JPH0223820Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an electromagnetic fuel injector that is mainly used in multi-point or single-point electronically controlled fuel injection devices for internal combustion engines (hereinafter also referred to as engines) of automobiles.

The applicant of this application has filed a series of applications (patent application 1983-
No. 127032, No. 1982-203066, Utility Model Registration Application No. 185081/1983, etc.) have provided a valve structure for an electromagnetic fuel injector having a spherical valve portion. However, in a valve structure with a spherical valve element, there is little room for the viscosity coefficient to contribute as a characteristic value that determines the flow rate of the injected fuel, and for this reason, when the temperature of the injected fuel increases, its specific weight decreases. There was a problem that the effect was directly manifested and the flow rate of the injected fuel decreased. As a solution to these problems, the applicant filed an application for utility model registration in 1983.
No. 119438 is provided.

The purpose of this invention is to provide an electromagnetic fuel injector that solves the above-mentioned problems in the same way as the above-mentioned application, and can supply a mixture with a stable air-fuel ratio to an engine with little change in the flow rate of injected fuel even at high temperatures. .

The electromagnetic fuel injector according to the present invention has a substantially spherical valve element at the tip of an on-off valve and a substantially cone fixed to the substantially spherical valve element. Moreover, this substantially conical body is located downstream of the seal portion of the substantially spherical valve element portion, and its tip does not reach into the fuel injection port.

According to the present invention, the seal part where the valve element contacts the valve seat to seal the fuel is spherical, and even if the on-off valve is tilted with respect to the valve seat, the seal can be reliably sealed.

In other words, it has not lost its self-centering function, which is the advantage of ball valves. The substantially conical body added to the downstream side of the ball valve solves the above-mentioned problems of the ball valve.

An embodiment of this invention will be described below based on the drawings. In the electromagnetic fuel injector 1 shown in FIG. 1, the valve housing 2 has a stepped cylindrical shape, and has a fuel injection port 3 at the center of its tip, which communicates with a guide hole 4 provided at the center of the shaft. . The intermediate portion between the fuel injection port 3 and the guide hole 4 is a valve seat 3a having a conical surface.
and a fuel reservoir 4a machined to have a larger diameter than the guide hole 4.
is provided. The on-off valve 11 is of a plunger type, and its hollow cylindrical slide portion 12 is slidably inserted into the guide hole 4 .

A substantially spherical valve portion 1 is provided at the front end of the slide portion 12.
3, and an armature 14 having a hole in the center is connected to the outer periphery of the rear end. The inside of the slide portion 12 forms a fuel passage 12a together with the hole in the armature 14, and an outlet 12b is provided on the front side surface thereof and communicates with the fuel reservoir 4a. The fixed core 5 is a cylindrical body having a flange portion 5a on the outer periphery of the center in the longitudinal direction, and has a fuel passage 6 formed therein that penetrates in the axial direction. A fuel filter 18 is attached to the fuel filter 18. The magnetic case 9 has a valve housing mounting hole 9a at the front end, and an electromagnetic coil housing hole 9b from the center to the rear. These holes communicate with each other through holes that are larger than the outer diameter of the armature 14.

The rear large diameter portion of the valve housing 2 is inserted into the valve housing mounting hole 9a and crimped, and the fixed core inserted from the rear into the electromagnetic coil housing hole 9b is similarly crimped at its flange 5a. It is being In this state, the valve housing 2 and the fixed iron core 5 are placed coaxially. A compression spring 7 is inserted between the rear end of the on-off valve 11 and the front end of the sleeve 6a, and urges the on-off valve 11 forward to maintain it in a closed state.

In this state, the gap between the rear end surface of the armature 14 and the front end surface of the fixed iron core 5 has a value predetermined as the opening/closing stroke of the on-off valve 11.

A cylindrical electromagnetic coil 8 is mounted in a space formed by the electromagnetic coil receiving hole 9b of the magnetic case 9 and the outer periphery of the fixed iron core 5. This electromagnetic coil 8
is electrically connected to an input terminal 10 located at the rear of the magnetic case 9. 15, 16 and 17 are all O-rings for sealing.

As shown enlarged in FIGS. 2 and 3, the valve part 13 of the on-off valve 11 has an apex angle of the conical surface of the valve seat 3a on the front (downstream side) of the seal part 13a that comes into contact with the valve seat 3a. A constriction forming member 13b, which is a substantially conical body having an apex angle θ3 slightly larger than θ1 and having a conical surface coaxial with the on-off valve 11, is fixed. Note that as shown in FIG. 2, the substantially conical body 13b
is attached to the downstream side with a slight clearance from where the valve element 13 comes into contact with the valve seat 3a when it is coaxial with the valve housing 2.
Therefore, even if the opening/closing valve 11 is slightly bent, the valve element 13 is structured to reliably abut and seal the valve seat 3a with its circumferential surface. That is, the seal portion 13a is not a perfect line, but is a spherical surface within the limit of the bending of the on-off valve 11, and has a structure in which it seals at any of its circumferential lines.

In the valve closed state (Fig. 2), this valve part 13
The peripheral surface 13a of the valve seat 3a contacts the conical surface of the valve seat 3a to seal the fuel. In addition, in the valve open state (Fig. 3), the conical annular space (length) formed by the downstream conical surface (length) of the valve element 13 and the conical surface of the valve seat 3a is the constricted part of the fuel passage. Configure f.

In the above configuration, in the electromagnetic fuel injector 1, the on-off valve 11 is normally urged forward by the compression spring 7 and is in a closed state (FIG. 2). When the input terminal 10 receives a valve opening signal, the electromagnetic coil 8
When current flows through the on-off valve 11, the compression spring 7
The tip of the fixed iron core 5 and the rear end of the armature 14 come into contact with each other, resulting in an open state as shown in FIG. 3. and fuel filter 18, fuel passages 6, 12a, fuel outlet 12b,
The pressurized fuel sent via the fuel reservoir 4a passes through the constriction part f formed by the conical surface of the valve seat 3a and the conical surface of the valve element 13, and is injected from the fuel injection port 3.

Now, if the flow of fuel in the throttle part f is approximated by the flow in a parallel double pipe, the following relationship holds true.

Gf≒CA√2(−△) (1) △P≒48μV/De ² (2) Here, Gf fuel flow rate, C: flow coefficient downstream of the throttle section, A: flow path cross-sectional area downstream of the throttle section , rf: specific weight of fuel, P: fuel pressure, △P: pressure loss at the throttle section, μ: viscosity coefficient of fuel, V: flow velocity of fuel at the throttle section,: length of the throttle section, De: length of the throttle section gap (difference between both diameters). Considering the case where the fuel temperature increases according to this equation,
As the fuel temperature increases, both the specific weight rf of the fuel and the viscosity coefficient μ of the fuel decrease. Therefore, by appropriately selecting and De to regulate the change in (P-△P) due to temperature, it is possible to minimize the change in the value of rf (P-△P). That is, the effects of changes in the specific weight of the fuel and changes in the viscosity coefficient cancel each other out, so that changes in the fuel flow rate Gf at the throttle portion f due to temperature can be reduced. On the other hand, in the conventional valve structure without a throttle part, in equation (2), ≒O,
This is considered to be the case when De is large, and △P≒O.
Therefore, equation (1) becomes Gf≒CA√2 (1)′, and the fuel flow rate Gf is directly affected by the decrease in the specific weight rf of the fuel due to the temperature increase, and the fuel flow rate Gf decreases significantly. FIG. 4 shows the results of an experiment in which the weight change rate of the injected fuel was investigated with respect to the fuel temperature for the electromagnetic fuel injector according to the prior art and the present embodiment. In the case of the conventional technology represented by the dotted line, the injected fuel flow rate decreases significantly as the fuel temperature rises, whereas in the case of this embodiment represented by the solid line, the rate of decrease in the injected fuel flow rate is small. It can be seen that the effect of the diaphragm part f in the above-mentioned invention has been verified. Furthermore, in this embodiment, since the sealing portion 13a of the valve element 13 that comes into contact with the conical surface of the valve seat 3a in the closed state is a part of the spherical surface, the self-aligning function of the on-off valve having the spherical valve element is provided. It is possible to secure the advantages associated with this, such as weight reduction and ease of processing.

Furthermore, in the case of this embodiment, the aperture part forming member 13
b is connected to the valve part 13 as a separate part. Therefore, the length of the throttle part and the gap De can be set more freely, so that the rate of decrease in the flow rate of the injected fuel can be kept small.

Furthermore, according to this embodiment, by providing the throttle part downstream of the valve part seal part 13a, the space volume formed between the valve part seal part 13a and the fuel injection port 3 is reduced. The formation of paper, which tends to occur near the fuel injection port 3, is suppressed, and so-called trailing of fuel after the valve is closed is reduced.

As explained above, in an electromagnetic fuel injector having an on-off valve with a valve element, the valve seat is a conical surface, and the valve seat is located downstream of the sealing part of the valve element that comes into contact with the conical surface of the valve seat. A substantially conical surface is fixed to the valve, and the gap between the conical surface of the valve seat and the conical surface of the valve element forms a constriction part when the valve is open, thereby controlling the injected fuel flow rate even when the fuel is at a high temperature. This has the effect of being able to supply the engine with a mixture with a stable air-fuel ratio.

In addition, by providing the above-mentioned throttle part on the flow side of the seal part of the valve element, it is possible to suppress the generation of vapor near the fuel injection port, and it is also possible to reduce the amount of fuel dripping after the valve is closed. This has the effect of improving the flow rate control characteristics of the injected fuel.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an embodiment of this invention, FIG. 2 is an enlarged sectional view of the valve part of FIG. 1 in the closed state, and FIG. FIG. 4 is an explanatory diagram showing the rate of change in the flow rate of the injected fuel depending on the fuel temperature for the embodiment according to the present invention and the prior art. 2...Valve housing, 3...Fuel injection port, 3a...Valve seat, 4...Guide hole, 11...Opening/closing valve, 12...Slide part, 13...Valve part, 1
3a...Seal portion, 13b...Aperture forming member,
f...Aperture section.

Claims (1)

[Scope of Claim for Utility Model Registration] A fuel injector that injects and supplies fuel, comprising: a fuel injection port at the tip; a valve seat having a conical surface connected to the fuel injection port; and a guide hole connected to the valve seat. an on-off valve that is slidably inserted into the guide hole and comes into contact with the valve seat to seal the fuel; and the on-off valve is reciprocated between an open position and a closed position. an on-off valve drive mechanism, the on-off valve has a substantially spherical valve element portion and a substantially conical body at its tip, and the substantially conical body is slightly larger than the conical surface of the valve seat. an electromagnetic valve having an apex angle and fixed to the valve element in such a manner that its tip does not reach the inside of the fuel injection port downstream of the seal part where the valve element contacts the valve seat in the valve closing position; fuel injector.