JP2003106236A - Electromagnetic fuel injection valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic fuel injection valve capable of inhibiting the generation of open valve bounce without impairing the responding characteristic in rising and lowering of a valve element, and reducing the variation of the fuel injection quantity. SOLUTION: In this fuel injection valve 1 having a pipe 21, a fixed core 22, a movable core 23, a solenoid coil 24 and a needle valve 31, at least one of both toric end faces opposite to each other of the fixed core and the movable core is provided with an inner toric projection 239 and an outer toric projection 230 respectively at a center side and a centrifugal side through a radial central part. A speed in collision of the movable core with the fixed core is reduced by hydraulic damper action of an area defined by the inner toric projection, the outer toric projection, the movable core end face and the fixed core end face which can be raised when the movable core is sucked, whereby the open valve bounce can be inhibited.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection valve operated by electromagnetic force.

[0002]

2. Description of the Related Art Recent gasoline engines and diesel engines are required to satisfy not only high output and low noise but also low fuel consumption and strict exhaust gas regulations. For this reason,
Fuel is accurately supplied to the engine by the fuel injection valve. The fuel injection valve, as can be seen by referring to FIG.
For example, a fixed core and a movable core coupled to the valve body are housed in a cylindrical pipe, and an electromagnetic coil is arranged on the outer peripheral side of them. The fixed core and the movable core form part of a magnetic circuit. When the electromagnetic coil receives power and generates a magnetomotive force, a magnetic path is formed between the fixed core and the movable core. Then, the movable core is attracted to the fixed core by the electromagnetic force, and the valve body rises to open the fuel injection hole. vice versa,
When the power supply to the electromagnetic coil is cut off, the movable core is separated from the fixed core by the spring (biasing means), the valve body descends, and the fuel injection hole is closed. This fuel injection valve is controlled by a control unit (ECU), and is usually performed by adjusting the voltage (drive pulse) applied to the electromagnetic coil. Then, by controlling the opening / closing time and opening / closing timing of the fuel injection hole by the valve body, the injection amount and injection timing of the fuel injected into the intake pipe and the cylinder can be controlled with high accuracy.

In order to achieve the high output, low noise, low fuel consumption, and clean exhaust gas required for automobile engines, it is necessary to improve the precision of such control of the fuel injection valve. That is, it is required to improve the controllability of the fuel injection amount and to shorten the injection start time and the end time, and in order to meet these demands, increase the responsiveness of the valve body that opens and closes the fuel injection hole. is necessary.

The shape of the movable core for the purpose of improving the responsiveness of the valve element is disclosed in Japanese Patent Publication No. 8-506876 and Japanese Patent Laid-Open No. 2000-506876.
-265919. Special table flat 8-5
Japanese Patent Publication No. 06876 discloses that an annular protrusion is formed on the end surface of the movable core. According to this, when the movable core is sucked by the fixed core and collides with it, the collision surface is small, so that the movable core is fixed by hydraulic pressure (when the movable core separates from the fixed core, negative pressure is generated at the interface, and the force against the separation is generated It is said that the phenomenon of sticking because of working, also referred to as metal contact) is avoided, and the responsiveness of the movable core on the separating side (downward movement of the valve body) is improved. Further, Japanese Patent Laid-Open No. 2000-265919 discloses that the end surface of the movable core facing the fixed core is a tapered surface that slightly descends toward the fuel passage located at the center thereof. According to this, when the movable core is sucked by the fixed connector, the fuel interposed between the movable core and the fixed core is guided by the tapered surface to the central fuel passage according to the movement of the movable core. Missed. As a result, the damper action due to the intervening fuel is reduced, and the response on the suction side of the movable core is improved. On the other hand, when the movable core separates, air is introduced by the taper surface and negative pressure is generated between the movable core and the fixed core (with suction).
Is suppressed. Therefore, it is similarly disclosed that the responsiveness of the movable core on the separated side is improved.

However, in each of the fuel injection valves disclosed in these publications, since only one protrusion is formed on the movable core, when the movable core is sucked by the fixed core, the gap between the movable core and the fixed core is reduced. The fuel intervening in the fuel will escape and the damper effect of the fuel will be reduced. As a result, the movable core collides with the fixed core at high speed, and the impact reaction force separates the movable core from the fixed core. If the suction force of the fixed core becomes larger than the impact reaction force due to the separation, a phenomenon occurs in which the suction and the separation are repeated, such as suction and collision. Since the movable core and the valve body move integrally, the suction side of the movable core is the rising side of the valve body. The behavior of the valve body ascending and descending is schematically shown in FIG. 4, and the phenomenon in which the movable core repeats suction and separation is the initial stage of the valve body rising (the area surrounded by the circle in FIG. 4), that is, the valve opening. Corresponding to the initial behavior, it is said to be valve open bounce (valve bounce). FIG. 5 schematically shows the relationship between the drive pulse applied to the electromagnetic coil and the fuel injection amount. When the movable core adsorbs to the fixed core, the valve is in a constant open state. After that, the number of drive pulses is as shown by the dotted line. The injection amount increases in proportion to.
However, when there is valve opening bounce, the injection amount fluctuates as shown by the solid line, and the fluctuation range Δq of the injection amount increases as the valve opening bounce increases. As described above, the fuel injection valve disclosed in the publication has a problem that the valve opening bounce occurs and the injection amount varies.

[0006]

SUMMARY OF THE INVENTION The present invention provides an electromagnetic fuel injection valve in which the occurrence of valve opening bounce is suppressed and the fluctuation range of the fuel injection amount is made small without impairing the responsiveness of the valve body to rise and fall. The purpose is to do.

[0007]

A first means for solving the problems is a cylindrical pipe, an electromagnetic coil, and an inner peripheral side of the pipe which forms a magnetic path of magnetic flux by excitation of the electromagnetic coil. A fixed core fitted and fixed to the movable core, a movable core slidably inserted into the inner peripheral side of the pipe that is attracted to the fixed core in response to the excitation of the electromagnetic coil, and the movable core. A valve body that is integral and that can open and close the fuel injection hole, and is provided on the center side of the fixed core and the movable core.
An electromagnetic fuel injection valve having a fuel passage communicating with the fuel injection hole, wherein at least one of the annular end faces of the fixed core and the movable core facing each other has a center side. Also, the electromagnetic fuel injection valve (claim 1) is characterized in that it has an inner ring-shaped projection and an outer ring-shaped projection on the centrifugal side with a radial center portion therebetween.

A hydraulic damper of a region (volume V portion in FIG. 2 according to the embodiment) defined by the inner annular projection, the outer annular projection, the movable core end surface and the fixed core end surface, which are formed by the movable core being raised during suction. By the action, the speed at which the movable core collides with the fixed core can be suppressed, and the valve opening bounce can be suppressed. During the valve opening process, the gap between the inner annular protrusion and the outer annular protrusion and the fixed core is large, so that the fuel in V is easily discharged to the outside of V (the valve opening response is not deteriorated). Immediately before full lift (the inner ring-shaped projection collides with the fixed core), the fuel in V is discharged only from a minute gap between the outer ring-shaped projection and the fixed core (the fuel cannot escape and the fuel in V The pressure rises abruptly) and the valve opening bounce can be suppressed. Further, since the collision surface (contact surface) between the movable core and the fixed core is small, the movable core easily separates from the fixed core when the driving pulse is off, and the valve body response (valve closing response) does not deteriorate. The heights of the inner annular projection and the outer annular projection may be the same, but if they are the same, the partition area becomes a completely closed area, and the hydraulic damper action is increased. Depending on the conditions such as the electromagnetic attraction of the fixed core, the hydraulic damper action becomes too large and the valve opening bounce can be suppressed, but when the drive pulse is off, the movable core is hard to separate from the fixed core, and the valve closing response deteriorates. . Therefore, it is preferable that the heights are not the same. If the height is different,
Since the fuel can escape from the gap (air gap A / G) between the lower annular projection and the facing surface, the hydraulic damper action can be optimized. The effect of squeezing the inner annular protrusion and the outer annular protrusion immediately before the full lift and the opposing surface (fixed core) also suppresses the collision speed of the valve and effectively works to reduce the valve opening bounce.

The second means for solving the problem is the first
The inner annular protrusion is an electromagnetic fuel injection valve higher than the outer annular protrusion (claim 2).

The inner annular projection may be lower than the outer annular projection if A / G is optimized.

The third means for solving the problem is the second means.
The height of the outer annular protrusion is 1 to 2
An electromagnetic fuel injection valve having a size of 5 μm (claim 3).

The volume of the region defined by the inner annular protrusion, the outer annular protrusion, the fixed core end face, and the movable core end face is V, the amount of fuel flowing into V is ΔV, and the volume elastic coefficient of fuel is E. Then, the pressure increase ΔP in the region of the volume V is expressed by the following equation. ΔP = EΔV / V Therefore, the hydraulic damper action is inversely proportional to V, and the valve opening bounce can also be suppressed by reducing V. FIG. 5 shows the fluctuation range Δq and V of the injection amount due to the valve opening bounce.
In the graph showing the relationship between A and G and A / G, when V is made small as indicated by an arrow, the valve opening bounce is suppressed and Δq becomes small. Since V is proportional to the height of the outer annular protrusion (see FIG. 2 according to the embodiment), the height may be reduced, but
According to the experiments by the inventors, when the thickness is less than 1 μm, the hydraulic damper action becomes large, and it is necessary to increase the magnetic attraction force. If the magnetic attraction force is increased, the valve closing speed will be reduced due to the deterioration of the magnetic disconnection, so the lower limit of the height is 1 μm.
m is suitable. On the other hand, if the height is increased, the action of the hydraulic damper is reduced, so naturally there is an upper limit. According to the experiments by the inventors, it was 25 μm.

A fourth means for solving the problem is the first
The electromagnetic fuel injection valve according to any one of claims 1 to 3, wherein the height difference between the inner annular protrusion and the outer annular protrusion is 1 to 50 µm.

Immediately before the movable core collides with the fixed core, the fuel in the above-mentioned partitioned area of the volume V has no gap between the inner annular projection and the facing surface. Escape only from the gap (A / G) between
When G becomes smaller, the hydraulic damper action becomes larger and A /
As G increases, the hydraulic damper action decreases. Therefore, as shown in FIG. 5, the fluctuation range Δq of the injection amount is A
Since it is proportional to / G, in order to make Δq a predetermined value,
It is understood that A / G should be selected according to the above V. Since a combination of V and A / G can be used, it is easy to suppress the valve opening bounce and to make Δq a predetermined value without deteriorating the responsiveness of the valve body. However, if A / G is made too small, the hydraulic damper action will become too large,
If A / G is made too large, the hydraulic damper action becomes too small, so there is an optimum range for A / G, that is, the difference in height between the inner annular projection and the outer annular projection. According to the experiments by the inventors, when the height difference is 1 to 10 μm, the hydraulic damper action works effectively, the valve opening bounce can be suppressed, and the fluctuation range Δq of the injection amount can be set to a predetermined value. It was found that the responsiveness of the valve body was not deteriorated while it was possible.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described more specifically with reference to embodiments. FIG. 1 shows a vertical sectional view of a fuel injection valve 1 which is an embodiment of the present invention. This fuel injection valve 1
It is arranged in the cylinder head of a gasoline engine for automobiles. That is, it is a so-called direct injection type electromagnetic fuel injection valve that directly injects fuel into the cylinder. The fuel injection valve 1 includes a fuel supply unit 10, an electromagnetic drive unit 20,
It comprises a valve section 30 and an electrical connector section 40. The fuel supply unit 10 is a common rail (not shown) to which high-pressure fuel is supplied.
A fuel connector 11 connected to the fuel connector 11, a fuel filter 12 provided in a fuel passage 111 formed therein,
The O-ring 13 is fitted on the outer peripheral side of the fuel connector 11. The common rail and the fuel connector 11 are oil-tightly connected via the O-ring 13.

The electromagnetic drive unit 20 includes a bottomed cylindrical pipe 21 having an open bottom center, a stepped cylindrical fixed core 22 press-fitted and fixed in the pipe 21, a fixed core 22 and a fuel injection valve 1. A magnetic circuit is formed between the stepped cylindrical movable core 23 arranged coaxially with the axis 1A, the electromagnetic coil 24 for generating a magnetomotive force, the pipe 21 and a nozzle holder 33 described later. It includes a magnetic plate 25, a spring 26 for urging the movable core 23 downward in the figure, and an adjuster 27 for adjusting the urging force. Fixed core 22
Is a press-fitting portion 221 press-fitted into the pipe 21, and a press-fitting portion 2
21 and a reduced diameter reduced portion 222 that extends coaxially downward in the drawing. The fixed core 22 has the press-fitting portion 221 press-fitted into the pipe 21 and is welded and fixed at that portion in an oil-tight manner. In addition, a fuel passage 223 communicating with the fuel passage 111 is formed in the axial center portion of the fixed core 22. A spring 26 and a cylindrical adjuster 27 are also housed in the fuel passage 223.

The movable core 23 is inserted into the pipe 21 and slides on the inner peripheral surface thereof.
1, a reduced diameter portion 232 that extends coaxially downward in the drawing, and a bottomed cylindrical support portion 233 that projects downward from the reduced diameter portion 232 and is open to the lower surface. A head portion of a needle valve 31, which will be described later, is press-fitted through a cylindrical opening of the support portion 233 and fixed by welding. A fuel passage 234 is formed in the center of the movable core 23. A seating surface of the spring 26 is located above the fuel passage 234 in the figure. The fuel passage 234 communicates with a through hole 235 formed in the support portion 233.

The opening of the pipe 21 above the drawing is
The above-mentioned fuel connector 11 is fitted and the fuel seal is fixed by welding. The pipe 21, the fixed core 22, the movable core 23, the magnetic plate 25, and the nozzle holder 33 described later are made of iron-based magnetic material.

The valve portion 30 includes a needle valve 31 which is a valve body.
A cylindrical nozzle 32 having a fuel injection hole 321 at its tip, and a nozzle holder 33 for fixing and holding the nozzle 32.
Consists of. The needle valve 31 reciprocates while sliding the guide portion 311 and the inner peripheral surface of the nozzle 32. By the reciprocating movement of the needle valve 31, the tip tapered surface of the needle valve 31 and the tapered seat surface of the fuel injection hole 321 are seated on and off, and the fuel injection hole 321 is opened and closed (valve open / close). A plurality of injection holes 322 are formed at the tip of the fuel injection hole 321. The fuel is the injection holes 322.
Is injected into the cylinder (not shown).

The electrical connector section 40 is a resin molding member fitted to the pipe 21 and the nozzle holder 33. The electrical connector portion 40 includes a connector 41 extending from the side of the pipe 21, a terminal 42 protruding from the inside of the connector 41, a terminal 42 and an electromagnetic coil 24.
And an embedded conductive wire 43 connected to. When a voltage is applied (drive pulse is supplied) from the electronic control unit (ECU), which is a power supply source, to the terminal 42, the electromagnetic coil 2
Current flows through 4. The electromagnetic coil 24 is excited to generate a magnetomotive force corresponding to the amount of current. And the movable core 2
3 → Fixed core 22 → Pipe 21 → Magnetic plate 25 → Nozzle holder 33 → Pipe 21 → Movable core 23 The magnetic flux is transmitted through the formed magnetic circuit, and the movable core 23 and the needle valve 31 resist the urging force of the spring 26. To raise. When the supply of the drive pulse is stopped, the magnetomotive force disappears, and the movable core 23 and the needle valve 31 move to the spring 2
It descends with the urging force of 6.

FIG. 2 is an enlarged sectional view of the fixed core 22 and the movable core 23 of the injection valve shown in FIG. The reduced diameter portion 222 of the fixed core 22 has a horizontal fixed action surface 228 (perpendicular to the axis 1A of the injection valve 1). The guide portion 231 of the movable core 23 has a horizontal movable action surface 238 opposed to the fixed action surface 228, an outer annular protrusion 230 having a height of 5 μm, for example, on the outer peripheral portion, and a height of 10 μm for the inner peripheral portion. It has an inner annular projection 239.

When a magnetomotive force is generated in the electromagnetic coil 24 by the drive pulse, the movable core 23 rises and the inner annular projection 239 collides with the fixed action surface 228 of the fixed core 22,
The valve will open. At that time, the fixed action surface 22
8 and the movable working surface 238, the fuel is present in the gap A / G between the outer annular projection 230 and the fixed working surface 228.
Escape while receiving resistance through (through escape, and further receiving resistance through the gap between the outer peripheral portion of the guide portion 231 and the inner peripheral portion of the pipe 21). Therefore, the movable core 2
3, the hydraulic damper action of the fuel came to work, the rising speed of the inner annular projection 239 became small, and the valve opening bounce could be suppressed.

FIG. 3 is an enlarged cross-sectional view in the vicinity of both end surfaces of the fixed core 22 and the movable core 23 facing each other in the electromagnetic fuel injection valve according to the second embodiment of the present invention. The same numbers are given to the same elements as those in FIG. 2 of the first embodiment. The difference from the first embodiment is that the movable action surface 238 is not horizontal and the guide portion 23
1 is a taper toward the outer peripheral portion, and the end of the taper is connected to one end of the upper surface of the outer annular projection 230.

The effect that the valve opening bounce is suppressed by the hydraulic damper action of the fuel interposed between the fixed action surface 228 and the movable action surface 238 is the same as that of the first embodiment, but the movable action surface 238 is the outer peripheral portion. Since it is tapered toward and the end thereof is connected to one end of the upper surface of the outer annular protrusion 230, the outer annular protrusion and the inner annular protrusion can be easily formed on the guide portion 231 of the movable core 23. It is advantageous in terms.

The movable working surface 238 is connected to the guide portion 231.
It goes without saying that the taper may be tapered toward the inner peripheral portion and the end of the taper may be connected to one end of the upper surface of the inner annular projection 239.

[0026]

According to the fuel injection valve of the present invention, at least one of the annular end faces of the fixed core and the movable core facing each other has the central portion in the radial direction separated from the central side and the centrifugal side. Since the movable core has an inner ring-shaped protrusion and an outer ring-shaped protrusion, the movable core can be lifted at the time of suction to divide the inner ring-shaped protrusion, the outer ring-shaped protrusion, the movable core end face, and the fixed core end face into regions ( Due to the hydraulic damper action of the volume V), the speed at which the movable core collides with the fixed core can be suppressed, and valve opening bounce can be suppressed. Moreover, since the hydraulic damper action depends on the volume V and the height difference (A / G) between the inner annular protrusion and the outer annular protrusion, the injection by the valve opening bounce does not decrease the responsiveness of the movable core. Amount fluctuation range Δq
Can be performed with a combination of V and A / G to set a predetermined value, and can be easily implemented.

[Brief description of drawings]

FIG. 1 is a cross section showing a fuel injection valve according to a first embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a fixed core and a movable core of the fuel injection valve according to the first embodiment of the present invention.

FIG. 3 is an enlarged sectional view of a fixed core and a movable core of a fuel injection valve according to a second embodiment of the present invention.

FIG. 4 is a schematic diagram for explaining ascending and descending behavior of a valve body.

FIG. 5 is a graph showing the relationship between the injection amount and the drive pulse for explaining the fluctuation range of the injection amount.

FIG. 6 is a graph showing the relationship between the fluctuation range Δq of the injection amount, the volume V between the fixed core and the movable core, and the air gap A / G.

[Explanation of symbols]

1 fuel injection valve 21 pipes 22 fixed core 23 Movable core 24 electromagnetic coil 31 Needle valve (valve body) 111,234 Fuel passage 230 Outer annular protrusion 239 Inner annular protrusion 321 Fuel injection hole

Claims (4)

[Claims] 1. A cylindrical pipe, an electromagnetic coil, a fixed core fitted and fixed to an inner peripheral side of the pipe forming a magnetic path of magnetic flux generated by excitation of the electromagnetic coil, and excitation of the electromagnetic coil. In response to, the movable core slidably fitted to the inner peripheral side of the pipe that is sucked by the fixed core, and the valve body that is integral with the movable core and that can open and close the fuel injection hole. While having, in the central portion side of the fixed core and the movable core,
An electromagnetic fuel injection valve in which a fuel passage communicating with the fuel injection hole is formed, wherein at least one of the annular end surfaces of the fixed core and the movable core facing each other has a center side. And an electromagnetic fuel injection valve having an inner ring-shaped protrusion and an outer ring-shaped protrusion on the centrifugal side with a radial center portion therebetween. 2. The electromagnetic fuel injection valve according to claim 1, wherein the inner annular protrusion is higher than the outer annular protrusion. 3. The height of the outer annular projection is 1 to 25 μm.
The electromagnetic fuel injection valve according to claim 2, wherein m is m. 4. The electromagnetic fuel injection valve according to claim 1, wherein the height difference between the inner annular projection and the outer annular projection is 1 to 50 μm.