JP2009108842A - Fuel injection valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To set a second spring set load to a desired value without set length adjustment by an adjustment means such as a spacer, and precise part dimension management in a fuel injection valve allowing relative motion of a needle and a movable core and provided with a second spring abutting on the movable core and urging the needle and the movable core to a valve open direction. <P>SOLUTION: The spring constant of a second spring 42 abutting on the movable core 30 and biasing the needle 20 and the movable core 30 in the valve open direction is set smaller than the spring constant 38 of a first spring 38 abutting on the needle 20 and biasing the needle 20 and the movable core 30. Consequently, variation of set load of the second spring 42 due to variation of set length of the second spring 42 can be reduced. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fuel injection valve that intermittently injects fuel.

  In the fuel injection valve disclosed in Patent Document 1, a needle is slidably inserted into a movable core, and the needle and the movable core can be moved relative to each other. However, when the movable core is sucked toward the fixed core, the needle and the movable core are engaged, and the needle and the movable core move together in the valve opening direction. Also, when the needle moves in the valve closing direction, the needle and the movable core are engaged with each other so that the needle and the movable core move integrally.

Further, as the needle and the movable core can be moved relative to each other, two types of springs for biasing the needle and the movable core are provided. Specifically, the needle and the movable core are urged in the valve closing direction by the first spring that contacts the needle, and the needle and the movable core are urged in the valve opening direction by the second spring that contacts the movable core. Yes. And the set load of a 1st spring is set with the pushing amount of an adjusting pipe.
JP-T-2001-511868

  However, since the set length of the second spring cannot be adjusted after the assembly, in order to adjust the set length of the second spring in advance by adjusting means such as a spacer, or to reduce variations in the set length of the second spring. The set load of the second spring is set to a desired value by precisely managing the component dimensions. Therefore, there is a problem of high cost.

  In view of the above, the present invention provides a fuel injection valve in which the needle and the movable core can move relative to each other, without adjusting the set length by an adjusting means such as a spacer, or performing precise component dimensional management. Is set to a desired value.

  In the fuel injection valve in which the needle (20) and the movable core (30) are assembled so as to be relatively movable, the present invention is in contact with the needle (20) so that the needle (20) and the movable core (30) are closed. A first spring (38) for urging and a second spring (42) for abutting the movable core (30) and urging the needle (20) and the movable core (30) in the valve opening direction; The spring constant of the spring (42) is set to be smaller than the spring constant of the first spring (38).

  In this way, it is possible to reduce the set load variation of the second spring (42) due to the set length variation of the second spring (42). The set load of the second spring (42) can be set to a desired value without managing the dimensions.

  In this case, if the set load of the first spring (38) is set larger than the set load of the second spring (42), the valve can be reliably closed when the coil is not energized.

  In addition, the code | symbol in the bracket | parenthesis of each means described in a claim and this column shows the correspondence with the specific means as described in embodiment mentioned later.

(First embodiment)
A first embodiment of the present invention will be described. FIG. 1 is a cross-sectional view showing the configuration of the fuel injection valve according to the first embodiment.

  As shown in FIG. 1, the fuel injection valve includes a metal cylindrical housing 10, which has a magnetic part 10a and a nonmagnetic part 10b. The magnetic part 10a and the nonmagnetic part 10b are: For example, they are joined by laser welding. The nonmagnetic portion 10b prevents a magnetic short circuit between the magnetic portion 10a and a nozzle holder 16 described later. In addition, the housing 10 may be formed into a cylindrical integrated body using a magnetic material, and the portion corresponding to the nonmagnetic portion 10b may be made nonmagnetic by heat processing.

  An inlet member 12 is installed at one end of the housing 10 in the axial direction. More specifically, the inlet member 12 is press-fitted to the inner peripheral side of the housing 10. An inlet portion fuel passage hole 120 is formed in the inlet member 12, and fuel is supplied to the inlet portion fuel passage hole 120 from a pressure pump (not shown). Further, a filter member 14 for removing foreign matter is inserted into the inlet fuel passage hole 120, and the fuel supplied to the inlet fuel passage hole 120 passes through the filter member 14 to the inner peripheral side of the housing 10. Inflow.

  At the other end of the housing 10 in the axial direction, a cylindrical nozzle holder 16 made of a magnetic metal is installed. The nozzle holder 16 is joined to the nonmagnetic portion 10b of the housing 10 by, for example, laser welding.

  A metal cylindrical nozzle body 18 is installed at an end of the nozzle holder 16 on the side opposite to the housing 10. More specifically, the nozzle body 18 is fixed to the nozzle holder 16 by, for example, press fitting or welding. The nozzle body 18 is formed with an injection hole 180 and a truncated cone valve seat 181.

  On the inner peripheral side of the housing 10, the nozzle holder 16, and the nozzle body 18, a metal columnar needle 20 is accommodated so as to be movable in the axial direction. The needle 20 is disposed substantially coaxially with the nozzle body 18, and a nozzle body portion fuel passage 22 through which fuel flows is formed between the needle 20 and the nozzle body 18.

  A contact portion 200 that opens and closes between the nozzle hole 180 and the nozzle body portion fuel passage 22 by being in contact with and separated from the valve seat 181 of the nozzle body 18 is formed at the end portion of the needle 20 on the nozzle body 18 side. On the other end side of the needle 20, a flange portion 201 that can be engaged with a movable core 30 described later is formed.

  A needle fuel passage vertical hole 202 extending in the axial direction from the end surface of the needle 20 on the side opposite to the nozzle body 18 is formed at the center of the needle 20 in the radial direction. In addition, a needle fuel passage lateral hole 203 that connects the needle fuel passage vertical hole 202 and the nozzle body portion fuel passage 22 to each other is formed at an intermediate portion in the axial direction of the needle 20.

  The fuel injection valve has a drive unit that drives the needle 20 with a magnetic attractive force. The drive unit includes a spool 24, a coil 26, a fixed core 28, a movable core 30, and magnetic members 32 and 39. Yes.

  The spool 24 is formed of a resin into a cylindrical shape and is installed on the outer peripheral side of the housing 10. A coil 26 is wound around the outer periphery of the spool 24, and the coil 26 is connected to a connector terminal 36 of the connector portion 34.

  A fixed core 28 is installed on the inner peripheral side of the coil 26 with the housing 10 in between. The fixed core 28 is formed in a cylindrical shape from a magnetic material such as iron, and is fixed to the inner peripheral side of the housing 10 by, for example, press fitting. A spring insertion hole 280 extending in the axial direction and penetrating through is formed at the center of the fixed core 28 in the radial direction. The spring insertion hole 280 communicates with the inlet fuel passage hole 120 and the needle fuel passage vertical hole 202. To do.

  The movable core 30 is formed in a cylindrical shape using, for example, a magnetic material such as iron, and is disposed on the inner peripheral side of the housing 10 and the nozzle holder 16 and opposed to the surface of the fixed core 28 on the nozzle body 18 side. It is housed in a movable state.

  A needle insertion hole 300 extending in the axial direction and penetrating through is formed at the radial center of the movable core 30, and the needle 20 is slidably inserted into the needle insertion hole 300. In other words, the needle 20 and the movable core 30 are assembled so as to be relatively movable.

  The collar portion 201 of the needle 20 can be engaged with the surface of the movable core 30 on the fixed core 28 side. When the needle 20 moves in a direction that blocks between the nozzle hole 180 and the nozzle body portion fuel passage 22 (that is, in the valve closing direction), the flange portion 201 is engaged with the movable core 30 to move the movable core 30. Also move together. Further, when the movable core 30 moves toward the fixed core 28 (that is, in the valve opening direction), the movable core 30 engages with the flange portion 201 and the needle 20 also moves integrally.

  The magnetic member 32 is formed of a magnetic material such as iron, and covers the outer peripheral side of the coil 26.

  A first spring 38 that urges the needle 20 and the movable core 30 in the valve closing direction is inserted into the spring insertion hole 280 of the fixed core 28, and an adjusting pipe 40 that adjusts the set load of the first spring 38. It is press-fitted.

  The first spring 38 has one end in contact with the needle 20 and the other end in contact with the adjusting pipe 40. The set load of the first spring 38 can be adjusted by adjusting the fixing position of the adjusting pipe 40 with respect to the fixed core 28.

  The nozzle body fuel passage 22 is provided with a second spring 42 that abuts the surface of the movable core 30 on the side opposite to the fixed core 28 and biases the needle 20 and the movable core 30 in the valve opening direction.

  Both the first spring 38 and the second spring 42 are compression coil springs. The spring constant k2 of the second spring 42 is set smaller than the spring constant k1 of the first spring 38. Further, the set load F1 of the first spring 38 is set larger than the set load F2 of the second spring 42.

  Next, the operation of the fuel injection valve configured as described above will be described. First, when energization of the coil 26 is stopped, no magnetic attractive force is generated between the fixed core 28 and the movable core 30. Since the set load of the first spring 38 is larger than the set load of the second spring 42, the needle 20 and the movable core 30 are urged toward the valve closing direction by the first spring 38. As a result, the contact portion 200 of the needle 20 contacts the valve seat 181 of the nozzle body 18 and the gap between the nozzle hole 180 and the nozzle body portion fuel passage 22 is blocked, so that fuel is not injected.

  On the other hand, when the coil 26 is energized, magnetic flux flows through the magnetic members 32 and 39, the nozzle holder 16, the movable core 30, the fixed core 28, and the magnetic part 10a by the magnetic field generated in the coil 26, thereby forming a magnetic circuit. As a result, a magnetic attractive force is generated between the fixed core 28 and the movable core 30. Then, the movable core 30 moves toward the fixed core 28 by the magnetic attraction force, and the needle 20 also moves integrally with the movable core 30 because the flange portion 201 is engaged with the movable core 30. As a result, the contact portion 200 of the needle 20 is separated from the valve seat 181 of the nozzle body 18 so that the nozzle hole 180 and the nozzle body portion fuel passage 22 communicate with each other. As a result, the fuel flowing into the fuel injection valve from the inlet fuel passage hole 120 is injected through the spring insertion hole 280, the needle fuel passage vertical hole 202, the needle fuel passage lateral hole 203, and the nozzle body portion fuel passage 22. It reaches the hole 180 and is ejected from the nozzle hole 180.

  In the fuel injection valve of the present embodiment, the spring constant k2 of the second spring 42 is set smaller than the spring constant k1 of the first spring 38. Hereinafter, the reason why k1> k2 will be described.

  First, there are the following two points as preconditions and restrictions when designing the second spring 42. First, variation in the set length L2 of the second spring 42 occurs due to the influence of the processing and assembly accuracy of the nozzle holder 16, the nozzle body 18, the needle 20 and the movable core 30. In addition, since the single product processing accuracy is generally about ± 0.05 mm, the variation in the set length L2 of the second spring 42 is ± 0.2 mm. Second, in order to ensure the performance of the fuel injection valve, the variation in the set load F2 of the second spring 42 needs to be suppressed to ± 1N or less.

  Here, FIG. 2 is a diagram for examining a range in which the spring constant k2 of the second spring 42 is established under the two preconditions and restrictions. As shown in FIG. 2, when the variation ΔF2a of the set load F2 of the second spring 42 due to the variation of the free length of the second spring 42 and the variation of the spring constant k2 of the second spring 42 is about 0.8N, the second spring 42 The variation ΔF2b in the set load F2 of the second spring 42 due to the variation 0.4mm in the set length L2 of 42 should be about 1.2 N or less. Therefore, the spring constant k2 of the second spring 42 needs to be about 3 N / mm or less.

  On the other hand, as a restriction at the time of designing the first spring 38, there is a restriction on the set length L1 of the first spring 38. Incidentally, there is a restriction to suppress the increase in the total length of the fuel injection valve due to the restriction of mounting the fuel injection valve on the engine (interference with other parts / installation in the engine room). At that time, it is difficult to shorten the entire length of the filter member 14 in order to secure the filtration area of the filter member 14, and the adjusting pipe 40 must have a press-fit length so as not to move after press-fitting. Because it has to be, this too can not shorten the total length. Therefore, there is a restriction on the set length L1 of the first spring 38.

  Considering general engine mounting conditions, the set length L1 of the first spring 38 is desirably set to 20 mm or less. In that case, the spring constant k1 of the first spring 38 must be about 4 N / mm or more from the relationship between the contact height and the spring constant shown in FIG.

  From the above, by setting k1> k2, the set load F2 of the second spring 42 is set to a desired value without adjusting the set length by adjusting means such as a spacer or performing precise part dimension management. be able to. In other words, by setting k1> k2, it is possible to provide a fuel injection valve that satisfies the required performance without adjusting the second spring 42 while keeping the mounting restrictions and component accuracy.

(Other embodiments)
In the above embodiment, one compression coil spring is used as the second spring 42, but the second spring 42 may be a spring of a modified example described below. The second spring 42 of the first modification shown in FIG. 4 is formed in a cylindrical shape with an elastic body (for example, rubber or resin) whose volume is changed by an external force. The second spring 42 of the second modified example shown in FIG. 5 is a thin metal plate formed into a bellows shape. The 2nd spring 42 of the 3rd modification shown in Drawing 6 is a leaf spring which consists of a metal thin plate. In the fourth modified example shown in FIG. 7, two compression coil springs are used as the second spring 42.

It is sectional drawing which shows the structure of the fuel injection valve which concerns on 1st Embodiment of this invention. It is a figure for examining the range where the spring constant k2 of the 2nd spring 42 is materialized. It is a figure which shows the relationship between contact | adherence height and a spring constant. FIG. 7 is a cross-sectional view of a main part showing a first modification of the second spring. FIG. 10 is a cross-sectional view of a main part showing a second modification of the second spring. FIG. 10 is a cross-sectional view of a main part showing a third modification of the second spring. FIG. 10 is a cross-sectional view of a main part showing a fourth modification of the second spring.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 20 ... Needle, 26 ... Coil, 28 ... Fixed core, 30 ... Movable core, 38 ... 1st spring, 42 ... 2nd spring, 180 ... Injection hole.

Claims (3)

The needle (20) and the movable core (30) assembled so as to be relatively movable are provided, and the movable core (30) is sucked toward the fixed core (28) by energizing the coil (26), thereby In the fuel injection valve in which the needle (20) and the movable core (30) are engaged to move integrally in the valve opening direction and fuel is injected from the injection hole (180),
A first spring (38) that abuts the needle (20) and urges the needle (20) and the movable core (30) in a valve closing direction, and abuts the needle (20) to the movable core (30). 20) and a second spring (42) for urging the movable core (30) in the valve opening direction, and the spring constant of the second spring (42) is larger than the spring constant of the first spring (38). A fuel injection valve characterized by being set small. The fuel injection valve according to claim 1, wherein the first spring (38) and the second spring (42) are compression coil springs. The fuel injection valve according to claim 1 or 2, wherein a set load of the first spring (38) is set larger than a set load of the second spring (42).

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