The invention relates to a device for controlling a heat engine. The heat engine is a four-stroke internal combustion engine that can be used to propel motor vehicles.
Such a heat engine comprises a block in which are defined combustion chambers (or cylinders) that have an end that is sealed by a cylinder head and an opposite end that is sealed by a piston that is received and slides in the block and is connected by a connecting rod to a crankshaft converting the reciprocating translational movement of the piston into a continuous rotary movement. The cylinder head is provided with means for introducing air or an air-fuel mixture into each cylinder and exhaust means for the burnt gases. These means comprise an intake duct and an exhaust duct respectively blocked by intake valves and at least one exhaust valve.
It will be recalled that the overall torque supplied at the output of a heat engine with N cylinders is the sum of the individual torques supplied by the pistons of the N cylinders.
Since the individual torque value depends on the filling of the cylinder with the air-fuel mixture, the individual efficiency of a cylinder of the heat engine increases with the individual torque to be supplied at the output of said cylinder.
It will also be recalled that, for an engine with controlled ignition, the ignition advance of a cylinder is the time difference between the moment when a spark is produced in the chamber of said cylinder and the moment when the piston moving in said cylinder reaches its top dead center point.
In order to reduce pollutant emissions, and in particular greenhouse gas emissions, heat engines consuming increasingly less fuel are emerging. On a conventional heat engine, the most polluting operating point is reached when all the cylinders of the engine are operating at partial load. On engines with a high cubic capacity, in particular on V8s, it is thus known practice to cut the supply of fuel to half of the cylinders around these operating points so as to increase the individual load of the remaining cylinders and therefore increase their efficiency, which makes the engine less polluting.
The overall torque supplied at the output of the heat engine with a high cubic capacity is then only slightly discontinuous on the transition from the deactivation of half of the cylinders. In practice, the number of cylinders in the heat engine is high enough for the remaining cylinders to have to provide only a relatively low additional individual load. Thus, if the heat engine is used to propel a car, the driver will not in the least sense this discontinuity in the overall torque.
On the other hand, for an engine with fewer cylinders, if half of the cylinders are deactivated, the remaining cylinders will have to supply a high additional individual load. This will result in a significant jump in torque for each remaining cylinder: the overall torque supplied at the output of the heat engine will then be greatly discontinuous. The driver will necessarily sense the transition from all cylinders active to half the cylinders active.
One aim of the invention is to at least partly remedy the above mentioned problem.
In order to achieve this aim, there is proposed a device for controlling a heat engine comprising a plurality of cylinders at least one of which is provided with at least two intake valves. According to the invention, the device comprises a control unit arranged to successively deactivate said intake valves.
Thus, the individual torque of each of the active cylinders increases by degree with each deactivation of one of the intake valves of the cylinder to be deactivated. The overall torque supplied at the output of the heat engine is then only slightly discontinuous upon the deactivation of said cylinder, even for an engine of small cubic capacity.
The invention will be better understood in light of the following description of a particular nonlimiting embodiment of the invention.
Reference will be made to the appended figures, in which:
With reference to
The cylinders 1, 2, 3, 4 are linked to an air intake and fuel injection system, and to an exhaust system.
Each cylinder is equipped with a fuel injector and is here equipped with a first intake valve 1a, 2a, 3a, 4a and a second intake valve 1b, 2b, 3b, 4b as well as a first exhaust valve 1c, 2c, 3c, 4c and a second exhaust valve 1d, 2d, 3d, 4d. The intake valves (in white) 1a and 1b, 2a and 2b, 3a and 3b, 4a and 4b link the associated cylinder 1, 2, 3, 4 to the intake system and the exhaust valves (in black) 1c and 1d, 2c and 2d, 3c and 3d, 4c and 4d link the associated cylinder 1, 2, 3, 4 to the exhaust system. Here, the intake valves 1a and 1b, 2a and 2b, 3a and 3b, 4a and 4b and the exhaust valves 1c and 1d, 2c and 2d, 3c and 3d, 4c and 4d are associated with electromagnetic valve actuators, known per se, allowing for individual actuation of the valves such that they can be opened or closed independently of the other valves.
The control device also comprises a control unit 5 or ECU (engine control unit) which determines engine control instructions (such as the quantity of fuel injected and the intake air flow rate) as a function of an acceleration demand from the driver (depression of the accelerator pedal) and the detected values of operating parameters of the engine.
To limit the fuel consumption of the engine, it is known practice to cut the supply of fuel to half of the cylinders around the most polluting operating point of the engine. The individual load of the remaining cylinders, and therefore their efficiency, are thus increased. In the example illustrated, in order to limit a cooling of the cylinders of the engine during a deactivation, priority is given to deactivating the second and the third cylinders 2 and 3. This is because the first and the fourth cylinders 1 and 4 are at the periphery of the engine block, so they provide a better heat distribution toward the centre of the engine block 100 than the second and third cylinders 2 and 3 toward the peripheries of the engine block 100.
According to the invention, the control unit 5 is arranged so as to successively deactivate the intake valves 2a and 2b of the second cylinder 2 and successively deactivate the intake valves 3a and 3b of the third cylinder 3.
To this end, the control device comprises a first device 7 for managing the valve actuators of the first intake valve 2a and of the first exhaust valve 2c of the second cylinder 2 as well as the valve actuators of the second intake valve 3b and of the second exhaust valve 3d of the third cylinder 3. The control device also comprises a second device 8 for managing the valve actuators of the second intake valve 2b and of the second exhaust valve 2d of the second cylinder 2 as well as the valve actuators of the first intake valve 3a and of the first exhaust valve 3c of the third cylinder 3.
The control unit 5 is thus arranged in such a way as to generate, initially, a valve closure signal intended for the first managing device 7 to deactivate the first intake valve 2a and the first exhaust valve 2c of the second cylinder 2 as well as the second intake valve 3b and the second exhaust valve 3d of the third cylinder 3. In a second stage, the control unit 5 generates a valve closure signal intended for the second managing device 8 to deactivate the second intake valve 2b and the second exhaust valve 2d of the second cylinder 2 as well as the first intake valve 3a and the first exhaust valve 3c of the third cylinder 3.
The deactivation of the second and third cylinders 2 and 3 is thus carried out gradually. The two cylinders are initially completely active, then half active, then completely deactivated. With reference to
By contrast, referring to
With reference to
In practice, if the butterfly valve for the gases were opened only once the second and third cylinders 2, 3 are deactivated, the overall torque would decrease greatly before reverting to its initial value, since the pressure in the intake manifold of the engine cannot increase instantaneously. In parallel, to compensate for the increase in the pressure in the intake manifold due to the opening of the gas butterfly valve, the ignition advance of all of the cylinders is degraded so as to lower the individual efficiency of all of the cylinders. At the time of the deactivation of the second and third cylinders 2, 3, the optimum ignition advance is then restored for the first and fourth cylinders 1, 4.
With reference to
The invention is not limited to what has just been described and encompasses any variant falling within the framework defined by the claims.
In particular, although here the control device is associated with a heat engine with four cylinders, the control device will be able to be associated with any type of heat engine. The invention will thus be able to be applied to an engine without controlled ignition such as a diesel engine or even an engine of greater cubic capacity. It will also be possible to apply the invention to an engine in which the cylinders have mutually different configurations, provided that the cylinder or cylinders to be deactivated has/have at least two intake valves. The invention will also be able to be used with any system that allows individual actuation of the valves such as hydraulic actuators.
Furthermore, the invention can be applied to any cylinder configuration provided that the cylinder or cylinders to be deactivated has/have at least two intake valves. With reference to
Furthermore, although here the control unit 5 is arranged to deactivate intake valves and exhaust valves, the control unit 5 will be able to be arranged in such a way as to deactivate only the intake valves. However, in a preferred embodiment, intake valves and exhaust valves will be deactivated to maintain a high pressure in the deactivated cylinder. In practice, if the pressure in the deactivated cylinders decreases gradually, it ends up being less than atmospheric pressure: oil is thus sucked from the sump into the deactivated cylinders. This oil will then be burned and the polluting products from the combustion will be expelled by the exhaust system when said cylinders are next invoked.
Number | Date | Country | Kind |
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1061096 | Dec 2010 | FR | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/FR11/53092 | 12/20/2011 | WO | 00 | 8/5/2013 |