Fuel Injection Valve For Internal Combustion Engines

Abstract

An injection valve which injects fuel directly into the inlet valve for a cylinder in an internal combustion engine comprises a piston which is reciprocable in the chamber of a cylinder member from a neutral position to a retracted position to thereby admit into the chamber a metered quantity of fuel, and thereupon from neutral to an extended position to thereby inject such quantity of fuel into the inlet valve. The piston is moved by an electromagnetic drive which receives signals from an electronic control circuit.

Description

BACKGROUND OF THE INVENTION

The present invention relates to internal combustion engines in general, and more particularly to improvements in engines of the type wherein the fuel is injected into the cylinders. Still more particularly, the invention relates to improvements in valves which atomize and inject metered quantities of fuel into the cylinders of an internal combustion engine, especially to valves whose operation is controlled by electronically regulated electromagnetic drive means.

Recently developed electronic control circuits which regulate the admission of fuel to the cylinders of an internal combustion engine render it possible, in theory, to control the admission of fuel with a high degree of precision so that the cylinders receive an optimum mixture of fuel and oxygen under all operating conditions. However, it was found that the presently available valves which atomize and inject fuel are not entirely satisfactory. As a rule, such valves are actuated by electromagnets which receive signals from the electronic control circuit and inject fuel to the suction manifold. The valves are opened in response to energization of associated electromagnets and remain open for intervals whose length is determined by the control circuit to thus insure injection of predetermined quantities of fuel per unit of time. It is preferred to inject atomized fuel directly into the inlet valves for the cylinders. This brings about the advantage that the engine operates in the same way as if the fuel were injected directly into the cylinder chambers without, however, necessitating pressurization of the fuel to the same extent as in engines where the fuel is actually injected into the cylinder chambers proper. Thus, the injection valves which direct fuel into the inlet valves need not pressurize the fuel to the same degree as in engines where the orifices of injection valves discharge directly into the chambers of the corresponding cylinders.

Another advantage of engines wherein the injection valves admit fuel into the inlet valves rather than into the cylinder chambers proper is that the mist formed by nonevaporated minute fuel particles is caused to enter the cylinder chambers and produces a desirable cooling action.

All such advantages were duly recognized in the art; however, the presently known injection valves are incapable of insuring that a requisite amount of fuel is injected during the intervals when the associated inlet valves for the cylinders remain open, especially if the engine operates at a high speed so that the intervals during which the inlet valves remain open are very short. Attempts to overcome such drawbacks of presently known injection valves include an increase in pressurization of fuel which, in turn, creates additional problems without invariably insuring that a desired quantity of fuel is injected into an inlet valve during the short interval when the inlet valve is open.

SUMMARY OF THE INVENTION

An object of the invention is to provide a novel and improved fuel injection valve which is constructed and assembled in such a way that it can invariably inject a desired quantity of fuel into an inlet valve during the intervals when the inlet valve is open.

Another object of the invention is to provide an injection valve which can insure timely injection and atomization of fuel even if the fuel is supplied thereto at a relatively low pressure.

A further object of the invention is to provide an injection valve whose operation can be regulated by presently known electronic control circuits and which can be used with equal advantage in many types of electronically regulated internal combustion engines.

The invention is embodied in a fuel injection valve for internal combustion engines, particularly for direct injection of fuel into the inlet valve for a cylinder in an internal combustion engine. The injection valve comprises a cylinder member defining a chamber and provided with fuel admitting opening means and fuel-discharging orifice means, a piston reciprocably received in the chamber, and electric drive means (preferably including an electromagnetic drive which is regulated by the electronic control circuit for the engine) operative to move the piston from a neutral position to a second position whereby the piston effects admission of fuel by way of the opening means, and from the neutral position to a third position whereby the piston expels the thus admitted fuel by way of the orifice means.

The injection valve preferably further comprises a sealing device which is operatively connected with the piston and seals the orifice means when the piston dwells in the neutral or second position as well as during movement of the piston between neutral and second positions.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved fuel injection valve itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic axial sectional view of a fuel injection valve which embodies the invention;

FIG. 2 is a diagram showing a curve representing the signals which are used to effect movements of the piston to second position in which the piston permits entry of fuel into the cylinder member;

FIG. 3 is a similar diagram showing a curve representing those signals which are used to effect movements of the piston in a direction to expel fuel from the cylinder member; and

FIG. 4 is a diagram showing the sequence of movements and duration of dwells of the piston in neutral, second and third positions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIG. 1, there is shown a fuel injection valve which comprises a cylinder member 13 defining a cylinder chamber 13a, a piston 12 which is reciprocable in the chamber 13a, and an electromagnetic drive 10 which serves to reciprocate the piston 12 with reference to the cylinder member between a neutral position a, a retracted or second position b and an extended or third position c. The movable armature 14 of the electromagnetic drive 10 is operatively connected with the piston 12 by a rod or shaft 11. The arrows 15 indicate those forces which are generated by the electromagnetic drive 10 to move the piston 12 to the retracted position b. The forces indicated by arrows 16 are applied to move the piston 12 to the extended position c. The numeral 29 denotes an electronic control circuit which supplies signals to the drive 10.

The piston 12 is formed with an internal compartment 12a and with an axial bore 17 which accommodates the intermediate portion or stem 18 of a sealing device having a conical head 19 and a plunger 21 which is accommodated in the compartment 12a and is biased toward the bottom surface 12b of the compartment by a helical spring 23 which reacts against an internal shoulder of the piston 12. The numeral 22 denotes a clearance (having a width eta) which develops between the plunger 21 and bottom surface 12b when the piston 12 dwells in the illustrated neutral position a.

The cylinder member 13 is formed with a fuel admitting opening 24 which is sealed by the peripheral surface of the plunger 12 when the latter dwells in the neutral position a, and with a divergent fuel discharging orifice 20 which is sealed by the head 19 when the piston 12 assumes the neutral position a or moves between the positions a, b or dwells in the position b. The maximum width eta of the clearance 22 depends on the dimensions of the valve.

The operation of the valve will be described with reference to FIGS. 2, 3 and 4. The diagram of FIG. 2 indicates the electric signals Jd which are furnished to the drive 10 by the circuit 29 and serve to effect movement of piston 12 from the neutral position a to the retracted position b (suction stroke of the piston). The diagram of FIG. 3 illustrates the electric signals Js which are transmitted to the drive 10 and serve to effect movement of the piston 12 from the neutral position a to the extended position c (injection stroke of the piston). The minimum duration of a signal Jd is tl and its maximum duration is tmax. The duration ts of each signal Js is the same; such duration is selected in such a way that it is less than the minimum duration of opening of the associated inlet valve 30 (FIG 1) which admits fuel into the chamber of the corresponding cylinder in the internal combustion engine.

FIG. 4 shows a diagram which represents movement of the piston 12 between and its dwells in the positions a, b and c. When the piston 12 dwells in the retracted position b, it exposes the discharge end of the opening 24 and permits admission of a metered quantity q of fuel into the chamber 13a. It is assumed that the rate of fuel admission is constant; therefore, when the piston 12 dwells in the position b for an interval tl, it permits the chamber 13a to receive a quantity gl of fuel. If the electronic control circuit 29 which regulates the length of signals Jd changes the length of such signals from tl to tmax, the chamber 13a receives a quantity gmax of fuel. The length of signals Jd is regulated in dependency on one or more factors which influence the operation of the internal combustion engine, such as the pressure in the intake manifold, the pressure of atmospheric air, the position of the gas pedal, and/or others.

The fuel which is admitted into the chamber 13a in response to movement of the piston 12 to the retracted position b remains in the cylinder member 13 until the piston moves to the extended position c, i.e., until the drive 10 receives a signal Js.

When the piston 12 dwells in the neutral position a, its peripheral surface seals the discharge end of the opening 24. The spring 23 is stressed sufficiently to insure that the head 19 of the sealing device seals the fuel discharging orifice 20 in neutral position of the piston 12. Such sealing position of the head 19 is illustrated in FIG. 1.

As stated above, the transmission of a signal Jd to the drive 10 results in movement of the piston 12 to the position b whereby the cylinder member 13 receives a fuel quantity gl if the length of the signal Jd equals t. After elapse of such interval, the piston 12 returns to the neutral position a under the action of the spring 23 and its peripheral surface seals the opening 24 to entrap the quantity gl in the chamber 13a. The drive 10 gl receives a signal Js substantially simultaneously with opening of the inlet valve 30, and such signal causes the piston 12 to move to the extended position c and to dwell in this position for the interval ts. During the initial stage of movement of piston 12 from the position a to the position c, the front end face 12c of the piston compresses the fuel in the chamber 13a because the bottom surface 12b moves toward the plunger 21 until the width (eta) of the clearance 22 is reduced to zero. Thus, the sealing device trails behind the piston 12 when the latter starts to perform its working stroke. The head 19 is lifted off its seat in the orifice 20 when the bottom surface 12b engages and pushes the plunger 21 toward the chamber 13a. The orifice 20 then discharges atomized fuel directly into the open inlet valve 30. On termination of the interval ts, the piston 12 returns to the neutral position a to thereby return the head 19 into sealing engagement with the seat in the orifice 20. This takes place as soon as the bottom surface 12b moves away from the plunger 21, i.e., as soon as the width of the clearance 22 exceeds zero. During return movement of the head 19 to the sealing position of FIG. 1, the piston 12 draws air through the orifice 20 and the quantity of such air depends on the maximum width of the clearance 22. If such clearance is substantial, the amount of air which is sucked into the chamber 13a is small because the head 19 can reassume its sealing position at an earlier stage of movement of the piston from the position c to the position a.

It is possible to increase the width of the clearance 22 to such an extent that the bottom surface 12b is never in contact with the plunger 21. The head 19 then moves to open position exclusively under the pressure of fuel in the chamber 13a while the piston 12 moves from the position a toward the position c. The head 19 then returns to sealing position as soon as the piston 12 leaves the position c.

It was found that the improved fuel injection valve operates in a most satisfactory way if the orifice 20 is immediately adjacent to the intake end of the inlet valve 30. As stated above, the inlet valve 30 should open not later than when the piston 12 begins to move toward the position c and should remain open at least during the interval ts.

The numeral 31 denotes in FIG. 1 a throttle or flow restrictor installed in a conduit which supplies fuel to the opening 24.

The improved fuel injection valve can be provided with means for adjusting the bias of the spring 23 and/or for regulating the width of the clearance 22 to thus regulate the exact moment when the head 19 opens or seals the orifice 20 during axial movement of the piston 12, i.e., during movement between the positions a and c.

An important advantage of our valve is that the entire interval between two successive movements of the piston 12 to extended position c is available for admission of fuel into the chamber 13a. Such interval is long enough to insure that the chamber 13a receives a desired quantity of fuel even if such fuel is admitted at a relatively low pressure. Moreover, suction which is created in the chamber 13a while the piston 12 moves to the retracted position b promotes the inflow of fuel by way of the opening 24. Therefore, the engine which utilizes the improved injection valves can employ a relatively simple and inexpensive fuel pump which merely subjects the fuel to a pressure sufficing to admit into the chamber 13a a desired quantity of fuel which is a function of the length of the interval (tl-1-tmax) during which the piston 12 dwells in the retracted position b. The flow restrictor 31 in the fuel supply conduit for the opening 24 insures that the quantity of fuel admitted into the cylinder member 13 is independent of the pressure in chamber 13a while the piston 12 moves toward and dwells in the position b. Similar results can be achieved by providing the cylinder member 13 with an auxiliary opening which is temporarily sealed by the piston 12 and is exposed at least during a portion of the suction stroke of piston 12 to insure that the pressure in the chamber 13a cannot unduly influence the inflow of fuel. The control circuit 29 shows in FIG. 1 is of the type disclosed, for example, in the German Pat. No. 1,100,377.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of our contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the claims.

Claims

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. A fuel injection valve for internal combustion engines, particularly for direct injection of fuel into the inlet valve for a cylinder in an internal combustion engine, comprising a cylinder member defining a chamber and provided with a fuel admitting opening means and fuel discharging orifice means; a piston reciprocably received in said chamber; a device for sealing said orifice means; connecting means for operating said device by said piston; drive means operative to move said piston from a neutral position in which said piston is sealing said opening means and the device is sealing said orifice means, to a retracted second position whereby the piston effects admission of fuel by way of said opening means into said chamber, and from said neutral position to an extended third position whereby the piston operates said device to open said orifice means and expels the previously admitted fuel by way of said orifice means from said chamber.

2. A fuel injection valve as defined in claim 1, wherein said drive means comprises an electromagnetic drive having a movable portion operatively connected with said piston.

3. A fuel injection valve as defined in claim 1, wherein said device for sealing said orifice means opens said orifice means in response to rising fuel pressure in said chamber during movement of said piston from neutral to third position.

4. A fuel injection valve as defined in claim 1, said device having a first portion coupled to said piston with a predetermined clearance which is reduced to zero during movement of said piston from neutral to third position and a second portion which exposes said orifice means in response to such reduction of said clearance while said piston continues to move toward said third position.

5. A fuel injection valve as defined in claim 4, wherein said device further comprises an intermediate portion disposed between said first and second portions thereof and wherein said orifice means diverges in a direction away from said piston, said second portion comprising a substantially conical head which enters and seals said orifice means not later than when said piston effects admission of fuel into said chamber, said piston having an internal compartment and a bottom surface in said compartment, said first portion of said device comprising a plunger received in said compartment and further comprising means for biasing said plunger toward said bottom surface, said clearance being provided between said plunger and said bottom surface in neutral position of said piston and while said head seals said orifice means.

6. A fuel injection valve as defined in claim 5, wherein said piston is further provided with an axial bore connecting said compartment with said chamber and said intermediate portion of said device is a stem which is slidably guided in said bore.

7. A fuel injection valve as defined in claim 1, wherein said cylinder member is provided with auxiliary opening means which is sealed from said chamber during predetermined stages of movement of said piston.

8. A fuel injection valve as defined in claim 1, further comprising means for throttling the flow of fuel into said chamber by way of said opening means.

9. A fuel injection valve as defined in claim 1, wherein said drive means is arranged to respectively maintain said piston in said second and third positions for first and second intervals of time and wherein the duration of said first intervals at least equals the duration of said second interval.