EP1143116A1 - Internal combustion engine - Google Patents

Abstract

The movement of the inlet valve in opening or closing w.r.t the valve seats (10,13), is controlled using an electromagnetic actuator (15), while that of the exhaust valve is controlled by an assembly (16) including a lever (28) controlled by a cam (27) shaft (26), this assembly being independent of the electromagnetic actuator. The IC engine has an inlet valve (6) and an exhaust valve (7) co-operating respectively with valve seats (10,13) fitting on the cylinders (2).

Description

The present invention relates to a combustion engine internal for motor vehicle and concerns more specially a special arrangement of the valves intake and exhaust associated with the cylinders of this motor, as well as actuation means for these valves.

A classic solution in combustion engines internal for motor vehicle consists in ordering the movement of the intake and exhaust valves by means of a camshaft which operates directly or indirectly, for example using rockers acting on their stem, these valves against springs of recall to cause displacement of these valves vis-à-vis of their seat by opening or closing cylinders formed in the cylinder head of the engine and, according to the case, allow the admission of the combustible mixture injected or otherwise admitted into these cylinders or ejection burnt gases, the various engine valves being ordered in sequence to perform the cycle with several time of this engine.

Another, more modern solution is to remove the camshaft, whose action on the valves is purely mechanical, and to substitute a set of electromagnetic distribution where, schematically, each valve stem is associated with a metal frame which struggles back and forth in the air gap of an electromagnet, with spring return of the valve in one position medium intermediate.

Particular embodiments of such actuators electromagnetic valves of a combustion engine for example, the subject of patent applications 99 09 618 of July 23, 1999, 00 01 321 of February 2 and 00 01492 of February 7, 2000 in the name of the plaintiff. In particular, these patent applications relate to improvements to an electromagnetic actuator of this type type, whose interest is among others to allow easily deactivate certain engine cylinders during cycle, that is to say to put them out of service when certain times of the latter depending on the charging conditions and engine speed, providing a reduction significant consumption of the engine without harming its performances.

In particular, the aforementioned electromagnetic actuators allow to design and realize in a very efficient variable distribution, modifying immediate opening and closing angles of valves, that is to say, during the cycle, the precise instant where each valve, both intake and exhaust, opens or closes, this moment can thus be optimally adapted according to needs.

The main gain on the overall consumption of the engine comes from the implementation of this type of actuator and the distribution it achieves in the cylinders when is fitted on an engine intake valve, the control of the openings and closings of this valve allowing to adjust the air load which is injected into the cylinder, in the same way as the realizes the throttle valve of a petrol engine, with the advantage that it avoids any pumping inherent in this last solution, as long as the opening angles and closing the valve are properly timed.

At full load, the variable setting of the angles of the intake valve allows you to take full advantage of internal aerodynamic effects of the intake manifold and therefore have a maximum filling. The maximum torque curve of the motor is then strongly improved, especially at low revs. This results in a gain immediate on the consumption of the engine under partial load and also on its maximum torque curve.

Other benefits arise from load control directly through the valves with a control presenting an almost instantaneous response time, in which the inertia of moving parts is greatly reduced by compared to the conventional solution. This results in a reduction in the advance ignition reserve required in common engines and allows operation in conditions where this advance can be perfectly optimized.

However, if the same control actuator solution electromagnetic is also considered for the valves exhaust, thus eliminating the entire mechanism classic camshaft and therefore simplifying the mechanical structure of the engine due to the suppression means of training this tree, we grow without doubt the possibilities of adjusting the valve movement and in particular to adjust their opening angle and closing, further allowing more efficient deactivate some of the cylinders during the cycle of engine, regardless of the load thereof.

So in a four-cylinder engine, it turns out interesting, when the engine load is low, i.e. when the quantity of air admitted per cycle is weak, to deactivate two cylinders by not realizing only closing the intake valves and exhaust from these cylinders, but also by cutting injection and ignition, this solution being revealed particularly effective in reducing significant motor consumption.

In this case, the other two engine cylinders which stay active, work with more powerful high (usually about twice as high) and therefore with better yields.

Finally, in the solution where all the valves are controlled by electromagnetic means, control opening and closing angles of each of these valves allows easy adjustment of the gas rate residual in each cylinder and reduce the levels of pollutants in the flue gases.

However, the implementation of this solution where the engine only comprises electromagnetic actuators for all the intake and exhaust valves, a solution known in the art under the term of " Camless ", poses significant technical problems. for its implementation.

Indeed, with regard to an exhaust valve, we immediately understand that the actuator, which controls directly the armature carried by the valve stem, is placed in an environment where the temperature is significantly higher than that surrounding the same actuator when associated with an intake valve.

The overheating caused results in an acceleration of the aging of the actuator, in particular of the winding electromagnet and the electrical insulators it behaves.

In addition, unlike what occurs for a intake valve, opening a valve exhaust, especially when the engine load is growing, requires significant energy to overcome the residual pressure in the cylinder, which can reach up to 8 bars at the time of opening. To open this valve, by opposing this pressure, it is necessary that the actuator can provide a force whose order of quantity represents the product of the valve surface by the difference between the pressure in the cylinder and that which prevails in the exhaust manifold, which is relatively close to atmospheric pressure.

The energy required requires that the current in the coils of the electromagnet is considerably increased, resulting in a heat dissipation in these coils which increases with the intensity square, further increasing the temperature by the environment of this actuator.

In practice, the current demand is such that it exceeds the capabilities of the conventional alternator equipping conventional motor vehicles, the solution demanding unconventional architectures alternators (for example two alternators coupled in the case of a 12 V on-board network or a generator 42 V coupled to the 12 V network), which significantly increases the cost price of the solution.

Finally, due to the residual pressure at high load that the exhaust valve must counter during opening, this results in a reduction in performance of the motor. Indeed, the transition from the closed state to the state valve open requires transition time increased, which is penalizing at high speed and reduced the efficiency of the extraction of the burnt gases from the cylinder, the maximum engine power is thus more limited.

The present invention relates to a new arrangement of means for actuating the intake valves and exhaust from an internal combustion engine for motor vehicle, which overcomes these drawbacks.

To this end, the engine considered, comprising at least one intake valve and at least one exhaust valve cooperating respectively with seats provided on each of its cylinders, the movement of the intake valve to opening and closing with respect to its seat being controlled and controlled using an actuator electromagnetic, while the exhaust valve is controlled by a set comprising at least one system mechanical such as a lever or the like operated by a camshaft, this assembly being independent of the electromagnetic actuator, is characterized in that, to increase its yield, it includes means able, during a cycle, to deactivate at least one of its cylinders, by simultaneously closing on it the inlet valve and exhaust valve, maintained each applied to its seat.

Preferably also, the closing of the valve intake and exhaust valve is accompanied by cutting off the injection of the fuel mixture into the cylinder and the ignition in that cylinder.

For this purpose and according to a particular characteristic of the invention, the lever operated by the camshaft to control the exhaust valve, acts simultaneously on a stop capable of providing a variable reaction force such as that the camshaft causes, as the case may be, the command to the exhaust valve or the depression of the stop, in which case the valve remains applied on its seat, the cylinder being deactivated.

Other characteristics of an internal combustion engine including control of intake and exhaust valves is carried out according to the invention will appear again through the following description of an example of realization, given as an indication and not limitative, in reference to the single figure in the accompanying drawing which illustrates schematically a partial sectional view of the cylinder head of the engine with the means for actuating these valves.

In this figure, the reference 1 schematically designates part of the cylinder head of the engine, in particular in line with a cylinder 2, joined to two pipes, respectively 3 and 4, the first being reserved for admission into this cylinder 2 a mixture of gasoline and air, the second at the exhaust burnt gases after ignition and combustion of this mixture.

The injection of the mixture into the cylinder can be carried out in any appropriate way, which in itself does not matter to the invention, for example using an injector 5 schematically illustrated in the drawing and mounted in communication with the intake manifold 3.

Cylinder 2 is associated with at least one valve intake 6 and at least one exhaust valve 7. In the figure, the intake valve 6 has a head 8 extended by a rod 9, the head 8 being supported on a seat 10 provided on the cylinder head 1, to the right of the link between the intake manifold 3 and the cylinder 2.

Similarly, the exhaust valve 7 has a head 11, a rod 12 integral with this head and a seat 13 provided at the end of the tube 4 through which the burnt gases escape.

A spark plug or similar ignition member 14 is mounted on cylinder head 1 to the right of cylinder 2, so as to allow creating in the cylinder the spark causing the combustion of the mixture, according to a process in itself perfectly known.

In accordance with the invention, the two valves 6 and 7, respectively intake and exhaust, are separately associated, the first with an actuator electromagnetic 17, the second to a device fully mechanical with camshaft 16, independent one the other.

The electromagnetic actuator which controls the intake valve 6 and in particular the control of its deflections with respect to its seat 10, consists of known manner and in particular as described in the requests for aforementioned patent in the name of the plaintiff, by a electromagnet 17 itself consisting of two coils 18 and 19 providing an air gap 20 between them, delimiting a relatively narrow cavity in which to struggle a metal frame 21, integral with a support 22 extending the rod 9 of this valve axially. Of return springs, respectively 23 and 24, are associated to the rod 9 and to the support 22.

Spring 23 tends to close the valve and spring 24 to open it: in the absence of current, the valve is half opened. When current flows through the upper coil 18, it draws the metal frame 21 towards it, closing so the valve. When current flows through the coil lower 19, the latter draws the reinforcement towards it 21 and the valve opens.

The mechanism 16, which actuates the exhaust valve 7, essentially comprises a rotary shaft 26 having in its outer surface a projecting cam 27, suitable for come to act during the rotation of the shaft, on a lever or analog 28 bearing 29 at the end of the rod 12 of the valve 7. A spring 30 is provided to ensure the reminder of the head 11 of the latter on its seat 13, when the cam 27 is not in contact with the lever 28.

The lever 28 is also supported on a stop 31 whose positioning is adjustable, made up in particular in the example shown, by means of a hydraulic system essentially consisting of a piston, linked to the stop 31, located inside a cylinder whose cavity 32 is permanently supplied by a pipeline intake 33 of an incompressible fluid, in particular consisting of the engine lubricating oil.

The oil in the cylinder cavity may evacuate out of it by another line 34, on which a solenoid valve is provided 35.

In normal operation, the lever 28, pressing on the stop 31, causes each passage of cam 27 to the shaft 26 a force on the rod 12 of the valve 7 to against the spring 30, by opening the valve which is detached from its seat 13, thus ensuring the communication of the cylinder and the tubing 4 for the exhaust of burnt gases.

However, the means thus used to control respectively the two valves 6 and 7, allow simple way to deactivate cylinder 2 if necessary now closed during an operating cycle, heads 8 and 11 of the valves remaining applied to their respective seats 10 and 13.

As regards the electromagnetic actuator 15, we immediately understands that disabling the valve 6 can be obtained in the simplest way by electrically supplying the coil 18.

On the other hand, for mechanism 16, the same function can be carried out by opening the solenoid valve 35 on the line 34 so as to drop the pressure in the cavity 32, the lever 28, during the passage of the cam 27, pushing back the stop 31, without exerting any force on the rod 12 of the valve which thus remains closed by the force of the return spring 30.

The inventors have found that the system of the invention allowed to reduce the consumption of the engine and that the cylinder deactivation allowed to further increase the gain on consumption, especially when the diet motor is weak, around 700 to 3500 rpm minute, the control of the hydraulic stop not requiring at these rotations particularly switching times limits.

In parallel, we can of course, when the cylinder 2 is deactivated, its valves remaining closed, delete injection and switch off the ignition.

An internal combustion engine of simple design, which combines the advantages of a electromagnetic actuator and a conventional actuator to camshaft, purely mechanical, implementation simultaneous of these two solutions, respectively on the intake and exhaust valves, which involves only one reduced cost, not leading to a limitation on possibilities for piloting the crossing, i.e. on the choice of the time when, in normal operation, each valve at the same time as the valve opens of admission.

Of course, it goes without saying that the invention is not limited to the embodiment more specifically described above with reference to the accompanying drawings; she embraces it on the contrary all the variants.

Claims (3)

Internal combustion engine for a motor vehicle, comprising at least one intake valve (6) and at least one exhaust valve (7) cooperating respectively with seats (10, 13) formed on each of its cylinders (2), the movement of the intake valve at the opening and at the closure with respect to its seat being controlled and controlled using an electromagnetic actuator (17), while the exhaust valve is controlled by an assembly (16) comprising at least one mechanical system such as a lever or the like (28) operated by a camshaft (26), this assembly being independent of the electromagnetic actuator, said motor being characterized in which , in order to increase its efficiency, it comprises means (31-35) suitable, during a cycle, for deactivating at least one of its cylinders (2), by simultaneously closing thereon the intake valve (6) and the exhaust valve (7), kept applied c nobody in his seat. Engine according to claim 1, characterized in that the closing of the intake valve (6) and the exhaust valve (7) is accompanied by cutting off the injection of the fuel mixture into the cylinder (2) and ignition in this cylinder. Engine according to claims 1 and 2, characterized in that the lever (28) operated by the camshaft (26) for controlling the exhaust valve (7), acts simultaneously on a stop (31) capable to provide a variable reaction force such that the camshaft causes, as the case may be, the control of the exhaust valve or the depression of the stop.

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