JP4352301B2 - Electromagnetic fuel injection valve - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection valve that operates by electromagnetic force.
[0002]
[Prior art]
Recent gasoline engines and diesel engines are required to satisfy strict exhaust gas regulations with low fuel consumption and high fuel efficiency in addition to high output and low noise. For this reason, the fuel supply to the engine is accurately performed by the fuel injection valve.
As shown in FIG. 1, for example, a fuel injection valve includes a cylindrical core in which a fixed core and a movable core coupled to a valve body are housed, and an electromagnetic coil is disposed on the outer peripheral side thereof. Yes. The fixed core and the movable core form part of the magnetic circuit. When the electromagnetic coil receives power and generates 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 electromagnetic force, and the valve body rises to open the fuel injection hole. Conversely, 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 is lowered, 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. 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 are controlled with high accuracy.
[0003]
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 control of such fuel injection valves. That is, there is a demand for improved controllability of the fuel injection amount, and further shortening of the injection start time and end time. In order to meet these demands, the responsiveness of the valve body that opens and closes the fuel injection hole is improved. is required.
[0004]
The shape of the movable core for the purpose of improving the responsiveness of the valve body is disclosed in JP-T-8-506876 and JP-A-2000-265919. Japanese Patent Laid-Open No. 8-506876 discloses that an annular protrusion is formed on the end surface of the movable core. According to this, when the movable core is attracted to and collides with the fixed core, the collision surface is small, so that the pressure is fixed due to hydraulic pressure (negative pressure is generated at the interface when the movable core is separated from the fixed core, and the force against the separation is The phenomenon of sticking to work, also referred to as metal contact) is avoided, and the movable core separation (valve element lowering) side response is improved. 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 into 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. To be missed. As a result, the damper action by the intervening fuel is reduced, and the responsiveness on the suction side of the movable core may be improved. On the other hand, when the movable core separates, air is introduced by the tapered surface, and generation (sucking) of negative pressure between the movable core and the fixed core is suppressed. Therefore, it is disclosed that the responsiveness on the separation side of the movable core is improved similarly.
[0005]
However, since the fuel injection valves disclosed in these publications all have only one protrusion formed on the movable core, when the movable core is attracted to the fixed core, it is interposed between the movable core and the fixed core. The fuel escapes and the damper effect by the fuel is reduced. As a result, the movable core collides with the fixed core at high speed, and the movable core separates from the fixed core by the impact reaction force. If the suction force of the fixed core becomes larger than the impact reaction force after separation, a phenomenon occurs in which suction and separation such as suction and collision are repeated. Since the movable core and the valve body move together, the suction side of the movable core is the ascending 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 in which the valve body ascends (region surrounded by a circle in FIG. 4), that is, valve opening. Corresponding to the initial behavior, it is said to be a valve opening 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 is attracted to the fixed core, the valve is in a constant valve open state, and thereafter, the number of drive pulses as indicated by the dotted line. The injection amount increases in proportion to However, if there is a valve opening bounce, the injection amount varies 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 valve opening bounce occurs and the injection amount fluctuates.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide 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 reduced without impairing the responsiveness of rising and lowering of the valve body.
[0007]
[Means for Solving the Problems]
A first means for solving the problem is a fixed core that is fitted and fixed to a cylindrical pipe, an electromagnetic coil, and an inner peripheral side of the pipe that forms a magnetic path of magnetic flux by excitation of the electromagnetic coil A movable core that is slidably fitted on the inner peripheral side of the pipe that is attracted to the fixed core in response to excitation of the electromagnetic coil, and that is integral with the movable core and opens and closes the fuel injection hole An electromagnetic fuel injection valve having a fuel passage communicating with the fuel injection hole at a central portion side of the fixed core and the movable core,
At least one of the annular end surfaces of the fixed core and the movable core facing each other has an inner annular projection and an outer annular projection on the center side and the distal side with a radial center portion therebetween. This is an electromagnetic fuel injection valve characterized by the following.
[0008]
With the hydraulic damper action of the region (volume V part of 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 that can be raised when the movable core is lifted, 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 gaps between the inner annular protrusion and the outer annular protrusion and the fixed core are large, so that the fuel in V is easily discharged out of V (does not deteriorate the valve opening response). Immediately before the full lift (the inner annular protrusion collides with the fixed core), the fuel in V is discharged only from a minute gap between the outer annular protrusion and the fixed core (the fuel does not escape, the fuel in V The pressure rises rapidly, 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 is easily separated from the fixed core when the drive pulse is turned off, and the responsiveness (valve closing response) of the valve body is not deteriorated.
The inner annular projection and the outer annular projection may have the same height, but if they are the same, the partition region becomes a completely closed region and the hydraulic damper action increases. Depending on conditions such as the electromagnetic attraction force of the fixed core, the hydraulic damper action becomes too large and valve opening bounce can be suppressed, but the movable core is difficult to separate from the fixed core when the drive pulse is off, resulting in poor valve closing response. . Therefore, it is preferable that the heights are not the same. If the heights are different, the fuel can escape from the gap (air gap A / G) between the lower annular projection and the opposing surface, so that the hydraulic damper action can be optimized. The effect of the squeeze of the inner annular projection and the outer annular projection 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.
[0009]
First means for solving the problem, further, the inner annular protrusion is a high electromagnetic fuel injection valve than the outer annular projection.
[0011]
Second means for solving the problems is a first means, the height of the outer annular projection is an electromagnetic fuel injection valve is 1 to 25 m.
[0012]
If 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 modulus of the fuel is E, the volume The pressure increase ΔP in the region V is as follows.
ΔP = EΔV / V
Therefore, the hydraulic damper action is inversely proportional to V, and the valve opening bounce can be suppressed by reducing V. FIG. 5 is a graph showing the relationship between the fluctuation range Δq of the injection amount due to valve opening bounce and V and A / G. When V is reduced as shown by the arrow, the valve opening bounce is suppressed and Δq is reduced. Since V is proportional to the height of the outer annular projection (see FIG. 2 according to the embodiment), the height may be reduced. However, according to the experiments by the inventors, the hydraulic damper action is increased below 1 μm. It was necessary to increase the magnetic attractive force. If the magnetic attractive force is increased, the valve closing speed is lowered due to the deterioration of the magnetic breakage, so that the lower limit of the height is appropriately 1 μm. On the other hand, if the height is increased, the hydraulic damper action decreases, so there is naturally an upper limit. According to the experiments by the inventors, it was 25 μm.
[0013]
A third means for solving the problem is any one of the first and second means, wherein a difference in height between the inner annular protrusion and the outer annular protrusion is 1 to 50 μm. It is an injection valve .
[0014]
Immediately before the movable core collides with the fixed core, the fuel in the partition region of the volume V described above has no gap between the inner annular protrusion and the opposing surface, so that the gap between the outer annular protrusion and the opposing surface is eliminated. Escape only from the gap (A / G), but when A / G decreases, the hydraulic damper action increases, and when A / G increases, the hydraulic damper action decreases. Therefore, as shown in FIG. 5, the fluctuation range Δq of the injection amount is proportional to A / G. Therefore, in order to set Δq to a predetermined value, A / G may be selected according to V described above. I understand that. Since a combination of V and A / G can be used, valve opening bounce can be suppressed and Δq can be easily set to a predetermined value without deteriorating the responsiveness of the valve body. However, if A / G is too small, the hydraulic damper action becomes too large, and if A / G is too large, the hydraulic damper action becomes too small. There is an optimum range for the difference in height of the annular protrusions. 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.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be described more specifically with reference to embodiments.
FIG. 1 shows a longitudinal sectional view of a fuel injection valve 1 according to an embodiment of the present invention. The fuel injection valve 1 is disposed in a cylinder head of an automobile gasoline engine. That is, it is a so-called direct injection type electromagnetic fuel injection valve that directly injects fuel into a cylinder.
The fuel injection valve 1 includes a fuel supply unit 10, an electromagnetic drive unit 20, a valve unit 30, and an electrical connector unit 40.
The fuel supply unit 10 includes a fuel connector 11 connected to a common rail (not shown) to which high pressure fuel is supplied, a fuel filter 12 provided in a fuel passage 111 formed therein, and an outer peripheral side of the fuel connector 11. It is composed of an inserted O-ring 13. The common rail and the fuel connector 11 are connected in an oil-tight state via the O-ring 13.
[0016]
The electromagnetic drive unit 20 includes a bottomed cylindrical pipe 21 having an open bottom center, a stepped cylindrical fixed core 22 that is press-fitted into the pipe 21, an axis 1 </ b> A of the fixed core 22 and the fuel injection valve 1. A stepped cylindrical movable core 23 disposed coaxially, an electromagnetic coil 24 that generates magnetomotive force, and a magnetic plate 25 that forms a magnetic circuit between the pipe 21 and a nozzle holder 33 described later. And a spring 26 for urging the movable core 23 downward in the figure and an adjuster 27 for adjusting the urging force.
The fixed core 22 includes a press-fit portion 221 that is press-fitted into the pipe 21, and a reduced diameter portion 222 that is reduced in diameter and extends coaxially with the press-fit portion 221 downward in the figure. The fixed core 22 is press-fitted into the pipe 21 with the press-fitted portion 221 and fixed in an oil-tight manner at that portion. A fuel passage 223 that communicates with the fuel passage 111 is formed in the central portion of the shaft of the fixed core 22. A spring 26 and a cylindrical adjuster 27 are also accommodated in the fuel passage 223.
[0017]
The movable core 23 is inserted into the pipe 21 and slides with the inner peripheral surface thereof, the reduced diameter portion 232 coaxially extending from the guide portion 231 downward in the figure, and the reduced diameter portion 232 downward in the figure. A bottomed cylindrical support portion 233 that protrudes and opens on the lower surface. Below the support portion 233 in the figure, a head of a needle valve 31 to be described later is press-fitted through a cylindrical opening and fixed by welding. A fuel passage 234 is formed in the central portion of the movable core 23. Above the fuel passage 234 in the figure is a seating surface of the spring 26. The fuel passage 234 communicates with a through hole 235 formed in the support portion 233.
[0018]
Note that the above-described fuel connector 11 is fitted into the opening of the pipe 21 in the upper part of the figure, 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 an iron-based magnetic material.
[0019]
The valve section 30 includes a needle valve 31 that is a valve body, a cylindrical nozzle 32 having a fuel injection hole 321 formed at the tip, and a nozzle holder 33 that holds the nozzle 32 fixedly.
The needle valve 31 reciprocates while sliding between the guide portion 311 and the inner peripheral surface of the nozzle 32. By the reciprocation of the needle valve 31, the tip tapered surface of the needle valve 31 and the tapered seating surface of the fuel injection hole 321 are separated from each other, and the fuel injection hole 321 is opened and closed (opened / closed). A plurality of injection holes 322 are formed at the further tip of the fuel injection holes 321. The fuel is injected from the injection hole 322 into a cylinder (not shown).
[0020]
The electrical connector portion 40 is a resin molded member fitted to the pipe 21 and the nozzle holder 33. The electrical connector portion 40 includes a connector 41 that extends from the side of the pipe 21, a terminal 42 that protrudes from the inside of the connector 41, and a buried conductor 43 that connects the terminal 42 and the electromagnetic coil 24.
When a voltage is applied to the terminal 42 from an electronic control unit (ECU) that is a power supply source (a drive pulse is supplied), a current flows through the electromagnetic coil 24. The electromagnetic coil 24 is excited to generate a magnetomotive force corresponding to the amount of current. The magnetic flux is transmitted through the magnetic circuit formed by the movable core 23 → the fixed core 22 → the pipe 21 → the magnetic plate 25 → the nozzle holder 33 → the pipe 21 → the movable core 23, and the movable core 23 and the needle valve 31 are attached to the spring 26. Raise against the power. When the supply of the drive pulse is stopped, the magnetomotive force disappears, and the movable core 23 and the needle valve 31 are lowered by the urging force of the spring 26.
[0021]
FIG. 2 is an enlarged cross-sectional view of the vicinity of both opposing end surfaces of the fixed core 22 and the movable core 23 of the injection valve of 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 opposite to the fixed action surface 228, and has an outer annular protrusion 230 having a height of, for example, 5 μm on the outer peripheral portion and a height of 10 μm, for example, on the inner peripheral portion. It has an inner annular protrusion 239.
[0022]
When a magnetomotive force is generated in the electromagnetic coil 24 by the drive pulse, the movable core 23 rises, and the inner annular protrusion 239 collides with the fixed action surface 228 of the fixed core 22 to open the valve. At that time, the fuel that has been interposed between the fixed acting surface 228 and the movable acting surface 238 until then is subjected to resistance through the gap A / G between the outer annular projection 230 and the fixed acting surface 228 (escapes, And escapes while receiving resistance through the gap between the outer peripheral portion of the guide portion 231 and the inner peripheral portion of the pipe 21. Accordingly, when the movable core 23 is lifted, the hydraulic damper action of the fuel is activated, the rising speed of the inner annular protrusion 239 is reduced, and the valve opening bounce can be suppressed.
[0023]
FIG. 3 is an enlarged cross-sectional view of the vicinity of both end faces 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 elements as those in FIG. 2 of the first embodiment are denoted by the same reference numerals.
The difference from the first embodiment is that the movable action surface 238 is not horizontal but is tapered toward the outer periphery of the guide portion 231, and the end of the taper is connected to one end of the upper surface of the outer annular protrusion 230. It is a point.
[0024]
The effect that the valve opening bounce is suppressed by the hydraulic damper action by 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 faces the outer peripheral portion. Since it is tapered and its terminal end is connected to one end of the upper surface of the outer annular protrusion 230, it is advantageous in that it is easy to form the outer annular protrusion and the inner annular protrusion on the guide portion 231 of the movable core 23. is there.
[0025]
Of course, the movable action surface 238 may be tapered toward the inner peripheral portion of the guide portion 231, and the end of the taper may be connected to one end of the upper surface of the inner annular protrusion 239.
[0026]
【The invention's effect】
According to the fuel injection valve of the present invention, the annular end surface of at least one of the two annular end surfaces where the fixed core and the movable core face each other has an inner annular projection with a central portion in the radial direction separated from the center side and the centrifugal side. And the outer annular projection, the hydraulic pressure in the region (volume V) defined by the inner annular projection, the outer annular projection, the movable core end surface, and the fixed core end surface that can be raised when the movable core is raised. Due to the damper action, the speed at which the movable core collides with the fixed core can be suppressed, and the valve opening bounce can be suppressed. In addition, since the hydraulic damper action depends on the volume V and the height difference (A / G) between the inner annular projection and the outer annular projection, the injection by the valve opening bounce without reducing the responsiveness of the movable core. The amount of fluctuation range Δq can be set to a predetermined value by a combination of V and A / G, which can be easily implemented.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view 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 cross-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 the ascent and descent behavior of the valve body.
FIG. 5 is a graph showing a relationship between an injection amount and a drive pulse for explaining a fluctuation range of the injection amount.
FIG. 6 is a graph showing the relationship between the injection amount fluctuation range Δq, 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 Pipe 22 Fixed Core 23 Movable Core 24 Electromagnetic Coil 31 Needle Valve (Valve)
111,234 Fuel passage 230 Outer annular protrusion 239 Inner annular protrusion 321 Fuel injection hole

Claims (3)

A cylindrical pipe, an electromagnetic coil, a fixed core that is fitted and fixed on the inner peripheral side of the pipe that forms a magnetic path of magnetic flux by excitation of the electromagnetic coil, and in response to excitation of the electromagnetic coil, A movable core that is slidably fitted on the inner peripheral side of the pipe that is sucked into the fixed core, and a valve body that is integral with the movable core and that can open and close the fuel injection hole. An electromagnetic fuel injection valve in which a fuel passage communicating with the fuel injection hole is formed on a central portion side of the core and the movable core,
At least one of the annular end surfaces of the fixed core and the movable core facing each other has an inner annular projection and an outer annular projection on the center side and the distal side with a radial center portion therebetween. ,
The electromagnetic fuel injection valve, wherein the inner annular protrusion is higher than the outer annular protrusion . The electromagnetic fuel injection valve according to claim 1, wherein a height of the outer annular protrusion is 1 to 25 μm. 3. The electromagnetic fuel injection valve according to claim 1, wherein a difference in height between the inner annular protrusion and the outer annular protrusion is 1 to 50 μm.

Images