JP2005194880A - Fuel injection valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection valve smoothly reciprocatingly moving a movable core by facilitating the processing of a tubular member covering the outer peripheries of a fixed core and the movable core. <P>SOLUTION: The tubular member 12 covers the outer peripheries of the movable core 26 and the fixed core 30 to form a magnetic circuit with the movable core 26 and the fixed core 30. A valve body 20 supports a valve member 22 so as to be reciprocatingly moved. A gap 110 formed at the entire outer periphery of the movable core 26 by the movable core 26 and the small diameter part 14 of the tubular member 12 is set approximately to such a size that does not come into contact with the small diameter part 14 of the movable core 26. The size of the gap 10 formed on the radial one side of the movable core is desirably be 50 μm or more. Also, the size of the gap 110 on one side is desirably set to 500 μm or less to secure a magnetic attractive force acting between the fixed core 30 and the movable core 26. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel injection valve that covers the outer periphery of a fixed core and a movable core with a cylindrical member.

  Conventionally, as in Patent Document 1, a fuel injection valve in which the outer periphery of a fixed core and a movable core is covered with a magnetic pipe is known.

JP 2002-206468 A

In the configuration in which the outer periphery of the fixed core and the movable core is covered with a cylindrical member and the movable core is supported by the cylindrical member, not limited to the magnetic pipe shown in Patent Document 1, the movable core and the cylindrical shape when the movable core reciprocates. In order to reduce the sliding resistance with the member, it may be necessary to ensure the accuracy of the coaxiality, roundness and surface roughness of the cylindrical member. Therefore, there is a problem that the number of processing steps for the cylindrical member increases and the manufacturing cost increases.
The present invention has been made to solve the above problems, and provides a fuel injection valve that facilitates the processing of a cylindrical member that covers the outer periphery of a fixed core and a movable core, and smoothly reciprocates the movable core. Objective.

According to the first aspect of the present invention, a gap is formed on the entire outer periphery of the movable core so as to prevent the cylindrical member covering the outer periphery of the movable core from contacting the movable core. Since the cylindrical member that covers the outer periphery of the movable core does not contact the movable core, the movable core smoothly reciprocates. Moreover, since the cylindrical member which covers the outer periphery of a movable core and a movable core do not contact, a process of a cylindrical member is easy.
According to the first aspect of the present invention, since the valve member that reciprocates together with the movable core is supported by the valve body so as to be capable of reciprocating, the axial displacement of the movable core can be reduced.

  According to the second aspect of the present invention, at least a portion covering the outer periphery of the movable core of the cylindrical member is formed of a magnetic material. As described above, since the cylindrical member that covers the outer periphery of the movable core does not contact the movable core, for example, a plate-like magnetic base material is pressed to form a magnetic pipe, and the inner periphery of the magnetic pipe facing the movable core The surface can be used as it is without being processed. Therefore, it is easy to manufacture the cylindrical member. Moreover, since the part which covers the outer periphery of the movable core of a cylindrical member is a magnetic material, the amount of magnetic flux which flows between a movable core and a cylindrical member increases. Accordingly, the magnetic attractive force for attracting the movable core increases.

  Here, when the gap between the cylindrical member covering the outer periphery of the movable core and the movable core is smaller than 50 μm, it is difficult to manage the gap so that the cylindrical member and the movable core do not contact each other. Further, when the gap between the cylindrical member and the movable core is larger than 500 μm, the amount of magnetic flux flowing between the movable core and the cylindrical member decreases, and the magnetic attractive force acting between the fixed core and the movable core decreases. . Here, the size of the gap formed on the entire circumference of the movable core between the movable core and the cylindrical member represents the size of the gap on one side of the gap formed on both sides in the radial direction. Therefore, in the invention described in claim 3, by making the gap between the cylindrical member and the movable core 50 μm or more and 500 μm or less, it is possible to easily manage the gap where the movable core and the cylindrical member are not in contact with each other and to fix the gap. A decrease in magnetic attractive force acting between the core and the movable core can be prevented.

  By the way, in the configuration in which the valve body supports the valve member so as to be able to reciprocate as in the first aspect of the invention, if the sliding clearance between the valve body and the valve member is larger than 15 μm, the movable core is displaced. There is a risk of waking up and coming into contact with the tubular member. Further, if the sliding clearance between the valve body and the valve member is smaller than 3 μm, the sliding resistance between the valve body and the valve member is increased, which may hinder the reciprocating movement of the valve member. Here, the size of the sliding clearance between the valve body and the valve member represents the size of the sliding clearance on one side of the sliding clearance formed on both sides in the radial direction. Therefore, in the invention described in claim 4, the sliding clearance between the valve body and the valve member is set to 3 μm or more and 15 μm or less. As a result, the axial displacement of the movable core can be reduced, and the sliding resistance between the valve body and the valve member can be reduced.

  The magnetic flux flowing on the opposite side of the fixed core facing the movable core mainly flows between the movable core and acts as a magnetic attractive force that attracts the movable core. On the other hand, in the magnetic flux flowing through the fixed core at a position away from the side facing the movable core toward the non-movable core, the ratio of the magnetic flux that does not act as a magnetic attractive force increases. Therefore, in the invention described in claim 5, the magnetic path area of the fixed core on the side of the non-movable core is made larger than the outer diameter of the movable core by increasing the outer diameter of the fixed core on the side of the movable core. It is larger than the magnetic path area on the opposite side. As a result, the magnetic path area of the fixed core at a high ratio where a magnetic flux that does not act as a magnetic attraction force is flowing increases, and the amount of magnetic flux that acts as a magnetic attraction force increases.

  Furthermore, the opposing end surface side of the opposing portion facing the movable core, that is, the opposing end surface side facing the movable core of the fixed core is recessed radially inward from the large diameter portion of the fixed core. As a result, since the outer diameter of the opposed end surface of the fixed core is smaller than the outer diameter of the large diameter portion, the area where the opposed end surface of the fixed core faces the magnetic member installed on the outer periphery of the movable core is reduced. Accordingly, it is possible to suppress a part of the magnetic flux flowing between the fixed core and the movable core from flowing between the magnetic member installed on the outer periphery of the movable core and the fixed core. Thereby, as described above, the decrease in the magnetic flux flowing between the fixed core and the movable core, which is increased by providing the large-diameter portion having an outer diameter larger than that of the movable core on the non-movable core side of the fixed core, can be reduced. Therefore, the magnetic attractive force for attracting the movable core is increased, and the valve opening response is improved.

In the invention of claim 5, the outer diameter is increased to increase the magnetic path area of the fixed core. Therefore, if the amount of change in diameter is the same, the increase amount of the magnetic path area is increased compared to the inner diameter. be able to.
Further, when a coil spring is accommodated as an urging member for urging the movable core and the valve member in one direction on the inner periphery of the fixed core, when the inner diameter of the fixed core is reduced, the coil spring accommodated on the inner periphery of the fixed core is reduced. The diameter becomes smaller. As a result, the spring constant of the coil spring rises and the adjustment range of the urging force becomes narrow, which causes a problem that adjustment of the urging force becomes difficult. On the other hand, in the first aspect of the present invention, the magnetic path area of the fixed core can be increased by increasing the outer diameter without changing the inner diameter of the fixed core. An increase in the spring constant of the spring can be prevented. Therefore, the adjustment range of the urging force is widened and the adjustment of the urging force is easy.

Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
The fuel injection valve according to the first embodiment of the present invention is shown in FIG. The fuel injection valve 10 is a fuel injection valve for a gasoline engine.
The magnetic pipe 12 as a cylindrical member is entirely formed of a magnetic material, and is formed in a bottomed cylindrical shape from the fuel inlet to the bottom outer wall of the valve body 20 with a substantially uniform thickness. For example, as shown in FIG. 3, the magnetic pipe 12 is integrally formed as a single member from a plate-like magnetic base material 200 such as SUS by pressing and drawing. A fuel passage 100 is formed in the magnetic pipe 12, and a valve body 20, a valve member 22, a movable core 26, a spring 28 as a biasing member, a fixed core 30, and the like are accommodated in the fuel passage 100.

  The magnetic pipe 12 has a small-diameter portion 14 covering the outer periphery of the valve body 20 and the movable core 26, an intermediate-diameter portion 16 covering the outer periphery of the fixed core 30, and a large-diameter portion 18 on the fuel inlet side in this order from the fuel injection side. doing. The small diameter portion 14 and the medium diameter portion 16 are magnetic portions that cover the outer periphery of the movable core 26 and the fixed core 30. The magnetic pipe 12 has a stepped shape, and a step 15 is formed between the small-diameter portion 14 and the medium-diameter portion 16 in accordance with the outer diameter difference between the movable core 26 and the fixed core 30.

The valve body 20 is fixed to the inside of the bottom of the nozzle hole side tip of the small diameter portion 14 by welding. The valve body 20 has a valve seat 21 on the inner peripheral wall on which a valve member 22 can be seated.
The valve member 22 is coupled to the movable core 26 and reciprocates together with the movable core 26. As shown in FIG. 1, four chamfers 23 are formed in the circumferential direction where the valve member 22 slides with the inner peripheral surface of the valve body 20, and the chamfer 23 and the inner peripheral surface of the valve body 20 are formed. Fuel flows between the two. Between the chamfer 23 and the chamfer 23, four sliding portions 24 extending in the axial direction are formed in the circumferential direction. The sliding portion 24 slides with the inner peripheral wall of the valve body 20. In the first embodiment, the chamfer 23 and the sliding portion 24 are formed at four locations in the circumferential direction. However, in order to prevent the valve member 22 from being inclined with respect to the valve body 20, it is sufficient that the number is three or more.

  The movable core 26 is fixedly coupled to the end of the valve member 22 on the side opposite to the valve body by welding or the like. A fuel passage 102 that communicates the fixed core 30 side and the valve body 20 side is formed at the joint between the movable core 26 and the valve member 22. The spring 28 as an urging member is directly locked to the fixed core 30 and urges the movable core 26 and the valve member 22 in the direction in which the valve member 22 is seated on the valve seat 21.

As shown in FIG. 2, the fixed core 30 is formed in a cylindrical shape and is accommodated in the magnetic pipe 12. The fixed core 30 is installed on the side opposite to the valve member 22 with respect to the movable core 26 and faces the movable core 26.
As shown in FIG. 1, the area of the opposed surface 32 of the fixed core 30 facing the movable core 26 is substantially equal to the area of the opposed surface 27 of the movable core 26. The fixed core 30 includes a straight portion 34 having an equal magnetic path area in the axial direction from the facing surface 32 to the non-movable core side, a tapered portion 35 having an outer diameter increasing from the straight portion 34 toward the non-movable core side, and A large-diameter portion 36 having a magnetic path area larger than that of the straight portion 34 is provided on the side of the tapered portion 35 opposite to the movable core.

The magnetic members 40 and 42 shown in FIG. 2 are magnetically connected to each other and installed on the outer peripheral side of the coil 44. The magnetic member 40 is magnetically connected to the small diameter portion 14, and the magnetic member 42 is magnetically connected to the medium diameter portion 16. The magnetic pipe 12, the movable core 26, the fixed core 30, and the magnetic members 40 and 42 form a magnetic circuit.
A spool 46 around which the coil 44 is wound is attached to the outer periphery of the magnetic pipe 12. The resin housing 50 covers the outer periphery of the magnetic pipe 12 and the coil 44. The terminal 52 is electrically connected to the coil 44 and supplies a drive current to the coil 44.

  The fuel that has flowed into the fuel passage 100 from above in FIG. 2 of the magnetic pipe 12 flows between the fuel passage in the fixed core 30, the fuel passage 102 of the movable core 26, the chamfer 23 of the valve member 22, and the inner peripheral surface of the valve body 20. In the meantime, when the valve member 22 is separated from the valve seat 21, it passes through the opening formed between the valve member 22 and the valve seat 21, and is injected from the injection hole 20a.

In the fuel injection valve 10 configured as described above, when energization to the coil 44 is turned off, the valve member 22 is moved downward in FIG. 2, that is, in the valve closing direction by the spring 28, and the valve member 22 is moved to the valve seat 21. The injection hole 20a is closed and fuel injection is shut off.
When energization of the coil 44 is turned on, magnetic flux flows through a magnetic circuit including the magnetic pipe 12, the movable core 26, the fixed core 30, and the magnetic members 40 and 42, and a magnetic attraction force is generated between the fixed core 30 and the movable core 26. Will occur. Then, together with the movable core 26, the valve member 22 moves toward the fixed core 30 against the urging force of the spring 28, and the valve member 22 is separated from the valve seat 21. Thereby, fuel is injected from the nozzle hole 20a. The maximum lift amount of the valve member 22 is defined by the movable core 26 being locked to the fixed core 30.

Next, the gap 110 between the movable core 26 and the small diameter portion 14 and the sliding clearance 112 between the valve body 20 and the valve member 22 will be described.
A gap 110 (d shown in FIG. 1B) formed on the entire outer periphery of the movable core 26 between the movable core 26 and the small diameter portion 14 is large enough that the movable core 26 does not contact the small diameter portion 14. The thickness is set to 50 μm or more. Further, if the gap between the movable core 26 and the small diameter portion 14 becomes too large, the amount of magnetic flux flowing between the movable core 26 and the small diameter portion 14 decreases, and magnetic attraction acting between the fixed core 30 and the movable core 26 is achieved. Power is reduced. Therefore, it is desirable that the gap between the movable core 26 and the small diameter portion 14 is set to 500 μm or less to ensure a magnetic attractive force acting between the fixed core 30 and the movable core 26. Here, the size of the gap 110 formed between the movable core 26 and the small diameter portion 14 on the entire outer periphery of the movable core 26 represents the size of one side of the gap 110 formed on both sides in the radial direction. To do.

  The sliding clearance 112 formed in the radial direction between the valve body 20 and the sliding portion 24 of the valve member 22 is set to such an extent that the movable core 26 can be prevented from being off-axis and contacting the small diameter portion 14. It is desirable that it is 15 μm or less. If the sliding clearance 112 becomes too small, the sliding resistance between the valve body 20 and the valve member 22 increases, and smooth reciprocation of the valve member 22 is hindered. Therefore, it is desirable to set the sliding clearance 112 to 3 μm or more. Here, the size of the sliding clearance 112 formed in the radial direction between the valve body 20 and the sliding portion 24 of the valve member 22 is the size of one side of the sliding clearance 112 formed on both sides in the radial direction. .

Next, the magnetic flux flowing through the fixed core 30 will be described.
Magnetic flux that flows in the vicinity of the facing surface 32 of the fixed core 30, which is the facing side facing the movable core 26, mainly flows between the movable core 26 and serves as a magnetic attractive force that attracts the movable core 26 toward the fixed core 30. Works. On the other hand, in the large-diameter portion 36 on the side opposite to the movable core 30 of the fixed core 30, the ratio of the magnetic flux that does not flow between the movable core 26 and does not act as a magnetic attractive force is higher than that on the facing surface 32 side. Yes. Therefore, the total amount of magnetic flux flowing is larger on the large diameter portion 36 side than on the facing surface 32 side of the fixed core 30. Accordingly, in the first embodiment, the magnetic path area of the movable core 26 is not increased, and the outer diameter of the large diameter portion 36 on the side opposite to the movable core of the fixed core 30 is made larger than that of the opposing surface 32 side, so The magnetic path area is made larger than the facing surface 27 side of the movable core 26. Thereby, without increasing the weight of the movable core 26, the amount of magnetic flux acting as a magnetic attractive force can be increased, and the magnetic attractive force for attracting the movable core 26 to the fixed core 30 can be increased. Therefore, the valve opening response is improved.

  Further, since the magnetic path area of the straight portion 34 of the fixed core 30 is smaller than the magnetic path area of the large-diameter portion 36 on the non-movable core side of the fixed core 30 and acts as a magnetic diaphragm, an increase in saturation attractive force can be suppressed. Accordingly, the amount of residual magnetic flux decreases, and the magnetic attractive force acting between the fixed core 30 and the movable core 26 at the start of valve closing decreases. Accordingly, the valve closing response is improved.

  As the taper angle of the taper portion 35 with respect to the facing surface 32 increases, the suction force increases. This is because when the taper angle is increased, the outer peripheral side surface of the fixed core 30 on the facing surface 32 side does not suddenly approach the inner peripheral surface of the magnetic pipe 12 from the straight portion 34 toward the large diameter portion 36, and the fixed core 30 is movable. This is because magnetic flux leakage from the side facing the core 26 to the magnetic pipe 12 is reduced.

(Second Embodiment)
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.
Four spline grooves 62 are formed in the circumferential direction obliquely with respect to the shaft on the outer peripheral surface of the valve member 60 at a position sliding with the valve body 20. Between the spline groove 62 and the spline groove 62, four sliding portions 63 that slide on the inner peripheral surface of the valve body 20 are formed in the circumferential direction. In the second embodiment, four spline grooves 62 and four sliding portions 63 are formed in the circumferential direction. However, in order to prevent the valve member 60 from tilting with respect to the valve body 20, the number may be three or more.

Since the spline groove 62 is formed obliquely with respect to the shaft, the periphery of the spline groove 62 of the valve member 60 is gripped by a processing jig in order to process the contact portion 64 of the valve member 60 seated on the valve seat 21. However, the shape of the spline groove 62 is not transferred to the contact portion 64.
In the above-described plurality of embodiments of the present invention described above, the gap is such that the outer periphery of the fixed core 30 and the movable core 26 is covered with the integrally formed magnetic pipe 12 and the entire outer periphery of the movable core 26 is not in contact with the magnetic pipe 12. 110 is formed. Since the movable core 26 does not contact the magnetic pipe 12, the movable core 26 reciprocates smoothly.
Moreover, since the magnetic material covers the outer periphery of the movable core 26 and the fixed core 30, the magnetic attractive force for attracting the movable core 26 increases.

  In addition, the size of the gap 110 is set to be larger than the normal sliding clearance of about 20 to 30 μm so that the movable core 26 does not contact the magnetic pipe 12 due to the axis deviation. It is possible to prevent the magnetic pipe 12 and the movable core 26 from coming into contact with each other even if a machining error occurs in the magnetic flux 26. Therefore, it is easy to manage the gap 110 that prevents the movable core 26 and the magnetic pipe 12 from contacting each other, and the magnetic pipe 12 and the movable core 26 can be easily processed. As a result, the processing accuracy of the coaxiality and roundness of the magnetic pipe 12 and the roughness of the sliding surface sliding with the movable core 26 can be reduced. Therefore, it can be used as a cylindrical member without finishing the inner peripheral surface of the magnetic pipe 12 formed by, for example, pipe pressing and drawing.

  Further, in the above embodiments, the magnetic path area on the anti-movable core side is made larger than the magnetic path area of the fixed core 30 on the side facing the movable core 26. Thereby, since the magnetic attraction force which attracts the movable core 26 increases without increasing the weight of the movable core 26, the valve opening response is improved. In addition, since the magnetic path area of the fixed core 30 on the side facing the movable core 26 is smaller than that on the anti-movable core side and acts as a magnetic diaphragm, the saturation attractive force is reduced. As a result, the amount of residual magnetic flux decreases, and the valve closing response is improved.

  The magnetic pipe 12 that forms a magnetic circuit with the fixed core 30 and the movable core 26 covers the outer periphery of the fixed core 30 and the movable core 26 and supports the fixed core 30. If the axial position of the fixed core 30 is adjusted in the magnetic pipe 12, variations in the gap between the movable core 26 and the fixed core 30 can be prevented. Alternatively, by adjusting the axial position of the fixed core 30 in the magnetic pipe 12, the gap between the movable core 26 and the fixed core 30 can be adjusted to obtain a desired injection amount.

(Other embodiments)
In the above embodiments, one magnetic pipe 12 is formed from the magnetic base material 200, but a plurality of magnetic pipes may be joined by welding or the like to form a magnetic pipe used in the present invention. Moreover, you may form the cylindrical member which has a nonmagnetic part between the magnetic parts which cover the outer periphery of a fixed core and a movable core from a composite magnetic material. Further, if a cylindrical member that has a magnetic part covering the outer periphery of the fixed core and the movable core and forms a magnetic circuit with the fixed core and the movable core is formed, the entire cylindrical member is formed of a magnetic material. There is no need, for example, a cylindrical member may be formed by joining a magnetic member and a non-magnetic member by welding or the like. In addition, if the cylindrical member covers the outer periphery of the fixed core and the movable core and forms the magnetic circuit with the fixed core and the movable core, the cylindrical member may be entirely formed of a nonmagnetic material.
Further, although the magnetic path area of the fixed core on the side opposite to the movable core is larger than the magnetic path area of the movable core on the side facing the fixed core, the magnetic path areas of the fixed core and the movable core may be the same.

(A) is sectional drawing which shows the periphery of the movable core and valve member by 1st Embodiment of this invention, (B) is BB sectional drawing of (A), (C) is (A). It is a CC sectional view taken on the line. It is sectional drawing which shows the fuel injection valve by 1st Embodiment. It is explanatory drawing which shows the manufacturing process of a magnetic pipe. It is sectional drawing which shows the fuel injection valve by 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel injection valve, 12 Magnetic pipe (cylindrical member), 14 Small diameter part (magnetic part), 16 Medium diameter part (magnetic part), 20 Valve body, 21 Valve seat, 20a Injection hole, 26 Movable core, 28 Spring ( Urging member), 30 fixed core, 44 coils

Claims (5)

A fixed core;
A movable core facing the fixed core;
A valve member that reciprocates with the movable core and intermittently injects fuel from the nozzle hole;
A valve body having a valve seat that shuts off fuel injection from the nozzle hole when the valve member is seated, and permits fuel injection from the nozzle hole when the valve member is seated;
A coil that generates a magnetic attractive force between the fixed core and the movable core by energization;
A cylindrical member provided to cover the outer periphery of the fixed core and the movable core, and forming a magnetic circuit with the fixed core and the movable core;
A fuel injection valve comprising:
The valve body supports the valve member in a reciprocable manner,
A fuel injection valve, wherein a gap for preventing contact between the movable core and the cylindrical member is formed between the cylindrical member and the entire outer periphery of the movable core.   The fuel injection valve according to claim 1, wherein at least a portion of the cylindrical member covering an outer periphery of the movable core is formed of a magnetic material.   The fuel injection valve according to claim 1 or 2, wherein the gap formed between the magnetic part and the movable core is not less than 50 µm and not more than 500 µm.   The fuel injection valve according to any one of claims 1 to 3, wherein a sliding clearance between the valve body and the valve member is 3 µm or more and 15 µm or less.   The fixed core has a facing portion facing the movable core and a magnetic path area which is provided on a side opposite to the movable core of the facing portion and larger than an outer diameter of the movable core than a side of the movable core facing the fixed core. The opposed end surface side of the opposed portion facing the movable core is recessed radially inward of the large diameter portion. The fuel injection valve according to item.

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