes 35. That is, the skeleton part 38 does not have an outer cylinder. The fixed core 30 is press-fitted on the inner peripheral side of the housing 11. Therefore, the radially outer end of the spoke 35 is in contact with the inner peripheral surface of the housing 11.
In the third embodiment, the magnetic part 32 of the fixed core 30 is accommodated in the skeleton part 31 as in the first embodiment. Therefore, damage to the magnetic part 32 is prevented, and both improvement in responsiveness and improvement in durability can be achieved.

As shown in FIG. 7, the skeleton portion 71 of the fixed core 70 according to the fourth embodiment has an inner cylinder 76 in addition to the inner cylinder 73, the outer cylinder 74, and the spoke 75. The middle cylinder 76 is disposed between the inner cylinder 73 and the outer cylinder 74 in the radial direction. By adding the middle cylinder 76, the accommodation chamber 77 formed from the inner cylinder 73, the outer cylinder 74, the spoke 75, and the middle cylinder 76 is formed in a lattice shape. Therefore, the storage chamber 77 and the magnetic part 72 stored in the storage chamber 77 are subdivided as compared to the first embodiment.
In the fourth embodiment, in addition to the same effects as those of the first embodiment, the structural strength of the skeleton 71 is increased. Therefore, the strength of the fixed core 70 can be further improved.

(Other embodiments)
In each of the above-described embodiments, the example in which the fixed core is configured from the skeleton portion and the magnetic portion has been described. However, not only the fixed core but also the movable core may be composed of a skeleton part and a magnetic part. Moreover, you may comprise both a fixed core and a movable core from a frame | skeleton part and a magnetic part.
Moreover, in each embodiment mentioned above, the example which applies the electromagnetic drive device of this invention to the injector of a gasoline engine was demonstrated. However, the electromagnetic drive device of the present invention can be applied as a drive device that opens and closes at high speed and drives a valve that requires high responsiveness, such as a pressure control valve, an ABS actuator, or an intake valve or exhaust valve of an engine.
Furthermore, in each embodiment mentioned above, the example which forms a frame | skeleton part in a single ring, a double ring, or a triple ring was demonstrated. However, the skeleton may be formed in a quadruple ring or more, and the number of spokes may be arbitrarily changed.

It is sectional drawing which shows the principal part of the injector by 1st Embodiment to which the electromagnetic drive device by this invention is applied. It is sectional drawing which shows the injector by 1st Embodiment to which the electromagnetic drive device by this invention is applied. It is a figure which shows the fixed core of the injector by 1st Embodiment to which the electromagnetic drive device by this invention is applied, Comprising: (A) is sectional drawing, (B) is the arrow view seen from the arrow B direction of (A). FIG. It is sectional drawing in the IV-IV line of FIG. It is sectional drawing which shows the principal part of the injector by 2nd Embodiment to which the electromagnetic drive device by this invention is applied. It is a figure which shows the fixed core of the injector by 3rd Embodiment to which the electromagnetic drive device by this invention is applied, Comprising: (A) is sectional drawing, (B) is the arrow view seen from the arrow B direction of (A). FIG. It is a figure which shows the fixed core of the injector by 4th Embodiment to which the electromagnetic drive device by this invention is applied, Comprising: (A) is sectional drawing, (B) is the arrow view seen from the arrow B direction of (A). FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Injector (fuel injection valve), 15 Movable core, 21 Coil, 30, 70 Fixed core, 31, 38, 71 Frame | skeleton part, 32, 72 Magnetic part, 37 Contact surface, 51 Needle (valve member), 60 Nozzle body 63 hole

Claims (8)

An electromagnetic drive device comprising: a fixed core; and a movable core that is attracted to the fixed core by a magnetic attraction generated between the fixed core by energizing a coil and can contact the fixed core,
At least one of the fixed core and the movable core is:
The skeleton,
A magnetic part housed in the skeleton part and formed from a magnetic material having a lower mechanical strength and a higher electrical resistance than the skeleton part;
An electromagnetic drive device comprising: 2. The electromagnetic driving device according to claim 1, wherein an end portion of the skeleton portion facing the fixed core or the movable core protrudes in an axial direction from the magnetic portion. 3. The electromagnetic drive device according to claim 2, wherein the skeleton portion has a radial contact surface on a side facing the fixed core or the movable core. The electromagnetic drive device according to claim 2, wherein the skeleton has a lattice-shaped contact surface on a side facing the fixed core or the movable core. 5. The electromagnetic drive device according to claim 1, wherein the skeleton portion is formed of a magnetic material. The electromagnetic drive device according to claim 5, wherein an electric resistance of the magnetic part is 10 times or more that of the skeleton part. The electromagnetic drive device according to claim 6, wherein the magnetic part is formed of a compacted material obtained by solidifying a magnetic powder with a resin. A nozzle body having a nozzle hole;
An electromagnetic drive device according to any one of claims 1 to 7,
A valve member capable of moving integrally with the movable core and opening and closing the nozzle hole;
A fuel injection valve comprising:

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