EP0150138A2 - Safety device for constant-pressure fuel-injection valve of an internal combustion engine - Google Patents

Abstract

Safety device for constant pressure injection valve of internal combustion engine. According to the invention, it closes the main supply pipe (14) of this valve permanently and definitively in the event of exceeding the maximum admissible quantity of fuel injected or of exceeding the control frequency for a given injected quantity, lower than the maximum allowable quantity. Application: in particular to diesel injection of the pressure - time type.

Description

The invention relates to safety devices carried by the injection valves of internal combustion engines. The injection principle known as "Pressure-Time" is known, characterized by the use of injection valves, supplied under a normally constant pressure, delivering an amount of fuel in proportion to their opening time. Injection valves of this kind have the disadvantage that in the event of needle seizure, rupture of the injector nozzle or failure of the control system, it is no longer possible to regulate the quantity of fuel injected, the engine can then suffer major damage.

A known device of this type is described in patent FR 1 555 369. It consists of an apparatus placed in the inlet pipe of the injection valve and / or in the exhaust pipe of the / or control which are electromagnetically actuated, which closes one or other of the lines described above, this in case of exceeding the maximum admissible quantity of fuel injected.

This equipment mainly consists of a piston moving in a bore. This piston is held on one side by a spring, a pipe comprising a restriction is formed parallel to the bore of the piston, this pipe opens into the bore on the spring side. The side of the piston opposite the spring is connected to the fuel inlet and to the other end of the pipe designated above; the face of the piston, spring side, is in communication with the injection valve. When the injection occurs, the pressure drops on the face of the piston causing the latter to move by compressing the spring, at the end of injection the piston is brought back by the spring. In the event that the injection valve is defective, the piston performs a movement such that it closes the pipe described above, thus interrupting the flow. The restriction provided in the pipeline is provided so that the piston can be returned to its original position under the action of the spring between two successive injections, even at the highest speed of the engine.

The invention aims to limit injection when the quantity of fuel injected exceeds a maximum admissible value but also when the engine speed exceeds a given level.

• - simplicité de fabrication ;
• - fiabilité de l'étanchéité en cas de fermeture du dispositif ;
• - indication de la/des soupape(s) d'injection concernée(s) par un défaut ;
• - possibilité d'utiliser les autres soupapes d'injection bien que l'une d'elles soit défectueuse et ceci sans perte de carburant dans la soupape défectueuse ; et
• - possibilité de remettre en fonctionnement le moteur utilisant ce type de soupape d'injection bien que l'une d'entre elles soit défectueuse, sans perte de carburant par cette dernière.

The invention proposes to provide a device of the type described above which presents an improvement in the following points:

• - simplicity of manufacture;
• - reliability of the seal in the event of closure of the device;
• - indication of the injection valve (s) affected by a fault;
• - possibility of using the other injection valves although one of them is defective and this without loss of fuel in the defective valve; and
• - possibility of restarting the engine using this type of injection valve although one of them is defective, without loss of fuel by the latter.

To this end, and according to a feature of the invention, this safety device closes the main supply line for the electromagnetically controlled injection valve, permanently and permanently in the event of the maximum admissible quantity of fuel being exceeded. injected or exceeding the order frequency for a given injected quantity, less than the maximum admissible quantity.

According to another feature of the invention, this safety device comprises a ball, a piston provided with a calibrated orifice arranged in series with the main pipe, a guide sleeve for this piston and a return spring for this piston, these constituent elements being assembled so as to allow on the one hand, this piston to travel during each injection, a path varying according to the quantity delivered and to return to the rest position between two successive injections by the action of this spring , and secondly, this ball to close the single section of passage of this sleeve as soon as the stroke of the piston reaches a preset value corresponding to a maximum admissible quantity injected.

• - les figures 1, 2 et 3 représentent des vues schématiques de trois modes de réalisation respectifs d'un dispositif de sécurité conforme à l'invention ;
• - la figure 4 est une courbe illustrant le déplacement de la bille d'un dispositif de sécurité représenté aux figures 1, 2 et 3 en fonction du temps ;
• - la figure 5 est une courbe correspondant à celle de la figure 4 et illustrant la variation de la quantité injectée de combustible en fonction du temps ;
• - les figures 6, 7 et 8 représentent, pour un cas de dépassement de la quantité injectée maximale, des courbes de variation en fonction du temps, respectivement du signal de commande d'une soupape électromagnétique, de la quantité injectée de combustible et du déplacement de la bille correspondant à l'un des dispositifs de sécurité des figures 1, 2 et 3 ;
• - les figures 9, 10 et 11 représentent, pour un cas de dépassement du régime moteur, des courbes analogues à celles des figures 6, 7 et 8 ; et
• - la figure 12 représente une courbe de variation extrême du régime moteur en fonction de la quantité injectée de combustible avec un dispositif de sécurité conforme à l'invention, qui permet de définir les limites de fonctionnement du moteur.

Other features and advantages of the invention will appear more clearly on reading the following description of three embodiments, given by way of non-limiting examples and with reference to the appended drawings in which:

• - Figures 1, 2 and 3 show schematic views of three respective embodiments of a security device according to the invention;
• - Figure 4 is a curve illustrating the movement of the ball of a safety device shown in Figures 1, 2 and 3 as a function of time;
• - Figure 5 is a curve corresponding to that of Figure 4 and illustrating the variation of the quantity of fuel injected as a function of time;
• - Figures 6, 7 and 8 show, for a case of exceeding the maximum injected quantity, variation curves as a function of time, respectively of the control signal of an electromagnetic valve, the quantity injected with fuel and the displacement the ball corresponding to one of the safety devices of Figures 1, 2 and 3;
• - Figures 9, 10 and 11 show, for a case of exceeding the engine speed, curves similar to those of Figures 6, 7 and 8; and
• - Figure 12 shows an extreme variation curve of the engine speed as a function of the quantity of fuel injected with a safety device according to the invention, which makes it possible to define the operating limits of the engine.

According to the invention, the safety device for a constant pressure injection valve of an internal combustion engine, shown in FIG. 1, comprises a ball 2 of diameter D resting on a hollow piston 4 quid by a sleeve 6 and recalled by an inner spring 8. This piston has a calibrated orifice with nozzle 10 of diameter d which connects the inlet 12 of the main pipe 14 supplying a non-electromagnetic control valve shown, at exit 16 of the safety device. The sleeve 6 is made of a metal that is relatively softer than the material of the ball 2 and the diameter D ′ for guiding the piston or internal diameter of the sleeve is slightly less than that D of the ball.

The center of the ball 2 is separated from the edge 18 of the sleeve 6 by a maximum distance X + E (ε> 0), X representing the maximum displacement of this ball until contact with the sleeve 6.

According to another mode of construction illustrated in FIG. 2, the piston is arranged above the ball itself raised by the return spring.

Another constructive arrangement illustrated in FIG. 3 can be adopted by leaving a clearance between the ball and the bore 20 in which it moves, such that the passage section thus defined is identical to that of the nozzle 10 represented in FIGS. 1 and 2.

With reference to FIGS. 1 to 12, the safety device described above operates in the following manner: At the time of injection, there is a vacuum at the outlet 16 of the safety device in the pipe 14. The latter causes displacement A of piston 4 by the effect of the pressure drop existing between the two faces of piston by through the calibrated orifice 10. At the end of the injection, the quantity which will have been charged will be: Q = Π / 4.D ' ² .Δ. The flow is stopped due to the closing of the injector and the vacuum at the outlet 16 disappears. The return spring 8 then pushes the piston 4 and the ball 2 and returns them to their initial positions awaiting the next injection.

In the event of a fault, for example an injection time that is too long, an injector that remains open or a fuel leak, the displacement of the piston 4 reaches a value A = X. At this instant, the flow is stopped by the interposition of the ball 2 in the guide sleeve 6 on the one hand, and all the pressure of the circuit being exerted on the section of the ball 2, the latter is pushed against this sleeve with an internal diameter D '(DI 4 D ) under the effect of the force thus created. As this thrust force is much greater than the force of the return spring 8, the ball retains this support position and perfectly isolates the defective circuit.

Figure 4 shows the movement of the ball 2 bearing on the piston 4, as a function of time. This movement and the injection rate shown in FIG. 5 are synchronized for a duration of time Ti. The return time of the ball under the effect of the return spring corresponds to Tr. The sum Ti + Tr is provided at a value slightly less than an injection period. The value X represents the maximum stroke of the ball, provided to allow the maximum amount of fuel to be injected, which causes the locking of the safety device.

Figures 6, 7 and 8 illustrate a case of exceeding the maximum amount injected resulting in safety. The second pulse of the control signal shown in Figure 6 for an electromagnetic valve is too long; the injection time Ti then reaches a fixed value Tm causing a maximum displacement X of the ball, which causes the safety device (cf. FIGS. 7 and 8).

Figures 9, 10 and 11 illustrate a case of exceeding the engine speed resulting in safety.

Figure 9 shows the periodic control signal of an electromagnetic valve. Figure 10 shows the quantity injected as a function of time. As can be seen in FIG. 11, the period Pc of the control signal is less than the sum (Ti + Tr) representing the period specific to the safety device. When ball 2 returns, it cannot return to its rest position and is offset by a value x ₀ (see Figure 11); with each injection, the displacement of the ball increases by the value x. When we arrive at the identity of X with Xi + nx, the device goes into safety (Xi represents the initial displacement of the ball and n the number of abnormal injections).

FIG. 12 shows the overall operation of the safety device with the point Qi indicating the maximum quantity that can be injected, the point Ni indicating the start of the regression of the maximum flow rate as a function of the speed, the point Nm indicating the maximum speed that can theoretically be obtained with a very small amount injected. The engine operating limits must be limited to this trapezoid, for example the OQMN rectangle.

Claims (3)

1. Safety device for a constant pressure injection valve of an internal combustion engine, characterized in that it closes the main supply pipe for this valve permanently and permanently in the event of the maximum admissible quantity of fuel injected or exceeding the order frequency for a given injected quantity, less than the maximum admissible quantity. 2. Safety device according to claim 1, characterized in that it comprises a ball (2), a piston (4) provided with a calibrated orifice (10) disposed in series with the main pipe (14), a sleeve (6) for guiding this piston (4) and a return spring (8) for this piston, these constituent elements being assembled so as to allow, on the one hand, this piston to travel during each injection, a path varying according to the quantity delivered and to return to the rest position between two successive injections by the action of this spring (8), and on the other hand, to this ball (2) to close the single passage section (18 ) of this sleeve (6) as soon as the piston stroke (4) reaches a preset value corresponding to a maximum admissible injected quantity. 3. Safety device according to claim 1, characterized in that it comprises a ball (2), a bore (20), a machon (6) and a return spring (8), these constituent elements being arranged so to allow on the one hand, to this ball (2) to travel during each injection, a path varying according of the quantity delivered and through this bore (20) with a determined clearance, and to return to the rest position between two successive injections by the action of this spring (8), and on the other hand, to this ball (2) to close the single passage section (18) of this sleeve (6) as soon as its stroke reaches a predetermined value corresponding to a maximum admissible quantity injected.

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