JP2002310029A - Fuel injection valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection valve for easily improving responsiveness. SOLUTION: This fuel injection valve 1 has a pipe 21, a fixed connector 22, a movable core 23, an electromagnetic coil 24, and a needle valve 31, and is characterized by forming a chamfer 227 in a fixed outer peripheral corner part 226 formed of an outer peripheral surface of the fixed connector and a fixed action surface 228 for operating electromagnetic force. Since the chamfer is arranged in the outer peripheral corner part of the fixed connector, an outer peripheral side magnetic flux reaching the fixed connector from the movable core becomes almost vertical to the action surface so that the electromagnetic force can be efficiently converted into attraction force of the movable core.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In recent years, 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,
The fuel supply to the engine is accurately performed by the fuel injection valve. The fuel injection valve, as can be seen with reference to FIG.
For example, a fixed connector and a movable core coupled to a valve body are housed in a cylindrical pipe, and an electromagnetic coil is disposed on the outer peripheral side thereof. The fixed connector 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 connector and the movable core. Then, the movable core is attracted to the fixed connector by the electromagnetic force, and the valve body opens the fuel injection hole. Conversely, when power supply to the electromagnetic coil is cut off, the movable core is separated from the fixed connector by a spring (biasing means), and the valve body closes the fuel injection hole. This fuel injection valve is controlled by a control device (ECU), and is usually performed by adjusting an applied voltage to an 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 the injection timing of the fuel injected into the intake pipe and the cylinder are controlled with high accuracy.

[0003]

In order to control the fuel injection valve more precisely, it is necessary to improve the responsiveness of a valve element that opens and closes a fuel injection hole. For that purpose, it is effective to increase the suction force acting on the movable core. Increasing the electromagnetic force by increasing the number of turns of the electromagnetic coil or the current flowing through the electromagnetic coil can also increase the attraction force, but this will increase the size of the fuel injection valve and increase power consumption. They also involve major design changes and increase costs.

[0004] The present invention has been made in view of such circumstances. In other words, the fuel that enables the electromagnetic force generated between the fixed connector and the movable core to be efficiently used by relatively easy means, enhances the suction force acting on the movable core, and improves the responsiveness of the valve element It is intended to provide an injection valve.

[0005] Japanese Patent Application Laid-Open No. 2000-265919 discloses a shape of a movable core for improving the response of a valve element. Specifically, it is disclosed that the end surface of the movable core facing the fixed connector is a tapered surface slightly descending 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 connector 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 effect due to the intervening fuel is reduced, and the response of the movable core on the suction side is improved. On the other hand, when the movable core separates, air is introduced by the tapered surface, and generation of negative pressure (sucking) between the movable core and the fixed connector is suppressed. Therefore, it is disclosed that the responsiveness of the movable core on the separation side is similarly improved.

[0006] However, the fuel injection valve disclosed in this publication does not attempt to improve the responsiveness by efficiently utilizing the electromagnetic force between the fixed connector and the movable core. Therefore, the object of the publication is completely different from the object of the present invention, and as described below, both configurations are completely different.

[0007]

The inventor of the present invention has conducted intensive studies to solve the above-mentioned problems, and as a result of repeated trial and error, chamfering the outer peripheral corner of the surface where the fixed connector and the movable core face each other. As a result, the inventors have found that the electromagnetic force (attraction force) generated between the two increases, and have completed the present invention. That is, the fuel injection valve of the present invention is a cylindrical pipe, and a fixed connector made of a magnetic material having a fixed working surface on one end side, which is fitted and fixed on the inner peripheral side of the pipe,
A movable core made of a magnetic material having a movable working surface on one end side slidably fitted to the inner peripheral side of the pipe coaxially with the fixed connector and facing the fixed working surface, and supplied with power from a power supply source; An electromagnetic coil that generates a magnetic flux passing through the fixed working surface and the movable working surface to generate an attractive force between the fixed connector and the movable core; and an electromagnetic coil that moves together with the movable core and supplies power to the electromagnetic coil. In a fuel injection valve having a valve body that opens and closes a fuel injection hole depending on the presence or absence, a fixed outer peripheral corner formed by an outer peripheral surface of the fixed connector and the fixed operation surface, an outer peripheral surface of the movable core, and the movable operation surface And at least one of the movable outer corners formed by the above is chamfered.

[0008] By appropriately chamfering at least one of the fixed outer peripheral corner and the movable outer peripheral corner, contrary to conventional expectations, the electromagnetic force generated between the fixed connector and the movable core is increased. The inventor has discovered. Based on this,
When a movable core or a fixed connector having a fixed outer peripheral corner or a movable outer peripheral corner chamfered is used for a fuel injection valve, the suction acting on the movable core can be relatively easily performed without substantially changing the structure of the conventional fuel injection valve. The force increases, and the responsiveness of the valve element can be improved. Of course, if the same electromagnetic force as in the related art is sufficient, the present invention can be used to further reduce the size and power consumption of the electromagnetic coil.

The reason why the above-mentioned phenomenon occurs is not always clear, but can be considered as follows.
The electromagnetic force generated between the fixed connector and the movable core is basically determined by the effective area on which the electromagnetic force acts (that is, the area between the fixed working surface and the movable working surface). For this reason, conventionally, in order to increase the effective area even a little, the fixed outer peripheral corner and the movable outer peripheral corner are managed in a so-called pin angle state. However, near the pin angle, the direction of the magnetic flux vector is not substantially perpendicular to the fixed working surface or the movable working surface,
It turned out that it inclines to a radial direction (refer FIG.2 and FIG.3 which concern on embodiment). This is considered to be because the magnetic flux from one of the working surfaces of the fixed connector or the movable core tends to fly to the pin angle. Then, it is considered that the magnetic flux flying at the pin angle affects the magnetic flux in the vicinity, and the direction of the magnetic flux vector in the vicinity is inclined inward in the radial direction (inner side).

In any case, since the direction of the magnetic flux acting between the working surfaces deviates from the normal direction of the working surface, the vertical component of the electromagnetic force (the component in the normal direction of the working surface) decreases, and the fixed connector The suction force generated between the and the movable core was reduced. On the other hand, according to the present invention, since the fixed outer peripheral corner or the movable outer peripheral corner is chamfered (that is, the above-described pin angle is chamfered), there is no magnetic flux flying at the pin angle. Then, the magnetic flux near the outer periphery is suppressed and prevented from being disturbed by the magnetic flux flying at the pin angle as in the related art. That is, the direction of the magnetic flux between the working surfaces is substantially the normal direction of the working surface. Therefore, the electromagnetic force generated between the working surfaces is efficiently used as the attractive force of the movable core, and the attractive force can be easily increased without changing the electromagnetic coil or the coil current.
Then, the responsiveness of the movable core, that is, the responsiveness of the valve body is improved, the minimum fuel injection amount and the like can be optimized, and more precise control of the fuel injection valve can be performed. In the present invention, since the fixed outer corner portion or the movable outer corner portion is chamfered, the conventional management of the pin angle is not required, and the component management becomes easy. Further, by providing the chamfer, the occurrence of dents is suppressed, and the occurrence of burrs and the like can be prevented.

By the way, it is considered that the above-mentioned phenomenon that the magnetic flux flies to the pin angle easily occurs when the magnetic flux flies from the wide working surface to the outer peripheral corner (pin angle) on the narrow side of the working surface.
In addition, when the fixed outer peripheral corner portion is provided with a chamfer in consideration of the attachment property of the fixed connector to the pipe (fitting property, press-fitting property, etc.),
Often convenient. Therefore, for example, it is preferable that the outer peripheral diameter of the fixed operation surface before chamfering is smaller than the outer peripheral diameter of the movable operation surface before chamfering, and the chamfer is formed at the fixed outer peripheral corner. In particular, when the fixed connector is pressed into the pipe and fixed, the chamfer can be used as a guide, which is preferable. In this case, for example, the chamfer angle is set to 10
It is good to be 20 degrees.

Further, when the fixed connector is press-fitted into the pipe, if the press-fitting surface is long in the axial direction, the press-fitting property is poor. Therefore, the end of the fixed connector may be slightly reduced in diameter in order to improve the press-fitting property without reducing the substantial volume of the fixed connector. In such a case, the fixed connector has a press-fit portion to be press-fitted on the inner peripheral side of the pipe, a coaxial extension extending coaxially from the press-fit portion and a diameter slightly smaller than the press-fit portion, and having the fixed outer peripheral corner portion at an end. It is preferable to include the reduced diameter portion. Note that “slightly reduced in diameter” means that the reduced diameter portion does not serve as a press-fit surface, and may be determined in consideration of a press-fit amount of the press-fit portion. As an example, the outer diameter of the reduced diameter portion may be reduced by about 1 to 5% with respect to the outer diameter of the press-fitted portion.

If this chamfering becomes too large, the effective area on which the electromagnetic force acts is reduced, which causes a decrease in the aforementioned attractive force. Therefore, for example, the chamfer width of the chamfer is one of the outer diameter of the fixed working surface or the movable working surface before chamfering.
It is preferable that it is ７7%. If it is less than 1%, there is not much difference from the case where no chamfer is provided, and if it exceeds 7%, the suction force is reduced. The chamfer width is 4 to 6% of the outer diameter before chamfering,
More preferably, it is set to 4 to 5%.

Here, the chamfer width is a radius difference between before and after chamfering on the fixed working surface or the movable working surface. The chamfer angle is not particularly limited, but if a general C chamfer (45 ° chamfer) is used, the processing is easy. Therefore, it is preferable that the chamfer is a 45 ° chamfer. The “chamfer” in the present invention can be rephrased as a tapered surface having a small diameter on the fixed working surface side or the movable working surface side. Further, the fuel injection valve of the present invention may be for a gasoline engine or a diesel engine as long as it is an electromagnetic fuel injection valve, and may be one that injects into a cylinder or one that injects into an intake manifold.

[0015]

Next, the present invention will be described more specifically with reference to embodiments. (Structure of Fuel Injection Valve) FIG. 1 is a longitudinal sectional view of a fuel injection valve 1 according to an embodiment of the present invention. The fuel injection valve 1 is provided in a cylinder head of a gasoline engine for an automobile. That is, it is a so-called direct injection type electromagnetic fuel injection valve that injects fuel directly 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, a fuel filter 12 provided in a fuel passage 111 formed therein,
An O-ring 13 is fitted on the outer peripheral side of the fuel connector 11. The common rail and the fuel connector 11 are connected via the O-ring 13 in an oil-tight state.

The electromagnetic drive unit 20 includes a bottomed cylindrical pipe 21 having an open bottom center, a stepped cylindrical fixed connector 22 press-fitted into the pipe 21, and a fixed connector 2.
2, a stepped cylindrical movable core 23 disposed coaxially opposite to the magnetic core 2, an electromagnetic coil 24 for generating a magnetomotive force, and a magnetic material for forming a magnetic circuit between the pipe 21 and a nozzle holder 33 described later. It comprises a plate 25, a spring 26 for urging the movable core 23 downward in the figure, and an adjuster 27 for adjusting the urging force. The fixed connector 22 is a pipe 21
Press-fit portion 221 (φ9.8 mm) press-fitted into the press-fit portion, and reduced-diameter reduced portion 222 coaxial with press-fit portion 221 and extending downward in the figure.
(Φ9.6 mm). And fixed connector 2
Reference numeral 2 indicates that the press-fitting portion 221 is press-fitted into the pipe 21 and that portion is oil-tightly welded and fixed. Further, a fuel passage 223 communicating with the fuel passage 111 is formed at the center of the shaft of the fixed connector 22. The fuel passage 223 contains the spring 26 and the cylindrical adjuster 27.

A movable core 23 is inserted into the pipe 21 and slides on the inner peripheral surface thereof.
1 and a reduced diameter portion 232 extending coaxially with
32, a bottomed cylindrical support 233 projecting downward in the figure and opening on the lower surface. Below the support 233 in the figure,
The head of a needle valve 31 described later is press-fitted from its cylindrical opening and fixed by welding. Further, a fuel passage 234 is formed in the center of the movable core 23. This fuel passage 2
The upper part of FIG. 34 is a seat surface of the spring 26. Further, the fuel passage 234 communicates with a through hole 235 formed in the support portion 233.

At the opening of the pipe 21 at the upper part of the figure,
The above-described fuel connector 11 is fitted and fixed to the fuel seal by welding. Also, a pipe 21, a fixed connector 22,
The movable core 23, the magnetic plate 25, and a nozzle holder 33 described later are made of an iron-based magnetic material. However, the pipe 21
Near the center (near the boundary between the fixed connector 22 and the movable core 23), the nonmagnetic portion 21 demagnetized by the high-frequency heat treatment.
1 is provided. This is for preventing a short circuit of the magnetic circuit described later.

The valve portion 30 includes a needle valve 31 which is a valve body.
A cylindrical nozzle 32 having a fuel injection hole 321 formed at a tip thereof; 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. Due to the reciprocating motion of the needle valve 31, the tapered end surface of the needle valve 31 and the tapered seat surface of the fuel injection hole 321 are separated and seated, and the fuel injection hole 321 is opened and closed. Note that a plurality of injection holes 322 are formed at the tip of the fuel injection holes 321. Fuel is injected from the injection holes 322 into a cylinder (not shown).

The electric connector section 40 is a resin molded member fitted to the pipe 21 and the nozzle holder 33. The electrical connector section 40 includes a connector 41 extending from the side of the pipe 21, a terminal 42 projecting from the inside of the connector 41, a terminal 42 and the electromagnetic coil 24.
And a buried conducting wire 43 connected thereto. Here, an electronic control unit (EC) which is a power supply source is connected to the terminal 42.
When a voltage is applied from U), a current flows through the electromagnetic coil 24. The electromagnetic coil 24 is excited to generate a magnetomotive force according to the amount of current. Then, the magnetic flux is transmitted through a magnetic circuit formed by the movable core 23 → the fixed connector 22 → the pipe 21 → the magnetic plate 25 → the nozzle holder 33 → the pipe 21 → the movable core 23.

(Evaluation of Chamfering) Next, FIG. 2A is an enlarged cross-sectional view showing the vicinity where the fixed connector 22 and the movable core 23 face each other. Reduced diameter portion 222 of fixed connector 22
Has a fixed action surface 228, and a fixed outer peripheral corner 226 can be formed at the intersection of the outer circumferential surface of the reduced diameter portion 222 and the fixed action surface 228. However, in the present embodiment, the fixed outer peripheral corner 2
26 is chamfered, and a tapered surface 227 is formed at that portion. This chamfer is a so-called C chamfer having a 45 ° taper. The chamfer width is t shown in the figure.

The movable core 23 has a movable working surface 238 facing the fixed working surface 228, and a movable outer corner 236 is formed at the intersection of the movable working surface 238 and the outer peripheral surface of the guide portion 231. . In the present embodiment, the movable outer corner 236
The thread is chamfered for deburring, but no further chamfering is done. Note that the movable working surface 238 and the fixed working surface 2
A slight protrusion 239 is provided to prevent sticking or the like occurring between the protrusions 239. Therefore, the planar movable working surface 238 and the fixed working surface 228 are
Even at the time of suction, a slight gap (several to several tens of μm) is formed.

(1) Direction of magnetic flux By the way, based on the shapes of the fixed connector 22 and the movable core 23, they are modeled, and the manner in which the magnetic flux is transmitted is simulated. The results are shown using magnetic flux vectors. Model specifications are as follows: inner diameter of pipe 21: 9.8 mm, wall thickness: 0.8 mm, outer diameter of reduced diameter portion 222 of fixed connector 22 (outer diameter before chamfering): 9.6 mm, chamfer width: 0.1 mm. 15 mm, outer diameter of guide part 231 of movable core 23: φ9.8 mm (0.05
mm chamfer). The magnetomotive force of the electromagnetic coil 24 is 6
(A) × 172 (times).

On the other hand, FIG. 3 shows the fixed connector 22 'in a case where the fixed outer peripheral corner 226' is not chamfered. FIG. 6A shows the base shape, and FIG. 6B shows the same simulation results as described above using magnetic flux vectors. As can be understood from a comparison between FIG. 2B and FIG. 3B, when chamfering is performed as in the present embodiment, the magnetic flux vectors from the movable working surface 238 to the fixed working surface 228 are on the outer peripheral side thereof. However, it is almost oriented in the normal direction of the fixed action surface. On the other hand, when the chamfering is not performed, the magnetic flux vector on the outer peripheral side shifts (inclines) toward the inner peripheral side, and the component in the normal direction decreases.

(2) Influence of Coil Current or Chamfer Width on Static Attraction Force Using the fixed connector 22 and the movable core 23 shown in FIG. The effect on force was also determined by simulation. The results are shown in FIGS. 4A and 4B. FIG. 4 (a)
The following can be understood from When the chamfer width is set to about 0.5 mm, regardless of the coil current, the static attraction force of the movable core 23 is improved as compared with the case without the chamfer. However, if the chamfer width is too large, the effective working area of the electromagnetic force decreases, and conversely, the static suction force decreases.

The following can be understood from FIG. By providing a chamfer with a chamfer width of about 0.1 mm or more, the static attraction force is improved regardless of the magnitude of the coil current. However, if the chamfer width dimension exceeds about 0.7 mm, the effective working area of the electromagnetic force decreases. For this reason, the static suction force in that case is less than or equal to that without chamfering. Therefore, in the case of the present embodiment, it is understood that it is preferable to determine the chamfer width in the range of 0.1 to 0.7 mm. In particular, it is more preferable that the chamfer width is in the range of 0.3 to 0.5 mm. However, since the chamfer width at which the static suction force is improved is related to the effective working area of the electromagnetic force, it varies depending on the original dimensions (dimensions of the fixed working surface). Therefore, it is appropriate to express the ratio by the ratio or the percentage of (dimension of chamfer width) / (dimension of fixed working surface). Expressing the above example in terms of the ratio, since the outer diameter of the fixed working surface 228 before chamfering is φ9.6 mm, the chamfer width is 0.01 to 0.07 of the outer diameter before chamfering.
(That is, 1 to 7%), and more preferably 0.03 to 0.
05 (3 to 5%). As can be understood from FIG. 4, by performing appropriate chamfering in a normal range, the suction force acting on the movable core increases. And, by the improvement of the suction force, the stable minimum fuel injection amount can be optimized and the controllability of the fuel injection valve can be further improved.

[0027]

According to the fuel injection valve of the present invention, the generated electromagnetic force can be efficiently converted into the attraction force of the movable core, and the attraction force can be increased. Moreover, since only an appropriate chamfer is provided at the outer peripheral corner of at least one of the cores, it can be easily implemented without major design changes or the like. Also, by providing the chamfer, it is possible to prevent the occurrence of dents and the like, and it becomes easy to manage parts.

[Brief description of the drawings]

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

FIG. 2A is an enlarged cross-sectional view of a fixed connector and a movable core according to the embodiment, and FIG. 2B is a model obtained by simulating a state of a magnetic flux appearing between the fixed connector and the movable core; FIG.

FIG. 3A is an enlarged sectional view of a fixed connector and a movable core in a case where no chamfer is provided, and FIG. It is a result figure of having simulated.

FIG. 4 is a graph showing an influence of a coil current or a chamfer width on a static attraction force, and FIG. 4A is a graph showing a relationship between a coil current and a static attraction force with the chamfer width as a parameter. FIG. 4B is a graph showing the relationship between the chamfer width dimension using the coil current as a parameter and the static attraction force.

[Explanation of symbols]

 Reference Signs List 1 fuel injection valve 21 pipe 22 fixed connector 23 movable core 24 electromagnetic coil 31 needle valve (valve element) 226 fixed outer peripheral corner 236 movable outer peripheral corner 228 fixed working surface 238 movable working surface 227 tapered surface (chamfered)

Continued on front page F term (reference) 3G066 AA01 AA07 AB02 AD10 AD12 BA00 BA19 BA54 BA56 BA63 CC06U CC14 CD30 CE23 CE24 CE26 3H106 DA07 DA13 DA23 DB02 DB12 DB23 DB32 DC06 DC17 DD03 EE04 EE16 GA13 GA15 KK18

Claims (5)

[Claims] 1. A fixed connector made of a magnetic material which is fitted and fixed to an inner peripheral side of the pipe and has a fixed working surface at one end side, and a coaxial connector with the fixed connector. A movable core made of a magnetic material having a movable working surface on one end side slidably fitted on the circumferential side and facing the fixed working surface; and the fixed working surface and the movable working surface being supplied with power from a power supply source. An electromagnetic coil that generates a magnetic flux passing through the fixed connector and generates a suction force between the fixed connector and the movable core; and a valve that moves together with the movable core and opens and closes a fuel injection hole depending on whether power is supplied to the electromagnetic coil. A fuel injection valve comprising: a fixed outer peripheral corner formed by the outer peripheral surface of the fixed connector and the fixed operating surface; and a movable outer peripheral corner formed by the outer peripheral surface of the movable core and the movable operating surface. At least one is chamfered A fuel injection valve characterized in that: 2. The fixed outer peripheral surface according to claim 1, wherein the outer peripheral diameter of the fixed operating surface before chamfering is smaller than the outer peripheral diameter of the movable operating surface before chamfering, and the chamfer is formed at the fixed outer peripheral corner portion. Fuel injection valve. 3. The fixed connector has a press-fitted portion press-fitted into the inner peripheral side of the pipe, a coaxial extension extending coaxially from the press-fitted portion, a diameter slightly reduced from the press-fitted portion, and the fixed outer peripheral corner portion at an end. The fuel injection valve according to claim 2, comprising a reduced diameter portion. 4. The fuel injection valve according to claim 1, wherein the chamfer width of the chamfer is 1 to 7% of an outer peripheral diameter of the fixed working surface or the movable working surface before chamfering. 5. The fuel injection valve according to claim 1, wherein the chamfer is a 45 ° chamfer.