JPH0828360A - Fuel injection device - Google Patents

Abstract

PURPOSE:To provide a fuel injection device by which a plunger can be smoothly actuated without spoiling responsiveness by using an inexpensive ordinary driving circuit. CONSTITUTION:A fuel injection device 10 is provided with an electromagnetic coil 24 arranged in a tubular main body 12 having fuel injection valves 52 and 54, a plunger 36 which is arranged inside of the electromagnetic coil and opens and closes the valves by reciprocating in the axial direction by controlling current-carrying to the electromagnetic coil and a guide 20 arranged between the electromagnetic coil and the plunger in order to guide the plunger. In such a fuel injection device, the guide is formed of a magnetic material. Therefore, a side air gap between the electromagnetic coil and the plunger is substantially reduced, and magnetic resistance can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device for an internal combustion engine, and more particularly to a compressed natural gas (Compres
sed Natural Gas; hereinafter referred to as "CNG") and the like for a fuel injection device for controlling injection of fuel.

[0002]

2. Description of the Related Art There are various types of fuel injection devices used in internal combustion engines that use CNG as fuel, but so-called electromagnetic control type devices are widely used. The electromagnetically controlled fuel injection device is generally configured to reciprocate a plunger in a tubular body by electromagnetic action of an electromagnetic coil to open / close a valve to control fuel injection.

As a conventional electromagnetically controlled fuel injection device,
Japanese Utility Model Laid-Open No. 59-186472 is available. Here, the electromagnetic coil is formed in a ring shape or a cylindrical shape, and the plunger is arranged inside thereof. The cylindrical guide disposed between the electromagnetic coil and the plunger is made of a non-magnetic material, and the plunger is slid along the inner surface of the guide, that is, the guide surface.

[0004]

In the above-mentioned fuel injection device, it is preferable to move the plunger at high speed in order to improve the response of fuel control. Further, in the multipoint system, the stroke of the plunger may be increased in order to cover the entire flow rate range with one fuel injection device.

When the plunger is moved at a high speed or when the stroke of the plunger is increased, it is necessary to increase the attraction force of the plunger when the electromagnetic coil is excited. In order to increase this attractive force, the magnetic flux density passing through the plunger during excitation may be increased. Conventionally, as the means, the magnetomotive force itself generated by the electromagnetic coil has been increased by increasing the number of coil turns of the electromagnetic coil or providing a special drive circuit such as a step-up driver.

However, the method of increasing the number of coil turns has a problem that the responsiveness is deteriorated due to the increase of the inductance. On the other hand, a special drive circuit such as a boost driver has a problem that the drive circuit itself is expensive.

Therefore, an object of the present invention is to operate the plunger at high speed or with a large stroke without damaging the response by increasing the number of coil turns of the electromagnetic coil or using an expensive drive circuit. An object of the present invention is to provide a fuel injection device that can be used.

[0008]

To achieve the above object, in a fuel injection device according to the present invention, a tubular main body having a valve for fuel injection, an electromagnetic coil provided in the main body, It is arranged coaxially inside the electromagnetic coil,
A plunger, which reciprocates in the axial direction to open and close the valve by controlling energization to the electromagnetic coil, and a guide made of a magnetic material, arranged between the electromagnetic coil and the plunger to guide the plunger, are provided. It is characterized by that.

Further, in the fuel injection device having the above structure,
It is preferable to form a coating made of a material having a small coefficient of friction, for example, a fluororesin on either or both of the guide surface of the guide and the surface of the plunger in contact with the guide surface.

Further, when the restriction member for restricting the movement of the plunger due to the excitation of the electromagnetic coil by contacting the end face of the plunger is arranged facing the plunger, the restriction member is magnetic. Made from materials,
A taper toward the plunger is preferred.

[0011]

In the fuel injection device according to the present invention, when the energization of the electromagnetic coil is controlled, the plunger reciprocates in the axial direction to open and close the valve. A guide for guiding the plunger is arranged between the electromagnetic coil and the plunger and is made of a magnetic material. Therefore, the side air gap between the electromagnetic coil and the plunger is substantially reduced. That is, since the guide is made of a magnetic material, a magnetic circuit having a low magnetic resistance can be formed, and the magnetic flux density passing through the plunger can be increased.

Further, although the plunger slides in contact with the guide surface of the guide, either one or both of the guide surface of the guide and the surface of the plunger in contact with the guide surface,
The operation of the plunger is facilitated by providing the coating made of fluororesin or the like.

Further, when the regulating member is tapered, the magnetic flux density passing through the plunger is increased to increase the attractive force acting on the plunger, and the magnetomotive force of the electromagnetic coil is effective. Can be used for.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the fuel injection device according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment of a fuel injection device 10 for CNG according to the present invention. In FIG. 1, reference numeral 12 denotes a tubular main body of the fuel injection device 10, and the main body 12 is coaxial with a tubular housing 14 and one end side of the housing 14 (hereinafter, this side is referred to as a “front” side). And a fuel introduction pipe 18 coaxially attached to the other end side of the housing 14 (hereinafter, this side is referred to as a “rear” side).

The housing 14 is made of a magnetic material, and the central portion in the front-rear direction has a double pipe structure composed of an inner pipe portion 20 and an outer pipe portion 22. An annular space that opens rearward is formed between the inner pipe portion 20 and the outer pipe portion 22, and an annular electromagnetic coil 24 is mounted in this annular space.

The fuel introducing pipe 18 is connected to a pipe (not shown) from a CNG tank (not shown), and is for introducing CNG from the CNG tank into the housing 14, and like the housing 14, Made from magnetic material. A flange 26 is provided on the outer peripheral surface of the fuel introducing pipe 18.
Are integrally formed. As shown, the fuel introduction pipe 1
When 8 is assembled to the housing 14, the front surface of the flange 26 is in contact with the rear end portion of the electromagnetic coil 24 mounted inside the housing 14, and the outer peripheral surface of the front end portion of the fuel introduction pipe 18 is inside the electromagnetic coil 24. Touch the surface. In addition, a constant distance is provided between the front end surface of the fuel introduction pipe 18 and the rear end surface of the inner pipe portion 20 of the housing 14. Furthermore,
The front end portion 19 of the fuel introduction pipe 18 is tapered so that the diameter becomes smaller toward the front. In the illustrated embodiment, the hole 2 provided in the flange 26 of the fuel introducing pipe 18
A lead wire 30 is connected to the electromagnetic coil 24 through 8.

The nozzle head 16 attached to the front end portion of the housing 14 uses the CNG introduced into the housing 14 from the fuel introduction pipe 18 to the outside (actually, the intake manifold of the internal combustion engine to which the fuel injection device is attached). Etc.), and a through hole 32 as a fuel injection nozzle hole is formed in the center thereof.

The inner space 34 of the housing 14, more specifically, the inner tube portion 20 of the housing 14, the nozzle head 1
A plunger 36 made of a magnetic material is arranged in a space 34 surrounded by 6 and the fuel introduction pipe 18. The plunger 36 is slidable in the front-rear direction using the inner pipe portion 20 of the housing 14 as a guide.

Further, as clearly shown in FIG. 2, the inner peripheral surface (guide surface) 38 of the inner pipe portion 20 of the housing 14 and the outer peripheral surface 4 of the plunger 36 slidably contacting the inner peripheral surface 38.
0, coatings 42 and 44 made of a material having a small friction coefficient are provided over the entire circumference. This film 4
As the material of Nos. 2 and 44, a non-adhesive fluororesin having excellent wear resistance and a small friction coefficient is preferable.

A fuel hole 46 is formed inside the plunger 36. The fuel hole 46 extends from the center of the rear end surface of the plunger 36 along the central axis, and is provided with four oblique holes 48 extending outward from a certain point near the front end surface of the plunger 36, so that the inside of the front side of the housing 14 is extended. Space 34
It leads to. Therefore, the CNG introduced by the fuel introducing pipe 18 is the fuel hole 46 and the oblique hole 48 of the plunger 36.
Through the inner space 34 on the front side of the housing 14.

A compression spring 50 is arranged between the plunger 36 and the fuel introducing pipe 18, and the spring force of the compression spring 50 causes the plunger 36 to be constantly pressed forward, that is, toward the nozzle head 16 side. The valve body 52 is fixed to the front end surface of the plunger 36, and the rear end surface 54 of the nozzle head 16 facing the valve body 52 functions as a valve seat. Therefore, when the plunger 36 is moved forward by the spring force of the compression spring 50, the valve body 52 comes into close contact with the valve seat 54 and closes the fuel injection valve including the valve body 52 and the valve seat 54.

On the other hand, the plunger 36 includes the electromagnetic coil 24.
Is excited, the electromagnetic force causes it to move backward against the spring force of the compression spring 50. Due to this rearward movement of the plunger 36, the valve is opened and the through hole 32 of the nozzle head 16 is inserted into the internal space 34 of the housing 14.
Be communicated to. The backward movement of the plunger 36 is regulated by the front end surface of the fuel introduction pipe 18 which also functions as a regulation member. A rubber shock absorbing member 56 is attached to the front end surface of the fuel introducing pipe 18 in order to prevent direct contact with the plunger 36 and reduce impact at the time of contact.

In the above structure, the CNG supplied from the CNG tank (not shown) to the rear end of the fuel introduction pipe 18
Is introduced into the housing 14 after being filtered through a strainer 58 provided in the fuel introduction pipe 18. The CNG introduced into the housing 14 further passes from the fuel hole 46 of the plunger 36 through the oblique hole 48 and is guided to the internal space 34 on the nozzle head 16 side.

Here, when the electromagnetic coil 24 is in the non-excited state, the plunger 36 is pressed toward the nozzle head 16 side by the compression spring 50, and the valve element 52 is in close contact with the rear end surface of the nozzle head 16 which is the valve seat 54. . At this time, CNG is not ejected from the through hole 32 of the nozzle head 16.

On the other hand, when the electromagnetic coil 24 is energized and excited, the plunger 36 moves rearward against the spring force of the compression spring 50, and the valve body 52 separates from the nozzle head 16, so that CNG is in the housing. It is ejected from the internal space 34 of the nozzle 14 to the outside through the through hole 32 of the nozzle head 16.

In this embodiment, since the inner tube portion 20 of the housing 14 serving as the guide of the plunger 36 is made of a magnetic material, the side air gap between the plunger 36 and the electromagnetic coil 24 is greatly reduced. The thicknesses of the fluororesin coatings 42 and 44 are substantially the same. As a result, the magnetic resistance in the magnetic circuit constituted by the electromagnetic coil 24, the inner pipe portion 20, the plunger 36, and the fuel introduction pipe 18 becomes small, so that the electromagnetic coil 2
When 4 is excited, a strong plunger attraction force is generated. Therefore, when the plunger 36 is moved at a high speed or when the stroke of the plunger 36 is large, a desired suction force can be obtained without using a special drive circuit or increasing the number of coil turns.

Further, the presence of the coatings 42 and 44 having a small coefficient of friction allows the plunger 36 to operate smoothly in the inner pipe portion 20. Further, when a fluorine resin is used as the material of the coatings 42 and 44, it has excellent characteristics such as wear resistance and non-adhesiveness, and therefore wear due to the reciprocating movement of the plunger 36 and between the plunger 36 and the inner pipe portion 20. Sticking is prevented.

As described above, the magnetic circuit formed by the electromagnetic coil 24 shown in FIG.
4), the fuel injection pipe 18 (regulating member), the plunger 36, and the inner pipe portion 20 (a part of the housing), and the magnetic flux passes through these parts in this order. When the electromagnetic coil 24 is excited by this magnetic circuit, the fuel introduction pipe 18
The front end face of the plunger 36 and the rear end face of the plunger 36 attract each other. At this time, it is desirable that all the magnetic flux that has passed through the front end face of the fuel introducing pipe 18 be guided to the rear end face of the plunger 36, but if the front end portion 19 of the fuel introducing pipe 18 is not tapered, then a part of the magnetic flux will be generated. Is the inner pipe portion 20
Be led to. This is because the magnetic flux guided to the inner pipe portion 20 does not penetrate the rear end face of the plunger 36, so that the rear end face of the plunger 36 cannot be attracted to the front end face of the fuel introducing pipe 18. Therefore, in this embodiment, the front end portion 19 of the fuel introduction pipe 18 that is in contact with the electromagnetic coil 24 is tapered so that the magnetic flux guided to the inner pipe portion 20 is reduced and the magnetic flux guided to the rear end face of the plunger 36 is increased. It is a thing. As a result, the attractive force of the plunger 36 is strengthened, and the magnetomotive force of the electromagnetic coil 24 can be effectively used.

The rear end portion 70 of the inner pipe portion 20 is also tapered. That is, a taper is provided at the rear end of the inner pipe member 20. As a result, the magnetic flux guided to the inner pipe portion 20 is reduced and the magnetic flux guided to the rear end surface of the plunger 36 is increased, so that the attractive force of the plunger 36 is strengthened.

The preferred embodiments of the present invention have been described above in detail, but it goes without saying that the present invention is not limited to the above embodiments. For example, in the above embodiment, the inner tube portion 20 of the housing 14 made of a magnetic material serves as a guide for the plunger 36. However, as in the fuel injection device 10 'shown in FIG. It is also possible to provide it separately from ′ and arrange it between the electromagnetic coil 24 and the plunger 36. As a result, surface treatment such as Teflon treatment can be easily applied to the guide 60, and the guide 60 itself can be easily processed.

In the above embodiment, the coatings 42 and 44 made of a non-magnetic material are formed on both the inner tube portion 20 of the housing 14 and the plunger 36, but either one may be used.

Further, although the above fuel injection devices 10 and 10 'are for CNG, the present invention is also applicable to liquid fuel such as gasoline or liquefied natural gas (LPG).

[0034]

As described above, according to the present invention, the side air gap between the electromagnetic coil and the plunger is substantially reduced by using the magnetic guide for the plunger. Magnetic resistance can be reduced by using a magnetic material for the guide, as compared with the case where a guide made of a non-magnetic material is used as in the related art. Therefore, the plunger can be operated at a high speed or with a large stroke without using an expensive drive circuit such as a booster driver or increasing the number of coil turns of the electromagnetic coil. This is particularly effective when it is desired to increase the stroke of the plunger in order to increase the flow rate of the injected fuel in the multipoint system or the like.

Further, since it is not necessary to increase the number of coil turns of the electromagnetic coil, it is possible to maintain or reduce the inductance, thus preventing the response from being lowered.

Further, when a coating made of a material having a small coefficient of friction such as fluororesin is provided between the guide and the plunger, the sliding of the plunger in the guide is smoothed, and the sticking between the two is caused. Etc. can also be prevented.

Further, by making the tip of the regulating member arranged opposite to the plunger into a tapered shape, the magnetic flux density passing through the plunger is increased, the attractive force acting on the plunger is increased, and the magnetomotive force of the electromagnetic coil is effective. Can be used for. This can also improve the responsiveness of the fuel injection device.

[Brief description of drawings]

FIG. 1 is a view showing an embodiment of a fuel injection device according to the present invention and is a cross-sectional view taken along an axis of a main body.

FIG. 2 is an enlarged partial sectional view showing the periphery of a plunger of the fuel injection device shown in FIG.

FIG. 3 shows a modified example of the fuel injection device according to the present invention.
It is a sectional view similar to FIG.

[Explanation of symbols]

10, 10 '... Fuel injection device, 12 ... Main body, 14, 1
4 '... Housing, 16 ... Nozzle head, 18 ... Fuel introduction pipe (regulating member), 19 ... Tapered front end portion,
20 ... Inner pipe part (guide), 22 ... Outer pipe part, 24 ... Electromagnetic coil, 32 ... Through hole, 34 ... Internal space, 36 ... Plunger, 38 ... Inner peripheral surface (guide surface) of inner pipe part, 40 ... Outer surface of plunger, 42, 44 ... Coating, 46 ... Fuel hole,
48 ... Oblique hole, 50 ... Compression spring, 52 ... Valve body, 54 ... Valve seat, 60 ... Guide, 70 ... Tapered rear end.

Claims (4)

[Claims] 1. A tubular main body having a valve for fuel injection, an electromagnetic coil provided in the main body, coaxially arranged inside the electromagnetic coil, and controlling energization to the electromagnetic coil. A plunger that reciprocates in the axial direction to open and close the valve, and a guide made of a magnetic material, which is arranged between the electromagnetic coil and the plunger to guide the plunger. Fuel injection device. 2. The coating of a material having a small coefficient of friction is formed on one or both of the guide surface of the guide and the surface of the plunger in contact with the guide surface. Fuel injection device. 3. The fuel injection device according to claim 2, wherein the coating film is made of a fluororesin. 4. The plunger is arranged so as to face the plunger and is tapered toward the plunger so as to restrict the movement of the plunger due to the excitation of the electromagnetic coil by contacting the end face of the plunger. The fuel injection device according to any one of claims 1 to 3, further comprising a regulating member made of a magnetic material.