EP0677138A1

EP0677138A1 - Pneumatic valve return system for internal combustion engine

Info

Publication number: EP0677138A1
Application number: EP94903917A
Authority: EP
Inventors: Jean-Pierre Boudy
Original assignee: Automobiles Peugeot SA; Automobiles Citroen SA
Current assignee: Automobiles Peugeot SA; Automobiles Citroen SA
Priority date: 1993-10-29
Filing date: 1993-12-28
Publication date: 1995-10-18
Anticipated expiration: 2013-12-28
Also published as: EP0677138B1; US5664527A; FR2711729A1; ATE172782T1; JP3415847B2; WO1995012059A1; FR2711729B1; DE69321850D1; JPH08505454A; AU5817794A; DE69321850T2

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

PNEUMATIC VALVE RECALL SYSTEM FOR A MOTOR

INTERNAL COMBUSTION.

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

To ensure the correct operation of an engine, it is necessary to use a reminder system for maintaining the intake or ^exhaust valves in the closed position thereof opening at the desired time under the action cams or rocker arms driven by a camshaft.

The valves are generally returned using helical metal springs, but these have a certain number of drawbacks, in particular the phenomenon known as "valve alignment".

We know that the natural frequency of vibration of a spring ^is even lower than its deflection is great. This is how the valve springs start to vibrate at relatively low engine speeds when the valve lift has been set large. The result on this type of engine is too low power at high speed despite good theoretical power. This is why pneumatic systems have been proposed for the valve return.

Document FR-A-2529616 describes such a system wherein the valve stem is integral with ^a piston sliding in a cylinder, thus defining a chamber filled with a compressible fluid such as air. Since this chamber cannot be perfectly sealed, air leaks and oil infiltration still occur. Therefore there is provided an air supply system ^and oil discharge, the one and the other being through conduits provided with valves calibrated, these ducts being provided in the body of air springs themselves mounted in the cylinder head of the engine. This system is however complex to carry out because there are numerous conduits to be drilled and a delicate adjustment since it is necessary to introduce and tare a large number of springs.

Also, the present invention aims to eliminate these drawbacks by proposing a pneumatic valve return system which is simpler to produce, therefore less expensive, and easier to operate.

According to the main characteristic of the return system object of the invention, it, of the type comprising a piston integral with a valve stem and sliding in a cylinder, the piston, the valve stem and the cylinder forming a chamber which contains a compressible fluid, characterized in that said chamber is connected by a single calibration orifice to an oil evacuation and fluid pressure regulation system located outside the cylinder head of the engine.

The term "single calibration port" used herein means that there is a single calibration port associated with a given chamber.

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 above a predetermined threshold is mounted between the two oil evacuation and pressure regulation systems:

- the oil evacuation and pressure regulation system comprises a container, the upper part of which communicates on the one hand with the calibration orifice and on the other hand with a source of pressurized gas, if necessary by via a calibrated valve, the lower part of which, where the oil collects, communicates with an evacuation pipe fitted with at least one device controlling the evacuation of oil;

- 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 membrane into a first compartment where said discharge pipe opens out and a second compartment containing return means applying the membrane against the opening of a pipe provided in the first compartment:

- The return means of the membrane 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 includes 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 d oil rises above a predetermined threshold;

the oil level detection means comprise a hot wire sensor;

the system includes means for discharging any oil that may have 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 ramp 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 as a function of the number of engine cycles e / or of the oil level in the container.

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;

FIG. 2 is a schematic sectional view showing the installation of the system which is the subject of the invention in an internal combustion engine cylinder head:

- Figure 3 is a graph showing the pressure variation during a cycle in a valve cylinder equipped with the system object 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;

FIG. 6 is a view similar to FIG. 1 illustrating a second embodiment of the system which is the subject of the invention: FIGS. 7 to 9 are schematic views illustrating three possible embodiments for the oil evacuation system: and

- Figures 10 to 14 are views similar to Figure 1 illustrating other embodiments of the system object of the invention.

FIG. 1 schematically shows a valve 1 comprising a head 2 and a rod 3. The end of the latter opposite 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 jack and define inside of it a chamber 6 filled with a compressible fluid (generally a gas such as air) which constitutes the pneumatic return spring of the valve recalling the latter in closed position. The seal 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, it is not possible to prevent air leaks from chamber 6 to the outside, nor oil penetrations inside it. This is why it is necessary to provide an air supply and an oil outlet.

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 an air supply and oil evacuation system. This system essentially comprises a container 10 connected to the ramp 9 by a pipe 11. The container 10 is maintained under constant pressure (for example 10 bars) thanks to a pressure source (not shown in FIG. 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 (for example 1 liter) on board the vehicle can constitute the pressure source.

It is therefore understood that, if the pressure inside the chamber 6 falls below a certain value (for example at the end of an upward stroke of the valve towards its closed position illustrated in FIG. 1) , this is replenished with air by 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 stroke of compression of the piston 4), the oil which may have entered the chamber 6 is expelled through the orifice 8, the ramp 9 and the pipe 11 into the container 10 and collects at the bottom thereof (indicated in H in Figure 1). It is then evacuated (preferably to the crankcase) through a line 14 equipped 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 on 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 on the cylinder head by screws 18. Joints 19,20 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 via a passage 21. The air supply and oil discharge system is outside 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 Vi 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 FIG. 1: the volume of the chamber 6 is equal to ^" 2 and the pressure inside it equal to Pi, which corresponds to the point A of Figure 3. During a compression stroke of the piston, if the chamber was closed, we would follow the curve Ci shown in phantom, however, as air escapes through the orifice 8, we follow curve C2 up to point B corresponding to a pressure P2 lower than it would have been if we had followed curve Ci- Always for the same reason, during the next stroke of the cylinder expansion, we are not following the curve C2, but curve C3 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 reach the end of the travel at point D at a pressure P3 lower than Pi, then the chamber cont inue to fill with air at constant volume until the pressure Pi is found, which corresponds to the segment DA.

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 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 P2 , then the 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. This is how at the end of the first cycle A1B1C1D1 (figure 5), we find ourselves not at point Ai, but at point A2 which corresponds to a lower pressure. The next cycle will be A2B2C2D2, then the system stabilizes according to AiBiCiDi: everything happens as if the supply pressure was equal to Pu slightly lower than Pi, Pu corresponding to point Ai.

It is therefore understood that it is by choosing the diameter of the orifice 8 and the setting pressure of the container 10 that the ABCD cycle is mastered.

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, there is 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, via 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 serving to control 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 pipe 14 is equipped with a filter F and the solenoid valve 15 is connected to the management system by a liaison 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 to give a pressure of 10.5 bars and the valve 13 introducing a pressure drop 0.5 bar to hold the container 10 to 10 bar. Under these conditions, the pressure in the return cylinder of the valve varies between 10 and 25 bars, the 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 the gas contained in it varies as well as its pressure. As the latter must be kept as constant as possible, the evacuation of oil will be triggered by opening the solenoid valve 15 either when the pressure reaches a predetermined maximum value (for example 11 bars), or when the oil reaches the level maximum indicated "MAX" in figure 6. This evacuation will be stopped when the pressure returns to its initial level of 10 bars or when the oil reaches the minimum level "MIN".

FIG. 7 shows a variant of the oil evacuation system in which the solenoid valve 15 is replaced by a diaphragm valve 29.

This consists of a body 30 separated by a membrane 31 in a lower compartment where the oil emerging from the pipe 14 is collected and an upper compartment in which there is a spring 32 which presses the membrane 31 against the opening of a pipe 33.

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

As a safety measure, it may be advantageous to provide a double evacuation system by mounting a solenoid valve and a diaphragm valve in parallel, as illustrated in FIG. 8. All the elements already described have the same reference, set to except that line 14 separates 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 leak and that its pressure does not increase, even if the oil exceeds the maximum level. In this case, the valve 29 will not be triggered and the 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, a double air supply and oil evacuation system can be provided in order to ensure safety by redundancy. Figure 9 shows how the solenoid valve evacuation system of Figure 7 was doubled, the corresponding elements having the same references assigned the index a or b to distinguish the two sides of the engine. Note that an anti-transfer valve 34 is provided on a pipe 35 connecting the two containers 10a and 10b in order to avoid transfers from one container to the other in the event of significant lateral acceleration. If there is little or no lateral acceleration, the valve is on 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 provide redundancy even if there is only one row of cylinders.

In the variant of FIG. 10, the same elements are found as in FIGS. 6 to 8, but the spring 32 of the diaphragm valve 29 is eliminated: the corresponding compartment is kept under pressure by a pipe 36 which connects it to the pipe 12 at a point located between the regulator 22 and the valve 13. Again, it may be advantageous to double the diaphragm valve with a system sensitive to the oil level. However, it is also possible to analyze the variations in pressure in the container 10 and cause the valve to open when these variations exceed a predetermined level. This results in an increase in the pressure variation in the manifold 9: it therefore suffices to provide a pressure sensor 37 measuring the pressure in the manifold and connected to the engine management system by a link 38. This system is connected by a link 39 to a solenoid valve 40 mounted on the pipe 36 and of which it causes the communication with a discharge pipe 41 if the pressure variations measured by the sensor 37 exceed a predetermined threshold.

It will be noted in FIG. 10 that the compartment of the valve 29 containing the oil is not necessarily the lower compartment since it is the pressure of the oil which controls the deformation of the membrane against the return means of this one.

The level can be detected 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 may be proximity detectors, magnetic contacts, etc.) are connected to the engine management system by links 45 and 46 respectively.

FIG. 12 shows another system ensuring redundancy in the case where a diaphragm valve mounted like that of FIG. 10 is used. The float 42 is found again, but this is articulated at its lower part on one end d 'A pivoting lever 47 whose other end acts on the ball of a calibrated valve 48 so as to open it if the oil level in the container 10 rises: the oil can then escape into the line 14 downstream of the diaphragm valve 29. A spring 51 is provided to hold the float and prevent it from inadvertently climbing under the effect of vertical accelerations undergone by the vehicle.

FIG. 13 illustrates an arrangement in which two systems like that of FIG. 10 are used corresponding to the two rows of cylinders of the engine, the bottle 23 and the valve 13 being common to the two systems. The elements already described have the same reference assigned the index a or b depending on the side. It is also possible to provide floats 42a and 42b held in guides Ga and Gb and associated with level detectors 43a and 43b connected to the engine management system by links 45a and 45b. Of course, there is the non-transfer valve 34 mounted on the pipe 35 as in the case of FIG. 9.

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

It is also possible that the oil does not drain well from the manifold or manifolds 9 and that foam collects in the latter. This is why the system illustrated in FIG. 14 has been provided, in which a valve 1 with its associated jack 4.5 and its calibration orifice 8 and a set of manifolds 9a and 9b is shown very schematically. The containers 10a and 10b are connected to the bottle 23 not directly, but through the ramps 9a and 9b, the valve 13 being between the bottle 23 and the ramps 9. The evacuation is ensured by the membrane 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 adjusted to 15 bars and the valve 13 to 5 bars (always to have about 10 bars in the containers 10a and 10b), these values obviously being able to vary depending on the case. At predetermined intervals, for example after a certain number of engine cycles, a solenoid valve 49 mounted in parallel with the valve 13 is opened to significantly increase the pressure in the ramps 9 and expel the foam in the containers 10a and 10b . Level detectors such as 50a, 50b make it possible to control the evacuation and to continuously adapt the opening frequency of the solenoid valve 49, the latter being able to be doubled by an emergency solenoid valve 52.

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

The realization of the engine is facilitated by the fact that there are no more valves in the cylinder head, the circuits in the latter being practically limited to the manifold and to the connections between the latter and the various chambers on the one hand, and with the oil recovery containers on the other hand, which allows adaptation to many types of engines.

In addition, the evacuation of oil from the chambers 6 is facilitated by the presence of the calibration orifice and, as this evacuation is permanent, the pressure evolution in the jacks is better controlled (with the valve system of document FR-A-2529616, this evacuation is sequential).

Finally, the system which is the subject of the invention results in a reduction in the load at the level of contact between the cams and the pushers, in particular at low speed, which allows a reduction in mechanical losses and better deceleration. It is understood that the invention is not limited to the embodiments described and shown, but that one can imagine many variants without departing from the scope of the invention. In addition, it can be applied to any type of internal combustion engine and not only to the automotive field.

Claims

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 in a cylinder (5), the piston (4), the stem valve (3) and the cylinder (5) forming a chamber (6) which contains a compressible fluid, characterized in that said chamber is connected by a single calibration orifice (8) to an oil and regulation of the fluid pressure located outside the cylinder head of the engine.

2. Return system according to claim 1, characterized in that the calibration orifice (8) is connected to a manifold (9) communicating with the oil evacuation and pressure regulation system.

3. Return system according to any one of claims 1 and 2, characterized in that the diameter of the calibration orifice is between 0.5 and 1.5 mm.

4. Recall system according to any one of claims 1 to 3, characterized in that it comprises two systems for discharging oil and regulating the pressure in order to ensure redundancy.

5. Return system according to claim 4, characterized in that a non-transfer valve (34) capable of preventing the transfer of oil in the event of lateral acceleration greater than a predetermined threshold is mounted between the two systems. oil evacuation and pressure regulation.

6. Return system according to any one of claims 1 to 5, characterized in that the oil evacuation and pressure regulation system comprises a container (10) of which ia upper part communicates on the one hand with the calibration orifice (8) and on the other hand with a source of pressurized gas (23, 22), if necessary by means of a calibrated valve (13), and the lower part of which, where the oil collects, communicates with a discharge pipe (14) equipped with at least one device controlling the discharge of oil.

7. Return system according to claim 6, characterized in that the device controlling the evacuation of oil is sensitive to the pressure prevailing in said container (10).

8. Return system according to claim 6, characterized in that the device controlling the evacuation of oil is sensitive to the oil level in the container (10).

9. Return system according to any one of claims 6 to 8, characterized in that the device controlling the evacuation of oil is a solenoid valve (15).

10. Return system according to any one of claims 6 to 8, characterized in that the device controlling the evacuation of oil is a diaphragm valve (29).

11. Return system according to claim 10, characterized in that the diaphragm valve (29) comprises a body (30) separated by a membrane (31) in a first compartment where said discharge pipe opens (14) and a second compartment containing return means applying the membrane (31) against the opening of a pipe (33) provided in the first compartment.

12. Return system according to claim 11, characterized in that the return means of the membrane (31) are mechanical means such as a spring (32).

13. Return system according to claim 11, characterized in that the membrane return means (31) are pneumatic means, the second compartment communicating with the source of pressurized gas (23,22) via a pipe (36 ).

14. Return system according to claim 13, characterized in that said pipe (36) is equipped with a solenoid valve (40) controlled to open when the pressure variations in the container (10) exceed a predetermined threshold.

15. Return system according to claims 2 and 14, characterized in that said solenoid valve (40) is controlled by an engine management system according to the indications of a sensor (37) measuring the pressure in the manifold (9 ).

16. Return system according to claim 8, characterized in that it comprises means for detecting the oil level in the container (10).

17. Return system according to claim 16, characterized in that the means for detecting the oil level comprise a float (42) capable of actuating contacts (43,44) connected to an engine management system.

18. Return system according to claim 16, characterized in that the oil level detection means comprise a float (42) articulated at its lower part on one end of a lever (47) whose other end acts on the ball of a calibrated valve (48) so as to open it if the oil level rises above a predetermined threshold.

19. Return system according to claim 16, characterized in that the means for detecting the oil level comprise a hot wire sensor.

20. Return system according to claim 2, characterized in that it comprises means for discharging the oil possibly accumulated in the manifold (9).

21. Return system according to claims 6 and 20, characterized in that the means for discharging the oil from the manifold (9) comprise a solenoid valve (49) mounted in parallel with said calibrated valve (13) between the source of pressurized gas (23,22) and the manifold (9), the container (10) being mounted downstream of the manifold (9) relative to the calibrated valve (13) and the solenoid valve (49) being controlled for s '' open at a predetermined frequency.

22. Recall system according to claim 21, characterized. in that the opening of said solenoid valve (49) is controlled as a function of the number of engine cycles and / or of the oil level in the container (10).