JP2014015857A - Electromagnetic fuel injection valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve an engine combustion performance by reducing a return time of a movable core that is constituted so that it can be relatively displaced from a valve body in a fuel injection valve.SOLUTION: An electromagnetic fuel injection valve has: a cylindrical member 2 having an injection hole at a tip; a stationary core 3 housed inside the cylindrical member 2; a movable core 4 that is housed inside the cylindrical member 2 opposite to side end faces of injection holes 71, 72 of the stationary core 3 and that can move forward and backward; and a spring 10 energizing the movable core 4 toward the stationary core 3. Flexion and a load of the spring 10 have a non-linear shape.

Description

  The present invention relates to a fuel injection valve for an automobile internal combustion engine.

  2. Description of the Related Art Conventionally, a fuel injection valve used in an internal combustion engine supplies magnetic flux to a magnetic path including a movable core and a fixed core by flowing a current through a coil, and forms a magnetic attraction gap between the movable core end surface and the fixed core end surface. The valve body is opened and closed by generating a magnetic attractive force and attracting the movable core toward the fixed core. When the movable core is configured to be relatively displaceable in the axial direction of the valve body and the valve body and the movable core cooperate with each other, the original movable core stationary position is passed in the process of reaching the valve closing state. An overshoot may occur, and in order to limit this overshoot and return to the original movable core stationary position, a return spring is installed on the lower side of the movable core to apply a forcing force in the upper direction of the movable core. . (For example, refer to Patent Document 1).

Japanese Patent No. 4211814

  Patent Document 1 describes that a return spring is installed on the lower side (opposite to the fixed core) of the movable core that cooperates with the valve body. This return spring generates a forcing force necessary to stop the valve body in contact with the movable core when the valve body is stationary, and the movable core is lower than the original stationary position when the valve is closed. Force is required to suppress excessive overshoot to the side. In addition, when the movable core returns to the original movable core stationary position from the lowest point of the overshoot and comes into contact with the valve body, the valve body is prevented from being re-actuated to prevent secondary operation. It becomes possible to prevent injection. The secondary injection is one of important functions that must be prevented for the fuel injection valve because not only the flow rate required for engine combustion cannot be optimally controlled but also the exhaust performance is deteriorated.

In recent years, further reduction of exhaust gas and reduction of fuel consumption are required against the background of mitigation of environmental load, and fuel injection valves are required to further reduce minimum injection amount and variation in valve body behavior. Specifically, the required function of the fuel injection valve requires divided injection in one combustion stroke, that is, multiple injections in a minute time.
In response to such a demand for the function of the fuel injection valve, the structure of Patent Document 1 alone is not structurally sufficient to satisfy multiple injections in a very short time.
An object of the present invention is to provide a market with a fuel injection valve that expands the return spring function under the movable core and enables multiple fuel injections in a minute time.

  In order to solve the above problem, in the present invention, in the region where the movable core overshoots below the original stationary position, the spring constant in the region where the overshoot amount is large is larger than the spring constant in the region where the overshoot amount is small. Also, the load characteristic of the return spring on the lower side of the movable core is set so as to be larger.

  According to the present invention, since the spring constant of the return spring increases when the movable core is located in a region where the overshoot amount is large, the forcing force applied in the upward direction of the movable core, that is, the movable core is returned to the original position. The power to return increases. Therefore, it can be seen that the overshoot amount (the lowest point) of the movable core can be reduced as compared with the overshoot amount of the conventional movable core. As a result of reducing the amount of overshoot, the time required for the movable core to return to the original stationary position is shortened, so the time required for the next operation of the valve body can be shortened. It is definitely possible to increase.

The longitudinal cross-sectional view which shows the whole structure of a fuel injection valve. Detailed enlarged view of conventional structure Example drawing Another form of description in the examples Another form of description in the examples Another form of description in the examples

  Embodiments according to the present invention will be described.

  FIG. 1 is a longitudinal sectional view showing the overall configuration of a fuel injection valve according to an embodiment of the present invention. The fuel injection valve of the present embodiment is a fuel injection valve that directly supplies fuel such as gasoline into the cylinder (combustion chamber) of the engine.

  The fuel injection valve body 1 includes a nozzle body 2 that is a metal cylindrical member, a hollow fixed core 3 that is coupled to the inner periphery of the nozzle body 2, and a movable core 4 that is disposed on the opposite surface of the fixed core and is accommodated in the nozzle body 2. The electromagnetic coil 6 disposed on the outer periphery of the nozzle body 2 and the housing 5 disposed on the outer side of the electromagnetic coil 6 include these components as magnetic circuit components.

A valve body 41 is assembled so as to penetrate the inner diameter of the movable core 4, and the movement of the movable core 4 in the axial direction is synchronized with the valve body 41. An orifice cup 7 to which a guide member 12 is assembled is accommodated on the tip side of the nozzle body 2, and injection holes 71 and 72 are arranged in the orifice cup 7. Although there are two nozzle holes 71 and 72 in this cross-sectional view, there may be one or a plurality of three or more.
The fuel is supplied from the upstream side of the fixed core 2, passes through the fixed core 3 and the nozzle body 2, and reaches the orifice cup 7.

  The valve body 41 is provided with a spring force by the spring 8 housed in the fixed core 2, and the valve body 41 contacts the orifice cup 7 by the spring force. This spring force is generated by compressing the spring 8 and transmitted to the valve body 41. This spring force needs to be set appropriately, and is adjusted by the position of the adjuster 9 installed in the fixed core 3 and on the top of the spring 8. The adjuster 9 is on the opposite side of the valve body 41 via the spring 8 and is fixed to the inner diameter of the fixed core 2 by press fitting or the like. When the electromagnetic coil 6 is not energized, the valve body 41 and the orifice cup 7 constitute a metal seal, and fuel is not ejected from the injection holes 71 and 72.

  Further, two guide members 11 and 12 are disposed in the nozzle body 2 at positions separated in the axial direction of the valve body 41. Further, a return spring 10 is installed on the lower side of the movable core 4. In this embodiment, the return spring 10 is installed so as to be sandwiched between the movable core 4 and the guide member 11.

  When an appropriate current is transmitted to and applied to the electromagnetic coil 6 through the lead terminal 13, a magnetic field is generated around the electromagnetic coil 6, and the magnetic circuit (the fixed core 2, the movable core 3, the housing 6, the nozzle holder 2). ), A magnetic force is generated, and an attractive force is generated in the movable core 4 so as to narrow the gap formed at the boundary between the fixed core 3 and the movable core 4. Since the valve body 41 is restricted from moving in the radial direction by the guide members 11 and 12, the valve body 41 starts to move away from the orifice cup 7 as the movable core 4 moves in the axial direction. Therefore, the fuel blocked by the orifice cup 7 and the valve body 41 flows into the injection holes 71 and 72 and is supplied from the fuel injection valve body into the combustion chamber of the engine.

  Thereafter, when the current applied to the electromagnetic coil 5 is interrupted, the magnetic field of the electromagnetic coil 6 disappears, and the magnetic flux decreases from the magnetic circuit. The valve body 41 and the movable core 4 together with the movable core 4 are obtained because the fuel pressure inside the fuel injection valve and the spring force applied to the valve body 41 by the spring 8 exceed the magnetic attractive force generated in the movable core 4 and the spring force by the return spring 10. It moves in the direction of the orifice cup 7, and the valve element 41 finally comes into contact with the orifice cup 7 to constitute a metal seal, thereby supplying the fuel into the combustion chamber. This series of processes is called the operation of the fuel injection valve, that is, the stroke.

  Further, as a control example of the fuel injection valve of the present embodiment, the length of the suction time of the movable core 4 is changed by controlling the length of the current applied to the electromagnetic coil 6, and as a result, the valve body 41 becomes an orifice. There is a method for controlling the time away from the cup 7. Thereby, the fuel injection amount per stroke of the valve body 41 can be controlled.

  Further, in the latter half of the stroke, when the valve body 41 starts to come into contact with the orifice cup 7, the movable core 4 moves away from the original stationary position of the valve body 41 and moves downward (in the direction opposite to the fixed core 3, that is, in the direction of the orifice cup 7. ) To overshoot by inertia force. The overshoot indicates a behavior of moving downward from the origin when the position of the movable core 4 at rest (original rest position) is determined as the origin. The movable core 4 continues overshooting to a position where the inertial force and the force of the return spring 10 are balanced, and resumes the upward movement (the fixed core 3 side) from there. In order to determine the origin, the valve body 41 is provided with a restricting portion 41 a that restricts relative displacement of the movable core 4 with respect to the valve body 41. The restricting portion 41a is configured as an enlarged diameter portion having a diameter larger than the diameter of the through hole 4a of the movable core 4 through which the valve body 41 passes. The restricting portion 41a restricts relative displacement of the movable core 4 in the valve opening direction with respect to the valve element 41.

  As a result, the movable core 4 comes into contact with the valve body 41 again, and the metal seal between the valve body 41 and the orifice cup 7 is maintained by the impact force generated when the movable core 4 contacts the valve body 41, that is, the valve The forcing force of the return spring 10 is determined so that the body 41 does not open again.

  2a and 2b show a detailed enlarged view of a conventional structure and an example of a movable core behavior.

  FIG. 2B is a diagram in which the time axis response of the movable core 4 passes over the vicinity of the origin and overshoots is expressed as the horizontal axis time and the vertical axis as the movable core 4 displacement. As described above, the movable core 4 continues to move downward with inertial force after passing through the vicinity of the origin. However, the movable core 4 becomes the lowest point at a position that balances with the return spring 10 and then switches to the upward movement. Thereafter, it is a problem to shorten the time until the movable core 4 comes into contact with the valve body 41 and stops.

  FIG. 3 shows an embodiment in which compression springs having unequal pitches are installed on the return spring 10. 3a, 3b and 3c show a detailed enlarged view of the invention and an example of a movable core behavior.

  The relationship between spring load and spring deflection when using an unequal pitch compression spring is shown in FIG. 3b. A solid line represents an unequal pitch compression spring, and a broken line represents the characteristics of the uniform pitch compression spring. In both cases, the spring constant at the beginning of deflection is the same. In the case of an unequal pitch compression spring, it is known that the spring constant increases from the point where the deflection is exceeded to some extent. When a load larger than the load that changes the spring constant is applied, the amount of deflection of the unequal pitch compression spring and the equal pitch compression spring can be shortened by the unequal pitch compression spring. When this is applied to the embodiment, if the load balanced with the inertial force of the movable core 4 is in a region where the unequal pitch compression spring constant is changed, the deflection amount of the return spring 10 can be reduced by h.

  Therefore, when the reduction amount h of the deflection amount is combined with the movable core displacement, it is as shown in FIG. As the lowermost point is shortened by the deflection shortening length h, the time to reach the lowermost point is also shortened, and further, the time until the movable core 4 comes into contact with the valve body 41 and stops is shortened by t. I understand.

  The same effect can be obtained with the conical return spring shown in FIG. 4a, the drum-like return spring shown in FIG. 4b, and the return spring shown in FIG. Is obtained.

  At this time, the speed at which the movable core 4 contacts the valve body 41 does not change unless the lower region (see FIG. 3b) of the load characteristic of the return spring changes. There is no particular need to think about it.

  Moreover, even if the pitch is uniform, the same effect can be obtained in the compression spring using the tapered wire shown in FIG. As shown in FIG. 5, the relationship between the winding start wire diameter d1 and the wire diameter d2 in the middle or at the end is such that d1 <d2.

  Further, as shown in FIG. 6, even when the return spring 10 and the return spring 20 installed so as to be accommodated inside the return spring 10 are installed on the lower side of the movable core 4, the same effect as in FIG.

  In this case, the return spring 20 does not need to be in contact with the movable core 4 in the natural length, and therefore, the return spring 20 may be configured to contact the return spring 20 only after the movable core 4 overshoots. As a result, the movable core 4 is subjected to a forcing force by the return spring 10 and the return spring 20, and thus the same effect as in FIG. In FIG. 6, there are two return springs, but the same effect can be expected with two or more return springs.

  Further, the load characteristics of the return spring 10 and the return spring 20 may be non-linear or linear as shown in the above-described embodiment, and the combination of load characteristics can be freely selected.

  It is considered that the use of a non-linear spring for the return spring 10 is useful for preventing entanglement between the return springs 10 in manufacturing. When the fuel injection valve is manufactured, the return springs are usually aligned using a parts feeder or the like in the manufacturing line. Since a large amount of return springs are inserted at a time in the parts feeder, there is a possibility that the return springs 10 may be entangled with each other. However, if return springs with different unequal pitches or shapes are used, it is considered that the probability of contact with the gap between the spring pitches of parts can be reduced more than necessary, and as a result, entanglement between parts will be prevented. Therefore, it is thought that the occurrence of a chocolate stop etc. can be suppressed and the production efficiency can be improved.

  Although the present invention makes the load characteristic of the return spring nonlinear as described above, the upper limit of the spring constant must be determined in actual use. By increasing the spring constant without limitation, the return speed of the movable core 4 after overshooting becomes extremely fast, and the impact force that collides with the valve body 41 becomes excessive, causing secondary injection of the valve body 41. Sometimes. Therefore, it is necessary to determine the load characteristics of the return spring 10 by taking into account the mass of the movable core 4 and the set load of the spring 8 applied to the valve body 41.

  DESCRIPTION OF SYMBOLS 1 ... Injection valve body, 2 ... Nozzle body, 3 ... Fixed core, 4 ... Movable core, 41 ... Valve body, 5 ... Housing, 6 ... Electromagnetic coil, 7 ... Orifice cup, 71, 72 ... Injection hole, 8 ... Spring , 9 ... Adjuster, 10 ... Return spring, 11, 12 ... Guide member, 13 ... Lead terminal, 14 ... Resin cover, 20 ... Return spring, 101 ... Center axis.

Claims (4)

A cylindrical member having a nozzle hole at the tip, a fixed core housed inside the cylindrical member, and a reciprocating motion housed inside the cylindrical member so as to face the nozzle hole side end surface of the fixed core In an electromagnetic fuel injection valve having a movable core capable of moving and a spring for biasing the movable core toward the fixed core side,
The electromagnetic fuel injection valve, wherein the spring deflection and load have non-linearity. The fuel injection valve according to claim 1,
The electromagnetic fuel injection valve according to claim 1, wherein the load increases nonlinearly as the amount of deflection of the spring increases. The electromagnetic fuel injection valve according to claim 1 or 2,
The electromagnetic fuel injection valve, wherein the spring is composed of a plurality of springs having linearity or nonlinearity. The fuel injection valve according to any one of claims 1 to 3,
The electromagnetic fuel injection valve according to claim 1, wherein the spring is in contact with a movable core portion on a side opposite to a surface where the fixed core and the movable core are opposed to each other to apply a biasing force to the movable core.