EP0677138B1 - Pneumatic valve return system for internal combustion engine - Google Patents

Abstract

A pneumatic valve recoil system includes a piston that is unitary with the stem of a valve and which slides in a cylinder, such that the piston, valve stem, and cylinder cooperate to form a chamber containing a compressible fluid. The chamber is connected through a single calibration port to an oil-evacuation and fluid-pressure-regulating system located outside the cylinder head of the engine.

Description

The subject of the invention is a pneumatic return system for valve for internal combustion engine usable mainly, but not exclusively, in the field automobile.

In order to ensure the correct functioning of an engine, it is necessary to use a reminder system to maintain the intake or exhaust valves in the closed position, these open at the desired moment under the action of cams or rocker arms driven by a camshaft.

The valve recalls are generally made using metal coil springs, but these have a a number of drawbacks, especially the phenomenon known as "valve panic".

We know that the natural frequency of vibration of a spring is the lower the greater the deflection. This is how the valve springs start to vibrate at high speeds relatively low engines when the valve lift was defined great. This results in this type of engine powers too low at high speed despite good theoretical food. This is why we have proposed pneumatic systems for valve return.

The document FR-A-2529616 describes such a system in which the valve stem is integral with a piston sliding in a cylinder thus defining a chamber filled with a fluid compressible like air. This room cannot be perfectly waterproof, it still produces leaks air and oil infiltration. That is why it is planned an air supply and oil evacuation system, one and the other being done through conduits fitted with valves calibrated, these conduits being formed in spring bodies tires themselves mounted in the cylinder head of the engine.

This system is however complex to implement because there are many conduits to drill and a delicate adjustment since a large number of springs must be introduced and tared.

Also, the present invention aims to eliminate these disadvantages by proposing a pneumatic booster system valve simpler to produce, therefore less expensive, and of a easier operation.

The invention relates to a reminder system as defined in claim 1.

The expression "single calibration port" used here means that there is only one calibration port associated with a given room.

• l'orifice de calibrage est relié à une rampe collectrice communiquant avec le système d'évacuation d'huile et de régulation de la pression;
• le diamètre de l'orifice de calibrage est compris entre 0,5 et 1,5 mm;
• il comprend deux systèmes d'évacuation d'huile et de régulation de la pression afin d'assurer une redondance;
• un clapet anti-transfert apte à empêcher le transfert d'huile en cas d'accélération latérale supérieure à un seuil prédéterminé est monté entre les deux systèmes d'évacuation d'huile et de régulation de la pression;
• le dispositif commandant l'évacuation d'huile est sensible à la pression régnant dans ledit récipient;
• le dispositif commandant l'évacuation d'huile est sensible au niveau d'huile dans le récipient;
• le dispositif commandant l'évacuation d'huile est une électrovanne;
• le dispositif commandant l'évacuation d'huile est un clapet à membrane;
• le clapet à membrane comprend un corps séparé par une membrane en un premier compartiment où débouche ladite conduite d'évacuation et un deuxième compartiment contenant des moyens de rappel appliquant la membrane contre l'ouverture d'une conduite prévue dans le premier compartiment;
• les moyens de rappel de la membrane sont des moyens mécaniques tels qu'un ressort;
• les moyens de rappel de la membrane sont des moyens pneumatiques, le deuxième compartiment communiquant avec la source de gaz sous pression par une conduite;
• ladite conduite est équipée d'une électrovanne commandée pour s'ouvrir lorsque les variations de pression dans le récipient dépassent un seuil prédéterminé;
• ladite électrovanne est commandée par un système de gestion du moteur en fonction des indications d'un capteur mesurant la pression dans la rampe collectrice;
• le système comprend des moyens de détection du niveau d'huile dans le récipient;
• les moyens de détection du niveau d'huile comprennent un flotteur apte à actionner des contacts reliés à un système de gestion du moteur;
• les moyens de détection du niveau d'huile comprennent un flotteur articulé à sa partie inférieure sur une extrémité d'un levier dont l'autre extrémité agit sur la bille d'un clapet taré de manière à ouvrir celui-ci si le niveau d'huile monte au-dessus d'un seuil prédéterminé;
• les moyens de détection du niveau d'huile comprennent un capteur à fil chaud;
• le système comprend des moyens pour évacuer l'huile éventuellement accumulée dans la rampe collectrice;
• les moyens pour évacuer l'huile de la rampe collectrice comprennent une électrovanne montée en parallèle avec ledit clapet taré entre la source de gaz sous pression et la rampe collectrice, le récipient étant monté en aval de la rampe par rapport au clapet taré et l'électrovanne étant commandée pour s'ouvrir à une fréquence prédéterminée;
• l'ouverture de ladite électrovanne est commandée en fonction du nombre de cycles du moteur et/ou du niveau d'huile dans le récipient.

According to other characteristics of the recall system which is the subject of the invention:

• the calibration orifice is connected to a manifold communicating with the oil evacuation and pressure regulation system;
• the diameter of the calibration orifice is between 0.5 and 1.5 mm;
• it includes two oil evacuation and pressure regulation systems to ensure redundancy;
• an anti-transfer valve capable of preventing the transfer of oil in the event of lateral acceleration greater than a predetermined threshold is mounted between the two oil discharge and pressure regulation systems;
• the device controlling the evacuation of oil is sensitive to the pressure prevailing in said container;
• the device controlling the oil discharge is sensitive to the oil level in the container;
• the device controlling the oil discharge is a solenoid valve;
• the device controlling the oil discharge is a diaphragm valve;
• the diaphragm valve comprises a body separated by a diaphragm in a first compartment where said discharge pipe opens and a second compartment containing return means applying the membrane against the opening of a pipe provided in the first compartment;
• the membrane return means are mechanical means such as a spring;
• the membrane return means are pneumatic means, the second compartment communicating with the source of pressurized gas by a pipe;
• said pipe is equipped with a solenoid valve controlled to open when the pressure variations in the container exceed a predetermined threshold;
• said solenoid valve is controlled by an engine management system according to the indications of a sensor measuring the pressure in the manifold;
• the system comprises means for detecting the oil level in the container;
• the oil level detection means comprise a float capable of actuating contacts connected to an engine management system;
• the oil level detection means comprise a float articulated at its lower part on one end of a lever, the other end of which acts on the ball of a calibrated valve so as to open it if the level of oil rises above a predetermined threshold;
• the oil level detection means comprise a hot wire sensor;
• the system comprises means for discharging the oil possibly accumulated in the manifold;
• the means for discharging the oil from the manifold include a solenoid valve mounted in parallel with said calibrated valve between the source of pressurized gas and the manifold, the container being mounted downstream of the manifold relative to the calibrated valve and the solenoid valve being controlled to open at a predetermined frequency;
• the opening of said solenoid valve is controlled according to the number of engine cycles and / or the oil level in the container.

• la figure 1 est une vue schématique illustrant le principe de l'invention selon un premier mode de réalisation;
• la figure 2 est une vue schématique en coupe montrant l'implantation du système objet de l'invention dans une culasse de moteur à combustion interne;
• la figure 3 est un graphe montrant la variation de pression au cours d'un cycle dans un vérin de soupape équipé du système objet de l'invention;
• la figure 4 est un graphe semblable à celui de la figure 3 montrant l'évolution de ce cycle entre les hauts régimes et les bas régimes;
• la figure 5 est une vue semblable à celle des figures 3 et 4 montrant comment ce cycle se stabilise au cours du temps;
• la figure 6 est une vue semblable à la figure 1 illustrant un deuxième mode de réalisation du système objet de l'invention;
• les figures 7 à 9 sont des vues schématiques illustrant trois modes de réalisation possibles pour le système d'évacuation d'huile; et
• les figures 10 à 14 sont des vues semblables à la figure 1 illustrant d'autres modes de réalisation du système objet de l'invention.

The invention will appear better on reading the description which follows, given solely by way of example, with reference to the appended drawings, in which:

• Figure 1 is a schematic view illustrating the principle of the invention according to a first embodiment;
• Figure 2 is a schematic sectional view showing the layout of the system object of the invention in an internal combustion engine cylinder head;
• FIG. 3 is a graph showing the pressure variation during a cycle in a valve actuator equipped with the system which is the subject of the invention;
• Figure 4 is a graph similar to that of Figure 3 showing the evolution of this cycle between high speeds and low speeds;
• Figure 5 is a view similar to that of Figures 3 and 4 showing how this cycle stabilizes over time;
• Figure 6 is a view similar to Figure 1 illustrating a second embodiment of the system object of the invention;
• Figures 7 to 9 are schematic views illustrating three possible embodiments for the oil discharge system; and
• Figures 10 to 14 are views similar to Figure 1 illustrating other embodiments of the system object of the invention.

Figure 1 schematically shows a valve 1 having a head 2 and a rod 3. The end of the latter opposite to the head 2 is integral with a piston 4 which slides in a cylinder 5. The piston 4, the cylinder 5 and the rod 3 constitute a cylinder and define inside it a chamber 6 filled with a compressible fluid (generally a gas such as air) which constitutes the pneumatic return spring of the valve reminding the latter in the closed position. Sealing between the cylinder 5 and the piston 4 or the rod 3 is provided by dynamic seals 7 having good resistance to friction, wear and high temperatures.

Despite the quality of the seals, we cannot prevent leaks of air from chamber 6 to the outside, nor penetrations of oil inside it. That's why it is necessary to provide air supply and exhaust oil.

According to the invention, these two functions are performed through a calibration orifice 8 associated with each cylinder. The different orifices 8 communicate with a manifold 9 formed in the cylinder head and itself connected to a system air supply and oil discharge. This system essentially comprises a container 10 connected to the ramp 9 by a pipe 11. The container 10 is kept under pressure constant (for example 10 bar) thanks to a pressure source (not shown in Figure 1) to which it is connected by a line 12 fitted with a calibrated valve 13. A compressor or a small volume compressed gas cylinder (e.g. 1 liter) on board the vehicle can be the source of pressure.

We therefore understand that, if the pressure inside the room 6 falls below a certain value (for example at the end of a valve lift stroke to its position shown in Figure 1), it is replenished in air through the container 10 through the pipe 11, the ramp 9 and the calibration orifice 8. Conversely, if the pressure increases to a sufficient value (for example during a piston compression stroke 4), the oil which may have penetrated in the chamber 6 is driven through the orifice 8, the ramp 9 and the pipe 11 into the container 10 and collects at the bottom of it (indicated at H in Figure 1), It is then discharged (preferably to the crankcase) through a pipe 14 fitted with a solenoid valve 15 controlled by the electronic engine management system (not shown).

The implantation of the system in the cylinder head of the engine appears in the sectional view of FIG. 2. The cylinder head 16 is machined, in known manner, to receive a valve guide 17 and a part forming the cylinder 5 fixed to the cylinder head by screws 18. Seals 19.20 ensure the seal between the cylinder head 16, the guide 17 and the cylinder 5. The bottom of the latter is relatively thick and pierced with an orifice which constitutes the aforementioned calibration orifice 8, this communicating with the manifold 9 through a passage 21. The system air supply and oil outlet is outside of the cylinder head and has not been shown in FIG. 2.

We will now describe the operation of the system which is the subject of the invention, in particular in conjunction with FIGS. 3 to 5 which are graphs representing the evolution of the pressure P inside the chamber 6 as a function of the variation in the volume V thereof during a cycle: the values V ₁ and V ₂ are the minimum and maximum values of the volume V, corresponding to the limit switches of the piston 4.

It is first assumed that the piston 4 is in its position illustrated in Figure 1: the volume of the chamber 6 is equal to V ₂ and the pressure inside it equal to P ₁ , which corresponds to the point A in FIG. 3. During a compression stroke of the piston, if the chamber were closed, we would follow curve C ₁ shown in phantom. However, as air escapes through the orifice 8, the curve C ₂ is followed up to point B corresponding to a pressure P ₂ lower than it would have been if the curve C ₁ had been followed. Always for the same reason, during the next expansion stroke of the jack, we do not follow the curve C ₂ , but the curve C ₃ which corresponds to a lower pressure. When we arrive at point C, which corresponds to the minimum setting pressure of chamber 6, there is a bending of the curve because the cylinder is replenished with air by the supply system. We thus arrive at the end of the race at point D at a pressure P ₃ lower than P ₁ , then the chamber continues to fill with air at constant volume until we find the pressure P ₁ , which corresponds to the DA segment.

It should be noted that the cycle which has just been described varies according to the engine speed. This is illustrated in Figure 4 where we have resumed the ABD cycle which corresponds to high speed operation: the pressure increases sharply during a compression stroke. At low speed, the air flow rate passing through the calibration orifice 8 increases because the speed of movement of the piston is lower: we follow the curve C ' ₂ from A to B' corresponding to a pressure P ' ₂ less than P ₂ , then curve C ' ₃ from B' to D '.

Depending on the system setting and the engine speed, the cylinder may not have time to re-inflate at the end of a cycle. Thus at the end of the first cycle A ₁ B ₁ C ₁ D ₁ (Figure 5), we find ourselves not at point A ₁ , but at point A ₂ which corresponds to a lower pressure. The next cycle will be A ₂ B ₂ C ₂ D ₂ , then the system stabilizes according to A _i B _i C _i D _i : everything happens as if the supply pressure was equal to P _1i slightly lower than P ₁ , P _1i corresponding to point Ai.

We therefore understand that it is by choosing the diameter of the orifice 8 and the setting pressure of the container 10 which is master the ABCD cycle.

We will now describe different embodiments of the system which is the subject of the invention with reference to FIGS. 6 to 14.

Referring first to Figure 6, we find the valve 1 and the cylinder 4,5,6 as well as the calibration orifice 8, the ramp 9 and the container 10. The latter communicates, by through the calibrated valve 13, with the regulator 22 of a compressed gas cylinder 23 on board the vehicle and containing, for example, a liter of air under 200 bars. The regulator 22 is equipped with a pressure sensor 24 connected to the engine management system by a link 25 and used to check the pressure in the bottle 23.

The container 10 is itself equipped with a pressure sensor 26 connected to the engine management system by a link 27. The line 14 is fitted with a filter F and the solenoid valve 15 is linked to the management system by a link 28.

By way of example, the diameter of the calibration orifice 8 can be between 0.5 and 1.5 mm, the regulator 22 adjusted for give a pressure of 10.5 bars and the valve 13 introducing a pressure drop of 0.5 bar to hold the container 10 at 10 bars.

Under these conditions, the pressure in the return cylinder of the valve varies between 10 and 25 bar, pressure in the manifold 9 and the container 10 being approximately constant.

As the oil H collects at the bottom of the container 10, the volume of gas contained therein varies as well as its pressure. As the latter must be maintained as constant as possible, the oil drain will be triggered by opening of the solenoid valve 15 either when the pressure will reach a predetermined maximum value (by example 11 bars), i.e. when the oil reaches the level indicated "MAX" in figure 6. This evacuation will be stopped when pressure returns to its original level from 10 bars or when the oil reaches the minimum level "MIN".

Figure 7 shows a variant of the oil drain system in which the solenoid valve 15 is replaced by a check valve membrane 29.

This consists of a body 30 separated by a membrane 31 in a lower compartment where the oil coming out of line 14 and an upper compartment in which finds a spring 32 which presses the membrane 31 against opening a pipe 33.

When the pressure increases in the container 10, this increase is transmitted to the mass of oil, which has for effect of lifting the membrane 31 and allowing the evacuation oil through line 33.

For security reasons, it may be advantageous to provide a double evacuation system by mounting in parallel one solenoid valve and a diaphragm valve, as shown in Figure 8. All the elements already described have the same reference, except that line 14 splits into a line 14a carrying the solenoid valve and a line 14b carrying the valve.

Indeed, it may be that the container 10 has a slight leaking and its pressure does not increase, even if the oil exceeds the maximum level. In this case, the valve 29 is not not trigger and evacuation will be ensured by the solenoid valve which is sensitive to the oil level. Conversely, the valve will take over from the solenoid valve in the event of its failure.

In the case of an engine with two rows of cylinders, provide a double air supply and exhaust system oil to ensure redundant security. Figure 9 shows how we doubled the evacuation system to solenoid valve of Figure 6, the corresponding elements having the same references assigned the index a or b for distinguish the two sides of the engine. Please note that a check valve 34 on a pipe 35 connecting the two containers 10a and 10b in order to avoid transfers of a container to the other in the event of significant lateral acceleration. If there is little or no lateral acceleration, the valve is passing and allows for example the evacuation of oil from the container 10a by the solenoid valve 15b.

Of course, a double system can be used to ensure redundancy even if there is only one row of cylinders,

In the variant of Figure 10, we find the same elements as in Figures 6 to 8, but the spring 32 of the valve membrane 29 is deleted; the corresponding compartment is kept under pressure by a line 36 which connects it to the line 12 at a point between the regulator 22 and the valve 13.

Again, it may be advantageous to double the valve to membrane by a system sensitive to the oil level. House can also analyze pressure variations in the container 10 and cause the valve to open when these variations exceed a predetermined level. This translates by an increase in the pressure variation in the boom manifold 9: it is therefore sufficient to provide a pressure sensor 37 measuring the pressure in the boom and connected to the engine management by a link 38. This system is connected by a link 39 to a solenoid valve 40 mounted on line 36 and of which it causes the communication with a conduit of discharge 41 if the pressure variations measured by the sensor 37 exceeds a predetermined threshold.

Note in Figure 10 that the valve compartment 29 containing the oil is not necessarily the compartment lower since it is the oil pressure which controls the deformation of the membrane against the return means of this one.

Level detection can be done using a float 42 (figure 11) which closes a contact when the maximum or minimum level is reached. The corresponding detectors 43 and 44 (which can be proximity switches, contacts magnetic, etc.) are connected to the management system of the motor by connections 45 and 46 respectively.

Figure 12 shows another system providing redundancy in the case where a diaphragm valve mounted as that of Figure 10. We find the float 42, but this one is hinged at its bottom on one end of a pivoting lever 47, the other end of which acts on the ball a calibrated valve 48 so as to open it if the level of oil in the container 10 rises: the oil can then escape into line 14 downstream of the diaphragm valve 29. A spring 51 is provided to hold the float and prevent it from climbing inadvertently under the effect vertical accelerations suffered by the vehicle.

Figure 13 illustrates an arrangement in which we use two systems like the one in figure 10 corresponding to two rows of engine cylinders, bottle 23 and the valve 13 being common to both systems. Elements already described have the same reference assigned the index a or b according to the side. It is also possible to provide floats 42a and 42b maintained in Ga and Gb guides and associated with level detectors 43a and 43b connected to the management system of the motor by links 45a and 45b. Of course, we find the non-transfer valve 34 mounted on the pipe 35 as in the case of Figure 9.

It will also be noted here that, in this variant as in the others, level detection can be done by others means, for example by hot wire sensors.

It is still possible that the oil does not drain well from the manifolds 9 and that foam collects in these past. This is why the system illustrated in Figure 14 on which there is shown very schematically a valve 1 with its associated cylinder 4.5 and its orifice calibration 8 as well as two sets of collecting ramps 9a and 9b. The containers 10a and 10b are connected to the bottle 23 not directly, but through ramps 9a and 9b, the valve 13 located between the bottle 23 and the ramps 9. Evacuation is ensured by diaphragm valves 29a and 29b and there is the non-transfer valve 34.

In this arrangement, the bottle 23 (which may have a volume of 0.6 liters) is always inflated to 200 bars, but the regulator 22 is set at 15 bars and the valve 13 at 5 bars (always for have about 10 bars in containers 10a and 10b), these values can obviously vary depending on the case.

At predetermined intervals, for example after a number of engine cycles, we open a solenoid valve 49 mounted in parallel with the valve 13 to increase notably the pressure in the ramps 9 and expel the foam in receptacles 10a and 10b, level detectors such that 50a, 50b make it possible to control the evacuation and to adapt permanently the opening frequency of the solenoid valve 49, the latter can be doubled by a solenoid valve rescue 52.

The system object of the invention has many advantages the main one of which is its simplicity both in terms of design than operation. Indeed, there is no risk of failure or leakage at the valves and, as the system is simple, assembly time is shorter.

The realization of the engine is facilitated by the fact that there is no longer of valves in the cylinder head, the circuits in the latter are practically limiting to the manifold and connections between it and the different rooms on the one hand, and with the oil collection vessels on the other hand, which allows adaptation to many types of motors.

In addition, the evacuation of oil from the chambers 6 is facilitated thanks to the presence of the calibration hole and, like this evacuation is permanent, we better control the evolution of pressure in cylinders (with document valve system FR-A-2529616, this evacuation is sequential).

Finally, the system which is the subject of the invention results in a reduction of the load at the contact between the cams and the pushers, especially at low speed, which allows a reduction mechanical losses and better deceleration.

It is understood that the invention can apply to everything type of internal combustion engine and not just in the field automobile.

Claims (21)

1. Pneumatic valve return system for an internal combustion engine, of the type comprising a piston (4) integral with a valve stem (3) and sliding within a cylinder (5), the piston (4), the valve stem (3) and the cylinder (5) forming a chamber (6) that encloses a compressible fluid, characterised in that said chamber is connected via a single calibration orifice (8) to a system located outside the cylinder head of the engine and allowing simultaneously the discharge of the oil and the regulation of the fluid pressure, this system comprising a container (10), the upper portion of which communicates on the one hand with the calibration orifice (8) and on the other hand with a pressurised gas source (22, 23), if appropriate via a calibrated valve (13), and the lower portion of which, where the oil accumulates, communicates with a discharge conduit (14) equipped with at least one device controlling the discharge of oil.
2. Return system according to Claim 1, characterised in that the calibration orifice (8) is connected to a collecting manifold (9) communicating with the oil discharge and pressure regulation system.
3. Return system according to any one of Claims 1 and 2, characterised in that the diameter of the calibration orifice is comprised between 0.5 and 1.5 mm.
4. Return system according to any one of Claims 1 to 3, characterised in that it comprises two oil discharge and pressure regulation systems in order to ensure redundancy.
5. Return system according to Claim 4, characterised in that an anti-transfer valve (34) capable of preventing the transfer of oil in the case of lateral acceleration above a predetermined threshold is mounted between the two oil discharge and pressure regulation systems.
6. Return system according to any one of Claims 1 to 5, characterised in that the device controlling the oil discharge is sensitive to the pressure prevailing in said container (10).
7. Return system according to any one of Claims 1 to 5, characterised in that the device controlling the oil discharge is sensitive to the oil level in the container (10).
8. Return system according to any one of Claims 1 to 7, characterised in that the device controlling the oil discharge is a solenoid valve (15).
9. Return system according to any one of Claims 1 to 7, characterised in that the device controlling the oil discharge is a membrane valve (29).
10. Return system according to Claim 9, characterised in that the membrane valve (29) comprises a body (30) separated by a membrane (31) into a first compartment into which said discharge conduit opens (14) and a second compartment containing return means applying the membrane (31) against the opening of a conduit (33) provided in the first compartment.
11. Return system according to Claim 10, characterised in that the return means for the membrane (31) are mechanical means such as a spring (32).
12. Return system according to Claim 10, characterised in that the return means for the membrane (31) are pneumatic means, the second compartment communicating with the pressurised gas source (23, 22) via a conduit (36).
13. Return system according to Claim 12, characterised in that said conduit (36) is equipped with a solenoid valve (40) controlled so as to open when the pressure variations in the container (10) exceed a predetermined threshold.
14. Return system according to Claims 2 and 13, characterised in that said solenoid valve (40) is controlled by a system for managing the engine as a function of information from a sensor (37) measuring the pressure in the collecting manifold (9).
15. Return system according to Claim 7, characterised in that it comprises means for detecting the oil level in the container (10).
16. Return system according to Claim 15, characterised in that the means for detecting the oil level comprise a float (42) capable of actuating contacts (43, 44) connected to a system for managing the engine.
17. Return system according to Claim 15, characterised in that the means for detecting the oil level comprise a float (42) articulated in its lower portion to one end of a lever (47), the other end of which acts on the ball of a calibrated valve (48) so as to open it if the oil level rises above a predetermined threshold.
18. Return system according to Claim 15, characterised in that the means for detecting the oil level comprise a hot-wire sensor.
19. Return system according to Claim 2, characterised in that it comprises means for discharging any oil that may have accumulated in the collecting manifold (9).
20. Return system according to Claim 19, characterised in that the means for discharging the oil from the collecting manifold (9) comprise a solenoid valve (49) mounted in parallel with said calibrated valve (13) between the pressurised gas source (23, 22) and the collecting manifold (9), the container (10) being mounted downstream of the manifold (9) with respect to the calibrated valve (13), and the solenoid valve (49) being controlled so as to open at a predetermined frequency.
21. Return system according to Claim 20, characterised in that the opening of said solenoid valve (49) is controlled as a function of the number of cycles of the engine and/or the oil level in the container (10).

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