FR2818693A1 - Automotive vehicle having selectively controlled IC engine cylinder valve actuators, has arrangement that always ensures adequate vacuum in actuator servomotors - Google Patents

Abstract

The vehicle has four cylinders (12,14,16,18), of the type in which the cylinder valves of the engine are moved by controlled actuators (36,38,40,42,44,46,48,50), each having a vacuum servomotor whose chamber is connected to an inlet tube of the engine, upstream of the inlet butterfly valve, with units to control the butterfly valve. There are controllers for the actuators and control unit for the butterfly valve. The actuators (38,42,46,50) for two cylinder (14,16) valves are controlled by a sequence (SFM 14, SFM 18) called engine brake sequence, and the actuators (36,44,40,48) of the cylinder (12,16) valves are controlled along a four stroke sequence (S4T12,S4T16) for forming an adequate vacuum in the servomotor chamber.

Description

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"Motor vehicle comprising an engine fitted with selectively controlled valve actuators"
The invention relates to a motor vehicle with an internal combustion engine.

 The invention relates more particularly to a motor vehicle with an internal combustion engine, of the type in which the engine comprises at least two cylinders and drives at least one wheel of the vehicle, of the type in which the intake and exhaust valves of the engine cylinders are driven by individual controlled actuators, of the type in which a braking circuit of said vehicle wheel comprises at least one vacuum brake booster of which at least one chamber is connected to an intake manifold of the downstream engine a supply butterfly for the intake manifold, and of the type which includes means for controlling the opening of the supply butterfly to provide adequate vacuum inside the chamber of the booster.

 Numerous examples of motor vehicles of this type are known, known under the name of "camless" motor vehicles.

In known manner, such a vehicle comprises a braking control unit which comprises the means for controlling the opening of the supply butterfly. When the vehicle is accelerating, the throttle valve is generally open to supply air to the intake manifold, and when the vehicle is decelerating, following the release of a vehicle accelerator pedal and / or the actuation of the '' a vehicle brake pedal, the throttle valve is closed so as to maintain an optimum level of adequate vacuum in the chamber of the brake booster
Furthermore, it is known to control the actuators of the valves of all the cylinders of the vehicle according to an operating mode in engine brake following the release of an accelerator pedal of the vehicle.

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 In this latter configuration, the cylinder intake valves are always closed.

 The cylinder exhaust valves can be controlled in a so-called "compression engine brake" sequence in which they are closed when each piston reaches its bottom dead center position, and in which they are opened at the latest when the piston reaches its top dead center position.

 As a variant, the exhaust valves of the cylinders can be controlled according to a sequence called "vacuum engine brake" according to which they are closed when each piston reaches its top dead center position, and according to which are opened at the latest when the piston reaches its bottom dead center position.

The disadvantage of such a configuration is that it is substantially incompatible with a braking request initiated by the actuation of a vehicle brake pedal.
In fact, in the event of requested braking, the intake valves cannot be closed, because in this case the intake manifold could not be subjected to a sufficient vacuum, which would risk preventing the maintenance of a level optimal vacuum in the actuator chamber.

 Consequently, such a vehicle is necessarily without an engine brake when braking is requested.

 One known solution consists in nonetheless operating the actuators of the vehicle valves according to an engine brake sequence and overcoming the lack of vacuum in the booster chamber by connecting it to a vacuum pump which is triggered as soon as the vacuum level is insufficient in the actuator chamber.

 This solution has the drawback of requiring the installation of said vacuum pump and a vacuum sensor in the chamber of the booster. As such, this

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 solution is technically complex, cumbersome, and above all expensive.

 To overcome these drawbacks, the invention provides a vehicle of the type described above, which allows to naturally benefit from an engine brake while maintaining an optimum level of vacuum in the booster chamber.

 To this end, the invention provides a vehicle of the type described above, characterized in that it comprises actuator control means and means for controlling the opening of the throttle valve which are capable of operating according to a determined mode according to which : - they control the actuators of the intake and exhaust valves of at least one cylinder of the engine according to a determined sequence called engine brake to provide a deceleration torque to at least one wheel of the vehicle, - they control the actuators intake and exhaust valves of the remaining cylinder (s) in a conventional four-stroke sequence of operation to provide adequate vacuum in the intake manifold and inside the chamber servomotor.

 According to other characteristics of the invention: - the control means are capable of operating in the determined mode in response to the release of an accelerator pedal from the vehicle, - the control means are capable of operating in the determined mode in response to the actuation of a vehicle brake pedal, - the control means comprise means for determining the number of cylinders for which they are capable of controlling the actuators according to the determined sequence of engine brake, - the number of cylinder actuators controlled according to the determined engine brake sequence is a function of the vacuum prevailing in the actuator chamber,

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. au moins une sous-séquence conventionnelle de fonctionnement à quatre temps, + au moins une sous-séquence, dite de frein moteur pur, au cours de laquelle les soupapes d'amission d'un cylindre déterminé sont toujours fermées et au cours de laquelle : . les soupapes d'échappement de ce cylindre sont fermées lorsque le piston de ce cylindre atteint sa position de point mort haut et sont ouvertes au plus tard quand le piston atteint sa position de point mort bas, ou bien . les soupapes d'échappement de ce cylindre sont fermées lorsque le piston de ce cylindre atteint sa position de point mort bas et sont ouvertes au plus tard quand le piston atteint sa position de point mort haut. la séquence déterminée de frein moteur intervient dès lorsque le régime du moteur est supérieur à une valeur de seuil déterminée, - les actionneurs sont des actionneurs électromagnétiques. - according to the determined sequence of engine braking, the intake valves are always closed, - according to the determined sequence of engine braking, the exhaust valves of a determined cylinder are closed when the piston of this cylinder reaches its point position dead low, and are opened at the latest when the piston reaches its top dead center position, - according to the determined engine brake sequence, the exhaust valves of a given cylinder are closed when the piston of this cylinder reaches its position top dead center, and are open at the latest when the piston reaches its bottom dead center position, - the determined sequence of engine brake comprises cyclically:

. at least one conventional four-stroke operating sub-sequence, + at least one sub-sequence, known as pure engine brake, during which the intake valves of a given cylinder are always closed and during which: . the exhaust valves of this cylinder are closed when the piston of this cylinder reaches its top dead center position and are opened at the latest when the piston reaches its bottom neutral position, or else. the exhaust valves of this cylinder are closed when the piston of this cylinder reaches its bottom dead center position and are opened at the latest when the piston reaches its top dead center position. the determined engine brake sequence occurs as soon as the engine speed is greater than a determined threshold value, - the actuators are electromagnetic actuators.

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 Other characteristics and advantages of the invention will appear on reading the detailed description which follows for the understanding of which reference will be made to the appended drawings in which: - Figures 1 to 3 are schematic views of an engine a vehicle and an associated booster represented in three positions of the intake throttle; and - Figures 4 and 5 are schematic diagrams showing two control variants of the valve actuators of an engine according to the invention.

 In the following description, identical reference numerals designate identical parts or having similar functions.

 FIGS. 1 to 3 show a heat engine 10 of a motor vehicle (not shown) produced in accordance with the invention.

 In known manner, the engine comprises at least two cylinders. In particular, as shown in Figures 1 to 3, the engine is a four-cylinder engine 12,14, 16,18, arranged in line, but this configuration is not limiting of the invention.

 The motor 10 is intended to drive at least one wheel of the vehicle via a transmission (not shown).

 In known manner, the intake valves 20, 22, 24, 26 and exhaust 28, 30, 32, and 34 respectively of the cylinders 12, 14, 16, 18 of the engine are moved by individual actuators controlled. In particular, the intake valves 20, 22, 24, 26 are moved by associated actuators 36, 38, 40, and 42 and the exhaust valves 28, 30, 32, and 34 are driven by associated actuators 44 , 46, 48, and 50.

 Preferably, the actuators 36,38, 40,42, 44,46, 48, and 50 are electromagnetic actuators, but this configuration is not limitative of the invention.

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 In known manner, the vehicle comprises a braking circuit for said wheel (not shown) which comprises at least one booster motor 52 for vacuum braking assistance, at least one chamber 54 of which is connected to an intake manifold 56 for the engine in downstream of a throttle valve 58 for supplying the intake manifold. The servomotor 52 is controlled by a brake pedal 51. The vehicle also includes means for controlling (not shown) the opening of the feed butterfly valve 58 which are intended to provide adequate vacuum inside the chamber 54 servomotor 52.

 According to the invention, the vehicle comprises means for controlling the actuators 36, 38, 40, 42, 44, 46, 48, and 50 and means for controlling the opening of the throttle valve 58 which are capable of operating according to a determined mode according to which: its controls the actuators of the intake and exhaust valves of at least one cylinder of the engine 10 according to a determined sequence SFM14, SFM18 known as the engine brake to supply a retarding torque to at least one wheel of the vehicle, - they control the actuators of the intake and exhaust valves of the remaining cylinder (s) according to a conventional sequence S4T12, S4T18 of four-stroke operation to provide adequate vacuum in the manifold intake 56 and inside chamber 54 of the booster.

 Thus, in the determined mode, at least one of the cylinders 12, 14, 16 or 18 provides, by means of pistons 13, 15, 17, and 19 associated with the crankshaft 60, a deceleration torque, known as a "brake" engine "to the wheel of the vehicle, while the remaining cylinder or cylinders allow the establishment of a vacuum inside the intake manifold 56, which consequently makes it possible to maintain an optimal vacuum at

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 inside the chamber 54 of the servomotor 52 to provide, if necessary, a braking force on the wheel.

 More particularly, in the preferred embodiment of the invention, the control means are capable of operating in the mode determined in response to the release of an accelerator pedal (not shown) of the vehicle.

 In this way, the control means allow the establishment of a "motor brake" torque to the wheel as soon as the driver releases the accelerator pedal of the vehicle. This configuration does not prejudge the subsequent actuation of the brake pedal 51 by the driver of the vehicle. Indeed, commonly, as the driver of the vehicle releases the accelerator pedal of the vehicle before actuating the brake pedal of the vehicle, the "engine brake" torque is already established at the wheel when the driver actuates the vehicle brake pedal.

 However, in the preferred embodiment of the invention, the control means are also capable of operating according to the mode determined in response to the actuation of the brake pedal 51 of the vehicle. The purpose of this configuration is to guarantee the establishment of the engine brake torque in the event that the driver mishandles and presses the accelerator pedal at the same time as he presses the brake pedal 51.

 In an alternative embodiment, it is possible to envisage that the control means are capable of operating according to the determined mode only in response to the actuation of a brake pedal 51 of the vehicle. Indeed, in the absence of force exerted on the brake pedal 51, the vacuum which prevails in the chamber 54 of the booster 52 is stable and does not need to be replenished. In this configuration, it is only in the case where the brake pedal 51 is actuated, and therefore when the vacuum risks running out inside the chamber 54 of the servomotor 52 that the control means

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 control the actuators of a determined number of cylinders of the engine 10 so that a vacuum prevails in the intake manifold 56 of the engine 10.

 Whatever the embodiment of the invention, the control means comprise means for determining the number of cylinders for which they are capable of controlling the actuators according to the determined sequence SFM14, SFM18 of engine brake. This configuration makes it possible to provide the vehicle wheel with a maximum engine brake while guaranteeing optimum vacuum within the intake manifold 56 and therefore optimum vacuum within the chamber 54 of the booster 52.

 Preferably, the number of cylinder actuators controlled according to the engine brake sequence SFM14, SFM18 determined is a function of the vacuum prevailing in the chamber 54 of the servomotor 52. The vehicle may for example may include a vacuum sensor, arranged at inside the chamber 54 of the servomotor 52, which transmits information to the control means so that they determine the adequate number of cylinder actuators which must continue to operate according to a conventional sequence S4T12, S4T16 of four-stroke operation in order to maintain optimum vacuum in chamber 54 of the servomotor.

 Furthermore, in this configuration, the control means are capable of controlling the means for controlling the opening of the throttle valve 58 at different positions, as shown in FIGS. 1 to 3.

 FIG. 1 represents, for example, a configuration for closing the throttle valve 58. This configuration corresponds to a case in which the driver has released the accelerator pedal and actuates the brake pedal 51, in particular so that the vehicle brakes d at high speed. In this case, the control means control the control means

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 to close the throttle valve 58 so that the vacuum supplied by those of the cylinders whose actuators operate according to the conventional sequence S4T12, S4T16 of four-stroke operation provides a maximum vacuum suitable for guaranteeing the establishment of a maximum braking torque at the wheel.

 For example, such a depression is of the order of 800 millibars.

 FIG. 2 represents, for example, an intermediate opening configuration of the throttle valve 58. This configuration corresponds to a case in which the driver has only released the accelerator pedal, for example so that the vehicle slows down without braking. In this case, the control means command the control means to partially close the throttle valve 58 so that the vacuum supplied by those of the cylinders whose actuators operate according to the conventional sequence S4T12, S4T16 of four-stroke operation provides sufficient vacuum so that subsequent braking can be carried out, the butterfly valve 58 then being subsequently closed as shown in FIG. 1. This configuration makes it possible to considerably reduce the time for establishing, in the chamber 54 of the servomotor 52, the maximum vacuum of 800 millibars required for emergency braking.

 For example, the vacuum prevailing in the chamber 54 of the booster 52 according to this intermediate opening position of the butterfly valve 58 is of the order of 400 to 500 millibars.

 By way of comparison, FIG. 3 represents, for example, a configuration of full opening of the butterfly 58.

This configuration corresponds to a case in which the driver actuates the accelerator pedal without actuating the brake pedal 51, for example so that the vehicle drives normally. In this case, the control means do not control the throttle control means, and, all

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 actuators operating normally in a four-stroke operating sequence, the vacuum prevailing in the chamber 54 of the servomotor 52 results only from the vacuum reserve previously accumulated in the chamber 54.

 According to the invention, two variants of the determined operating mode can be envisaged.

 FIGS. 4 and 5 show "open" or "closed" states of the actuators 36, 38, 40, and 42 of the intake valves and of the actuators 44, 46, 48, 50 of the exhaust valves of the cylinders 12 , 14, 16.18. The "open" or closed "state of each actuator corresponds respectively to the opening or closing of each associated valve. The" open "or" closed "states are put in position relative to the top dead center positions PMH13, PMH17 , PMH19 and PMH15, which coincide respectively with the bottom dead center positions PMB15, PMB13, PMH17 and PMH19 of the pistons 13,15, 17, and 19 according to a conventional cycle of rotation of the crankshaft of a four-cylinder engine.

 According to a first variant which is shown in FIGS. 4 and 5, the intake valves associated with the actuators 38 and 42 of the cylinders 14 and 18 which operate according to the sequence SFM14, SFM18 determined for the engine brake are always closed.

 In known manner, the top dead center positions of the pistons 13 and 19 and the bottom dead center positions of the pistons 15 and 17 intervene for the same first angle of rotation of the crankshaft 60. Likewise, the bottom dead center positions of the pistons 13 and 19 and the top dead center positions of the pistons 15 and 17 intervene for the same second angle of rotation of the crankshaft 60.

 According to a first embodiment of the first variant which is represented in FIG. 4, the actuators which operate according to the determined sequence SFM14, SFM18 of engine brake are "closed" when the piston of the associated cylinder reaches its

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 low neutral position, and are opened at the latest when the piston reaches its high neutral position.

 Thus, as illustrated in FIG. 4, during the sequence SFM14, the actuator 46 of the cylinder 14 is "closed" when the piston 15 of the cylinder 14 reaches its bottom dead center position PMB15 and is "open" at most late when the piston 15 of the cylinder 14 reaches its top dead center position TDC15.

 Similarly, during the sequence SFM18, the actuator 50 of the cylinder 18 is "closed" when the piston 19 of the cylinder 18 reaches its bottom dead center position PMB19 and is "open" at the latest when the piston 19 of the cylinder 18 reaches its top dead center position PMH19.

 In FIG. 4, the closings of the actuators 46 and 50 are shown as intervening exactly when the associated pistons 15 and 19 reach their respective top dead center positions PMH15 and PMH19, but it will be understood that the closure can occur before, it that is to say that the opening of the actuator 46 can for example intervene between the position PMB15 and the position TDC15 and that, likewise, the opening of the actuator 50 can for example intervene between the position PMB19 and the position TDC19 . This configuration modulates the engine brake torque exerted.

 According to this first embodiment, the sequence SFM14, SFM18 determined is called "engine brake by compression" because the engine brake torque exerted on the crankshaft 60 is obtained by compression of the gases in the cylinders considered.

 According to a second embodiment of the first variant which is represented in FIG. 5, the actuators which operate according to the determined sequence SFM14, SFM18 of engine brake are closed when the piston of the associated cylinder reaches its top dead center position, and are open at the latest when the piston reaches its bottom dead center position.

 Thus, as illustrated in FIG. 5, during the sequence SFM14, the actuator 46 of the cylinder 14 is "closed" when the

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 piston 15 of cylinder 14 reaches its top dead center position PMH15 and is "open" at the latest when the piston 15 of cylinder 14 reaches its bottom dead center position PMB15.

 Likewise, during the sequence SFM18, the actuator 50 of the cylinder 18 is "closed" when the piston 19 of the cylinder 18 reaches its top dead center position PMH19 and is "open" at the latest when the piston 19 of the cylinder 18 reaches its bottom dead center position PMB19.

 In FIG. 5, the closings of the actuators 46 and 50 are shown as occurring exactly when the associated pistons 15 and 19 reach their respective positions of bottom dead center PMB15 and PMB19, but it will be understood that the closure can occur before, it that is to say that the opening of the actuator 46 can for example intervene between the PMH15 position and the PMB15 position and that, similarly, the opening of the actuator 50 can for example intervene between the PMH19 position and the PMB19 position . This configuration modulates the engine brake torque exerted.

 According to this second embodiment, the determined sequence SFM14, SFM18, is called "engine brake by vacuum" because the engine brake torque exerted on the crankshaft 60 is obtained by expansion of the gases in the cylinders considered.

 According to a second variant (not shown) of the invention, the determined sequence of engine brake comprises in a cyclic manner: - at least one conventional sub-sequence of four-stroke operation, which is analogous to the sequences, of control S4T12, S4T16 of the actuators 36, 44, 40 and 48 which have been shown in FIGS. 4 and 5; - at least one sub-sequence, called "pure" engine brake, which is analogous to the control sequences SFM14, SFM18 for controlling the actuators 38, 46, 42 and 50 which have been shown in FIG. 4 or in FIG. 5 .

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 The second variant therefore comprises two embodiments of the pure engine brake sub-sequence. In the two embodiments of the pure engine brake sub sequence, the intake valves of the cylinder concerned are always closed. In the first embodiment of the pure engine brake sub sequence, the exhaust valves of this cylinder are closed when the piston of this cylinder reaches its top dead center position and are opened at the latest when the piston reaches its position. from bottom dead center. The sub sequence is called "pure engine brake by compression", because the engine brake torque exerted on the crankshaft 60 is obtained by compression of the gases in the cylinders considered.

 Conversely, in the second embodiment of the pure engine brake sub sequence, the exhaust valves of this cylinder are closed when the piston of this cylinder reaches its bottom dead center position and are opened at the latest when the piston reaches its top dead center position. The sub-sequence is called "pure engine brake by vacuum", because the engine brake torque exerted on the crankshaft 60 is obtained by expansion of the gases in the cylinders considered.

 In practice, this second variant of the engine brake mode therefore consists in controlling the actuators of the intake and exhaust valves of at least one engine cylinder according to a succession of pure engine brake sub-sequences, during which the actuators of the cylinder are controlled in a manner analogous to that in which the actuators 38, 46, 42 and 50 are controlled during the sequences SFM14 and SFM18 previously described, and sub-sequences of normal four-stroke operation.

 Of course, the number of sub-sequences of normal four-stroke operation which are inserted between two sub-sequences of engine brake can be variable and in particular function of the vacuum which is required in the intake manifold 54 of the engine.

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 Furthermore, preferably, this determined sequence of engine brake intervenes when the engine speed is greater than a determined threshold value, that is to say in particular for high engine rotation speeds, this in order to avoid deterioration engine 10 and too sudden deceleration of the vehicle.

 The invention therefore advantageously makes it possible to produce a vehicle benefiting both from the advantages of a so-called "camtess" engine and from a conventional braking circuit.

Claims (11)

 CLAIMS 1. Motor vehicle with thermal engine, of the type in which the engine (10) comprises at least two cylinders (12,14, 16,18) and drives at least one wheel of the vehicle, of the type in which the intake valves (20,22, 24,26) and exhaust (28,30, 32,34) of the cylinders (12,14, 16,18) of the engine are driven by individual actuators (36,38, 40,42, 44,46,48,50), of the type in which a braking circuit of said wheel of the vehicle comprises at least one vacuum brake booster (52) of which at least one chamber (54) is connected to a intake manifold (56) of the engine downstream of a throttle valve (58) for supplying the intake manifold, and of the type which comprises means for controlling the opening of the throttle valve (58) for provide an adequate vacuum inside the chamber (54) of the servomotor (52), characterized in that it includes actuator control means (36,38, 40,42, 44,46, 48,50)and means for controlling the opening of the throttle valve (58) which are capable of operating in a determined mode according to which: - they control the actuators (38,42, 46,50) of the intake valves (22, 26) and exhaust (30,34) of at least one cylinder (14,18) of the engine (10) according to a determined sequence (SFM14, SFM18) called engine brake to provide a deceleration torque to at least one wheel of the vehicle, - they control the actuators (36,44, 40,48) of the intake (20,24) and exhaust (28,32) valves of the remaining cylinder (s) (12,16) ( s) according to a conventional sequence (S4T12, S4T16) of four-stroke operation to provide adequate vacuum in the intake manifold (56) and inside the chamber (54) of the booster (52).  2. Vehicle according to the preceding claim, characterized in that the control means are capable of <Desc / Clms Page number 16>  operate in the mode determined in response to the release of a vehicle accelerator pedal.  3. Vehicle according to one of the preceding claims, characterized in that the control means are capable of operating according to the mode determined in response to the actuation of a brake pedal (51) of the vehicle.  4. Vehicle according to any one of the preceding claims, characterized in that the control means comprise means for determining the number of cylinders of which they are capable of controlling the actuators according to the determined sequence (SFM14, SFM18) of engine brake.  5. Vehicle according to the preceding claim, characterized in that the number of cylinder actuators controlled according to the engine brake sequence (SFM14, SFM18) determined is a function of the vacuum prevailing in the chamber (54) of the booster (52) .  6. Vehicle according to any one of the preceding claims, characterized in that, according to the determined sequence (SFM14, SFM18) of the engine brake, the intake valves (38,42) are always closed.  7. Vehicle according to the preceding claim, characterized in that, according to the determined sequence (SFM14, SFM18) of engine brake, the exhaust valves (46,50) of a determined cylinder (14,18) are closed when the piston (15,19) of this cylinder (14,18) reaches its bottom dead center position (PMB15, PMB19), and are opened at the latest when the piston (15,19) reaches its position (PMH15, PMH19) of top dead center.  8. Vehicle according to claim 6, characterized in that, according to the determined sequence (SFM14, SFM18) of engine brake, the exhaust valves (46,50) of a determined cylinder (14,18) are closed when the piston (15,19) of this cylinder (14,18) reaches its top dead center position (PMH15, PMH19), and are opened at the latest when the piston reaches its bottom dead center position (PMB15, PMB19). <Desc / Clms Page number 17>  9. Vehicle according to any one of claims 1 to 5, characterized in that the determined sequence of engine brakes comprises cyclically: - at least one conventional four-stroke operating sub-sequence, - at least one sub-sequence , called pure engine brake, during which the intake valves of a given cylinder are always closed and during which:. the exhaust valves of this cylinder are closed when the piston of this cylinder reaches its top dead center position and are open at the latest when the piston reaches its bottom neutral position, or else the exhaust valves of this cylinder are closed when the piston of this cylinder reaches its bottom dead center position and are opened at the latest when the piston reaches its top dead center position.  10. Vehicle according to claim 9, characterized in that the determined engine brake sequence occurs as soon as the engine speed (10) is greater than a determined threshold value.  11. Vehicle according to any one of the preceding claims, characterized in that the actuators (36,38, 40, 42,44, 46,48, 50) are electromagnetic actuators.